Stereo-complementary two-step cascades using a two-enzyme system leading to enantiopure epoxides

A novel one-pot, two-step, two-enzyme cascade is described. Pro-chiral alpha-chloro ketones are stereoselectively reduced to the corresponding halohydrins as an intermediate by a biocatalytic hydrogen transfer process. The intermediate is transformed to the corresponding epoxide by a non-enantioselective halohydrin dehalogenase. Thus, by combining a Prelog- or anti-Prelog alcohol dehydrogenase with a non-selective halohydrin dehalogenase, enantiopure (R)- as well as (S)-epoxides were obtained.