| 摘要 |
beta -lactam antibiotics of the formula <IMAGE> in particular cephamycin and cephalosporin derivatives, are prepared by reacting a compound of the formula <IMAGE> with an acyl halide of the formula R<1>-Y in the presence of a halogenated aliphatic hydrocarbon solvent, forming a compound of the formula <IMAGE> The phenacyl or halophenacyl protective group is then removed by reaction with zinc and an acid. The acid is selected from inorganic acids, mono-esters of dibasic inorganic acids and sulphonic acids. The resulting compound of the formula I can then be converted into a pharmaceutically acceptable salt. In this way, compounds can be obtained in a high yield with a minimum of secondary reactions. In the formulae, R<1>, R<2>, R<3>, R<4>, R<5>, X and Y have the definitions given in Patent Claim 1.
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