| 摘要 |
<p>Cephem derivatives of the following formula <IMAGE> in which the substituents are defined in Claim 1, are prepared by a novel process. In this process, an appropriate 7-acylamidocephem derivative having a protected carboxyl group in the 4-position is reacted in the presence of a molecular sieve with an acylating agent donating the desired acyl radical. The original acyl group is removed from the initially resulting 7-diacylamidocephem derivative. The free acid is obtained by removal of the protective group R'', which preferably represents an easily removable ester group. The said compounds are used as antibiotics.</p> |
