To a solution of H-DNle-OBzl.TsOH (1.27 g) in dichloromethane (20 ml) were added NMM (0.53 ml), Boc-DTrp-OH (1.22 g), HOBT.H2O (734 mg) and EDCI.HCl (926 mg) successively under ice cooling. The mixture was stirred at the same temperature for 1 h and at room temperature for 2 h. The mixture was diluted with ethyl acetate, washed with sat. aq. NaHCO3, 10% aq. citric acid, and brine successively, dried over MgSO4 and evaporated in vacuo. The residue was recrystallized from ethyl acetate and hexane to give Boc-DTrp-DNle-OBzl (1.56 g).
