Biocatalytic oxidation of sec-alcohols via hydrogen transfer

The oxidations of alcohols via hydrogen transfer represents an environmental benign ‘green’ redox protocol. In this context biocatalytic hydrogen transfer employing the alcohol dehydrogenase ADH-‘A’ from Rhodococcus ruber DSM 44541 results in oxidation of sec-alcohols in aqueous medium at room temperature. High concentrations of the hydrogen acceptor (acetone, up to 50% v/v) are tolerated by the enzyme. Examples for the enantio-, and regioselective oxidation of sec-alcohols employing ADH-‘A’ in the wild type strain as well as over-expressed ADH-‘A’ in E. coli are given.

Employing acetone as hydrogen acceptor various sec-alcohols can be oxidized to the corresponding ketone in an asymmetric fashion. The enzyme exhibits exclusive regioselectivity for secondary alcohols, primary alcohols remain untouched. This protocol does not only provide a simple ‘green’ oxidation method for organic synthesis at ambient conditions, but also allows the preparation of ketones, which are labeled ‘natural’ for flavor and fragrance applications. Figure optionsDownload as PowerPoint slide