Asymmetric reactions of α-ketoacid-derived hemiacetals: Stereoselective synthesis of α-hydroxy acids

Article abstract of DOI:10.1016/S0040-4020(98)00914-4

N-Acylation of prolinol with α-ketoacid chlorides results in concomitant hemiacetalization of the α-keto amide by the prolinol hydroxyl group. (R) or (S) α-hydroxy acids are obtained with good enantiomeric excess by stereodivergent reduction of these hemiacetals. Reaction with Grignard reagents at ambient temperature furnishes (R) α-alkyl mandelic acids with good stereoselectivity.