Biotransformation of Organic Sulfides. Part 11. Preparation of Functionalised Phenyl Propyl Sulfoxides UsingHelminthosporiumSpecies andMortierella Isabellina

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 biotransformation with Helminthosporium species NRRL 4671 or Acinetobacter calcoaceticus NCIMB 9871. The stereoselectivity of these oxidations was consistent with that predicted by examination of previously published models for sulfoxidation by these biocatalysts. In several cases ((R)- and (S)-p-cyanophenyl 3-chloropropyl sulfoxide, (S)-p-cyanophenyl 3-hydroxypropyl sulfoxide, and (R)-p-methoxyphenyl 3-chloropropyl sulfoxide) enantiopure materials were obtained by crystallisation of the biotransformation products. The latter are valuable chiral starting materials for the synthesis of analogues of the cardiovascular agent verapamil.