Biotransformation of organic sulfides - Part. 10. Formation of chiral ortho- and meta-substituted benzyl methyl sulfoxides by biotransformation usingHelminthosporium species NRRL 4671

Benzyl methyl sulfides substituted with methyl, chloro, cyano, bromo, metho xy, nitro and amino groups in the ortho or meta positions of the aromatic r ing have been converted to (S) sulfoxides by biotransformation using the fu ngal biocatalyst Helminthosporium species NRRL 4671. The enantiomeric exces ses for meta-substituted examples were high in those cases where the substi tuent was of a polar nature, and comparable to those observed for the corre sponding para-substituted substrates. With one exception (o-amino), the ort ho-substituted examples gave sulfoxides of lower enantiomeric purity. The r ole of a suitably located polar substituent on an aryl ring of the substrat e in ensuring a high enantiomeric excess in sulfoxidation by Helminthospori um species has been confirmed by the biotransformations of 4-(methylthiomet hyl)benzyl alcohol and 2-(4-nitrophenyl) ethyl methyl sulfide, which give s ulfoxides of much higher optical purity than those obtained from the corres ponding unsubstituted substrates. (C) 1999 Elsevier Science B.V. All rights reserved.