To a solution of 2-methyl-1-(phenylsulfonyl)-5-(3-pyridyl)-1H-pyrrole-3-carbaldehyde (276 mg) in methanol (2 mL) and tetrahydrofuran (2 mL) were added 40% methylamine methanol solution (1.0 mL) and anhydrous magnesium sulfate (270 mg), and the reaction mixture was stirred at room temperature for 4 hr. To the reaction mixture was added sodium borohydride (43 mg) at room temperature and the mixture was stirred for 30 min. The reaction mixture was concentrated under reduced pressure, saturated aqueous sodium hydrogencarbonate solution was added to the residue, and the mixture was extracted with ethyl acetate. The extract was washed with saturated aqueous sodium hydrogencarbonate solution, water and saturated brine, dried over anhydrous sodium sulfate, and the solvent was evaporated under reduced pressure. The residue was purified by basic silica gel column chromatography (eluent: ethyl acetate) to give a free base of the title compound as a yellow oil. To a solution (4 mL) of the obtained free base in ethanol was added a solution (2 mL) of oxalic acid (18 mg) in ethanol. The mixture was stirred at room temperature for 10 min, and concentrated under reduced pressure. The residue was recrystallized from ethanol to give the title compound as white crystals (yield 103 mg, 59%).
