GB1591438A - Clavem derivatives - Google Patents

Description

(54) CLAVEM DERIVATIVES (71) We, GLAXO LABORATORIES LIMITED, a British Company of Greenford, Middlesex, 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 new ss-lactams and to a process for their production.

In our German OLS 2 604 697 we have described the isolation, from fermentations of Streptomyces clavuligerus, of clavulanic acid and salts thereof in pure form.

The bicyclic compounds in this specification are named with reference to "clavam"; the name being 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.

We have now been able to prepare derivatives of clavulanic acid having the formula (I)

wherein R represents a carboxyl or esterified carboxyl group and R1 represents a hydrogen atom, a hydroxyl group, an etherified hydroxyl group, an acylated hydroxyl group or the residue of a sulphur nucleophile, and salts of such compounds in which R is a carboxyl group. 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 group R may represent an etherified hydroxyl group -OR, wherein R is an unsubstituted or substituted hydrocarbyl group, e.g. an aliphatic, araliphatic or aromatic group, or a C-attached heterocyclic group. Thus, for example, R2 may be an unsubstituted alkyl, alkenyl or alkynyl group, which may contain 1-6 carbon atoms, or a C16 alkyl group carrying a substituted hydroxy, acyl (e.g. C2~6 alkanoyl), carboxyl, esterified carboxyl (e.g.

C26 alkoxycarbonyl) or cyano group; a hydroxyalkyl group having 2-6 carbon atoms; an aralkyl group which may have 1-6 carbon atoms in the alkyl portion or an aryl group, such aryl and alkyl groups preferably being monocyclic and optionally carrying one or more nitro, halo or C14 alkoxy substituents; a cycloalkyl group, which may have 3-7 carbon atoms, or a carbon-attached saturated or unsaturated 5-7 membered heterocyclic ring containing, for example, an oxygen atom, such cycloalkyl or heterocyclic rings optionally carrying a C14 alkoxy group, preferably attached to the ether-linked carbon atom.

Representative groups R2 include methyl, ethyl, propyl, isopropyl, butyl, allyl, propargyl, hydroxyethyl, 1-ethoxyethyl, acetonyl, 4-nitrobenzyl, cyanomethyl, carboxyethyl, ethoxycarbonylmethyl, phenyl, benzyl, phenethyl, cyclohexyl, 1-methoxycyclohexyl and tetrahydropyranyl.

Substituted hydroxy groups as referred to above include acylated and etherified hydroxy groups. In general, acylated hydroxy groups may have the formula R CO2 where R is a hydrocarbyl group as defined for R-, relatively simple R3 groups such as C14 alkyl, e.g. methyl, being preferred, while etherified hydroxy groups may have the formula R30, simple R3 groups such as C14 alkyl, e.g. methyl or ethyl, again being preferred.

R2 may also be a silyl group having up to 24 carbon atoms, which may carry three hydrocarbyl groups. The groups, which may be the same or different, may be selected from alkyl, alkenyl, cycloalkyl, aralkyl and aryl groups. Such groups will preferably be C14 alkyl, e.g. methyl, ethyl, propyl or butyl, groups. Representative silyl groups include trimethylsilyl and t-butyldimethylsilyl groups.

The group Rl may further represent an acylated hydroxyl group -OR4 wherein R4 preferably represents an acyl group R5CO- wherein R5 is -an aliphatic, araliphatic or aromatic group, for example a C18 alkyl, C28 alkenyl, C28 alkynyl, C3-12 cycloalkyl, C415 aryl-C1~6-alkyl or C415 aryl group, which may be substituted, for example, by one or more hydroxyl, C14 alkoxy, phenoxy or cyano groups, or an amino or mono- or di-substituted amino group, or a carboxyl or esterified carboxyl group. The group Rsmay also represent an amino or mono- or di-substituted amino group, thus making the group R a carbamoyloxy group which may, for example, be represented as -O.CO.NR6R', where R6 and R7, which may be the same or different, are hydrogen; C15 alkyl or C26 alkanoyl, which may be substituted by, for example, halogen; aralkyl, e.g. benzyl; or aryl, e.g. phenyl, groups, or R6 and R may together with the nitrogen atom to which they are attached form a heterocyclic ring preferably having 5-7 ring members, which may optionally contain another heteroatom. e.g. a nitrogen, oxygen or sulphur atom. R1 may additionally be represented as O.CS.NHR6 where R6 is as defined above other than hydrogen.

Representative R5 groups include C14 alkyl groups such as methyl, ethyl, propyl, isopropyl, and butyl; amyl, allyl, propenyl, propargyl, cyclopentyl, cyclohexyl, cycloheptyl, adamantyl, benzyl, thienylmethyl, phenyl,. thienyl, amino, methylamino, anilino, a benzyloxycarbonylbenzyl , a-phenoxycarbonylbenzyl, aminomethyl or a-aminobenzyl groups.

The group R1 may also represent the residue of a sulphur nucleophile, for example an acylthio or thioacylthio group, a thioether group or a sulphone or sulphoxide derivative of said thioether grou, ore or group. In general these residues may be represented by the formulae -SH, -SR8, -SO.R8 or R8 (where R8 is an aliphatic, araliphatic, aromatic or heterocyclic group) or by -SC=Y.R9 (where Y is O or S and R9 is a group as defined above for R8 or a group OR8 or SR8, where R8 is as defined above, or a group NR10R11, where R10 and R11, which may be the same or different, are hydrogen atoms or aliphatic, araliphatic or aromatic groups or together with the nitrogen atom to which they are attached represent a heterocyclic ring).

Thus, for example, R8, R9, R10 and R1l may each be an alkyl, alkenyl or alkynyl group, which may contain 1-6 carbon atoms; 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, preferably 5 or 6, carbon atoms; or a carbon-attached 5-7 membered heterocyclic ring containing one or more heteroatoms such as nitrogen, sulphur or oxygen, and optionally carrying one or more alkyl groups which may have 1-6 carbon atoms. Such groups may themselves carry substituents such as hydroxyl or substituted hydroxyl, carboxyl or substituted carboxyl, amino or substituted amino or cyano groups.

Representative groups R8 include methyl, ethyl, propyl, butyl, allyl, propargyl, 2-aminoethyl, cyanomethyl, hydroxyethyl, ethoxyethyl, phenyl, benzyl, cyclohexyl and pyridyl. Representative groups R9.C=Y. include ethoxythiocarbonyl, carbamoyl, thiocarbamoyl dimethylthiocarbamoyl, thiobenzoyl, benzoyl, thioacetyl and acetyl. Where NR1ORI1 represents a heterocyclic ring, this may, for example, contain 5-7 ring atoms, including one or more other heteroatoms, e.g. nitrogen, oxygen or sulphur atoms, and may be, for example, a piperidino, piperazino, morpholino or thiamorpholino ring.

Substituted hydroxy groups include acylated and etherified hydroxy groups as referred to above. Substituted carboxyl groups may have the formula COOR , where R12 is an aliphatic, araliphatic or aromatic group as defined above, while substituted amino groups may have the formula NR1OR11 as defined above, one of R10 and R11 being other than hydrogen. Preferred groups R10, R11 and R12 are C14 alkyl groups, e.g. methyl.

The compounds of the invention may be esters wherein the group R represents an esterified carboxyl 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 carboxyl group preferably contains not more than 24 carbon atoms.

Thus, the group R may be represented as COOR13 wherein R13 represents a straight or branched unsubstituted or substituted alkyl or alkenyl group, preferably having from 1-8 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 or pivaloyloxy; acyl, e.g. p-bromobenzoyl, and alkoxycarbonyl, e.g. ethoxycarbonyl; an aralkyl group having up to 20 carbon atoms, especially an arylmethyl group, e.g. a benzyl or substituted benzyl group, suitable ring substituents being halo, e.g. chloro; nitro, e.g. o - or p-nitro; inorganic sulphonyl; cyano; alkyl, e.g. p-methyl, or alkoxy, e.g. p-methoxy; a diphenylmethyl, or triphenylmethyl group or a fur-2-ylmethyl, thien-2- ylmethyl or pyridylmethyl group, the heterocyclic groups of which may also be substituted, e.g. by a lower alkyl group, preferably methyl; an aryl group having up to 12 carbon atoms, e.g. a phenyl or substituted phenyl group, suitable substituents being halo, e.g. chloro; nitro, e.g. o- or p-nitro; cyano; alkyl, e.g. p-methyl, or alkoxy, e.g. p-methoxy; a cycloalkyl group containing not more than 12 carbon atoms, e.g. adamantyl; a heterocyclic group containing not more than-12 carbon atoms, the hetero atom being, for example, oxygen, as in the tetrahydropyranyl or phthalidyl groups; 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 selected from alkyl, alkenyl, aryl, aralkyl, cycloalkyl, alkoxy, or aralkoxy groups. Such groups will include methyl, ethyl, propyl, n-butyl, phenyl and benzyl groups.

The esters which will be used when it is desired ultimately to prepare a carboxylic acid or salt thereof will desirably be those which may be cleaved under conditions which will not result in undesirable side reactions. Suitable esters for this purpose include the arylmethyl esters, for example p-nitrobenzyl and benzhydryl esters; such esters may be cleaved by reduction, for example by hydrogenolysis, e.g. on a noble metal catalyst.

The compounds of the invention have been found to possess the ability to inhibit p-lactamase enzymes produced by both gram-positive and gram-negative organisms, such as strains of Proteus mirabilis, Escherichia coli, Staphylococcus aureus, Proteus morganii, Klebsiella aerogenes, Salmonella typhimurium, Shigella sonnei, Haemophilus influenzae, Enterobacter cloacae, Pseudomonas aeruginosa, indole-positive Proteus species and Bacteroides fragilis. Thus compounds of the invention have the ability to protect p-lactamase susceptible p-lactam antibiotics from -lactamase hydrolysis.

Compounds of the invention have shown inhibition of the -lactamase produced by the Enterobacter cloacae P 99, an enzyme that is not susceptible to inhibition by a number of derivatives of clavulanic acid.

The compounds of the invention are also useful as intermediates in the production of further P-lactams. In particular, certain of them may be used for preparing diene esters of formula (II)

wherein R is an esterified carboxyl group, as more particularly described hereinafter.

Such dienes are described in our Cognate copending Application Nos. 26595/76 and 37446/76 (Serial No. 1588015) and are valuable intermediates in the preparation of, inter alia, antibiotic and t3-lactamase inhibitory thio-derivatives of clavulanic acid of the type reported in our German OLS 2708330; these diene esters have also been reported as possessing g-lactamase inhibitory activity.

The compounds of formula (I) may be prepared in a variety of ways. Thus, according to one feature of the invention, we provide a process for the preparation of a compound of formula (I) from compounds of formula (III)

wherein R1 is as defined above, and R is an esterified carboxyl group by treatment thereof at elevated temperature with a base whereby a compound of formula (I) is obtained followed, if desired, by cleavage of the esterified carboxyl group when a free acid is required and subsequent salt formation when a salt is required.

Preferred bases for use in this reaction are tertiary organic bases, e.g. tertiary amines.

Such amines will desirably have the formula RXRYRZN, where Rx, RY and RZ, which may be the same or different, may each represent an aliphatic, araliphatic or aromatic group, e.g. alkyl groups having up to eight carbon atoms; aralkyl groups having up to six carbon atoms in the alkyl portion, or aryl groups, such aryl and aralkyl groups desirably being monocyclic, and including also cycloaliphatic, e.g. C37 cycloalkyl, groups; or amines wherein two of RX, RY and RZ form, together with the nitrogen atom to which they are attached, a five-, six- or seven-membered heterocyclic ring optionally containing a further heteroatom, e.g. a nitrogen, oxygen or sulphur atom as in a piperidino or morpholino group, or, wherein RX, RY and RZ form, together with the nitrogen atom to which they are attached, a polycyclic, e.g. bicyclic, non-aromatic heterocyclic ring system, for example quinuclidine.

Reaction will desirably be carried out in a suitable inert solvent. Such solvents will preferably have some degree of polarity and include esters, e.g. ethyl acetate, ethers, e.g. tetrahydrofuran, ketones, e.g. acetone, amides, e.g. dimethylformamide or halogenated hydrocarbons, e.g. 1,2-dichloroethane or chloroform.

Reaction will desirably be effected under reflux, a temperature of from 50 to 1000C being preferred.

The compounds of formula (I) may also be prepared by removal of the group NRXRYRZ from compounds of formula (IV)

(wherein R' is as defined above, RX, RY and RZ are as defined above or additionally may, together with the nitrogen atom to which they are attached, form an aromatic heterocyclic group, such as a pyridinium group, and R is an esterified carboxyl group) or an acid addition salt thereof, followed, if desired, by cleavage of the esterified carboxyl group when a free acid is required and subsequent salt formation when a salt is required. Such compounds of formula (IV) are described in our cognate copending Application Nos.

37481/76 and 37444/76 (Serial No. 1591437).

Removal of NRXRYRZ may, for example, be achieved by heating, e.g. at 50-1000C, preferably under reflux in a suitable liquid medium. Where an acid addition salt of a compound of formula (IV) is used, it may be advantageous to include one equivalent of an acid binding agent. The liquid medium will preferably be a low-boiling inert, liquid, e.g. an ester, such as ethyl acetate, a halogenated hydrocarbon such as 1,2-dichloroethane or chloroform, a hydrocarbon such as benzene, a ketone such as acetone or an ether such as tetrahydrofuran. Higher boiling liquids such as amides, e.g. dimethyl-formamide, can also be used.

Acid addition salts which may be useful include those formed with either organic or inorganic acids. Suitable organic acids include carboxylic acids, e.g. citric, formic, tartaric and acetic acids, or sulphonic acids, e.g. p-toluene sulphonic acid. Suitable inorganic acids include mineral acids, e.g. nitric, hydrochloric, sulphuric acid perchloric acids.

The compounds of formula (IV) and their acid-addition salts may readily be obtained from compounds of formula (III) by a ring-opening reaction employing an amine RXRYRZN wherein RX, RY and RZ are as defined above in relation to compound (IV). Where -NR"RYR" is to be the residue of a weak base such as pyridine it may be possible to perform the ring-opening by reaction with the weak base in the presence of a catalytic quantity of a strong base.

In both of the foregoing reactions, use of the simpler trialkylamines, e.g. having 1-6 carbon atoms in each alkyl group, especially methyl, ethyl, propyl or butyl groups, is preferred and trimethylamine or triethylamine is especially preferred.

The compounds of formula (IV) will in general be mixtures of the azetidin-2-one 4-position epimers and in solution will also constitute a mixture of geometric isomers around the double-bond in the 1-position side chain due to the possibility of equilibration arising from keto-enol tautomerisms, although the crystalline material will normally exist as one or the other of the possible E and Z isomers.

Reaction may be carried out in a suitable non-hydroxylic solvent, e.g. an ester such as ethyl acetate, an amide such as dimethylformamide, a halogenated hydrocarbon such as dichloromethane or chloroform, a ketone such as acetone or an ether such as diethyl ether.

Alternatively, the amine itself may serve as the solvent. It is preferred to use ethyl acetate or dimethylformamide as the solvent.

Reaction may be carried out at a temperature of from -40" to +300C, a temperature of from +10 to +20"C being preferred; in some cases subsequent cooling may be advantageous in order to facilitate the isolation of a product of formula (I) in a pure state.

The compounds of formula (IV) may readily be separated from the reaction mixture by conventional separation and isolation techniques.

The compounds of formula (IV) are betaines and normally crystallise readily from some of the above solvents. It is often the case that the compounds of formula (IV) crystallise out from the reaction solution on allowing it to stand over a period of time but if an oil should be formed, for example, solid product may often readily be obtained by simple purification means, e.g. trituration with fresh solvent. For the preparation of acid-addition salts of the compounds of formula (IV) it is preferred to dissolve the isolated butaine in a suitable solvent such as dimethylformamide or water and add one equivalent of the appropriate acid.

The compounds of the invention may themselves readily be converted into compounds of formula (IV) by treatment with an amine base RXRYRZN as.defined in relation to formula (IV), desirably in a suitable solvent. This conversion may generally be effected using a weaker base than is needed for conversion of the compounds of formula i (it) into compounds of formula (IV). Thus, for example, an aromatic tertiary base, such as pyridine alone may successfully be employed.

The value of this procedure, namely conversion of compounds of formula (I) into compounds of formula (IV) and back again, lies in the fact that the compounds of formula (IV) are betaines which frequently provide crystalline material from which the compounds of the invention may readily be regenerated in a high state of purity.

The compounds of formula (I) in which R1 is a hydrogen atom may also be prepared from dienes of formula (II) by reduction, e.g. by mild catalytic hydrogenation. The hydrogenation catalyst is normally a noble metal catalyst, e.g. palladium, platinum or rhodium. The catalyst may be supported, e.g. on charcoal or Kieselguhr; the metal catalyst is preferably palladium e.g. as 10% palladium on charcoal. Suitable solvents for the hydrogenation include ethers such as tetrahydrofuran; esters such as ethyl acetate; ketones such as acetone; amides such as dimethylformamide; or halogenated hydrocarbons such as methylene chloride.

Where the ester of the diene used as starting material is susceptible to catalytic hydrogenolysis the free acid will be obtained. This may, if desired, be subjected to re-esterification or salt formation by the methods described hereinafter.

The initial product obtained in the processes described above is normally an ester of formula (I) and where an acid or salt is required these may be obtained by de-esterification followed, where desired, by salt formation. For this purpose, readily cleavable esters, for example, arylmethyl esters which may be cleaved by reduction, e.g. by hydrogenolysis, are preferred. Cleavage of arylmethyl esters may be accomplished using similar methods to those described above for the catalytic hydrogenation of the diene esters of formula (II).

Where it is desired to produce a salt of the compound of formula (I), 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 for example, e.g. sodium or potassium salts, an alkanoate is a preferred base e.g. a 2-ethyl hexanoate.

Where an ester of formula (I) is required, different from that initially obtained, the initial ester product may be subjected to de-esterification as described above and the free acid thus obtained or a reactive derivative thereof subjected to esterification by the methods described hereinafter in connection with the preparation of esters of formula (III), use of a diazoalkane or diazoaralkane being preferred.

In a particular embodiment of the invention, the compound of formula (I) wherein R1 is a hydroxyl group and R is an esterified carboxyl group may be prepared in situ from the compound of formula (IV) wherein R1 is a hydroxyl group and R an esterified carboxyl group and then converted directly into the diene ester compound of formula (II) by the methods described herein, preferably via the mesyloxy compound.

The compounds of formula (III) whence both the compounds of the invention and the compounds of formula (IV) may be prepared may themselves be prepared in a variety of ways from clavulanic acid or its esters or salts, and reactive derivatives thereof, such as halo derivatives (i.e. compounds of formula (III) in which R' is a halogen atom). These halo derivatives are described in our German OLS 2 657 081.

The compounds of formula (III) wherein R' is a hydrogen atom may advantageously be prepared by catalytic hydrogenolysis as described in our German OLS 2 657 081 and South African Patent No. 76/1953.

Compounds of formula (III) wherein R1 represents an etherified hydroxyl group may be prepared by etherification of an ester of clavulanic acid. Etherification may be effected, for example, by reaction of the starting hydroxy ester with an etherifying agent, e.g. a diazoalkane. The reaction temperature is preferably in the range -70" +70 C.

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 +15"C. This method is preferred for the production of ethers in which Rl is a C14 alkyl group. The ester starting material may if desired be formed from clavulanic acid 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.

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

This method is especially useful for production of tetrahydropyranyl ethers, using 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.

Silyl ethers may be prepared using the appropriate silyl halide e.g. trimethyl silyl chloride or t-butyl-dimethyl silyl chloride.

Compounds of formula (III) wherein R1 represents an acylated hydroxyl group -OCOR5 wherein R5 is as defined above may be prepared by reaction of clavulanic acid or an ester thereof with a compound of formula R5COY (wherein R5 is as defined above and Y represents a hydroxyl group or a readily eliminatable substituent). The 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 C and +35 C is preferred. Where a carboxylic acid is initially produced this may be converted into an ester by the methods described hereinafter.

Thus, clavulanic acid or an ester thereof may be reacted with a reactive derivative of a carboxylic acid, e.g. a halide or anhydride, for example, an acid chloride. In this case reaction may be effected using either the free antibiotic carboxylic acid or, more preferably, an ester thereof, deisrably under mild basic conditions, e.g. in the presence of a pyridine base in a solvent such as an ether, e.g. tetrahydrofuran or dioxan, or ester, e.g. ethyl acetate, or halogenated hydrocarbon, e.g. methylene chloride, or a substituted amide, e.g. dimethylacetamide.

Alternatively, a mono-N-substituted carbamate or thiocarbamate may be prepared using an isocyanate of formula R6NCO or an isothiocyanate of formula R6NCS in which R6 is as defined above. The reaction will preferably be carried out by allowing an ester of clavulanic acid to react with an isocyanate or isothiocyanate, optionally in the presence of a mild organic base, e.g. pyridine, to yield the acylated derivative of the compound of formula (III).

Disubstituted carbamates may be prepared by reaction of an ester of clavulanic acid with a carbamoyl halide of the formula R6R7NCOX (where R6 and R7 are as defined above other than hydrogen and X is a halogen atom, e.g. a chlorine atom), preferably in the presence of a weak base as hydrogen halide acceptor.

The carbamoyl halide may be prepared by reaction of a carbonyl dihalide such as phosgene with a secondary amine. Alternatively, an ester of clavulanic acid may be reacted with a carbonyl dihalide followed by reaction with a secondary amine.

Compounds of formula (III) wherein R1 represents the residue of a sulphur nucleophile may readily be prepared by reaction ofan ester of a halo derivative of clavulanic acid with a sulphur nucleophile as described in our German OLS 2 708 330. Other methods for preparing such sulphur compounds are also- described in our above application.

Compounds of formula (I) in which R1 is an etherified or acylated hydroxyl group-may be prepared from compounds of formula (I) in which R9 is hydroxyl by etherification or acylation as described above in relation to compounds of formula (III). As described above the compounds of formula (I) may be converted into compounds of formula (IV) by reaction with bases, e.g. of the formula RXRYRZN; consequently the use of such bases in the above etherification and acylation reaction is preferably avoided. Thus, where the presence of an acid binding agent is desirable this will preferably not be a base as described above in relation to the conversion of compounds of formula (I) into compounds of formula (IV).

Suitable acid binding agents include amides, e.g. carboxylic acid amides such as acetamides, metal carbonates, e.g. calcium carbonate, oxiranes, e.g. propylene oxide, or molecular sieves.

The reaction will preferably be carried out in an inert solvent, e.g. a halogenated hydrocarbon, for example methylene chloride.

The esters of formula (III) may be prepared from the corresponding acids or reactive derivatives thereof by reaction with heterocyclic aromatic bases). Suitable amines will include amines bearing aliphatic, araliphatic or aromatic groups, e.g. alkyl groups having up to 8 carbon atoms, aralkyl groups having up to 6 carbon atoms in the alkyl portion, or an aryl group, such aryl and aralkyl groups desirably being monocyclic. Amines bearing cycloaliphatic, e.g. C37 cycloalkyl, groups or amines wherein the nitrogen atom forms part of a five-, six- or seven-membered heterocyclic ring optionally containing a further heteroatom, e.g.

N-alkyl-piperidines or N-alkyl-morpholines are also suitable. Suitable aromatic heterocyclic bases include pyridine bases, e.g. collidine.

Preferred bases include trialkylamines, preferably having 1-6 carbon atoms in each alkyl group, especially methyl, ethyl, propyl or butyl groups, and triethylamine is particularly suitable.

Reaction will generally be effected in a suitable inert solvent. Such solvents will preferably have some degree of polarity and include esters, e.g. ethyl acetate, ethers, e.g. tetrahydrofuran, ketones, e.g. acetone, amides, e.g. dimethylformamide or halogenated hydrocarbons, e.g. dichloromethane or 1,2-dichloroethane.

Reaction may be effected at temperatures in the range -30"C to +1000C. The preferred temperature range for reaction of the compound of formula (I) is +20 to +1000C.

The reagent capable of replacing the hydroxyl group by a readily eliminatable substituent will desirably be a halogenating agent such as a thionyl halide or a sulphonylating agent, e.g. a mesylating or tosylating agent, in the presence or absence of halide ions.

Sulphonylating agents include mesylating and tosylating agents, mesyl chloride being preferred.

The invention will now be further described in the following Preparations and Examples which should not be construed as limiting the invention.

The following Preparations illustrate the means whereby the starting materials for the preparation of the compounds of the invention may be obtained.

All temperatures are in C.

PREPARATION 1 Methyl (3R,5R, Z)-2-ethylideneclavam-3-carboxylate A suspension of lithium (3R,5R,Z)-2-(2-hydroxyethylidene)clavam-3-carboxylate (4.0 g) in a mixture of brine (50 ml) and ethyl acetate (50 ml) was acidified with 2N hydrochloric acid (15 ml) and shaken. The separated aqueous phase was further extracted with ethyl acetate and the combined organic solutions were dried, and filtered. The resulting ethyl acetate solution of free acid was hydrogenated at atmospheric pressure and ambient temperature over 5% palladium on carbon (6.0 g). Hydrogenation was terminated after 3 minutes when the initial rapid uptake of hydrogen (ca 630 ml) had ceased. The mixture was filtered through Kieselguhr and the organic solution was washed successively with water and brine and dried. The solution was filtered, concentrated by evaporation to ca 50 ml, cooled to 0 and treated dropwise with an excess of ethereal diazomethane. Evaporation of the solvents afforded an oil which was chromatographed on a dry column of silica gel and eluted with ether-petroleum (b.p. 40-60 ) (1:2). Fractions were combined on the basis of t.l.c. examination and evaporated to afford a colourless oil, which was redissolved in chloroform and evaporated to yield the title ester (1.42 g) which contained about 15% of the corresponding E-isomer, [a]D +97.8 (c 0.8; DMSO), vmax (CHBr3) 1788 cm-' (ss-lactam); T (CDC13) values for Z-isomer include 4.35 (d, J 2Hz, C-5 H), 6.23 (s, methyl ester), 8.32 (dd, J 1 and 7Hz, C=C-CH3); X (CDC13) values for E-isomer include 4.90 (m, C-5H).

PREPARATION 2 4-Nitrobenzyl (3R, 5R, Z) -2-ethylideneclavam 3-carboxylate A stirred solution of sodium (3R,SR,Z)-2-ethylidene-clavam-3-carboxylate (3.0 g) in N,N-dimethylformamide (40 ml) was cooled in ice and treated with 4-nitrobenzyl bromide (3.16 g). The resulting solution was stirred at room temperature for 2 hr, and was then partitioned between ethyl acetate and brine. The organic solution was washed successively with brine, water and brine and was then dried. Evaporation afforded an oil which crystallised on standing. Recrystallisation from ether-petroleum b. . 40-60 ) gave the title ester (2.67 g) which contained less than 2% E-isomer, m.p. 81.6 , a +73 (c 0.7, DMSO) BE'a ,4263 nm (E 10,200), vmax (CHBr3) 1780 cm-1 (P-lactam), T (CDCl3) values include 4.35 (3, J 2Hz, C-5 H), 8.36 (dd, J 1 and 7Hz, C=C-CH3).

PREPARATION 3 4-Nitrobenzyl (3R, 5R, Z) -2- (2-benzoyloxyethylidene)clavam-3-carboxylate A solution of 4-nitrobenzyl (3R,5R,Z)-2-(2-hydroxyethylidene)clavam-3-carboxylate (2.0 g) in ethyl acetate (40 ml.) was cooled to 00, stirred and treated with pyridine (3.22 ml) and benzoyl chloride (1.39 ml). The mixture was allowed to reach ambient temperature, stirred for 1 hour and then partitioned between ethyl acetate and 0.5 N hydrochloric acid.

The organic phase was washed with 0.5 N aqueous sodium hydrogen carbonate and water.

The solution was dried over sodium sulphate and evaporated to dryness in the presence of chromotographic silica gel (7g). The resulting powder was added to the top of a dry column of silica gel and eluted with mixtures of petroleum spirit (b.p. 40-60 ) and ether. Fractions were collected and combined on the basis of t.l.c. examination and evaporated to afford the title ester (2.267 g), [α]D (c 0.43, DMSO) +18 , #max (EtOH) 260 nm (# 12,360), #max (CHBr3) 1798 cm-1 (ss-lactam), # (CDCl3) values include ca. 1.95 and ca. 2.5 (m, COPh), 4.21 (d, J 3Hz, C-5 H).

PREPARATION 4 1-(4-Nitrobenzyloxycarbonyl)-1-(2-oxo-4-triethylammonioazetidin-1-yl)but-1-en-2-olate A solution of 4-nitrobenzyl (3R,5R,Z)-2-ethylideneclavan-3-carboxylate (1.0 g) and triethylamine (0.84 ml) in ethyl acetate (15 ml) was stood at ambient temperature for 24 hours. The resulting crystalline mass was broken up, collected, washed with ethyl acetate and with ether and was then dried in vacuo to afford the title salt (0.812 g), m.p. 110-112 , [α]D 0 #1 (c 1.0, H2O), #max (pH6 buffer) 273.5 nm (# 29,800) #max (Nujol), (Nujol is a Registered Trade Mark) 1770 cm-1 (ss-lactam), # (DMSO-d6) values for ca. 1:1 mixture of isomers include 4.48 + 4.90 [obscured] (m,azetidinyl C-4 H), 7.2 to 7.7 (m, CH2CH3), 8.82 + 8.90 (t, J 8Hz, N(CH2CH3)3), and 9.06 + 9.08 (t, J 8Hz, CH2CH3).

A portion of the product (0.2 g) was recrystallised from water (3 ml) to give material (0.066 g) with m.p. 116-118 and spectral characteristics similar to those above.

PREPARATION 5 1-Benzyloxycarbonyl-1-(2-oxo-4-triethylammonioazetidin-1-yl)but-1-en-2-olate A solution of benzyl (3R,5R,Z)-2-ethylideneclavam-3-carboxylate (0.547 g) and triethylamine (0.55 ml) in N,N-dimethylformamide (1 ml) was stood at ambient temperature for 18 hours and then diluted with ether. The resulting oil was triturated with ethyl acetate to give a solid which was collected and dried in vacuo to afford the title salt (0.358 g), m.p.

107 , #max (pH6 buffer) 272.5 nm (α 19,100), #max (Nujol) 1762 cm-1 (ss-lactam) # (D2O) values for mixture of isomers include 4.42 + 4.78 (m, azetidinyl C-4 H), 7.0 to 7.4 (m, CH2CH3) 8.59 + 8.76 (t, J 7Hz, CH2CH3) and 8.88 (t, J 7Hz, N(CH2CH3)3).

PREPARATION 6 1-Methoxycarbonyl-1-(2-oxo-4-triethylammonioazetidin-1-yl)-but-1-en-2-olate A solution of methyl (3R,5R,Z)-2-ethylidene-clavam-3-carboxylate (0.5 g) and triethylamine (0.7 ml) in N,N-dimethylformamide (0.5 ml) was stood at ambient temperature for 4 hours and then diluted with ethyl acetate. The resulting crystalline precipitate was collected, washed with ethyl acetate and with ether, and then dried in vacuo to yield the title salt (0.398 g), m.p. 109-109.5 , #max (pH 6 buffer) 270 nm (α 20,500), #max (Nujol) 1767 cm-1 (ss-latam), # (DMSO-d6) values for ca 1:1 mixture of isomers include 4.48 + 4.80 (m, azetidinyl C-4 H), 6.30 (s, CO2CH3), -7.1 to 7.7 (m, CH2CH3), 8.78 (t; J 7Hz, N(CH2CH3)3), and 9.06 + 9.08 (t, J 7Hz, CH2CH3).

PREPARATION 7 4-Benzoyloxy-1-(4-nitrobenzyloxycarbonyl)-1-(2-oxo-4-triethylammonioazetidin-1-yl)but-1en-2-olate A solution of 4-nitrobenzyl (3R,5R,Z)-2-(2-benzoyloxyethylidene)clavam-3-carboxylate (0.657 g) and triethylamine (3.03 g) in ethyl acetate (15 ml) was stood at ambient temperature for 5 hours. The supernatant was decanted from deposited solid which was then washed with ethyl acetate and with ether. The solid was dried in vacuo to give the title salt (0.502 g) m.p. 133-4 , #max (Nujol) 1784 cm-1 (ss-lactam), # (DMSO-d6) values for mixtures of isomers include 4.44 + 4.80 (m, azetidinyl C-4 H), 5.50 (CHOCOPh), ca. 6.64 (azetidinyl C-3 protons and N(CH2CH3)3), 8.84 + 8.90 (t, N(CH2CH3)3).

PREPARATION 8 4-Hydroxy-1-(4-nitrobenzyloxycarbonyl)-1-(2-oxo-4-triethylammonioazetidin-1-yl)but-1-en2-olate A solution of 4-nitrobenzyl (3R,5R,Z)-2-(2-hydroxyethylidene)clavam-3-carboxylate (0.334 g) and triethylamine (0.27 ml) in ethyl acetate (10 ml) was stirred at ambient temperature for 6 hours, during which time an oil was deposited. The mixture was stood for a further 18 hours and the supernatant then decanted from the oil. Trituration of the oil with ethyl acetate gave a solid which was collected, washed with ether and dried in vacuo to yield the title salt (0.261 g), [α]D 0 #1 (c 1.0, H2O), #max (pH 6 buffer) 274.5 nm (# 25,000), #max (Nujol) 1764 cm-1 (ss-lactam), # (DMSO-d6) values for ca. 1:1 mixture of isomers include 4.50 + 4.65 (m, azetidinyl C-4 H), and 8.81 + 8.88 (t, J 7Hz, N(CH2CH3)3).

PREPARATION 9 1-(4-Nitrobenzyloxycarbonyl)-1-(2-oxo-4-trimethylammonioazetidin-1-yl)but-1-en-2-olate A solution of 4-nitrobenzyl (3R,SR,Z)-2-ethylideneclavam-3-carboxylate (0.5 g) in ethyl acetate (2.5 ml) was treated with a solution of trimethylamine in ethyl acetate (1.3M, 2.5 ml). An oil soon began to separate and the mixture was diluted with ethyl acetate and left at ambient temperature for 24 hours. The resulting crystalline solid was collected, washed with ethyl acetate and with ether, and then dried in vacuo to give the title salt (0.39 g), m.p.

131" (dec.), fmax (H2O) 273 nm (E 27,400), vmax (Nujol) 1772 cm-1 (p-lactam), T (DMSO-d6) values for ca. 1:1 mixtures of isomers include 4.64 + 4.96 (m, azetidinyl C-4 H), 6.78 (s, N(CH3)3), and 9.04 (t, J 7Hz, CH2CH3).

PREPARATION 10 i-(4-Nitrobenzyloxycarbonyl) -i- (2-oxo-4-triethylammonioazetidin-i-yl) but-i -en-2-ol 4 toluenesulphonate 4-Toluenesulphonic acid monohydrate (0.095 g) was added to a solution of 1-(4nitrobenzyloxycarbonyl)-1-(2-oxo-4-triethylammonioazetidin-1-yl)but-1-en-2-olate (0.205 g) in dimethylformamide (1 ml). After 10 minutes the solution was diluted with ether and the supernatant was decanted from the deposited oil. Trituration of the oil with ether gave a solid which was collected, washed with ether, and dried in vacuo to yield the title salt (0.150 g), Xmax (pH 6 buffer) 273.5 nm (E 27,300), vmax (Nujol) 1790 cm-l (p-lactam), and 1032 cm (SO3-), n (DMSO-d6) values include 2.50 and 2.90 (doublets, J 9Hz, -O3SC6H4CH3), 6.2 to 6.9 (m, C-3 protons, N(CH2CH3)3, and CH2CH3), 7.50 (s, -03SC6H4CH3), 8.82 and 8.88 (multiplets, N(CH2CH3)3 and CH2CH3).

PREPARATION 11 I - (4-Nitrobenzyloxyearbonyl) -i - (2-oxo-4-triethylammonioazetidin-i-yl) -4-phenylthiobut-i- en-olate A solution of 4-nitrobenzyl (3R,5R,Z)-2-(2-phenylthioethylidene)clavam-3-carboxylate (0.548 g) and triethylamine (0.35 ml) in ethyl acetate (2 ml) was stood at ambient temperature for 1 hour and the supernatant was then decanted from the deposited oil.

Trituration of the oil with ethyl acetate gave a solid which was collected, washed with ether, and dried in vacuo to yield the title salt (0.272 g), [a]D 0 #1 (c 1.0, H2O), vmax (Nujol) 1768 cm-1 (P-lactam), z (DMSO-d6) values for mixture of isomers include 2.5 to 2.9 (m, SPh), 4.48 + 4.90 [obscured] (m, azetidinyl C-4H), 8.82 + 8.89 (t, J 7Hz, N(CH2CH3)3).

PREPARATION 12 4-Methylthio-1-(4-nitrobenzyloxycarbonyl)-1-(2-oxo-4-triethylammonioazetidin-1-yl)but-1en-2-olate A solution of 4-nitrobenzvl (3R,5R,Z) 2-(2-methylthioethylidene)clavam-3-carboxylate (2.263 g) and triethylamine (1.73 ml) in ethyl acetate (20 ml) was stood at 230 for 1.5 hours.

The precipitated oil was triturated with ether to afford a solid which was collected and dried in vacuo to give the title salt (1.97 g), m.p. 91.0 (Mettler) (Mettler is a Registered Trade Mark), vmax (Nujol) 1772 cm-' (ss-lactam), T (DMSO-d6) values for mixture of isomers include 4.46 + 4.61 (m, azetidinyl C-4 H), 7.95 (s, SMe), 8.79 + 8.86 (t, J 7Hz, N(CH2CH3)3).

PREPARATION 13 1 - ( 4 - N i t r o b e n z y l o x y c a r b o n y l ) - 1 - ( 2 - o x o - 4 - t r i e t h y l a m m o n i o a z e t i d i n - 1 - y l ) - 4 (tetrahydropyran-2-yloxy) but-l -en -2-olate A solution of 4-nitrobenzyl (3R,5R,Z)-2-(2-[(2RS)-tetrahydropyran-2- yloxy]ethylidene}clavam-3-carboxylate (5.73 g) and triethylamine (2.76 g) in ethyl acetate (30 ml) was stood at ambient temperature for 16 hours. The resulting oil was triturated with ether to give a solid which was collected and dried in vacuo to afford the title salt (3.29 g), may (pH 6 buffer) 274 nm (E 23,400), Vmax (Nujol) 1774 cm-1 (p-lactam), T (DMSO-d6) values for ca. 1:1 mixture of isomers include 4.52 + 4.62 (m,azetidinyl C-4 H), 5.48 (m, tetrahydropyranyl C-2 H), 8.1 to 8.7 (m, tetrahydropyranyl C-3, C-4 and C-5 protons), 8.82 and 8.89 (t, J 7Hz, N(CH2CH3)3).

PREPARATION 14 4-Nitrobenzyl (3R,SR, Z) -2-tert-butyldimethylsilyloxyethylidene) -ctavam-3-caThoxytate A solution of imidazole (1.67 g) in ethyl acetate (25 ml) was added to a stirred solution of 4-nitrobenzyl (3R,5R,Z)-2-(2-hydroxyethylidene)clavam-3-carboxylate (8.44 g) in ethyl acetate (125 ml) contaning tert-butyldimethylsilyl chloride (3.69 g). After 30 minutes the mixture was filtered and the filtrate was evaporated to dryness and then fractionated on a column of silica gel. Appropriate fractions were combined and evaporated to give the title ester (6.5 g), #max (CHBr3) 1798 (ss-lactam), 1752 (ester), 1522 and 1348 cm-1 (NO2), # (CDCl3) 1.79 and 2.51 (doublets, J 9 Hz, aromatic protons), 4.33 (d, J 3 Hz, C-5H), 4.73 (s, benzylic protons), 4.90 (d, J 1 Hz, C-3H), 5.18 (dt, J 7 and 1 Hz, olefinic proton), 5.73 (d, J 7 Hz, C=CH-CH2), 6.49 and 6.96 (dd, J 17 and 3 Hz, and d, J 17 Hz, C-6 protons), 9.11 (s, Si(CH3)2-C(CH3)3), 9.91 (s, Si(CH3)2-C(CH3)3).

PREPARATION 15 4-Nitrobenzyl (3R,5R,Z)-2-(2-acetoxyethylidene)clavam-3-carboxylate A stirred solution of 4-nitrobenzyl (3R,5R,Z)-2-(2-hydroxyethylidene)clavam-3carboxylate (1.0 g) in ethyl acetate (25 ml) at 0 was treated with pyridine (1.61 ml), followed by acetyl chloride (0.43 ml). The mixture was stirred at ambient temperature for 31/2 hours and then partitioned between ethyl acetate and 0.5 N hydrochloric acid. The organic phase was washed with saturated aqueous sodium hydrogencarbonate, water and brine and was then dried over sodium sulphate. Evaporation of the solvent gave an oil which crystallised on standing to yield the title ester (1.19 g), m.p. 62.5-63.5 , [α]D + 42 (c 0.96; DMSO), #max (EtOH) 264.5 nm (# 11,000), #max (CHBr3) 1792 (ss-lactam), # (CDCl3) values include 4.27 (d, J 2.5 Hz, C-5H), 5.33 (d, J 7 Hz, -CH2OCOCH3), 7.95 (s, CH3).

PREPARATION 16 1-(4-Nitrobenzyloxycarbonyl)-1-(2-oxo-4-N,N,N-benzyldimethylammonioazetidin-1-yl)but1-en-2-olate A solution of 4-nitrobenzyl (3R,5R,Z)-2-ethylidene-clavam-3-carboxylate (320 mg) and N,N-dimethylbenzylamine (0.29 ml) in ethyl acetate (10 ml) was stood at ambient temperature for 18 hours and deposited an oil. Trituration of the oil gave a solid which was collected, washed and dried to yield the title (180 mg) #max (pH 6 buffer) 274 nm (# 31,700), #max (Nujol) 1778 cm-1 (ss-lactam), # (DMSO-d6) values for mixture of isomers include 4.62 (m, azetidinyl C-4H), 2.46 h(D).MSOd6) values (s, Ph). of isomers PREPARATION 17 1-(4-Nitrobenzyloxycarbonyl)-1-(2-oxo-4-N-methylpiperidinioazetidin-1-yl)but-1-en-2-olate A solution of 4-nitrobenzyl (3R,5R,Z)-2-ethylideneclavam-3-carboxylate (320 mg) and N-methylpiperidine (0.245 ml) in ethyl acetate (10 ml) was stood at ambient temperature for 18 hours. The resulting solid was collected, washed and dried to give the title salt (290 mg), #max (pH 6 buffer) 273.5 nm (# 27,300), #max (Nujol) 1780 cm-1 (ss-lactam), # (DMSO-d6) values for mixtures of isomers include 4.60 (m, azetidinyl C-4H), 6.75 and 6.95 (singlets, N-CH3).

PREPARATION 18 1-(4-Nitrobenzyloxycarbonyl)-1-(2-oxo-4-triethylammonioazetidin-1-yl)but-1-en-2-olhydrochloride A mixture of 1-(4-nitrobenzyloxycarbonyl)-1-(2-oxo-4-triethylammonioazetidn-1-yl)but1-en-2-olate (210 mg) in water (10 ml) and 0.1N hydrochloric acid (5 ml) was lyophilised and the residue triturated with ether to afford the title salt (220 mg), #max (Nujol) 1790 cm-1 (P-lactam), T (DMSO-d6) values for mixture of isomers include 4.50 (m, azetidinyl C-4 H), 6.3-6.8 (m, NCH2), 6.7-7.3

PREPARATION 19 1-(4-Nitrobenzyloxycarbonyl)-1-(2-oxo-4-triethylammonioazetidin-1-yl)but-1-en-2-ol nitrate A mixture of 1-(4-nitrobenzyloxycarbonyl)-1-(2-oxo-4-triethylammonioazetidin-1-yl)but1-en-2-olate (210 mg) in water (10 ml) and 1.0 N nitric acid (0.5 ml) was lyophilised and the residue triturated with ether to give the title salt (240 mg), #max (CHBr3) 1794 cm-1 (p-lactam), T (DMSO-d6) values for mixture of isomers include 4.50 (m, azetidinyl C-4H), 6.7-7.4

PREPARATION 20 1-(4-Nitrobenzyloxycarbonyl) -1- (2-oxo-4-triethylammonioazetidin-i -yl) but-i -en-2-ol citrate A solution of 1-(4-nitrobenzyloxycarbonyl)-1-(2-oxo-4-triethylammonioazetidin-1- yl)but-1-en-2-olate (180 mg) and citric acid (90 mg) in water (10 ml) was lyophilised and the residue triturated with ether to yield the title salt (260 mg), vmax (Nujol) 1784 (p-lactam), 1720 and 2650 (CO2H) and 1580 cm-1 (CO2-), T (DMSO-d6) values for mixtures of isomers include 4.50 (m, azetidinyl (C-4H), 7.32 (citrate CH2).

PREPARATION 21 4-Acetoxy-1-(4-nitrobenzyloxycarbonyl)-1-(2-oxo-4-triethylammonioazetidin-1-yl)but-1-en2-olate A stirred solution of 4-hydroxy-1-(4-nitrobenzyloxycarbonyl)-1-(2-oxo-4triethylammonioazetidin-1-yl)but-1-en-2-olate (400 mg) in dimethylformamide (20 ml) at 0 was treated with triethylamine (0.136 ml) followed by acetyl chloride (0.72 ml). After 10 minutes the reaction mixture was poured into stirred ether (ca 400 ml) and diluted with petroleum spirit (ca 100 ml, b.p. 40-60 ). The deposited gum was triturated to afford a solid which was collected, washed with ether and dried. The product (483 mg) was washed with water (ca 5 ml) and the insoluble residue was collected and dried to yield the title salt (102 mg), kmax (pH 6 buffer) 273 nm (e 22,700), vmax (Nujol) 1768 (ss-lactam) and 1720 cm (OAc).

PREPARATION 22 4 - N - M e t h y l c a r b a m o y l o x y - 1 - (4 - n i t r o b e n z y l o x y c a r b o n y l) - 1 - (2 - o x o - 4 triethylammonioazetidin-1-yl)but-1-en-2-olate A stirred solution of 4-hydroxy-1-(4-nitrobenzyloxycarbonyl)-1-(2-oxo-4triethylammonioazetidin-1-yl)but-1-en-2-olate (400 mg) in dimethylformamide (10 ml) was treated with methyl isocyanate (0.06 ml). Further portions of methyl isocyanate (0.1 ml) were added after 30 mins and after a further 3 hours. The mixture was stirred for an hour after the final addition and was then poured into ether. The deposited gum was triturated with fresh ether to give the title salt as a solid (256 mg), Xmax (pH 6 buffer) 274.5 nm 26,250), vmax (Nujol) 3320 (NH), 1770 (P-lactam), 1706 and 1512 cm-1 (OCONH), t (DMSO-d6) values for mixture of isomers include 3.24 (m, OCONH), 4.50 (m, azetidinyl C-4H), 7.44 and 7.48 (OCONHCH3).

PREPARATION 23 4 - t e r t - B u t y l d i m e t h y l s i l y l o x y - 1 - (4 - n i t r o b e n z y l o x y c a r b o n y l) - 1 - (2 - o x o - 4 triethylammonioazetidin-1-yl) but-1-en-2-olate A solution of 4-nitrobenzyl (3R,5R,Z)-2-(2-tert-butyldimethylsilyloxyethylidene)clavam3-carboxylate (1.346 g) in ethyl acetate (4 ml) containing triethylamine (0.61 g) was stood at room temperature for 18 hours. The resulting solid was collected and dried in vacuo to afford the title salt (1.10 g(, m.p. 109.0 (Mettler), #max (Nujol) 1764 cm-1 (ss-lactam), # (DMSO-d6) values for mixture of isomers include 4.56 (m, azetidinyl C-4H), 8.85 + 8.93 (t, J 7 Hz, N(CH2CH3)3), 9.16 (s, OSi-(CH3)2-C(CH3)3), 10.0 (s, OSi-(CH3)-C(CH3)3).

PREPARATION 24 4-Acetylthio-1-(4-nitrobenzyloxycarbonyl)-1-(2-oxo-4-triethylammonioazetidin-1-yl)but-1en-2-olate A solution of 4-nitrobenzyl (3R,5R,Z)-2-(2-acetylthioethylidene)clavam-3-carboxylate (0.078 g) and triethylamine (0.06 ml) in ethyl acetate (1 ml) was stood at ambient temperature for 1 hour and then diluted with ether. The resulting oil was triturated with ether to give a solid which was collected and dried in vacuo to afford the title salt (0.035 g) vrnax (Nujol) 1770 (ss-lactam), 1680 cm-l (SCOR), # (DMSO-d6) values for ca. 1:1 mixture of isomers include 4.50 + 4.90 [obscured] (m, azetidinyl C-4 H), 6.9 to 7.3 (m, -CH2CH2S-), 8.80 + 8.88 (t, J 7Hz, N(CH2CH3)3).

PREPARATION 25 4-Mercapto-1-(4-nitrobenzyloxycarbonyl)-1-(2-oxo-4-triethylammonioazetidin-1-yl)but-1en-2-olate Triethylamine (0.085 ml) was added to a solution of 4-nitrobenzyl (3R,5R,Z)-2-(2mercaptoethylidene)clavam-3-carboxylate (0.105 g) in ethyl acetate (3 ml) containing N,N-dimethylformamide (0.5 ml). After 1 hour the reaction mixture was diluted with petroleum ether (40-60 ) (50 ml) and the precipitated solid was collected and deried in vacuo to give the title salt (0.06 g), #max (Nujol) 1774 (ss-lactam), # (DMSO-d6) values for mixture of isomers include 4.52 + 4.66 (m, azetidinyl C-4 H), 8.81 + 8.89 (m, N(CH2CH3)3).

PREPARATION 26 4-(1-Ethoxyethoxy)-1-(4-nitrobenzyloxycarbonyl)-1-(2-oxo-4-triethylammonioazetidin-1yl)but-1-en-2-olate A solution of 4-nitrobenzyl (3R,5R,Z)-2-{2-[(1RS)-1-ethoxyethoxy]ethylidene}clavam-3carboxylate (9.92 g) and triethylamino (6.81 ml) in ethyl acetate (20 ml) was stood at ambient temperature for 18 hours. The resulting solid was collected and washed with ether, and then dried in vacuo to afford the title salt 8.66 g) Xmax (pH 6 buffer) 273.5 nm (E 27,600), vmax (Nujol) 1758 cm 1 (ss-lactam), T (DMSO-d6) values include for mixture of isomers 4.52 + 4.86 (m, azetidinyl C-4 H), 5.40 (q, J 5 Hz, O-CH(CH3)OEt), 8.82+8.90 (t, J 7 Hz, N(CH2CH3)3, 8.90 [partially obscured (m, OCH(CH3)0Et).

EXAMPLE 1 4-Nitrobenzyl 2-ethylclav-2-em-3-carboxylate A solution of -4-nitrobenzyl (3R,SR,Z)-2-ethylideneclavam-3-carboxylate (5.0 g.) and triethylamine (4.3 ml.) in ethyl acetate (100 ml.) was heated under reflux for 11/4 hours. The cooled mixture was evaporated in vacuo to afford an'oil which was redissolved in a small volume of ethyl acetate and diluted with ether. A small amount of insoluble material was removed by filtration and the filtrate then concentrated to afford a crystalline precipitate.

The solid was collected, washed with ether and dried in vacuo to yield the title ester (2.3g.).

The physical and spectral characteristics of the product were similar to those described below in Example 4.

EXAMPLE 2 4-Nitrobenzyl 2-(2-hydroxyethyl) clav-2-em-3-carboxylate A solution of 4-nitrobenzyl (3R,5R,Z)-2-(2-hydroxyethylidene clavam-3-carboxylate (0.5g.) and triethylamine (0.45 ml.) in ethyl acetate (40ml.) was heated under reflux for 12 minutes and then evaporated to give an oil. The oil was redissolved in ethyl acetate and the solvent again removed by evaporation. The residue was dissolved in ethyl acetate and diluted with an excess of ether. Some insoluble material was removed by filtration and the filtrate- evaporated to afford the title ester (ca. 0.3g.), vmax(CHBr3) 1808 cm-l (ss-lactam), (DMSO-d6) values include, 3.87(d, J 3Hz, C-5 H), 6.30(t, J 7Hz, CH2OH), 7.11(q, J 7Hz, CH2CH20H).

EXAMPLE 3 2-Ethylclav-2-em-3-carboxylic acid A solutidn of 4-nitrobenzyl 2-ethylclav-2-em-3-carboxylate (0.10g.) in ethyl acetate (7ml.) was hydrogenated for ca. 1 minute at atmospheric pressure and ambient temperature over 10% palladium on carbon (0.10g.). The catalyst was removed by filtration through kieselguhr and washed with ethyl acetate (lOml.). The combined'organic solutions wer'e extracted with pH7 buffer (2x10ml.). The aqueous extract was washed with ether and made up to a volume of 100ml. with pH7 buffer to afford a solution of the title acid. A portion of the above freshly prepared solution diluted 1 in 10 with pH 7 buffer shows Xmax 263 nm with an absorbence of 1.49 in a lcm cell.

EXAMPLE 4 4-Nitrobenzyl 2-ethylclav-2-em-3-carboxylate A suspension of 1-(4-nitrobenzyloxycarbonyl)-1-(2-oxo-4-triethylammonioazetidin-1-yl) but-1-en-2-olate (4.5g.) in ethyl acetate (250ml.) was heated rapidly and refluxed for 2 minutes to dissolve. The cooled solution was concentrated to ca. 20ml., diluted with ether and allowed to crystallise. The resulting crystalline was broken up, collected, washed with ether and dried in vacuo to afford the title ester (2.65g.), m.p. 116-118 , [a]O0+'l0 (c 1.0, DMSO), vmax (Nujol) 1806 cm-1 (p-lactam), T (DMSO-d6) values include 3.96(m, C-5 H), 7.1 to 7.5 (m, CH2CH3) and 8.90(t, J 7Hz, CH2CH3).

EXAMPLE 5 Benzyl 2-ethylclav-2-em-3-carboxylate A suspension of 1-benzyloxycarbonyl-1-(2-oxo-4-triethylammonioazetidin-1-yl)but-1-en2-olate (0.187g.) in ethyl acetate (50ml.) was heated under reflux for 5 minutes. The reaction mixture was filtered and the resulting solution evaporated to afford the title ester (0.117g.), 2-olate (1.0g.) in ethyl acetate (75ml.) was heated until dissolved. The solution was evaporated in vacuo to give an oil which was redissolved in ether. The ethereal solution was filtered and evaporated to yield an oil which crystallised on refrigeration to afford the title ester (0.61g.), [α]D0 #1 (c 1.0, DMSO), #max(CHBr3) 1810 cm-1 (ss-lactam), #(DMSO-d6) values includes 3.96(d, J 3Hz, C-5 H), 6.26(s, CO2CH3), 7.1 to 7.5(m, CH2CH3) and 8.89 (t, J 7Hz, CH2CH3).

EXAMPLE 7 4-Nitrobenzyl 2-(2-benzyloxyethyl)clav-2-em-3-carboxylate A s u s p e n s i o n o f 4 - b e n z o y l o x y - 1 - ( 4 - n i t r o b e n z y l- o x y c a r b o n y l ) - 1 - (2 - o x o - 4 triethylammonioazetidin-1-yl) but-1-en-2-olate (0.215g.) in ethyl acetate (30ml.) was heated under reflux for 5 minutes. The solution was decanted from some remaining solid which was then heated with fresh ethyl acetate (40ml.) for 5 minutes. The combined ethyl acetate solutions were evaporated in vacuo to afford the title ester (0.101g.), vmax(CHBr3) 180Scm-l (ss-lactam), n(CDCl) values include 4.00 (m, C-5 H), 5.40 (t, J 6Hz, CH2CH2OCOAr), and 6.76 (m, CH2CH2OCOAr).

EXAMPLE 8 4-Nitrobenzyl 2- (2-hydroxyethyl) clav-2-em-3-carboxylate A s u s p e n s i o n o f 4 -h y d r o xy - 1 - (4 - n i t r o b e n z y l o x y c a r b o n y l ) - 1- ( 2 - o x o - 4 triethylammonioazetidin-1-yl)but-1-en-2-olate (0.25g.) in chloroform (10 ml., ethanolfreed) was heated under reflux for 2 minutes to dissolve. The solvent was evaporated to give an oil which was shown by n.m.r. and i.r. spectroscopy to contain the title ester described in Example 2.

EXAMPLE 9 4-Nitrobenzyl 2-ethylclav-2-em-3-carboxylate A suspension of 1-(4-nitrobenzyloxycarbonyl)-1-(2-oxo-4-trimethylammonioazetidin-1yl)but-1-en-2-olate (0.05g.) in ethyl acetate (20ml.) was heated until dissolved. The solvent was removed by evaporation to afford the title ester (0.035g.). The spectral characteristics of the product were similar to those described in Example 4.

EXAMPLE 10 4-Nitrobenzyl 2-ethylclav-2-em-3-carboxylate A suspension of 1-(4-nitrobenzyloxycarbonyl)-1-(2-oxo-4-pyridiniumazetidin-1-yl)but-1- en-2-olate (0.05g.) in ethyl acetate (10ml.) was heated under reflux for 5 minutes to dissolve. The solution was evaporated to give an oil which crystallised on trituration with ether to afford the title ester (0.035g.). The spectral characteristics of the product were similar to those described in Example 4.

EXAMPLE 11 1-(4-Nitrobenzyloxycarbonyl)-1-(2-oxo-4-triethylammoniazetidin-1-yl)but-1-en-2-olate A stirred suspension of 4-nitrobenzyl 2-ethylclav-2-em-3-carboxylate (0.32g.) in ethyl acetate (3ml.) was treated with triethylamine (0.27ml.). The mixture was stirred for 18 hours and the precipitate collected, washed with ethyl acetate and with ether, and then dried in vacuo to give the title salt (0.363g.). The physical and spectral characteristics of the product were similar to those described in Preparation 4 above.

EXAMPLE 12 1-(4-Nitrobenzyloxycarbonyl)-1-(2-oxo-4-pyridinium-azetidin-1-yl)but-1-en-2-olate A solution of 4-nitrobenzyl 2-ethylclav-2-em-3-carboxylate (0.69g.) and pyridine (0.37ml.) in ethyl acetate (9 ml.) was stood at ambient temperature for 3 hours and deposited an oil. The supernatant was removed and the oil triturated with ethyl acetate to give a solid. The solid was collected, washed with ethyl acetate and with ether, and was then dried in vacuo to afford the title salt (0.44g.), Xmax (pH 6 buffer) 272nm (E 26,100) vmlx(Nujol) 1781cm-i (p-lactam), z(DMSO-d6) values include 3.53(m, azetidinyl C-4 H), 6.37 and 6.69(dd, J 17 and 4Hz, and d, J 17Hz, azetidinyl C-3 protons) and 9.09 (t, J 7H2, CH2CH3).

EXAMPLE 13 4-Nitrobenzyl 2-ethylclav-2-em-3-carboxylate A suspension of 1-(4-nitrobenzylcarbonyl)-1-(2-oxo-4-triethylammonioazetidin-1yl)but-1-en-2-ol 4-toluenesulphonate (0.041g) in ethyl acetate (30ml) was heated gently under reflux for 5 minutes. The resulting mixture was cooled to 25 and then filtered. The filtrate was evaporated to afford the title ester (0.032g), whose spectral characteristics were similar to those as described in Example 4.

EXAMPLE 14 4-Nitrobenzyl 2- (2-phenylthioethyl)clav-2-em-3-carboxylate A suspension of 1- (4-nitrobenzyloxycarbonyl)- 1-(2-oxo-4-triethylammonioazetidin-1-yl)4-phenylthiobut-1-en-2-olate (0.053 g) in ethyl acetate (20 ml) was heated gently under reflux for 15 minutes. The resulting solution was cooled to 25 and then evaporated to afford the title ester (0.041 g), vmax (CHBr3) 1810 cm I((j-lactam), z(CDCl3) values include 2.6 to 2.8 (m, SPh), 4.16 (m, C-5 H), 6.8 to 7.0 (m, -CH2CH2SPh).

EXAMPLE 15 4-Nitrobenzyl 2- (2-methylthioethyl) clav-2-em-3-carboxylate A suspension of 4-methylthio-1-(4-nitrobenzyloxycarbonyl)-1-(2-oXo-4- triethylammonioazetidin-1-yl)but-1-en-2-olate (0.140 g) in ethyl acetate (30 ml) was heated gently to reflux for 5 minutes. The resulting solution was cooled to ambient temperature and then evaporated to afford the title ester (0.075 g), vmay(CHBr3) 1805 cm-l (p-lactam), n(CDCl3) values include 4.05 (m, C-5 H), 6.8 to 7.4 (m, -CH2CH2SCH3, 7.92 (s, SCH3).

EXAMPLE 16 4-Nitrobenzyl 2-[2- (tetrahydropyran-2-yloxy) ethylyclav-2-em-3-carboxylate A suspension of 1-(4-nitrobenzyloxyCarbonyl)-l-(2-oxo-4-triethylammonioazetidin-l-yl)- 4-(tetrahydropyran-2-yloxy)but-1-en-2-olate (3.20 g) in ethyl acetate (30 ml) was heated gently to reflux for 10 minutes. The resulting solution was evaporated to afford the title ester (2.50 g), vmax(CHBr3) 1806 cm-l (p-lactam), T(CDCl3) values include 4.00 (d, J 3Hz, C-5 H), 5.40 (m, tetrahydropyranyl C-2 H), 7.20 (m, -CH2CH2O-), 8.1 to 8.7 (m. tetrahydropyranyl C-3, C-4, and C-5 protons).

EXAMPLE 17 4-Nitrobenzyl 2-vinylclav-2-em-3-carboxylate A solution of 4-hydroxy-1- 4-nitrobenzyloxycarbonyl)-1-(2-oxo-4- triethylammonioazetidin-1-yl)but-1-en-2-olate (0.435g.) in chloroform (25ml., ethanolfreed) was heated under reflux for 12 minutes. T.l.c. examination at this time indicated complete conversion to 4-nitrobenzyl 2-(2-hydroxyethyl) clav-2-em-3-carboxylate. The solution was treated with triethylamine (0.101g.), followed by mesyl chloride (0.1ml.) and reflux continued for a further 5 minutes. The cooled solution was diluted with petroleum spirit (ca. 225 ml.) and some precipitated solid removed by filtration; The filtrate was washed with brine, dried over sodium sulphate and concentrated to afford a crystalline solid. The solid was collected, washed with petroleum spirit and dried in vacuo to give the title ester (0.112g.), [a]D 0 t 10 (c 1.0, DMSO). vmax(cHBr3) 1810 cm-1(ss-lactam), x(CDCl3) values include 2.94 (dd, ( 10 and 17 Hz, -CH=CH2), 4.01 (dd, J2 and 3 Hz, C-5 H), 4.03 (dd, 52 and 17 Hz, olefinic proton), 4.32 (dd, J2 and 10 Hz, olefinic proton).

EXAMPLE 18 4-Nitrobenzyl 2-vinylclav-2-em-3-carboxylate A solution of 4-nitrobenzyl (3R,SR,Z)-2-(2-hydroxyethylidene) clavam-3-carboxylate (0.S01g.) and triethylamine (0.415ml.) in ethyl acetate (35ml.) was heated under reflux for 20 minutes. T.l.c. examination at this time indicated almost complete conversion of the starting ester into 4-nitrobenzyl 2-(2-hydroxyethyl)clav-2-em-3-carboxylate. Mesyl chloride (0.12ml.) was added and the mixture heated under reflux for a further 5 minutes. The cooled solution was diluted with ether, washed successively with 0.5N hydrochloric acid, saturated aqueous sodium hydrogen carbonate and water and then dried over sodium sulphate. Evaporation of the solvent gave an oil which was triturated with ether to give a crystalline solid. The solid was collected, washed with petroleum spirit and dried in vacuo to yield the title ester (0.195g.) [a]D 0 + 1" (c 1.0; DMSO). The spectral characteristics of the product were similar to those described in Example 17.

EXAMPLE 19 Methyl 2-ethylclav-2-em-3-carboxylate 4-Nitrobenzyl 2-vinylclav-2-em-3-carboxylate (0.316g.) in ethyl acetate (25ml) was hydrogenated for 3 minutes over 5% palladium on carbon at ambient temperature and atmospheric pressure. The catalyst was removed by filtration to afford a solution containing 2-ethylclav-2-em-3-carboxylic acid. The solution was treated with an excess of ethereal diazomethane at 00. The excess of diazomethane was removed by passing a stream of nitrogen through the solution for 5 minutes and the solution was then washed with 0.5N hydrochloric acid and with brine, dried over magnesium sulphate and evaporated to afford the title ester (0.101 g), T (CDCl3) values include 4.12 (d, J 3 Hz, C-SH), 6.20 (S, CO2CH3), 7.13 - 7.42 (m, CH2CH3), and 8.83 (t, J 7 Hz, CH2 CH3).

EXAMPLE 20 4-Nitrobenzyl 2-vinylclav-2-em-3-carboxylate To a stirred solution of triethylamine (0.027ml) in tetrahydrofuran (2ml.) at 20 was added 4-nitrobenzyl (SR)-2-vinylclav-2-em-3-carboxylate (0.316g., [a]D +9 in DMSO).

The mixture was stirred for 20 minutes at 200 and was then poured into ether. The solution was washed with 0.5N hydrochloric acid and with water and was then dried over magnesium sulphate. Concentration of the solution by evaporation gave a slurry of crystals which were collected and dried in vacuo to give the title ester (0.17g.), [a]D 00i10 (c 1.0; DMso). The spectral characteristics of the product were similar to those described in Example 17.

EXAMPLE 21 4-Nitrobenzyl 2-ethylclav-2-em-3-carboxylate A suspension of 1-(4-nitrobenzyloxycarbonyl)-1-(2-oxo-4-N,N,N- benzyldimethylammonioazetidin-1-yl) but-1-en-2-olate (120 mg) in ethyl acetate (10 ml) was heated under reflux for 10 minutes to dissolve. Evaporation of the solvent gave an oil which was triturated with ether to afford the title ester as a crystalline solid (80 mg). The spectral characteristics of the product were similar to those described in Example 4.

EXAMPLE 22 4-Nitrobenzyl-2-ethylclav-2-em-3-carboxylate A suspension of 1-(4-nitrobenzyloxyCarbonyl)-1-(2-oxo-4-N-methyl-piperidinioazetidin- 1-yl)but-1-en-2-olate (200.mg) in ethyl acetate (15 ml) was heated under reflux for 10 minutes. Evaporation of the resulting solution and trituration of the residue with ether gave the title ester (1so) mg). The spectral characteristics of the product were similar to those described in Example 4.

EXAMPLE 23 4-Nitrobenzyl 2-ethylclav-2-em-3-carboxylate 1-(4-NitrobenzyloxyCarbonyl)-1-(2-oXo-4-triethylammonioazetidin-1-yl)but-1-en-2-ol chloride (40 mg) was dissolved in dimethylformamide (ca 0.25 ml) and the solution diluted with ethyl acetate (10 ml). The mixture was heated under reflux for 10 minutes.

Evaporation of the solution and trituration of the residue with ether gave the title ester (20 mg). The spectral characteristics of the product resembled those described in Example 4.

EXAMPLE 24 4-Nitrobenzyl 2-ethylclav-2-em-3-carboxylate 1-(4-Nitrobenzyloxycarbonyl)-1-(2-oxo-4-triethylammonioazetidin-1-yl)but-1-en-2-ol nitrate (40 mg) was dissolved in dimethylformamide (ca 0.25 ml) and the solution diluted with ethyl acetate (10 ml). The resulting suspension was heated under reflux for 3 minutes.

Evaporation of the solution and trituration of the residue with ether afforded the title ester (25 mg). The spectral characteristics of the product resembled those described in Example 4.

EXAMPLE 25 4-Nitrobenzyl 2-ethylclav-2-em-3-carboxylate 1 -(4-Nitrobenzyloxycarbonyl)- 1-(2-oxo-4-triethylammonioazetidin-1-yl)but-1-en-2-ol citrate (100 mg) was dissolved in dimethylformamide (ca 0.25 ml) and the solution diluted with ethyl acetate (10 ml). The resulting suspension was heated under reflux for 3 minutes.

Evaporation of the solution and trituration of the residue with ether gave a solid containing the title ester (40 mg). The spectral characteristics of the product resembled those described in Example 4.

EXAMPLE 26 4-Nitrobenzyl 2-(2-acetoxyethyl) clav-2-em-3-carboxylate A solution of 4-nitrobenzyl (3R,SR,Z)-2-(2-acetoxyethylidene)-clavam-3-carboxylate (100 mg) and triethylamine (0.08 ml) in ethyl acetate (10 ml) was heated under reflux for 10 minutes. Evaporation of the solvent gave a residue which was redissolved in ethyl acetate (10 ml) with triethylamine (0.03 ml) and heated under reflux for a further 3 minutes. The solvent was evaporated to afford a gum which was shown by i.r. and n.m.r. to contain the title ester.

EXAMPLE 27 4-Nitrobenzyl 2-(2-acetoxyethyl)clav-2-em-3-carboxylate A s u s p e n s i o n o f 4 - a c e t o x y - 1 - ( 4 - n i t r o b e n z y l o x y c a r b o n y l ) - 1 - ( 2- o x o - 4 triethylammonioazetidin-1-yl)but-1-en-2-olate (100 mg) in ethyl acetate (10 ml) was heated under reflux for 5 minutes. The resulting solution was evaporated to give the title as an. oil, #max(CHBr3) 1810 (ss-lactam) itid 1732 cm-1 (OAc), T (DMSO-d6) values include 4.01 (m, C-5H), 5.82 (t, J 7 Hz, CH@OAc), 8.09 (s, OCOCH3)-., EXAMPLE 28 4-Nitrobenzyl 2-(2-N-methylcarbamoyloxy-ethyl)clav-2-em-3-carboxylate A solution of 4-N-methylcarbamoyloxy-1-(4-nitrobenzyloxycarbonyl)-1-(2-oxo-4triethylammonioazetidin-1-yl)but-1-en-2-olate (15() mg) in 1,2-dichloroethane (10 ml) was heated under reflux for 2 minutes. Uhe solution was concentrated, filtered and evaporated to afford the title ester (108 mg), #max(CHBr3) 3460 (NH), 1806 (ss-lactam), 1715 and 1518 cm-1 (OCONH), # (DMSO-d6) values include 3.90 (m, C-5H), 5.80 (t, J 7 Hz, CH2OCONHCH3), 7.45 (s, CH3).

EXAMPLE 29 4-Nitrobenzyl 2-(2-tert-butyldimethylsilyloxyethyl)clav-2-em-3-carboxylate A suspension of 4-tert-butyldimethylsilyloxy-1-(4-nitrobenzyloxycarbonyl)-1-(2-oxo-4triethylammonioazetidin-1-yl)but-1-en-2-olate (()SS g) in ethyl acetate (50 ml) was heated gently to boiling for 2 minutes. The resulting pale yellow solution was cooled to 25 and then evaporated to an oil. Trituration with ether gave a solid which was collected and dried in vacuo to afford the title ester (0.325 g), m.p. 105.9 (Mettler), #max(CHBr3) 1806 cm-1 (ss-lactam), t (CDCl3) values include 4.11 br (d, J 3 lIz, C-SH), 6.28 and 6.61 (dd, J 17 and 3 Hz, and d, J 17 Hz, C-6 protons), 9.20 (s, OSi-C(CH3)2-C(CH3)3), 10.02 (s, OSi-(CH3)2- C(CH3)3).

EXAMPLE 30 4-Nitrobenzyl 2-(2-acetylthioethyl)clav-2-em-3-carboxylate A suspension of 4-acetylthio-1-(4-nitrobenzyloxycarbonyl)-'1-(2-oXo-4- triethylammonioazetidin-1-yl)but-1-en-2-olate (100 mg) in ethyl acetate (10 ml) was heated under reflux for 5 minutes. The mixture was filtered and the filtrate evaporated to afford the title ester as an oil (90 mg), #max (CHBr3) 1808 (P-lactam) 1690 cm-1(SCOCH3), T (CDCl3) values includes 4.05 (m, C-SH), 7.73 (s, CH3).

EXAMPLE 31 4-Nitrobenzyl 2-[2-(1-ethoxyethoxy)ethyl]clav-2-em-3-carboxylate A suspension of 4-(1-ethoxyethoxy)-1-(4-nitrobenzyloxycarbonyl)-1-(2-oxo-4triethylammonioazetidin-1-yl)but-1-en-2-olate (0.507 g) in ethyl acetate (50 ml) was heated gentyl under reflux for 2 minutes. The resulting solution was cooled to 25 and then evaporated to afford the title ester (0.4 g), #max(CHBr3) 1800 cm-1 (ss-lactam), #(CDCl3) values include 4.09 (m, C-5H), 5.34 (q, J 5 Hz, OCH(CH3)OEt), 6.20 and 6.58 (dd, J 17 and 3 Hz, and d, J 17 Hz, C-6 protons), 6.2 to 6.7 (m, OCH2CH3) 8.82 (d, J 5 Hz, OCH(CH3)OEt), 8.86 (t, J 8 Hz, OCH2CH3).

EXAMPLE 32 4-Nitrobenzyl 2-(2-mercaptoethyl)clav-2-em-3-carboxylate A s u sp e n s i o n o f 4 - m e r c a p t o - 1 - ( 4 - n i t r o b e n z y l o x y c a r b o n y l ) - 1 - ( 2 - o x o - 4 triethylammonioazetidin-1-yl)but-1-en-2-olate (90 mg) in 1, 2-dichloroethane (10 ml) was heated under reflux for 2 minutes. The solution was decanted from some oil and evaporated to give the title ester #max(CHBr3) 1805 cm-l ((3-lactam), T (CDCl3) values include 4.12 (m, C-SH), 6.8-7.4 (m, CH2CH2) 8.78 (t, J 7 Hz, SH).

EXAMPLE 33 4-Nitrobenzyl 2-(2-methoxyethyl)clav-2-em-3-carboxylate A solution of 4-nitrobenzyl (3R, 5R,Z)-2-(2-methoxyethylidene)-clavam-3-carboxylate (3.48 g) in ethyl acetate (50 ml) containing triethylamine (2.77 ml) was heated gently under reflux for 7 minutes. Evaporation afforded the title ester as an unstable oil (3.5g), vmax(CHBr3) 1802 cm-1, (ss-lactam)# (CDCl3) values include 4.07 (dd, J 3 and 1.5 Hz, C-SH), 6.21 and 6.53 (dd, J 16 and 3 Hz; and dd, J 16 and 1.5 Hz, C-6 protons), 6.69 (s,, OCH3).

EXAMPLE 34 Potassium (5R) 2-ethylclav-2-em-3-carboxylate A solution of 4-nitrobenzyl (5R)-2-vinylclav-2-em-3-carboxylate {1.26 g, [α]D+8.5 (c 1.63, DMSO)} in ethyl acetate AR (50 ml, ex basic alumina) was hydrogenated for 10 minutes at atmospheric pressure and ambient temperature over 10% palladium on charcoal (1.26 g). The catalyst was removed by filtration through kieselguhr and washed with ethyl acetate AR (ex basic alumina). The filtrate was treated with a solution of potassium 2-ethylhexanoate (0.243 g) in ethyl acetate AR (5 ml, ex basic alumina), then concentrated to low volume (ca 2 ml), and diluted with anhydrous diethyl ether to give a solid which was collected and dried in vacuo to afford the title salt (0.16 g), [α]D + 84 (c 1.34, H2O), #max(H2O) 261.5 nm (# 5,600), #max(Nujol) 1772 (ss-lactam), 1616 cm-1 (CO2-), # (D2O) 4.17 (d, J 3 C-5H), 6.24 and 6.60 (dd, J 17 and 3 Hz, and d, J 17 Hz, C-6 protons), 7.36 (m, CH2CH3), 8.92 (t, J 7 Hz, CH2CH3).

EXAMPLE 35 Potassium (5RS) -2-ethylclav-2-em-3-carboxylate A solution of 4-nitrobenzyl (SR)-2-vinylclav-2-em-3-carboxylate (0.316 g, [a]D + 9.3 (c 1.04, DMSO)} in ethyl acetate AR (30 ml) was hydrogenated for 10 minutes at atmospheric pressure and ambient temperature over 10% palladium on charcoal (0.32 g). The catalyst was removed by filtration through kieselguhr and washed with ethyl acetate AR. The filtrate was treated with a solution of potassium 2-ethylhexanoate (0.06 g) in ethyl acetate AR (5 ml), then concentrated to low volume (ca 2 ml), and diluted with anhydrous diethyl ether to give a solid which was collected and dried in'vacuo to afford the title salt (0.07 [a]D 0+1 (c 1.02, H2O), Xrnox(H2O)260.5 nm (E 5,800), vrn0,c(Nujol) 1772 (ss-lactam), 1570 cm (CO2-), T (D2O) 4.17 (d, J 3 Hz, C-SH), 6.24 and 6.60 (dd, J 17 and 3 Hz, and d, J 17 Hz, C-6 protons), 7.36 (m, CH2CH3), 8.92 (t, J 7 Hz, CH2CH3).

EXAMPLE 36 Potassium (5RS)-2-ethylclav-2-em-3-carboxylate A solution of 4-nitrobenzyl 2-ethylclav-2-em-3-carboxylate (1.30 g) in ethyl acetate AR (50 ml) was hydrogenated over 10% palladium on charcoal (1.30 g) for 5 minutes. Work-up as in Example 35 gave the title salt (0.16 g), [α]D0#1 (c 1.02, H2O) whose spectroscopic properties resembled those as given in Example 35.

EXAMPLE 37 4-Nitrobenzyl 2- (2-N-ethylcarbamoyloxyethyl) clav-2-em-3-carboxylate A solution of 4-nitrobenzyl 2-(2-hydroxyethyl)clav-2-em-3-carboxylate in ethyl acetate (25 ml) was treated with ethyl isocyanate (0.5 ml), followed by bis-tri-n-butyltin oxide (0.1 ml) and was then stirred for 1 hour. The mixture was diluted with ether and a small amount of insoluble material removed by filtration. The filtrate was concentrated dnd passed through a short column of silica gel, eluting with petroleum spirit-ethyl acetate (1:1) and then with ethyl acetate, Fractions were combined and evaporated to yield the title ester (170 mg) #max(CHBr3) 1804 (ss-lactam), 1720 and 1520 cm-1 (OCONHR), # (CDCl3) values include 4.08 (d, J 2 Hz, C-5H), 5.72 (t, J 6 Hz, CH2OCONH), 8.94 (t, J 7 Hz, CH2CH3).

Claims (46)

WHAT WE CLAIM IS:

1. A compound of the formula (I)

wherein R represents a carboxyl or esterified carboxyl group and R represents a hydrogen atom, a hydroxyl group, an etherified hydroxyl group, an acylated hydroxyl group or the residue of a sulphur nucleophile, together with salts thereof when R is carboxyl.

2. A compound as claimed in claim 1 wherein R represents an etherified hydroxyl group or -OR, wherein R is an unsubstituted alkyl, alkenyl or alkynyl group, containing 1-6 carbon atoms; a C1-6 alkyl group carrying an acylated or etherified hydroxyl, acyl, carboxyl, esterified carboxyl or cyano group; a hydroxy-alkyl group having 2-6 carbon atoms; an aralkyl group which may have 1-6 carbon atoms in the alkyl portion or an aryl group, such aryl and aralkyl groups being monocyclic and optionally carrying one or more nitro, halo or C1-4 alkoxy substituents; a cyloalkyl group having 3-7 carbon atoms or a carbon-attached saturated or unsaturated 5-7 membered heterocyclic ring, such cycloalkyl or heterocyclic rings optionally carrying a C1-4 group; or R represents an acylated hydroxyl group -OR4 wherein R4 represents an acyl group, R5CO- wherein R5 is a C1-8 alkyl, C2-8 alkenyl, C2-8 alkynyl, C3-12 cyloalkyl, C4-15 aryl-C1-6 alkyl or C4-15 aryl group, which group may be substituted by one or more hydroxyl, C1-4 alkoxyl, phenoxy or cyano groups, or an amino or mono- or di- substituted amino group, or a carboxyl or esterified carboxyl group; or R may represent a group O.CO.NR6R7 where R6 and R7, which may be the same or different, represent hydrogen; C1-5 alkyl or C2-6 alkanoyl, which groups may be substituted by halogen; aralkyl; or aryl groups, or R6 and R7, together with the nitrogen atom to which they are attached, form a 5-7 membered heterocyclic ring optionally containing a further oxygen, nitrogen or sulphur atom; or R1 may represent a group O'.CS.NHR6 wherein R6 is as defined above other'than a hydrogen atom; or R represents the residue of a sulphur nucloephile represented by -SH, -SR8, -SO.R8 or -SO2R8 or -S.C=Y.R9 wherein R8 represents a C1-6 alkyl, alkenyl or alkynyl group; an aralkyl group having 1-6 carbon atoms in the alkyl portion or an aryl group, such aralkyl and aryl groups being monocyclic; a C31 cycloalkyl group; or a carbon-attached 5-7 membered heterocyclic ring containing one or more heteroatoms and optionally carrying one or more C16 alkyl groups, all such groups R8 being unsubstituted or substituted by a hydroxyl or substituted hydroxyl, carboxyl or substituted carboxyl, amino or substitutèd amino, or cyano group; and R9 is a group as defined for R8, or is group -OR8 or -SR8 or NR10R11 where R10 and R11, which may be the same or different, represent hydrogen atoms or alkyl, alkenyl, alkynyl, cycloalkyl, aralkyl and aryl groups as defined above for R8 or together with the nitrogen atom to which they are attached, represent a heterocyclic ring containing 5-7 ring atoms; and Y represents oxygen or sulphur; or R represents a silylated hydroxyl group OR wherein R represents a trihydrocarbyl silyl group having up to 24 carbon atoms.

3. A compound as claimed in claim 1 wherein R1 represents an etherified hydroxyl group -OR2, wherein R2 represents an unsubstituted alkyl, alkenyl or alkynyl group contaning 1-6 carbon atoms; a C16 alkyl group carrying an acylated or etherified hydroxyl group; a C2-6 hydroxyalkyl group; an aralkyl group having 1-6 carbon atoms in the alkyl portion or an aryl group, such aryl or aralkyl group being monocyclic; a C3-7 cycloalkyl group or a carbon-attached saturated or unsaturated 5-7 membered heterocyclic ring; or R represents an acylated hydroxyl group -OR4 wherein R4 represents an acyl group R5CO wherein R5 is a C-18 alkyl, C2-8 alkenyl, C2-8 alkynyl, C3-12 cycloalkyl, C4-15 aryl-C1-6 alkyl or C4-15 aryl group, which group may be substituted by one or more hydroxyl, C1-

4 alkoxy, phenoxy or cyano groups, or an amino or mono- or di-substituted amino roup, or R may represent a group O.CO.NR6N' where R6 and R' which may be the same or different, represent hydrogen; C1-5 alkyl or C2-6 alkanoyl, which groups may be substituted by halogen; aralkyl; or aryl groups, or R6 and R7, togeteher with the nitrogen atom to which they are attached, from a 5-7 membered heterocyclic ring optionally containing a further oxygen, nitrogen or sulphur atom; or R1 represents the residue of a sulphur nucleophile represented by -SR8, -SO.R8 or -SO2R8 or -S.C=Y.R9 wherein R8 represents a C1-6 alkyl, alkenyl or alkynyl group; an aralkyl group having 1-6 carbon atoms in the alkyl portion, an aryl group, such aralkyl and aryl groups being monocyclic; a C3-7 cycloalkyl group, a carbon-attached C5-7 heterocyclic group containing one or more heteroatoms and optionally carrying one or more C16 alkyl groups, all such groups R8 being unsubstituted or substituted by a hydroxyl or substituted hydroxy, carboxyl or substituted carboxyl or amino or susbtituted amino group; and R9 is group as defined for R8, or is a group OR8 or -SR8 or -NR10R11 where R10 and R11, which may be the same or different, represent hydrogen atoms or alkyl, alkenyl, alkynyl, cycloalkyl, aralkyl or aryl groups as defined above for R8, or together with the nitrogen atom to which they are attached, represent a heterocyclic ring containing 5-7 ring atoms; and Y represents oxygen or sulphur. 2 4. A compound as claimed in claim 3 wherein R represents a methyl, ethyl, propyl, butyl, allyl, propargyl, hydroxyethyl, 1-ethoxyethyl, phenyl, benzyl, phenethyl, cyclohexyl or tetrahydropyranyl group; or R5 represents a C14 alkyl group, a benzyl group, a phenyl group or a methylamino or anilino 8group; or R represents a methyl, ethyl, propyl, butyl, alkyl, propargyl, hydroxyethyl, ethoxyethyl, phenyl, benzyl, cyclohexyl or pyridyl group; or R9C=Y represents ethoxythiocarbonyl, carbamoyl, thiocarbamoyl, dimethylthiocarbamoyl, thiobenzoyl, benzoyl, thioacetyl, or acetyl group.

5. A compound as claimed in claim 2 wherein R2 represents a t-butyldimethylsilyl or 1-methoxycyclohexyl group.

6. A compound as claimed in any of claims 1, 3 and 4 wherein R represents a group -COORl2 wherein Rl2 represents a substituted or unsubstituted C18 alkyl or alkenyl group, 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 unsaturation optionally being present when a heteroatom is present, or a stannyl group having up to 24 carbon atoms.

7. A compound as claimed in claim 6 wherein Rl2 is an arylmethyl group.

8. A compound as claimed in claim 7 wherein R12 is a p-nitrobenzyl or benzyl group.

9. An alkali metal, alkaline earth metal or ammonium salt as claimed in any of claims 1, 3 or 4.

10. The sodium, lithium, potassium, calcium, magnesium, ammonium or other organic base salt as claimed in any of claims 1, 3 or 4.

11. A compound as claimed in any of claims 6-10 wherein R1 is as defined in claim 2.

12. 2-Ethylclav-2-em-3-carboxylic acid and salts and esters thereof.

13. (SR)-2-ethylclav-2-em-3-carboxylic acid and salts thereof.

14. 2-[2-( 1.Ethoxyethoxy)ethyl]clav-2-em-3-carboxylic acid esters.

15. A process for the preparation of a compound of formula (I) or salts thereof as defined in claim 1 which comprises treating a compound of formula (III)

(wherein R1 is as defined in claim 1 and R is an esterified carboxyl group) with a base at elevated temperature whereby a compound of formula (I) is obtained, followed, if desired, by cleavage of the esterified carboxyl group when a free acid is required and subsequent salt formation when a salt is required.

16. A process as claimed in claim 15 wherein the base is a tertiary amine.

17. A process as claimed in claim 16 wherein the amine has the formula RXRYRZN, wherein R , RY and RZ, which may be the same or different, represent alkyl groups having up to eight carbon atoms; aralkyl groups having up to six carbon atoms in the alkyl portion, or aryl groups, such aryl and aralkyl groups being monocyclic; or C31 cycloalkyl groups, or two of RX, RY and RZ form, together with the nitrogen atom to which they are attached, a five, six or seven-membered heterocyclic ring optionally containing a further heteroatom.

18. A process as claimed in claim 17 wherein RX, RY and RZ, which may be the same or different, represent C16 alkyl groups.

19. A process as claimed in claim 16 wherein the amine has the formula RXRYRZN wherein R , RY and RZ form, together with the nitrogen atom to which they are attached, a polycyclic non-aromatic heterocyclic ring system.

20. A process as claimed in any of claims 15-18 wherein treatment is effected at +500C to +100"C.

21. A process as claimed in claim 15 substantially as hereinbefore described.

22. A process as claimed in claim 15 substantially as hereinbefore described with reference to the Examples.

23. A process for the preparation of a compound of formula (I) or salt thereof as defined in claim 1 which comprises heating a compound of formula (IV)

wherein R is an esterified carboxyl group, R is as defined in claim 1 and Rx, Ry and Rz are as defined in claim 17 or additionally together with the nitrogen atom to which they are attached represent an aromatic heterocyclic group, or an acid addition salt thereof, followed, if desired, by cleavage of the esterified carboxyl group when a free acid is required and subsequent salt formation when a salt is required.

24. A process as claimed in claim 23 wherein heating is effected at from +50 C to +1000C.

25. A process as claimed in claim 23 or claim 24 wherein the compound of formula (IV) is prepared by a ring-opening reaction from a compound of formula (III) as defined in claim 15 using an amine RxRyRzN wherein Rx, Ry and Rz are as defined in claim 23.

26. A process as claimed in claim 25 wherein ring-opening is carried at from -40 to +30 C.

27. A process for the preparation df a compound of formula (I) as defined in claim 1 which comprises heating a compoun'd of formula (IV), shown in claim 23, wherein Rand Rl are as defined in claim 23 and Rx, RY and RZ form, together with the nitrogen atom to which they are attached, a polycyclic non-aromatic ring'heterocyclic system.

28. A process as claimed in claim 23 substantially as hereinbefore described.

29. A process as claimed in claim 23 substantially as hereinbefore described with reference to the Examples.

30. A method of purifying a 'compound of formula-(I) as claimed in claim 1 which comprises treating it with an amine base RXRYRZN as defined'in claim 23, isolating crystalline material of formula (IV) which is formed by regenerating the compound of formula (I) by a process as claimed in claim 23.

31. A process for the preparation of a compound of formula (II)

wherein R is an esterified carboxyl group which comprises treating a compound of formula (I) as claimed in claim 1 wherein Ri is hydroxyl with a reagent capable of replacing the hydroxyl group by a readily eliminatable substituent, which undergoes elimination in the presence of a base, whereby a compound of formula (II) is produced.

32. A process as claimed in claim 31 wherein the reagent capable of replacing the hydroxyl group by a readily eliminatable substituent is a halogenating agent or a sulphonylating agent in the presence or absence of halide ions.

33. A process as claimed in claim 32 wherein the reagent is mesyl chloride.

34. A process as claimed in any of claims 31-33 wherein the base is a tertiary amine.

35. A process as claimed in claim 34 wherein the amine carries alkyl groups having up to 8 carbon atoms, aralkyl groups having up to 6 carbon atoms in the alkyl portion, or an aryl group, such aryl and aralkyl groups being monocyclic, or C37 cycloalkyl groups; or the nitrogen atom of the amine forms part of a five-, six- or seven-membered heterocyclic ring optionally containing a further heteroatom, and which may be aromatic.

36. A process as claimed in claim 35 wherein the amine is a trialkyl amine having 1-6 carbon atoms in each alkyl group.

37. A process as claimed in claim 36 wherein the trialkylamine is triethylamine.

38. A process as claimed in any of claims 31-37 wherein reaction is effected at from +20 to +100 C.

39. A process as claimed in claim 31 substantially as hereinbefore described.

40. A process as claimed in claim 31 substantially as hereinbefore described with reference to the Examples.

41. A compound of formula (II) as defined in claim 31 whenever prepared by a process as claimed in any of claims 31-40.

42. A process for the preparation of a compound of formula (I) or salt thereof as defined in claim 1 wherein R represents a carboxyl or esterified carboxyl group and R1 represents an etherified or acylated hydroxyl group, which comprises etherifying an ester of formula (I) wherein R' is a hydroxyl group or acylating a compound of formula (I) wherein R1 represents a hydroxyl group, followed, if desired, by de-esterification and/or salt formation.

43. A process for the preparation of a compound of formula (I) shown in claim 1 wherein R is as defined in claim 1 and R represents an esterified carboxyl group which comprises esterifying a compound of formula (I) wherein R represents a carboxyl group or a reactive derivative thereof.

44. A process for the preparation of a compound of formula (I), shown in claim 1, wherein R is as defined in claim 1 and R represents a carboxyl group which comprises deesterifying a compound of formula (I) wherein R represents an esterified carboxyl group.

45. A process as claimed in claim 44 wherein deesterification is effected by catalytic hydrogenation.

46. A process for the preparation of a compound of formula (I), shown in claim 1 wherein R represents a carboxyl or esterified carboxyl group, or a salt thereof, and represents a hydrogen atom which comprises reducing a compound of formula (II) as defined in claim 31, followed by deesterification and/or salt formation if desired.