Lewis Acids
Scandium
Cyclization
Stereoisomerism
Acetals
Imines
Cycloaddition Reaction
Boranes
Catalysis
Alkenes
Lewis Blood-Group System
Acids
Ketones
Molecular Structure
Rhodium
Ionic Liquids
Carcinoma, Lewis Lung
Indicators and Reagents
Silanes
Combinatorial Chemistry Techniques
Ion pair receptors. (1/35)
(+info)A straightforward route to functionalized trans-Diels-Alder motifs. (2/35)
(+info)Efficient Lewis acid ionic liquid-catalyzed synthesis of the key intermediate of coenzyme Q10 under microwave irradiation. (3/35)
(+info)Development of atom-economical catalytic asymmetric reactions under proton transfer conditions: construction of tetrasubstituted stereogenic centers and their application to therapeutics. (4/35)
The development of atom-economical catalytic asymmetric reactions based on two distinct sets of catalyst, a rare earth metal/amide-based ligand catalyst and a soft Lewis acid/hard Bronsted base catalyst, is reviewed. These catalytic systems exhibit high catalytic activity and stereoselectivity by harnessing a cooperative catalysis through hydrogen bond/metal coordination and soft-soft interactions/hard-hard interactions, respectively. The effectiveness of these cooperative catalysts is clearly delineated by the high stereoselectivity in reactions with highly coordinative substrates, and the specific activation of otherwise low-reactive pronucleophiles under proton transfer conditions. The rare earth metal/amide-based ligand catalyst was successfully applied to catalytic asymmetric aminations, nitroaldol (Henry) reactions, Mannich-type reactions, and conjugate addition reactions, generating stereogenic tetrasubstituted centers. Catalytic asymmetric amination and anti-selective catalytic asymmetric nitroaldol reactions were successfully applied to the efficient enantioselective synthesis of therapeutic candidates, such as AS-3201 and the beta(3)-adrenoreceptor agonist, showcasing the practical utility of the present protocols. The soft Lewis acid/hard Bronsted base cooperative catalyst was specifically developed for the chemoselective activation of soft Lewis basic allylic cyanides and thioamides, which are otherwise low-reactive pronucleophiles. The cooperative action of the catalyst allowed for efficient catalytic generation of active carbon nucleophiles in situ, which were integrated into subsequent enantioselective additions to carbonyl-type electrophiles. (+info)NHC-catalyzed/titanium(IV)-mediated highly diastereo- and enantioselective dimerization of enals. (5/35)
(+info)From bifunctional to trifunctional (tricomponent nucleophile-transition metal-lewis acid) catalysis: the catalytic, enantioselective alpha-fluorination of acid chlorides. (6/35)
(+info)Solvent enhancement of reaction selectivity: a unique property of cationic chiral dirhodium carboxamidates. (7/35)
(+info)Lewis acid-catalyzed propargylic etherification and sulfanylation from alcohols in MeNO(2)-H(2)O. (8/35)
Direct scandium- and lanthanum-catalyzed etherifications of propargyl alcohols 1 and 6 in MeNO(2)-H(2)O provided propargyl ethers 3, 4 and 7 in high yields. In addition, reactions of 1 and 6 with thiols exclusively yielded the corresponding propargyl sulfides. (+info)I'm sorry for any confusion, but "Lewis acids" is actually a term from the field of chemistry rather than medicine. It was named after Gilbert N. Lewis, who proposed the concept in 1923. A Lewis acid is defined as an electron-pair acceptor in a chemical reaction. In simpler terms, it's a molecule or ion that can accept a pair of electrons from another molecule or ion to form a covalent bond. Common examples of Lewis acids include aluminum chloride (AlCl3), boron trifluoride (BF3), and iron(III) chloride (FeCl3).
I'm sorry for any confusion, but "Scandium" is not a medical term. It is a chemical element with the symbol Sc and atomic number 21. It is a silvery-white metal that is soft, workable, and highly resistant to corrosion. In medicine, scandium and its compounds are not used in therapy or diagnosis.
Cyclization is a chemical process that involves forming a cyclic structure or ring-shaped molecule from a linear or open-chain compound. In the context of medicinal chemistry and drug design, cyclization reactions are often used to synthesize complex molecules, including drugs, by creating rings or fused ring systems within the molecule's structure.
Cyclization can occur through various mechanisms, such as intramolecular nucleophilic substitution, electrophilic addition, or radical reactions. The resulting cyclized compounds may exhibit different chemical and biological properties compared to their linear precursors, making them valuable targets for drug discovery and development.
In some cases, the cyclization process can lead to the formation of stereocenters within the molecule, which can impact its three-dimensional shape and how it interacts with biological targets. Therefore, controlling the stereochemistry during cyclization reactions is crucial in medicinal chemistry to optimize the desired biological activity.
Overall, cyclization plays a significant role in the design and synthesis of many pharmaceutical compounds, enabling the creation of complex structures that can interact specifically with biological targets for therapeutic purposes.
Chloranil is the common name for 2,3,5,6-tetrachloro-1,4-benzoquinone, which is an organic compound with the formula C6Cl4O2. It is a light yellow to orange crystalline powder that is slightly soluble in water and more soluble in organic solvents.
Chloranil is used as a chemical intermediate in the synthesis of other organic compounds, including dyes and pigments. It is also used as a catalyst in some chemical reactions and has been studied for its potential use as a bactericide or fungicide.
Like many other halogenated aromatic compounds, chloranil can be harmful if swallowed, inhaled, or contacted on the skin. It can cause irritation to the eyes, skin, and respiratory tract, and prolonged exposure may lead to more serious health effects. Therefore, it is important to handle chloranil with care and follow appropriate safety precautions when working with this compound.
Stereoisomerism is a type of isomerism (structural arrangement of atoms) in which molecules have the same molecular formula and sequence of bonded atoms, but differ in the three-dimensional orientation of their atoms in space. This occurs when the molecule contains asymmetric carbon atoms or other rigid structures that prevent free rotation, leading to distinct spatial arrangements of groups of atoms around a central point. Stereoisomers can have different chemical and physical properties, such as optical activity, boiling points, and reactivities, due to differences in their shape and the way they interact with other molecules.
There are two main types of stereoisomerism: enantiomers (mirror-image isomers) and diastereomers (non-mirror-image isomers). Enantiomers are pairs of stereoisomers that are mirror images of each other, but cannot be superimposed on one another. Diastereomers, on the other hand, are non-mirror-image stereoisomers that have different physical and chemical properties.
Stereoisomerism is an important concept in chemistry and biology, as it can affect the biological activity of molecules, such as drugs and natural products. For example, some enantiomers of a drug may be active, while others are inactive or even toxic. Therefore, understanding stereoisomerism is crucial for designing and synthesizing effective and safe drugs.
An acetal is a chemical compound that contains two ether functional groups (-O-) bonded to two carbon atoms, which in turn are bonded to two other carbon atoms forming a six-membered ring. Acetals are formed by the reaction of an aldehyde with two equivalents of an alcohol under acid catalysis, followed by removal of water. They are stable compounds that do not easily hydrolyze back to their starting materials, making them useful in various chemical and industrial applications. In the context of organic chemistry, acetals are a subclass of hemiacetals, which contain only one ether functional group bonded to a carbon atom that is also bonded to another oxygen-containing group.
In the field of organic chemistry, imines are a class of compounds that contain a functional group with the general structure =CR-NR', where C=R and R' can be either alkyl or aryl groups. Imines are also commonly referred to as Schiff bases. They are formed by the condensation of an aldehyde or ketone with a primary amine, resulting in the loss of a molecule of water.
It is important to note that imines do not have a direct medical application, but they can be used as intermediates in the synthesis of various pharmaceuticals and bioactive compounds. Additionally, some imines have been found to exhibit biological activity, such as antimicrobial or anticancer properties. However, these are areas of ongoing research and development.
A cycloaddition reaction is a type of chemical reaction involving the formation of one or more rings through the coupling of two unsaturated molecules. This process typically involves the simultaneous formation of new sigma bonds, resulting in the creation of a cyclic structure. Cycloaddition reactions are classified based on the number of atoms involved in each component molecule and the number of sigma bonds formed during the reaction. For example, a [2+2] cycloaddition involves two unsaturated molecules, each containing two atoms involved in the reaction, resulting in the formation of a four-membered ring. These reactions play a significant role in organic synthesis and are widely used to construct complex molecular architectures in various fields, including pharmaceuticals, agrochemicals, and materials science.
Boranes are a group of chemical compounds that contain only boron and hydrogen. The most well-known borane is BH3, also known as diborane. These compounds are highly reactive and have unusual structures, with the boron atoms bonded to each other in three-center, two-electron bonds. Boranes are used in research and industrial applications, including as reducing agents and catalysts. They are highly flammable and toxic, so they must be handled with care.
Catalysis is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst, which remains unchanged at the end of the reaction. A catalyst lowers the activation energy required for the reaction to occur, thereby allowing the reaction to proceed more quickly and efficiently. This can be particularly important in biological systems, where enzymes act as catalysts to speed up metabolic reactions that are essential for life.
Alkenes are unsaturated hydrocarbons that contain at least one carbon-carbon double bond in their molecular structure. The general chemical formula for alkenes is CnH2n, where n represents the number of carbon atoms in the molecule.
The double bond in alkenes can undergo various reactions, such as addition reactions, where different types of molecules can add across the double bond to form new compounds. The relative position of the double bond in the carbon chain and the presence of substituents on the carbon atoms can affect the physical and chemical properties of alkenes.
Alkenes are important industrial chemicals and are used as starting materials for the synthesis of a wide range of products, including plastics, resins, fibers, and other chemicals. They are also found in nature, occurring in some plants and animals, and can be produced by certain types of bacteria through fermentation processes.
The Lewis blood-group system is one of the human blood group systems, which is based on the presence or absence of two antigens: Lea and Leb. These antigens are carbohydrate structures that can be found on the surface of red blood cells (RBCs) as well as other cells and in various body fluids.
The Lewis system is unique because its antigens are not normally present at birth, but instead develop during early childhood or later in life due to the action of certain enzymes in the digestive tract. The production of Lea and Leb antigens depends on the activity of two genes, FUT3 (also known as Lewis gene) and FUT2 (also known as Secretor gene).
There are four main phenotypes or blood types in the Lewis system:
1. Le(a+b-): This is the most common phenotype, where individuals have both Lea and Leb antigens on their RBCs.
2. Le(a-b+): In this phenotype, individuals lack the Lea antigen but have the Leb antigen on their RBCs.
3. Le(a-b-): This is a rare phenotype where neither Lea nor Leb antigens are present on the RBCs.
4. Le(a+b+): In this phenotype, individuals have both Lea and Leb antigens on their RBCs due to the simultaneous expression of FUT3 and FUT2 genes.
The Lewis blood-group system is not typically associated with transfusion reactions or hemolytic diseases, unlike other blood group systems such as ABO and Rh. However, the presence or absence of Lewis antigens can still have implications for certain medical conditions and tests, including:
* Infectious diseases: Some bacteria and viruses can use the Lewis antigens as receptors to attach to and infect host cells. For example, Helicobacter pylori, which causes gastritis and peptic ulcers, binds to Lea antigens in the stomach.
* Autoimmune disorders: In some cases, autoantibodies against Lewis antigens have been found in patients with autoimmune diseases such as rheumatoid arthritis and systemic lupus erythematosus (SLE).
* Pregnancy: The Lewis antigens can be expressed on the surface of placental cells, and changes in their expression have been linked to pregnancy complications such as preeclampsia and fetal growth restriction.
* Blood typing: Although not a primary factor in blood transfusion compatibility, the Lewis blood-group system is still considered when determining the best match for patients who require frequent transfusions or organ transplants.
In medical terms, acids refer to a class of chemicals that have a pH less than 7 and can donate protons (hydrogen ions) in chemical reactions. In the context of human health, acids are an important part of various bodily functions, such as digestion. However, an imbalance in acid levels can lead to medical conditions. For example, an excess of hydrochloric acid in the stomach can cause gastritis or peptic ulcers, while an accumulation of lactic acid due to strenuous exercise or decreased blood flow can lead to muscle fatigue and pain.
Additionally, in clinical laboratory tests, certain substances may be tested for their "acidity" or "alkalinity," which is measured using a pH scale. This information can help diagnose various medical conditions, such as kidney disease or diabetes.
Ketones are organic compounds that contain a carbon atom bound to two oxygen atoms and a central carbon atom bonded to two additional carbon groups through single bonds. In the context of human physiology, ketones are primarily produced as byproducts when the body breaks down fat for energy in a process called ketosis.
Specifically, under conditions of low carbohydrate availability or prolonged fasting, the liver converts fatty acids into ketone bodies, which can then be used as an alternative fuel source for the brain and other organs. The three main types of ketones produced in the human body are acetoacetate, beta-hydroxybutyrate, and acetone.
Elevated levels of ketones in the blood, known as ketonemia, can occur in various medical conditions such as diabetes, starvation, alcoholism, and high-fat/low-carbohydrate diets. While moderate levels of ketosis are generally considered safe, severe ketosis can lead to a life-threatening condition called diabetic ketoacidosis (DKA) in people with diabetes.
Molecular structure, in the context of biochemistry and molecular biology, refers to the arrangement and organization of atoms and chemical bonds within a molecule. It describes the three-dimensional layout of the constituent elements, including their spatial relationships, bond lengths, and angles. Understanding molecular structure is crucial for elucidating the functions and reactivities of biological macromolecules such as proteins, nucleic acids, lipids, and carbohydrates. Various experimental techniques, like X-ray crystallography, nuclear magnetic resonance (NMR) spectroscopy, and cryo-electron microscopy (cryo-EM), are employed to determine molecular structures at atomic resolution, providing valuable insights into their biological roles and potential therapeutic targets.
I'm sorry for any confusion, but "Rhodium" is not a medical term. It is a chemical element with the symbol Rh and atomic number 45. It is a rare, silvery-white, hard, corrosion-resistant, and chemically inert transition metal. It is found in small quantities in platinum or nickel ores along with some other rare metals.
It's primarily used in industrial applications, such as being a key component in catalytic converters in automobiles, which helps to reduce harmful emissions. It's also used in jewelry, electronics, and scientific instruments due to its properties of resistance to corrosion and heat.
If you have any medical terms or concepts that you would like me to explain, please let me know!
Ionic liquids are not a medical term, but rather a term used in the field of chemistry and physics. They refer to salts that exist in the liquid state at temperatures below 100 degrees Celsius. Ionic liquids are composed entirely of ions and have unique properties such as low volatility, high thermal stability, and good conductivity, making them useful in various applications including chemical reactions, energy storage, and biomedical devices. However, they do not have a direct relation to medical definitions or healthcare.
Aldehydes are a class of organic compounds characterized by the presence of a functional group consisting of a carbon atom bonded to a hydrogen atom and a double bonded oxygen atom, also known as a formyl or aldehyde group. The general chemical structure of an aldehyde is R-CHO, where R represents a hydrocarbon chain.
Aldehydes are important in biochemistry and medicine as they are involved in various metabolic processes and are found in many biological molecules. For example, glucose is converted to pyruvate through a series of reactions that involve aldehyde intermediates. Additionally, some aldehydes have been identified as toxicants or environmental pollutants, such as formaldehyde, which is a known carcinogen and respiratory irritant.
Formaldehyde is also commonly used in medical and laboratory settings for its disinfectant properties and as a fixative for tissue samples. However, exposure to high levels of formaldehyde can be harmful to human health, causing symptoms such as coughing, wheezing, and irritation of the eyes, nose, and throat. Therefore, appropriate safety measures must be taken when handling aldehydes in medical and laboratory settings.
"Carcinoma, Lewis lung" is a term used to describe a specific type of lung cancer that was first discovered in strain C57BL/6J mice by Dr. Margaret R. Lewis in 1951. It is a spontaneously occurring undifferentiated carcinoma that originates from the lung epithelium and is highly invasive and metastatic, making it a popular model for studying cancer biology and testing potential therapies.
The Lewis lung carcinoma (LLC) cells are typically characterized by their rapid growth rate, ability to form tumors when implanted into syngeneic mice, and high levels of vascular endothelial growth factor (VEGF), which promotes angiogenesis and tumor growth.
It is important to note that while the LLC model has been useful for studying certain aspects of lung cancer, it may not fully recapitulate the complexity and heterogeneity of human lung cancers. Therefore, findings from LLC studies should be validated in more clinically relevant models before being translated into human therapies.
Indicators and reagents are terms commonly used in the field of clinical chemistry and laboratory medicine. Here are their definitions:
1. Indicator: An indicator is a substance that changes its color or other physical properties in response to a chemical change, such as a change in pH, oxidation-reduction potential, or the presence of a particular ion or molecule. Indicators are often used in laboratory tests to monitor or signal the progress of a reaction or to indicate the end point of a titration. A familiar example is the use of phenolphthalein as a pH indicator in acid-base titrations, which turns pink in basic solutions and colorless in acidic solutions.
2. Reagent: A reagent is a substance that is added to a system (such as a sample or a reaction mixture) to bring about a chemical reaction, test for the presence or absence of a particular component, or measure the concentration of a specific analyte. Reagents are typically chemicals with well-defined and consistent properties, allowing them to be used reliably in analytical procedures. Examples of reagents include enzymes, antibodies, dyes, metal ions, and organic compounds. In laboratory settings, reagents are often prepared and standardized according to strict protocols to ensure their quality and performance in diagnostic tests and research applications.
Silanes are a group of chemical compounds that contain silicon and hydrogen. The general formula for silanes is Si_xH_(2x+2), where x is a positive integer. Silanes are named after their parent compound, silane (SiH4), which contains one silicon atom and four hydrogen atoms.
Silanes are colorless and highly flammable gases at room temperature. They are typically prepared by the reaction of metal silicides with acids or by the reduction of halogenated silanes. Silanes have a variety of industrial applications, including as intermediates in the production of silicon-based materials such as semiconductors and polymers.
In medical contexts, silanes are not typically used directly. However, some silane-containing compounds have been investigated for their potential therapeutic uses. For example, some organosilanes have been shown to have antimicrobial properties and may be useful as disinfectants or in the development of medical devices. Other silane-containing materials have been studied for their potential use in drug delivery systems or as imaging agents in diagnostic procedures.
It is important to note that some silanes can be hazardous if not handled properly, and they should only be used by trained professionals in a controlled environment. Exposure to silanes can cause irritation to the eyes, skin, and respiratory tract, and prolonged exposure can lead to more serious health effects.
Combinatorial chemistry techniques are a group of methods used in the field of chemistry to synthesize and optimize large libraries of chemical compounds in a rapid and efficient manner. These techniques involve the systematic combination of different building blocks, or reagents, in various arrangements to generate a diverse array of molecules. This approach allows chemists to quickly explore a wide chemical space and identify potential lead compounds for drug discovery, materials science, and other applications.
There are several common combinatorial chemistry techniques, including:
1. **Split-Pool Synthesis:** In this method, a large collection of starting materials is divided into smaller groups, and each group undergoes a series of chemical reactions with different reagents. The resulting products from each group are then pooled together and redistributed for additional rounds of reactions. This process creates a vast number of unique compounds through the iterative combination of building blocks.
2. **Parallel Synthesis:** In parallel synthesis, multiple reactions are carried out simultaneously in separate reaction vessels. Each vessel contains a distinct set of starting materials and reagents, allowing for the efficient generation of a series of related compounds. This method is particularly useful when exploring structure-activity relationships (SAR) or optimizing lead compounds.
3. **Encoded Libraries:** To facilitate the rapid identification of active compounds within large libraries, encoded library techniques incorporate unique tags or barcodes into each molecule. These tags allow for the simultaneous synthesis and screening of compounds, as the identity of an active compound can be determined by decoding its corresponding tag.
4. **DNA-Encoded Libraries (DELs):** DELs are a specific type of encoded library that uses DNA molecules to encode and track chemical compounds. In this approach, each unique compound is linked to a distinct DNA sequence, enabling the rapid identification of active compounds through DNA sequencing techniques.
5. **Solid-Phase Synthesis:** This technique involves the attachment of starting materials to a solid support, such as beads or resins, allowing for the stepwise addition of reagents and building blocks. The solid support facilitates easy separation, purification, and screening of compounds, making it an ideal method for combinatorial chemistry applications.
Combinatorial chemistry techniques have revolutionized drug discovery and development by enabling the rapid synthesis, screening, and optimization of large libraries of chemical compounds. These methods continue to play a crucial role in modern medicinal chemistry and materials science research.
I'm happy to help! "Rats, Inbred Lew" is a specific strain of laboratory rats that have been inbred for research purposes. The "Lew" part of the name refers to the location where they were first developed, the Lewis Institute in Lake Bluff, Illinois, USA.
Inbreeding is a process of mating closely related individuals over many generations to create a genetically homogeneous population. This results in a high degree of genetic similarity among members of the strain, making them ideal for use as experimental models because any differences observed between individuals are more likely to be due to the experimental manipulation rather than genetic variation.
Inbred Lew rats have been widely used in biomedical research, particularly in studies related to hypertension and cardiovascular disease. They exhibit a number of unique characteristics that make them useful for these types of studies, including their susceptibility to developing high blood pressure when fed a high-salt diet or given certain drugs.
It's important to note that while inbred strains like Lew rats can be very useful tools for researchers, they are not perfect models for human disease. Because they have been bred in a controlled environment and selected for specific traits, they may not respond to experimental manipulations in the same way that humans or other animals would. Therefore, it's important to interpret findings from these studies with caution and consider multiple lines of evidence before drawing any firm conclusions.