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M W Anders - One of the best experts on this subject based on the ideXlab platform.

  • cysteine conjugate beta lyase dependent biotransformation of the cysteine s conjugates of the sevoflurane degradation Product 2 fluoromethoxy 1 1 3 3 3 pentafluoro 1 propene compound a
    Chemical Research in Toxicology, 1997
    Co-Authors: Ramaswamy A Iyer, M W Anders
    Abstract:

    2-(Fluoromethoxy)-1,1,3,3,3-pentafluoro-1-propene (1, Compound A) is a fluoroalkene formed by the base-catalyzed degradation of sevoflurane that is nephrotoxic in rats. Fluoroalkene 1 is a structural analog of other nephrotoxic haloalkenes that undergo glutathione S-conjugate formation and cysteine S-conjugate beta-lyase-dependent bioactivation to reactive intermediates. The present experiments were designed to study the beta-lyase-dependent biotransformation of S-[2-(fluoromethoxy)-1,1,3,3,3-pentafluoropropyl]-L-cysteine (4) and S-[2-(fluoromethoxy)-1,3,3,3-tetrafluoro-1-propenyl]-L-cysteine (5) by 19F NMR and UV spectroscopy and GC/MS. Incubation of cysteine S-conjugate 4 with rat kidney cytosol or a pyridoxal model system showed the formation of inorganic fluoride, pyruvate, and 2-(fluoromethoxy)-3,3,3-trifluoropropanoic Acid (9), the expected Products of a beta-lyase-catalyzed reaction. The ratio of fluoride to pyruvate ranged from 2.3 to 2.5. The amount of Acid 9 formed in the rat kidney cytosol and the pyridoxal model system was, however, less than 5% of the amount of pyruvate formed. Incubation of conjugate 4 with rat kidney cytosol and analysis by 19F NMR spectroscopy showed resonances that were assigned to 3,3,3-trifluorolactic Acid (10); the formation of Acid 10 was observed in the pyridoxal model only after prolonged incubation (> 18 h). Lactic Acid 10 was identified as a degradation Product of Acid 9. Cysteine S-conjugate 5 was not stable in pH 7.4 buffer and underwent a rapid cyclisation reaction (t1/2 approximately 5 min) to form 2-[1-(fluoromethoxy)-2,2,2-trifluoroethyl]-4,5-dihydro-1,3-thiazol e-4 -carboxylic Acid (14). These data show that fluoroalkene 1-derived cysteine S-conjugates are substrates for renal beta-lyase and that Acid 9 is formed as a terminal Product. Acid 9 is, however, unstable and affords lactic Acid 10 as a degradation Product.

Ramaswamy A Iyer - One of the best experts on this subject based on the ideXlab platform.

  • cysteine conjugate beta lyase dependent biotransformation of the cysteine s conjugates of the sevoflurane degradation Product 2 fluoromethoxy 1 1 3 3 3 pentafluoro 1 propene compound a
    Chemical Research in Toxicology, 1997
    Co-Authors: Ramaswamy A Iyer, M W Anders
    Abstract:

    2-(Fluoromethoxy)-1,1,3,3,3-pentafluoro-1-propene (1, Compound A) is a fluoroalkene formed by the base-catalyzed degradation of sevoflurane that is nephrotoxic in rats. Fluoroalkene 1 is a structural analog of other nephrotoxic haloalkenes that undergo glutathione S-conjugate formation and cysteine S-conjugate beta-lyase-dependent bioactivation to reactive intermediates. The present experiments were designed to study the beta-lyase-dependent biotransformation of S-[2-(fluoromethoxy)-1,1,3,3,3-pentafluoropropyl]-L-cysteine (4) and S-[2-(fluoromethoxy)-1,3,3,3-tetrafluoro-1-propenyl]-L-cysteine (5) by 19F NMR and UV spectroscopy and GC/MS. Incubation of cysteine S-conjugate 4 with rat kidney cytosol or a pyridoxal model system showed the formation of inorganic fluoride, pyruvate, and 2-(fluoromethoxy)-3,3,3-trifluoropropanoic Acid (9), the expected Products of a beta-lyase-catalyzed reaction. The ratio of fluoride to pyruvate ranged from 2.3 to 2.5. The amount of Acid 9 formed in the rat kidney cytosol and the pyridoxal model system was, however, less than 5% of the amount of pyruvate formed. Incubation of conjugate 4 with rat kidney cytosol and analysis by 19F NMR spectroscopy showed resonances that were assigned to 3,3,3-trifluorolactic Acid (10); the formation of Acid 10 was observed in the pyridoxal model only after prolonged incubation (> 18 h). Lactic Acid 10 was identified as a degradation Product of Acid 9. Cysteine S-conjugate 5 was not stable in pH 7.4 buffer and underwent a rapid cyclisation reaction (t1/2 approximately 5 min) to form 2-[1-(fluoromethoxy)-2,2,2-trifluoroethyl]-4,5-dihydro-1,3-thiazol e-4 -carboxylic Acid (14). These data show that fluoroalkene 1-derived cysteine S-conjugates are substrates for renal beta-lyase and that Acid 9 is formed as a terminal Product. Acid 9 is, however, unstable and affords lactic Acid 10 as a degradation Product.

Toshio Okuhara - One of the best experts on this subject based on the ideXlab platform.

  • alkylation of 1 3 5 trimethylbenzene with γ butyrolactone over heteropolyAcid catalysts
    Applied Catalysis A-general, 2003
    Co-Authors: Jianxin Mao, Yuichi Kamiya, Toshio Okuhara
    Abstract:

    Abstract A Friedel–Crafts-type reaction of 1,3,5-trimethylbenzene with γ-butyrolactone was conducted over various solid Acid catalysts such as zeolites, polymer resins, and heteropolyAcids. The alkylation to 4-(2,4,6-trimethylphenyl) butyric Acid proceeded exclusively with these catalysts; no acylation to the ketone occurred. The heteropolyAcids, such as H3PW12O40 and H4SiW12O40, were superior in activity to the other catalysts; they also accelerated the reaction of the Product Acid with γ-butyrolactone to the corresponding carboxylic Acid. When the heteropolyAcids were supported on silica, alkylation proceeded efficiently with high mass balance, suppressing further reaction. The reusability of the supported heteropolyAcids also was confirmed.

Jianxin Mao - One of the best experts on this subject based on the ideXlab platform.

  • alkylation of 1 3 5 trimethylbenzene with γ butyrolactone over heteropolyAcid catalysts
    Applied Catalysis A-general, 2003
    Co-Authors: Jianxin Mao, Yuichi Kamiya, Toshio Okuhara
    Abstract:

    Abstract A Friedel–Crafts-type reaction of 1,3,5-trimethylbenzene with γ-butyrolactone was conducted over various solid Acid catalysts such as zeolites, polymer resins, and heteropolyAcids. The alkylation to 4-(2,4,6-trimethylphenyl) butyric Acid proceeded exclusively with these catalysts; no acylation to the ketone occurred. The heteropolyAcids, such as H3PW12O40 and H4SiW12O40, were superior in activity to the other catalysts; they also accelerated the reaction of the Product Acid with γ-butyrolactone to the corresponding carboxylic Acid. When the heteropolyAcids were supported on silica, alkylation proceeded efficiently with high mass balance, suppressing further reaction. The reusability of the supported heteropolyAcids also was confirmed.

Yuichi Kamiya - One of the best experts on this subject based on the ideXlab platform.

  • alkylation of 1 3 5 trimethylbenzene with γ butyrolactone over heteropolyAcid catalysts
    Applied Catalysis A-general, 2003
    Co-Authors: Jianxin Mao, Yuichi Kamiya, Toshio Okuhara
    Abstract:

    Abstract A Friedel–Crafts-type reaction of 1,3,5-trimethylbenzene with γ-butyrolactone was conducted over various solid Acid catalysts such as zeolites, polymer resins, and heteropolyAcids. The alkylation to 4-(2,4,6-trimethylphenyl) butyric Acid proceeded exclusively with these catalysts; no acylation to the ketone occurred. The heteropolyAcids, such as H3PW12O40 and H4SiW12O40, were superior in activity to the other catalysts; they also accelerated the reaction of the Product Acid with γ-butyrolactone to the corresponding carboxylic Acid. When the heteropolyAcids were supported on silica, alkylation proceeded efficiently with high mass balance, suppressing further reaction. The reusability of the supported heteropolyAcids also was confirmed.