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CyclizationStereoisomerismMolecular StructureAlkenesAlkynesIntramolecular LyasesPalladiumAcetalsCatalysisKetonesPolyisoprenyl PhosphatesChemistry, OrganicAlkadienesPyransPeptides, CyclicCycloparaffinsLewis AcidsRhodiumCombinatorial Chemistry TechniquesIsomerasesIndole AlkaloidsIminesCyclotidesHeterocyclic CompoundsMolecular ConformationHeterocyclic Compounds with 4 or More RingsAminationCarbon-Carbon LyasesFuransTerpenesEpoxy CompoundsPolyketide SynthasesMacrocyclic CompoundsProtein SplicingOldenlandiaBoranesModels, MolecularSolid-Phase Synthesis TechniquesNorbornanesHeterocyclic Compounds, 2-RingCyclodextrinsSqualeneInteinsCystine Knot MotifsMagnetic Resonance SpectroscopyPolyketidesMonoterpenesAbiesAldehydesDiterpenesNaphtholsStrychnosSpiro CompoundsStreptomycesAlkaloidsCycloaddition ReactionBromine CompoundsMolecular Sequence DataSesquiterpenesCrystallography, X-RayPhosgeneBicyclo CompoundsGlycogen Debranching Enzyme SystemSemicarbazidesGuanosine Diphosphate SugarsModels, Chemical
Cyclization
Changing an open-chain hydrocarbon to a closed ring. (McGraw-Hill Dictionary of Scientific and Technical Terms, 5th ed)
Stereoisomerism
The phenomenon whereby compounds whose molecules have the same number and kind of atoms and the same atomic arrangement, but differ in their spatial relationships. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 5th ed)
Molecular Structure
The location of the atoms, groups or ions relative to one another in a molecule, as well as the number, type and location of covalent bonds.
Alkenes
Unsaturated hydrocarbons of the type Cn-H2n, indicated by the suffix -ene. (Grant & Hackh's Chemical Dictionary, 5th ed, p408)
Alkynes
Hydrocarbons with at least one triple bond in the linear portion, of the general formula Cn-H2n-2.
Intramolecular Lyases
Enzymes of the isomerase class that catalyze reactions in which a group can be regarded as eliminated from one part of a molecule, leaving a double bond, while remaining covalently attached to the molecule. (From Enzyme Nomenclature, 1992) EC 5.5.
Palladium
A chemical element having an atomic weight of 106.4, atomic number of 46, and the symbol Pd. It is a white, ductile metal resembling platinum, and following it in abundance and importance of applications. It is used in dentistry in the form of gold, silver, and copper alloys.
Acetals
Catalysis
The facilitation of a chemical reaction by material (catalyst) that is not consumed by the reaction.
Ketones
Polyisoprenyl Phosphates
Phosphoric or pyrophosphoric acid esters of polyisoprenoids.
Chemistry, Organic
The study of the structure, preparation, properties, and reactions of carbon compounds. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)
Alkadienes
Acyclic branched or unbranched hydrocarbons having two carbon-carbon double bonds.
Pyrans
Peptides, Cyclic
Peptides whose amino and carboxy ends are linked together with a peptide bond forming a circular chain. Some of them are ANTI-INFECTIVE AGENTS. Some of them are biosynthesized non-ribosomally (PEPTIDE BIOSYNTHESIS, NON-RIBOSOMAL).
Cycloparaffins
Alicyclic hydrocarbons in which three or more of the carbon atoms in each molecule are united in a ring structure and each of the ring carbon atoms is joined to two hydrogen atoms or alkyl groups. The simplest members are cyclopropane (C3H6), cyclobutane (C4H8), cyclohexane (C6H12), and derivatives of these such as methylcyclohexane (C6H11CH3). (From Sax, et al., Hawley's Condensed Chemical Dictionary, 11th ed)
Lewis Acids
Any chemical species which accepts an electron-pair from a LEWIS BASE in a chemical bonding reaction.
Rhodium
Rhodium. A hard and rare metal of the platinum group, atomic number 45, atomic weight 102.905, symbol Rh. (Dorland, 28th ed)
Combinatorial Chemistry Techniques
A technology, in which sets of reactions for solution or solid-phase synthesis, is used to create molecular libraries for analysis of compounds on a large scale.
Isomerases
A class of enzymes that catalyze geometric or structural changes within a molecule to form a single product. The reactions do not involve a net change in the concentrations of compounds other than the substrate and the product.(from Dorland, 28th ed) EC 5.
Indole Alkaloids
Group of alkaloids containing a benzylpyrrole group (derived from TRYPTOPHAN)
Imines
Cyclotides
A continuous circle of peptide bonds, typically of 2-3 dozen AMINO ACIDS, so there is no free N- or C-terminus. They are further characterized by six conserved CYSTEINE residues that form CYSTINE KNOT MOTIFS.
Heterocyclic Compounds
Ring compounds having atoms other than carbon in their nuclei. (Grant & Hackh's Chemical Dictionary, 5th ed)
Molecular Conformation
The characteristic three-dimensional shape of a molecule.
Heterocyclic Compounds with 4 or More Rings
A class of organic compounds containing four or more ring structures, one of which is made up of more than one kind of atom, usually carbon plus another atom. The heterocycle may be either aromatic or nonaromatic.
Amination
The creation of an amine. It can be produced by the addition of an amino group to an organic compound or reduction of a nitro group.
Carbon-Carbon Lyases
Enzymes that catalyze the cleavage of a carbon-carbon bond by means other than hydrolysis or oxidation. This subclass contains the DECARBOXYLASES, the ALDEHYDE-LYASES, and the OXO-ACID-LYASES. EC 4.1.
Furans
Compounds with a 5-membered ring of four carbons and an oxygen. They are aromatic heterocycles. The reduced form is tetrahydrofuran.
Terpenes
A class of compounds composed of repeating 5-carbon units of HEMITERPENES.
Epoxy Compounds
Organic compounds that include a cyclic ether with three ring atoms in their structure. They are commonly used as precursors for POLYMERS such as EPOXY RESINS.
Polyketide Synthases
Large enzyme complexes composed of a number of component enzymes that are found in STREPTOMYCES which biosynthesize MACROLIDES and other polyketides.
Macrocyclic Compounds
Cyclic compounds with a ring size of approximately 1-4 dozen atoms.
Protein Splicing
The excision of in-frame internal protein sequences (INTEINS) of a precursor protein, coupled with ligation of the flanking sequences (EXTEINS). Protein splicing is an autocatalytic reaction and results in the production of two proteins from a single primary translation product: the intein and the mature protein.
Oldenlandia
A plant genus of the family RUBIACEAE. Some species are used as an ingredient in Chinese and African traditional medicines. Members contain kalata B1, a macrocyclic peptide.
Boranes
The collective name for the boron hydrides, which are analogous to the alkanes and silanes. Numerous boranes are known. Some have high calorific values and are used in high-energy fuels. (From Grant & Hackh's Chemical Dictionary, 5th ed)
Models, Molecular
Models used experimentally or theoretically to study molecular shape, electronic properties, or interactions; includes analogous molecules, computer-generated graphics, and mechanical structures.
Solid-Phase Synthesis Techniques
Techniques used to synthesize chemicals using molecular substrates that are bound to a solid surface. Typically a series of reactions are conducted on the bound substrate that results in either the covalent attachment of specific moieties or the modification of existing function groups. These techniques offer an advantage to those involving solution reactions in that the substrate compound does not have to be isolated and purified between the reaction steps.
Norbornanes
Heterocyclic Compounds, 2-Ring
A class of organic compounds containing two ring structures, one of which is made up of more than one kind of atom, usually carbon plus another atom. The heterocycle may be either aromatic or nonaromatic.
Cyclodextrins
A homologous group of cyclic GLUCANS consisting of alpha-1,4 bound glucose units obtained by the action of cyclodextrin glucanotransferase on starch or similar substrates. The enzyme is produced by certain species of Bacillus. Cyclodextrins form inclusion complexes with a wide variety of substances.
Squalene
Inteins
The internal fragments of precursor proteins (INternal proTEINS) that are autocatalytically removed by PROTEIN SPLICING. The flanking fragments (EXTEINS) are ligated forming mature proteins. The nucleic acid sequences coding for inteins are considered to be MOBILE GENETIC ELEMENTS. Inteins are composed of self-splicing domains and an endonuclease domain which plays a role in the spread of the intein's genomic sequence. Mini-inteins are composed of the self-splicing domains only.
Cystine Knot Motifs
Amino acid sequence in which two disulfide bonds (DISULFIDES) and their connecting backbone form a ring that is penetrated by a third disulfide bond. Members include CYCLOTIDES and agouti-related protein.
Magnetic Resonance Spectroscopy
Spectroscopic method of measuring the magnetic moment of elementary particles such as atomic nuclei, protons or electrons. It is employed in clinical applications such as NMR Tomography (MAGNETIC RESONANCE IMAGING).
Polyketides
Natural compounds containing alternating carbonyl and methylene groups (beta-polyketones), bioenergenetically derived from repeated condensation of acetyl coenzyme A via malonyl coenzyme A, in a process similar to fatty acid synthesis.
Monoterpenes
Compounds with a core of 10 carbons generally formed via the mevalonate pathway from the combination of 3,3-dimethylallyl pyrophosphate and isopentenyl pyrophosphate. They are cyclized and oxidized in a variety of ways. Due to the low molecular weight many of them exist in the form of essential oils (OILS, VOLATILE).
Abies
A plant genus in the family PINACEAE, order Pinales, class Pinopsida, division Coniferophyta. Balm of Gilead is a common name more often referring to POPULUS and sometimes to COMMIPHORA.
Aldehydes
Organic compounds containing a carbonyl group in the form -CHO.
Diterpenes
Twenty-carbon compounds derived from MEVALONIC ACID or deoxyxylulose phosphate.
Naphthols
Naphthalene derivatives carrying one or more hydroxyl (-OH) groups at any ring position. They are often used in dyes and pigments, as antioxidants for rubber, fats, and oils, as insecticides, in pharmaceuticals, and in numerous other applications.
Strychnos
A plant genus of the family LOGANIACEAE (classified by some botanists as Strychnaceae).
Spiro Compounds
A group of compounds consisting in part of two rings sharing one atom (usually a carbon) in common.
Streptomyces
A genus of bacteria that form a nonfragmented aerial mycelium. Many species have been identified with some being pathogenic. This genus is responsible for producing a majority of the ANTI-BACTERIAL AGENTS of practical value.
Alkaloids
Organic nitrogenous bases. Many alkaloids of medical importance occur in the animal and vegetable kingdoms, and some have been synthesized. (Grant & Hackh's Chemical Dictionary, 5th ed)
Cycloaddition Reaction
Synthetic organic reactions that use reactions between unsaturated molecules to form cyclical products.
Bromine Compounds
Inorganic compounds that contain bromine as an integral part of the molecule.
Molecular Sequence Data
Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.
Sesquiterpenes
Crystallography, X-Ray
The study of crystal structure using X-RAY DIFFRACTION techniques. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)
Phosgene
A highly toxic gas that has been used as a chemical warfare agent. It is an insidious poison as it is not irritating immediately, even when fatal concentrations are inhaled. (From The Merck Index, 11th ed, p7304)
Bicyclo Compounds
Glycogen Debranching Enzyme System
1,4-alpha-D-Glucan-1,4-alpha-D-glucan 4-alpha-D-glucosyltransferase/dextrin 6 alpha-D-glucanohydrolase. An enzyme system having both 4-alpha-glucanotransferase (EC 2.4.1.25) and amylo-1,6-glucosidase (EC 3.2.1.33) activities. As a transferase it transfers a segment of a 1,4-alpha-D-glucan to a new 4-position in an acceptor, which may be glucose or another 1,4-alpha-D-glucan. As a glucosidase it catalyzes the endohydrolysis of 1,6-alpha-D-glucoside linkages at points of branching in chains of 1,4-linked alpha-D-glucose residues. Amylo-1,6-glucosidase activity is deficient in glycogen storage disease type III.
Semicarbazides
Guanosine Diphosphate Sugars
Esters formed between the aldehydic carbon of sugars and the terminal phosphate of guanosine diphosphate.
Models, Chemical
Theoretical representations that simulate the behavior or activity of chemical processes or phenomena; includes the use of mathematical equations, computers, and other electronic equipment.

Do enzymes obey the Baldwin rules? A mechanistic imperative in enzymatic cyclization reactions. (1/1346)

It is commonly assumed that enzymes have evolved to abide by the same energetic and stereoelectronic principles that govern reactions in solution. The principles formulated for organic ring-closure reactions can be used to develop a hypothesis for analysis of enzyme-catalyzed cyclization reactions.  (+info)

Purification and characterization of 2-deoxy-scyllo-inosose synthase derived from Bacillus circulans. A crucial carbocyclization enzyme in the biosynthesis of 2-deoxystreptamine-containing aminoglycoside antibiotics. (2/1346)

The biosynthesis of 2-deoxystreptamine, the central aglycon of a major group of clinically important aminoglycoside antibiotics, commences with the initial carbocycle formation step from D-glucose-6-phosphate to 2-deoxy-scyllo-inosose. This crucial step is known to be catalyzed by 2-deoxy-scyllo-inosose synthase, which has not yet been characterized so far. Reported in this paper is the first purification of 2-deoxy-scyllo-inosose synthase from butirosin-producing Bacillus circulans SANK 72073 to electrophoretic homogeneity. The enzyme was isolated as a heterodimeric protein comprising from a 23 kDa- and a 42 kDa polypeptide chains. The Km of the enzyme for D-glucose-6-phosphate was estimated to be 9.0 x 10(-4) M and that for NAD+ 1.7 x 10(-4) M, kcat for D-glucose-6-phosphate being 7.3 x 10(-2) s(-1). The presence of Co2+ was essential for the enzyme activity, but Zn2+ was totally inhibitory. While the reaction mechanisms are quite similar, 2-deoxy-scyllo-inosose synthase appears to be distinct from dehydroquinate synthase in the shikimate pathway, with respect to the quaternary structure, metal ion requirement, and the kinetic parameters.  (+info)

Elucidating the mechanism of chain termination switching in the picromycin/methymycin polyketide synthase. (3/1346)

BACKGROUND: A single modular polyketide synthase (PKS) gene cluster is responsible for production of both the 14-membered macrolide antibiotic picromycin and the 12-membered macrolide antibiotic methymycin in Streptomyces venezuelae. Building on the success of the heterologous expression system engineered using the erythromycin PKS, we have constructed an analogous system for the picromycin/methymycin PKS. Through heterologous expression and construction of a hybrid PKS, we have examined the contributions that the PKS, its internal thioesterase domain (pikTE) and the Pik TEII thioesterase domain make in termination and cyclization of the two polyketide intermediates. RESULTS: The picromycin/methymycin PKS genes were functionally expressed in the heterologous host Streptomyces lividans, resulting in production of both narbonolide and 10-deoxymethynolide (the precursors of picromycin and methymycin, respectively). Co-expression with the Pik TEII thioesterase led to increased production levels, but did not change the ratio of the two compounds produced, leaving the function of this protein largely unknown. Fusion of the PKS thioesterase domain (pikTE) to 6-deoxyerythronolide B synthase (DEBS) resulted in formation of only 14-membered macrolactones. CONCLUSIONS: These experiments demonstrate that the PKS alone is capable of catalyzing the synthesis of both 14- and 12-membered macrolactones and favor a model by which different macrolactone rings result from a combination of the arrangement between the module 5 and module 6 subunits in the picromycin PKS complex and the selectivity of the pikTE domain.  (+info)

Heterologous expression, purification, reconstitution and kinetic analysis of an extended type II polyketide synthase. (4/1346)

BACKGROUND: Polyketide synthases (PKSs) are bacterial multienzyme systems that synthesize a broad range of natural products. The 'minimal' PKS consists of a ketosynthase, a chain length factor, an acyl carrier protein and a malonyl transferase. Auxiliary components (ketoreductases, aromatases and cyclases are involved in controlling the oxidation level and cyclization of the nascent polyketide chain. We describe the heterologous expression and reconstitution of several auxiliary PKS components including the actinorhodin ketoreductase (act KR), the griseusin aromatase/cyclase (gris ARO/CYC), and the tetracenomycin aromatase/cyclase (tcm ARO/CYC). RESULTS: The polyketide products of reconstituted act and tcm PKSs were identical to those identified in previous in vivo studies. Although stable protein-protein interactions were not detected between minimal and auxiliary PKS components, kinetic analysis revealed that the extended PKS comprised of the act minimal PKS, the act KR and the gris ARO/CYC had a higher turnover number than the act minimal PKS plus the act KR or the act minimal PKS alone. Adding the tcm ARO/CYC to the tcm minimal PKS also increased the overall rate. CONCLUSIONS: Until recently the principal strategy for functional analysis of PKS subunits was through heterologous expression of recombinant PKSs in Streptomyces. Our results corroborate the implicit assumption that the product isolated from whole-cell systems is the dominant product of the PKS. They also suggest that an intermediate is channeled between the various subunits, and pave the way for more detailed structural and mechanistic analysis of these multienzyme systems.  (+info)

Protein aging hypothesis of Alzheimer disease. (5/1346)

Alzheimer disease (AD), the most common form of aging-related neurodegenerative disorders, is associated with formation of fibrillar deposits of amyloid beta-protein (Abeta). While the direct involvement of Abeta in AD has been well documented, the relations between Abeta production, amyloid formation, and neurodegeneration remain unknown. We propose that AD is initiated by a protein aging-related structural transformation in soluble Abeta. We hypothesize that spontaneous chemical modification of aspartyl residues in Abeta to transient succinimide induces a non-native conformation in a fraction of soluble Abeta, rendering it amyloidogenic and neurotoxic. Conformationally altered Abeta is characterized by increased stability in solution and the presence of a non-native beta-turn that determines folding of Abeta in solution and the structure of Abeta subunits incorporated into amyloid fibrils. While the soluble 'non-native' Abeta is both the factor triggering the neurodegenerative cascade and the precursor of amyloid plaques, these two events result from interaction of Abeta with different sets of cellular components and need not coincide in space and time. Extensive literature data and experimental evidence are provided in support of this hypothesis.  (+info)

Site-directed mutagenesis of squalene-hopene cyclase: altered substrate specificity and product distribution. (6/1346)

BACKGROUND: Two regions of squalene-hopene cyclase (SHC) were examined to define roles for motifs posited to be responsible for initiation and termination of the enzyme-catalyzed polyolefinic cyclizations. Specifically, we first examined the triple mutant of the DDTAVV motif, a region deeply buried in the catalytic cavity and thought to be responsible for the initiation of squalene cyclization. Next, four mutants were prepared for Glu45, a residue close to the substrate entrance channel proposed to be involved in the termination of the cyclization of squalene. RESULTS: The DDTAVV motif in SHC was changed to DCTAEA, the corresponding conserved region of eukaryotic oxidosqualene cyclase (OSC), by the triple mutation of D377C/V380E/V381A; selected single mutants were also examined. The triple mutant showed no detectable cyclization of squalene, but effectively cyclized 2,3-oxidosqualene to give mono- and pentacyclic triterpene products. Of the Glu45 mutants, E45A and E45D showed reduced activity, E45Q showed slightly increased activity, and E45K was inactive. A normal yield of pentacyclic products was produced, but the ratio of hopene 2 to hopanol 3 was significantly changed in the less active mutants. CONCLUSIONS: Initiation and substrate selectivity may be determined by the interaction of the DDTAVV motif with the isopropylidene of squalene (for SHC) and of the DCTAEA motif with the epoxide of oxidosqualene (for OSC). This is the first report of a substrate switch determined by a central catalytic motif in a triterpenoid cyclase. At the termination of cyclization, the product ratio may be largely controlled by Glu45 at the entrance channel to the active site.  (+info)

Aureusidin synthase: a polyphenol oxidase homolog responsible for flower coloration. (7/1346)

Aurones are plant flavonoids that provide yellow color to the flowers of some popular ornamental plants, such as snapdragon and cosmos. In this study, we have identified an enzyme responsible for the synthesis of aurone from chalcones in the yellow snapdragon flower. The enzyme (aureusidin synthase) is a 39-kilodalton, copper-containing glycoprotein catalyzing the hydroxylation and/or oxidative cyclization of the precursor chalcones, 2',4',6',4-tetrahydroxychalcone and 2',4',6',3,4-pentahydroxychalcone. The complementary DNA encoding aureusidin synthase is expressed in the petals of aurone-containing varieties. DNA sequence analysis revealed that aureusidin synthase belongs to the plant polyphenol oxidase family, providing an unequivocal example of the function of the polyphenol oxidase homolog in plants, i.e., flower coloration.  (+info)

Intramolecular proton transfer in the cyclization of geranylgeranyl diphosphate to the taxadiene precursor of taxol catalyzed by recombinant taxadiene synthase. (8/1346)

BACKGROUND: The committed step in the biosynthesis of the anticancer drug taxol in yew (Taxus) species is the cyclization of geranylgeranyl diphosphate to taxa-4(5),11(12)-diene. The enzyme taxadiene synthase catalyzes this complex olefin cation cyclization cascade involving the formation of three rings and three stereogenic centers. RESULTS: Recombinant taxadiene synthase was incubated with specifically deuterated substrates, and the mechanism of cyclization was probed using MS and NMR analyses of the products to define the crucial hydrogen migration and terminating deprotonation steps. The electrophilic cyclization involves the ionization of the diphosphate with closure of the A-ring, followed by a unique intramolecular transfer of the C11 proton to the re-face of C7 to promote closure of the B/C-ring juncture, and cascade termination by proton elimination from the beta-face of C5. CONCLUSIONS: These findings provide insight into the molecular architecture of the first dedicated step of taxol biosynthesis that creates the taxane carbon skeleton, and they have broad implications for the general mechanistic capability of the large family of terpenoid cyclization enzymes.  (+info)

An arene-alkene photocycloaddition-radical cyclization cascade: The first synthesis of cis,cis,cis,trans-[5.5.5.5]-fenestranes<...
TY - JOUR. T1 - An arene-alkene photocycloaddition-radical cyclization cascade. T2 - The first synthesis of cis,cis,cis,trans-[5.5.5.5]-fenestranes. AU - Wender, Paul A.. AU - Dore, Timothy. AU - DeLong, Mitch A.. PY - 1996/10/21. Y1 - 1996/10/21. N2 - The first cis,cis,cis,trans-[5.5.5.5]-fenestranes have been synthesized in three steps using a novel arene-alkene photocycloaddition-radical cyclization cascade, which creates overall 5 new rings and 8 stereogenic centers. A lead tetraacetate mediated ring expansion of a 5,5-fused ring system, discovered in the course of exploring the chemistry of these new materials, is also described.. AB - The first cis,cis,cis,trans-[5.5.5.5]-fenestranes have been synthesized in three steps using a novel arene-alkene photocycloaddition-radical cyclization cascade, which creates overall 5 new rings and 8 stereogenic centers. A lead tetraacetate mediated ring expansion of a 5,5-fused ring system, discovered in the course of exploring the chemistry of these new ...
https://nyu-staging.pure.elsevier.com/en/publications/an-arene-alkene-photocycloaddition-radical-cyclization-cascade-th
Investigation of the nitronate Nazarov cyclizationInvestigation of the nitronate Nazarov cyclization
The Nazarov cyclization is a common synthetic tool in the synthesis of cyclopentenone rings. The reaction is characterized by a divinyl ketone starting reagent that undergoes a 4π-electron electrocyclization after addition of a Lewis/Brønsted acid; forming the cyclopentadienyl cation that undergoes cyclization. An extension of this methodology involves using a divinyl imine starting reagent. This cyclization is less favoured due to the electron donating ability of the nitrogen atom, causing the pentadienyl cation to be relatively stable and unwilling to undergo cyclization. To improve this cyclization, the imine is replaced with the electron withdrawing nitronate functionality. It is hypothesized that by doing so the addition of an acid will form the cyclopentadienyl cation that will readily undergo Nazarov cyclization. The synthesis of an aryl vinyl silyl nitronate was optimized and the compound was tested with a number of different acid catalysts to determine if the nitronate Nazarov ...
http://library2.smu.ca/handle/01/26258
DocMe.su: cyclizationDocMe.su: cyclization
Effect of primary polymer chain rigidity on intramolecular cyclization and intramolecular crosslinking in free-radical crosslinking monomethacrylatedimethacrylate copolymerizations., The effluent analysis of several pyrrone and polyimide precursors during cyclization., Reduction and cyclization to form poly(benzimidazole amide imide) copolymers., Thermal degradation of polymers. Part XIX. The thermal cyclization and characterization of quinazolone pre-polymers, Cationic cyclization of cis-1 4-polybutadiene I. Synthesis and technological evaluation of the polymer, ThreeFourFive-Component Diastereoselective Cyclization of Fischer Carbene Complexes Lithium Enolates and Allylmagnesium Bromide., Evolution of aggregation structure of polyacrylonitrile fibers in the cyclization reaction., Epoxy resins based on aromatic glycidylamines. III. Kinetics of intramolecular cyclization of N N-bis(2-hydroxy-3-chloropropyl)aniline, Cyclization during polyesterification Isolation of an 18-member ring compound from
https://www.docme.ru/tag/457681/cyclization
Exploring the Monoterpene Cyclization Mechanism by Studying (+)-Limonene Synthase Using Novel Fluorinated Substrate AnaloguesExploring the Monoterpene Cyclization Mechanism by Studying (+)-Limonene Synthase Using Novel Fluorinated Substrate Analogues
A proposed universal monoterpene synthases (cyclases) cyclization mechanism topologically requires an isomerization step of the substrate geranyl diphosphate (GPP) to the formation of the proposed universal intermediate linalyl diphosphate (LPP), which has never been directly observed. The study described here was designed to investigate the cyclization mechanism by studying a model enzyme, (4R)-(+)-limonene synthase ((+)-LS), a monoterpene cyclase that produces (+)-limonene by using substrate GPP. The study synthesized two novel difluorinated substrate analogues, 8,9-difluorogeranyl diphosphate (DFGPP) and 8,9-difluorolinalyl diphosphate (DFLPP), which were designed to retard the cyclization step in order to observe the intermediate at the enzyme active site. Both analogues are proved to be substrates for (+)-LS. Compared to GPP, which has a kcat value of 0.0905 +/- 0.0070 s-1, DFGPP has a reduced kcat value at 0.00144 +/- 0.00002 s-1, showing a 69-fold slower rate in the catalytic reaction. ...
https://bir.brandeis.edu/handle/10192/33932?show=full
Systematic investigations on fused π-system compounds of seven benzene rings prepared by photocyclization of...
TY - JOUR. T1 - Systematic investigations on fused π-system compounds of seven benzene rings prepared by photocyclization of diphenanthrylethenes. AU - Fujino, Shota. AU - Yamaji, Minoru. AU - Okamoto, Hideki. AU - Mutai, Toshiki. AU - Yoshikawa, Isao. AU - Houjou, Hirohiko. AU - Tani, Fumito. N1 - Publisher Copyright: © 2017 The Royal Society of Chemistry and Owner Societies.. PY - 2017. Y1 - 2017. N2 - We studied the photoproducts of 1-(n-phenanthryl)-2-(m-phenanthryl)ethenes (nEm; n, m = 1, 3 and 9) for understanding photocyclization patterns based on NMR spectroscopy. The crystal structures of the photoproducts were analyzed by X-ray crystallography, and the photophysical features of the photocyclized molecules were investigated based on emission and transient absorption measurements. Phenanthrene derivatives substituted at the 1- and 3-positions were prepared for synthesizing nEm by photocyclization of stilbene derivatives. We obtained four types of primary photoproducts ([email protected]) from the ...
https://okayama.pure.elsevier.com/en/publications/systematic-investigations-on-fused-%CF%80-system-compounds-of-seven-be
Molecules | Free Full-Text | Iodine-Catalyzed Prins Cyclization of Homoallylic Alcohols and AldehydesMolecules | Free Full-Text | Iodine-Catalyzed Prins Cyclization of Homoallylic Alcohols and Aldehydes
The iodine-catalyzed Prins cyclization of homoallylic alcohols and aldehydes was investigated under metal-free conditions and without additives. Anhydrous conditions and inert atmosphere are not required. The reaction of 2-(3,4-dihydronaphthalen-1-yl)propan-1-ol and 21 aldehydes (aliphatic and aromatic) in CH2Cl2 in the presence of 5 mol % of iodine gave 1,4,5,6-tetrahydro-2H-benzo[f]isochromenes in 54%-86% yield. Under similar conditions, the Prins cyclization of six alcohols containing an endocyclic double bond (primary, secondary, or tertiary) led to dihydropyrans in 52%-91% yield. The acyclic homoallylic alcohols gave 4-iodo-tetrahydropyran in 29%-41% yield in the presence of 50 mol % of iodine. This type of substrate is the main limitation of the methodology. The relative configuration of the products was assigned by NMR and X-ray analysis. The mechanism and the ratio of the products are discussed, based on DFT calculations.
http://mdpi.com/1420-3049/18/9/11100
Metal-mediated Heterocyclization: Synthesis of Heterocyclic Compounds Containing More Than One Heteroatom Through Carbon...Metal-mediated Heterocyclization: Synthesis of Heterocyclic Compounds Containing More Than One Heteroatom Through Carbon...
Title: Metal-mediated Heterocyclization: Synthesis of Heterocyclic Compounds Containing More Than One Heteroatom Through Carbon-Heteroatom Bond Forming Reactions. VOLUME: 14 ISSUE: 8. Author(s):K. C. Majumdar, B. Roy, P. Debnath and A. Taher. Affiliation:Department of Chemistry, University of Kalyani, Kalyani- 741 235, India.. Abstract: Heterocyclic compounds are versatile building blocks in organic synthesis. These are important part in various natural products and bioactive compounds. Several methodologies have been developed to synthesize these heterocyclic compounds. This review article covers an updated (published during 2005 to 2008) summary of transition-metal catalyzed approaches for the syntheses of commonring heterocycles containing more than one heteroatom via the selective formation of carbon-heteroatom bonds. The five-membered ring heterocycles with two nitrogen atoms include imidazoles, pyrazoles, indazoles, imidazoindolones etc. and heterocycles with one nitrogen and one oxygen ...
https://www.eurekaselect.com/71436/article/metal-mediated-heterocyclization-synthesis-heterocyclic-compounds-containing-more-one
Ammonia synthons for the multicomponent assembly of complex γ-lactams<...
TY - JOUR. T1 - Ammonia synthons for the multicomponent assembly of complex γ-lactams. AU - Tan, Darlene Q.. AU - Martin, Kevin S.. AU - Fettinger, James C.. AU - Shaw, Jared T.. PY - 2011/4/26. Y1 - 2011/4/26. N2 - The synthesis of γ-lactams that are unsubstituted at the 1-position (nitrogen) as well as their subsequent N-functionalization is reported. A recently discovered four-component reaction (4CR) is employed with either an ammonia precursor or a protected form of ammonia that can be deprotected in a subsequent synthetic step. These methods represent the first multicomponent assembly of complex lactam structures that are unsubstituted at nitrogen. In addition, two methods for the introduction of nitrogen substituents that are not possible through the original 4CR are reported. X-ray crystallographic analysis of representative structures reveals conformational changes in the core structure that will enable future deployment of this chemistry in the design and synthesis of diverse ...
https://ucdavis.pure.elsevier.com/en/publications/ammonia-synthons-for-the-multicomponent-assembly-of-complex-%CE%B3-lac
Squaramide-catalyzed asymmetric Michael/cyclization cascade reaction of 3-isothiocyanato oxindoles with chalcones for synthesis...Squaramide-catalyzed asymmetric Michael/cyclization cascade reaction of 3-isothiocyanato oxindoles with chalcones for synthesis...
A highly efficient method for the construction of pyrrolidinyl spirooxindoles with 3-isothiocyanato oxindoles and chalcones via a Michael/cyclization cascade reaction has been developed by using bifunctional cinchona-derived squaramide organocatalysts. A series of complex pyrrolidinyl spirooxindoles could be
http://pubs.rsc.org/en/content/articlelanding/2017/qo/c6qo00852f
Intramolecular Diels-Alder Cycloaddition: Brombyin II (Lygo), Ptilocaulin (Livinghouse), Bistellettadine A (Snider), (-)...Intramolecular Diels-Alder Cycloaddition: Brombyin II (Lygo), Ptilocaulin (Livinghouse), Bistellettadine A (Snider), (-)...
It seemed plausible that the biosynthesis of Bistellettadine A (9) was proceeding by intermolecular dimerization of the monomeric carboxylic acid corresponding to 7. Barry B. Snider of Brandeis University found (Org. Lett. 2010, 12, 828. ) that that intermolecular dimerization did proceed efficiently, but to give a 5:4 mixture of diastereomers. In contrast, the linked diester 7 cyclized with exclusive diastereocontrol. The product 8 was readily carried on to Bistellettadine A 9. This raises the possibility that a chiral template, attached either covalently or through salt formation, could be designed that would direct the absolute configuration of the cycloaddition.. ...
https://www.organic-chemistry.org/Highlights/2011/29August.shtm
Reviews - RSC Medicinal Chemistry BlogReviews - RSC Medicinal Chemistry Blog
In this review James C. Collins and Keith James from the Scripps Research Institute critically analyse macrocyclization reactions published over the last three years. Based upon on this analysis, and first-hand experience of macrocyclization, Collins and James propose a macrocyclization efficiency index, Emac, as a means of determining the true efficiency of a macrocyclization reaction.. Emac takes into account both reaction yield and concentration, which Collins & James state addresses the key factors that determine the practicality of using a given reaction in a drug discovery context. In other words, the Emac for a reaction indicates the likelihood of being able to conduct the reaction on a sufficiently large scale whilst remaining resource efficient.. This index also allows comparison of a large number of literature macrocyclization reactions and identifies those which deliver the powerful combination of high yield and high practicality. Collins and James hope that those who are actively ...
https://blogs.rsc.org/md/category/reviews/?doing_wp_cron=1606981543.5366408824920654296875
3+2)-Cycloaddition Reactions of Oxyallyl Cations by Jimmy Wu and Hui Li3+2)-Cycloaddition Reactions of Oxyallyl Cations by Jimmy Wu and Hui Li
The (3+2)-cycloaddition reaction involving oxyallyl cations has proven to be a versatile and efficient approach for the construction of five-membered carbo- and heterocycles, which are prevalent frameworks in natural products and pharmaceuticals. The following article will provide a brief summary of recent disclosures on this process featuring chemo-, regio- and diastereoselective oxyallyl cycloadditions with both electron-rich and electron-deficient 2π partners.
https://digitalcommons.dartmouth.edu/facoa/3652/
Highly enantioselective oxidative tandem cyclization reaction: a chiral ligand and an anion cooperatively control...Highly enantioselective oxidative tandem cyclization reaction: a chiral ligand and an anion cooperatively control...
The unprecedented combination of a palladium(ii) complex with a chiral Bu-QUOX ligand and a chiral phosphoric acid enables the highly efficient asymmetric oxidative tandem cyclization of N-(2,2-disubstituted hex-5-en-1-yl)acrylamides, providing a straightforward method to access chiral 6,5-bicyclic aza-heter
http://pubs.rsc.org/en/Content/ArticleLanding/QO/2014/C4QO00042K
One-pot reductive cyclization to antitumor quinazoline precursorsOn resonance interactions in methyl 4-X-benzoates and the...
List of : One-pot reductive cyclization to antitumor quinazoline precursorsOn resonance interactions in methyl 4-X-benzoates and the effect of 2,6-dimethyl substitution. 13C or 17O NMR chemical shifts as effective indicators of π-electron-density distribution?Open-chain and cyclic amidrazones forming persistent radicals. An electrochemical and quantum chemical studyOne-pot synthesis of stable phosphorus ylides using aldehyde phenylhydrazone derivativesOne-pot synthesis of 5-carboxanilide-dihydropyrimidinones using etidronic acid
http://www.easechem.com/pdfmap/o13.html
Active and Recyclable Catalytic Synthesis of Indoles by Reductive Cyclization of 2-(2-Nitroaryl)acetonitriles in the Presence...Active and Recyclable Catalytic Synthesis of Indoles by Reductive Cyclization of 2-(2-Nitroaryl)acetonitriles in the Presence...
A cobalt-rhodium heterobimetallic nanoparticle-catalyzed reductive cyclization of 2-(2-nitroaryl)acetonitriles to indoles proceeds without any additives under mild conditions. The catalytic can be reused more than ten times without loss of catalytic activity.. ...
http://www.organic-chemistry.org/abstracts/lit5/650.shtm
SYNTHESIS OF FUSED PYRAZOLES |i|VIA|/i| INTRAMOLECULAR CYCLIZATION OF APPROPRIATELY |i|ortho|/i|-SUBSTITUTED NITROARENES AND...SYNTHESIS OF FUSED PYRAZOLES |i|VIA|/i| INTRAMOLECULAR CYCLIZATION OF APPROPRIATELY |i|ortho|/i|-SUBSTITUTED NITROARENES AND...
SYNTHESIS OF FUSED PYRAZOLES VIA INTRAMOLECULAR CYCLIZATION OF APPROPRIATELY ortho -SUBSTITUTED NITROARENES AND NITROHETEROARENES
http://hgs.osi.lv/index.php/hgs/article/view/3522
Visible light photocatalysis of radical cation Diels-Alder cycloadditions: preparation of tris(2,2-bipyrazyl)ruthenium(II) bis...Visible light photocatalysis of radical cation Diels-Alder cycloadditions: preparation of tris(2,2-bipyrazyl)ruthenium(II) bis...
Home » Visible light photocatalysis of radical cation Diels-Alder cycloadditions: preparation of tris(2,2-bipyrazyl)ruthenium(II) bis(tetrakis(3,5-bis(trifluoromethyl)phenyl)borate ...
https://yoon.chem.wisc.edu/content/visible-light-photocatalysis-radical-cation-diels-alder-cycloadditions-preparation-tris22
SilverCatalyzed Cascade Carboxylation and Cyclization of Trimethyl(2-methylenebut-3-yn-1-yl)silane Derivatives<...
TY - JOUR. T1 - SilverCatalyzed Cascade Carboxylation and Cyclization of Trimethyl(2-methylenebut-3-yn-1-yl)silane Derivatives. AU - Sekine, Kohei. AU - Sadamitsu, Yuta. AU - Yamada, Tohru. PY - 2015/11/20. Y1 - 2015/11/20. N2 - C-C bond-forming carboxylation and cyclization of trimethyl(2-methylenebut-3-yn-1-yl)silane derivatives and carbon dioxide was developed. Silver catalysts and CsF promoted the reaction to afford the corresponding 2-furanone and 2-pyrone derivatives in good-to-high yields. The structure of the 2-furanone was confirmed by single-crystal X-ray crystallography, which revealed that the geometry of the exo-olefin was that of a Z-isomer. When an aromatic ring-substituted alkyne was used, 2-furanone derivatives were selectively obtained via 5-exo-dig cyclization, whereas the reaction of alkyl-substituted alkynes produced 2-pyrone derivatives with high selectivity.. AB - C-C bond-forming carboxylation and cyclization of trimethyl(2-methylenebut-3-yn-1-yl)silane derivatives and ...
https://keio.pure.elsevier.com/en/publications/silvercatalyzed-cascade-carboxylation-and-cyclization-of-trimethy
Regio- and stereoselective cyclization reactions of unsaturated silyl enol ethers by photoinduced electron transfer -...
Oxidative photoinduced electron transfer (PET) reactions have been performed with various silyl enol ethers and silyloxy-2H-chromones bearing an olefinic or silylacetylenic side chain, The reactions result in regioselective ring closure with the formation of bi- to tetracyclic ring systems with a well-defined ring juncture, e.g. perhydrophenanthrenones 13 or benzo-annellated xanthenones 24. Our investigations have focussed on the optimization of this cyclization method with regard to irradiation time and product yield. The irradiation times could be reduced by using the cosensitized PET method. Modifying the substrate at the silyl group led to enhanced yields. In addition, we found that solvent and pressure dependences are important tools, allowing control of the regiochemistry. Both the synthesis of 6-endo products by radical cationic reaction pathways, as well as 5-exo ring closure by radical intermediates was achieved. Mechanistic details, including findings from deuterium labelling ...
https://pub.uni-bielefeld.de/record/2402474
Enantioselective organo-SOMO cascade cycloadditions: A rapid approach to molecular complexity from simple aldehydes and olefins...Enantioselective organo-SOMO cascade cycloadditions: A rapid approach to molecular complexity from simple aldehydes and olefins...
TY - JOUR. T1 - Enantioselective organo-SOMO cascade cycloadditions. T2 - A rapid approach to molecular complexity from simple aldehydes and olefins. AU - Jui, Nathan T.. AU - Lee, Esther C.Y.. AU - MacMillan, David W.C.. PY - 2010/7/28. Y1 - 2010/7/28. N2 - A highly selective, radical-mediated (4 + 2) coupling reaction of aldehydes and conjugated olefins has been achieved through asymmetric SOMO-catalysis. A radical-polar crossover mechanism is proposed wherein olefin addition to a transient enamine radical cation and oxidation of the resulting radical furnishes a cation which is vulnerable to nucleophilic addition. A range of aromatic aldehydes are shown to couple with styrenes and dienes to provide cyclic products with high chemical efficiency, regioselectivity, and stereoselectivity.. AB - A highly selective, radical-mediated (4 + 2) coupling reaction of aldehydes and conjugated olefins has been achieved through asymmetric SOMO-catalysis. A radical-polar crossover mechanism is proposed ...
https://collaborate.princeton.edu/en/publications/enantioselective-organo-somo-cascade-cycloadditions-a-rapid-appro
Sacred Heart College | ESI Induced Gas-Phase Nazarov Cyclization of (2E)-3-(2-Methoxyphenyl)-1-(thiophen-2-yl)-prop-2-en-1...Sacred Heart College | ESI Induced Gas-Phase Nazarov Cyclization of (2E)-3-(2-Methoxyphenyl)-1-(thiophen-2-yl)-prop-2-en-1...
ESI Induced Gas-Phase Nazarov Cyclization of (2E)-3-(2-Methoxyphenyl)-1-(thiophen-2-yl)-prop-2-en-1-one and its Oxygen Analogue ...
http://www.shcollege.ac.in/publication/1-esi-induced-gas-phase-nazarov-cyclization-of-2e-3-2-methoxyphenyl-1-thiophen-2-yl-prop-2-en-1-one-and-its-oxygen-analogue/
I. The acid catalyzed reactions of certain 1,5-epoxyolefins. II. The alkylative cyclization of 1,5-hexadiene. III. The acid...I. The acid catalyzed reactions of certain 1,5-epoxyolefins. II. The alkylative cyclization of 1,5-hexadiene. III. The acid...
I. The acid catalyzed reactions of certain 1,5-epoxyolefins. The monoxides of a number of 1,5-dienes were prepared and treated with a variety of acidic reagents known to induce cyclization of the parent diolefins. In all cases the major reaction observed was the isomerization of the epoxide to a carbonyl function. No cyclic products were observed. These results are discussed in terms of the general requirements for cyclization.. II. The alkylative cyclization of 1,5-hexadiene The alkylation of 1,5 -hexadiene with t-butyl chloride in the presence of aluminum trichloride was studied. The major monomeric reaction products were cyclic, and both the t-butylcyclohexane and neopentylcyclopentane skeletons were identified among them. Formation of the latter ring system appeared to be slightly favored over formation of the six-membered ring. This preference is undoubtedly due to both steric and electronic factors.. III. The acid catalyzed cyclization of cis, cis- and trans, trans-2,6-octadiene. Both cis, ...
https://thesis.library.caltech.edu/7230/
Electrocyclic reaction - WikipediaElectrocyclic reaction - Wikipedia
In organic chemistry, an electrocyclic reaction is a type of pericyclic rearrangement where the net result is one pi bond being converted into one sigma bond or vice versa. These reactions are usually categorized by the following criteria: Reactions can be either photochemical or thermal. Reactions can be either ring-opening or ring-closing (electrocyclization). Depending on the type of reaction (photochemical or thermal) and the number of pi electrons, the reaction can happen through either a conrotatory or disrotatory mechanism. The type of rotation determines whether the cis or trans isomer of the product will be formed. The Nazarov cyclization reaction is a named electrocyclic reaction converting divinylketones to cyclopentenones. A classic example is the thermal ring-opening reaction of 3,4-dimethylcyclobutene. The cis isomer exclusively yields cis,trans-2,4-hexadiene whereas the trans isomer gives the trans,trans diene: This reaction course can be explained in a simple analysis through the ...
https://en.wikipedia.org/wiki/Electrocyclic_reaction
Cascade Oxidative Dearomatization/Semipinacol Rearrangement: An Approach to 2-Spirocyclo-3-oxindole Derivatives - Peng - 2013 -...Cascade Oxidative Dearomatization/Semipinacol Rearrangement: An Approach to 2-Spirocyclo-3-oxindole Derivatives - Peng - 2013 -...
A novel cascade reaction involving oxidative dearomatization/semipinacol rearrangement of indol-2-yl cyclobutanols is explored with N-sulfonyloxaziridine (Davis oxaziridines) as oxidant, generating various 2-spiroquaternary 3-oxindoles in modest to good yields. This method might be useful in the synthesis of indole-based alkaloids bearing 2-spiroquaternary carbon centers. PTS=p-toluenesulfonic acid monohydrate. ...
http://onlinelibrary.wiley.com/doi/10.1002/asia.201300032/full?xmlid=asia201300032-eo-0013
Metal-Catalyzed Cyclization Reactions - Thieme Chemistry - Georg Thieme VerlagMetal-Catalyzed Cyclization Reactions - Thieme Chemistry - Georg Thieme Verlag
These two SOS volumes present the broad scope of metal-catalyzed reactions for the synthesis of cyclic compounds, from long-established methods to state-of-the-art approaches. The power of these reactions is highlighted by selected examples of application in natural product/drug synthesis.. Significant advances in metal-catalyzed reactions, especially cyclizations, have dramatically improved the efficiency of organic synthesis over the last three decades. To date, these transformations are widely used in the area of synthesis of both natural products and therapeutic agents. Science of Synthesis: Metal-Catalyzed Cyclization Reactions presents the most commonly used and significant metal-catalyzed reactions for modern organic synthesis. The basic principles, the current state of the art, scope, limitations, and mechanism of these reactions are also discussed. Typical examples of target synthesis are provided to help inspire further applications.. Volume 1 covers intramolecular coupling reactions ...
https://www.thieme.de/en/thieme-chemistry/sos-metal-catalyzed-cyclization-reactions-100781.htm
Science of Synthesis: Metal-Catalyzed Cyclization Reactions Vol. 1 - Thieme.de - Thieme Webshop - Shuanhu Gao, Shengming MaScience of Synthesis: Metal-Catalyzed Cyclization Reactions Vol. 1 - Thieme.de - Thieme Webshop - Shuanhu Gao, Shengming Ma
Significant advances in metal-catalyzed reactions, especially cyclizations, have dramatically improved the efficiency of organic synthesis over the last three decades. To date these transformations are widely used in the area of synthesis of both natural products and therapeutic agents. Science of Synthesis: Metal-Catalyzed Cyclization Reactions presents the most commonly used and significant metal-catalyzed reactions for modern organic synthesis. The basic principles, the current state of the art, scope, limitations, and mechanism of these reactions are also discussed. Typical examples of target synthesis are provided to help inspire further applications ...
https://www.thieme.de/shop/SoS--Houben-Weyl/Gao-Ma-Science-of-Synthesis-Metal-Catalyzed-Cyclization-9783131998712/p/000000000285610201?categoryCode=1004
Science of Synthesis: Metal-Catalyzed Cyclization Reactions Vol. 1 - Thieme eBooks
Thieme eBooks, Significant advances in metal-catalyzed reactions, especially cyclizations, have dramatically improved the efficiency of organic synthesis over the last three decades. To date these transformations are widely used in the area of synthesis of both natural products and therapeutic agents. Science of Synthesis: Metal-Catalyzed Cyclization Reactions presents the most commonly used and s...
http://ebookstore.thieme.com/product/science-synthesis-metalcatalyzed-cyclization-reactions-vol-1
Tandem reactions in synthesis: the synthesis of carcocyclic compounds using organocobalt complexes in the key cyclisation step ...Tandem reactions in synthesis: the synthesis of carcocyclic compounds using organocobalt complexes in the key cyclisation step ...
This programme of work has focused at developing novel cyclisation reactions in order to furnish a variety of carbocyclic ring systems. The formation of these ring systems have all been based around a key cyclisation step, which has involved a novel intramolecular Nicholas reaction. The use of organcobalt clusters for our work is based around the Nicholas reaction which is the reaction of cobalt complexed propargyl alcohol/ethers with a Lewis acid. This provides an in situ cobalt stabilised carbocation that can be reacted with a range of nucleophiles to provide alkylated products. The first chapter reviews tandem cyclisation reactions and their role in organic chemistry. This is followed by a review of the chemistry of organocobalt clusters and the following chapter reports the results of our investigations. The initial investigation followed existing studies, carried out at Kingston University, in an attempted synthesis of bicycle(4:4:0)decanes. These fused carbocycles represent the AB ring ...
https://eprints.kingston.ac.uk/id/eprint/20641/
Synthesis of Novel Steroid-Peptoid Hybrid Macrocycles by Multiple Multicomponent Macrocyclizations Including Bifunctional...
Synthesis of Novel Steroid-Peptoid Hybrid Macrocycles by Multiple Multicomponent Macrocyclizations Including Bifunctional Building Blocks MiBs. . Biblioteca virtual para leer y descargar libros, documentos, trabajos y tesis universitarias en PDF. Material universiario, documentación y tareas realizadas por universitarios en nuestra biblioteca. Para descargar gratis y para leer online.
http://libros.duhnnae.com/2017/jun5/149751502845-Synthesis-of-Novel-Steroid-Peptoid-Hybrid-Macrocycles-by-Multiple-Multicomponent-Macrocyclizations-Including-Bifunctional-Building-Blocks-MiBs.php
HKU Scholars Hub: Silver catalyzed enyne cyclization reactionsHKU Scholars Hub: Silver catalyzed enyne cyclization reactions
Chen, H. [陳浩國]. (2009). Silver catalyzed enyne cyclization reactions. (Thesis). University of Hong Kong, Pokfulam, Hong Kong SAR. Retrieved from http://dx.doi.org/10.5353/th_ ...
http://hub.hku.hk/handle/10722/57689
Computational Organic Chemistry » Dynamics in 1,3-dipolar cycloadditionsComputational Organic Chemistry » Dynamics in 1,3-dipolar cycloadditions
The importance of dynamics in simple reactions is made yet again in a recent study by Doubleday and Houk in 1,3-dipolar cycloadditions.1 They looked at the reaction of acetylene or ethylene with either nitrous oxide, diazonioazanide, or methanediazonium. The transition state for these 6 reactions all show a concerted reaction. The transition vector has three major components; (a) symmetric formation/cleavage of the two new σ bonds, (b) bending of the dipolar component, or (c) symmetric bending of the hydrogens of ethylene or acetylene.. Classical trajectories were traced from the transition state back to reactant and forward to product. In the approach of the two fragments, the dipole bend vibrates, but then after the TS, it needs to bend quickly to close the 5-member ring. This means that the bending mode effectively has to turn a corner in phase space, and without energy in this mode, the molecules will simple bounce off of each other. Analysis of the reactants indicates significant ...
http://comporgchem.com/blog/?p=154
Intramolecular Anodic Olefin Coupling Reactions: Using Radical Cation Intermediates to Trigger New Umpolung Reactions | The...Intramolecular Anodic Olefin Coupling Reactions: Using Radical Cation Intermediates to Trigger New Umpolung Reactions | The...
Synlett, 2009, 1208-1218. Anodic electrochemistry is a powerful tool for generating radical cation intermediates and initiating new cyclization reactions. Like most electrochemical reactions, the transformations involve umpolungs. In this review, recent studies examining the intramolecular coupling of radical cations derived from enol ethers, vinyl sulfides, and ketene acetals with carbon, oxygen, and nitrogen trapping groups are discussed to highlight their synthetic potential.. ...
https://pages.wustl.edu/moellergroup/articles/8171
Steric acceleration of some pericyclic reactions. - Surrey Research Insight Open AccessSteric acceleration of some pericyclic reactions. - Surrey Research Insight Open Access
Steric effects are important in synthesis. Whilst steric hindrance is well known in hindering reactions, steric effects can also be employed to accelerate reactions, in particular cycloaddition reactions, and even to promote reactions that otherwise do not occur. A survey is included in previous work on steric effects in chemical reactions, principally cycloadditions. This includes a brief discussion on the importance of orientation and solvent effects on Diels-Alder cyclisations and ene reactions. The effect of substituents on the cyclisation of N-allyl furfurylamines has been studied. It was shown that bulky N-protecting groups enhance cyclisation, an effective buttress being the trityl (triphenylmethyl) group. The latter has the added advantage of being particularly easy to remove. A study of some ene reactions has also been carried out and steric acceleration of these processes has also been observed. A novel reaction involving an intermolecular cycloaddition followed by a sterically ...
http://epubs.surrey.ac.uk/843609/
Total Synthesis of (-)-Calyciphylline N by Artem ShvartsbartTotal Synthesis of (-)-Calyciphylline N by Artem Shvartsbart
The dissertation herein describes the first total synthesis of the complex Daphniphyllum alkaloid, (-)-calyciphylline N. This alkaloid was chosen as the target in our synthetic program due its unprecedented structure, the inherent challenges associated with its synthesis, and limited reports of synthetic studies towards members of this family of natural products. An initial unsuccessful approach is discussed, followed by a revised, ultimately successful approach. Highlights of the synthesis include a substrate controlled, intramolecular Diels-Alder reaction to build the bicyclo[2.2.2]octane core and set four contiguous stereocenters, a transannular enolate alkylation to secure ring D, a highly efficient Stille carbonylation/Nazarov cyclization sequence to construct ring E with concomitant activation of a hindered silyl group towards Fleming-Tamao oxidation, and an unprecedented, homogeneous hydrogenation of an exceptionally hindered diene ester to complete the eastern hemisphere, a structural motif that
https://repository.upenn.edu/edissertations/1442/
Constraining Peptide Conformations with the Help of Ring-Closing Metathesis :: MPG.PuReConstraining Peptide Conformations with the Help of Ring-Closing Metathesis :: MPG.PuRe
Autor: Glas, Adrian et al.; Genre: Zeitschriftenartikel; Im Druck veröffentlicht: 2015-01; Keywords: cyclic peptides; hydrophobic cross-links; ring-closing metathesis; protein-protein interactions; Pseudomonas aeruginosa; Titel: Constraining Peptide Conformations with the Help of Ring-Closing Metathesis
http://pubman.mpdl.mpg.de/pubman/faces/viewItemOverviewPage.jsp?itemId=escidoc:2084876
Synthetic studies of cis-3a-aryloctahydroindole derivatives by copper- catalyzed cyclization of N-allyltrichloroacetamides:...
TY - JOUR. T1 - Synthetic studies of cis-3a-aryloctahydroindole derivatives by copper- catalyzed cyclization of N-allyltrichloroacetamides. T2 - Facile construction of benzylic quaternary carbons by carbon-carbon bond-forming reactions. AU - Iwamatsu, Sho Ichi. AU - Matsubara, Kouki. AU - Nagashima, Hideo. PY - 1999/12/24. Y1 - 1999/12/24. N2 - Cyclization of N-(2-aryl-2-cyclohexen-1-yl)trichloroacetamides by a copper catalyst was investigated. It is crucially important for successful cyclization under mild conditions that alkoxycarbonyl groups are introduced to the nitrogen atom of the N-allyltrichloroacetamides as well as that CuCl- (bipyridine) is used as the catalyst. Three compounds, N-(2-phenyl-2- cyclohexen-1-yl)-, N-[2-(3,4-dimethoxyphenyl)-2-cyclohexen-l-yl]-, and N-[2- (3,4-methylenedioxyphenyl)-2-cyclohexen-1-yl]trichloroacetamides, where the Cbz or MeO2C- group was attached to the nitrogen atom, were instantly converted to the corresponding trichlorinated cis-3a-aryloctahydroindol-2- ...
https://kyushu-u.pure.elsevier.com/ja/publications/synthetic-studies-of-cis-3a-aryloctahydroindole-derivatives-by-co
Lecture 19 - Aromatic Transition States: Cycloaddition and Electrocyclic ReactionsLecture 19 - Aromatic Transition States: Cycloaddition and Electrocyclic Reactions
This video was recorded at CHEM 125b: Freshman Organic Chemistry II. Cyclic conjugation that arises when p-orbitals touch one another can be as important for transition states as aromaticity is for stable molecules. It is the controlling factor in pericyclic reactions. Regiochemistry, stereochemistry, and kinetics show that two new sigma bonds are being formed simultaneously, if not symmetrically, in the 6-electron Diels-Alder cycloaddition. Although thermal dimerization of thymine residues in DNA is forbidden, photochemistry allows the 4-electron cycloaddition. Electrocyclic ring opening or closing chooses a conrotatory Möbius pathway, or a disrotatory Hückel pathway, according to the number of electron pairs involved and whether light is used in the process. Dewar benzene provides an example of a very unstable molecule that can be formed photochemically and then persists because of unfavorable orbital overlap in the transition state for ring opening ...
http://www.merlot.org/merlot/viewMaterial.htm?id=986262
New PDF release: Chemistry of Heterocyclic Compounds: The Purines, Supplement - Rigid Flex PCB LibraryNew PDF release: Chemistry of Heterocyclic Compounds: The Purines, Supplement - Rigid Flex PCB Library
Extra info for Chemistry of Heterocyclic Compounds: The Purines, Supplement 1, Volume 54. Sample text. C. D. E. F. G. 2. 3. 4. 5. . . . . . . . . . 22 Cyclization with Formic Acid (H33) . . . . . . . . . . . . . . Cyclization with Dithioformic Acid (H38) . . . . . . . . . . . . Cyclization with Other Carboxylic Acids (H41) . . . . . . . . . . . Cyclization with Acid Anhydrides (H44) . . . . . . . . . . . . Cyclization with Acid Chlorides (H47) . . . . . . . . . . . . . Cyclization with Orthoesters and Diethoxymethyl Acetate (H50) . It is postulated that 63 arises from attack by a second molecule of thiourea on the 5-thioureidopyrimidine initially formed, displacing the 4-amino group; the product (64)then cyclizes with elimination of g ~ a n i d i n e . ~ ~ 59 60 61 0. Cyclizationwith Cyanates, lsocyanates and Derivatives (H61) Under reflux conditions methyl isocyanate and 4,5-diamino-l,2,3,6-tetrahydro-2-oxo-6-thioxopyrimidinein pyridine (3 h) give the corresponding 5-(N- * Removal of an ...
http://www.rctpcb.com/pdf/chemistry-of-heterocyclic-compounds-the-purines-supplement-1-volume-54
中国科学院上海有机化学研究所机构知识库(SIOC OpenIR): Asymmetric total synthesis of (-)-Alkaloid 223A and its 6-epimer
The enantiopure γ-amino alcohols 7 and 18 are prepared by using the diastereoselective michael addition of lithium N-benzyl ( R )-α-methylbenzylamide to α,β-unsaturated esters as a key step. The michael addition of 7 or 18 to an alkynone 8 followed by an intramolecular cyclization afford the cyclic enzmine 10 or 20. which are subjected to the diastereoselective hydrogenation, and the subsequent transformations provide 6-epi-alkaloid 223A and alkaloid 223A, respectively ...
http://ir.sioc.ac.cn/handle/331003/15449
Photochemical Electrocyclic Ring Closure and Elimination Reactions of by Himali Devika JayasekaraPhotochemical Electrocyclic Ring Closure and Elimination Reactions of by Himali Devika Jayasekara
Photochemical cleavage reactions have found a widespread used in biological applications that require the photorelease of biologically active molecules such as proteins, peptides, neurotransmitters, and nucleotide phosphates. This research focuses on the design of photoremovable protecting groups which can be utilized to release these biomolecules by photolysis. These biomolecules are attached to the photoremovable protecting group at the sites of functional groups that are present within these substrates. Such functional groups are carboxylates, phosphates, thiolates, or phenolates, which upon exposure to light, are released as anions of varying basicities. The photochemical reaction involved is an electrocyclic ring closure between aromatic groups that are bridged by a carboxamide linkage. The key intermediate produced by electrocyclization is thought to have zwitterionic character. This zwitterionic intermediate is believed to expel the leaving group as the anion. One of the aromatic groups attached
http://epublications.marquette.edu/dissertations_mu/629/
Gold-Catalyzed Synthesis of 5 and 6-Membered Rings for the Construction of Molecular DiversityGold-Catalyzed Synthesis of 5 and 6-Membered Rings for the Construction of Molecular Diversity
The research developed in this Doctoral Thesis comprises from the preparation of polyaromatic compounds to the synthesis of natural product derivatives, highlighting the proficiency of homogeneous gold catalysis for the construction of molecular diversity.. A novel approach for the synthesis of a new trindane-based crushed fullerene C60 was developed by a threefold palladium-catalyzed cross-coupling of four suitably functionalized C15 trindene fragments. The trindane C15 skeleton of the central motif was constructed through a triple gold(I)-catalyzed oxidative cyclization.. The scope of the intramolecular gold(I)-catalyzed formal [2+2+2] cycloaddition reaction was extended to O-protected homopropargylic and allylic oxo-1,5-enynes. Under the optimized reaction conditions, the cyclization of (Z)- and (E)- isomers takes place with moderate to excellent yield and increased selectivity in most of the cases, providing access to octahydro-1H-indenes skeletons.. The mastery of gold(I) complexes for the ...
http://www.iciq.org/agenda/gold-catalyzed-synthesis-of-5-and-6-membered-rings-for-the-construction-of-molecular-diversity/
Solid-Phase Iminium Cyclization Reactions for the Synthesis of Natural Product-Like Diketopiperazines</em>...Solid-Phase Iminium Cyclization Reactions for the Synthesis of Natural Product-Like Diketopiperazines</em>...
TY - BOOK. T1 - Solid-Phase Iminium Cyclization Reactions for the Synthesis of Natural Product-Like Diketopiperazines. AU - Petersen, Rico. PY - 2012. Y1 - 2012. N2 - The development of methodology for the solid-phase synthesis of fused 2,5-diketopiperazines with an emphasis on structural and stereochemical control, has been accomplished through two different approaches. The first approach was based on a highly trans-stereoselective (82% d.e.) intramolecular N-acyliminium ion cyclization of N-terminal peptide glyoxylamides, assembling the complete molecular skeleton in a single step. The second approach aimed for the use of a cis-stereoselective intermolecular Pictet-Spengler cyclization to construct the first part of the ringsystem and a subsequent diketopiperazine formation to close the second ring. In the first approach, four different methods for accessing the glyoxylamide cyclization precursor were developed; oxidative cleavage of a serine, dihydroxylation/oxidative cleavage of an ...
https://orbit.dtu.dk/en/publications/solid-phase-iminium-cyclization-reactions-for-the-synthesis-of-na
Carbene and silicon routes as methods for the generation and dipolar cycloaddition reactions of methyl nitrile ylide<...
TY - JOUR. T1 - Carbene and silicon routes as methods for the generation and dipolar cycloaddition reactions of methyl nitrile ylide. AU - Padwa, Albert. AU - Gasdaska, John R.. AU - Tomas, Miguel. AU - Turro, Nicholas J.. AU - Cha, Yuan. AU - Gould, Ian. PY - 1986. Y1 - 1986. N2 - Methyl nitrile ylide was generated by both a photochemical and desilylation route and has been characterized by UV spectroscopy and by its kinetic and cycloaddition behavior. The dipole is formed by the addition of singlet methylene to acetonitrile and shows a strong transient absorption at 280 nm which is quenched by the addition of standard dipolarophiles. The relative rates of formation of 1,3-dipolar adducts and the relative rates of quenching of the transient absorption are in excellent agreement. Generation of the dipole from a silylthioimidate followed by dipolar cycloaddition also gave rise to related cycloadducts. The ratio of cycloadducts obtained from an unsymmetrically substituted dipolarophile was found ...
https://asu.pure.elsevier.com/en/publications/carbene-and-silicon-routes-as-methods-for-the-generation-and-dipo
A Planning Strategy for Diversity-Oriented Synthesis<...A Planning Strategy for Diversity-Oriented Synthesis<...
TY - JOUR. T1 - A Planning Strategy for Diversity-Oriented Synthesis. AU - Burke, Martin D.. AU - Schreiber, Stuart L.. PY - 2004/12/22. Y1 - 2004/12/22. N2 - In contrast to target-oriented synthesis (TOS) and medicinal or combinatorial chemistry, which aim to access precise or dense regions of chemistry space, diversity-oriented synthesis (DOS) populates chemical space broadly with small-molecules having diverse structures. The goals of DOS include the development of pathways leading to the efficient (three- to five-step) synthesis of collections of small molecules having skeletal and stereochemical diversity with defined coordinates in chemical space. Ideally, these pathways also yield compounds having the potential to attach appendages site- and stereoselectively to a variety of attachment sites during a post-screening, maturation stage. The diverse skeletons and stereochemistries ensure that the appendages can be positioned in multiple orientations about the surface of the molecules. TOS as ...
https://experts.illinois.edu/en/publications/a-planning-strategy-for-diversity-oriented-synthesis
Endo-Selective Enyne Ring-Closing Metathesis Promoted by Stereogenic-at-Mo Monoalkoxide and Monoaryloxide Complexes. Efficient...Endo-Selective Enyne Ring-Closing Metathesis Promoted by Stereogenic-at-Mo Monoalkoxide and Monoaryloxide Complexes. Efficient...
Stereogenic-at-Mo monoalkoxide and monoaryloxide complexes promote enyne ring-closing metathesis (RCM) reactions, affording the corresponding endo products with high selectivity (typically ,98:,2 endo:exo). All catalysts can be prepared and used in situ. Five-, six-, and seven-membered rings are obtained through reactions with enyne substrates that bear all-carbon tethers as well as those that contain heteroatom substituents. The newly developed catalytic protocols complement the related exo-selective Ru-catalyzed processes. In cases where Ru-based complexes deliver exo and endo products nondiscriminately, such as when tetrasubstituted cyclic alkenes are generated, Mo-catalyzed reactions afford the endo product exclusively. The efficiency of synthesis of N- and O-containing endo diene heterocycles can be improved significantly through structural modification of Mo catalysts. The modularity of Mo-based monopyrrolides is thus exploited in the identification of the most effective catalyst variants. ...
https://dspace.mit.edu/handle/1721.1/82540
Multicomponent reactions of phosphines, diynedioates, and aryl aldehydes generated furans appending reactive phosphorus ylides...Multicomponent reactions of phosphines, diynedioates, and aryl aldehydes generated furans appending reactive phosphorus ylides...
TY - JOUR. T1 - Multicomponent reactions of phosphines, diynedioates, and aryl aldehydes generated furans appending reactive phosphorus ylides through cumulated trienoates as key intermediates. T2 - A phosphine α-addition-δ-evolvement of an anion pathway. AU - Deng, Jie Cheng. AU - Chuang, Shih-Ching. PY - 2014/11/7. Y1 - 2014/11/7. N2 - Multicomponent reactions of phosphines, diynedioates, and aryl aldehydes have been demonstrated, providing trisubstituted furans appending reactive phosphorus ylides, through cumulated trienoates as key intermediates. The proposed trienoate intermediates, 1,5-dipolar species formed via nucleophilic α-attack of phosphines toward diynedioates (α-addition-δ-evolvement of an anion, abbreviated αAδE), undergo addition to aryl aldehydes followed by 5-endo-dig cyclization, proton transfer, and resonance to give trisubstituted furans. Furthermore, the phosphorus ylides are oxidized to α-keto ester furans and utilized as Wittig reagents.. AB - Multicomponent ...
https://scholar.nctu.edu.tw/en/publications/multicomponent-reactions-of-phosphines-diynedioates-and-aryl-alde
Organocatalyzed Transient Dienamine-Mediated Diels-Alder Reactions between α,β-Unsaturated Ketones and Alkenes |...Organocatalyzed Transient Dienamine-Mediated Diels-Alder Reactions between α,β-Unsaturated Ketones and Alkenes |...
Title:Organocatalyzed Transient Dienamine-Mediated Diels-Alder Reactions between α,β-Unsaturated Ketones and Alkenes. VOLUME: 15 ISSUE: 5. Author(s):Iosune Arrastia, Ana Arrieta and Fernando P. Cossio*. Affiliation:Donostia International Physics Center, San Sebastian/Donostia, Donostia International Physics Center, San Sebastian/Donostia, Donostia International Physics Center, San Sebastian/Donostia. Keywords:Organocatalysis, diels-Alder reactions, cycloadditions, michael additions, pericyclic reactions, stepwise mechanisms.. Abstract:Organocatalyzed (4+2) cycloadditions (Diels-Alder reactions) are reviewed in this manuscript. Among the different catalytic alternatives, reactions involving α,β-unsaturated ketones and alkenes are considered. In these processes, substituted cyclohexanones are obtained via HOMO activation generated by amine organocatalysis that generate transient dienamine species. Both concerted and stepwise mechanisms are described. In most cases, excellent regio-, ...
http://www.eurekaselect.com/158779/article
Enantioselective total synthesis of (-)-zampanolide, a potent microtubule-stabilizing agent. - Semantic ScholarEnantioselective total synthesis of (-)-zampanolide, a potent microtubule-stabilizing agent. - Semantic Scholar
An enantioselective total synthesis of zampanolide has been accomplished using a novel DDQ/Brønsted acid promoted cyclization as the key reaction. The synthesis features cross-metathesis to construct the trisubstituted olefin and a ring-closing metathesis to form the macrolactone. The final N-acyl aminal formation was stereoselectively accomplished by an organocatalytic reaction.
https://www.semanticscholar.org/paper/Enantioselective-total-synthesis-of-zampanolide-a-Ghosh-Cheng/733b7ffc2e5d0e19aba36cf087bc42fa925c02ff
Gold( i )-catalyzed 6-endo-dig azide-yne cyclization: efficient access to 2H-1,3-oxazines - Ecole polytechnique
Denitrogenative 6-endo-dig azide-yne cyclization of α-propargyloxy-β-haloalkylazides was enabled by gold catalysis, thus providing 2H-1,3-oxazines. This rare cyclization mode in gold-catalyzed reactions of azide-yne substrates was demonstrated to be facilitated and controlled by electronic and resonance effects of the alkyne substituents. Molecular transformations of the as-prepared 2H-1,3-oxazines were also investigated.
https://hal-polytechnique.archives-ouvertes.fr/hal-02091713
Mouse Glutaminyl-peptide cyclotransferase-like protein (QPCTL) ELISA Kit - Abbkine - Antibodies, proteins, biochemicals, assay...Mouse Glutaminyl-peptide cyclotransferase-like protein (QPCTL) ELISA Kit - Abbkine - Antibodies, proteins, biochemicals, assay...
This Mouse Glutaminyl-peptide cyclotransferase-like protein (QPCTL) ELISA Kit employs a two-site sandwich ELISA to quantitate QPCTL.,QPCTL; FLJ20084; glutaminyl cyclase-like,QPCTL, also termed Iso-glutaminyl cyclase catalyzes the intramolecular cyclization of N-terminal glutamine residues into pyroglutamic acid with liberation of ammonia and the intramolecular cyclization of N-terminal glutamate residues into pyroglutamic acid with liberation of water. Glutaminyl cyclase (QPCT) catalyzes the intramolecular cyclization of N-terminal glutamine residues into pyroglutamic acid liberating ammonia. In contrast, the physiological function of the plant QC is less clear. In case of the enzyme from C. papaya, a role in the plant defence against pathogenic microorganisms was suggested. Putative QCs from other plants were identified by sequence comparisons. The physiological function of these enzymes, however, is still ambiguous.
http://www.abbkine.com/product/mouse-glutaminyl-peptide-cyclotransferase-like-protein-qpctl-elisa-kit-kte70585/
Computational Organic Chemistry » C1-C5 cyclization of enediynes - Alternative to the Bergman reactionComputational Organic Chemistry » C1-C5 cyclization of enediynes - Alternative to the Bergman reaction
Pascal begins with the assumption that terminal aryl substitution on the enediyne will both (a) inhibit the C1-C6 cyclization due to steric interactions and (b) the C1-C5 cyclization should be enhanced due to stabilization of the radical by the neighboring aryl group. He computed the activation energies of a series of analogues, some of which are listed in Table 1. The transition state structures are shown in Figure 1 for 1b and 1c. Phenyl substitution does accomplish both suggestions: the activation barrier for the Bergman cyclization increases by 4 kcal mol-1, while the barrier for the C1-C5 cyclization is lowered by nearly 6 kcal mol-1. Further substitution of the phenyl ring by either chloro or methyl groups brings the barriers into near degeneracy.. Table 1. RBLYP/6-31G(d) Activation energies (kcal mol-1) ...
http://comporgchem.com/blog/?p=98
Synthesis, spectroscopy, and applications of small nitrile oxides<...
TY - JOUR. T1 - Synthesis, spectroscopy, and applications of small nitrile oxides. AU - Pasinszki, Tibor. AU - Westwood, Nicholas P.C.. PY - 2011/6. Y1 - 2011/6. N2 - Small covalent nitrile oxides are important transient species in organic synthesis and widely used especially for dipolar cycloaddition reactions. Due to their instability, their isolation and characterization are challenging. This review focuses on the generation, spectroscopy, structural properties, and synthetic application of small nitrile oxides, XCNO, where the X substituent group is smaller than five atoms, viz. X= hydrogen, halogen, pseudohalogen, alkyl, vinyl, ethynyl, or nitro.. AB - Small covalent nitrile oxides are important transient species in organic synthesis and widely used especially for dipolar cycloaddition reactions. Due to their instability, their isolation and characterization are challenging. This review focuses on the generation, spectroscopy, structural properties, and synthetic application of small ...
https://hungary.pure.elsevier.com/en/publications/synthesis-spectroscopy-and-applications-of-small-nitrile-oxides
Quantum Chemistry Study on the Cycloaddition Reaction of Dibromocarbene and Formaldehyde
Abstract: The mechanisms of cycloaddition reactions of singlet dibromocarbene and formaldehyde have been studied using density functional theory of quantum chemistry method at B3LYP/6-31G* level. The geometrical parameters, harmonic vibrational frequencies and energies of stationary points on the potential energy surface are calculated. The structures of the stationary points were optimized, and the intermediates and transition states were detected by the frequency analysis. The calculation results show that the reaction has four possible reaction pathways. According to the data of the activation energy, we predict that path c would be the major reactive channel of the cycloaddition reactions of singlet dibromocarbene with formaldehyde, which proceeds in three steps and the energy barrier for the key step is 13.7 kJ·mol－1. Key words: Density functional theory, Cycloaddition reaction, Transition states, Dibromocabene, B3LYP level ...
http://www.whxb.pku.edu.cn/EN/abstract/abstract26293.shtml
Diversity-oriented synthesis yields a new drug lead for treatm...Diversity-oriented synthesis yields a new drug lead for treatm...
Diversity-oriented synthesis yields a new drug lead for treatment of chagas disease.: A phenotypic high-throughput screen using ∼100,000 compounds prepared usin
https://www.mysciencework.com/publication/show/diversity-oriented-synthesis-yields-new-drug-lead-treatment-chagas-disease-82c5ffe1
Trifluoromethanesulfonic acid-catalyzed tandem semi-pinacol rearrangement/alkyne-aldehyde metathesis reaction of...Trifluoromethanesulfonic acid-catalyzed tandem semi-pinacol rearrangement/alkyne-aldehyde metathesis reaction of...
TY - JOUR. T1 - Trifluoromethanesulfonic acid-catalyzed tandem semi-pinacol rearrangement/alkyne-aldehyde metathesis reaction of arylpropagylsulfonamide- tethered 2,3-epoxycyclohexan-1-ols to spiropiperidines. AU - Lin, Ming Nan. AU - Wu, Shih Hui. AU - Yeh, Ming-Chang P.. PY - 2011/12/1. Y1 - 2011/12/1. N2 - A simple and efficient trifluoromethanesulfonic acid-catalyzed cycloisomerization of arylpropagylsulfonamide-tethered 2,3-epoxycyclohexan-1-ols is described. The cyclization proceeds via tandem semi-pinacol rearrangement/alkyne-aldehyde metathesis to afford spiropiperidines under mild reaction conditions.. AB - A simple and efficient trifluoromethanesulfonic acid-catalyzed cycloisomerization of arylpropagylsulfonamide-tethered 2,3-epoxycyclohexan-1-ols is described. The cyclization proceeds via tandem semi-pinacol rearrangement/alkyne-aldehyde metathesis to afford spiropiperidines under mild reaction conditions.. KW - alkyne/aldehyde metathesis. KW - semi-pinacol rearrangement. KW - ...
https://scholar.lib.ntnu.edu.tw/en/publications/trifluoromethanesulfonic-acid-catalyzed-tandem-semi-pinacol-rearr
Pharmaceuticals | Free Full-Text | Synthesis and Neuroprotective Action of Optically Pure Neoechinulin A and Its AnalogsPharmaceuticals | Free Full-Text | Synthesis and Neuroprotective Action of Optically Pure Neoechinulin A and Its Analogs
We developed an efficient, stereoselective synthetic method for the diketopiperazine moiety of neoechinulin A and its derivatives. The intramolecular cyclization at 80 ºC proceeded with minimal racemization of the stereogenic center at C-12 on neoechinulin A, even though the cyclization at 110 ºC caused partial racemization. In contrast with these results, the cyclization on diketopiperazine of 8,9-dihydroneoechinulin A derivatives did not cause epimerization of the stereogenic centers, even at 110 °C. We examined the structure-activity relationships for the cytoprotective activity against cytotoxicity induced by 3-morpholinosydnonimine (SIN-1) in nerve growth factor (NGF)-differentiated PC12 cells. The C-8/C-9 double bond, but not the stereogenic center derived from alanine, was found to play a key role in the cytoprotective activity.
http://www.mdpi.com/1424-8247/3/4/1063
Regioselective synthesis of thiophene fused sultam derivatives via iodocyclization approach and their application towards...Regioselective synthesis of thiophene fused sultam derivatives via iodocyclization approach and their application towards...
TY - JOUR. T1 - Regioselective synthesis of thiophene fused sultam derivatives via iodocyclization approach and their application towards triazole linker. AU - Barange, Deepak Kumar. AU - Kavala, Veerababurao. AU - Kuo, Chun Wei. AU - Wang, Cheng Chuan. AU - Rajawinslin, R. R.. AU - Donala, Janreddy. AU - Yao, Ching Fa. PY - 2014/10/14. Y1 - 2014/10/14. N2 - An efficient regioselective synthesis of 4-iodo-2,3-disubstituted-2H-thieno[3,2-e][1,2]thiazine-1,1-dioxide derivatives via iodocyclization approach using iodine under mild reaction condition described herein. This coupling-iodocyclization strategy tolerated a variety of functional groups such as alkyl, cycloalkyl, phenyl producing the six-membered heterocyclic ring selectively. The resulting 4-iodo-2,3-disubstituted-2H-thieno[3,2-e][1,2]thiazine-1,1-dioxide was coupled with a variety of boronic acids (Suzuki coupling) and activated alkenes (Heck coupling). The iodo group was utilized for Sonogashira coupling followed by efficient ...
https://scholar.lib.ntnu.edu.tw/en/publications/regioselective-synthesis-of-thiophene-fused-sultam-derivatives-vi
Nicotinamide 2-fluoroadenine dinucleotide unmasks the NAD+ glycohydrolase activity of Aplysia californica adenosine 5...Nicotinamide 2-fluoroadenine dinucleotide unmasks the NAD+ glycohydrolase activity of Aplysia californica adenosine 5...
ADP-ribosyl cyclases catalyze the transformation of nicotinamide adenine dinucleotide (NAD+) into the calcium-mobilizing nucleotide second messenger cyclic adenosine diphosphoribose (cADP-ribose) by adenine N1-cyclization onto the C-1 position of NAD+. The invertebrate Aplysia californica ADP-ribosyl cyclase is unusual among this family of enzymes by acting exclusively as a cyclase, whereas the other members, such as CD38 and CD157, also act as NAD+ glycohydrolases, following a partitioning kinetic mechanism. To explore the intramolecular cyclization reaction, the novel nicotinamide 2-fluoroadenine dinucleotide (2-fluoro-NAD+) was designed as a sterically very close analogue to the natural substrate NAD+, with only an electronic perturbation at the critical N1 position of the adenine base designed to impede the cyclization reaction. 2-Fluoro-NAD+ was synthesized in high yield via Lewis acid catalyzed activation of the phosphoromorpholidate derivative of 2-fluoroadenosine 5-monophosphate and coupling
https://pharm.ox.ac.uk/publications/677820
Hypervalent iodine in synthesis 93. A facile synthesis of 2-substituted imidazo[1,2-a]pyrimidines by cyclocondensation of...Hypervalent iodine in synthesis 93. A facile synthesis of 2-substituted imidazo[1,2-a]pyrimidines by cyclocondensation of...
TY - JOUR. T1 - Hypervalent iodine in synthesis 93. A facile synthesis of 2-substituted imidazo[1,2-a]pyrimidines by cyclocondensation of alkynyl(phenyl)iodonium salts and 2-aminopyrimidine. AU - Zhi, Liu. AU - Chen, Zhen-Chu. AU - Zheng, Qinguo. PY - 2003/9. Y1 - 2003/9. N2 - Simple stirring of a mixture of the alkynyl(phenyl)iodonium salts 1 with 2-aminopyrimidine 2 in chloroform under reflux for two hours in the presence of K2CO3 gave, after workup, the 2-substituted imidazo[1,2-]pyrimidines 3 in moderate to good yields. A possible mechanism for the formation of 3 involves the intramolecular cyclization of the intermediate alkylidenecarbene 6.. AB - Simple stirring of a mixture of the alkynyl(phenyl)iodonium salts 1 with 2-aminopyrimidine 2 in chloroform under reflux for two hours in the presence of K2CO3 gave, after workup, the 2-substituted imidazo[1,2-]pyrimidines 3 in moderate to good yields. A possible mechanism for the formation of 3 involves the intramolecular cyclization of the ...
https://research.aston.ac.uk/en/publications/hypervalent-iodine-in-synthesis-93-a-facile-synthesis-of-2-substi
Oxidative Cyclizations in a Nonpolar Solvent Using Molecular Oxygen and Studies on the Stereochemistry of Oxypalladation -...Oxidative Cyclizations in a Nonpolar Solvent Using Molecular Oxygen and Studies on the Stereochemistry of Oxypalladation -...
Oxidative cyclizations of a variety of heteroatom nucleophiles onto unactivated olefins are catalyzed by palladium(II) and pyridine in the presence of molecular oxygen as the sole stoichiometric oxidant in a nonpolar solvent (toluene). Reactivity studies of a number of N-ligated palladium complexes show that chelating ligands slow the reaction. Nearly identical conditions are applicable to five different types of nucleophiles: phenols, primary alcohols, carboxylic acids, a vinylogous acid, and amides. Electron-rich phenols are excellent substrates, and multiple olefin substitution patterns are tolerated. Primary alcohols undergo oxidative cyclization without significant oxidation to the aldehyde, a fact that illustrates the range of reactivity available from various Pd(II) salts under differing conditions. Alcohols can form both fused and spirocyclic ring systems, depending on the position of the olefin relative to the tethered alcohol; the same is true of the acid derivatives. The racemic ...
https://authors.library.caltech.edu/74395/
Generation of Diverse Molecular Complexity from Simple Hydrocarbons by Anobick SarGeneration of Diverse Molecular Complexity from Simple Hydrocarbons by Anobick Sar
In an effort to make diverse molecular complexity from simple hydrocarbons, tricarbonyl(cyclohexadienyl)iron(+1) cation was prepared in two steps from 1, 3-cycloxehadiene. Reactivity of the symmetric iron cation with heteroatom nucleophiles and stabilized carbon nucleophiles was studied. Nucleophilic attack of potassium phthalimide at the dienyl terminus of the cation followed by oxidative decomplexation with Ce4+ provided the ligand N-(2,4-cyclohexadiene-1-yl)phthalimide. A series of stereochemically diverse polyhydroxyl aminocyclohexane aminocyclitols derivatives and a number of racemic and optically active hydroxy-and polyhydroxy 1,3-diaminocyclohexane derivatives have been synthesized from N-(2,4-cyclohexadiene-1-yl)phthalimide. The relative stereochemistries of the compounds ware assigned on the basis of the 1H NMR data as well as X-ray single crystal diffraction analysis. In a similar attempt tricabonyl(η5-6-styrylcyclohepta-2,4-diene-1-yl)iron(+1) cation was synthesized in three steps from 1,
http://epublications.marquette.edu/dissertations_mu/140/
Selective [3+2] Cycloadditions of β-Amino-α,β-unsaturated Pentacarbonylcarbenechromium Complexes to Alkynes-A New Approach to...
TY - JOUR. T1 - Selective [3+2] Cycloadditions of β-Amino-α,β-unsaturated Pentacarbonylcarbenechromium Complexes to Alkynes-A New Approach to Functionally Substituted Cyclopentadienes. AU - Flynn, Bernard L.. AU - Funke, Frank J.. AU - Silveira, Claudio C.. AU - Meijere, Armin De. PY - 1995/10/1. Y1 - 1995/10/1. N2 - (3-Amino-1-ethoxyalkenylidene)pentacarbonylchromium complexes 2 react with alkynes in pyridine or acetonitrile to give highly substituted 5-amino-3-ethoxycyclopentadienes 3 as formal [3+2]-cycloadducts selectively in high yields rather than the usually favored [2+2+1]-cycloadducts, 5-methylene-2-cyclopenten-1-ones.. AB - (3-Amino-1-ethoxyalkenylidene)pentacarbonylchromium complexes 2 react with alkynes in pyridine or acetonitrile to give highly substituted 5-amino-3-ethoxycyclopentadienes 3 as formal [3+2]-cycloadducts selectively in high yields rather than the usually favored [2+2+1]-cycloadducts, 5-methylene-2-cyclopenten-1-ones.. KW - 1-Metalla-1,3,5-hexatrienes. KW - ...
https://research.monash.edu/en/publications/selective-32-cycloadditions-of-%CE%B2-amino-%CE%B1%CE%B2-unsaturated-pentacarbon
Computational Chemistry Highlights: Quantifying Possible Routes for SpnF-Catalyzed Formal Diels-Alder CycloadditionComputational Chemistry Highlights: Quantifying Possible Routes for SpnF-Catalyzed Formal Diels-Alder Cycloaddition
Medvedev, et al. have examined the cyclization step in the formation of Spinosyn A, which is catalyzed by the putative Diels-Alderase enzyme SpnF.1 This work follows on the computational study done by Houk, Singleton and co-workers,2 which I have discussed in this post (Dynamics in a reaction where a [6+4] and [4+2] cycloadditons compete). In fact, I recommend that you read the previous post before continuing on with this one. In summary, Houk, et al. found that a single transition state connects reactant 1 to both 2 and 3. The experimental product with the enzyme SpnF is 3. In the absence of enzyme, Houk, et al. suggest that reactions will cross the bispericyclic transition state TS-BPC (TS1 in the previous post) leading primarily to 2, which then undergoes a Cope rearrangement to get to product 3. Some molecules will follow pathways that go directly to 3 ...
http://www.compchemhighlights.org/2017/04/quantifying-possible-routes-for-spnf.html
Dienes - product, double, conjugated, bonds, dienophile, reaction and products
Conjugated dienes exist in two conformation called s-cis and s-trans. They interconvert freely in open-chain dienes, by single bond rotation, but may not be able to in some cyclic cases. For the Diels-Alder reaction to occur, the s-cis conformation needs to be present, so the two carbons of the alkene can connect to both of them simultaneously. The reaction occurs in a single step during which the pi electrons reorganize through a cyclic transition state, forming two new single bonds to the ends of the diene. It is one of the reactions among a larger class called cycloaddition, and cycloaddition falls into a broader class called pericyclic - reactions which involve no intermediate, only a cyclic reorganization of electrons. Good yields of Diels-Alder products are obtained when the dienophile (alkene) has electron-withdrawing groups, often carbonyl groups, ester groups or cyano groups. Maleic anhydride is often used as a dienophile. ...
http://gluedideas.com/Professor-Veronica-Curtis-Palmer-Organic-Chemistry/Dienes.html
Cloning and characterization of triterpene synthasesCloning and characterization of triterpene synthases
Oxidosqualene cyclases are a group of enzymes that cyclize 2,3-oxidosqualene to any of over 80 triterpene skeletons. Sequence correlation suggests these enzymes share a common overall structure and subtle changes in active site residues are responsible for differences in the structure of the cyclization product. Further characterization of conserved residues has lead to a better understanding of the mechanisms through which regio- and stereo-selective cyclization occurs. This work has resulted in the cloning of three new oxidosqualene cyclases. By cloning triterpene synthases from far-diverged organisms, new sequence data has been added for correlation and has provided new information regarding evolution of the enzymes from a common ancestor. Arabidopsis thaliana lupeol synthase was cloned and the full-length cDNA expressed in yeast. Degenerate PCR primers designed from regions of highly conserved sequence were used to clone cycloartenol synthase and a presently uncharacterized triterpene ...
https://scholarship.rice.edu/handle/1911/19506
Controlled Degradation of Poly(ester amide)s via Cyclization of Pendan by Jose Samuel MejiaControlled Degradation of Poly(ester amide)s via Cyclization of Pendan by Jose Samuel Mejia
Polyesters have been used for many biomedical applications ranging from sutures to drug delivery vehicles. However, their bulk degradation results in an accumulation of acidic byproducts, which is detrimental to the human body. In order to circumvent this problem, as well as to impart new properties and functions to polymers for biomedical applications, poly(ester amide)s (PEAs) have been proposed as a different class of biodegradable polymers. However, up to date, there exists no way to stimulate the degradation of these polymers. The Gillies research group has previously incorporated self-immolative spacers into polymers and has been able to stimulate their degradation by adding the appropriate trigger. The objective of this thesis was to incorporate amino acids capable of 1,5-cyclization into the PEA backbone such that upon activation of the functional moiety, a 1,5-cyclization was induced, leading to degradation of the PEA backbone. PEAs containing L-2,4-diaminobutyric acid and DL-homocysteine were
https://ir.lib.uwo.ca/etd/954/
Desiging of the Style sheetDesiging of the Style sheet
A carbohydrate-based synthesis of both cis- and trans-fused bicylic ethers has been achieved by radical cyclization of epoxides using a transition-metal radical source. Thus, 6-exo radical cyclizations of the carbohydrate derivatives using [bis(cyclopentadienyl) titanium(III)]chloride (Cp2TiCl) as the radical source has resulted in corresponding cis- and trans-fused bicyclic ethers. While the trans-fused compound has allowed stereoselective radical cyclization, the cis-fused has ended up only in a mixture of isomers. The functionalities present in the bicyclic compounds are potential intermediates as multifunctional conformationally rigid scaffolds ...
http://www.niscair.res.in/ScienceCommunication/ResearchJournals/rejour/IJCB/ijcb2k7/ijcb_oct07.asp
Todd:Catalytic, Asymmetric Pictet-Spengler Reaction - OpenWetWareTodd:Catalytic, Asymmetric Pictet-Spengler Reaction - OpenWetWare
Enantioselective approaches, where the stereocontrol of the cyclization is not governed by a stereocentre already in the cyclization precursor, have received much less attention than the diastereoselective, racemic or achiral version of the PS reaction. It was shown in 1996 that the PS reaction could be effected with superstoichiometric Lewis acid - in this case the cyclization of the (Z)-nitrone derived from Nb-hydroxytryptamine using diisopinocampheylchloroborane (Ipc2BCl) to give the corresponding tetrahydro-β-carboline products (Scheme Nakagawa 1998).(10.1016/0957-4166(96)00134-6 and 10.1021/jo980810h) The racemic cyclization could be effected with Bronsted acid and a number of achiral Lewis acids, but it was found that Ipc2BCl gave high yields and ee with reduced temperatures. Lowering the quantity of Ipc2BCl to 0.5 eq. caused a significant reduction of yield, while attempts to alter the Lewis acidity by substitution of the chloride (with e.g. fluoride or triflate) did not improve yield or ...
https://openwetware.org/wiki/?title=Todd:Catalytic%25252C_Asymmetric_Pictet-Spengler_Reaction&oldid=607996
Difference between revisions of Todd:Catalytic, Asymmetric Pictet-Spengler Reaction - OpenWetWareDifference between revisions of Todd:Catalytic, Asymmetric Pictet-Spengler Reaction - OpenWetWare
Enantioselective approaches, where the stereocontrol of the cyclization is not governed by a stereocentre already in the cyclization precursor, have received much less attention than the diastereoselective, racemic or achiral version of the PS reaction. It was shown in 1996 that the PS reaction could be effected with superstoichiometric Lewis acid - in this case the cyclization of the (Z)-nitrone derived from Nb-hydroxytryptamine using diisopinocampheylchloroborane (Ipc2BCl) to give the corresponding tetrahydro-β-carboline products (Scheme Nakagawa 1998).(10.1016/0957-4166(96)00134-6 and 10.1021/jo980810h and 10.3987/REV-98-SR1) The racemic cyclization could be effected with Bronsted acid and a number of achiral Lewis acids, but it was found that Ipc2BCl gave high yields and ee with reduced temperatures. Lowering the quantity of Ipc2BCl to 0.5 eq. caused a significant reduction of yield, while attempts to alter the Lewis acidity by substitution of the chloride (with e.g. fluoride or triflate) ...
https://openwetware.org/wiki/?title=Todd:Catalytic%25252C_Asymmetric_Pictet-Spengler_Reaction&diff=677990&oldid=637315
Microwave-assisted deacylation of unactivated amides using ammonium-salt-accelerated transamidation<...
TY - JOUR. T1 - Microwave-assisted deacylation of unactivated amides using ammonium-salt-accelerated transamidation. AU - Shimizu, Yuhei. AU - Morimoto, Hiroyuki. AU - Zhang, Ming. AU - Ohshima, Takashi. PY - 2012/8/20. Y1 - 2012/8/20. N2 - Easy does it! The chemoselective oxidative ?-C(sp3)H alkylation/cyclization reaction of N-benzyl carbamates using simple mono-, di-, and trisubstituted olefins provides functionalized N-heterocycles such as oxazinones (see picture). A TEMPO oxoammonium salt serves as the oxidant, making it possible to carry out the reaction at low temperatures. Neither a metal catalyst nor preactivation in the ?-position to the nitrogen group are needed.. AB - Easy does it! The chemoselective oxidative ?-C(sp3)H alkylation/cyclization reaction of N-benzyl carbamates using simple mono-, di-, and trisubstituted olefins provides functionalized N-heterocycles such as oxazinones (see picture). A TEMPO oxoammonium salt serves as the oxidant, making it possible to carry out the ...
https://kyushu-u.pure.elsevier.com/en/publications/microwave-assisted-deacylation-of-unactivated-amides-using-ammoni
Intramolecular Ketene Alkene CycloadditionsIntramolecular Ketene Alkene Cycloadditions
Although the [2 + 2] cycloaddition of alkenes and ketenes to form cyclobutanones is one of the few general methods for the construction of four-membered rings, the intramolecular version of this reaction had been little explored when we started work in this area in the early 1980s.109 These reactions differ from most other pericyclic reactions in that the ketene is a reactive intermediate, which will either rapidly form a cyclobutanone or decompose. The yield is determined by the relative rate of these two processes. Alkenyloxyketenes were chosen for the initial exploratory work because the alkenyloxy carboxylic acids were easily prepared by alkylation of unsaturated alcohols with α-bromo carboxylic acids. The electronic effects of the alkyl substituents on the alkene control the regiochemistry of the cycloaddition and the yield depends on the balance between the nucleophilicity of the alkene and steric hindrance.83,90,109 Leading bond formation occurs between the electrophilic carbonyl carbon ...
http://blogs.brandeis.edu/snidergroup/research/intramolecular-ketene-alkene-cycloadditions/
The Medicinal Chemistry Information Portal - Microwave-Assisted Organic Synthesis in Near-Critical Water at 300°C. A Proof-of...
Microwave-assisted organic synthesis in near-critical water (NCW) in the 270-300 °C temperature range has been investigated in a dedicated multimode microwave reactor utilizing heavy-walled quartz reaction vessels. Several different known transformations such as the hydrolysis of esters or amides, the hydration of alkynes, Diels-Alder cycloadditions, pinacol rearrangements, and the Fischer indole synthesis were successfully performed in microwave-generated NCW without the addition of an acid
https://www.combichem.net/index_id_74940.html
Electrocyclic | Article about Electrocyclic by The Free DictionaryElectrocyclic | Article about Electrocyclic by The Free Dictionary
Looking for Electrocyclic? Find out information about Electrocyclic. The interconversion of a linear π-system containing n π-electrons and a cyclic molecule containing π-electrons which is formed by joining the ends of the... Explanation of Electrocyclic
https://encyclopedia2.thefreedictionary.com/Electrocyclic
Regioselective synthesis of isocoumarins by ruthenium-catalyzed aerobic oxidative cyclization of aromatic acids with alkynesRegioselective synthesis of isocoumarins by ruthenium-catalyzed aerobic oxidative cyclization of aromatic acids with alkynes
A free platform for explaining your research in plain language, and managing how you communicate around it - so you can understand how best to increase its impact.
https://www.growkudos.com/publications/10.1039%25252Fc2cc16916a/reader
Tuning the supramolecular chirality of one-and two-dimensional aggregates with the number of stereogenic centers in the...Tuning the supramolecular chirality of one-and two-dimensional aggregates with the number of stereogenic centers in the...
A synthetic strategy was developed for the preparation of porphyrins containing between one and four stereogenic centers, such that their molecular weights vary only as a result of methyl groups which give the chiral forms. The low-dimensional nanoscale aggregates of these compounds Reveal the profound effects of this varying molecular chirality on their supramolecular structure and optical activity. The number of stereogenic centers influences significantly the self-assembly and chiral structure of the aggregates of porphyrin molecules described here. A scanning tunneling microscopy study of monolayers on graphite shows that the degree of structural chirality with respect to the surface increases almost linearly with the number of stereogenic centers, and only one handedness is formed in the monolayers, whereas the achiral compound forms a mixture of mirror-image domains at the surface. In solution, four hydrogen bonds induce the formation of an H-aggregate, and circular dichroism measurements ...
http://kth.diva-portal.org/smash/record.jsf?pid=diva2:740668
Awardees of the 2019 IUPAC-Zhejiang NHU International Award for Advancements in Green Chemistry - IUPAC | International Union...Awardees of the 2019 IUPAC-Zhejiang NHU International Award for Advancements in Green Chemistry - IUPAC | International Union...
Fabio Aricò has started working in the field of Green Chemistry in 2005 after being awarded his Ph.D. at Reading University and post-doc position at UCLA, Los Angeles, CA. He is now associate professor of organic chemistry at Ca Foscari University, Venice, Italy. His research interest within Green Chemistry is to develop innovative reaction pathways focussing on chlorine-free synthetic approaches via dialkyl carbonate (DAC) chemistry. Fabio Aricò has exploited dialkyl carbonates chemistry in the phosgene-free synthesis of carbonates and carbamates with potential applications as monomers for polycarbonate/polyurethane. He also contributed to demonstrate that DACs are highly selective alkylating agents that can be used in substitution of alkyl halides and dimethyl sulphate for alkylation of numerous nitrogen and oxygen substrates. He has reported on the DAC-mediated cyclization reactions can be used as sacrificial molecules in cyclization reaction instead of halogenated compound. As a result, ...
https://iupac.org/awardees-of-the-2019-iupac-zhejiang-nhu-international-award-for-advancements-in-green-chemistry/
1,5-hydride shift of alkenyl sulfoximine/[4+3] cycloaddition and ring opening/novel hydrazine synthesis from Trögers base...1,5-hydride shift of alkenyl sulfoximine/[4+3] cycloaddition and ring opening/novel hydrazine synthesis from Trögers base...
Three synthetic methodologies are studied in details in this dissertation. For 1,5-hydride shift of alkenyl sulfoximine methodology, the reaction mechanism was studied using deuterium labeling. An uncommon 6-endo-trig 1,5-hydride shift process was discovered. The scope and limitation were studied using N-alkyl, N-allyl, and N-benzyl-substituted S-alkenyl sulfoximines. N-H-S-alkyl sulfoximines, four- and six-membered heterocyclic rings and a new class of chiral dienes were obtained. In [4+3] cycloaddition and ring opening chapter, we demonstrated an ene-like reaction using a symmetric oxyallylic cation can provide α-substituted cyclopentenones. Enantio pure products are potentially accessible by this method. [4+3] Cycloaddition of the symmetric oxyallylic cation with substituted furans, and the ring-opening process of the resulting 8-oxabicyclo[3.2.1]oct-6-en-3-one were also studied. The reaction conditions and scope were investigated. An acid-catalyzed mechanism was proposed for the ...
https://mospace.umsystem.edu/xmlui/handle/10355/36669
CCCC 2004, Volume 69, Issue 5, Abstracts pp. 945-965 | Collection of Czechoslovak Chemical Communications
The thermal cyclisation of enediynes to benzene-1,4-diyl diradicals (Bergman cyclisation) is affected by geometrical and electronic conditions. While the effect of ring strain or conformational constrains on the cyclisation temperature has been investigated in detail, electronic contributions have been less studied. Often geometrical and electronic contributions cannot be clearly distinguished. In most cases metal ion chelation does involve both. In this review we have summarised clear-cut observations of electronic substituents effects on the thermal enediyne reactivity. The effects of substituents in the vinylic and terminal alkyne position, the influence of benzo-fusion and hetarene fusion, as well as the changes induced by heteroatoms in the enediyne skeleton, are within the scope of this review. With the exception of more complex heterocyclic hetarene-fused enediynes the experimental data of electronic substituent effects on the thermal Bergman cyclisation of enediynes follow theoretical ...
http://cccc.uochb.cas.cz/69/5/0945/
Diels Alder Reaction | China-Mainland | Sigma-AldrichDiels Alder Reaction | China-Mainland | Sigma-Aldrich
The Diels-Alder reaction is the reaction between a conjugated diene and an alkene (dienophile) to form unsaturated six-membered rings. Since the reaction involves the formation of a cyclic product via a cyclic transition state, it is also referred to as a cycloaddition. The Diels-Alder reaction is an electrocyclic reaction, which involves [4+2]‑cycloaddition of 4 π-electrons of the conjugated diene and 2 π-electrons of the dienophile (an alkene or alkyne). The reaction involves the formation of new σ-bonds, which are energetically more stable than the π-bonds. This reaction has great synthetic importance and was discovered by two German chemists, Otto Diels and Kurt Alder in 1928. They were awarded the Nobel Prize in 1950.1 ...
https://www.sigmaaldrich.com/china-mainland/zh/technical-documents/articles/chemistry/diels-alder-reaction.html
Sumanirole - WikipediaSumanirole - Wikipedia
Sumanirole (PNU-95,666) is a highly selective D2 receptor full agonist, the first of its kind to be discovered. It was developed for the treatment of Parkinsons disease and restless leg syndrome. While it has never been approved for medical use it is a highly valuable tool compound for basic research to identify neurobiological mechanisms that are based on a dopamine D2-linked (vs. D1, D3, D4, and D5-linked) mechanism of action. In 2004, Pfizer announced the end of their clinical development program for sumanirole, citing recent studies that failed to sufficiently distinguish sumanirole from currently available therapies. Ropinirole Romero AG, et al. Synthesis of the selective D2 receptor agonist PNU-95666E from D-phenylalanine using a sequential oxidative cyclization strategy. Journal of Organic Chemistry. 1997; 62(19):6582. McCall RB, Lookingland KJ, Bédard PJ, Huff RM (September 2005). Sumanirole, a highly dopamine D2-selective receptor agonist: in vitro and in vivo pharmacological ...
https://en.wikipedia.org/wiki/Sumanirole
EnediyneEnediyne
For Bergman cyclization to occur, the epoxide must be removed. Myers-Saito cyclization is another triggering mechanism by which ... The diradicals generated by Bergman and Myers-Saito cyclization are highly reactive. The cyclization of the enediyne functional ... Bergman cyclization restructures the enediyne ring into two smaller rings. One electron from each of the enediyne triple bonds ... "Bergman Cyclization". www.organic-chemistry.org. Retrieved 2018-05-05. Smith AL, Nicolaou KC (May 1996). "The enediyne ...
https://en.wikipedia.org/wiki/Enediyne
Pauson-Khand reactionPauson-Khand reaction
In addition to using a rhodium catalyst, this synthesis features an intramolecular cyclization that results in the normal 5- ... Shambayani, Soroosh; Crowe, William E.; Schreiber, Stuart L. (1990-01-01). "N-oxide promoted pauson-khand cyclizations at room ... Negishi, Eiichi; Holmes, Steven J.; Tour, James M.; Miller, Joseph A. (1985-04-01). "Metal promoted cyclization. 7. Zirconium- ... "Asymmetric Pauson-Khand Cyclization: A Formal Total Synthesis of Natural Brefeldin A". The Journal of Organic Chemistry. 60 (21 ...
https://en.wikipedia.org/wiki/Pauson–Khand_reaction
HydroquinoneHydroquinone
"Cyclization of Acetylenic Compounds". Angewandte Chemie International Edition in English. 8 (10): 727-733. doi:10.1002/anie. ...
https://en.wikipedia.org/wiki/Hydroquinone
CycloalkeneCycloalkene
Cyclization reactions, or intramolecular addition reactions, can be used to form cycloalkenes. These reactions primarily form ... Intramolecular Addition (Cyclization) Reactions". Chemistry LibreTexts. 2015-01-12. Retrieved 2022-11-17. "ELECTROCYCLIC ...
https://en.wikipedia.org/wiki/Cycloalkene
PropynePropyne
"Cyclization of Acetylenic Compounds". Angewandte Chemie International Edition in English. 8 (10): 727-733. doi:10.1002/anie. ...
https://en.wikipedia.org/wiki/Propyne
FlavaglineFlavagline
Trost, B. M.; Greenspan, P. D.; Yang, B. V.; Saulnier, M. G. (1990). "An unusual oxidative cyclization. A synthesis and ...
https://en.wikipedia.org/wiki/Flavagline
AcetyleneAcetylene
doi:10.1016/S0040-4020(01)92395-6. Reppe, Walter; Kutepow, N; Magin, A (1969). "Cyclization of Acetylenic Compounds". ...
https://en.wikipedia.org/wiki/Acetylene
SuritozoleSuritozole
Cyclization to Suritozole (6). GABAA receptor negative allosteric modulator GABAA receptor § Ligands Miller JA, Dudley MW, ...
https://en.wikipedia.org/wiki/Suritozole
2-Butyne2-Butyne
Reppe, Walter; Kutepow, N; Magin, A (1969). "Cyclization of Acetylenic Compounds". Angewandte Chemie International Edition in ...
https://en.wikipedia.org/wiki/2-Butyne
RocaglamideRocaglamide
Trost BM, Greenspan PD, Yang BV, Saulnier MG (November 1990). "An unusual oxidative cyclization. A synthesis and absolute ...
https://en.wikipedia.org/wiki/Rocaglamide
Scott E. DenmarkScott E. Denmark
Denmark, S. E.; Jones, T. K. (1982-05-01). "Silicon-directed Nazarov cyclization". Journal of the American Chemical Society. ... From Polyene Cyclizations to Origin of Biomolecular Homochirality. ETH Zurich (Switzerland). Retrieved 2019-11-16. ... where his laboratory's early work focused on investigation of the Nazarov cyclization reaction and Claisen rearrangement. This ...
https://en.wikipedia.org/wiki/Scott_E._Denmark
BiosynthesisBiosynthesis
This causes cyclization and gives rise to (2S,4S)-4-hydroxy-2,3,4,5-tetrahydrodipicolinate. 4-hydroxy-tetrahydrodipicolinate ... this prevents spontaneous cyclization. The enzyme N-acetylglutamate synthase (glutamate N-acetyltransferase) is responsible for ...
https://en.wikipedia.org/wiki/Biosynthesis
Biomimetic synthesisBiomimetic synthesis
A more recent example is E.J. Corey's carbenium-mediated cyclization of an engineered linear polyene to provide a tetracyclic ... The key step in Heathcock's synthetic route involves a cyclization of acyclic dialdehydes A or B to form proto-daphniphylline. ... Eschenmoser A, Felix D, Gut M, Meier J, Stadler P (1959). "Some aspects of acid-catalysed cyclizations of terpenoid polyenes". ... Stork G, Burgstrahler AW (1955). "The stereochemistry of polyene cyclization". J. Am. Chem. Soc. 77 (19): 5068-77. doi:10.1021/ ...
https://en.wikipedia.org/wiki/Biomimetic_synthesis
CyclopentyneCyclopentyne
The importance of cyclization effects". International Journal of Quantum Chemistry. doi:10.1002/qua.25489. (Chemical pages ...
https://en.wikipedia.org/wiki/Cyclopentyne
Thiol-ene reactionThiol-ene reaction
The use of thiyl radicals as initiators of cyclization has been employed in the synthesis of a number of natural products, ... This section examines intramolecular thiol-ene cyclization reactions, which yields a mixture of 5-exo and 6-endo products in ... The conditions under which these cyclization reactions occur follow Baldwin's rules for ring closure. Given the reversibility ... Lynch, Dylan M.; Scanlan, Eoin M. (2020-07-07). "Thiyl Radicals: Versatile Reactive Intermediates for Cyclization of ...
https://en.wikipedia.org/wiki/Thiol-ene_reaction
Oxidosqualene cyclaseOxidosqualene cyclase
This cyclization is one of the most complex known enzyme functions and is highly selective. In the enzyme's active site, a ... Oxidosqualene cyclases (OSC) are enzymes involved in cyclization reactions of 2,3-oxidosqualene to form sterols or triterpenes ... Stork, Gilbert; Burgstahler, A. W. (1955-10-01). "The Stereochemistry of Polyene Cyclization". Journal of the American Chemical ...
https://en.wikipedia.org/wiki/Oxidosqualene_cyclase
Pictet-Spengler reactionPictet-Spengler reaction
B. E. Maryanoff; H.-C. Zhang; J. H. Cohen; I. J. Turchi; C. A. Maryanoff (2004). "Cyclizations of N-acyliminium ions". Chem. ... Larghi, E. L.; Kaufman, T. S. (2006). "The oxa-Pictet-Spengler Cyclization. Synthesis of Isochromanes and Related Pyran-Type ... Instead of catalyzing the Pictet-Spengler cyclization with strong acid, one can acylate the iminium ion forming the ...
https://en.wikipedia.org/wiki/Pictet–Spengler_reaction
Methanesulfonyl chlorideMethanesulfonyl chloride
Chamberlin, A. R.; Nguyen, H. D.; Chung, J. Y. L. (1984). "Cationic cyclization of ketene dithioacetals. A general synthesis of ...
https://en.wikipedia.org/wiki/Methanesulfonyl_chloride
Combes quinoline synthesisCombes quinoline synthesis
Johnson, W.S.; Mathews, F.J. (1944). "Cyclization studies in the benzoquinoline series". J. Am. Chem. Soc. 66 (2): 210-215. doi ... Johnson, W.S.; Mathews, F.J. (1944). "Cyclization studies in the benzoquinoline series". J. Am. Chem. Soc. 66 (2): 210-215. doi ...
https://en.wikipedia.org/wiki/Combes_quinoline_synthesis
Cope rearrangementCope rearrangement
Tang, Man-Cheng; Zou, Yi; Watanabe, Kenji; Walsh, Christopher T.; Tang, Yi (2017-04-26). "Oxidative Cyclization in Natural ...
https://en.wikipedia.org/wiki/Cope_rearrangement
IndenofluoreneIndenofluorene
Youngs, Wiley J.; Djebli, Abdellah.; Tessier, Claire A. (1991-07-01). "Lithium-induced cyclization of tribenzo cyclotriynes". ...
https://en.wikipedia.org/wiki/Indenofluorene
Azide-alkyne Huisgen cycloadditionAzide-alkyne Huisgen cycloaddition
At this point cyclization takes place. This is followed by protonation; the source of proton being the hydrogen which was ...
https://en.wikipedia.org/wiki/Azide-alkyne_Huisgen_cycloaddition
Peptide synthesisPeptide synthesis
Off-resin cyclization is a solid-phase synthesis of key intermediates, followed by the key cyclization in solution phase, the ... A variety of cyclization reagents can be used such as HBTU/HOBt/DIEA, PyBop/DIEA, PyClock/DIEA. Head-to-tail peptides can be ... Once cyclization has taken place, the peptide is cleaved from resin by acidolysis and purified. The strategy for the solid- ... The deprotection of the C-terminus at some suitable point allows on-resin cyclization by amide bond formation with the ...
https://en.wikipedia.org/wiki/Peptide_synthesis
Cre-Lox recombinationCre-Lox recombination
"Cyclization recombinase [Escherichia coli] - Protein - NCBI". Sternberg N, Hamilton D (August 1981). "Bacteriophage P1 site- ... The Cre protein (encoded by the locus originally named as "Causes recombination", with "Cyclization recombinase" being found in ...
https://en.wikipedia.org/wiki/Cre-Lox_recombination
Metal-centered cycloaddition reactionsMetal-centered cycloaddition reactions
Padwa, Albert; Kassir, Jamal M.; Xu, Simon L. (1 March 1997). "Cyclization Reactions of Rhodium Carbene Complexes. Effect of ...
https://en.wikipedia.org/wiki/Metal-centered_cycloaddition_reactions
Intramolecular Heck reactionIntramolecular Heck reaction
5-Exo cyclization, which establishes a five-membered ring with an exocyclic alkene, is the most facile cyclization mode in ... 7) Endo cyclization is observed most often when small or large rings are involved. For instance, 5-endo cyclization is ... 12) The closest competing method to IMHR is radical cyclization. Radical cyclizations are often reductive, which can cause ... 6) 6-Exo cyclization is also common. The high stability of Heck reaction catalysts permits the synthesis of highly strained ...
https://en.wikipedia.org/wiki/Intramolecular_Heck_reaction
Enone-alkene cycloadditionsEnone-alkene cycloadditions
the Intramolecular Cyclization of Carvone to Carvonecamphor". J. Am. Chem. Soc. 79 (17): 4741. doi:10.1021/ja01574a042. Cookson ...
https://en.wikipedia.org/wiki/Enone–alkene_cycloadditions
NifurquinazolNifurquinazol
... cyclization then affords the observed product (4). The amide function is then converted to the iminochloride with phosphorus ...
https://en.wikipedia.org/wiki/Nifurquinazol
ThiopheneThiophene
Another method is the Volhard-Erdmann cyclization. Thiophene is produced on a modest scale of around 2,000 metric tons per year ...
https://en.wikipedia.org/wiki/Thiophene
Thiol-yne reactionThiol-yne reaction
The radical intermediate can engage in secondary reactions such as cyclisation. With diaddition the 1,2-disulfide or the 1,1- ... "Sulfanyl radical mediated cyclization of aminyl radicals". Tetrahedron Letters. 39 (49): 9077. doi:10.1016/S0040-4039(98)01998- ...
https://en.wikipedia.org/wiki/Thiol-yne_reaction
Extended π-Participation in Biomimetic Cyclization of Squalene DerivativesExtended π-Participation in Biomimetic Cyclization of Squalene Derivatives
... Stanko Borčić ; Department of Chemistry, Faculty of ... "Extended π-Participation in Biomimetic Cyclization of Squalene Derivatives." Croatica Chemica Acta, vol. 69, br. 4, 1996, str. ... "Extended π-Participation in Biomimetic Cyclization of Squalene Derivatives." Croatica Chemica Acta 69, br. 4 (1996): 1347-1359 ... 1996). Extended π-Participation in Biomimetic Cyclization of Squalene Derivatives, Croatica Chemica Acta, 69(4), str. 1347- ...
https://hrcak.srce.hr/clanak/200510
All Cyclisation articles | Chemistry WorldAll Cyclisation articles | Chemistry World
All Cyclisation articles. * Research 40-year-old mystery of why some molecules break all cyclisation rules has been solved 2022 ... Molecules that blatantly violate Woodward-Hoffmann rules could lead to general theory of cyclisation in polar compounds ...
https://www.chemistryworld.com/cyclisation/622.tag
Synthesis of coumarins via PIDA/I2-mediated oxidative cyclization of substituted phenylacrylic acids - RSC Advances (RSC...Synthesis of coumarins via PIDA/I2-mediated oxidative cyclization of substituted phenylacrylic acids - RSC Advances (RSC...
Synthesis of coumarins via PIDA/I2-mediated oxidative cyclization of substituted phenylacrylic acids J. Li, H. Chen, D. Zhang- ... Synthesis of coumarins via PIDA/I2-mediated oxidative cyclization of substituted phenylacrylic acids† ...
https://pubs.rsc.org/en/Content/ArticleLanding/2013/RA/C3RA23188G
cyclization type flag in simple cycpep predict | RosettaCommonscyclization type flag in simple cycpep predict | RosettaCommons
While I explicitely asked for a terminal disulfide cyclization (using the flag -cyclic_peptide:cyclization_type terminal_ ... As I said in my comment, disulfide cyclization did not work for me in v3.8 but did for weekly release 2017.52. You may give it ... The reason I want 3.8 is because I want to use the disulfide cyclization type. Is this a database issue? Thanks for your help! ... Hi Thanks Florent - however, the issue is arising here even without the -cyclization_type flags. Unfortuntately, I have no ...
https://rosettacommons.org/comment/10626
Microwave Chemistry Highlights: Tandem Cyclization/Claisen Rearrangements, Primary Thioamides, Aminoquinazolines, 4...Microwave Chemistry Highlights: Tandem Cyclization/Claisen Rearrangements, Primary Thioamides, Aminoquinazolines, 4...
Tandem Cyclization/Claisen Rearrangements. The base-catalyzed intramolecular cyclization of appropriately substituted 4-alkyn-1 ... The tandem cyclization-Claisen rearrangements were best carried out in DMF or phenetole as solvent in the presence of 10 mol% ...
https://www.organic-chemistry.org/Highlights/2005/15January.shtm
EVIDENCE FOR A RADICAL PROCESS IN THE DARK CYCLIZATION REACTION OF ALIPHATIC ALCOHOLS WITH SILVER OXIDE AND BROMINE. - Nokia...EVIDENCE FOR A RADICAL PROCESS IN THE DARK CYCLIZATION REACTION OF ALIPHATIC ALCOHOLS WITH SILVER OXIDE AND BROMINE. - Nokia...
Nokia sites use cookies to improve and personalize your experience and to display advertisements. The sites may also include cookies from third parties. By using this site, you consent to the use of cookies. Learn more ...
https://www.bell-labs.com/institute/publications/bl6690815/
Choreographing cyclizations and fragmentations in radical cascadesChoreographing cyclizations and fragmentations in radical cascades
Cyclization of 2′-Nitrobiphenyl-2-carboxylic Acids - ScienceOpenCyclization of 2′-Nitrobiphenyl-2-carboxylic Acids - ScienceOpen
1Cyclization of 2-Alk-1-ynylbenzoic Acids. *. pp. 1Cyclization of 1-(2-Hydroxyphenyl)alkane-1,3-diones with Sulfonic Acid ... 1Cyclization of Carbon Dioxide and Two Alkynes. *. pp. 1Rhodium-Catalyzed Carbonylative Cyclization of (2-Hydroxyphenyl)alkynes ... 1Cyclization of Ester Enolates with Unsaturated Thiocarbonyl Compounds. *. pp. 1Cyclization of 9,10-Dioxo-9,10- ... 1Cyclizations Utilizing Carbon Dioxide. *. pp. 1With Formation of the 4a-10 and 9-9a, the 8a-9 and 10-10a, the 4a-10 and 8a-9, ...
https://www.scienceopen.com/book?vid=584f2cdc-ff0e-4197-965c-5c35c0f52d72
cyclization of glutamine involved in intein-mediated protein splicing - Ontology Report - Rat Genome Databasecyclization of glutamine involved in intein-mediated protein splicing - Ontology Report - Rat Genome Database
cyclization of glutamine involved in intein-mediated protein splicing. go back to main search page ... The cyclization of glutamine to yield an L-glutamimide residue at the C-terminus of an excised intein during protein splicing. ...
https://rgd.mcw.edu/rgdweb/ontology/annot.html?acc_id=GO:0019802&species=Rat
BJOC - A diastereoselective approach to axially chiral biaryls via electrochemically enabled cyclization cascadeBJOC - A diastereoselective approach to axially chiral biaryls via electrochemically enabled cyclization cascade
A diastereoselective approach to axially chiral biaryls via electrochemically enabled cyclization cascade ... A diastereoselective approach to axially chiral biaryls via electrochemically enabled cyclization cascade. Hong Yan, Zhong-Yi ... Rhodium-catalyzed intramolecular reductive aldol-type cyclization: Application for the synthesis of a chiral necic acid lactone ...
https://www.beilstein-journals.org/bjoc/articles/15/76/downloads
Development of Catalytic Cyclization/Coupling Reactions for New Chemical Space - Penn State
Development of Catalytic Cyclization/Coupling Reactions for New Chemical Space. *Giri, Ramesh (PI) ... Beta-hydride elimination is a competing process in cyclization/coupling reactions that has significantly limited the scope of ... To further broaden the scope of cyclization/coupling strategies towards accessing a broader range of complex molecules, this ... Ramesh Giri and his research team are developing catalysts to advance cyclization/coupling strategies for alkene ...
https://pennstate.pure.elsevier.com/en/projects/development-of-catalytic-cyclizationcoupling-reactions-for-new-ch
Structure of the Product from a Novel Cyclization Reaction Involving a C(6)-Substituted Uridine AnalogStructure of the Product from a Novel Cyclization Reaction Involving a C(6)-Substituted Uridine Analog
... ... 1993). "Structure of the Product from a Novel Cyclization Reaction Involving a C(6)-Substituted Uridine Analog." Acta ...
https://kuscholarworks.ku.edu/handle/1808/16206
Iodoheptene Radical Cyclisation ExoIodoheptene Radical Cyclisation Exo
Interactive 3D chemistry animations of reaction mechanisms and 3D models of chemical structures for students studying University courses and advanced school chemistry hosted by University of Liverpool
https://www.chemtube3d.com/rad-iodoheptanecyclisation-exo/
Palladium-mediated cyclizations of gamma-oxoallenes: synthesis of structurally modified nucleic acidsPalladium-mediated cyclizations of gamma-oxoallenes: synthesis of structurally modified nucleic acids
Reversible cyclisation of a sulfonated arylazo compound containing an o-acetylamino substituent - StrathprintsReversible cyclisation of a sulfonated arylazo compound containing an o-acetylamino substituent - Strathprints
Gibson, D.I. and Parkinson, J.A. and Jones, A.C. and Ebenezer, W.J. and Hutchings, M.G. (2008) Reversible cyclisation of a ... Reversible cyclisation of a sulfonated arylazo compound containing an o-acetylamino substituent ... arylazo, benzo-1, 2, 4-triazine, cyclisation, photoisomerism, Chemistry, Biochemistry, Organic Chemistry, Drug Discovery. ...
https://strathprints.strath.ac.uk/19765/
A Chiral Tetrahydro-Gamma-Pyrannonecarboxylate Ester for Asymmetric Nazarov Cyclization - Kent Academic RepositoryA Chiral Tetrahydro-Gamma-Pyrannonecarboxylate Ester for Asymmetric Nazarov Cyclization - Kent Academic Repository
A Chiral Tetrahydro-Gamma-Pyrannonecarboxylate Ester for Asymmetric Nazarov Cyclization. Acta Crystallographica Section C- ...
https://kar.kent.ac.uk/20391/
Raw data for new compounds described in the paper Catalytic enantioselective arylative cyclizations of alkynyl 1,3-diketones...Raw data for new compounds described in the paper "Catalytic enantioselective arylative cyclizations of alkynyl 1,3-diketones...
Raw data for new compounds described in the paper "Catalytic enantioselective arylative cyclizations of alkynyl 1,3-diketones ... Raw data for new compounds described in the paper "Catalytic enantioselective arylative cyclizations of alkynyl 1,3-diketones ... Raw NMR data for new compounds described in the paper: "Catalytic enantioselective arylative cyclizations of alkynyl 1,3- ...
https://unow.nottingham.ac.uk/handle/internal/8248
The synthesis of heteroaromatic prostacyclin analogues via keto alkyne cyclisationThe synthesis of heteroaromatic prostacyclin analogues via keto alkyne cyclisation
... Stuart Cook, Douglas Henderson, Kevan A. ... The synthesis of heteroaromatic prostacyclin analogues via keto alkyne cyclisation. , Journal of the Chemical Society Perkin ...
https://www.growkudos.com/publications/10.1039%25252Fp19870001825/reader
Enzymatic Cyclization to Labdanes and Related Diterpenoid Natural Products - Reuben PetersEnzymatic Cyclization to Labdanes and Related Diterpenoid Natural Products - Reuben Peters
Enzymatic Cyclization to Labdanes and Related Diterpenoid Natural Products Peters, Reuben John Iowa State University, Ames, IA ... We propose to investigate these consecutive cyclization reactions as a first step towards our long-term goal of engineering ... To characterize class II cyclization more basic mechanistic enzymology studies are proposed to identify the determinants for ... and will have a broader impact in further increasing our understanding and use of terpenoid enzymatic cyclization more ...
https://grantome.com/grant/NIH/R01-GM076324-05
A formylation-cyclization method of synthesis of cycloalkenones from unsaturated ketones - Publications of the IAS FellowsA formylation-cyclization method of synthesis of cycloalkenones from unsaturated ketones - Publications of the IAS Fellows
A formylation-cyclization method of synthesis of cycloalkenones from unsaturated ketones Journal of Organic Chemistry, 45 (6). ...
http://repository.ias.ac.in/12366/
Interplay of ortho- with spiro-cyclisation during iminyl radical closures onto arenes and heteroarenesInterplay of ortho- with spiro-cyclisation during iminyl radical closures onto arenes and heteroarenes
Cyclisation energetics were investigated by DFT computations which gave insights into factors influencing the two cyclisation ... Interplay of ortho- with spiro-cyclisation during iminyl radical closures onto arenes and heteroarenes. ... Walton , J C & McBurney , R T 2013 , Interplay of ortho- with spiro-cyclisation during iminyl radical closures onto arenes ... For benzofuran and benzothiophene acceptors, spiro-cyclisation predominated at low temperatures but thermodynamic control ...
https://research-repository.st-andrews.ac.uk/handle/10023/3959
Intramolecular cyclization of alkynoic acid catalyzed by Na-salt-modified Au nanoparticles supported on metal oxides<...
Intramolecular cyclization of alkynoic acid catalyzed by Na-salt-modified Au nanoparticles supported on metal oxides」の研究トピックを掘り ... Intramolecular cyclization of alkynoic acid catalyzed by Na-salt-modified Au nanoparticles supported on metal oxides. Applied ... Intramolecular cyclization of alkynoic acid catalyzed by Na-salt-modified Au nanoparticles supported on metal oxides. In: ... Intramolecular cyclization of alkynoic acid catalyzed by Na-salt-modified Au nanoparticles supported on metal oxides. / Huang, ...
https://kyushu-u.pure.elsevier.com/ja/publications/intramolecular-cyclization-of-alkynoic-acid-catalyzed-by-na-salt-
Triruthenium dodecacarbonyl-catalized reductive carbonylation of nitroarenes: cyclization, carbon monoxide insertion and...
The cyclization to indole occurred also at room temperature under irradiation or with zinc. The use of cis-cyclooctene as the ... The cyclization to indole occurred also at room temperature under irradiation or with zinc. The use of cis-cyclooctene as the ... Nitrones were formed in this reaction and were suggested to be intermediate in certain cyclizations. Force-field calculations ... Nitrones were formed in this reaction and were suggested to be intermediate in certain cyclizations. Force-field calculations ...
https://air.unimi.it/handle/2434/177966
IUPAC - cyclization (C01494)
The IUPAC Compendium of Chemical Terminology
https://dev.goldbook.iupac.org/terms/view/C01494
Intramolecular cyclization of benzyl-substituted cyclopentadienyl titanum dichlorides promoted by boron tribromide<...Intramolecular cyclization of benzyl-substituted cyclopentadienyl titanum dichlorides promoted by boron tribromide<...
Qian, Y, Huang, J, Ding, K, Zhang, Y, Huang, Q, Chen, XP, Chan, ASC & Wong, WT 2002, Intramolecular cyclization of benzyl- ... Intramolecular cyclization of benzyl-substituted cyclopentadienyl titanum dichlorides promoted by boron tribromide. Journal of ... Intramolecular cyclization of benzyl-substituted cyclopentadienyl titanum dichlorides promoted by boron tribromide. In: Journal ... Intramolecular cyclization of benzyl-substituted cyclopentadienyl titanum dichlorides promoted by boron tribromide. / Qian, ...
https://research.polyu.edu.hk/en/publications/intramolecular-cyclization-of-benzyl-substituted-cyclopentadienyl
Ruthenium-catalyzed aerobic oxidative cyclization of aromatic and heteroaromatic nitriles with alkynes: A new route to...Ruthenium-catalyzed aerobic oxidative cyclization of aromatic and heteroaromatic nitriles with alkynes: A new route to...
Reddy MC, Manikandan R, Jeganmohan M. Ruthenium-catalyzed aerobic oxidative cyclization of aromatic and heteroaromatic nitriles ... Reddy, M. C., Manikandan, R., & Jeganmohan, M. (2013). Ruthenium-catalyzed aerobic oxidative cyclization of aromatic and ... title = "Ruthenium-catalyzed aerobic oxidative cyclization of aromatic and heteroaromatic nitriles with alkynes: A new route to ... Ruthenium-catalyzed aerobic oxidative cyclization of aromatic and heteroaromatic nitriles with alkynes: A new route to ...
https://cris.bgu.ac.il/en/publications/ruthenium-catalyzed-aerobic-oxidative-cyclization-of-aromatic-and
Cyclizations | PepscanCyclizations | Pepscan
CLIPS cyclization (mono- and bicyclic peptides). Cys-Cys cyclization is the result from formation of a disulfide (S-S) bond ... An important challenge with head-to-tail cyclizations is the fact that the peptide cyclization is often slow due to entropic ... Most often backbone-amide cyclized peptides are prepared via head-to-tail cyclization or side-chain-to-side-chain cyclization. ... Effective head-to-tail cyclization therefore requires thorough expertise with respect to the optimal cyclization reagent and ...
https://www.pepscan.com/fr/synthese-peptidique-a-facon/modification-des-peptides/cyclizations/
Gold Redox Catalysis for Cyclization/Arylation of Allylic Oximes: Synt by Abiola Azeez Jimoh, Seyedmorteza Hosseyni et al."Gold Redox Catalysis for Cyclization/Arylation of Allylic Oximes: Synt" by Abiola Azeez Jimoh, Seyedmorteza Hosseyni et al.
... redox catalysis toward allylic oxime cyclization/aryl coupling. Functional isoxazolines were prepared with good to excellent ... Base-assisted diazonium activation has been employed to promote gold(I)/(III) redox catalysis toward allylic oxime cyclization/ ... Gold Redox Catalysis for Cyclization/Arylation of Allylic Oximes: Synthesis of Isoxazoline Derivatives ... "Gold Redox Catalysis for Cyclization/Arylation of Allylic Oximes: Synthesis of Isoxazoline Derivatives" (2019). Chemistry ...
https://digitalcommons.usf.edu/chm_facpub/148/
Intramolecular cyclization assistance for fast degradation of ornithine-based poly(ester amide)s<...
Intramolecular cyclization assistance for fast degradation of ornithine-based poly(ester amide)s. / De Gracia Lux, Caroline; ... Intramolecular cyclization assistance for fast degradation of ornithine-based poly(ester amide)s. In: Journal of Polymer ... De Gracia Lux C, Olejniczak J, Fomina N, Viger ML, Almutairi A. Intramolecular cyclization assistance for fast degradation of ... De Gracia Lux, C., Olejniczak, J., Fomina, N., Viger, M. L., & Almutairi, A. (2013). Intramolecular cyclization assistance for ...
https://utsouthwestern.pure.elsevier.com/en/publications/intramolecular-cyclization-assistance-for-fast-degradation-of-orn
Paul OMaillePaul O'Maille
... suppress or reactivate cyclization. Remarkably, this epistatic network of equivalent residues also controls cyclization in a ... Emergence of terpene cyclization in Artemisia annua. Paul OMaille February 3, 2015. ... Here we report the first discovery of an epistatic network of residues that controls the onset of terpene cyclization in ... To analyze the molecular mechanisms of emergence of terpene cyclization, we have carried out in-depth examination of mutational ...
https://www.sri.com/author/paul-omaille/
IntramolecularReactionSynthesisChemistryOxidative cyclizationEstersReactionsDerivativesPeptidesReductiveAmideDisulfideArylTandemRadicalTerpeneCatalystsBenzofuranSubstratesDeprotectionSequenceStabilityMethodProductsMainProductChallengeGave
Intramolecular8
  • The base-catalyzed intramolecular cyclization of appropriately substituted 4-alkyn-1-ols, followed by in situ Claisen rearrangement was investigated by Ovaska and co-workers ( Synlett 2004 , 2579. (organic-chemistry.org)
  • Intramolecular cyclization of α,α-alkyl-ortho-methoxybenzylcyclopentadienyl titanium complexes to form titanoxacycle complexes promoted by BBr3has been studied. (edu.hk)
  • Zirconia-supported sodium-salt-modified Au(0) nanoparticles (NPs) (Na-Au/ZrO 2 ) catalyst was prepared, and it was stable and recyclable in the intramolecular cyclization of alkynoic acids. (elsevier.com)
  • Inspired by the spontaneous cyclization of ornithine in peptides, polyesters containing protected ornithine (Orn) side chains along the backbone were synthesized and shown to degrade rapidly upon deprotection through intramolecular cyclization. (elsevier.com)
  • GPC confirmed that 1-Boc degrades over 40 times faster than 2-Boc following deprotection into the designed intramolecular cyclization products. (elsevier.com)
  • In addition, cyclization of the title compounds by intramolecular coupling of the amine and ester has led to the analogous bicyclic thiazin-3(2H)-ones. (elsevier.com)
  • This step results from an intramolecular cyclization reaction in which the carbonyl (C=O) group that was a part of the original isocyanate group (-N=C=O), is effectively extracted to yield perimidone and the amine corresponding to the original isocyanate species. (cdc.gov)
  • ED3A can react spontaneously to ketopiperazinediacetate (KPDA) by intramolecular cyclisation [Ternes et al. (europa.eu)
Reaction9
  • Nitrones were formed in this reaction and were suggested to be intermediate in certain cyclizations. (unimi.it)
  • Moreover, detailed kinetic studies revealed that the cyclization was a zero-order reaction with respect to substrate concentration, and the rate-determining step of the reaction is presumed to be protodeauration. (elsevier.com)
  • A Bergman cyclization landscape that is influenced by the bonding of metal to an enediyne ligand but whose reaction barrier is ultimately dominated by the coordinating ability of the accompanying anion. (semanticscholar.org)
  • Subsequent cyclization of these compounds by reaction between the amine and activated methylene has led to various ester-substituted thiazine- and thiadiazine-based bicyclic derivatives. (elsevier.com)
  • 3-allyl-3-methylthio-𝛽-lactams, which are synthesized through a Lewis acid mediated C-3 alkylation of the trans -3-chloro-3-methylthio-𝛽-lactams, undergo a facile intrasulfenyl cyclization reaction in the presence of halogens like bromine and iodine to give spiro 𝛽-lactams in good yield. (ias.ac.in)
  • Ugi Four-Component Reaction Based on the in situ Capture of Amines and Subsequent Modification Tandem Cyclization Reaction: "One-Pot" Synthesis of Six- and Seven-Membered Heterocycles[J]. Chinese Journal of Organic Chemistry , 2021, 41(6): 2374-2383. (sioc-journal.cn)
  • Structure analysis of product was conducted by GC-MS. Kinetic of the cyclisation-acetylation reaction was analyzed according to the Langmuir-Hinshelwood mechanism. (ugm.ac.id)
  • Rate constant of cyclisation-acetylation reaction catalyzed by Zn 2+ -Natzeo was 30.964-47.619 mmol(min. (ugm.ac.id)
  • In Chapter 3, a tandem palladium-catalyzed deallylation/cyclization reaction was designed to occur under a mild condition: weakly acidic (acetic acid) and room temperature, which enables the synthesis of perylene monoanhydrides with many labile R groups for the first time. (cuny.edu)
Synthesis2
  • Wenkert, Ernest (1980) A formylation-cyclization method of synthesis of cycloalkenones from unsaturated ketones Journal of Organic Chemistry, 45 (6). (ias.ac.in)
  • Stephens, CE & Walter Sowell, J 1998, ' Synthesis and Cyclization Reactions of 2-Amino-3-[(methoxycarbonyl)methylsulfonyl]pyrroles and Thiophene ', Journal of Heterocyclic Chemistry , vol. 35, no. 4, pp. 933-938. (elsevier.com)
Chemistry1
  • β-Nitrostyrenes as Electrophiles in Parham Cyclization Chemistry. (tcnj.edu)
Oxidative cyclization1
  • Reddy, MC, Manikandan, R & Jeganmohan, M 2013, ' Ruthenium-catalyzed aerobic oxidative cyclization of aromatic and heteroaromatic nitriles with alkynes: A new route to isoquinolones ', Chemical Communications , vol. 49, no. 54, pp. 6060-6062. (bgu.ac.il)
Esters1
  • While the most frequently formed pattern for cyclization is the amide bond, side-chain cyclizations can consist of lactones (cyclic esters), thioethers, disulfide bridges, thioesters, and β-lactams (amide bonds). (eurogentec.com)
Reactions4
  • Dr. Ramesh Giri and his research team are developing catalysts to advance cyclization/coupling strategies for alkene difunctionalization reactions. (elsevier.com)
  • Beta-hydride elimination is a competing process in cyclization/coupling reactions that has significantly limited the scope of these transformations. (elsevier.com)
  • We propose to investigate these consecutive cyclization reactions as a first step towards our long-term goal of engineering terpenoid natural product biosynthesis for pharmaceutical purposes. (grantome.com)
  • Thus, the proposed studies will elucidate the structure-function relationships underlying the consecutive class I I/class I cyclization reactions in labdane-related diterpene biosynthesis, and will have a broader impact in further increasing our understanding and use of terpenoid enzymatic cyclization more generally. (grantome.com)
Derivatives4
  • 1996). 'Extended π-Participation in Biomimetic Cyclization of Squalene Derivatives', Croatica Chemica Acta , 69(4), str. (srce.hr)
  • Borčić S, Humski K, Kronja O, Malnar I. Extended π-Participation in Biomimetic Cyclization of Squalene Derivatives. (srce.hr)
  • penicillin and derivatives) and thus, lactam ring cyclization represents a potential antimicrobial drug development opportunity. (eurogentec.com)
  • Methods: The 2,3-dihydro-1,3,4-oxadiazole derivatives 4a-h were synthesized by cyclization of N'-(substituted-benzylidene) isonicotinohydrazide 3a-e in refluxing acetic anhydride. (who.int)
Peptides4
  • Constraining peptides via cyclization is a frequently used strategy for the mimicry of (protein) secondary structures (e.g. peptide loops) or for the creation of peptides with enhanced conformational stability (compared to their linear analogs). (pepscan.com)
  • Amide bond cyclization is frequently used for cyclic peptides. (pepscan.com)
  • Most often backbone-amide cyclized peptides are prepared via head-to-tail cyclization or side-chain-to-side-chain cyclization. (pepscan.com)
  • Efficient Enzymatic Cyclization of Disulfide-Rich Peptides by Using Peptide Ligases. (cipps.org.au)
Reductive1
  • Triruthenium dodecacarbonyl-catalized reductive carbonylation of nitroarenes: cyclization, carbon monoxide insertion and reduction : An overview / A. Bassoli, S. Cenini, F. Farina, M. Orlandi, B. Rindone. (unimi.it)
Amide2
  • While I explicitely asked for a terminal disulfide cyclization (using the flag -cyclic_peptide:cyclization_type terminal_disulfide), the output models are cyclized with a mainchain bond (the default n_to_c_amide_bond). (rosettacommons.org)
  • Similar to Cys-Cys cyclization, some synthetic challenges are encountered with amide cyclizations. (pepscan.com)
Disulfide2
  • The reason I want 3.8 is because I want to use the disulfide cyclization type. (rosettacommons.org)
  • Cys-Cys cyclization is the result from formation of a disulfide (S-S) bond between the thiol side chains of two cysteine residues in a peptide. (pepscan.com)
Aryl1
  • Base-assisted diazonium activation has been employed to promote gold(I)/(III) redox catalysis toward allylic oxime cyclization/aryl coupling. (usf.edu)
Tandem2
  • The tandem cyclization-Claisen rearrangements were best carried out in DMF or phenetole as solvent in the presence of 10 mol% MeLi base. (organic-chemistry.org)
  • This is followed by a discussion of a tandem enamine formation cyclisation sequence using allenic substrates for the preparation of substituted cyclopentanones. (ucl.ac.uk)
Radical1
  • II (same R). The 3-exo trig radical cyclization, i.e., homoallylic (cyclopropyl)methyl radical cyclization, of I and II gave tricyclooctanes III (same R). (iisc.ac.in)
Terpene1
  • To analyze the molecular mechanisms of emergence of terpene cyclization, we have carried out in-depth examination of mutational space around (E)-β-farnesene synthase, an Artemisia annua enzyme which catalyzes production of a linear hydrocarbon chain. (sri.com)
Catalysts1
  • Substrates containing dienophiles bearing two electron-withdrawing groups underwent uncatalysed cyclisation readily, whereas unactivated substrates were unreactive even in the presence of catalysts. (hud.ac.uk)
Benzofuran2
  • For benzofuran and benzothiophene acceptors, spiro-cyclisation predominated at low temperatures but thermodynamic control ensured ortho-products, benzofuro- or benzothieno-isoquinolines, formed at higher temperatures. (st-andrews.ac.uk)
  • Etherification with chloroacetic acid followed by cyclisation gives the heterocycle benzofuran. (chemeurope.com)
Substrates1
  • To further broaden the scope of cyclization/coupling strategies towards accessing a broader range of complex molecules, this research program is also testing new enamine and silyl enol ether substrates, as well as exploring linearizable substrates with cleavable tethers. (elsevier.com)
Deprotection1
  • Versatile options enabling orthogonal deprotection for modifications like branching and cyclization. (cem.com)
Sequence1
  • C) Nucleotide alignment of cyclization sequence (D) Nucleotide alignment of upstream AUG region. (cdc.gov)
Stability1
  • Most frequently used cyclization conferring greater stability. (eurogentec.com)
Method1
  • Synthetically, this is the most frequently used peptide cyclization method. (pepscan.com)
Products1
  • Small amounts of six-membered cyclization products such as acridane dimers, phenothiazine, quinoxalines were also found. (unimi.it)
Main2
  • To note, I also had to modify slightly the file main/source/src/basic/options/options_rosetta.py prior to compiling as the routine simple_cycpep_predict routine used to complain (ERROR: Option matching -cyclic_peptide:cyclization_type not found in command line top-level context). (rosettacommons.org)
  • The main problem to be prevented is that of dimerization, but this can be minimized by performing the cyclization under 'high dilution' conditions. (pepscan.com)
Product1
  • To characterize class II cyclization more basic mechanistic enzymology studies are proposed to identify the determinants for catalysis, as well as initial investigations of product specificity. (grantome.com)
Challenge1
  • An important challenge with head-to-tail cyclizations is the fact that the peptide cyclization is often slow due to entropic reasons. (pepscan.com)
Gave2
  • Cyclisation energetics were investigated by DFT computations which gave insights into factors influencing the two cyclisation modes. (st-andrews.ac.uk)
  • and bromination of S)-carvone gave 7-bromo-4,7-dimethyl[2.2.2]bicyclooct-5-en-2-one derivs. (iisc.ac.in)
Paul O'Maille
Paul O'Maille (sri.com)
PDF] Lanthanide(III) Nitrobenzenesulfonates as New Nitration Catalysts: The Role of the Metal and of the Counterion in the...
PDF] Lanthanide(III) Nitrobenzenesulfonates as New Nitration Catalysts: The Role of the Metal and of the Counterion in the... (semanticscholar.org)
All Cyclisation articles | Chemistry World
All Cyclisation articles | Chemistry World (chemistryworld.com)
(researchgate.net)
Stereodivergent total synthesis of rocaglaol initiated by synergistic dual-metal-catalyzed asymmetric allylation of benzofuran...
Stereodivergent total synthesis of rocaglaol initiated by synergistic dual-metal-catalyzed asymmetric allylation of benzofuran... (cell.com)
Synthesis of coumarins via PIDA/I2-mediated oxidative cyclization of substituted phenylacrylic acids - RSC Advances (RSC...
Synthesis of coumarins via PIDA/I2-mediated oxidative cyclization of substituted phenylacrylic acids - RSC Advances (RSC... (pubs.rsc.org)
Journal of Chemical Sciences | Indian Academy of Sciences
Journal of Chemical Sciences | Indian Academy of Sciences (ias.ac.in)
HeteroCycles
HeteroCycles (heterocycles.jp)
Micrometre-long covalent organic fibres by photoinitiated chain-growth radical polymerization on an alkali-halide surface |...
Micrometre-long covalent organic fibres by photoinitiated chain-growth radical polymerization on an alkali-halide surface |... (nature.com)
Liberty Lite 2.0 - Microwave Peptide Synthesizer
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Recombinant Bacteriophage P1 Cre recombinase protein (ab134845) | Abcam
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Domestic cat damage to plant leaves containing iridoids enhances chemical repellency to pests: iScience
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David A. Vosburg Research | Chemistry | Harvey Mudd College
David A. Vosburg Research | Chemistry | Harvey Mudd College (hmc.edu)
Frontiers | Metabolic Profiling of Cannabis Secondary Metabolites for Evaluation of Optimal Postharvest Storage Conditions
Frontiers | Metabolic Profiling of Cannabis Secondary Metabolites for Evaluation of Optimal Postharvest Storage Conditions (frontiersin.org)
Cyclization of 2′-Nitrobiphenyl-2-carboxylic Acids - ScienceOpen
Cyclization of 2′-Nitrobiphenyl-2-carboxylic Acids - ScienceOpen (scienceopen.com)
New Technology to Control the Dispersion of Single-Wall Carbon Nanotubes with Light | NextBigFuture.com
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Publications Since 1929 | Carbohydrates Section | NIDDK
Publications Since 1929 | Carbohydrates Section | NIDDK (niddk.nih.gov)
Tetrahydrofuran (THF) Market Share, Size, Trends - 2017-2022
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BJOC - Authors
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BJOC - A diastereoselective approach to axially chiral biaryls via electrochemically enabled cyclization cascade
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A stereospecific cyclization catalyzed by an antibody<...
A stereospecific cyclization catalyzed by an antibody<... (pennstate.pure.elsevier.com)
Publikationen | Max-Planck-Institut für Polymerforschung
Publikationen | Max-Planck-Institut für Polymerforschung (mpip-mainz.mpg.de)
Family Lab Hall of Fame
Family Lab Hall of Fame (hmc.edu)
Electronic and Atomic Protein Modeling (EAPM) | BSC-CNS
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BJOC - Authors
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Find Research outputs - University of Huddersfield Research Portal
Find Research outputs - University of Huddersfield Research Portal (pure.hud.ac.uk)