Synthesis of Enantiomerically Pure (−)-Wine Lactone Based on a Palladium-Catalyzed Enantioselective Allylic Substitution

The first enantioselective synthesis of enantiomerically pure (−)-wine lactone, (−)-1a, a fragrance constituent of various white wines, and its epimer (+)-1b, was carried out. The key steps are allylic substitution of (±)-2-cyclohexen-1-yl acetate (2) with dimethylmalonate using palladium complexes of phosphanyldihydrooxazol L1 or of the phosphanylcarboxylic acid L2 as catalyst, subsequent decarboxylation, iodolactonization and elimination, furnishing enantiomerically pure bicyclic lactone (+)-7 in 47% overall yield. The diastereoselective introduction of methyl groups by SN2′-type substitution with an organocopper compound and by enolate alkylation gave lactone (−)-1a in 43% overall yield from (+)-7.