GB2183629A - Cephalosporin antibiotics - Google Patents

Abstract

Cephalosporin antibiotics of formula (I> <IMAGE> [wherein R<1> is a methyl group or a group -CH=CHR<2> where R<2> is a hydrogen atom or a -C IDENTICAL C-CH3 group] and non-toxic salts and non-toxic metabolically labile esters thereof are disclosed. Processes for their preparation and pharmaceutical compositions containing them are also described.

Description

SPECIFICATION "Cephalosporin antibiotics" This invention relates to improvements in or relating to cephalosporins. More 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 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 development of various types of broad spectrum cephalosporin antibiotics.

Our British Patent Specification No. 1342241 describes a class of cephalosporin antibiotics characterised in that they are substituted at the 3-position by a vinyl group which may optionally be substituted by a substituted or unsubstituted aliphatic, cycloaliphatic, aromatic or araliphatic group.

Our British Patent Specification No. 1399086 describes a novel class of cephalosporin antibiotics containing a 7ss-(x-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. This interest is reflected in the very large numbers of patent applications which have been filed relating to cephalosporin antibiotics having particular oxyimino etherifying groups in combination with particular substituents both on the 7B-acylamido side chain and at the 3-position of the cephalosporin nucleus.

In British Patent Specification Nos. 1604971 and 1603212 a wide variety of cephalosporin antibiotics are generically disclosed in which the 7ss-position side-chain may be selected from, inter alia, a 2-(2-aminothiazol4-yl)-2-(etherified oxyimino)acetamido group, in which the etherifying group, amongst very many possible meanings, may be an alkyl group (e.g. methyl substituted by a halogen atom, although there is no specific exemplification of compounds having such a group and the preferred etherifying group is stated to be an unsubstituted methyl group. Halogen atoms which, when present, are preferred are stated to be chlorine and bromine atoms. The 3-position group may also be selected from a very large number of alternatives and one possible 3-substituent is methyl.GB 1604971 describes cephalosporins having sulphur at the 1-position while GB No. 1603212 describes related 1 -sulphoxides.

In British Patent Application No. 2039890A a wide variety of cephalosporin antibiotics are generically disclosed in which the 7ss-position side chain is a 2-(2-aminothiazol-4-yl)-2-etherified oxyimino)-acetamido group. One possible etherifying group recited is a halo-lower-alkyl group (with the fluoromethyl group being mentioned inter alia as an illustration). The only haloalkyl compounds actually exemplified contain a 2-bromoethyl, 2-chloroethyl or a 2,2,2-trifluoroethyl group. According to the generic definition, the 3-position may carry, inter alia, a methyl group.

British Patent Application No. 201 7702A describes etherified oxyimino cephalosporin antibiotics in which the oxyimino etherifying group, according to the generic definition, may inter alia be a straight chain C14 alkyl group terminally monosubstituted e.g. by a halogen atom. In the compounds specifically exemplified, only 2-bromoethyl and 2-iodoethyl groups are found as examples of haloalkyl groups. The groups at the 3-position include, inter alia, Cs 5 alkyl such as methyl.

Japanese Patent Specification No. 5816794 describes cephalosporin antibiotics having in the 7ss-position a 2- (2-aminothiazol-4-yl) -2-(etherified oxyimino)acetamido group in which the etherifying group is lower alkyl optionally substituted inter alia by fluorine. The 3-substituent is lower alkyl or lower alkoxymethyl and the 4-substituent is esterified carboxyl.

We have now discovered that by the selection of a (Z)-2-(2-aminothiazol-4-yl)-2-(etherified oxyimino)-acetamido group at the 7ss-position in combination with 3 particular substituents at the 3-position, and also by the selection of a monofluoromethoxyimino group as the etherified oxyimino grouping, cephalosporin compounds having a particularly advantageous profile of activity (described in more detail below) against a wide range of commonly encountered pathogenic organisms may be obtained.

According to one aspect of the invention we provide cephalosporin antibiotics of formula (I)

[wherein R1 is a methyl group or a group - CH = CHR2 where R2 is a hydrogen atom or a - C=C- CH3 group] and non-toxic salts and non-toxic metabolically labile esters thereof.

The compounds according to the invention are syn isomers with respect to the configuration of the oximino group. The syn isomeric form is defined by the configuration of the - OCH2F group with respect to the carboxamido group. In this specification, the syn configuration is denoted structurally as

It will be understood that since the oxime group in the 7-side chain in such compounds of the invention resuits in geometrical isomerism, then some admixture with the corresponding anti isomer may occur.

It will further be appreciated that the compounds of formula (I) wherein R' represents the group - CH = CH - C C- CH3 exist as geometrical isomers with respect to the 3-substituent. Thus, the substituent on the double bond may be in the cis i.e.

or trans i.e.

isomer forms. Both such geometrical isomers as well as mixtures thereof are intended to be within the scope of the invention. The compound wherein the 3-substituent is in the trans configuration is preferred.

The compounds of the invention may exist in tautomeric forms (for example in respect of the 2-aminothiazolyl group) and it will be understood that such tautomeric forms, e.g. the 2-iminothiazolyl form, are included within the scope of the invention.

The invention also includes within its scope the solvates (especially the hydrates) of the compounds of formula (I). It also includes within its scope the solvates of non-toxic salts of the compounds of formula (I) and non-toxic salts and solvates of non-toxic metabolically labile esters of the compounds of formula (I).

The compounds according to the invention exhibit broad spectrum antibiotic activity both in vitro and in vivo.

They have high activity against Gram-positive and Gram-negative organisms, including many p-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 high activity against strains (including penicillinase-producing strains) of Gram-positive bacteria such as Staphylococcus aureus, Staphylococcus epidermidis and Streptococcus species. This is coupled with high activity against various members of the Enterobacteriaceae (e.g. strains of Escherichia coli, Klebsiella pneumoniae, Citrobacter diversus, Enterobacter cloacae, Serratia mercescens, Proteus mirabilis and indole-positive Proteus organisms such as Proteus vulgaris, Proteus morgenii and Providence species), and strains of Haemophilus influenzae, as well as activity against Acinetobacter calcoaceticus.This combination of high activity against Gram-positive organisms with high activity against Gram-negative organisms possessed by the compounds of the invention is particularly advantageous.

A preferred compound according to the invention is (6 R, 7 R)-7- (6R, 7R)-7-[(Z)-2-(2-aminothiazol-4-yl)-2-(2- fluoromethoxyimino) -acetamido] -3-vinylceph-3-em-4-carboxylic acid. This compound exhibits high broad spectrum antibiotic activity including high activity against Gram-positive organisms such as Staphylococcus aureus.

Non toxic salt derivatives which may be formed by reaction of the carboxyl group present in the compounds of 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-methylglucosamine 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 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.

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 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 such as ethoxycarbonyloxyethyl esters. 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 compounds of formula (I).

The compounds of formula (i) according to 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. The compounds of formula (I) wherein R1 represents the group -CH = CH2 may also be used for treating skin and soft tissue 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 forming a compound of the formula (lea)

[wherein B is -S- or -SO- (Q- or ss-); R1 is as defined previously, R3 represents hydrogen or a carboxyl blocking group, e.g. the residue or 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;R4 is an amino or protected amino 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, 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) by one of the following processes:: (A) acylating a compound of the formula (II)

(wherein B, R3 and the dotted line are as defined above) or a 7-N-silyl derivative thereof, with an acid of formula (III)

(wherein R4 is as defined above) or a salt thereof, or with an acylating agent corresponding thereto; (B) (to form a compound where R1 represents the group -CH=CHR2) reacting a compound of formula (IV)

(wherein R3, R4, B and the dotted line are as defined above; and Y represents a substituent capable of reacting with one or more reagents to form or introduce a group of formula -CH = CH- R2 at the 3-position) with one or more said reagents, If necessary and/or desired in each instance, where it is desired to form a compound of formula (I) as defined above or a non-toxic salt, solvate, I-oxide or non-toxic metabolically labile ester thereof any of the following steps, in any appropriate sequence, may be 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) oxidation of a compound wherein B is -S-, to form a compound wherein B is -SO iv) formation of a non-toxic salt, v) formation of a solvate, vi) formation of a non-toxic metabolically labile ester, vii) (where R1 represents the group -CH=CH-C=C-CH3) separation of isomers, viii) (where R' represents the group -CH=CH-C=C-CH3) isomerisation of the double bond in the 3-position side-chain from the cis to the trans configuration, or vice versa, and ix) removal of any carboxyl blocking and/or 0- or N-protecting groups.

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

Compounds of formula (la) are new compounds and constitute a feature of the invention.

Acylating agents which may be employed in process (A) for the preparation of compounds of formula (I) include acid halides, particularly acid chlorides or bromides. Such acylating agents may be prepared by reacting a suitable acid, e.g. an acid (Ill) 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 dimethyl-acetamide, 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 (lil) are desirably conducted in the presence of a condensing agent, for example a carbodiimide such as N,N'-dicyclohexylcarbodiimide or N-ethyl-N'-oc-dimethylaminopropylcarbodiimide; a carbonyl compound such as carbonyldiimidazole; an isoxazolium salt such as N-ethyl-5-phenylisoxazolium perchlorate; or N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline.

Acylation may also be effected with other amide-forming derivatives of acids (e.g. acids of formula (III)) such as, for example, an activated ester, a symmetrical an hydride 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, I-hydroxybenzotriazole 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 (e.g. 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 acid may then be reacted with a 7-amino compound of formula (II) in a suitable solvent or mixture of solvents for example halogenated hydrocarbons e.g. dichloromethane; alcohols, e.g. ethanol or industrial methylated spirits; ethers, e.g. tetrahydrofuran or dioxan; esters, e.g. ethyl acetate; ketones, e.g.

acetone; amides, e.g. N,N-dimethylacetamide; acetonitrile; water and mixtures thereof. The acylation reaction may conveniently be effected at temperatures of from - 50D to + 50*C, preferably - 40 C to +30'C, if desired in the presence of an acid binding agent, for example as described above (e.g. dimethylaniline, triethylamine or sodium bicarbonate).

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.

Examples of compounds of formula (IV) employed as starting materials in process (B) above include compounds wherein Y represents a group selected from: i) CH = PRe3 [wherein the groups Re, which may be the same or different, are alkyl, aralkyl, aryl or dialkylamino groups or such a group substituted by one or more halogen atoms, nitro groups, cyano groups, amino groups, substituted amino groups (e.g. alkyl- or acyl-substituted amino groups) or acyl groups] or a Zwitterionic form of the group; ii) CH2Q (where 0 represents the group [PRe3] < 3 (where R" is a defined above), or the group P(O)R::, where the groups R', which may be the same or different, represent an alkoxy, aryloxy or aralkoxy group, which groups may optionally be substituted by one or more halogen atoms, nitro groups, cyano groups, amino groups, substituted amino groups (e.g. alkyl- or acyl-substituted amino groups) or acyl groups);; iii) (CH2)eCHO (where n is zero or 1) or where n is 1, an enol form or derivative (e.g. an acyl derivative) thereof or iv) (CH2)nZ (where n is as defined above and Z represents a readily displaceable atom or group such as a halogen atom, e.g. chlorine or bromine, or an acyloxy group such as trifluoro methanesulphonyloxy, toluene-p-sulphonyloxy, methanesulphonyloxy or acetoxy) Process (Bj may be carried out in an inert solvent, preferably an inert organic solvent, and conveniently at a temperature of from - 80 to + 1 20 C, preferably from 0 to 80"C. Suitable inert organic solvents include, for example, a hydrocarbon, e.g. benzene or toluene; a halogenated hydrocarbon, e.g. dichloromethane; an ether, e.g. diethyl ether, tetrahydrofuran or dioxan; an amide, e.g. dimethylformamide, dimethylacetamide or hexamethyl phosphoramide; a sulphoxide, e.g. dimethylsulphoxide; or a sulphone, e.g. sulpholane.

In a particular embodiment of process (B), a compound according to the invention may be prepared by reacting a compound of formula (IV) wherein Y represents the group -C PRe3, or a Zwitterionic form thereof, with a carbonyl compound of the formula (V) R2-CHO (V) (wherein R2 is as defined previously).

In this embodiment of the process, the reaction is preferably carried out in a two-phase system containing water and a water immiscible organic solvent, such as a halogenated hydrocarbon, e.g. dichloromethane.

The compounds of formula (IV) wherein Y represents the group -CH = PRe3 may be formed in situ from a phosphonium compound of formula CH2ePR%, by reaction with a base. Suitable bases include, for example, alkali metal and alkaline earth metal hydroxides, carbonates and hydrogen carbonates, e.g. sodium hydroxide or sodium hydrogen carbonate; disodium hydrogen phosphate; hydrides, e.g. sodium hydride; and organic bases such as tertiary nitrogen bases, e.g. triethylamine; or alkyl lithiates, e.g. butyl lithium.

In a further embodiment of Process (B) a compound of formula (IV) wherein Y represents the group -CH2Q, or a salt thereof, may be reacted with a carbonyl compound of formula (V) in the presence of a base, to form a compound according to the invention. Suitable bases include those described above.

The compounds of formula (IV) wherein Y represents the groups -C= PRe3 or -CH2Q may be prepared in conventional manner, for example by methods analogous to those described in British Patent Specifications No.1,342,241 or European Patent Application No.30,630.

According to another embodiment of process (B), a compound of the invention may be prepared by reacting a compound of formula (IV) wherein Y represents the group -(CH2)nCHO or an enol form or derivative thereof, with a metal salt having an anion of formula R2(CH2) len (Vl) (wherein R2 is as defined previously and m is zero when n in the group Y is 1, or is 1 when n is zero).

Examples of metals capable of forming a salt with an anion of formula (Vl) include lithium, magnesium, mercury, zinc, cadmium and copper.

When Y represents the group -CHO (i.e. when n is zero), a compound of formula (IV) may be reacted with a compound of formula (VII) R2-CH=PR'3 (ill) or a compound of formula (VIII) R2CH2Q (veil) (wherein R2, Re and Q are as defined previously), the reaction with a compound of formula (VIII) being carried out in the presence of a base. Suitable bases include alkali metal and alkaline earth metal hydroxides, carbonates and hydrogen carbonates, e.g. sodium hydroxide and sodium hydrogen carbonate; and organic bases such as tertiary nitrogen bases, e.g. triethylamine and alkyl lithiates, e.g. butyl lithium.

If desired, a compound of formula (VII) may be generated by reaction of a corresponding phosphonium compound with a base. Suitable bases include those described above for the reaction of a compound of formula (VIII) with a compound of formula (IV).

Compounds of formula (IV) wherein Y represents the group -(CH2)nCHO may be prepared in conventional manner, for example, by the methods described in British Patent Specification No. 1155024, United States Patent No.3351596 or European Patent Application No.53962.

According to a still further embodiment of Process (B), a compound of the invention may be prepared by reacting a compound of formula (IV) wherein Y represents the group -(CH2)nz (wherein n and z are as defined above) with a metal salt having an anion of formula [R2CHU]e (IX) [wherein R2 is as defined previously and U represents = CH when n in the group Y is zero, or the group S(O)WR or Se(O)wR (where w is 1 or 2 and R is an aryl or an aralkyl group) when n in the group Y is 1].

Examples of metals capable of forming a salt with an anion of formula (IX) include those described above.

When U represents = CH, the metal salt having the anion of formula (IX) may be in the form of a metal (e.g.

copper) complex, for example LiCu(CH = CHR2) T, where T may represent the group (CH = CH R2) or an organic group capable of forming a complex with copper but which will not participate in the reaction.

Compounds of formula (IV) wherein Y represents the group -(CH2)nZ may be prepared in conventional manner, for example, by the methods described in British Patent Specifications Nos. 1326531 and 1461323.

It will be appreciated that in the above reaction of a compound of formula (IV) where Y represents a group -(CH2)nCHO with a metal salt having an anion of formula (VI) an intermediate alcohol may be formed; this may be converted to a compound of the invention with the required carbon-carbon double bond by elimination of water. It may be convenient to convert the intermediate alcohol to an acylated derivative, such as a tosylate, mesylate or acetate and effect an elimination reaction on the acylate so formed.The intermediate which may be formed by reaction of a compound of formula (IV) wherein Y represents the group -(CH2)nZ with a metal salt having an anion of formula (IX), wherein U represents the group S(O)WR or Se(O)"R may be converted into a compound of the invention with the required carbon-carbon double bond at the 3-position, by elimination of a sulphenic or sulphinic acid (or the corresponding selenic acid).

Such elimination reactions described above may be effected in a conventional manner, for example, in an inert organic medium, such as that in which the intermediate was formed and at a temperature of from 0 to 100"C. If desired the elimination reaction may be effected in the presence of a catalyst such as a non-nucleophilic base e.g. triethylamine.

The reaction product from the above processes 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.

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 A2-ester with a base, such as pyridine or triethylamine.

A ceph-2-em or ceph-3-em reaction product may also be oxidised to yield the corresponding ceph-3-em 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 desired ceph-3-em sulphide.

Where a compound is obtained in which B is -SO- this may, if desired, be coverted 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 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.

Where any of the above processes produce a mixture of cis and trans geometrical isomers, these may be separated, as desired, by conventional techniques, e.g. by crystallisation, fractional crystallisation or chromatography. Similarly, where the compounds contain an oxime group in the 7-side chain and are obtained as a mixture of syn and anti isomers, the syn isomer may be obtained by such conventional methods.

In order to facilitate the separation of the cis and trans isomers, it may be convenient to oxidise the mixture of cephalosporin cis and trans isomers to the corresponding sulphoxides, separate the cis and trans isomers by the methods described above and, if desired, reduce the sulphoxides to the required sulphides, for example by the methods herein described.

If necessary and/or desired, the cis isomer may be isomerised to the corresponding trans isomer, for example, by heating a mixture of the cis and trans isomers in an inert solvent such as toluene at a temperature of, for example, from 80 to 11 0 C.

In some cases, for example, when no oxime substituent is present, the reaction mixture may advantageously contain an isomerisation catalyst, such as iodine.

Metabolically labile ester derivatives of the compounds of formula (I) may be prepared by reacting the compound of formula (I) or a salt or protected derivative thereof with the appropriate esterifying agent such as an acyioxyalkyl 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 the 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.

Compounds of formula (ill) used as starting materials in process (A) may generally be prepared by N-deacylating compounds of formula (X)

(wherein R2, R3, B and the dotted line are as defined above, and R5 represents a carboxylic acyl group selected from e.g. formyl, phenoxyacetyl, phenylacetyl, substituted phenoxy- or phenlacetyl, thienylacetyl, or 5-aminoadipoyl, or the latter having one or both of the carboxyl and amino groups thereof blocked; or t-butoxycarbonyl or such carbonic acyl group; or the group R5 and the adjacent hydrogen atom together represent a diacyl grouping derived from a diacarboxylic acid, e.g. a phthalimido or maleimido group, R5NH thus being an N-attached heterocyclic group. The compounds of formula (X) may themselves be prepared by methods analogous to process (B) above.The N-deacylation may be effected in conventional manner, e.g. using PCl5 as described in British Patent Specification No. 1241655.

Alternatively the compound of formula (II) may be prepared from a 7-amino cephalosporin compound by methods analogous to process (B) above.

Acids of formula (III) and their derivatives may be prepared by etherification of a compound of formula (XI).

(wherein R4 is as hereinbefore defined and R6 represents hydrogen or a carboxyl blocking group) or a salt thereof, by selective reaction with a compound of general formula (XII).

A.CH2-F (ill) (wherein A is halogen, such as chloro, bromo or iodo; sulphate; or sulphonate, such as tosylate), followed by removal of any carboxyl blocking group R6. Separation of isomers may 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 tetrahydrofuran or dioxan, or an N, N-disubstituted amide such as dimethlyformamide. 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 (Xl) is used.The base should be used in sufficient quantity to neutralise rapidly the acid in question.

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

(wherein R4 and Re are as hereinbefore defined) with a compound of formula (XIV) H2N.O.CH2-F (XIV) followed by removal of any carboxyl blocking group R6, 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.

For use as starting materials for the preparation of compounds of general formula (I), compounds of general formula (III) and acid halides and anhydrides corresponding thereto, as well as compounds of formula (IV) are preferably used 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.

It should be appreciated that in some of the above transformations it may be necessary to protect any sensitive groups in the compound in question to avoid undesirable side reactions. Suitable protecting group are described in, e.g. "Protective Groups in Organic Chemistry" by J.F.W. McOmie (Plenum Press, London, 1973) and "Protective Groups in Organic Synthesis" by Theodora W. Greene (Wiley Interscience, New York, 1981). For example, during any of the reaction sequences referred to above it may be necessary to protect any NH2 group e.g. in an aminothiazolyl moiety, for example by tritylation, acylation (e.g. chloroacetylation or formylation), 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 or hydroxyl protecting groups used in the preparation of compounds of the invention 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 acyloxymethyl or -ethyl groups (e.g.

acetoxymethyl or -ethyl or pivaloyloxymethyl) and retain these in the final product to give an appropriate ester derivative of the compound of formula (I).

Suitable carboxyl blocking and hydroxyl protecting groups are well known in the art, a list of representative blocked carboxyl groups being included in British Patent No. 1399086. Preferred blocked carboxyl groups include aryl lower alkoxycarbonyl groups such as p-methoxybenzyloxycarbonyl, p- nitrobenzyloxycarbonyl and diphenylmethoxycarbonyl; lower alkoxycarbonyl groups such as t-butoxycarbonyl; and lower haloalkoxycarbony groups such as 2,2,2-trichloroethoxycarbonyl. Representative hydroxyl protecting groups include alkyl, aralkyl, aryl and acyl groups. The blocking and/or protecting groups may subsequently be removed by any of the appropriate methods disclosed in the literature; thus, for example, acid catalysed hydrolysis or reduction is applicable in many cases, as are enzymically-catalysed hydrolyses.

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, for example, 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.

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 1 00-30G0 mg of the active ingredient e.g. 200-2000 mg. The daily dosage for adult human treatment will preferably range from 200 to 12000 mg e.g. 1000-9000 mg per day, depending inter alia on the nature of the infection and the route and frequency of administration. In general, intravenous or intramuscular administration will be employed, for example using 400 to 6000 mg per day, e.g. 500 to 4000 mg per day of the active ingredient in adult human treatment. 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 illustrates the invention. All temperatures are in "C; DMSO is dimethylsulphoxide; EtOH is ethanol. Sorbsil U30 is silica gel manufactured by Joseph Crosfield and Son of Warrington, Cheshire, England. (Sorbsil is a registered Trade Mark). Kieselgel 60 is silica gel manufactured by E. Merck and Co. of Darmstadt, West Germany. (Kieselgel is a registered Trade Mark.) INTERMEDIATE 1 Ethyl (Z) -2-fluoromethoxyimino-2- (2-tdphenylmethyl-aminothiazol-4-yl)acetate Ethyl (Z) -2-hydroxyimino-2- (2-triphenylmethyl-aminothiazol-4-yl)acetate, hydrochloride salt (8.79) was stirred with potassium carbonate (15.359) in dimethyl sulphoxide (30ml) under nitrogen at 21".

Bromofluoromethane (ca 39) was added. The nitrogen flow was stopped and the stirring continued for two hours. The mixture was poured into an ice-water mixture with stirring and the solid was collected by filtration and washed with water. The solid was dissolved in methylene chloride and the organic layer was separated and dried with magnesium sulphate. Evaporation gave a foam. This was dissolved in methylene chloride and pre-absorbed onto Kieselgel 60 (509). This was added to the top of a column of similar silica (1 25g) set up in 1 ouzo ethyl acetate in cyclohexane. The column was eluted successively with 10%, 20% and 33% ethyl acetate in cyclohexane. After combination of appropriate fractions, evaporation gave the title compound (8.06g) as a foam; 7Lm,, (EtOH) 302nm (Ei1cm 92), kinfl include 227.5nm (Ei1cm 546) and 259nm (E1cm 221), Vmax (CHBr3) 3400 (NH), 1739 (ester) and 1 533cam~' (C= N).

INTERMEDIATE 2 (Z) -2-Fluoromethoxyimino -2- (2-triphenylmethylamino - thiazol-4-yl)acetic acid.

Intermediate 1 (7.89) was stirred under reflux with sodium hydroxide (0.83g) in ethanol (50ml) and water (1 Oml) for 15 minutes. The mixture was cooled and the crystalline precipitate was collected by filtration and washed with ethanol and ether and dried. This solid was partitioned between methylene chloride (80ml) and water (40ml) with vigorous stirring and 88% orthophosphoric acid (2ml) was added. Solid remained and this was collected by filtration. This solid was suspended in tetrahydrofuran (75ml) and 2M hydrochloric acid (8ml) was added when a solution formed. Evaporation reduced the volume of solution by one half and methylene chloride (50ml) was added.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 solid, the title compound (4.82g); #infi include 224nm (Ei%m 564), 254.5nm (Elcm 213) and 260nm (Elem 205); T (d6DMSO) 1.02 (s; NH), 2.64 (s; phenyl protons) 2.91 (s; thiazole 5-H), and 4.29 (d, J 56Hz; CH2F).

EXAMPLE 1 (a) Diphenylmethyl (6R, 7R) -3-methyl- 7-f(Z) -2-fluoromethoxyimino -2- (2-triphenylmethylaminothiazol-4- yl)acetamidojceph-3-em-4-carhoxylate Oxalyi chloride (0.19 ml) was added to a solution of DMF (0.19 ml) in methylene chloride (10 ml) with stirring at -20' under nitrogen and the mixture was then stirred for 10 minutes with ice-water cooling. The mixture was recooled to -20' and (Z)-2-fluoromethoxyimino-2-(2-triphenylmethylaminothiazol-4-yI)acetic acid (1 g) was added. The solution was stirred with ice-water cooling for 10 minutes before recooling to - 20'.

A solution of diphenylmethyl (6R,7R) -7-amino-3-methylceph-3-em-4-carboxylate (761 mg) and N,Ndimethylaniline (0.63 ml) in methylene chloride (10 ml) was added and the solution was allowed to warm to 21 over 30 minutes. The solution was washed with dilute hydrochloric acid and water twice, each time back extracting with methylene chloride. The combined organic layers were dried with magnesium sulphate and evaporated. The concentrated solution was loaded onto a column of Sorbsil U30 (50 g) set up in 10% ethyl acetate in petroleum ether (b.p. 40 to 60 ) and the column was eluted with 10% to 60% mixtures of these solvents and finally with ethyl acetate.Combination of appropriate fractions and evaporation gave the title compound(1.21 g) [a2J -15.8 (C 0.44, chloroform), nmay (CHBr3) 3390 (NH), 1784 (ss-lactam), 1726 (ester), and 1690 and 1525 cm-' (amide).

(b) (6R,7R)- 7-f (Z) -2- (2-Aminothiazol-4-yl) -2-fluoromethoxyAminoacetamido]-3-methylceph-3-em-4- cerhoxyllc acid The above ester (1.12 g) was dissolved in anisole (3 ml) and trifluroacetic acid (12 ml) was added. After 45 minutes at 21 , water (1.5 ml) was added.After a further 4 minutes, the solution was diluted with diisopropylether (150 ml) and the precipitate was collected by filtration, washed with diisopropyl ether and dried in vacuo at 50 for one hour to give the title compound (510 mg) [0!]2D2 + 72.7 (c 1.07, DMSO), Xmax (pH 6 buffer) 227 nm (Elcm 382), #infi 252 nm (E"Cm 280), Xinfl 294 nm (E1tMcm 119).

EXAMPLE 2 (a) Diphenylmethyl (3E,6R,7R,2Z)-7-[2-fluoromethoxyimino-2-(2-tritylaminothiazol-4- yl) acetamido]-3- (pen- 1-ene-3-yne- 1 -ylJceph-3-em-4-carboxylate Oxalyl chloride (0.15 ml) was added to a solution of DMF (0.2 ml) in methylene chloride (10 ml) with stirring under nitrogen at -20 and the mixture was stirred with ice-water cooling before recooling to -20'.

(Z) -2-fluoromethoxyimino-2- (2-tritylaminothiazol -4-yl)acetic acid (750 mg) was added and the solution stirred with ice-water cooling for 10 minutes before recooling to -20'. A solution of diphenylmethyl (3E,6R,7R)-7amino-3-(pent-1 -ene-3-yne-1 -yl)ceph-3-em-4-carboxylate, hydrochloride salt (700 mg) in methylene chloride (10 ml) containing N,N-dimethylaniline (1 ml) was added and the solution was allowed to warm to 21 over 30 minutes. The solution was washed successively with dilute hydrochloric acid and water twice, each time back extracting with methylene chloride.The organic layer was dried (sodium sulphate) and the solution was concentrated and loaded onto a column of Sorbsil U30 (50 g) set up in ethyl acetate (10%) in petroleum ether (b.p. 40 to 60 ) and the column was eluted with mixtures of ethyl acetate (10 to 50%) in petroleum ether (b.p.

40 to 60). Combinations and evaporation of appropriate fractions gave the title compound (1.1 3g), [a]3D1 99.4 (C6.87, chloroform), vmax (CHBr3) 3385 (NH), 2212 (C=C), 1782 (p-lactam), 1721 (ester), and 1688 and 1512cm- (amide).

(b) (3E,6R,7R,2'Z))-7-[2-(2-Aminothiazol-4-yl)-2-fluoromethoxyiminoacetamido]-3- (pent- 1 -ene-3-yne- 1 - yl)ceph-3-em-4-carhoxylic acid The above protected ester (1.05 g) was dissolved in anisole (3 ml) and trifluoroacetic acid (12 ml) was added.

After one hour at 21 , water (1.5 ml) was added. After one minute, the solution was poured into diisopropyl ether (300 ml). The precipitate was collected by filtration, washed with diisopropyl ether and dried to give the title compound (500 mg), ;imax (pH6 buffer), 227.5nm (E,CYom 353), 313 nm (Elcm 526), #infi 250 nm (E1cm 230), max (Nujol) 3700 to 2100 (NH2, NH, COOH), 2215 (C=C), 1770 (ss-lactam), 1690 (COOH), and 1665 and 1539 cm-1 (amide).

EXAMPLE 3 (a) Diphenylmethyl (6R, 7R,2 2) -[2-fluoromethoxyimino-2- (2-tritylaminothiazol-4-yl)acetemido-3- vinylceph3-em-4-carboxylate Oxalyl chloride (0.19 ml) was added to a solution of DMF (0.19 ml) in methylene chloride (10 ml) with stirring under nitrogen at - 20 and the mixture was stirred with ice-water cooling for ten minutes before recooling to -20 . (Z)-2-fluoromethoxyimino-2-(2-tritylaminothiazol-4-yl) acetic-acid (1.0 g) was added and the solution was stirred with ice-water cooling for ten minutes before recooling to - 20 . A slurry of diphenylmethyl (6R,7R) -7-amino-3-vinylceph-3-em-4-carboxylate, hydrochloride salt (860 mg) in methylene chloride (10 ml) containing N,N-dimethylaniline (0.95 ml) was added and the solution was allowed to warm to 20 over 30 minutes. This solution was washed successively with dilute hydrochloric acid and water twice, each time back extracting with methylene chloride. The combined organic layers were dried (sodium sulphate) and concentrated before loading onto a column of Sorbsil U30 (50 g) set up in 10% ethyl acetate in petroleum ether (b.p. 40 to 60 ). The column was eluted with this mixture, then 20%, then 30% and finally 40% ethyl acetate in petroleum ether (b.p. 40 to 60 ). Combination of the appropriate eluate and evaporation gave the title compound (1.21 g), [e]2D1 -69.0 (C0.83, chloroform), vmax (CHBr3) 3390 (NH), 1786 (ss-lactam),1726 (ester),1690 and 1520 (amide) and 914 cm- (=CH2.

(b) (6R,7R,2 2)- -7-[2-(2-Aminothiazol-4-yl) -2-fluoromethoxyAminoaetamido]-3- vinylceph-3-em-4-carboxylic acid The above protected ester (1.12 g) was dissolved in anisole (3 ml) and trifluoroacetic acid (12 ml) was added.

After 45 minutes at 21 , water (1.5 ml) was added. After one further minute, the solution was poured into diisopropyl ether (150 ml). The precipitate was collected by filtration, washed with diisopropyl ether and dried to give the titie compound (590 mg), [&alpha;]21D - 71.5 (C 1.01, DMSO), Vmax (pH6 buffer) 225.5 nm (E4i%m 381), 289 nm (Ei1,'m 428).

Claims (3)

1. Cephalosporin antibiotics of formula (I)

[wherein R1 is a methyl group or a group -CH=CHR2where R2 is a hydrogen atom ora -C~C-CH3 group] and and non-toxic salts and non-toxic metabolically labile esters thereof.

2. The compound of claim 1 wherein R1 is a group -C=CH-C=C-CH3 in the trans configuration.

3. The compound of claim 1 wherein R1 is a group -CH = CH2.