[O:1]=[C:2]1[C:7]2[CH:8]=[CH:9][CH:10]=[CH:11][C:6]=2[S:5][C:4]([C:12]2[N:17]=[CH:16][C:15]([CH2:18][CH2:19][CH2:20][O:21][CH2:22][CH2:23][C:24]([O:26]C(C)(C)C)=[O:25])=[CH:14][CH:13]=2)=[N:3]1.FC(F)(F)C(O)=O>>[O:1]=[C:2]1[C:7]2[CH:8]=[CH:9][CH:10]=[CH:11][C:6]=2[S:5][C:4]([C:12]2[N:17]=[CH:16][C:15]([CH2:18][CH2:19][CH2:20][O:21][CH2:22][CH2:23][C:24]([OH:26])=[O:25])=[CH:14][CH:13]=2)=[N:3]1tert-Butyl 3-{3-[6-(4-oxo-4H-1,3-benzothiazin-2-yl)-3-pyridyl]propoxy}propanoate (1.0 g, 2.3 mmol) and trifluoroacetic acid (4.0 ml) was stirred under ice cooling condition for 5 hrs. The reaction mixture was concentrated under reduced pressure, diluted with chloroform, washed with water and dried. The solvent was evaporated. The residue was subjected to a silica gel column chromatography, eluted with ethyl acetate-methanol (20:1, v/v) and recrystallized from chloroform-ethyl acetate to give the titled compound (0.55 g, 66%).
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