Aza penem compounds

A compound having the following structural formula:

• ##STR15## wherein R.sub.1 is hydrogen;
• lower alkyl;
• R.sub.8 -C-amino wherein R.sub.8 is lower alkyl, lower alkyl substituted by one or more of one or two ring carbocyclic aromatic groups, lower alkoxy, phenyloxy, alkenyl of 2 to 6 carbon atoms, alkynyl of 2-6 carbon atoms, cycloalkyl of 4-6 carbon atoms, unsubstituted or substituted heteroaryl or heteroarylloweralkyl wherein the heteroaryl contains one or two hetero atoms selected from oxygen, nitrogen or sulfur and wherein the substituents in the heteroaryl are from 1 to 3 lower alkyl groups, wherein said R.sub.8 substituents are optionally substituted by hydroxy, thiol, loweralkylthio, lower alkyl, lower alkoxy, halogen, cyano, carboxy, nitro, amino, aminoloweralkyl or haloloweralkyl;
• or ##STR16## wherein R.sub.4 is hydrogen, lower alkyl, phenyl substituted by lower alkyl, lower alkoxy or halogen, heteroaryl wherein the heterocyclic ring is an aromatic heterocyclic containing a hetero atom selected from sulfur, oxygen or nitrogen, and R.sub.5 is hydrogen or an O-protecting group;
• R.sub.2 is lower alkyl, phenyl substituted by lower alkyl, lower alkoxy or halogen, alkylaryl, aminoloweralkyl, an N-protected amino-lower alkyl, hydroxy lower alkyl, an O-protected hydroxyloweralkyl, thio lower alkyl, an .alpha.-amino acid ester, an .alpha.-(N-protected) amino acid ester or a lower alkyl carboxylic acid ester;
• R.sub.3 is nitrile, tetrazole, or --COOR.sub.6 wherein R.sub.6 is lower alkyl, loweralkyltrihalogenomethyl, phenyl substituted by lower alkyl, lower alkoxy or halogen, allyl, a metabolisable ester, hydrogen, or an alkali metal cation;
• Z is sulfur, oxygen, --(CH.sub.2).sub.n -- wherein n is 1 or 2, or NR.sub.7 wherein R.sub.7 is hydrogen, lower alkyl, phenyl substituted by lower alkyl, lower alkoxy or halogen, ##STR17## wherein R 8 is as defined above, or an N-protecting group;
• and the pharmaeutically acceptable salts thereof.