observed that diastereoselectivity in an addition reaction to chiral 2-acyl oxazolidine, derived from (S)-prolinol, can be fully regulated under appropriate conditions. Addition of organotitanium triisopropoxides provided (S)-tertiary alcohols, while organolithium reagents afforded the corresponding (R)-alcohols. Application of this methodology was demonstrated in the synthesis of (+)- and (−)-trihexyphenidyl