[OH:1][C:2]1[CH:3]=[C:4]2[C:9](=[CH:10][C:11]=1[OH:12])[O:8][C:7]([CH3:13])=[C:6]([C:14]([OH:16])=[O:15])[C:5]2=[O:17].CN(C)C=O.[C:23](OC(=O)C)(=[O:25])[CH3:24].[C:30](OCC)(=[O:32])[CH3:31]>N1C=CC=CC=1>[C:23]([O:1][C:2]1[CH:3]=[C:4]2[C:9](=[CH:10][C:11]=1[O:12][C:30](=[O:32])[CH3:31])[O:8][C:7]([CH3:13])=[C:6]([C:14]([OH:16])=[O:15])[C:5]2=[O:17])(=[O:25])[CH3:24]A mixture of 6,7-dihydroxy-2-methylchromone-3-carboxylic acid (2.24 g), dimethylformamide (30 ml), ethyl acetate (10 ml), pyridine (2.3 ml) and acetic anhydride (2.3 ml) was stirred at room temperature for 3 hours. Ethyl acetate (100 ml) was added to the reaction mixture, and the organic layer was washed successively with 6N-HCl and water, and thereafter dried over anhydrous magnesium sulfate. The solvent was evaporated and ethyl ether was added to the residue. The resulting solid was collected by filtration. It was washed with a 1:1 mixed solvent of ethyl acetate and ethyl ether and then dried, to obtain the desired product (1.93 g).
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