Biotransformation of organic sulfides. Part 11. Preparation of functionalised phenyl propyl sulfoxides using Helminthosporium species and Mortierellaisabellina

Para-substituted phenyl 3-chloropropyl and phenyl 3-hydroxypropyl sulfides have been oxidised to the corresponding (R)-sulfoxides by biotransformation with Mortierella isabellina ATCC 42613, and to the (S)-sulfoxides by biotr ansformation with Helminthosporium species NRRL 4671 or Acinetobacter calco aceticus NCIMB 9871. The stereoselectivity of these oxidations was consiste nt with that predicted by examination of previously published models for su lfoxidation by these biocatalysts. In several cases ((R)- and (S)-p-cyanoph enyl 3-chloropropyl sulfoxide, (S)-p-cyanophenyl 3-hydroxypropyl sulfoxide, and (R)-p-methoxyphenyl 3-chloropropyl sulfoxide) enantiopure materials we re obtained by crystallisation of the biotransformation products. The latte r are valuable chiral starting materials for the synthesis of analogues of the cardiovascular agent verapamil.