F[C:2](F)(F)[C:3]([OH:5])=O.[NH2:8][CH2:9][C:10]1[N:15]=[C:14]([C:16]2[S:17][C:18]3[CH:26]=[CH:25][CH:24]=[CH:23][C:19]=3[C:20](=[O:22])[N:21]=2)[CH:13]=[CH:12][CH:11]=1.CCC[C:30](Cl)=[S:31].[C:33](OCC)(=O)C.O>CN(C)C(=O)C>[CH3:33][S:31][CH2:30][CH2:2][C:3]([NH:8][CH2:9][C:10]1[CH:11]=[CH:12][CH:13]=[C:14]([C:16]2[S:17][C:18]3[CH:26]=[CH:25][CH:24]=[CH:23][C:19]=3[C:20](=[O:22])[N:21]=2)[N:15]=1)=[O:5]2-[6-(Aminomethyl)-2-pyridyl]-4H-1,3-benzothiazine-4-one trifluoroacetic acid salt (0.80 g, 2.1 mmol) was dissolved in N,N-dimethylacetamide (10 ml), and 3-methylthiopropionyl chloride (0.86 g, 6.2 mmol) was added thereto. The reaction mixture was stirred at 60° C. for 15 hrs and combined with ethyl acetate and water. The organic layer was washed with saturated brine and dried over anhydrous magnesium sulfate. The solvent was evaporated, and the residue was subjected to a silica gel column chromatography. The fractions eluted with methanol-ethyl acetate (1:10, v/v) were collected, concentrated and recrystallized from diisopropyl ether-tetrahydrofuran to give the titled compound (0.18 g, 24%) as white crystals.
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