摘要:
gamma- and- delta-Lactams [(R,R)-5a-e] bearing a propionic acid alpha-side-chain were synthesized in good overall yields (38 - 58 %, two steps) and diastereo- and enantiomeric excesses (de = greater than or equal to 96%, ee = 90 - greater than or equal to 96%) by 1,4-addition of metalated N-dialkylamino lactams [(S)-2a,b] to enoate Michael accepters (3) followed by saponification of the ester group and subsequent removal of the chiral auxiliary by reductive cleavage of the N-N-bond with lithium in liquid ammonia.