- Oxidation of maleic acid by tetraethylammonium chlorochromate in an aquo-acetic acid medium- A kinetic and mechanistic study
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The oxidation of maleic acid by tetraethylammonium chlorochromate (TEACC) was studied, in the presence of perchloric acid and in acetic acid-water mixtures (50 % v/v). The reaction is first order with respect to maleic acid, tetraethylammonium chlorochromate and acid. Ionic strength changes have no significant effect on the reactivity. The reaction does not induce polymerization of acrylonitrile. The reaction rates were determined at different temperatures and the activation parameters were computed. The reaction rate increased with increasing amount of acetic acid in the mixture. A suitable mechanism consistent with the observed kinetic results has been proposed.
- Awasthi, Anupam,Tomer, Ashish,Singh
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experimental part
p. 431 - 433
(2011/11/14)
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- EPOXY-CONTAINING POLY(ESTER AMIDES) AND METHODS OF USE
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The invention provides aliphatic epoxy-containing PEA polymer compositions with film-forming properties. The aliphatic epoxy di-acids used in the invention PEA compositions include non-toxic fatty aliphatic epoxy homologs. A second, C-protected L-lysine-based monomer can be introduced into the polymer to provide additional chain flexibility. The invention PEA polymer compositions are useful for delivery of bioactive agents when administered internally or used in the manufacture of implantable medical devices. Biodegradable hydrogels can be made using the invention epoxy-containing PEAs.
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Page/Page column 45
(2010/11/30)
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- Design, Synthesis, and Evaluation of Aza-Peptide Epoxides as Selective and Potent Inhibitors of Caspases-1, -3, -6, and -8
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Aza-peptide epoxides, a novel class of irreversible protease inhibitors, are specific for the clan CD cysteine proteases. Aza-peptide epoxides with an aza-Asp residue at P1 are excellent irreversible inhibitors of caspases-1, -3, -6, and -8 with second-order inhibition rates up to 1 910 000 M-1 s-1. In general, the order of reactivity of aza-peptide epoxides is S,S > R,R > trans > cis. Interestingly, some of the R,R epoxides while being less potent are actually more selective than the S,S epoxides. Our aza-peptide epoxides designed for caspases are stable, potent, and specific inhibitors, as they show little to no inhibition of other proteases such as the aspartyl proteases porcine pepsin, human cathepsin D, plasmepsin 2 from P. falciparum, HIV-1 protease, and the secreted aspartic proteinase 2 (SAP-2) from Candida albicans; the serine proteases granzyme B and α-chymotrypsin; and the cysteine proteases cathepsin B and papain (clan CA), and legumain (clan CD).
- James, Karen Ellis,Asgian, Juliana L.,Li, Zhao Zhao,Ekici, ?zlem Do?an,Rubin, John R.,Mikolajczyk, Jowita,Salvesen, Guy S.,Powers, James C.
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p. 1553 - 1574
(2007/10/03)
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- Kinetics and mechanism of the oxidation of some unsaturated acids by quinolinium bromochromate
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The oxidation of maleic, fumaric, crotonic and cinnamic acids by quinolinium bromochromate (QBC) in dimethylsulphoxide (DMSO) leads to the formation of corresponding epoxide. The reaction is of first order with respect to QBC and the acid. The reaction is catalysed by hydrogen ions. The hydrogen-ion dependence has the form: kobs = a + b [H+]. The oxidation of these acids was studied in nineteen different organic solvents. The solvent effect was analyzed by Kamlet's and Swain's multiparametric equations. Solvent effect indicated the importance of the cation-solvating power of the solvent. A mechanism involving a three-centre transition state has been postulated.
- Vyas, Shweta,Sharma, Pradeep K.
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p. 820 - 823
(2007/10/03)
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- Configuration and enantioselective synthesis of the fungal metabolite WF14861
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A short enantioselective synthesis of the cathepsine inhibitor WF14861 (1) from the funghi Colletotrichum sp. as well as of its diasteroisomer 21 is presented. Comparison of the NMR data of the final products and, in particular, of the [α]D values of the intermediates allowed the confirmation of the formerly proposed structure 1. In addition, the so far unknown absolute configuration of all three stereogenic centres of WF14861 could be established by this synthesis.
- Detterbeck, Richard,Hesse, Manfred
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p. 222 - 232
(2007/10/03)
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- Aza-peptide epoxides: A new class of inhibitors selective for clan CD cysteine proteases
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Aza-peptide epoxides, a new class of irreversible protease inhibitors, are specific for the clan CD cysteine proteases. The inhibitors have second-order rate constants up to 105 M-1 s-1, with the most potent epoxides having the S,S stereochemistry. The aza-Asn derivatives are effective legumain inhibitors, while the aza-Asp epoxides were specific for caspases. The inhibitors have little or no inhibition with other proteases such as chymotrypsin, papain, or cathepsin B.
- Asgian, Juliana L.,James, Karen Ellis,Li, Zhao Zhao,Carter, Wendy,Barrett, Alan J.,Mikolajczyk, Jowita,Salvesen, Guy S.,Powers, James C.
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p. 4958 - 4960
(2007/10/03)
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- A stereocontrolled approach to electrophilic epoxides
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Lithium t-butyl hydroperoxide (easily generated by addition of an alkyl-lithium to anhydrous t-butyl hydroperoxide in THF solution) is a powerful reagent for the epoxidation of electrophilic alkenes at -20 to 0 °C under full stereocontrol. Thus αβ-unsaturated esters, sulphones, sulphoximines, and amides are readily epoxidised with complete regio- and stereo-specificity and with considerable chiroselectivity (20-100%) when appropriate chiral auxiliaries such as menthyl, 8-phenylmenthyl, or a camphor-sulphonamide derivative are used. Asymmetric αβ-unsaturated sulphoximines undergo epoxidation with 100% diastereoselectivity. The only exceptions to stereocontrol noted are heavily substituted maleate esters such as di-t-butyl maleate. The αβ-epoxy amides are shown to be valuable sources of the corresponding epoxy ketones by treatment with an organolithium, allowing a stereo- and chemoselective entry in high yield to these useful intermediates.
- Meth-Cohn, Otto,Moore, Clive,Taljaard, Heinrich C.
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p. 2663 - 2674
(2007/10/02)
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- SYNTHESIS OF A NEW CARBAPENEM WITH A 6-METHYL HYDROXYACETATE SIDE CHAIN
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The synthesis of the 2-(4-pyridinylthio)-carbapen-2-em-3-carboxylic acid 1b, bearing a 6-methyl hydroxyacetate side chain, is decribed.
- Haebich, Dieter,Hartwig, Wolfgang
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p. 781 - 784
(2007/10/02)
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- Process for preparing CIS-epoxysuccinic acid salts of high purity
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High purity cis-epoxysuccinic acid and salts thereof are economically and systematically prepared by contacting an aqueous solution, obtained by reacting a maleic acid salt and hydrogen peroxide in the presence of a tungstate or molybdate catalyst under a specified condition, with a strongly basic Type II anion exchange resin.
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