STEREOSELECTIVITY OF ENZYMATIC AND CHEMICAL OXYGENATION OF SULFUR-ATOMS IN 2-METHYL-1,3-BENZODITHIOLE

S-Monooxygenation of 2-methyl-1,3-benzodithiole, to yield cis- and trans-2-methyl-1,3-benzodithiole 1-oxide, has been studied as a new stereochemical probe using achiral and chiral chemical oxidants and enzymes from microbial and animal sources. Chemical oxidants showed a preference for trans S-oxide formation, and this preference was enhanced in the presence of a chiral matrix. The ability of pure enzymes to stereodifferentiate between geminal lone pairs on a prochiral sulfur atom, or geminal sulfur atoms on a prochiral carbon atom, has been observed. Thus, intact fungal and bacterial oxidations showed a marked selectivity (87-96%) for formation of the cis S-oxide isomers. In addition, highly purified hog liver and rabbit lung flavin-containing monooxygenases showed a marked preference for formation of the cis S-oxide and the pro-R sulfur atom. Other monooxygenase-catalyzed sulfoxidations of 2-methyl-1,3-benzodithiole, including cytochrome P-450 2B1 (P450PB-B), showed a markedly lower stereoselectivity.