[OH:1][C:2]1[CH:3]=[C:4]([CH:10]=[CH:11][C:12]=1[OH:13])[CH:5]=[CH:6][C:7]([OH:9])=[O:8].[OH-].[Na+].CN(C)C=O.[CH:21]1[C:26](=[O:27])[C:25]([OH:28])=[CH:24][O:23][C:22]=1[CH2:29]Cl>CO.C(OCC)(=O)C>[OH:1][C:2]1[CH:3]=[C:4]([CH:10]=[CH:11][C:12]=1[OH:13])[CH:5]=[CH:6][C:7]([O:9][CH2:29][C:22]1[O:23][CH:24]=[C:25]([OH:28])[C:26](=[O:27])[CH:21]=1)=[O:8]0.81 g(4.5 mmol) of 3,4-dihydroxycinnamic acid and 0.18 g (4.5 mmol) of sodium hydroxide were dissolved into 40 ml of methanol. Residues obtained after distillating in methanol dissolved into 70 ml of N,N-dimethylformamide and 0.65 g (4.05 mmol) of chlorokojic acid prepared in the Reference Example was added thereto. The resulting mixture was heated with stirring for 2 hours in an oil bath of 110° C. After distillating the solvent, the residue was dissolved in 300 ml of ethyl acetate. The ethyl acetate solution was washed with 5% hydrochloric acid and distilled water, dried over magnesium sulfate, decolored with active charcoal and filtered. The filtrate was concentrated to give 0.66 g(48.8%) of 2-(3,4-dihydroxycinnamoyl) oxymethyl-5-hydroxy-4H-pyran-4-one as a solid.
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