NO761241L - - Google Patents

Description

"Procedure for the manufacture of

antibacterial compounds"

The invention relates to a method for the production of -3-lactam-containing compounds which are useful in antibacterial therapy.

Belgian patent no. 827926 discloses, among other things that the compound of formula (I): and its salts and esters possess anti-bacterial and 3-lactamase inhibitory activity. The compound of formula (I) is designated clavulanic acid. Acylated derivatives of the above-mentioned compounds are disclosed in Dutch Patent Application No. 75/12348 and BRD Application No. 2555626 discloses i.a. Isoclavulanic acid and its salts and esters, whereby isoclavulanic acid has the formula (II):

Isoclavulanic acid and its salts and esters also have anti-bacterial and B-lactamase inhibitory activity. A further group of compounds with useful antibacterial and 3-lactamase inhibitory properties has now been discovered.

Accordingly, the invention provides compounds of formula (III):

and salts and esters thereof.

The stereochemistry at C-2 and C-5 of the compounds of formula (III)

is the same as that found in naturally occurring penicillins.

The two° isomeric acids of formulas (IV) and (V):

are therapeutic agents and useful intermediates in the formation of their esters, but generally their are more highly valued

pharmaceutically acceptable salts due to their improved stability. The compound of formula (IV) is here designated deoxyclavulanic acid and the compound of formula (V) isodeoxyclavulanic acid.

In general, deoxyclavulanic acid and its derivatives represent a more favorable aspect of the present invention than isodeoxyclavulanic acid and its derivatives, because of their generally easier preparation.

Suitable salts of the compound of formula (III) include conventional pharmaceutically acceptable salts, e.g. sodium,

potassium, calcium, magnesium, ammonium and conventional substituted ammonium salts formed with benzylpenicillin, e.g. 1-ephenamine, procaine, benzathine and similar salts.

Particularly suitable salts of deoxyclavulanic acid and isodeoxyclavulanic acid include their sodium and potassium salts. Preferred salts according to the invention include those of formulas (VI) and (VII)t

The sodium salt of deoxyclavulanic acid is a particularly suitable compound according to the invention.

Non-pharmaceutically acceptable salts of the compounds of formula (III) may also be useful, as they may serve as intermediates in the preparation of esters of the compounds of formula (III);

for example by reaction with pivaloyloxymethyl chloride so that a useful antibacterial agent is obtained.

Suitable esters of the compounds of formula (III) include those of formula (VIII):

where R is an organic group such that the alcohol ROH is pharmaceutically acceptable.

It should be appreciated that the esters of deoxyclavulanic acid and deoxyisoclavulanic acid owe much of their antibacterial activity to their ability to serve as prodrugs for deoxyclavulanic acid and isodeoxyclavulanic acid and their salts. Thus, preferred esters are those which can be converted into the corresponding acid or its salts

under physiological conditions.

Particularly suitable esters of the compound of formula (VIII) include those of formula (IX):

where R is as defined with respect to formula (VIII).

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

In order not to increase the molecular weight unreasonably, the groups R normally include no more than 16 carbon atoms, more suitably no more than 12 carbon atoms and preferably no more than 8 carbon atoms. In general, the CO 2 R group is such that the compound of formula • (VIII) has a molecular weight of not more than 400.

Preferably, the group R is conceptually 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, raethylcyclohexyl, cyclopentyl-methyl, cyclohexylmethyl, benzyl, benzhydryl, phenylethyl, naphthylmethyl, naphthyl, phenyl, propynyl, tolyl, 2-chiorethyl, 2,2,2-trichloroethyl, 2,2,2-trifluoroethyl, acetylmethyl, benzoylmethyl, 2- methoxyethyl, p-chlorobenzyl, p-methoxybenzyl, p-nitrobenzyl, p-bromobenzyl, m-chlorobenzyl, 6-methoxynaphthyl-2-methyl, p-chlorophenyl, p-methoxyphenyl, 0-2•-pyridyl-ethyl or the like.

Suitable ester groups CX^R which can be readily hydrolyzed in vivo include, but are not limited to, acyloxyalkyl and lactone groups, e.g. such as are represented by sub-formulas (a) and (b):

where A is a hydrogen atom or a methyl groupj A is a hydrogen atom or a methyl, ethyl or phenyl groupj Ag is an alkyl or

alkoxyl group with 1-6 carbon atoms or a feryl- or benzyl-. group; A4, is -CH2CH2~,.-CH:CH-,

and X is an oxygen or sulfur atom. Most suitable, X is an oxygen atom. and A 2 is a methyl or t-butyl group, bg A 2 is a phenylene-. group. A further particularly suitable subgroup of esters a<y>

the formulas (VIII) or (IX) are those where R is one group R1 or

2 3 CHR R where R is one hydrocarbon group of 1<-9 carbon atoms optionally substituted with halogen, lower alkoxy-7 lower acyl, hydroxy or lower acyloxy groups, and R is an optionally substituted phenyl group^ and R • 3 e' r an optionally substituted phenyl group..

The term "lower" as used herein means that the group contains up to 6 carbon atoms. The term "optionally substituted phenyl" includes a phenyl group and a phenyl group which is substituted with a halogen atom or one lower alkyl or lower alkoxy group. An alternative aspect of the present invention provides a pharmaceutical preparation containing a compound of

formula (III) or a pharmaceutically acceptable salt or ester thereof and a pharmaceutically acceptable carrier. Such preparations often contain: a pharmaceutically acceptable salt or an in vivo hydrolysable ester of a compound of formula (III).

More suitable, the pharmaceutical preparation according to up-. the invention contain a pharmaceutically acceptable salt of the compound of formula (III). The preparations according to the invention will normally be adapted for administration to humans and mammals, e.g. by conventional treatment methods for diseases of the urinary tract, respiratory system and soft tissues as well as diseases such as. e.g. otitis media in humans and mastitis in livestock o.T.

Suitable forms of the preparations according to the invention'

includes tablets, capsules, creams, syrups, suspensions,

solutions, reconstitutable powders and sterile forms suitable .for. injection, or infusion. Such preparations may contain conventional pharmaceutically acceptable materials such as diluents, binders, dyes, flavoring agents, preservatives,

disintegrants and the like in accordance with conventional pharmaceutical practice and experience with regard to the composition of antibiotic preparations.

Preparations adapted for oral administration may also include a buffering agent or may be protected from gastric juice in other conventional ways if desired.

The compound of formula (III) may be present in the preparation as the sole therapeutic agent, or it may be present together with other therapeutic agents such as B-lactam antibiotic. Suitable B-lactam antibiotics for incorporation into such preparations include not only those known to be sensitive to B-lactamase, but also those which have a degree of intrinsic resistance to B-lactamases. Therefore, suitable B-lactam antibiotics include for incorporation into the preparation according to the invention benzylpenicillin, phenoxymethylpenicillin, carbenicillin, methicillin, propicillin, hetacillin, ampicillin, amoxycillin, ticarcillin, cephaloridine, cephalothin, cephalexin, cephaloglycin, cefamandole and in vivo hydrolyzable esters of such compounds, e.g. the phenyl, tolyl and 5-indanyl esters of carbenicillin and ticarcillin, the acetoxymethyl ester of benzylpenicillin and the acetoxymethyl, pivaloyloxymethyl and phthalidyl esters of ampicillin, amoxycillin, cephaloglycin, cephalexin, mecillinam and the like or salts of such compounds.

When present in a pharmaceutical preparation together with an O-lactam antibiotic, the ratio between the compound of formula (III) or its salt or ester and the O-lactam antibiotic can be from e.g. 20:1 to 1:5, e.g. 10:1 to 1:3, and advantageously from 5:1 to 1:2, e.g. 3:1 to 1:1. The total amount of antibacterial agents present in any unit dosage form will normally be between 50 and 1500 mg and will usually be between 100 and 1000 mg. However, injectable or infusible preparations can contain larger amounts if desired, e.g. 4 g or more of active material. Normally between 50 and 6000 mg of the preparations according to the invention will be administered every day during the treatment, but more commonly between 500 and 3000 mg of the preparation according to the invention will be administered per day. Generally, the equivalent of no more than 2000 mg of a compound of formula (III) will be administered per day, e.g.

100-1000 mg.

In a further aspect, the invention provides synergistic preparations containing a compound of formula (III) or a pharmaceutically acceptable salt or ester thereof, and ampicillin, amoxycillin or a prodrug thereof. ampicillin or amoxycillin. Such preparations are preferably adapted for administration to humans and contain 50-500 mg of a salt or an in vivo hydrolysable ester of a pea compound of formula (III) and 200-1000 mg of the penicillin; Particularly suitable forms of the penicillins for incorporation into orally administrable forms of such preparations include ampicillin trihydrate, amoxycillin trihydrate, ampicillin anhydrous, ampicillin pivaloyloxymethyl ester and ampicillin phthaldyl ester or salts such as the hydrochloride of such esters. Particularly suitable forms of the penicillins for incorporation into injectable forms include sodium ampicillin and sodium amoxycillin, sodium ampicillin being preferred. Such preparations can be used in the treatment of infections in the urinary tract and respiratory organs and are particularly useful in the treatment of infections caused by strains of Klebsiella aeroginosa, Proteus or E. coli. *

In a further aspect, the invention provides synergistic preparations containing a compound of formula (III) or a pharmaceutically acceptable salt or ester thereof, and carbenicillin and ticarcillin or their salts or a prodrug of carbenicillin or ticarcillin, e.g. carbericillin-phenyl-α-ester, carbenicillin-5-indanyl-α-ester, ticarcillin-phenyl-o-ester or ticarcillin-tblyl-α-ester or their salts Such preparations are preferably adapted for administration to humans and contain 50-1500 mg of a salt or an in vivo hydrolysable ester of a compound of formula (III) and 200-1500 mg of the penicillin. Such preparations can be used in the treatment of infections in the urinary tract.

The aforementioned preparations preferably contain a pharmaceutically acceptable salt of a compound of formula (III) such as the sodium or potassium salt, e.g. a compound of formula (VI).

In a further aspect, the invention provides a process for the preparation of a compound of formula (III)

as defined above or a salt or ester thereof, and the process comprises hydrogenating a corresponding compound of formula (X) :

or a salt or ester thereof, where Rg is a hydrogen atom or an acyl group.

It is often particularly convenient to use a compound of formula (X) where Rg is a hydrogen atom. It is also often convenient

to use a compound of formula (X) in the form of a salt thereof.

Normally, such a reaction takes place in the presence of a transition metal-containing catalyst, e.g. ehfe. palladium, platinum oxide or the like. A particularly suitable catalyst is palladium on charcoal, e.g. 10% palladium on charcoal. The catalyst used is usually in a highly active form, e.g. such as is achieved by using a new catalyst batch. Most suitable is the weight of catalyst present

(with a total of 10% palladium and charcoal or equivalent values)

at least 1/3 of the weight of the compound of formula (X) or a salt or ester present. It is advantageous to have at least as much catalyst present as the amount of the compound of formula (X), especially for those compounds where Rg is H. The method according to the invention normally takes place at a temperature which is not extreme. For example, the reaction can take place in a lower alkanol at a temperature of from -10°C to +50°C, more commonly from 0 to 25°C, e.g. from 5 to 20°C. The method according to the invention normally takes place in an inert solvent, e.g. a lower alkanol, water or an aqueous alkanol. Most suitable is the solvent used a lower alkanol, e.g. methanol or ethanol. For those compounds of

formula (X) where Rg is H, are also spring-miscible ethers, e.g. tetrahydrofuran, also suitable solvents, but such ether solvents are not generally suitable for use when Rg is an acyl group.

An elevated, medium or low pressure of hydrogen can be used in this reaction. In general, it is preferred to use an atmospheric or slightly subatmospheric hydrogen pressure.

A preferred form of the method according to the invention comprises the hydrogenation of clavulanic acid or a salt or a hydrogenizable ester thereof in the presence of a palladium catalyst. Such a method leads to the production of a compound of formula (IV) or a salt thereof. If it is necessary to prepare a salt and the clavulanic acid is not already in salt form, a base, e.g. sodium bicarbonate or the like, is included in the reaction rail oil.

Hydrogenation of isoclavulanic acid or a derivative thereof often leads to a deoxyisoclavulanic acid derivative which is contaminated

with a corresponding deoxyclavulanic acid deriv. A purer product can then be obtained by chromatography.

The nature of an acyl group Rg which may be present in a compound of formula (X) is relatively unimportant as long as it does not lead to rapid decomposition of the compound of formula (X). Suitable acyl derivatives are described in Dutch Application No. 75/12348. Particularly suitable acyl groups ft£ contain up to 16 carbon atoms and may optionally be substituted with groups such as halogen, lower alkoxy, lower alkoxycarbonyl, lower acyloxy, hydroxy and the like. Most suitable are such acyl groups unsubstituted or substituted with only non-reactive groups.

Esters of the compound of formula (III) can be prepared by reacting a compound of formula (III) or a salt thereof with an alcohol ROH or a compound of formula RQ where Q is a group which easily disappears, e.g. a chlorine, bromine or iodine atom or an activated ester group or a sulphonic ester, e.g. a mesylate or tosylate group or another conventional group which readily disappears. Alternatively, the acid of formula (III) can be treated with a diazo compound, e.g. diazomethane or the like, or with an alcohol ROH in the presence of a dehydrating agent, e.g. a carbodiimide or its chemical equivalent.

The reaction with RQ is normally carried out in an organic solvent with a relatively high dielectric constant, e.g. dimethylformamide, acetone, dioxane, tetrahydrofuran or the like and at a non-extreme temperature, e.g. -5 to 100°C, more commonly +5 to 30°C, e.g. at ambient temperature.

The reaction of an acid of formula (III) with a diazoalkane is a mild method for the preparation of alkyl, aralkyl or similar esters. The diazotization reaction can be carried out under conventional reaction conditions, e.g. at a non-extreme temperature and in a conventional solvent. Such reactions are normally carried out between -5 and 100°C, more commonly from 5 to 30°C, e.g. at ambient temperature. Suitable solvents for this reaction include lower alkanols, e.g. methanol and ethanol and solvents such as tetrahydrofuran, dioxane, etc. Ethanol has proven to be a particularly useful solvent for this reaction. "

The reaction of an acid of formula (III) with an alcohol in the presence of a condensation agent will normally take place in an inert organic solvent,* e.g. dichloromethane or acetonitrile. This reaction is usually carried out at ambient temperature or reduced temperature, e.g. at -10 to +22°C, more commonly from -5 to +18°C, e.g. initially at 0°C and then gradually heating to approx. 15°C. The condensation-inducing agent used is normally one that removes water from the reaction mixture. Suitable agents include carbodiimides, carbodiimidazoles or equivalent reagents. Dicyclohexylcarbodiimide has been found to be a particularly suitable condensation-inducing agent for use in this process.

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

where is an inert organic group; and also (b) reacting a compound of formula (XI) with alcohol ROH. The compound of formula (XI) can be prepared by reacting a salt of a compound of formula (III) with Cl.CO.0*R^ or the chemical equivalent thereof.

Salts of the compounds of formula (III) can be prepared by hydrolysis of an ester of a compound of formula (III), - General

this can be accomplished by keeping the ester of the compound of formula (III) in an aqueous environment which is kept at a pH value of approx. 7-9 for up to 1 hour.' Certain reactive esters, e.g. Pivaloyloxymethyl, acetoxymethyl, phthalidyl and similar esters hydrolyse within a few minutes when kept in an aqueous environment at a pH value of approx.

The following examples illustrate the invention:

Example 1 Sodium deoxyclavulanate 220 mg of benzylclavulanate in 20 ml of ethanol was hydrogenated over 70 mg of 10% Pd/C and 60 mg of sodium bicarbonate for 60 minutes. The catalyst was filtered, washed with water and then ethanol, and the combined filtrates were evaporated. This material was chromatographed on a silica gel column with n-butanol/ethanol/water; 4:1:1^/^, and the fastest moving component was collected. The solvents were removed under low pressure to give the sodium salt of deoxyclavulanic acid. i.r. (KBr) :. 1780, 1700, 1605 cm"1" n.m.r. (D20): 1.52 (3H, dd, J 7Hz, J<1>1.5Hz)» 2.98 (1H, d, J 18Hz, 6B-CH)> 3.52 (1H, dd, J 18Hz, J' 2.5Hz, 6<x-CH) » 4.5-4.9 (m, eclipsed by HOD peak) in 5.64 (1H, d, J 2.5Hz, 5-CH).

[The sodium salt of clavulanic acid was also obtained from the column by further elution].

Example 2

Sodium deoxyclavulanate

8.25 g of benzylclavulanate was dissolved in 75 ml of tetrahydrofuran. To the solution was added 10% palladium on charcoal (8.25 g), and the mixture was hydrogenolyzed at room temperature under vigorous shaking and using 1 atmosphere of hydrogen pressure for 30 min.

The suspension was filtered, and the filtrate was treated with a solution

of 2.39 g of sodium bicarbonate dissolved in the smallest amount of water.

The solution was concentrated under reduced pressure on a rotary evaporator at room temperature, and the residue was triturated with acetone and ether to give 4.7 g of a pale yellow solid.

Example 3

Sodium deoxyclavulanate

140 mg of benzylphenoxyacetylclavulanate was dissolved in ethanol/ethyl acetate (5:1, 6 ml) and 56 mg of sodium bicarbonate, and 10% palladium on charcoal (47 mg) was added to the solution. The solution was hydrogenated at ambient temperature (approx. 18°C) for 15 minutes. The catalyst was filtered off and washed well with water. The filtrate from the washing waters was combined and evaporated to dryness so that a quantitative yield of sodium deoxyclavulanate was obtained. Sodium deoxyclavulanate can be separated from the mixture with sodium phenoxyacetate by careful column chromatography using silica gel and elution with butanol/ethanol/water (physical characteristics of the product as 1 example 1). The preceding example can be varied by replacing the benzylphenoxyacetylclavulanate with equivalent amounts of benzylacetylclavulanate, berizyl-a-phenyloxycarbonylphenylacetylclavulanate, p-bromobeirzylphenoxyacetylclavulanate and the like. The previous example is also varied by replacing the benzylphenoxyacetylclavulanate with a equivalent amount of benzyl-α-benzyloxycarbonylphenylacetamido-clavulanate and increasing the amount of sodium bicarbonate to 2 equivalents. Example 4 p-bromben zyIdeoxyclavulanate

A solution of 50 mg of p-bromobenzyl bromide was added to a solution.

of 10 mg of sodium deoxyclavulanate in 0.5 ml of dimethylformamide, and the mixture was kept at ambient temperature (about 18°C) for 2 hours;

The reaction mixture was fractionated on silica gel eluting with ethyl acetate/hexane (1:4) to give p-bromobenzyldeoxyclavulanate (as an oil) by evaporation. i.r. (CHCl3): 1790, 1740, 1695 cm"<1>N.m.r. (CDCI3): 1.62 (3H, dd, J 7Hz, J' 1.4Hz, CH3)} 2.95 (1H, dd,

J 17Hz, J':1.0Hz, 60-CH)} 3.48 (1H, dd, ,J 17Hz, J<«>2.6Hz> 6a-CH)}

.4.58 (1H, dq, J 7Hz, J» 1Hz, =CHCH 3 ); 5.03 (1H, dd, J 1.4Hz,

J' 1.0Hz, 3-CH)} 5.12 (2H, s, CO 2 CH 2 -); 5.65 (1H,,dd, J 2.6Hz,

J'. 1.0Hz, 5-CH) ; 3.38 (4H, ABq, J 8.5Hz, aromatic protons).

The previous example can be repeated by replacing atp-bromobenzyl bromide with an equivalent amount of methyl iodide, ethyl bromide, l-bromo-2~methoxyethane, pivaloyloxymethyl chloride, phthalidyl bromide,

1-chloro-2-thiomethylethane, 1-chloro-2-phenylsulfonyethane, 1-bromononane, 4-methoxybenzyl bromide, benzyl bromide, benzyl chloride, phenacetyl bromide etc. Example 5 Sodium deoxyisoclavulanate

50 mg of benzyl isoclavulanate in 0.5 ml of tetrahydrofuran was hydrogenated at room temperature (about 18°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 off-white solid (20 mg).

[The n.m.r. spectrum in DjO showed that the title compound was contaminated with sodium deoxyclavulanate].

Example 6

Pharmacology

Sodium deoxyclavulanate was found to produce no obvious toxic effects in mice when administered intraperitoneally at 500 mg/kg.

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

Claims (1)

Process for the preparation of compounds of formula (III): and salts and esters thereof, characterized by hydrogenation of a compound of formula (IV): or an O-substituted derivative or a salt or ester thereof.: 2. Process for the preparation of a compound of formula (V) or a salt or an ester thereof, caracterized by hydrogenation of clavulanic acid or a salt or an ester thereof. 3. Process as stated in claim 2, adapted for the preparation of one salt of the compound of formula (V). 4. Process for the production of a compound of formula (III) as stated in claim 1 or a salt thereof, characterized by hydrogenation of a hydrogenolysable ester of the compound of formula (III). Process for the preparation of an ester of a compound of formula (III) as stated in claims characterized by esterification of the compound of formula. (III) or a salt thereof.