WO1999006365A1

WO1999006365A1 - Mercaptoacylamino acids as metallo-beta-lactamase inhibitors

Info

Publication number: WO1999006365A1
Application number: PCT/EP1998/004974
Authority: WO
Inventors: John Hargreaves Bateson; Desmond John Best
Original assignee: SmithKline Beecham Ltd
Current assignee: SmithKline Beecham Ltd
Priority date: 1997-07-31
Filing date: 1998-07-21
Publication date: 1999-02-11
Anticipated expiration: 2000-01-31
Also published as: CA2298682A1; EP1000024A1; JP2001512099A

Abstract

Amino acid derivatives of formula (I): R4S-C(R5R6)-C(=CHR3)-CON(R2)-CH(R1)-CO2R, in which the variables are as defined in claim 1, having metallo-$G(b)-lactamase inhibitory properties, useful for the treatment of infections in animals.

Description

MERCAPTOACYLAMINO ACIDS AS METALLO-BETA-LACTAMASE INHIBITORS

This invention relates to chemical compounds having metallo-β-lactamase inhibitory and antibacterial properties The invention also relates to methods for the preparation of such compounds, to pharmaceutical compositions containing them, and to uses thereof.

Metallo-β-lactamases confer resistance to the vast majority of β-lactam based therapies, including carbapenems and jeopardise the future use of all such agents. As a result of the increased use of carbapenems and other β-lactam antibiotics the clinical climate is becoming more favourable for the survival of clinical strains which produce metallo-β-lactamases, and metallo-β-lactamases have now been identified m common pathogens such as Bacteroides fragilis, Klebsiella, Pseudomonas aeruginosa and Serratia marcescens. Emerging knowledge emphasises that metallo-β-lactamases have the potential to present a crisis situation for antimicrobial chemotherapy WO97/30027 (21 August 1997) and WO98/17639 (30 April 1998) disclose certain β-thiopropionyl amino acid derivatives and their use as β lactamase inhibitors.

A novel series of amino acid derivatives have now been discovered, which compounds have metallo-β-lactamase inhibitory properties, and are useful for the treatment of infections in animals. According to the present invention there is provided a compound of formula (I) or a pharmaceutically acceptable salt, solvate or in vivo hydrolysable ester thereof:

R₄S-C(R₅R₆)-C(=CHR3)-CON(R2)-CH(R \ )-CO₂R

(I) wherein:

R is hydrogen, a salt forming cation or an in vivo hydrolysable ester-forming group;

R [ is hydrogen, (C ι_g)alkyl optionally substituted by up to three halogen atoms or by a mercapto, (C ι_6)alkoxy, hydroxy, amino, nitro, carboxy, (C } _ ) alkylcarbonyloxy, (C ] _6)alkoxycarbonyl, formyl or (C 1.5) alkylcarbonyl group, (C3_7)cycloalkyl, (C3_7)cycloalkyl(C2-6)alkyl. (C2-6)^alkenyl, (C2-6)alkynyl, aryl, aryl(C \ _5>alkyl, heterocyclyl or heterocyclyl(C ; _^)alkyl or is selected from

(α)

in which A is a monocyclic aryl or heteroaryl ring and B is a monocyclic aryl, alicyclic or heterocyclic ring, C and D are independently -Zp-(CRgRc;)q- or -(CRgRoJq-Zpwhere p is 0 or 1 , q is 0 to 3 provided that p + q in C is not 0, Rg and R9 are independently hydrogen or (Ci _6)alkyl or together represent oxo and Z is O, NRJQ or S(O)_x where R^j is hydrogen, (Cμg)alkyl or aryl(Cι _g)alkyl and x is 0-2, and wherein C and D are linked ortho to one another on each of rings A and B in formula (b); R2 is hydrogen, (Cι_g)alkyl or aryl(C i.g)alkyl;

R3 is hydrogen, (Cι _5)alkyl optionally substituted by up to three halogen atoms, (C3_7)cycloalkyl, fused aryl(C3_7)cycloalkyl, (C3_7)cycloalkyl(C2-6)^alkyl, (C2- g)alkenyl, (C2-6)al y yl, aryl, aryl-(Cι_5)alkyl, heterocyclyl or heterocyclyl-(Cι_6)alkyl; R4 is hydrogen, or an in vivo hydrolysable acyl group; and R5 and Rg are independently hydrogen and (C _[. )alkyl or together represent (CH2)_r where r is 2 to 5. The compound of formula (I) may exist in a number of isomeric forms, all of which, including E- and Z- geometric isomers and racemic and diastereoisomeric forms, are encompassed within the scope of the present invention.

It is preferred that the stereochemistry at the carbon atom marked * is D-, particularly when R[ is selected from phenyl, (a) or (b). The term 'aryl' includes phenyl and naphthyl, each optionally substituted with up to five, preferably up to three, groups selected from halogen, mercapto, (C ι_6)alkyl optionally substituted by 1 -3 halo, phenyl, phenyl(C ι _6)alkyl, phenyl(C ι _6)alkoxy, (C ι_ g)alkoxy optionally substituted by 1 -3 halo, hydroxy(C ι_.g)alkyl, mercapto(C ι _6)alkyl, hydroxy, CO2 7, N(R7)2 or CON(R7)2 where each R7 is independently hydrogen. (C \ . 5) alkyl or (C 1.5) alkanoyl, OCONH2, nitro, (C \ .5) alkylcarbonyloxy , (C 1. 6)alkoxycarbonyl(C ι_6) alkyl, formyl and (C _j.g) alkylcarbonyl groups.

Each alicyclic ring suitably has from 4 to 7, preferably 5 or 6, ring carbon atoms. Alicyclic rings may be unsubstituted or substituted by, for example, up to five, preferably up to three, groups selected from those mentioned above for substitution on aryl

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 each ring selected from oxygen, nitrogen and sulphur, which rings may be unsubstituted or substituted by, for example, up to three groups selected from those mentioned above for substitution on aryl and. for non-aromatic heterocyclic rings, oxo groups Each heterocyclic ring suitably has from 4 to 7, preferably 5 or 6, ring atoms. The term 'heteroaryl' refers to heteroaromatic heterocyclic ring or ring system, suitably having 5 or 6 ring atoms in each ring A fused heterocyclic ring system may include alicyclic rings and need include only one heterocyclic ring Examples of heterocyclyl groups include pyπdyl, tπazolyl, tetrazolyl, mdolyl, thienyl, isoimidazolyl, thiazolyl, furanyl, tetrahydrofuranyl, quinolmyl, lmidazolidinyl and benzothienyl Compounds within the invention containing a heterocyclyl group may occur in two or more tautometric forms depending on the nature of the heterocyclyl group, all such tautomeπc forms are included within the scope of the invention

When used herein the terms 'lower alkyl', 'lower alkenyl', 'lower alkynyl' 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

In one aspect, examples of R\ optionally substituted alkyl include methyl, isobutyl, carboxymethyl, mercaptomethyl and 1-hydroxyethyl Examples of Rj arylalkyl incude optionally substituted benzyl Examples of R\ aryl include phenyl optionally substituted with up to five, preferably up to three, groups selected from halogen, mercapto, (C \. ) alkyl optionally substituted by 1-3 halo, phenyl, (C ^.g) alkoxy optionally substituted by 1-3 halo. hydroxy(C ι _6)alkyl, mercapto(C ι _6)alkyl, hydroxy, amino, nitro, carboxy, (C j .g) alkylcarbonyloxy, (C _[_5)alkoxycarbonyl, formyl or (C j.g) alkylcarbonyl groups, preferably unsubstituted phenyl Examples of R j heteroaryl include indolyl, thienyl, isoimidazolyl, thiazolyl, furyl and benzothienyl, preferably 2- thienyl. 2-turyl or 2-benzothιenyl

In another preferred aspect when R \ is formula (a), ring A is selected from 2,5- thienyl. 2 5-turyl, 1 ,2-phenyl, 1 ,3-phenyl and 1 ,4-phenyl, ring B is selected from phenyl optionally substituted by one or two hydroxy or by methoxy, dimethylamino, carboxy, nitro, amino, acetylamino, tπfluoromethoxy or benzyloxy, 2-furyl, 2-, 3- or 4-pyπdyl, 1 - tetrazolyl, 2-tetrazolyl 1 -tπazolyl 2-tπazolyl, 2 thienyl and ιmιdazohn-2,5-dιone- l-yl and C is selected from CH2, O or OCH2. In a more preferred aspect R\ is 4- benzyloxyphenyl 3- or 4-substituted in the benzyl group by asubstituent listed above for phenyl or naphthyl. Preferred substituents are carboxy or dimethylamino.

In a further preferred aspect, when R_j is formula (b), rings A and B are both phenyl, C is O, CH2 or NR JQ and D is a bond (p+q=0).

Preferred examples of R\ include phenyl, (5-benzyl)thien-2-yl, (5-benzyl)furan-2- yl, 5-(l-tetrazolylmethyl)thien-2-yl, 5-(2-tetrazolylmethyl)thien-2-yl, 5-(imidazolin-2,5- dione- 1 -ylmethyl)thien-2-yl, 5-( 1 -tπazolylmethyl)thιen-2-yl, 5-(2-triazolylmethyl)thιen- 2-yl, 3-phenoxyphenyl, 2-phenoxyphenyl, 4-phenoxyphenyl, 3-(4-hydroxybenzyl)phenyl, 3-(4-methoxybenzyl)phenyl, 4-benzyloxyphenyl, 4-(2-thienylmethyloxy)phenyl, 1- fluorenyl, 3-(N-ethylcarbazolyl), 4-hydroxybenzyloxy-4-phenyl, 4-methoxybenzyloxy-4- phenyl, 4-dimethylaminobenzyloxy-4-phenyl, 4-carboxybenzyloxy-4-phenyl, 3- carboxybenzyloxy-4-phenyl, (2-pyridyl)-methoxy-4-phenyl, (4-pyridyl)-methoxy-4- phenyl, 5-[ 1 -(4-carbamoyltriazoly l)-methyl]-thien-2-yl, 5-[ 1 -(4-carboxytriazoly 1)- methyl]-thien-2-yl, (2-furyl)-methoxy-4-phenyl, dibenzofuranyl, 4-(4- acetamidobenzyloxy)phenyl, 3-(3-carboxybenzyloxy)phenyl, 3-(4- carboxybenzyloxy)phenyl, 4-(3-aminobenzyloxy)phenyl, 4-(4- dimethylaminobenzyloxy)phenyl, 4-(4-benzyloxybenzyloxy)phenyl and 4-(4- trifluoromethoxybenzyloxy)phenyl. Suitable examples of R2 include hydrogen, methyl and benzyl.

R2 is preferably hydrogen.

Examples of R3 include methyl, isobutyl, phenyl-(CH2) i-5, 1-ιndanyl, 3,4- dihydroxybenzyl, 4-hydroxycarbonyl-phenylethyl, 2-trifluoromethylquinolin-6-yl, 4- difluoromethoxy-phenylethyl, 3-dιfluoromethoxyphenylethyl and 3-methyl-2,4,5- tπcarbonyhmιdazolidin- 1-yl.

Preferably R3 is aryl or aryl-(C ι_6)alkyl. R3 is most preferably phenyl. Examples of R₄ include hydrogen, lower alkylcarbonyl, optionally substituted benzoyl or optionally substituted phenyl lower alkyl carbonyl, more preferably hydrogen and acetyl. R₄ is preferably hydrogen.

R₅ and R. are preferably independently hydrogen or methyl Suitable pharmaceutically acceptable salts of the carboxylic acid group of the compound of formula (I) (or of other carboxylic acid groups which may be present as optional substituents) include those in which R is a metal ion e.g. aluminium salts, alkali metal salts (e g. sodium, lithium or potassium salts), alkaline earth metal salts (e.g calcium or magnesium salts), ammonium salts, and substituted ammonium salts, for example those with lower alkylamines (e g tπethylamine), hydroxy-lower alkylamines (e.g. 2-hydroxyethylamine), bis-(2-hydroxyethyl)amine, tris-(2-hydroxyethyl) amine, lower-cycloalkylamines (e.g. dicyclohexyl-amine), or with procaine, dibenzylamine, ,N-dibenzyl- ethylenediamine, 1-ephenamine, N-methylmorpholine, N-ethylpiperidine, N-benzyl-β-phenethylamine, dehydroabietylamine, ethylenediamine, ,N'-bishydroabietylethylenediamine, bases of the pyridine type (e.g. pyridine, collidine and quinoline), and other amines which have been or can be used to form quaternary ammonium salts.

Pharmaceutically acceptable salts may also be acid addition salts of any amino or substituted amino group(s) that may be present as optional substituents on the compound of formula (I), or of a heterocyclic group ring nitrogen atom. Suitable salts include for example hydrochlorides, sulphates, hydrogen sulphates, acetates, phosphates etc. and other pharmaceutically acceptable salts will be apparent to those skilled in the art. Suitable addition salts are the hydrochlorides and hydrogen sulphates. Preferred salts are sodium salts. Examples of suitable pharmaceutically acceptable in vivo hydrolysable ester- forming groups R include those forming esters which break down readily in the human body to leave the parent acid or its salt. Suitable groups of this type include those of part formulae (i), (ii), (iii), (iv) and (v): R^a

(i)

^■CH-O.CO.R

^■ F -N< _Re

(ϋ)

^■ CH, — OR'

(iϋ)

wherein R^a is hydrogen, (C \. ) alkyl, (C3.7) cycloalkyl, methyl, or phenyl, R^D is (C \. ) alkyl, (C j.g) alkoxy, phenyl, benzyl, (C3.7) cycloalkyl, (C3.7) cycloalkyloxy, (C \. ) alkyl (C3.7) cycloalkyl, 1 -amino (Ci .g) alkyl, or l-(C \. alkyl)amιno (C 1.5) alkyl, or R^a and R^D together form a 1 ,2-phenylene group optionally substituted by one or two methoxy groups, R^c represents (Ci .g) alkylene optionally substituted with a methyl or ethyl group and R^ and R^e independently represent (C ι_6) alkyl, R^ represents (C \. ) alkyl, R^§ represents hydrogen or phenyl optionally substituted by up to three groups selected from halogen, (C 1.5) alkyl, or (C\. ) alkoxy, Q is oxygen or NH, Rⁿ is hydrogen or (Cj.g) alkyl, R¹ is hydrogen, (C \. ) alkyl optionally substituted by halogen, (C2-6) alkenyl, (C \.β) alkoxycarbonyl, aryl or heteroaryl, or Rⁿ and R¹ together form (C\._β) alkylene, RJ represents hydrogen, (C i .g) alkyl or (C\. ) alkoxycarbonyl, and R^ represents (C g) alkyl, (C g) alkoxy, (Ci .g) alkoxy(Cj_6)alkoxy or aryl

Examples of suitable in vivo hydrolysable ester-forming groups include, for example, acyloxyalkyl groups such as acetoxymethyl, pivaloyloxymethyl, α-acetoxyethyl, α-pivaloyloxyethyl, l-(cyclohexylcarbonyloxy)prop-l-yl, and ( l-amιnoethyl)carbonyloxymethyl, alkoxycarbonyloxyalkyl groups, such as ethoxycarbonyloxymethyl, α-ethoxycarbonyloxyethyl and propoxycarbonyloxyethyl, dialkylaminoalkyl especially di-loweralkylamino alkyl groups such as dimethylaminomethyl, dimethylammoethyl, diethylaminomethyl or diethylammoethyl, 2-(alkoxycarbonyl)-2-alkenyl groups such as 2-(ιsobutoxycarbonyl)pent-2-enyl and 2-(ethoxycarbonyl)but-2-enyl, and lactone groups such as phtha dyl and dimethoxyphtha dyl

A further suitable pharmaceutically acceptable in vivo hydrolysable ester-forming group is that of the formula

wherein R^ is hydrogen, C [, alkyl or phenyl

R is preterably hydrogen

It w ill be appreciated that also included within the scope of the invention are pharmaceutically acceptable salts and pharmaceutically acceptable esters, including in wvo hydrolysable esters, of any carboxy groups that may be present as optional substituents in compounds of formula (I)

Some compounds of formula (I) mav be crystallised or recrystallised from solvents such as organic solvents In such cases solvates mav be formed This invention includes within its scope stoichiometric solvates including hydrates as well as compounds containing variable amounts of solvents such as water that may be produced by processes such as lyophilisation. Compounds of formula (I) may be prepared in crystalline form by for example dissolution of the compound in water, preferably in the minimum quantity thereof, followed by admixing of this aqueous solution with a water miscible organic solvent such as a lower aliphatic ketone such as a di-(C ι_6) alkyl ketone, or a (C\. ) alcohol, such as acetone or ethanol.

The compounds of formula (I) are metallo-β-lactamase inhibitors and are intended for use in pharmaceutical compositions. Therefore it will readily be understood that they are preferably each provided in substantially pure form, for example at least 60% pure, more suitably at least 75% pure and preferably at least 85% pure, 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 59% of a compound of the formula (I) or salt, solvate or in vivo hydrolysable ester thereof.

The present invention also provides a process for the preparation of a compound of formula (I) as defined above, which comprises reacting a compound of formula (II)

Y-C(R₅ ^,R₆ C(=CHR'3^,)-CO-W

(II) with a compound of formula (III)

X ^[-CH(R. ')-CO R^x (III) wherein W is a leaving group, Y is R S or a group convertible thereto, R^x is R or a carboxylate protecting group, χ l is N„ or NHR ' and R ' R \ RJ R₄', Rr and Rg' are R. , R₀, Ry R₄, R₅ and R, or groups convertible thereto, wherein R, R, , R , R,, R₄. R^ and R, are as defined in formula (I), and thereafter, where necessary, converting Y into R₄'S, R\ R _j', R_?', R₃' R₄\ R. and/or R₆ into R. R R_?, R_y R₄, R₅ and/or R_fi and optionally inter-converting R, R j , R , R3, R4, R_<- and/or R,.

Suitable ester-forming carboxyl-protecting groups R^x other than in vivo hydrolysable ester forming groups are those which may be removed under conventional conditions. Such groups for R^λ include methyl, ethyl, benzyl, p-methoxybenzyl, benzoylmethyl, p-nitrobenzyl, 4-pyridylmethyl. 2,2.2-tπchloroethyl, 2,2,2-tribromoethyl. t-butyl, t-amyl, allyl, diphenylmethyl, triphenylmethyl, adamantyl, 2-benzyloxyphenyl, 4-methylthiophenyl, tetrahydrofur-2-yl. tetrahydropvran-2-vl, pentachlorophenyl. acetonyl, p-toluenesulphonylethyl, methoxymethyl, a silyl (such as trimethylsilyl), stannyl or phosphorus- containing group or an oxime radical of formula -N=CHRj2 where R^2 is axyl or heterocyclyl, or an in vivo hydrolysable ester radical such as defined above. Certain compounds of formulae (II) and (III) may 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 if required without disruption of the remainder of the molecule.

Examples of amino protecting groups include (C\. ) alkanoyl; benzoyl; benzyl optionally substituted in the phenyl ring by one or two substituents selected from (C1 -4) alkyl, (C 1-4) alkoxy, trifluoromethyl, halogen, or nitro; (C1 -4) alkoxycarbonyl; benzyloxycarbonyl or trityl substituted as for benzyl above; allyloxycarbonyl, trichloroethoxycarbonyl or chloroacetyl.

When χ in the compound of formula (III) is NHR-', the compound is preferably presented as the anion prepared by treatment of the amine with an organic base such as triethylamine, pyridine or morpholine, and suitable examples of the leaving W group in the compound of formula (II) include halo such as chloro and mixed sulphonic anhydrides such as those where W is methanesulphonyloxy, toluene-p-sulphonyloxy or trifluoromethanesulphonyloxy in mixed sulphonic anhydrides. The compound of formula (III) may be presented as the trimethylsilyl ester hydrochloride.

The reaction of the compounds of formula (II) and (UI) is preferably carried out at ambient temperature, for example 15-25°C, in an inert solvent such as chloroform tetrahydrofuran, dichloromethane, dioxan or dimethylformamide.

When X in the compound of formula (III) is N„, the leaving group W in the compound of formula (II) is preferably SH and the reaction is carried out at elevated temperature, such as at reflux, in an inert solvent such as toluene.

Examples of Y convertible into R 'S include halo such as bromo which may be displaced by thiobenzoic acid or thioacetic acid

Examples of groups R ' R ', R ' R ' convertible to R. , R R^ and R₄ include those where any carboxy or amino group is protected by carboxy or amino protecting groups. Additionally, examples of R \ convertible to R \ include those containing ring A substituted by hydroxy which can generate R _j groups of formula (a) where linker C is of the form -0-(CRgRc)q- and where ring B is an aromatic ring or heterocycle, optionally substituted This may be effected, for example, by alkylation of the hydroxy substituent with a benzyl bromide derivative or with a heterocyclylalkyl bromide derivative.

Alternatively, the hydroxy group may be coupled with a benzyl alcohol derivative or with a heterocyclylalkyl alcohol derivative in established ways, for example in the presence of diethyl azodicarboxylate and triphenylphosphine (Mitsunobo et al, Bull. Chem. Soc. Jpn., 1967, 40, 2380).

R₄' in the compound of formula (II) is preferably other than hydrogen, such as an acyl protecting group as described above for carboxy protecting groups, for example acetyl.

The acid derivative of formula (II) is preferably prepared from the corresponding free acid by treatment with strong base such as sodium hydride followed by a source of the anion leaving group W, such as oxalyl chloride where W is Cl, or hydrogen sulphide where W is SH. The initial product of the reaction of compounds of formulae (II) and (III) is a compound of formula (IV):

Y-C(R5^'R₆')-C(=CHR₃ ^,)-CON(R ')-CH(R₁')-Cθ R^x

(IV)

wherein the variables are as defined in formulae (II) and (III). Novel intermediates of formula (IV) wherein R^x is other than R when R, \ R₂', R3', R₄', Rs' ^and R5' are R_j, R₂, R₃, R_4> R5 and R also form part of the invention. In one aspect Y is R₄'S Compounds of formula (IV) where R 1 ' is -( A)-OH or -(A)-CH2OH may be converted to compounds with R\ as defined in (a) where C is -OCH2- or -CH2O- using alcohols of formula (B')-CH2OH or (B')-OH, respectively under Mitsunobu conditions (Synthesis 1981, 1), using a coupling reagent such as tπphenyl phosphine and diethyl azodicarboxylate. B' is B or a group convertible thereto, for example where a carboxy or amino substituent on B is protected.

When R^x is other than hydrogen, the carboxy group -COOR^x may be deprotected, that is to say, converted to a free carboxy, carboxy salt or carboxy ester group -COOR in a conventional manner, for example as described in EP0232966A.

Simultaneous deprotection of -COOR^x and R4'S and any protecting group in R \ may be achieved by treatment with sodium sulphide nonahydrate in water/methanol When it is desired to obtain a free acid or salt of the preferred isomer of the formula (I) from an lsomeπc mixture, this may be effected by chromatographic separation of the isomers of the product. Where this is an ester and/or where R is other than hydrogen, the desired isomer may then be deprotected to give the corresponding free acid or salt In some cases, however, it has been found particularly convenient first to deprotect the lsomeπc mixture to give an lsomeπc mixture of the free acid or salt of formula (I), followed by fractional recrystallisation to give the desired acid or salt isomer Where *D isomer of formula (I) is desired, it is preferred to use the corresponding *D isomer of the intermediate of formula (III)

A carboxyl group may be regenerated from any of the above esters by usual methods appropriate to the particular R^x 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 For example, in the case of acetonyl, by hydrolysis in acetonitπle with 0 1M aqueous potassium hydroxide solution

Pharmaceutically acceptable salts may be prepared from such acids by treatment with a base, after a conventional work-up if necessary Suitable bases include sodium hydrogen carbonate to form sodium salts

Crystalline forms of the compounds of formula (I) where R is a salt forming cation may for example be prepared by dissolving the compound (I) in the minimum quantity of water, suitably at ambient temperature, then adding a water miscible organic solvent such as a (Cj.g) alcohol or ketone such as ethanol or acetone, upon which crystallisation occurs and which may be encouraged for example by cooling or tπturation

Compounds of formulae (II) and (III) are known compounds or may be prepared by procedures analogous to those described in the prior art

Compounds of formula (II) may be prepared from the readily available α-substituted cinnamic acids (IIA)

R₃'CH=C(CR₅ R₆'H)-CO₂H (IIA) for example, by bromination of an α-methylcinnamic acid in carbon tetrachloπde using N-bromosuccmimide under tungsten lamp illumination to give an α- bromomethylcinnamic acid of formula (IIB) R3'CH=C(CR₅'R₆'Br)-CO₂H (IIB)

Compounds of formula (II) where Y is R S may be obtained from compounds of formula (II) where Y is a group convertible into R₄'S such as halo, e g bromo, which may be displaced by thiobenzoic acid or thioacetic acid in the presence of an amine such as tπethylamine Compounds of formula (III) may be prepared by procedures analogous to those described in the prior art references listed above

Novel compounds of formula (III), which are -amino acids, may be prepared by anv conventional amino acid synthesis, for example from the corresponding α-keto ester R _j -CO-CO R via the oxime ester R ₍ -C(=N-OH)-CO₀R^X by conventional routes The α-keto ester is obtainable from the R ₍ -H, R . -CH₉CO₉R or R , '-CO₉R^x by routine methods (J March, vide infra) Alternatively the compounds of formula (III) may be prepared from the aldehyde intermediate R -CHO by the Strecker synthesis [cf Advanced Organic Chemistry; Mechanism and Structure, 4th Edn, by J. March, Section 6-50, p.965; 1992, John Wiley and Sons Inc, ISBN 0-471-60180-2] or by the method of Monianari et al. (Synthesis 1979, 26). The invention also extends to novel compounds of formula (III). A compound of formula (I) or a salt, solvate or in vivo hydrolysable ester thereof, may be administered in the form of a pharmaceutical composition together with a pharmaceutically acceptable carrier and the invention also relates to such compositions. The compounds of formula (I) have metallo-β-lactamase inhibitory properties, and are useful for the treatment of infections in animals, especially mammals, including humans, in particular in humans and domesticated (including farm)animals. The compounds may be used, for example, for the treatment of infections of, inter alia, the respiratory tract, the urinary tract, and soft tissues and blood, especially in humans.

Accordingly, the invention further provides a method of treatment of bacterial infections in humans or animals which comprises administering, in combination with a β- lactam antibiotic, a therapeutically effective amount of a compound of formula (I) or a pharmaceutically acceptable salt, solvate or in vivo hydrolysable ester thereof.

The compounds may be used in combination with an antibiotic partner for the treatment of infections caused by metallo-β -lactamase producing strains, in addition to those infections which are subsumed within the antibacterial spectrum of the antibiotic partner. Metallo-β-lactamase producing strains include:- Pseudomonas aeruginosa, Klebsiella pneumoniae, Xanthomonas maltophilia, Bacteroides fragilis, Serratia marcescens, Bacteroides distasonis, Pseudomonas cepacia, Aeromonas hydrophila, Aeromonas sobria, Aeromonas salmonicida, Bacillus cereus, Legionella gormanii and Flavobacterium spp.

It is generally advantageous to use a compound according to the invention in admixture or conjunction with a carbapenem, penicillin, cephalosporin or other β-lactam antibiotic and that can result in a synergistic effect, because of the metallo-β-lactamase inhibitory properties of the compounds according to the invention. In such cases, the compound of formula (I) and the β-lactam antibiotic can be administered separately or in the form of a single composition containing both active ingredients as discussed in more detail below. 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 compounds of formula (I) are particularly suitable for parenteral administration.

The compounds of formula (I) may be formulated for administration in any convenient way for use in human or veterinary medicine, by analogy with other antibiotics and other β-lactam antibiotic/β-lactamase inhibitor combinations. The composition may be formulated for administration by any route, such as oral, topical or parenteral. 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 m unit dose presentation form, and may contain conventional excφients such as binding agents, for example syrup, acacia, gelatin, sorbitol, tragacanth, or polyvinylpyrolhdone, fillers, for example lactose, sugar, maize-starch, calcium phosphate, sorbitol or glycme, tabletting 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, if desired, conventional flavouring or colouring agents Suppositories will contain conventional suppository bases, e g cocoa-butter or other glyceπde

For parenteral administration, fluid unit dosage forms are prepared utilizing the compound and a sterile vehicle, water being preferred The compound, depending 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

- n - Advantageously, agents such as a local anaesthetic, preservative and buffering 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 sterilisation 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 toxicological effects are indicated when a compound of formula (I) or a pharmaceutically acceptable salt thereof is administered in the above-mentioned dosage range.

A composition according to the invention may comprise a compound of formula (I) or a salt, solvate or in vivo hydrolysable ester thereof together with one or more additional active ingredients or therapeutic agents, for example a β-lactam antibiotic such as a carbapenem, penicillin or cephalosporin or pro-drug thereof. Carbapenems, penicillins, cephalosporins and other β-lactam antibiotics suitable for co-administration with the compound of formula (I) - whether by separate administration or by inclusion in the compositions according to the invention - include both those known to show instability to or to be otherwise susceptible to metallo-β-lactamases and also those known to have a degree of resistance to metallo-β-lactamases. A serine β-lactamase inhibitor such as clavulanic acid, sulbactam or tazobactam may also be co-administered with the compound of the invention and the β-lactam antibiotic, either by separate administration, or co-formulation with one, other or both of the compounds of the invention and the β-lactam antibiotic.

Examples of carbapenems that may be co-administered with the compounds according to the invention include imipenem, meropenem, biapenem, BMS 18 1 139 ([4R- [4alpha,5beta,6beta(R*)]]-4-[2-[(aminoiminomethyl)amino]ethyl]-3-[(2-cyanoethyl)thio]- 6-( l -hydroxyethyl)-7-oxo- l-azabicyclo[3.2.0]hept-2-ene-2-carboxylic acid), BO2727 ([4R- 3[3S*,5S*(R*)],4alpha,5beta,6beta(R*)]]-6-(l-hydroxyethyl) -3-[[5-[l-hydroxy-3- (methylamιno)propyl]-3-pyrrohdιnyl]thιo]-4-methyl-7-oxo-l-azabιcyclo[3 2 0] hept-2-ene- 2-carboxyhc acid monohydrochloπde), ER35786 ((1R, 5S, 6S)-6-[l(R)-Hydroxymethyl]-2- [2(S)-[l(R)-hydroxy-l-[pyrrohdιn-3(R)-yl] methyl]pyrrohdin-4(S)-ylsulfanyl]- l -methyl- 1- carba-2-penem-3-carboxyhc acid hydrochloπde) and S4661 ((lR,5S,6S)-2-[(3S,5S)-5- (sulfamoylaminomethyl) pyrrohdιn-3-yl]thιo-6-[(lR)-l-hydroxyethyl]- l-methylcarbapen- 2-em-3-carboxyhc acid)

Examples of penicillins suitable for co-administration with the compounds according to the invention include benzylpenicil n, phenoxymethylpemcillin, carbenicil n, azidocilhn, propicil n, ampicillin, amoxycillin, epicilhn, ticarcil n, cyclacil n, pirbenicil n, azlocilhn, mezlocillm, sulbenicil n, piperacil n, and other known penicillins The penicillins may be used in the form of pro-drugs thereof, for example as in vivo hydrolysable esters,for example the acetoxymethyl, pivaloyloxymethyl, α-ethoxycarbonyloxyethyl and phthahdyl esters of ampicillin. benzylpenicilhn and amoxycillin, as aldehyde or ketone adducts of penicillins containing a 6-α-amιnoacetamιdo side chain (for example hetacilhn, metampicilhn and analogous derivatives of amoxycillin), and as α-esters of carbenicilhn and ticarcilhn, for example the phenyl and indanyl α-esters

Examples of cephalosponns that may be co-administered with the compounds according to the invention include, cefatπzme, cephaloπdme, cephalothin, cefazolin cephalex , cephacetπle, cephapiπn cephamandole nafate, cephradme, 4-hydroxycephalexιn, cephaloglycin. cefoperazone, cefsulodin, ceftazidime, cefuroxime cefmetazole, cefotaxime, ceftnaxone and other known cephalosponns, all of which may be used in the form of pro-drugs thereof Examples of β-lactam antibiotics other than penicillins and cephalosponns that mav be co-administered with the compounds according to the invention include aztreonam, latamoxef (Moxalactam - Trade Mark), and other known β-lactam antibiotics, all of which may be used in the form of pro-drugs thereof

Particularly suitable penicillins for co-administration with the compounds according to the invention include ampicillin amoxycillin, carbenicilhn, piperacilhn, azlocilhn mezlocillm, and ticarcilhn Such penicillins may be used in the form of their pharmaceutically acceptable salts, for example their sodium salts Alternatively, ampicillin or amoxycillin may be used in the form of fine particles of the zwitteπonic form (generally as ampicillin tπhydrate or amoxN Cilhn tπhydrate) for use in an injectable or infusable suspension, tor example, in the manner hereinbefore described in relation to the compounds according to the invention Amoxycillin, for example in the form of its sodium salt or the tπhydrate, is particularly preferred for use in synergistic compositions according to the invention

Particularly suitable cephalosponns for co-administration with the compounds according to the invention include cefotaxime and ceftazidime, which may be used in the form of their pharmaceutically acceptable salts, for example their sodium salts

A compound of formula (I) may be administered to the patient in conjunction with a β-lactam antibiotic such as a carbapenem, penicillin or cephalosporin in a synergistically effective amount

The compounds of formula (I) may suitably be administered to the patient at a daily dosage of from 0 7 to 50 mg/kg of body weight For an adult human (of approximately 70 kg body weight), from 50 to 3000 mg, preferably from 100 to 1000 mg, of a compound according to the invention may be administered daily, suitably in from 1 to 6, preferably from 2 to 4, separate doses Higher or lower dosages may, however, be used in accordance with clinical practice When the compositions according to the invention are presented in unit dosage form, each unit dose may suitably comprise from 25 to 1000 mg, preferably from 50 to 500 mg, of a compound according to the invention Each unit dose may, for example, be 62 5, 100, 125, 150, 200 or 250 mg of a compound according to the invention

When the compounds of formula (I) are co-adrmmstered with a penicillin, cephalosporin, carbapenem or other β-lactam antibiotic, the ratio of the amount of the compound according to the invention to the amount of the other β-lactam antibiotic may vary within a wide range The said ratio may, for example, be from 100 1 to 1 100, more particularly, it may, for example, be from 2 1 to 1 30

The amount of carbapenem, penicillin, cephalosporin or other β-lactam antibiotic in a synergistic composition according to the invention will normally be approximately similar to the amount in which it is conventionally used per se, for example from about 50 mg, advantageously from about 62 5 mg, to about 3000 mg per unit dose, more usually about 125, 250, 500 or 1000 mg per unit dose

The present invention further provides a compound of formula (I) or a pharmaceutically acceptable salt, solvate or in vivo hvdrolvsable ester thereof for use in the treatment of bacterial infections

The present invention also includes the use of a compound of formula (I) or a pharmaceutically acceptable salt solvate or in

hvdrolvsable ester thereof in the manufacture of a medicament for the treatment of bacterial infections The present invention also includes the use of a compound of formula (I) or a pharmaceutically acceptable salt solvate or in hvdrolvsable ester thereof as a metallo-β-lactamase inhibitor All the above compositions and methods may optionally include a serine β- lactamase inhibitor as above described.

The compounds of the present invention are active against metallo-β-lactamase enzymes produced by a wide range of organisms including both Gram-negative organisms and Gram-positive organisms.

The following Examples illustrate compounds useful in the present invention, and intermediates in their preparation. (All temperatures are in °C).

EXAMPLES Description 1 (E)-α-Bromomethylcinnamic acid

A solution of α-methylcinnamic acid (Aldrich) (1.62g, lOmmol) and N- bromosuccinimide (1.78g, lOmmol) in carbon tetrachloride (20ml) was refluxed under illumination (150W; tungsten lamp) for 30 minutes. The solution was cooled to room temperature, filtered and evaporated to give the title compound (0.55g, 23%); δ_H (CDC1₃) 4.42 (2H, s), 7.40-7.70 (5H, m), 7.97 ( 1H, s); m/z (ΕS-) 239,241 (M-H).

Description 2

(E)-α-Acetylthiomethylcinnamic acid

A solution of (E)-α-bromomethylcinnamic acid (540mg) in ethyl acetate (20ml) was treated with triethylamine (0.74ml) and thiolacetic acid (0.18ml). After lh at room temperature the solution was washed with 1M hydrochloric acid (15ml), water (3 x 15ml), brine (15ml) and was dried (MgSO4) and evaporated to yield the title compound (590mg, 100%); δπ (CDCI3) 2.35 (3H, s), 4.09 (2H, s), 7.43 (5H, m), 7.95 (1H, s); m/z (ΕS") 235 (M-H).

Description 3 Methyl /?-hydroxy-[D]-phenylglycinate

The title compound was prepared from D-p-hydroxyphenylglycine by stirring in methanol, presaturated with hydrogen chloride gas, overnight. The methanol was removed under reduced pressure and the residue partitioned between ethyl acetate and an excess of saturated NaHCO3 solution. The organic layer was washed with water and dried and solvent removed.

Description 4 N-(E-α-AcetyIthiomethyI-3-ρhenylprop-2-enoyI)-/?-hydroxy-[D]- phenylglycinate

A solution of (E)-α-acetylthiomethylcinnamic acid (Description 2, 1 mmol) in dichloromethane (5ml) at room temperature was treated with oxalyl chloride (0.3ml) and N,N-dimethyl-formamide (1 drop). After 30 minutes, the solution was evaporated and then re-evaporated from dichloromethane (2 x 5ml). The acid chloride in dichloromethane (5ml) was added dropwise to an ice-cold solution of methyl p-hydroxy-[D]-phenylglycinate (Description 3, lmmol) and triethylamine (0.35ml, 2.5mmol) in dichloromethane (15ml). The reaction mixture was warmed to room temperature and stirred for 2h. The mixture was washed with water (2 x 10ml), brine (10ml), was dried (MgSO4) and evaporated. Flash-chromatography on silica, eluting with 10-25% ethyl acetate in hexane gave the title compound (0.5mmol), m/z (ΕS+) 400 (MH⁺).

Description s

N-(E-α-Acetylthiomethyl-3-phenylprop-2-enoyl)-p-(/n-methoxycarbonyl)- benzyloxyphenylglycine methyl ester

To a stirred solution of the p-hydroxyphenylglycine derivative from Description 4, (0.5mmol) in dry tetrahydrofuran was added triphenylphosphine (O.όmmol) and m- methoxycarbonylbenzyl alcohol (O.όmmol), followed by diethyl azodicarboxylate (O.όmmol). The yellow solution was stirred at room temperature for 15min and then diluted with ethyl acetate. The organic layer was washed with water and dried (MgSOJ. The solvent was removed to afford a gum which was chromatographed on silica gel. Εlution with 25% ethyl acetate in hexane the title compound as a gum (235mg;0.42mmol), ΕIMS M⁺ 547.

Description 6 D-Phenylglycine methyl ester

Acetyl chloride (4ml) was added cautiously and dropwise to methanol (20ml) at 0°C over 2 minutes. When the addition was completed, D-phenylglycine ( l g, 5.9 mmol, Aldrich) was introduced in a single portion. The mixture was stirred until dissolved then allowed to stand at RT for 24 hours. The solvent was evaporated then coevaporated twice from toluene to afford D-Phenylglycine methyl ester hydrochloride as a white crystalline solid in quantitative yield. δ_H (CD_jOD) 3.80 (3H, s, MeO), 5. 19 ( 1 H, s, HCN), 7.42-7.50 (5H, m, Ar-H).

The title compound was obtained from the hydrochloride by treatment with triethylamine Description 7

Methyl [D]-N-(E-α-acetylthiomethyl-3-phenylprop-2-enoyl)phenylglycinate

A solution of (E)-α-acetylthiomethylcinnamic acid (Description 2) (236mg, lmmol) in dichloromethane (5ml) at room temperature was treated with oxalyl chloride (0.3ml) and N,N-dimethyl-formamide (1 drop). After 30 minutes, the solution was evaporated and then re-evaporated from dichloromethane (2 x 5ml). The acid chloride in dichloromethane (5ml) was added dropwise to an ice-cold solution of methyl D-phenylglycinate (Description 6) (202mg, lmmol) and triethylamine (0.35ml, 2.5mmol) in dichloromethane ( 15ml). The reaction mixture was warmed to room temperature and stirred for 2h. The mixture was washed with water (2 x 10ml), brine (10ml), was dried (MgSO4) and evaporated. Flash-chromatography on silica, eluting with 10-25% ethyl acetate in hexane gave the title compound (194g, 51%); δ[(CT)3)2SO] 2.31 (3H, s), 3.65 (3H, s), 3.98 (2H, s), 5.53 (1H, s, J = 7.0Hz), 7.38 (10H, m), 8.96 (1H, d, J = 7Hz); m/z (ΕS+) 384 (MH+).

Example 1 N-(E-α-Mercaptomethyl-3-phenyl-prop-2-enoyI)-p-(m-carboxy)-benzyloxy-[D]- phenylglycine

The methyl ester (lOOmg; 0.2mmol) from Description 5 was suspended in methanol (3ml) and treated with a solution of sodium sulphide nonahydrate (200mg; 0.84mmol) in water (2ml). The suspension was stirred under argon for 3 hours. The reaction mixture was washed with ethyl acetate and the aqueous layer was acidified by addition of 5M hydrochloric acid solution (10 drops) and then extracted with ethyl acetate. The organic layer was washed with water and dried (MgSO . Removal of the solvent afforded title compound as a foam (0. lmmol), APCI [M-H]^" 476.

Example 2

N-(E-α-Mercaptomethyl-3-phenylprop-2-enoyl)-[D]-phenylglycine

A solution of methyl [D]-N-(£-α-acetylthiomethyl-3-phenylprop-2- enoyl) phenylglycinate (Description 7) ( 185mg) in methanol (5ml) at room temperature was treated with a solution of sodium sulphide nonahydrate (350mg) in water (2.5ml). After 40 minutes, the solution was diluted with ethyl acetate (25ml), was washed with 1 M hydrochloric acid ( 10ml), water (2 x 10ml), and then dried (MgSO4) and evaporated. The residue was flash-chromatographed on silica, eluting with 5% grading to 10% methanol in dichloromethane to give the title compound (1 14mg, 72%); δ[CD₃)₂SO] 3.53 (2H, s), 5.22 (1H, d, J 6.8Hz), 7.05-7.55 (1H, m), 8.38 (1H, d, J = 6.8Hz); m/z (ES") 326 (M-H).

BIOLOGICAL ACTIVITY

I_;o screen

The inhibitory activity of the compounds of the invention is measured in 25mM PIPES pH 7 buffer at 10 concentrations (1000, 333, 111 , 37, 12.3, 4.1, 1.4, 0.46, 0.15 and 0.05μM) at 37°C using nitrocefin (91μM final concentration) as the reporter substrate. The assays are performed with a 5 minute preincubation of enzyme and inhibitor and are conducted in the presence of added zinc sulphate (Zn^2* lOOμM, final concentration). The methodology is described in detail in the following references: Payne et al (1991), I. Antimicrob. Chemother., 28:255; Payne et al (1994), Antimicrob. Agents and Chemother., 38:767.

Results

Compounds of the invention may be tested and found to inhibit Bacteroides fragilis CfiA metallo-β-lactamase with 150 values <1000μM. The compound of the Example 2 exhibits ah I₅₀ value against B. fragilis CfiA metallo-β-lactamase of <lμM and exhibited significant inhibition of the Stenotrophomonas maltophilia L-l (formerly Xanthomonas maltophilia L-l) and Bacillus cereus II metallo-β-lactamases, with I₅₀ values in the range 0.2 - 14μM.

Antibacterial activity of compounds of the invention in combination with the carbapenem antibiotic, meropenem, against the Bacteroides fragilis 262 strain, which produces CfiA metallo-β-lactamase:-

[MIC = minimum inhibitory concentration (μg/ml)] Antibacterial activity of meropenem was potentiated as follows:-

MIC (μg/ml) of meropenem alone: >128

Claims

1. A compound of formula (I) or a pharmaceutically acceptable salt, solvate or in vivo hydrolysable ester thereof:

* R4S-C(R₅R₆)-C(C=HR3)-CON(R2)-CH(Rι)-CO₂R

(I) wherein:

R is hydrogen, a salt forming cation or an in vivo hydrolysable ester-forming group; Rj is hydrogen, (Cι .g)alkyl optionally substituted by up to three halogen atoms or by a mercapto, (Ci _6)alkoxy, hydroxy, amino, nitro, carboxy, (C\ . ) alkylcarbonyloxy, (Cι _6)alkoxycarbonyl, formyl or (Ci .g) alkylcarbonyl group, (C3_7)cycloalkyl, (C3_7)cycloalkyl(C2-6)alkyl, (C2-6)^alkenyl, (C2-6)^alkYⁿy¹ _' ^aryl. aryl(Cι_6)alkyl, heterocyclyl or heterocyclyl( r is selected from

(α)

(b) in which A is a monocyclic aryl or heteroaryl ring and B is a monocyclic aryl, alicyclic or heterocyclic ring, C and D are independently -Zp-(CRgCRc)q- or -(CRgCRαJq-Zpwhere p is 0 or 1, q is 0 to 3 provided that p + q in C is not 0, Rg and R9 are independently hydrogen or (C[.β)alky\ or together represent oxo and Z is O, NR10 or S(O)_x where R Q is hydrogen, (C ι.g)alkyl or aryl(C ι_6)alkyl and x is 0-2, and wherein C and D are linked ortho to one another on each of rings A and B in formula (b);

R2 is hydrogen, (C j.6)alkyl or aryl(C i_g)alkyl;

R3 is hydrogen, (C ι_g)al yl optionally substituted by up to three halogen atoms,

(C3_7)cycloalkyl, fused aryl(C3_7)cycloalkyl, (C3_7)cycloalkyl(C2-6)alkyl, (C2- ζ)alkenyl, (C2-ό)alkynyl, aryl, aryl-(C ι _g)alkyl, heterocyclyl or heterocyclyl-(C ι_6)alkyl;

R4 is hydrogen, or an in vivo hydrolysable acyl group; and

R5 and R6 are independently hydrogen and (C _j _6)alkyl or together represent

(CH2)_r where r is 2 to 5.

2. A compound according to claim 1 wherein R \ is formula (a) and ring A is selected from 2,5-thienyl, 2,5-furyl. 1 ,2-phenyl, 1 ,3-phenyl and 1 ,4-phenyl, ring B is selected from phenyl optionally substituted by one or two hydroxy or by methoxy, dimethyla ino, carboxy, nitro, amino, acetylamino, trifluoromethoxy or benzyloxy, 2- furyl, 2-, 3- or 4-pyridyl, 1-tetrazolyl, 2-tetrazolyl, 1-triazolyl, 2-triazolyl, 2 thienyl and imidazolin-2,5-dione-l-yl and C is selected from CH2, O or OCH2-

3. A compound according to claim 1 wherein R^ is formula (b), rings A and B are both phenyl, C is O, CH2 or NR JQ ^and D is a bond (p+q=0).

4. A compound according to claim 1 wherein R_j is selected from methyl, isobutyl, carboxymethyl, mercaptomethyl, 1 -hydro xyethyl, optionally substituted benzyl, phenyl optionally substituted with up to five, preferably up to three, groups selected from halogen, mercapto, (C\.β) alkyl optionally substituted by 1-3 halo, phenyl, (C\.β) alkoxy optionally substituted by 1-3 halo, hydroxy(Cι _6)alkyl, mercapto(C ι _6)alkyl, hydroxy, amino, nitro, carboxy, (C\.β) alkylcarbonyloxy, (Ci_g)alkoxycarbonyl, formyl or (C\.β) alkylcarbonyl groups, indolyl, thienyl, isoimidazolyl, thiazolyl, furyl and benzothienyl.

5. A compound according to claim 1 wherein R^ is selected from phenyl, (5- benzyl)thien-2-yl, (5-benzyl)furan-2-yl, 5-(l-tetrazolylmethyl)thien-2-yl, 5-(2- tetrazolylmethyl)thien-2-yl, 5-(imidazolin-2,5-dione-l-ylmethyl)thien-2-yl, 5-(l- triazolylmethyl)thien-2-yl, 5-(2-triazolylmethyl)thien-2-yl, 3-phenoxyphenyl, 2- phenoxyphenyl, 4-phenoxyphenyl, 3-(4-hydroxybenzyl)phenyl, 3-(4- methoxybenzyl)phenyl, 4-benzyloxyphenyl, 4-(2-thienylmethyloxy)phenyl, 1-fluorenyl, 3-(N-ethylcarbazolyl) 4-hydroxybenzyloxy-4-phenyl, 4-methoxybenzyloxy-4-phenyl, 4- dimethylaminobenzyloxy-4-phenyl, 4-carboxybenzyloxy-4-phenyl, 3-carboxybenzyloxy- 4-phenyl, (2-pyridyl)-methoxy-4-phenyl, (4-pyridyl)-methoxy-4-phenyl, 5-[l-(4- carbamoyltriazolyl)-methyl]-thien-2-yl, 5-[l-(4-carboxytriazolyl)-methyl]-thien-2-yl, (2- furyl)-methoxy-4-phenyl and dibenzofuranyl.

6. A compound according to claim 1 wherein R\ is 4-benzyloxyphenyl 3- or 4- substituted in the benzyl group by a substituent selected from halogen, mercapto, (C i . g)alkyl optionally substituted by 1-3 halo, phenyl, phenyl(C ι_6)alkyl, phenyl(Cι_ g)alkoxy, (C ] _6)alkoxy optionally substituted by 1-3 halo, hydroxy(C ι_6)alkyl, mercapto(C i_6)alkyl, hydroxy, CO2R7, N(R7)2 or CON(R7)2 where each R7 is independently hydrogen, (C \.β) alkyl or (C \._β) alkanoyl, OCONH2, nitro, (C \.β) alkylcarbonyloxy, (C ι_6)alkoxycarbonyl(C ι_6) alkyl, formyl and (C \.β) alkylcarbonyl groups.

7. A compound according to any preceding claim wherein R2 is hydrogen, methyl or benzyl.

8. A compound according to any preceding claim wherein R2 is hydrogen. 9. A compound according to any preceding claim wherein R3 is aryl or aryl-(C ι_

6)alkyl. iθ. A compound according to any preceding claim wherein R₄ is hydrogen and R₅ and

R₆ are independently hydrogen or methyl.

1 1. A compound according to any preceding claim wherein the stereochemistry at the carbon atom marked * is D-.

12. A compound according to claim 1 which is:

N-(E-α-Mercaptomethyl-3-phenyl-prop-2-enoyl)-p-(m-carboxy)-benzyloxy-[D]- phenylglycine or

N-(E-α-Mercaptomethyl-3-phenylprop-2-enoyl)-[D]-phenylglycine or a pharmaceutically acceptable salt, solvate or in vivo hydrolysable ester thereof.

13. A process for the preparation of a compound according to claim 1 , which comprises reacting a compound of formula (II)

Y-C(R₅'R₆')-C(=CHR3')-CO-W

(II) with a compound of formula (IT!)

wherein W is a leaving group, Y is R₄'S or a group convertible thereto, R^x is R or a carboxylate protecting group, X¹ is N₃ or NHR₂' and R ' R₂', R₃', R₄', R₅' and R₆' are R. , R₂, R^, R₄, R₅ and Rg or groups convertible thereto, wherein R, R R₂, R₃, R₄, R5 and R₆ are as defined in claim 1, and thereafter, where necessary, converting Y into R₄'S, R^x, R R₂', R₃' R₄', R₅' and/or R_g' into R, R_χ, R₂, R₃, R₄, R₅ and/or R_g and optionally inter-converting R, R\, R2, R3, R4, R₅ and/or R_fi.

14. A pharmaceutical composition comprising a compound according to any of claims 1 to 12 together with a pharmaceutically acceptable carrier.

15. A pharmaceutical composition according to claim 14 which additionally comprises a β-lactam antibiotic.

16. A composition according to claim 15 wherein the β-lactam antibiotic is a carbapenem selected from imipenem, meropenem, biapenem, BMS 181 139 ([4R- [4alpha,5beta,6beta(R*)]]-4-[2-[(aminoiminomethyl)amino]ethyl]-3-[(2-cyanoethyl)thio]- 6-( l -hydroxyethyl)-7-oxo- l-azabicyclo[3.2.0]hept-2-ene-2-carboxylic acid), BO2727 ([4R- 3[3S*,5S*(R*)],4alpha,5beta,6beta(R*)]]-6-( l-hydroxyethyl) -3-[[5-[l-hydroxy-3- (methylamino)propyl]-3-pyrrolidinyl]thio]-4-methyl-7-oxo- l-azabicyclo[3.2.0] hept-2-ene- 2-carboxylic acid monohydrochloride), ΕR35786 ((IR, 5S, 6S)-6-[l(R)-Hydroxymethyl]-2- [2(S)-[ 1 (R)-hydroxy- 1 -[pyrrolidin-3(R)-yl] methyl]pyrrolidin-4(S)-ylsulfanyl]- 1 -methyl- 1 - carba-2-penem-3-carboxylic acid hydrochloride) and S4661 ((lR,5S,6S)-2-[(3S,5S)-5-

(sulfamoylaminomethyl) pyrrolidin-3-yl]thio-6-[(lR)-l-hydroxyethyl]-l-methylcarbapen-

2-em-3-carboxylic acid).

17. A compound according to claim 1 for use in the treatment of bacterial infections.

18. The use of a compound according to claim 1 , in the manufacture of a medicament for the treatment of bacterial infections

19. A method of treatment of bacterial infections in humans or animals which comprises administering, in combination with a β-lactam antibiotic, a therapeutically effective amount of a compound of claim 1.

20. A compound of formula (IV):

Y-C(R5'R₆')-C(=CHR₃')-CON(R2')-CH(R ι ')-CO₂R^x

(IV)

wherein the variables are as defined in claim 13, provided that R^x is other than R when R_λ', R₂', R₃', R₄', R5' and Rg' are R_p R₂, R₃, R₄, R₅ and Rβ.