GB2028305A - Cephem derivatives and processes for their manufacture - Google Patents

Abstract

Cephem derivatives, having good antimicrobial activity, have the general formula <IMAGE> in which R1 denotes a hydrogen, an optionally substituted alkyl, acyl, arylsulphonyl or alkylsulphonyl group, or an amino- protective group; R2 denotes a hydrogen atom or an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, aralkyl, acyl, aryl, arylsulphonyl, alkylsulphonyl or heterocyclic group; R3 denotes a hydrogen atom, an ester-forming group or a cation; R4 denotes a hydrogen atom, an alkoxy group or a group which can be converted to this; X denotes a sulphur or oxygen atom or the group -CH2- or -NH-; and A denotes a hydrogen atom, an optionally substituted alkoxy or alkenyloxy group, a halogen atom or a group -CH2Y, in which Y represents a hydrogen or halogen atom or the radical of a nucleophilic compound; and in which the R2O group is in the syn-position. The compound in which R1, R3, R4 and A are hydrogen, X is sulphur and R2 is methyl or ethyl and the corresponding compound in which R3 is sodium, are particularly effective against Pseudomonas. The invention also relates to a method for producing the compound of formula I and to their use in pharmaceutical preparations.

Description

SPECIFICATION Cephem derivatives and processes for their manufacture This invention relates to cephem derivatives.

The invention provides a cephem derivative of the general formula

in which R1 denotes a hydrogen atom, an optionally substituted alkyl, acyl, arylsulphonyl or alkylsulphonyl group, or an amino-protective group; R2 denotes a hydrogen atom or an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, aralkyl, acyl, aryl, arylsulphonyl, alkylsulphonyl or heterocyclic group; R3 denotes a hydrogen atom, an ester-forming group or a cation; R4 denotes a hydrogen atom, a lower alkoxy group or a group which can be converted to this; X denotes a sulphur or oxygen atom or the group -CH2- or -NH-; and A denotes a hydrogen atom, an optionally substituted alkoxy or alkenyloxy group, a halogen atom or a group -CH2Y, in which Y represents a hydrogen or halogen atom or the radical of a nucleophilic compound; and in which the R20 group is in the syn-position.

The invention also provides a process for the manufacture of a cephem derivative of the general formula I, which comprises a) reacting a lactam of the general formula II

wherein A, X, R3 and R4 have the meanings indicated above with the proviso that R3 cannot represent a hydrogen atom, with a reactive derivative of a carboxylic acid of the general formula Ill

in which the radicals R1 and R2 have the meanings indicated above, with the proviso that R1 cannot represent a hydrogen atom, or b) reacting a cephem compound of the general formula IV

in which the radicals R1, R2, Fl3, R4 and X have the meanings indicated above, with the proviso that R3 cannot represent an ester group, and B represents a group which can be replaced by a nucleophile, with a compound containing the nucleophilic radical Yin the presence of a base to give a compound of the general formula I in which A represents -CH2Y, and, if desired, in the compound of formula I resulting from a) orb) carrying out any one or more of the following procedures in any appropriate order:: a) converting a resulting salt into the free carboxylic acid and optionally esterifying this, or converting a resulting salt directly into an ester, ss) saponifying a resulting ester and optionally converting the resulting product into a salt, y) splitting off a radical R1 and/or R2, if this denotes a protective group, o) if R represents a hydrogen atom, introducing a radical R1 which denotes optionally substituted acyl, alkylsulphonyl or arylsulphonyl groups by reaction with the corresponding activated carboxylic or sulphonic acid derivative, or introducing an optionally substituted alkyl group R1 by reaction with an alkylating agent, and e) if R4 represents a group which can be converted into a lower alkoxy group, carrying out this conversion.

Above and throughout the specification, the term "optionally substituted" means "substituted or unsubstituted", and polysubstituted includes disubstituted. Unless indicated otherwise, if two or more substituents are present on a radical they may be the same or different.

In the compounds of the general formula I, R, R4 and A preferably represent hydrogen atoms and X preferably represents a sulphur atom. R2 preferably represents an alkyl group having 1 to 4 carbon atoms, especially a methyl or ethyl group, and R3 preferably represents a hydrogen atom or a cation.

If R3 denotes a cation, it may represent an inorganic metal ion or an organic ammonium ion. Examples which may be mentioned are, in particular, physiologically tolerable ions e.g. alkali metal ions or alkaline earth metal ions, preferably the sodium, potassium, calcium or magnesium ion, the ammonium ion and, from the organic ammonium ions, in particular, an optionally substituted, alkylated ammonium ion, such as, for example, the triethylammonium or diethanolammonium ion, as well as the morpholineammonium, benzylammonium, procaineammonium, L-arginineammonium and L-lysine-ammonium ion. Alkali metal ions are preferred, with sodium ions being advantageous.

Compounds of the general formula I which are especially preferred are the compound in which R1, R3, R4 and A each represents a hydrogen atom, X represents a sulphur atom, and R2 represents a methyl or ethyl group, and the compound in which R1, R4 and A each represent a hydrogen atom, X represents a sulphur atom, R2 represents a methyl or ethyl group and R3 represents a sodium ion.

These compounds have a particularly good effect against Pseudomonas.

The cephem compounds of the general formula il which are to be employed according to the invention are known from the literature or can be manufactured according to information in the literature, for example according to the information in E.F. Flynn, Cephalosporins and Penicillins, Chemistry and Biology, Academic Press, New York and London, 1972, or, if X represents oxygen or CH2 in the formula II, according to J. Amer.

Chem. Soc. 96, S. 7582 and 7584(1974). Compounds in which A denotes -CH2S- heterocyclic ring, and R3 denotes ester groups are the subject of German Offenlegungsschrift 2,359,402.

In order to obtain the compounds of the formula I with the R20 group in the syn-position, which in the present text is represented throughout as

to differentiate from the anti-position

it is appropriate to ensure that the starting material of the general formula III is already present as the syn-compound. If the mild reaction conditions customary for reactions with syn-compounds are then adhered to, syn-end products are as a rule obtained. Nevertheless it can sometimes happen that small amounts of the corresponding anticompound are also obtained as an impurity in the end product, and, if desired, this impurity can be separated off by methods which are known in the laboratory, such as, for example, recrystallization.

The carboxylic acids of the general formula Ill used for the acylation can be manufactured by various processes.

Thus, for example, a compound of the formula Ill in which R1 denotes hydrogen and R2 denotes alkyl maybe obtained by reaction of thiourea with

and subsequent saponification of the ester group, whereby the reaction should appropriately be effected with a stoichiometric amount of thiourea at room temperature in a water-containing solvent, such as, for example, acetone, and the reaction should not be carried out for longer than a few hours, for example a maximum of about 2 - 3 hours.

It is also possible to react the a-carbonyl group of a 2-aminothiazole-4-glyoxylic acid alkyl or aralkyl ester, substituted on the amino group by R1, with a hydroxylamine compound of the general formula H2N-OR2 and then to saponify the resulting ester in a manner which is in itself known.

The manufacture of the aminothiazole-glyoxylic acid esters used for this reaction is described in German Patent Application P 2,710,902. Most of the hydroxylamine derivatives required for the reaction are known, or they can be easily manufactured according to the information in the literature.

The reaction of the two components is carried out under the conditions, described in the literature, for the reaction of glyoxylic acid derivatives with carbonyl reagents.

A compound of the formula Ill in which R1 represents an acyl group can be obtained easily and in high yields by acylating a compound described above of the general formula

in which Z' represents lower alkyl or aralkyl, with a reactive carboxylic acid derivative.

It has proved favourable to use an acid halide, in particular an acid chloride or an acid bromide. However, it is particularly advantageous to employ a symmetric or unsymmetric anhydride. The acylation is generally carried out in the presence of a base, such as, for example, triethylamine, preferably at room temperature or, in particular, at a temperature which is lowered still further, in an organic solvent which does not interfere with the reaction, in particular in a halogenated hydrocarbon, such as, for example, methylene chloride, chloroform or tetrachloroethylene. The resulting ester is then converted into the free carboxylic acid.

If in the formula Ill R1 in the meaning of acyl represents an aliphatic acyl radical which is also substituted by a nucleophilic radical defined under Y, such as, for example, a nitrogen- or oxygen- nucleophile, but in particular by the S-nucleophilic group R5-S-, Rg having the meaning indicated above, the acylation described above is appropriately carried out with an activated a-halogenoalkyl acid derivative, such as, for example, chloroacetyl chloride, a-bromopropionyl chloride or bromoacetyl bromide, which can also further carry an aryl, preferably phenyl, in the a-position, and the halogen is then reacted with a mercaptan of the formula HS-RS and thus replaced by -SR5.

The replacement reaction is generally carried out in organic or inorganic solvent, preferably in water, in the presence of an organic or inorganic base, such as, for example, triethylamine or sodium bicarbonate, for example at temperatures between about 10 and 80"C, but in particular at room temperature.

If in the formula Ill the radial R1 represents an arylsulphonyl or alkylsulphonyl group, such a compound of the formula Ill may be obtained by reacting an activated alkylsulphonic acid derivative or arylsulphonic acid derivative with a compound of the formula

and then saponifying the product.

The activated sulphonic acid derivatives are, in particular, the sulphonic acid halides known from the literature, such as, for example, sulphonic acid chlorides, as well as the symmetric anhydrides.

The reaction is generally carried out in the presence of a base in an organic solvent which does not interfere with the reaction. Suitable bases are, above all, organic bases, such as, for example, N,N-dimethylaniline or triethylamine. Examples of possible organic solvents which do not interfere with the reaction are halogenated hydrocarbons, such as, for example, methylene chloride or ch!oroform, or tertiary am ides, such as, for example, dimethylformamide or dimethylacetamide. The reaction is appropriately carried out at room temperature.

If in the general formula Ill the radical R1 represents a group which can be easily removed again, its introduction into the amino group can be effected in the manner known from peptide chemistry for amino-protective groups (compare the book mentioned below by Schrnder and Luke, The Peptides, volume 1 (1965), page 3). If such a group is, for example, triphenylmethyl, its introduction can be effected with triphenylchloromethane, the reaction appropriately being carried out in an organic solvent, such as, for example, a halogenated hydrocarbon, in the presence of a base.

Chloroform and methylene chloride have proved particularly suitable halogenated hydrocarbons here.

Bases which can be mentioned are, in particular, tertiary amines, such as, for example, triethylamine or N-methylmorpholine.

The mercaptoheterocyclic compounds FLUSH used as a starting material are known from the literature or can be manufactured according to information in the literature.

It is appropriate, not only in the manufacture of starting material which contains a group

position, but also in all further reactions, to use reaction conditions which are as mild and gentle as possible, such as are known to the expert, from the literature, for reactions with syn-compounds, such as, for example, no elevated temperatures, no prolonged reaction times, no substantial excesses of an acid reactant and the like, in order to avoid any possible flipping over of the oxime grop into the anti-form.

The reactive derivatives of the carboxylic acids of the general formula Ill

which are employed, according to the invention, for the acylation reaction a) and which are capable of amide formation can be obtained from the carboxylic acids by processes which are known from the literature.

Examples of reactive derivatives which may be mentioned are the activated esters, such as, for example, p-nitrophenyl esters or trichlorophenyl esters, azides or anhydrides. A preferred process for activating the carboxyl group consists in converting it into a symmetric anhydride. The processes for the manufacture of symmetric anhydrides are known from the literature and correspond to the methods generally used in peptide chemistry. For example, the inner anhydrides, which are subsequently reacted with the aminocephemcarboxylic acids of the formula II in organic solvents, are obtained from the carboxylic acids of the general formula Ill using condensing agents, such as, for example, N,N-disubstituted carbodiimides, such as, for example, dicyclohexylcarbodiimide.

The manufacture of a compound of the general formula I by acylating a compound of the formula II with a carboxylic acid of the formula Ill can be carried out under variable experimental conditions, for example using various solvents. Examples of suitable solvents are organic solvents, such as, for example, halogenated hydrocarbons, for example methylene chloride or chloroform, but also water or mixtures of water and organic solvents, which are mixed intensively with water. In order to carry out the reaction well, it is appropriate to dissolve the aminoiactam derivatives of the formula II.

If an aminocephem ester of the general formula II in which R3 thus represents one of the ester groups defined above are used, the reaction is preferably carried out in an organic solvent in which the ester is readily soluble. Examples of such solvents which may be mentioned are halogenated hydrocarbons, such as, for example, methylene chloride or chloroform, but also tertiary amides, such as, for example, dimethylformamide or dimethylacetamide.

The ester groups listed above under R3 include on the one hand those such as, for example, are known from peptide chemistry as carboxyl-protective groups which can be easily split off (compare, for example, E.

Schröder and K. Lijbke, The Peptides, volume 1, Academic Press, New York and London, 1965, page 52).

However, they preferably include ester groups, the use of which can be therapeutically advantages in the administration of the end products. In this case also the restrictions can be somewhat flexible, since, for example, a benzhydryl ester is therapeutically usuable and at the same time can also serve as a protective group.

If an aminocephemcarboxylic acid of the general formula II (R3 = hydrogen) is used, the compounds must generally be dissolved, with the addition of a base.

Suitable bases which can be used for dissolving the 7-amino-cephemcarboxylic acids, as well as a number of 7-amino-A3-cephem-4-carboxylic acids, are inorganic or organic bases. Thus, tertiary amines, such as triethylamine, N,N-dimethylaniline or N-methylmorpholine, have proved particularly suitable for the preparation of solutions in organic solvents, and alkali metal bicarbonates, such as sodium bicarbonate or potassium bicarbonate, and tertiary amines have proved particularly suitable for the preparation of aqueous solutions. In general, the base is added in at least stoichiometric amount, relative to the desired reaction. An excess of base of, for example, about 0.1 to 2, in particular about 0.2 to 0.8, moles can be advantageous.

In the case of compounds of the formula li which are sensitive towards bases, depending on the course of the reaction the pH can be kept constant at about 4 to 8, preferably 6 to 7, by continuously adding the base.

The aminolactam derivatives of the formula II can be dissolved in a wide temperature range. However, appropriately it should not exceed a temperature of about 40"C. In the case of derivatives which are sensitive towards bases, it is advisable, however, to choose a temperature range from about 0 to 1 5 C.

The activated derivative of the carboxylic acid of the general formula Ill is generally added to the aminocephem derivative of the formula II, which is present in solution or appropriately in suspension. The reaction is carried out in a manner which is in itself known. If water or mixtures of water and organic solvent(s) are used as the reaction medium, it is advisable to maintain the temperature in a range from about -5 to +10"C. If an organic solvent is used, it is also possible to carry out the acylation at temperatures up to about 65"C, preferably at room temperature.

In order to carry out the reaction better, the activated carboxylic acid derivative of the formula III is preferably taken up in a solvent which does not interfere with the reaction and is introduced in dilute form. If the acylation is carried out in an aqueous medium, it is possible to use, for example, an anhydrous ketone, such as acetone or methyl ethyl ketone, or, with intensive stirring, an ether, such as, for example, diethyl ether or diisoproyl ether, as the solvent for the activated carboxylic acid derivative.

If the acylation is carried out in a non-aqueous medium, it is advisable to use the same solvent for diluting the acid derivative as is used for the acylation.

In order to achieve higher yields, the activated acid derivative of the formula Ill is preferably employed in an at least stoichiometric amount. An excess of about 5-25 % can prove appropriate.

Compounds of the formula I in which A denotes CH2Y can also be obtained by reacting a compound of the formula IV in which A denotes -CH2B, B having the meaning indicated initially, with a compound which contains the nucleophilic radical Y. B can represent, in particular, acyloxy with 1 to 4 carbon atoms, preferably acetoxy, halogen, preferably chlorine or bromine, an azido group, a carbamoyloxy group or a 2-mercapto-pyridine-N-oxide radical. The use of the said pyridine compound as a group which can be exchanged is described in Tetrahedron Letters, Volume 23, (1972), page 2345.

Compounds containing the nuclephilic radical Y which may be mentioned are, in particular, compounds of the formula HS-Rs, hydrazoic acid and optionally substituted pyridine, quinoline or isoquinoline compounds.

The reaction proceeds particularly smoothly if R3 in the general formula I represents hydrogen or a cation.

The synthesis is preferably carried out by reacting one mole of a compound of the general formula IV with one mole of a compound containing the nucleophilic radical Y, in particular of the compounds mentioned above as preferred, in a solvent which does not interfere with the reaction.

An excess of the nucleophile, in particular of the thiol, pyridine, quinoline or isoquinoline component, has an advantageous effect on the yield. Should small amounts of the corresponding anti-compound be obtained here, they can be removed in the customary manner, for example by recrystallization.

Examples of solvents which do not interfere with the reaction are water, acetone, chloroform, nitrobenzene, methylene chloride, ethylene chloride, dimethylformamide, methanol, ethanol, ether, tetrahydrofuran, dimethylsulfoxide or any other solvents which do not have an adverse effect on the reaction. Strongly polar solvents are favorable, preferably water. Of the solvents, the hydrophilic solvents, preferably acetone, methanol, ethanol, dimethylformamide and dimethylsulfoxide, can also be used in mixtures with water.

The reaction is generally carried out in a pH range from 5 to 8, preferably at the neutral pH value.

If the compound IV (R3 = hydrogen) or the nucleophilic compound, in particular HS-R5, is used in the free form, the reaction is preferably carried out in the presence of a base, for example an inorganic base, such as an alkali metal hydroxide, alkali metal carbonate or alkali bicarbonate, such as, for example, sodium bicarbonate or potassium bicarbonate, an organic base, such as a trialkylamine, or a tertiary ammonium base. The compounds of the formula IV and the HS-R5 can also be employed directly in the form of their salts, preferably the sodium or potassium salts.

The reaction temperature can be varied within a wide range. As a rule, the reaction is carried out at room temperature or the mixture is warmed up to the reflux temperature of the solvents or solvent mixtures used, but appropriately not above about 80"C.

The isolation of the compound of the formula I from the reaction medium can be effected by methods which are in themselves known and which depend on the solubility of the resulting compounds.

Thus, for example, the reaction product can be taken up in water, if appropriate after evaporating offthe organic solvent, and after appropriate purification operations, such as, for example, filtration or centrifugation, can be precitated in the form of the free carboxylic acid (rig = hydrogen) by adding a mineral acid, appropriately in an approximately stoichiometric amount, to the clarified reaction mixture. Suitable mineral acids are, in particular, dilute acids, such as dilute hydrochloric acid or sulfuric acid. It is also possible to use very low-molecular organic acids, such as, for example, formic acid or trifluoroacetic acid, or also arylsulfonic acids, such as, for example, toluenesulfonic acids or naphthalenesulfonic acids.

Lyophilization of the solution can occasionally also be appropriate.

The amidocephem acids of the formula I usually precipitate as amorphous solids, or in the crystalline form. They can be separated out, if appropriate, as the free acids by extraction at pH 2 to 1. Various water-immiscible organic solvents can be used as extraction agents, for example halogenated hydrocarbons, such as, for example, methylene chloride, or esters, such as, for example, ethyl acetate or n-butyl acetate, but also ketones, such as methyl isobutyl ketone.

The amidocephem acids of the formula I formed may be isolated from the extracts, for example, by evaporation of the solvent and trituration, for example with ether. If symmetric anhydrides of the carboxylic acids of the formula Ill have been used as the starting component, the carboxylic acid constituent liberated during the acylation must also be separated off by customary experimental methods, which depend, for example, on its solubility, crystallinity or ease of extraction.

If desired, protective group(s) which have been introduced for intermediate protection of the amino group of the aminothiazole radical can be removed by processes which are known from the literature, such as are described, for example, for peptide chemistry. For example, if R1 represents a triphenylmethyl group, the splitting off is effected in an acid medium. Mixtures of formic acid and water, in particular mixtures of water and formic acid in the ratio 1:1 to 4:1, have proved suitable.

The compounds of the formula I containing a free amino and carboxyl group can be isolated by known experimental methods, for example in the case where a triphenylmethyl group is split off as triphenylcarbi nol and then concentrating the solution.

Esters obtained in the reaction according to the invention, the ester group of which has a protective group for the carboxyl group, such as, for example, p-methoxybenzyl, p-nitrobenzyl or tert.-butyl esters, can, if desired, also be converted into the corresponding free carboxylic acids of the formula I in a manner which is known from the literature. However, as already mentioned, it is also possible to retain for therapeutic use ester groups which also serve as carboxyl-protective groups, such as, for example, benzhydryl esters.

A compound of formula I having a free a-oxime group (R2 = hydrogen) can be prepared by the process of the invention, for example by exchange of B in the definition of acetoxy in a compound of formula IV in which R2 denotes hydrogen or by splitting off a group R2 having the character of a protective group from a compound of formula I in known manner by acid hydrolysis or hydrogenolysis, groups of this type being, for example tert. butyloxycarbonyl, dibenzyl, carbobenzyloxy, formyl, trichloroethoxycarbonyl, 2tetrahydropyranyl, preferablytriphenylmethyl.

For acid hydrolysis they may be used, for example, formic acid, trifluoroacetic acid or acetic acid which can be used either in anhydrous form or in aqueous solutions. Zinc/acetic acid may also be used.

Preferred agents for acid hydrolysis are anhydrous trifluoroacetic acid, aqueous formic acid or acetic acid if tert. butoxycarbonyl or triphenyl methyl shall be split off. Dibenzyl or carbonbenzyl, for example, are preferably split off by catalytic hydrogenation agents.

If R2 denotes chloroacetyl, this may be split off also with thiourea, preferably in a neutral or acid medium (cf. JACS 90 (1968), page 4508).

Simultaneously with R2, a radical R1 denoting a protective group can be split off by acid hydrolysis, hydrogenolysis or with thiourea. It is the same with the radical R3 provided it can be eliminated by hydrolysis or hydrogenolysis. In the case of compounds containing radicals, Fl1, R2 and R3 having the function of protective groups which can be split off in different manner only, for example by hydrolysis and hydrogenolysis or with different hydrolysis agents, these methods should be applied successively.

The resulting acids of the formula I can be converted into their physiologically tolerable salts, in particular into alkali metal salts, such as, for example, the sodium salts, or into salts with organic bases, preferably tertiary amines, such as, for example, the procaine salt.

The conversion into salts can be effected in a manner which is in itself known by reacting a carboxylic acid of the general formula I with the desired base, for example with sodium bicarbonate, or the sodium salts of organic carboxylic acids, such as, for example, sodium acetate, sodium propionate, sodium hexanoate or sodium 2-ethyl-hexanoate, or potassium acetate.

It is also possible to isolate salts directly from the reaction solution, for example by precipitation with suitable organic solvents or by lyophilization.

Compounds of the formula I in which R3 represents an ester group, in particular a physiologically acceptable ester, can be obtained directly by using the appropriately esterified starting material of the formula II, or they can be obtained by subsequent esterification of compounds of the formula I in which the carboxyl group is present in the free form or as a salt, by processes which are known from the literature.

Because it is easier to carry out, subsequent esterification can be advantageous for the manufacture of physiologically tolerable esters and a variation of the ester group.

For example, esters are obtained by subsequent reaction when the salts, preferably the triethylammonium salts orthe alkali metal salts, preferably the sodium salts, are reacted with reactive halogenoalkyl compounds, such as, for example, chloroalkyl, bromoalkyl or iodoalkyl compounds, ortrialkylammoniumal- kyl compounds, in particularthe corresponding chloromethyl, bromomethyl, iodoethyl or triethylammoniummethyl compounds.Examples of reactive halogenoalkyl compounds which can be used are halogenomethoxycarbonyl compounds, such as chloromethyl acetate, chloromethyl propionate or chloromethyl pivalate, or the o)-halogenomethyl ketones, such as, for example, o-bromoacetophenone, chloroacetone or o)-bromoacetophenone substituted in the aryl nucleus, such as, for example, in the phenyl nucleus, such as, for example, 5-sulfamyl-4-chloro-o-bromoacetophenone, but also halogenoalkylcarboxylic acid derivatives, in particular the halogenomethyl-carboxylic acid derivatives, such as chloroacetic acid, bromoacetic acid and bromoacetic acid esters, such as, for example, the low-molecular alkyl esters and optionally the benzyl esters, such as the p-methoxybenzyl ester. Halogenomethyl ketones in which the 2-alkyl group is monosubstituted or polysubstituted by alkoxycarbonyl, oximino, oxido or alkoximino radicals, such as, for example, 1 -chloro-(3-methoximino-3-carbethoxy)-acetone or 1 -bromo-3-methoximino- 3-carbethoxyacetone, but also bromo-3-oxido-3-carbethoxyacetone, have proved suitable reactive halogenomethyl derivatives.

Further reactive halogenoalkyl derivatives which may be mentioned are the alkyl iodides, such as, for example methyl iodide, ethyl iodide or isopropyl iodide, and the corresponding bromides.

The reaction with a diazoalkane, such as, for example, diazomethane or diazoethane, or with a diarylmethyldiazomethane, such as, for example, diphenyldiazomethane, may furthermore be mentioned for the manufacture of optionally substituted esters.

A further esterification method consists in reacting the alkali metal salts, preferably in alcohol, such as, for example, methanol, with alkyl sulfochlorides, such as, for example, methyl sulfochloride.

The reaction of the salts of the cephem compounds of the formula I with alkyl halides is appropriately carried out in a solvent which does not interfere with the reaction, such as, for example, dimethylformamide or dimethylacetamide, or also dimethylsulfoxide. The reaction can be carried out within a wide temperature range, for example at 0 to 80"C, but preferably at 30 - 50"C, depending on the activity of the halogenoalkane.

In order to achieve good yields, the halogenoalkane is employed in an at least equimolar amount. An excess of up to 5 equivalents has sometimes proved favorable.

On parental and oral administration, the physiologically acceptable esters obtained according to the invention exhibit surprising anti-bacterial activities in vivo and in vitro.

Compounds of the formula I in which R1 represents acyl can be obtained by subsequent acylation of the free amino group of the corresponding cephem compound. The subsequent acylation is carried out with an activated carboxylic acid derivative in an organic solvent which does not hinder the reaction, such as, for example, halogenated hydrocarbons, such as, for example, methylene chloride or chloroform, in a temperature range which is limited by the solvents. Acid halides, such as, for example, acid chlorides or acid bromides, and symmetric or unsymmetric anhydrides have proved particularly suitable activated carboxylic acid derivatives. If acid halides are used, it is appropriate to add abase in order to achieve high yields.

The temperature range can be between about -50" and the boiling point of the solvent, preferably between -30 and +40"C. The temperature range from 0 to 25"C has proved particularly advantageous.

If cephem acids of the formula I in which R3 represents hydrogen or an alkali metal cation are used, it is advisable to employ the anhydride in a relatively large excess, for example an excess of about 11 5 moles, or even to employ it as the solvent. An alternative preparation method which has proved very suitable is toconvert the acids or salts of the formula I into their silyl esters, then to acylate the esters and subsequently to split off the silyl group.

If acid halides are used, it is advisable to remove the moisture present by distilling it out azeotropicajly immediately before the reaction.

Examples which may be mentioned of carboxylic acids which are particularly suitable for the acylation are optionally substituted arylcarboxylic acids, such as, for example, benzoic acid,p-chlorobenzoic acid, p-sulfamoylbenzoic acid, m-sulfamoylbenzoic acid and 4-chloro-5-sulfamoylbenzoic acid, optionally substituted arylacetic acids, such as, for example, phenylacetic acid, p-nitrophenylacetic acid, 3-methoxyphenylacetic acid, 2,4-dichlorophenylacetic acid and p-amidino-phenylacetic acid, optionally substituted aryloxyacetic acids, such as, for example, phenoxyacetic acid, p-hydroxyphenoxy-acetic acid, pmethoxyphenoxyacetic acid, p-oxdiazolyl-phenoxyacetic acid or 3,5-dinitrophenoxyacetic acid, optionally substituted thiophenoxyacetic acids, such as, for example, thiophen-3-oxyacetic acid, as well as the corresponding S analogs, such as for example, phenylthioacetic acids, optionally substituted alkylcarboxylic acids with 1 to 4 C atoms, such as, for example, acetic acid, propionic acid or butyric acid, chloroacetic acid, bromoacetic acid, a-bromopropionic acid, alkoxyacetic acids with 1 to 5 C atoms in the alkoxy part, such as, - for example, methoxyacetic acid or butoxyacetic acid, and the analogous mercapto and amino compounds, such as, for example, alkylthioacetic acids or alkyl- or dialkyl-aminoacetic acids.

If a-halogenocarboxylic acids of the general formula

in which Hal represents a chlorine, bromine or iodine atom and R22 denotes hydrogen, alkyl with 1 to 5 C atoms or aryl, in particular phenyl, are used, the halogen can subsequently be replaced, by reaction with a nucleophilic radical defined under Y, such as, for example, a nitrogen nucleophile or oxygen nucleophile, by the nucleophilic radical, but in particular, by reaction with mercapto compounds of the formula HS-R5, by the S-nucleophilic radical -SRS, wherein R5 has the meanings indicated initially.

The replacement of halogen in the aliphatic acyl radical R1 by the nucleophile can be carried out in organic or inorganic solvents, depending on the radical R3. If R3 represents hydrogen or a cation, the replacement reaction is advantageously carried out in an aqueous solution in the presence of organic or inorganic bases, such as, for example, triethylamine or alkali metal carbonates or bicarbonates, such as, for example, sodium bicarbonate. lf R3 represents an ester group, the reaction can also be carried out successfully in organic solvents, such as halogenated hydrocarbons, such as, for example, methylene chloride or chloroform, or in amides, such as, for example, dimethylformamide or dimethylacetamide, or sulfoxides, such as, for example, dimethylsulfoxide, in the presence of organic bases, such as, for example, trialkylamines, in particular triethylamine or N,N-dimethylaniline.

The reaction can be carried out within a wide temperature range; the range from about 10 - 400C, in particular from 15 - 30"C, has proved advantageous.

Depending on the desired end product, the process steps a) to ) which are possible according to the invention can be combined with one another, it frequently being possible to rearrange the sequence. Thus, for example, it is possible to first carry out a nucleophilic replacement reaction in the 3-position of the cephem ring, then an esterification of the carboxyl group, followed by a subsequent acylation of the aminothiazole group, or the acylation of the amino group in the thiazole ring is first carried out, and then the esterification. These rearrangements possibilities of the reaction steps, which are self-evident to any expert, also belong to the subject of the invention.

If R4 is present in the form of one of the groups described above which can be converted into lower alkoxy, preferably methoxy, this conversion can be carried out in a manner which is known from the literature (compare, for example, German Offenlegungsscrift 2 440 790).

The compounds of the general formula I according to the invention are valuable chemotherapeutic agents which possess a surprisingly powerful antimicrobial action against Gram-positive and Gram-negative bacteria, have an unexpedtedly good action against penicillinase-forming Staphylococci and in some cases also have a fungistatic activity.

The compounds of the general formula I are distinguished, for example, by a considerably antimicrobial activity against a number of bacteria against which the known cephalosporins are scarcely active. The compounds of formula I that are particularly preferred i.e. that in which R1, Fl3, and R4 and A each represents a hydrogen atom, X represents a sulphur atom and R2 represents a methyl or ethyl group, and that in which R1, R4 and A each represents a hydrogen atom, X represents a sulphur atom, R2 represents a methyl or ethyl group and R3 represents a sodium ion, are very effective against Pseudomonas.

Since the compounds of the formula I furthermore exhibit favourable toxicological and pharmacokinetic properties, they are valuable antimicrobial active compounds for the treatment of infectious diseases.

The invention therefor also provides a pharmaceutical preparation which comprises a compound of the general formula I in which R3 represents a hydrogen atom, or a physiologically tolerable ester or salt thereof, our a mixture of two or more such compounds, salts and esters as active substance, in admixture or conjunction with a pharmaceutically suitable carrier. There is especially used one of the preferred compounds names above or a mixture thereof.

The pharmaceutical preparations of the invention may also comprise one or more further active substances, for example selected from penicillins, aminoglycosides, cephalosporins and compounds which influence the symptoms of bacterial infections, for example, antipyratic agents, analgesic agents and antiphlogistic agents.

The pharmaceutical preparation may be in a form suitable for oral, intramuscular or intravenous administration.

The pharmaceutical preparations may be prepared by mixing the active substance with one or more pharmaceutically suitable carriers, for example, fillers, emulsifiers, lubricants, flavour-correcting agents, dyestuffs and buffer substances, and converting the mixture into a suitable galenic formulation form, for example, tablets, drag es, capsules, or a solution or suspension suitable for parenteral administration.

Examples of carriers are tragacanth, lactose, talc, agar-agar, polyglycols, ethanol and water. Suspensions or solutions in water are preferably used for parenteral administration.

Individual (unit) doses or, in general, multiple doses may be administered, pharmaceutical preparations in unit dosage form generally comprising the active compound in an amount of from 50 to 1,000 mg, preferably 100 to 500 mg.

Suitable doses of the compounds of the general formula I are about 0.4 to 20 g/day, preferably 0.5 to 4 g/day, for an adult having a body weight of about 60 kg. The invention accordingly provides a method of treating or combating a bacterial infection in a commercially reared animal, which comprises administering to the animal an active substance comprising a compound of the general formula I as claimed in claim 1 in which R3 represents a hydrogen atom, or a physiologically tolerable salt or ester thereof, or a mixture of two or more such compounds, salts and esters. The compound of formula I is especially one of the preferred compounds named above. The active substance is preferably in the form of a pharmaceutical preparation of the invention.

The following Examples illustrate the invention.

EXAMPLE 1 7-Beta-(2-aminothiazol 4 yl)-2-syn-methoximino-acetamido)-ceph-3-em-4-carboxylic acid 3.4 g of 2-syn-methoximino-2-(2-tritylamino-thiazol-4-yl)-acetic acid in 14 ml chloroform are added dropwise to a solution, cooled to 5 degrees C, of 0.97 g of dicyclohexycarbodiimide in 8 ml of chloroform, whilst stirring. After stirring at room temperature for two hours, the dicyclohexylurea, which has precipitated is separated off. A mixture of 0.8 g 7-amino-ceph-3-em-4-carboxylic acid (Helv. Chim. Acta 75, 2044 (1974) and 1.4 ml of triethylamine in 20 ml of methylene chloride is added dropwise to the filtrate, which has been cooled to -10 degrees C, whilst stirring. After stirring the mixture at room temperature for three hours, it is carefully acidified with 1 N hydrochloric acid, the mixture is filtered and the filtrate is washed with water until neutral, dried and concentrated. The residue is dissolved in dioxan, the solution is filtered with a little charcoal, ether and 1.2 ml diethylamine are added to the filtrate. On cooling in ice, the diethylamine salt of 2-syn-methoximino-2-(2-tritylaminothiazol-4-yl)-acetic acid precipitated. The diethylamine salt is filtered off, the filtrate is connected and the residue is triturated with ether. After filtering off and drying the solid of the crude diethylamine salt of the coupling product are obtained.The salt is dissociated in methylene chloride by adding the equivalent amount of 1 N hydrochloric acid, the methylene chloride solution is separated off, washed with water until neutral, dried and filtered with charcoal and the filtrate is concentrated.

The residue is dissolved in 4 ml of 80% strength aqueous formic acid and the solution is stirred at room temperature for 2 hours. After adding 5 ml water, the triphenylcarbinol is filtered off, the filtrate is concentrated and the residue is triturated with ether and dried in vacuo over phosphorus pentoxide. 0.58 g of the title compound are obtained.

IR (KBr) 1770 cm~ (ss-lactam band) NMR (D2O plus Na2CO3) 5 = 3.4 ppm (AB, 2-CH2) 5= 3.8 ppm (S, 3 H, = N OCH3) 5=5.1 ppm (d, 1 H, 6-ch-) 5 = 5.7 ppm (d, 1 h, 7-CH-) 5 = 6.5 ppm (q, 1 H, 3-CH-) 6 = 6.7 ppm (s, 1 H, thiazol-proton) EXAMPLE2 7-Beta-(2-syn-ethoximino-2-r2-aminothiazol-4-yl)-acetamido)-ceph-3-em-4carboxylic acid The procedure is as according to Example 1, using 3.7 g 2-syn-ethoximino-2-(-2-tritylamino-thiazol-4-yl)acetic acid. 0.57 g of the title compound are obtained.

IR (KBr) 1770 cm~ (ss-lactam band) NMR (D2O + Na2CO3) 5 = 1.2 ppm (t, 3 H, = N-O-C-CH3) 6 = 3.5 ppm (AB, 2-CH2-) 5 = 4.1 ppm (q, 2 H, = N-O-CH2-C) 5 = 5.1 ppm (d, 1 H, 6-CH-) 5 = 5.7 ppm (d, 1 H, 7-CH-) 5 = 6.5 ppm (q, 1 H, 3-CH-) 5 = 6.7 ppm (s, 1 H,thiazol-proton)

Claims (22)

1. A cephem derivative of the general formula I

in which R1 denotes a hydrogen, an optionally substituted alkyl, acyl, arylsulphonyl or alkylsulphonyl group, or an amino-protective group; R2 denotes a hydrogen atom or an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyi, aralkyl, acyl, aryl, arylsulphonyl, alkylsulphonyl or heterocyclic group; Fls denotes a hydrogen atom, an esterforming group or a cation; R4 denotes a hydrogen atom, an alkoxy group or a group which can be converted to this; Xdenotesasulphur or oxygen atom or the group -CH2- or -NH-; and A denotes a hydrogen atom, an optionally substituted alkoxy or alkenyloxy group, a halogen atom or a group -CH2Y, in which Y represents a hydrogen or halogen atom or the radical of a nucleophilic compound; and in which the R2O group is in the syn-position.

2. A compound as claimed in claim 1, in which R1 represents a hydrogen atom, R2 represents an alkyl group having 1 to 4 carbon atoms, R3 represents a hydrogen atom or a cation, R4 represents a hydrogen atom, X represents a sulphur atom and A represents a hydrogen atom.

3. A compound as claimed in claim 2, wherein an alkyl group R2 is a methyl or ethyl group, and a cation R3 is an alkali metal cation.

4. A compound as claimed in claim 1, wherein R1, R3, R4 and A each represents a hydrogen atom, X represents a sulphur atom, and R2 represents a methyl or ethyl group.

5. A compound as claimed in claim 1, wherein R1, R4 and A each represents a hydrogen atom, X represents a sulphur atom, R2 represents a methyl or ethyl group and R3 represents a sodium ion.

6. A compound as claimed in claim 1, substantially as described in any one of the Examples herein.

7. A compound as claimed in claim 1, in the form of a physiologically tolerable salt.

8. A process for the manufacture of a cephem derivative of the general formula I as claimed in claim 1, which comprises a) reacting a lactam of the general formula II

wherein A, X, R3 and R4 have the meanings given in claim 1 with a carboxylic acid of the general formula Ill or a reactive derivative thereof.

in which the radicals R1 and R2 have the meanings given in claim 1, or b) reacting a cephem compound of the general formula IV

in which the radicals R1, R2, R3, R4 and X have the meanings given in claim 1, and ss represents a group which can be replaced by a nucleophile, with a compound containing the nucleophilic radical Yin the presence of a base to give a compound of the general formula I in which A represents -CH2Y, and, if desired, in the compound of formula I resulting from a) orb), carrying out any one or more of the following procedures, in any suitable order: a) converting a resulting salt into the free carboxylic acid and optionally esterifying this, or converting a resulting salt directly into an ester, ss) saponifying a resulting ester and optionally converting the product into a salt, y) splitting off a radical R1 and/or R2, if this denotes a protective group, a) if R1 represents a hydrogen atom, introducing a radical R1 which denotes an optionally substituted acyl, alkylsulphonyl or arylsulphonyl group, by reaction with the corresponding, activated carboxylic or sulphonic acid derivative, or introducing an optionally substituted alkyl group R1 by reaction with an alkylating agent, and E) if R4 represents a group which can be converted into a lower alkoxy group, carrying out this conversion.

9. A process as claimed in claim 8, wherein in the general formula IV, B represents an acyloxy group having 1 to 4 carbon atoms, a halogen atom, an azido group, a carbamoyloxy group or a 2-mercaptopyridine-N-oxide radical.

10. A process as claimed in claim 8, wherein an acyl radical B is an acetoxy group and a halogen atom B is a chlorine or bromine atom.

11. A process as claimed in any one of claims 8 to 10, wherein the compound containing the nucleophilic radical Y is a compound of the formula HS-R5, R5 being defined as in claim 1, hydrazoic acid, or an optionally substituted pyridine, quinoline or isoquinoline compound.

12. A process as claimed in claim 8, carried out substantially as described in any one of the Examples herein.

13. A compound as claimed in claim 1, whenever produced by a process as claimed in any one of claims 8 to 12.

14. A compound as claimed in claim 4 or claim 5, whenever produced by a process as claimed in any one of claims 8 to 12.

15. A pharmaceutical preparation which comprises, as active substance, a compound as claimed in claim 1 in which R3 represents a hydrogen atom or a physiologically tolerable salt or ester thereof or a mixture of two or more such compounds, salts and esters, in admixture or conjunction with a pharmaceutically suitable carrier.

16. A pharmaceutical preparation as claimed in claim 15, wherein the active substance is a compound as claimed in claim 4, claim 5 or claim 14.

17. A pharmaceutical preparation as claimed in claim 15 or claim 16, which comprises one or more further active substance(s).

18. A pharmaceutical preparation as claimed in claim 17, wherein the further active substance(s) is or are selected from penicillins, aminoglycosides, cephalosporins, antipyretic agents, analgesic agents, and antiphlogistic agents.

19. A pharmaceutical preparation as claimed in claim 18, in a form suitable for oral, intramuscular or intravenous administration.

20. A pharmaceutical preparation as claimed in any one of claims 15 to 19, in unit dosage form.

21. A pharmaceutical preparation as claimed in claim 20, which comprises from 50 to 1000 mg of the active substance per unit dose.

22. A pharmaceutical preparation as claimed in claim 21, which comprises from 100 to 500 mg of the active substance per unit dose.