| 摘要 |
beta -Lactam antibiotics are disclosed which have the formulae (Ia) or pharmaceutically acceptable salts or pharmaceutically acceptable in vivo hydrolysable esters thereof: <IMAGE> (Ia) wherein R1 is phenyl, substituted phenyl, cyclohexenyl, cyclohexadienyl, or an optionally substituted 5- or 6-membered heterocyclic ring containing up to three hetero-atoms selected from oxygen, sulphur or nitrogen; R2 is hydrogen or optionally substituted C1-6 alkyl; R3 is an optionally substituted 5- or 6- membered heterocyclic group containing one or two nitrogen heteroatoms; or R2 and R3 together with the nitrogen atom to which they are attached form an optionally substituted 5- or 6- membered heterocyclic group contaning one or two nitrogen heteroatoms; R4 is a substituted pyridinium group; and CO2R is carboxy or a carboxylate anion; and also the use thereof. Processes for the preparation of the compounds are disclosed together with intermediates for use therein.
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