BAKERS-YEAST REDUCTION OF ARYLIDENECYCLOALKANONES

The baker's yeast reduction of arylidene cycloalkanones 5, 6 and 7 occurs initially through the catalysis of different enzymes to give the saturation of the double bond leading to the saturated ketones 9, 15 and 22 and the carbonyl reduction to the (S) allylic alcohols 8a, 14 and 23, possessing 0.99, 0.85 and 0.66 ee, respectively. The latter act as inhibitors for the carbonyl reducing enzyme thus preventing the further reduction of the saturated ketone. These compounds in the absence of allylic alcohols are further reduced to a mixture of diastereomeric saturated (S) alcohols of high-moderate enantiomeric purity. Reduction experiments in D2O indicate that saturation of the double bond of 5 occurs by beta re face addition of hydrogen, as shown by the obtainment of 10'.