[CH3:1][O:2][C:3](=[O:23])[C:4]1[CH:9]=[CH:8][C:7]([O:10][CH3:11])=[C:6]([NH:12][C:13](=[NH:22])[C:14]2[CH:19]=[CH:18][C:17]([F:20])=[CH:16][C:15]=2[Cl:21])[CH:5]=1.[O-]Cl.[Na+].C([O-])([O-])=O.[Na+].[Na+]>CO>[CH3:1][O:2][C:3]([C:4]1[C:5]2[N:22]=[C:13]([C:14]3[CH:19]=[CH:18][C:17]([F:20])=[CH:16][C:15]=3[Cl:21])[NH:12][C:6]=2[C:7]([O:10][CH3:11])=[CH:8][CH:9]=1)=[O:23]3-[(2-chloro-4-fluoro-benzimidoyl)-amino]-4-methoxy-benzoic acid methyl ester (10 g, 29.76 mmol) obtained in step 1 was dissolved in 50% methanol and 5% NaOCl (53 ml, 35.71 mmol) was added dropwise thereto at room temperature. After 5 min, Na2CO3 (6.31 g, 59.52 mmol) was added dropwise thereto and refluxed for 5 min. The resulting solution was cooled to room temperature, extracted with ethyl acetate, the extract was concentrated under a reduced pressure. The resulting residue was purified by silica gel column chromatography to obtain the title compound (5.17 g, 15.48 mmol) in a yield of 52%.
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