CC(O[CH2:5][C:6]1[CH2:15][S:14][C@@H:9]2[C@H:10]([NH2:13])[C:11](=[O:12])[N:8]2[C:7]=1[C:16]([OH:18])=[O:17])=O.[S:19]1[N:23]=[CH:22][C:21]([S-:24])=[N:20]1.[K+].B(F)(F)F.CCOCC>FC(F)(F)C(O)=O>[NH2:13][CH:10]1[C:11](=[O:12])[N:8]2[C:7]([C:16]([OH:18])=[O:17])=[C:6]([CH2:5][S:24][C:21]3[CH:22]=[N:23][S:19][N:20]=3)[CH2:15][S:14][C@H:9]127-Aminocephalosporanic acid (0.272 g) was added to the solution of potassium 1,2,5-thiadiazole-3-thiolate (0.136 g) in trifluoroacetic acid (5 ml) and the mixture was stirred for a few minutes until the solution turned clear, and then, boron trifluoride etherate (0.434 g) was added thereto and the mixture was stirred for 12 hours at room temperature. The reaction mixture was evaporated under reduced pressure and the residue was adjusted to pH 3.0 with 2% aqueous solution of ammonium hydroxide. The precipitates were collected by filtration, washed with cool water, acetone and diethyl ether and dried to give 7-amino-3-(1,2,5-thiadiazol-3-yl)thiomethyl-3-cephem-4-carboxylic acid (0.210 g).
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