1 4BQ (2s)-2-amino-5-oxo-5-[(4-phenylmethoxyphenyl)amino]pentanoic acid 1.000 2 4BS 4-amino-N-[4-(benzyloxy)phenyl]butanamide 0.875 3 4BO (3s)-3-amino-4-oxo-4-[(4-phenylmethoxyphenyl)amino]butanoic acid 0.741 4 4BG N-[4-(benzyloxy)phenyl]glycinamide 0.720