To a mixture of 7-(benzyloxy)-5-[4-(methylsulfonyl)phenoxy]-1H-indole-2-carboxamide (840 mg), pyridine (0.23 mL) and N,N-dimethylformamide (20 mL) was added dropwise oxalyl chloride (0.25 mL) under ice-cooling, and the mixture was stirred for 2 hr. Pyridine (0.23 mL) and oxalyl chloride (0.25 mL) were successively added, and the mixture was further stirred for 30 min. Water was added to the reaction solution, and the mixture was subjected to extraction with ethyl acetate. The organic layer was washed successively with 1M hydrochloric acid, saturated aqueous sodium hydrogen carbonate solution and saturated brine, dried over magnesium sulfate, filtered, and concentrated under reduced pressure. The obtained solid was washed with a mixed solvent of diethyl ether-hexane to give the title compound (660 mg, yield 92%) as yellow crystals. The obtained yellow crystals were recrystallized from ethanol-hexane to give yellow crystals. melting point 209-210° C.
