An expedient preparation of enantio-enriched ambergris odorants starting from commercial ionone alpha

We report the enantioselective synthesis of the ambergris odorants (+)-(S)-gamma-ionone, (+)-(S)-gamma-dihydroionone, (-)-alpha-ambrinol, (+)-(S)-gamma-coronal, (-)-(S)-gamma-homocyclogeranyl chloride and (+)-(S)-gamma-homocyclogeraniol. At first, the enantio-enriched (4R,6S)-4-acetoxy-g-ionone was prepared starting from commercial racemic ionone alpha by means of a chemo-enzymatic process. This chiral building block was then converted into (S)-gamma-dihydroionone which was used as the starting material for the synthesis of the aforementioned odorants. Copyright (C) 2012 John Wiley & Sons, Ltd.