Biotransformation of αβ-unsaturated carbonyl compounds: sulfides, sulfoxides, sulfones, nitriles and esters by yeast species: carbonyl group and carbon–carbon double bond reduction

The reduction of αβ-unsaturated ketones with γ-sulfide, sulfoxide, sulfone, nitrile and ester functions has been investigated. Both CO and CC reduction was observed. In the sulfur series, CO bond reduction was always observed, but significant CC bond reduction was observed only with the sulfide. The unsaturated nitriles gave the corresponding alcohol as the major bioreduction product, with smaller but significant amounts of fully reduced product. A similar result was obtained with the ester substrate. Relative and absolute configurations of bioreduction products were determined. A comparison was made between reductions catalysed by bakers' yeast (Saccharomyces cerevisiae) and by other yeasts (Zygosaccharomyces rouxii, Pichia capsulata, P. farinosa, Candida chalmersi and C. diddensiae). The tendency of Z. rouxii to give products enantiomeric with those obtained using S. cerevisiae was noted. The relationship between substrate structure and the stereochemistry of CC double bond reduction is discussed.