Acetylation of racemic cis- and trans-alpha-irols, mediated by porcine pancreatic lipase (PPL) - A new route to (-) and (+)-cis-alpha-irone

The mixture of the four racemic stereoisomers of alpha-irol (5-8) was submi tted to PPL-mediated acetylation; cis-alpha-irol 8b was converted more quic kly than any other diastereoisomer and in enantiopure fashion. By chance, t his latter derivative was the precursor of (-)-cis-alpha-irone, the stereoi somer showing the strongest Orris butter character. Suitable manipulation o f the material left unchanged by PPL provided (+)-cis-alpha-irone. PPL's mo de of transformation of epoxy trans- and cis-alpha-irols was investigated, in order to ascertain the effect of chemical structure on the discriminatin g properties of this enzyme.