[OH:1][C:2]1[C:11]([OH:12])=[C:10]2[C:5]([C:6]([C:14]3[CH:19]=[CH:18][CH:17]=[CH:16][CH:15]=3)=[CH:7][C:8](=[O:13])[O:9]2)=[CH:4][CH:3]=1.[O:20]1[CH:25]=[CH:24][CH2:23][CH2:22][CH2:21]1.C1(C)C=CC(S([O-])(=O)=O)=CC=1.[NH+]1C=CC=CC=1>C1COCC1.C(Cl)Cl.CCOC(C)=O>[OH:12][C:11]1[C:2]([O:1][CH:21]2[CH2:22][CH2:23][CH2:24][CH2:25][O:20]2)=[CH:3][CH:4]=[C:5]2[C:10]=1[O:9][C:8](=[O:13])[CH:7]=[C:6]2[C:14]1[CH:15]=[CH:16][CH:17]=[CH:18][CH:19]=1To 7,8-dihydroxy-4-phenyl-2H-chromen-2-one (500 mg, 2 mmol) and 3,4-dihydro-2H-pyran in 4 mL THF and 4 mL DCM was added pyridinium paratoluene sulfonate (PPTS, 8 mg). The mixture was stirred at rt for 15 h under Ar atmosphere and diluted with EtOAc (50 mL). It was washed with NaHCO3 (sat. 30 mL) and water (50 mL) and dried over MgSO4 and concentrated under reduced pressure. The residue was chromatographed (hexane/EtOAc) to afford 8-hydroxy-4-phenyl-7-(tetrahydro-2H-pyran-2-yloxy)-2H-chromen-2-one as a yellow solid (180 mg, 26%). MS (ESI) m/z 339 (M+H+).
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