IE42370B1 - Isoclavulanic acid derivatives - Google Patents

Abstract

Isoclavulanic acid and derivatives of it are disclosed which have .beta.-lactamase inhibitory and antibacterial properties, the preferred compounds being of the formula (I) wherein R is hydrogen or wherein n is 0 or an integer from 1 to 6; R1 is a hydrogen or a phenol or phenoxy group and R2 is a hydrogen or halogen atom or a C1-4 alkyl, C1-4 alkoxy, -CO2R3 group where R3 is a hydrocarbon group of 1-8 carbon atoms or ; or pharmaceutically acceptable salts thereof of the group of sodium, potassium, calcium, magnesium and aluminum; or pharmaceutically acceptable esters thereof of the formula . wherein A is a hydrocarbon group of 1 to 9 carbon atoms or a hydrocarbon group of 1 to 9 carbon atoms substituted by one or more halogen, lower alkyl, lower acyl, lower etherified or acylated hydroxy groups. These compounds are prepared by isomerization of clavulanic acid or derivatives, for example in the presence of a transition metal catalyst and hydrogen, or by ultra-violet irradiation.

Description

The present invention relates to novel β-lactam containing compounds, to their preparation and to compositions containing them, the said β-lactam containing compounds possessing β-lactamase inhibiting activity as well as a degree of anti-bacterial activity.

Belgian Patent No. 827,926 discloses inter alia clavulanic acid which is the compound of the formula (0): and its salts and esters. Clavulanic acid is a β10 lactamase inhibitor and an antibacterial agent.

We have now discovered a distinct group of compounds which have β-lactamase inhibitory and antibacterial properties.

Accordingly, the present invention provides compounds 15 of the formula (I): II c°2h wherein R is a hydrogen atom or an acyl group and salts and esters thereof.

The compound of the formula (I) wherein R- is a 5 hydrogen atom is designated isoclavulanic acid. Suitably R is a hydrogen atom or an acyl group containing up to 16 carbon atoms.

Preferably R is a hydrogen atom.

Suitably when R is an acyl group it is one that occurs in the acylamino side chain of a known antibacterially active penicillin or cephalosporin,for example R may be an n-aminoacetyl, a-aminophenylacetyl, ci-amino-4-hydroxyphenylacetyl, phenylacetyl, phenoxyacetyl, 2-thienylacetyl, 3-thienylacetyl, α-hydroxyphenylacetyl, a-carboxyphehyl15 acetyl, u-carboxy-3-thienylacetyl, α-azidophenylacetyl or p-hydroxyphenylacetyl group. When there is an amino group present this may be protected by conventional means, for example by a carboxybenzyl group.

Most suitably when R is an acyl group it is one of the sub-formula: —CO—CH—(CH,) "R2 ι ζ n K wherein n is 0 or an integer from 1 to 6; R^ is a hydrogen 2 atom or a phenyl or phenoxy group and R is a hydrogen or halogen atom or a 4 alkyl, alkoxy or CO^R^ group where R8 is a hydrocarbon group of 1 to 8 carbon atoms.

Preferably n is O or an integer from 1 to 3; R1 is 2 a hydrogen atom or a phenyl or phenocy group and R is a 4 4 hydrogen atom or CC^R group where R is a phenyl or benzyl group.

Suitable salts or esters of those compounds of the invention wherein R is an acyl group are those described hereinafter as suitable for those compounds of the inven10 tion wherein R is a hydrogen atom.

A particularly suitable group of compounds of the formula (I) are those of the formula (II): H ι (II) and pharmaceutically acceptable salts and esters thereof.

Suitable salts include sodium, potassium, calcium, magnesium, aluminium and conventional substituted ammonium salts.

Most suitably the salts of the compounds of the formula (II) are those of the formula (III): H ch2oh (III) - 5 θ wherein Μ is a sodium or potassium ion.

Such salts may form hydrates.

Further particularly suitable groups of compounds of the formula (I) are those of the formula (IV): wherein A is a group such that CO^A is an ester group.

Suitably A is an organic group of up to 16 carbon atoms and most suitably an organic group of up to 12 carbon atoms.

Suitable values for A include alkyl, alkenyl, alkynyl, aryl or aralkyl groups any of which may be substituted if desired.

Suitable substituents which may be included in the group A include halogen atoms and lower alkoxy, hydroxy, lower acyloxy or lower aryloxy groups.

When used herein the term 1 lower' means the group contains up to 7 carbon atoms.

Thus for example A may be methyl, ethyl, n-propyl, iso-propyl, straight or branched butyl, pentyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, allyl, butenyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclohexenyl, cyclohexadienyl, methylcyclopentyl, methylcyclohexyl, benzyl, benzhydryl, phenylethyl, naphthylmethyl, phenyl, naphthyl, propynyl, tolyl, 242370 ί. chloroethyl, 2,2,2-trichloroethyl, 2,2,2-trifluoroethyl, acetyImethyl, benzoyImethyl, 2-methoxyethyl; p-chlorobenzyl, p-methoxybenzyl, p-nitrobenzyl, p-bromobenzyl, mchlorobenzyl, 6-methoxynaphthy1-2-methyl, p-chlorophenyl or p-methoxyphenyl group.

A preferred group of compounds of the formula (IV) arc those wherein A is a group selected from those of the sub-formulae (a) to (d): (a) (b) -^ha4a5 (c) A6 wherein A^ is a hydrogen atom or a methyl group; A^ is a hydrogen atom or a C^_4 alkyl, phenyl or benzyl group; Ao is a lower alkyl, aryl or aralkyl group; X is oxygen or sulphur; Z is a divalent organic group; A^ is a hydrogen atom or an aryl group; A^_ is an aryl group; A^ is a hydrocarbon group of 1 to 9 carbon atoms optionally substituted by halogen atoms or by lower alkyl, lower acyl, lower etherified or acylated hydroxy groups.

In the above sub-formulae most suitably A^ is a hydrogen atom; A.> is a hydrogen atom or a methyl group; A^ is a methyl, t-butyl or phenyl group; X is oxygen; Z is -CH2CH2—, -CH=CH-, 337 0 OCH, OCH, is hydrogen, phenyl, tolyl, halophenyl or methoxyphenyl group; is a phenyl, tolyl, halophenyl or methoxyphenyl group and A& is a hydrocarbon group of 1 to 6 carbon atoms optionally substituted by Cl, Br, I, CF C(CH ) , methoxy, Jf J J acetyl, benzoyl or acetoxy groups.

A further preferred group of compounds of the formula (IV) are those wherein A is a group of the subformula (e) or (f): I A8 —CH (e) I12 C = A (f) wherein A is a hydrogen atom or a methyl group; A is a 7 σ hydrogen atom of a methyl, ethyl or phenyl group; A is an alkyl group of 1 to 6 carbon atoms or a phenyl or benzyl group; A and A^^ and A^ are oxygen or sulphur atoms.

In the above sub-formulae (e) and (f) A is more 8 suitably a hydrogen atom; Αθ is more suitably a methyl, ethyl, propyl, butyl or phenyl group; A^ and A^^ are more suitably oxygen atoms and Α^θ is most suitably a The esters of the compounds of the formula (I) wherein the ester group is convertible to the free carboxylic acid or a salt thereof are valuable intermediates in the prepara tion of the compounds of the formula (II) or a salt thereof One particularly suitable group of intermediates of this kind are those of the formula (V): wherein R is as defined in relation to formula (I) and the 5 group CO^R is an ester group which is convertible to a carboxylic acid group or a salt thereof by hydrogenolysis.

Suitable groups R include the benzyl, naphthylmethyl, benzhydryl, or trityl groups and their substituted derivatives such as the 4-bromobenzyl, 3,4-dimethoxybutyl, 620 methoxy-2-naphthylmethyl, 4,4'-dimethoxybenzhydryl or 2nitro-benzyl group.

In a composition aspect, the present invention provides a pharmaceutical composition which comprises a compound of the formula (I) as hereinbefore described.

Such compositions will also comprise a pharmaceutically acceptable carrier.

The compositions of this invention will normally be adapted for administration to humans and other mammals, for example, in conventional modes of treatment of diseases of the urinary tract, respiratory system and soft tissues as well as diseases such as otitis media and mastitis.

Suitable forms of the compositions of this invention include tablets, capsules, creams, syrups, suspensions, solutions and reconstitutable powders; sterile forms suitable for injections or infusion may be used, Such compositions may contain conventional pharmaceutically acceptable materials such as diluents, binders, colours, flavours, preservatives and disintegrants in accordance with conventional pharmaceutical practice.

The compound of formula (I) may be present in the composition as sole therapeutic agent or it may be present together with other therapeutic agents such as a penicillin or cephalosporin antibiotic. Thus, suitable penicillin or cephalosporin antibiotics for inclusion in the composition of this invention include benzylpenicillin, phenoxymethylpenicillin, carbenicillin, methicillin, propicillin, hetacillin, ampicillin, amoxycillin, ticarcillin, cephaloridine, cephalothin, cephalexin, cephamandole, cephaloglycin, cefuroxime and in vivo hydrolysable esters of such compounds such as the phenyl and indanyl esters of carbenicillin and ticarcillin, the acetoxymethyl ester of benzylpenicillin and the pivaloyloxymethyl and phthalidyl ester of ampicillin and amoxycillin. 2370 When present in a pharmaceutical composition together with a penicillin or cephalosporin, the ratio of the compound of formula (I) present to penicillin or cephalosporin present may be from, for example, 10:1 to 1:3 and advantageously may be 5:1 to 1:2, for example, 3:1 to 1:1.

The total quantity of antibacterial agents present in any unit dosage form will normally be between 50 and 1500 mg and will usually be between 100 and 1000 mg. However, injectable or infusable compositions may contain greater quantities if desired, for example,4 g or more of active material.

Normally between 50 and 6000 mg of the compositions of the invention will be administered each day of treatment but more usually between 500 and 3000 mg of the compositions of the invention will be administered per day. However, for the treatment of severe systemic infections or infections of particularly intransigent organism, higher doses may be used in accordance with clinical practice.

The present invention also provides a process for the preparation of a compound of the formula (I) as hereinbefore defined or a salt or ester thereof which comprises the isomerisation of a compound of the formula (VI): H c°2h or salt or ester thereof wherein R is a hydrogen atom or an acyl group, by contacting the compound of the formula 2370 - 11 (VI) or its salt or ester with a transition metal catalyst in the presence of hydrogen, and thereafter isolating the compound of the formula (I) or its salt or ester.

Preferably the reaction is carried out on a compound 5 of the formula (VI) wherein R is a hydrogen atom.

If the isomerisation is carried out on an ester of a compound of the formula (VI) then if this ester group is a 5 5 group CO^R wherein CO2R is as defined in relation to formula (V), the end product is often a compound of the formula (I) or a salt thereof.

A particularly suitable method of preparing a compound of the formula (II) or a salt thereof comprises contacting a compound of the formula (VII): H I wherein C02R is as defined in relation to formula (V) with a transition metal catalyst in the presence of hydrogen, the said reaction being carried out in the presence of base when it is desired to prepare a salt of the compound of the formula (II), and thereafter isolating the compound of the formula (II, or its salt.

A particularly suitable transition metal catalyst for carrying out the isomerisation reaction is palladium, for example 10% palladium on charcoal. - 12 When carrying out the isomerisation reaction the ratio of the weight of transition metal catalyst present to the weight of compound of the formula (VI) present will suitably be less than 1:3, for example 1:2.5 to 1:3. When used herein, the term 'the weight of transition metal catalyst' includes the weight of any support provided for the transition metal catalyst. If the reaction is carried out in the presence of 1 atmosphere of hydrogen, then the reaction will normally be over in less than 10 hours. Particularly prolonged reaction times should be avoided as they can lead to an unacceptable degree of reduction of the exocyclic double bond of compounds of the formula (I).

The reaction may be carried out at any non-extreme temperature, for example -20°C. to +100°C., such as -5°C. to +40°C., for example, 0°C. to +20°C.

The reaction is normally carried out in an organic solvent inert under the reaction conditions. Suitable solvents include lower alkanols such as methanol and ethanol, low boiling halohydrocarbons such as chloroform and dichloromethane, and ethers such as tetrahydrofuranIt should be realised that the compounds of formulae (VI) are not always entirely converted to the corresponding compounds of the formula (I) and that frequently an equilibrium mixture of compounds (VI) and (I) is produced. Such mixtures may then be separated if desired by conventional means, for example, chromatographicaIly. From a further aspect the isomerisation reaction comprises the ultra-violet irradiation of a compound of the formula (VI): 2 3 7 0 C02H or a salt or ester thereof wherein R is a hydrogen atom or an acyl group.

This ultra-violet irradiation is most suitably carried out on the benzyl ester of a compound of the formula (VI), for example the benzyl ester of the compound of the formula (VI) wherein R is hydrogen.

This reaction is normally carried out in a degassed organic solvent such as benzene, carbon tetrachloride, acetonitrile or other conventional solvents.

This reaction is normally carried out in an inert atmosphere such as argon or nitrogen.

This reaction is normally carried out at ambient temperature for the sake of convenience but any non-extreme temperature may be used, for example, -20° C. to +80° C , although moderate temperatures are preferred, for example, 0° C. to +30° C.

In accordance with conventional practice a photosensitizer may be included if desired. Thus such agents as dibenzyl, iodine, acetophenone and benzophenone may be included.

Wide or narrow spectrum u.v. may be employed to produce photolytic isomerisation of the compound of formula 2370 - 14 (VI). We have found that Hanovia low and medium pressure mercury lamps give satisfactory results. In use such lamps may employ a water-cooling jacket of silica or glass (Pyrex). (Hanovia and Pyrex are Registered Trade Marks).

When a compound of the formula (VI) is irradiated with ultra-violet light the compound of the formula (I) may be formed in admixture with the starting material or with a number of other products. This mixture may be separated by conventional means, for example, by chromatography. We have found that separation of the compounds of the formula (I) may often suitably be effected by column chromatography, for example by column chromatography on silica gel with an ethyl acetate/cyclohexane mixture.

A free, salted or esterified carboxyl group at the 215 position of the compounds of the formula (I) may be converted to another free, salted or esterified carboxyl group by conventional methods well known· to those skilled in the art.

Thus when there is a free carboxylic acid group at the 2-position this may be converted to an ester group by reaction with an alcohol AOH wherein A is as defined in relation to formula (IV) in the presence of a condensation promoting agent, such as dicyclohexylcarbodiimide, or by reaction with a diazocompound, such as diazomethane or alternatively it may be converted into a salt by treatment with base, such as sodium or potassium bicarbonate.

A salt of a compound of the formula (I) may be converted into an ester by a conventional nucleophilic substitution reaction by reaction with a compound AQ wherein A is as defined in relation to formula (IV) and Q is a readily displaceable group such as Cl, Br, I, OSO-CIL· or OSO„C Ii,CH_. 3 2 6 H 3 - 15 The compounds of the formula (I) wherein R is an acyl group may be prepared from the corresponding compound of the formula (I) wherein R is a hydrogen atom by conventional acylation procedures, for example by reaction with a compound of the formula ROH wherein R is an acyl group. Suitably this reaction is carried out in the presence of a condensation promoting agent, such as dicyclohexylcarbodiimide. Suitable acylation procedures are described in Patent Specification No.

The following Examples illustrate the invention: EXAMPLE 1.

CO_CH_COC.H z z o o H (1) (2) A dilute solution of phenacyl clavulanate (1) in dry benzene was irradiated in a quartz vessel using a 450 watt Hanovia medium pressure mercury lamp (obtained from Engelhard Hanovia Lamps, Bath Road, Slough, Buckinghamshire, England) (Hanovia*'is a registered Trade Mark) under nitrogen for 3 hours. The solvent was removed and t.l.c. of the residue showed two components which were separated by chromatography on silica gel. The more polar component was examined spectroscopically and found to be identical with the starting material. The less polar component was examined by h.p.l.c. and found to be a mixture of two compounds which were separated by preparative h.p.l.c. The second eluted component was obtained as a colourless oil and was 2 3 TO - 16 assigned the structure (2) on spectroscopic evidence.

I.r. (film): 348C6 1790, 1750, 1690cm1.

N.rn.r. (CDC13): 3.02 (IH, dd, J 17Hz, J' 1Hz, 6β-Η); 3.52 (IH, dd, J 17Hz, J' 3Hz, 6a-H); 4.27 (2H, d, J 9Hz, CH„0H); 5.43 (IH, s, CEKX^R); 5.48 (IH, m, CHCf^OH); 5.52 (2H, s, CE^COPh); 5.73 (IH, dd, J 3Hz, J* 1Hz, 5—Ii) and 7.7 (5H, m, aromatic -H).

EXAMPLE 2.

A solution of benzyl clavulanate (3) in dry benzene was irradiated under nitrogen in a quartz vessel using a Hanovia Photochemical 'Reading Reactor (Hanovia" is a registered Trade Mark) to give benzyl isoclavulanate (4) as a colourless oil, yield 40% after column chromatography.

The lamp unit (obtained from Engelhard Hanovia Lamps, Bath Road, Slough, Buckinghamshire, England) contains two low pressure ultra-violet lamps of 45 watts each with an energy max. at 254 n.m.

I.r. (CH2CI2): 3550, 1795, 1740, 1685 cm1.

N.rn.r. (CDC13): 1.85 (IH, s, CH2OH); 2.98 (1H, dd, J 17Hz, J' 1Hz, 6β—H); 3.45 (IH, dd, J 17Hz, J' 2.5Hz, 6cr—H); 4.05 (2H, d, J 7Hz, CH.OH); 5.18 (2H, s, CH_CcH_) 5.32 (IH, s, 5SC°2CH2C6H5’? 8,88 (IH, m' obscured by signal at 5.32, 23 7« - 17 CHCH2OH); 5.63 (1H, dd, J2.5Hz,J' 1Hz, 5—H) ; 7.36 (5H, s, aromatic —H,. The mass spectrum of the product showed a molecular ion at m/e 289.0949 (C15H15NO5 requires 289.0950).

EXAMPLE 3.

Benzyl clavulanate (3, (94 mgs) in ethanol (8 mis) was hydrogenated over 10% Pd/c (30 mgs) and sodium hydrogen carbonate (28 mgs) for 60 minutes. The catalyst was filtered, washed with water and then ethanol and the combined filtrates were evaporated. The residue was dissolved in dry dimethylformamide (2.5 ml) containing p-brcmobenzyl bromide (245 mgs) and the solution was left at ambient temperature for 2 hours. The solution was fractionated on silica gel eluting first with ethyl acetate-hexane - 18 (1:) and finally ethyl acetate. Fractions 16—19 were evaporated to give p-bromobenzyl isoclavulanate (5) (11 mgs) as thin rods, m.p. 134°—134.5° C. (after recrystallisa tion from methylene chloride—carbon tetrachloride). Frac5 tions 21—24 were evaporated to give p-bromobenzyl clavulanate (6) (52 mgs) as needles, m.p. 103°—104° C. (after recrystallisation from methylene chloride—carbon tetrachloride) .

The structures and absolute stereochemistry of the two products (5) and (6) were confirmed by X-ray analysis.

EXAMPLE 4.

A mixture of benzyl sodium hydrogen carbonate 15 charcoal (20 mg) in ethanol was hydrogenated at 20° C. and atmosphere pressure for 105 minutes after which time t.l.c (ethyl acetate—cyclohexane; 1:1) showed the reaction to be complete. The catalyst was filtered off and washed with water and the filtrate and combined washings evaporated.

The residue was twice treated with ethanol and evaporated, and acetone and evaporated, and triturated with acetone/ diethyl ether to give sodium isoclavulanate (7) (30 mg) as an off-white powder. 4237ο - 19 N.m.r. (D20): 3.10 (IH. d, J 17.5H, 6β—CH); 3.64 (IH, dd, J 17.5Hz, J' 3.0Hz); 4.18 (2H, d, J 7.5Hz, CH20H); 5.22 (2H, m, =CH—CH20H, 3—CH); 5.86 (IH, d, J 3.0Hz, 5—CH).

The minimum inhibitory concentrations (MIC) in p,g/ml of sodium isoclavulanate, ampicillin and combinations of sodium isoclavulanate with ampicillin against certain βlactamase producing organisms are given below in Table 1. The results were obtained by the microtitre technique with an inoculum of 1/500 of overnight broth. - 20 I ε m 3 lH Φ Η ϋ 4J Ό O C O 10 fi CO -rl rH ο Ο ιη TABLE 1 MICs in p,g/ml of Sodium Isoolavulanate, Ampicillin and Mixtures thereof against Staphylococcus Aureus Russel and Klebsiella Aerogenes E70 E Φ •rl + O fi fi (0 fi ♦rl ι—1 r-l r-l 3 r-i ε > -rt \ fi O tprd •H d. O 04 0 ε O 01 rfj CM -rl ε fi 3 +> + fi Ό C fi O fi •rl W rd r4 3 Η H > •H £ fi O \ r-i ή tn o & =L O ε w < in -h ε fi 3 -P + Ή fi V fi fi O fi •rl 01 ι-H r-i 3 H r-l > -rl £ fi Ο \ r4 ♦ri tn fi ft 3. O £ to < rH -rl •rl fi •rl ε1 ε ία Ή fi fi tp M O O ..

CM Φ ιη CM ft ►4 CO„CH-C(.H_Br σ» cn Ο Ο in Ο Ο ιη Φ Μ fi fi ϋ Ο ϋ Ο r-l r—I φ fi φ tP ο Μ Φ fi ι-l -rl Λ Φ * a 01 n fi ro Φ o «Ρ 3 r-l r*- CO (X w - 21 Sodium isoclavulanate (7) (19.5 mg) was treated with p-bromobenzyl bromide (22.5 mg) in dry dimethylformamide for 3 hours after which time t.l.c. (butanol-ethanolwater; 16:4:7) showed the reaction to be almost complete.

The solvent was removed in vacuo and the residue chromatographed on silica gel (elution with ethyl acetate—cyclohexane; 1:1) to give the product (5) (14.5 mg) m.p. 132°— 134°C.

EXAMPLE 6.

C H CHCO-H 6 5 ι 2 COCHCH 2 2 6 5 Benzyl isoclavulanate (4) (82 mg) was dissolved in dry methylene chloride and benzyl phenyImalonic acid (76 mg) added. The solution was cooled to 0° C. and dicyclohexylcarbodiimide (57.7 mg) added. The mixture was stirred at 0° C. for 1 hour and at room temperature overnight; the mixture was filtered and the filtrate concentrated to give - 22 the crude product (8). The crude product was purified by fractionation on silica gel and gradient elution with ethyl acetate/cyclohexane gave the product (8) (42 mg; 32% yield) as a colourless gum.

I.r. (film): 1805, 1745, 1695 cm1; N.m.r. (CDClg): 2.95 (IH, dd, J 17Hz, J' 1H2, 6β—H); 3.42 (IH, dd, J 17Hz, J' 3Hz, 6ar~H); 4.57 (2H, m, C=CHCH2); 4.59 (IH, s, OCOCHPh) ; 5.08 (2H, s CHPhCO^H^Ph); 5.12 (IH, m, obscured, C=CHCH,); 5.14 (2H, s, NCHCO„CH„Ph)- 5.35 (IH, bs, NCHCO.CHCH); 5.63 (IH, dd, J 3Hz, J' 1Hz, 5—H) — 2 2 6 5 — " and 7.28 δ(15Η, s, aromatic —H); m.w. (mass spectrometry) 541.

EXAMPLE 7.

C.H CH 0C0MHCH.C0 H o 5 2 2 2 H C°2CH2C6H5 (9) - 23 Benzyl isoclavulanate (4) (120 mg) was treated with benzyloxycarbonyl glycine (84 mg), pyridine (32 mg) and dicyclohexylcarbodiimide (82 mg) in methylene chloride at 0° C. The solution was stirred overnight at room temperature and filtered. Silica gel chromatography yielded the desired product (9) as a colourless gum in 72% yield.

I.r. (film): 3370, 1810, 1700—1760, 1665 cm-1; n.m.r. (CDCl3): 3.02 (IH, dd, J 17.5Hz, J’ 1Hz, 6fi—H) ; 3.49 (IH, dd, J 17.5Hz, J' 3HZ, 6α~H) ; 3.9 (2H, d, J, 6H2, CH2NH),- 4.67 (2H, m, C=CH . CH.^ 5.14 (2H, s, NCHCO^B^Ph); 5.21 (2H, s, I NHCOCHCH); —2 6 5 .46 (IH, bs, NCH . C0.CH.CX); 5.72 (IH, dd, J 3Hz, J1 Z Zoo 1Hz, 5—H); 7.38 (1OH, s, aromatic —H).

Claims (58)

1. CLAIMS:1. Compounds of the formula (I): wherein R is a hydrogen atom or an acyl group and salts and esters thereof.

2. A compound' according to claim 1 of the formula (II) co 2 h (II) or a salt or ester thereof.

3. A compound according to claim 2 of the formula (II) or a pharmaceutically acceptable salt thereof.

4. A compound according to claim 3 of the formula (III) - 25 wherein M is a sodium or potassium ion.

5. A compound according to claim 2 of the formula (IV): wherein A is a group such that CC^A is an ester group. 5

6. A compound according to claim 5 wherein A is an organic group of up to 16 carbon atoms.

7. A compound according to claim 6 wherein A is an organic group of up to 12 carbon atoms.

8. A compound according to any of claims 5 to 7 10 wherein A is an alkyl, alkenyl, alkynyl, aryl or aralkyl group optionally substituted by halogen, lower alkoxy, hydroxy, lower acyloxy or lower aryloxy groups.

9. A compound according to claim 5 wherein A is a methyl, ethyl, n-propyl, isopropyl, straight or branched 15 butyl, pentyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, allyl, butenyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclohexenyl, cyclohexadienyl, methyleyclopentyl, methylcyclohexyl, benzyl, benzhydryl, phenylethyl, naphthyImethyl, phenyl, naphthyl, propynyl, tolyl, 20 2-chloroethyl, 2,2,2-trichloroethyl, 2,2,2-trifluoroethyl, acetylmethyl, benzoyImethyl, 2-methoxyethyl, p-chlorobenzyl, p-methoxybenzyl, p-nitrobenzyl, p-bromobenzyl, m-chlorobenzyl, 6-methoxynaphthyl-2-methyl, p-chlorophenyl or pmethoxyphenyl group. - 26 CA 1 A 2 —X—co—ft 3

10. A compound according to claim 5 wherein A is a group selected from tho^e of sub-formulae (a) to (d): (a) (b) :h— z 5 . —CHA A (c) -a 6 (d) wherein A^ is a hydrogen atom or a methyl group; A^ is a hydrogen atom or a C^ alkyl, phenyl or benzyl group; is a C^_ 7 alkyl, aryl or C ? aralkyl group; X is oxygen 10 or sulphur; Z is a divalent organic group; A^ is a hydrogen atom or an aryl group; A^ is an aryl group; A^ is a hydrocarbon group of 1—9 carbon atoms optionally substituted by halogen atoms or by 7 alkyl, ? acyl or C^_ 7 etherified or acylated hydroxy groups.

11. A compound according to claim 10 wherein A^ is a hydrogen atom; A^ is a hydrogen atom or a methyl group; A 3 is a methyl, butyl or phenyl group; X is oxygen; Z is A^ is hydrogen, phenyl, tolyl, halophenyl or methoxyphenyl; A$ is a phenyl, tolyl, halophenyl or methoxyphenyl group and Ag is a hydrocarbon group of 1—6 carbon atoms optionally 4237ο - 27 substituted by Cl, Br, I, CF^, CtCH^)^, methoxy,acetyl, benzoyl or acetoxy.

12. A compound according to claim 5 wherein A is a group of the sub-formula (e) or (f): (e) —CH10 C=A (f) wherein A is a hydrogen atom or a methyl group; A is a 7 8 hydrogen atom or a methyl, ethyl or phenyl group; A g is an alkyl group of 1—6 carbon atoms or a phenyl or benzyl group; V\ OCH OCHL and A and A^ 2 are oxygen or sulphur atoms.

13. A compound according to claim 12 wherein Αθ is a hydrogen atom; A g is a methyl, ethyl, propyl, butyl or phenyl group; A^^ and A^ 2 are oxygen atoms and A is a z AZ group. 43370 - 28

14. A compound according to claim 1 of the formula (V): wherein R is as defined in relation to claim 1 and the group CO^R-” is an ester group convertible to a carboxylic group or a salt thereof by hydrogenolysis.

15. A compound according to claim 14 wherein R 3 is a benzyl, naphthyImethyl, benzhydryl, trityl, 4-bromobenzyl, 3,4-dimethoxybenzyl', 6-methoxy-2-naphthyImethyl or 4,4'dimethoxybenzhydryl group.

16. A compound according to either claim 14 or 15 wherein R is a hydrogen atom.

17. A compound according to claim 1 wherein R is an acyl group containing up to 16 carbon atoms. 15

18. A compound according to claim 1 wherein R is an acyl group of the sub-formula: , 2 —CO—CH—(CH„) —R | 2 Π I 1 wherein n is 0 or an integer from 1 to 6? R^is a hydrogen 2 atom or a phenyl or phenoxy group and R is a hydrogen or 3 halogen atom or a alkyl, alkoxy or CO^R group where R 3 is a hydrocarbon group of 1 to 8 carbon atoms. - 29

19. Λ compound according to claim 18 wherein n is 0 or an integer from 1 to 3; R^ is a hydrogen atom or a 2 4 phenyl or phenoxy group and R is a hydrogen atom or C0_R 4 2 group where R is a phenyl or benzyl group. 5

20. A process for the preparation of a compound according to claim 1 which process comprises the isomerisation of a compound of the formula (VI): or a salt or ester thereof wherein R is as defined in rela10 tion to claim 1 by contacting the compound of the formula (VI) or its salt or ester with a transition metal catalyst in the presence of hydrogen, and thereafter, if desired, converting the free, salted or esterified carboxyl group at the 2-position to another free, salted or esterified 15 carboxyl group and/or converting one group R to another group R by conventional methods, and thereafter isolating the compound of the formula (I) or its salt or ester.

21. A process according to claim 20 wherein R is a hydrogen atom. 20.

22. A process for the preparation of a compound of the formula (II): 43370 - 30 Η or a salt thereof which process comprises contacting a compound of the formula (VII): 5 wherein CC^R^ is as defined in relation to claim 14 with a transition metal catalyst in the presence of hydrogen, the said reaction being carried out in the presence of base when it is desired to prepare a salt of the compound of the formula (II), and thereafter isolating the compound of the 10 formula (II) or its salt.

23. A process according to either one of claims 21. Or 22. Wherein the hydrogen is at a pressure of 1 atmosphere.

24. A process according to any one of claims 21 to 23. Wherein the transition metal catalyst is palladium. 15

25. A process according to any one of claims 21 to 24. Wherein the reaction is carried out in a solvent inert under the reaction conditions. - 31

26. A process according to claim 25 wherein the solvent is methanol, ethanol, dichloromethane or tetrahydrofuran. 25.

27. A process for the preparation of a compound 5 according to claim 1 which process comprises the ultraviolet irradiation of a compound of the formula (VI): or a salt or ester thereof wherein R is as defined in claim 1. 26.

28. A process according to claim 27 wherein R is 10 hydrogen. 27.

29. A process according to claim 27 or claim 28 for the preparation of benzyl ester of a compound of the formula (I). 28.

30. A process according to any one of claims 27 to 15 29 wherein the reaction is carried out in an organic solvent. 29.

31. A process according to claim 30 wherein the organic solvent is benzene, carbon tetrachloride or acetonitrile. 30.

32. A process according to any one of claims 27 to 31 wherein the isomerisation reaction is carried out in the 20 presence of a photosensitizer. 31.

33. A process according to any one of claims 27 to 32 wherein the ultra-violet radiation is emitted by a medium pressure mercury lamp. - 32 32.

34. A process for the preparation of a compound according to claim 1 wherein R is an acyl group which process comprises the· acylation of a compound according to claim 1 wherein R is a hydrogen atom by conventional 5 acylation procedures. 33.

35. A process according to claim 34 wherein the t acylation reaction comprises the reaction of a compound according to claim 1 wherein R is a hydrogen atom with a compound of the formula ROH wherein R is an acyl group. 10

36. A process according to claim 35 wherein the process is carried out in the presence of a condensation promoting agent.

37. A process for the preparation of an ester of a compound of the formula (I) as defined in claim 1, which 15 process comprises the esterification of a compound of the formula (I) or a salt thereof by conventional methods.

38. A process according to claim 37 which process comprises the reaction of a compound of the formula (I) with an alcohol AOH, wherein A is as defined in claim 5, 20 in the presence of a condensation promoting agent.

39. A process according to claim 37 which process comprises the reaction of a compound of the formula (I) with a diazocompound.

40. A process according to claim 37 which process 25 comprises the reaction of a salt of a compound of the formula (I) with a compound AQ wherein A is as defined in claim 5 and Q is a readily displaceable group.

41. A process for the preparation of a salt of a compound of the formula (I) as defined in claim 1, which - 33 process comprises the treatment of a compound of the formula (I) with a base.

42. A pharmaceutical composition which comprises a compound according to claim 1 together with a pharmaceutically acceptable carrier.

43. A pharmaceutical composition according to claim 42 wherein a penicillin or cephalosporin is also present.

44. A pharmaceutical composition according to claim 43 wherein the penicillin or cephalosporin is benzylpenicillin, phenoxymethylpenicillin, carbenicillin, methicillin, propicillin, hetacillin, ampicillin, amoxycillin, ticarcillin, cephaloridine, cephalothin, cephalexin, cefuroxime, cephamandole, the acetoxymethyl ester of benzylpenicillin, the pivolyloxymethyl or phthalidyl ester of ampicillin or amoxycillin or the phenyl or indanyl esters of carbenicillin or ticarcillin.

45. A pharmaceutical composition according to either claim 43 or 44 wherein the ratio of the compound of the formula (I) present to the second β-lactam present is from 10:1 to 1:3.

46. A pharmaceutical composition according to claim 45 wherein the ratio of the compound of the formula (I) present to the second β-lactam present is from 3:1 to 1:1.

47. A pharmaceutical composition according to any one of claims 42 to 46 wherein the total quantity of antibacterial agents present in any unit dosage form is between 50 and 1500 mg.

48. A pharmaceutical composition according to claim 47 wherein the total quantity of antibacterial agents present in any unit dosage form is between 100 and 1000 mg. - 34

49. A compound according to claim 1 whenever prepa red by the process of any one of claims 20 to 26.

50. A compound according to claim 1 whenever prepared by the process of any one of claims 27 to 33. 5

51. A compound according to claim 1 whenever prepared by the process of any one of claims 34 to 36.

52. A compound according to claim 1 whenever prepared by the process of any one of claims 37 to 40.

53. A compound according to claim 1 whenever 10 prepared by the process of claim 41.

54. A process according to any one of claims 20 to 26 substantially as described in Example 3.

55. A process according to any one of claims 27 to 31 or 33 substantially as described in Examples 1 and 2. 15

56. A process according to any one of claims 34 to 34. 36 substantially as described in Examples 6 and 7.

57. A process according to claim 37 or claim 40 substantially as described in Example 5.

58. A process according to claim 41 substantially 20 as described in Example 4.