.beta.-Lactam compounds, their preparation and use

The present invention relates to the preparation of compounds of the formula: ##STR1## wherein CO.sub.2 R.sub.1 is a free, salted or esterified carboxyl group, n is 0 or 1, and R.sub.2 is hydrogen or an acyl group or a group of the sub-formula (a): EQU R.sub.3 O.sub.3 S (a) wherein R.sub.3 is a salting ion or a methyl or ethyl group, with the proviso that when R.sub.2 is a group of the formula (a), the compound has cis stereochemistry about the .alpha.-lactam ring; which have been found to possess antibacterial and .alpha.-lactamase inhibitory activity.

This invention relates to novel compounds having anti-bacterial and 
.beta.-lactamase inhibitory activity. 
British Pat. Nos. 1489235 and 1467413 disclose that the compounds of the 
formula (I) and (II): 
##STR2## 
and their salts and esters have anti-bacterial and .beta.-lactamase 
inhibitory activity. 
British Patent Application No. 9366/77 discloses that the compounds of the 
formula (III): 
##STR3## 
and salts and esters thereof also have anti-bacterial and .beta.-lactamase 
inhibitory activity. 
British Patent Application No.: 16886/78 discloses that compounds of the 
formula (IV): 
##STR4## 
and salts and esters thereof wherein X is a --CH.sub.2 --CH.sub.2 -- or 
trans --CH.dbd.CH-- group and R is a group R.sup.1 or NH.R.sup.1 wherein 
R.sup.1 is an alkyl group of up to 6 carbon atoms, an alkenyl group of up 
to 6 carbon atoms, an aryl group or an alkyl group of up to 6 carbon atoms 
substituted by an aryl or aryloxy group, have antibacterial activity. 
British Patent Application No. 18100/78 discloses that compounds of the 
formulae (V) and (VI): 
##STR5## 
and salts and esters thereof wherein X.sup.1 is a --CH.sub.2 --CH.sub.2 -- 
or trans --CH.dbd.CH-- group and 
##STR6## 
is a group R.sup.3 or NH.R.sup.3 wherein R.sup.3 is an alkyl group of up 
to 6 carbon atoms, an alkenyl group of up to 6 carbon atoms, an aryl 
group, or an alkyl group of up to 6 carbon atoms substituted by an aryl or 
aryloxy group, have anti-bacterial activity. 
We have now discovered a further group of compounds which have 
antibacterial and .beta.-lactamase inhibitory activity. 
Accordingly, this invention provides the compounds of the formula (VII): 
##STR7## 
wherein CO.sub.2 R.sub.1 is a free, salted or esterified carboxyl group, n 
is 0 or 1, and R.sub.2 is hydrogen or an acyl group or a group of the 
sub-formula (a): 
EQU R.sub.3 O.sub.3 S (a) 
wherein R.sub.3 is a salting ion or a methyl or ethyl group, with the 
proviso that when R.sub.2 is a group of the sub-formula (a), the compound 
has cis stereochemistry about the .beta.-lactam ring. 
Preferably, n is 0. 
Preferred esterifying groups R.sub.1 include lower alkyl, benzyl, 
substituted benzyl and phthalidyl groups. 
Suitable substituted benzyl groups include methyl-, methoxy-, nitro- and 
halo-benzyl groups, for example, p-nitrobenzyl. 
A preferred group of compounds (VII) are those wherein R.sub.1 is an alkali 
or alkaline earth metal ion, for example, sodium or potassium. 
One preferred group R.sub.2 is a group of the sub-formula (a) wherein 
R.sub.3 is a salting ion as defined for R.sub.1 above. 
A further preferred group of compounds (VII) are those wherein R.sub.2 is a 
hydrogen atom. 
Yet a further preferred group of compounds (VII) are those wherein R.sub.2 
is an acyl group of the sub-formula R.sup.4 CO wherein R.sub.4 is a group 
R.sub.5 or NH.R.sub.5 wherein R.sub.5 is an alkyl group of up to 6 carbon 
atoms, an alkenyl group of up to 6 carbon atoms, an aryl group, or an 
alkyl group of up to 6 carbon atoms substituted by an aryl or aryloxy 
group. 
When used herein the term "aryl" means a phenyl group or a phenyl group 
substituted by an alkyl group of up to 3 carbon atoms, an alkoxyl group of 
up to 3 carbon atoms, a chlorine atom or fluorine atom. 
Suitably R.sub.4 is a group NH.R.sub.5. More suitably R.sub.4 is a group 
R.sub.5. 
The compounds of this invention when R.sub.2 is H or acyl may have either 
cis or trans stereochemistry about the .beta.-lactam ring. This invention 
accordingly provides the compounds (VII) where R.sub.2 is H or acyl as the 
cis isomers, the trans isomers, or mixtures of the cis and trans isomers. 
This invention also provides a compound of the formula (VII) when in 
admixture with the corresponding (E)-isomer. 
Particularly suitable compounds of this invention include that of the 
formula (VIII): 
##STR8## 
in the form of a pharmaceutically acceptable di-basic salt or of a 
pharmaceutically acceptable mono-basic of an in-vivo hydrolysable ester of 
the carboxylate group. Suitable di-basic salts include di-sodium and 
di-potassium. Suitable mono-salts mono-esters include the sodium and 
potassium salts of the phthalidyl ester. 
The present invention also provides a pharmaceutical composition which 
comprises a compound of the formula (VII) and a pharmaceutically 
acceptable carrier therefor. 
Suitably the compositions comprise a compound of the formula (VII) in the 
form of a pharmaceutically acceptable mono- or di-salt. 
Suitably the compositions comprise an ester of a compound of the formula 
(VIII). 
The compositions of this invention may be adapted for oral, topical or 
parenteral administration and may be used for the treatment of bacterial 
infections in humans or domestic animals such as infections of the 
respiratory and urinary tracts in humans and mastitis in cattle. 
The compositions may be formulated in similar manner to that described in 
the aforementioned patent applications. 
In general unit dosage forms of the compositions will contain from 50 to 
500 mg of a compound of this invention, more usually 100 to 300 mg, for 
example 125, 150, 200 or 250 mg. Such compositions may be administered 
once or more times a day (usually 3 or 4 times daily) so that the total 
daily dose is about 300 to 1000 mg for an average adult human. 
The compositions of this invention may be used to treat inter alia 
infections due to Staphylococcus aureus, E.coli and Klebsiella aerogenes. 
The compositions described above may have a compound of the invention as 
sole active ingredient, when that compound is the sole or principal 
anti-bacterial agent used during treatment. 
In addition, the .beta.-lactamase activity of the compounds of the 
invention renders them particularly useful for concurrent administration 
with a further .beta.-lactam antibiotic, such as a penicillin or 
cephalosporin. A composition comprising a compound of the invention may be 
administered together with a composition comprising the further 
.beta.-lactam antibiotic, or the two anti-bacterial agents may be 
administered in a single composition. 
Accordingly, this invention further provides a pharmaceutical composition 
as hereinbefore defined and also comprising a penicillin or cephalosporin. 
The ratio of the compound of the invention to penicillin or cephalosporin 
may be from 10:1 to 1:10 by weight, for example, 3:1 to 1:3. 
The penicillin or cephalosporin in unit dose forms of such compositions 
will be present at about the level normally used in conventional unit dose 
forms of that penicillin or cephalosporin. 
Particularly suitable penicillins for inclusion in such compositions 
include ampicillin and amoxycillin, and salts and esters thereof, for 
example the sodium salt or the phthalidyl or pivaloyloxymethyl ester. 
Compositions comprising a compound of the invention and a further 
.beta.-lactam antibiotic may be formulated in a similar manner to those 
described above. 
This invention further provides a process for the preparation of the 
compounds of the formula (VII), which process comprises the isomerisation 
of a compound of the formula (VIII): 
##STR9## 
wherein R.sub.1 and R.sub.2 and the stereochemistry about the 
.beta.-lactam ring are as defined in relation to formula (VII), by 
contacting the compound of the formula (VIII) with a mercuric salt in the 
presence of an inert solvent, and thereafter, if desired carrying out one 
or both of the following processes: 
(a) converting a compound (VII) wherein R.sub.1 is a p-nitrobenzyl group to 
a corresponding compound wherein R.sub.1 is a alternative group R.sub.1 ; 
(b) oxidising the compound of the formula (VII) wherein n is 0 to produce a 
corresponding compound wherein n is 1. 
The presence of a buffering agent to control the pH of the system has 
proved advantageous. A suitable agent for this purpose is calcium 
carbonate. 
Preferably, the process of the invention is carried out on a compound 
(VIII) wherein R.sub.1 is an esterifying group, since separation of the 
corresponding compound (VII) from other materials may then generally be 
achieved more easily than when the compounds contain a free or salted acid 
group. 
The solvent used in the process will be selected primarily on the basis of 
the solubility of the compound (VIII) therein, a large number of solvents 
being suitable; for example, acetonitrile, acetone, dichloromethane, 
chloroform and water. A suitable solvent mixture is acetonitrile-water. 
The reaction is generally carried out at a moderate temperature, for 
example, from -30.degree. to +50.degree. C., room temperature being 
particularly convenient, when the reaction is generally complete in a few 
minutes. 
When the compound of the formula (VII) contains no free or salted acid 
group, it may be isolated from the reaction mixture by extracting it into 
an organic solvent, washing with aqueous sodium bicarbonate solution, 
removing the solvent, and subjecting the product to further purification 
by chromatography. 
When the compound of the formula (VII) contains a free or salted acid 
group, it may be isolated from the reaction mixture by washing an aqueous 
solution of the product with an organic solvent such as ethyl acetate, 
removal of the aqueous solvent, and chromatography of the product. 
Suitable systems for chromatographic purification of the product include 
silica gel, using ethyl acetate-petrol or chloroform-ethanol mixtures as 
eluants. 
The conversion of a p-nitrobenzyl group R.sub.1 to an alternative group 
R.sub.1 may be achieved by hydrogenolysis, optionally in the presence of a 
base to form a salt, and optionally thereafter, re-esterifying the 
resulting free acid or salt, or neutralising a free acid to form a salt. 
The hydrogenolysis may be effected using a low, medium or high pressure of 
hydrogen, slightly superatmospheric pressure being most convenient. 
Preferably, a transition metal catalyst is present during the 
hydrogenolysis, for example, palladium on carbon. 
The re-esterification of the free acid or salt may be effected by 
conventional methods, for example, reaction of the acid with a diazo 
compound, or reaction of a salt with a compound R.sub.1 Z where Z is a 
good leaving group such as Cl, Br, I, OSO.sub.2 CH.sub.3 or OSO.sub.2 
C.sub.6 H.sub.4 CH.sub.3, and R.sub.1 is a group such that CO.sub.2 
R.sub.1 is an esterified carboxyl group. 
Suitable mercuric salts for use in the isomerisation include chloride, 
bromide, iodide, sulphate and acetate. 
Compounds of formula (VII) wherein n is 1 may be prepared from compounds of 
formula (VII) wherein n is 0 by oxidation with a suitable oxidising agent, 
such as m-chloroperbenzoic acid, in a suitable solvent, such as 
dichloromethane or water. 
The following Examples illustrate the invention: