MICROBIOLOGICAL TRANSFORMATIONS .33. FUNGAL EPOXIDE HYDROLASES APPLIED TO THE SYNTHESIS OF ENANTIOPURE PARASUBSTITUTED STYRENE OXIDES - A MECHANISTIC APPROACH

The biohydrolysis of differently para-substituted styrene oxide deriva tives was studied, using whole cells of the fungi Aspergillus niger or Beauveria sulfurescens. These microorganisms proved to be equipped wi th epoxide hydrolases which are able to achieve these hydrolyses with high enantioselectivity. This allowed the preparation of the optically active epoxides and of the corresponding vicinal diols which were obt ained with good to excellent enantiomeric purity. These two microorgan isms proved to be enantiocomplementary. A mechanistic study, carried o ut using a crude lyophilized enzymatic extract from A. niger, indicate d via Hammet coefficient plotting that this hydrolysis is very probabl y due to a general base-catalyzed process.