To a solution of tert-butyl [(4-fluoro-5-(2-fluoropyridin-3-yl)-1-{[5-(hydroxymethyl)-2-furyl]sulfonyl}-1H-pyrrol-3-yl)methyl]methylcarbamate (223 mg) in ethyl acetate (2 mL) and 2-propanol (1 mL) was added 4 mol/L hydrogen chloride-ethyl acetate solution (3 mL), and the mixture was stirred at room temperature for 1 hr. The solvent was concentrated under reduced pressure, the residue was diluted with ethyl acetate, and washed with saturated aqueous sodium hydrogen carbonate solution. The separated aqueous layer was extracted again with ethyl acetate. The combined organic layer was washed with saturated brine, dried over anhydrous magnesium sulfate, and concentrated under reduced pressure. The residue was purified by basic silica gel column chromatography (eluent: hexane-ethyl acetate=2:3→ethyl acetate) to give the title compound as a free base (basic TLC:Rf=0.03 (hexane:ethyl acetate=1:1)) (yield 142 mg). A solution of the obtained free base (141 mg) in ethyl acetate (2 mL) was added dropwise to a solution of fumaric acid (43 mg) in ethanol (2 mL) and the mixture was concentrated under reduced pressure. The residue was recrystallized from a mixed solvent of ethyl acetate-ethanol to give the title compound as a white solid (yield 107 mg, 42%).
