The compound of Example 14 (a) (7-amino-5-chloro-2-[1-(4-tert-butyloxycarbonyl) homopiperazinyl]benzoxazole, 48 mg, 0.130 mmol) was dissolved in methylene chloride (2 ml), and the solution was successively added with triethylamine (0.056 ml) and benzoyl chloride (0.031 ml) at 0° C. After the reaction mixture was stirred for 3 hours, the reaction was stopped by using saturated aqueous solution of sodium hydrogencarbonate. The reaction mixture was diluted with ethyl acetate, and the organic layer was washed with water and dried over anhydrous magnesium sulfate. The solution was added with 4 N hydrochloric acid in ethyl acetate (1 ml), and the deposited solids were collected by filtration to obtain the title compound (20 mg).
