To a solution of 2-(1H-indazol-5-ylamino)benzoic acid (102 mg, 0.402 mmol) in N,N-dimethylformamide (0.5 ml) were added 1-benzylpiperazine (210 μl, 1.21 mmol), 1-hydroxybenzotriazole (74 mg, 0.484 mmol) and 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride (94 mg, 0.490 mmol) in that order, and the resulting mixture was stirred at room temperature for 21 hours. The mixture was dissolved in a 2N-aqueous sodium hydroxide solution (10 ml) and then extracted twice with ethyl acetate/toluene/tetrahydrofuran (2/2/1, 10 ml). The extract solution was washed with a saturated aqueous sodium chloride solution, dried over sodium sulfate, and then distilled under reduced pressure to remove the solvent, whereby a crude product was obtained. The crude product was purified by a silica gel column chromatography (eluent: chloroform/methanol=100/3) to obtain N-{2-[(4-benzylpiperazin-1-yl)carbonyl]phenyl}-1H-indazol-5-amine (162 mg, 100%).
