GB1572259A - Clavulanic acid derivatives - Google Patents

Description

(54) CLAVULANIC ACID DERIVATIVES (71) We, BEECHAM GROUP LIMITED, of Beecham House, Great West Road, Brentford, Middlesex, a British Company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed. to be particularly described in and by the following statement: The present invention relates to ci process for the preparation of ethers. to new ethers and to compositions containing them.

British Patent Application No. 41897/75 - 19000/76 - 02629/76 Serial No. 1565209 (equivalent to Belgian Patent No. 847045, and U.S. Serial No. 730.475) discloses that esters of clavulanic acid may be esterified in conventional manner, for example by reaction with a diazo compound. It has now been discovered that if a metalic catalyst is included in the reaction mixture then particularly favourable results can be obtained. l'he present invention provides a process for the preparation of the compounds of the formula (I):

wherein A is a group such that CO2A is a carboxylic acid group or a salt or ester thereof: R is a CO@R3. CO2R3, SOnR-. CN. NO2, PO(OR4). or phenyl group where R3 is a lower alkyl, lower alkenyl phenyl or lower alkyl phenyl group, R4 is a lower alkyl, phenyl or lower alkyl phenyl group; and R2 is a hydrogen atom ar a CO.R5, CO2R5 or CONR5R5 group where R5 is a lower alkyl, phenyl or lower alkyl phenyl group and R5 is a lower alkyl group optionally jointed to R5: which process comprises the reaction of a compound of the formula (II): N2CR1R2 (II) wherein R, and R2 are as defined in relation to formua (I) with an ester of clavulanic acid in the presence of a carbene generating transition metal or transition metal salt catalyst and thereafter if desired converting the thus formed ester to the free acid or salt thereof and thereafter if desired converting the thus formed acid or salt to an ester.

The term "lower" when used herein means that the group contains up to 4 carbon atoms.

It is believed that the etherification reaction according to this invention proceeds primarily via the generation of a carbene of the formula (111): :CR1R2 (III) wherein R1 and R. are as defined in relation to formula (11). Once formed the carbene of the formula (III) reacts rapidly with the allylic hydroxyl group of the clavulanic acid ester.

Suitable carbene generating transition metal or transition metal salt catalysts include finely divided metalic copper. copper salts such as cupric acetylacetate, cuprous chloride, cupric chloride or rhodium salts such as rhodium acetate. Other similar agents known to induce the elimination of nitrogen from diazo compound with the formation of a carbene may also be used.

A preferred catalyst is finely divided copper powder.

The etherification reaction is normally effected in an inert organic solvent such as benzene, toluene or dimethoxyethane. The reaction medium is normally kept scrupulously dry and is most suitably maintained under an inert atmosphere such as nitrogen or argon.

In general any non-extreme temperature may be employed for the etherification, for example 0 to 120 C. but in general a somewhat elevated reaction temperature is most suitable, for example 10 to 100 C. A favoured temperature for the reaction is 15 - 85 C.

A particularly suitable method of carrying out the etherification is to slowly add the diazo compound to a heated mixture of the ester of clavulanic acid and.the catalyst in the inert solvent.

A suitable method of recovering the ether from the reaction mixture is to filter the reaction mixture and evaporate the filtrate under reduced pressure to yield a concentrated solution. This may then be applied to a chromatography column. for example of silica gel, and the purified product gradiently eluted therefrom in conventional manner, for example using mixtures of ethyl acetate and cyclohexane. The fraction containing the ether, may be detected by potassium permanganate spray on a standard tic plate. These fractions may be combined and evaporated to yield the purified ester.

Suitable groups R1 for inclusion in the compounds of the formula (I) and (II) include the CO.CH3, CO.C2H5, CO.CH=CH2. CO.CH2C6H5, CO.C6H5 CO2CH3, CO2C2H5, CO2CH2C6H5, and CO2C6H5.

Suitable groups R2 for inclusion in the compounds of the formula (I) and (II) include the hydrogen atom and the CO.CH3, CO.C2H5, CO.CH=CH2, CO.CH2C6H5, CO.C6H5, CO2C2H5, CO2CH3, CO2CH2C6H5, and CO2C6H5.

Particularly suitable esters of clavulanic acid for use in the etherification reaction include those of the formulae (IV) and (V):

wherein A1 is an alkyl group of 1-6 carbon atoms optionally substituted by an alkoxyl or acvloxyl group of 1-7 carbon atoms: A2 is an alkenyl group of up to 5 carbon atoms or is a phenyl group optionally substituted bv fluorine. chlorine, bromine, nitro or alkyl or alkoxyl of up to 4 carbon atoms; and A3 is a hydrogen atom, an alkyl group of up to 4 carbon atoms; and A3 is a hydrogen atom, an alkyl group of up to 4 carbon atoms or a phenyl group optionally substituted by a fluorine, chlorine or bromine atom or an alkyl or alkoxyl group of up to 4 carbon atoms.

Particularly suitable esters of clavulanic acid for use in the etherification process include the methoxymethyl. benzvl and p-methoxybenzyl esters.

The compounds of the formula (1) wherein A is a group such that CO2A is an ester group mav be converted to the corresponding free carboxylic acid or salt thereof by those processes known to be suitable for converting esters of clavulanic acid into clavulanic acid per se or a salt thereof. Particularly suitable methods include the mild base hydrolysis of the methoxymethyl ester or hydrogenolysis of the benzvl or p-methoxybenzyl ester.

Salts within formula (I) may he prepared from esters within formula (I) be very mild basic hydrolysis. for example bv hvdrolvsis in an aqueous solution maintained at pH 7 to 9 by the slow addition of base.

Acids and salts within formula (I) may be prepared from hydrogenolysable esters within formula (1) by hydrogenation using a medium or low pressure of hydrogen in the presence of a transition metal catalyst.

Palladium, for example 10% palladium on charcoal, has proved a particularly useful catalyst. We have found that on charcoal used to the weight of ether used is 1:3.

The hydrogenation reaction preferably occurs in a solution in a solvent which consists of or contains tetrahydrofuran.

If a base such as sodium hydrogen carbonate, potassium hydrogen carbonate, lithium carbonate. or calcium carbonate is included in the reaction mixture then the resulting compound is in the form of a salt. If no such base is included the product is in the form of the free acid.

Acids within formula (1) may also be prepared by the careful acidification of the corresponding sodium salt.

Esters within the formula (I) may be prepared by the reaction of a corresponding salt such as an alkali metal salt within the formula (I) with an esterifying agent such as a halide or active ester such as a chloride, bromide, iodide, methane sulphonate or toluene sulphonate or by reaction of an acid within formula (1) with a diazo-compound. Such reactions proceed under conventional conditions.

In a further aspect the present invention provides the compounds of the formulae (VI) and (VII):

wherein R and A are as defined in relation to formula (I) and R6 is a CO.R5. CO2R5 or CO.NR5R group where R5 and R1 are defined as in formula (I) and R7 is a SO2R3. NO. or PO(OR4)2 group where R3 and R4 are defined in relation to formula (I).

Suitable values for R1 in the compounds of the formula (VI) include the CO.CH3, CO.C2H5, CO.CH=CH2, CO.CH2C6H5, CO.C6H5, CO2CH3, CO2C2H5, CO2CH2C6H5, CO2C6H5, PO(OCH3)2 or PO(OC2H5)2.

Suitable values for R6 in the compounds of the formula (VI) include the COCH3, CO.C2H5, CO.CH=CH2, CO.CH2C6H5, CO.C6H5, CO2CH3, CO2C2H5, CO2CH2C6H5 or CO2C6H5.

Suitable values for R7 in the compounds of the formula (VII) include the SO2CH3, SO2C6H5, PO(OCH3)2 or PO(OC2H5)2.

Suitable values for A in the esters within formulae (VI) and (VII) include A1 and CHA2A3 as defined in relation to formula (IV) and (V). Particularly suitable values for A in esters within formula (VI) and (VII) include the methoxymethyl, benzyl and pmethoxvbenzyl groups.

Suitable values for A in the salts within formulae (VI) and (ill) include the lithium, sodium. potassium and calcium ions.

The present invention also provides pharmaceutical compositions which comprise 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 and disintegrants 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 salts of a compound of the formula (1) are particularly suitable as high tissue levels of a compound of the formula (I) can occur after administration bv injection or infusion. ?'huts, one preferred composition aspect of this invention comprises a salt of a compound of the formula (I) in sterile form.

Unit dose compositions comprising a compound of the formula (1) or a salt or ester thereof adapted for oral administration form a further preferred composition aspect of this invention.

The compound of the formula (I) or its salt or ester may be present in the composition as sole therapeutic agent or it may be present together with other therapeutic agents such as a -lactam antibiotic. Suitable -lactam antibiotics for inclusion in the compositions of this invention include benzylpenicillin, phenoxymethylpenicillin, carbenicillin, azidocillin, propicillin. ampicillin, amoxycillin, epicillin, ticarcillin, cyclacillin, cefatriazine. pirbenicil lin, a-sulphonyloxybenzylpenicillin, cephaloridine, cephalothin, cefazolin, cephalexin, cefoxitin, cephacetrile, cephamandole nafate, cephapirin, cephradine. 4-hydroxy cephalexin, cefaparole, cephaloglycine. and other well known penicillins and cephalospor ins or pro-drugs therefore such as hetacillin, metampicillin, 4-acetoxyampicillin, the acetoxymethyl, ethoxycarbonyloxymethyl, pivaloyloxymethyl or phthalidyl esters of benzylpenicillin or ampicillin. or the phenyl or indanyl esters of carbenicillin or ticarcillin.

Such compounds are frequently used in the form of a salt or hydrate.

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.

When present in a pharmaceutical composition together with a -lactam antibiotic. the ratio of a compound of the formula (I) or its salt or ester present to -lactam antibiotic present may vary over a wide range of ratios, for example 3:1 to 1:10 and advantageously may be from 2:1 to 1:8. for example, 1:1, 1:2. 1:3. 1:4 or 1:5.

The quantity of compound of this invention in anv unit dosage form will normally be between 25 and 750 mg and will usually be between 5() and 500 mg. for example 62.5, 10, 150 or 200 mg.

Compositions of this invention may be used for the treatment of infections or inter alia, the respiratory tract. the urinarv tract and soft tissues and mastitis in cattle.

Normally between 50 and 1()()0 mg of the compounds of the invention will be administered each day of treatment but more usually between 100 and 750 mg of the compounds of the invention will be administered per day, for example as 1-6 doses. more usually 2-4 doses.

The penicillin or cephalosporin in synergistic compositions of this invention will normally be present in an amount at which it is conventionally used.

Particularly favoured compositions of this invention will contain from 150-1000 mg of amoxycillin. ampicillin or a pro-drug therefore and from 50-500 mg of a compound of the formula (1) or a salt or ester thereof and more suitably from 200 to 500 mg of amoxycillin or a salt therefore and from 50-250 mg of a compound of the formula (I) or a salt thereof.

The materials present in such compositions may be hydrated if required. for example ampicillin trihvdrate or amoxycillin trihydrate may be employed. The weights of the antibiotics in such compositions are expressed on the basis of antibiotic theoretically available from the composition and not on the basis of the weight of pro-drug.

The following Examples illustrate this invention: EXAMPLE I p-Methoxybenzyl 9-0-(dimethoxycarbonyl)methylclavulanate

p-Methoxybenzyl clavulanate ( I ) (1.7X g) in l,2-dimethoxyethane (5 ml) was treated with rhodium acetate (X mg) in l,2-dimethoxyethane (I ml). The mixture was heated at 80" under an atmosphere of argon and dimethyl diazomalonate (950 mg) in 1,2dimethoxyethane (3 ml) was added dropwise. After 2 hours more dimethyl diazomalon ate (316 mg) was added and heating was continued a further 2 hours. The solvent was removed in vacuo and the residue was chromatographed on silica gel, eluting with ethyl a c e t a t e / c y c l o h e x a n e m i x t u r e s t o g i v e p - m e t h o x y b e n z y l 9 - 0 (dimethoxycarbonyl)methylclavulanate (2) (614 mg) as a oil, #max (CHCl3) 1805, 1750, 1695 cm-1, # (CDCl3) 3.01 (1H, d, J 17Hz, 6 -CH), 3.45 (1H, dd, J 17Hz and 3Hz, 6α-CH), 3.74 (9H, s, 3 x OCH3), 4.20 (2H, d, J 8HZ, 9-CH2), 4.44 [s, 1H, 0-CH(CO2)2], 4.79 (1H, broad t, J 8Hz, 8-CH), 5.00 (1H, broadened s, 3-CH), 5.08 (2H, s, OCH2Ar), 5.61 (1H, d, J 3Hz, 5-CH), 6.81 (2H, d, J 9 Hz, 2 x Ar-H), 7.22 (2H, d, J 9Hz, 2 x Ar-H).

EXAMPLE 2 Sodium 9-0-(di-methoxycarbonyl)methylclavulanate

p-Methoxybenzyl 9-0-(di-methoxycarbonyl)methylclavulanate (191 mg) was taken up in tetrahydrofuran (8 ml) and water (1.8 ml) and sodium hydrogen carbonate (36 mg), followed by 10% Pd/C catalyst (60 mg), was added. The mixture was hydrogenated for 20 minutes and then the catalyst was filtered and washed with water. The filtrate and washings were combined, the tetrahydrofuran was evaporated on a rotary evaporator and ethyl acetate and water were added to the residual solution. After shaking and separation the aqueous layer was evaporated in the following sequence: CH2CN (2x), toluene (1x), CH3CN (1x, evaporated to leave a small quantity of CH3CN) and finally toluene. This left sodium 9-0-(dimethoxycarbonyl)methylclavulanate as a white solid (132 mg). Found: C, 43.27; H, 4.21; N, 3.83%. C13H14NO9H2O requires C, 43.33; H, 4.17; N, 3.89%; #max (KBr) 1790, 1765-1745 (br), 1695, 1620 cm-1; # (D2O, CH3CN internal standard at # 2.00), 3.08 (1H, d, J 17Hz, 6 -Ch), 3.60 (1H, dd, J 17Hz and 3Hz, 6α-CH), 3.74 (6H, s, 2x CO2CH3), 4.29 (2H, d, J 8Hz, 9-CH2), 5.75 (1H, d, J 3Hz, 5-CH) p.p.m.

EXAMPLE 3 p-Methoxybenzyl 9-0-ethoxycarbonylmethylclavulanate

Method I p-Methoxybenzyl clavulanate (320 mg) in dry toluene (3 ml) was heated at 800 under an atmosphere of argon and ethyl diazoacetate (130 mg) in toluene (1.5 ml) was added slowly.

No evolution of nitrogen was observed until copper powder (200 mg) was added, whereupon a slow evolution of gas was observed. When all the diazo acetate had been consumed (the reaction was monitored by t.l.c.), more ethyl diazoacetate (100 mg) in toluene (1 ml) was added and heating was continued until this had been consumed. The reaction mixture was then filtered and the solution was evaporated to low volume on a rotary evaporator and then chromatographed on silica gel. eluting with toluene and then ethyl acetate/cyclohexane mixtures (gradient elution from 2:8 to 1:) to give pmethoxybenzyl 9-0-ethoxycarbonylmethylclavulanate (340 mg, 83% yield), #max (CHCl3) 1800, 1745, 1695, 1610 cm-1; # p.p.m. (CDCl3) 1.27 (3H, t, J 7Hz, CH3CH2), 2.98 (1H, d, J 17Hz, 6 -CH), 3.51 (1H, dd, J 17 and 3Hz, 6α-CH), 3.80 (3H, s, OCH3), 3.98 (2H, s, -OCH2CO2-), 4.16 (2H, d, J 8Hz, 9-CH2), 4.20 (2H, q, J 7Hz, -CH2CH3), 4.83 (1H, dt, J 8HZ and 1Hz,, 8-CH), 5.08 (1H, broad s, 3-CH), 5.13 (2H, s, OCH2Ar), 5.67 (1H, d, J 3Hz, 5-CH), 6.88 (2H, d, J 9Hz, 2xAr-H), 7.30 (2H, d, J 9Hz, 2xAr-H).

Method 2 p-Methoxybenzyl clavulanate (320 mg) and rhodium acetate (3 mg) in toluene (3 ml) were heated to 800 under an atmosphere of argon and ethyl diazoacetate (120 mg) in toluene (1.5 ml) was added slowly (over ca. 10 minutes). The diazoacetate was rapidly consumed, and more ethyl diazoacetate (130 mg) in toluene (1 ml) was added over ca. 15 min. After heating for a further 10 minutes the reaction mixture was cooled, filtered and the toluene was evaporated on a rotary evaporator. The residue was chromatographed on silica gel, eluting with toluene, followed by ethyl acetate/cyclohexane mixtures (gradient elution from 2:8 to 1:1) to give the ether (237 mg, 58% yield), together with recovered starting clavulanate (30 mg, 9%).

Method 3 p-Methoxybenzylclavulanate (320 mg) and cupric acetylacetonate (262 mg) in toluene (4 mg) was heated to 80 under an atmosphere of argon and ethyldiazoacetate (150 mg) in toluene (2 ml) was added dropwise over ca. hr. The mixture was heated at 80 for a further 1 hour. cooled, filtered, and the toluene evaporated to leave a gum which was chromatographed as in method 2 to give the ether (62 mg, 15% yield).

Method 4 p-Methoxybenzyl clavulanate (107 mg) in 1,2-dimethoxyethane (1 ml) containing rhodium acetate (2 mg) was stirred and ethyl diazoacetate (50 mg) was added. The mixture was stirred for 2 hr, when more diazoacetate (100 mg) was added. Stirring was continued for 16 hr and then ethyl diazoacetate (100 mg) was added and stirring was continued for 3 days. The 1.2-dimethoxyethane was evaporated. The residue was chromatographed to give, after evaporation of the fractions containing the ether, an oil (110 mg).

Method 5 p-Methoxybenzylclavulanate (110 mg) and copper (II) chloride dihydrate (100 mg) in benzene (5 ml) were heated under reflux in an atmosphere of argon for 20 minutes and then ethyldiazoacetate (50 mg) was added. The mixture was heated under reflux for a further 1 hour. and was then cooled and filtered. The benzene was removed in vacuo to leave an oil which was chromatographed on silica gel as in method 2 to give the ether (12 mg. 8% yield).

Method 6 p-Methoxybenzylclavulanate (110 mg) was treated with copper (I) chloride (100 mg) and ethyldiazoacetate (50 mg) in an analogous manner to method 5 to give the ether (20 mg, 14% yield).

EXAMPLE 4 p-Methoxybenzyl 9-0-(1-methoxycarbonyl-2-oxo)propylclavulanate

p-Methoxybenzyl clavulanate (960 mg) and copper powder (600 mg) in dry toluene (10 ml) were heated to 80 under an atmosphere of argon and methyl α-diazoacetoacetate (500 mg) in toluene (3 ml) was added. After heating for 1 hr nearly all of the diazo-compound had been consumed, and more diazo compound (110 mg) in toluene (2 ml) was added; heating was continued for a further 2 hr. After cooling the mixture was filtered. the solvent evaporated, and the crude product chromatographed on silica gel to give p-methoxybenzyl 9-0-(1-methoxycarbonyl-2-oxo(propylclavulanate (525 mg, 40.5%) as an oil; spectral data revealed that it was a mixture of the two ketoforms (ca. 1:1), together with a small amount of enol from (ca. 10%). #max (CHCl3) 1805, 1750, 1700 (sh) 1660, 1615 cm-1, # p.p.m.

(CDCl3) (of two ketoforms) 2.20 (3H, s, COCH3), 3.02 (1H, d, J 17Hz, 6 -CH), 3.53 (1H, dd, J 17 and 3Hz, 6α-CH), 3.76 (3H, s, -OCH3), 3.79 (3H, s, -OCH3), 4.21 (2H, broadened d, J 8Hz, 9-CH2), 4.34 and 4.37 (1H, 2 singlets,

-2 forms), 4.7 - 5.0 (1H, m, 8-CH), 5.07 (1H, m 3-CH), 5.13 (2H, s, OCH2Ar), 5.60 (1H, m, 5-CH), 6.90 (2H, d, J 8Hz, 2xAr-H), 7.21 (2H, d, J 8Hz, 2xAR-H). The signal due to the hydroxy group of the enol form appears at # 11.0 p.p.m. Later fractions also yielded slightly impure ether (211 mg, 16%).

EXAMPLE 5 Sodium 9-0-(1-methoxycarbonyl-2-oxo)propylclavulanate

p-Methoxybenzyl 9-0-(1-methoxycarbonyl-2-oxo)propylclavulanate (205 mg), sodium hydrogen carbonate (40 mg) and 10% Pd/C catalyst (60 mg) were hydrogenated in tetrahydrofuran (8 ml) containing water (1.8 ml) for 20 minutes, and the reaction was then worked up by a similar procedure to that described for sodium 9-0-(dimethoxycarbonyl)methylclavulanate. Sodium 9-0-(1-methoxycarbonyl-2oxo)propylclavulanate was obtained as a white solid, #max (KBr) 1790, 1750, 1725, 1690 and 1620 cm-1.

EXAMPLE 6 Methoxy 9-0-phenacylclavulanate

Methoxymetyl clavulanate (3.3 g) and diazoacetophenone (2.5 g) were dissolved in sodium-dried benzene (30 ml) and copper powder (1.0 g) added. The solution was stirred at room temperature for twenty hours after which the copper was removed by filtration, and the solution evaporated. Chromatography over silica gel (eluting with ethyl acetate/petrol ether (60-80) yielded the title compound (620 mg) as a clear oil; #max (L.F.) 1805, 1750, 1700, 1690 CM-1; # (CDCl3) 3.04 (1H, d, J 17Hz, 6 -CH), 3.57 (1H, dd, J 17Hz and 2.5Hz, 6α-CH), 3.50 (3H, s, CH2OCH3). 4.33 (2H, d, J 8Hz, 9-CH2), 4.80 (2H, s, OCH2CO), 5.04 (1H, t, J 8Hz, 8-CH), 5.20 (1H, s, 3-CH),5.30, 5.43 (2H, ABq, J 7Hz, OCH2O), 5.75 (1H, d, J 2.5Hz, 5-CH). 7.5 - 8.1 (5H, m, aromatic).

Further solvent elution yielded starting material (490 mg).

EXAMPLE 7 Benzyl 9-0-acetonylclavulanate

Benzvl clavulanate (6. g) and diazo-acetone (2.0 g) were dissolved in sodium-dried benzene (50 ml). and copper powder (2.0 g) added. The solution was stirred at room temperature for fortv-eight hours, after which the copper was removed bv filtration. and the solution evaporated. Chromatography over silica gel [eluting with ethyl acetate/petrol ether (60-80)] yielded the title compound (2.31) g; 33% or 50% based on recovered starting material: #max (CHCl3) 1800, 1740-1760, 1700 cm-1; b (CDCl3) 2.1() (3H. s.

(1H, d, J 17Hz, 6 -CH), 3.55 (1H, dd. J 17Hz and 2.5Hz, 6α-CH), 3.93 (2H, s, OCH2CO), 4.16 (2H, d, J 7HZ. 9-CH2), 4.85 (1H, t, J 7Hz, 8-CH), 5.15 (1H, s, 3-CH), 5.25 (2H, s, CO2CH2Ph), 5.75 (1H, d, J 2.5Hz, 5-CH), 7.40 (5H, s, CO2CH2Ph).

Further solvent elution yielded benzyl clavulanate (2.18 g).

EXAMPLE 8 p-Methoxybenzyl 9-0-(ethoxycarbonyl)diethylphosphonomethylclavulanate

p-Methoxybenzyl clavulanate (320 mg) in toluene (3 ml) was heated to 84 under argon and copper powder (200 mg), followed by triethyl diazophosphonoacetate (200 mg), was added. After heating for 3 hours the mixture was cooled, the copper removed by filtration, and the toluene evaporated in vacuo. The residual oil was chromatographed on silica gel to give p-methoxybenzyl 9-0-(ethoxycarbonyl)diethylphosphonometyl clavulanate (310 mg, 57%), #max (CHCl3) 1805, 1745, 1700 (sh), 1615 cm-1; (CDCl3) 1.1 - 1.5 (9H, m, 3xCH3CH2-), 2.98 (1H, d, J 17Hz,6 -CH), 3.41 (1H, dd, J 17 and 3Hz. 6α-CH).

3.74 (3H, s, OCH3), 3.9 - 4.4 (9H, m, 3x0CH2CH3, 9-CH2.

4.75 (1H, t J 8HZ, 8-CH), 4.98 (1H, m, 3-CH), 5.05 (2H, s, OCH2Ar), 5.57 (1H, d, J 3Hz, 5-CH), 6.80 (2H, d, J 9Hz, 2xAr-H), 7.20 (2H, d, J 9Hz, 2xAr-H).

EXAMPLE 9 Sodium 9-0-(ethoxycarbonyl)diethylphosphonomethylclavulanate

p-Methoxybenzyl 9-0-(ethoxycarbonyl)diethylphosphonomethylclavulanate (541 mg) in tetrahydrofuran (10 ml) containing water (2 ml), sodium hydrogen carbonate (36 mg), and 10% Pd/C catalyst, was hydrogenated for 25 minutes. The catalyst was filtered and washed with water. The filtrate and washings were combined and the tetrahydrofuran was removed in vacuo. The remaining aqueous solution was diluted with water and washed with ethyl acetate, and then evaporated. Acetonitrile, toluene and ethanol were added and evaporated in vacuo in the following sequence: CH3CN (2x), toluene (1x), CH3CN (2x), toluene (3x), ethanol (1x) and finally toluene (2x) to leave sodium 9-0-(ethoxycarbonyl)diethylphosphonomethylclavulanate as a glass which solidified on trituration with ether.

The sodium salt was soluble in water, toluene, acetonitrile and chloroform and showed the following spectral characteristics: #max (CHCl3) 1790, 1745, 1695, 1630 cm-1.

EXAMPLE 10 Sodium 9-0-(1-Acetyl-2-oxopropyl) clavulante

p-methoxybenzyl 9-0-(1-acetyl-2-oxopropyl) clavulanate (320 mg) in tetrahydrofuran (10 ml) and water (2 ml) was hydrogenated over 10% Palladium on carbon catalyst (100 mg) in the presence of sodium hydrogen carbonate (63 mg). After 20 min. the catalyst was filtered off and washed with water and tetrahydrofuran. The tetrahydrofuran was evaporated in vacuo and ethyl acetate was added to the remaining aqueous solution. After shaking and separation the water was removed in vacuo from the aqueous solution, ethanol was added to the residue and evaporated in vacuo (2x), toluene was then added to the residue and evaporated in vacuo (2x) to give sodium 9-0-(1-acetyl-2-oxopropyl) clavulanate, #max (KBr) 1785, 1710-1690 (broad), 1620 (broad) cm-1.

EXAMPLE 11 p-Methoxybenzyl 9-0-(1-Acetyl-2-oxopropyl) clavulanate

p-Methoxybenzyl clavulanate (960 mg) in benzene (10 ml) was treated with diazoacetylacetone (400 mg) in benzene (2.5 ml). Copper powder (800 mg) was added and the mixture was stirred at ambient temperature for two weeks. The reaction mixture (copper included) was placed on the top of a silica gel column (50 g) and the column was eluted with toluene (20 ml), followed by ethyl acetate/cyclohexane mixtures: 4:6 (200 ml), 1:1 (200 ml).

The ether was obtained as an oil (322 mg) by combination and evaporation in vacuo of the requisite fractions. The ether showed the following spectral characteristics: #max (CH2Cl2) 1810, 1750, 1710 cm-1. # (CDCl3) (diketo form) 2.12 (6H. s. 2X COCH3. 3.00 (1H, d, J 17Hz, 6 -CH), 3.51 (1H. dd, J 17 and 3Hz, 6α-CH), 3.82 (3H. s. OCH3), 4.C-4.4 [3H, m. 9-CH2, OCH (COMe)2], 4.77 (1H, broad t. J 7Hz. 8-CH), 5.10 (1H. broad s, 3-CH), 5.18 (2H, s, OCH2 Ar) 5.69 (1H, d, J 3Hz, 5-CH), 6.89 (2H, d, J 9Hz, 2 x Ar-H), 7.31 (2H, d, J 9Hz, 2 x Ar-H).

EXAMPLE 12 Synergistic activity The minimum inhibitory concentration (MIC) of ampicillin alone or in the presence of certain compounds of this invention was determined for certain strains of bacteria. The results are shown below.

Claims (31)

MIC Ampicillin ( g/ml) Concentration Compound of Example Staph.aureus Klebsiella aerogenes No. Russell E70 2 0 500 1000 1 0.6 3.1 5 0.15 3.1 Compound alone 62 125 5 0 500 > 2000

1 0.3 3.1

5 0.15 1.6 Compound alone 62 125 WHAT WE CLAIM IS: 1. A process for the preparation of a compound of the formula (I):

wherein A is a group such that CO2A is a carboxylic acid group or a salt or ester thereof, R1 is a CO.R3, CO2R3, SO2R3, CN, NO2, PO(OR4)2 or phenyl group where R3 is a lower alkyl, lower alkenyl phenyl or lower alkyl phenyl group, R4 is a lower alkyl, phenyl or lower alkyl phenyl group;, and R2 is a hydrogen atom or a CO.R5, CO2R5 or CONR5R5 group where R5 is a lower alkyl, phenyl or lower alkyl phenyl group and R5 is a lower alkyl group optionally joined to R5; which process comprises the reaction of a compound of the formula (II): N2CR1R2 (II) wherein R1 and R2 are as defined in relation to formula (I) with an ester of clavulanic acid in the presence of a carbene generating transition metal or transition metal salt catalyst and thereafter if desired converting the thus formed ester to the free acid or salt thereof and thereafter if desired converting the thus formed acid or salt to an ester.

2. A process as claimed in claim 1 wherein the carbene-generating catalyst is finely divided metallic copper. a copper salt or a rhodium salt.

3. A processs as claimed in claim 1 or claim 2 wherein the catalyst is cupric acetylacetate. cuprous chloride, cupric chloride or rhodium acetate.

4. A process as claimed in claim 1 or claim 2 wherein the catalyst is finely divided copper powder.

5. A process as claimed in any of claims 1-4 wherein the etherification reaction is effected in an inert, dry solvent under an inert atmosphere at a temperature of from 0 to 120 .

6. A process as claimed in any one of claims 1-5 wherein the etherification reaction is effected at a temperature of from 10 to 100 C.

7. A process as claimed in any one of claims 1-6 wherein the etherification reaction is effected at a temperature of from 15 to 850C.

8. A process as claimed in any one of claims 1-7 wherein R1 is a CO.CH3, CO.C2H5, CO.CH=CH2,, CO.CH2C6H5, CO.C6H5, CO2CH3, CO2C2H5, CO2CH2C6H5 or CO2C6H5 group.

9. A process as claimed in any one of claims 1-8 wherein R, is a CO.CH3, CO.C2H5.

CO.CH=CH2, CO.CH2C6H5, CO.C6H5, CO2CH3, CO2C2H5, CO2CH2C6H5 or CO2C6H5 group.

10. A process as claimed in any one of claims 1-9 wherein the ester of clavulanic acid used in the etherification is of the formula (IV) or (V):

wherein A1 is an alkyl group of 1-6 carbon atoms optionally substituted by an alkoxyl or acyloxyl group of 1-7 carbon atoms: A is an alkenyl group of up to 5 carbon atoms or is a phenyl group optionally substituted by fluorine, chlorine, bromine, nitro or alkyl or alkoxyl of up to 4 carbon atoms: and A3 is a hydrogen atom, an alkyl group of up to 4 carbon atoms or a phenyl group optionally substituted by a fluorine, chlorine or bromine atom or an alkyl or alkoxyl group of up to 4 carbon atoms.

11. A process as claimed in any one of claims 1-10 wherein the ester of clavulanic acid used in the etherification process is the methoxymethyl, benzyl or p-methoxybenzyl ester.

12. A process as claimed in any one of claims 1-11 wherein the group A in formula (1) is a group such that CO2A is a carboxyl or salted carboxyl group which process comprises the mild base hydrolysis of the corresponding compound wherein A is a methoxymethyl group.

13. A process as claimed in any one of claims 1-11 wherein the group A in formula (I) is a group such that COnA is a carboxyl or salted carboxyl group which process comprises the hydrogenolysis of the corresponding compound wherein A is a benzyl or p-methoxybenzyl group.

14. A compound of the formula (VI) or (VII):

wherein R1 and A are as defined in claim 1 and R6 is a CO.R5, CO2R or CO.NR5R' group where R and R are defined as in claim 1 and R7 is a SO2R3. NO2 or PO(OR4)2 group were R3 and R4 are as defined in claim 1.

15. A compound of the formula (VI) as claimed in claim 14 wherein R1 is a CO.CH3, CO.C2H5, CO.CH=CH2, CO.CH2C6H5, CO.C6H5, CO2CH3, CO2C2H5, CO2CH2C6H5, CO2C6H5. PO(OCH3). or PO(OC2H5)2 group.

16. A compound ofthe formula (VI) as claimed in claim 14 or claim 15 wherein R6 is a COCH3, CO.C2H5, CO.CH=CH2, CO.CH2C6H5, CO.C6H5, CO2CH3, CO2C2H5.

CO2CH2C6H5 or CO2C6H5 group.

17. A compound of the formula (VII) as claimed in claim 14 wherein R7 is a SO2CH3, SO2C6H5, PO(OCH3)2 or PO(OCnHs) group.

18. A compound as claimed in any one of claims 14-17 wherein A is a group A1 or CHA2A3 wherein A,, A, and A3 are as defined in claim 10.

19. A compound as claimed in any one of claims 14-18 wherein A is a methoxymethyl, benzyl or p-methoxybenzyl group.

20. A compound as claimed in any one of claims 14-18 wherein A is a lithium. sodium, potassium or half calcium ion.

21. A pharmaceutical composition comprising a compound as claimed in any one of claims 14-20 and a pharmaceutically acceptable carrier.

22. A composition as claimed in claim 21 adapted for oral topical or parenteral use.

23. A composition as claimed in claim 21 or claim 22 which comprises a ,(3-lactam antibiotic.

24. A composition as claimed in claim 23 wherein the ratio of the compound of the formula (I) or its salt or ester to penicillin or cephalosporin is from 3:1 to 1:10.

25. A composition as claimed in claim 24 wherein the ratio is from 2:1 to 1:8.

26. A composition as claimed in any of claims 21-25 in unit dosage form comprising from 25 to 750 mg of a compound as claimed in any of claims 14-20.

27. A composition as claimed in claim 26 comprising from 50 to 500 mg of a compound as claimed in any of claims 14-20.

28. A composition as claimed in claim 27 comprising from 150 to 1000 mg of amoxycillin, ampicillin or a pro-drug therefor and from 50 to 500 mg of a compound of the formula (I) or a salt or ester thereof.

29. A composition as claimed in claim 28 comprising from 200 to 500 mg of amoxycillin or a salt thereof and from 50 to 250 mg of a compound of the formula (I) or a salt thereof.

30. A compound as claimed in any of claims 14-20 when prepared by a process of any of claims 1-13.

31. A compound as claimed in claim 14 substantially as described with reference to any of Examples 1-11 herein.