[OH:1][C:2]1[CH:7]=[CH:6][C:5]([CH2:8][CH2:9][C:10]([OH:12])=[O:11])=[C:4]([O:13][CH3:14])[CH:3]=1.OS(O)(=O)=O.C([O-])([O-])=O.[Na+].[Na+].[CH3:26][CH2:27]O>>[OH:1][C:2]1[CH:7]=[CH:6][C:5]([CH2:8][CH2:9][C:10]([O:12][CH2:26][CH3:27])=[O:11])=[C:4]([O:13][CH3:14])[CH:3]=1To a stirring solution of 3-[4-hydroxy-2-(methyloxy)phenyl]propanoic acid (229 mg, 1.17 mmol) in EtOH (14 mL) was added concentrated H2SO4 (0.031 mL, 0.58 mmol) and the reaction heated at reflux under nitrogen for 1 h. The mixture was then cooled to ambient temperature poured into ice (ca. 30 mL) and saturated aqueous Na2CO3 (60 mL) added. The mixture was then extracted with EtOAc (2×50 mL) and the combined organic layer washed with brine (70 mL) and concentrated under vacuum. The residue was then purified by SPE (silica, 5 g cartridge) eluting with cyclohexane:EtOAc (gradient 10:1 to 2:1) to afford the title compound (217 mg).
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