| 摘要 |
Preparation of the syn isomer or of a mixture of syn and anti isomers, the content of the syn isomer being at least 90%, of antibiotic 7-acylaminoceph-3-em-4-carboxylic acids of the formula I <IMAGE> in which B denotes &rdurule& S or &rdurule& S->O; R<1> denotes furyl, thienyl or phenyl; and R<2> denotes C1-C4-alkyl, C3-C7-cycloalkyl or phenyl and of their non-toxic salts, including their solvates, and esters, by reaction of the corresponding 3-hydroxymethyl compound, optionally with intermediate protection of the 4-carboxyl group, with a carbamoylating agent, to introduce a carbamoyloxymethyl group in the 3-position and subsequent isomerisation of a ceph-2-em compound which may be obtained to the ceph-3-em compound. The compounds are distinguished by a broad spectrum of action against pathogenic microorganisms, resistance against beta -lactamases and by a good stability in vivo.
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