BIOTRANSFORMATION OF ALPHA-BETA-UNSATURATED CARBONYL-COMPOUNDS - SULFIDES, SULFOXIDES, SULFONES, NITRILES AND ESTERS BY YEAST SPECIES - CARBONYL GROUP AND CARBON-CARBON DOUBLE-BOND REDUCTION

The reduction of alpha beta-unsaturated ketones with gamma-sulfide, su lfoxide, sulfone, nitrile and ester functions has been investigated. B oth C=O and C=C reduction was observed. In the sulfur series, C=O bond reduction was always observed, but significant C=C bond reduction was observed only with the sulfide. The unsaturated nitriles gave the cor responding alcohol as the major bioreduction product, with smaller but significant amounts of fully reduced product. A similar result was ob tained with the ester substrate. Relative and absolute configurations of bioreduction products were determined, A comparison was made betwee n reductions catalysed by bakers' yeast (Saccharomyces cerevisiae) and by other yeasts (Zygosaccharomyces rouxii, Pichia capsulata, P. farin osa, Candida chalmersi and C. diddensiae). The tendency of Z. rouxii t o give products enantiomeric with those obtained using S. cerevisiae w as noted. The relationship between substrate structure and the stereoc hemistry of C=C double bond reduction is discussed.