[CH:1]1([O:6][C:7]2[C:8]([OH:18])=[C:9]([C:15](=[O:17])[CH3:16])[CH:10]=[CH:11][C:12]=2[O:13][CH3:14])[CH2:5][CH2:4][CH2:3][CH2:2]1.[H-].[Na+].[C:21](=O)(OCC)[O:22]CC.Cl.CC(C)([O-])C.[K+]>O>[CH:1]1([O:6][C:7]2[C:12]([O:13][CH3:14])=[CH:11][CH:10]=[C:9]3[C:8]=2[O:18][C:21](=[O:22])[CH:16]=[C:15]3[OH:17])[CH2:2][CH2:3][CH2:4][CH2:5]11-[3-(Cyclopentyloxy)-2-hydroxy-4-methoxyphenyl]ethanone (4.25 g, 17 mmol) was added portionwise to a mixture of sodium hydride (1.4 g, 60%, 35 mmol) and diethyl carbonate (30 mL) at rt under N2. The reaction was refluxed for 1 h and then cooled to rt. 10% Hydrochloric acid (30 mL) was added, and the mixture was stirred for 1 h. The reaction was diluted with water (100 mL) and extracted with ethyl acetate (200 mL×2). The combined extracts were dried, filtered, concentrated, and redissolved in t-butanol (50 mL). Potassium t-butoxide (4.0 g, 36 mmol) was added, and the reaction was refluxed. After 42 h, additional potassium t-butoxide (2.0 g, 18 mmol) was added. After an additional 2 d, the reaction was allowed to cool to rt, concentrated, diluted with 1N HCl (100 mL), and extracted with ethyl acetate (200 mL×2). The combined extracts were dried, filtered, concentrated, and purified by silica gel chromatography (3:2→0:1; hexanes:ethyl acetate) to give 8-(cyclopentyloxy)-4-hydroxy-7-methoxy-2H-chromen-2-one: MS (ESI): 277.1.
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