EP0651755A1 - Cephalosporins and 1-carba-1-dethia cephalosporins - Google Patents

Abstract

A compound of formula (I) or a salt thereof, wherein: R1 is hydrogen, methoxy or formamido; R2 is an acyl group; CO¿2R?3 is a carboxy group or a carboxylate anion, or R3 is a readily removable carboxy protecting group or a pharmaceutically acceptable salt-forming group or in vivo hydrolysable ester group; X is S, SO, SO¿2? or CH2; R?4¿ is a bicyclic group (a), where m is 1 or 2; wherein one of Y or Z is O, S, SO or SO¿2? and the other is CH2, and wherein R?4¿ may be unsubstituted or may have one or more optional substituents R5. The compounds of formula (I) have antibacterial activity. Processes for making them and formulations including them are described.

Description

Cephalosporins and l-carba-l-deth1a cephalosporlns

This invention relates to novel β-lactam compounds, their preparation and their use, and in particular to a novel class of cephalosporins. These compounds have antibacterial properties, and are therefore of use in the treatment of bacterial infections in humans and animals caused by a wide range of organisms.

EP 0487996 Al (Bayer AG) discloses cephems of general formula (A):

(A) wherein R^a, and R^D arc various substituents, and R^c is a ring system selected from:

where A and D may be the same or different and may be CH=CH, oxygen or sulphur, and R^a and R^D may be various substituents.

We have found a particularly advantageous class of cephems and carbacephems bearing a bicyclic substituent at the 3-position of the cephem nucleus, which includes a 5- or 6- membered cyclic ether or cyclic thio-ether moiety.

The present invention provides a compound of formula (I) or a salt thereof:

ω wherein:

R! is hydrogen, methoxy or formamido;

R2 is an acyl group, in particular that of an antibacterially active cephalosporin;

CO2R3 is a carboxy group or a carboxylate anion, or R^ is a readily removable carboxy protecting group or a pharmaceutically acceptable salt-forming group or in vivo hydrolysable ester group;

X is S, SO, SO2 orCH2;

R is a bicyclic group where m is 1 or 2; wherein one of Y or Z is O, S, SO or SO2 and the other is CH2, and wherein R^ may be unsubstituted or may have one or more optional substituents R^, which may be present on any of the carbon atoms in the bicyclic ring system shown, selected from alkyl, alkenyl, alkynyl, alkoxy, hydroxy, halogen, amino, alkylamino, acylamino, dialkylamino, CO2R, OCOR, CONR2, SO2NR2 ^{nere R is} hydrogen or alkyl; aryl and heterocyclyl, which may be the same or different and wherein any R^ alkyl substituent is optionally substituted by one or more substituents selected from the list from which R^ is selected, in place of any of the hydrogen atoms in the bicyclic system.

The bonding carbon atom of the heterocyclic moiety of R^ which links R^ to the cephalosporin nucleus is generally asymmetric. The present invention includes either stereoisomer, as well as mixtures of both isomers. In compounds of formula (I) wherein R is formamido, the formamido group can exist in conformations wherein the hydrogen atoms of the -NH-CHO moiety are cis- or trans-: of these the cj conformation normally predominates.

Since the compounds of the present invention are intended for use as therapeutic agents for antibacterial use in pharmaceutical compositions, it will be readily appreciated that preferred compounds within formula (I) are pharmaceutically acceptable, i.e. are compounds of formula (la) or pharmaceutically acceptable salts or pharmaceutically acceptable in thereof:

da) wherein Rl, R^, and R^ are as defined with respect to formula (I) and the group CO2R * is CO2R where CO2R^ is a carboxy group or a carboxylate anion.

Accordingly, the present invention provides a compound of formula (la) or a pharmaceutically acceptable salt or in vivo hydrolysable ester thereof, for use as a therapeutic agent, and in particular an in vivo hydrolysable ester thereof for use as an orally administrable therapeutic agent.

The present invention further provides a compound of formula (la) or a pharmaceutically acceptable salt or in vivo hydrolysable ester thereof, for use in the treatment of bacterial infections, more particularly an in vivo hydrolysable ester thereof for use in the oral treatment of bacterial infections.

The present invention also includes a method of treating bacterial infections in humans and animals which comprises the administration of a therapeutically effective amount of an antibiotic compound of the formula (la) or a pharmaceutically acceptable in vivo hydrolysable ester thereof, in particular the oral administration of a therapeutically effective amount of an in vivo hydrolysable ester.

In addition, the present invention includes the use of a compound of formula (la) or a pharmaceutically acceptable salt or in vivo hydrolysable ester thereof, for the 0 manufacture of a medicament for the treatment of bacterial infections, in particular the use of an in vivo hydrolysable ester for the manufacture of a medicament for the oral treatment of bacterial infections.

When used herein the term 'aryl' includes phenyl and naphthyl, each optionally substituted with up to five, preferably up to three, groups selected from 5 halogen, mercapto, (Cι_g) alkyl, phenyl, dC\.^) alkoxy, hydroxy(Cι_6)alkyl, mercapto(Cι_6)alkyl, halo(Cι_(5) alkyl. hydroxy, amino, nitro, carboxy, (Cj. 6)alkylcarbonyloxy, (Cι_ j)alkoxycarbonyl, formyl, or (Cι_6)alkylcarbonyl groups.

The terms 'heterocyclyl' and 'heterocyclic' as used herein include aromatic and non-aromatic, single and fused, rings suitably containing up to four hetero-atoms in 0 each ring selected from oxygen, nitrogen and sulphur, which rings may be unsubstituted or substituted by, for example, up to three groups selected from halogen, (Cι_g)alkyl, (Cι_6)alkoxy, halo(Cι_.6)alkyl, hydroxy, carboxy, carboxy salts, carboxy esters such as (Cι_6)alkoxycarbonyl, (Cι_6)alkoxycaτbonyl(Cι_ _ .. β z&yl' ^aryl» a*¹** oxo groups. Each heterocyclic ring suitably has from 4 to 7, preferably 5 or 6, ring atoms. The term Tieteroaryl' refers to heteroaromatic heterocyclic rings. A fused heterocyclic ring system may include carbocyclic rings and need include only one heterocyclic ring. Compounds within the invention containing a heterocyclyl group may occur in two or more tautometric forms 3_Q depending on the nature of the heterocyclyl group; all such tautomeric forms are included within the scope of the invention.

The term 'heteroaryl' as used herein means a heteroaromatic heterocyclic ring or ring system, suitably having 5 or 6 ring atoms in each ring.

When used herein the terms 'alkyl', 'alkenyl', 'aikynyl' and 'alkoxy' include ~ straight and branched chain groups containing from 1 to 6 carbon atoms, such as methyl, ethyl, propyl and butyl. A particular alkyl group is methyl.

When used herein the term 'halogen' refers to fluorine, chlorine, bromine and iodine.

Those compounds of the formula (I) wherein R^ is a readily removable hydrolysable ester or which are in non-pharmaceutically acceptable salt form are primarily useful as intermediates in the preparation of compounds of the formula (la) or a pharmaceutically acceptable salt or pharmaceutically acceptable in vivo hydrolysable ester thereof. Suitable readily removable carboxy protecting groups for the group R-- include groups forming ester derivatives of the carboxylic acid, including in vivo hydrolysable esters. The derivative is preferably one which may readily be cleaved in vivo.

Also included within the scope of the invention are salts and carboxy-protected derivatives, including in vivo hydrolysable esters, of any carboxy groups that may be present as optional substituents in compounds of formula (I) or (la). Also included within the scope of the invention are acid addition salts of any amino group or substituted amino group that may be present as optional substituents in compounds of formula (I) or (la). Suitable ester-forming carboxyl-protecting groups are those which may be removed under conventional conditions. Such groups for R^ include benzyl, p-methoxybenzyl, benzoylmethyl, p-nitrobenzyl, 4-pyridylmethyl, 2,2,2-trichloroethyl, 2,2,2-tribromoethyl, l-butyl, i-amyl, allyl, diphenylmethyl, triphenylmethyl, adamantyl, 2-benzyloxyphenyl, 4-methylthiophenyl, tetrahydrofur-2-yl, tetrahydropyran-2-yl, pentachlorophenyl, acetonyl, β-toluenesulphonylethyl, methoxymethyl, a silyl, stannyl or phosphorus- containing group, an oxime radical of formula -N=CHR^ where R^ is aryl or heterocyclic, or an in vivo hydrolysable ester radical such as defined below.

A carboxyl group may be regenerated from any of the above esters by usual methods appropriate to the particular R^ group, for example, acid- and base- catalysed hydrolysis, or by enzymically-catalysed hydrolysis, or by hydrogenolysis under conditions wherein the remainder of the molecule is substantially unaffected. Examples of suitable pharmaceutically acceptable in vivo hydrolysable ester groups which R-- may comprise include those which break down readily in the human body to leave the parent acid or its salt. Suitable ester groups of this type include those of part formulae (i), (ii), (iii), (iv) and (v):

c /

-C0₂ -R -N^ _β

(ϋ)

-C0₂CH₂— OR (Hi)

wherein R^a is hydrogen, (C\. ) alkyl, (C3.7) cycloalkyl, methyl, or phenyl, R^D is (Cι_6) alkyl, (Cj_6) alkoxy, phenyl, benzyl, (C3.7) cycloalkyl, (C3.7) cycloalkyloxy, (Cι_6) alkyl (C3.7) cycloalkyl, 1-amino (C\. ) alkyl, or l-((Cι_6) alkyl)amino (Cμ 5) alkyl; or R^a and R*³ together form a 1,2-phenylene group optionally substituted by one or two methoxy groups; R^c represents (Cj.g) alkylene optionally substituted with a methyl or ethyl group and R^ and R^e independently represent (Cj.g) alkyl; R^ represents (C .^) alkyl; RS represents hydrogen or phenyl optionally substituted by up to three groups selected from halogen, (C\. ) alkyl, or (C\. ) alkoxy; Q is oxygen or NH; Rⁿ is hydrogen or (Cj.g) alkyl; R* is hydrogen, (Cj.g) alkyl optionally substituted by halogen, (C2-6) alkenyl, (C\. ) alkoxycarbonyl, aryl or heteroaryl; or Rⁿ and R* together form (Cj.β) alkylene; R represents hydrogen, (C\. ) alkyl or (Cι_6) alkoxycarbonyl; and R^ represents (Cι_s) alkyl, (Cj. ) alkoxy, (Cι_6) alkoxy((Cι_6))alkoxy or aryl. Examples of suitable in vivo hydrolysable ester groups include, for example, acyloxyalkyl groups such as acetoxymethyl, pivaloyloxymethyl, α-acetoxyethyl, α-pivaloyloxyethyl, l-(cyclohexylcarbonyloxy)prop- 1 - yl, and (l-aminoethyl)carbonyloxymethyl; alkoxycarbonyloxyalkyl groups, such as ethoxycarbonyloxymethyl, α-ethoxycarbonyloxyethyl and propoxycarbonyloxyethyl; dialkylaminoalkyl especially di-loweralkylamino alkyl groups such as dimethylaminomethyl, dimethylaminoethyl, diethylaminomethyl or diethylaminoethyl; 2-(alkoxycarbonyl)-2-alkenyl groups such as

2-(isobutoxycarbonyl)pent-2-enyl and 2-(ethoxycarbonyl)but-2-enyl; lactone groups such as phthalidyl and dimethoxyphthalidyl; and esters linked to a second β-lactam antibiotic or to a β-lactamase inhibitor. A further suitable pharmaceutically acceptable in vivo hydrolysable ester group is that of the formula: '

wherein R^m is hydrogen, (Cj.g) alkyl or phenyl.

A preferred in vivo hydrolysable ester group is the pivaloyloxymethyl ester. Suitable pharmaceutically acceptable salts of the carboxy group of the compound of formula (I) include metal salts, eg aluminium, alkali metal salts such as sodium or potassium, especially sodium, alkaline earth metal salts such as calcium or magnesium, and ammonium or substituted ammonium salts, for example those with lower alkylamines such as triethylamine, hydroxy-lower alkylamines such as 2-hydroxyethylamine, bis-(2-hydroxyethyl)amine or tris-(2-hydroxyethyl)- amine, cycloalkylamines such as dicyclohexylamine, or with procaine, dibenzylamine, £LN-dibenzylethylene- diamine, 1-ephenamine, N-methylmorpholine, N-ethylpiperidine, N-benzyl-β-phenethylamine, dehydroabietylamine, H-M'-bisdehydro-abietylamine, ethylenedia ine, or bases of the pyridine type such as pyridine, collidine or quinoline, or other amines which have been used to form salts with known penicillins and cephalosporins. Other useful salts include the lithium salt and silver salt. Salts of formula (I) may be prepared by salt exchange in conventional manner.

In compounds of formula (I) or (la), the group X may be an oxidised sulphur atom, i.e. a sulphoxide (SO) or sulphone (SO2) group. When X is a sulphoxide group it will be understood that α- and β-isomers may exist; both such isomers are encompassed within the scope of the present invention. Preferably X is S or CH2. Advantageously, R* is hydrogen. Suitable acyl groups R^ include those of formulae (a) - (f): A,(CH₂)_p-CH-(CH₂)m-Cα

I (a) x.

A₂CO (b)

A₃-C-CO-

N II w

OA,

A₃-C-C -

(f)

A₄ wherein p is 0, 1 or 2; m is 0, 1 or 2; A 1 is (C\. ) alkyl, substituted (Cj.g) alkyl wherein the substituents may be as for R^ above, (C3.6) cycloalkyl, cyclohexenyl, cyclohexadienyl, an aryl (including heteroaryl) group, such as phenyl, substituted phenyl, thienyl, pyridyl, or an optionally substituted thiazolyl group, a (Cj.g) akylthio group or (Cj.g) alkyloxy; X\ is a hydrogen or halogen atom, a carboxy lie acid, carboxylic ester, sulphonic acid, azido, tetrazolyl, hydroxy, acyloxy, amino, ureido, acylamino, heterocyclylamino, guanidino or acylureido group; A2 is an aryl group, for example a phenyl, 2,6-dimethoxyphenyl,2-alkoxy-l-naphthyl, 3-arylisoxazolyl, or a 3-aryl-5-methylisoxazolyl group, such as 3-(2-chloro-6-fluorophenyl)-5-methylisoxazol-4-yl; a substituted alkyl group; or a substituted dithietane; X2 is a -CH2OCH2-, -CH2SCH2- or alkylene group; X3 is an oxygen or sulphur atom; A3 is an aryl or heteroaryl group such as phenyl, substituted phenyl, furyl, aminothiazolyl or aminothiadiazolyl in which the amino group is optionally protected; and A4 is hydrogen, (Cι_6)alkyl, (C3.8) cycloalkyl, (C3.8) cycloalkyl(Cι_6)alkyl, (Cι_6) alkoxycarbonyl(Cι_6) alkyl, (C2-6) alkenyl, carboxy(Cι_6)alkyl, (C2-6) alkynyl, aryl or (Cj_6)alkyl substituted by up to three aryl groups.

Suitably when R² is a group (a), A is (C\. ) alkyl, (C3..6) cycloalkyl, cyclohexenyl, cyclohexadienyl, phenyl, substituted phenyl (eg substituted as for "aryl" above) such as hydroxyphenyl, thienyl or pyridyl; and X\ is a hydrogen or halogen atom, or a carboxy, carboxylic ester, azido, tetrazolyl, hydroxy, acyloxy, optionally protected amino, ureido, guanidino or acylureido group.

Suitably when R² is a group of formula (d), A2 is phenyl, X3 is oxygen and p is O. Alternatively when R² is a group of formula (e) or (f) suitable values for the group A3 include those commonly found in antibacterially active cephalosporins containing a hydroxyimino, substituted hydroxyimino or vinyl group in the side chain attached to position 7 of the cephalosporin nucleus, for example phenyl, thien-2-yl, thien-3-yl, fur-2-yl, fur-3-yl, pyrid-2-yl, pyrid-3-yl, pyrid-4-yl, 5-amino-l,2,4-thiadiazol-3-yl and

2-aminothiazol-4-yl in each of which the amino group is optionally protected. Preferred groups for A3 include phenyl, 2-aminothiazol-4-yl, fur-2-yl, thien-2-yl, 2-(2-chloroacetamido)thiazol-4-yl, 2-tritylamino-thiazol-4-yl, 5-amino-l,2,4-thiadiazol-3-yl and 4-aminopyrimid-2-yl. In compounds of formula (la) a preferred acyl group R-- is one of formula (e), having a group, A3 which is 2-aminothiazol-4-yl.

Suitable values for the group A4 include hydrogen, methyl, ethyl, cyclopropylmethyl, triphenylmethyl (trityl), cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, phenyl, carboxymethyl, carboxypropyl and i-butoxycarbonylmethyl.

Preferred values for A4 in compounds of formula (la) include methyl and hydrogen.

In the bicyclic substituent R^, one of Y or Z is preferably O or S. Examples of such groups R^ include dihydrobenzofuranyl, dihydroisobenzofuranyl, dihydrothianaphtiiyl and dihydrooxanaphthyl, and such groups may be linked to the cephalosporin nucleus by any of the available ring positions on the 5- or 6- membered heterocyclic ring of R^. For example R^ may be linked to the nucleus at a ring position adjacent to the O or S atom of the heterocyclic ring. A suitable example of such a group R^ is dihydrobenzofuran-2-yl. Suitably R^ may carry up to three substituents R^. Preferably R^ is unsubstitued.

It will be appreciated that compounds of the invention wherein R² is a group of formula (e) or (f) can exist as ≤y_n and ami (or E and Z) isomers or mixtures thereof. Both isomers are encompassed within the scope of this invention.

Preferably the compounds of the invention wherein R² is a group of formula (e) have the sy configuration (i.e. have the group OA4 ≤yn to the amide linkage) or are enriched in that isomer.

Similarly, when R² is a group of formula (f), the group A4 is preferably cjs to the amide linkage, i.e. when group (f) is 2-amino-thiazol-4-yl, the Z-configuration is preferred.

It will be appreciated that the 5- or 6- membered ring of the heterocyclic moiety of R^ may exist in a number of isomeric forms. All isomeric forms, including mixtures of isomeric forms, are included within the scope of this invention.

Certain compounds of the invention include an amino group which may be protected. Suitable amino protecting groups are those well known in the art which may be removed under conventional conditions without disruption of the remainder of the molecule.

Examples of amino protecting groups include (Cj.g) alkanoyl; benzoyl; benzyl optionally substituted in the phenyl ring by one or two substituents selected from (C1.4) alkyl, (C1.4) alkoxy, trifluoromethyl, halogen, or nitro; (C1.4) alkoxycarbonyl; benzyloxycarbonyl or trityl (ie triphenylmethyl) substituted as for benzyl above; allyloxycarbonyl, trichloroethoxycarbonyl or chloroacetyl.

Some of the compounds of this invention may be crystallised or recrystallised from solvents such as organic solvents. In such cases solvates may be formed. This invention includes within its scope stoichiometric solvates including hydrates as well as compounds containing variable amounts of water that may be produced by processes such as lyophilisation.

Since the antibiotic compounds of the invention are intended for use in pharmaceutical compositions it will readily be understood that they are each provided in substantially pure form, for example at least 60% pure, more suitably at least 75% pure and preferably at least 85%, especially at least 95% pure, particularly at least 98% pure (% are on a weight for weight basis). Impure preparations of the compounds may be used for preparing the more pure forms used in the pharmaceutical compositions; these less pure preparations of the compounds should contain at least 1%, more suitably at least 5% and preferably from 10 to 49% of a compound of the formula (I) or salt thereof.

Specific compounds within this invention of formula (la) include the following pharmaceutically acceptable carboxylic acids, and salts and in-vivo hydrolysable esters thereof: (6R,7S)-7-[2-(2-Aminothiazol-4-yl)-2-(Z)-methyoxyiminoacεtamido]-3-[(S)- dihydrobenzofuran-2-yl]ceph-3-em-4-carboxylic acid.

(6R,7S)-7-[2-(2-aminothiazol-4-yl)-2-(Z)-methoxyimino-acetamido]-3-[(2S)- 2,3-dihydrobenzofuran-2-yl]- 1 -carba- l-dethiaceph-3-em-4-carboxylate

The present invention provides a process for the preparation of a compound of formula (I) or (la) as defined above in which -CO2R^ is a carboxy group or carboxylate anion or R^ is a pharmaceutically acceptable salt-forming group or in- vivo hydrolysable ester group, wherein a compound of formula (I) as defined above in which R3 is a carboxy protecting group has its group CC^R^ replaced by a group CO2R which is a carboxy group or a carboxylate anion, or in which R^ is a pharmaceutically acceptable salt-forming group or in-vivo hydrolysable ester group.

The present invention further provides a process for the preparation of a compound of formula (I), which process comprises treating a compound of formula (II) or a salt thereof:

(II) wherein X, R*, CQ &, and R^ are as hereinbefore defined, wherein any reactive groups may be protected, and wherein the amino group is optionally substituted with a group which permits acylation to take place; with an acid of formula (III) or a N- acylating derivative thereof:

R²OH (m)

wherein R² is the acyl group as defined with respect to formula (I) and wherein any reactive groups may be protected; and thereafter, if necessary or desired, carrying out one or more of the following steps: i) removing any protecting groups; ii) converting the group CO2R^ into a different group CO2R^; iii) converting the group R² into a different group R²; iv) converting the group X and/or Y and/or Z into a different group X and/or Y and/or Z, for example S into SO or SO2; v) converting the product into a salt or ester.

Acids of formula (III) may be prepared by methods known in the art, or methods analogous to such processes. Suitable processes include those described, for example, in UK Patent 2 107 307 B, UK Patent Specification No. 1,536,281, and

U.K. Patent Specification No. 1,508,064.

Suitable groups which permit acylation to take place and which are optionally present on the amino group of the starting material of the formula (II) include N-silyl,

N-stannyl and N-phosphorus groups, for example trialkylsilyl groups such as trimethylsilyl, trialkyltin groups such as tri-n-butyltin, groups of formula -P.R^RS wherein R? is an alkyl, haloalkyl, aryl, aralkyl, alkoxy, haloalkyl, aryl, aralkyl, alkoxy, haloalkoxy, aryloxy, aralkyloxy or dialkylamino group, R° is the same as R ' or is halogen or R and R** together form a ring; suitable such phosphorus groups being -P(OC₂H₅)₂, -P(C₂H₅)₂,

A group which may optionally be introduced onto the amino group in the compound of formula (II) is trimethylsilyl. '

Advantageously the silylation reaction may be carried out in situ, prior to the acylation reaction, with a silylating agent that does not require concomitant addition of base. Suitable silylating agents include, for example, ϋ-(trimethylsilyl)-acetamide, ϋ,Ω-bis-( methylsilyl)acetamide, H»Q-bis(trimethylsilyl)- trifluoroacetamide, ϋ-methyl-M-trimethylsilylacetamide, N-methyl-N-trimethylsilyl-trifluoroacetamide, £LN'-bis(trimethylsilyl)urea, and H»_Q-bis(trimethylsilyl)carbamate. A preferred silylating agent is MQ-bis(trimethylsilyl)acetamide. The silylation reaction may suitably be carried out in an inert, anhydrous organic solvent such as dichloromethane at room temperature or at an elevated temperature, for example 30 - 60°C, preferably 40 - 50°C.

The above process may optionally be carried out in the presence of a small quantity, for example 0.1 equivalents, of a silyl halide, for example a tri(Cι_ 6)alkylsilyl halide, especially trimethylsilyl chloride.

A reactive N-acylating derivative of the acid (III) is employed in the above process. The choice of reactive derivative will of course be influenced by the chemical nature of the substituents of the acid.

Suitable N-acylating derivatives include an acid halide, preferably the acid chloride or bromide or alternatively a symmetrical or mixed anhydride. The acylation may be effected in the presence of an acid binding agent for example, tertiary amine (such as pyridine or dimethylaniline), molecular sieves, an inorganic base (such as calcium carbonate or sodium bicarbonate) or an oxirane, which binds hydrogen halide liberatec' in the acylation reaction. The oxirane is preferably a (Cι_6)-l,2-alkylene oxide - jch as ethylene oxide or propylene oxide. The acylation reaction using an acid halide may be carried out at a temperature in the range -50°C to +50°C. preferably -20°C to +20°c, in aqueous or non-aqueous media such as water, acetone, tetrahydrofuran, ethyl acetate, dimethylacetamide, dimethylformamide, acetonitrile, dichloromethane, 1,2-dichloroethane, or mixtures thereof. Alternatively, the reaction may be carried out in an unstable emulsion of water-immiscible solvent, especially an aliphatic ester or ketone, such as methyl isobutyl kietone or butyl acetate. The acylation with acid halide or anhydride is suitably carried out in the presence of a basic catalyst such as pyridine or 2,6-lutidine.

Acid halides may be prepared by reacting the acid (III) or a salt or a reactive derivative thereof with a halogenating (eg chlorinating or brominating) agent such as phosphorus pentachloride, thionyl chloride, oxalyl chloride or phosgene.

Suitable mixed anhydrides are anhydrides with, for example, carbonic acid monoesters, trimethyl acetic acid, thioacetic acid, diphenylacetic acid, benzoic acid, phosphorus acids (such as phosphoric, phosphorous, and phosphi e acids) or aromatic or aliphatic sulphonic acids (such as p.-toluenesulphonic acid or methanesulphonic acid).

Alternative EJ-acylating derivatives of acid (III) are the acid azide, or activated esters such as esters with 2-mercaptopyridine, cyanomethanol, β-nitrophenol, 2,4-dinitrophenol, thiophenol, halophenols, including pentachlorophenol, monomethoxyphenol, M-hydroxy succinimide, H-hydroxybenzotriazole, or

8-hydroxyquinoline; or amides such as ϋ-acylsaccharins, N-acylthiazolidin-2-thione or H-acylphthalimides; or an alkylidene iminoester prepared by reaction of the acid (HI) with an oxime.

Other reactive M-acylating derivatives of the acid (III) include the reactive intermediates formed by reaction in situ with a condensing agent such as a carbodiimide, for example, £LN'-diethyl-, dipropyl- or diisopropylcarbodiimide, N-N'-di-cyclohexyl-carbodiimide, or H-ethyl-H'-[3-(dimethylamino)propyl]- carbodiimide; a suitable carbonyl compound, for example, N,N'-carbonyldiimidazole or N,N'-carbonyldi- triazole; an isoxazolinium salt, for example, N-ethyl-5-phenylisoxazolinium-3-sulphonate or N-t-butyl-5- methylisoxazolinium perchlorate; or an N-alkoxycarbonyl 2-alkoxy-l,2-dihydroquinoline, such as N-ethoxycarbonyl 2-ethoxy-l,2-dihydroquinoline. Other condensing agents include Lewis acids (for example BBr3 - CόHg); or a phosphoric acid condensing agent such as diethylphosphorylcyanide. The condensation reaction is preferably carried out in an organic reaction medium, for example, methylene chloride, dimethylformamide, acetonitrile, alcohol, benzene, dioxan or tetrahydrofuran.

A further method of forming the N-acylating derivative of the acid of formula (HI) is to treat the acid of formula (III) with a solution or suspension preformed by addition of a carbonyl halide, preferably oxalyl chloride, or a phosphoryl halide such as phosphorus oxychloride, to a halogenated hydrocarbon solvent, preferably dichloromethane, containing a lower acyl tertiary amide, preferably N,N-dimethylformamide. The N-acylating derivative of the acid of formula (III) so derived may then be caused to react with a compound of formula (II). The acylation reaction may conveniently be carried out at -40° to +30°C, if desired in the presence of an acid binding agent such as pyridine. A catalyst such as 4-dimethylaminopyridine may optionally also be added. A preferred solvent for the above acylation reaction is dichloromethane. The optional removal of protecting group (i), the optional conversion of

CO2R (ϋ), the optional conversion (iii) of R² to a different R², CC^R^ to a different C I^R^ and (iv), X and/or Y and/or Z to a different X and/or Y, and/or Z and (v) the optional formation of a salt or ester, may be carried out using methods well known in the art of cephalosporin and penicillin chemistry. For example, when the group X, Y or Z is S, SO, or SO2, the group X, Y or Z may be converted into a different group Y by methods of oxidation or reduction well known in the art of cephalosporin and penicillin synthesis, as described, for example, in European Patent Application Publication No. 0 114752. For example, sulphoxides (in which X or Y is SO) may be prepared from the corresponding sulphide (in which X, Y or Z is S) by oxidation with a suitable oxidising agent, for example an organic peracid such as m-chloroperbenzoic acid.

A reduction step is generally effected by processes well known in the art of β- lactam chemistry, for example using phosphorus trichloride in dimethylformamide. For example, removal of protecting groups may be carried out by any convenient method known in the art such that unwanted side reactions are minimised. When for example R-- is the protecting group p-methoxybenzyl, this group may suitably be removed by treatment of the protected compound with aluminium chloride in the presence of anisole. Separation of unwanted by-products may be carried out using standard methods. Compounds of formula (II) in which X is S, SO or SO2 may be prepared starting from known compounds of formula (IV):

(IV) wherein R²* is an amino protecting group, for example as discussed above. A suitable group R² is phenoxyaetyl. Compounds of formula (IV) may be reacted with compounds of formula R^-CO-CH2-X where R^ is as defined above and X is a halogen, suitably chlorine, to form a compound of formula (V):

(N) Compounds of formula R^-CO-CH2-X may themselves be prepared from known compounds of formula R^-CO2H by reaction of such acids with oxalyl halides, such as oxalyl chloride.

Similarly compounds of formula (II) in which X is CH2 may be prepared starting from known compounds of formula (VI):

(VI) wherein R² and R²² are amino-protecting groups, for example as discussed above. A suitable group R²* is phenylacetyl, and a suitable group R²² is 4-methoxyphenyl. Compounds of formula (VI) may be reacted with compounds of formula R^- CO.CH=PR3 where R^ is as defined above and R is aryl, suitably phenyl, to form a compound of formula (VII):

(NH)

Compounds of formula R^-CO.CH=PR3 may themselves be prepared by reaction of an acylating derivative of known compounds R^CC^H, such as the acyl halide, with compound such as [CH2-P(R3)]⁺Br in the presence of phenyl lithium. Compounds of formula (Nil) may be reduced, e.g by Pd/C:H2 and the protecting group R²² removed to form compounds of formula (Nm):

(VIII) Compounds of formula (V) and (VIE) may be converted to compounds of formula

(IX) where R31 is a group R^ or a group which can be converted into or replaced by R^.

Suitably R^l may be a carboxyl protecting group, for example as discussed above, suitably 4-methoxybenzyl. Compounds of formula (IX) may for example be prepared by reaction of the compound (V) or (VIII) with the corresponding R^l-glyoxylate.

Compounds of formula (IX) may be converted to compounds of formula (X):

(X) wherein R is an organic hydrocarbon group such as alkyl or phenyl, suitably n-butyl, by replacement of the hydroxy group shown in (IX) by halogen, e.g. by treatment of (IX) with a thionyl halide such as thionyl chloride, followed by reaction with a compound PR^.

The compound (X) then be cyclised, typically by heating, e.g. under refluxs to form a compound of formula (XI):

(XI)

Deprotection of the 7-amino group, i.e. removal of R² , yields a compound of formula (II). The deprotection may for example be carried out using the knowing Delft procedure, e.g. using phosphorus pentachloride in the presence of N- methylmorpholine, Deprotection of the 4-acyl group, i.e. removal of R^l may be carried out using standard procedures, and known procedures may be used for formation of compounds of formula (I) which are salts or esters. Compounds of formula (I) in which X is other then sulphur may be prepared by analogous routes which will be apparent to those skilled in the art.

During the course of the above synthesis the compound may be isomerically resolved if necessary to separate compounds containing the R and S isomers of the 5- or 6- membered heterocyclic ring of R^. This may conveniently be done with compounds of formula (XI).

Compounds of formulae (II), (V), (VI), (Nil), (Nm), (IX), (X) and (XI) are believed to be novel and as such comprise a further aspect of this invention.

The present invention also provides a pharmaceutical composition which comprises a compound of formula (la) or a pharmaceutically acceptable salt or in vivo hydrolysable ester thereof and a pharmaceutically acceptable carrier. The compositions of the invention include those in a form adapted for oral, topical or parenteral use and may be used for the treatment of bacterial infection in mammals including humans. The antibiotic compounds according to the invention may be formulated for administration in any convenient way for use in human or veterinary medicine, by analogy with other antibiotics.

The composition may be formulated for administration by any route, such as oral, topical or parenteral, especially oral. The compositions may be in the form of tablets, capsules, powders, granules, lozenges, creams or liquid preparations, such as oral or sterile parenteral solutions or suspensions.

The topical formulations of the present invention may be presented as, for instance, ointments, creams or lotions, eye ointments and eye or ear drops, impregnated dressings and aerosols, and may contain appropriate conventional additives such as preservatives, solvents to assist drug penetration and emollients in ointments and creams.

The formulations may also contain compatible conventional carriers, such as cream or ointment bases and ethanol or oleyl alcohol for lotions. Such carriers may be present as from about 1% up to about 98% of the formulation. More usually they will form up to about 80% of the formulation.

Tablets and capsules for oral administration may be in unit dose presentation form, and may contain conventional excipients such as binding agents, for example syrup, acacia, gelatin, sorbitol, tragacanth, or polyvinylpyroUidone; fillers, for example lactose, sugar, maize-starch, calcium phosphate, sorbitol or glycine; tablctting lubricants, for example magnesium stearate, talc, polyethylene glycol or silica; disintegrants, for example potato starch; or acceptable wetting agents such as sodium lauryl sulphate. The tablets may be coated according to methods well known in normal pharmaceutical practice. Oral liquid preparations may be in the form of, for example, aqueous or oily suspensions, solutions, emulsions, syrups or elixirs, or may be presented as a dry product for reconstitution with water or other suitable vehicle before use. Such liquid preparations may contain conventional additives, such as suspending agents, for example sorbitol, methyl cellulose, glucose syrup, gelatin, hydroxyethyl cellulose, carboxymethyl cellulose, aluminium stearate gel or hydrogenated edible fats, emulsifying agents, for example lecithin, sorbitan monooleate, or acacia; non-aqueous vehicles (which may include edible oils), for example almond oil, oily esters such as glycerine, propylene glycol, or ethyl alcohol; preservatives, for example methyl or propyl p-hydroxybenzoate or sorbic acid, and, i desired, conventional flavouring or colouring agents. Suppositories will contain conventional suppository bases, e.g. cocoa-butter o other glyceride. ^v

For parenteral administration, fluid unit dosage forms are prepared utilizing the compound and a sterile vehicle, water being preferred. The compound, dependin on the vehicle and concentration used, can be either suspended or dissolved in the vehicle. In preparing solutions the compound can be dissolved in water for injection and filter sterilised before filling into a suitable vial or ampoule and sealing.

Advantageously, agents such as a local anaesthetic, preservative and bufferin agents can be dissolved in the vehicle. To enhance the stability, the composition can be frozen after filling into the vial and the water removed under vacuum. The dry lyophilized powder is then sealed in the vial and an accompanying vial of water for injection may be supplied to reconstitute the liquid prior to use. Parenteral suspensions are prepared in substantially the same manner except that the compound is suspended in the vehicle instead of being dissolved and sterilization cannot be accomplished by filtration. The compound can be sterilised by exposure to ethylene oxide before suspending in the sterile vehicle. Advantageously, a surfactant or wetting agent is included in the composition to facilitate uniform distribution of the compound.

The compositions may contain from 0.1% by weight, preferably from 10-60 by weight, of the active material, depending on the method of administration. Where the compositions comprise dosage units, each unit will preferably contain from 50-500 mg of the active ingredient. The dosage as employed for adult human treatment will preferably range from 100 to 3000 mg per day, for instance 1500 mg per day depending on the route and frequency of administration. Such a dosage corresponds to 1.5 to 50 mg/kg per day. Suitably the dosage is from 5 to 20 mg/kg per day.

No unacceptable toxicological effects are expected when a compound of formula (la) or a pharmaceutically acceptable salt or in vivo hydrolysable ester thereof is administered in the above-mentioned dosage range.

The compound of formula (la) may be the sole therapeutic agent in the compositions of the invention or a combination with other antibiotics or with a β-lactamase inhibitor may be employed.

Advantageously, the compositions also comprise a compound of formula (XII) or a pharmaceutically acceptable salt or ester thereof:

(XII) wherein

A is hydroxyl, substituted hydroxyl, thiol, substituted thiol, amino, mono- or di-hydrocarbyl- substituted amino, or mono- or di-acylamino; an optionally substituted triazolyl group; or an optionally substituted tetrazolyl group as described in EP-A-0053 893.

A further advantageous composition comprises a compound of formula (la) or a pharmaceutically acceptable salt or in vivo hydrolysable ester thereof together with a compound of formula (XIII) or a pharmaceutically acceptable salt or in vivo hydrolysable ester thereof:

(XIII) wherein

B represents hydrogen, halogen or a group of formula:

in which R^x and Ry are the same or different and each represents hydrogen, (C\. ) alkoxycarbonyl or carboxy, or a pharmaceutically acceptable salt thereof.

Further suitable β-lactamase inhibitors include 6-alkylidene penems of formula (XIN):

(XIV) or a pharmaceutically acceptable salt or in vivo hydrolysable ester thereof, wherein R^m and Rⁿ are the same or different and each represents hydrogen, or a (Cj.io) hydrocarbon or heterocyclic group optionally substituted with a functional group; and RP represents hydrogen or a group of formula R 3 or -SR¹^ where R -^ is an optionally substituted (Cι_ιo) hydrocarbon or heterocyclic group, as described in EP-A-0041 768.

Further suitable β-lactamase inhibitors include 6β-bromopenicillanic acid and pharmaceutically acceptable salts and in vivo hydrolysable esters thereof and 6β-iodopenicillanic acid and pharmaceutically acceptable salts and in vivo hydrolysable esters thereof described in, for example, EP-A-0410768 and EP-A-0 154 132 (both Beecham Group).

Such compositions of this invention which include a β-lactamase inhibitory amount of a β-lactamase inhibitor are formulated in a conventional manner using techniques and procedures per se known in the art.

The antibiotic compounds of the present invention are active against a wide range of organisms including both Gram-negative organisms such as E.coli and Gram-positive organisms such as S.aureus.

The following Examples illustrate the preparation of compounds of the invention and intermediates thereto, and the processes of the invention.

EXAMPLE 1

Sodium (6R,7R)-7-[2-(2-AminothiazoI-4-yl)-2-(Z)-methoxyiminoacetamido]-3- [(S)-dihydrobenzofuran-2-yI]ceph-3-em-4-carboxyIate and Sodium (6R,7R)-7-[2- (2-Aminothiazol-4-yI)-2-(Z)-methoxyiminoacetamido]-3-[(R)- dihydrobenzofuran-2-yI]ceph-3-em-4-carboxylate. a) (RS)-2-ChloroacetyI-2,3-dihydrobenzofuran

Oxalyl chloride (2.68ml) was added to a stirred mixture of 2,3-dihydro-2- benzofurancarboxylic acid (3.28g) and dichloromethane (48ml). Dimethyl- formamide (2 drops) was added and the mixture stirred at room temperature for 50 min. and then at reflux for a further 10 min. The solvent was evaported and chloroform was evaporated from the residue twice. The residue was dissolved in dichloromethane (200ml) and the solution cooled in an ice bath. A stream of diazomethane in argon was then passed into the solution until all the acid chloride was consumed, and then air was passed through the solution to remove excess diazomethane. Hydrogen chloride gas was then passed into the solution until all the diazoketone had been consumed. The solution was washed with water and brine, dried over magnesium sulphate and evaporated. The title compound (3.93g) was obtained by column chromatography of the residue (silica gel, 4:1 hexane: ethyl acetate); υ _max (CHC1₃) 1744cm" 1; δ (CDCI3) 3.40 (1H, dd, J 16.13, 6.33Hz), 3.57 (1H, dd, J 16.15, 10.75Hz), 4.41 (1H, d, J 17.12Hz), 4.61 (1H, d, J 17.20Hz), 5.26 (1H, dd, J 10.75, 6.30Hz), 6.87-6.96 (2H, m) and 7.15-7.21 (2H, m).

b) (3R,4R)-4-[(R5)-2^-Dihydrobenzofuran-2-ylcarbonylmethylthio]-3- phenoxyacetamidoazetidin-2-one.

Potassium carbonate (4.5g) was added to a stirred solution of (RS)-2-chloro- acetyl-2,3-dihydrobenzofuran (3.93g) and (3R,4R)-4-mercapto-3-phenoxy- acetamidoazetidin-2-one (5.0g) in dimethylformamide (50ml) under argon. The mixture was stirred at room temperature for 1.5h and then partitioned between ethyl acetate and water. The organic phase was washed three times with water, then brine, dried over magnesium sulphate and evaporated. Flash chromatography (silica gel: 1:1 hexane:ethyl acetate going to neat ethyl acetate) gave the title compound (7.09g) as a gum which was used without further purification; υ _max (CHCI3) 3410, 1783 and 1690cm"¹.

c) 4-MethoxybenzyI (RS)-2-[(3R,4R)-4-[(RS)-2,3-Dihydrobenzofuran-2- yIcarbonylmethylthio]-3-phenoxyacetamidoazetidin-2-on-l-yl]-2- hydroxyacetate.

4-Methoxybenzyl glyoxylate (3.10g) in dichloromethane (30ml) was heated at reflux for lh. using an inverse water entrainer. The mixture was cooled at room temperature and the solution of (3R,4R)-4-[(R5)-2,3-dihydrobenzofuran-2- ylcarbonylmethylthio]-3-phenoxyacetamidoazetidin-2-one (7.09g) in dichloromethane (45ml) was added followed by triethylamine (0.22ml). The mixture was stirred at room temperature for lh. and then the solvent was evaporated and the product purified by flash chromatography (silica gel; 1 : 1 hexane:ethyl acetate going to neat ethyl acetate) to give the title compound (6.22g) as a gum which was used without further purification; υ _max (CHCI3) 3411, 1783, 1742 and 1691cm"¹.

d) 4-Methoxybenzyl 2-[(3R,4R)-4-[(RS)-2,3-Dihydrobenzofuran-2- ylcarbonylmethylthio]-3-phenoxyacetamidoazetidin-2-on-l-yl]-2-tri-n-butyl- phosphoranylideneacetate.

A solution of thionyl chloride (1.15ml) in tetrahydrofuran (9ml) was added to a stirred solution of 4-methoxybenzyl (RS)-2-[(3R,4R)-4-[(RS)-2,3- dihydrobenzof uran-2-ylcarbonylmethylthio] -3-phenoxyacetamidoazetidin-2-on- 1 -yl] 2-hydroxyacetate (6.22g crude) and 2,6-lutidine (1.86ml) in tetrahydrofuran (47ml). The mixture was stirred at room temperature for 2h, then the solid was filtered off and washed with tetrahydrofuran. The combined filtrates were evaporated and toluene was evaporated from the residue. The residue was dissolved in dioxan (57ml under argon and tri-n-butylphosphine (5.7ml) was added. The mixture was stirred fo 50 min. and then diluted with ethyl acetate and the solution was washed successively with sodium bicarbonate solution, water and brine. The solution was dried over magnesium sulphate and evaporated. Flash chromatography of the residue (silica gel; 1:1 hexane:ethyl acetate going to neat ethyl acetate) gave the title compound (3.09g); υ _max (CHC1₃) 3420, 1761, 1689,, 1612 and 1600cm"¹.

e) 4-Methoxybenzyl (6R,7Λ)-3-[(R5)-2^-Dihydrobenzofuran-2-yl]-7- phenoxyacetamidoceph-3-em-4-carboxylate.

A solution of 4-methoxybenzyl 2-[(3R, 4R)-4-[(R5)-2,3-dihydrobenzofuran-2- ylcarbonylmethylthio]-3-phenoxyacetamidoazetidin-2-on- 1 -yl]-2-tri-n-butyl- phosphoranylideneacetate (3.09g) in toluene (150ml) was heated to reflux for 3h. The solvent was evaporated and the products separated by column chromatography using gradient elution (silica gel; 3:1 going to 1:1 hexane:ethyl acetate). Eluted first was the (S)-isomer of the title compound (465mg); υ _max (CHCI3) 3409, 1788, 1720 and 1697cm"¹; δ (CDCI3) 3.02 (IH, dd, J 16..52, 8.37Hz), 3.32 (IH, d, J 18.80Hz), 3.59-3.75 (IH, m), 3.37 (IH, d, / 16.65Hz), 3.81 (3H, s)„ 4.55 (2H, s), 5.00 (IH, d, / 4.92Hz), 5.23 (2H, s), 5.88-5.96 (2H, m) and 6.74-7.37 (14H, m). Eluted next was a mixture of compounds containing the (R)-isomer of the title compound (745mg).

f) 4-Methoxybenzyl (6R,7/f)-7-Amino-3-[(S)-2,3-dihydrobenzofuran-2- yI]ceph-3-em-4-carboxylate.

A solution of 4-methoxybenzyl (6R,7R)-3-[(S)-2,3-dihydrobenzofuran-2-yl]- 7-phenoxyacetamidoceph-3-em-4-carboxylate (465mg) in dichloromethane (6.5ml) was cooled to -15° to -20°C, then N-methylmorpholine (0.179ml) was added followed by phosphorus pentachloride (6.4ml of a solution in dichloromethane containing 40mg ml^-1). The solution was stirred at the same temperature for 0.5h then methanol (1.6ml) was added and the mixture stirred at room temperature for 0.5h. Water (2.19ml) was then added and the mixture was vigorously stirred for 0.5h. The aqueous phase adjusted to pH6.2 with IN aqueous ammonia and the mixture extracted with chloroform. The chloroform solution was washed with water and brine, dried over magnesium sulphate and evaporated. Column chromatography of the residue using gradient elution (silica gel; 1:1 hexane:ethyl acetate going to neat ethyl acetate) gave the title compound (98mg); υ _max (CHCI3) 1780 and 1720cm"¹; δ (CDCI3) 1.68 (2H, s), 3.04 (IH, dd, J 16.51, 8.41Hz), 3.32 (IH, d, J 18.68Hz), 3.36-3.78 (IH, m), 3.65 (IH, d, J 18.79Hz), 3.81 (3H, s), 4.76 (IH, d, J 5.02Hz), 4.92 (IH, d, /5.05Hz), 5.19 (IH, d, 7 11.88Hz), 5.24 (IH, d, / 11.85Hz), 5.89 (IH, dd, 79.66, 8.63Hz), 6.76 (IH, d,/7.89Hz), 6.84-6.91 (3H, m), 7.10-7.19 (2H, m) and 7.36 (2H, d, / 8.63Hz). g) 4-Methoxybenzyl (6R,7_R)-7-[2-(2-Aιnihothiazol-4-yl)-2-(Z)- methoxyiminoacetamido]-3-[(5)-2,3-dihydrobenzofuran-2-yl]ceph-3-em-4- carboxylate.

A stirred solution of 2-(2-aminothiazol-4-yl)-2-(Z)-methoxyiminoacetic acid (50mg) and N,N-disopropylethylamine (0.043ml) in dimethylformamide (0.9ml) was cooled to -30° to -40°C and methanesulphonyl chloride (0.19ml) was added. The mixture was stirred at the same temperature for 0.5h and then a solution of 4- methoxybenzyl (6R,7R)-7-amino-3-[(S)-2,3-dihydrobenzo-furan-2-yl]ceph-3-em-4- carboxylate (98mg) in dimethylformamide (1ml) was added followed by pyridine (0.018ml). The mixture was then stirred at 0° for lh. then at room temperature for 0.5h. The mixture was partitioned between ethyl acetate and citric acid solution, and the organic phase was washed with water and brine over magnesium sulphate and evaporated. Column chromatography of the residue using gradient elution (silica gel, 1:1 hexane:ethyl acetate going to neat ethyl acetate) gave the title compound (112mg); υ _ma (CHCI3) 3490, 3398, 1783, 1720, 1683 and 1611cm"¹; δ (CDCI3) 3.06 (IH, dd, 716.53, 8.20Hz), 3.35 (IH, d, J 18.87Hz), 3.64 (IH, dd, J 16.68, 9.87Hz), 3.69 (IH, d, 718.92Hz), 3.81 (3H, s), 4.04 (3H, s), 5.06 (IH, d, 74.91Hz), 5.19 (IH, d, 7 11.82Hz), 5.25 (IH, d, 7 11.81Hz), 5.60 (2H, s), 5.92 (IH, t, 79.73), 605 (IH, dd, 79.02, 4.89Hz), 6.77 (IH, d, 77.95Hz), 6.84-6.92 (4H, m), 7.14 (IH, dd, J 14.08, 6.75Hz), 7.35 (IH, d, 78.61Hz) and 7.62 (IH, d, J 9.08Hz).

h) Sodium (6R,7R)-7-[2-(2-AminothiazoI-4-yl)-2-(Z)-methoxyimino- acetamido]-3-[(S)-2,3-dihydrobenzofuran-2-yl]ceph-3-em-4-carboxyIate.

A stirred mixture of anisole (2.7ml) and dichloromethane (1.35ml) under argon was cooled to -20°C and powdered aluminium chloride (70mg) was added. The mixture was stirred for a further 15 min. at -20°C. A solution of 4- methoxybenzyl (6R,7R)-7-[2-(2-aminothiazol-4-yl)-2-(Z)-methoxyimino-acetamido]- 3-[(S)-2,3-dihydrofuran-2-yl]ceph-3-em-4-carboxylate (112mg) in dichloromethane (9ml) was then added and the mixture stirred at -20°C for 5 min. Sodium citrate solution (5.95ml of 0.5M) was then added and the mixture vigorously stirred at room temperature for 10 min. The aqueous phase was separated and washed twice with dichloromethane. The aqueous phase was evaporated and the product purified by column chromatography (HP 20SS, water with increasing proportins of acetone as eluent). Fractions containing product were combined and evaporated and the residue dissolved in water (5ml) and freeze-dried to give the title compound (61mg); υ _max (KBr) 1763, 1680 and 1597cm"¹; δ [(CD₃)₂SO] 2.98 (IH, dd, J 16.32, 9.16Hz), 3.18 (IH, d, J 17.32Hz), 3.31-3.40 (IH, m), 3.43 (IH, d, 7 17.32Hz), 3.82 (3H, s), 5.04 (lH, d, 75.79Hz), 5.59 (lH, dd, 78.05, 4.71Hz), 6.01 (IH, t, 79.23Hz), 6.71-6.83 (3H, m), 7.08 (IH, t, 77.45Hz), 7.18-7.24 (3H, m) and 9.53 (IH, d, 78.08Hz); mlz (FAB, +ve ion, thioglycerol) 524 (Λ/H+), 546 (MNά⁺).

i) 4-Methoxybenzyl (6R,7J?)-7-Amino-3-[(R)-2,3-dihydrobenzofuran-2- yl]ceph-3-em-4-carboxylate. A solution of impure 4-methoxybenzyl (6R,7R)-3-[(R)-2,3- dihydrobenzofuran-2-yl]-7-phenoxyacetamidoceph-3-em-4-carboxylate (745mg) in dichloro-methane (10.4ml) was cooled to -15° to -20° and N-methoxymorpholine (0..286ml) was added followed by a solution of phosphorus pentachloride in dichloromethane (10.2ml of a solution containing 40mg ml"¹). The mixture was stirred at the same temperature for 0.5h, then methanol (2.6ml) was added and the mixture stirred at room temperature for 0.5h. Water (3.5ml) was added and the mixture vigorously stirred for a further 0.5. ^"he dichloromethane was removed on a rotary evaporator and the aqueous phase was rred with ethyl acetate and adjusted to pΗ6.2 with IN aqueous ammonia. The organic phase was evaporated, washed with water and brine, dried over magnesium sulphate and evaporated. Column chromatography of the residue using gradient elution (silica gel; 1:1 hexane:ethyl acetate goint to neat ethyl acetate) gave the title compound (lOlmg); υ _max (CHCI3) 1779 and 1726cm"¹; δ (CDCI3) 1.77 (2H, s), 2.99 (IH, dd, 7 15.84, 7.96Hz), 3.35 (IH, dd, 715.88, 9.89Hz) 3.40 (IH, d, 7 17.97Hz), 3.56 (IH, d, 7 18.07Hz), 3.80 (3H, s), 4.72 (IH, d, 74.78Hz), 4.91 (IH, άj 5.01Hz), 5.16 (IH, d, 711.82Hz), 5.26 (IH, d, 11.81Hz), 6.03 (IH, dd, 79.64, 8.20Hz), 6.80-6.90 (4H, m), 7.12 (2H, d, 7 9.52Hz) and 7.33 (2H, d, 78.65Hz).

j) 4-Methoxybenzyl (6R,7R)-7-[2-AminothiazoI-4-yl)-2-(Z)-methoxy- iminoacetamido]-3-[(R)-2,3-dihydrobenzofuran-2-yI]ceph-3-em-4-carboxylate- A stirred solution of 2-(2-aminothiazol-4-yl)-2-(Z)-methoxyiminoacetic acid (51mg) and N,N-diisopropylethylamine (0.044ml) in dimethylformamide (1ml) was cooled to -30° to -40° and methanesulphonyl chloride (0.020ml) was added. The mixture was stirred at the same temperature for 0.5h. and then a solution of 4- methoxybenzyl (6R,7R)-7-amino-3-[(R)-2,3-dihydrobenzofuran-2-yl]ceph-3-em-4- carboxylate (lOlmg) in dimethylformamide (1ml) was added. The mixture was then stirred at 0°C for lh. and then at room temperature for 0.5h. The reaction mixture was then partitioned between ethyl acetate and citric acid solution. The organic phase was washed with water and brine, dried over magnesium sulphate and evaporated. Column chromatography of the residue using gradient elution (silica gel; 1:1 hexanexthyl acetate going to neat ethyl acetate) gave the title compound (93mg); υ _max (CHCI3) 3491,, 3398, 1783, 1726, 1683 and 1607cm"¹; δ (CDCI3) 2.99 (IH, dd, 7 15.96, 7.90Hz) 3.36-3.46 (IH, dd, 7 15.83, 9.81Hz), 3.40 (IH, d, 7 17.29Hz), 3.61 (IH, d, 7 18.15Hz), 3.80 (3H, s), 4.04 (3H, s), 5.05 (IH, d, 74.83Hz), 5.16 (IH, d, 7 11.85Hz), 5.26 (IH, d, 7 11.82Hz), 5.39 (2H, s), 5.99 (IH, dd, 78.98, 4.82Hz), 6.13 (IH, t, 78.12Hz), 6.79-6.90 (4H, m), 7.10-7.16 (2H, m), 7.32 (2H, d, 78.57Hz) and 7.64 (lH, d, 78.96Hz).

k) Sodium (6R,7R)-7-[2-(2-Aminothiazol-4-yl)-2-(Z)-methoxyimino- acetamido]-3-[(R)-2-3-dihydrobenzofuran-2-yI]ceph-3-em-4-carboxylate.

A stirred mixure of anisole (2.25ml) and dichloromethane (1.12ml) under argon was cooled to -20°C and aluminium chloride (58mg) was added. The mixture was stirred at the same temperature for 15 min. and then a solution of 4- methoxybenzyl (6R,7R)-7-[2-(2-aminothiazol-4-yl)-2-(Z)-methoxyimino-acetamido]- 3-[(R)-2,3-dihydroxybenzofuran-2-yl]ceph-3-em-4-carboxylate (93mg) ita dichloromethane (7.5ml) was added. The mixture was stirred at -20°C for a further 5 min. and then sodium citrate solution (4.95ml of 0.5M) was added and the mixture vigorously stirred for a further 10 min. The aqueous phase was separated, washed twice with dichloromethane, and evaporated. The product was purified by column chromatography (HP 20SS, water with increasing proportions of acetone as eluent). Fractions containing product were combined and evaporated. The residue was dissolved in water (5ml) and freeze dried to give the title compound (54mg); υ _max (KBr) 1763 and 1597cm"¹; δ [(CD₃)₂SO] 2.99-3.25 (2H, m), 3.10 (IH, d, 7 16.09Hz), 3.46 (IH, d, 7 16.83Hz), 3.83 (3H, s), 5.00 (IH, d, 74.75Hz), 5.55 (IH, dd, 78.00, 4.65Hz), 6.27 (IH, t, 79.03Hz), 6.71-6.82 (2H, m), 6.74 (IH, s), 7.07 (IH, t, 76.66Hz), 7.17 (IH, d, 77.36Hz), 7.23 (2H, s) and 9.56 (IH, d, 78.07); mlz (FAB, +ve ion, thioglycerol) 524 ( H+).

EXAMPLE 2

Sodium (6R,7S)-7-[2-(2-aminothiazol-4-yl)-2-(Z)-methoxyimino- acetamido]-3-[(2S)-2,3-dihydrobenzofuran-2-yI]-l-carba-l-dethiaceph-3-em-4- carboxylate a) 2,3-Dihydrobenzofuran-2-ylcarboxyIic acid

2-Benzofurancarboxylic acid (9.66g, 59.6mmol) was dissolved in ethanol (100ml) and hydrogenated over 10% palladium on carbon (900mg) for 16h. The catalyst was removed by filtering through celite and the filtrate concentrated in vacuo to yield the title compound (9.52g, 98%); v_max (CΗ2CI2) 1731, 1598, 1481 and 1221cm"¹; δ_H (CDCI3) 3.40 (IH, dd, 7 16.0, 6.6Hz), 3.64 (IH, dd.7 16.0, 10.8Hz), 5.25 (IH, dd, 7 10.8, 6.6Hz), 6.86-6.97 (2H, m), 7.10-7.22 (2H, m) and 7.98 (IH, br. s, exch.).

b) 23-Dihydrobenzofuran-2-ylcarbonyImethylenetriphenyl-phosphorane Oxalyl chloride (530μl, 6.08mmol) was added to a solution of 2,3- dihydrobenzofuran-2-ylcarboxylic acid (500mg, 3.05mmol) in dichloromethane (20ml) containing one drop of DMF. After stirring for 2h, the mixture was concentrated, re-dissolved in dichloromethane and concentrated again. Meanwhile, a suspension of methyltriphenylphosphonium bromide (2.18g,

6.1 lmmol) in diethyl ether (30ml) was treated with phenyl lithium (2.06M solution in cyclohexane-ether, 3ml, 6.18mmol). After stirring for 2h at room temperature, a solution of the above acid chloride in diethyl ether (30ml) was added and stirred vigorously for 5min. Water (20ml) was added and stirring continued for a further 5min. The aqueous phase was separated and re-extracted with ether. The combined organic layers were washed witii water (x3), and brine, dried over magnesium sulphate and then concentrated in vacuo. The residue was purified by chromatography on silica gel eluting with 50, 70 and 100% ethyl acetate in hexane to yield the title compound (850mg, 66%); (Found: ⁺ 422.1433. C28H23O2P requires M 422.1436); v_max(CH₂Cl2) 1536, 1481, 1438, 1405, 1268, 1232 and 1106cm^"1; δ_H (CDCI3) 3.36 (IH, dd, 7 16.0, 7.9Hz), 3.53 (IH, dd, 7 16.0, 10.3Hz), 4.27 (IH, d, 7 25.2Hz), 6.80-6.88 (2H, m), 7.06-7.20 (2H, m) and 7.40-7.68 (15H, m); mlz (Cl, +ve ion, ammonia) 423 (MH⁺).

c) (3S,4R)-l-(4-Methoxyphenyl)-4-[3-oxo-3-(2,3-dihydrobenzofuran-2- yl)propenyl]-3-phenylacetamidoazetidin-2-one

A suspension of (3S,4S)-4-formyl-l-(4-methoxyphenyl)-3-phenyl- acetamidoazetidin-2-one (4.13g, 12.2mmol) in acetonitrile (100ml) was treated with 2,3-dihydrobenzofuran-2-ylcarbonylmethylenetriphenyl-phosphorane (5.20g, 12.3mmol) and heated at 80°C for 2h. The bulk of the product (3.75g) was collected by filtration and washed with acetonitrile. The remainder of the product was purified by chromatography on silica gel eluting with ethyl acetate yielding a further 1.28g of the title compound (total 5.03g, 86%); (Found: + 482.1846. C25H26N2O5 requires M 482.1842); v_max(KBr) 1772, 1703, 1659, 1512 and 1253cm"¹; δ_H (CDCI3) 3.22- 3.47 (2H, m), 3.53 (2H, s), 3.76 (3H, s), 4.87 (IH, t, 75.4Hz), 5.18 (IH, dd, 7 10.3, 7.1Hz), 5.46 (IH, dd, 78.1, 5.4Hz), 6.18 (IH, t, 78.1Hz), 6.58-6.92 (5H, m) and 7.06-7.28 (8H, m); mlz (Cl, +ve ion, ammonia) 500 (MH+).

d) (3S,4R)-l-(4-Methoxyphenyl)-4-[3-oxo-3-(2,3-dihydrobenzofuran-2- yI)propyl]-3-phenylacetamido zetidin-2-one

A solution of (3S,4R)-l-(4-methoxyphenyl)-4-[3-oxo-3-(2,3- dihydrobenzof uran-2-yl)propenyl] - 3-phenylacetamidoazetidin-2-one (5.0g, 10.37mmol) in tetrahydrofuran (250ml) was hydrogenated over 10% palladium on carbon (300mg) for 3.5h. After filtration through celite, the filtrate was concentrated in vacuo to yield die title compound (5.04g, 100%); (Found: M⁺ 484.1999. C29H28 2O5 requires M 484.1998); v_max (KBr) 1757, 1721, 1659, 1513 and 1247cm"¹; δ_H (CDCI3) 1.50 (IH, m), 2.24 (IH, m), 2.42-2.62 (2H, m), 3.25 (IH, m), 3.45 (IH, m), 3.54 (2H, s), 3.73 (3H, s), 4.15 (IH, m), 4.98 (IH, m), 5.29 (IH, m), 6.66 (IH, d, 77.9Hz), 6.79 (2H, m), 6.89 (2H, m) and 7.13-7.36 (9H, m); mlz (Cl, +ve ion, ammonia) 485 (MH+), 502 (MNH₄+).

e) (3S,4R)-4-[3-Oxo-3-(2,3-dihydrobenzofuran-2-yl)propyl]-3- phenylacetamidoazetidin-2-one A suspension of (3S,4R)-l-(4-methoxyphenyl)-4-[3-oxo-3-(2,3- dihydrobenzofuran-2-yl)-propyl]-3-phenylacetamidoazetidin-2-one (3.80g, 7.85mmol) in tetrahydrofuran (380ml) was treated with a solution of eerie ammonium nitrate (25.8g, 47.08mmol) in water (160ml) at 0°C. After stirring for 5min. at 0°C, the reaction mixture was diluted with ethyl acetate and the aqueous phase extracted four times with a mixture of tetrahydrofuran and ethyl acetate (2: 1 ). The combined organic extracts were washed successively witii 5% aqueous sodium hydrogen carbonate solution, 10% aqueous sodium sulphite solution (x2), 5% aqueous sodium hydrogen carbonate solution, water and then brine. After drying over magnesium sulphate, the solvent was evaporated in vacuo to yield the crude title compound (1.64g, 55%); v_max (CH₂C1₂) 3412, 1772, 1683 and 1507cm"¹.

f) 4-Methoxybenzyl (RS)-2-hydroxy-2-[(3S,4R)-4-[3-oxo-3-(2,3- dihydrobenzofuran-2-yl)propyI]-3-phenylacetamidoazetidin-2-on-l-yl]acetate p-Methoxybenzyl glyoxylate (1.13g, 5.82mmol) in 1,2-dichloroethane (18ml) was heated at reflux for lh. using Dean and Stark apparatus. The solution was cooled in ice and treated successively with (3S,4R)-4-[3-oxo-3-(2,3-dihydrobenzofuran-2- yl)propyl]-3-phenylacetamidoazetidin-2-one (1.64g, 4.34mmol) and triethylamine (60μl, 0.43mmol). After stirring at room temperature overnight the reaction mixture was concentrated in vacuo. The residue was purified by chromatography on silica gel eluting with 30, 50 then 70% ethyl acetate in hexane to yield the title compound (626mg, 25%); v_max (CH₂C1₂) 1763, 1743, 1671, 1612 and 1515cm"¹; mlz (FAB, +ve ion, 3-nitrobenzyl alcohol/sodium acetate) 533 ( Na⁺).

g) 4-MethoxybenzyI 2-[(3S,4R)-4-[3-oxo-3-(2,3-dihydrobenzofuran-2- yl)propyI]-3-phenylacetamidoazetidin-2-on-l-yI]-2-tri-n-butylphosphoranyiidene acetate

A solution of thionyl chloride (146μl, 2.00mmol) in THF (2ml) was added to the hydroxy compound (763mg, 1.33mmol) and 2,6-lutidine (233μl, 2.00mmol) in THF (20ml) at -20°C . After stirring for lh the reaction mixture was filtered through a pad of celite, and the filtrate evaporated in vacua. Toluene was added and re- evaporated to yield 4-methoxybenzyl (R5)-2-chloro-2-[(3S,4R)-4-[3-oxo-3-(2,3- dihydrobenzofuran-2-yl)propyl]-3-phenylacetamidoazetidin-2-on- 1 -yljacetate as an oil. The crude chloro compound was dissolved in dioxan (10ml) and treated with tri-/z-butylphosphine (731μl, 2.93mmol). After stirring for 30min. at room temperature, the reaction mixture was diluted with ethyl acetate and washed successively with dilute sodium hydrogen carbonate solution, water and brine. The organic solution was dried, concentrated and then chromatographed on silica gel eluting with 30, 50 then 70% ethyl acetate in hexane, to give the title compound as a foam (733mg, 73%); v_max (CH₂Cl2) 3418, 1751, 1679, 1612, 1514 and 1464cm"¹; mlz (Cl, +ve ion, ammonia) 757 (Λ/H⁺).

h) 4-Methoxybenzyl (6R,75)-7-Phenylacetamido-3-[(5) and (R)-2,3- dihydrobenzofuran-2-yI]-l-carba-l-dethiaceph-3-em-4-carboxylate

A solution of the phosphorane (733mg, 0.97mmol) and benzoic acid (lOmg) in toluene (15ml) was heated at reflux for 1 lh. The reaction mixture was cooled, concentrated and the residue purified by chromatography on silica gel eluting with 30, then 50% ethyl acetate in hexane yielding the title compound as separate diastereoisomers. The (S)-isomer was obtained as a pale yellow foam (72mg, 14%); (Found: M+ 538.2126. C32H30N2O6 requires M 538.2104); v_max (CH₂C1₂) 3418, 1771, 1719, 1684, 1612, 1516, 1480, 1392 and 1232cm"¹; δ_H (CDCI3) 1.07 (IH, m), 1.87 (IH, m), 2.19-2.52 (2H, m), 2.88 (IH, dd, 7 16.3, 8.3Hz), 3.56 (IH, dd, 7 16.3, 9.8Hz), 3.59 (2H, s), 3.78 (3H, s), 3.82 (IH, m), 5.12 and 5.20 (2H, ABq, 7 11.9Hz), 5.29 (IH, dd, 76.7, 4.9Hz), 5.93 (IH, dd, 79.8, 8.3Hz), 6.0 (IH, d, 76.7Hz), 6.73 (IH, d, 77.9Hz), 6.80-6.89 (3H, m) and 7.06-7.39 (9H, m); mlz (Cl, +ve ion, ammonia) 539 (MH+), 556 (MNH4+).

Further elution of the column yielded d e (R)-isomer (41mg, 8%); (Found: M+ 538.2121. C32H30N2O6 requires M 538.2104); v_max (CH₂Cl2) 3417, 1772, 1722, 1684, 1612, 1516, 1480, 1389 and 1232cm"¹; δ_H (CDCI3) 1.25 (IH, m), 1.87 (IH, m), 2.10 (IH, m), 2.58 (IH, m), 2.96 (IH, dd, 7 15.9, 7.8Hz), 3.33 (IH, dd, 7 15.9, 10.0Hz), 3.58 (2H, s), 3.74 (3H, s), 3.76 (IH, m), 5.19 (2H, s), 5.27 (IH, dd, 7 6.3, 5.3Hz), 5.94 (IH, d, 76.3Hz), 6.09 (IH, dd, 7 10.0, 7.8Hz), 6.73-6.88 (4H, m), and 7.07-7.37 (9H, m); mlz (Cl, +ve ion, ammonia) 539 (MH+), 556 (MNH4+).

i) 4-Methoxybenzyl (6R,7S)-7-amino-3-[(2S)-2,3-dihydrobenzofuran-2-yl]- l-carba-l-dethiaceph-3-em-4-carboxylate

A solution of 4-methoxybenzyl (6R,7S)-7-phenylacetamido-3-[(2S)-2,3- dihydrobenzofuran-2-yl]-l-carba-l-dethiaceph-3-em-4-carboxylate (70mg, 0.13mmol) and N-methylmorpholine (30μl, 0.27 mmol) in dichloromethane (6ml) was treated with phosphorus pentachloride (44mg, 0.21 mmol) in dichloromemane (1.1ml) at -25°C. The reaction was stirred at -10±5°C for 45min., then methanol (15ml) was added, and stirring continued for 45min. at room temperature. Water (32ml) was then added, and the mixture vigorously stirred for a further lh. The dichloromethane was evaporated in vacuo, and the aqueous residue adjusted to pH7 with concentrated ammonia solution in the presence of ethyl acetate. The mixture was extracted twice with ethyl acetate, dried and concentrated in vacuo. The residue was purified by chromatography on silica gel eluting with ethyl acetate yielding the title compound as a pale yellow foam (36mg, 66%); (Found: + 420.1689. C24H24N2O5 requires M 420.1685); v_max(CH₂Cl₂) 1764, 1718, 1612, 1516, 1480 and 1395cm^"1; δ_H (CDCI3), 1.49(1H, m,), 2.02-2.49 (5H, m, 2 exch.), 2.93 (IH, dd, 7 16.3, 8.3Hz), 3.56 (IH, dd, 7 16.3, 9.7Hz), 3.72 (IH, m), 3.79 (3H, s), 4.52 (IH, d, 75.4Hz), 5.19 (2H, s), 5.93 (IH, dd, 79.7, 8.3Hz), 6.74 (IH, d, 77.9Hz), 6.80-6.90 (3H, m), 7.06- 7.16 (2H,m) and 7.34 (2H, m); mlz (Cl, +ve ion, ammonia) 421 (MH+), 438( NH4+).

j) 4-Methoxybenzyl (6R,7S)-7-[2-(2-aminothiazol-4-yl)-2-(Z)- methoxyiminoacetamido]-3-[(2S)-2,3-dihydrobenzofuran-2-yI]-l-carba-l- dethiaceph-3-em-4-carboxylate

Methanesulphonyl chloride (7μl, 0.090mmol) was added to 2-(2-thiazol-4-yl)- 2-(Z)-methoxyiminoacetic acid (19mg, 0.095mmol) and NN-diisopropylethylamine (16μl, 0.092mmol) in DMF (2ml) at -30°C. After stirring at -30±10°C for 30min., a solution of 4-methoxybenzyl (6R,7S)-7-amino-3-[(2S)-2,3-dihydrobenzofuran-2-yl]- l-carba-l-dedιiaceph-3-em-4-carboxylate (35mg, 0.083mmol) in DMF (3ml) was added, followed by pyridine (7μl, 0.087mmol). The reaction mixture was transferred to an ice-bath and stirring continued for a further lh. After dilution with ethyl acetate, the solution was washed successively with saturated sodium hydrogen carbonate solution, 5% aqueous citric acid, water (x2) and brine, dried and then concentrated in vacuo. The residue was purified by chromatography on silica gel eluting with ethyl acetate to give the title compound as a pale yellow foam (33mg, 66%); v_max (CH₂C1₂) 1761, 1718, 1676, 1612 and 1516cm"¹; δ_H (CDCI3) 1.63 (IH, m), 2.02 (IH, m), 2.28-2.58 (2H, m), 2.93 (IH, dd, 7 16.4, 8.2Hz), 3.58 (IH, dd, 7 16.4, 10.1Hz), 3.78 (3H, s),3.89 (3H, s), 3.93 (IH, m), 5.19 (2H, s), 5.64 (IH, dd, 7 7.7, 5.0Hz), 5.93 (IH, dd, 7 10.1, 8.2Hz), 5.94 (2H, br.s, exch.), 6.71-6.92 (5H, m), 7.05-7.16 (2H, m), 7.35 (2H, d, 78.7Hz) and 8.32 (IH, d, 77.7Hz); mlz (Cl, +ve ion, ammonia) 604 (MH⁺). k) Sodium (6R,75)-7-[2-(2-aminothiazol-4-yl)-2-(Z)-methoxyimino- acetamido]-3-[(25)-2,3-dihydrobenzofuran-2-yI]-l-carba-l-dethiaceph-3-em-4- carboxylate

Aluminium chloride (22mg, 0.17mmol) was added to anisole (0.9ml) and dry dichloromethane (0.5ml) at -20°C and stirred for 15min. The temperature of the cooling bath was then lowered to -40°C before addition of 4-methoxybenzyl (6R,7S)- 7-[2-(2-aminothiazol-4-yl)-2-(Z)-methoxy-iminoacetamido]-3-[(2S)-2,3- dihydrobenzofiιran-2-yl] - 1 -carba- 1 -dethiaceph-3-em-4-carboxylate (33mg, 0.055mmol) in dichloromemane (2ml). After 15min., the solution was treated with trisodium citrate (0.5M, 1.7ml) and then vigorously stirred for lOmin. at room temperature. The aqueous phase was separated, washed twice with dichloromethane and concentrated in vacuo. The residue was chromatographed on HP20SS eluting with water, then 1, 2, 4, 8, 10, 15 and 20% THF in water. Fractions containing the product (h.p.Lc. analysis) were combined, concentrated and freeze-dried to give the title compound (20mg, 77%); v_max (KBr) 1751, 1664, 1597, 1530, 1480, 1388, 1232 and 1039cm"¹; δ_H (d₆-DMSO) 1.48 (IH, m), 1.80 (IH, m), 2.02-2.15 (2H, m), 2.92 (IH, dd, 7 16.2, 8.4Hz), 3.38 (IH, dd, 716.2, 9.6Hz), 3.68 (IH, m), 3.81 (3H, s), 5.28 (IH, dd, 78.6, 4.9Hz), 6.10 (IH, dd, 79.6, 8.4Hz), 6.66-6.83 (3H, m), 7.07 (IH, m), 7.14-7.26 (3H, m) and 9.22 (IH, d, 78.6Hz); mlz (FAB, +ve ion, thioglycerol) 505 (MH+), 528 (MNa+).

Claims

Claims:

1. A compound of formula (I) or a salt thereof:

wherein: R¹ is hydrogen, methoxy or formamido; R² is an acyl group;

CO₂R³ is a carboxy group or a carboxylate anion, or R³ is a readily removable carboxy protecting group or a pharmaceutically acceptable salt-forming group or in vivo hydrolysable ester group; X is S, SO, SO₂ or CH₂;

R₄ is a bicyclic group: where m is 1 or 2; wherein one of Y or Z is O, S, SO or SO₂ and the other is CH₂, and wherein R⁴ may be unsubstituted or may have one or more optional substituents R⁵, which may be present on any of the carbon atoms in the bicyclic ring system shown, selected from alkyl, alkenyl, alkynyl, alkoxy, hydroxy, halogen, amino, alkylamino, acylamino, dialkylamino, CO₂R, OCOR, CONR₂, SO₂NR₂ where R is hydrogen or alkyl; aryl and heterocyclyl, which may be the same or different and wherein any R⁵ alkyl substituent is optionally substituted by one or more substituents selected from the list from which R⁵ is selected, in place of any of the hydrogen atoms in the bicyclic system.

2. A compound of formula (I) according to claim 1, wherein X is S or CH₂, and R¹ is hydrogen.

3. A compound of formula (I) according to claim 1 or 2, wherein R²NH is 2-(2-aminothiazol-4-yl)-2-(Z)-methoxyiminoacetamido.

4. A compound of formula (I) according to any one of claims 1, 2 or 3 in which in the bicyclic substituent R⁴, one of Y or Z is O or S.

5. A compound of formula (I) according to claim 4 wherein R⁴ is selected from dihydrobenzofuranyl, dihydroisobenzofuranyl, dihydrothianaphthyl and

dihydrooxanaphthyl, and such groups may be linked to the cephalosporin nucleus by any of the available ring positions on the 5- or 6- membered heterocyclic ring of R⁴.

6. A compound of formula (I) according to claim 5 wherein R⁴ is unsubstituted dihydrobenzofuran-2-yl.

7. A compound of formula (I) according to claim 1 selected from

(6R,75)-7-[2-(2-Aminothiazol-4-yl)-2-(Z)-methyoxyiminoacetamido]-3-[(S)-dihydrobenzofuran-2-yl]ceph-3-em-4-carboxylic acid, and

(6R,7S)-7-[2-(2-aminothiazol-4-yl)-2-(Z)-methoxyimino-acetamido]-3-[(2S)-2,3-dihydrobenzofuran-2-yl]-1-carba-1-dethiaceph-3-em-4-carboxylic acid.

8. A process for the preparation of a compound of formula (I) according to claim 1, which process comprises treating a compound of formula (II) or a salt thereof:

wherein R¹, CO₂R³, and R⁴ are as hereinbefore defined, wherein any reactive groups may be protected, and wherein the amino group is optionally substituted with a group which permits acylation to take place; with an acid of formula (III) or a N-acylating derivative thereof:

R²OH (III) wherein R² is the acyl group as defined with respect to formula (I) and wherein any reactive groups may be protected; and thereafter, if necessary or desired, carrying out one or more of the following steps: i) removing any protecting groups;

ii) converting the group CO₂R³ into a different group CO₂R³;

iii) converting the group R² into a different group R²;

iv) converting the group X and/or Y and/or Z into a different group X and/or Y and/or Z, for example S into SO or SO₂;

v) converting the product into a salt or ester.

9. A compound of formula (II) as defined in claim 8; or of formula (V):

or of formula (VI):

wherein R²¹ and R²² are amino-protecting groups; or of formula (VII):

or of formula (VIII):

or of formula (IX):

where R³¹ is a group R³ or a group which can be converted into or replaced by R³; or of formula (X):

wherein R is an organic hydrocarbon group; or of formula (XI):

10. A pharmaceutical composition which comprises a compound of formula (I) or a pharmaceutically acceptable salt or in vivo hydrolysable ester thereof and a pharmaceutically acceptable carrier.

11. A compound of formula (I) or a pharmaceutically acceptable salt or in vivo hydrolysable ester thereof, for use as a therapeutic agent.

12. A compound of formula (I) or a pharmaceutically acceptable salt or in vivo hydrolysable ester thereof, for use in the treatment of bacterial infections.

13. A method of treating bacterial infections in humans and animals which comprises the administration of a therapeutically effective amount of an antibiotic compound of the formula (I) or a pharmaceutically acceptable in vivo hydrolysable ester thereof.

14. The use of a compound of formula (I) or a pharmaceutically acceptable salt or in vivo hydrolysable ester thereof, for the manufacture of a medicament for the treatment of bacterial infections.