Optically active and racemic isomers of aspartic acid (1) were transfo
rmed into the corresponding N-trifluoroacetyl-5-bromo-4-oxonorvaline m
ethyl esters (6, R = Me) and N-trifluoroacetyl-3-formylalanine methyl
esters 13, which were used as starting compounds in the synthesis of b
eta-heteroaryl substituted-alpha-amino acids.