GB2036724A - Cephalosporin compounds - Google Patents

Abstract

Cephalosporin antibiotics of general formula <IMAGE> (wherein R<a> and R<b>, which may be the same or different, each represent a C1-4 alkyl group or R<a> and R<b> together with the carbon atom to which they are attached from a C3-7 cycloalkylidene group; and R<1> represents a C1-4 alkyl group) exhibit broad spectrum antibiotic activity with unusually high activity against strains of Pseudomonas organisms as well as high activity against various members of the Enterobacteriaceae. The invention also includes the non-toxic salts and non-toxic metabolically labile esters of compounds of formula (I). Also described are compositions containing the antibiotics of the invention and processes for the preparation of the antibiotics.

Description

SPECIFICATION Cephalosporin Compounds This invention is concerned with cephalosporin compounds possessing valuable antibiotic properties.

The cephalosporin compounds in this specification are named with reference to "CEPHAM" afterJ.Amer.

Chem. Soc., 1962, 84, 3400, the term "cephem" referring to the basic cepham structure with one double bond.

Cephalosporin antibiotics are widely used in the treatment of diseases caused by pathogenic bacteria in human beings and animals, and are especially useful in the treatment of diseases caused by bacteria which are resistant to other antibiotics such as penicillin compounds, and in the treatment of penicillin-sensitive patients. In many instances it is desirable to employ a cephalosporin antibiotic which exhibits activity against both gram-positive and gram-negative microorganisms, and a significant amount of research has been directed to the developent of various types of broad spectrum cephalosporin antibiotics.

Thus, for example, in our British Patent Specification No. 1,399,086, we describe a novel class of cephalosporin antibiotics containing a 7Q-(a-etherified oxyimino)-acylamido group, the oxyimino group having the syn configuration. This class of antibiotic compounds is characterised by high antibacterial activity against a range of gram-positive and gram-negative organisms coupled with particularly high stability to p-lactamases produced by various gram-negative organisms.

The discovery of this class of compounds has stimulated further research in the same area in attempts to find compounds which have improved properties, for example against particular classes of organisms especially gram-negative organisms.

In our British Patent Specification No. 1,496,757, we describe cephalosporin antibiotics containing a 7ss-acylamido group oftheformula

(wherein R is a thienyl or fury group; RA and RB may vary widely and may, for example, be C14 alkyl groups or together with the carbon atom to which they are attached form a C37 cycloalkylidene group, and m and n are each 0 or 1 such that the sum of m and n is 0 or 1), the compounds being syn isomers or mixtures of syn and anti isomers containing at least 90% of the syn isomer. The 3-position of the cephalosporin molecule may be unsubstituted or may contain one of a wide variety of possible substituents.These compounds have been found to have particularly good activity against gram-negative organisms.

Other compounds of similar structure have been developed from these compounds in further attempts to find antibiotics having improved broad spectrum antibiotic activity and/or high activity against gramnegative organisms. Such developments have involved variations in not only the 7ss-acylamido group of formula (A) but also the introduction of particular groups in the 3-position of the cephalosporin molecule.

Thus, for example, South African Patent Specification 78/1870 discloses cephalosporin antibiotics wherein the 7ss-acylamido side chain is inter alia a 2-(2-amino-thiazol-4-yl)-2-(optionally substituted alkoxyimino)acetamido group and the 3-position may be substituted, for example, by the group -CH2Y in which Y represents the residue of a nucleophile, the Specification containing numerous examples of such nucleophiles, including nitrogen nucleophiles. The Specification contains, among numerous other examples, references to compounds in which the above-mentioned optionally substituted alkoxyimino group is a carboxyalkoxyimino or carboxycycloalkoxyimino group.South African Patent Specification 78/2168 discloses in broad terms sulphoxide compounds corresponding to the sulphides described in the last-mentioned Specification.

Furthermore, Belgian Patent Specification No. 836,813 discloses cephalosporin compounds wherein the group R in formula (A) above may be replaced by, for example, 2-aminothiazol-4-yl, and the oxyimino group is a hydroxyimino or blocked hydroxyimino group, e.g. a methoxyimino group. In such compounds, the 3-position of the cephalosporin molecule is substituted by a methyl group which may itself be optionally substituted by any of a large number of residues of nucleophilic compounds therein described. In the above-mentioned Specification no antibiotic activity is ascribed to such compounds which are only mentioned as intermediates for the preparation of antibiotics described in that Specification.

We have now discovered that by an appropriate selection of a small number of particular groups at the 7P-position in combination with a 3-alkyl-1 ,2,3-tri-azolium-1 -ylmethyl group at the 3-position, cephalosporin compounds having particularly advantageous activity (described in more detail below) against a wide range of commonly encountered pathogenic organisms may be obtained.

The present invention provides cephalosporin antibiotics of the general formula:

(wherein Ra and Rb, which may be the same or different, each represent a C14 alkyl group (preferably a straight chain alkyl group, i.e. a methyl, ethyl, n-propyl or n-butyl group and particularly a methyl or ethyl group) or Ra and Rb together with the carbon atom to which they are attached form a C3 cycloalkylidene group, preferably a C3 cycloalkylidene group; and R1 represents a C14 alkyl group, e.g. a methyl group) and non-toxic salts and non-toxic metabolically labile esters thereof.

The compounds according to the invention are syn isomers. The syn isomericform is defined by the configuration of the group

with respect to the carboxamido group. In this Specification the syn configuration is denoted structurally as

It will be understood that since the compounds according to the invention are geometric isomers, some admixture with the corresponding anti isomer may occur.

The invention also includes within its scope the solvates (especially the hydrates) of the compounds of formula (I). It also includes within its scope salts of esters of compounds of formula (I).

The compounds according to the present invention may exist in tautomeric forms (for example in respect of the 2-aminothiazolyl group) and it will be understood that such tautomericforms, e.g. the 2iminothiazolinyl form, are included within the scope of the invention. Moreover, the compounds of formula (I) depicted above may also exist in alternative zwitterionic forms, for example wherein the 4-carboxyl group is protonated and the carboxyl group in the 7-side chain is deprotonated. These alternative forms, as well as mixtures of zwitterionic forms, are included within the scope of the present invention.

It will also be appreciated that when Ra and Rb in the above formula represent different C14 alkyl groups, the carbon atom to which they are attached will comprise a centre of asymmetry. Such compounds are diastereoisomeric and the present invention embraces individual diastereoisomers of these compounds as well as mixtures thereof.

The compounds according to the invention exhibit broad spectrum antibiotic activity. Against gramnegative organisms the activity is unusually high. This high activity extends to many ss-lactamase-producing gram-negative strains. The compounds also posses high stability to ss-lactamases produced by a range of gram-negative and gram-positive organisms.

Compounds according to the invention have been found to exhibit unusually high activity against strains of Pseudomonas organisms, e.g. strains of Pseudomonas aeruginosa as well as high activity against various members of the Enterobacteriaceae (e.g. strains of Escherichia coli, Kiebsiefla pneumoniae, Salmonella typhimurium, Shigella sonnei, Enterobacter cloacae, Serratia marcescens, Providence species, Proteus mirabilis, and especially indole-positive Proteus organisms such as Proteus vulgaris and Proteus morganii) and strains of Haemophilus influenzae.

The antibiotic properties of the compounds according to the invention compare very favourably with those of the aminoglycosides such as amikacin or gentamicin. In particular, this applies to their activity against strains of various Pseudomonas organisms which are not susceptible to the majority of existing commercially available antibiotic compounds. Unlike the aminoglycosides, cephalosporin antibiotics normally exhibit low toxicity in man. The use of aminoglycosides in human therapy tends to be limited or complicated by the relatively high toxicity of these antibiotics. The cephalosporin antibiotics of the present invention thus posses potentially great advantages over the aminoglycosides.

Non-toxic salt derivatives which may be formed by reaction of either or both of the carboxyl groups present in the compounds of general formula (i) include inorganic base salts such as alkali metal salts (e.g.

sodium and potassium salts) and alkaline earth metal salts (e.g. calcium salts); amino acid salts (e.g. lysine and arginine salts); organic base salts (e.g. procaine, phenylethylbenzylamine, dibenzylethylenediamine, ethanolamine, diethanolamine and N-methylglycosamine salts). Other non-toxic salt derivatives include acid addition salts, e.g. formed with hydrochloric, hydrobromic, sulphuric, nitric, phosphoric, formic and trifluoroacetic acids. The salts may also be in the form of resinates formed with, for example, a polystyrene resin or cross-linked polystyrene divinylbenzene copolymer resin containing amino or quaternary amino groups or sulphonic acid groups, or with a resin containing carboxyl groups, e.g. a polyacrylic acid resin.

Soluble base salts (e.g. alkali metal salts such as the sodium salt) of compounds of formula (I) may be used in therapeutic applications because of the rapid distribution of such salts in the body upon administration.

Where, however, insoluble salts of compounds (I) are desired in a particular application, e.g. for use in depot preparations, such salts may be formed in conventional manner, for example with appropriate organic amines.

These and other salt derivatives such as the salts with toluene-p-sulphonic and methanesulphonic acids may be employed as intermediates in the preparation and/or purification of the present compounds of formula (I), for example in the processes described below.

Non-toxic metabolically labile ester derivatives which may be formed by esterification of either or both carboxyl groups in the parent compound of formula (I) include acyloxyalkyl esters e.g. lower alkanoyloxymethyl or -ethyl esters such as acetoxy-methyl or -ethyl or pivaloyloxymethyl esters. In addition to the above ester derivatives, the present invention includes within its scope compounds of formula (I) in the form of other physiologically acceptable equivalents, i.e. physiologically acceptable compounds which, like the metabolically labile esters are converted in vivo into the parent antibiotic compound of formula (I).

Preferred compounds according to the present invention include those compounds of formula (I) wherein R' represents a methyl group. Preference is also expressed for those compounds wherein Ra and Rb both represent methyl groups or together with the carbon atom to which they are attached form a cyclobutylidene group.Particularly preferred compounds according to the invention include the following compounds of formula (I) and their non-toxic salts and non-toxic metabolically labile esters:- (6R,7R)-7-[(Z)-2-(2 aminothiazol-4-yl)-2-(2-carboxyprop-2-oxyimino)acetamido]-3-(3-methyl-1 ,2,3-triazolium-1 -yl)-methyl-ceph3-em-4-carboxylate; and (6R,7R)-7-[(Z)-2-(2-aminothiazol-4-yl)-2-(1 -carboxycyclobut-1 -oxyimino) acetamido]-3-(3-methyl-l ,2,3-triazolium-1 -yl)methyl-ceph-3-em-4-carboxylate.

Other compounds according to the present invention include those for example wherein the groups Ra, Rb and R' are as follows: Ra Rb R1 a) Alkylgroups -CH3 -C2H5 -CH3 -C2H5 -C2H5 -CH3 -CH3 -CH3 -C2H5 -CH3 -C2H5 -C2H6 -c2H5 -c2H5 -c2H5 b) Cycloalkylidene groups (Ra-C-Rb) cyclopropylidene -CHs cyclopentylidene -CH3 cyclopropylidene -C2H5 cyclobutylidene -C2H5 cyclopentylidene -C2H5 The compounds of formula (I) may be used for treating a variety of diseases caused by pathogenic bacteria in human beings and animals, such as respiratory tract infections and urinary tract infections.

According to another embodiment of the invention we provide a process for the preparation of an antibiotic compound of general formula (I) as hereinbefore defined or a non-toxic salt or non-toxic metabolically labile ester thereof which comprises (A) acylating a compound of the formula

[wherein R' is as defined above;B is > S or > S~O (a- or ss-); and the dotted line bridging the 2-, and 4-positions indicates that the compound is a ceph-2-em or ceph-3-em compound] or a salt, e.g. an acid addition salt (formed with, for example, a mineral acid such as hydrochloric, hydrobromic, sulphuric, nitric or phosphoric acid or an organic acid such as methanesulphonic or toluene-p-sulphonic acid) or an N-silyl derivative thereof, or a corresponding compound having a group of formula - COOR2 at the 4-position [where R2 is a hydrogen atom or a carboxyl blocking group, e.g. the residue of an ester-forming aliphatic or araliphatic alcohol or an ester-forming phenol, silanol or stannanol (the said alcohol, phenol, silanol or stannanol preferably containing 1-20 carbon atoms and having an associated anion AO such as a halide, e.g. chloride or bromide, ortrifluoroacetate anion, with an acid of formula

(wherein Ra and Rb are as hereinbefore defined; R3 represents a carboxyl blocking group, e.g. as described for R2; and R4 is an amino or protected amino group) or with an acylating agent corresponding thereto; (B) reacting a compound of formula

(wherein Ra, Rb, R4, B and the dotted line are as hereinbefore defined;R5 and R5a may independently represent hydrogen or a carboxyl blocking group; and Xis a replaceable residue of a nucleophile, e.g. an acetoxy or dichloroacetoxy group or a halogen atom such as chlorine, bromine or iodine) or a salt thereof, with a compound of the formula

(wherein Rl is as defined above); or (C) alkylating a compound of the formula

(wherein Ra, Rb, R4, B and the dotted line are as herein before defined; and R5 and R5a both represent carboxyl blocking groups) with an alkylating agent serving to introduce the R7 substituent into the above triazole ring in formula (VI); whereafter, if necessary and/or desired in each instance, any of the following reactions, in any appropriate sequence, are carried out:i) conversion of a A2-isomer into the desired A3-isomer, ii) reduction of a compound wherein B is > S < O to form a compound wherein B is > S, iii) conversion of a carboxyl group into a non-toxic salt or non-toxic metabolically labile ester function, and iv) removal of any carboxyl blocking and/or N-protecting groups.

In the above-described process (A), the starting material of formula (li) is preferably a compound wherein the dotted line represents a ceph-3-em compound.

Acylating agents which may be employed in the preparation of compounds of formula (I) include acid halides, particularly acid chlorides or bromides. Such acylating agents may be prepared by reacting an acid (III) or a salt thereof with a halogentating agent e.g. phosphorus pentachloride, thionyl chloride or oxalyl chloride.

Acylations employing acid halides may be effected in aqueous and non-aqueous reaction media, conveniently at temperatures of from -50 to +500C, preferably -20 to +30"C, if desired in the presence of an acid binding agent. Suitable reaction media include aqueous ketones such as aqueous acetone, esters such as ethyl acetate, halogenated hydrocarbons such as methylene chloride, amides such as dimethylacetamide, nitriles such as acetonitrile, or mixtures of two or more such solvents. Suitable acid binding agents include tertiary amines (e.g. triethylamine or dimethylaniline), inorganic bases (e.g. calcium carbonate or sodium bicarbonate), and oxiranes such as lower 1,2-alkylene oxides (e.g. ethylene oxide or propylene oxide) which bind hydrogen halide liberated in the acylation reaction.

Acids of formula (III) may themselves be used as acylating agents in the preparation of compounds of formula (I). Acylations employing acids (III) are desirably conducted in the presence of a condensing agent, for example a carbodiimide such as N,N'-dicyclohexylcarbodimide or N-ethyl-N'-y- dimethylaminopropylcarbodiimide; a carbonyl compound such as carbonyldiimidazole; or an isoxazolium salt such as N-ethyl-5-phenylisoxazolium perchlorate.

Acylation may also be effected with other amide-forming derivatives of acids of formula (ill) such as, for example, an activated ester, a symmetrical anhydride or a mixed anhydride (e.g. formed with pivalic acid or with a haloformate, such as a lower alkylhaloformate). Mixed anhydrides may also be formed with phosphorus acids (for example phosphoric or phosphorous acids), sulphuric acid or aliphatic or aromatic sulphonic acids (for example toluene-p-sulphonic acid). An activated ester may conveniently be formed in situ using, for example, 1-hydroxy-benzotriazole ih the presence of a condensing agent as set out above.

Alternatively, the activated ester may be preformed.

Acylation reactions involving the free acids or their above-mentioned amide-forming derivatives are desirably effected in an anhydrous reaction medium, e.g. methylene chloride, tetrahydrofuran, dimethylformamide or acetonitrile.

If desired, the above acylation reactions may be carried out in the presence of a catalyst such as 4-dimethylaminopyridine.

The acids offormula (Ill) and acylating agents corresponding thereto may, if desired, be prepared and employed in the form of their acid addition salts. Thus, for example, acid chlorides may conveniently be employed as their hydrochloride salts, and acid bromides as their hydrobromide salts.

The compound of formula (V) may act as a nucleophile to displace a wide variety of substituents X from the cephalosporin of formula (IV). To some extent the facility of the displacement is related to the pKa of the acid HX from which the substituent is derived. Thus atoms or groups X derived from strong acids tend, in general, to be more easily displaced than atoms or groups derived from weaker acids. The facility of the displacement is also related, to some extent, to the precise identity of the alkyl group in the compound of formula (V).

The displacement of X by the compound of formula (V) may conveniently be effected by maintaining the reactants in solution or suspension. The reaction is advantageously effected using from 1 to 20, preferably 1 to 4, moles of the compound (V).

Nucleophilic displacement reactions may conveniently be carried out on those compounds of formula (IV) wherein the substituent X is a halogen atom or an acyloxy group for example as discussed below.

Acyloxy groups Compounds of formula (IV) wherein Xis an acetoxy group are convenient starting materials for use in the nucleophilic displacement reaction with the compound of formula (V). Alternative starting materials in this class include compounds of formula (IV) in which X is the residue of a substituted acetic acid e.g.

chloroacetic acid, dichloroacetic acid and trifluoroacetic acid.

Displacement reactions on compounds (IV) possessing X substituents of this class, particularly in the case where X is an acetoxy group, may be facilitated by the presence in the reaction medium of iodide or thiocyanate ions.

The substituent X may also be derived from formic acid, a haloformic acid such as chloroformic acid, or a carbamic acid.

When using a compound of formula (IV) in which X represents an acetoxy or substituted acetoxy group, it is generally desirable that the group R5 in formula (IV) should be a hydrogen atom and that B should represent > S. In this case, the reaction is advantageously effected in an aqueous medium, preferably at a pH of 5 to 8, particularly 5.5 to 7.

The above-described process employing compounds of formula (IV) in which Xis the residue of a substituted acetic acid may be carried out as described in British Patent Specification No. 1,241,657.

When using compounds of formula (IV) in which Xis an acetoxy group, the reaction is conveniently effected at a temperature of 30 to 110 C, preferably 50 to 80"C.

Halogens Compounds of formula (1V) in which Xis a chlorine, bromine or iodine atom can also be conveniently used as starting materials in the nucleophilic displacement reactions with the compound of formula (V). When using compounds of formula (IV) in this class, B may represent > S < O and R5 may represent a carboxyl blocking group. The reaction is conveniently effected in a non-aqueous medium which preferably comprises one or more organic solvents, advantageously of a polar nature, such as ethers, e.g. dioxan or tetrahydrofuran, esters, e.g. ethyl acetate, amides, e.g. formamide and N, N-dimethylformamide, and ketones, e.g. acetone. Other suitable organic solvents are described in more detail in British Patent Specification No. 1,326,531.The reaction medium should be neither extremely acidic nor extremely basic. In the case of reactions carried out on compounds of formula (IV) in which R5 and R5a are carboxyl blocking groups the 3- (3-alkyl-1 ,2,3-triazolium)-methyl product will be formed as the corresponding halide salt which may, if desired, be subjected to one or more ion exchange reactions to obtain a salt having the desired anion.

When using compounds of formula (IV) in which Xis a halogen atom as described above, the reaction is conveniently effected at a temperature of -10" to +50 C, preferably + 10 to +30"C.

In process (C) above, the triazolylmethyl compound of formula (IV) is advantageously reacted with a C14 alkylating agent of the formula R'Y wherein R1 is as defined above and Y is a leaving group such as a halogen atom (e.g. iodine, chlorine or bromine) or a hydrocarbylsulphonate (e.g. mesylate or tosylate) group, or R1Y represents dimethyl sulphate. The alkylation reaction is preferably carried out at a temperature in the range of 0 to 60 C, advantageously 20 to 30"C. The reaction may be conveniently effected in an inert solvent such as an ether e.g. tetrahydrofuran, an amide, e.g. dimethylformamide, or a halogenated hydrocarbon, e.g. dichloromethane.Alternatively, where the alkylating agent is liquid under the reaction conditions, this agent can itself serve as a solvent.

The compound of formula (VI) used as starting material in process (C) may be prepared for example by reaction of a compound of formula (IV) (as defined above) with a triazole of formula

in an analogous manner to the nucleophilic displacement reaction described with respect to process (B). This reaction is preferably carried out in the presence of an acid scavenging agent. The triazole itself may act as an acid scavenging agent.

The reaction product may be separated from the reaction mixture, which may contain, for example, unchanged cephalosporin starting material and other substances, by a variety of processes including recrystallisation, ionophoresis, column chromatography and use of ion-exchangers (for example by chromatography on ion-exchange resins) or macroreticular resins.

A2-Cephalosporin ester derivatives obtained in accordance with the process of the invention may be converted into the corresponding A3-derivative by, for example, treatment of the A2-ester with a base such as pyridine ortriethylamine.

A ceph-2-em reaction product may also be oxidised to yield the corresponding ceph-3-em 1-oxide, for example by reaction with a peracid, e.g. peracetic or m-chloroperbenzoic acid; the resulting sulphoxide may, if desired, subsequently be reduced as described hereinafter to yield the corresponding ceph-3-em sulphide.

Where a compound is obtained in which B is > S~O this may be converted to the corresponding sulphide by, for example, reduction of the corresponding acyloxysulphonium or alkoxysulphonium salt prepared in situ by reaction with e.g. acetyl chloride in the case of an acetoxysulphonium salt, reduction being effected by, for example, sodium dithionite or by iodide ion as in a solution of potassium iodide in a water-miscible solvent e.g. acetic acid, acetone, tetrahydrofuran, dioxan, dimethylformamide or dimethylacetamide. The reaction may be effected at a temperature of from -20" to +50 C.

Metabolically labile ester derivatives of the compounds of formula (I) may be prepared by reacting a compound of formula (I) or a salt or protected derivative thereof with an appropriate esterifying agent such as an acyloxyalkyl halide (e.g. iodide) conveniently in an inert organic solvent such as dimethylformamide or acetone, followed, where necessary, by removal of any protecting groups.

Base salts of the compounds of formula (I) may be formed by reacting an acid of formula (I) with the appropriate base. Thus, for example, sodium or potassium salts may be prepared using the respective 2-ethylhexanoate or hydrogen carbonate salt. Acid addition salts may be prepared by reacting a compound of formula (I) or a metabolically labile ester derivative thereof with the appropriate acid.

Where a compound of formula (I) is obtained as a mixture of isomers, the syn isomer may be obtained by, for example, conventional methods such as crystallisation or chromatography.

For use as starting materials for the preparation of compounds of general formula (I) according to the invention, compounds of general formula (III) and acid halides and anhydrides corresponding thereto in their syn isomeric form or in the form of mixtures of the syn isomers and the corresponding anti isomers containing at least 90% of the syn isomer are preferably used.

Acids of formula (III) (provided that Ra and Rb together with the carbon atom to which they are attached do not form a cyclopropylidene group) may be prepared by etherification of a compound of formula

(wherein R4 is as herein before defined and R6 represents a carboxyl blocking group), by reaction with a compound of general formula

(wherein Ra, Rb and R3 are as hereinbefore defined and T is halogen such as chloro, bromo or iodo; sulphate; or sulphonate such as tosylate), followed by removal of the carboxyl blocking group R6. Separation of isomers may be effected either before or after such etherification.The etherification reaction is generally carried out in the presence of a base, e.g. potassium carbonate or sodium hydride, and is preferably conducted in an organic solvent, for example dimethylsulphoxide, a cyclic ether such as tetrahydrofuran or dioxan, or an N,N-disubstituted amide such as dimethylformamide. Under these conditions the configuration of the oxyimino group is substantially unchanged by the etherification reaction. The reaction should be effected in the presence of a base if an acid addition salt of a compound of formula (VIII) is used. The base should be used in sufficient quantity to neutralise rapidly the acid in question.

Acids of general formula (III) may also be prepared by reaction of a compound of formula

(wherein R4 and R6 are as hereinbefore defined) with a compound of formula

(wherein Ra, Rb and R3 are as defined above), followed by removal of the carboxyl blocking group R6, and where necessary by the separation of syn and anti isomers.

The last-mentioned reaction is particularly applicable to the preparation of acids of formula (III) wherein Ra and Rb together with the carbon atom to which they are attached form a cyclopropylidene group. In this case, the relevant compounds of formula (Xl) may be prepared in conventional manner, e.g. by means of the synthesis described in Belgian Patent Specification No. 866,422forthe preparation of t-butyl 1-aminooxycyclopropane carboxylate.

The acids of formula (Ill) may be converted to the corresponding acid halides and anhydrides and acid addition salts by conventional methods, for example as described hereinabove.

Where Xis a halogen (i.e. chlorine, bromine or iodine) atom in formula (IV), ceph-3-em starting compounds may be prepared in conventional manner, e.g. by halogenation of a 7ss-protected amino-3methylceph-3-em-4-carboxylic acid ester 1 B-oxide, removal of the 7(3-protecting group, acylation of the resulting 7ss-amino compound to form the desired 7ss-acylamido group, e.g. in an analogous manner to process (A) above, followed by reduction of the 1 B-oxide group later in the sequence.This is described in British Patent No. 1,326,531. The corresponding ceph-2-em compounds may be prepared by the method of Dutch published Patent Application No.6,902,013 by reaction of a 3-methylceph-2-em compound with N-bromosuccinimide to yield the corresponding 3-bromomethylceph-2-em compound.

Where X in formula (IV) is an acetoxy group, such starting materials may be prepared for example by acylation of 7-aminocephalosporanic acid, e.g. in an analogous manner to process (A) above. Compounds of formula (IV) in which X represents other acyloxy groups can be prepared by acylation of the corresponding 3-hydroxymethyl compounds which may be prepared for example by hydrolysis of the appropriate 3-acetoxymethyl compounds, e.g. as described in British Patent Specifications Nos. 1,474,519 and 1,531,212.

The starting materials of formula (II) are new compounds. These compounds may be prepared in conventional manner, for example, by nucleophilic displacement of the corresponding 3-acetoxymethyl compound with the appropriate nucleophile.

A further method for the preparation of the starting materials of formula (II) comprises deprotecting a corresponding protected 7ss-amino compound in conventional manner e.g. using PC15.

It should be appreciated that in some of the above transformations it may be necessary to protect any sensitive groups in the molecule of the compound in question to avoid undesirable side reactions. For example, during any of the reaction sequences referred to above it may be necessary to protect the NH2 group of the aminothiazolyl moiety, for example by tritylation, acylation (e.g. chloroacetylation), protonation or other conventional method.The protecting group may thereafter be removed in any convenient way which does not cause breakdown of the desired compound, e.g. in the case of a trityl group by using an optionally halogenated carboxylic acid, e.g. acetic acid, formic acid, chloroacetic acid or trifluoroacetic acid or using a mineral acid, e.g. hydrochloric acid or mixtures of such acids, preferably in the presence of a protic solvent such as water or, in the case of a chloroacetyl group, by treatment with thiourea. Carboxyl blocking groups used in the preparation of compounds of formula (I) or in the preparation of necessary starting materials are desirably groups which may readily be split off at a suitable stage in the reaction sequence, conveniently at the last stage.It may, however, be convenient in some instances to employ non-toxic metabolically labile carboxyl blocking groups such as acyloxy-methyl or -ethyl groups (e.g. acetoxymethyl or -ethyl or pivaloyloxymethyl) and retain these in the final product to give an appropriate ester derivative of a compound of formula (I).

Suitable carboxyl blocking groups are well known in the art, a list of representative blocked carboxyl groups being included in British Patent No. 1,399,086. Preferred blocked carboxyl groups include aryl lower alkoxycarbonyl groups such asp-methoxybenzyloxycarbonyl,p-nitrobenzyloxycarbonyl and diphenylmethoxycarbonyl; lower alkoxycarbonyl groups such as t-butoxycarbonyl; and lower haloalkoxycarbonyl groups such as 2,2,2-trichloroethoxycarbonyl. Carboxyl blocking group(s) may subsequently be removed by any of the appropriate methods disclosed in the literature; thus, for example, acid or base catalysed hydrolysis is applicable in many cases, as are enzymically-catalysed hydrolyses.

The following Examples illustrate the invention.

All temperatures are in C. 'Petrol' means petroleum ether (b.p. 40-60").

T.l.c is thin-layer chromatography using pre-coated plates (Merck F2540.25 mm thick coating) which were examined under ultra-violet light at 254 nm and were developed with iodine.

Proton magnetic resonance (p.m.r.) spectra are inserted where appropriate and were determined at 100 MHz. The integrals are in agreement with the assignments, coupling constants, J, are in Hz, the signs not being determined; s = singlet, d = doublet, dd = double doublet, m = multiplet and ABq = AB quartet.

PREPARATION 1 Ethyl (Z)-2-(2-aminothiazol-4-yl)-2-(hydroxyimino) acetate To a stirred and ice-cooled solution of ethyl acetoacetate (292 g) in glacial acetic acid (296 ml) was added a solution of sodium nitrite (180 g) in water (400 ml) at such a rate that the reaction temperature was maintained below 10"C. Stirring and cooling were continued for about 30 min., when a solution of potassium chloride (160 g) in water (800 ml) was added. The resulting mixture was stirred for one hour. The lower oily phase was separated and the aqueous phase was extracted with diethyl ether. The extract was combined with the oil, washed successively with water and saturated brine, dried, and evaporated.The residual oil, which solidified on standing, was washed with petrol and dried in vacuo over potassium hydroxide, giving ethyl (Z)-2-(hydroxyimino)-3-oxobutyrate (309 g).

A stirred and ice-cooled solution of ethyl (Z)-2-(hydroxyimino)-3-oxobutyrate (150 g) in dichloromethane (400 ml) was treated dropwise with sulphuryl chloride (140 g). The resulting solution was kept at room temperature for 3 days, then evaporated. The residue was dissolved in diethyl ether, washed with water until the washings were almost neutral, dried, and evaporated. The residual oil (177 g) was dissolved in ethanol (500 ml) and dimethylaniline (77 ml) and thiourea (42 g) was added with stirring. After two hours, the mixture was filtered and the residue washed with ethanol and dried to give the title compound (73 g); m.p. 188" (decomp.).

PREPARATION 2 Ethyl rZ)-2-hydroxyimino-2-r2-tritylaminothiazol-4-yl)-acetate, hydrochloride Trityl chloride (16.75 g) was added portionwise over 2 hours to a stirred and cooled (-30") solution of the product of Preparation 1 (12.91 g) and triethylamine (8.4 ml) in dimethylformamide (28 ml). The mixture was allowed to warm to 15 over one hour, stirred for a further 2 hours and then partitioned between water (500 ml) and ethyl acetate (500 ml). The organic phase was separated, washed with water (2 x 500 ml) and then shaken with 1 N HCI (500 ml). The precipitate was collected, washed successively with water (100 ml), ethyl acetate (200 ml) and ether (200 ml) and dried in vacuo to provide the title compound as a white solid (16.4 g); m.p. 184 to 186 (decomp.).

PREPARATION 3 Ethyl (Z)-2-(2-t-butoxycarbon ylprop-2-oxyimino)-2-(2-tritylaminothiazol-4-yl)acetate Potassium carbonate (34.6 g) and t-butyl 2-bromo-2-methylpropionate (24.5 g) were added to a stirred solution under nitrogen of the product of Preparation 2 (49.4 g) in dimethylsulphoxide (200 ml) and the mixture was stirred at room temperature for 6 hours. The mixture was poured into water (2 1), stirred for 10 mins., and filtered. The solid was washed with water and dissolved in ethyl acetate (600 ml). The solution was washed successively with water, 2N hydrochloric acid, water, and saturated brine, dried, and evaporated. The residue was recrystallised from petrol to give the title compound (34 g), m.p. 123.5 to 125'.

PREPARATION 4 (Z)-2-(2-t-Butoxycarbon ylprop-2-oxyimino)-2-(2-trityl-aminothiazol-4-yl)acetic acid The product of Preparation 3 (2 9) was dissolved in methanol (20 ml) and 2N sodium hydroxide (3.3 ml) was added. The mixture was refluxed for 1.5 hours and then concentrated. The residue was taken up in a mixture of water (50 ml), 2N hydrochloric acid (7 ml), and ethyl acetate (50 ml). The organic phase was separated, and the aqueous phase extracted with ethyl acetate. The organic solutions were combined, washed successively with water and saturated brine, dried and evaporated. The residue was recrystallised from a mixture of carbon tetrachloride and petrol to give the title compound' (1 g), m.p. 152 to 156 (decomp.).

PREPARATION 5 Ethyl (Z)-2-(2-tritylaminothiazol-4-yl)-2-( i-t-butoxy-carbonylcyclobut- 1-oxyimino) acetate The product of Preparation 2 (55.8 g) was stirred under nitrogen in dimethylsulphoxide (400 ml) with potassium carbonate (finely ground, 31.2 g) at room temperature. After 30 minutes, t-butyl 1bromocyclobutanecarboxylate (29.2 g) was added. After 8 hours further potassium carbonate (31.2 g) was added. More potassium carbonate (6 x 16 g portions) was added during the next three days and further t-butyl 1-bromocyclobutanecarboxylate (3.45 g) was added after 3 days. After 4 days in all, the mixture was poured into ice-water (ca. 3 litres) and the solid was collected by filtration and washed well with water and petrol.The solid was dissolved in ethyl acetate and the solution washed with brine (twice), dried with magnesium sulphate and evaporated to a foam. This foam was dissolved in ethyl acetate-petrol (1:2) and filtered through silica gel (500 g). Evaporation gave the title compound (60 g) as a yellow foam, Vmax (CHBr3) 3400 (NH) and 1730 cm -1 (ester).

PREPARATION 6 (Z)-2-( 1-t-Butoxycarbon ylcyclobut- 1-oxyimino)-2-g2-trityl-aminothiazol-4yl) acetic acid A mixture of the product of Preparation 5 (3.2 g) and potassium carbonate (1.65 g) was refluxed in methanol (180 ml) and water (20 ml) for 9 hours and the mixture was cooled to room temperature. The mixture was concentrated and the residue partitioned between ethyl acetate and water, to which was added 2N HCI (12.2 ml). The organic phase was separated and the aqueous phase extracted with ethyl acetate. The combined organic extracts were washed with saturated brine, dried and evaporated to give the title compound (2.3 g); Xmax (ethanol) 265 nm (Ei1cm 243).

EXAMPLE 1 a) Diphenylmethyl (1S, 6R, 7R)-3-Bromomethyl-7-[(Z)-2-(2-t-butoxycarbonyl-prop-2-oxyimino)-2-(2- tritylaminothiazol-4-yl)acetamido]ceph-3-em-4-carboxylate, 1-Oxide A solution of the product of Preparation 4 (0.5269) in dry tetrahydrofu ran (6 ml) was treated successively with 1-hydroxybenztriazole monohydrate (0.141 g) and N,N'-dicyclohexylcarbodiimide (0.198 g) in tetrahydrofuran (4 ml). The developing suspension was stirred for 30 minutes at 23 and then filtered.A solution of diphenylmethyl (1 S,6R,7R)-7-amino-3-bromomethylceph-3-em-4-carboxylate, 1-oxide (0.427 g) in dichloromethane (260 ml) was treated at 23 with the above fi Itrate.The solution was stirred for 18 hours at 20" to 259, evaporated to dryness, then the residue was dissolved in dichloromethane and washed successively with saturated aqueous sodium bicarbonate, water and brine, then dried and evaporated in vacuo to a foam (1.01 g).

This foam was purified by chromatography on preparative silica plates using toluene:ethyl acetate: acetic acid = 190:50:2.5 as eluant. The purified product was isolated as a foam which was dissolved in ethyl acetate (5 ml) and precipitated from petrol (200 ml) to give the title compound (0.69 g) as a colourless powder; Xmax (EtOH) 268 nm EicXron 182) with an inflection at 242 nm (Ei'm 230),vmax(Nujol) 3375 (NH), 1805 (p-lactam), 1730 lCO2R) and 1688 and 1515 cm-' (CONH).

b) Diphenylmethyl (iS, 6R, 7R)-3-(3-methyl- 1,2, 3-triazolium- i-yljmethyl-7-J(Z)-2-(2-t-butoxycarbon ylprop-2- ox yim in o) -2- (2-trit ylamin othiazol-4-yl]acetamido]-ceph-3-em-4-carboxylate, 1-oxide Bromide salt A mixture of diphenylmethyl (1 S, 6R, 7 R)3-bro momethyl-7-[(Z)-2-(2-t-butoxycarbonyl prop-2-oxyimino)-2- (2-tritylaminothiazol-4-yl)acetamido]ceph-3-em-4-carboxylate,1-oxide (1.05 9) and 1-methyl-1,2,3-triazole (1.19 g) in tetrahydrofuran (15 ml) was stirred at 22 to 30 for 4.7 days in the absence of light.The mixture was evaporated and the residue triturated with ether and ethyl acetate to give the title compound (1 g) as a solid; #infection (CHC13) 267 nm (E jC%n 155 E 17,300) and Vmax (Nujol) 3600 to 2500 (NH and water), 1798 (B-iactam, 1725 (CO2R) and 1678 and 1515 cm-l (CONH).

c) Diphenylmethyl (6R, 7R)-3-(3-methyl- 1,23-triazolium- i-yljmeth yl- 7-[(Z)-2-(2-t-butoxycarbon ylprop-2- oxysmino)-2-(2-tritylaminothiazol-4-yl)acetamidolceph-3-em-4-carboxylate, Bromide and Iodide salts The product of stage b) (0.8 g) in acetone (5 ml) at -10" was treated with potassium iodide (0.427 g) and stirred for 10 minutes.

Afurther portion of potassium iodide (0.427 g) and acetyl chloride (0.11 ml) was added and the mixture was stirred vigorously at - 10 to 0" over 30 minutes. The mixture was added dropwise to a solution of sodium metabisulphite (0.35 g) in water (20 ml) to give a gummy solid. The mixture was extracted with dichloromethane and brine and the organic phase was washed with brine then dried and evaporated to a foam (t.l.c indicated some unchanged starting material).

The above reduction sequence using potassium iodide and acetyl chloride was repeated exactly as described above to give the title compound (0.6 g), mainly as the iodide salt, t.l.c., Rf 0.7 (chloroform: methanol acetic acid = 90:16:20), T (DMSO+d6) 1.08 and 1.15 (2s, triazole 4 and 5-H), 3.22 (s, thiazol-5-yl proton), 4.03 (dd, J 9 and 5Hz, 7-H), 5.70 (s, NMe), and 8.60 (broad s, CMe2 and t-butyl).

d) (6R, 7R)- 7- J(Z)-2- (Amino thiazol-4-yl)-2-(2-carb oxyprop-2-oxyimin o)acetamido]-3-(3-methyl- 1,2,3- triazolium- 1-yl)-methylceph-3-em-4-carboxylate The product of stage c) (1.72 g) was suspended in a mixture of anisole (1.7 ml) and trifluoroacetic acid (7 ml) at 22 for 1 minute. The mixture was evaporated in vacuo to an oil which was then azeotroped with toluene. The toluene was removed in vacuo and the resulting oil triturated with ether to give a solid (1.3 g).

A suspension of the above solid in anisole (1.3 ml) andtrifluoroacetic acid (15 ml) was stirred for 15 minutes. The supernatant liquid was decanted off and the solid was washed with trifluoroacetic acid (10 ml).

The combined trifluoroacetic acid solutions were concentrated in vacuo to an oil which, on trituration with ether gave a solid (0.9 g).

A portion (0.85 g) of this solid was stirred for 10 minutes with a mixture of trifluoroacetic acid (4 ml) and water (150 ml) and the mixture was successively extracted with ethyl acetate and ether. The aqueous layer was freeze-dried to give the title compound (0.75 g) as a solid associated with 1.3 moles of trifluoroacetic acid [a]2 -17.9 (c 0.56, DMSO), Binf (pH 6 phosphate) 235 nm (E1cm 224) with further inflections at 255 nm (E1jCV,n 207) and 200 nm (E1c/om 82).

EXAMPLE 2 a) Diphenylmeth yl (1S, 6R, 7R)-3-Bromomethyl-7-[(Z)-2-(1-t-butoxycarbonylcyclobut- i-oxyimino)-2-(2- tritylaminothiazol-4-yl)acetamidojceph-3-em-4-carboxylate, 1-Oxide A stirred solution of the product of Preparation 6(1.167 g) in tetrahydrofuran (15 ml) was treated successively with 1-hydroxybenztriazole hydrate (0.337 g) and N,N'-dicyclohexylcarbodiimide (0.495 g) for 30 minutes at 22 .

Filtration afforded a solution of the activated ester which was added to a solution of diphenylmethyl (1 S,6R,7R)-7-amino-3-bromomethylceph-3-em-4-carboxylate 1-oxide (0.95 g) in dichloromethane (550 ml).

The solution was stirred for 16 hours then evaporated to dryness. A solution of the residue in dichloromethane was washed successively with aqueous sodium bicarbonate, and brine, and then dried and evaporated to a foam (2.2 g) which was purified by preparative thin-layer chromatography (using toluene:ethyl acetate: acetic acid = 40:10:1 for development) to give the title compound (1.4 g) with Xmax (EtOH) 266 nm (E1l m 192) and an inflection at 242.5 nm (E1C'm224),vmax (Nujol) 3360 (NH), 1805 (ss-lactam), 1730 (CO2R) and 1689 and 1520 cm~1 (CONH).

b) Diphenylmethyl /7S,6R, 7R)-3-{3-methyl- 1,2,3-triazolium- l -yl) methyl-7-[(Z)-2-(i4- butoxycarbonylcyclobut-1-oxyimino)-2-(2-tritylaminothiazol-4yl)acetamidosceph-3-em-4-carboxylate, 1oxide, Bromide Salt A mixture of diphenylmethyl (1 S,6R,7R)-3-bromomethyl-7-[(Z)-2-(1 -t-butoxycarbonylcyclobut-1- oxyimino)-2-(2-tritylaminothiazol-4-yl )aceta mido]ceph-3-em-4-carboxylate,1 oxide (1.04 g) and 1-methyl- 1,2,3 triazole (1.240 g) in tetrahydrofuran (8 ml) was stirred at ca 21'for 50 hours.

The solution was evaporated to an oil which, on leaching several times with ether gave the title compound (0.910 g) as an amorphous solid [a]2Dt2 (c 0.9, DMSO) ainfl (EtOH) 243 nm (E1tC',n 207, E23,270) with further in flections at 265 nm (E1icm 170, #19,110), and 310 nm (Ej / m50 50, E5,620) and rna'390 nm (E: 31, E3,485).

c)Diphenylmethyl (6R, 7R)-3-(3-methyl- 1,2,3-triazolium- i-yl) methyl-7-[(Z)-2-(1-t-butoxycarbonylcyclobut- l- oxysmino)-2-(2-tritylaminothiazol-4-yl)acetamido]ceph-3-em-4carboxylate, lodide Salt Potassium iodide (0.481 g) was added to a cooled (-10 ) mixture ofthe product of stage b) (0.816 g) and the mixture was stirred for 10 minutes at - 10 . A further portion of potassium iodide (0.481 g) was added, followed by acetyl chloride (0.12 ml) and the resulting suspension stirred for 30 minutes at -10 to toO'. The mixture was poured into a stirred solution of sodium metabisulphite (0.36 g) in water (20 ml) and the gummy solid extracted with dichloromethane.The organic layer was washed with brine, dried and evaporated to a foam (t.l.c. indicated some starting material).

The above product was subjected to a similar reduction sequence (using potassium iodide and acetyl chloride as described above) to give the title compound(0.713 g) as a foam, t.l.c. Rf0.45 (chloroform:metha- nol:acetic acid = 90:16:20), and T(DMSO-d6) 1.06 and 1.12 (2s, triazole 4 and 5-H), 3.22 (s, thiazol-5-yl proton), 4.05 (dd, J 9 and 5Hz, 7-H), 5.70 (s, NMe), 7.2 to 7.8 (m,cyclobut-2-yl protons) and 7.8 to 8.4 (m, cyclobut-3-yl protons).

d) (6R, 7R)-7-J(Z)-2-(2-Aminothiazol-4-yl)-2-(i-carhoxycyclobut- 1-oxyimino)acetamido]3-(3-methyl- 1,2,3 triazolium- 1-yl)methylceph-3-em-4-carboxylate The product of stage c) (0.65 g) in anisole (0.6 ml) and trifluoroacetic acid (2.4 ml) was stirred at 20 for 1 minute and concentrated in vacuo to give an oil.

Trituration of this oil with ether gave a powder which was treated with anisole (0.6 ml) and trifluoroacetic acid (12 ml). After stirring for 15 minutes the solution was decanted to leave a black amorphous paste which was leached with trifluoroacetic acid.

The combined trifluoroacetic acid solutions were concentrated in vacuo to an oil which, on treatment with ether gave a colourless solid (0.35 g). A portion (0.32 g) of this solid was treated with a mixture of anisole (0.6 ml), trifluoroacetic acid (10 ml) and water (10 drops) at 22 for 15 minutes.

The mixture was concentrated to ca 3 ml then poured into benzene (100 ml). Ethyl acetate and tetrahydrofuran were added to give a solution. This slution was concentrated in vacuo to an oil which was stirred with ether to give a powder (0.31 g).

A portion (0.1 g) of this powder was stirred with water (50 ml) and trifluoroacetic acid (1 ml) for 10 minutes.

The mixture was washed with ethyl acetate and ether and the aqueous phase was freeze-dried to give the title cmpound (0.09 g) associated with 1.2 moles of trifluoroacetic acid; [&alpha;]D28-1 3.2 (c 0.49, DMSO), #max (pH6 phosphate) 248.5 nm (E 1cm 221, 16,050) with inflections at 243 nm (E1cm 221, E16,000) and 296 nm (E1cm 98, #6,860).

EXAMPLE 3 a) Diphenylmethyl llS,6R, 7R)-7-formamido-3-(3-methyl- 1,2,3-triazolium- 1-yl)methylceph-3-em-4- carb oxyla te, 1-oxide, Bromide Salt A solution of diphenylmethyl (1 S,6R,7R)-3-bromomethyl-7-formamidoceph-3-em-4-carboxylate,1 oxide (1 g) in N,N-dimethylformamide (3 ml) was stirred for 19 hours at 22 with 1 -methyl-1 ,2,3-triazole (1.10 g).The reaction mixture was added dropwise to ether to give the title compound (1.13 g) as a solid; Vmax (Nujol) 3390 (NH), 1795 (J)-lactam),1726 (CO2R) and 1684cm-' (CONH) and #(DMSO-d6) 1.07 and 1.22J2striazol-4H and 5H respectively), 1.77 (s, HCONH), 3.82 (dd, J 9 and 5Hz, 7-H), 4.84 (d, J 5Hz, 6-H), 5.73 (s, -Me) and 5.90 and 6.19 (ABq J 18Hz, 2-H2).

b) Diphenylmethyl (iS, 6R, 7R)-7-amino-3-(3-meth yl- 1,2,3-triazolium- l-yl)methylceph-3-em-4-carboxylate, 1-Oxide hydrochloride and Bromide Salts A stirred suspension of the product of stage a) (1.00 g) in dry methanol was treated with phosphoryl chloride (0.48 ml) at 0'to 5' for 2 hours. The resulting solution was added dropwise to ether (100 ml) to give a gum which was stirred with ethyl acetate (50 ml) for 11/2 hours.

The resulting powder was washed with ether to give the title compound (0.700 g) as a solid, may (EtOH) 278 nm (Ei1cm 107) Vmax (Nujol) 3700 to 2200 (NH3), 1805 (ss-lactam) and 1729 cm-5 (CO2R).

c) Diphen ylmethyl (iS, 6R, 7R)-3-(3-methyl- 1,2,3-triazollum- 1-yl)methyl-7-[Z)-2-(2-t-butoxyearbonylprop-2- oxyimino)-2-(2-tritylamin othiazol-4-yl)acetamido]-ceph-3-em-4-carboxylate, oxide, Bromide Salt Phosphorus pentachloride (0 11 g) in dry dichloromethane (10 ml) at 0 was treated with the product of Preparation 4 (0.295 g) and the solution was stirred for 30 minutes at 0'. Triethylamine (0.16 ml) was added and stirring was continued for 10 minutes at 0 . The resulting solution was added dropwise over 5 minutes to a vigorously stirred suspension of the product of stage b) (0.303 g) in dichloromethane (15 ml) at 0'. The mixture was stirred at 0 to 15 for 13/4 hours and the resulting solution was stored at -20 for 15 hours. The solution was poured into ethyl acetate (100 ml) and water (100 ml). The organic phase was separated and washed successively with water and brine, then dried and evaporated in vacuo to a foam (0.4 g). This foam was stirred with ether (30 ml) for 30 minutes to give a solid which was washed with ether to give the title compound (0.35 g) as a solid, [ &alpha;]D22-16 (c 1.0, DMSO), #inf (CHCl3) 267 nm (E1cm 169).

The title compound may then be converted into (6R,7R)-7-[(Z)-2-(2-aminothiazol-4-yl)-2-(2-carboxyprop-2- oxyimino)acetamido]-3(3-methyl-1 ,2,3-triazolium-1 -yl)methylceph-3-em-4-carboxylate as described in Ex ample 1.

EXAMPLE 4 a) Diphenylmethyl (1S,6R, 7R)-3-(i,2,3-triazolium- i-yl)methyl-7-[(Z)-2-(1-t-butoxycarbonylcyclobut- 1oxyiminoj-2-(2-tritylamin othiazol-4-ylacetamido]ceph-3-em-4-carboxylate, oxide A solution of the product of Example 2a) (1 g) in N,N-dimethylformamide (3 ml) was treated with 1,2,3-triazole (0.113 g). The reaction mixture was stirred at ca 20" for 24 hours and then more triazole (0.113 g) was added and the mixture was stirred for ca. 2 hours at ca 20 and then refrigerated for ca. 60 hours. The mixture was diluted with ethyl acetate (150 ml) and the organic solution was washed with 2N-hydrochloric acid (2 x 50 ml) and brine (50 ml) then dried over magnesium sulphate and evaporated in vacuo to a foam (0.88 g).Chromatography of this foam on preparative thin-layer plates using toluene:ethyl acetate:acetic acid = 20:40:1 as eluant gave the title compound (0.1 g) as a solid with kinf into(EtOH) 260 nm (E1cm 199) and 300.5 nm (E1 C m 61) and T (DMSO-d6),2.03 and 2.26 (2s, triazolium protons), 3.19 (s, thiazol 5-H), 3.8 to 4.1 (m, 7-H), 4.92 (d, J 5Hz, 6-H), 7.4 to 7.8 (m, cyclobut-2 and 4-yl protons), 7.8 to 8.2 (m, cyclobut-3-yl protons) and 8.62 (s,t-butyl) b) Diphenylmethyl (iS, 6R, 7R)-3-(3-meth yl- 1,2,3-triazolium- i-yl)methyl- 7-[(Z)-2-(i-t-butoxycarbonyl- cyclobut-1-oxyimino)-2-(2-tritylaminothiazol-4yl)-acetamido]ceph-3-em-4carboxylate, oxide, lodide Salt A solution of the Product from stage a) (0.08 g)] in iodomethane (2 ml) was stirred at 22 for 66 hours.

Excess iodomethane was evaporated in vacuo to give a solid. This product was triturated with ether and the solid collected by filtration and dried in vacuo over phosphorus pentoxide to give the title compound (0.067 g) as a solid [a]2D216.2 (c 0.5; DMSO), #inf (EtOH) 260 nm (E1 / m 160) and 305 nm (E1C' m 58).

EXAMPLE 5 a) t-Butyl /6R, 7R-3-A cetoxym eth y/- 7-2-2-(2-t-6 utoxy-carb onylprop-2-oxyiminol-2-12-tritylamino thiazol- 4-yl) acetamidoj ceph-3-em-4-carboxylate A stirred solution of the product of Preparation 4(572 mg) and t-butyl (6R,7R)-3-acetoxymethyl-7aminoceph-3-em-4-carboxylate (328 mg) in dimethylformamide (10 ml) was cooled toO,, and 1hydroxybenzotriazole (150 mg) was added, followed by dicyclohexylcarbodiimide (225 mg). The mixture was warmed to room temperature, stirred for 5 hours, and allowed to stand overnight. The mixture was filtered, and the white solid washed with a little ether. The filtrate and washings were diluted with water (50 ml) and extracted with ethyl acetate.The organic extracts were combined, washed successively with water, 2N hydrochloric acid, water, sodium bicarbonate solution, and saturated brine, dried and evaporated. The residue was eluted through a silica column with ether. The product-containing eluate was collected and concentrated to give the title compound (533 mg). A portion was recrystallised from di-isopropyl ether, m.p.

103 to 113'(decomp.); [a]2+ 8.5'(c, 1.0, DMSO).

b) (6R, 7R)-3-A cetoxymeth yl- 7-J(Z)-2-(2-amin othiazol-4-yl)-2-(2-carboxyprop-2-oxyimino)-acetamido]-ceph- 3-em-4carboxylic Acid Hydrochloride The product of Stage a) (200 g) was dissolved in formic acid (800 ml) pre-cooled to + 10 and concentrated hydrochloric acid (60 ml) was added over 5 minutes to the stirred mixture. Stirring was continued at 20 to 22"for 11/4 hours before cooling to +10 and filtering. The bed was washed with formic acid (30 ml). The combined filtrate and wash were concentrated by evaporation at 20 to a yellow foam which was triturated with ethyl acetate (800 ml).The solid which deposited was collected by filtration, washed with ethyl acetate (200 ml) and dried in vacuo at room temperature overnight to give the title compound (124.6 g) X max (ethanol) 234.5 nm (E1C'm 311).

c) (6R, 7R)-7-[(Z)-2-(2-A min othiazol-4-yl)-2-(2-carb oxyprop-2-oxyimino)acetamido]-3- (3-methyl- 1,2,3- triazolium- i-yl)meth yl-ceph-3-em-4-carb oxyla te, Sodium Salt (6R,7R)-3-Acetoxymethyl-7-[(Z)-2-(2-a mi nothiazol-4-yl )-2-(2-carboxyprop-2-oxyimino)acetamidoj-ceph-3- em-4-carboxylic acid, hydrochloride salt (0.564 g), sodium hydrogen carbonate (0.27 g), sodium iodide (1.8 g), water (0.30 ml) and 1-methyl-1,2,3-triazole (0.25 ml) were heated to 80 for 11/4 hours and the solution was left to cool. The resulting solid was triturated with acetone (10 ml) and the product was filtered off, washed with acetone and ether and dried rapidly in-vacuo to give a solid (0.66 g).This product was purified on a column of Amberlite XAD-2 resin (100 g) which was eluted successively with water then water:ethanol (4:1).

Appropriate fractions were combined, evaporated to ca 150 ml then freeze-dried to give the title compound (0.203 g) as a foam with kmax (pH6 buffer) 238 nm (E11'c'm 295) with inflections at 256 nm (E1 Cm 270) ar;;;i 295 nm (E1icm 141) and T(D2O) 1.39 and 1.49 (2 broad s, triazole protons), 3.00 (broad s, thiazol 5-H), 5.69(s, NCH3), 6.29 and 6.62 (ABq, J ca. 18 Hz, 2-H2) and 8.52 (s, CMe2).

The antibiotic compounds of the invention may be formulated for administration in any convenient way, by analogy with other antibiotics and the invention therefore includes within its scope pharmaceutical compositions comprising an antibiotic compound in accordance with the invention adapted to use in human or veterinary medicine. Such compositions may be presented for use in conventional manner with the aid of any necessary pharmaceutical carriers or excipients.

The antibiotic compounds according to the invention may be formulated for injection and may be presented in unit dose form in ampoules, or in multi-dose containers, if necessary with an added preservative. The compositions may also take such forms as suspensions, solutions, or emulsions in oily or aqueous vehicles, and may contain formulatory agents such as suspending, stabilising and/or dispersing agents. Alternatively the active ingredient may be in powder form for reconstitution with a suitable vehicle, e.g. sterile, pyrogen-free water, before use.

If desired, such powder formulations may contain an appropriate non-toxic base in order to improve the water-solubility of the active ingredient and/or to ensure that when the powder is reconstituted with water, the pH of the resulting aqueous formulation is physiologically acceptable. Alternatively, the base may be present in the water with which the powder is reconstituted. The base may be, for example, an inorganic base such as sodium carbonate, sodium bicarbonate or sodium acetate, or an organic base such as lysine or lysine acetate.

The antibiotic compounds may also be formulated as suppositories, e.g. containing conventional suppository bases such as cocoa butter or other glycerides.

For medication of the eyes or ears, the preparations may be formulated as individual capsules, in liquid or semi-solid form, or may be used as drops.

Compositions for veterinary medicine may, for example, be formulated as intramammary preparations in either long acting or quick-release bases.

The compositions may contain from 0.1% upwards, e.g. 0.1-99%, of the active material, depending on the method of administration. When the compositions comprise dosage units, each unit should preferably contain 50-1500 mg of the active ingredient. The dosage as employed for adult human treatment will preferably range from 500 to 6000 mg per day, depending on the route and frequency of administration. For example, in adult human treatment 1000 to 3000 mg per day administered intravenously or intramuscularly will normally suffice. In treating Pseudomonas infections higher daily doses may be required.

The antibiotic compounds according to the invention may be administered in combination with other therapeutic agents such as antibiotics, for example penicillins or other cephalosporins.

The following formulation illustrates how a compound according to the invention may be made up into a pharmaceutical composition Formulation - For Injection Formula per vial (6R,7R)-7-((Z)-2-(2-Aminothiazol-4-yl)-2-(1 -carboxycyclobut-1 -yloxyimino)acetamido] 3-(3-methyl-1 ,2,3-triazoliu m-l -yl )methylceph-3-em-4-ca rboxylate 500 mg sodium carbonate, anhydrous 47 mg Method Blend the sterile cephalosporin antibiotic with sterile sodium carbonate under aseptic conditions. Fill aseptically into glass vials under a blanket of sterile nitrogen. Close the vials using rubber discs, or plugs, held in position by aluminium overseals, thereby preventing gaseous exchange or ingress of microorganisms. Reconstitute the product by dissolving in Water for Injections or other suitable sterile vehicle shortly be before administration.

(6R,7R)-7-[(Z)-2-(aminothiazol-4-yl)-2-(2-carboxyprop-2-oxyimino)-acetamido]-3-(3-methyl-1 ,2,3triazolium-1-yl) methyl-ceph-3-em-4-carboxylate may be formulated in a similar manner.

Claims (10)

1. Cephalosporin antibiotics of general formula

(wherein Ra and Rb, which may be the same or different, each represent a C1 4 alkyl group or Ra and Rb together with the carbon atom to which they are attached form a C3 7 cycloalkylidene group; and R represents a C14 alkyl group) and non-toxic salts and non-toxic metabolically labile esters thereof.

2. Compounds as claimed in claim 1 wherein at least one of Ra and Rb represents a methyl or ethyl group.

3. Compounds as claimed in claim 1 wherein Ra and Rb together with the carbon atom to which they are attached form a C35 cycloalkylidene group.

4. Compounds as claimed in any of the preceding claims wherein R' represents a methyl group.

5. (6R,7R)-7-[(Z)-2-(2-Aminothiazol-4-yl)-2-(2-carboxyprop-2-oxyimino)-acetamido]-3-(3-methyl-1,2,3- tri azol i u m-1 -yl ) m ethyl -ceph-3-em-4-ca rboxyl ate.

6. The non-toxic salts of the compound of claim 5.

7. (6R,7R)-7-[(Z)-2-(2-Aminothiazol-4-yl)-2-(1 -carboxycyclobut-1 -oxyimino)-acetamido]-3-(3-methyl-1 2,3- triazolium-1-yl)methyl-ceph-3-em-4-carboxylate.

8. The non-toxic salts of the compound of claim 7.

9. A process for the preparation of an antibiotic compound of general formula (I) as defined in claim 1 or a non-toxic salt or non-toxic metabolically labile ester thereof which comprises (A) acylating a compound of formula

(wherein R1 is as defined in claim 1; B is > S or > S < O and the dotted line bridging the 2-, and 4-positions indicates that the compound is a ceph-2-em or ceph-3-em compound), or a salt or N-silyl derivative thereof or a corresponding compound having a group of formula -COOR2 at the 4-position (where R2 is a hydrogen atom our a carboxyl blocking group) and having an associated anion with an acid of formula

(wherein Ra and Rb are as defined in claim 1;R3 represents a carboxyl blocking group; and R4 is an amino or protected amino group) or with an acylating agent corresponding thereto; (B) reacting a compound of formula

(wherein Ra, Rb, R6, B and the dotted line are as hereinbefore defined; R5 and R5a may independently represent hydrogen or a carboxyl blocking group; and X is a replaceable residue of a nucleophile) or a salt thereof with an alkyltriazole of the formula

(wherein R1 is as defined above); or (C) alkylating a compound of formula

(wherein R", Rb, B and the dotted lines are as hereinbefore defined; and R5 and R5a both represent carboxyl blocking groups with an alkylating agent serving to introduce the R1 substituent into the triazole ring in formula (VI); whereafter if necessary and/or desired in each instance, any of the following reactions, in any appropriate sequence, are carried out:i) conversion of a A2-isomer into the desired A3-isomer.

ii) reduction of a compound wherein B is > SO to form a compound wherein B is > S, iii) conversion of a carboxyl group into a non-toxic salt or non-toxic metabolically labile ester function, and iv) removal of any carboxyl blocking and/or N-protecting groups.

10. A pharmaceutical composition for use in human or veterinary medicine comprising an antibiotic compound as claimed in any one of claims 1 to 8 in association with a pharmaceutical carrier or excipient.