15 mg of 2,5-difluoro-phenol and 28 mg of cesium carbonate were added to an N-methylpyrrolidinone (0.5 ml) solution of 26 mg of pyrazine-2-carboxylic acid (5-fluoro-4-(6-methanesulfonyl-pyridin-3-yloxy)-2-nitro-phenyl)-amide obtained in (step 1), and the reaction liquid was stirred at 90° C. for 15 minutes, and 100 mg of tin(II) chloride dihydrate was added to the reaction liquid. The reaction liquid was stirred at 90° C. for 1 hour, and ethyl acetate and aqueous saturated sodium bicarbonate were added to it. The deposit was removed through filtration, the solvent was evaporated away under reduced pressure, and the residue was purified through reversed-phase middle-pressure liquid chromatography [ODS-AS-360-CC (by YMC), mobile phase: water-acetonitrile-0.1% trifluoroacetic acid]. The solvent of the resulting fraction was diluted with ethyl acetate, washed with aqueous saturated sodium bicarbonate, and dried with anhydrous sodium sulfate. The solvent was evaporated away under reduced pressure to obtain the entitled compound as a pale yellow solid.
