[CH3:1][O:2][CH2:3][O:4][C:5]1[CH:10]=[CH:9][C:8](/[C:11](=[C:17](\[C:20]2[CH:25]=[CH:24][CH:23]=[CH:22][C:21]=2[CH3:26])/[CH2:18][CH3:19])/[C:12]([O:14]CC)=[O:13])=[CH:7][CH:6]=1.[OH-].[Na+].Cl>CO>[CH3:1][O:2][CH2:3][O:4][C:5]1[CH:6]=[CH:7][C:8](/[C:11](=[C:17](\[C:20]2[CH:25]=[CH:24][CH:23]=[CH:22][C:21]=2[CH3:26])/[CH2:18][CH3:19])/[C:12]([OH:14])=[O:13])=[CH:9][CH:10]=1To a solution of 2a (240 mg, 0.677 mmol) in MeOH (7 ml) was added 2N NaOH (3.4 ml) and the mixture was stirred at 80° C. for 18 h. After cooling, 2 N HCl (3.4 ml) was added drop wise under ice cooling, and the whole was extracted with AcOEt, the organic layer was washed with brine, dried over Na2SO4, then concentrated. The residual solid was triturated with hexanes to give 3a (79%). 3a: colorless powder; 1H-NMR (CDCl3) δ 1.05 (3H, t, J=7.5 Hz), 2.08 (3H, s), 2.68 (1H, m), 2.77 (1H, m), 3.41 (3H, s), 5.07 (2H, s), 6.75 (2H, d, J=8.7 Hz), 6.93 (2H, d, J=8.7 Hz), 7.01 (2H, m), 7.05-7.09 (3H, m).
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