((S)-2-{(S)-2-[(S)-2-[(S)-2-((R)-2-tert-Butoxycarbonylamino-3-phenyl-propionylamino)-4-carbamoyl-butyrylamino]-3-(1H-indol-3-yl)-propionylamino]-propionylamino}-3-methyl-butyrylamino)-acetic acid benzyl ester