The Experts below are selected from a list of 243 Experts worldwide ranked by ideXlab platform
C A G M Weijers - One of the best experts on this subject based on the ideXlab platform.
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Enantioselectivities of yeast Epoxide hydrolases for 1,2-Epoxides
Tetrahedron-asymmetry, 1999Co-Authors: Adriana Leonora Botes, C A G M Weijers, Piet J. Botes, Martie S. Van DykAbstract:Abstract Kinetic resolution of homologous series of unbranched 1,2-epoxyalkanes (C-4 to C-12), 1,2-epoxyalkenes (C-4, C-6 and C-8), a 2,2-dialkylsubstituted Epoxide (2-methyl-1,2-epoxyheptane) and a benzyloxy-substituted Epoxide (benzyl glycidyl ether) was investigated using resting cells of 10 different yeast strains. Biocatalysts with excellent enantioselectivity (E>100) and high initial reaction rates (>300 nmol/min/mg dry weight) were found for the 2-monosubstituted aliphatic Epoxides C-6 to C-8. Yeast strains belonging to the genera Rhodotorula , Rhodosporidium and Trichosporon all preferentially hydrolyzed ( R )-1,2-Epoxides with retention of configuration. The Epoxide hydrolases of all the yeast strains are membrane-associated.
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enantioselective hydrolysis of unbranched aliphatic 1 2 Epoxides by rhodotorula glutinis
Tetrahedron-asymmetry, 1998Co-Authors: C A G M Weijers, Adriana Leonora Botes, Jan A. M. BontAbstract:Abstract Epoxide hydrolase catalysed resolution of aliphatic terminal Epoxides has been demonstrated for the hydrolysis of a homologous range of unbranched 1,2-epoxyalkanes by the yeast Rhodotorula glutinis . Both enantioselectivity and reaction rate were strongly influenced by the chain length of the Epoxide used. Enantioselectivity showed an optimum in the hydrolysis of 1,2-epoxyhexane (E=84). Resolution of (±)-1,2-epoxyhexane resulted in ( S )-1,2-epoxyhexane (e.e.>98%, yield=48%) and ( R )-1,2-hexanediol (e.e.=83%, yield=47%).
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enantioselective hydrolysis of aryl alicyclic and aliphatic Epoxides by rhodotorula glutinis
Tetrahedron-asymmetry, 1997Co-Authors: C A G M WeijersAbstract:Abstract Enantioselective Epoxide hydrolysis by yeasts has been demonstrated for the hydrolysis of several aryl, alicyclic and aliphatic Epoxides by a strain of Rhodotorula glutinis. High enantioselectivity was obtained in the hydrolysis of methyl substituted arylryl and aliphatic Epoxides whereas selectivity towards terminal Epoxides in all cases was lower. Homochiral vicinal diols were formed from several methyl substituted Epoxides and also from meso Epoxides. Kinetic resolution of trans-1-phenyl-1,2-epoxypropane was studied in more detail.
John E. Casida - One of the best experts on this subject based on the ideXlab platform.
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1 3 dichloropropene Epoxides intermediates in bioactivation of the promutagen 1 3 dichloropropene
Chemical Research in Toxicology, 1998Co-Authors: Manfred Schneider, Gary B Quistad, John E. CasidaAbstract:1,3-Dichloropropene (1,3-D), a major soil fumigant nematicide, is genotoxic in many types of assays, leading to its classification as possibly carcinogenic in humans. This study tests in three steps the hypothesis that 1,3-D is a promutagen activated by epoxidation and further reaction of the 1,3-D-Epoxides. Stereospecific epoxidation of 1,3-D (examined as the cis/trans mixture and as individual isomers) to the corresponding cis- and trans-1,3-D-Epoxides is demonstrated here for the first time, both in vitro in a mouse liver microsome−NADPH system and in vivo in the liver of ip-treated mice, using GC/MS for product identification and quantitation. The cis Epoxide is observed in higher yield than the trans Epoxide, both in vitro and in vivo, and the cis isomer also reacts slower than the trans isomer with GSH alone or catalyzed by GSH S-transferase. cis- and trans-1,3-D-Epoxides are stable in acetone or chloroform but degrade completely in Me2SO exclusively to 2-chloroacrolein (30 min at 40 °C). Epoxide de...
Jan A. M. Bont - One of the best experts on this subject based on the ideXlab platform.
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enantioselective hydrolysis of unbranched aliphatic 1 2 Epoxides by rhodotorula glutinis
Tetrahedron-asymmetry, 1998Co-Authors: C A G M Weijers, Adriana Leonora Botes, Jan A. M. BontAbstract:Abstract Epoxide hydrolase catalysed resolution of aliphatic terminal Epoxides has been demonstrated for the hydrolysis of a homologous range of unbranched 1,2-epoxyalkanes by the yeast Rhodotorula glutinis . Both enantioselectivity and reaction rate were strongly influenced by the chain length of the Epoxide used. Enantioselectivity showed an optimum in the hydrolysis of 1,2-epoxyhexane (E=84). Resolution of (±)-1,2-epoxyhexane resulted in ( S )-1,2-epoxyhexane (e.e.>98%, yield=48%) and ( R )-1,2-hexanediol (e.e.=83%, yield=47%).
Manfred Schneider - One of the best experts on this subject based on the ideXlab platform.
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1 3 dichloropropene Epoxides intermediates in bioactivation of the promutagen 1 3 dichloropropene
Chemical Research in Toxicology, 1998Co-Authors: Manfred Schneider, Gary B Quistad, John E. CasidaAbstract:1,3-Dichloropropene (1,3-D), a major soil fumigant nematicide, is genotoxic in many types of assays, leading to its classification as possibly carcinogenic in humans. This study tests in three steps the hypothesis that 1,3-D is a promutagen activated by epoxidation and further reaction of the 1,3-D-Epoxides. Stereospecific epoxidation of 1,3-D (examined as the cis/trans mixture and as individual isomers) to the corresponding cis- and trans-1,3-D-Epoxides is demonstrated here for the first time, both in vitro in a mouse liver microsome−NADPH system and in vivo in the liver of ip-treated mice, using GC/MS for product identification and quantitation. The cis Epoxide is observed in higher yield than the trans Epoxide, both in vitro and in vivo, and the cis isomer also reacts slower than the trans isomer with GSH alone or catalyzed by GSH S-transferase. cis- and trans-1,3-D-Epoxides are stable in acetone or chloroform but degrade completely in Me2SO exclusively to 2-chloroacrolein (30 min at 40 °C). Epoxide de...
Craig W Byrdwell - One of the best experts on this subject based on the ideXlab platform.
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characterization of model triacylglycerol triolein trilinolein and trilinolenin autoxidation products via high performance liquid chromatography coupled with atmospheric pressure chemical ionization mass spectrometry
Journal of Chromatography A, 1998Co-Authors: W. E. Neff, Craig W ByrdwellAbstract:Abstract Oxidation products from the autoxidation of three triacylglycerol standards have been analyzed using reversed-phase high-performance liquid chromatography (RP-HPLC) coupled to mass spectrometry via an atmospheric pressure chemical ionization (APCI) source. Triolein, trilinolein and trilinolenin were autoxidized in the dark at 50–60°C until the oxidation products represented approximately 30% of the starting material. These oxidation product mixtures were then analyzed using RP-HPLC–APCI-MS. Several classes of oxidation products were directly detected and identified. Monohydroperoxides were present in the largest amounts in the oxidation products mixtures. The hydroperoxides were found to provide several structurally useful fragments: Epoxide intermediates were formed which then underwent further fragmentation, and other fragments were formed from concerted loss of the hydroperoxide group to form a site of unsaturation. Fragments formed by intra-annular cleavage of Epoxide intermediates allowed identification of several hydroperoxide isomers. Bishydroperoxides were observed which underwent similar fragmentation pathways. Mono- and diEpoxides were also formed by the autoxidation reaction. Two classes of Epoxides were observed: those in which an Epoxide formed in place of an existing double bond, and those in which an Epoxide formed away from a double bond. Two distinct fragmentation mechanisms were observed for Epoxides which were not formed across a double bond. Other oxidation products which were observed included hydroxy trilinolenin, epidioxy trilinolenin and hydroperoxy, epidioxy trilinolenin.
