THERAPEUTIC COMPOUNDS CONTAINING BETA-LACTAMS

Abstract: A compound of formula (I) or a pharmaceutically acceptable salt or in vivo hydrolysable ester thereof: wherein R¹ is a group of structure (II) wherein R² and R³ may be the same or different and each represents C₁₋₆ alkyl optionally substituted by C₁₋₆ alkoxy, phenyl, hydroxy, carboxy or C₁₋₆ alkoxycarbonyl, or phenyl optionally substituted by C₁₋₆ alkyl, halogen, C₁₋₆ alkoxy, hydroxy, carboxy or C₁₋₆ alkoxycarbonyl or structure (III) wherein Z¹ and Z² may be the same or different and each represents S, SO or SO₂ and Y represents a C₂₋₃ saturated hydrocarbon radical optionally substituted by C₁₋₆ alkyl, C₁₋₆ alkoxy, hydroxy, carboxy, or C₁₋₆ alkoxycarbonyl. Process for the preparation of the compound (I) and pharmaceutical compositions comprising the compound (I) alone or together with amoxycillin.

Description: THERAPEUTIC COMPOUNDS CONTAINING ss-LACTAMS This invention relates to a class of novel ss- lactam compounds, to the process for their preparation and to pharmaceutical compositions containing them. Belgian Patent No 850 779 discloses a class of compounds of the formula (A): EMI1.1 wherein X is S, SO or S02 and R is an organic group of up to 20 carbon atoms and A is a group such that CO2A represents a carboxylic acid group or a salt or ester thereof. We have now found a novel class of compounds containing the thioacetal group, which have antibacterial and 8-lactamase inhibitory activity. Accordingly the present invention provides a compound of formula (I) or a pharmaceutically acceptable salt or in vivo hydrolysable ester thereof: EMI2.1 wherein R1is a group of structure (II): EMI2.2 wherein Rê and R may be the same or different and each represents C1-6 alkyl optionally substituted by C16 alkoxy, phenyl, hydroxy, carboxy or C1-6 alkoxycarbonyl, or phenyl optionally substituted by C1-6 alkyl, halogen, C1-6 alkoxy, hydroxy, carboxy or C16 alkoxycarbonyl; or structure (III): EMI2.3 wherein Z and Z may be the same or different and each represents S, SO or SO2 and Y represents a C23 saturated hydrocarbon radical optionally substituted by C16 alkyl, C16 alkoxy, hydroxy, carboxy or C 1-6 alkoxycarbonyl. Suitable groups Rê and R include methyl, ethyl, n- or iso-propyl, n-, such, tert- and iso-butyl, benzyl and phenyl. Suitably the groups Rê and R are the same. Suitable pharmaceutically acceptable salts of the compounds of formula (I) include metal salts, eg aluminium, alkali metal salts such as sodium or potassium, 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 tri-(2-hydroxyethyl)-amine, cycloalkylamines such as bicyclohexylamine, or with procaine, dibenzylamine, N,N-dibenzylethylenediamine, l-ephenamine, N-ethylpiperidien, N-benzyl-ss-phenethylamine, dehydroabietylamine, N,N"-bisdehydroabietylamine, ethylenediamine, or bases or the pyridine type such as pyridine, collidine or quinoline. Examples of suitable pharmaceutically acceptable in vivo hydrolysable ester groups include those which break down readily in the human body to leave the parent acid or its salts, for example acyloxyalkyl groups such as acetoxymethyl, pivaloyloxymethyl, a-acetoxyethyl and and a-pivaloyloxymethyl groups; alkoxycarbonyloxyalkyl groups, such as ethoxycarbonyloxymethyl; dialkylamino alkyl groups such as dimethylaminomethyl, dimethylaminoethyl, diethylaminomethyl or diethylaminoethyl; and a-ethoxyGarbonyloxyethyl; and lactone groups such as phthalidyl or dimethoxyphthalidyl. One subgroup of compounds within the scope of this invention comprises compounds of formula (ivy) or a pharmaceutically acceptable salt or in vivo hydrolysable ester thereof: EMI4.1 wherein Z1 and Z are as defined hereinbefore with respect to formula (I), and n is an integer from 2 to 3. Suitably n is 2. Suitably ZÚ and Zê are the same and represent S or S02. Preferably ZÚ and Zê are both S02. Suitable examples of Z1 and Z being different are Z1 being S and z2 being SO. The compounds of the present invention may be in the form of the Z-isomer, the E-isomer or a mixture of the E- and Z-isomer. It will be appreciated that oxidation of compounds of formula (I) wherein Z is S may lead to a number of optically active isomers, and accordingly the present invention includes such isomers and mixtures thereof. The present invention also provides a pharmaceutical composition which comprises a compound of this invention 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 the infection in mammals including humans. Suitable forms of the compositions of this invention include tablets, capsules, creams, syrups, suspensions, solutions, reconstitutable powders and sterile forms suitable for injection or infusion. Such compositions may contain conventional pharmaceutically acceptable materials such as diluents, binders, colours, flavours, preservatives, disintegrant and the like in accordance with conventional pharmaceutical practice in the manner well understood by those skilled in the art of formulating antibiotics. Injectable or infusable compositions of a compound of the invention are particularly suitable as high blood levels of the compound can occur after administration by injection or infusion. Thus, one preferred composition aspect of this invention comprises a compound of the invention in sterile form and most suitably in sterile crystalline form. The injectable solution of the compound of this invention may be made up in a sterile pyrogen-free liquid such as water, aqueous ethanol or the like. An alternative approach to administering the compounds of this invention is to utilise an injectable suspension. Such suspensions may be made up in sterile water; sterile saline or the like and may also contain suspending agents such as polyvinylpyrrolidone, lecithin or the like Alternatively such compositions may be prepared in an acceptable oil suspending agent such as arachis oil or its equivalent. For use in such suspensions the compounds of this invention should be in the form of fine particles. Unit dose compositions comprising a compound of this invention adapted for oral administration form a further suitable composition aspect of this invention. Unit dose compositions comprising a compound of this invention adapted for topical administration are also presented by this invention. In this instance 'topical administration' also includes local administration to internal surfaces of mammary glands of cattle, for example during the treatment of mastitis by intra-mammary administration. The compound of the formula may be present in the composition as sole therapeutic agent or it may be present together with other therapeutic agents such as a penicillin or cephalosporin. Considerable advantages accrue from the inclusion of a penicillin or cephalosporin which shows Instability to ss-lactamases since the resulting composition shows enhanced effectiveness (synergy). Suitable penicillins cephalosporins or other -lactam antibiotic for inclusion in such synergistic compositions include not only those knownto be highly susceptible to ss-lactàmases but also those which have a degree of intrinsic resistance to P-lactamases. Suitable penicillins for inclusion in the compositions of this invention include benzylpenicillin, phenoxymethylpenicillin, carbenicillin, azidocillin, propicillin, ampicillin, amoxycillin, epicillin, ticarcillin, cyclacillin, pirbenicillin, azlocillin, mezlocillin, celbenicillin, pipericillin, and other known peni cillins including pro-drugs thereof such as their in vivo hydrolysable esters such as the acetoxymethyl, pivaloyloxymethyl, a-ethoxycarbonyloxyethyl or phthalidyl esters of ampicillin, benzylpenicillin or amoxycillin, and aldehyde or ketone adducts of penicillins containing a 6-a-aminoacetamide side chain (such as hetacillin, metampicillin and analogous derivatives of amoxycillin) or esters of carbenicillin or ticarcillin such as their phenyl or indanyl esters. Suitable cephalosporins for inclusion in the compositions of this invention include cefatrizine, cephaloridine, cephalothin, cefazolin, cephalexin, cephacetrile, cephamandole nafate, cephapirin, cephradine, 4-hydroxycephalexin, cefaparole, cephaloglycin, cefoperazone, and other known cephalosporins or prodrugs thereof. Such compounds are frequently used in the form of a salt or hydrate of the like. Naturally if the penicillin or cephalosporin present in the composition is not suitable for oral administration then the composition will be adapted for parenteral administration. Highly favoured penicillins for use in the compositions of this invention include ampicillin, amoxycillin, carbenicillin and ticarcillin. Such penicillins may be used as a pharmaceutically acceptable salt such as the sodium salt. Alternatively the ampicillin or amoxycillin may be used in the form of fine particles of the zwitterionic form (generally as ampicillin-trihydrate or amoxycillin trihydrate) for use in an injectable suspension, for example, in the manner hereinbefore described for a compound of this invention. The preferred penicillin for use in the synergistic composition is amoxycillin, for example as its sodium salt or trihydrate. Particularly suitable cephalosporins for use in the compositions of this invention include cephaloridine and cefazolin which may be in the form of a pharmaceutically acceptable salt for example the sodium salt. When present together with a cephalosporin or penicillin, the ratio of a compound of the invention to the penicillin or cephal;osporin agent may vary over a wide range of ratios, such as from 10:1 to 1:10 for example about 3:1, 2:1, 1:1, 1:2, 1:3, 1:4, 1:5 or 1:6, (wt/wt, based on pure free antibiotic equivalent). Orally adminstrable compositions containing a compound of the invention will normally contain relatively more synergist than corresponding injectable compositions. The total quantity of a compound of the invention in any unit dosage form will normally be between 25 and 1000 mg and will usually be between 50 and 500 mg, for example about 62.5, 100, 125, 150, 200 or 250 mg. Compositions of this invention may be used for the treatment of infections of inter alia, the respiratory tract, the urinary tract and soft tissues in humans and mastitis in cattle. Normally between 50 and 3000 mg of the compounds of the invention will be administered each day of treatment but more usually between 100 and 1000 mg of the compounds of the invention will be adminstered per day, for example at 1-6 doses, more usually as 2, 3 or 4 doses. However for the treatment of more severe systemic infections or infections of particularly intransigent organisms higher doses may be used in accordance with clinical practice. The penicillin or cephalosporin in the synergistic composition of this invention will normally be present at approximately the amount at which it is conventionally used which will usually be expected to be from about 62.5 to 3000 mg per dose, more usually about 125, 250, 500 or 1000 mg per dose. One particularly favoured composition of this invention will contain from 150 to 1000 mg of amoxycillin as the trihydrate or sodium salt and from 25 to 500 mg of a compound of this invention. A further particularly favoured composition of this invention will contain from 150 to 1000 mg of ampicillin or a pro-drug thereof and from 25 to 500 mg of a compound of this invention. Most suitably this form of composition will contain ampicillin trihydrate, ampicillin anhydrate, sodium ampicillin, hetacillin, pivampicillinhydrochloride, bacampicillin hydrochloride, or talampicillin hydrochloride. Most suitably this form of the composition will contain a compound of the formula (I) when in crystalline form. Most suitably the preceding composition will contain from 200 to 700 mg of the penicillin component. Most suitably the preceding composition will comprise from 50 to 250 mg of a compound of the formula (I) preferably in crystalline form. Such compositions may be adapted for oral or parenteral use except when containing an in vivo hydrolysable ester of ampicillin or amoxycillin in which case the compositions will not be adapted for parenteral administration. Another particularly favoured composition of this invention will contain from 200 to 2000 mg of carbenicillin, ticarcillin or a pro-drug thereof and from 50 to 500 mg of a compound of the invention. Suitably this form of composition will contain di-sodium carbenicillin. Suitably this form of the composition will contain di-sodium ticarcillin. More suitably this form of the composition will contain from 75 to 250 mg of a compound of the formula (I) preferably in crystalline form. Such compositions containing di-salts of carbenicillin and ticarcillin will be adapted for parenteral administration. The present invention also provides a method of treating bacterial infections in humans or domestic mammals which comprises the administration of a composition of this invention. Commonly the infection treated will be due to a strain of Staphylococcus aureus, Klebsiella aerogenes, Escherichia coli, Proteus sp., Bacteroides fragilis or the like. The organism believed to be most readily treated by an antibacterially effective amount of a compound of this invention is Staphylococcus aureus. The other organisms named are more readily treated by using a synergistically effective amount of the compound of the invention and a penicillin or cephalosporin. The administration of the two components may take place separately but in general we prefer to use a composition containing both the synergist and the penicillin or cephalosporin. The indications for treatment include respiratory tract and urinary tract infections in humans and mastitis in cattle. The present invention also provides a process for the preparation of a compound of formula (I) or a pharmaceutically acceptable salt or in vivo hydrolysable ester thereof which process comprises reacting a compound of formula (V): EMI13.1 wherein Rx is a carboxyl blocking group; (1) with compounds R2SH and R3SH wherein R and R3 are as defined with respect to formula (I) and wherein any reactive groups may be protected; or (2) with a compound of formula HS-Y-SH wherein Y is as defined with respect to formula (I) and wherein any reactive groups may be protected; in the presence of a Lewis acid catalyst; and thereafter where necessary carrying out one or more of the following steps: (a) oxidising a sulphide to a sulphoxide or sulphone derivative; (b) removing the carboxy blocking group R (c) removing any protecting groups on Rê or R , or Y; and (d) converting the compound to a free carboxylic acid, a pharmaceutically acceptable salt or in-vivo hydrolysable ester. It will be appreciated that when R2 and R3 are the same in formula (I) then compounds R2SH and R3SH will also be the same, and when Rê and R are different in formula (I) then a mixture of compounds RêSH and and R SH will be used. The starting material of formula (V) is disclosed in UK Patent No 1 504 426. Suitable carboxyl-blocking derivatives for the group CO2Rx in formula (V) include ester derivatives of the carboxylic acid. The derivative is preferably one which may readily be cleaved at a later stage of the reaction. Suitable ester-forming carboxyl-blocking groups are those which may be removed under conventional conditions. Such groups for R include benzyl, pmethoxybenzyl, 2,4, 6-trimethylbenzyl, 3,5-di-t-butyl 4-hydroxybenzyl, benzoylmethyl, p-nitrobenzyl, 4pyridylmethyl, 2,2,2-trichloroethyl, 2,2,2-tribromoethyl, allyl, diphenylmethyl, triphenylmethyl, 2-benzyloxyphenyl, 4-methylthiophenyl, methoxymethyl, a silyl, stannyl or phosphorus-containing group, or an in vivo hydrolysable ester radical such as defined above. The carboxylic group or a salt thereof may be regenerated from any of the above esters by usual methods appropriate to the particular R group, for example, base-catalysed hydrolysis, or by enzymicallycatalysed hydrolysis, or by hydrogenation. Suitable Lewis acid catalysts include boron trifluoride or its equivalent such as a boron trifluoride etherate, for example BF3.O(C2H5)2. The preceding reaction normally takes place in a solvent inert under the reaction conditions such as chloroform, dichloromethane, tetrahydrofuran or dioxane or may be carried out using the thiol or dithiol reagent as solvent. The reaction is generally carried out at a depressed or non-elevated temperature, for example -800C to +300C, and preferably at a depressed temperature, for example -200C to OOC, and conveniently at about OOC. Those compounds of formula (I) wherein Z is SO or SO2 can be prepared from the corresponding compound wherein Z is S by mild oxidation. Such reactions may take place at an ambient or depressed temperature, for example at -200C to 0 0 0 +20 C, more suitably at -12 C to +5 C, for example at about OOC. The oxidation is best brought about using an organic per-acid as the oxidizing agent. Suitable acids include m-chloroperbenzoic acid and equivalent reagents. Use of two equivalents of the oxidizing agent leads to a compound of the formula (I) wherein Z is SO whereas the use of an excess of the oxidising agent leads to a compound of the formula (I) wherein Z is S02 The use of one equivalent of the oxidising agent leads to compounds wherein only one sulphur has been oxidised to the sulphoxide. It is normal to carry out the oxidation in an inert solvent such as methylene chloride or the like. Acids within formula (I) may be prepared by the careful acidification of a corresponding salt such as the sodium salt. Salts within formula (I) may also be prepared by salt exchange in conventional manner, for example a solution of the lithium salt in water may be passed through a bed of ion exchange resin in the sodium form (eg Amberlite 120; a sodium salt of a sulphonated polystyrene divinyl benzene co-polymer) in about ten-fold excess until elution is complete; the resulting sodium salt may be obtained by freeze drying or the like. Similarly a sodium salt may be converted to a lithium salt or to a potassium salt in similar manner. The following Examples illustrate the invention. Example 1 Benzyl 2-E- (2' ,2 '-diethylthioethylidene) clavam-3- carboxylate and benzyl 2-Z-(2',2'-diethylthioethylidene) clavam-3-carboxylate EMI17.1 A mixture of E and Z isomers of benzyl 2-(2'-oxo ethylidene)clavam-2-carboxylate (el) (150 mg, 0.523 mmole) was dissolved in ethane thiol (5 ml). Boron trifluoride diethyletherate (1 drop) was added, the mixture stirred for 30 minutes and diluted with ethyl acetate (20 ml). This solution was washed with 1N aqueous sodium bicarbonate solution (20 ml), dried over anhydrous magnesium sulphate and evaporated under reduced pressure. The residue was chromatographed on silica (30 g, Merck Kieselgel 60, 230-400 mesh, in a 3 cm diameter column), eluting wih ethyl acetate/petrol 1:4. The title compounds (e2) and (e3) were detected on t.l.c. (silica, eluent ethyl acetate/petrol 1:1) by spraying the plates with dilute potassium permanganate solution. Less polar isomer (e2) (colourless gum, 70 mg, 34%): Icr320;32.00 D (c. 0.7; CHCl3); max (CHC13) 1800 and 1680 cm ; 6 (CDC13) 1.18 and 1.22 (6H, 2t, -SCH2CH3), 2.55 (4H, broad q, -SCH2CH3), 3.01 (1H, d, J 17 Hz, 6&beta;-CH), 3.46 (1H, dd, J 17 and 2.5 Hz, 6a-CH), 4.56 (1H, d, J 12 Hz, 8-CH or 9-CH), 5.0-5.4 (4H, m, -OCH2Ph, 3-CH and 8-CH or 9-CH), 5.68 (1H, d, J 2.5 Hz, 5-CH), 7.35 (5H, s, Ph-H). More polar isomer (e3) (colourless gum, 40 mg, 19%): [&alpha;]20 + 5.60 (c. 1.3; CHCl3); max (CHCl3) 1800, D 1750 and 1680 cm-1; 6 (CDCl3) 1.18 and 1.24 (6H, 2t, -SCH2CH3), 2.47 and 2.59 (4H, 2q, -SCH2CH3),3.01 (1H, d, J 17 Hz, 6&beta;-CH), 3.48 (1H, dd, J 17 and 2.5 Hz, 6a-CH), 4.78 (2H, s, 8-CH and 9-CH), 5.10 (1H, s, 3-CH), 5.18 (2H, s, -OCH2Ph), 5.68 (1H, d, J 2.5 Hz, 5-CH), 7.34 (5H, s, Ph-H). Example 2 p-Nitrobenzyl 2-E-(2',2'-diethylthioethylidene)clavam- 3-carboxylate and p-nitrobenzyl 2-Z- (2'2' -diethyl thioethylidene)clavam-3-carboxylate EMI19.1 A mixture of E and Z isomers of p-nitrobenzyl 2-(2'-oxoethylidene)clavam-3-carboxylate (e4) (700 mg, 2.11 mmole) was dissolved in ethanethiol (8 ml), ice cooled and boron trifluoride diethyl etherate (3 drops) added. The mixture was stirred for 45 minutes at 0-5 0C and diluted with dichloromethane (30 ml). The resulting solution was washed with 1N aqueous sodium bicarbonate solution (30 ml), dried over anhdrous magnesium sulphate and evaporated under reduced pressure. The residue was chromatographed on silica (35 g), eluent ethyl acetate/petrol 1:4, in a similar manner to that described in Example 1 to provide two compounds (e5) and (e6) with Rf 'S of 0.72 and 0.67 respectively on t.l.c. (silica, eluent ethyl acetate/petrol 1:1). Less polar isomer (eS) (colourless gum, 230 mg, 288): [a]20-3O.8o (c. 1.2; CHCl3); #max (CHCl3) 1800, D 1750 and 1680 cm-1; 6 (CDC13) 1.17 and 1.23 (6H, 2t, -SCH2CH3), 2.4-2.8 (4H, m, -SCH2CH3), 3.04 (1H, d, J 17 Hz, 6ss-CH), 3.48 (1H, dd, J 17 and 2.5 Hz, 6-CH), 4.52 (1H, d, J 11 Hz, 8-CH or 9-CH), 5.1-5.5 (4H, m, -OCH2Ar, 3-CH, 8-CH or 9-CH), 5.68 (1H, d, J 2.5 Hz, 5-CH), 7.52 and 8.23 (4H, 2d, Ar-H); Found 438.0885 (M+); C19H22N20652 requires 438.0919. More polar isomer (e6) (colourless gum, 195 mg, 20 23%): [a]D +5.9 (c. 1.1; CHCl3); #max (CHCl3) 1800, 1750 and 1680 cm-1; # (CDCl3) 1.20 and 1.24 (6H, 2t, -SCH2CH3), 2.52 and2.60 (4H, 2q, -SCH2CH3), 3.04 (1H, d, J 17 Hz, 6&beta;-CH), 3.51 (1H, dd, J 17 and 2.5 Hz, 6a-CH), 4.78 (2H, s, 8-CH and 9-CH), 5.14 (1H, s, 3-CH), 5.29 (2H, ABq, -OCH2Ar), 5.69 (lH, d, J 2.5 Hz, 5-CH), 7.51 and 8.23 (4H, 2d, Ar-H); Found 438.0925(M+); C19H22N2O6S2 requires 438.0919. Example 3 Mixture of E and Z isomers of p-nitrobenzyl 2-(2',2' diethylthioethylidene) clavam-3-carboxylate EMI21.1 A mixture of E and Z isomers of p-nitrobenzyl 2 (2' -oxoethylidene) clavam-3-carboxylate (e4) (185 mg, 0.558 mmole) was dissolved in a mixture of dichloromethane (3 ml) and ethanethiol (2 ml), ice cooled and treated with boron trifluoride diethyletherate (3 drops). The mixture was stirred 45 minutes at 0-5 0C, diluted with dichloromethane (10 ml), washed with 1N aqueous sodium bicarbonate solution (20 ml), dried over anhydrous magnesium sulphate and evaporated under reduced pressure. Chromatography of the residue as decribed in Example 1, eluting with ethyl acetate/petrol 1:3, provideda mixture of E and Z isomers of p-nitrobenzyl 2-(2',2'-diethylthio ethylidene)clavam-3-carboxylate (e5) and (e6) (0.12 g, 49%). Example 4 Lithium 2-(2',2'-diethylthioethylidene)clavam-3- carboxylate (less polar isomer) EMI22.1 A solution of p-nitrobenzyl 2-(2',2'-diethylthio ethylidene)clavam-3-carboxylate (e5) (less polar product of Example 2, 120 mg, 0.274 mmole) in tetrahydrofuran (5 ml) was added to a pre-hydrogenated suspension of 10% Pd/C (180 mg) in tetrahydrofuran (5 ml). Hydrogenolysis was continued at atmospheric pressure for 1i hours, the suspension filtered and the filtrate evaporated to 2 ml under reduced pressure. With ice cooling, water (5 ml) and O.lM aqueous lithium carbonate solution (1.37 ml) were added. The resulting solution was washed with ethyl acetate (3 x 10 ml), adjusted to pH 7 with O.lN hydrochloric acid and evaporated to dryness under reduced pressure. The residue was chromatographed on cellulose (15 g in a 2.5 cm diameter column, Whatman CC31), eluting with n-butanol/ethanol/water 4:1:1. Appropriate fractions were combined and evaporated to provide lithium 2 (2'-2'-diethylthioethylidene)clavam-3-carboxylate (e7) (30 mg, 24%, less polar isomer on a silica t.l.c., eluting with chloroform/acetone/glacial acetic acid 50:50:7) as a yellow solid. [&alpha;]20-13.1 D (c. 0.5; DMSO); may (KBr) 1785, 1680 and 1620 cm-1; max 6 (D2O-HOD#4.60) 1.18 and 1.20 (6H, 2t, -SCH2CH3), 2.58 and 2.62 (4H, 2q, -SCH2CH3), 3.03 (1H, d, J 17 Hz, 6ss-CH), 3.53 (1H, dd, J 17 and 2.5 Hz, 6a CH), 4.82 (1H, d, J 11.5 Hz, 9-CH), 4.9-5.2 (2H, m, 3-CH and 8-CH), 5.73 (1H, d, J 2.5 Hz, 5-CH). Example 5 Lithium 2-(2',2'-diethylthioethylidene)clavam-3carboxylate (more polar isomer) EMI24.1 A solution of p-nitrobenzyl 2-(2',2'-diethylthio ethylidene)clavam-3-carboxylate (e6) (more polar product of Example 2, 100 mg, 0.228 mmole) in tetrahydrofuran (5 ml) was added to a pre-hydrogenated suspension of 10% Pd/C 1150 mg) in tetrahydrofuran (5 ml). Hydrogenolysis was carried out at atmospheric pressure for 1i hours, the mixture filtered and the filtrate evaporated to 2 ml under reduced pressure. With ice cooling, water (5 ml) and O.lM aqueous lithium carbonate solution (1.14 ml) were added. The resulting solution was washed with ethyl acetate (3 x 10 ml), adjusted to pH7 with 0,1N hydrochloric acid and evaporated to dryness under reduced pressure. The residue was chromatographed as described in Example 4 to provide lithium 2-(2',2'-diethylthioethylidene) clavam-3-carboxylate (e8) (38 mg, 53%, more polar isomer on silica t.l.c., eluting with chloroform/acetone/glacial acetic acid 50:50;7) as a yellow solid. [&alpha;]D20+19.8 (c. 0.5; DMSO); '?max (KBr) 1785, 1685 and 1620 cm-1; 6 (D2O-HOD#4.60) 1.18 and 1.20 (6H, 2t, -SCH C 2.58 and 2.63 (4H, 2q, -SCH2CH3), 3.04 (1H, d, J 17 Hz, 6ss -CH), 3.54 (1H, dd, J 17 and 2.5 Hz, 6a-CH), 4.6-5.1 (3H, m, 8-CH, 9-CH and 3-CH), 5.70 (1H, d, J 2.5 Hz, 5-CH). Example 6 Mixture of E and Z isomers of benzyl 2-(1',3'-dithiolan2'-yl methylene)clavam-3-carboxylate EMI26.1 A mixture of E and Z isomers of benzyl 2-(2' oxoethylidene)clavam-3-carboxylate (el) (800 mg, 2.79 mmole) was dissolved in ethane-1,2-dithiol (5 ml), ice cooled and treated with borontrifluoride diethyl etherate (2 drops). The mixture was stirred at 0-50C for 1 hour, diluted with dichloromethane (100 ml), washed with 1N aqueous sodium bicarbonate solution (50 mD, dried over magnesium sulphate and run on to a silica column (40 g of silica on a 3 cm diameter column). Chromatography was carried out in the manner of Example 1, eluting with ethyl acetate/ petrol (15% ethyl acetate), to provide an approximately 1:1 mixture of E and Z isomers of benzyl 2-(1',3'dithiolan-2'-ylmethylene)clavam-3-carboxylate (e9) (520 mg, 51%) as a colourless gum. [Qi DO+1l.5o -l (c. 1t3; CHC13); vmax (CHCl3) 1800, 1750 and 1680 cm # (CDCl3) 3.00 and 3.04 (1H, 2d, J 17 Hz, 6$-CH), 3.1-3.6 (5H, m, -SCH2CH2S- and 6&alpha;-CH), 4.86 (broad d, J 10.5 Hz, 8-CH of isomer A), 5.04 (broad s, 3-CH of isomer A), 5.1-5.4 (m, -OCH2Ph and 3-CH, 8-CH, 9-CH of isomer B), 5.46 (d, J 10.5 Hz, 9-CH of isomer A), 5.6-5.8 (1H, m, 5-CH), 7.35 (5H, s, Ph-H). N.B. The Letters A and B are assigned arbitrarily and do not define which isomer is E or Z. Example 7 Mixture of E and Z isomers of benzyl 2-(1',3'-dithio lan-2'-ylmethylene)clavam-3-carboxylate EMI28.1 A mixture of E and Z isomers of benzyl 2-(2' oxoethylidene) clavam-3-carboxylate (el) (500 mg, 1.74 mmole) was dissolved in a mixture of dichloromethane (3 ml) and ethane-1,2-dithiol (2 ml), ice cooled and treated with boron trifluoride diethyl etherate (3 drops). The mixture was stirred at 0-50C for 45 minutes and worked up exactly as described in Example 6, to provide a mixture of E and Z isomers of benzyl 2-(1',3|-dithiolan-2'-ylmethylene)clavam -3-carboxylate (e9) (290 mg, 46%), identical on t.l.c. and spectroscopically to the product of Example 6. Example 8 Mixture of E and Z isomers of benzyl 2-(1',3'-dithio lan-2'-ylmethylene)clavam-3-carboxylate EMI29.1 A mixture of E and Z isomers of benzyl 2-(2'oxoethylidene)clavam-3-carboxylate (el) (150 mg, 0.523 mmole) was dissolved in ethane-1,2-dithiol (3 ml) and pyridine hydrochloride (5 mg) was added. The mixture was stirred 2 days at room temperature, diluted with dichloromethane (50 ml), washed with water (50 ml) and dried over magnesium sulphate. The resulting solution was added to a silica column and chromatographed as described in Example 6 to provide a mixture of E and Z isomers of benzyl 2-(1',3'-dithiolan-2' ylmethylene)clavam-3-carboxylate (e9) (70 mg, 37%). NMR spectroscopy showed the geometric isomers to be present in a ratio of approximately 85:15, and by t.l.c. and IR 20 the product was identical to that of Example 6. [a]D + 3.2 (c. 1.26; Chic13). Example 9 Mixture of E and Z isomers of p-nitrobenzyl 2-(1',3' dithiolan-2 '-ylmethylene) clavam-3-carboxylate EMI30.1 A mixture of E and Z isomers of p-nitrobenzyl 2 (2'-oxoethylidene)clavam-3-carboxylate (e4) (700 mg, 2.11 mole) was dissolved in ethane-1,2-dithiol (5 ml), ice cooled and treated with boron trifluoride diethyl etherate (3 drops). The mixture was stirred at 0-5 C for 45 minutes, diluted with dichloromethane (100 ml), washed with 1N aqueous sodium bicarbonate solution (50 ml) and dried over magnesium sulphate. The resulting solution was run on to a silica column (40 g of silica in a 3 cm diameter column) and chromatographed in the manner of Example 1, eluting with ethyl acetate/petrol (30% of ethylacetate) to provide a mixture of E and Z isomers of p-nitrobenzyl 2-(1',3'dithiolan-2'-ylmethylene)clavam-3-carboxylate (elO) 20 ing, 50%). ]20 90 (c. 1.2; CHCl3); ';max (CHCl3) 1805, 1755 and 1680 cm ; A (EtOH) 264 nm max (13310); #(CDCl3) 2.9-3.7 (6H, m, 6-CH2 and -SCH2CH2S-), 4.83 (dd, J 10 and 1Hz, 8-CH of one isomer), 5.05.5 (m, -OCH2Ar, 3-CH, 9-CH, and 8-CH of one isomer), 5.6-5.8 (1H, m, 5-CH), 7.50 and 7.54 (2H, 2d, 2 Ar-H), 8.23 (2H, d, 2 Ar-H); Found 408.0474 C17H16N206S2 requires 408.0447. Example 10 Mixture of E and Z isomers of lithium 2-(1'3'-dithiolan2'-ylmethylene)clavam-3-carboxylate EMI32.1 A solution of a mixture of E and Z isomers of p-nitrobenzyl 2-(1',3'-dithiolan-2'-ylmethyleneNclavam- 3-carboxylate (elO) (170 mg, 0.416 mmole) in tetrahydrofuran (5 ml) was added to a pre-hydrogenated suspension of 10% Pd/c in tetrahydrofuran (5 ml). Hydrogenolysis was carried out at atmospheric pressure for 1i hours and the mixture filtered through celite. The filtrate was evaporated to 2 ml, treated with water ( 5 ml) and 0.1M aqueous lithium carbonate solution (2.13 ml), and washed with ethyl acetate (3 x 10 ml). The aqueous solution was then saturated with sodium chloride, acidified to pH 2 with 1N hydrochloric acid and extracted with ethyl acetate (3 x 10 ml). The combined organic extracts were dried over magnesium sulphate and evaporated under reduced pressure. The residue was taken up in a mixture of tetrahydrofuran (2 ml) and water (2 ml) and brought to pH7 with 0.1M aqueous lithium carbonate solution. Organic solvent was removed under reduced pressure and the remaining aqueous solution freeze dried to provide a mixture of E and Z isomers of lithium 2-(1',3'-dithiolan-2'-ylmethylene)clavam-3-carboxylate (ell) (50 mg, 32-g6) as a yellow solid. [&alpha;]20+22.5 D (c. 0.7; H20); #max (KBr) 1785, 1680 and 1620 cm-1; 6 (D20-CH3CNE2.00) 2.99 and 3.04 (1H, 2d, J 17.5 Hz, 6&beta;-CH), 3.1-3.7 (5H, m, 6a-CH and -SCH2CH2S-), 4.83 and 5.12 (1H, 2d, J 1.5 Hz, 3-CH), 4.84 (dd, J 10.5 and 1.5 Hz) and 5.11 (dd, J 11.5 and 1.5 Hz) (1H, 8-CH), 5.40 (d, J 11.5 Hz) and 5.47 (d, J 10.5 Hz) (1H, 9-CH), 5.6-5.7 (lH, m, 5-CH). Example 11 Mixture of E and Z isomers of p-nitrobenzyl 2-(1',1',3', 3'-tetraoxido-1',3'-dithiolan-2'-ylmethylene)clavam- 3-carboxylate EMI34.1 A solution of a mixture of E and Z isomers of p-nitrobenzyl 2-(1',3l-dithiolan-2'-ylmethylene)clavam -3-carboxylate (elm) (404 mg, 0.975 mmole) in dichloromethane (10 ml) was ice cooled and treated dropwise with a solution of m-chloroperbenzoic acid (1.73 g, 10 mmole) in dichloromethane (10 ml). The mixture was stirred at 0-5 C for 4 hours, washed with saturated aqueous sodium thiosulphate solution (20 ml), 1N aqueous sodium bicarbonate solution (2 x 20 ml) and water (20 ml), dried over magnesium sulphate and evaporated under reduced pressure. The residue was chromatographed on silica (30 g) in the mnse of Example 1, eluting with ethyl acetate/petrol 3:1 to provide a mixture of E and Z isomers of p-nitrobenzyl 2-(1',1',3',3'-tetraoxido1',3'-dithiolan-2'-ylmethylene)clavam-3-carboxylate (e12) (191 mg, 41%) as a white solid. [&alpha;]D20+3.2 (c. 1.4; DMSO); ';max (CHC13) 1810, 1755 and 1680 cm-1; 6 (d6-DMSO) 3.14 and 3.25 (1H, 2d, J 17 Hz, 6ss-CH), 3.5-4.3 (5H, m, 6a-CH and -SO2CH2CH2SO2-), 4.70 and 4.99 (1H, 2dd, J 12 and 1.5 Hz, 8-CH), 5.1-6.1 (5H, m, -OCH2Ar, 9-CH, 3-CH and 5-CH), 7.63 and 7.67 (2H, 2d, 2 Ar-H), 8.20 and 8.23 (2H, 2d, 2Ar-H). Example 12 Mixture of E and Z isomers of lithium 2-(1',1',3',3'- tetraoxido-l',3'-dithiolan-2'-ylmethylene)clavam-3- carboxylate EMI36.1 A solution of a mixture of E and Z isomers of p-nitrobenzyl 2-(1',1',3',3'-tetraoxido-1',3'-dithiolan- 2' -ylmethylene) clavam-3-carboxylate (e12) (160 mg, 0.340 mmole) in tetrahydrofuran (5 mi) was added to a pre-hydrogenated suspension of 10% Pd/c(240 mg) in tetrahydrofuran (5 ml). Hydrogenolysis was carried out for 45 minutes at one atmosphere pressure and the mixture filtered through celite. The filtrate was evaporated under reduced pressure to 2 ml, treated with water (5 ml) and 0.1M aqueous lithium carbonate solution (1.7 ml), and washed with ethyl acetate (3 x 10 ml). The aqueous solution was adjusted to pH7 with O.lN hydrochloric acid and evaporated under reduced pressure. The residue was chromatographed on cellulose in the manner of Example 4 to provide a mixture of E and Z isomers of lithium 2-(1',1',3',3'-tetraoxido-1',3'- dithiolan-2-ylmethylene)clavam-3-carboxylate (e13) (60 mg, 52%) as a yellow solid. NMR spectroscopy showed the geometric isomers to be present in a ratio of about 4: :1. [&alpha;]D20-18.6 (c. 0.9; H20);vmax (XBr) 1790, 1680 and 1620 cm a (d6-DMSO) 2.91 (minor) and 3.03 (major) (1H, 2d, J 17 Hz, 6ss-CH), 3.4-4.3 (5H, m, 6a-CH and -S02CH2CH2S02-), 4.50 (minor) and 4.59 (major) (1H, 2dd, J 10 and 1 Hz, 8-CH), 4.78 (minor) and 4.83 (major) (1H, 2d, J 1Hz, 3-CH), 5.43 (minor) and 6.57 (major) (1H, 2d, J 10 Hz, 9-CH, exchanges with D20), 5.73 (1H, d, J 2.5 Hz, 5-CH). Example 13 Benzyl 2-E-(1',1',3',3'-tetraoxido-1',3'-dithiolan- 2'-ylmethylene)clavam-3-carboxylate and benzyl 2-Z (1',1',3',3'-tetraoxido-1',3'-dithiolan-2'-ylmethylene) clavam-3-carboxylate EMI38.1 A solution of a mixture of E and Z isomers of benzyl 2-(1,3' -dithiolan-2' -ylmethylene) clavam- 3' -carboxylate (e9) (290 mg, 0.80 mmole) in dichloromethane (5 ml) was ice cooled and treated dropwise with a solution of m-chloro perbenzoic acid (2.21 g, 12.8 mmole) in dichloromethane (15 ml). The mixture was stirred at 0-5 C for 4 hours, washed with saturated aqueous sodium thiosulphate solution (20 ml), 1N aqueous sodium bicarbonate solution (2 x 20 ml) and water (20 ml), dried over magnesium sulphate and evaporated under reduced pressure. The residue was chromatographed on silica (20 g) in the manner described in Example 1 eluting with ethyl acetate/petrol (40% ethyl acetate) to produce benzyl 2-E-(1',1',3',3'- tetraoxido-1',3'-dithiolan-2-ylmethylene)clavam-3carboxylate and benzyl 2-Z-(1',1',3',3'-tetraoxido 1',3'-dithiolan-2'-ylmethylene)clavam-3-carboxylate. Less polar isomer (e14) (colourless gum, 44 mg, -1 13%): v (CHCl3) 1810, 1750 and 1680 cm ; 6 (CDCl3) 3.11 (1H, d, J 17 Hz, 6$-CH), 3.49 (1H, dd, J 17 and 2.5 Hz, 6&alpha;-CH), 3.68 (4H, broad s, -SO2CH2CH2SO2-), 5.05.5 (5H, m, -OCH2Ph , 3-CH, 8-CH and 9-CH), 5.76 (1H, d, J 2.5 Hz, 5-CH), 7.35 (5H, s, Ph-H). More polar isomer (e15) (colourless gum, 30 mg, 9%): #max (CHCl3) 1810, 1755 and 1685 cm-1, 6 (CDCl3) 3.14 (1H, d, J 17 Hz, 6ss-CH), 3.53 (1H, dd, J 17 and 2.5 Hz, 6&alpha;-CH), 3.71 (4H, broad s, -SO2CH2CH2SO2-), 4.76 (1H, broad d, J 10 Hz, 8-CH), 5.07 (1H, d, J 10 Hz, 9-CH), 5.21 (2H, s, -OCH2Ph), 5.31 (1H, broad s, 3-CH), 5.79 (1H, d, J 2.5 Hz, 5-CH), 7.35 (5H, s, Ph-H). Example 14 Lithium 2-(1',1',3',3'-tetraoxido-1',3'-dithiolan-2'- ylmethylene)clavam-3-carboxylate (less polar isomer) EMI40.1 A solution of benzyl 2-(1',1',3',3'-tetraoxido 1' , 3' -dithiolan-2' -ylmethylene) clavam-3-carboxylate (e14) (less polar product of Example 13, 40 mg, 0.094 mmole) in tetrahydrofuran (2 ml) was added to a prehydrogenated suspension of 10% Pd/c (80 mg) in tetrahydrofuran (4 ml). Hydrogenolysis of the mixture was carried out at atmospheric pressure for 5 hours and the resulting suspension was filtered through celite. The filtrate was treated with water (8 ml) and O.lN aqueous lithium hydroxide solution to pH7. Organic solvent was evaporated at reduced pressure and the aqueous solution filtered through celite and freeze dried to produce lithium 2-(1',1',3',3'- tetraOxido-1',3'-dithiolan-2'-ylmethylene)clavam-3- carboxylate (e16) (less polar isomer on silica t.l.c., eluent chloroform/acetone/acetic acid 50:50:7, 28 mg, 88%) as a pale yellow solid [&alpha;]D20-23 (c. 1.0; H20); #max (KBr) 1795, 1675 and 1620 cm-1; # (D20-OH3ON=2. 00) 3.11 (1H, d, J 17.5 Hz, 6ss-CH), 3.56 (1H, dd, J 17.5 and 3 Hz, 6a-CH), 3.8-4.2 (4H, m, -S02OH2OH2SO2-), 5.23 (1H, d, J 1 Hz, 3-CH), 5.79 (1H, d, J 3Hz, 5-CH). Example 15 Lithium 2-(1',1',3',3'-tetraoxido-1',3'-dithiolan-2'- ylmethylene)clavam-3-carboxylate (more polar isomer) EMI42.1 A solution of benzyl 2-(1',1',3',3'-tetraoxido 1',3'-dithiolan-2'-ylmethylene)clavam-3-carboxylate (el5) (more polar product of Example 13, 30 mg, 0.070 mmole) in tetrahydrofuran (2 ml) was added to a prehydrogenated suspension of 10% Pd/c (30 mg) in tetrahydrofuran (4 ml). Hydrogenolysis was carried out for 30 minutes at atmospheric pressure and the mixture filtered through celite. The filtrate was evaporated to 2 ml, treated with water (5 ml) and 0.1N aqueous lithium hydroxide solution to pH7. Organic solvent was evaporated at reduced pressure and the aqueous solution filtered through celite and freeze dried to produce lithium 2-(1',1',3',3'-tetraoxido-1',3'- dithiolan-2 '-ylmethylene) clavam-3-carboxylate (e17) (more polar isomer on silica t.l.c., eluent chloroform/ acetone/glacial acetic acid 50:50:7, 20 mg, 83%) as a yellow solid. [&alpha;]20-64.5 (c. 0.8; H20); #max (KBr) D 1785, 1680 and 1625 cm-1; #(D2O-CH3CN#2.00) 3.14 (1H, d J 17 Hz, 6ss-CH), 3.57 (1H, dd, J 17 and 2.5 Hz, 6a-CH), 3.9-4.2 (4H, m, -SO2CH2CH2SO2-), 5.15 (1H, broad, s, 3-CH), 5.80 (1H, d, J 2.5 Hz, 5-CH). Example 16 Mixture of E and Z isomers of p-nitrobenzyl 2-(1'- oxido-1',3'-dithiolan-2'-ylmethylene)clavam-3-carboxylate EMI44.1 A solution of a mixture of E and Z isomers of pnitrobenzyl 2-(1',3'-dithiolan-2'-ylsethylene)clavam- 3-carboxylate (elO) (185 mg, 0.45 mmole) in dichloromethane (5 ml) was ice cooled and treated dropwise with a solution of m-chloroperbenzoic acid (86 mg, .50 mmole) in dichloromethane (2 ml). The mixture was stirred at 0-5 C for 1 hour, washed with 1N aqueous sodium bicarbonate solution (2 x 10 ml) and water (10 ml), dried over magnesium sulphate and evaporated under reduced pressure. The residue was chromatographed on silica as described in Example 1, eluting with ethyl acetate/ petrol 3:1 to provide a mixture of E and Z isomers of p-nitrobenzyl 2-(1'-oxido-l',3'-dithiolan-2'-ylmethylene) clavam-3-carboxylate (e18) (98 mg, 51%) as a colourless gum. Besides being a mixture of geometric isomers, the product was also a mixture of diastereoisomers and a t.l.c. on silica (eluent ethyl acetate) showed 4 zones between Rf 0.28 and 0.51. #max (CHCl3) 1805, 1755, 1680 and 1030 cm-1. Example 17 p-Nitrobenzyl 2-E-(2' ,2'-diphenylthioethylidene)clavam- 3-carboxylate and p-nitrobenzyl 2-Z- (2' , 2' -diphenyl thioethylidene) c lavam- 3-carboxylate EMI46.1 A mixture of E and Z isomers of p-nitrobenzyl 2 (2 -oxoethylidene) clavam-3-carboxylate (e4) (680 mg, 2.04 mmole) was dissolved in a mixture of dichloromethane (4 ml) and thiophenol (3 ml), ice cooled and treated with borontrifluoride diethyletherate (3 drops). The mixture was stirred at 0-50C for 1i hours, diluted with dichloromethane (50 ml) washed with 1N aqueous sodium bicarbonate solution (30 ml), dried over anhydrous magnesium sulphate and run onto a silica column (40 g silica). Chromatography was carried ot as described in Example 1, eluting with ethyl acetate/petol 1:4 to provide p-nitrobenzyl 2-E-(2',2'-diphenylthioethylidene) clavam-3-carboxylate and p-nitrobenzyl 2-Z-(2',2'-diphenylthioethylidene)clavam-3-carboxylate. Less polar isomer (e19) (colourless gum, 114 mg, 10.5%): [&alpha;]20-59.0 (c. 1.1; CHCl3); Vmax (CHC13) D 1805, 1755 and 1680 cm-1; # (CDCl3) 2.91 (1H, d, J 17 Hz, 6ss-CH), 3.39 (1H, dd, J 17 and 2.5 Hz, 6&alpha;-CH), 4.77 (1H, d, J 1.5 Hz, 3-CH), 4.9-5.4 (4H, m, -OCH2Ar, 8-CH and 9-CH), 5.61 (1H, d, J 2.5 Hz, 5-CH), 7.1-7.6 12H, m, Ph-H and 2 nitrobenzyl-H), 8.14 (2H, d, 2 nitrobenzyl-H). More polar isomer (e20) (colourless gum, 137 mg, 12.5): [&alpha;]20+17.4 (c. 1.0; CHC13); #max (CHCl3) D 1805, 1755 and 1685 cm-1; 6 (CDCl3) 2.63 (lH, d, J 17 Hz, 6ss-CH), 3.32 (1H, dd, J 17 and 2.5 Hz, 6&alpha;-CH), 4.74 (1H, dd, J 10.5 and 1.5 Hz, 8-CH), 5.00 (1H, d, J 1.5 Hz, 3-CH), 5.16 (2H, s, -OCH2Ar), 5.32 (1H, d, J 10.5 Hz, 9-CH), 5.43 (1H, d, J 2.5 Hz, 5-CH), 7.1-7.6 (12H, m, Ph-H and 2 p-nitrobenzyl-H), 8.19 (2H, d, 2 p-nitrobenzyl-H). Example 18 Lithium 2-(2',2'-diphenylthiethylidene)clavam-3 carboxylate (less polar isomer) EMI48.1 A solution of p-nitrobenzyl 2-(2',2'-diphenylthio ethylidene)clavam-3-carboxylate (less polar product of Example 17, 43 mg, .080 mmole) in tetrahydrofuran (2 ml) was added to a pre-hydrogenated suspension of 10% Pd/c (65 mg) in tetrahydrofuran (4 ml). Hydrogenolysis was carried out for 1 hours, the suspension filtered through celite and the filtrate evaporated to 2 ml under reduced pressure. This solution was ice cooled, treated with water (5 ml) and 0.1M aqueous lithium carbonate solution (0.81 ml) and washed with her (3 x 10 ml). The aqueous solution was adjusted to pH7 with 0.1N hydrochloric acid and evaporated under reduced pressure. The residue was chromatographed as described in Example 4 to provide lithium 2-(2',2' diphenylthioethylidene) clavam-3-carboxylate (less polar isomer on silica t.l.c., eluent chloroform/acetone/ glacial acid 50:50:7, 20 mg, 62%) as a buff solid. #max (KBr) 1785, 1675(s) and 1625 cm-1; # (D20-HODE4.60) 2.68 (1H, d, J 17 Hz, 6&beta;-CH), 3.24 (1H, dd, H 17 and 2.5 Hz, 6a-OH), 4.82 (1H, dd, J 11.5 and 1.5 Hz, 8-CH), 5.27 (1H, d, J 11.5 Hz, 9-CH), 5.43 (1H, d, J 2.5 Hz, 5-CH), 7.1-7.5 (10H, m, Ph-H). Example 19 Lithium 2-(2t2-diphenYlthioethYlidene)clavam-3 carboxylate (more polar isomer) EMI50.1 A solution of p-nitrobenzyl 2-(2',2'-diphenyl thioethylidene)clavam-3-carboxylate (more polar product of Example 17, 65 mg, 0.122 mmole) in tetrahydrofuran (2 ml) was added to a pre-hydrogenated suspension of 108 Pd/c (100 mg) in tetrahydrofuran (5 ml). Hydrogenolysis was carried out for 1i hours, the suspension filtered through celite and the filtrate evaporated to 2 ml under reduced pressure. The solution was ice cooled, treated with water (5 ml) and 0.1M aqueous lithium carbonate solution (1.22 ml) and washed with ether (3 x 10 ml). The aqueous solution was adjusted to pH7 with 0.1N hydrochloric acid and evaporated under reduced pressure. The residue was chromatographed as described in Example 4 to provide lithium 2-(2',2'-diphenylthioethylidene) clavam-3-carboxylate (more polar isomer on silica t.l.c., eluent chloroform/acetone/glacial acetic acid 50:50:7, 20 mg, 41%) as a yellow solid. may (KBr) 1785, 1680 -1 max and 1620 cm ; 6 (D2O-HOD#4.60)2.48 (1H, d, J 17 Hz, 6$-CH), 3.21 (1H, dd, J 17 and 2.5 Hz, 6a-CH), 5.25 (1H, d, J 2.5 Hz, 5-CH), 7.0-7.5 (10H, m, Ph-H). Preparation 1 Benzyl 2-(2'-oxoethylidene)clavam-3-carboxylate This compound is described by Corbett, Howarth and Stirling, JCS, CHem Comm (1977) 808. Pyridinium chlorochromate (5.46 g) and powdered, anhydrous sodium acetate (0.37 g) were suspended in dichloromethane (150 ml), ice cooled and stirred vigorously. A solution of benzyl clavulanate (4.34 g) in dichloromethane (10 ml) was added and after 2 minutes the ice bath was removed. The mixture was stirred 45 minutes at room temperature, ethyl acetate (200 ml) added and the suspension filtered through celite. The filtrate was evaporated and the residue taken up in ethyl acetate/petrol 1:1 and filtered through a lem thick pad of silica (Merck Kieselgel 60, 230-400 mesh). The filtrate was evaporated and the residue chromatographed rapidly on silica (50 g in a 4 cm diameter column) to provide benzyl 2-(2' oxoethylidene) clavam-3-carboxylate (750 mg) as a mixture of E and Z isomers: may (CHC1 ) 1810, 1750, 1675, -l max 3 1650 and 1605 cm Preparation 2 Benzyl 2- (2 '-oxoethylidene) clavam-3-carboxylate (a) Benzyl 9-o-pyruvXl clavulanate EMI53.1 Benzyl clavulanate (2.89 g, 0.01 mole) was dissolved in dichloromethane (20 ml) and pyridine (0.81 ml, 0.01 mole), cooled to -30 C and treated dropwise with a solution of pyruvyl chloride (1.07 g, 0.01 mole) in dichloromethane (5 ml). The mixture was stirred for 30 minutes, washed with 0.5N hydro chloric acid (20 ml) and water (20 ml), dried over magnesium sulphate and evaporated under reduced pressure. The residue was chromatographed on silica, eluting with ethyl acetate/petrol (30% ethyl acetate) to provide benzyl 9-0-pyruvyl clavulanate (1.70 g, 47%) as a colourless gum. [a]20+41.40 (c. 1.1; CHCl3); D #max (CHCl3) 1810, 1750(s), 1740 and 1700 cm-1; # (CDCl3) 2.41 (3H, s, -COCH3), 3.04 (1H, d, J 17 Hz, 6ss-CH), 3.48 (1H, dd, J 17 and 3 Hz, 6a-OH), 4.7-5.0 (3H, m, 8-CH and 9-C), 5.09 (1H, s, 3-CH), 5.17 (2H, s, -0OH2Ph), 5.71 (1H, d, J 3 Hz, 5-CH), 7.33 (5H, s, Ph-H). (b) Benzyl 2- (2 '-oxoethylidene)clavam-3-carboxylate Benzyl 9-O-pyrwyl clavulanate (100 mg, 0.28 mmole) was dissolved in dry benzene (200 ml) in a quartz vessel and dry nitrogen bubbled through the solution for 1 hours. The nitrogen flow was continued and the vessel water cooled while being irradiated from a Hanovia medium pressure W lamp for 45 minutes. T.l.c. (silica, eluent ethyl acetate/petrol 1:1) indicated complete conversion of benzyl 9-0-pyruvyl clavulanate to benzyl 2-(2'-oxoethylidene)clavam3-carboxylate. The solution was evaporated under reduced pressure and the residue chromatographed rapidly on silica (5 g) to provide benzyl 2-(2'-oxoethylidene) clavam-3-carboxylate (50 mg, 62%) as a mixture of E and Z isomers. Preparation 3 p-Nitrobenzyl 2-(2'-oxoethylidene)clavam-3-carboxylate Pyridinium chlorochromate (4.85 g) and powdered anhydrous sodium acetate (0.37 g) were suspended in dichloromethane (150 ml), ice cooled and stirred vigorously. A solution of p-nitrobenzyl clavulanate (5 g) in dichloromethane (20 ml) was added and after 2 minutes the ice bath was removed. The mixture was stirred for 45 minutes at room temperature and worked up exactly as described in Preparation 1 to provide p-nitrobenzyl 2-(2'-oxoethylidene)clavam-3-carboxylate (600 mg)as a yellow oil (mixture of E arid Z isomers). max (CHC13) 1810, 1750, 1670, 1645 and 1605 cam . Preparation 4 p-Nitrobenzyl 2-(2'-oxoethylidene)clavam-3-carboxylate (a) p-Nitrobenzyl 9-0-pyruvyl clavulanate EMI56.1 p-Nitrobenzyl clavulanate (2.0 g, 6 mmole) was dissolved in dichloromethane (20 ml) and pyridine (0.507 ml, 6.3 mole, cooled to -30 C and treated dropwise with a solution of pyruvyl chloride (0.67 g, 6.3 mmole) in dichloromethane (5 ml). The solution was stirred 30 minutes, washed with 0.5N hydrochLoric acid (20 ml) and water (20 ml), dried over magnesium sulphate and evaporated under reduced pressure. The residue was chromatographed on silica, eluting with ethyl acetate/petrol (40% ethyl acetate) to provide p-nitrobenzyl 9-0-pyruvyl clavulanate (1.2 g, 50%) as a pale yellow gum. may (CHC1 ) 1810, 1755, 1735 -l max 3 and 1700 cm ; 6 (CDC13) 2.44 (3H, s, -COCH ), 3.11 3 (1H, d, J 17 Hz, 66-CH), 3.54 (lH, dd, J 17 and 2.5 Hz, 6a-CH), 4.7-5.1 (3H, m, 8-CH and 9-CH2), 5.14 (1H, s, 3-CH), 5.28 (2H, s, -ocH2Ar) 5.73 (1H, d, J 2.5 Hz, 5-CH), 7.51 and 8.24 (4H, 2d, Ar-H). (b) p-Nitrobenzvl 2- (2' -oxoethylidene) clavam-3- carboxylate p-Nitrobenzyl 9-0-pyruvyl clavulanate (200 mg) was dissolved in dry benzene (200 ml) in a quartz vessel and dry nitrogen bubbled through the solution for 1 hour. The nitrogen flow was continued and the vessel water cooled while being irradiated from a Hanovia medium pressure W lamp for-4 hours. The solution was then evaporated under reduced pressure and the residue chromatographed rapidly on silica (5 g) to provide p-nitrobenzyl 2-(2'-oxoethylidene) clavam-3-carboxylate (50 mg, 30%) as a mixture of E and Z isomers. BIOLOGICAL DATA Synergistic activity in vitro of some of the Compounds of the present invention. EMI58.1 <tb> Inhibitor <SEP> Staph <SEP> Klebsiella <SEP> E. <SEP> coli <tb> Compound <SEP> Conc <SEP> aureus <SEP> aerogenes <SEP> JT <SEP> 39 <tb> <SEP> (m5/ml) <SEP> Russell <SEP> E70 <tb> Amoxycillin <SEP> alone <SEP> - <SEP> 500 <SEP> 250-500 <SEP> W2000 <SEP> <tb> Amoxycillin <SEP> with <SEP> Compound <SEP> 5 <SEP> 0.3 <SEP> 12.5 <SEP> 8 <tb> of <SEP> Example <SEP> No <SEP> 10 <tb> <SEP> 1 <SEP> 0.6 <SEP> 50 <SEP> 31.2 <tb> Amoxycillin <SEP> with <SEP> Compound <SEP> 5 <SEP> 0.6 <SEP> 3.1 <SEP> 2 <tb> of <SEP> Example <SEP> No <SEP> 12 <tb> <SEP> 1 <SEP> 1.25 <SEP> 3.1 <SEP> 8 <tb> Amoxycillin <SEP> with <SEP> Compound <SEP> 5 <SEP> 0.6 <SEP> 50 <SEP> > 500 <tb> of <SEP> Example <SEP> No <SEP> 4 <tb> <SEP> 1 <SEP> 2.5 <SEP> > 100 <SEP> > 500 <tb> Amoxycillin <SEP> with <SEP> Compound <SEP> 5 <SEP> 0.08 <SEP> 25 <SEP> 62.5 <tb> of <SEP> Example <SEP> No <SEP> 5 <tb> <SEP> 1 <SEP> 0.6 <SEP> 100 <SEP> > 500 <tb>

Claims: CLAIMS 1. A compound of formula (I) or a pharmaceutically acceptable salt or in vivo hydrolysable ester thereof: EMI59.1 wherein R1 is a group of structure (II) or (III): EMI59.2 wherein Rê and R may be the same or different and each represents C16 alkyl optionally substituted by C1-6 alkoxy, phenyl, hydroxy, carboxy or C16 alkoxycarbonyl, or phenyl optionally substituted by C1-6 alkyl, halogen, C1¯6 alkoxy, hydroxy, carboxy or C1-6 alkoxycarbonyl; ZÚ and Zê may be the same or different and each represents S, SO or SO2 and Y represents a C2 3 saturated hydrocarbon radical optionally substituted by C1-6 alkyl, C1-6 alkoxy, hydroxy, carboxy, or C1-6 alkoxycarbonyl. 2. A compound as claimed in claim 1 wherein R2 and R3 may be the same or different and each represents methyl, ethyl, n- or iso-propyl, n-, sec-, tert- or iso-butyl, benzyl or phenyl. 3. A compound as claimed in claim 1 or claim 2 wherein Rê and R are the same. 4. A compound as claimed in claim 1 of formula (IV) or a pharmaceutically acceptable salt or in vivo hydrolysable ester thereof: EMI60.1 wherein Z1 and z2 are as defined hereinbefore with respect to formula (I), and n is an integer from 2 to 3. 5. A compound as claimed in claim 4 wherein n is 2. 6. A compound as claimed in claim 4 or claim 5 wherein zl and z2 are the same and represent S or 802. 7. A compound as claimed in claim 6 wherein Z and Z are the same and represent S02, 8. A process for the preparation of a compound of formula (I) or a pharmaceutically acceptable salt or in vivo hydrolysable ester thereof which process comprises reacting a compound of formula (V): EMI61.1 wherein RX is a carboxyl blocking group; (1) with compounds R2SH and R SH wherein R2 and are as defined with respect to formula (I) and wherein any reactive groups may be protected; or (2) with a compound of formula HS-Y-SH wherein Y is as defined with respect to formula (I) and wherein any reactive groups may be protected; in the presence of a Lewis acid catalyst: and thereafter where necessary carrying out one or more of the following steps: (a) oxidising a sulphide to a sulphoxide or sulphone derivative; (b) removing the carboxy blocking group Rx; (c) removing any protecting groups on R2 or R3 or Y; and (d) converting the compound to a free carboxylic acid, a pharmaceutically acceptable salt or in vivo hydrolysable ester. 9. A pharmaceutical composition which comprises a compound as claimed in any one of claims 1 to 7 together with a pharmaceutically acceptable carrier. 10. A method of treating bacterial infections in humans or domestic mammals which comprises the administration of a compound as claimed in claim 1.

Inventors: BROOKS, GERALD
Applicants: BEECHAM GROUP PLC
Application year: 1981
Main classification: C07D498
IPC codes: A61P31, C07D503, A61K31