Synthesis of the insect pheromone (2S,3S,7RS)-diprionyl acetate by diastereoselective protonation

The insect pheromone (2S,3S,7RS)-diprionyl acetate (1) was prepared from (S ,S)-2,3-dimethylcyclohexanone (2), which in turn was obtained by the 1,4-ad dition of lithium dimethyl-cuprate to (S)-(+)-carvone (3) and diastereosele ctive protonation of the resulting enolate with phenyl salicylate, followed by removal of the isopropenyl group and hydrogenation. Baeyer-Villiger rea rrangement of (S,S)-2 and opening of the lactone (S,S)-8 with octyllithium provided the hydroxy ketone (S,S)-9, which was transformed into the target molecule (2S,3S,7RS)-1 by carbonyl olefination with Petasis' reagent, acyla tion and hydrogenation.