GB1591437A - Azetidinones - Google Patents

Description

(54) AZETIDINONES (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 antibiotic intermediates and to a process for their production.

In our German OLS 26 04 697 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 monocyclic betaines related to clavulanic acid and according to one aspect of the invention, we provide compounds of the formula (I)

wherein R represents an esferified carboxyl group; N 6 RlR2R3 represents the residue of a nitrogen base; and R4 represents a hydrogen atom, a hydroxyl group, an etherified hydroxyl group, an acylated hydroxyl group or the residue of a sulphur nucleophile.

R , R2 and R3, 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 g,roup2s desir3ably being monocyclic; or cycloaliphatic e.g. C3.7 cycloalky, groups, or two of R, R and R3 may form, together with the nitrogen atom to which they are attached, a five-, six- or seven-membered heterocyclic ring optionally containing a further hetero-atom, e.g. an oxygen, nitrogen or sulphur atom as in a piperidino, morpholino or thiamorpholino group, or Rl, R2 and R3 together with the nitrogen atom to which they are attached may form a heterocyclic aromatic ring, e.g. a pyridinium or collidinium group, or a polycyclic, e.g. a bicyclic, heterocyclic system, e.g. a quinuclidino group.

R', R2 and R3 are each preferably a C1.6 alkyl group, such as a methyl, ethyl, propyl or butyl group. Trimethylammonium and triethylammonium groups are especially preferred.

The invention further includes acid-addition salts of the compounds of formula (I). Such salts may be formed with ether 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 and perchloric acids.

The compounds of the invention 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 tautomerism, although the crystalline material will normally exist as one or the other of the possible E and Z isomers.

The group R4 may represent an etherified hydroxyl group -OR5, wherein R5 is a substituted or unsubstituted hydrocarbyl group, e.g. an aliphatic, araliphatic or aromatic group or a C-attached heterocyclic group. Thus, for example, R5 may be an unsubstituted alkyl, alkenyl or alkynyl group, which may contain 1-6 carbon atoms, or such an alkyl group carrying a substituted hydroxy, acyl (e.g. C2.6 alkanoyl), carboxyl, esterified carboxyl (e.g.

C2.6 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 aralkyl groups preferably being monocyclic and optionally carrying one or more nitro, halo or C1.4 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 as cycloalkyl or heterocyclic rings optionally carrying a C1.4 alkoxy groups preferably attached to the ether-linked carbon atom.

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

Substituted hydroxy groups as referred to above include acetylated and etherified hydroxy groups. In general, acylated hydroxy groups may have the formula R6CO2 where R6 is a hydrocarbyl group as defined for R5, relatively simple R6 groups such as C1.4 alkyl, e.g. methyl being preferred, while etherified hydroxy groups have have the formula R6O, simple R groups such as C1.4 alkyl, e.g. methyl or ethyl, again being preferred.

R5 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 a C1.4 alkyl, e.g. methyl, ethyl, propyl or butyl, groups. Representative silyl groups include trimethylsilyl and t-butyldimethylsilyl groups.

The group R4 may further represent an acylated hydroxyl group -OR7 wherein R7 preferably represents an acyl group R8CO- wherein R8 is an aliphatic, araliphatic or aromatic group, for example a C1.8 alkyl, C2.8 alkenyl, C2.8 alkynyl, C3 12 cycloalkyl, C4.15 aryl-C1.6-alkyl or C4 ls aryl group, which may be substituted, for example, by one or more hydroxyl, C1.4 alkoxy, phenoxy or cyano groups, or an amino or mono- or di- substituted amino group, or a carboxyl or esterified carboxyl group. The group R8 may also represent an amino or mono- or di- substituted amino group, thus making the group R4 a carbamoyloxy group which may, for example, be represented as -O.CO.NR R , where R9 and Rl(, which may be the same or different, are hydrogen; C1.5 alkyl or C2.6 alkanoyl, which may be substituted by for example, halogen; aralkyl, e.g. benzyl; or aryl, e.g. phenyl, groups, or R9 and R10 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. R4 may additionally be represented as O.CS.NH R9 where R is as defined above other than hydrogen.

Representative R8 groups include methyl, ethyl, propyl, isopropyl, butyl, amyl, allyl, propenyl, propargyl, cyclopentyl, cyclohexyl, cycloheptyl, adamantyl, benzyl, thienylmethyl, phenyl, thienyl, amino, methylamino, anilino, o-benzyloxycarbonylbenzyl, aphenoxycarbonylbenzyl, aminomethyl or a-aminobenzyl groups.

The group R 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 group or a thiol group. In general these residues may be represented by the formulae -SH, -SR11, -SO.R1l or -S02Rllz(where R11 is an aliphatic araliphatic, aromatic or heterocyclic group) or by-SC=Y.R12 (where Y is O or S and R12 is a group as defined above for R11 or a group OR11 or SR11, where R11 is as deffined above, or a group NR13R14, where R13 and R14, whichmay be the same or different, are hydrogen atoms or NR13Rl4, where R13 and Rl4, 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 heterocydic ring containing 5-7 ring atoms).

Thus for example, R11, R12, R1 and R1 may be alkyl, alkenyl or alkynyl groups, which may contain 1-6 carbon atoms; aralkyl groups which may have 1-6 carbon atoms in the alkyl portion or aryl groups, such aryl and aralkyl groups preferably being monocyclic; cycloalkyl groups, which may have 3-7, preferably 5 or 6, carbon atoms; or carbon-attached 5-7 membered heterocyclic rings 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 R11 include methyl, ethyl, propyl, butyl, allyl, propargyl, 2-aminoethyl, cyanomethyl, hydroxyethyl, ethoxyethyl, phenyl, benzyl, cyclohexyl and pyridyl.

Representative groups R12. C Y. - include ethoxythiocarbonyl, carbamoyl, thiocarbamoyl, dimethylthiocarbamoyl, thiobenzoyl, benzoyl, thioacetyl and acetyl. Where NR13R14 represents a heterocyclic ring, this may for example, contain 5-7 ring atoms, including one or more 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 COOT, where R15 is an aliphatic, araliphatic or aromatic group, while substituted amino groups may have the formula NR13R14 as defined above, one of R13 and R14 being other than hydrogen.

Preferred groups Rut3, R14 and R15 are C14 alkyl groups, e.g. methyl.

The compounds of the invention are 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 COOR16 wherein R16 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-bromobenzyl 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- orp-nitro; organic sulphonyl; cyano; alkyl, e.g. p-methyl, or alkoxy, e.g. p-methoxy; a diphenylmethyl or triphenylmethyl group or a fur-2-yl-methyl, 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 and one or more heteroatoms in the ring system, the heteroatom 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 are useful intermediates in the synthesis or purification of further -lactam compounds, for example compounds having the formula (II)

wherein R4 is as defined above and R'7 represents a carboxyl or esterified carboxyl group and salts of the compounds in which R'7 is a carboxyl group. Such compounds are described and claimed in our copending Cognate Application Nos. 37482/76 and 37445/76 (Serial No.

1591438) of even date herewith.

Compounds of formula (II) possess the ability to inhibit -lactamase enzymes produced by both gram-positive and gram-negative organisms such as strains of Proteus mirabilis, Staphylococcus aureus, Escherichia coli, Proteus morganii, Klebsiella aerogenes, Salmonella typhimurium, Shigella sonnei, Ha em ophilus influenzae, Enterobacter cloacae, Pseudomonas aeruginosa, indole-positive Proteus species and Bacteroidesfragilis. Thus compounds of formula (II) have the ability to protect -lactamase susceptible -lactam antibiotics from -lactamase hydrolysis.

The compounds of formula (I) have also been found to be valuable in the purification of esters of formula (II) above since they can provide crystalline material from which the esters of formula (II) may readily be regenerated in a high state of purity.

The compounds of formula (II) may readily be prepared from compounds of formula (I) or their acid addition salts by removal of the group NR'R2R3. Such removal may, for example, be achieved by heating, e.g. at 50-100 C, preferably under reflux, in a suitable liquid medium. Where an acid addition salt of a compound of formula (I) 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. dimethylformamide can also be used. Where an acid of formula (II) or a salt thereof is required, this may be prepared by cleavage of an ester initially produced.

Certain compounds of formula (I) are also useful in the production of diene esters of formula (III)

(wherein R represents 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 -lactamase inhibitory thio-derivatives of clavulanic acid of the type described in our German OLS 2708330; these diene esters have also been reported as possessing B-lactamase inhibitory activity.

The compounds of the invention may conveniently be prepared by the reaction of a compound of formula (II) wherein R'7 is an esterified carboxyl group or a compound of formula (IV)

wherein R and R4 are as defined above, with an amine of formula R1R2R3N (wherein R1, R2 and R3 are as described above) whereby the desired compound of formula (I) is obtained.

Where R4 is a group which may be readily eliminated, e.g. a dichloroacetoxy group, there will be a tendency for elimination to occur in the presence of the base, whereby a diene of formula (III) is produced. Where a compound of formula (I) is required in which R4 represents such a readily eliminatable group, these are conveniently prepared from a compound of formula (I) in which R4 is hydroxy.

In general, the conversion of a compound of formula (II) into a compound of formula (I) can be effected using a weaker base than is required for the conversion of a compound of formula (IV). Thus, for example, an aromatic tertiary base such as pyridine can be used successfully for conversion of a compound of formula (II), whereas a stronger base such as triethylamine is generally required for the conversion of a compound of formula (IV).

On the other hand a compound of formula (IV) may be converted into a compound of formula (I) wherein NR1R2R3 is the residue of a weak base such as pyridine by reaction with the weak base in the presence of a catalytic quantity of a strong base.

Use of the simpler trialkylamines, however, e.g. having 1-6 carbon atoms in each alkyl group, especially methyl, ethyl, propyl or butyl groups is preferred and trimethylamine and triethylamine are especially preferred for both series of compounds.

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"C to +300C, a temperature of from +10 to +200C 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 (I) may readily be separated from the reaction mixture by conventional separation and isolation techniques. As mentioned above, the compounds of the invention are betaines and normally crystallise readily from some of the above solvents.

It is often the case that the compounds of the invention 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 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 (I) it is preferred to redissolve the isolated betaine in a suitable solvent such as dimethylformamide or water and add one equivalent of the appropriate acid.

The compounds of formula (IV) whence the compounds of the invention may be prepared may themselves be prepared in a variety of ways from clavulanic acid or its salt or esters and reactive derivatives thereof, such as halo derivatives (i.e. compounds of formula (IV) in which R4 is a halogen atom). These halo derivatives are described in our German OLS 2657081.

The compounds of formula (IV) wherein R4 is a hydrogen atom may be prepared by catalytic hydrogenolysis as described in our German OLS 2657081 and South African Patent No. 76/1953.

Compounds of formula (IV) wherein R4 represents an etherified hydroxyl group may be prepared by etherification of an ester of clavulanic acid as described in our German OLS 2657048 and South African Patent No. 76/5560.

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

Compounds of formula (IV) wherein R4 represents an acylated hydroxyl group -OCOR8 wherein R8 is as defined above may be prepared by reaction of clavulanic acid or an ester thereof with a compound of formula R8COY (wherein R8 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, desirably 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 R9NCO or an isothiocyanate of formula R9NCS in which R9 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 (it).

Di-substituted carbamates may be prepared as described below in relation to the compounds of formula (I).

Compounds of formula (it) wherein R4 represents the residue of a sulphur nucleophile may readily be prepared by reaction of an ester of a halo derivative of clavulanic acid with a sulphur nucleophile as described in our German OLS 2708330. Other methods for preparing such sulphur compounds are also described in our above application.

Compounds of formula (I) in which R4 is an acyloxy group may be prepared from compounds of formula (I) in which R4 is hydroxyl by acylation as described above in relation to the compounds of formula (IV). In addition compounds of formula (I) in which R4 is a disubstituted carbamate group may be prepared by reaction of a compound of formula (I) in which R4 is hydroxyl with a carbamoyl halide of formula R9R10NCOX (in which R9 and R 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, a compound of formula (I) in which R4 is hydroxyl may be reacted with a carbonyl dihalide followed by reaction with a secondary amine.

The esters of clavulanic acid may be prepared from the acid or a reactive derivative thereof by reaction with an alcohol, phenol or stannanol or a reactive derivative thereof to form the desired ester as described in our German OLS 2657081. Other esters of formula (IV) may be prepared in similar manner.

The preparation of the compounds of formula (IV) often results in the production of small amounts of the E isomer, i.e. where the -CH2R4 group is trans with respect to the ring oxygen atom, the major product being the Z isomer. Thus, the starting material of formula (IV) may be a mixture of E and Z isomers, but the shift of the double bond in the process of the invention renders this of no consequence.

The compounds of formula (IV) in their E-isomeric form may also be prepared directly from the E-isomer of clavulanic acid by methods analogous to those described above.

The compounds of formula (II) wherein R'7 and R4 are as defined above may readily be prepared from corresponding compounds of formula (IV) by reaction at elevated temperature in the presence of a tertiary organic base such as, for example, an amine of formula RlR2R3N, wherein Rl, R2 and R3 are as defined above, other than an aromatic heterocyclic amine, in a suitable inert solvent, e.g. an ester such as ethyl acetate. Reaction will desirably be carried out at from 50 to 1000C, preferably under reflux.

As indicated above certain compounds of formula (I) are useful for the preparation of compounds of formula (III).

Such compounds of formula (I) are those in which R4 is hydroxyl or a readily eliminatable substituent.

The compounds of formula (I) in which R4 is a readily eliminatable substituent, such as a dichloroacetoxy group, can be converted into compounds of formula (III) by reaction with a tertiary organic base. The compounds of formula (I) in which R4 is hydroxyl can be converted into compounds of formula (III) by reaction with reagents serving to replace the hydroxyl group by a readily eliminatable group which then undergoes elimination in the presence of a tertiary organic base. The tertiary organic base may be present during replacement of the hydroxyl group or may be added subsequently. The base may, for example, be a tertiary amine (including a heterocyclic aromatic amine).

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 aryl groups, 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 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. 1,2-dichloroethane or chloroform.

Reaction will be effected at elevated temperature, desirably under reflux, a temperature of from 50"C to 1000C being preferred Thus, for example, a compound of formula (I) in which R4 is hydroxyl may be reacted in the presence of the tertiary organic base, e.g. triethylamine, with a sulphonylating agent such as a mesyl or tosyl halide in the presence or absence of halide ions, or with other acylating reagents serving to introduce a readily eliminatable group or with a halogenating reagent such as thionyl chloride to produce a diene ester of formula (III).

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-ethylideniclavam-3-carboxylate A suspension of lithium (3R ,SR ,Z)-2-(2-hydroxy-ethylidene)clavam-3-carboxylate (4.0g) in a mixture of brine (50 ml) and ethyl acetate (50 ml) was acidified with 2N hydrochloric acid (lSml) 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) has 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 OOC 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"C) (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-1 (P-lactam); X (CDCl3) values for Z-isomer include 4. 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), vrnox (CHBr3) 1798 (P-lactam), 1752 (ester), 1522 and 1348 cm-1 (NO2), X (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=C-C6H2), 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 S 4-Nitrobenzyl (3R,SR, Z) -2- (2-acetoxyethylidene) clavam-3-carboxylate A stirred solution of 4-nitrobenzyl (3R,5R,Z)-2-(2-hydroxyethylidene)clavam-3- carboxylate (1.0g) in ethyl acetate (25 ml) at 0 C 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 hydrogen carbonate, 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 C. [a]D + 42 (c 0.96; DMSO), Xmax (EtOH) 264.5 nm (e 11,000), #max (CHBr3) 1792 (ss-lactam), # (CDCl3) values include 4.27 (d, J 2.5 Hz, C-SH), 5.33 (d, J 7 Hz, -CH2OCOCH3), 7.95 (s, CH3).

EXAMPLE 1 1 - (4-Nitrobenzyloxycarbonyl) -1-(2-oxo-4-triethylammonioazetidin-1-yl) but-1-en-2-olate A solution of 4-nitrobenzyl (3R,SR,Z)-2-ethylidene-clavam-3-carboxylate (1.0g) 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 , [cr]D t 10 (c 1.0, H2O), #max (pH6 buffer) 273.5 nm ( 29,800), vmax (Nujol) (Nujol is a registered Trade Mark) 1770 cm (ss-lactam), T (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, J8Hz, N(CH2CH)3), and 9.06 + 9.08 (t, J 8Hz, CH2CH3).

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

EXAMPLE 2 1 -Benzyloxycarbonyl-1 - (2-oxo-4-triethylammonioazetidin -yl) but-1 -en-2 -olate A solution of benzyl (3R,5R,Z)-2-ethylideneclavam-3-carboxylte (0.547g) 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 (# 19,100), #max (Nujol) 1762 cm-1 (ss-lactam) # (D2O) values for mixture of isomers include 4.41 + 4.78 (m, azetidinyl C-4H), 7.0 to 7.4 (m, CH2CH3), 8.59 + 8.76 (t, J 7Hz, CH2CH3) and 8.88 (t, J 7Hz, N(CH2CH3)3).

EXAMPLE 3 1 -Methoxycarbonyl-i - (2-oXo-4-triethylammonioazetidin-1-yl)but-1-en-2-olate A solution of methyl (3R,5R,Z)-2-ethylidenclavam-3-carboxylate (0.5g) 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 (0.398g), m.p. 109-109.5 , Xmax (pH 6 buffer) 270 nm (e 20,500), vmax (Nujol) 1767 cm-1 (P-lactam) T (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).

EXAMPLE 4 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 (0.502g) m.p. 133-4 . #max (Nujol) 1784 (ss-lactam), 1712 cm-1 (-OCOPh), #(DMSO- d6) values for mixtures of isomers include 4.44 + 4.80 (m, azetidinyl C-4 H), 5.50 (CH2OCOPh), ca. 6.64 (azetidinyl C-3 protons and N(CH2CH3)3), 8.84 + 8.90 (t, N(CH2CH3)3 EXAMPLE 5 4-Hydroxy-1-methoxycarbonyl-1-(2-oxo-4-triethylammonioazetidin-1-yl)but-1-en-2-olate A solution of methyl (3R,5R,Z)-2-(2-hydroxyethylidene)clavam-3-carboxylate (2.0 g) and triethylamine (2.8 ml) in ethyl acetate (50 ml) was stood at ambient temperature for 1l/2 hours, diluted with ethyl acetate (25 ml) and stood for a further 18 hours. The resulting crystalline solid was collected, washed with ethyl acetate and with ether, and was then dried in vacuo to yield the title salt (1.84 g), [α]D 0 #1 (c 1.0, DMSO), #max(pH 6 buffer) 270.5 nm (# 16,800), #max (nujol) 1760 cm-1 (ss-lactam) # (DMSO-d6 values for ca. 1:1 mixture of isomers include 4.48 + 4.80 (m azetidinyl C-4H), 6.50 (s, CO2CH3), and 8.78(t, J 7Hz, N(CH2CH3)3).

EZAMPLE 6 4-Hydroxy-1-(4-nitrobenzyloxycarbonyl)-1-(2-oxo-4-triethylammonioazetidin-1-yl)but-1-en2-olate A solution of 4-nitrobenzyl (3R,SR,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 S 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 geve a solid which was collected, washed with ether and dred in vacuo to yield the title salt (0.261 g), [α]D 0 #1 (c 1.0, H2O),#max(pH6 buffer) 274.5nm (# 25,000), vmax (Nujol) 1764 cm (ss-lactam), z (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).

EXAMPLE 7 1-(4-Nitrobenzyloxycarbonyl)-1-(2-oxo-4-triethylammonioazetidin-1-yl)but-1-en-2-olate A solution of 4-nirtrobenzyl (3R,5R,Z)-2-ethylidenclavem-3-carboxylate (0.5 g) in ethyl acetate (2.5ml) was treated with a solution of trimethylamine in ethyl acetate 1.3M, 2.5ml).

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 dired in vacuo to give the title salt (0.39g), m.p.

131 (dec.),#max(H2O) 273 nm (# 27,400),#max #(DMSO-d6) values for ca. 1:1 mixture of isomers include 4.64 + 4.96 (m, zaetidinyl C-4 H), 6.78 (s, N(CH3)3), and 9.04 (t, J 7Hz, CH2CH3).

EXAMPLE 8 1-(4-Nitrobenzyloxycarbonyl)-1-(2-oxo-4-triethylammonioazetidin-1-yl)but-1-en-2-olate A stirred suspension of 4-nitrobenzyl 2-ethylcav-2-em-3-carboxylate (0.32g) in ethyl acetate (3ml) was treated with triethylamine (0.27 ml). 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 (0.363 g). The physical and spectral characteristics of the product were similar to those described in Example 1.

EXAMPLE 9 1-(4-Nitrobenzyloxycarbonyl)-1-(2-oxo-4-triethylammonioazetidin-1-yl)but-1-en-2-olate A solution of 4-itrobenzyl2-ethylcdav-2-em-3-carboxylate (0.69g) and pyridine (0.37 ml) 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 (0.44 g), #max (pH 6 buffer) 272nm (E 26,100), vmax (Nujol) 1781 (p-lactam), T (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 7Hz, CH2CH3).

EXAMPLE 10 1-(4-Nitrobenzyloxycarbonyl)-1-(2-oxo-4-triethylammonioazetidin-1-yl)but-1-en-2-ol-4 toluensulphonate 4-Toluenesulphonic acid monohydrate (0.095 g) was added to a solution of 1-(4 nitrobenzyloxycaronyl)-1-(2-oxo-4-triethylammonioazetidin-1-yl)but-1-en-2-olate (0.205 g) in dimethylformamide (1ml). 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 (0.15g)#max(pH6 buffer) 273.5nm (# 27,300), #max(Nujol) 2640 (OH), 1790 (ss-lactam), 1032 mc-1 (SO3-), #,(DMSO-d6) values include 2.50 and 2.90 (doublets, J 9 Hz, -O3SC6H4CH3), 6.2 to 6.9 (m, C-3 protons, N(CH2CH3)3, and CH2CH3), 7.50 (s, -O3SC6H4CH3). 8.82 and 8.88 (multiplets, N(CH2CH3)3 and CH2CH3).

EXAMPLE 11 4-N,N-Dimethylthiocarbamoylthio-1-(4-nitrobenzylocycarbonyl)-1-(2-oxo-4triethylammonioazetidin-1-yl)but-1-en-2-olate A solution of 4-nitrobenzyl (3R,5R,Z)-2-(2-N,N-dimethylthiocarbamoylthioethylidene)clavam-3-carboxylate (0.044 g) and triethylamine (0.03 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 (0.04 g), vmax (Nujol) 1772 cm-l (P-lactam), T (DMSO-d6) values for ca. 1:1 mixture of isomers include 4.50 + 4.90 [obscured] (m, azetidinyl C-4 H), 8.82 + 8.90 (t, J 7Hz, N(CH2CH3)3).

EXAMPLE 12 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)clavam0-3-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), vmax (Nujol) 1770 (B-lactam), 1680 cm-l (SCOR), z (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).

EXAMPLE 13 4-Benzoylthio-1-(4-nitrobenzyloxycarbonyl)-1-(2-oxo-4-triethylammonioazetidin-1-yl)buten-2-olate A solution of 4-nitrobenzyl (3R,SR,Z)-2-(2-benzoylthioethylidene)clavam-3-carboxylate (0.045 g) and triethylamine (0.03 ml) in ethyl acetate (1 ml) was stood at ambient temperature for 1 hour. The resulting crystalline solid was collected and dried in vacuo to yield the title salt (0.039 g), vmax (CHBr3) 1782 (p-lactam), 1626 cm-l (SCOAr), X (DMSO-d6) values for mixture of isomers include 2.13+2.45 (complex multiplets (COPh), 4.48 + 4.90 [obscured] (m, azetidinyl C-4 H), 8.82 + 8.90 (t, J 7Hz, N(CH2CH3)3).

EXAMPLE 14 1-(4-Nitrobenzyloxycarbonyl)-1-(2-oxo-4-triethylammonioazetidin-1-yl)-4-phenylthiobut-1en-2-olate A solution of 4-itrobenzyl (3R,5R,Z)-2-(2-phenylthioethylidene)clavam0-3-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 00.272 g), [a]D 0 +1 (c 1.0,H2O), may (Nujol) 1768 cm (P-lactam), X (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).

EXAMPLE 15 1-(4-Nitrobenzyloxycarbonyl)-1-(2-oxo-4-triethylammonioazetidin-1-yl)-4phenylsulphonylbut-1-en-2-olate A solution of 4-nitrobuenyl (3R,5R,Z)-2-phenylsulphonylethylidene)clavam-3carboxylate (0.046 g) and triethylamine (0.02 g) in ethyl acetate (1 ml) was stood at ambient temperature for 1 hour. The mixture was diluted with ether and the precipitated solid was collected and dried in vacuo to afford the title salt (0.018 g), Vmax (Nujol) 1778 cm-l (P-lactam), X (DMSO-d6) values for mixture of isomers include 2.0 to 2.4 (m, SO2Ph), 4.56 + 4.64 (m, azetidinyl C-4 H), 8.80 + 8.88 (t, J 7Hz, N(CH2CH3)3).

EXAMPLE 16 4-Mercapto-1- (4-nitrobenzylcarbonyl) -1- (2-oxo-4-triethylammonioazetidin-1 -yl) but-l-en-2- olate Triethylamine (0.085 ml) was added to a solution of 4-nitrobenzyl (3R,SR,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 dried in vacuo to give the title salt (0.06 g), vrnox (Nujol) 1774 cm-l (p-lactam), T (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).

EXAMPLE 17 4-Methylthio-1 - (4-nitrobenzyloxyearbonyl) -1 - (2-oxo-4-triethylammonioazetidin-1-yl)but-1- en-2-olate A solution of 4-nitrobenzyl (3R ,SR ,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-l (p-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.

EXAMPLE 18 1-(4-Nitrobenzyloxycarbonyl) -1 - (2-oxo-4-triethylammonioazetidin-1-yl) -4 (tetrahydropyran-2-yloxy) but-l-en-2-olate A solution of 4-nitrobenzyl (3R,SR,Z)-2-42-[(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), AmaX (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-4H), 5.48 (m, tetrahydropyranyl C-2 H), 8.1 to 8.7 (m, tetrahydropyranyl C-3, C-4, and C-S protons), 8.82 and 8.89 (t, J 7Hz, N(CH2CH3)3).

EXAMPLE 19 4-Methoxy-1 - (4-nitrobenzyloxycarbonyl) -1-(2-oxo-4-triethylammonioazetidin-1-yl)but-l -en- 2-olate A solution of 4-nitrobenzyl (3R ,SR , Z)-2- (2-methoxyethylidene)clavam-3-carboxylate (10.45 g) and triethylamine (8.36 ml) in ethyl acetate (50 ml) was stood at ambient temperature for 23 hours and then diluted with ether (150 ml). The resulting oil was triturated with ether to give a solid which was collected and dried in vacuo to afford the title salt (13.27 g), Xmax (pH 6 buffer) 274 nm (E 26,600), vmax (Nujol) 1770 cm-l (p-lactam), X (DMSO-d6) values include for mixture of isomers 4.47 + 4.63 (m, azetidinyl C-4 H), 6.78 (s, OCH3), 8.79 + 8.86 (t, J 7 Hz, N(CH2CH3)3).

EXAMPLE 20 4-(1-Ethoxyethoxy)-1-(4-nitrobenzyloxcarbonyl)-1-(2-oxo-4-triethylammonioazetdidin-1yl)but-1-en-2-olate A solution of 4-nitrobenzyl (3R,5R,Z)-2-{2-[(1RS)-1-ethoxyethoxy]ethylidene}clavam-3carboxvalte (9.92 g) and triethylamine (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-l (ss-lactam), T (DMSO-d6) values include for mixture of isomers 4.52 + 4.86 (m, azetidinyl C-4 H), 5.40 (q, J S Hz, O-CH(CH3)OEt), 8.82 + 8.90 (t, J 7 Hz, N (CH2CH3)3), 8.90 [partially obscured] (m, OCH(CH3)OEt).

EXAMPLE 21 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 (0.435 g) in chloroform (25 ml ethanol freed) 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 (0.101 g), followed by mesyl chloride (0.1 ml) and reflux continued for a further S 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 (0.112 g), [a]D 0 1 10 (c 1.0, DMSO). vmax (CHBr3) 1810 cm-l (p-lactam), T (CDC13) values include 2.94 (dd, J 10 and 17 Hz, -CH = CH2), 4.01 (dd, J2 and 3 Hz, C-SH), 4.03 (dd, J2 and 17 Hz, olefinic proton), 4.32 (dd, J2 and 10 Hz, olefinic proton).

EXAMPLE 22 4-Nitrobenzyl 2-vinylclav-2-em-3-carboxylate To a suspension of 4-hydroxy-1-(4-nitrobenzyloxycarbonyl)-1-(2-oXo-4- triethylammonioazetidin-1-yl)but-1-en-2-olate (0.217 g) in alumina-dried chloroform (30 my) was added triethylamine (0.050 g), followed by methane-sulphonyl chloride (0.068 g).

The mixture was heated gently under reflux for 17 minutes and then allowed to cool to 250.

The reaction mixture was poured into petroleum ether (40-60 ) (200 ml) at 0 and the resulting suspension was filtered. The filtrate was evaporated to an oil which solidified on standing to afford the title ester (0.038 g). Spectral characteristics of the product were similar to those described in Example 21.

EXAMPLE 23 1 - (4-Nitrobenzyloxycarbonyl) -1- (2-oxo-4-N,N, N-benzyldimethylammonioazetidin-l -yl)but 1 -en-2-oleate A solution of 4-nitrobenzyl (3R,SR,Z)-2-ethylideneclavam-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 depostied an oil. Trituration of the oil gave a solid which was collected, washed and dried to yield the title salt (180 mg) #max(pH 6 buffer) 274 nm (# 31,700),#max(Nujol) 1778 cm-1 (ss-lactam), #(DMSO-d6) valudes for mixture of isomers include 4.62 (m, azetidinyl C-4H), 2.46 (s, Ph).

EXAMPLE 24 1 - (4-Nitrobenzyloxycarbonyl) -1 - (2-oxo -4-N-methylpiperidinioazetidin-l -yl) but-i -en-2-olate A solution of 4-nitrobenzyl (3R,SR,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 mixture of isomers include 4.60 (m, azetidinyl C-4H), 6.75 and 6.95 (singlets, N-CH3).

EXAMPLE 25 1- (4-Nitrobenzyloxycarbonyl) -1- (2-oxo-4-pyridiniumazetidin-1-yl) -but-l -en-2-olate A solution of 4-nitrobenzyl (3R,SR,Z)-2-ethylideneclavam-3-carboxylate (0.316 g) in dry pyridine (2 ml) containing one drop of dry triethylamine was stood at room temperature for 18 hours. The resulting solution was diluted with ethyl acetate (3 ml), followed by ether (30 ml) and the deposited solid was collected, washed with ether, and was then dried in vacuo to afford the title salt (0.28 g) whose spectral characteristics resembled those as given in Example 9.

EXAMPLE 26 1-(4-Nitrobenzyloxycarbonyl)-1-(2-oxo-4-triethylammonioazetidin-1-yl)but-1-en-2-ol hydrochloride A mixture of 1-(4-nitrobenzyloxcarbonyl)-1-(2-oxo-4-triethylammonioazetidin-1-yl)but 1-en-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 (ss-lactam), #(DMSO-d6) values for mixture of isomers include 4.50 (m, azetidinyl C-4H), 6.3-6.8 (m, NCH2), 6.7 - 7.3

EXAMPLE 27 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 resideu triturated with ether to give the title salt (240 mg), #max (CHBr3) 1794 cm-1 (ss-lactam), #(DMSO-d6) values for mixtrue of isomers include 4.50 (m, azetidinyl C-4H), 6.7 - 7.4

EXAMPLE 28 1-(4-Nitrobenzyloxycarbonyl)-1-(2-oxo-4-triethylammonioazetidin-1-yl)but-1-en-2-ol citrate A solution of 1-(4-nitribenzyloxycarbnyl)-1-(2-oxo-4-triethylammonioazetidin-1yl)but-1-en-2-olate (180 mg) and citric acid (90 mg) in water (10 ml) was lyophilised and the residue triturated with ether toyield the title salt (260 mg), #max (Nujol) 1784 (ss-lactam), 1720 and 2650 (CO2H) and 1580 cm-1 (CO2-), #(DMSO-d6) vaules for mixture of isomers include 4.50 (m, azetidinyl C-4H), 7.32 (citrate CH2).

EXAMPLE 29 4-Acetoxy-1-(4-nitrobenzyloxycarbonyl)-1-(2-oxo-4-triethylammonioazetidin-1-yl)but-1-en2-olate A solution of 4-nitrobenzyl (3R,5R,Z)-2-(2-acetoxy-ethylidene)calvam-3-carboxylate (375 mg) and triethylamine (0.27 ml) in ethyl acetate (15 ml) was stood at ambient temperature for 30 minutes and then diluted with ether until cloudiness was produced. The mixture was stood for a further 2 hours and the resulting precipitate collected, washed and dried to yield the title salt (260 mg), vmax (Nujol) 1760 (P-lactam), 1720 cm-l (OAc), X (DMSO-d6) values for mixture of isomers include 4.54 (m, azetidinyl C-4H), 5.83 (t, J 7 Hz, CH2OAc), 8.10 (s, OCOCH3).

EXAMPLE 30 4NMethylcarbamoyloxy-i-(4-nitrobenzyloxycarbonyl)-i-(2-oxo-4- triethylammonioazetidin-l -yl) but-l -en-2-olate A stirred solution of 4-hydroxy-1-(4-nitrobenzyloxycarbonyl)-1-(2-oxo-4triethylammonioazethidin-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 (E 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).

EXAMPLE 31 4-tert-Butyladinethylsilyloxy-1-(4-nitrobenzyloxycarbonyl)-1-(2-oxo-4trethylammo9nioazetidin-1-yl)but-1-en-2-olate A solution of 4-nitrobenzyl (3R,5R,Z)-2-tert-butyldinethylsilyoxyethylidene)clavam-3carboxyvlate (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), vmax (Nujol) 1764 cm-l (B-lactam), T (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)2-(CH3)3).

EXAMPLE 32 4-Acetoxy-1-(4-nitrobenzyloxycarbonyl)-1-(2-oxo-4-triethylammonioazetidin-1-yl)but-1-en2-olate A stirred solution of 4-hydroxy-1-(4-nitrobenzyloxcyrbonyl)-1-(2-oxo-4triethylammonioazetidin-1-yl)but-1-en-2-olate (400 mg) in dimethylformatide (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 resideu was collected and dried to yield the title salt (102 mg),#max(pH 6 buffer) 273 nm (# 22,700),#max (Nujol) 1768 (ss-lactam) and 1720 cm-1 (OAc), #(DMSO-d6) values resemble those described in Example 29.

Claims (36)

WHAT WE CLAIM IS:

1. A compound of the formula (I)

0+ wherein R represents an esterified carboxyl group, -NR1R2R3 represents the residue of a nitrogen base, and R4 represents a hydrogen atom, a hydroxyl group, an etherified hydroxyl group, an acylated hydroxyl group or the residue of a sulphur nucleophile, together with acid-addition salts thereof.

2. A compound as claimed in claim 1 wherein R1, R2 and R3, 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 C3.7 cycloalkyl groups, or two of R, R2 and R3 form, together with the nitrogen atom to which they are attached, a five, six or seven-membered heterocyclic ring optionally containing a further heteroatom or R1, R2 and R3 together with the nitrogen atom to which they are attached form a heterocyclic aromatic ring.

3. A compound as claimed in claim 1 or claim 2 wherein Rl, R2 and R3, which may be the same or different represent C16 alkyl groups.

4. A compound as claimed in claim 1 wherein Rl, R2 and R3, together with the nitrogen atom to which they are attached, form a polycyclic heterocyclic system.

5. A compound as claimed in any of the preceding claims wherein R4 represents an etherified hydroxyl group -OR5, wherein R5 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 carboxy or cyano group; a hydroxyalkyl group having 2-6 carbon atoms; an aralkyl group having 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 cycloalkyl group having 3-7 carbon atoms or a carbon-attached saturated or undaturated 5-7 membered heterocyclic ring, such cycloalkyl or heterocyclic rings optionally carrying a C14 alkoxy group; or R4 represents an acylated hydroxyl group -OR7 wherein R7 represents an acyl group R8OC- wherein R8 is a C1.8 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 group or a carboxyl or esterified carboxyl group, or R4 represents a group O.CO.NR9Rl0 where R9 and R10, which may be the same or differnt, represent hydrogen; C1-5 alkyl or c2-6 alkanoyl, which groups may be substituted by halogen; aralky; or aryl groups or R9 and R10, together with the nitrogen atom to which they are attached, form a 5-7 membered heterocyclic ring optionally containing a further oxygen nitrogen or suphur atom; or R4 may rpresent a group O.CS.NHR9 wherein R9 is as defeined above other than a hydrogen atom; or R4 represents the residue of a sulphur nucleophile represented by -SH, -SR11, -SO.R11 or -SO2Rll or -S.C=Y.R'2 where R11 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 C3.7 cycloalkyl group; or a carbon-attached 5-7 membered heterocyclic ring containing one or more heteroatoms and optionally carrying one or more C1.6 alkyl groups, all such groups R11 being unsubstituted or substituted by a hydroxyl or substituted hydroxyl, carboxyl or substituted carboxyl, amino or substituted amino, or cyano group; and R12 is a group as defined for R11, or is a group -ORll or -SRll or -NR13R14 where Rl3 and Rl4, which may be the same or different, represent hydrogen atoms or alkyl, alkenyl, alkynyl, cycloalkyl, aralkyl or aryl groups as defined above for Rill, 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 R4 represents a silylated hydroxyl group OR5 wherein R5 represents a trihydrocarbyl silyl group having up to 24 carbon atoms.

6. A compound as claimed in any of claims 1-3 wherein R4 represents an etherified hydroxyl group -OR5, wherein R5 represents an unsubstituted alkyl, alkenyl or alkynyl group containing 1-6 carbon atoms; a C1-6 alkyl group carying 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 groups being monocyclic; a C3.

7 cycloalkyl group or a carbon-attached saturated or unsaturated 5-7 membered heterocyclic ring; or R4 represents an acylated hydroxyl group -OR', wherein R' represents an acyl group R8 CO- wherein R8 is a C1-8 alkyl, C2-8 alkenyl, C2-8 alkynyl, C3-13 cycloalkkyl, C4-15 aryl-C1-6 alkyl or C4-15 zaryl group, which group may be substituted by one or more hydroxyl, C1-4 alkoxy, phenoxy, cyano groups, or an amino or mono- or di-substituted amino group; or R4 may represent a group O.CO.NR9R10 where R9 and R10, which may be the same or different, represent hydrogen; C1-5 alkyl or C2-76 alkanoyl, which groups may be substituted by halogen; aralkyl; or aryl groups or R9 and R10, together with the nitrogen atom to which they are attached, form a 5-7 membered heterocyclic ring optionally contining a further, oxygen, nitrogen or sulphur atom; or R4 represents the residue of a suplphr nucleophile represented by -SR11, -SO.R11 or -SO2R11 or -S.C=Y.R12 wherein R1l 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 C3.7 cycloalkyl group; or a carbon-attached C5.7 heterocyclic group containing one or more heteroatoms and optionally carrying one or more C1.6 alkyl groups, all such groups R11 being unsubstituted or substituted by a hydroxyl or substituted hydroxyl, carboxyl or substituted carboxyl or amino substituted amino group; and R12 is a group as defined for R11, or is a group -OR11 or -SR11 or -NR13R14 where R13 and R14, which may be the same or different, represent hydrogen atoms or alkyl, alkenyl, alkynyl, cycloalkyl, aralkyl or aryl groups as defined above for R11, 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. 5 7. A compound as claimed in claim 6 wherein R represents a methyl, ethyl, propyl, butyl, allyl, propargyl, hydroxyethyl, 1-ethoxyethyl, phenyl, benzyl, phenethyl, cyclohexyl or tetrahydropyranyl; or R8 represents a methyl, ethyl, propyl, butzl or amyl group, a benzyl group, a phenyl group, or a methylamino or anilino group; or R l represents a methyl, ethyl, propyl, butyl, allyl, propargyl, hydroxyethyl, ethoxyethyl, phenyl, benzyl, cyclohexyl or pyridyl group; or R12. C = Y. represents an ethoxythiocarbonyl, carbamoyl, thiocarboamoyl, dimethylthiocarbamoyl, thiobenzyl, thioacetyl, or acetyl group.

8. A compound as claimed in claim S wherein R5 represents a t-butyldimethylsilyl group.

9. A compound as claimed in any of claims 1-3, 6 and 7 wherein R represents a group -COOR16 wherein R16 represents a substituted or unsubstituted C,.8 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, a heterocyclic group containing up to 12 carbon atoms, and 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 9 wherein R16 is an arylmethyl group.

11. A compound as claimed in claim 10 wherein R16 is ap-nitrobenzyl or benzyl group.

12. The acid addition salt as claimed in any of claims 1-3, 6, 7, and 9-11 formed with a carboxylic, sulphonic or mineral acid.

13. A salt as claimed in claim 12 formed with citric, formic, tartaric, acetic, p toluenesulphonic, nitric, hydrochloric, sulphuric or perchloric acid.

14. A compound as claimed in any of claims 1-3, 6, 7 and 9-13 in crystalline form.

15. A process for the preparation of a compound of formula (I) or salt thereof as claimed in claim 1 wherein a compound of formula (II)

(wherein R4 is as defined in claim 1 and R17 is an esterified carboxyl group), or a compound of formula (IV)

(wherein R4 and R are as defined in claim 1) is reacted with an amine of formula R1R2R3N, (wherein R'R2R3N is is as defined in claim 1) whereby a compound of formula (I) is obtained, followed by salt formation if desired.

16. A process as claimed in claim 15 wherein the amine is a trialkylamine having 1-6 carbon atoms in each alkyl group.

17. A process as claimed in claim 15 or claim 16 wherein reaction is carried out in a non-hydroxylic solvent and the compound of formula (I) obtained crystallises from solution.

18. A process as claimed in any of claims 15-17 wherein reaction is carried out at from -40 C to +300C.

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

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

21. A process as claimed in any of claims 15-20 wherein the compound of formula (II) is prepared by reaction of a compound of formula (IV) at elevated temperature in the presence of a tertiary organic base and an inert solvent.

22. A process as claimed in claim 21 wherein reaction is effected at from 500C to 1000C in the presence of an amine R'R2R3N wherein R', R2 and R3 are as defined in claim 2 other than a heterocyclic aromatic amine.

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

24. A process as claimed in claim 21 substantially as hereinbefore described with reference to the Examples.

25. A process for the preparation of a compound of formula (III)

wherein R is an esterified carboxyl group, in which a compound of formula (I). according to claim 1 wherein R4 is a hydroxyl group is reacted with a reagent serving to replace a hydroxyl group by a readily eliminatable group which then undergoes elimination in the presence of a tertiary organic base.

26. A process as claimed in claim 25 wherein said reagent is a sulphonylating agent, in the presence or absence of halide ions, or a halogenating agent.

27. A process as claimed in claim 25 or claim 26 wherein the base is a tertiary amine bearing aliphatic, araliphatic or aromatic groups.

28. A process as claimed in claim 27 wherein the tertiary amine carries alkyl groups having up to 8 carbon atoms, aralkyl groups having up to 6 carbon atoms in the alkyl portion, aryl groups, such aryl or aralkyl groups being monocyclic, or C3.7 cycloalkyl groups.

29. A process as claimed in claim 28 wherein the base is a trialkylamine having 1-6 carbon atoms in each alkyl group.

30. A process as claimed in any of claims 25-29 wherein reaction is effected from 50 to 100"C.

31. A process for the preparation of a compound of formula (III) as defined in claim 25 wherein a compound of formula (I) as defined in claim 1 in which R4 is a readily eliminatable substituent is reacted with a tertiary organic base.

32. A process as claimed in claim 25 substantially as hereinbefore described.

33. A process as claimed in claim 25 substantially as hereinbefore described with reference to the Examples.

34. A compound of formula (III) as defined in claim 25 whenever prepared by a process as claimed in any of claims 25-30, 32 and 33.

35. A compound of formula (III) as defined in claim 25 whenever prepared by a process as claimed in claim 31.

36. A process for the preparation of a compound of formula (I) wherein R4 is an acylated hydroxyl group and R, Rl, R2 and R3 are as defined in claim 1 which comprises reacting a compound of formula (I) wherein R4 is a hydroxyl group with an acylating agent.