To a solution (5 mL) of tert-butyl {[1-(6-chloro-5-methyl-3-pyridinesulfonyl)-5-phenyl-1H-pyrrol-3-yl]methyl}methylcarbamate (237 mg) in tetrahydrofuran was added hydrazine (160 mg) at room temperature with stirring. After stirring at the same temperature for 3 hr, a saturated aqueous sodium hydrogencarbonate solution was added, and the mixture was extracted with ethyl acetate. The extract was washed with water and saturated brine, dried over anhydrous magnesium sulfate, and concentrated under reduced pressure. The residue was dissolved in tetrahydrofuran (30 mL), manganese dioxide (75% chemically treated product, 1.0 g) was added, and the mixture was stirred at room temperature for 10 min. The reaction mixture was filtered through celite, and celite was washed with ethyl acetate. The filtrate was concentrated under reduced pressure, and the residue was purified by silica gel column chromatography (eluent: hexane-ethyl acetate=19:1→1:1) to give an oil. The obtained oil was dissolved in ethanol (2 mL), and a 4 mol/L hydrogen chloride-ethyl acetate solution (1 mL) was added. After stirring at room temperature for 2 hr, the solvent was evaporated under reduced pressure, a saturated aqueous sodium hydrogencarbonate solution was added, and the mixture was extracted with ethyl acetate. The extract was washed with water and saturated brine, dried over anhydrous magnesium sulfate, and concentrated under reduced pressure. The residue (93 mg) was dissolved in ethanol (3 mL), and fumaric acid (29 mg) was added. After allowing to stand at room temperature for 30 min, the precipitated crystals were collected by filtration and washed with methanol to give the title compound as a colorless solid (yield 91 mg, 40%).
