GB2210877A - Cephalosporins - Google Patents

Abstract

Cephalosporin compounds are disclosed of the general formula (I> <IMAGE> wherein R<1> represents a hydrogen atom or a carboxyl blocking group; R<2> represents a hydrogen atom or an amino protecting group; R<3> and R<4> each represents a hydroxy or substituted hydroxy group or R<3> and R<4> together represent a cyclic protected diol group; Z is @S or @S->O ( alpha - or beta -); the dotted line bridging the 2-, 3-, and 4-positions indicates that the compound is a ceph-2-em or ceph-3-em compound; and non-toxic salts and solvates thereof.

Description

CHEMICAL COMPOUNDS The present 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 beinas and animals.

Cephalosporins 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.

Thus, for example, in our British Patent Specification No.

1399086, we describe a novel class of cephalosporin antibiotics containing a 7p-(a-etherified oxyimino)acylamido side chain. This class of antibiotic compounds is characterised by good antibacterial activity against a range of Gram-positive and Gram-negative organisms coupled with particularly high stability to ss-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 substituents both on the 78-acylamido side chain and at the 3-position of the cephalosporin nucleus.

For example, British Patent Specification No. 1576625 contains a generic definition of cephalosporin antibiotics having a 7 > (a- etherified oxyimino)acetamido side chain wherein the etherifying group is an aliphatic hydrocarbon group which may have suitable substituents including, amongst a large number of possibilities a phenyl group substituted by up to three hydroxy groups. The side chain is further a-substituted by a group which inter alia may be an aminothiazolyl group. None of the compounds specifically exemplified contains a phenylalkyl etherifying group. The substituent at the 3-position may also be selected from a large number of alternatives but a hydrogen atom is not included in the list of substituents.

In British Patent Specification No. 1604971 a wide variety of cephalosporin antibiotics are generally disclosed in which the 7ss-position side chain may be selected from inter alia a 2-(2-aminothiazol-4-yl)-2-(etherified oxyimino)acetamido group, in which the etherifyinq aroup, amongst very many possible meanings, may be. an alkyl group (for example methyl) substituted by a phenyl group. There is no specific exemplification of compounds having a phenylalkyl group and the preferred etherifying group is stated to be an unsubstituted methyl group. The 3-position group may also be selected from a large number of alternatives and possible 3-substituents within the generic definition include a hydrogen atom.

In European Patent Specification No. 178527 the oxyimino substituent, according to the generic definition, may be a benzoyl or benzoylalkyl group, the phenyl group of which may be substituted by hydroxy, alkanoyloxy or alkoxycarbonyloxy groups. The 3-position may also be selected from a number of alternatives and a 3-hydrogen atom is included in the list of substituents.

European Patent Specification No. 197409 generically discloses cephalosporin antibiotics in which the 7 & osition side chain is a 2-(2-aminothiazol-4-yl)-2-(etherified oxyimino) acetamido group. The oxyimino etherifying group may be inter alia a catechol methyloxyimino group. The 3-position substituent may be selected from a number of alternatives but these do not include a hydrogen atom.

We have now discovered that by the selection of a (Z)-2-(2- aminothiazol-4-yl)-2-(etherified oxyimino)acetamido group at the 7P-position in combination with a hydrogen atom at the 3-position, and by the selection of a substituted phenylmethoxyimino group as the etherified oxyimino grouping, cephalosporin compounds may be obtained that have a particularly advantageous profile of activity (described in more detail below) against a wide range of commonly encountered pathogenic organisms and/or that are of use as intermediates in the preparation of other active compounds.

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

wherein R1 represents a hydrogen atom or a carboxyl blocking group; R2 represents a hydrogen atom or an amino protecting group; R3 and R4 each represents a hydroxy or substituted hydroxy group or R3 and R4 together represent a cyclic protected diol group; Z is > S or > S4O (a- or & ; the dotted line bridging the 2-, 3-, end 4-positions indicates that the compound is a ceph-2-em or ceph-3-em compound; and non-toxic salts and solvates (especially hydrates) thereof.

In the compounds of formula (I), where Rl represents a carboxyl blocking group, the blocking group may be for example the residue of an ester-forming aliphatic or araliphatic alcohol or of an ester-forming phenol, silanol or stannanol (the said alcohol, phenol, silanol or stannanol preferably containinq from 1 to 20 carbon atoms) or a symmetrical or mixed anhydride blocking group derived from an appropriate acid. Particular examples of R1 include t-butyl, 2,2,2trichloroethyl, diphenylmethyl and p-nitrobenzyl.

Where R2 is an amino protecting group, the protecting group may be for example a C7-20 aralkyl group (for example a triphenylmethyl or 4-methoxybenzyl group), an acyl group, such as an optionally substituted C16 alkanoyl group (for example a formyl or chloroacetyl group) or an optionally substituted C16 alkoxycarbonyl group (for example a t-butoxycarbonyi or 2,2,2-trichloroethoxycarbonyl group), or a C7-10 aralkyloxycarbonyl group (for example a benzyloxycarbonyl group) or a silyl group (for example a tri-methylsilyl group).

When R3 or R4 represents a substituted hydroxy group it may be for example an alkoxy group [for example a group of formula -OR5 (where R5 is a C18 alkyl group) for example a methoxy or ethoxy group], an arylalkoxy group (for example an O-benzyl group), an acyloxy group te.g. a formyloxy group or a group of formula -OCOR5 (where R5 is as defined above), for example an acetoxy group ], a carbonate group -OCû2R5 (where R5 is as defined above) or a silyloxy group [for example a (C,4alkyl)silyloxy group such as a trimethylsilyloxy or a t-butyldimethylsilyloxy group).

Where R3 and R4 together form a cyclic protected diol grouping, this may be an alkylidenedioxy group, preferably having 1-20 carbon atoms, e.g. a methylenedioxy, ethylenedioxy or isopropylidenedioxy group which may carry one or more substituents e.g. phenyl, C1,4alkoxy, or oxo substituents, for example methoxymethylenedioxy, diphenylmethylenedioxy or carbonyldioxy groups; a cyclic borate group, for example -OB(OH)O-, or -OB(OR6)0- (where R6 is a C14 alkyl group), a cyclic phosphate group, for example -OP(O)(OH)O-, or -EP(O)(OR6)0- (where R6 is as defined above) or a cyclic silyl ether group, e.g. a di(C1-4alkyl)silyldioxy group for example a dimethylsilyldioxy group.

In general, such silyloxy, borate or phosphate groups represent protected hydroxy groups which may be cleaved to provide a compound of formula (I) having free hydroxyl groups.

In the compounds of formula (I), Z is preferably > S.

Ceph-3-em compounds of the invention are particularly preferred.

Where the compound is to be used in medicine any metabolically labile ester function in the molecule should be non-toxic. Examples of non-toxic metabolically labile ester derivatives include acyloxyalkyl esters, for example, lower alkanoyloxymethyl or alkanoyloxyethyl esters such as acetoxymethyl or acetoxyethyl or pivaloyloxymethyl esters, alkoxycarbonyloxyethyl esters, for example, lower aikoxycarDonyloxyethyl esters such as the ethoxycarbonyloxyethyl ester, dioxenolone esters, for example a 5-methyl-2-oxo-1 , 3-dioxolen-4-yl methyl ester group and phthal idyl esters.

In addition to the above ester derivatives, it will be understood that the present invention includes within its scope the active compounds of the invention 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 the invention.

Non-toxic salt derivatives of 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 crosslinked polystyrene divinylbenzene copolymer resin containing amino or quaternary amino groups or sulphonic acid groups, or with a resin containing carDoxyl 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 De readily 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.

The compounds according to the invention are syn isomers. The syn isomeric form is defined by the configuration of the O-substituent group with respect to the carboxamido group. In this specification, the syn confiquration is denoted structurally as shown in formula (I). 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 compounds according to the present invention may exist in different tautomeric forms (for example in respect of the 2-aminothiazolyl group) and it will be understood that such tautomeric forms, e.g. the 2-iminothiazolinyl form, are included within the scope of the invention.

As indicated previously, the compounds of the invention are active against a wide range of commonly encountered pathogenic organisms and/or are of use as intermediates for the preparation of other active compounds. In general, when the compounds of the invention are to be used as intermediates the group R1 will often be a carboxyl blocking group; the group R2 will often be an amino protecting group, and the groups R3 and R4 will often be protected hydroxy groups such as silyloxy groups, or together will be a cyclic protected diol group. Non-toxic derivatives wherein R3 and/or R4 represent acyloxy groups such as acetoxy groups may serve as either intermediates or as active compounds.

In general, active compounds of the invention will be ceph-3-em compounds of formula (I) in which R1 and R2 represent hydrogen atoms Z represents > S and R3 and R4 which may be the same or different represent hydroxy or CrC4 acyloxy groups e.g. acetoxy groups.

Important active compounds according to the invention have the formula (lea)

wherein R3a is a hydroxy or acetoxy group; R4a is a hydroxy or acetoxy group; and the non-toxic salts, solvates (including hydrates) and metabolically labile esters thereof.

A particularly preferred compound of the invention is: (6R,7R,2'Z)-7-t2-(2-aminothiazol-4-yl)-2-[(3,4-dihydroxy- phenyl)methoxyimino]acetamido]ceph-3-em-4-carboxylic acid; and the non-toxic salts, solvates (including hydrates) and metabolically labile esters thereof.

Compounds according to the invention exhibit broad spectrum antibiotic activity against both Gram-positive and Cram-negative organisms, including many ss-lactamase producing strains. The compounds also possess high stability to ss-lactamases produced by a range of Gram-negative and Gram-positive orqanisms.

Compounds acccording to the invention have been found to exhibit high activity against strains (including penicillinaseproducing strains) of Gram-positive bacteria such as Staphylococcus aureus, Staphylococcus epidermidis and Streptococcus species. This is coupled with excellent activity against Pseudomonas species, and also with high activity against various members of the Enterobacteriaceae (e.g. strains of Escherichia coli, Kiebsiella 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.This combination of high activity against Gram-positive organisms with high activity against Gram-negative organisms, more particularly against Pseudomonas, that is possessed by the compounds of the invention is unusual and particularly advantageous.

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.

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 composition may also be presented in a form suitable for absorption by the gastro-intestinal tract, for example, tablets, capsules, syrups or suspensions for oral adminstration, and suppositories.

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 0.1S 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 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, dependinq inter alia on the nature of the infection and the route and freauency of administration.

In general, intravenous or intramuscular administration will be employed, for example using 400 to 4000 mg per day of the active ingredient in adult human treatment. 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, cephalosporins or other & actam compounds.

The compounds of the invention may be prepared by a number of processes, discussed below.

Thus, according to another embodiment of the invention we provide for the preparation of an antibiotic compound of general formula (I) as hereinbefore defined or a non-toxic salt, solvate or hydrate thereof by acyleting a compound of the formula (II)

(wherein Rl, Z and the dotted line are as defined for general formula (I)) 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-g-sulphonic acid) or a 7-N-silyl derivative thereof, with an acid of formula (III)

(wherein R2, R3 and R4 are as defined above) or a salt thereof, or with an acylating agent corresponding thereto; 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 a desired A3-isomer, ii) reduction of a compound wherein Z is > S+O to form a compound wherein Z is > S, iii) conversion of a carboxyl group into a non-toxic metabolically labile ester function, iv) formation of a non-toxic salt or solvate, v) removal of any carboxyl blocking and/or N-protecting groups, and vi) removal of any hydroxy blockina groups.

The above reactions i) to vi) may be carried out in conventional manner.

In the acylation process, the starting material of formula (II) is preferably a compound wherein Z is > S and the dotted line represents a ceph-3-em compound.

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

Acylations employing acid halides may be effected in aqueous and non-aqueous reaction media, conveniently at temperatures of from -50 to +500C, preferably -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-phenyl isoxazol ium perchlorate; or N-ethoxycarbonyl 2-ethoxy-l,2-dihydroquinoline.

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 alkyl haloformate). 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, l-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, acetonitrile, dimethylacetamide or dimethyl sulphoxide.

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 phosphorus 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 of formula (III) 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 such as an alkanol, e.g. ethanol or industrial methylated spirits; esters, e.g. ethyl acetate; ethers, e.g. tetrahydrofuran or dioxan; ketones, e.g. acetone; amides, e.g.

dimethylacetamide; acetonitrile; water and mixtures thereof.

The acylation reaction may conveniently be effected at temperatures of from -500 to 50 C, preferably -400 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 and where appropriate, 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.

Starting materials for the preparation of compounds of general formula (I) according to the invention are preferably in their syn isomeric form or in the form of mixtures of the syn isomers and the corresponding anti isomers containing at least 90S of the syn isomer.

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.

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

(wherein R2 is as hereinbefore defined and R7 represents a hydrogen atom or a carboxyl blocking group) or a salt thereof, by selective reaction with a compound of general formula (V)

(wherein R3 and R4 are as defined above and T is a chloro, bromo or iodo atom; a sulphate group; or a sulphonate group, such as p-toluene sulphonate), followed by removal of any carboxyl blocking group R7.

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 dimethylformamide.

Separation of isomers may be effected either before or after such etherification. Under the conditions described above the configuration of the oxyimino group is substantially unchanged by the etherification reaction.

When the compound of formula (IV) is employed in the form of a free acid or a salt with a base, the etherification reaction is generally carried out in the presence of a strong base e.g. potassium t-butoxide, sufficient base being added to form a dianion.

Furthermore, the reaction should be effected in the presence of a base if an acid addition salt of a compound of formula (IV) is used, the amount of base being sufficient to neutralise rapidly the acid in question.

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

(wherein R2 and R7 are as hereinbefore defined) with a compound of formula (VII)

(wherein R3 and R4 are as hereinbefore defined) followed by removal of any carboxyl blocking group R7, and where necessary the separation of syn and anti isomers.

The reaction is conveniently carried out in a solvent such as dimethylformamide, dimethylacetamide, dimethyl sulphoxide, tetrahydrofuran or methanol, all optionally in the presence of water, at a temperature of -200 to +500C, preferably OO to 300C.

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.

Intermediates of formula (VII) may be prepared by treating compounds of formula (VII I)

(wherein R3 and R4 are as defined above and A is an imido group, for example a phthalimido, succinimido or maleimido group) with a hydrazine reagent such as hydrazine hydrate or an alkyl hydrazine such as methyl hydrazine. The reaction will generally be performed in an inert solvent, for example a halogenated hydrocarbon such as methylene chloride at a low temperature, for example -700 to +3O0C.

Intermediates of formula (VIII) may be prepared by alkylation with compounds of formula (IX)

(wherein R3 and R4 are as defined above and X is a halogen atom such as a chlorine or bromine atom) of an appropriate N-hydroxyimide, (e.g.

N-hydroxyphthalimide, N- hydroxysuccinimide or N-hydroxymaleimide) in the presence of a base such as triethylamine in a solvent such as acetonitrile at for example -100 to +300C.

Intermediates of formula (IX) are either known compounds or may be prepared using methods analogous to those used for the preparation of the known compounds.

Compounds of formula (II) used as starting materials in the acylation process are known from the literature e.g. British Patent Application No. 2159817 or can be prepared according to information from the literature.

A A2-cephalosporin ester derivative obtained in accordance with the above 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 reaction product may also be oxidised to yield the corresponding ceph-3-em l-oxide, for example by reaction with a peracid, e.g. peracetic or m-chloroperbenzoic acid; the resulting sulphide may subsequently be reduced as described hereinafter to yield the corresponding desired ceph-3-em sulphide.

Where a compound is obtained in which Z is > S+O 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 solvent e.q. acetic acid, acetone, tetrahydrofuran, dioxan, dimethylformamide or dimethylacetamide. The reaction may be effected at a temperature of from -20 to +5O0C.

In the oxidation and reduction processes described above, the groups R3 and R4 in the starting materials are desirably other than hydroxyl groups.

Reaction products 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, high pressure liquid chromatography, ion-exchange chromatography or chromatography on macroreticular resins.

Metabolically labile ester derivatives of the carboxyl groups in 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, alkoxycarbonyloxyalkyl halide (e.g. iodide) or dioxenolonealkyl halide 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 acetate, 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.

A salt may also be produced directly from an ester by splitting off the ester group under suitable reaction conditions, for example, catalytic reduction in an aqueous/organic solvent in the presence of a metal salt, to yield the salt directly.

It should be appreciated that in some of the above transformations it may be necessary to protect any sensitive groups in the molecule of the compound in question to avoid undesirable side reactions. Examples of suitable protecting groups are given in "Protective Groups in Organic Synthesis" by Theodora W. Greene (John Wiley and Sons, 1981).

For example, during any of the reaction sequences referred to above it may be necessary to protect the NH2 group of the aminothiazolyl moiety, for example by tritylation, acylation (e.g.

chloroacetylation 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.

Similarly, the hydroxy groups of the catechol moiety may need to be protected during any of the above reaction sequences. Hydroxy protecting groups which may be removed under mild conditions will generally be suitable, for example acetyl or silyl groups. Such groups may be introduced in conventional manner and, when desired, removed such that breakdown of the product does not occur. For example in the case of an acetyl group the group may be removed by solvolysis with an aqueous solvent such as aqueous methanol or aqueous ethanol in the presence of a base for example sodium bicarbonate, ammonium hydroxide, ammonium carbonate or ammonium carbamate. A trimethyl silyl group may be cleaved, for example by treatment with a dilute aqueous acid.

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) 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. 1399086. Preferred blocked carboxyl groups include aryl lower alkoxycarbonyl groups such as p-methoxybenzyloxycarbonyl, =-nitrobenzyloxyzarbonyl and diphenylmethoxycarbonyl; lower alkoxycarbonyl groups such as t-butoxycarbonyl; 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 catalysed hydrolysis or reduction is applicable in many cases, as is enzymically-catalysed hydrolysis.

The following Examples illustrate the invention. In the Examples temperatures are in degrees Celsius. Nujol is a registered trade mark.

Intermediate 1 (3,4-Carbonyldioxyphenyl)methyl chloride Piperonyl alcohol (40.09) was added in portions to a stirred suspension of phosphorus pentachloride (219.bug) in chlorobenzene (480ml) and then the mixture was heated to reflux. After 3.5 hours the resulting solution was concentrated to an oil and poured onto ice (4009). The precipitated solid was collected by filtration, washed with water, petrol (b.p. 40-60 ) and vacuum dried to give the title product (12.129); vmax (Nujol) 1850-1830cm~l; 6 (CDCl3) 7.36 (H-2), 7.29 (H-6), 7.24 (H-5) and 4.63 (CH2Cl).

Intermediate 2 N-[(3,4-Carbonyldioxyphenyl)methoxy]phthalimide The solution obtained by the addition of triethylamine (37.79) to a stirred suspension of N-hydroxyphthalimide (44.189) in acetonitrile (250ml) was added under nitrogen to a stirred, icechilled solution of (3,4-carbonyldioxyphenyl)methyl chloride (50.09) in acetonitrile (1OOml) to give an immediate white precipitate. The mixture was allowed to warm to room temperature, then after a total of 2 hours was added to 2N-hydrochloric acid (500ml) diluted with water (1.5Q). The resulting solid was collected by filtration, washed successively with water and ether and then vacuum dried (50.479).

A portion of the above product (17.0a) was crystallised from acetonitrile (450ml) to give the title compound as colourless needles (12.979), m.p. 219-220 ; vmax (Nujol) 1830 and 1730cm-1.

Intermediate 3 (Z)-2-(2-Formamidothiazol-4-yl)-2-[(3,4-dihydroxyphenyl)methoxyimino]- acetic acid Stage 1. A suspension of N-[(3,4-carbonyldioxyphenyl)methoxy]- phthalimide (12.59) in dioxan (SOml) and methanol (600ml) was treated with 2N hydrochloric acid (10ml) and the mixture was stirred at ca 550 for 24 hours. The resulting solution was concentrated to an oil which was dissolved in ethyl acetate (400ml). This solution was washed with water (x2) and brine (x2), then dried (MgS04) and evaporated to give an isomeric mixture of N-[(3-hydroxy-4-methoxyphenyl)methoxy] phthalimide and N-[ (4-hydroxy-3-methoxyphenyl)methoxy)phthalimide as a foam (14.939).

Stage 2. A portion (2.09) of the above mixture was dissolved in methanol (20ml) and dichloromethane (70ml), then chilled to -500 under nitrogen and treated with hydrazine monohydrate (lml). The mixture was allowed to warm to room temperature and after 5 hours the precipitate was filtered off. The filtrate was evaporated to an oil and triturated with ethyl acetate (100ml) to give a solid. This was washed with more ethyl acetate (2x25ml). Evaporation of the ethyl acetate extracts gave (3,4-dihydroxyphenyl)methoxyamine as a foam (1.419).

Stage 3. A stirred suspension of 3-(2-formamidothiazol-4-yl)glyoxylic acid (1.59) in N,N-dimethylformamide (30ml) was treated with (3,4-dihydroxyphenyl)methoxyamine (1.889). A transient clear solution was produced before a hazy precipitate formed. After 45 minutes the mixture was partitioned between ethyl acetate (150ml) and water (50ml) and the organic layer was separated and washed with brine (x2), dried (MgS04) and evaporated to a white solid. The solid was washed with diethyl ether and vacuum dried to give the title product (639ma); vmax (Nujol) 3340, 3170, 1700 and 1660cm-1; 6 (DMSO-d6) 8.52 (HCO), 7.52 (thiazole H), 6.77 (H-2), 6.70 (H-5), 6.64 (H-6), 5.00 (CH2).

Example 1 Diphenylmethyl (6R,7R,2'Z)-7- [2-(2-Aminothiazol-4-yl)-2-[(3,4- dihydroxyphenyl ) methoxyimino] acetamido iceph-3-em4-carboxylate (Z)-2-(2-Formamidothiazol-4-yl)-2-[(3 ,4-dihydroxyphenyl- methoxyimino)] acetic acid (860mg) was dissolved in methylene chloride (15ml) containing N,N-dimethylacetamide (3ml) at 210 with stirring under nitrogen. The solution was cooled to 200 and phosphorus oxychloride (0.32ml) was added. After one hour at 200 a solution of diphenylmethyl (6R ,7R)-7-aminoceph-3-em-4-carboxylate [prepared from its tosylate salt (1g) by treatment with aqueous sodium bicarbonate solution] in methylene chloride (15ml) containing N,N-dimethylaniline (2ml) was added.The reaction mixture was then placed in an ice-water bath and stirred thus for 30 minutes. The solution was washed twice with dilute aqueous hydrochloric acid and then twice with water, each time back extracting the aqueous layers with more methylene chloride.

The combined organic solutions were dried with magnesium sulphate and concentrated. The residue was triturated with diethyl ether to give a solid (1.34g).

Most of this solid (1.31g) was dissolved in methanol (20ml) containing dioxan (5ml) at 210 with stirring and 60 < aqueous perchloric acid (1.lml) was added. After 1.5 hours the solution was poured into dilute aqueous sodium bicarbonate solution with stirring.

The precipitate was collected by filtration, washed with water and diethyl ether and dried to give the crude product (930mg). This was chromatographed on silica gel (150g) using 4% methanol in chloroform as eluate to give the title compound (540mg); [&alpha;]18D+30.45 (c 0.94, DMSO); kinf (Ethanol) 231.2 (E1%1cm 311), 248.0 (El 225), 273.0 (E4Cm 148) and 297.2nm (E1%1cm 105).

Example 2 (6R,7R,2'Z)-7-[2-(2-Aminothiazol-4-yl)-2-[(3,4-dihydroxyphenyl)- methoxyimino)]acetamido]ceph-3-em-4-carboxylic acid, trifluoroacetic acid salt The ester of Example 1 (1.029) was mixed with anisole (2ml) and treated with trifluoroacetic acid (10ml) at 21 . After three minutes diisopropyl ether (100ml) was added and the precipitate was collected by filtration, washed with diisopropyl ether and dried in vacuo to give the title compound (770mg); [&alpha;]18D+73.9 (c 0.52, DMSO); #max (pH6 buffer) 234.8nm (E%cm 347), "inf 248.8 (E1%1cm 273), 280.4 (E1%1cm 170) and 293.2nm (E1%1Cm 145).

Claims (3)

Claims

1. Compounds of the general formula (I)

wherein R1 represents a hydrogen atom or a carboxyl blocking group; R2 represents a hydrogen atom or an amino protecting group; R3 or R4lrepresents a hydroxy or substituted hydroxy group or R3 and R together represent a cyclic protected diol group; Z is =S or oS-+O (a- or B-); the dotted line bridging the 2-, 3-, and 4-positions indicates that the compound is a ceph-2-em or ceph-3-em compound; and non-toxic salts and solvates thereof.

2. Compounds as claimed in claim 1 of formula (Ia)

wherein R 3a is a hydroxy or acetoxy group; R4a is a hydroxy or acetoxy group; and the non-toxic salts, solvates (including hydrates) and metabolically labile esters thereof.

3. The compound (6R,7R,2'Z)-7-[2-(2-aminothiazol 4-yl)-2-[(3,4-dihydroxy-phenyl)methoxyimino]acetamido] ceph-3-em-4-carboxylic acid; and the non-toxic salts, solvates (including hydrates) and metabolically labile esters thereof.