环氧化物生物催化转化的研究进展

Progress in Biocatalytic Conversion of Epoxides

环氧化物是合成手性目标产物的高价值中间体。环氧化物生物催化转化包括环氧化物水解酶催化的动力学拆分和对映会聚的酶水解,前者可生成相应二醇和剩余的手性底物,后者可从外消旋混合物中得到高产率的单一对映体。而用选择性的阴离子亲核试剂,卤醇脱卤酶则催化环氧化物非水解型对映选择性开环。这些酶的催化机理包括天门冬氨酸羧酸酯作为亲核试剂的共价催化和酪氨酸作为广义酸碱试剂的非共价催化。本文介绍了环氧化物生物催化转化中的新进展。

Epoxides were attractive intermediates for producing chiral compounds. Important biocatalytic reactions involving epoxides included epoxide hydrolase mediated kinetic resolution, leading to the formation of diols and enantiopure remaining substrates, and enantioconvergent enzymatic hydrolysis, which given high yields of a single enantiomer from racemic mixtures. Epoxides could also be converted by nonhydrolytic enantioselective ring opening, using alternative anionic nucleophiles; these reactions could be catalyzed by haloalcohol dehalogenases. The differences in scope of these enzymatic conversions were related to their different catalytic mechanisms, which involved, respectively, covalent catalysis with an aspartate carboxylate as the nucleophile and non-covalent catalysis with a tyrosine that acted as a general acidbase. The emerging new possibility for enantioselective biocatalytic conversion of epoxides suggested that their importance in green chemistry would grow.