Enantioselective synthesis of (R)- and (S)-alpha-amino acids using (6S)- and (6R)-6-methyl-morpholine-2,5-dione derivatives

The alkylation of both 3 and 4 gives exclusively the trans derivatives 5 and 6, respectively, with >98% diastereoselectivity. Cleavage of the morpholine-2,5-dione ring of 5 and 6 leads to enantiomerically pure (S)- and (R)-alpha-aminoacids, respectively. The configurations of stereogenic centers introduced on 3, 4, 5 and 6 have been assigned on the basis of the H-1-NMR data, conformational analysis and nOe measurements.