C([O:3][C:4]([C:6](O)([CH2:12][C:13]([C:15]1[CH:20]=[CH:19][C:18]([CH3:21])=[C:17]([F:22])[CH:16]=1)=O)[C:7](OCC)=[O:8])=[O:5])C.O.[NH2:25][NH2:26].[OH-].[Na+].Cl>C(O)(C)C>[C:4]([C:6]1[C:7](=[O:8])[NH:25][N:26]=[C:13]([C:15]2[CH:20]=[CH:19][C:18]([CH3:21])=[C:17]([F:22])[CH:16]=2)[CH:12]=1)([OH:3])=[O:5]
To a solution of ethyl 2-ethoxycarbonyl-4-(3-fluoro-4-methylphenyl)-2-hydroxy-4-oxobutanoate (8.41 g, 25.8 mmol) in isopropanol (100 mL) was added hydrazine monohydrate (2.84 g, 56.8 mmol), and the mixture was heated under stirring at 100° C. for 6 hours. Then, 2 mol/L sodium hydroxide was added, and the mixture was stirred further at the same temperature for 4 hours. The reaction mixture was ice-cooled, and concentrated hydrochloric acid was added to acidify the system. The precipitate was collected by filtration, thoroughly washed with water and dried to yield the title compound as a slightly yellow crystalline powder (5.67 g, 87.7%).
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