(S)-2-tert-Butoxycarbonylamino-3-phenyl-propionic acid (R)-3-((S)-2-tert-butoxycarbonylamino-3-phenyl-propionylamino)-2-oxo-pyrrolidin-1-yl ester
N-tert-butoxycarbonyl-L-phenylalanine
[(S)-1-((R)-1-Hydroxy-2-oxo-pyrrolidin-3-ylcarbamoyl)-2-phenyl-ethyl]-carbamic acid tert-butyl ester