| 摘要 |
<p>Process for the manufacture of 7-amino-3-cephem-4-carboxylic acids and the esters thereof of the formula I in which A stands for hydrogen, alkyl, acyloxy, alkyloxy or hydroxy and R stands for hydrogen, optionally substituted linear or branched alkyl, cycloalkyl, aryl, aralkyl, aryloxyalkyl, alkoxyalkyl, acryloxyalkyl, aroylalkyl, or a heterocyclic radical and the salts thereof which comprises reacting 7-acylamino-3-cephem-4-carboxylic acid esters of the general formula II in which R' stands for optionally substituted alkyl, aryl, aralkyl, aryloxyalkyl, alkoxyalkyl or a heterocyclic radical and R'' has the meaning given for R but cannot stand for hydrogen and A is defined as above, in an inert solvent with a silylating agent in the presence of a base, converting the amido group activated by the silylation into the iminohalide by adding a halogenating agent, allowing it to react with an alcohol to yield the iminoether hydrohalide, hydrolyzing the iminoether hydrohalide and optionally splitting the 7-amino-3-cephem-4-carboxylic acid ester of the general formula I to yield the free acid, the esters obtained being valuable intermediates.</p> |
