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

We report the enantioselective synthesis of the ambergris odorants (+)-(S)--ionone, (+)-(S)--dihydroionone, (-)--ambrinol, (+)-(S)--coronal, (-)-(S)--homocyclogeranyl chloride and (+)-(S)--homocyclogeraniol. At first, the enantio-enriched (4R,6S)-4-acetoxy--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)--dihydroionone which was used as the starting material for the synthesis of the aforementioned odorants.