C([O:4][CH2:5][CH2:6][N:7]1[C:16]2[C:11](=[CH:12][C:13]([CH2:17][C:18]3[CH:23]=[CH:22][CH:21]=[C:20]([Cl:24])[C:19]=3[Cl:25])=[CH:14][CH:15]=2)[C:10](=[O:26])[C:9]([C:27]([O:29]CC)=[O:28])=[CH:8]1)(=O)C.[OH-].[Na+]>C(O)C>[Cl:25][C:19]1[C:20]([Cl:24])=[CH:21][CH:22]=[CH:23][C:18]=1[CH2:17][C:13]1[CH:12]=[C:11]2[C:16](=[CH:15][CH:14]=1)[N:7]([CH2:6][CH2:5][OH:4])[CH:8]=[C:9]([C:27]([OH:29])=[O:28])[C:10]2=[O:26]Ethyl 1-(2-acetoxyethyl)-6-(2,3-dichlorobenzyl)-1,4-dihydro-4-oxo-3-quinolinecarboxylate (6.0 g, 13.0 mmol) obtained in Step 4 was suspended in ethanol (480 ml), 4N aqueous sodium hydroxide solution (84 ml, 21 mmol) was added, and the mixture was heated under reflux for 30 min. After allowing to cool, the reaction mixture was partially concentrated under reduced pressure and hydrochloric acid was added. The precipitated solid was collected by filtration, washed with water and ethanol, and vacuum dried to give the object product (4.5 g, yield 85%) as a white solid.
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