CA1074802A

CA1074802A - Deoxyclavulanic acid, salts and esters

Info

Publication number: CA1074802A
Application number: CA250,165A
Authority: CA
Inventors: Thomas T. Howarth; Roger J. Ponsford; Jennifer Goodacre
Original assignee: Beecham Group PLC
Current assignee: Beecham Group PLC
Priority date: 1975-04-14
Filing date: 1976-04-13
Publication date: 1980-04-01
Also published as: FR2336130B1; ATA215576A; MX3453E; HU175444B; DE2616088A1; AT342199B; AU497577B2; GR58256B; DK144066B; JPS51127093A; SE427037B; ES446468A1; PT64897A; FR2336130A1; AR208773A1; NO761241L; SE7604287L; DK156576A; LU74749A1; PT64897B

Abstract

A N T I B I O T I C S

ABSTRACT OF THE DISCLOSURE

The compounds of the formula:

and salts and esters thereof are useful agents for the treatment of bacterial infections either alone or in combination with a penicillin or cephalosporin derivative.
The proceeding compounds may be prepared by the hydrogenation of a compound of the formula:

Description

:~74~0Z
The present invention relates to novel ~-lactam con-taining compounds useful in anti-bacterial therapy, to compositions containing these novel compounds and to the method of their preparation.

Belgian Patent No. 827,926 discloses inter alia that the compound of the formula (I):
H
~ (I) 0~

and its salts and esters possess anti-bacterial and ~-lactamase inhibitory activity. ~he compound of the formula (I) is designated clavulanic acid. Acylated deriva-tives of the above compounds are ~ n~cJ;~n disclosed in copendin~hPatent Application No. 237,296, filed October 8~ 1975 and West German Patent Application No. 2,555j626 discloses inter alia isoclavulanic acid and its salts and esters which compound isoclavulanlc acid has the formula H

tII) o ~/ ~ CH 20H -, ~ ~3~ ~

_ ~ .

. . ~ . .
- . ~ . . , . : -, 1~7~8~1;Z

Isoclavulanic acid and its salts and esters also have an-ti-bacterial and ~-lactamase inhibitory activity. A further group of compounds with useful anti-bacterial and ~-lactamase inhibiting properties has now been discovered.

Accordingly the present invention provides the compounds of the formula (III): H

CH.CH3 (III) N

C02H : " :' and salts and esters thereof.

More particularly the present invention provides alkali metal salts and esters selected from lower alkyl, lower alkylthio-lower alkyl, benzyl, halobenzyl or benzoylmethyl esters of the above compounds.

The stereochemistry at C-2 and C-5 of the compounds of formula (III) is the same as that found in naturally occurrin~ penicillins~

The two isomeric acids of the formulae (IV) and (V):

H H
~ ~ 3 o i O
C02E~ C02H
(IV) ~4_ (V) : : .. .. ., . :: : .

are therapeutic agents and are useful intermediates in the formation of their esters but in general their pharmaceutically acceptable salts are more favoured because of their improved stability. The compound of the formula (IV) is designated herein as deoxyclavulanic acid and the compound of the formula tV) is designated herein isodeoxyclavulanic acid.

In general deoxyclavulanic acid and its derivatives form a more favourable aspect of this invention than does isodeoxyclavulanic acid and its derivatives because of their generally more facile production.

Suitable salts of the compounds of the ~ormula (III) include conventional pharmaceutically acceptable salts such as the sodium, potassium, calcium, magnesium, ammonium and conventional substituted ammonium salts formed with benzylpenicillin such as the 1-ephenamine, procaine, benzathine and the like salts.

Particularly suitable salts o deoxyclavulanic acid and isodeoxyclavulanic acid include their sodium and potassium salts.

Preferred salts of this invention include those of the Eormulae (VI) and ~VII):
H

~l3 ~ ~ C~3 O ~`~/ O ~ ' C2Na 2 (Vl) '`(VI~) ' ' ' ': . '' :

: . : .. . . . . . : . : . ... : . :. .: . : . . - . , :,: . .. : , , ~ ,:; :

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The sodium salt of deoxyclavulanic acid is a particularly suitable compound of this invention.

Non-pharmaceutically acceptable salts of the compour~ds of the formula (III) can also be useful as they can serve as intermediates in the preparation of esters of the compounds of formula (III); for example, by reaction with pivaloyloxymethyl chloride to give a useul antibacterial agent.

Suitable esters of the compounds- of formula (III) include those of the formula (VIII):
H
,_ 0 CH.CH3 (VIII) ~ N
O

wherein R is an organic group such that the alcohol ROH is pharmaceutically acceptable.
, It is envisaged that the esters of deoxyclavulanic acid and deoxyisoclavulanic acid owe much of their antibacterial activity to their ability to act as pro-drugs for deoxyclavulanic and isodeoxyclavulanic acids and their salts.
15 Thus preferred esters are those which are cor~vertible to the corresponding - -acid or its salts under physiological conditions.

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Particularly suitable esters of the compounds of the formula (VIII) include those of the formula ~IX):
H

(IX) O

wherein R is as defined in relation to formula (VIII).

Suitable groups R for inclusion in the compounds of formula (VIII) and (IX) include alkyl, alkenyl, alkynyl, aryl, arylalkyl or other similar groups any of which may be substituted if desired.

In order not to increase the molecular weight to an unreasonable extent, groups R do not normally include more than 16 carbon atoms, more suitably not more than 12 carbon atoms and most suitably, not more than 8 carbon atoms.
Generally the C02R group is such that the compound of the formula (V~II) has a molecular weight of not more than 400. ;

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Preferably, the group R is notionally derived from an alcohol ROH which is pharmaceutically acceptable. Suitable groups R include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, vinyl, allyl, butenyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclohexenyl, cyclohexadienyl, methylcyclopentyl, methylcyclohexyl, cyclo-pentylmethyl, cyclohexylmethyl, benzyl, benzhydryl, phenylethyl, naphthyl-methyl, naphthyl, phenyl, propynyl, tolyl, 2-chloroethyl, 2,2,2-trichloroethyl,

2,2,2-trifluoroethyl, acetylmethyl, benzoylmethyl, 2-methoxyethyl, p-chloro-benzyl, p-methoxybenzyl, p-nitrobenzyl, p-bromobenzyl, m-chloro~enzyl, 6-methoxynaphthyl-2-methyl, p-chlorophenyl, p-methoxyphenyl, ~ -2'-pyridylethyl or like group.

Suitable readily in-vivo hydrolysable ester groups C02R include but are not limited to acyloxyalkyl and lactone groups such as those represented by the sub-formulae (a) and (b):

- CO - O - CAlA2 - X - CO - A3 (a) - CO - O - CH - A4 (b) X - C= O
wherein Al is a hydrogen atom or a methyl group; A2 is a hydrogen atom or a methyl, ethyl or phenyl group; A3 is an alkyl or alkoxyl group of 1-6 carbon atoms or a phenyl or benzyl group; A4 is -CH2CH2-, -CH:CH-, , ~ .
., , ' ' . .

:: ' ~7~13QZ

~ , ~ or / ~ OC33 and X is an oxygen or sulphur atom. Most suitably X is an oxygen atom and A2 is a methyl or t-butyl group and A4 is a phenylene group.

A further particularly suitable sub-group of esters of formulae (VIII) or 5 (IX) are those wherein R is a group R or CHR R wherein R is a hydrocarbon .
group of 1 - 9 carbon atoms optionally substituted by halogen, lower alkoxy, lower acyl, hydroxy or lower acyloxy groups and R is an optionally substituted phenyl group and R3 is an optionally su`ostituted phenyl group.

, The term 'lower' used herein means the group contains up to 6 carbon atoms. .
The term 'optionally substituted phenyl' includes a phenyl group and a phenyl group substituted by a halogen atom or a lower alkyl or lower alkoxy group.

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An alternative aspect of the present invention provides a pharmaceutical composition which contains a compound of the formula tIII) or a pharmaceu~
tically acceptable salt or ester thereof and a pharmaceutically acceptable carrier. Favourably such compositions contain a pharmaceutically acceptable salt or in-vivo hydrolysable ester of a compound of the formula (III).

More suitably, the pharmaceutical composition of this invention will contain a pharmaceutically acceptable salt of the compound of the formula (III). The compositions of this invention will normally be adapted for administration to humans and other mam~als, for example, in conventional modes of treatment o~ diseases of the urinary tract, respiratory system and soft tissues as well as diseases such as otitis media in humans and mastitis in domestic animals and the like.

' Suitable forms of the compositions of this invention include tablets, capsules, creams, syrups, suspensions, solutions, reconstitutable powders and sterile forms suitable for injection or in~usion may be used. Such compositlons may contain conventional pharmaceutically acceptable materials such as diluents, binders, colours, flavours, preservatives, disintegrants and the like in accordance with conventional pharmaceutical practice and the arts of formulating antibiotic compositions.

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- ~748~2 Compositions adapted for oral administration may also comprise a buffering agent or may be protected from gastric juice in other conventional manner if so desired.

The compound of formula (III) may be presen~ in the composition as sole therapeutic agent or it may be present together ~ith other therapeutic agents such as a ~ -lactam antibiotic. Suitable ~ -lactam antibiotics for inclusion in such compositions include not only those known to be susceptible to ~ -lactamases but also those which have a degree of intrinsic resistance to ~ -lactamases. Thus, suitable ~ -lactam antibiotics for inclusion in the composition of this invention include benzylpenicillin, phenoxymethyl-penicillin, carbenicillin, methicillin, propicillin, he-tacillin, ampicillin, amoxycilli.n, ticarcillin, cephaloridine, cephalothin, cephalexin, cephalo-glycin, cephamandole and in-vivo hydrolysable esters of such compounds such as the phenyl, tolyl and 5-indanyl esters of carbenicillin and ticarcillin, the acetoxymethyl ester of benzylpenicillin and the acetoxymethyl, pivaloyl-oxymethyl and phthalidyl esters of ampicillin, amoxycillin, cephaloglycin, cephalexin, mecillinam and the like or salts of such compounds .. .

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When present in a pharmaceutical composition -together with a ~ -lactam antibiotic, the ratio of the compound of formula (III) or its salt or ester present to ~ ~lactam antibiotic present may be from, for example, 20:1 to 1:5, such as 10:1 to 1:3, and advantageously may be 5:1 to 1:2, for example,

3:1 t~ 1:1.

The total quantity of antibacterial agents present in any unit dosage form will normally be between 50 and 1500 mg and will usually be betwéen 100 and 1000 mg. However, injectable or infusable compositions may contain greater quantities if desired, for example, 4 g or more of active material. Normally, between 50 and 6000 mg of the compositions of this invention will be administered each day of treatment but more usually between 500 and 3000 mg of the composition of the invention will be administered per day. In general the equivalent of not more than 2000 mg of a compound of the formula (III) will be administered per day, for example, 100 - 1000 mg.

In a further aspect this invention provides synergistic compositions which contain a compound of the formula (III) or a pharmaceutically acceptable salt or ester thereof and ampicillin, amoxycillin or a pro-drug for ampicillin or ~noxycillin. Such compositions are preferably adapted for administration to humans and contain 50 - 500 mg of a salt or in-vivo hydrolysable ester of a compound of the formuLa (III) and 200 - 1000 mg of the penicillin. Particu-larly suitable forms of the peniaillins for inclusion in orally administrable :.

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forms of such compositions include ampicillin trihydrate, amoxyaillin trihydrate, aeetylamoxycillin trihydrate, anhydrous arnpicillin, ampicillin pivaloyloxymethyl ester and ampicillin phthalidyl ester or salts such as the hydrochloride of such esters. Particularly suitable forms of the penicillins for inclusion in in~ectable forms include sodium ampicillin and sodium amoxycillin, sodium ampicillin being preferred. Such compositions may be used in treating infections of the urinary tract and respiratory tract and are particularly useful in treating infections due to strains of Klebsiella aeroginosa, Proteus, or E. coli.

In a further aspect this invention provides synergistic co~positions which contain a compound of the formula (III) or a pharmaceutically acceptable salt or ester thereof and carbenicillin or ticareillin or their salts or a pro-drug for carbenicillin or ticarcillin such as earbenieillin phenylC~-ester, earbenieillin 5-indanylCX-ester, tiearcillin phenylC~-ester or tieareillin tolylCX-ester or their salts. Sueh compoqitions are preferably adapted for administration to humans and contain 50 - 1500 mg of a salt or in-vivo hydrolysable ester of a eompound of the formula ~III) and 200 - 1500 mg of the penieillin. Sueh eompositions may be used in treating infeetions of the urinary traet.

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The preceding compositions preferably contain a pharmaceutically acceptable salt of a compound of the formula (III) such as the sodium or potassium salt, for example, a compound of the formula (VI).

In a further aspect this invention provides a process for the preparation of a compound of the formula (III) as her~inbefore defined or a salt or ester thereof which process comprises the hydrogenation of a corresponding compound o~ the formula (X): H

O
rJf-- >e CH.CH20R6 , (X) ~.

O ~ --or a salt or ester thereof wherein R6 is a hydrogen atom or an acyl group.

It is frequently particularly convenient to use a compound oE the formula ~X) wherein R6 is a hydrogen atom. It is also frequently convenient to use a compound of the formula (X) in the form of a salt -thereof.

Normally, such a reaction takes place in the presence of a transition metal containing catalyst such as palladium, platinum oxide or the like. A
particularly suitable catalyst is palladium on charcoal, for example, 10%
palladium on charcoal.

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7~8~2 The catalyst emplo~ed is suitably in highly active form, for e~ample, the sort obtained by using a fresh batch of catalyst.

Most suitably the weight of catalyst (as total 10~ palladium and charcoal or the equivalent) present is at least 1/3 of the weight of the compound of formula (X) or salt or ester present. It is advantageous to have at least as much catalyst present as compound of formula (X) present, especially for those compounds wherein R6 is H.

The process of this invention normally takes place at a non-extreme temperature; for example, the reaction may take place in a lower~alkanol at a temperature of -10C to ~50C, more usually from 0C to 25C, for example, from 5C to 20C.

The process of this invention normally takes place in an inert solvent such as a lower alkanol, water or an aqueous alkanol. Most suitab~y the solvent employed is a lower alkanol such as methanol or ethanol.
For those compounds of the formula (X) wherein R6 is H water miscible ethers such as tetrahydrofuran are also suitable solvents but such ether solvents are not generally suitable for use when R6 is an acyl group.

An elevated, medium or low pressure of hy~rogen may be used in this reaction.
Generally, it is preferred to use an atmospheric or slightly super atmos-pheric pressure of hydrogen.

.

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A preferred form of the proces~ of this invention comprises the hydrogenation of clavulanic acid or a salt or hydrogenisable ester thereof in the presence of a palladium catalyst. Such a process leads to the preparation of a compound of the formula (~V) or a salt thereof. If a salt is required and the clavulanic acid is not already in salt form a base such as sodium bicarbonate or the like may be included in the reaction medium.

Hydrogenation of isoclavulanic acid or a derivative thereof frequently leads to a deoxyisoclavulanic acid derivative contamin-ated with a corresponding deoxyclavulanic acid derivative. Apurer product may then be obtained by chromatography.

The nature of an acyl group R6 which may be present in a compound of the formula (X) is relatively unimportant as long as it does not lead to the rapid breakdown of the compound oE formula ~X).
~na~
Suitable acyl derivatives are described in copending~Application No. 237,296, filed October 8, 1975.

The group R6 in the formula (X) may represent a wide variety of acyl groups of the formula R2CO which may contain up to 16 carbon atoms, although in general, it more suitably contains up to 12 carbon atoms and is an acyl group found in the acylamino side chain of the known antibacterially active penicillins and cephalosporins.

Most suitably the group R6 does not contain any highly reactive substituents. Thus particularlyrsuitable values for R6 include groups of the formula CO.R where R2 is a hydrocarbon group of up , . : .
.

3LCl17~8~
to 12 carbon atoms which is unsubstituted or substituted only by inert groups such as lower alkoxy, lower acyloxy, fluorine or chlorine atoms or the like. Most suitably R is an alkyl, alkenyl or alkynyl group of up to 12 carbon atoms or such a group substituted by one, two or three inert substituents such as phenyl, phenoxy or inertly substituted phenyl or phenoxy groups or by C2 8 ester, or lower alkoxy groups or by fluorine or chlorine atoms.

Suitable acyl groups include these of the sub-formula (a):
-CO-CH-(CH2)n-R
14 (a) wherein n is O or an integer from 1 to 6i R3 is a hydrogen atom or a phenyl or phenoxy group; and R4 is a hydrogen or halogen a-tom or a lower alkyl, lower alkoxy or Co2R5 group where R5 is a hydro-carbon group of 1 to 8 carbon atoms.

Suitably n is O or an integer from 1 to 3; R3 is a hydrogen atom or a phenyl or phenoxy group and R4 is a hydrogen atom or CO2R5 group where R5 is a phenyl, benzyl or benzhydryl group.

PreEerred acyl groups include those of the sub-Eormula - CO - Ra, wherein Ra is a methyl group or a methyl group substituted by a Cl 3 alkyl group, a phenyl or a phenoxy group or by a phenyl group and an ester group CO2R wherein R is a phenyl benzyl or benzhydryl group.

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When used herein the term "lower" means that a group has 1 to 6 carbon atoms.

Suitable salts of the compounds o formula (X) include the sodium, potassium, calcium, magnesium and other conventional pharmaceuti-cally acceptable salts.

The sodium and potassium salts of the compounds of formula (X) are particularly suitable.

Particularly suitable acyl groups R6 contain up -to 16 carbon atoms and may be optionally substituted by groups such as halogen, lower alkoxy, lower alkoxycarbonyl, lower acyloxy, hydroxy and the like.
Most suitably such acyl groups are unsubstituted or substituted by non-reactive groups only.

Esters of the compounds of formula (III) may be prepared by the reaction of a compound of the formula (III) or a salt thereof with an alcohol ROH or a compound of the formula RQ where Q is a good leaving group such as a chlorine, bromine or iodine -16b-? `

. . . .

7~302 atom or an activated ester group or a sulphonic ester such as a mesylate or tosylate group or other conventional good leaving group. Alternatively, the acid of the formula (III) may be treated with a dia7ocompound such as diazomethane or the like or with an alcohol ROH in the presence of a dehydrating agent such as a carbodiimide or its chemical equivaLent.

The reaction with RQl is normally carried out in an organic solvent of relatiuely high dielectric constant such as dimethylformamide, acetone, dioxane, tetrahydrofuran or the like and at a non-extreme temperature such as -5C to loo&, more usually +5C to 30 C, for example, at amoient temperature.
,',~ .

The reaction of an acid of formula (III) with a dia7oalkane is a mild method of making alkyl, aralkyl or similar esters. The diazoti2ation reaction may be performed under conventional reaction aonditions, for example at a non-extreme temperature and in a conventional solvent. Such reactions are 15 normally carried out at between -5 C and 100C, more usually from 5 C to 30 C, for example at ambient temperature. Suitable solvents for this reaction include lower alkanols such as methanol and ethanol and solvents such as tetrahydrofuran, dioxane and the like. Ethanol has proved a particularly :
useful solvent for this reaction.

The reaction of an acid of formula (III) with an alcohol in the presence of a condensation promoting agent will normally take place in an inert organic solvent such as dichloromethane or acetonitrile. This reaction is usually carried out at an ambient or depressed temperature, for example at -10C to ~22 C, more usually -5C to +18QC, for example initially at 0 C

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and thereafter gradually warming to about 15 C. The condensation promotlng agent used is normally one which removes water from the reaction mixture.
Suitable agents include carbodiimides, carbodiimidazoles or equivalent reagents. Dicyclohexylcarbodiimide has proved to be a particularly suitable condensation promoting agent for use in this process.

Other less suitable methods of ester formation include (a) removal of the elements of carbon dioxide from a compound of the formula (XI):
H

CH.CH3 (Xl) O
CO-O-CO-O-R

wherein R7 is an in~rt organic groupi and also (b) reaction of a compound of the formula (XI) with alcohol ROH.

The compound of the formula tXI) may be prepared by the reaction of a salt of a compound of the formula (III) with Cl.CO.O.R7 or the chemical equivalent thereof.

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' ~7~ 2 Salts of the compounds of the formula tIII) may be prepared by the hydrolysis of an ester of a compound of the formula (III). Generally this may be brought about by keeping the ester of the compound of formula (III) in an aqueous medium maintained at pH of about 7 - 9 for up to one hour. Certain reactive esters such as the pivaloyloxymethyl, acetoxymethyl, phthalidyl and like esters hydrolyse in a few minutes when maintained in an aqueous medium at a pH of c~bout 6 - 8.

~he following Examples illustrate the invention:

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Sodium Deoxyclavulanate H H

N NaHCO3~ N ~
2 2 6 5 ~C2Na Benzyl clavulanate t220 mg) in ethanol (20 ml) was hydrogenated over 10%
Pd/C (70 mg) and sodium hydrogen carbonate (60 mg) for 60 minutes. The catalyst was filtered, washed with water and then ethanol and the combined filtra-tes were evaporated. This material was chromatographed on a silica gel column with n-butanol/ethanol/water; 4:1:1 /4 and the fastest moving component was collected. The solvents were removed under low pressures to yield the sodium salt of deoxyclavulanic acid.

I.r. (KBr): 1780, 1700, 1605 cm ; n.m.r. (D2O): 1.52 (3H, dd, J 7Hz, J' 1.5Hz); 2.98 (lH, d, J 18Hz, 6~ -CH); 3.52 (lH, dd, J 18Hz, J' 2.5Hz, 6~ -CH); 4.5 - 4.9 (m, obscured by HOD peak); 5.64 (lH, d, J 2.5Hz, 5-C_).

~The sodium salt of clavulanic acid was also obtained from the column on further elution~

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EX~MPLE 2 Sodium Deoxyc.lavulanate H

O ~ ~ ~ ~ / 3 C2CH2C6H5 ~ \CO H

N

~ C02Na Benzyl clavulanate (8.25 g) was dissolved in tetrahydrofuran (75 ml).
To the solution was added 10% palladium on charcoal (8.25 g) and the mixture was hydrogenolysed at room temperature with vigorous shaking and using 1 atmosphere pressure of hydrogen for 30 minutes. The suspension was filtered and the filtrate was treated with a solution of sodium .
bicarbonate (2.39 g) dissolved in the minimum amount of water. The solution 10 was concentrated under reduced pressure on a rotary evaporator at room -temperature and the residue was triturated with acetone and ether to give a pale yello~ solid (4.7 g).

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Sodium Deoxyclavulanate H H
Fr~H20 . CO C:~ ~ G?~ ICH3 NaHC03 C02CH2C6H5 C2Na senzyl phenoxyacetylclavulanate (140 mg) was dissolved in ethanol/ethyl acetate (5:1, 6 ml) and sodium bicarbonate (56 mg) and lO~ palladium on char~oal ~47 mg) were added to the solution. The solution was hydro~enated at ambient temperature (^J18 C) for 15 minutes. The catalyst was filtered off and washed well wi-th water. The filtrate and washings were combined and evaporated to dryness to give a quantitati~e yield of sodium deoxy-elavulanate. Sodium deoxyelavulanate may be separated from the mixturewith sodium phenoxyacetate by careful eolumn chromatography using silica gel and el~lting with butanol/ethanol/water. (Physieal characteristics of produet as in Example l.) The preeeding example may be varied by replacing the benzyl phenoxyacetyl-clavulanate with equivalent amounts of benzyl aeetylclavulanate, benzyl ~'-phenyloxycarbonylphenylacetylclavulanate, p-bromobenzyl phenoxyaeetyl-elavulanate and the like. The preeeding example may also be varied by replacing the benzyl phenoxyacetylclavulanate with an equivalent amount of benzyl CX-benzyloxycarbonylphenylacetamidoclavulanate and increasing the amount of sodium bicarbonate to 2 equivalents.
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p-Bromobenzyl Deoxyclavulanate ~ CH3 1 CH3 \~=/ Br C6H4 CH2Br rr ~
N ~ 0 ~
C2Na C02CH2 ~ Br A solution of p-bromobenzyl bromide ~50 mg) was added to a solution of sodium deoxyclavulanate (10 mg) in dimethylformamide (0.5 ml) and the mixture was kept at ambient temperature (about 18C) for 2 hours. The reaction mixture was fractionated on silica gel eluting with ethyl acetate/hexane (1:4) to yield p-bromobenzyl deoxyclavulanate (as an oil) on evaporation.

I.r. (CHC13): 1790, 1740, 1695 cm 10 N.m.r. (CDC13): 1.62 (3H, dd, J 7Hz, J' 1.4Hz, CH3);
2.95 (lH, dd, J 17Hz, J' l.OHz, 6~ -CH); 3.48 (lH, dd, J 17Hz, J' 2.6Hz, 6C~-CH); 4.58 (lH, dq, J 7Hz, J' lHz, =CHCH3);
5.03 (lH, dd, J 1.4Hæ, J' l.OHz, 3-CH); 5.12 (2H, s, C02CH2-);
5.65 (lH, dd, J 2.6Hz, J' l.OHz, 5-CH); 3.38 (4~, ABq, J 8.5Hz, aromatic protons).

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The preceding example may be repeated replacing p-bromobenzyl bromide with an equivalent quantity of methyl iodide, ethyl bromide, l-bromo-2-methoxy-ethane, pivaloyloxymethyl chloride, phthalidyl bromide, 1-chloro-2-thiomethyl-ethane, l-chloro-2-phenylsulphonylethane, l-bromononane, 4-methoxybenzyl-bromide, benzylbromide, benzylchloride, phenacetyl bro~ide or the like.

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~, Sodlum Deoxyisoclavulanate H
rr ~ 1~ rl~
2H O ~ N ~ `

2 2 6 9 CO2Na Benzyl isoclavulanate (50 mg) in tetrahydrofuran (0.5 ml) was hydrogenated at room temperature (rv18 C) and atmospheric pressure using 10~ palladium on charcoal (50 mg) as catalyst. After 30 minutes the catalyst was filtered off and an equivalent amount of aqueous sodium bicarbonate added. The solvent was removed by evaporation and the residue triturated with ethanol, acetone and acetone/ether to give the product as an of~-white solid (20 mg).
~The n.m.r. spectrum in D2O showed that the title compound was contaminated with sodium deoxyclavulanate~

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~ ~74~2 Pharmacolo~y Sodium deoxyclavulanate did not appear to produce any overt toxic efeets in mice when administered intra peritoneally at 500 mg/kg.

The antibacterial and synergistic properties of sodium deoxyclavulanate are illustrated by the following in-vitro results:

__ Organism ~ r, ~ ation of Sodium Deoxyclavulanate (~ g/ml) . _ ~
Bacillus subtilis A ~ 62.5 Enterobacter cloaeae Nl 125 .
Escherichia coli 10418 62.5 Klebsiella aerogenes ~ 62.5 Proteus mirabilis C 977 125 . .
Pseudomonas aeruginosa A 1000 :~

Salmonella typhimurium CT10 125 _ Serratia marcescens US 39 125 Staph. aureus Oxford 15.6 .
aureus Russell 31 !``~ ;` ' - 26 - . :

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', ' ~ ` . ` , :

79~8(~
Z-~f~ ZZ-AZZ ~ZZ~ ~CIZZ~UZ J ZZ ~ ZZ~ ~ ~ I S C L 0 5 ~Z~ .

Methylthioe-thyl deox~clavulanate ~ ~ CH3 0~ "-Deoxyclavulanic acid (220mg) in -tetrahydrofuran (8ml) was cooled -to 0 and -treated with methylthioethanol (550mg) and dicyclohexylcarbodiimide (2LZ9mZ~) ~ The reac-tion was stirred for 5 hours at room temperature and set aside a-t 0 over-nigh-t. The suspension was fil-tered and -the residue evapor-a-ted Chromatography on silica gel, eluting wi-th ethyl ace-tate - hexZane (1:1) gave the required produc-t (150mg) as an oil; ~ (CHCl~) 1800, 1750 and 1700 cm 1; nmr (CDCl3) 1.68 (3H, dd, =CHCH3), 2.19 (3H, s, SCH3), 2.82 (2H, -t, J 7Hz, CH2SCH3), 3.10 (1H, d, J 16.5Hz, 6îZ-CH), 3.56 (1H, dd, J
16.5 and 2.5Hz, 6x-CH), 4 . 43 ( 2H, -t, J 7Hz, -C02CH2CH2S-), 4.76 (1H, dq, J 7 and 1.5Hz, =CHCH3), 5.10 (1H, q, J 1.5Hz, 3-CH) 5.78 (1H, d, J 2.5Hz, 5-CH).

., :, , J
..`Z ,~
`

.: .
. . . ~ . .

~374~3V'~

2-Benzyloxyc_rbonyl-2-benzyloxycarb~ amino-~-th c vu~anate N
C02CH2C, H-C02CH2Ph NH C02CH2Ph This ester was prepared in a manner similar to the above by coupling deoxyclavulanic acid with benzyl (N-benzyloxycarbon-yl)-serine in -the presence oE dicyclohexylcarbodiimide.
The product was isolated by silica gel chromatography, eluting wi-th e-thyl aceta-te - hexane (1~ (CHC13) 1800, 1755-1730, 1695 (shoulder)cm 1. N.m.r (CDCl3) 1.56 (3H, dd, J 7 and 1.5Hz, =CHCH3), 2.95 (1H, d, J 17Hz, 6~-CH), 3 35 (1H, dd, J 17 and 2.5Hz, 6~-CH), 4.3-4.8 (m, C02CH2CH, =CHCH3), 4.92 (1H, m, 3-CH), 5.10 (2H, s, C02CH2Ph), 5.18 (2H, s, C02CH2Ph), 5.50 (1H, d, J 2-5Hz,

5-CH), 5.60 (1H, br.d., J 8Hz, NH), 3.32 (10H, S, 2 x C6H5).

": ' ' , , ' ' ' ` , ' . ~' ' ' ~ ', `, : , ' '' , '.' ' " , .-' " ' "., '""''' ' ' '' ';' '~. ~. ' ' ', , ,' ' , ' ., '~ . ' 7~ 2 . _ Methyl deoxyclavulana-te Benzyl clavulana-te (1.45g) in methanol (/~Ornl) was hydro-genated over 10% Pd/C (0.4g) a-t ambient -temperature and pressure for 30 minutes. The catalys-t was fil-tered and the filtrate cooled -to 0 and treated with excess ethereal diazome-thane. The solvent was evaporated and -the residual oil frac-tiona-ted on silica-gel; -the first eluted produc-t was methyl deoxyclavulanate (365mg);~ max (CHCl3) 1800, 1745, 1700 cm~1; ~ (CDC13) 1.68 (3H, dd, J 7.5 and 1.5Hz, =CH-CH~), 3.07 (1H, d, J 17Hz, 6~-CH), 3.59 (1H, dd, J 17 and 2.5Hz,

6~-CH), 3.84 (3H, S, C02CH3), 4.71 (1~-I, dq, J 7.5 and 1.5 Hz, =CH-CH3), 5.08 (1H, m, 3-CH), 5.76 (1H, d, J 2.5Hz, 5-CH),; M~ 197.0688.

~ 30~
':,`'': . , . ~. . . ,"
. , .
, . . . . .
.- . .. , - . . , . .: . . : , .

., -: . ' ' . - . ' ' ' . -,, . - . : : ,:. . ' : ~ :, ' .

74~

E~AMPLE lO
Phenacyl deoxyclavulanate + C6H5COCH2Br > ~ N ~
co2Na O C02CH2COPh Phenacyl bromide (0.2g) was added -to a solutlon of sodi~n deoxyclavulana-te (0.2g) in dimethylformamide (5ml) and the mixture was stirred at room tempera-ture for three hours.
The solven-t was removed and the residue dissolved in e-thyl aceta-te, washed wi-th wa-ter, dried and evapora-ted. Gradient chroma-tography on silica gel using cyclohexane/e-thyl ace-tate as eluan-t gave -the produc-t which on recrys-tallisation ~rom e-ther was ob-tained as colourless crystals (0.15g);
mass measuremen-t showed a molecular ion a-t m/e 301;
~max (Nujol) 1798. 1755, 1702cm 1; ~ (CDCl3) 1.7 (3H, dd, J

7 and 1.5 Hz, =CHCH3), 3.0 (1H, dd, J 17 and 1Hz, 6~-CH), 3.5 (1H, dd, J 17 and 3Hz, 6~-CH), 4.81 (1H, m, CE~CH3) 5.17 (1H, m, 3-CH), 5.4 (2H, s, CH2COPh), 5.7 (1H, dd, J 3 and 1Hz, 5-CH),7.7 (5H, m, ArH).

..

, - ,:

.. .. ~ .

.

Claims

THE EMBODIMENlS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR PRIVILEGE
IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for the preparation of compounds of the formula (III):

(III) and isomers thereof, pharmaceutically acceptable alkali metal salts, lower alkyl, lower alkylthio-lower alkyl, benzyl, halobenzyl or benzoylmethyl esters thereof, which comprises hydrogenating a corresponding compound of the formula (X):

(X) or a salt or ester thereof selected from those set forth above wherein R6 is a hydrogen atom or an acyl group of the sub-formula (a):

(a) wherein n is 0 or an integer from 1 to 3; R3 is a hydrogen atom or a phenyl or phenoxy group; and R4 is a hydrogen atom or CO2R5 group, where R5 is a phenyl, benzyl or benzhydryl group and when required converting the rssulting acid to the desired pharmaceutically acceptable salt or esterifying the acid or salt to obtain the desired pharmaccutically acceptable ester.

2. A process for the preparation of the sodium and potassium salts of compounds of the formula (III) as set forth and defined in Claim 1 which comprises hydrogenating a corresponding compound of the formula (X) as set forth in Claim 1 and defined therein, or the corresponding salt thereof and when required converting the resulting acid to the sodium or potassium salt.

3. A process for the preparation of a compound of the formula (VI):

(VI) which comprises hydrogenating clavulanic acid or the sodium salt thereof in the presence of a palladium catalyst and when required converting the resulting acid to the sodium salt.

4. A process as claimed in Claim 3 wherein the sodium salt of clavulanic acid is formed in situ prior to hydrogenation by the addition of a correspond-ing base to the free acid.

5. A process for the preparation of a com~ound of the formula (VII):

(VII) which comprises hydrogenating clavulanic acid or the potassium salt thereof in the presence of a palladium catalyst and when required converting the acid to the potassium salt.

6. A process as claimed in Claim 5 wherein the potassium salt of clavulanic acid is formed in situ prior to hydrogenation by the addition of a corresponding base to the free acid.

7. Compounds of the formula (III), isomers thereof pharmaceutically acceptable alkali metal salts and lower alkyl, lower alkylthio-lower alkyl, benzyl, halobenzyl or benzoylmethyl esters thereof as set forth and defined in Claim 1 whenever prepared by the process of Claim 1 or an obvious chemical equivalent thereof.

8. The sodium and potassium salts of the compounds of the formula (III) as defined in Claim 1 whenever prepared by the process of Claim 2 or an obvious chemical equivalent thereof.

9. A compound of the formula (VI) as set forth in Claim 3 whenever prepared by the process of Claim 3 or 4 or an obvious chemical equivalent thereof.

10. A compound of the formula (VII) as set forth in Claim 5 whenever prepared by the process of Claim 5 or 6 or an obvious chemical equivalent thereof.

CLAIMS SUFPORTED BY THE SUPPLEMENTARY DISCLOSURE

11. A process for the preparation of compounds of the formula (III):

(III) and isomers thereof, alkali metal salts, lower alkyl, lower alkylthio-lower alkyl, benzyl, halobenzyl or benzoylmethyl esters thereof, which comprises hydrogenating a corresponding compound of the formula (X):

(X) or a salt or ester thereof selected from those set forth above wherein R6 is a hydrogen atom or an acyl group of the sub-formula (a):

(a) wherein n is 0 or an integer from 1 to 3; R is a hydrogen atom or a phenyl or phenoxy group; and R4 is a hydrogen atom or CO2R5 group, where R5 is a phenyl, benzyl or benzhydryl group and whell required converting the resulting acid to the desired salt or esterifying the acid or salt to obtain the desired ester.