BIOTRANSFORMATION OF ORGANIC SULFIDES .5. FORMATION OF CHIRAL PARA-ALKYL BENZYL METHYL SULFOXIDES BY HELMINTHOSPORIUM SPECIES NRRL-4671

The fungus Helminthosporium species NRRL. 4671 has been used for the biotransformation of a series of para-alkylbenzyl sulfides with alkyl groups consisting of methyl, ethyl, n.propyl, isopropyl, n.butyl, and t.butyl. For the majority of substrates, sulfoxide formation occurred in moderate yield and with predominant (S) chirality at sulfur; lesser amounts of sulfone product were also obtained. For substrates with alkyl groups other than methyl, hydroxylation of the alkyl substituent at the terminal carbon atom was also observed. The latter reaction was investigated by the use of isopropylbenzene, t.butylbenzene, and (+/-) pal a n.butylbenzyl methyl sulfoxide as substrates. The data so obtained suggest that, during biotransformation of pma-alkyl benzyl methyl sulfides by Helminthosporium, S-oxidation precedes carbon hydroxylation.