[OH:1][C:2]1[C:10]([CH3:11])=[C:9]2[C:5]([C:6](=[O:12])[O:7][CH2:8]2)=[C:4]([O:13][S:14]([C:17]2[CH:22]=[CH:21][C:20]([CH3:23])=[CH:19][CH:18]=2)(=[O:16])=[O:15])[C:3]=1[CH2:24][CH:25]=[C:26]([CH3:32])[CH2:27][CH2:28][C:29]([OH:31])=[O:30].[C:33]1(C)C=CC(S(O)(=O)=O)=CC=1.O.C(OCC)(=O)C>CO>[CH3:33][O:30][C:29](=[O:31])[CH2:28][CH2:27]/[C:26](/[CH3:32])=[CH:25]/[CH2:24][C:3]1[C:4]([O:13][S:14]([C:17]2[CH:18]=[CH:19][C:20]([CH3:23])=[CH:21][CH:22]=2)(=[O:16])=[O:15])=[C:5]2[C:9](=[C:10]([CH3:11])[C:2]=1[OH:1])[CH2:8][O:7][C:6]2=[O:12]A solution of (E) 6-(1,3-dihydro-6-hydroxy-7-methyl-3-oxo-4-p-toluenesulfonyloxyisobenzofuran-5-yl)-4-methyl-4-hexenoic acid (23 g) and p-toluenesulfonic acid (0.8 g) in methanol (150 ml) was stirred for 18 hours then added to water and ethyl acetate. The organic layer was dried and evaporated and the residue was chromatographed on silica gel, eluting with hexane:ethyl acetate:methanol 40:58:2, to afford methyl (E) 6-(1,3-dihydro-6-hydroxy-7-methyl-3-oxo-4-p-toluene sulfonyloxyisobenzofuran-5-yl)-4-methyl-4-hexenoate.
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