To a solution of 6.00 g of BOC-Leu-OH.H2O, 3.49 g of HOBT and 9.59 of H-Gly-OBzl.TosOH dissolved in 30 ml of DMF, under cooling at -5° C. and stirring, a solution of 4.97 ml of WSC dissolved in 10 ml of DMF was added dropwise, and after one hour, the temperature was regulated to room temperature, at which stirring was continued overnight. The reaction mixture was concentrated under reduced pressure to evaporate DMF, and the residue was dissolved in ethyl acetate. The ethyl acetate layer was washed successively with 1N hydrochloric acid, water, 5% aqueous sodium hydrogen carbonate and water, dried over anhydrous sodium sulfate and concentrated under reduced pressure to obtain 9.2 g of BOC-Leu-Gly-OBzl as oily product. Rf1 =0.59.
