ASYMMETRIC ALDOL REACTIONS OF CHIRAL NI(II)-COMPLEX OF GLYCINE WITH ALIPHATIC-ALDEHYDES - STEREODIVERGENT SYNTHESIS OF SYN-(2S)-BETA-ALKYLSERINES AND SYN-(2R)-BETA-ALKYLSERINES

Stereoselectivity of aldol reactions between aliphatic aldehydes and N i(II)-complex of chiral non-racemic Schiff base of glycine with (S)-o- [N-(N-benzylprolyl)amino]benzophenone (BPB) in the presence of excess of MeONa, has been studied as a function of time, reaction conditions and nature of an aldehyde. Two salient features of the reaction, very high pseudokinetic syn-(2S)-diastereoselectivity, and dependence of th ermodynamic syn-(2R)-diastereoselectivity on the steric bulk of an ald ehyde side chain, were disclosed and used for efficient (more than 90% de and ee) asymmetric synthesis of both syn-(2S) and syn-(2R)-3-alkyl substituted serines. Synthetic potential and reliability of this asym metric method are demonstrated with the large scale (2-20 g) preparati on of enantiomerically pure amino acids.