Polymer-Supported m-Hydrobenzoin-Derived Chiral Auxiliary

Significance

m-Hydrobenzoin-derived chiral auxiliary immobilized on a solid support was used in the diastereoselective addition of organozinc reagents to α-keto esters. Reaction of the Wang resin supported chiral m-hydrobenzoin auxiliary 1 with phenylglyoxylic acid or pyruvic acid in the presence of diisopropylcarbodiimide (DIC) and 4-(N,N-dimethylamino)pyridine (DMAP) gave the polymer-supported α-keto ester 2 (eq. 1). The addition of alkyl- and arylzinc halides to α-keto esters 2 afforded polymer-supported α-hydroxy esters 3 (eq. 2). Saponification of α-hydroxy esters 3 gave α-hydroxy carboxylic acids 4 in 50-95% yield with 30-90% ee (eq. 3). The polymer-supported chiral auxiliary 1 was reused two times.