Enantiocontrolled synthesis of trialkyl-substituted stereogenic carbons.: A general route to cis-3,5-dialkyl γ-lactones

[GRAPHICS] Lewis acid treatment of tertiary Co-2(CO)(6)-propargylic alcohols having a stereochemically defined benzyloxy group at the gamma-benzyl position yielded after cobalt demetalation sec-dialkyl bishomopropargylic alcohols in good yields. The reaction is highly stereoselective and predictable, providing pure stereoisomers. The use of benzyl-alpha,alpha'-d(2) ethers permitted the stereoselective d-labeling of methines and methylenes, Very simple chemical manipulations provided a general methodology to obtain the enantiomers of 3,5-dialkyl-gamma-lactones.