Totally stereocontrolled synthesis of α,β-diamino acids by addition of Grignard reagents to nitrones derived from L-serine

The asymmetric synthesis of protected (2R,3S)- and (2R,3R)-3-substituted 2,3-alpha-amino acids is reported. The key step in the synthesis of these compounds is the diastereoselective addition of Grignard reagents to alpha-amino nitrones derived from L-serine. Total stereocontrol of the addition step is achieved by changing the protecting groups in the starting material. The predominant selectivity in each case can be reasonably interpreted in terms of steric effects of the substituents. (C) 1998 Elsevier Science Ltd. All rights reserved.