C(OC(=O)C)(=O)C.[CH3:8][C:9]1[O:10][C:11]([CH3:32])=[C:12]([CH:14]([OH:31])[CH2:15][O:16][C:17]2[CH:30]=[CH:29][C:20]([CH2:21][CH:22]3[S:26][C:25](=[O:27])[NH:24][C:23]3=[O:28])=[CH:19][CH:18]=2)[N:13]=1.O>CS(C)=O>[CH3:8][C:9]1[O:10][C:11]([CH3:32])=[C:12]([C:14](=[O:31])[CH2:15][O:16][C:17]2[CH:18]=[CH:19][C:20]([CH2:21][CH:22]3[S:26][C:25](=[O:27])[NH:24][C:23]3=[O:28])=[CH:29][CH:30]=2)[N:13]=1Acetic anhydride (1.0 ml) was added to a solution of 5-{4-[2-(2,5-dimethyl-4-oxazolyl)-2-hydroxyethoxy]benzyl}-2,4-thiazolidinedione (0.5 g) in dimethylsulfoxide (10 ml), and the mixture was allowed to stand overnight and poured into water. The mixture was extracted with ethyl acetate. The ethyl acetate layer was washed with water, dried (MgSO4) and concetrated. The oily residue was chromatographed on a column of silica gel (40 g), and from the fractions eluted with benzene-acetone (9:1 V/v), there was obtained 5-{4-[2-(2,5-dimethyl-4-oxazolyl)-2-oxoethoxy]benzyl}-2,4-thiazolidinedione (0.24 g, 48.3%). Recrystallization from ethyl acetate-hexane afforded colorless plates, m.p. 161°-162° C. Elemental analysis for C17H16N2O5S, Calcd.: C, 56.66; H, 4.47; N, 7.77. Found: C, 56.62; H, 4.38; N, 7.60.
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