DERACEMIZATION OF (+ -)-2,3-DISUBSTITUTED OXIRANES VIA BIOCATALYTIC HYDROLYSIS USING EPOXIDE HYDROLASES - KINETICS OF AN ENANTIOCONVERGENT PROCESS/

Asymmetric biocatalytic hydrolysis of (+/-)-2,3-disubstituted oxiranes leading to the formation of vicinal diols in up to 97% ee at 100% con version was accomplished by using the epoxide hydrolase activity of va rious bacterial strains. The mechanism of this deracemization was eluc idated by (OH2)-O-18-labelling experiments using a partially purified epoxide hydrolase from Nocardia EH1. The reaction was shown to proceed in an enantioconvergent fashion by attack of OH- at the (S)-configure d oxirane carbon atom with concomitant inversion of configuration, A m athematical model developed for the description of the kinetics was ve rified by the determination of the four relative rate constants govern ing the regio-and enantio-selectivity of the process.