503-11-7Relevant articles and documents
Characterization of the enantioselective properties of the quinohemoprotein alcohol dehydrogenase of Acetobacter pasteurianus LMG 1635. 1. Different enantiomeric ratios of whole cells and purified enzyme in the kinetic resolution of racemic glycidol
Machado, Sonia Salgueiro,Wandel, Ute,Jongejan, Jaap A.,Straathof, Adrie J. J.,Duine, Johannis A.
, p. 10 - 20 (1999)
Resting cells of Acetobacter pasteurianus LMG 1635 (ATCC 12874) show appreciable enantioselectivity (E=16-18) in the oxidative kinetic resolution of racemic 2,3-epoxy-1-propanol, glycidol. Distinctly lower values (E=7-9) are observed for the ferricyanide-coupled oxidation of glycidol by the isolated quinohemoprotein alcohol dehydrogenase, QH-ADH, which is responsible for the enantiospecific oxidation step in whole cells. The accuracy of E-values from conversion experiments could be verified using complementary methods for the measurement of enantiomeric ratios. Effects of pH, detergent, the use of artificial electron acceptors, and the presence of intermediate aldehydes, could be accounted for. Measurements of E-values at successive stages of the purification showed that the drop in enantioselectivity correlates with the separation of QH-ADH from the cytoplasmic membrane. It is argued that the native arrangement of QH-ADH in the membrane-associated complex favors the higher E-values. The consequences of these findings for the use of whole cells versus purified enzymes in biocatalytic kinetic resolutions of chiral alcohols are discussed.
Efficient epoxidation of electron-deficient alkenes with hydrogen peroxide catalyzed by [γ-PW10O38V2(μ-OH) 2]3-
Kamata, Keigo,Sugahara, Kosei,Yonehara, Kazuhiro,Ishimoto, Ryo,Mizuno, Noritaka
scheme or table, p. 7549 - 7559 (2011/08/03)
A divanadium-substituted phosphotungstate, [γ-PW10O 38V2(μ-OH)2]3- (I), showed the highest catalytic activity for the H2O2-based epoxidation of allyl acetate among vanadium and tungsten complexes with a turnover number of 210. In the presence of I, various kinds of electron-deficient alkenes with acetate, ether, carbonyl, and chloro groups at the allylic positions could chemoselectively be oxidized to the corresponding epoxides in high yields with only an equimolar amount of H2O2 with respect to the substrates. Even acrylonitrile and methacrylonitrile could be epoxidized without formation of the corresponding amides. In addition, I could rapidly (min) catalyze epoxidation of various kinds of terminal, internal, and cyclic alkenes with H;bsubesubbsubesub& under the stoichiometric conditions. The mechanistic, spectroscopic, and kinetic studies showed that the I-catalyzed epoxidation consists of the following three steps: 1) The reaction of I with H;bsubesubbsubesub& leads to reversible formation of a hydroperoxo species [I;circbsubesubbsubesubbsubesubcirccircbsupesup& (II), 2) the successive dehydration of II forms an active oxygen species with a peroxo group [ 2:2-O2)]3- (III), and 3) III reacts with alkene to form the corresponding epoxide. The kinetic studies showed that the present epoxidation proceeds via III. Catalytic activities of divanadium-substituted polyoxotungstates for epoxidation with H 2O2 were dependent on the different kinds of the heteroatoms (i.e., Si or P) in the catalyst and I was more active than [γ-SiW10O38V2(μ-OH)2] 4-. On the basis of the kinetic, spectroscopic, and computational results, including those of [γ-SiW10O38V 2(μ-OH)2]4-, the acidity of the hydroperoxo species in II would play an important role in the dehydration reactivity (i.e., k3). The largest k3 value of I leads to a significant increase in the catalytic activity of I under the more concentrated conditions. Copyright
Design, synthesis and biological evaluation of glutathione peptidomimetics as components of anti-Parkinson prodrugs
More, Swati S.,Vince, Robert
supporting information; experimental part, p. 4581 - 4588 (2009/06/06)
Plethoras of CNS-active drugs fail to effect their pharmacologic response due to their in vivo inability to cross the blood-brain barrier (BBB). The classical prodrug approach to overcome this frailty involves lipophilic derivatives of the polar drug, but we herein report a novel approach by which endogenous transporters at BBB are exploited for brain drug delivery. The crucial role played by glutathione in pathogenesis of Parkinson's and the presence of its influx transporters at the basolateral membrane of BBB served as the basis for our anti-Parkinson prodrug design strategy. A metabolically stable analogue of glutathione is used as a carrier for delivery of dopamine and adamantamine. An account of successful syntheses of these prodrugs along with their transport characteristics and stability determination is discussed.
