Abstract: The present invention provides a process for making a compound having a structure according to Formula (I) ##STR1## wherein A.sup.1, A.sup.2 and A.sup.3 are independently carbon or nitrogen and R.sup.1, R.sup.3, R.sup.4 and R.sup.6 are known quinolone substituents; and wherein one of R.sup.1, R.sup.3 or R.sup.6 may be a lactam-containing moiety;or a protected form, salt, pharmaceutically-acceptable salt, biohydrolyzable ester, or solvate thereof;the process comprising reacting one or more organosilicon compounds with a compound having a structure according to Formula (II) ##STR2## wherein A.sup.1, A.sup.2 and A.sup.3, R.sup.1, R.sup.3, R.sup.4 and R.sup.6 as described above; wherein one of R.sup.1, R.sup.3 or R.sup.6 may be a lactam-containing moiety; and X is a leaving group;or a protected form, salt, biohydrolyzable ester, or solvate thereof.

Abstract: The compounds, having a 4,10-dioxo-3-oxa-7-thia-1-azatricyclo[6,2,0,0.sup.2,6 ]decane-2-carboxylic acid skeleton as the base structure, their esters and their salts, are useful antibacterial agents.

Abstract: Beta-lactamase inhibiting compounds of the formula ##STR1## or a pharmaceutically acceptable acid addition or carboxylate salt thereof; where n is zero, 1 or 2; X.sub.3 is H or Br, R.sup.1 is H, the residue of certain carboxy-protecting groups or the residue of an ester group readily hydrolyzable in vivo; one of R.sup.12 and R.sup.13 is H and the other is vinyl, certain aryl, alkylthio, alkylsulfonyl or certain heterocyclyl, aminomethyl, thiocarboxamido or amidino groups; one or R.sup.2 and R.sup.3 is H and the other is as disclosed for the other of R.sup.12 and R.sup.13, or is Cl or CH.sub.2 OH, and R.sup.18 is H or certain acyl groups; intermediates useful in their production, methods for their preparation and use, and pharmaceutical compositions containing them.