Stereochemical aspects of flavour biogeneration through baker's yeast mediated reduction of carbonyl-activated double bonds

The baker's yeast mediated reduction of the unsaturated carbonyl compounds (4) under bar, (5) under bar and (6) under bar has been studied in the context of the generation of the natural forms of the flavour materials (1) under bar, (2) under bar and (3) under bar. The stereochemical aspects of these processes and of those regarding the reduction of the structurally related enones <(18)under bar>, <(19)under bar>, <(30)under bar>, <(31)under bar> and ($) under bar have been elucidated also by means of deuterium labeling experiments.