We describe a lethal poisoning in a healthy woman caused by deliberate ingestion of aluminium phosphide (AlP), a pesticide used to kill rodents and insects. Toxicity of AlP and review of cases reported to the National Poisons Information Service (London) 1997-2003 are discussed. (+info)
Synthesis of transient and stable C-amino phosphorus ylides and their fragmentation into transient and stable carbenes.
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Only basic phosphines, such as tris(dimethylamino)phosphine, allow for the synthesis of a stable acyclic beta-amino phosphonium salt 1c, which upon deprotonation with butyllithium affords the corresponding stable C-amino phosphorus ylide 2c. In contrast, cyclic beta-amino phosphonium salts 5a and 5b are stable despite the presence of weakly basic triarylphosphine fragments. They are prepared by intramolecular insertion of the carbene center of (amino)(phosphonio)carbenes into the CH bond of a phosphorus substituent. Deprotonation of 5a leads to the corresponding cyclic C-amino phosphorus ylide 6a, which has been fully characterized including an X-ray diffraction study. Deprotonation of 5b affords enamine 8, probably via fragmentation of ylide 6b into transient carbene 7b and a subsequent 1,2-hydrogen shift. Transient cyclic C-amino phosphorus ylides 6c and 6d have been prepared by intramolecular addition of a carbanion generated by deprotonation of a phosphorus substituent. Three-membered heterocycle 6c rearranges into alkene 9, whereas the four-membered ring system undergoes a ring opening affording the stable carbene 7d. The latter results pave the route for the synthesis of various mixed carbene-phosphine bidentate ligands. (+info)
Palladium-catalyzed chemo- and enantioselective oxidation of allylic esters and carbonates.
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The palladium-catalyzed oxidation of allylic esters and carbonates using a novel potassium nitronate has been developed. This method is highly chemoselective, leaving other esters, alcohols, thioethers, and amines undisturbed. The oxidation can be operated in two modes: an achiral mode, using either PPh3 or rac-2 as ligand, or a chiral and highly enantioselective mode, using 2 as ligand. The oxidative enantioselective desymmetrization of meso bis-esters provides a significantly shorter method to arrive at commonly used synthetic intermediates compared to other strategies. Highly efficient kinetic resolution is also possible using this methodology. (+info)
A novel ternary ligand system useful for preparation of cationic (99m)Tc-diazenido complexes and (99m)Tc-labeling of small biomolecules.
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This report describes a novel ternary ligand system composed of a phenylhydrazine, a crown ether-containing dithiocarbamate (DTC), and a PNP-type bisphosphine (PNP). The combination of three different ligands with (99m)Tc results in cationic (99m)Tc-diazenido complexes, [(99m)Tc(NNAr)(DTC)(PNP)]+, with potential radiopharmaceuticals for heart imaging. Synthesis of cationic (99m)Tc-diazenido complexes can be accomplished in two steps. For example, the reaction of phenylhydrazine with (99m)TcO4- at 100 degrees C in the presence of excess stannous chloride and 1,2-diaminopropane-N,N,N',N'-tetraacetic acid (PDTA) results in the [(99m)Tc(NNPh)(PDTA)n] intermediate, which then reacts with sodium N-(dithiocarbamato)-2-aminomethyl-15-Crown-5 (L4) and N,N-bis[2-(bis(3-ethoxypropyl)phosphino)ethyl]ethoxyethylamine (PNP6) at 100 degrees C for 15 min to give the complex, [(99m)Tc(NNPh)(L4)(PNP6)]+ in high yield (>90%). Cationic complexes [(99m)Tc(NNPh)(DTC)(PNP)]+ are stable for > or = 6 h. Their composition was determined to be 1:1:1:1 for Tc:NNPh:DTC:PNP using the mixed-ligand experiments on the tracer ((99m)Tc) level and was further confirmed by the ESI-MS spectral data of a model compound [Re(NNPh)(L4)(L6)]+. It was found that both DTCs and bisphosphines have a significant impact on the lipophilicity of their cationic (99m)Tc-diazenido complexes. Results from a (99m)Tc-labeling efficiency experiment showed that 4-hydrazinobenzoic acid (HYBA) might be useful as a bifunctional coupling agent for (99m)Tc-labeling of small biomolecules. However, the (99m)Tc-labeling efficiency of HYBA is much lower than that of 6-hydrazinonicotinic acid (HYNIC) with tricine and trisodium triphenylphosphine-3,3',3''-trisulfonate (TPPTS) as coligands. (+info)
Characterization of the terminal iron(IV) imides [[PhBP(t)(Bu)2(pz')]Fe(IV)NAd]+.
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New hybrid bis(phosphine)(pyrazole)borate tripodal ligands ([PhBPtBu2(pz')]-) are reported that support pseudotetrahedral iron in the oxidation states +1, +2, +3, and +4. The higher oxidation states are stabilized by a terminal FeNR linkage. Of particular interest is the generation and thorough characterization of an S = 1 FeIVNR+ imide cation using this new ligand system. The latter species can be observed electrochemically and spectroscopically, and its solid-state crystal structure is reported. (+info)
Analysis of fumigants and fumigant residues.
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The terms fumigant and fumigant residue are defined. Interrelationships between physically and chemically bound residues, storage environments, nature of the substrate and other influencing factors are outlined. Analytical methods include polarography by DME and RPE, titrimetry, spectrophotometry, and GC with microthermal conductivity, hydrogen flame ionization, electron capture, microcoulometric, thermionic, and flame photometric detector systems, with backup by enzymatic, radiometric, NAA and X-ray flourescence methods. Various aspects are illustrated with different fumigants used commercially. Supplementary methods to extend the power and usefulness of analytical methods in fumigant research are indicated. (+info)
Simple and rapid determination of hydrogen peroxide using phosphine-based fluorescent reagents with sodium tungstate dihydrate.
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A simple batch method for the fluorometric determination of hydrogen peroxide using phosphine-based fluorescent reagents has been developed. A rapid, mild and selective derivatization reaction was achieved by adding sodium tungstate dihydrate to the reaction mixture of hydrogen peroxide and a phosphine-based fluorescent reagent. When 4-diphenylphosphino-7-methylthio-2,1,3-benzoxadiazole was used as a reagent, the derivatization reaction was completed after 2 min at room temperature. The calibration curve was linear between 12.5 and 500 ng hydrogen peroxide in a 10 microL sample solution. This method is accurate and has potential for on-line applications. (+info)
Amide H/2H exchange reveals a mechanism of thrombin activation.
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Thrombin is a dual action serine protease in the blood clotting cascade. Similar to other clotting factors, thrombin is mainly present in the blood in a zymogen form, prothrombin. Although the two cleavage events required to activate thrombin are well-known, little is known about why the thrombin precursors are inactive proteases. Although prothrombin is much larger than thrombin, prethrombin-2, which contains all of the same amino acids as thrombin, but has not yet been cleaved between Arg320 and Ile321, remains inactive. Crystal structures of both prethrombin-2 and thrombin are available and show almost no differences in the active site conformations. Slight differences were, however, seen in the loops surrounding the active site, which are larger in thrombin than in most other trypsin-like proteases, and have been shown to be important for substrate specificity. To explore whether the dynamics of the active site loops were different in the various zymogen forms of thrombin, we employed amide H/(2)H exchange experiments to compare the exchange rates of regions of thrombin with the same regions of prothrombin, prethrombin-2, and meizothrombin. Many of the surface loops showed less exchange in the zymogen forms, including the large loop corresponding to anion binding exosite 1. Conversely, the autolysis loop and sodium-binding site exchanged more readily in the zymogen forms. Prothrombin and prethrombin-2 gave nearly identical results while meizothrombin in some regions more closely resembled active thrombin. Thus, cleavage of the Arg320-Ile321 peptide bond is the key to formation of the active enzyme, which involves increased dynamics of the substrate-binding loops and decreased dynamics of the catalytic site. (+info)