4-nitrophenyl chloroformate (242 mg, 1.2 mmol) was dissolved in tetrahydrofuran (3 ml), and a tetrahydrofuran (4 ml) solution of the 4-hydroxy-N-(4-aminophenyl)piperidine (211 mg, 1.0 mmol) obtained in Example 1(2) was added dropwise at −30° C. After stirring for 30 minutes at the same temperature, 1-[(1-methyl-1H-pyrrol-2-yl)carbonyl]piperazine hydrochloride (252 mg, 1.1 mmol) and triethylamine (0.49 ml, 3.5 mmol) were added to the mixture, followed by stirring at room temperature for 17 hours. A saturated sodium bicarbonate aqueous solution was added to the reaction mixture, followed by extraction with ethyl acetate. The organic layer was washed with water and saturated sodium chloride, and dried over anhydrous sodium sulfate. After the desiccant was filtered off, the residue obtained by evaporation under reduced pressure was purified using medium pressure silica gel flash column chromatography (NH silica gel, methanol:chloroform=0:1 to 1:50), thereby obtaining N-(4-(4-hydroxypiperidin-1-yl)-phenyl)-4-((1-methylpyrrol-2-yl)-carbonyl)-1-piperazinecarboxamide (256 mg, 62%) as a milky-white solid.
