GB1595177A - Clavulanic acid ethers - Google Patents

Description

(54) CLAVULANIC ACID ETHERS (71) We, BEECHAM GROUP LIMITED, of Beecham House, Great West Road, Brentford, Middlesex, England, 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 new ethers of clavulanic acid, to pharmaceutical compositions containing them and to a process for their preparation.

In Belgian Patent No. 847045 corresponding to British Patent Specification No. 1565209 it was disclosed that ethers of clavulanic acid could be prepared by the reaction of a corresponding ester of clavulanic acid with an etherifying agent such as a diazo compound.

It has now been found that certain classes of ethers can be prepared in good yield by a facile reaction. These new ethers form part of this invention.

Accordingly, the present invention provides the compounds of the formula (I):

and salts and esters thereof wherein X is an oxygen or sulphur atom; Rl is a hydrogen atom or a lower alkyl group; R2 is a hydrogen atom or a lower alkyl group which may if desired be joined to Rl when R is a lower alkyl group and R3 is a lower alkyl group or an optionally inertly substituted lower alkyl group or is joined to R2 when R2 is a lower alkyl group to form an optionally inertly substituted heterocyclic ring of 5- or 6- ring atoms, provided that Rl and R2 are not both hydrogen atoms when R is a lower alkyl group.

When used herein the term "lower" means that the group contains not more than 6 carbon atoms and more suitably not more than 4 carbon atoms.

When used herein the term "inertly substituted" means substituted by one or more groups of the formula CH2OR4 or OR4 where R4 is a hydrogen atom, a lower alkyl group, a benzyl group or a lower acyl group.

The preferred value for X is the oxygen atom.

Suitable values for Rl include the hydrogen atom and the methyl and ethyl groups.

The preferred value for R is the hydrogen atom.

Thus certain favoured compounds of this invention are those of the formula (II):

and salts and esters thereof wherein R2 and R3 are as defined in relation to formula (I).

For those compounds of the formulae (I) and (II) wherein R2 is not joined to R or R3, suitable values for R2 include the methyl and ethyl groups, the methyl group being especially suitable.

For those compounds of the formulae (I) and (II) wherein R2 and R3 are not joined, suitable values for R3 are the methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl and tert-butyl groups; more suitable values for R3 are the methyl, ethyl and propyl groups; and especially suitable values for R3 are the methyl and ethyl groups, and a preferred value for R3 is the methyl grou For those compounds of the formulae tI) and (II) wherein R2 and R3 are joined, particularly suitable values for the -CRR-XR moiety are those of the sub-formulae (a) and (b):

wherein R" is a group R4 or OR4; Rh is a group R4 or OR4; RC is a group R4 or OR4; Rd is a group R4 or OR4; R is a group R4 or OR4; R' is a group R4 or OR4; and R is a group R4 or CH2R4 wherein any R4 group can have any value as defined hereinbefore in relation to formula (I).

Particularly suitable values for Ra-Rf include hydrogen atoms, lower alkyl and OR5 groups where R5 is a hydrogen atom or an acetyl, benzoyl or benzyl group and particularly suitable values for Rg include the hydrogen atom, lower alkyl or CH2OR5. Favoured values for Ra~Rf include for Rg hydrogen atoms and lower alkyl groups such as the methyl group.

Preferred values for R-R include the hydrogen atom.

For those compounds of the formula (l) wherein Rl and R2 are joined include those wherein the -CR'R2- moiety represents a cyclopentyl or cyclohexyl group or such a group substituted by a R4 or OR4 group where R4 is as defined in relation to sub-formulae (a) and (b).

The compounds of the formula (I) are suitably in the form of a salt such as the lithium, sodium, potassium, calcium, magnesium, ammonium or substituted ammonium salt such as the methylamine, dimethylamine, trimethylamine, pyrrolidine, or other such lower alkylamine, di-lower alkylamine, tri-lower alkylamine or heterocyclic amine salts.

Particularly suitable salts include the lithium, sodium, potassium and calcium salts.

Preferred salts include the lithium, sodium and potassium salts.

Suitable esters of the compounds of the formula (II) include those of the formulae (III) and (IV):

wherein R', R2, X and R3 are as defined in relation to formula (I) and Al is an alkyl group of 1-8 carbon atoms optionally substituted by halogen or a group of the formula OA OCOA4, SA4 or SO2A4 wherein A4 is a hydrogen group of up to 6 carbon toms; A2 is a hydrogen atom, an alkyl group of up to 4 carbon atoms or a phenyl group optionally substituted by halogen or by a group At or OAs where A5 is an alkyl group of up to 6 carbon atoms; and A3 is a phenyl group optionally substituted by halogen or by a group A5 or OA5 where A5 is an alkyl group.

Particularly suitable values for the CRlR2XR3 moieties in the compounds of this invention include those of the following sub-formulae (a) - (c): - CH(CH3)0CH3 (a) - CH(CH3)0C2H5 (b) - CH(C2H5)OC2H5 (c) It is believed that the organisms most readily treated by the compounds of this invention are Staphylococcus, Proteus, Klebsiella and Escherichia coli.

The present invention also provides pharmaceutical compositions which comprise a compound of the formula (I) as hereinbefore defined or a salt or ester thereof and a pharmaceutically acceptable carrier.

Most suitably the compound of the formula (I) in the composition of this invention will be in the form of a pharmaceutically acceptable salt or in-vivo hydrolysable ester.

Preferably the compound of the formula (I) in the composition of this invention will be a pharmaceutically acceptable salt of a compound of the formula (II).

The composition of this invention may be presented orally or parenterally or in other convenient form. Generally the composition will be adapted for oral administration to humans or for administration by injection to humans. Veterinary compositions may also be prepared.

Normally the composition of this invention will be in unit dosage form containing from about 20 mg to 250 mg, for example about 50 or 100 mg, of the active ingredient.

Such compositions will usually be administered from 2 to 6 times daily, for example 3 or 4 times daily so that the daily dose is from about 60 mg to 1000 mg, more usually from about 200 mg to about 1000 mg.

Desirably the composition of this invention will also comprise a penicillin or cephalosporin. Most suitably the ratio of compound of this invention to penicillin or cephalosporin is from 1:10 to 10:1, more usually 2:1 to 1:5, for example 1:1 to 1:3 (by weight).

Suitable penicillins and cephalosporins for inclusion in such compositions include those named in Belgian Specification No. 827926.

Particularly suitable penicillins for inclusion in the compositions of this invention include ampicillin, amoxycillin and their pro-drugs such as their in-vivo hydrolysable esters.

Preferred penicillins for inclusion in the compositions of this invention include ampicillin trihydrate and amoxycillin trihydrate, particularly amoxycillin trihydrate. Other preferred penicillins include the pharmaceutically acceptable salts of amoxycillin.

Penicillins suitable for inclusion in orally administrable compositions of this invention include benzylpenicillin, phenoxymethylpenicillin, propicillin, amoxycillin, ampicillin, epicillin, cyclacillin and their salts and in-vivo hydrolysable esters and aldehyde and ketone adducts of those penicillins containing a 6-a-aminoacylamido side chain and their salts.

Suitable penicillin in-vivo hydrolysable esters include the acetoxymethyl, pivaloyloxymethyl, a-ethoxycarbonyloxyethyl and phthalidyl esters of ampicillin or amoxycillin or the phenyl, tolyl and indanyl a-esters of carbenicillin and ticarcillin and salts thereof. Suitable aldehyde and ketone adducts of penicillins containing a 6-a-aminoacylamido side chain include the formaldehyde and acetone adducts metampicillin and hetacillin and their salts.

Suitable penicillins for inclusion in injectably or infusably administrable compositions include the acceptable salts of benzylpenicillin, phenoxymethyl-penicillin, carbenicillin, propicillin, ampicillin, amoxycillin, epicillin, ticarcillin and cyclacillin.

Cephalosporins suitable for inclusion in orally administrable compositions of this invention include cephalexin, cephradine, cephaloglycine and their salts and in-vivo hydrolysable esters and aldehyde and ketone adducts of those cephalosporins containing a 7-a-aminoacylamido side chain and their salts. Suitable cephalosporins for inclusion in the injectable or infusable compositions of this invention include the salts of cephaloridine, cephalothin, cefazolin, cephalexin, cephacetrile, cephamandole, cephapirin, cephradine and cephaloglycine.

In a further aspect the present invention provides a process for the preparation of a compound of the formula (I) or a salt or ester thereof which comprises the reaction of an ester of clavulanic acid with a compound of the formula (V): Y C'RtR2 - XR3 (V) wherein X, Rt, R2 and R3 are as defined in relation to formula (I) and Y is a readily displaceable atom or group; and thereafter if desired converting the thus produced ester into the free acid or a salt or other ester thereof.

Suitable values for Y include I, Br, Cl, OSO2CH3, OSO2C6H4CH3 or other similar atoms or groups readily displaced by a nucleophile.

Particularly suitable moieties Y include bromine and chlorine atoms.

The etherification reaction will normally be effected in the presence of a base of low nucleophilicity such as 2, 4, 6-collidine, potassium carbonate, sodium bicarbonate or 2,6-lutidine.

The etherification will normally take place at a non-extreme temperature such as -20" to 30"C, for example about 0 to 20"C.

The solvent used for the reaction may comprise dichloromethane, chloroform, dimethylformamide or tetrahydrofuran.

In an alternative process aspect, this invention provides a process for the preparation of compounds of the formula (I) wherein Xis an oxygen atom and Rl is a hydrogen atom, or a salt or ester thereof wherein R2 contains at least 2 carbon atoms and is optionally joined to R3 which process comprises the reaction of an ester of clavulanic acid with a compound of the formula (VI): RhRiC = CH - 0 - R3 (VI) wherein RhRiCH is a group R2, and R3 is as defined in relation to formula (I): and thereafter, if desired, converting the thus produced ester into the free acid or a salt or other ester thereof.

Most suitably Rh is a hydrogen atom.

Most suitably R' is a hydrogen atom or is joined to R3.

Particularly suitable compounds of the formula (VI) include those of the formulae; (VII) and (VIII):

wherein Rb, RC, Rd, Rf and Rg are as defined in relation to sub-formulae (a) and (b).

Normally this reaction will take place in the presence of catalytic quantities of an acid or acid precursor such as HCI, POCI3, p-toluenesulphonic acid and BF3.

In another process aspect this invention also provides a process for the preparation of a.

compound of the formula (I) wherein X is an oxygen atom and R' is a hydrogen atom, or a salt or ester thereof which process comprises the reaction of an ester of clavulanic acid with a compound of the formula (IX): R5 - 0 - CHR2 -OR3 (IX) wherein R2 and R3 are as defined in relation to formula (I) and R5 is a tertiary alkyl group of 4 - 6 carbon atoms; and thereafter if desired converting the thus produced ester into the free acid or a salt or other ester thereof.

A particularly suitable group R5 is the t-butyl group.

Favourably R and R3 are linked so that the -CHR2-OR3 moiety is a heterocyclic ring.

When R2 and R3 are not linked it is more suitable that R5 and R3 each represent the same group, for example R5 and R3 each represent a methyl or ethyl group.

Most suitably the reaction utilizes an excess of the compound of the formula (IX).

Generally at least 1 molar excess and preferably 2 - 5 molar excess of the compound of the formula (IX) is employed. If the compound of the formula (IX) utilized is a volatile liquid it may be used as a solvent.

The present invention also provides a process for the preparation of the compounds of the formula (I) or a salt thereof which process comprises the de-esterification of a corresponding ester of a compound of the formula (I).

Such de-esterification processes may involve hydrolysis or hydrogenolysis. Thus, for example an ester may be subjected to mild base hydrolysis to yield a salt of the compound of the formula (I) or alternatively a hydrogenolysable ester may be catalytically hyrogenated to yield the free acid or, if a base is present or added later, a salt. More specifically a lower alkyl ester such as a methyl ester may be hydrolysed at pH 7-10 by the slow addition of equivalent of base or a benzyl, methoxybenzyl, nitrobenzyl or like ester may be hydrogenated in the presence of a transition metal catalyst such as palladium on charcoal optionally in the presence of a base such as NaHCO3, Na2CO3, KHCO3, K2CO3, Li2CO3 or the like.

This invention also provides a process for the preparation of esters of the compounds of the formula (I) which process comprises the esterification of the compound of the formula (I) or a salt thereof.

Thus a compound of the formula (I) may be reacted with a diazo compound or a salt of the compound of the formula (I) may be reacted with a reactive halocompound or the like.

The following Examples illustrate the invention: EXAMPLE 1 4-Methoxybenzyl 9-0- (1 -butoxy) ethyl clavulanate

To a solution of p-methoxybenzyl clavulanate (e10) (lgm) and vinyl n-butyl ether (1 ml) in ethyl acetate (10 ml) was added p-toluenesulphonic acid (50 mgs). After stirring for 30 mins at room temperature the mixture was passed through a short column of Kieselgel G using ethyl acetate as eluent. The solvent was evaporated, and the product isolated by column chromatography (Kieselgel G. 1:1 ethyl acetate: cyclohexane) to yield the title compound (0.848 g). Vmax (film) 1805, 1750, 1700cm-1. o(CDCll) 8.0-9.0 (3H, triplet, J = 7HZ), 1.26 (3H, doublet, J = 6Hz) 1.10-1.70 (4H, multiplet), 2.97 (1H, doublet J = 17Hz), 3.20-3.55 (3H, multiplet), 3.74 (3H, singlet), 4.0-4.2 (2H, multiplet), 4.45-4.75 (1H, multiplet), 4.75 (1H, triplet), 4.99 (1H, singlet), 5.07 (2H, singlet), 5.59 (1H, doublet, J = 3Hz), 6.80 (2H, doublet, J = 8Hz), 7.20 (2H, doublet J = 8Hz), EXAMPLE 2 Benzyl 9-0-tetrahydropyran-2'-yl clavulanate

Benzyl clavulanate (el) (1.0 g) in benzene (5 ml) and dihydropyran (4 ml) was treated with 1 drop of BF3-ether complex and stirred overnight. The solvents were evaporated isl vacuo and the residue subjected to column chromatography on silica gel using ethyl acetate and cyclohexane as eluents. After evaporation of the solvent the title compound (e12) was obtained (1.63 g) as an oil which was judged to be about 80% pure. (Contaminant resumed to be polymers derived from the pyran). #max (liquid film), 1805, 1755, 1700 cm'.

(CDCl3): 1.0 - 2.1 (excess H, br.m, 3',4',5'-CH2), 2.97 (1H, d, J 17Hz, 6- -CH), 3.41 (1H, dd, J 2.5 and 17Hz, 6-a-CH), 3.6 - 3.95 (excess H, m, 6'-CH2), 3.95 - 4.4 (2H m 9-CH2), 4.52 (1H, br,s, 2'-CH), 4.79 (1H, br.t, J 7.5Hz, 8-CH), 5.03 (1H, s, 3-CH), 5.12 (2H, s, PhCH2), 5.60 (1H, d, 2.5Hz, 5-CH) and 7.27 (5H, s, C6H5).

EXAMPLE 3 Lithium 9- 0-tetrahydropyran-2-ylclavulanate

Benzyl 9-O-tetrahydropyran-2-ylclavulanate (e12) (1.0 g) dissolved in tetrahydrofuran (1 ml) and water (0.05 ml) was hydrogenated over 10% palladised charcoal (0.3 g) during 45 min. to yield a solution of the corresponding acid (e13). The catalyst was removed, the filtrate was diluted with an equal volume of water and titrated to pH 7.0 with 1.0 M lithium hydroxide solution. The solution was evaporated to a syrup, 50 ml acetone added, re-evaporated, triturated with acetone (30 ml), filtered off, washed with acetone and ether and air-dried, to yield the title compound (e14) 0.46 g.

vmax (Nujol mull) 1783, 1790, 1700, 1620, 1625 cml; o(D20) 1.16 - 1.6 (6H, br.m, 3',4',5'-CH2), 2.89 (1H, d, J 17Hz, 6 CH), 3.39 (1H, dd, J 17 and 3Hz, 6a-CH), 3.55 3.91 (2H, m, 6'-CH2), 4.06 (2H, d, J 8Hz, '9-CH2), 4.5 -'4.9 (3H, m, 2'-CH, 8-CH, 3-CH), 5.55 (1H, d, J, 3Hz, 5-CH).

Nujol is a registered Trade Mark.

EXAMPLE 4 4-Methoxybenzyl 9-0-tetrahydrofuran-2-ylelavulanate

A crystal of p-toluenesulphonic acid was added to a solution of 4-methoxybenzyl clavulanate (e10) (3.19 g, 0.1 mole) and 2-tert-butoxytetrahydrofuran (4.32 g, 0.3 mole) in dry dichloromethane (30 ml) and the mixture was stirred at room temperature for 15 min.

The mixture was washed with aqueous sodium bicarbonate (50 ml) and then dried amd evaporated to give the title compound (e15) (3.8 g), vmax (liquid film) 1805, 1750, 1700, 1250, 1180, and 1025 cm1. b(CDCl) 7.20 (2H, d, J = 9Hz, ArH), 6.80 (2H, 9Hz, ArH), 5.59 (1H, d, J = 2.5 Hz, 5-CH), 5.08 (2H, s, CH2Ar), 5.00 (1H, s, 3-CH) 5.10-5.00 (1H, m, 2-CH), 4.65 (1H, t, J = 7Hz, 8-CH), 3.75 (3H, s, OCH3), 3.40 (2H, dd, J = 17 Hz, J' = 2.5 Hz, 6a-CH), 2.99 (1H, d, J = 17 Hz, 6p-CH), and 1.6-2.0 (4H, m, 3' and 4'-CH2).

EXAMPLE 5 Sodium 9-0-tetrahydrofuran-2-ylelavulanate

p-Methoxybenzyl 9-O-tetrahydrofuran-2-ylclavulanate (e15) (1.46 g) and sodium bicarbonate (0.315 g) in tetrahydrofuran/water (5:1, 30 ml) was hydrogenated at room temperature and pressure in the presence of 10% palladised charcoal (0.5 g) for 30 minutes.

The mixture was filtered and the solid washed with a little water and the combined liquids evaporated to remove the tetrahydrofuran. The aqueous solution was extracted with ethyl acetate (20 ml) and the aqeous phase freeze dried to yield the title compound (0.9 g). vmax (Nujol mull), 1785, 1695, 1615 (broad) cm-1.

vmax (KBr), 1785, 1693, 1615 (v. broad) cm~l.

b(D2O) 1.86 (4H, m, 3' and 4'-CH2), 3.02 (1H, d, J 17Hz, 6P-CH), 3.51 (1H, dd, J 17 and 2.5 Hz, 6a-CH), 3.83 (2H, m, 5'-CH2), 4.11 (2H, d, J 8Hz, 9-CH2), 4.82 (1H; t, J 8Hz, 8-CH), 4.90 (1H, s, 3-CH), 5.20 (1H, m, 2'-CH), and 5.66 (1H, d, J 2.5Hz, 5-CH).

EXAMPLE 6 Benzyl 9-O-(1-ethoxy)prop-1-ylclavulanate

To a stirred solution of benzyl clavulanate (e 1) (578 mg) and ethyl propenyl ether (0.3 ml) in ethyl acetate (10 ml) was added p-toluenesulphonic acid (5 mg). The mixture was stirred at room temperature for 1 hours and then passed through a short column of Kieselgel, eluting with ethyl acetate. After evaporation of the solvent the product was isolated by column chromatography using gradient elution (Kieselgel 3:1 cyclohexane:ethyl acetate going to 1:1 cyclohexane:ethyl acetate) to yield benzyl 9-O-(1-ethoxy)prop-1ylclavulanate (e 17) (601 mg).

v max (film) 1805, 1750 and 1700 cm~i. (CDCl3) 0.88 (3H, t, J = 7Hz), 1.17 (3H, t, J = 7Hz), 1.60 (2H, broad quintet, J = 7Hz), 2.99 (1H, d, J = 17Hz), 3.44 (1H, dd, J = 3 and 17Hz), 3.54 (2H, q, J = 7Hz), 4.0 - 4.2 (2H, m), 4.36 (1H, t, J = 6Hz), 4.79 (1H, broad t, J = 7Hz), 5.05 (1H, s), 5.15 (2H, s), 5.63 (1H, d, J = 3Hz), 7.29 (5H, s).

EXAMPLE 7 Sodium 9-0(1 -ethoxy)prop-1 -ylclavulanate

A solution of benzyl 9-O-(1-ethoxy)prop-1-ylolavulanate (e 17) (572 mg) and sodium bicarbonate (128 mg) in tetrahydrofuran (22.5 ml) and water (7.5 ml), was hydrogenated over 10% palladium charcoal (250 mg) for 1 hour. The solution was filtered through Celite (Celite is a registered trade mark), diluted with water and the tetrahydrofuran removed on a rotary evaporator. The aqueous solution was extracted with ethyl acetate and freeze dried to yield sodium 9-O-(1-ethoxyl)-prop-1-ylclavulanate (e 18) (370 mg).

v max (KBr) 1785 and 1615 cm~ . o(D2O) 0.85 (3H, t, J = 7Hz), 1.16 (3H, t, J = 7Hz), 1.59 (2H, broad quintet J = 7Hz), 3.05 (1H, d, J = 17Hz), 3.4 - 3.85 (4H, m), 4.19 (2H, d, J = 7Hz), 4.90 (1H, broad t, J = 7Hz), 4.93 (1H, s), 5.71 (1H, d, J = 3Hz).

EXAMPLE 8 Benzyl 9-0-(2-ethoxy)prop-2-ylclavulanate

To a stirred solution of benzyl clavulanate (1 g) and ethyl isopropenyl ether (0.5 ml) in ethyl acetate (10 ml) was added p-toluenesulphonic acid (5 mg). The mixture was stirred at room temperature for 20 minutes and then passed through a short column of Kieselgel, eluting with ethyl acetate. The solvent was evaporated and the product isolated by column chromatography (Kieselgel 3:1 cyclohexane:ethyl acetate as eluent) to yield benzyl 9-0-(2-ethoxy)prop-2-ylclavulanate (,e 19) (743 mg).

v max (film) 1805, 1750 and 1700cm . (CDCl3) 1.12 (3H, t, J = 7Hz), 1.31 (6H, s), 2.96 (1H, d, J = 17Hz), 3.37 (2H, q, J = 7Hz), 3.39 (1H, dd, J = 3 and 17Hz), 3.9 - 4.1 (2H, m), 4.73 (1H, broad t, J = 7Hz), 5.01 (1H, broad s), 5.13 (2H, s), 5.60 (1H, d, J = 3Hz), 7.26 (5H, s).

EXAMPLE 9 Benzyl 9-0-(1-ethoxy)cyclohexyl clavulanate

To a stirred mixture of benzyl clavulanate (578 mg) and ethyl cyclohexenyl ether (2 ml) was added mercuric trifluoroacetate (20 mg). The mixture was stirred at room temperature for 1.5 hours. Most of the solvent was removed on the rotary evaporator, and the product isolated by column chromatography of the residue (Kieselgel 4:1 cyclohexane:ethyl acetate) to yield (e 20) (767 mg).

v max (film) 1805, 1750, 1700 cam~1. (CDCl3) 1.14 (3H, t, J = 7Hz), 1.2 - 1.8 (10H, m), 2.96 (1H, d, J = 17Hz), 3.37 (2H, q, J = 7Hz), 3.43 (1H, dd, J = 3 and 17Hz), 3.9 - 4.15 (2H, m), 4.76 (1H, broad t, J = 7Hz), 5.04 (1H, s), 5.14 (2H, s), 5.60 (1H, d, J = 3Hz), 7.27 (5H, s).

EXAMPLE 10 p-Methoxybenzyl 9-0-(2,3, 4, 6-tetra-O-acetyl-cr-D-glucopyranosyl) clavulanate

A solution of p-methoxybenzyl clavulanate (e10) (6.38 g) in dry dimethylformamide (10 ml) was added dropwise over a few minutes to a stirred solution of aacetobromoglucose (16.78 g) and collidine (5.3 ml) in dry dimethylformamide (50 ml) at 0 C under nitrogen. The reaction mixture was then stirred at room temperature overnight.

This was poured into ice-water (100 ml) which was extracted with ethyl acetate (3 x 100 ml). The organic extract was washed with dilute hydrochloric acid (5 M, 200 ml), dried with anhydrous sodium carbonate - magnesium sulphate, and evaporated to give an oil which was chromatographed over silica gel (100 g). Elution of the column with cyclohexane - ethyl acetate afforded the title compound (e22) (5.7 g) as an oil, [a]D 45.8 (c. 1.7, CHCl3), vmax (CHCl3) 1805, 1745, 1700, 1230, 1175, 1040 and 980 cm1. b(CDCl) 7.22 (2H, d, J = 9Hz, ArH), 6.83 (2H, d, J = 9Hz, ArH), 5.64 (1H, d, J = 4Hz, 1'-CH), 5.61 (1H, d, J 2.5Hz, 5-CH), 5.08 (2H, s, -CH,Ar), 3.76 (3H, s, -OCH), 2.06 (9H, s, CH3CO2-), and 1.68 (3H, s, CHCO2-), m/e 649 (M+), 621, 607, 594, 403, 331, 289, 288, 271, 259, 200 and 169 (Found: C, 55.1; H, 5.4; N, 1.95%, C1(HX5NOl5 requires C, 55.45; H, 5.45; N, 2.15%), followed by a mixture (7.8 g) of the title compound (e22) and a small amount of starting material.

EXAMPLE 11 Sodium 9-0- (2,3,4, 6-tetra-0-acetyl-a-D-glucopyranosyl) davulanate

A mixture of p-methoxybenzyl 9-0-(2,3,4,6-tetra-O-acetyl-a-D-glucopyranosyl)- clavulanate (e22) (1.3 g) and sodium bicarbonate (0.168 g) in tetrahydrofuran - water (5:1, 24 ml) was hydrogenated at room temperature and pressure in the presence of 10% palladium on charcoal (0.4 g) for 15 minutes. The mixture was filtered and the filtrate evaporated to give the little compound (e23) (0.96 g).

[a]D +27.7 (c, 2.3, H2O), vmax (KBr) 1785, 1740, 1690, 1615 cam~1.

o(D2O) 5.83 (1H, d, J = 5Hz, 1'-CH), 5.75 (1H, d, J = 2.5Hz, 5-CH), 3.60 (1H, dd, J = 18Hz, J' = 2.5 Hz, 6a-CH), 3.07 (1H, d, J = 18Hz, 6 CH), 2.15 (9H, s, CH3CO2-), and 1.79 (3H, s, CH3CO2-).

EXAMPLE 12 p-Methoxybenzyl 9-0- (2,3,5, -tri-0-benzyl-D-arabinofuranosyl) -clavulanate

To a solution of 2,3,5-tri-O-benzyl-f3-D-arabinofuranose (1.68 g), collidine, (1.06 ml) and tetrabutylammonium bromide (1.29 g) in dry dichloromethane (5 ml) was added trifluoromethanesulphonic anhydride (1.13 g) at -700C, which reaction mixture was then stirred at room temperature for 1 hour. A solution of p-methoxybenzyl clavulanate (e10) (0.96 g) in dichloromethane (5 ml) was added to the reaction mixture which was then stirred at room temperature overnight. This was then washed with hydrochloric acid (SM, 10 ml) at 0 C, dried with anhydrous sodium carbonate - magnesium sulphate and evaporated to give an oil which was chromatographed over silica gel (20 g). Elution of the column with cyclohexane - ethyl acetate gave the title compound (e24) (0.7 g).

vmax (CHCl3): 1805, 1745 and 1700 cm o(CDCl3): 7.20 (17H, s, ArH), 6.80 (2H, d, J = 9Hz, ArH), 5.51 (1H, d, J = 2.5Hz, 5-CH), 5.30 (1H, m, 1'-CH), 5.05 (2H, s, CH2Ar), 4.98 (1H, m, 3-CH), 4.48 (6H, s, CH2Ar), 3.70 (3H, s, OCH3) and 2.90 (1H, d, J = 17Hz, 6p-CH).

EXAMPLE 13 Sodium 9-0-(1-butoxy)ethyl clavulanate

A solution of 4-methoxybenzyl 9-O-(1-butoxy)ethyl clavulanate (ell) (800 mg) and sodium bicarbonate (160 mg) in aqueous tetrahydrofuran (5 ml water, 25 ml tetrahydrofuran) was hydrogenated for 20 minutes over 10% palladium on charcoal (400 mg). The solution was filtered and most of the t

EXAMPLE 14 4-Methoxybenzyl 9-0-(1-ethoxy)ethyl clavulanate

To a solution of p-methoxybenzyl clavulanate (elO) (1.5 g) and vinyl ethyl ether (1 ml) in ethyl acetate (15 ml) was added p-toluenesulphonic acid (25 mg). The mixture was stirred for 15 minutes and then passed through a short column of Kieselgel G, eluting with ethyl acetate. The solvent was removed under vacuum and the product isolated by column chromatography (Kieselgel G, 3:1 cyclohexane: ethyl acetate as eluent) to yield (e26) (1.26 g).

vmax (film): 1805,1750, 1700 cam~'.

(CDCl3)5: 1.16 (3H, triplet, J = 8Hz), 1.27 (3H, doublet, J 5Hz), 2.97 (1H, doublet, J e 17Hz), 3.25 - 3.7 (3H, multiplet), 3.75 (3H, singlet), 4.0 - 4.15 (2H, multiplet), 4.5 - 4.85 (2H, multiplet), 5.0 (1H, singlet), 5.07 (2H, singlet), 5.60 (1H, doublet, J = 3Hz), 6.80 (2H, doublet, J = 9Hz), 7.21 (2H, doublet, J = 9Hz).

EXAMPLE 15 Sodium 9-0-(1-ethoxy)ethyl clavulanate

A solution of 4-methoxybenzyl 9-O-(1-ethoxy)ethyl clavulanate (e26) (1.185 g) and sodium bicarbonate (254 mg) in aqueous tetrahydrofuran (5 ml water, 25 ml tetrahydrofuran) was hydrogenated over 10% palladium charcoal (400 mg) for 25 minutes. The solution was filtered through Celite, and evaporated under vacuum until most of the tetrahydrofuran had been removed. The aqueous solution was extracted with three portions of ethyl acetate and freeze dried. The product was purified by column chromatography (Kieselgel G, 4:1:1 n-butanol:ethanol:water) and obtained by evaporation to yield the title compound (e27) (589 mg).

vmax (KBr): 1795, 1695, 1615 cm~'.

(D2O)6: 1.23 (3H, triplet, J = 8Hz), 1.34 (3H, doublet, J = 6Hz), 3.11 (1H, doublet, J = 18Hz), 3.45 - 4.0 (3H, multiplet), 4.25 (2H, doublet, J = 8Hz), 4.75 - 5.1 (3H, multiplet), 5.77 (1H, doublet, J = 3Hz).

EXAMPLE 16 Pharmacology: Using conventional methods the following results were obtained: a. Compound of Example 1 MIC (llg/ml) of Ampicillin Conch Inhibitor Staph. Kleb Proteus E. coli E. coli (g/ml) Russell E 70 C 889 JT 39 JT 410 20 - - 15.6 > 500 62.5 5 0.15 12.5 125 500 - 1 1.25 25 - - 0 500 1000 > 2000 2000 62.5 b. Compound of Example 13 MIC (llg/ml) of Ampicillin Conch Inhibitor Staph. Kleb. Proteus E. coli (Rg/ml) Russell E 70 C 889 JT 410 20 - - - 2000 5 (0.04) 1.6-3.1 15 > 2000 1 0.08 6-12 62.5 0 > 500 2000 > 2000 62.5 WHAT WE CLAIM IS: 1. A compound of the formula (I):

or a salt or ester thereof wherein X is an oxygen or sulphur atom; R' is a hydrogen atom or a lower alkyl group; R2 is a hydrogen atom or a lower alkyl group which may if desired be joined to R when R' is a lower alkyl group and R3 is a lower alkyl group or an optionally inertly substituted lower alkyl group or is joined to R2 when R2 is a lower alkyl group to form an optionally inertly substituted heterocyclic ring of 5- or 6- ring atoms, provided that R' and R2 are not both hydrogen atoms when R is a lower alkyl group.

2. A compound as claimed in claim 1 wherein X is an oxygen atom.

3. A compound as claimed in claims 1 or 2 wherein R' is a hydrogen atom or a methyl or ethyl group.

4. A compound as claimed in claims 1 or 2 wherein Rl is a hydrogen atom.

5. A compound as claimed in any of claims 1 - 4 wherein R2 is a methyl or ethyl group.

6. A compound as claimed in any of claims 1 - 4 wherein R2 is a methyl group.

7. A compound as claimed in any of claims 1 - 6 wherein R3 is a methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl or tert-butyl group.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (68)

1. **WARNING** start of CLMS field may overlap end of DESC **.

   EXAMPLE 16 Pharmacology: Using conventional methods the following results were obtained: a. Compound of Example 1 MIC (llg/ml) of Ampicillin Conch Inhibitor Staph. Kleb Proteus E. coli E. coli (g/ml) Russell E 70 C 889 JT 39 JT 410

   20 - - 15.6 > 500 62.5 5 0.15 12.5 125 500 - 1 1.25 25 - - 0 500 1000 > 2000 2000 62.5 b. Compound of Example 13 MIC (llg/ml) of Ampicillin Conch Inhibitor Staph. Kleb. Proteus E. coli (Rg/ml) Russell E 70 C 889 JT 410

   20 - - - 2000 5 (0.04) 1.6-3.1 15 > 2000 1 0.08 6-12 62.5 0 > 500 2000 > 2000 62.5 WHAT WE CLAIM IS: 1. A compound of the formula (I):

   or a salt or ester thereof wherein X is an oxygen or sulphur atom; R' is a hydrogen atom or a lower alkyl group; R2 is a hydrogen atom or a lower alkyl group which may if desired be joined to R when R' is a lower alkyl group and R3 is a lower alkyl group or an optionally inertly substituted lower alkyl group or is joined to R2 when R2 is a lower alkyl group to form an optionally inertly substituted heterocyclic ring of 5- or 6- ring atoms, provided that R' and R2 are not both hydrogen atoms when R is a lower alkyl group.
2. 2. A compound as claimed in claim 1 wherein X is an oxygen atom.
3. 3. A compound as claimed in claims 1 or 2 wherein R' is a hydrogen atom or a methyl or ethyl group.
4. 4. A compound as claimed in claims 1 or 2 wherein Rl is a hydrogen atom.
5. 5. A compound as claimed in any of claims 1 - 4 wherein R2 is a methyl or ethyl group.
6. 6. A compound as claimed in any of claims 1 - 4 wherein R2 is a methyl group.
7. 7. A compound as claimed in any of claims 1 - 6 wherein R3 is a methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl or tert-butyl group.
8. 8. A compound as claimed in any of claims 1 - 6 wherein R3 is a methyl, ethyl, n-propyl

   or iso propyl group.
9. 9. A compound as claimed in any of claims 1 - 6 wherein R is a .methyl group.
10. 10. A compound as claimed in any of claims 1 - 6 wherein R3 is an ethyl group.
11. 11. A compound as claimed in any of claims 1 - 4 wherein the CR1R2XR3 moiety is a group of the sub-formula (a) or (b)

    wherein Ra is a group R4 or OR4; Rb is a Uroup R4 or OR4; Re is a group R4 or OR4; Rd is a group R4 or OR4; R is a group R4 or OR, R is a group R4 or OR and Rg is a group R4 or CH2R4 wherein R4 is a hydrogen atom, an alkyl group of 1 - 4 carbon atoms, benzyl group or an acyl group of 1 - 4 carbon atoms.
12. 12. A compound as claimed in claim 11 wherein each of Ra, Rb, RC, Rd, Re, Rf and Rg is independently a hydrogen atom or methyl group.
13. 13. A compound as claimed in claim 11 wherein Ra, Rb, RC, Rd, Re, Rf and Rg all represent hydrogen atoms.
14. 14. A compound of the formula (II):

    or a salt or ester thereof wherein R2 and R3 are as defined in any of claims 5 - 13.
15. 15. A compound as claimed in claim 14 wherein CHR2OR3 is CH(CH)OCH.
16. 16. A compound as claimed in claim 14 wherein CHR2OR3 is CH(CH)OC2H5.
17. 17. A compound as claimed in claim 14 wherein CHR2OR3 is CH(C2H5)OC2H5.
18. 18. A compound as claimed in claim 14 wherein CHR2OR3 is
19. 19. A compound as claimed in claim 14 wherein CHR2OR3 is
20. 20. A compound as claimed in any of claims 1 - 19 in the form of the acid.
21. 21. A compound as claimed in any of claims 1 - 19 in the form of a salt.
22. 22. A compound as claimed in any of claims 1 - 19 in the form of a lithium, sodium, potassium, calcium, magnesium, ammonium or substituted ammonium salt.
23. 23. A compound as claimed in any of claims 1 - 19 in the form of a lithium salt.
24. 24. A compound as claimed in any of claims 1 - 19 in the form of a sodium salt.
25. 25. A compound as claimed in any of claims 1 - 19 in the form of a potassium salt.
26. 26. A compound as claimed in any of claims 1 - 19 which is an ester wherein the ester moiety is of the subformula (a) or (b):

    wherein Al is an alkyl group of 1-8 carbon atoms optionally substituted by halogen or a group of the formula OA4, OCOA4, SA4 or SO2A4 wherein A4 is a hydrocarbon group-of up to 6 carbon atoms; A2 is a hydrogen atom, an alkyl group of up to 4 carbon atoms or a phenyl group optionally substituted by halogen or by a group A or OA5 where A5 is an alkyl group of up to 6 carbon atoms; and A3 is a phenyl group optionally substituted by halogen or by a group A5 or OA5 where A5 is an alkyl group.
27. 27. A compound as claimed in any of claims 1 - 19 which is a hydrolysable ester.
28. 28. A compound as claimed in any of claims 1 - 19 which is a hydrogenolysable ester.
29. 29. A compound as claimed in claim 27 wherein the ester is the methyl ester.
30. 30. A compound as claimed in claim 28 wherein the ester is the benzyl ester.
31. 31. A compound as claimed in claim 28 wherein the ester is a methoxybenzyl ester.
32. 32. A compound as claimed in claim 28 wherein the ester is a nitrobenzyl ester.
33. 33. A pharmaceutical composition which comprises a compound as claimed in any of claims 1 - 32 and a pharmaceutically acceptable carrier.
34. 34. A composition as claimed in claim 33 which comprises a pharmaceutically acceptable salt of a compound as claimed in any of claims 1 - 19.
35. 35. A composition as claimed in claim 34 wherein the salt is as claimed in claim 24.
36. 36. A composition as claimed in claim 34 wherein the salt is as claimed in claim 25.
37. 37. A composition as claimed in any of claims 33 - 36 in unit dosage form which contains from 20 to 250 mg of a compound as claimed in any of claims 1-32.
38. 38. A composition as claimed in any of claims 33 - 37 which also comprises a penicillin.
39. 39. A composition as claimed in any of claims 33 - 37 which also comprises a cephalosporin.
40. 40. A composition as claimed in claims 38 or 39 wherein the weight ratio of a compound as claimed in any of claims 1-32 to penicillin or cephalosporin is 1:10 to 10:1.
41. 41. A composition as claimed in claim 40 wherein the ratio is 2:1 to 1:5.
42. 42. A composition as claimed in claim 40 wherein the ratio is 1:1 to 1:3.
43. 43. A composition as claimed in any of claims 38 or 40-42 wherein the penicillin is ampicillin, amoxycillin or a pro-drug therefore.
44. 44. A composition as claimed in any of claims 38 or 40 - 42 wherein the penicillin is ampicillin trihydrate.
45. 45. A composition as claimed in any of claims 38 or 40 - 42 wherein the penicillin is amoxycillin trihydrate.
46. 46. A process for the preparation of a compound of the formula (I) as defined in claim 1 or a salt or ester thereof which process comprises the reaction of an ester of clavulanic acid with a compound of the formula (V): Y-CR'R2-X-R3 (V) wherein X, Rl, R2 and R3 are as defined in claim 1 and Y is a readily displaceable atom or group; and thereafter, if desired, converting the thus produced ester into the free acid or a salt or other ester thereof.
47. 47. A process as claimed in claim 46 wherein Y is I, Br, Cl, OSO2CH3 or OSO2C6H4CH3.
48. 48. A process as claimed in claim 46 wherein Y is Br or Cl.
49. 49. A process as claimed in any of claims 46 - 48 wherein the etherification step is carried out in the presence of a base of low nucleophilicity.
50. 50. A process as claimed in any of claims 46 - 49 wherein the etherification step is carried out at -200C to 30"C.
51. 51. A process as claimed in any of claims 46 - 50 adapted to the preparation of an ester.
52. 52. A process for the preparation of a compound of the formula (I) as defined in claim 1 wherein X is an oxygen atom and R' is a hydrogen atom, or a salt or ester thereof wherein R2 contains at least 2 carbon atoms and is optionally joined to R3 which process comprises the reaction of an ester of clavulanic acid with a compound of the formula (VI): RhRlC = CH - 0 - R3 (VI) wherein RhRiCH is a group R2 and R3 is as defined in claim 1; and thereafter, if desired, converting the thus produced ester into the free acid or a salt or other ester thereof.
53. 53. A process as claimed in claim 52 wherein the etherification step is carried out in the presence of catalytic quantities of an acid.
54. 54. A process as claimed in claim 53 wherein the acid is HCI, POCK, ptoluenesulphonic acid or BF.
55. 55. A process for the preparation of a compound of the formula (I) as defined in claim 1 wherein X is an oxygen atom and Rl is a hydrogen atom, or a salt or ester thereof which process comprises the reaction of an ester of clavulanic acid with a compound of the formula (IX): R5-O-CHR2-OR3 (IX) wherein R2 and R3 are as defined in claim 1 and R5 is a tertiary alkyl group of 4 - 6 carbon atoms; and thereafter, if desired, converting the thus formed ester into the free acid or a salt or other ester thereof.
56. 56. A process as claimed' in claim 55 wherein R5 is a tert-butyl group.
57. 57. A process for the preparation of a compound of the formula (I) as defined in claim 1 or a salt thereof which process comprises the de-esterification of a corresponding ester of a compound of the formula (I).
58. 58. A process as claimed in claim 57 for the preparation of a salt of the compound of the formula (I) which process comprises the mild base hydrolysis of an ester of the compound of the formula (I).
59. 59. A process as claimed in claim 58 wherein the ester is the methyl ester.
60. 60. A process as claimed in claim 57 wherein the de-esterification is effected by hydrogenolysis.
61. 61. A process as claimed in claim 60 wherein the hydrogenolysis is of a benzyl ester.
62. 62. A process as claimed in claim 60 wherein the hydrogenolysis is of a methoxybenzyl ester.
63. 63. A process as claimed in claim 60 wherein the hydrogenolysis is of a nitrobenzyl ester.
64. 64. 4-Methoxybenzyl 9-O-(1-butoxy)ethylclavulanate.
65. 65. Benzyl 9-O-tetrahydropyran-2-ylclavulanate.
66. 66. Lithium 9-O-tetrahydropyran-2-ylclavulanate.
67. 67. 4-Methoxybenzyl 9-O-tetrahydrofuran-2-ylclavulanate.
68. 68. Sodium 9-O-tetrahydrofuran-2-ylclavulanate.