GB1573503A - Clavulanic acid derivatives - Google Patents

Description

(54) CLAVULANIC ACID DERIVATIVES (71) We, GLAXO LABORATORIES LIMITED, a British Company of Greenford, Middlesex, England; do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to novel antibiotics and p-lactamase inhibitors and to a process for their production.

In German OLS No. 2,604,697 we have described the isolation, from fermentations of Streptomyces clavuligerus, of the carboxylic acid having the formula (I) (clavulanic acid)

and salts thereof in pure form.

The compounds in this specification are named with reference to "clavam"; the name given to the parent heterocycle of formula A

by analogy with the term "cepham" used in the naming of cephalosporin compounds in J.Amer. Chem. Soc., 1962, 84, 3400. Thus, the compound of formula (I) is named (3R, 5R, Z)-2-(2-hydroxyethylidene) clavam-3-carboxylic acid.

The present invention relates to ethers of the compound of formula I above and their salts and esters. These are of use, as detailed below, as antibiotics or as p-lactamase inhibitors, or they may be useful as intermediates in the preparation of further active compounds or in purification or characterisation of the parent acids.

Accordingly, we provide compounds of the formula (II)

wherein R represents a group -ORl wherein R1 represents a methyl or ethyl group, an alkenyl group having 2-6 carbon atoms, a C1.6 alkyl group substituted by a C1.4 alkoxy group, a hydroxyalkyl group having from 2-6 carbon atoms, or a carbon-attached saturated 5-7 membered heterocyclic ring, and R4 represents a carboxyl or esterified carboxyl group, or a salt of a compound of formula (II) wherein R4 is a carboxyl group, with the proviso that when R represents a methoxy group, R4 does not represent a methoxycarbonyl group.

Representative groups R1 include methyl, ethyl, hydroxyethyl, methoxyethyl, ethoxyethyl and tetrahydropyranyl. The simpler C1.4 alkoxy groups are preferred, e.g. the ethyl and methyl groups.

The salts according to the invention include salts with inorganic bases, such as alkali metal salts, e.g. sodium, potassium and lithium salts; alkaline earth metal salts, e.g. calcium and magnesium salts; and ammonium salts, as well as salts with organic bases, for example amine salts.

The esters according to the invention may be represented as compounds of formula II in which R4 is a group COOT3 where R3 represents an organic group which is conveniently derived from an alcohol (aliphatic or araliphatic), a phenol, or a stannanol. Such an alcohol, phenol, or stannanol used to esterify the carboxy group preferably contains not more than 24 carbon atoms.

Thus, the group R3 may represent a straight or branched unsubstituted or substituted alkyl or alkenyl group, preferably having from 1-8 carbon atoms, most preferably 1-4 carbon atoms, for example a methyl, ethyl, propyl or isopropyl, butyl, sec-butyl, tert-butyl or allyl group desirable substituents being, for example, alkoxy, e.g. methoxy; halogen, i.e. fluorine, chlorine, bromine or iodine; cyano; acyloxy, e.g. alkanoyloxy, such as acetoxy orpivaloyloxy, or alkoxycarbonyloxy, such as ethoxycarbonyloxy; acyl, e.g. p-bromobenzoyl and alkoxycarbonyl, e.g. ethoxycarbonyl; an aralkyl group having up to 20 carbon atoms, expecially an arylmethyl group, e.g. a benzyl or substituted benzyl group, suitable substituents being either halo, e.g. chloro; nitro, e.g. o- orp-nitro; cyano; alkoxy, e.g.p-methoxy or alkyl, e.g.p-methyl, groups; a diphenylmethyl or triphenylmethyl group or a fur-2-ylmethyl, thien-2-ylmethyl or pyrid-4-ylmethyl group, the heterocyclic groups of which may also be substituted, e.g. by a C1.4 alkyl group, preferably methyl an aryl group having up to 12 carbon atoms, e.g. a phenyl or substituted phenyl group, suitable substituents being either halo, e.g. chloro; nitro, e.g. o- orp-nitro; cyano; alkoxy, e.g.

p-methoxy, or alkyl, e.g. p-methyl, groups; a cycloalkyl group containing up to 12 carbon atoms, e.g. adamantyl; such a cycloalkyl group optionally containing one or more heteroatoms in the ring system, the hetero atoms being selected from, for example, oxygen, as in the tetrahydropyranyl or phthalidyl group; or a stannyl group having up to 24 carbon atoms, for example a stannyl group carrying three substituents which may be the same or different and are selected from alkyl, alkenyl, aryl, aralkyl, cycloalkyl, alkoxy, and aralkoxy groups. Such groups will include methyl, ethyl, propyl, n-butyl, phenyl and benzyl groups.

We further provide compounds of the formula (II)

(where R is an etherified hydroxy group and R4 iS a p-nitrobenzyloxycarbonyl group).

In general, R may be rep-esented by OR5, ,l'ure is an aliphatic, araliphatic, aromatic or heterocyclic group. Thus, for example, R may be an alkyl, alkenyl or alkynyl group, which may contain 1-6 carbon atoms, or such an aElr7li group carrying a substituted hydroxy group; a hydroxyalkyl group having 2-6 carbon arr:4s; an aralkyl group which may have 1-6 carbon atoms in the alkyl portion or an aryl group, such aryl and aralkyl groups preferably being monocyclic; a cycloalkyl group, which may have 3-7 carbon atoms; or a carbon-attached saturated 5-7 membered heterocyclic ring containing, for example, an oxygen atom.

Substituted hydroxy group as referred to above include acylated and etherified hydroxy groups. In general, acylated hydroxy groups may have the formula R2CO2 where R2 is a hydrocarbyl group as defined for R5, relatively simple R2 groups such as C1.4 alkyl, e.g.

methyl, being preferred, while etherified hydroxy group may have the formula R2O, simple R2 groups such as C1.4 alkyl, e.g. methyl and ethyl, again being preferred.

The ethers according to the invention generally exhibit p4actamase inhibitory activity and are of use in the protection of p-lactam antibiotics susceptible to p-lactamase hydrolysis, e.g.

antibiotics such as ampicillin or cephalexin.

The ethers, particularly in the form of their acids, salts and metabolically labile esters, also in general show antibiotic activity against gram-positive and gram-negative microorganisms.

Where the ether grouping is readily cleaved, e.g. by hydrolysis, without significant degradation of the remainder of the molecule, the ethers may be useful as hydroxyl-protected derivatives of the acid of formula (I) or its esters. These may be of use either in the purification of the acid of formula (I) or as hydroxyl-protected intermediates for use in preparing further derivatives.

In general, the acid, salt and metabolically labile ester forms of the ethers of the invention are preferred forms for use in medicine. However, the other esters are also useful and, for example, where the ester grouping is readily cleaved, e.g. by hydrolysis or hydrogenolysis, without significant degration of the rest of the molecule, the esters are especially useful as carboxyl-protected derivatives of the parent ethers. Those esters which are readily cleaved and are primarily of use in this connection include arylmethyl esters, especially the benzyl, p-nitrobenzyl, benzhydryl and trityl esters as well as the stannyl, e.g. tri-n-butylstannyl, esters. As indicated above, the ester grouping may be metabolically labile, generating the parent acid in vivo, as in the case of, for example, the acyloxymethyl esters, e.g. acetoxymethyl and pivaloyloxymethyl esters, and phthalidyl esters.

Preferred ethers for use in medicine are those in which Rl is an alkyl group having 1-4 carbon atoms or such an alkyl group carrying a substituted hydroxy group. Ethers wherein R' represents an unsubstituted C1.4 alkyl group are most preferred and our tests have shown that the methyl and ethyl ethers, in the form of their carboxylic acid salts, are absorbed after oral administration to rats and mice. In general, the free acids according to-the invention and their salts and metabolically labile esters show greater antibiotic and ss-lactamase inhibitory activity than the corresponding metabolically stable esters.

The ethers, in the form of their acids, salts and metabolically labile esters, for which we have demonstrated antibiotic activity, have been active against a range of gram-positive and gram-negative microorganisms, for example, against strains of Staphylococcus aureus, Escherichia coli, Salmonella typhimurium, shigella sonnei, Enterobacter cloacae, Klebsiella aerogenes, Proteus mirabilis, Proteus organic, Serratia marcescens, Providencia species, Citrobacter koseri and Bacteroides species.

The new acids and their salts and esters are stable to the action of p-lactamases produced by gram-positive organisms, for example those produced by Staphylococcus aureus, and to p-lactamases produced by gram-negative organisms in classes I-V described by Richmond, M.H. and Sykes, R.B. (1973). ("The p-lactamases of gram-negative bacteria and their possible physiological role." Advances in Microbial Physiology, 9 31-88).

As indicated above, the new acids and their salts and esters generally also possess the ability to inhibit p4actamase enzymes, for example those produced by gram-positive organ isms, e.g. those produced by strains of Staphylococcus aureus and the enzymes classified in classes II-V from gram-negative bacteria produced, for example, by strains of Proteus mirabilis, Escherichia coli, Proteus organic, Klebsiella aerogenes, Salmonella typhimurium, Ha em ophilus influenzae and Neisseria gonorrhoeae and are useful in combination with ss-lactam antibiotics such as ampicillin and cephalexin.

A number of class I enzymes are also inhibited, for example those produced by strains of Bacteroides fragilis, Proteus vulgaris, Proteus organic, Proteus rettgeri, Enterobacter cloacae, Citrobacter freundii, Providencia species and Hafnia alvei. The new antibiotic acids and their salts and esters have the ability to protect p-lactamase susceptible p-lactam antibiotics from ss-lactamase hydrolysis.

As indicated above, certain of the compounds of the invention are also absorbed when administered orally as shown by studies in rats and mice. These compound are of interest for use in conjunction with both injectible and orally adsorbed p-lactam antibiotics which show susceptibility to p-lactamases from gram-positive and gram-negative organisms.

In general, it is preferred to use the new acids and their salts and metabolically labile esters in conjunction with a broad spectrum p-lactam antibiotic, which may be of a type conventionally administered by the oral or parenteral route.

Examples of orally absorbed broad spectrum p-lactam antibiotics include cephalexin, cephaloglycin, ampicillin and amoxycillin and their orally absorbed esters, e.g. the acyloxymethyl, a-alkoxycarbonyloxyalkyl and phthalidyl esters, and the orally absorbed esters of carbenicillin and tricarcillin, e.g. the indanyl and phenyl esters. Broad spectrum p-lactam antibiotics which are not orally absorbed include carbenicillin, ticarcillin, cephalothin, cephamandole, cephaloridine, cefazolin, cephacetrile and cephapirin. Examples of narrow spectrum p-lactam antibiotics are penicillin G, penicillin V, mecillinam and pivmecillinam.

The above antibiotics may also be in the form of their metabolically labile esters, pharmaceutical acceptable salts and/or solvates thereof.

An especially favourable combination of a compound of the present invention together with a further p-lactam antibiotic is the compound of the invention wherein R4 is carboxyl and R represents a methoxy group, or a pharmaceutically acceptable salt or metabolically labile ester thereof, together with either (6R,7R,2'R)-7- (2'-amino-2'-phenylacetamido)3-methylthio-ceph-3-em- 4-carboxylic acid or (6R,7R,2'R)-7- (2'-amino-2=phenylacetamido)- 3-methoxy-ceph-3-em- 4-carboxylic acid, or a pharmaceutically acceptable salt thereof. Such a combination has the further advantage that both of the p-lactam constituents are orally absorbed.

Combinations of the acids, salts and metabolically labile esters according to the invention with, for example, ampicillin generally show synergistic activity against p4actamase producing strains of Staphylococcus aureus, Escherichia coli, Klebsiella aerogenes, Proteus mirabilis, Salmonella typhimurium, Shigella sonnei, Bacteroides fragilis, Proteus organic, Proteus vulgaris, and Neisseria gonorrhoeae.

According to a further feature of the invention, we provide pharmaceutical compositions (including veterinary compositions) containing at least one of the acids, pharamceutically acceptable salts and metabolically labile esters according to the invention. In view of the protective action described above, the compositions can advantageously contain further p-lactam antibiotics, orally absorbed p-lactam antibiotics being especially preferred when the compound according to the invention is also orally absorbed. The compositions may normally also contain a pharmaceutically acceptable (including veterinary) carrier or excipient.

The compositions may, for example, take the form of powders, tablets, capsules, lozenges, solutions and syrups suitable for oral administration, and may include, for example, starch, lactose, talc, magnesium stereate, gelatin, distilled water and suspending, dispersing, emulsifying, flavouring or colouring agents.

The active compounds of the invention may further be formulated in compositions suitable for topical administration. Such formulations will thus comprise the active compounds of the invention formulated in hydrophobic or hydrophilic bases as ointments, creams, lotions, paints, powders, etc. Spray compositions for prophylactic use in surgery can also be formulated.

The active compounds may further be formulated in rectal compositions such as suppositories or retention enemas.

The active compounds of the invention may be formulated for parenteral administration.

The compounds may thus be formulated in ampoules for reconstitution before use, optionally together with a further p-lactam antibiotic.

In general, the weight ratio of the new antibiotic or a salt and/or ester thereof to the ss-lactam antibiotic to be protected will be in the range 10:1 to 1:10, more preferably 5:1 to 1:5, especially 2:1 to 1:2.

The active compounds of the invention will generally be administered to adults at a total daily dosage level of 50 mg to 20 g, preferably from 100 mg to 10 g, which may be in divided doses given 1-4 times per day. Where the composition contains a further p-lactam antibiotic, the total quantity of p-lactam antibiotic will desirably be from 100 mg to 20 g which may be given in divided doses from 1-4 times per day. Dosage units will in general contain 250 mg to 5 g of active compound according to the invention when used alone and 100 mg to 5 g of total P-lactam antibiotic where a further p-lactam antibiotic is present.

The novel ethers of formula (II) in which R represents a group -ORl as defined above and the ethers of formula (II) in which R represents an etherified hydroxyl group, as in the group -OR5 as defined above, and salts thereof may be prepared by etherification of an ester formed from the hydroxy acid of formula (I), followed, where the free acid or a salt is required, by de-esterification and, if desired salt-formation. Etherification may be effected, for example, by reaction of the starting hydroxy ester, or a reactive derivative thereof, with an etherifying agent, e.g. a diazoalkane or an alkyl fluorosulphate. Whatever method is used, high acid or base concentrations in aqueous solution should be avoided since the a-lactam molecule is unstable under such conditions. The reaction temperature is preferably in the range -70" to +70o.

According to one variation of the method, the hydroxy ester may be reacted with a diazoalkane as etherifying agent. This reaction will be preferably effected in the presence of a Lewis acid, such as boron trifluoride, aluminium trichloride or zinc chloride. The reaction may be effected in a solvent such as an ether, e.g. diethylether, dioxan or tetrahydrofuran, a hydrocarbon, e.g. a light petroleum fraction, or a halogenated hydrocarbon, e.g. dichloromethane or chloroform. The reaction temperature is preferably low, e.g. -15" to + 150C.

This method is preferred for the production of ethers in which R is a C14 alkyl group. The ester starting material may, if desired, be formed from the acid of formula (I) by reaction with the diazoalkane reagent and allowed to react in situ with further reagent together with a Lewis acid, e.g. BF3, to effect the desired etherification. A molar excess of diazoalkane will usually be employed.

Etherification may also be carried out by reaction of the hydroxyester with a vinyl ether.

This method is especially useful for production of tetrahydropyranyl ethers, using a dihydropyran as reagent, or 1-alkoxyalkyl ethers such as a 1-ethoxyalkyl ether, using an alkyl vinyl ether as reagent. the reaction is desirably carried out in the presence of a strong acid catalyst, for example a mineral acid such as sulphuric acid, or an organic sulphonic acid such as p-toluene-sulphonic acid, in a non-hydroxylic, substantially water-free solvent. Examples of suitable solvents include an ether, e.g. diethylether, dioxan or tetrahydrofuran, a hydrocarbon, e.g. a light petroleum fraction, or a halogenated hydrocarbon, e.g. dichloromethane or chloroform. the reaction temperature is preferably in the range -15" to + 35"C.

A further etherification procedure is the reaction of the above hydroxyester with an alkyl fluorosulphate. This reaction will desirably be carried out in an inert aprotic solvent, for example a halogenated hydrocarbon e.g. methylene chloride. The presence of an inorganic acid binding agent, e.g. sodium or potassium carbonate, is also desirable. The reaction temperature is preferably in the range -15x to +350C.

In general, etherification is effected on an ester of the acid of formula I and where an acid product or salt is required, the ester should subsequently be cleaved. For this purpose, arylmethyl esters which can be c,káved by reduction, e.g. by hydrogenolysis, are preferred.

Cleavage of an aryl methy] ester, e.g. a p-nitrobenzyl ester, may be effected by hydrogenolysis, for example using a metal catalyst, e.g. a noble metal such as platinum, palladium or rhodium. The catalys+ may be supported, e.g. on charcoal or kieselguhr. Ap-nitrobenzyl group may also be removed by reduction of the nitro group, e.g. using a dissolving metal reducing agent such is zinc in acetic acid, or zinc in aqueous hydrochloric acid controlled, for example, in the 1rI range 3-6, preferably 4.0 - 5.5; aluminium amalgam in a moist ether, e.g.

tetrahydrofi!., an; or iron and ammonium chloride in an aqueous ether, e.g. tetrahydrofuran, followed by hydrolysis either under the reduction conditions in the presence of sufficient acid or by subsequent treatment with acid. Where an ether of the invention is prepared from a hydroxy ester, care should, of course, be taken to ensure that the ester group is not labile under the conditions of the etherification reaction or isolation procedure unless cleavage of the ester is desired.

Mild solvolysis of stannyl esters may, for example, be effected by reaction with water, acidified or basified water, alcohols, phenols or carboxylic acids, e.g. acetic acid.

The compounds of the invention wherein R4 is an esterified carboxyl group may be prepared from an acid of formula II in which R4 is COOH or a reactive derivative thereof by reaction with an alcohol, phenol or stannanol or a reactive derivative thereof to form the desired ester. Reaction will desirably be effected under mild conditions in order to prevent rupture of the bicyclic nucleus. The use of neutral or mild acidic or basic conditions, therefore, at temperatures between -70" and +35"C is preferred.

The alkyl, alkoxyalkyl and aralkyl esters may be prepared by reaction of the acid of formula II (R4 = COOH) with the appropriate diazoalkane or diazoaralkane, e.g. diazomethane or diphenyldiazomethane. The reaction will generally be effected in an ether, ester, alcohol or halohydrocarbon solvent, e.g. diethyl ether, ethyl acetate, methanol, ethanol or dichloromethane. In general, reduced temperatures are preferred, for example -15" to + 15 C.

The esters derived from alcohols may be produced by reaction of a reactive derivative of the alcohol, for example, a halide such as the chloride, bromide or iodide, or a hydrocarbonsulphonyl derivative such as a mesyl or tosyl ester, with a salt of the acid of formula II, e.g. an alkali or alkaline earth metal salt such as a lithium, sodium, potassium, calcium or barium salt or an amine salt, such as a triethylammonium salt. This reaction is preferably carried out in a substituted sulphoxide or amide solvent, e.g. dimethyl sulphoxide, dimethylformamide or hexamethylphosphoramide.

Stannyl esters may conveniently be formed by reaction of the carboxylic acid of formula II or a salt thereof with reactive tetravalent tin reagents. Trialkyl tin oxides are preferred for the synthesis of tin compounds in view of their availability and low toxicity.

The esters of formula I derived from an alcohol, phenol or stannanol used as starting materials in the preparation of the ethers according to the invention may be prepared by procedures similar to those described above.

In the formation of salts, an acid initially formed in solution in an appropriate organic solvent may be reacted with an appropriate base, preferably under conditions favouring precipitation of the salt. In the formation of alkali metal salts, e.g. sodium salts, an alkanoate is a preferred base, e.g. a 2-ethylhexanoate.

The invention will now be more particularly described in the following Preparations and Examples, which should not be construed as limiting: Preparation 1 4-Nitrobenzyl(3R, 5R, Z) -2-(2-hydroxyethylidene) clavam-3-carboxylate A mixture of lithium (3 R,S R,Z)-2-(2-hydroxyethylidene)davam3carboxylate (10 g), 4-nitrobenzyl bromide (9.5 g) and hexamethylphosphoramide (65 ml) was stirred for 18hr. at room temperature. The suspension was then partitioned between ethyl acetate (800 ml) and 50% saturated aqueous sodium chloride solution (800 ml). The organic layer was separated, washed successively with water, 0.5M aqueous sodium hydrogen carbonate solution and water, dried and concentrated to a slurry and the colourless crystals collected to give the title ester (8.39 g.), m.p. 117.2"C (Mettler) (Mettler is a registered Trade Mark), WE'OOH 264 nm (e 11,000) Vmax (CHBr3) 1781 (ss-lactam), 1738(ester), 1680cm-' (O-C=C), TtCDC13) values include 4.30 (d, J 2Hz, C-SR 4.61 (s, benzylic prontons), 5.09 (t, J 7Hz, = CH-) and 5.78 (d, J 7Hz, -CH20H).

Preparation 2 Diphenylmethyl(3R, 5R,Z) -2- (2-hydroxyethylidene) -clavam-3-carboxylate To a suspension of lithium (3R,5R,Z)-2-(2-hydroxyethylidene)-clavam-3-carboxylate (3.075g.) in ethyl acetate (150ml) and brine (20ml) was added 2N hydrochloric acid (25ml).

The mixture was quickly shaken and the organic layer separated. The aqueous layer was extracted once with ethyl acetate (35ml). The combined organic extracts were dried over magnesium sulphate and concentrated in vacuo at below 20 to ca. 30ml. To this stirred solution was added dropwise a concentrated solution of diphenyldiazomethane (1.94g.) in methylene chloride (4ml). The resulting solution was concentrated in vacuo to an oil, which was chromatographed on a column of silica gel, eluting with ether:light petroleum (40-60 ) (1:1), followed by ether. The appropriate fractions were combined and the solvent evaporated to yield the title ester as a colourless crystalline solid (3.033g.) m.p. 82.9" (from ether).

vmax (Nujol) (Nuiol is a Registered Trade Mark) 3420cm-' (OH), 1800cm1 (p-lactam), 1740cm-' (ester5, 1692cm-1 (O-C=C). 7(CDC13) values 2.66 (s, aromatics), 3.08 (s, -CH(C6H5)2), 4.30 (d, J 3Hz, C-5H), 4.86 (s, C-3H), 5.14 (t, J 6Hz = CH-), 5.82 (d, J 6Hz, -CH20H), 6.52 (dd, J 17 and 3Hz, C-6aH), 6.96 (d, J 17Hz, C-6ssH), 8.48 (s, -OH).

Preparation 3 Acetoxymethyl (3R, 5R, Z) -2-(2-hydroxyethylidene) clavam3-carboxylate A mixture of lithium (3R,5R,Z)-2-(2-hydroxyethylidene)-clavam-3-carboxylate (2.28g), bromomethyl acetate (1.70g) and hexamethylphosphoramide (15ml) was stirred at room temperature for 4.75 hours. The suspension was then partitioned between ethyl acetate (200ml) and water (200ml). The ethyl acetate layer was separated, washed with water, 0.5 M aqueous sodium hydrogen carbonate and water, then dried and filtered. The filtrate was evaporated to leave a pale yellow oil which was dissolved in chloroform (8ml) and added to stirred petroleum (bp 40-60 )(250ml). The petroleum was decanted from the precipitated gum which was then redissolved in chloroform and precipitated from petroleum (bp 40-60 ).

Successive portions of chloroform (2 x 1 oil) were evaporated from the resulting pale yellow gum which was then dried in vacuo to afford the title ester (1.34g), AmaX (0.1 N NaOH)258nm e7,500), Vmax (CHBr3) 3580 (OH), 1800(p-lactam), L768(COzCH20COCH3), 1 69Scm1 (O-C = C), T (CDCl3) values include 4.21 (ABq, J6Hz, O-CH20), 4.30 (d, J2.5HZ, C-S H), 5.79 (d, J7Hz, CH2-OH), 7.89 (s, COCH3).

Example 1 Sodium (3R, 5R, Z) -2-(2-methoxyethylidene) clavam3-carboxylate (a) 4-Nitrobenzyl (3R, 5R, Z) -2-(2-methoxyethylidene) -clavam-3-carboxylate A solution of 4-nitrobenzyl (3R,5R,Z)-2-(2-hydroxyethylidene)-clavam-3-carboxylate (3.00 g) in dry dichloromethane (120ml) was stirred, cooled to 0 , and treated with an ethereal solution of diazomethane [50 ml; prepared from N-nitrosomethylurea (24g) in ether (3OOml)j followed by a 1% v/v solution of boron trifluoride etherate in ether (0.3ml.).

Two further successive diazomethane-boron trifluoride treatments at 15 minute intervals were required to compelete the conversion. The reaction mixture was treated with acetic acid (3 drops and then filtered through a bed of ether-moistened silica gel. The filtere bed was washed with ethyl acetate and the filtrate and washings were concentrated in vacuo and chromatographed on a column of silica gel, eluting with ether to afford the title ester as colourless needles (2.54g.), m.p. 82.7 (Mettler), AmaeXH 266 nm (8 11,700), Vmax (CHBr3) 1796 (p-lactam), 1750 (ester) 1694 cm~l (O-C=C), 7 (CDC13) values include 4.28 (d, J 2 Hz, C-S H), 4.66 (s, benzylic protons), 5.13 (t, J 7 Hz, = CH-), and 6.66 (s, -OMe).

(b) Sodium (3R,5R, Z) -2-(2-methoxyethylidene) clavam-3-carboxylate A solution of 4-nitrobenzyl (3R,5R,Z)-2-(2-methoxyethyli 0.5 hour at 00, a further portion of ethereal diazomethane was added, followed by 1% boron trifluoride etherate in ether (0.3 ml). The mixture was stirred for 0.5 hour and then evaporated under reduced pressure to leave an oil which was chromatographed on a column of silica gel, eluting with ether-petroleum (b.p. 40-60 ) (3:1) to afford the title ester as a colourless oil (1.47 g), [(y], (e 1.1, DMSO) +68 , Ol (0.1 N NaOH) 258 nm (e 15,950), may (CHBr3) 1785 (p-lactam), 1738 (ester),1686cm~ (0-C = C), 7 (CDCI3) values include 4.28 (d, J 2 Hz, C-S H), 5.13 (t, J 7 Hz, =CH-), 6.20 (s, CO2Me), 6.68 (s, CH2OMe).

Example 5 Sodium (3R,5R,Z)-2-(2-methoxyethylidene)clavam-3-carboxylate A solution of 4-nitrobenzyl (3 R,SR,Z)-2-(2-methoxyethylidene) clavam-3-carboxylate (0.418 g) in tetrahydrofuran (12 ml) was diluted with 1M aqueous ammonium chloride solution (16 ml) and stirred with iron powder (2.02g) at room temperature. After 20 minutes, a second portion of iron powder (2.02g) and 1M aqueous ammonium chloride solution (4ml) was added. Stirring was continued for 25 minutes and the mixture was then diluted with ethyl acetate (200 ml). Hydrogen sulphide was passed into the stirred mixture for 5 minutes and then the resulting black suspension was filtered through Kieselguhr. The aqueous layer of the filtrate was saturated with sodium chloride, 2N aqueous hydrochloric acid (2 ml) added, and the mixture immediately shaken. The ethyl acetate layer was separated, dried, filtered through Kieselguhr and then extracted with pH7 phosphate buffer. The combined aqueous extracts were saturated with sodium chloride, acidified with 2N aqueous hydrochloric acid (2 ml) and immediately extracted with ethyl acetate (ca. 150 ml). The ethyl acetate extract was dried, concentrated under reduced pressure to ca. 5 ml, treated with a 1M solution of sodium 2-ethylhexanoate in ethyl acetate (1.Oml), and diluted with ether to ca. 30ml. The resulting white precipitate was collected by filtration, washed with ether, and dried in vacuo to afford the title salt as an amorphous powde (0.225 g), [at]D (e 1.12, H20) + 50 , Am axl M NaOH) 257.5 nm (e 15,100), VmaX (Nujol) 1784(p-lactam), 1690 (O-C (O-C 1614cm-1 (carboxylate), 7 (D2O) values include 4.28 (d J2Hz, C-S H), 5.11 (t, J 7 Hz, =C-), 6.72 (s, OCH3).

Example 6 4-Nitrobenzyl (3R, SR, Z) -2- 2- [(1 RS) -2-ethoxyethoxy ]ethylidene clavam- 3-carboxylate A solution of 4-nitrobenzyl (3R,5R,Z)-2-(2-hydroxyethylidene)clavam-3-carboxylate (2.32g), ethyl vinyl ether (2ml) andp-toluenesulphonic acid (100 mg) in dry tetrahydrofuran (70ml) was kept at room temperature for 5 minutes and then diluted with ethyl acetate (1 litre). The diluted solution was washed with water, 0.5M aqueous sodium hydrogen carbonate and water (twice), dried over sodium sulphate, filtered, and evaporated to leave the title ester as a pale yellow oil (2.96g) AmaX (EtOH) 263 nm (8 9,800), Vmax (CHBr3) 1800 (ss-lactam), 1752 (ester), 1698 (O-C=C), 1524 and 1348cm-l (NO2), 7 (CDC13) 1.76,2.47 (ABq, J 8 Hz, aromatic protons), 4.29 (d, J 3 Hz, C-S H), 4.72 (s, benzylic protons), 4.88 (s, C-3 H), 5.13 (t, J 7 Hz, = CH-), 5.31 (q, J 6 Hz, O-CH(CH3)-O-), 5.7-6.0 (m, = CH-CH2-O), 6.48 (dd, J 18 and 3 Hz, C-6 a H) 6.3-6.6 (m, O.CH2CH3,), 6.92 (d, J 18Hz, C-6 ssH),8.70 (d, J 6 Hz, -O-CH-CH3), 8.82 (t, J 7Hz, O-CH2CH3).

Example 7 Sodium (3R, 5R,Z)-2- 2-[(2RS)-tetrakydropyran-2-yloxy]ethylidene clavam3-carboxylate a) 4-Nitrobenzyl (3R, SR, Z) -2- 2-[(2RS)-tetrahydroypran-2-yloxy]ethylidene clavam-3 carboxylate A solution of 4-nitrobenzyl (3R,5R,Z)-2-(2-hydroxyethylidene)clavam-3-carboxylate (2.32g), 2,3-dihydropyran (2.0ml) and p-toluenesulphonic acid (100 mg) in dry tetrahyd rofuran (70ml) was kept at room temperature for 2 hours. The solution was concentrated to ca. 25ml, diluted with ethyl acetate (400ml) and washed with water (twice), 0.5M aqueous sodium hydrogen carbonate, and water (twice). The ethyl acetate solution was then evapo rated to leave the title ester as an almost colourless oil (3.28g), z (CDCl3) 1.74, 2.45 (ABq, J9Hz, aromatic protons) 4.27 (d, J2.5Hz, C-5H), 4.68 (s, benzylic protons), 4.84 (s, C-3 H), 5.09 (t, J7Hz, = CH-), 5.38 (m, tetrahydropyran-2-proton), 5.6-6.3 (m' s, = CH-CH2-O- and tetrahydropyran-6-protons), 6.48 (dd, J2.5 and 16Hz, C-6 a H), 6.90 (d, J16Hz, C-6 p H), 7.9 to 8.6 (m, tetrahydropyran-3,4,5-protons).

b) Sodium (3R, SR, Z) -2- 2-[(2RS) -tetrahydropyran-2-yloxy ]ethylidene clavam 3-carboxylate A solution of 4-nitrobenzyl (3R,5R,Z)-2- 2-[(2RS)-tetrahydropyran-2-yloxy] ethylidene clavam-3-carboxylate (3.24g) in ethyl acetate (200ml) was stirred with 10% palladium on carbon (2.5g) under 1 atmosphere of hydrogen at 200 until hydrogen uptake fell to a small fraction of its initial rate. The suspension was then filtered through kieselguhr and the filtrate extracted with an aqueous pH7 buffer solution (4x 50ml, lx25ml). The com bined extracts were covered with ethyl acetate (300ml), saturated with sodium chloride, stirred rapidly, and acidified with 2N aqueous hydrochloric acid (lOml). The ethyl acetate layer was separated, washed with brine (15ml), dried, and concentrated to 50ml. 1.OM sodium 2-ethylhexanoate solution in ethyl aceta2r.e (6.Oml) was added, and the solution further concentrated to ca. 10ml. The cericentrated solution was stirred and diluted slowly with ether (140ml). The resulting white amorphous precipitate was collected by filtration, washed with ether, and dried in vacuo over phosphorus pentoxide to afford the title salt 1.63g,), [a]n+260 (c.0,98, water), AmaX (0.lN NaOH) 258nm (e 14,200),#max(Nujol) 1785 (ss-lactam), 1696(O-C=C), 1616cm-l (carboxylate), 7 (D20) 4.30 (d, J2Hz, C-5 H),5.08 (s, C-3 H), 5.11 (t, J7Hz, = CH-), 5.30 (m, tetrahydropyran-2-proton), 5.6-5.9 (m, =CH CH2-O-), 6.1-6.5 (m, tetrahydropyran-6-protons), 6.44 (d d, J16 and 2Hz, C-6 a H), 6.91 (d, J16Hz, C-6 p H), 8.1-8.7 (m, tetrahydropyran-3,4,5-protons).

Example 8 4-Nitrobenzyl(3R, 5R, Z) -2-(2-methoxyethylidene) clavam-3-carboxylate 4-Nitrobenzyl(3R,5R,Z)-2-(2-hydroxyethylidene)-clavam-3-carboxylate (3.34g) was dissolved in dry methylene chloride (50ml) containing suspended anhydrous sodium carbonate (5g). The mixture was stirred at ambient temperature (ca 20 ) and treated with methyl fluorosulphate (1.6 ml). After 24 hr, 32 hr and 48 hr similar further additions were made and after a total of 72 hr no starting material remained. The mixture was poured into water and the organic layer separated, dried over sodium sulphate and evaporated to give a bright orange oil (ca. 3.5g).

Column chromatography on silica gel, eluting with petroleum spirit (40-600) and diethyl ether, afforded fractions which appeared, by t.l.c., to contain the desired product. Combination of these fractions and evaporation of the solvent gave a yellow gum (400mg) which by careful addition of petrol to an ethyl acetate solution gave the title compound (20mg) as a white cyrstalline solid having physical constants similar to those described in Example 1(a).

Example 9 Diphenylmethyl (3R,5R,Z) -2-(2-methoxyethylidene) clavam3-carboxylate A stirred solution of diphenylmethyl (3R,5R,Z)-2-(2-hydroxyethylidene)clavam3-carboxylate (401mg) in ether (20ml), cooled to 0 C in an ice-bath, was treated with an ethereal diazomethane solution (10ml), followed by a 1%V/V solution of boron trifluoride etherate in ether (0.05ml), and stirred for 15 mins. Two further successive diazomethaneboron trifluoride etherate treatments (same quantities and procedure as above) were required to complete the reaction. Excess diazomethane was removed by blowing a stream of nitrogen into the solution for 5-6 mins. This was then filtered through a bed of silica gel. The silica gel was washed through with ether (60ml). The combined filtrates were concentrated in vacuo to yield the title ester as an oil (397mg) vmax (CHBr3) 750 (phenyl), 1798 (p-lactam), 1750 (ester), 1691cm1 (O-C =C). T (CDCls) 2.66 (s, aromatic), 3.07 (s, -CH(Ph)2) 4.31 (d, J3Hz, C-5H), 4.82 (s, C-3H), 5.18 (t, J7Hz, =CH), 5.8 to 6.2 (m, CH2-OCH3), 6.51 (dd, J17Hz and 3Hmz, C-6aR), 6.78 (s, OCH3), 6.95 (a, J17Hz, C-6pH).

Example 10 Sodium (3R, 5R, Z) -2-(2-methoxyethylidene) clavam-3-carboxylate A solution of diphenylmethyl (3R,5R,Z)-2-(2-methoxyethylidene)clavam-3-carboxylate (228mg.) in ethyl acetate (15ml) was hydrogenated by shaking with hydrogen over 10% palladium on carbon catalyst (228mg.). 17ml. of hydrogen were taken up in 5 minutes. The mixture was filtered through Kieselguhr and to the stirred filtrate was added a solution of sodium 2-ethylhexanoate (83mg.) in ethyl acetate (7ml). The solution was concentrated in vacuo at below 20 to ca. 5ml. and treated with a dropwise addition of ether (100ml). The precipitated solid was filtered off, washed thoroughly with ether and dried in vacuo over P205 to afford the title salt as a white amorphous powder (132mg.), Vmax (Nujol) 1788 (p-lactam), 1692 (O-C=C), 1618cm-l (COO). 7 (D2O 4.27 (d, J3Hz, C-5H), 5.03 (s, C-3H), 5.11 (t, J8Hz, =CH-), 5.95 (d, J8Hz, CH2-OCH3), 6.44 (dd, J17 and 3Hz, C-6 a H), 6.69 (s, -OCH3), 6.89 (d, J17Hz, C-6 BH).

Example 11 A cetoxymethyl (3R,5R,Z) -2 -(2-methoxyethylidene) clavam-3-carboxylate To a stirred, ice-cooled solution of acetoxymethyl (3R,5R,Z)-2-(2-hydroxyethylidene) clavam-3-carboxylate (542mg.) in ether (35ml) was added an ethereal solution of diazomethane (17ml), followed by a 1% V/V solution of boron trifluoride etherate in ether (0.15ml). The solution was stirred for 20 minutes. Four further successive diazomethaneboron trifluoride etherate treatments (same quantities and procedure as above) were carried out and the reaction mixture was stirred for 40 minutes after the final addition. Excess diazomethane was removed by blowing a stream of nitrogen into the solution for 6 minutes.

The mixture was filtered through a bed of silica gel which was washed through with ether (80ml). The combined filtrates were concentrated in vacuo to yield the title ester as an oil 55 lmg.). VmaX (CHBr3) 1798 (p4actam), 1764 (ester), 1695 1(-O-C = C-). 7 (CDCl3),4.21 (s, -CH2OCOCR3), 4.32 (d, J3Hz, C-5H), 4.91 (s, C-3H), 5.15 (t, J7Hz, =CH), 5.98 (t, J7Hz, CH2OCR3), 6.50 (dd, J17 and 3Hz, C-6 aH), 6.94 (d, J17Hz, C-6 pH), 7.89 (s, -COCH3).

Examples A - D In the following examples (3R,5R,Z)-2-(2-methoxyethylidene) clavam-3-carboxylic acid is used as densified granules containing 1% magnesium stearate, which are prepared as follows: Blend (3R,5R,Z)-2-(2-methoxyethylidene)elavam-3-earboxylie acid with 1 % magnesium stearate and prepare tablet slugs by direct compression on a tablet machine. Break down the slugs through a series of screens (12 mesh, 16 mesh and 20 mesh) on a rotary granulator to produce free flowing densified granules with an apparent bulk density of about 0.7 gms per ml (BSS method).

Ampicillin trihydrate granules may be prepared in a similar manner.

Example A Formula per tablet Densified (3R,SR,Z)-2-(2-methoxyethylidene)clavam-3-carboxylic acid granules containing 1 % magnesium stearate. 252.5mg Avicel PH 101 grade of microcrystalline cellulose to tablet core weight of 325 mg (Avicel is a registered Trade Mark) Method of Preparation Blend together the granules of the acid and Avicel and compress them on deep concave punches, 9.5mm in diameter.

Example B Formula per capsule Densified (3 R,SR,Z)-2-(2-methoxyethylidene)clavam-3-carboxylic acid granules containing 1% magnesium stearate 252.5mg Sodium starch glycollate (Primojel) 4.5mg Target capsule fill weight 257 mg Method of Preparation Remove a proportion of fine granules passing 40 mesh equal to the weight of Primojel from the bulk densified granules of the acid and blend with Primojel. Add the blend to the bulk and re-blend. Fill the granules into size 2 hard gelatin capsules (lock fitting type) on an automatic capsule filling machine.

Example C Formula per tablet Densified granules of ampicillin trihydrate containing 1% magnesium stearate equal to 250 mg ampicillin (approx) 300.0mg Densified (3R,5R,Z)-2-(2-methoxyethylidene) clavam-3-carboxylic acid granules containing 1% magnesium stearate 252.5mg Avicel PH 101 grade of microcrystalline cellulose to table core weight of 660 mg Method of Preparation Blend together the granules of the acid and ampicillin with Avicel and compress on deep concave punches, 11.5mm in diameter.

Example D Formula per capsule Densified (3R,5R,Z)-2-(2-methoxyethylidene)clavam-3-carboxylic acid granules containing 1% magnesium stearate 252.5mg Densified ampicillin trihydrate granules containing 1% magnesium stearate equal to 250 mg ampicillin (approx) 300.0mg Sodium starch glycollate (Primo;el) 11.5mg Target capsule fill weight 564.0mg Method of Preparation Blend the Primo.el as in Example B and blend with the ampicillin granules. Fill the composite granules into size 0 hard gelatin capsules (lock fitting type) on an automatic capsule filling machine.

Example Formula per capsule Sodium (3R,SR,Z)-2-(2-methoxyethylidene) clavam3-carboxylate 50mg (6R,7R,2' R)-7-(2' -Amino-2' -phenylacetamido)-3- methylthio-ceph-3-em-4-carboxylic acid 50mg Aerosil 200 (Aerosil is a registered Trade Mark) lmg Magnesium stearate lmg Method of Preparation Blend the ingredients together homogeneously and densify by compaction before distributing into hard gelatin capsules so that each contains 100mg of active ingredients.

Avicel PH 101 is available from F.M.C. Corporation, Pennsylvania, U.S.A., Primojel is available from W.A. Scholten Chemische Fabrieken, Foxhol (OR), Netherlands, and Aerosil 200 is a silicon dioxide available from Bush, Beach and Gent of Morton House, Lloyds Avenue, London E.C.3.

WHAT WE CLAIM IS: 1. A compound of formula (II)

wherein R represents a group -OR1 wherein R1 represents a methyl or ethyl group, an alkenyl group having 2-6 carbon atoms, a C1.6 alkyl group substituted by a C1.4 alkoxy group, a hydroxyalkyl group having from 2-6 carbon atoms, or a carbon-attached saturated 5-7 membered heterocyclic ring, and R4 represents a carboxyl or esterified carboxyl group, or a salt of a compound of formula (11) wherein R4 is a carboxyl group, with the proviso that when R represents a methoxy group, R4 does not represent a methoxycarbonyl group.

2. A compound as claimed in claim 1 wherein R represents a group OR in which R1 represents a C1.6 alkyl group substituted by a C1.4 alkoxy group.

3. A compound as claimed in claim 1 wherein R represents a group OR' in which R' represents a hydroxyethyl group.

4. A compound as claimed in claim 1 wherein R represents a group ORl in which R1 represents a carbon-attached saturated 5-7 membered heterocylic ring.

5. A compound as claimed in claim 1 wherein R represents a group ORl in which R represents a tetrahydropyranyl group.

6. A compound as claimed in claim 1 wherein R represents a methyl group.

7. A compound as claimed in claim 1 wherein R represents an ethyl group.

8. A compound as claimed in any of claims 1-7 wherein R4 represents an esterified carboxyl group -COOR3 wherein R3 represents an organic group derived from an aliphatic or araliphatic alcohol, a phenol or a stannanol.

9. A compound as claimed in claim 8 wherein R3 represents a straight or branched substituted or unsubstituted alkyl or alkenyl group having from 1-8 carbon atoms; an aralkyl group having up to 20 carbon atoms; an aryl group having up to 12 carbon atoms; a cycloalkyl group containing up to 12 carbon atoms, optionally containing one or more heteroatoms in the ring system, or a stannyl group having up to 24 carbon atoms.

10. A compound as claimed in claim 8 or claim 9 in which -COOR3 is a metabolically labile ester group.

11. A compound as claimed in any of claims 8 to 10 in which R3 is a C,.4 alkyl group which may carry an acyloxy group, an alkoxy group, a cyano group, an acyl group or a halogen atom.

12. A compound as claimed in claim 11 in which R3 is a C1.4 alkyl group which may carry an acetoxy, pivaloyloxy, methoxy, fluorine, chlorine, bromine, iodine, cyano, ethoxycarbonyloxy, p-bromobenzoyl or ethoxycarbonyl group.

13. A compound as claimed in claim 11 or claim 12 in which R3 is an ethyl, propyl, butyl, phthalidyl, acetoxymethyl or pivaloyloxymethyl group.

14. A compound as claimed in claim 11 wherein R represents an acetoxyethyl, ethox- ycarbonyloxymethyl, ethoxycarbonyloxyethyl or methoxymethyl group.

15. A compound as claimed in claim 9 wherein R3 represents an arylmethyl group.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (94)

**WARNING** start of CLMS field may overlap end of DESC **. Example Formula per capsule Sodium (3R,SR,Z)-2-(2-methoxyethylidene) clavam3-carboxylate 50mg (6R,7R,2' R)-7-(2' -Amino-2' -phenylacetamido)-3- methylthio-ceph-3-em-4-carboxylic acid 50mg Aerosil 200 (Aerosil is a registered Trade Mark) lmg Magnesium stearate lmg Method of Preparation Blend the ingredients together homogeneously and densify by compaction before distributing into hard gelatin capsules so that each contains 100mg of active ingredients. Avicel PH 101 is available from F.M.C. Corporation, Pennsylvania, U.S.A., Primojel is available from W.A. Scholten Chemische Fabrieken, Foxhol (OR), Netherlands, and Aerosil 200 is a silicon dioxide available from Bush, Beach and Gent of Morton House, Lloyds Avenue, London E.C.3. WHAT WE CLAIM IS:

1. A compound of formula (II)

wherein R represents a group -OR1 wherein R1 represents a methyl or ethyl group, an alkenyl group having 2-6 carbon atoms, a C1.6 alkyl group substituted by a C1.4 alkoxy group, a hydroxyalkyl group having from 2-6 carbon atoms, or a carbon-attached saturated 5-7 membered heterocyclic ring, and R4 represents a carboxyl or esterified carboxyl group, or a salt of a compound of formula (11) wherein R4 is a carboxyl group, with the proviso that when R represents a methoxy group, R4 does not represent a methoxycarbonyl group.

2. A compound as claimed in claim 1 wherein R represents a group OR in which R1 represents a C1.6 alkyl group substituted by a C1.4 alkoxy group.

3. A compound as claimed in claim 1 wherein R represents a group OR' in which R' represents a hydroxyethyl group.

4. A compound as claimed in claim 1 wherein R represents a group ORl in which R1 represents a carbon-attached saturated 5-7 membered heterocylic ring.

5. A compound as claimed in claim 1 wherein R represents a group ORl in which R represents a tetrahydropyranyl group.

6. A compound as claimed in claim 1 wherein R represents a methyl group.

7. A compound as claimed in claim 1 wherein R represents an ethyl group.

8. A compound as claimed in any of claims 1-7 wherein R4 represents an esterified carboxyl group -COOR3 wherein R3 represents an organic group derived from an aliphatic or araliphatic alcohol, a phenol or a stannanol.

9. A compound as claimed in claim 8 wherein R3 represents a straight or branched substituted or unsubstituted alkyl or alkenyl group having from 1-8 carbon atoms; an aralkyl group having up to 20 carbon atoms; an aryl group having up to 12 carbon atoms; a cycloalkyl group containing up to 12 carbon atoms, optionally containing one or more heteroatoms in the ring system, or a stannyl group having up to 24 carbon atoms.

10. A compound as claimed in claim 8 or claim 9 in which -COOR3 is a metabolically labile ester group.

11. A compound as claimed in any of claims 8 to 10 in which R3 is a C,.4 alkyl group which may carry an acyloxy group, an alkoxy group, a cyano group, an acyl group or a halogen atom.

12. A compound as claimed in claim 11 in which R3 is a C1.4 alkyl group which may carry an acetoxy, pivaloyloxy, methoxy, fluorine, chlorine, bromine, iodine, cyano, ethoxycarbonyloxy, p-bromobenzoyl or ethoxycarbonyl group.

13. A compound as claimed in claim 11 or claim 12 in which R3 is an ethyl, propyl, butyl, phthalidyl, acetoxymethyl or pivaloyloxymethyl group.

14. A compound as claimed in claim 11 wherein R represents an acetoxyethyl, ethox- ycarbonyloxymethyl, ethoxycarbonyloxyethyl or methoxymethyl group.

15. A compound as claimed in claim 9 wherein R3 represents an arylmethyl group.

16. A compound as claimed in claim 15 wherein R3 represents a benzyl group optionally

substituted by an o- orp-nitro, p-methoxy orp-methyl group, or a diphenylmethyl group.

17. A compound as claimed in claim 10 wherein R represents a benzyl group.

18. The alkali metal, alkaline earth metal, ammonium or organic base salts of any carboxylic acid compound as claimed in claims 1-7.

19. The sodium, potassium, lithium, calcium or magnesium salt of any carboxylic acid compound as claimed in claims 1-7.

20. (3R,5R,Z)-2-(2-Methoxyethylidene) clavam-3-carboxylic acid and its pharmaceuti cally acceptable salts.

21. (3R,5R,Z)-2-(2-Methoxyethylidene)elavam-3-earboxylie acid.

22. (3R,5R,Z)-2-(2-MethoxyethylideneBelavam-3-earboxylie acid in the form of a crystalline solid.

23. An alkali metal or alkaline earth metal salt of (3R,SR,Z)-2-(2-methoxyethylidene) clavam-3-carboxylic acid.

24. Sodium (3R,5R,Z)-2-(2-methoxyethylidene)elavam-3-earboxylate.

25. The lithium salt of (3R,5R,Z)-2-(2-methoxyethylidene)-elavam-3-earboxylate.

26. The potassium salt of (3R,5R,Z)-2-(2-methoxyethylidene)-elavam-3-earboxylate.

27. (3R,5R,Z)-2-(2-Ethoxyethylidene)elavam-3-carboxylie acid and its pharmaceuti cally acceptable salts.

28. An alkali metal or alkaline earth metal salt of (3R,5R,Z)-2-(2-ethoxyethylidene) clavam-3-carboxylic acid.

29. The lithium salt of (3R,5R,Z)-2-(2-ethoxyethylidene)-elavam-3-carboxylie acid.

30. The sodium salt of (3 R, 5R,Z)-2- (2-ethoxyethylidene)-clavam- 3-carboxylic acid.

31. The potassium salt of (3R,5R,Z)-2-(2-ethoxyethylidene)-elavam-3-earboxylie acid.

32. A compound as claimed in any of claims 1 or 8-19 wherein R represents a group -OR' in which Rl represents a methoxyethyl group.

33. Compound as claimed in any of claims 1 or 8-19 wherein Rrepresentsagroup OR' in which Rl represents an ethoxyethyl group.

34. (3R.5R.Z)-2- 2-[( IRS)- 1 -Ethoxyethoxyjethylidene - clavam-3-carboxylic acid and its pharmaceutically acceptable salts.

35. The lithium salt of (3R,5R,Z)-2- 2-[(lRS)-1-ethoxyethoxy]ethylidene clavam-3-carboxylic acid.

36. The sodium salt of (3R,5R,Z)-2- 2-[(lRS)-1-ethoxyethoxyjethylidene clavam-3-carboxylic acid.

37. The potassium salt of (3R,5R,Z)-2- 2-[( iRS)- 1 -ethoxyethoxyj ethylidene clavam-3-carboxylic acid.

38. (3R,5R.Z)-2- 2-[(2RS)-Tetrahydropyran-2-yloxyjethylidene clavam -3-carboxylic acid and its pharmaceutically acceptable salts.

39. The lithium salt of (3R,SR,Z)-2- 2-[(2Rs)-tetrahydropyran-2-yloxyjethylidene clavam-3-carboxylic acid.

40. The sodium salt of (3R,5R.Z)-2- 2-[(2RS)-tetrahydropyran-2-yloxyjethylidene clavam-3-carboxylic acid.

41. The potassium salt of(3R,SR,Z)-2- 2-[(2RS)-tetrahydropyran-2-yloxyj ethylidene clavam-3-carboxylic acid.

42. Acetoxymethyl (3R.5R.Z)-2-(2-methoxyethylidene)-clavam-3-carboxylate.

43. Diphenylmethyl (3R,5R.Z)-2-(2-methoxyethylidene)-clavam-3-carboxylate.

44. A compound of formula (II) as shown in claim 1 wherein R represents an etherified hvdroxvl group and R4 is ap-nitrobenzyloxycarbonyl group.

45. A compound of formula (II) as claimed in claim 44 wherein R represents a group -OR wherein R5 represent an alkyl, alkenyl or alkynyl group containing 1-6 carbon atoms, such an alkyl group optionally carrying a substituted hydroxyl group; a hydroxyalkyl group having 2-6 carbon atoms; an aralkyl group having 1-6 carbon atoms in the alkyl portion or an arvl group such aryl and aralkyl groups being monocyclic; a cycloalkyl group having 3-7 carbon atoms or a carbon-attached saturated 5-7 membered heterocyclic ring.

46. A compound of formula (II) as claimed in claim 1 wherein R4 represents a p-nitrobenzyloxycarbonyl group.

47. Thep-nitrobenzyl ester of any compound as claimed in any of claims 2 - 7 in which R4 is a carboxyl group.

48. The p-nitrobenzyl ester of any compound claimed in either of claims 32 and 33.

49. 4-Nitrobenzyl (3R,SR,Z)-2-(2-methoxyethylidene)-elavam-3-earboxylate.

50. 4-Nitrobenzyl (3R,5 RZ)-2-(2-ethoxyethylidene)-elavam-3-earboxylate.

5l. A-Nitrobenzyl (3R,5R.Z)-2- 2-[(lRS)- 1-ethoxyethoxyj-ethylidene clavam 3-carboxvlate.

52. i-Nitrobenyzl (3 R,5 R.Z)- 2- 2- [(2RS)-tetrahydropyran-2-yloxyj ethylidene clavam-3-carboxylate.

53. A pharmaceutical composition comprising at least one acid, pharmaceutically acceptable salt of metabolically labile ester as claimed in claim 1 in admixture with a pharmaceutically acceptable carrier or excipient and/or a further p-lactam antibiotic.

54. A composition as claimed in claim 53 wherein the composition is in a form suitable for oral, topical, parenteral or rectal administration.

55. A composition as claimed in claim 53 or claim 54 wherein the weight ratio of the compound of formula (II) to the further p-lactam is in the range 10:1 to 1:10.

56. A composition as claimed in claim 55 wherein the weight ratio of the compound of formula II to the further p-lactam is in the range 5:1 to 1:5.

57. A composition as claimed in any of claims 53-56 wherein the further p-lactam antibiotic is a cephalosporin or penicillin.

58. A composition as claimed in claim 57 in which the cephalosporin or penicillin antibiotic is cephalexin, cephaloglycin, cephalothin, cephaloridine, cefazolin, cephacetrile, cephapirin, penicillin G, penicillin V, ampicillin, amoxycillin, carbenicillin, or ticarcillin or a metabolically labile ester, pharmaceutically acceptable salt and/or solvate thereof.

59. A composition as claimed in either of claims 57 or 58 wherein the compound of formula (II) is (3R,5R,Z)-2-(2-methoxyethylidene)clavam-3-carboxylic acid or a pharmaceutically acceptable salt thereof.

60. A composition as claimed in either of claims 57 or 58 wherein the compounds of formula (II) is (3R,SR,Z)-2-(methoxyethylidene)clavam-3-carboxylic acid.

61. A composition as claimed in either of claims 57 or 58 wherein the compound of formula (II) is the sodium salt of (3R,5R,Z)-2-(2-methoxyethylidene)clavam-3-carboxylic acid.

62. A composition as claimed in either of claims 57 or 58 wherein the compound of formula (II) is the potassium salt of (3R,5R,Z)-2-(2-methoxyethylidene)clavam-3- carboxylic acid.

63. A composition as claimed in either of claims 57 or 58 wherein the compound of formula (II) is the calcium salt of (3R,5R.Z)-2-(2-methoxyethylidene)clavam-3-coarboxylic acid.

64. A composition as claimed in either of claims 57 or 58 wherein the compound of formula (ill) is (3R.5R,Z)-2-(2-cthoxyethylidene)clavam-3-carboxylic acid or a pharmaceutically acceptable salt thereof.

65. A composition as claimed in either of claims57 or 58 wherein the compound of formula (ill) is (3R.5RZ)-2-('-ethoxyethylidene)clavam-3-carboxylic acid.

66. A composition as claimed in either of claims 57 or 58 wherein the compound of formula (II) is the sodium salt of (3R.5R.Z)-2-(2-ethoxyethylidene)clavam-3-carboxylic acid.

67. A composition as claimed in either of claims 57 or 58 wherein the compound of formula (II) is thc potassium salt of (3R.3R.Z)-2-(2-ethoxyethylidene)clavam-3-carboxylic acid.

68. A composition as claimed in either of claims 57 or 58 wherein the compound of formula (II) is the calcium salt of (3R.5R.Z)-2-(2-ethoxyethylidene)clavam-3-carboxylic acid.

69. A composition as claimed in any of claims 53-68 wherein the p-lactam antibiotic is ampicillin or a pharmaceutically acceptable salt thereof.

70. A composition as claimed in any of claims 53-68 wherein the p-lactam antibiotic is amoxvcillin or a pharmaceutically acceptable salt thereof.

71. A composition as claimed in any of claims 53-68 wherein the -lactam antibiotic is (6R.7R.2' R)-7-(2' amino-2-phenylacetamido)-3-methylthio-ceph-3- em-4-carboxylic acid or a pharmaccutically acceptable salt thereof.

72. A composition as claimcd in any of claims 53-68 wherein the p-lactam antibiotic is (6R.7R.2'R)-7-(''-amino-2'-phenvlacetamido)-3-methoxyceph-3- em-4-carboxylic acid or a pharmaceutically acceptable salt thereof.

73. A composition as claimed in any of claims 53 to 72 in dosage unit form wherein each dosage unit contains 250 me to S g of a compound as claimed in claim 1 when used alone or from 1 OU mg to 5 g of total -lactam antibiotic when a further p4actam antibiotic is present.

74. A process for the preparation of a compound of formula (II) or a salt thereof as claimed in claim l or claim 44 wherein an ester of the compound of the formula (I)

is etherified, followed, where a free acid or salt is required, by deesterification and, if desired, salt formation.

75. A process for the preparation of a compound of formula (II) as shown in claim 1 wherein R is an etherified hydoxyl group and R4 is a carboxyl or esterified carboxyl group together with salts thereof which comprises etherifying an ester of the compound of formula (Iyas defined in claim 74 with a diazoalkane in the presence of a Lewis acid, followed, where a free acid or salt is required, by deesterification and, if desired, salt formation.

76. A process as claimed in claim 74 wherein etherification is effected by reaction of the ester of the compound of formula (I) with a diazoalkane in the presence of a Lewis acid.

77. A process as claimed in either of claims 75 or 76 wherein the Lewis acid is boron trifluoride.

78. A process as claimed in either of claims 75 or 76 wherein the Lewis acid is aluminium trichloride or zinc chloride.

79. A process as claimed in any of claims 75 to 77 wherein a compound of formula (I) is treated with a molar excess of diazoalkane in the presence of a Lewis acid whereby an ester of the compound of formula (I) is formed and is etherified in situ.

80. A process for the preparation of a compound of formula (II) as shown in claim 1 wherein R is an etherified hydroxyl group and R4 is a carboxyl or esterified carboxy group together with salts thereof which comprises etherifying an ester of the compound of formula (I) as defined in claim 74 with a vinyl ether in the presence of a strong acid catalyst.

81. A process as claimed in claim 74 wherein etherification is effected by reaction of the ester of the compound of formula (I) with a vinyl ether in the presence of a strong acid catalyst.

82. A process as claimed in either of claims 80 or 81 wherein the vinyl ether is a dihydropyran or an alkyl vinyl ether.

83. A process for the preparation of a compound of formula (II) as shown in Claim 1 wherein R is an etherified hydroxyl group and R4 is a carboxyl or esterified carboxyl group together with salts thereof which comprises etherifying an ester of the compound of formula (I) as defined in claim 74 with an alkyl fluorosulphate.

84. A process as claimed in claim 74 wherein etherification is effected by reaction of the ester of the compound of formula (I) with an alkyl fluorosulphate.

85. A process as claimed in either of claims 83 or 84 wherein an inorganic acid binding agent is present.

86. A process as claimed in any of claims 74 to 85 wherein said ester is an arylmethyl ester and said de-esterification is effected using reduction.

87. A process as claimed in claim 86 in which said ester is ap-nitrobenzyl ester and said reduction is effected by hydrogenolysis.

88. A process as claimed in any of claims 74 to 85 in which said ester is ap-nitrobenzyl ester and deesterification is effected by reduction using a dissolving metal reducing agent and hydrolysis.

89. Compounds of formula (II) as claimed in claim 1 substantially as hereinbefore described.

90. A pharmaceutical composition as claimed in claim 53 substantially as hereinbefore described.

91. A pharmaceutical composition as claimed in claim 53 substantially as hereinbefore described with reference to Examples A to D.

92. A process as claimed in claim 74 substantially as hereinbefore described.

93. A process as claimed in claim 74 substantially as hereinbefore described with reference to the Examples 1-5.

94. A process as claimed in claim 74 substantially as hereinbefore described with reference to the Examples 6-11.