ENANTIOSELECTIVITY IN SYNTHESIS AND ALKYLATION OF HIGHLY SUBSTITUTED GAMMA-LACTONES - SEMIEMPIRICAL MODEL

The enantioselective synthesis of some gamma-lactones by an intramolec ular Michael type addition on alpha,beta-unsaturated esters is rationa lized by the relative thermodynamic stabilities of the possible final products, examined by semi-empirical methods. The structure of the alp ha-anion obtained by basic treatment permits the remarkable diastereos election shown by the alkylation to be understood. Free anions and che lated ones with metal sparkles or a lithium cation (MNDO) are analyzed as well as the possible solvent effects.