[CH:1]([OH:3])=[O:2].C([NH:23][C:24]1[S:25][CH:26]=[C:27](/[C:29](=[N:53]/[O:54][CH3:55])/[C:30]([NH:32][C@@H:33]2[C:51](=[O:52])[N:35]3[C:36]([C:48]([OH:50])=[O:49])=[C:37]([CH2:40][S:41][C:42]4[N:46]([NH2:47])[N:45]=[N:44][N:43]=4)[CH2:38][S:39][C@H:34]23)=[O:31])[N:28]=1)(C1C=CC=CC=1)(C1C=CC=CC=1)C1C=CC=CC=1>O>[CH:1]([OH:3])=[O:2].[NH2:23][C:24]1[S:25][CH:26]=[C:27](/[C:29](=[N:53]/[O:54][CH3:55])/[C:30]([NH:32][C@@H:33]2[C:51](=[O:52])[N:35]3[C:36]([C:48]([OH:50])=[O:49])=[C:37]([CH2:40][S:41][C:42]4[N:46]([NH2:47])[N:45]=[N:44][N:43]=4)[CH2:38][S:39][C@H:34]23)=[O:31])[N:28]=1To 80% formic acid (17 ml) was added 7β-[2-(2-tritylaminothiazol-4-yl)-(Z)-2-methoxyiminoacetamido]-3-[(1-amino-1H-tetrazol-5-yl)thiomethyl]-3-cephem-4-carboxylic acid (4.3 g, 5.7 mmol) with stirring at room temperature and the mixture was stirred for an hour and a quarter. After adding water (85 ml), the mixture was filtered to remove insoluble material and the filtrate was concentrated below 45° C. The residue was treated with tetrahydrofuran (10 ml)-ether (5 ml) and concentrated again under reduced pressure. The residue was treated with ether to give pale yellow substances of 7β-[2-(2-aminothiazol-4-yl)-(Z)-2-methoxyiminoacetamido]-3-[(1-amino-1H-tetrazol-5-yl)thiomethyl]-3-cephem-4-carboxylic acid formate (2.98 g, 93.9%).
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