Enantioselective synthesis of alkyl-branched alkanes.: Synthesis of the stereoisomers of 7,11-dimethylheptadecane and 7-methylheptadecane, components of the pheromone of Lambdina species

The stereoisomers of 7,11-dimethylheptadecane and 7-methylheptadecane have been synthesized. The key step used has been the intramolecular hydride transfer from a secondary gamma -benzyloxy group with defined absolute stereochemistry to a cation generated by Lewis acid treatment of the suitable tertiary Co-2(CO)(6)-complexed propargylic alcohol. The application of this method provided stereochemically defined alpha -alkyl-gamma -hydroxy-acetylenes that after hydrogenation and further reductive elimination of the hydroxyl group yielded sec-alkyl hydrocarbons.