(S)-2-tert-Butoxycarbonylamino-3-methyl-butyric acid (1S,2S)-2-benzyloxycarbonylamino-1-((R)-4-tert-butylcarbamoyl-thiazolidine-3-carbonyl)-3-phenyl-propyl ester

{(S)-1-[(1S,2S)-1-Benzyl-3-((R)-4-tert-butylcarbamoyl-thiazolidin-3-yl)-2-hydroxy-3-oxo-propylcarbamoyl]-propyl}-carbamic acid tert-butyl ester