ASYMMETRIC-SYNTHESIS OF BETA-HYDROXY-ALPHA-AMINO ACIDS BY CONDENSATION OF ALIPHATIC AND AROMATIC-ALDEHYDES WITH ZINC(II) AND COPPER(II) COMPLEXES OF (1R)-3-HYDROXYMETHYLENE BORNAN-2-ONE GLYCINE IMINES

The stereochemical outcome of the condensation reactions of aliphatic and aromatic aldehydes with the metal complexes 1 is strongly dependent on the nature of the metal ion. The copper(II) complex la only affords threo-P-hydroxy-cr-amino acids with fairly good enantiomeric excesses when reacting with aromatic aldehydes. The zinc(II) complex Ib gives a mixture of three and erythro diastereoisomers with a predominance of the erythro forms in the case of aromatic aldehydes.