C1(CC([NH:10][C@@H:11]2[C:21](=[O:22])[N:13]3[C:14]([C:18]([OH:20])=[O:19])=[CH:15][CH2:16][S:17][C@H:12]23)=O)C=CC=CC=1.C[Si](C)(C)Cl.N1C=CC=CC=1.P(Cl)(Cl)(Cl)(Cl)Cl>C(Cl)Cl.C(N(CC)CC)C.O.CO>[NH2:10][C@@H:11]1[C:21](=[O:22])[N:13]2[C:14]([C:18]([OH:20])=[O:19])=[CH:15][CH2:16][S:17][C@H:12]12A solution of 0.955 g of 7β-(N-phenylacetyl-amino)ceph-3-em-4-carboxylic acid in 60 ml of absolute methylene chloride is treated with 0.720 g of trimethylchlorosilane and 0.474 g of absolute pyridine. The mixture is stirred for 60 minutes at room temperature and then cooled to -20° C., and a solution of 3.20 g of absolute pyridine in 30 ml of absolute methylene chloride, and 23.4 ml of an 8% solution of phosphorus pentachloride in absolute methylene chloride, are then added successively. The mixture is stirred for 60 minutes at -10° C. to -12° C. and is again cooled to about -20° C., and 15 ml of absolute methanol are then allowed to run in. The whole is stirred for 25 minutes at -10° C. and then for 35 minutes at room temperature, 15 ml of water are added, the pH value of the reaction mixture is increased from 1.8 to 2.2 by dropwise addition of triethylamine and the mixture is stirred for 20 minutes at room temperature. The pH value is raised to 3.8 by renewed addition of triethylamine and the two-phase mixture is stirred for 90 minutes whilst cooling in an ice bath and is then filtered. The filter residue is washed with methanol, methylene chloride and diethyl ether and is dried in a vacuum desiccator. 7β-amino-ceph-3-em-4-carboxylic acid of the formula ##STR27## is thus obtained in an amorphous form; the product is further processed without purification.
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