Penemcarbonzuur-verbindingen en farmaceutische preparaten die deze verbindingen bevatten

There are provided penem- carboxylic acids and esters of the general formula In the formula, n=0 or 1; R''=H, lower alkyl, CCl3CH2-, p.nitrobenzyl, p.methoxybenzyl, phenyl, p.nitrophenyl or benzhydryl or a residue known to undergo metabolic activation in vivo and having favourable pharmacokinetic properties; Z=H, halogen, OH, NH2, NH2COO, SH or pyridinium or OR1, OCOR1, NHCOR1 or SR1 wherein R1=lower alkyl, aryl or a heterocyclic ring, each of which may be substituted or unsubstituted; R'=H, lower alkyl, lower alkoxy cycloalkyl or hydroxyalkyl (the hydroxy group of which is free or protected). Pharmaceutically acceptable salts of these compounds, which are antibacterial agents and beta -lactamase inhibitors, are included in the invention, as is a process for their preparation from penicillanic acid S-oxide esters.