Boc-Val-Pro-OBzl was prepared by dissolving H-Pro-OBzl (20 g, 83 mmol) in 50 mL of chloroform and adding Boc-Val-OH (18.0 g, 83 mmol), HOBt (23.0g, 165 mmol), NMM ( 9.0 mL, 83 mmol) and DCC (17.0 g, 83 mmol). The reaction mixture was stirred overnight at room temperature. The mixture was filtered and solvent was evaporated. Ethyl acetate was added and insoluble material was removed by filtration. The filtrate was washed with 0.2N HCl, 5% NaHCO3, and saturated aqueous NaCl. It was dried over Na2SO4, filtered and evaporate to give a white solid (30 g, 75 mmol, 90%). ESI/MS calculated for C22H32N2O5 +H: 405.2. Found 405.6.
