While stirring a solution of DMF (50 mL) containing 4-(aminomethyl)-6-bromo-1-(4-methoxybenzyl)-4-(trifluoromethyl)-1,4-dihydro-2H-3,1-benzoxazin-2-one (13.67 g, 30.7 mmol), 4-fluorobenzoic acid (4.73 g, 33.8 mmol), hydroxybenzotriazole monohydrate (4.7 g, 30.7 mmol) and triethylamine (4.69 mL, 33.8 mmol) at 0° C., 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (6.47 g, 33.8 mmol) was added little by little thereto. After the reaction solution was stirred overnight at room temperature, water was slowly added thereto. After a solid began to precipitate, further excess water was added thereto, and the mixture was stirred at room temperature for 2 hours. The solid was collected by filtration and washed with water and then dried under reduced pressure, whereby the objective compound (15.6 g, 90%) was obtained as a white solid.
