Chiral homoenolate of methyl isobutyrate prepared in a few steps from optically active methyl A-hydroxy isobutyrate reacts with carbon electrophiles to give chiral o(-methyl esters.
Approaches to asymmetric synthesis employing "chiral building blocks" play important roles in the preparation of chiral molecules.' In the passed few years, we have addressed ourselves to this problem by exploring routes to a chiral homoenolate such as 1, which should find great synthetic utility, if it could at all be prepared in high optical purity, and its chirality maintained during the subsequent C-C bond forming reactions. A potential problem in dealing with such a homoenolate stems from the well-documented equilibrium between the primary (1) and the secondary anionic isomers (3) via cyclopropanolate 2 (eq 1),2 since the secondary anionic center is known to have marginal configurational stability,3 and consequently 1 might racemize via 3. We now report the first example of an optically active homoenolate by describing that a prototypical species (1: R' = Me, R2 = OMe) complexed with Zn(I1) remains optically active for an extended period, and reacts with various carbon electrophiles to give chiral M-methyl alkanoates.