C([Si](C)(C)[O:6][C:7]1[CH:12]=[CH:11][C:10]([CH2:13][CH:14]([O:18][CH3:19])[C:15]([OH:17])=[O:16])=[CH:9][C:8]=1[O:20][CH3:21])(C)(C)C.S(=O)(=O)(O)O.[CH2:29](O)[CH3:30]>>[CH2:29]([O:17][C:15](=[O:16])[CH:14]([O:18][CH3:19])[CH2:13][C:10]1[CH:11]=[CH:12][C:7]([OH:6])=[C:8]([O:20][CH3:21])[CH:9]=1)[CH3:30]To a solution of 3-[4-(tert-butyl-dimethyl-silanyloxy)-3-methoxy-phenyl]-2-methoxy-propionic acid (356 mg, 1.05 mmol) in absolute ethanol (8 mL) was added concentrated sulfuric acid (0.033 mL, 0.63 mmol). The reaction mixture was allowed to stir at room temperature for 17 hours. The solution was concentrated under vacuum, and water (10 mL) and solid NaHCO3 were added to neutralize the residue. The aqueous phase was extracted with ethyl acetate (2×10 mL). The combined organic layers were washed with water (20 mL) and brine (20 mL), dried (MgSO4), filtered, and concentrated to produce 3-(4-hydroxy-3-methoxy-phenyl)-2-methoxy-propionic acid ethyl ester (260 mg, 98%). 1H-NMR (200.15 MHz, CDCl3): δ 6.83 (d, 1H, J=8.1 Hz), 6.76–6.69 (m, 2H), 4.19 (q, 2H, J=7.3 Hz), 3.97–3.90 (m, 1H), 3.87 (s, 3H), 3.36 (s, 3H), 2.96–2.92 (m, 2H), 1.25 (t, 3H, J=7.3 Hz).
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