Highly Selective and Asymmetric Reductive Biotransformation of ^|^alpha;-Ionone by Epicoccum purpurascens

The biotransformation of terpenoid C13 norisoprenoid (±)-α-ionone (1) using the plant pathogenic fungus Epicoccum purpurascens as a biocatalyst was investigated for the production of useful novel organic compounds. There are no reported biotransformations using E. purpurascens. The biotransformation of compound 1 via reduction of the C-9 ketone position yielded α-ionol (2) as the major metabolic product. Reduction of the racemic α-ionone [(-)-(6S)- and (+)-(6R)-] resulted in the exclusive formation of the two enantiomers (-)-(6S,9R)- and (+)-(6R,9S)-α-ionol (2). Thus, the enzymatic reduction of α-ionone by E. purpurascens proceeds with high asymmetry.