GB1604722A

GB1604722A - 7-(2-(2-amino-4-thiozolyl)-2-oxymino-acetamido)-cephem derivatives

Info

Publication number: GB1604722A
Application number: GB22909/78A
Authority: GB
Original assignee: Glaxo Operations UK Ltd
Current assignee: Glaxo Operations UK Ltd
Priority date: 1978-05-26
Filing date: 1978-05-26
Publication date: 1981-12-16
Also published as: NL7904127A; JPS54154789A; FR2426693B1; BE876542A; DE2921288A1; FR2426693A1; BE876541A; JPS54154788A; IT1116196B; CH646704A5; ZA792584B; IT7949177A0

Abstract

A cephalosporin antibiotic of the formula <IMAGE> exhibits broad-band antibiotic activity, which is unusually high against Gram-negative organisms such as strains of Pseudomonas organisms. The invention also comprises non-toxic salts, non-toxic metabolically labile esters and solvates of the compound of the formula I. Also described are compositions containing the antibiotics according to the invention, and processes for preparing such antibiotics.

Description

(54) 7-[2-(2-AMINO-4-THIAZOLYL)-2-OXYIMINQ- ACETAMIDO]-CEPHEM DERIVATIVES (71) We, GLAXO OPERATIONS UK LIMITED, formerly known as Glaxo Laboratories Limited, a British Company of Greenford, Middlesex, do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention is concerned with cephalosporin compounds possessing valuable antibiotic properties.

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.

Thus, for example, in our British Patent Specification No. l;399,086, we describe a novel class of cephalosporin antibiotics containing a 7p - (ct - etherified oximino) - acylamido group, the compounds being syn isomers or mixtures of svn and anti isomers wherein the syn isomer predominates. This class of antibiotic compounds are characterised by high antibacterial activity against a range of gram positive and gram-negative organisms coupled with particularly high stability to p-lactamases produced by various gram-negative organisms.

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

For example, in our British Patent Specification No. 1,453,049 we describe cephalosporin antibiotics containing a 3-carbamoyloxymethyl group and a 7A- acylamido group of the formula

(wherein R' is a furyl, thienyl or phenyl group and R2 is a C1-C4 alkyl group, a C3-C7 cycloalkyl group or a phenyl group), the compounds being syn isomers or existing as mixtures of syn and anti isomers containing at least 90 /O of the svn isomer. These compounds exhibit high anti-bacterial activity against a broad range of gram positive and gram negative organisms and particularly high stability to p- lactamases produced by various gram negative organisms. They also show the advantageous property of good stability in vivo, particularly to esterases.

Furthermore, in our British Patent Specification No. 1,496,757, we describe cephalosporin antibiotics containing a 7p-acylamido group of the formula

(wherein R is a thienyl or furyl group; RA and Rb may be inter alia C14 alkyl groups or together with the carbon atom to which they are attached form a C37 cycloalkylidene group; and m and n are each 0 or 1 such that the sum of m and n is O or 1), the compounds being syn isomers or mixtures of syn and anti isomers containing at least 90 /O of the syn isomer. These compounds have been found to have particularly good activity against gram-negative organisms.

Other compounds of similar structure have been developed from these compounds in further attempts to find antibiotics having improved broad spectrum antibiotic activity and/or high activity against gram-negative organisms. Such developments have involved variations in not only the aromatic groups (R' and R) and the oximino etherifying groups in the above formulae but also the introduction of particular groups in the 3-position of the cephalosporin molecule.

Thus, for example, in Belgium Patent Specification No. 852,427, there are described cephalosporin antibiotic compounds falling within the general scope of our British Patent Specification No. 1,399,086 and wherein the group R in the above formula may be replaced by a variety of different organic groups, including 2-aminothiazol-4-yl, and the oximino group is an aliphatic hydrocarbon group which may be substituted by, for example, carboxy, while the 3-position contains certain specific groups.

We have now discovered that by an appropriate selection of groups constituting the 7,B and 3-positions compounds having particularly good activity against a wide range of gram-negative organisms may be obtained.

The present invention provides antibiotics of the general formula

(wherein R" and Rb, together with the carbon atom to which they are attached form a C37 cyclcoalkylidene group and Y represents an acetoxy, carbamoyloxy, Nmethylcarbamoyloxy or N-(2-chloroethyl) carbamoyloxy group) and non-toxic salts and non-toxic metabolically labile esters thereof.

The compounds according to the present invention which compounds are syn isomers, may exist in tautomeric forms (in respect of the 2-aminothiazolyl group) and it will be understood that such tautomeric forms, i.e. 2-aminothiazolyl and 2iminothiazolinyl, are included within the scope of the invention.

The compounds according to the invention exhibit good broad spectrum antibiotic activity. The compounds exhibit activity against microorganisms which produce p-lactamases, and also possess very high stability to plactamases produced by a range of gram-negative organisms. Furthermore they have been found to exhibit good activity against various members of the Enterobacteriaceae (e.g. strains of Escherichia coli. Klebsiella aerogenes and especially Proteus mirabilis Proteus moganii and Proteus vuigaris), as welasagaint Pseudomonas organisms e.g. strains of Pseudomonas aeruginosa.

As mentioned above, the compounds of 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.

Non-toxic salt derivatives which may be formed from the compounds of general formula (I) include inorganic base salts such as alkali metal salts (e.g.

sodium and potassium salts) and alkaline earth metal salts (e.g. calcium salts); amino acid salts (e.g. lysine and arginine salts); organic base salts (e.g. procaine, phenylethylbenzylamine, dibenzylethylenediamine, ethanolamine, diethanolamine and N-methylglucosamine salts); and, where appropriate, acid addition salts, e.g.

with hydrochloric, hydrobromic, sulphuric, nitric, phosphoric, formic, trifluoroacetic, toluene-p-sulphonic and methane-sulphonic 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, where appropriate, sulphonic acid groups, or, again where appropriate, with a resin containing carboxyl groups, e.g. a polyacrylic acid resin. Use of highly soluble base salts (e.g. alkali metal salts such as the sodium salt) of compounds of formula (I) is generally advantageous 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 a conventional manner, for example with appropriate organic amines.

Non-toxic metabolically labile ester derivatives which may be formed from the compounds of general formula (I) and which on administration are converted in vivo into the antibiotic compound of formula (I), include, for example, acyloxymethyl esters, e.g. (C,~6 alkanoyl)oxymethyl esters such as acetoxymethyl, acetoxyethyl and pivaloyloxymethyl esters.

Particularly preferred compounds according to the present invention by virtue of their high activity against Pseudomonas organisms, e.g. strains of Pseudomonas aeruginosa include those compounds of formula (I) wherein Ra and Rb together with the carbon atom to which they are attached form a cyclobutylidene group.

Also preferred are those compounds according to the invention wherein Y represents an acetoxy or a carbamoyloxy group.

The compounds of formula (I) may be used for treating a variety of diseases caused by pathogenic bacteria in human beings and animals, such as respiratory tract and urinary tract infections.

The compounds according to the invention may be prepared by any convenient method, for example by techniques analogous to those described in British Patent Specification No. 1,399,086.

Thus according to one embodiment of the invention we provide a process for the preparation of an antibiotic compound of formula (I) as hereinafter defined or a non-toxic salt or non-toxic metabolically labile ester thereof which comprises either (A) condensing a compound of the formula

[wherein Y' is the group Y as defined above or the group 0 .CO . NHRC where Rc is an N-protecting group; B is > S or > SoO (o- or A-); R3 represents hydrogen or a carboxyl blocking group, e.g. the residue of an ester-forming aliphatic or araliphatic alcohol ot' an ester-forming phenol, silanol or stannanol (the said alcohol, phenol, silanol or stannanol preferably containing 1--20 carbon atoms) or a symmetrical or mixed anhydride group derived from an appropriate acid; and the dotted line bridging the 2-, 3- and positions indicates that the compound is a ceph2-em or ceph-3-em compound], or a salt, e.g. an acid addition salt such as a hydrochloride, hydrobromide, sulphate, nitrate, phosphate, methane-sulphonate or tosylate, or an N-silylated derivative thereof with an acid of formula

(wherein Ra and Rb are as defined above; and R4 represents a carboxyl blocking group, e.g. as defined above for R3 and R5 is an amino or protected amino group) or with an acylating agent corresponding thereto; or (B) reacting a compound of formula

(wherein Ra, Rb, R5, B and the dotted line are as defined above; and R3 and R3a may independently represent hydrogen or a carboxy blocking group) or an acid addition salt thereof, with an acylating agent serving to form an acetoxymethyl, carbamoyloxymethyl, N-protected carbamoyloxymethyl, Nmethylcarbamoyloxymethyl or N-(2-chloroethyl)carbamoyloxymethyl group at the 3-position; whereafter, if necessary and/or desired in each instance, any of the following reactions (C) in any appropriate sequence, are carried out: (i) conversion of a A2-isomer into the desired A3-isomer, (ii) reduction of a compound wherein B is > S < O to form a compound wherein B is > S, (iii) conversion of a carboxyl group into a non-toxic metabolically labile ester function, and (iv) removal of any carboxyl blocking and/or N-protecting groups; and finally (D) recovering the desired compound of formula (I) or a non-toxic salt or non-toxic metabolically labile ester thereof, if necessary after separation of isomers.

Base salts of compounds of formula (I) may be formed by reaction of the cephalosporin acid with, for example, sodium 2-ethylhexanoate or potassium 2ethylhexanoate.

Non-toxic metabolically labile ester derivatives may be formed using conventional esterifying agents.

Acylating agents which may be employed in the preparation of compounds bf 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 nonaqueous reaction media, conveniently at temperatures of from -50 to +500C, preferably -20 to +300C, if-desired in the presence of an acid binding agent Suitable reaction media include aqueous ketones such as aqueous acetone, est-ers 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 amiMes (e.g.

triethylamine or dimethylaniline), inorganic bases (e.g. calcium carAr te or sodium bicarbonate), and oxiranes such as C26 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'-diethyl-, dipropyl- or diisopropylcarbodiimide, N,N'dicyclohexylcarbodiimide, or N-ethyl-N'-y-dimethylaminopropylcarbodiimide; carbonyl compound such as carbonyldiimidazole; or an isoxazolinium salt such as Nethyl-5-phenylisoxaxolinium 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. with pivalic acid or formed with aloformate such as a C16 alkylhaloformate). An activated ester may conveniently be formed in situ using, for example, l-hydroxy-benzotriazole in the presence of a condensing agent as set out above.

Mixed anhydrides may be formed with phosphorus acids (for example phosphoric or phosphorous acids), sulphuric acid or aliphatic or aromatic sulphonic acids (for example p-toluene sulphonic acid).

Acylation reactions involving the free acids or their above-mentioned amideforming derivatives are desirably effected in an anhydrous reaction medium, e.g.

methylene chloride, tetrahydrofuran, dimethylformamide or acetonitrile.

The acids of formula (III) may, if desired, be employed in the form of their acid addition salts e.g. their hydrochlorides.

Acylation of 3-hydroxymethyl compounds of formula (IV) may be effected by conventional methods. Thus, for example, a 3-hydroxymethyl cephalosporin may be reacted with an isocyanate of formula NCO (wherein Rd represents a labile substituent group or a methyl or 2-chloroethyl group) to give a compound containing a 3-position substituent having the formula -CH2O . CONHRd (wherein Rd has the above defined meaning). Where Rd is a labile substituent this substituent may if desired subsequently be cleaved, e.g. by hydrolysis, to form a 3carbamoyloxymethyl group. Labile groups Rd which are readily cleavable upon subsequent treatment include chlorosulphonyl and bromosulphonyl; halogenated C18 alkanoyl groups such as dichloroacetyl and trichloroacetyl; and halogenated C26 alkoxycarbonyl groups such as 2, 2, 2, 2,-trichloro-ethoxycarbonyl. These labile Rd groups may generally be cleaved by acid or base catalysed hydrolysis (e.g.

by base catalysed hydrolysis using sodium bicarbonate).

Acetylation of 3-hydroxymethyl compounds of formula (IV) may be effected by conventional methods, for example in an analogous manner to that described in British Patent Specification No. 1,141,293, i.e. by aralkylating the 4-carboxy group, acetylating the 3-hydroxymethyl group of the protected compound and subsequently removing the aralkyl group.

3-Hydroxymethyl starting materials of formula (IV) for use in process (B) above may be prepared by the methods described in British Patent Specification No. 1,474,519 and U.S. Patent Specification No. 3,976,546, or by acylating the corresponding 7-amino-3-hydroxymethyl compounds, for example, in an analogous manner to process (A) above.

h2-Cephalosporin ester derivatives obtained in accordance with the process of the invention may be converted into the corresponding A3-derivative by, for example, treatment of the 82ester with a base.

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 acid; the resulting sulphoxide may, if desired, subsequently be reduced as described hereinafter to yield the corresponding ceph-3-em sulphide.

Where a compound is obtained in which B is > SO this may be converted to the corresponding sulphide by, for example, reduction of the corresponding acyloxysulphonium or alkyloxysuiphonium 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 dimethyl-acetamide. The reaction may be effected at a temperature at 20C to +SOCC.

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.

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. Syn and anti isomers may be distinguished by appropriate techniques, e.g. by their ultraviolet spectra, by thin layer, paper, or high pressure liquid chromatography or by their proton magnetic resonance spectra.

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

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

(wherein R5 is as hereinbefore defined and Ra represents hydrogen or a carboxyl blocking group), by reaction with a compound of general formula

[wherein Ra, Rb and R' are as hereinbefore defined (provided that Ra and Rb together with the carbon atom to which they are attached do not form a cyclopropylidene group) and T 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 desirably carried out in the presence of a base, e.g. potassium carbonate or sodium hydride, and is preferably conducted in an organic solvent, for example dimethylsulphoxide, a cyclic ether such as tetrahydrofuran or dioxan, or an N,N-disubstituted amide such as dimethylformamide. Under these conditions the configuration of the oximino 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 (IV) is used. The base should be used in sufficient quantity to rapidly Acids of general formula (III) may also be prepared by reaction of a compound or formula

(wherein R3 and R4 are as hereinbefore defined) with a compound of formula

(wherein R", Rb and R4 are as defined for formula (III), followed by removal of any carboxyl bldcking group R6.

The last-mentioned reaction is particularly applicable for the preparation of compounds of formula (III) wherein Ra and Rb together with the carbon atom to which they are attached form a cyclopropylidene group; in this case, the compounds of formula (VIII) may be prepared in an analogous manner to that described in British Patent Application No. 17679/77 (Serial No. 1,602,725).

Reaction of (VII) with (VIII) may be followed where necessary by the separation of syn and anti isomers.

The acids of formula (III) may be converted to the corresponding acid halides and anhydrides and acid addition salts by conventional methods.

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 t-butoxycarbonylation, 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 aqueous solution of an optionally halogenated carboxylic acid, e.g. acetic acid, formic acid, chloroacetic acid or trifluoroacetic 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 as the last stage. It may, however, be convenient in some instances to employ nontoxic, metabolically labile carboxyl blocking groups such as acyloxymethyl groups (e.g. acetoxymethyl, acetoxyethyl and pivaloyloxymethyl groups) and retain these in the final product to give a non-toxic 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 Specification No. 1,399,086. Preferred blocked carboxyl groups include aryl C26 alkoxycarbonyl groups such as p-methoxybenzyloxycarbonyl, pnitrobenzyloxycarbonyl and diphenylmethoxycarbonyl; C26 alkoxycarbonyl groups such as t-butoxycarbonyl; and C26 haloalkoxycarbonyl groups such as 2,2,2-trichloroethoxycarbonyl. Carboxyl blocking group(s) may subsequently be removed by any of the appropriate methods disclosed in the literature; thus, for example, acid or base catalysed hydrolysis is applicable in many cases, as are enzymically-catalysed hydrolyses.

The 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 with an added preservative. The compositions may 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.

The antibiotic compounds may also be presented in a form suitable for absorption by the gastro-intestinal tract, e.g. as tablets or capsules. 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. 0.199%, preferably from 10 6(P/o of the active material, depending on the method of administration.

When the compositions comprise dosage units, each unit will preferably contain 50-1500 mg of the active ingredient. The dosage as employed for adult human treatment will preferably range from 250 to 6000 mg per day, depending on the route and frequency of administration, although in treating Pseudomonas infections higher daily doses may be required.

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

The following Examples illustrate the invention. All temperatures are in "C.

'Petrol' means petroleum ether (b.p. 40--60").

Preparation 1 Ethyl (Z)-2-(2-aminothiazol4-ylf2{hydroxyimino)acetate To a stirred and ice-cooled solution of ethyl acetoacetate (292 g) in glacial acetic acid (296 ml) was added a solution of sodium nitrite (180 g) in water (400 ml) at such a rate that the reaction temperature was maintained below 10 C. Stirring and cooling were continued for about 30 min., when a solution of potassium chloride (160 g) in water (800 ml) was added. The resulting mixture was stirred for one hour. The lower oily phase was separated and the aqueous phase was extracted with diethyl ether. The extract was combined with the oil, washed successively with water and saturated brine, dried, and evaporated. The residual oil, which solidified on standing, was washed with petrol and dried in vacuo over potassium hydroxide, giving ethyl (Z)-2-(hydroxyimino)-3-oxobutyrate (309 g).

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

Preparation 2 (Z)-2-hydroxyimino-22-trity aminothiazolA-yl)-acetate, hydrochloride Trityl chloride (16.75 g) was added portionwise over 2 hours to a stirred and cooled (-30") solution of the product of Preparation 1 (12.91 g) in dimethylformamide (28 ml) containing triethylamine (8.4 ml). The mixture was allowed to warm to 150 over one hour, stirred for a further 2 hours and then partitioned between water (500 ml) and ethyl acetate (500 ml). The organic phase was separated, washed with water (2x500 ml) and then shaken with IN HCI (500 ml)t The precipitate was collected, washed successively with water (100 ml), ethyl acetate (200 .ml) and ether (200 ml) and dried in vacuo to provide the title compound as a white solid (16.4 g); m.p. 184 to 1860 (decomp).

Preparation 3 Ethyl (Z)-2-(2-tritylaminothiazol-4-yl)-2-(1-t-butoxy- carbonylcyclobut-l-oxyimino) acetate The product of Preparation 2 (55.8 g) was stirred under nitrogen in dimethylsulphoxide (400 ml) with potassium carbonate (finely ground 31.2 g) at room temperature. After 30 minutes, t-butyl l-bromocyclobutane carboxylate (29.2 g) was added. After 8 hours further potassium carbonate (31.2 g) was added. More potassium carbonate (6x 16 g portions) was added during the next three days and further t-butyl l-bromocyclobutane carboxylate (3.45 g) was added after 3 days.

After 4 days in all, the mi was collected by filtration and washed well with water and petrol. The solid was dissolved in ethyl acetate and the solution washed with brine (twice), dried with magnesium sulphate and evaporated to a foam. This foam was dissolved in ethyl acetate-petrol (1:2) and filtered through silica gel (500 g). Evaporation gave the title compound (60 g) as a yellow foam, vmax (CHBr3) 3400 (NH) and 1730 cm-1 (ester).

Preparation 4 (Z)-2-( 1 -t-Butoxycarbonylcyclobut- I -oxyimino)-2-(2-trityl aminothiazol-4-yl) acetic acid A mixture of the product of Preparation 3 (3.2 g) and potassium carbonate (1.65 g) was refluxed in methanol (180 ml) and water (20 ml) for 9 hours and the mixture was cooled to room temperature. The mixture was concentrated and the residue partitioned between ethyl acetate and water, to which was added 2N HCI (12.2 ml). The organic phase was separated and the aqueous phase extracted with ethyl acetate. The combined organic extracts were washed with saturated brine, dried and evaporated to give the title compound (2.3 g); AmaX (ethanol) 265 nm (E,9bm 243).

Example 1 a) t-Butyl (6R,7Rt3-acetoxymethyl-7-[(Z) - 2 - (1 - t - butoxycarbonylcyclobut - I oxyimino)- 2 - (2 - tritylaminothiazol- 4 - yl)acetamidaiceph - 3 em - 4 - carboxylate A stirred solution of the product of Preparation 4 (24.2 g) and t-butyl (6R, 7R) - 3 - acetoxymethyl - 7 - aminoceph - 3 - em - 4 - carboxylate (13.6 g) in dimethylformamide (300 ml) Was, cooled to 00, and 1 - hydroxybenzotriazole monóhydrate (4.5 g) added, followed by dicyclohexylcarbodiimide (6.4 g). The mixture was warmed to room temperature and stirred overnight. The mixture was filtered, and the white solid washed with a little ether. The filtrate and washings were diluted with water (1.51) and extracted with ethyl acetate. The organic extracts were combined, washed successively with water and saturated brine, dried, and evaporated. The residue was taken up in ether, filtered, and re-evaporated.

The required product was isolated after elution through two silica columns with ether and concentrating the appropriate fractions. The residues were recrystallised from di-isopropyl ether to give the title compound (12.8 g), m.p. 113.5 to 116.50; [a]020+l5.00 (c 1.0, DMSO).

b) (6R,7R) - 3 - Acetoxymethyl - 7 - [(Z) - 2 - (2 - aminothiazol - 4 - yl) - 2 (1 - carboxycyclobut - 1 - oxyimino)acetamido]ceph - 3 - em - 4 - carboxylic acid Trifluoroacetic acid (100 ml) was added to a mixture of the product of Stage a) (12.5 g) and anisole (5 ml) at 00. The mixture was stirred at room temperature for 1 hour and concentrated. The residue was dissolved in ethyl acetate and reconcentrated. The residue was dissolved in ethyl acetate and extracted with saturated sodium bicarbonate solution. The aqueous extacts, at pH 7 to 7.5, were washed with ethyl acetate, acidified to pH 1.5, and extracted several times with ethyl acetate. These extracts were washed with saturated brine, dried, and evaporated. The residue was dissolved in formic acid (70 ml), water (18 mi) was added, and the mixture stirred at room temperature for 2 hours. The mixture was diluted with water (300 ml) and filtered. The filtrate was concentrated. The residue was taken up in water (400 ml), refiltered, and lyophilized to give the title compound (4 g), AmaX (pH 6 buffer) 246 nm (E1ic,, 264), find 295 nm (E'Cm 118), [a120+27.30 (c 1.0, DMSO).

Example 2 a) Diphenylmethyl (6R,7R) - 7 - [(Z) - 2 - (1 - t - butoxycarbonylcyclobut - I oxyimino)- 2 - (2 - tritylaminothiazol- 4- yl)acetamido] - 3 carbamoyloxymethyl ceph - 3 - em - 4 - carboxylate A stirred solution of the product of Preparation 4 (1.28 g) and diphenylmethyl (6R,7R) - 7 - amino - 3 - carbamoyloxymethyl ceph - 3 - em - 4 - carboxylate (0.88 g) in dimethylformamide (20 ml) was cooled to 0 , and 1hydroxybenzotriazole (0.3 g) added, followed bv dicyclohexylcarbodiimide (0.45 g).

The mixture was treated substantially according to the method of Example I a) eluting once through a silica column with ethyl acetate, to give the title compound (1.6 g), AmaX (ethanol) 240 nm (E1i"cm 242), Alnf 305 nm (E1%m 58); "max (CHBr) 1522, 1688 cm-' (CONH), 1685 cm-' (OCONH2), 1730 cm-' (CO2R), 1790 cm (- b) (6R,7R) - 7 - [(Z) - 2 - (2 - Aminothiazol - 4 - yl) - 2 - (1 - carboxycyclobut 1- - oxyimino)acetamido] - 3 - carbamoyloxymethyl ceph .3 - em - 4 - carboxylic acid Trifluoroacetic acid (8 ml) was added to a solution of the product of Stage a) (2.3 g) in anisole (2 ml) at 0 . The mixture was stirred for 3 minutes at room temperature and trifluoroacetic acid (32 ml) was added. The mixture was stirred at room temperature for 10 minutes and concentrated. The residue was worked-up substantially according to the method of Example lb) to give the title compound (258 mg), A (pH buffer) 239.5 nm (E'cv 194), Xf 292.5 nm (E1C% 129); [alD2C+32.50 (c 1.0, DMSO).

WHAT WE CLAIM IS: 1. Cephalosporins of the general formula

(wherein Ra and Rb, together with the carbon atom to which they are attached form a C37 cycloalkyidene group and Y represents an acetoxy, carbamoyloxy, Nmethylcarbamoyloxy or N-(2-chloroethyl)- carbamoyloxy group) and non-toxic salts and non-toxic metabolically labile esters thereof.

2. Compounds as claimed in claim 1 wherein Y represents an acetoxy group.

3. Compounds as claimed in claim 1 wherein Y represents a carbamoyloxy group.

4. Compounds as claimed in any of the preceding claims wherein Ra and Rb together with the carbon atom to which they are attached form a cyclobutylidene group.

5. (6R,7R - 3 - Acetoxymethyl - 7 - [(Z] - 2 - (2 - aminothiazol - 4 - yl) 2 - (I - carboxycyclobut - 1 - oxyimino)acetamido]ceph - 3 - em - 4 carboxylic acid and non-toxic salts and non-toxic metabolically labile esters thereof.

6. (6R,7R) - 7 - [(Z) - 2 - (2 - Aminothiazol - 4 - yl) - 2 - (1 carboxycyclobut - I - oxyimino)acetamido] - 3 - carbamoyloxymethyl - ceph 3 - em - 4 - carboxylic acid and non-toxic salts and non-toxic metabolically labile esters thereof.

7. A process for the preparation of a compound of formula (I) (as defined in claim 1) or a non-toxic salt or non-toxic metabolically labile ester thereof which comprises either (A) condensing a compound of the formula

[wherein Y' is the group Y as defined in claim 1 or the group 0 CO . NHRC where Rc is an N-protecting group; B is > S or > SO (a- or ss-); R represents hydrogen 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 an N- silylated derivative thereof with an acid ot formula

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. b) (6R,7R) - 7 - [(Z) - 2 - (2 - Aminothiazol - 4 - yl) - 2 - (1 - carboxycyclobut 1- - oxyimino)acetamido] - 3 - carbamoyloxymethyl ceph .3 - em - 4 - carboxylic acid Trifluoroacetic acid (8 ml) was added to a solution of the product of Stage a) (2.3 g) in anisole (2 ml) at 0 . The mixture was stirred for 3 minutes at room temperature and trifluoroacetic acid (32 ml) was added. The mixture was stirred at room temperature for 10 minutes and concentrated. The residue was worked-up substantially according to the method of Example lb) to give the title compound (258 mg), A (pH buffer) 239.5 nm (E'cv 194), Xf 292.5 nm (E1C% 129); [alD2C+32.50 (c 1.0, DMSO). WHAT WE CLAIM IS:

1. Cephalosporins of the general formula

2. Compounds as claimed in claim 1 wherein Y represents an acetoxy group.

3. Compounds as claimed in claim 1 wherein Y represents a carbamoyloxy group.

(wherein Ra and Rb are as defined in claim 1; R4 represents a carboxyl blocking group; and R5 is an amino or protected amino group) or with an acylating agent corresponding thereto; or (B) reacting a compound of formula

(wherein Ra, Rb, R5, B and the dotted line are as defined above; and R3 and R3a may independently represent hydrogen or a carboxyl blocking group), or an acid addition salt thereof, with an acylating agent serving to form an acetoxymethyl, carbamoyloxymethyl, N-protected carbamoyloxymethyl, Nmethylcarbamoyloxymethyl or N-(2-chloroethyl) carbamoyloxymethyl group at the 3-position; whereafter, if necessary and/or desired in each instance, any of the following reactions (C) in any appropriate sequence, are carried out: (i) conversion of a A2-isomer into the desired A3-isomer, (ii) reduction of a compound wherein B is > S < O to form a compound wherein B is > S.

(iii) conversion of a carboxyl group into a non-toxic metabolically labile ester function, and (iv) removal of any carboxyl blocking and/or N-protecting groups; and finally (D) recovering the desired compound of formula (I) or a non-toxic salt or non-toxic metabolically labile ester thereof, if necessary after separation of isomers.

8. A process as claimed in claim 7 wherein a compound of formula (II) is condensed with an acid halide corresponding to the acid of formula (III).

9. A process as claimed in claim 8 wherein the condensation is effected in the presence of an acid binding agent comprising a tertiary amine, an inorganic base or an oxirane.

10. A process as claimed in claim 7 wherein a compound of formula (II) is condensed with an acid of formula (III) in the presence of a condensing agent comprising a carbodiimide, carbonyldiimidazole or an isoxazolinium salt.

11. A process as claimed in claim 7 wherein a compound of formula (II) is condensed with an activated ester corresponding to the acid of formula (III).

12. A process as claimed in claim 11 wherein the condensation is effected in the presence of l-hydroxy-benzotriazole.

13. A process as claimed in claim 7 substantially as herein described.

14. A process as claimed in claim 7 substantially as herein described with reference to the Examples.

15. Compounds of the general formula (I) (as defined in claim 1) whenever prepared by a process as claimed in any of claims 7 to 14.

16. Pharmaceutical compositions comprising a compound as claimed in any of claims 16 and 15 in association with a pharmaceutical carrier or excipient.