[C:1](OC(=O)C)(=[O:3])[CH3:2].[OH:8][C:9]1[CH:22]=[C:21]([NH:23][S:24]([CH3:27])(=[O:26])=[O:25])[C:20]([O:28][C:29]2[CH:34]=[CH:33][CH:32]=[CH:31][CH:30]=2)=[CH:19][C:10]=1[C:11]([CH2:13][C:14]([O:16][CH2:17][CH3:18])=[O:15])=[O:12].[C:35]([O-])(=O)[CH3:36].[Na+].Cl>O.C(OCC)(=O)C>[C:1]([N:23]([C:21]1[C:20]([O:28][C:29]2[CH:30]=[CH:31][CH:32]=[CH:33][CH:34]=2)=[CH:19][C:10]2[C:11](=[O:12])[C:13]([C:14]([O:16][CH2:17][CH3:18])=[O:15])=[C:35]([CH3:36])[O:8][C:9]=2[CH:22]=1)[S:24]([CH3:27])(=[O:26])=[O:25])(=[O:3])[CH3:2]2.55 ml of acetic anhydride was added to 850 mg of ethyl 2-(2-hydroxy-4-methylsulfonylamino-5-phenoxybenzoyl)acetate and 540 mg of sodium acetate. The mixture was stirred for 10 minutes at 110°-120° C. The reaction mixture was introduced into a mixture of 20 ml of ethyl acetate and 20 ml of water. The resulting mixture was adjusted to pH 2 with 2N hydrochloric acid. The organic layer was separated, washed with water and a saturated aqueous sodium chloride solution in this order, and dried with anhydrous magnesium sulfate. The solvent was removed by distillation under reduced pressure. The residue was purified by a column chromatography (eluant: a 5 : 1 mixture of toluene and ethyl acetate) to obtain 550 mg (yield: 55.6%) of 7-(N-acetyl-N-methylsulfonylamino)-3-ethoxycarbonyl-2-methyl-6-phenoxy-4H-1-benzopyran-4-one.
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