Enzymatic transformations. Part 58: Enantioconvergent biohydrolysis of styrene oxide derivatives catalysed by the Solanum tuberosum epoxide hydrolase

The biohydrolysis of four racemic styrene oxide derivatives has been explored, using the (recombinant) Solanum tuberosum epoxide hydrolase. Interestingly, this enzyme showed a marked tendency to operate a so-called enantioconvergent process, thus affording the corresponding (R)-diol in a nearly quantitative yield and good to excellent ee. We have demonstrated that this is due to the fact that the (S)-enantiomer of these epoxides was preferably attacked at the (benzylic) more substituted carbon atom, whereas the (R)-epoxide was attacked at the (terminal) less substituted carbon atom. The thus obtained meta- and para-chlorostyrene diol derivatives are important building blocks in the synthesis of various biologically active molecules. A nine cycles repeated batch reactor was performed starting from racemic meta-chlorostyrene oxide and afforded a 100% analytical yield (88% preparative) of the corresponding diol, obtained with ees as high as 97%.