[(S)-2-(4-Chloro-benzyl)-3,6-dioxo-4-(3-phenyl-propyl)-piperazin-1-yl]-acetic acid tert-butyl ester

[[(S)-2-tert-Butoxycarbonylamino-3-(4-chloro-phenyl)-propionyl]-(3-phenyl-propyl)-amino]-acetic acid methyl ester