GB2132193A - Cephalosporin antibiotics - Google Patents

Abstract

Cephalosporin antibiotics of general formula <IMAGE> (wherein Y represents a carbon- linked 5- or 6-membered unsaturated heterocyclic ring containing at least one nitrogen atom, such as pyridine or tetrazole, which ring may also contain one or more sulphur atoms and/or may be substituted by one or more C1-4 alkyl, oxo, hydroxy or carbamoyl-methyl groups such as dioxotriazine), and non-toxic salts and non-toxic metabolically labile esters thereof and pharmaceutical compositions containing them are described. The compounds exhibit broad spectrum antibiotic activity both in vitro and in vivo, having good activity against both Gram-positive and Gram-negative organisms.

Description

SPECIFICATION Cephalosporin antibiotics This invention relates to improvements in or relating to cephalosporins. Ore particularly it relates to new cephalosporin compounds and derivatives thereof having valuable antibiotic activity.

The cephalosporin compounds in this specification are named with reference to "cepham" after J.Amer.Chem.Soc., 1962, 84, 3400, the ter, "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 anitbiotics 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 development 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 7ss(a-etherified oximino)-acylamido group, the oximino 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 fi-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 British Patent Specification No. 1,604,971 a wide variety of cephalosporin antibiotics are disclosed in which the 7ss-position side-chain may be selected from, inter alia, a 2-(2aminothiazol-4-yl)-2-(etherified oxyimino) acetamido group, in which the etherifying group, amongst very many possible meanings, may be an alkyl group substituted by a cycloalkyl group, although there is no specific exemplificatin of compounds having such a group. The 3-position group may also be selected from a large number of alternatives and a possible substituent is a thiomethyl group substituted by an optionally substituted 5--or 6-membered heterocyclic group containing one or more nitrogen, oxygen or sulphur atoms.

Our British Patent Application Specification No. 2027691A describes cephalosporin antibiotics in which the 7ss-side chain is a 2-(2-aminothiazol-4-yl)-2-(etherified oxyimino) acetamido group, where the etherifying group is a carboxyalkyl or carboxycycloalkyl group. The 3substituent is a group of formula -CH2SY in which Y is a carbon-linked 5- or 6-membered heterocyclic ring containing at least one nitrogen atom, which may be substituted by a C14 alkyl group.

We have now discovered that by the selection of a syn2-(2-aminothiazol-4-yl)-2-cyclopropyl- methoxyiminoacetamido group at the 7ssposition in combination with certain groups at the 3position, cephalosporin compounds having particularly advantageous activity (described in more detail below) against a wide range of commonly encountered pathogenic organisms may be obtained.

Accordingly, we provide cephalosporin antibiotics of the general formula (I)

(wherein Y represents a carbon-linked 5- or 6-membered unsaturated heterocyclic ring containing at least one nitrogen atom, which ring may also contain one or more sulphur atoms and/or may be substituted by one or more C14 alkyl, oxo, hydroxy or carbamoyl-methyl groups) and non-toxic salts and non-toxic metabolically labile esters thereof.

The compounds according to the invention are syn isomers. The syn isomeric form 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 (1). It also includes within its scope the solvates of nonttoxic salts of formula (I), and non-toxic salts and solvates of non-toxic metabolically labile esters of the compounds of formula (I). It will be appreciated that the solvates should be pharmacologically acceptable.

In formula (I) above, the heterocyclic ring represented by Y may for example contain 1 to 4 nitrogen atoms and, if desired, a sulphur atom, particular examples of these heterocyclic groups including imidazolyl, pyrazolyl, pyridyl, pyrimidyl, pyrazinyl, pyridazinyl, triazolyl, tetrazolyl, thiazolyl, thiadiazolyl, triazinyl and thiazolidinyl. The heterocyclic ring may, if desired, be substituted by one or more (for example, one to three) C14 alkyl (e.g. methyl), oxo, hydroxy or carbamoylmethyl groups. Alkyl or carbamoylmethyl substituents may be attached for example, to the nitrogen heteroatom(s).

The compounds according to the invention exhibit broad spectrum antibiotic activity both in vitro and in vivo. They have good activity against both Gram-positive and Gram-negative organisms, including many fi-lactamase producing strains. The compounds also possess high stability to fi-lactamases produced by a range of Gram-negative and Gram-positive organisms.

Compounds according to the invention have been found to exhibit good activity against strains of Staphylococcus aureus and Staphylococcus epidermidis species including penicillinase producing strains of these Gram-positive bacteria. This is coupled with good activity against various members of the Enterobacteriaceae (e.g. strains of Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, Serratia marcescens, Proteus mirabilis and indole-positive Proteus organisms such as Proteus vulgaris, Proteus morganii and Providence species), and strains of Haemophilus influenzae and Acinetobacter calcoaceticus as well as activity against some strains of Pseudomonas species.This combination of high activity against Gram-positive organisms with high activity against Gram-negative organisms possessed by compounds of the invention is particularly unusual.

Non-toxic salts derivatives which may be formed by reaction of the carboxyl group present in the compounds of formula (I) or by reaction of any acidic hydroxyl group which may be present on the heterocyclic group Y, 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) and other organic base salts (e.g. procaine, phenylethylbenzylamine, dibenzylethylenediamine, ethanolamine, diethanolamine and N-methylglucosamine salts). Other non-toxic salts derivatives include acid addition salts, e.g. formed with hydrochloric, hydrobromic, sulphuric, nitric, phosphoric, formic and trifluoroacetic acids. Where appropriate, the compounds may also be in Zwitterionic or internal salt form. 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 the 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.

It will be appreciated that the group Y may carry a positive charge, e.g. when Y is a 1-methylpyridinium-2-yl group, and when such is the case the positive charge must be balanced by a negative charge. Thus the compounds may be betaines, so that the negative charge is provided by a - COOB group at the 4-position. Alternatively, the negative charge may be provided by an anion AB; such an anion will be non-toxic and may be -derived from any of the acids described above which will form non-toxic salt derivatives.

Non-toxic metabolically labile ester derivatives which may be formed by esterification of the carboxyl group in the parent compound of formula (I) include acyloxyalkyl esters, e.g. lower alkanoyloxy-methyl or -ethyl esters such as acetoxy-methyl or -ethyl or pivaloyloxymethyl esters, and alkoxycarbonyloxyalkyl esters, e.g. lower alkoxycarbonyloxyethyl esters such as the ethoxycarbonyloxtethyl ester. In addition to the above ester derivatives, the present invention includes within its scope the 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 for formula (I).

These and other salts and ester derivatives such as the salts with toluene-p-sulphonic and methanesulphonic acids or the esters with t-butyl or diphenylmethyl esterifying groups, 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.

Preferred compounds according to the invention include those in which Y represents a 1methylpyridinium-2-yl, 1 -methylpyridin iu m-4-yl, 1 -methyltetrazol-5-yl, 1 -methylpyridinium-3-yl, 1 , 2-dimethylpyrazolium-3-yl, 1 , 3-dimethylimidatol ium-3-yl, 1 -methylpyrimidinium-2-yl, 1 -carba- moylmethylpyridinium-4-yl, 2, 5-dihydro-6-hydroxy-2-methyl-5-oxo- 1,2,4-triazin-3-yl, or 4, 5-dihy- dro-6-hydroxy-4-methyl-5-oxo- 1,2,4-triazin-3-yl group. A particularly preferred compound according to the invention is (6 R,7 R)-7-[(Z)-2-(2-aminothiazol-4-yl)-2-cyclopropyl methoxyiminoace tamidoj-3-E( 1 -methylpyridi nium-4-yl)thiomethyl]ceph-3-em-4-carboxylate and its non-toxic salts.

The compounds according to the present invention may exist in tautomeric forms (for example in respect to the 2-aminothiazolyl group or with respect to a 3-substituent such as a 2,5-dihydro 6-hydroxy-2-methyl-5-oxo-1 ,2,4-triazin-3-yl group) and it will be understood that such tautomeric forms are included within the scope of the invention.

The compounds of the invention 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 cephalosporin compounds of general formula

[wherein Y is as defined above, B is

(a- or ss-); the dotted line bridging the 2-, 3- and 4-positions indicates that the compound is a ceph-2-em or ceph-3-em compound; R1 represents hydrogen 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 to 20 carbon atoms) or a symmetrical or mixed anhydride blocking group derived from an appropriate acid; and R2 represents an amino or protected amino group] or salts thereof, which comprises (A) acylating a compound of the formula

(wherein Y, B, the dotted line and R' are as defined above) 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-4-sulphonic acid) or a 7-N-silyl derivative thereof, or alternatively (where Y contains a quaternary nitrogen atom) a corresponding compound having a group of formula -COO at the 4-position, with an acid of formula

(wherein R2 is as defined above) or a salt thereof, or with an acylating agent corresponding thereto;; (B) reacting a compound of formula

(wherein R1, R2, B and the dotted line are as hereinbefore defined, and X is 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 sulphur nucleophile serving to form the group -CH2SY (wherein Y is as defined above) at the 3-position; or (C) where Y in the compound of the invention contains a C14 alkyl-substituted or carbamoylmethyl-substituted quaternary nitrogen atom in the heterocyclic ring, reacting a compound of formula

(wherein R2, B and the dotted line are as defined above;R1 in this instance is a carboxyl blocking group; and Y' represents a carbon-linked 5- or 6-membered heterocyclic ring containing a tertiary nitrogen atom) with a C14 alkylating agent or a carbamoylmethylating agent serving to introduce a C14 alkyl group or a carbamoylmethyl group as a substituent on the tertiary nitrogen atom in the heterocyclic ring of Y'; 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

to form a compound wherein B is

iii) conversion of a carboxyl group into a non-toxic metabolically labile ester function, iv) formation of a non-toxic salt, and v) removal of any carboxyl blocking and/or N-protecting groups.

In the above-described process (A), the starting material of formula (II) is prefdrably a compound wherein B is

and the dotted line represents a ceph-3-em compound.

When the group Y in formula (II) is charged e.g. as in an N-alkylpyridinium group, and the compound contains a group of formula -COOR1 (wherein R1 is as defined above) at the 4position, the compound will include an associated anion Ee such as a halide, e.g. chloride or bromide, or trifluoroacetate anion.

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 halogenating 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 + 50"C, preferably - 40 to + 30"C, if desired in the presence of an acid binding agent. Suitable reaction media include aqueous ketones such as aqueous acetone, aqueous alcohols such as aqueous ethanol, 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'-dicyclohexylcarbodiimide 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 (III) 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-4-sulphonic acid). An activated ester may conventiently be formed in situ using, for example, 1-hydroxyben- zotriazole in 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.

An alternative method of activation is, for example, by reacting an acid of formula (III) with a solution or suspension preformed by adding a carbonyl halide, in particular oxalyl chloride or phosgene, or a phosphoryl halide such as phosphorous oxychloride to a solvent such as a halogenated hydrocarbon, for example methylene chloride, containing a lower acyl tertiary amide such as N,N-dimethylformamide. The activated form of the the acid of formula (III) may then be reacted with a amino compound of formula (II) in a suitable solvent or mixture of solvents for example a halogenated hydrocarbon e.g. dichloromethane.The acylation reaction may conveniently be effected at temperatures of from - 50" to + 50"C, preferably - 40" to + 30"C, if desired in the presence of an acid binding agent, for example as described above (e.g. dimethylaniline).

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

The acids of formula (III) 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.

In process (B) above, the sulphur nucleophile may be used 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 character of the sulphur nucleophile. The latter nucleophile may be employed for example in the form of an appropriate thiol or thione.

The displacement of X by the sulphur nucleophile may conveniently be effected by maintaining the reactants in solution or suspension. The reaction is advantageously effected using 1-10 molar equivalents of the nucleophile.

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 X is an acetoxy group are convenient starting materials for use in the nucleophilic displacement reaction with the sulphur nucleophile. 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 R1 in formula (IV) should be a hydrogen atom and that B should represent

In this case, the reaction is advantageously effected in an aqueous medium.

Under aqueous conditions, the pH value of the reaction solution is advantageously maintained in the range 6-8, if necessary by the addition of a base. The base is conveniently an alkali metal or alkaline earth metal hydroxide or bicarbonate such as sodium hydroxide or sodium bicarbonate.

When using compounds of formula (IV) in which X is an acetoxy group, the reaction is conveniently effected at a temperature of 10 to 110"C, preferably 20 to 80"C.

Halogens Compounds of formula (IV) in which X is a chlorine, bromine or iodine atom can also be conveniently used as starting materials in the nucleophilic displacement reaction with the sulphur nucleophile. When using compounds of formula (IV) in this class, B may conveniently represent

and R1 may represent a carboxyl blocking group. The reaction is conveniently effected in a nonaqueous 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-dimethyl-formamide, 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 R1 is a carboxyl blocking group and the resulting Y group contains a quaternary nitrogen atom, the 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 X is a halogen atom as described above, the reaction is conveniently effected at a temperature of - 20" to + 60 , preferably 0" to + 30"C.

When the incoming nucleophile does not yield a compound containing a quaternised nitrogen atom, the reaction is generally effected in the presence of an acid scavenging agent for example a base such as triethylamine or calcium carbonate.

In process (C) above, the compound of formula (V) is advantageously reacted with a compound of the formula R3Z wherein R3 is a C14 alkyl group or a group of formula H2NCOCH2-, and Z is a leaving group such as a halogen atom (e.g. iodine, chlorine or bromine) or a hydrocarbylsulphonate (e.g. mesylate or tosylate) group. Alternatively, a di-C1 4-alkyl sulphate, e.g. dimethyl sulphate, may be employed as an alkylating agent. lodomethane is preferred as the alkylating agent and iodoacetamide is- preferred as the carbamoylmethylating agent.The reaction is preferably carried out at a temperature in the range of 0 to 60"C, advantageously 20 to 30"C. Where the alkylating agent is liquid under the reaction conditions, as in the case of iodomethane, this agent can itself serve as a solvent. Alternatively, the reaction may be conveniently effected in an inert solvent such as an ether e.g. tetrahydrofuran, an amide, e.g. dimethylformamide, a lower alkanol, e.g. ethanol, a lower dialkylketone, e.g.

acetone, a halogenated hydrocarbon e.g. dichloromethane or an ester e.g. ethyl acetate.

The compound of formula (V) used as starting material in process (C) may be prepared for example by reaction of a compound of formula (IV) (as defined above) with an appropriate sulphur nucleophile in an analogous manner to the nucleophilic displacement reaction described with respect to process (B). If desired the above nucleophile may be used in the form of a metal thiolate salt.

When X in formula (IV) is halogen, the reaction is preferably effected in the presence of an acid scavenging agent, for example a base such as triethylamine or calcium carbonate.

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 ionexchangers (for example by chromatography on ion-exchange resins) or macroreticular resins.

A A2-cephalosporin ester derivative obtained in accordance with the process of the invention may be converted into the corresponding desired A3-derivative by, for example, treatment of the 1v2-ester with a base, such as pyridine or triethylamine.

Where a compound is obtained in which B is

this may be converted into 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 watermiscible 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 the appropriate esterifying agent such as an acyloxyalkyl halide or alkoxycarbonyloxyalkyl 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 an 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 the amide forming derivatives thereof such as 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) and their derivatives may by prepared by etherification of a compound of formula

(wherein R2 is as hereinbefore defined and R4 represents hydrogen or a carboxyl blocking group) or a salt thereof, by selective reaction with a compound of general formula

(wherein T is a halogen atom, such as a chlorine, bromine or iodine atom; a sulphate group; or a sulphonate group, such as p-toluenesulphonate), followed by removal of any carboxyl blocking group R4. Separation of isomers mayn be effected either before or after such etherification.The etherification reaction is conveniently 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 tetrahydro-furan 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 (VII) is used. The base should be used in sufficient quantity to neutralise rapidly the acid in question.

Acids of formula (III) may also be preparted by reaction of a compound of formula (IX)

(wherein R2 and R4 are as hereinbefore defined) with a compound of formula (X)

followed by removal of any carboxyl blocking group R4, and where necessary the separation of syn and anti isomers.

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

Where X is 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 protected amino-3-methylceph-3-em-4-carboxylic acid ester 1ss-oxide, removal of the 7ss-protect- ing group, acylation of the resulting 7amino compound to form the desired 7fl-acylamido group, e.g. in an analogous manner to process (A) above, followed by reduction of the 1oxide 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 for example in British Patent Specifications Nos. 1,474,519 and 1,531,212.

Compounds of formula (II) may also be prepared in conventional manner, e.g. by nucleophilic displacement of a corresponding 3-acyloxymethyl or 3-halomethyl compound with the appropriate nucleophile, e.g. as described in British Patent Specifications Nos. 1,012,943, 1,241,657, 2,027,691A and 2,046,261A.

A further method for the preparation of the starting materials of formula (II) comprises deprotecting a corresponding protected 7amino compound, for example in coventional manner, e.g. using PCI5.

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 reaction. 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. chloro-acetylation or formylation), protonation or other conventional method, so that the protected group is stable to the reaction conditions accompanying one or more synthetic steps.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. acetoxy-methyl or -ethyl or pivaloyloxymethyl) or alkoxycarbonyloxyalkyl groups (e.g. ethoxycarbonyloxyethyl) 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 as pmethoxybenzyloxycarbonyl, pnitrobenzyloxycarbonyl and diphenylmethoxycarbonyl; lower alkoxycarbonyl groups such as tbutoxycarbonyl; and lower haloalkoxycarbonyl groups such as 2,2,2-trichloroethoxycarbonyl.

The carboxyl blocking group 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.

It will be appreciated that the use of amino protecting and carboxyl blocking groups is well known in the art and relevant examples of such use are given in e.g. Theodora W. Greene, "Protective Groups in Organic Synthesis" (Wiley-lnterscience, New York, 1981), and J.F.W.

McOmie, "Protective Groups in Organic Chemistry" (Plenum Press, London, 1973).

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 for 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 for example be presented in a form suitable for absorption by the gastro-intestinal tract e.g. as tablets or capsules.

The antibiotic compounds may also, for example, be formulated as suppositories e.g.

containing conventional suppository bases such as cocoa butter or other glycerides.

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 will preferably contain 100-3000 mg e.g. 200-2000 mg of the active ingredient.

The dosage as employed for adult human treatment will preferably range from 200 to 1 2000 mg e.g. 1000-9000 mg per day, depending on the route and frequency of adminstration. For example, in adult human treatment 400 to 6000 mg per day adminstered intravenously or intramuscularly will normally suffice. In treating Pseudomonas infections higher daily doses may be required. It will be appreciated that in some circumstances, for example in the treatment of neonates, smaller dosage units and daily dosages may be desirable.

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 Examples illustrate the invention. All temperatures are in "C. Sorbsil U30 is silica gel manufactured by Joseph Crosfield and Son of Warrington, Lancashire, England. THF is tetrahydrofuran. DMF is N,N-dimethylformamide. DMSO is dimethylsulphoxide.

Preparation 1 Ethyl (Z)-2-Cyclopropylmethoxyimino-2-(2-tritylaminothiazol-4-yl) acetate Ethyl (Z)-2-hydroxyi m ino-2-(2-tritylaminoth iazol-4-yl) acetate, hydrochloride salt (30g) was stirred with cyclopropylmethyl bromide (13 59) in DMSO (150 ml) containing potassium carbonate (30g) under nitrogen at 21 for 7 hours. The mixture was partitioned between methylene chloride and water. The aqueous layer was extracted with more methylene chloride and the combined organic solutions were washed with water. After drying with magnesium sulphate, the solution was concentrated and loaded onto a column of Sorbsil U30 (2009). The column was eluted with ethyl acetate (10 to 30%) in petroleum ether (b.p. 40-60 ).

Evaporation of appropriate fractions gave the title compound (20.99); AmaX (ethanol) 234.5nm (E,C%m 403); Nnt 254.5nm (E,'C%m 302), 259.5nm (E'C%m 267), 265nm (E1C%m 229), 271.5nm (E1C%m 190) and 294nm (Ea%m 111); #max (CHBr3) 3398 (NH), 1730 (ester), and 1539 and 1491cm-1 (aromatic double bond).

Preparation 2 (Z)-2-Cyclopropylmethoxyimin o-2-(2-tritylaminothiazol-4-yl) acetic acid.

The product of Preparation 1 (20g) was dissolved in ethanol (200 ml) and sodium hydroxide (3.1 2g) in water (40ml) was added. The mixture was refluxed for 45 minutes during which precipitation occurred. Some of the ethanol (ca 150ml) was distilled off and the residue was cooled. The mixture was partitioned between methylene chloride and water containing 2N hydrochloric acid (70 ml). The organic layer was washed with water, each aqueous layer being back-extracted with more methylene chloride.The combined organic layers were dried with magnesium sulphate and evaporated to give the title compound (20 g); Nnt (ethanol) 234.5nm (Er1cm1% 383) 259.5nm (E1%1cm 242), 266.5nm (E1%1cm 226) and 272.5nm (E1%1cm 217); Vmax (Nujol) 3260 (NH) and 1685cm-1 (acid).

Preparation 3 Diphen ylmeth yl (6R, 7R)-3-Bromomethyl-7-[Z)-2-cyclopropylmethoxyimino-2-(2-tritylaminothia- zol-4-yl)-acetamido]ceph-3-em-4-carboxylate Oxalyl chloride (0.37ml) was added to a solution of DMF (0.38ml) in methylene chloride (10ml) at - 20" with stirring under nitrogen.The mixture was stirred with ice-water cooling for ten minutes before recooling to - 20". (Z)-2-Cyclopropylmethoxyimino-2-(2-tritylaminothiazol-4 yl)acetic acid (1.949) was added and the solution was stirred with ice-water cooling for ten minutes before recooling to - 20". A suspension of diphenylmethyl (6R,7R)-7-amino-3bromomethylceph-3-em-4-carboxylate hydrochloride salt (1.989) in methylene chloride (1 0ml) containing N,N-dimethylaniline (1.76ml) was added. A clear solution formed as the mixture was allowed to warm ro 21 over one hour.The solution was washed with dilute hydrochloric acid and water, each wash being back extracted with more methylene chloride and the combined extracts were dried with magnesium sulphate and evaporated to a small volume. This solution was filtered through Sorbsil U30 (50g) in ethyl acetate and the eluate was evaporated. The residue (3.549) was crystallised from diethyl ether-petroleum ether (bp 40 to 60 ) to give the title compound (2.439) mp 135 to 147 , (aTh1 - 1.9 (c 0.6, CHCl3).

Preparation 4 Diphenylmethyl (1 S, 6R, 7R)-3-Bromometh yl- 7-F(Z)-2-cyclopropylmethoxyimino-2-(24ritylaminothi- azol-4-yl)acetamido]ceph-3-em-4-carboxylate, 1-oxide Diphenylmethyl (6R,7R)-3-bromomethyl-7-[(Z)-2-cyclopropylmethoxyimino-2-(2-tritylaminothia- zol-4-yl)acetamido]ceph-3-em-4-carboxylate (1.2 g) was dissolved in methylene chloride (10 ml) and 3-chloroperbenzoic acid (292 mg) was added with stirring and ice-water cooling. After thirty minutes, the solution was washed with aqueous sodium bicarbonate solution and water (twice).

After drying with magnesium sulphate, the solution was concentrated and purified on a column of Sorbsil U30 (50 g) which was eluted with ethyl acetate (50 to 80%) in petroleum ether (b.p.

40 to 60 ) to obtain the title compound (1.1 g); (a]2D1+ 14.2 (c 1.23, CHCl3); Ain5 244.5nm (E3ç%m 260), 258.5nm (E3c%m 232), 266 nm (E3c%m 225), and 272 nm (E3C%m 214).

Example 1 (a) Diphenylmethyl (6R, 7R)-7-[(Z)-2-Cyclopropylmethoxyimino-2-(2-tritylaminothiazol-4-yl)ace- tamido]-3-[(1-methylpyridinium-4-yl)thiomethyl]ceph-3-em-4-carboxylate, bromide Diphenylmethyl (6R,7R)-3-bromomethyl-7-[(Z)-2-cyclopropylmethoxyimino-2-(2-tritylaminothia- zol-4-yl)acetamido]ceph-3-em-4-carboxylate (1.29) was dissolved in THF (20ml) with stirring at 21 and 1-methylpyrid-4-thione (162 mg) was added. After 2.25 hr and 3.75 hr two further portions of 1-methylpyrid-4-thione (50 mg each) were added. After six hours, the solution was diluted with diethyl ether (80 ml) and the mixture was stirred at ice-bath temperature for a few minutes. The precipitate was collected by filtration, washed with diethyl ether and dried to give the title compound (1.27 g), [&alpha;]D21 - 29.7 (c 0.71, DMSO), may (Nujol) 1784 (p-lactam), 1720 (ester) and 1675 and 1520 cm-1 (amide).

(b) (6R, 7R)- 7-C(z)-2-(2-A minoth iazol-4-yl)-2-cyclopropylmethoxyim inoacetamidoj-3-F( 1 -m eth ylpy- ridinium-4-yl)thiomethyl]ceph-3-em-4-carboxylate, dihydrochloride salt.

The above ester (1.1 g) was dissolved in formic acid (4ml) and concentrated hydrochloric acid (0.29ml) was added. After stirring at 21 for 1.5 hours, the mixture was filtered and the filtercake was leached with formic acid. The combined filtrates were evaporated to a gum which was triturated with acetone and dried to give the title compound (560mg), [oi]2D1 - 30.7' (c 1.03, DMSO), vmax (Nujol) 3680-2200 (OH, NH and NH3@), 1780 (ss-lactam), 1710 (C00H) and 1675 and 1550cm-1 (amide).

Example 2 (a) Diphenylmethyl (6R,7R)-7-(Z)-2-Cyclopropymethoxyimino-2-(2-tritylaminothiazol-4-yl)acetami- do]-3-[( 1 -methylpyridinium-2-yl)thiomethyl]ceph-3-em-4-carboxylate Diphenylmethyl (6R,7R)-3-bromomethyl-7-[(Z)-2-cyclopropylmethoxyimino-2-(2-tritylaminothia- zol-4-yl)acetamido]ceph-3-em-4-carboxylate was stirred with 1 -methylpyrid-2-thione (162mg) in THF (20ml) at 21" for two hours. Further 1-methylpyrid-2-thione (160mg) was added. After four days at 21", the solution was refluxed for three hours. Finely divided calcium carbonate (excess) was added and the mixture was stirred again at 21" for two days. The mixture was filtered and the filtrate was diluted with diethyl ether (80 ml).The precipitate was collected by filtration washed with ether and dried to give the title compound(540mg), Ainf (ethanol) 240.5 nm (E'C%m 245), 265nm (E11%m 208), 272nm (E,1%m 198), 308nm (E,1%m 91), vmax (Nujol) 3700-2500 (NH), 1790 (sslactam), 1725 (ester), 1680 and 1520 cm-1 (amide).

(b) (6R, 7R)- 7-[(Z)-2-(2-Aminothiazol-4-yl)-2-cyclopropylmethoxyiminoacetamido]-3-[( I -methylpy- ridinium-2-yl)thiomethyl]ceph-3-em-4-carboxylate, dihydrochloride salt The above ester (480mg) was dissolved in formic acid (2ml) and concentrated hydrochloric acid (0.13ml) was added. After stirring for one hour at 21" the mixture was filtered and the filter cake was leached with formic acid.The combined filtrates were evaporated and the residue was trituated with acetone to give the title compound (300mg) #max (Nujol) 3700-2300 (NH3#, NH and OH), 1780 (fi-lactam), 1710 (acid), and 1680 cm-1 (amide). T(d6-DMSO) includes 0.90(d,J6 Hz), 1.58 (t, J 6Hz), 1.88 (d, J 6Hz) and 2.12 (t, J 6Hz) pyridyl protons; 3.09 (thiazole proton); and 8.88, 9.30 to 9.80, multiplets, cyclopropyl protons.

Example 3 (a) Diphen ylmethyl (6R, 7R)-7-[(Z)-2-Cyclopropylmethoxyimino-2-(2-tritylaminothiazol-4-yl)ace- tamidoj-3j( 1-methyl-i -H-tetrazol- 5-yl)thiometh yl]ceph-3-em-4-carboxylate Oxalyl chloride (0.37ml) was added to a solution of DMF (0.38ml) in methyleme chloride (10ml) with stirring at - 20". The mixture was allowed to warm to 0 for 5 minutes before recooling to - 20". (Z)-2-Cyclopropylmethoxyimino-2-(2-tritylaminothiazol-4-yl)acetic acid (1.94g) was added and the solution was stirred at 0 for 5 minutes.After recooling to - 20", a suspension of diphenylmethyl (6R,7R)-7-amino-3-[(1-methyl-1-H-tetrazol-5-yl)thiomethyl]ceph-3- em-4-carboxylate (1.98g) in methylene chloride (1 Oml) containing dimethylaniline (1.26ml) was added. The solution was allowed to warm to 21 over one hour. The solution was diluted with more methylene chloride and washed with dilute hydrochloric acid. The aqueous layer was extracted with more methylene chloride and the combined organic layers were washed with water, dried with magnesium sulphate and evaporated to a small volume.The solution was chromatographed on Sorbsil U30 (709) in a gradient of ethyl acetate (10 to 50%) in petroleum ether (bp 40 to 60 ) to give the title compound (3.289) as a foam, (a]2D1 -83.4 (c 0.91, CHCI3), #max (CHBr3) 3400 (NH), 1780 (ss-lactam), 1725 (ester) and 1685 and 1515cm-1 (amide).

(b) (6R, 7R)- 7-[(Z)-2-(2-Aminothiazol-4-yl)-2-cyclopropylmethoxtiminoacetamido]-3-[( 1-methyl- 1 - H-tetrazol-5-yl)thiomethyl]ceph-3-em-4-carboxylic acid, trifluoroacetate salt The above ester (3.149) was dissolved in anisole (6.5ml) with stirring at 21" and trifluoroacetic acid (25 ml) was added. After one hour, water (1.5ml) was added. After a further five minutes, the solution was evaporated to half volume and diisopropyl ether (ca 100ml) was added.The precipitate was collected by filtration, washed with diisopropyl ether and dried to give the title compound (2.029), (a]2D1 - 40.7' (c 0.44, DMSO), #max (Nujol) 3700-220 (N H3, OH, NH), 1770 (ss-lactam), 1725 (acid) and 1690 cm~' (amide).

Example 4 a) Diphenylmethyl (1 S, 6R, 7R)-7-[(Z)-2-cyclopropylmethoxyimino-2-(2-tritylaminothiazol-4-yl) acetamidoj-3j( 1 -methylpyridinium-4-yl)thiomethyl]ceph-3-em-4-carboxylate, 1 -oxide, bromide Diphenylmethyl (1 S,6 R,7R)-3-bromomethyl-7-(Z)-2-cyclopropylmethoxyimino-2-(2-tritylamino- thiazol-4-yl)acetamido]ceph-3-em-4-carboxylate, 1-oxide (700 mg) was stirred with N-methylpy- rid-4-thione (125 mg) in THF (15 ml) at 21" for 3.5 hours.Diethyl ether was added and the precipitate was collected by filtration, washed with ether and dried to give the title compound (700 mg), (2D1-31.8' (c0.75, CHCI3), vial (Nujol) 1975 (ss-lactam), 1722 (ester) and 1675 and 1512 cm-' (amide).

b) Diphenylmethyl (6R, 7R)-7-[(Z)-(2-cyclopropylmethoxyimino-2-(2-tritylaminothiazol-4-yl)ace- tamidoj-3j( 1 -methylpyridinium-4-yl)thiomethyl]ceph-3-em-4-carboxylate, mixed halide Diphenylmethyl (1 S, 6 R, 7 R)-7-(Z)-2-cycloprnpylmethoxyimino-2-(2-tntyIa m inothiazol-4-yl)ace- tamido]-3-(( 1 -methylpyridinium-4-yl)thiomethyl]ceph-3-em-4-carboxylate, oxide, bromide (0.30 g) was stirred with potassium iodide (0.24 g) in acetone (2 ml) and DMF (2 ml) with ice-water cooling. Acetyl chloride (0.1 ml) was added and the stirring and cooling continued for three hours. The solution was poured into aqueous sodium metabisulphite solution and the precipitate was collected by filtration.The solid was washed with water and diethyl ether and dried to give the title compound (230 mg) with n.m.r., i.r, and HPLC in accordance with the product of Example 1(a).

The product may be deprotected as in Example 1(b) to give (6R,7R)-7-((Z)-2-(2-aminothiazol-4- yl)-2-cyclopropylmethoxyiminoacetamido]-3-[(1 -methylpyridinium-4-yl)thiomethyl]ceph-3-em-4- carboxylate, dihydrochloride salt.

Example 5 a) Diphenyl (1 S, 6R, 7R)- 7-[(Z)-2-cyclopropylmethoxyimino-2-(2-tritylaminothiazol-4-yl)acetami- do)-3-(pyrid-4-ylthiometh yl)ceph-3-em-4-carboxyla te, 1-oxide Diphenylmethyl (1 S,6R,7R)-3-bromomethyl-7-[(Z)-2-cyclopropylmethoxyimino-2-(2-tritylamino- thiazol-4-yl)acetamido]ceph-3-em-4-carboxylate, 1-oxide (700 mg) was stirred with 4-mercaptopyridine (115 mg) and finely divided calcium carbonate (700 mg) in acetone (20 ml) under reflux for 2hr 10 min. The mixture was cooled and filtered. The filtrate was concentrated and chromatographed on silica gel (50 g). The column was set up in methylene chloride and eluted successively with methylene chloride, ethyl acetate, and 10% ethanol in ethyl acetate.

Evaporation of the appropriate fractions gave the title compound (260 mg) as a foam; [o112d - 14.9'(c0.81, CHCl3) vial (CHBr3) 3485(NH), 1808 (ss-lactam), 1778 (ester) and 1681 and 1512 cm-' (amide).

b) Diphenylmeth yl ( 1 S, 6R, 7R)- 7-[(Z)-2-cyclopropylmeth oxyimino-2-(2-tritylaminothiazol-4-yl) acetamido]-3-[(-methylpyridinium-4-yl)thiomethyl]ceph-3-em-4-carboxylate, 1-oxide, iodide Diphenylmethyl (1 S,6R,7R)-7-[(Z)-2-cyclopropylmethoxyimino-2-(2-trutylaminothiazol-4-yl)ace- tamido]-3-(pyrid-4-ylthiomethyl)ceph-3-em-4-carboxylate, 1-oxide (100 mg) was dissolved in methyl iodide (0.5 ml). After two hours at 21", the solution was diluted with diethyl ether and the precipitate was collected by filtration. This was washed with ether and dried to give the title iodide (70 mg) which resembled the above bromide salt by n.m.r., i.r., and HPLC.

The product may be reduced as in Example 4(b) and deprotected as in Example 1 (b) to give (6 R,7R)-7-[(Z)-2-(2-aminothiazol-4-yl)-2-cyclopropylmethoxyiminoacetamido]-3[(1 -methyl-pyridi niu m-4-yl)thiomethyl]ceph-3-em-4-carboxylate, dihydrochloride salt.

Example 6 a) (6R, 7R)-7-[(Z)-2-cyclopropylmethoxyimino-2-(2-tritylaminothiazol-4-yl)acetamido]-3j( 1,2,5,6tetrahydro-2-methyl-5, 6-dioxo- 1,2, 4-triazin-3-yl)thiomethyl]ceph-3-em-4-carboxylic acid A solution of DMF (0.4 ml) in dichloromethane (0.5 ml) was treated at - 10" with oxalyl chloride (0.1 5 ml) and the mixture was stirred for 15 minutes at - 10'. (Z)-2-Cyclopropylmethoxyimino-2-(2-tritylaminothiazol-4-yl)acetic acid (721 mg) was added. This solution was stirred in an ice-bath for 15 minutes.It was then added to a solution of (6R,7R)-7-amino-3-[(1,2,5,6- tetrahydro-2-methyl-5,6-dioxo-1,2,4-triazin-3-yl)thiomethyl]ceph-3-em-4-carboxylic acid (500 mg) (which may be prepared as described in European Patent Application Specification No 0065748) in industrial methylated spirit (6 ml), water (0.65 ml) and triethylamine (1.9 ml). The resulting solution was stirred at 0" for 1 hour. After stirring for a further 10 minutes at 21", the reaction mixture was partitioned between dichloromethane and 2N hydrochloric acid solution.

The organic layer was separated, washed with water, dried and evaporated to leave the title acid as a foam (1.12 g); (aL-37.91' (c0.91; DMSO), Z',,ax (CHBr3) 3700-2700 (OH), 3395 (NH), 1789 (P-Iactam), 1738 (ester + other carbonyl groups), 1669 and 1523 cm~' (amide).

b) (6R, 7R)- 7-[(Z)-2-(2-aminothiazol-4-yl)-2-cyclopropylmethoxyiminoacetamido]-3-[1, 1,2,6, 6-tet- rahydro-2-methyl-5, 6-dioxo- 1, 2,4-triazin-3-yl)thiomethyl]ceph-3-em-4-carboxylic acid, formate salt The ester from stage (a) (1.169 g) was dissolved in formic acid (9.3 ml). The solution was stirred and water (3.2 ml) was added. The mixture was stirred at 21" for 1.5 hours. Then the solid was filtered off. The filtrate was concentrated to a small volume and diisopropyl ether was added. The resulting solid was collected by filtration washed with diisopropyl ether and dried to leave the title compound as a solid (654 mg); [a]D-51-35 (c0.74; DMSO), vial (Nujol) 3650-2700 (OH + NH), 1779 (fi-lactam), 1738 (ester + dioxo) 1675 + 1530 (amide) and 1625 cm-' (carboxylate).

Example A Dry Powder for injection Fill sterile (6R,7 R)-7-[(Z)-2-(2-aminothiazol-4-yl)-2-cyclopropylmethoxyiminoacetamido]-3-[(1 - methylpyridinium-4-yI)thiomethyl]ceph-3-em-4-carboxylate aseptically into glass via Is, such that each vial contains 1 g of the anhydrous, pure material. Purge the vial headspaces with sterile nitrogen; close the vials using rubber discs, or plugs, and metal overseals (applied by crimping).

The product may be constituted by dissolving in Water for Injections or other suitable sterile vehicle shortly before administration.

Claims (5)

1. Cephalosporin antibiotics of general formula

(wherein Y represents a carbon-linked 5- or 6-membered unsaturated heterocyclic ring containing at least one nitrogen atom, which ring may also contain one or more sulphur atoms and/or may be substituted by one or more C14 alkyl, oxo, hydroxy or carbamoylmethyl groups) and non-toxic salts and non-toxic metabolically labile esters thereof.

2. A compound according to claim 1 in which Y represents a 1-methylpyridinium-2-yl, 1methylpyridin iu m-4-yl, 1 -methyltetrazol-5-yl, 1 -methylpyrid i nium-3-yl, 1,2-d i methylpyrazol iu m-3yl, 1 ,3-dimethylimidazolium-3-yl, 1 -methylpyrimidinium-2-yl, 1 -carbamoylmethylpyridinium-4-yl, 2, 5-dihydro-6-hydroxy-2-methyl-5-oxo- 1,2, 4-triazin-3-yI, or on 4, 5-d ihydro-6-hydroxy-4-methyl-5- oxo-1 ,2,4-triazin-3-yl group.

3. A compound according to claim 1 which is (6R,7R)-7-[(Z)-2-(2-aminothiazol-4-yl)-2cyclopropylmethoxyiminoacetamido]-3-[(1 -methylpyridiniu m-4-yl)thiomethyl]ceph-3-em-4-carboxylate and non-toxic salts thereof.

4. A process for the preparation of compounds according to claim 1 which comprises (A) acylating a compound of formula

[wherein Y is as defined in claim 1; B is

(a- or ss); R1 represents a hydrogen atom or a carboxyl blocking group; and the dotted line bridging the 2-, 3- and 4-positions indicates that the compound is a ceph-2-em or ceph-3-em compound] or a salt or 7-N-silyl derivative thereof or a corresponding compound having a group of formula -COO at the 4-position, with an acid of formula

(wherein R2 is an amino or protected amino group) or a salt thereof, or with an acylating agent corresponding thereto;; (B) reacting a compound of formula

(wherein R', R2, B and the dotted line are as defined above, and X is a replaceable residue of a nucleophile) or a salt thereof, with a sulphur nucleophile serving to form the group -CH2SY (wherein Y is as defined in claim 1) at the 3-position; or (C) where Y in the desired compound according to claim 1 contains a C14 alkyl-substituted or carbamoylmethyl-substituted quaternary nitrogen atom in the heterocyclic ring, reacting a compound of formula

(wherein R2, B and the dotted line areas defined above;R1 in this instance is a carboxyl blocking group; and Y' represents a carbon-linked 5- or 6-membered heterocyclic ring containing a tertiary nitrogen atom) with a C14 alkylating agent or a carbamoylmethylating agent serving to introduce a C14 alkyl group or a carbamoylmethyl group as a substituent on the tertiary nitrogen atom in the heterocyclic ring of Y'; 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 b3-isomer ii) reduction of a compound wherein B is

to form a compound wherein B is

iii) conversion of a carboxyl group into a non-toxic metabolically labile ester function, iv) formation of a non-toxic salt, and v) removal of any carboxyl blocking and/or N-protecting groups.

5. A pharmaceutical composition comprising as active ingredient a compound according to claim 1 in association with a pharmaceutical carrier or excipient.