Enantiospecific and regioselective rhodium-catalyzed allylic alkylation: Diastereoselective approach to quaternary carbon stereogenic centers

[GRAPHICS] The enantiospecific and regioselective rhodium-catalyzed allylic alkylation of a series of chiral nonracemic allylic carbonates, followed by ozonolysis and reductive lactonization, provides a convenient route to optically active gamma-lactones, Sequential alkylation and reductive alkylation furnished the alpha-quaternary-beta-ternary substituted gamma-lactone derivative as a greater than or equal to 10:1 mixture of diastereoisomers.