[O:1]1[CH:7]2[CH:2]1[C:3]([CH3:17])([CH3:16])[O:4][C:5]1[CH:11]=[CH:10][C:9]([S:12]([CH3:15])(=[O:14])=[O:13])=[CH:8][C:6]=12.[Na].[S:19]1(=[O:25])(=[O:24])[CH2:23][CH2:22][CH2:21][NH:20]1.O>CS(C)=O>[OH:1][C@H:2]1[C@H:7]([N:20]2[CH2:21][CH2:22][CH2:23][S:19]2(=[O:25])=[O:24])[C:6]2[CH:8]=[C:9]([S:12]([CH3:15])(=[O:14])=[O:13])[CH:10]=[CH:11][C:5]=2[O:4][C:3]1([CH3:17])[CH3:16]To a solution of 3,4-dihydro-3,4-epoxy-6-mesyl-2,2-dimethyl-2H-1-benzopyran (1.5 g) in dimethyl sulfoxide (30 ml) was added sodium salt of isothiazolidine 1,1-dioxide (1.7 g). The mixture was stirred at room temperature overnight. Water was carefully added to the reaction mixture and the whole was extracted with ethyl acetate. The extract was washed with water, dried over anhydrous magnesium sulfate, and evaporated in vacuo. The residue was purified by column chromatography on silica gel (50 g) with a mixture of chloroform and methanol (50:1) as eluents to give trans-3,4-dihydro-3-hydroxy-4-(1,1-dioxoisothiazolidin-2-yl)-6-mesyl-2,2-dimethyl-2H-1-benzopyran (0.47 g).
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