Azetidinone derivatives

A compound of the formula (I) ##STR9## or a salt thereof with a carboxylic, sulphonic or mineral acid, wherein R is a group of formula --COOR.sup.16 and R.sup.16 is selected from the group consisting of C.sub.1-8 alkyl and C.sub.2-8 alkenyl, optionally substituted by methoxy, cyano, alkanoyloxy, p-bromobenzoyl or alkoxycarbonyl;

• benzyl;
• diphenylmethyl;
• triphenylmethyl;
• benzyl substituted on the ring by nitro, sulphonyl, cyano, alkyl or alkoxy, said substituted benzyl having up to 20 carbon atoms;
• a phenyl group optionally substituted by nitro, alkyl or alkoxy, said substituted phenyl group containing up to 12 carbon atoms;
• a cycloalkyl group containing up to 12 carbon atoms;
• a tetrahydropyranyl group;
• a phthalidyl group;
• and a stannyl group having up to 24 carbon atoms carrying three substituents selected from the group consisting of alkyl, alkenyl, phenyl, benzyl, cycloalkyl and alkoxy;
• R.sup.1, R.sup.2 and R.sup.3, which may be the same or different, represent an alkyl group having up to 8 carbon atoms, a benzyl group or a C.sub.3-7 cycloalkyl group, or two of R.sup.1, R.sup.2 and R.sup.3 form, together with the nitrogen atom to which they are attached, a piperidino, morpholino or thiamorpholino group or R.sup.1, R.sup.2 and R.sup.3 together may form part of a pyridinium, collidinium or quinuclidinium group;
• and R.sup.4 represents (i) a hydrogen atom;
• (ii) a hydroxyl group;
• (iii) a group --OR.sup.5, wherein R.sup.5 is an unsubstituted alkyl, alkenyl or alkynyl group containing up to 6 carbon atoms;
• a C.sub.1-16 alkyl group carrying a group R.sup.6 CO.sub.2 -- or R.sup.6 O-- where R.sup.6 is a C.sub.1-4 alkyl group, or carrying a C.sub.2-6 alkanoyl, carboxyl, C.sub.2-6 alkoxycarbonyl or cyano group;
• a hydroxyalkyl group having 2-6 carbon atoms;
• a 4-nitrobenzyl, benzyl, phenethyl, phenyl or tetrahydropyranyl group;
• or a cycloalkyl group having 3-7 carbon atoms optionally carrying a C.sub.1-4 alkoxy group;
• (iv) a group --OR.sup.7 wherein R.sup.7 represents a group R.sup.8 CO-- wherein R.sup.8 is a C.sub.1-8 alkyl, C.sub.2-8 alkenyl, or C.sub.3-12 cycloalkyl group, which R.sup.8 group may be substituted by a hydroxyl, C.sub.1-4 alkoxy, phenoxy, cyano or amino group or R.sup.8 is a benzyl, thienylmethyl, phenyl, thienyl, .alpha.-benzyloxycarbonylbenzyl, .alpha.-phenoxycarbonylbenzyl or .alpha.-aminobenzyl group;
• (v) a group O.CONR.sup.9 R.sup.10 wherein R.sup. 9 and R.sup.10, which may be the same or different, represent hydrogen;
• C.sub.1-5 alkyl;
• C.sub.2-6 alkanoyl, or a benzyl or phenyl group;
• (vi) a group OCSNHR.sup.9 wherein R.sup.9 is as hereinbefore defined other than hydrogen;
• (vii) the residue of a sulphur nucleophile represented by --SH, --SR.sup.11, --SOR.sup.11 or --SC.dbd.YR.sup.12 wherein R.sup.11 represents an alkyl, alkenyl or alkynyl group of up to 6 carbon atoms or a benzyl, phenyl or pyridyl group, all such groups R.sup.11 being unsubstituted or carrying a substituent selected from the group consisting of hydroxy, a group --OR.sup.6 or R.sup.6 CO.sub.2 --, where R.sup.6 is as hereinbefore defined, carboxyl, amino, cyano, a group of formula --COOR.sup.15 where R.sup.15 is C.sub.1-4 alkyl, and a group of formula --NR.sup.13 R.sup.14 where R.sup.13 and R.sup.14, which may be the same or different, represent hydrogen or C.sub.1-4 alkyl;
• and R.sup.12 is a group as defined for R.sup.11, or is a group --OR.sup.11, -- SR.sup.11 or --NR.sup.13 R.sup.14 where R.sup.13 and R.sup.14 are as hereinbefore defined;
• and Y represents oxygen or sulphur;
• or (viii) a group OR.sup.5 wherein R.sup.5 represents a silyl group carrying three substituents which may be the same or different C.sub.1-4 alkyl groups, wherein all substitution is monosubstitution.