20 ml of water and 4 g of 5% platinum-carbon catalyst were added to a 2-propanol (200 ml) solution of 12 g of t-butyl 2-(4-amino-2-(4-methanesulfonyl-phenoxy)-5-nitro-phenyl)-pyrrole-1-carboxylate, and the reaction liquid was stirred under a hydrogen atmosphere of 50 kgf/cm2 at 70° C. for 2 days. The catalyst was removed through filtration through Celite, the solvent was evaporated away under reduced pressure, and the resulting residue was purified through silica gel column chromatography (developing solvent: chloroform/methanol=50/1) to obtain the entitled compound as a dark brown oily substance.
