(Scheme 3). The latter compounds were used as starting materials to prepare the 3,4-didehydro-γ-ionones (+)- and (−)-6 and the 3,4-didehydro-7,8-dihydro-γ-ionones (+)- and (−)-7 in enantiomer-enriched form. The absoluteconfiguration of (+)-12b was determine by chemical correlation with (+)-(6S)-γ-ionone ((+)-3) and with (−)-(6S)-α-ionone ((−)-1) therefore allowing to assign the (S)-configuration to (+)-6