Synthesis of both enantiomers of cis-α-irone and cis-γ-irone, principal constituents of iris oil, via resolution of (±)-2,2,4-trimethyl-3-cyclohexene-1-carboxylic acid

The principal constituents of iris oil, (-)-cis-α-irone and (-)-cis-γ-irone, and their enantiomers, were synthesized from (-)- and (+)-2,2,4-trimethyl-3-cyclohexene-1-carboxylic acids. The racemic acid was resolved by recrystallization of its salt with a chiral amine, or by enzymatic hydrolysis of the corresponding alcohol. The fragrances of (-)-(1R,5S)-cis-α-irone and (-)-(1R,5S)-cis-γ-irone were superior to those of (+)-(1S,5R)-cis-α-irone and (+)-(1S,5R)-cis-γ-irone. Copyright (C) 2000 Elsevier Science Ltd.