4-[1-(3-Amino-2-pyridyl)piperazin4-yl-carbonyl]benzoic acid methyl ester (4 g) was dissolved in methanol (90 ml) and then, acetone (2 ml), acetic acid (5 ml) and sodium cyanoborohydride (2.4 g) were added at 10° C. in order. The reaction mixture was stirred at 10° C. for 4 hours and heated to 20~25° C. and stirred for 1 hour. The solution was neutralized (pH=~8) by addition of aqueous 3N-sodium hydroxide, and excess of water was added gradually for precipitation. The mixture was stirred for 1 hour, filtered, washed with water, methanol and ether in order and dried to give 3.5 g (yield: 78%) of the desired compound as white crystal.
