[CH2:1]([O:3][CH2:4][CH2:5]Br)[CH3:2].[OH:7][C:8]1[CH:9]=[C:10]([CH:13]=[CH:14][C:15]=1[OH:16])[CH:11]=[O:12].C(=O)([O-])[O-].[Na+].[Na+].CN(C)C=O>Cl.C(OCC)(=O)C.O>[CH2:1]([O:3][CH2:4][CH2:5][O:16][C:15]1[CH:14]=[CH:13][C:10]([CH:11]=[O:12])=[CH:9][C:8]=1[OH:7])[CH3:2]Commercially available 2-bromoethyl ethyl ether (33.8 g, 221 mmol) was added to a solution of commercially available 3,4-dihydroxybenzaldehyde (30.5 g, 221 mmol) and sodium carbonate (35.1 g, 331 mmol) in NP-dimethylformamide (310 mL) under nitrogen atmosphere at mom temperature. The liquid mixture was stirred at room temperature for 5 days. The reaction liquid was cooled to 0° C. and diluted with 2 M hydrochloric acid, ethyl acetate, and water. The aqueous layer was extracted with ethyl acetate. The combined organic layer was washed serially with water and a saturated saline solution and then dried over anhydrous magnesium sulfate. The drying agent was separated by filtration and then the filtrate was concentrated under vacuum. The insoluble matters were separated by filtration with dichloromethane and the raw material was removed. The filtrate was purified with silica gel column chromatography (n-heptane:ethyl acetate=17:3-1:1) to obtain the title compound (13.2 g, 28%).
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