GB1584398A

GB1584398A - Oxime derivatives of 3-carbamoyloxymethyl-7-amino-thiazolyl-acetamido-ceph-3-em-4-carboxylic acid processes for preparing them and pharmaceutical compositions containing them

Info

Publication number: GB1584398A
Application number: GB34847/77A
Authority: GB
Original assignee: Roussel Uclaf SA
Current assignee: Sanofi Aventis France
Priority date: 1976-08-20
Filing date: 1977-08-19
Publication date: 1981-02-11
Also published as: ES461764A1; FR2361895A1; JPS5325595A; DE2737504A1; NL7709258A; AU2806277A; LU77993A1; SU700065A3; IE45865L; PT66944B; IE45865B1; ATA601677A; SE7708626L; FR2361895B1; CH626088A5; BE857933A; IL52709A0; AT357671B; AU510300B2; IL52709A

Abstract

The syn isomers of the compounds of formula: <IMAGE> , in which R1 represents a saturated or unsaturated C1-C4 alkyl and A represents hydrogen or one equivalent of an alkali metal or alkaline-earth metal or of an amine organic base, are prepared from the syn isomers of the corresponding compounds in which the amino group of the thiazolyl radical is substituted by a group which can be removed by acid hydrolysis or by hydrogenolysis, or by a chloroacetyl group; in the first case, an acid hydrolysis or a hydrogenolysis is carried out, in the second case treatment is carried out with thiourea. The compounds obtained have antibacterial properties; they can be used in the treatment of infectious diseases, especially of staphylococcias and of colibacilloses.

Description

(54) NEW OXIME DERIVATIVES OF 3 CARBAMOYLOXYMETHYL-7-AMINO THIAZOLYLACETAMIDO-CEPH-3-EM-4 CARBOXYLIC ACID, PROCESSES FOR PREPARING THEM AND PHARMACEUTICAL COMPOSITIONS CONTAINING THEM (71) We, ROUSSEL-UCLAF, a French Body Corporate, of 35 Boulevard des Invalides, Paris 7eme, France, 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 relates to new oxime derivatives of 3 - carbamoyloxymethyl 7 - aminothiazolylacetamido - ceph - 3 - em - 4 - carboxylic acid, processes for preparing them and pharmaceutical compositions containing them. In particular it concerns certain derivatives of 3 - carbamoyloxymethyl - 7 - [2 - (2 - amino - 4 thiazolyl) - 2 - imino - acetamido] - ceph - 3 - em - 4 - carboxylic acid that may be of use in medicine.

Accordingly this invention provides the oxime derivatives of 3 carbamoyloxymethyl - 7 - aminothiazolylacetamido - ceph - 3 - em - 4 - carboxylic acid of the general formula:

in which R represents a hydrogen atom or a group removable by acid hydrolysis or by hydrogenolysis, Rl represents a saturated or unsaturated hydrocarbyl radical having from 1 to 4 carbon atoms, A represents either a hydrogen atom, an' alkali-metal atom, an equivalent of an alkaline-earth metal atom, an equivalent of a magnesium atom, or a substituted ammonium group, the compounds being in the form of the syn isomer.

The expression "a group removable by acid hydrolysis or by hydrogenolysis" is used herein to mean a group that may be cleaved from the remainder of the molecule without otherwise affecting its structure (other than cleaving other groups removable by acid hydrolysis or by hydrogenolysis, where more than one is present). Thus for example R may represent a t-butoxycarbonyl, trityl, benzyl, benzhydryl, trichloroethyl, carbobenzyloxy or formyl group, or an equivalent of a phthaloyl group. Of those groups, R preferably represents a t-butoxycarbonyl, trityl, benzhydryl, trichloroethyl or carbobenzyloxy group.

R1 may be an alkyl, alkenyl or an alkynyl group, and examples of suitable groups include the methyl, ethyl, propyl, isopropyl, sec-butyl, t-butyl, vinyl, propenyl, butenyl, ethynyl and propargyl radicals.

When A represents "an equivalent of an alkaline-earth metal atom" or "an equivalent of a magnesium atom", or when R represents an equivalent of a phthaloyl group, each molecule of the syn isomer shown in general formula I contains, as A or R, the fraction of the metal atom or phthaloyl group corresponding to a single valence.

When A represents a metal atom (and thus the compounds of general formula I are metal salts) A is preferably a sodium, potassium, lithium, calcium or magnesium atom. When A represents a substituted ammonium group (and thus the compounds of general formula I are amine salts) A is preferably derived from methylamine, propylamine, diethylamine, trimethylamine, triethylamine, N,Ndimethylethanolamine or tris-(hydroxymethyl)-aminomethane.

It will be appreciated that when R represents a group removable by acid hydrolysis or hydrogenolysis, the amine group at the 2-position of the thiazoyl ring is protected by the group removable by acid hydrolysis or hydrogenolysis. The amine group is released from protection when the group removable by acid hydrolysis or hydrogenolysis is cleaved from the molecule.

Thus the syn isomers of general formula I comprise the protected syn isomers of the general formula:

(wherein R' represents a group removable by acid hydrolysis or hydrogenolysis and R1 and A are as defined hereinbefore); and the unprotected syn isomers of the general formula:

(wherein R, and A are as defined hereinbefore).

A particularly preferred class of unprotected syn isomers falling within general formula Ib' are those wherein Rl represents a methyl radical and A represents a hydrogen atom or a sodium atom.

Amongst the unprotected syn isomers of general formula Ib' the following are especially preferred: 3 - carbamoyloxymethyl - 7 - [2 - (2 - amino - 4 - thiazolyl) - 2 (methoxyimino) - acetamido] - ceph - 3 - em - 4 - carboxylic acid syn isomer; 3- carbamoyhoxymethyl - - - [2 - (2 - amino - 4 - thiazdlyl) - 2 (methoxyimino) - acetamido] - ceph - 3 - em - 4 - carboxylic acid, syn isomer, as obtained according to the process described in Example 2; and the sodium salt of 3 - carbamoyloxymethyl - 7 - [2 - (2 - amino - 4 thiazolyl) - 2 - (methoxyimino) - acetamido] - ceph - 3 - em - 4 - carboxylic acid, syn isomer.

It should be understood that by virtue of tautomerism the syn isomers of general formula I can exist: a) either in the form indicated by general formula I; b) or in the form as shown in the following general formula:

wherein R, R, and A are as defined hereinbefore. All references herein to the syn isomers of general formula I and other compounds in which such tautomerism is possible should be construed as extending to both tautomeric forms, unless otherwise specified.

In another aspect this invention provides a process for the preparation of the protected syn isomers of general formula Ia' wherein A represents a hydrogen atom, in which process an appropriate syn isomer of the general formula:

(wherein R' is as defined hereinbefore, A' represents an alkali-metal or a hydrogen atom and R2 represents a group removable by hydrolysis) is treated with a hydrolysis agent effective at hydrolysing the group R2 and not the group R', and in the case where a basic hydrolysis agent is employed thereafter the hydrolysis product is treated with an acid, to give the desired product of the general formula:

wherein R' and R1 are as defined hereinbefore.

The hydrolysis of the syn isomer of general formula II is carried out in a manner that will remove the group R2 and not the group R', and naturally the group R2 is chosen accordingly. It is believed to be within the competance of one skilled in the art to choose both suitable substituents and reaction conditions, but by way of illustration it is pointed out that a basic medium such as sodium bicarbonate in water is preferably employed, although potassium bicarbonate or an alkali-metal carbonate in either water or a water/alcohol mixture may be employed. When such basic hydrolysis agents are employed the hydrolysis product is treated with an acid and dilute hydrochloric acid is preferred. However, other mineral acids such as sulphuric or phosphoric acid can also conveniently be used.

Alternatively, an acidic medium may be used to effect the hydrolysis of the group R2 provided the group R' is not also removed. A slightly acidic buffered medium is preferred to effect this hydrolysis.

By way of indication the substituent R2 is preferably a trichloroethyl, benzyl, p-methoxybenzyl or chlorosulphony radical.

The syn isomers of general formula II used in the above preparation are desirably prepared by reacting an appropriate syn isomer of the general formula:

(wherein R', A' and R, are as defined hereinbefore) with an isocyanate of the general formula: R2-N=C=O (wherein R2 is as defined hereinbefore) to give the desired product of general formula II.

The reaction to form the desired syn isomer of general formula II is preferably carried out in an inert solvent or mixture of inert solvents. Particularly preferred solvents are methylene chloride and chloroform, but dimethylformamide, tetrahydrofuran or pyridine may be used with advantage. If no solvent is used the reaction is carried out in the pure isocyanate.

The syn isomers of general formula III used in the above preparation wherein A' represents an alkali-metal atom are preferably prepared by reacting 7aminocephalosporanic acid of the formula:

with an alkali-metal alcoholate in an alcohol, and treating the formed product with a syn isomeric acid of the general formula:

(wherein R, and R' are as defined hereinbefore) or a functional derivative thereof to give the desired product of general formula III.

7-Aminocephalosporanic acid is preferably reacted with the alkali-metal alcoholate in a lower alcohol containing from 1 to 3 carbon atoms. In a particularly preferred process the alcoholate is sodium methylate and it is employed in methanol. However, other alcoholates such as potassium t-butylate may be used.

The product of the reaction with the alcoholate is then treated with the acid of general formula IV or a functional derivative thereof. Preferably a derivative such as the acid chloride or the acid anhydride is used, and the latter may be formed in situ, by the action of isobutyl chloroformate on the free acid. Other halides or other anhydrides formed in situ by the action of other alkyl chloroformates, of a dialkyl carbodiimide or of a dicycloalkyl carbodiimide such as dicyclo-hexyl carbodiimide may also be used. Still further acid derivatives such as the acid azide, the acid amide or an acid ester formed, for example, with hydroxysuccinimide, pnitrophenol or 2,4-dinitrophenol may also be used.

In a case where the reaction is carried out with a halide of the acid of general formula IV or with an anhydride thereof, the work is preferably carried out in the presence of a basic agent. Preferred basic agents include the alkali-metal bicarbonates and carbonates, and tertiary organic bases such as N-methylmorpholine, pyridine or a trialkylamine such as triethylamine.

In an alternative process the syn isomers of general formula III wherein A' represents an alkali-metal atom may be prepared by treating an appropriate syn isomer of the general formula:

(wherein R1, R' and A are as defined hereinbefore) with an alkali-metal alcoholate in an alcohol to obtain the desired product of general formula III.

In this alternative process the alkali-metal alcoholate is again preferably sodium methylate. The reaction is advantageously carried out in a lower alcohol containing from 1 to 3 carbon atoms.

The syn isomers of general formula III wherein A' represents a hydrogen atom may be prepared by treating an appropriate syn isomer of the general formula:

(wherein R' and R, are as defined hereinbefore) with a deacetylation enzyme to obtain the desired product of general formula III.

The substituent R' in the above formulae is preferably a t-butoxycarbonyl, trityl, benzyl, benzhydryl, trichloroethyl, carbobenzyloxy or formyl group, or an equivalent of a phthaloyl group.

The deacetylation enzyme is preferably a wheatgerm enzyme, employed at a temperature of substantially 37"C and at a substantially neutral pH.

The invention also provides an alternative process for preparing the protected syn isomers of general formula Ia, in which the compound of the formula:

is treated with an appropriate acid of general formula IV (as defined hereinbefore) or with a functional derivative thereof to obtain the desired product of general formula Ia.

In a preferred method of carrying out the process the compound of formula VI is treated with a functional derivative of the acid of general formula IV and preferred functional derivatives and preferred reaction conditions are as described hereinbefore in relation to the reaction of derivatives of the acid of general formula IV in the preparation of the syn isomers of general formula III wherein A' represents an alkali-metal atom.

This invention also provides a process for preparing the unprotected syn isomers of general formula Ib' wherein A represents a hydrogen atom, in which process an appropriate syn isomer of general formula Ia is subjected to acid hydrolysis or hydrogenolysis as necessary to remove the substituent R' and so form the desired product of the general formula:

wherein R, is as defined hereinbefore.

It is believed to be within the competance of one skilled in the art to determine whether acid hydrolysis or hydrogenolysis will be effective at removing a given substituent R', and to choose appropriate reaction conditions.

Preferred acid hydrolysis agents include trifluoroacetic acid, formic acid and acetic acid. These acids can be used in anhydrous form or in the presence of water.

A preferred hydrogenolysis agent is zinc-acetic acid system.

Preferably acid hydrolysis, using an agent such as anhydrous trifluoroacetic acid or aqueous formic or acetic acid, is used to eliminate t-butoxycarbonyl or trityl groups as substituent R'.

However, the zinc-acetic acid system is preferably used to eliminate the trichloroethyl group and catalytic hydrogenation to eliminate benzyl, benzhydryl and carbobenzyloxy groups.

The invention also provides an alternative process for the preparation of the unprotected syn isomers of general formula Ib, in which an appropriate syn isomer of the general formula:

(wherein R, is as defined hereinbefore) is treated with thiourea to obtain the desired product of general formula Ib.

The action of thiourea on the syn isomer of general formula VII is preferably carried out in a neutral or an acidic medium. A similar type of reaction is described by Masaki in J.A.C.S. 90, 4508 (1968).

The starting materials of general formula VII are conveniently prepared in a manner analogous to the preparation of the protected syn isomers of general formula Ia from the syn isomers of general formula V' by the route V'eIIIeIIOIa.

That is to say, the preferred multi-stage route is as follows: an appropriate syn isomer of the general formula:

is reacted with a deacetylation enzyme to obtain the corresponding product of the general formula:

which product of general formula IX is treated with an isocyanate of the general formula: R2-N=C=O to obtain a product of the general formula:

which product is treated with a hydrolysis agent, and when a basic hydrolysis agent has been used also treated with an acid, to obtain the desired product of general formula VII.

In the above sequence the substituent groups R1 and R2 are as defined hereinbefore, and the preferred substituents and reaction conditions for the various steps are also as previously described. However, it has been found desirable to use the preferred wheatgerm enzyme at a lower dilution than that employed in converting the syn isomers of general formula V' into the syn isomers of general formula III.

The invention also provides a process for preparing the protected or unprotected syn isomers of general formula I wherein A represents an alkali-metal atom, an equivalent of an alkaline-earth metal atom, an equivalent of magnesium or a substituted ammonium group, in which process an appropriate syn isomer of general formula Ia or Ib is salified by reaction with a suitable base to give the desired salt.

The salification can be effected in a conventional manner, for example, the salts may be obtained by the action on the syn isomers of general formulae Ia and Ib of a mineral base such as, for example, sodium or potassium hydroxide, sodium carbonate or bicarbonate or of an organic base such as triethylamine.

The salification is preferably carried out in one or more solvents such as water, methanol, ethanol, acetone and dioxan.

The invention extends of course to the syn isomers of general formula I whenever prepared by a process as described herein.

The syn isomers of general formula I and especially those of general formula Ib' possess very good antibiotic activity on the one hand against the Gram-positive bacteria such as the staphylococci and the streptococci, especially against the penicillin-resistant staphylococci, and on the other hand against the Gram-negative bacteria especially against the coliform bacteria, the klebsiella, the proteus and salmonella.

These properties may make the pharmaceutically-acceptable syn isomers of the invention suitable for use as medicaments in the treatment of diseases caused by sensitive microorganisms, particularly in the treatment of staphylococcal infections such as staphylococcal septicaemia, malignent facial or skin staphylococcal infections, pyodermatitis, septic or suppurating sores, anthrax, phlegmons, erysipelas, acute primary or post-influenza staphylococcal infections, bronchopneumonia and pulmonary suppurations.

The products may also be useful as medicaments in the treatment of colon bacillus and associated infections, of infections caused by Proteus, by Klebsiella and Salmonella and of other diseases caused by Gram-negative bacteria.

However, However, before any of the syn isomers of this invention may be used in medicine, they should preferably be formed into pharmaceutical compositions by association with suitable pharmaceutical vehicles.

The term "pharmaceutical" is used herein to exclude any possibility that the nature of the vehicle, considered of course, in relation to the route by which the composition is intended to be administered, could render the composition harmful rather than beneficial. The choice of a suitable mode of presentation, together with an appropriate vehicle, is believed to be within the competence of those accustomed to the preparation of pharmaceutical formulations.

Accordingly, in yet another aspect this invention provides pharmaceutical compositions containing as active material one or more syn isomers of general formula Ib', in association with a suitable pharmaceutical vehicle.

Preferably the active material is a syn isomer of a general formula Ib' wherein R, represents a methyl radical and A represents a hydrogen or sodium atom.

Amongst these preferred active materials the following are especially mentioned: 3- carbamoyloxymethyl- 7 - [2 - (2 - amino - 4 - thiazolyl) - 2 (methoxyimino) - acetamido] - ceph - 3 - em - 4 - carboxylic acid, syn isomer; 3 - carbamoyloxymethyl - 7 - [2 - (2 - amino - 4 - thiazolyl) - 2 (methoxyimino) - acetamido] - ceph - 3 - em - 4 - carboxylic acid, syn isomer, obtained according to the process described in Example 2; and the sodium salt of 3 - carbamoyloxymethyl - 7 - [2 - (2 - amino - 4 thiazolyl) - 2 - (methoxyimino) - acetamido] - ceph - 3 - em - 4 - carboxylic acid, syn isomer.

The compositions of this invention may be administered by buccal, rectal or parenteral route or by local route using a topical application to the skin or mucous membranes. For these and other applications the preferred vehicles are: a) the ingestible excipient of a plain or coated tablet, sublingual tablet or pill; the ingestible container of a capsule or cachet; the ingestible pulverent solid carrier of a powder or a granular preparation; or the ingestible liquid medium of a syrup, solution, suspension or elixir; b) the solid or liquid medium of a paste, lotion, cream ointment or gel; c) a sterile injectable liquid solution or suspension medium, or . d) a base material of low melting point capable of releasing the active material to perform its pharmacological function, which base material when appropriately shaped forms a suppository.

The compositions of the invention may be solid or liquid depending upon the particular form of presentation selected. Preferred forms of administration include plain or sugar-coated compressed tablets, gelatin capsules, granules, suppositories, injectable preparations, ointments, creams and gels; these forms may be prepared according to the usual methods. The vehicle employed generally comprises one or more of the excipients customarily employed in these pharmaceutical compositions, and thus may include one or more of talc, gum arabic, lactose, starch, magnesium stearate, cocoa butter, aqueous or nonaqueous vehicles, fatty substances of animal or vegetable origin, paraffin derivatives, glycols and various wetting, dispersing or emulsifying agents and/or preservatives.

The dose of the active material administered may be varied according to the complaint treated, the person concerned, the route of administration and the product under consideration. By way of illustration only, it can be from 0.250 g to 4 g per day for the product described in example 2 administered by oral route or from 0.500 g to 1 g for the products described in examples 2 and 5 administered three times daily by intra-muscular route.

It is believed that certain of the intermediates used in the preparation of syn isomers of general formula I are themselves new. These novel intermediates are: a) the syn isomers of the general formula:

wherein R', R1 and A' are as defined hereinbefore and B represents a hydrogen atom or the radical:

wherein R, is as defined hereinbefore; and b) the syn isomers of general formula:

wherein R, is as defined hereinbefore and D represents a hydrogen atom or a radical

in which R'2 represents a hydrogen atom or a group removable by hydrolysis.

The syn isomeric acids of general formula IV and the syn isomers of general formulae V and V' can be prepared by the processes described in the Applicants copending Application No. 2,640/77 (Serial No. 1580621).

The compound of formula VI is described in German Patent Application No.

2,203,653, and the syn isomers of general formula VIII are described in French Patent Application No. 77-01713, published as Specification No. 2,384,781.

The following Examples and Formulations are given, though only by way of illustration, to show some preferred aspects of the invention.

Example 1 3-carbamoyloxymethyl-7-[2-(2-tritylamino-4-thiazolyl)-2-(methoxyimino)- acetamido]-ceph-3-em-4-carboxylic acid, syn isomer Stage A: Sodium salt of 3 - hydroxymethyl - 7 - [2 - (2 - tritylamino - 4 thiazolyl)- 2 - (methoxyimino) - acetamido] - ceph - 3 - em - 4 - carboxylic acid, syn isomer 85 cm3 of methanol and 1.7 g of the diethylamine salt of 3 - acetoxymethyl 7 - [2 - (2 - tritylamino - 4 - thiazolyl) - 2 - (methoxyimino) - acetamido] ceph - 3 - em - 4 - carboxylic acid, syn isomer were mixed under nitrogen. The formed solution was cooled to -250C and over 2 minutes, 380 mg of sodium methylate were added, and the whole was agitated at -200C for 4 hours 30 minutes, then 126 mg of sodium methylate were added and the agitation continued for 4 hours. The reaction medium was then saturated with dry ice and poured at -200C into 680 cm3 of ether.

After one night in the refrigerator the whole was vacuum-filtered and washed with ether to obtain 1.89 g of white product. M.Pt.=210--230"C (with decomposition).

Stage B: 3 - carbamoyloxymethyl - 7 - [2 - (2 - tritylamino - 4 - thiazolyl) - 2 (methoxyimino) - acetamido] - ceph - 3 - em - 4 - carboxylic acid, syn isomer 30 cm3 of methylene chloride and 0.75 cm3 of trichloroacetyl isocyanate were mixed under nitrogen. The formed mixture was brought to between 0 and +5"C and, over four minutes, 1.5 g of product obtained in stage A were added. About half way through this addition, a further 0.25 cm3 of trichloroacetyl isocyanate were added, with an additional 0.25 cm3 at the end of the introduction. After 10 minutes' agitation at between 0 and +5"C, 1 cm3 of methanol were added, and the mixture was concentrated almost to dryness under vacuum, before being redissolved in 30 cm3 of methanol. A solution of 915 mg of sodium acid carbonate in 22.5 cm3 of water was added, and the mixture was agitated for 3 hours at ambient temperature, decanted, concentrated and then acidified to pH 2 with 1M hydrochloric acid. The formed precipitate was vacuum-filtered, washed with water, then ether, and finally made into a paste with ether and dried under vacuum.

600 mg of a solid (M.Pt.=approximately 2100C with decomposition) were obtained. Rf=0.28 (ethylacetate, ethanol, water 7:2:1).

The diethylamine salt of 3 - acetoxymethyl - 7 - [2 - (2 - trityl - amino - 4 thiazolyl) - 2 - (methoxyimino) - acetamido] - ceph - 3 - em - 4 carboxylic acid, syn isomer, was prepared as follows: Ethyl 2-(2-amino-4-thiazolyl)-2-methoxyimino-acetate, syn isomer I g of ethyl y - chloro - a - methoxyimino - acetylacetate, 3 cm3 of absolute ethanol and 0.42 g of crushed thiourea were placed in a reaction vessel, which was agitated at ambient temperature for about two hours. The mixture was diluted with 60 cm3 of ether, causing the hydrochloride to crystallise out, and agitated. The crystal were vacuum-filtered, washed and dried to give 685 mg of the hydrochloride, which were then dissolved in 4 cm3 of water at 500 C. Potassium acetate was added until pH 6 caused the desired amine salt to crystallise out, and the mixture was cooled. The crystals were recovered by vacuum-filtration, washed with water and dried to give 270 mg of the expected product. M.Pt.=161 C.

Ethyl 2 - (2 - tritylamino - 4 - thiazolyl) - 2 - methoxyimino - acetate, syn isomer 4.6 g of product prepared according to the previous stage were dissolved at 30"C in 92 cm3 of methylene chloride. The solution was cooled to -10"C, when 2.9 cm3 of triethylamine were added, and cooled again to -350C. 6.1 g of trityl chloride were then introduced over fifteen minutes and the mixture was allowed to return to ambient temperature, taking two hours, thirty minutes in all. The mixture was washed with water, then with 0.5 N hydrochloric acid, and sodium acetate in water, before being dried and concentrated. The residue was taken up with ether, concentrated again and dissolved in methanol. Next, water and ether were added, and the mixture was allowed to crystallise. The crystals were recovered by vacuumfiltration and washed with ether to obtain 6.15 g of the expected product.

M .Pt.= 120 C. n 2-(2-tritylamino-4-thiazolyl)-2-methoxyimino-acetic acid, syn isomer 7.01 g of the ester obtained above were dissolved in 35 cm3 of dioxan. The solution was brought to 1100C in an oil bath, then over five minutes, 9 cm3 of 2N sodium hydroxide were added. The mixture was refluxed for thirty minutes under agitation, during which time the sodium salt crystallised out, and then cooled. The crystals were recovered by vacuum-filtration, and washed with dioxan and then ether to give a first yield of 5.767 g of salt. The mother liquor was concentrated to give a second yield of 1.017 g: a total yield of 6.784 g of salt.

3.06 g of the salt were placed in a mixture of 65 cm3 of methylene chloride and 6.5 cm3 of 2N hydrochloric acid, and the mixture was washed with water, dried and concentrated to dryness to give the free acid quantitatively.

Diethylamine salt of 3-acetoxymethyl-7-[2-(2-tritylamino-4-thiazolyl)-2 methoxyimino-acetamido].ceph-3-em-4-carboxylic acid, syn isomer The acid obtained as in the previous stage (from 153.6 g of sodium salt) was dissolved in 450 cm3 of methylene chloride under an inert atmosphere. The solution was cooled with an ice bath, and at +50C 36 g of dicyclohexylcarbodiimide were added. The mixture was agitated for 40 minutes at +50C, and then for 30 minutes at +20"C. The precipitated dicyclohexylurea was vacuum-filtered. The filtrate was cooled to between -10"C and -15"C, then a solution, at -10"C, of 40.8 g of 7amino-cephalosporanic acid in 600 cm3 of methylene chloride and 41 cm3 of triethylamine was introduced. The mixture was allowed to return to ambient temperature, agitated, and washed twice with normal hydrochloric acid and three times with water, before being dried and concentrated. The residue was taken up with ethyl acetate, which was evaporated off to dryness. This residue was dissolved in 350 cm3 of dioxan, after which 350 cm3 of ether were added slowly, followed by 33 cm3 of diethylamine. The mixture was agitated for 20 minutes, filtered and the filtrate was concentrated before the addition of about 2.5 litres of ether. The ether was agitated and vacuum-filtered to give 110.3 g of the expected salt.

The ethyl y - chloro a - methoxyimino - acetylacetate used at the start of this preparation was prepared as follows: 22.5 g of ethyl y - chloro - a - oximino - acetylacetate was placed in 100 cm3 of methylene chloride. The mixture was placed on a

Example 3 3-carbamoyloxymethyl-7- [2-(2-tritylamino-4-thiazol)-2-(methoxyimino) acetamido]-ceph-3-em-4-carboxylic acid, syn isomer Stage A: Sodium salt of 3 - hydroxymethyl - 7 - [2 - (2 - tritylamino - 4 thiazolyl) - 2 - (methoxyimino) - acetamido] - ceph - 3 - em - 4 carboxylic acid, syn isomer a) 15 cm3 of dry methanol and 272 mg of 7-amino-cephalosporanic acid were mixed under nitrogen. The formed mixture was cooled to -200C, and a total of 136 mg of sodium methylate were introduced, in three additions. The mixture was agitated for 7 hours 30 minutes at --150C and then used immediately in stage c) below.

b) 1 g of the sodium salt of 2-(2-tritylamino - 4- thiazolyl)- 2methoxyimino - acetic acid, syn isomer, was introduced into a mixture of 8 cm3 of methylene chloride, I cm3 of ether and 4 cm3 of normal hydrochloric acid. The formed mixture was agitated until dissolution, decanted and re-extracted with methylene chloride. The extracts were washed with water, dried and evaporated to dryness, and the residue obtained was redissolved in 4 cm3 of dry methyl chloride.

235 mg of dicyclohexylcarbodiimide were added, and the mixture was agitated for 30 minutes at ambient temperature, after which the dicyclohexylurea formed was separated by vacuum-filtration and rinsed with methylene chloride.

c) The solution prepared at b) was added to the mixture a) which had been previously saturated with dry ice. The mixture was agitated for 30 minutes at -15"C, and then left for a night at +50C. The product was precipitated by the addition of isopropyl ether, and 800 mg of a product identical to that obtained in Stage A of Example 1 were obtained.

Stage B: 3 - carbamoyloxymethyl - 7 - [2 - (2 - tritylamino - 4 - thiazolyl) - 2 (methoxyimino) - acetamido] - ceph - 3 - em - 4 - carboxylic acid, syn isomer.

The method of Stage B of Example 1 was employed to obtain the expected product.

Example 4 3-carbamoyloxymethyl-7-[2-(2-tritylamino-4-thiazolyl)-2-(methoxyimino)- acetamido]-ceph-3-em-4-carboxylic acid, syn isomer Some 2-(2-tritylamino-4-thiazolyl)-2-methoxyimino acetic acid obtained as described above (from 1.81 g of the sodium salt) was dissolved in 20 cm3 of dry chloroform. 0.48 g of dicyclohexylcarbodiimide were added and the mixture was agitated for 45 minutes at ambient temperature. The urea formed was separated by vacuum-filtration, and the filtrate was cooled to --100C before the addition of 0.5 g of 3 - carbamoyloxymethyl - 7 - amino - ceph - 3 - em - 4 - carboxylic acid in 8 cm3 of chloroform and 0.5 cm3 of triethylamine.

After one night at +50C the mixture was extracted with a 4% solution of bicarbonate. The aqueous solution was washed with ether and acidified to pH 2.

The precipitate formed was recovered by vacuum-filtration, washed with water and then ether and dried to give a product identical to that obtained in Example 1.

Example 5 3-carbamoyloxymethyl-7-[2-(2-amino.4-thiazolyl)-2.(methoxyimino).acetamido].

ceph-3-em-4-carboxylic acid, syn isomer Stage A; 3 - hydroxymethyl - 7 - [2 - (2 - chloracetamido - 4 - thiazolyl) - 2 (methoxyimino) - acetamido] - ceph - 3 - em - 4 - carboxylic acid, syn isomer.

240 cm3 of distilled water at 370C and 40 g of cleansed wheatgerm were mixed.

The mixture was agitated for 30 minutes at 370C and centrifuged at +50C to give 205 cm3 of supernatent enzyme solution at pH 6.6.

Separately, 1.6 g of 3 - acetoxymethyl - 7 - [2 - (2 - chloroacetamido - 4 thiazolyl) - 2 - (methoxyimino) - acetamido] - ceph - 3 - em - 4 - carboxylic acid, syn isomer were introduced into 96 cm3 of distilled water. A suspension at pH 4.3 was obtained, which was brought to pH 6.7 by the addition of 11.9 cm3 of 0.2N potassium hydroxide. The solution became clear.

Under agitation, at 370C, and in an atmosphere of nitrogen, 192 cm3 of the fresh enzyme solution prepared as above were mixed with the above acid solution at pH 6.7. The pH was then maintained at 6.5 by addition of 0.2N potassium hydroxide, as required, and the progress of the reaction was followed by means of thin layer chromatography. The reaction was stopped at the end of 4 hours, when the mixture was centrifuged at +50C. The residue formed was triturated with 19 cm3 of iced water and centrifuged at 50C for 30 minutes, after which the supernatant layers were combined and concentrated to 67 cm3. 168cm3 of acetone were added to precipitate the proteins, which were separated by filtration and then washed 3 times by formation of a paste with 16 cm3 portions of a water-acetone solution (1:2:5). The filtrate and washing waters were combined and 640 mg of carbon black were added to the mixture, which was agitated for I hour at ambient temperature and then filtered. The precipitate was washed with a water-acetone mixture, and the washing waters and filtrate were united and concentrated in a water bath. 5 cm3 of formic acid were added to cause crystallisation. The mixture was left for one night at 50C, after which the crystals were recovered by vacuumfiltration and washed with water to give 76.1 g of the expected product, which was recrystallised as follows: 727.4 mg of the product obtained above were added to 28 cm3 of distilled water. 134 mg of sodium bicarbonate were introduced, and the mixture formed was agitated. The insoluble matter was separated and 50 mg of sodium bicarbonate were added to the mixture, which was agitated for another 15 minutes. 142 mg of carbon black were added, and the mixture was agitated for 30 minutes at ambient temperature. The carbon black was then separated by filtration and washed 3 times with 2 cm3 of water. The washing waters and filtrate were combined, and 1 cm3 of acetic acid and 0.5 cm3 of formic acid were added. The product slowly crystallised out, and was recovered by vacuum-filtration and washed with distilled water to give 635.9 mg of product, after drying. [a],=+63.40, with 0.5% product in 0.5 M sodium acid carbonate. NMR (DMSO 60 MHz): 7.48 p.p.m:-- proton of the thiazole ring, 3.91 p.p.m.- methoxy of the oxime, 4.28 p.p.m.- methylene of the group -CH2OH.

Stage B: 3 - carbamoyloxymethyl - 7 - [2 - (2 - chloroacetamido - 4 - thiazolyl) 2 - (methoxyimino) - acetamido] - ceph - 3 - em - 4 - carboxylic acid, syn isomer 1.56 g of 3 - hydroxymethyl - 7 - [2 - (2 - chloracetamido - 4 - thiazolyl) 2 - (methoxyimino) - acetamido] - ceph - 3 - em - 4 - carboxylic acid, syn isomer (as prepared in Stage A), 18 cm3 of pyridine and 60 cm3 of tetrahydrofuran were mixed. The mixture formed was cooled to 250C, and 3 cm3 of trichloroacetyl isocyanate were added in one portion. The temperature rises to -180C then falls back, when 600 cm3 of a saturated solution of sodium bicarbonate in water, diluted to half concentration, were added. The mixture was agitated at ambient temperature and extracted 4 times with 25 cm3 portions of ethyl acetate. Each extract was then washed with 125 cm3 of a saturated solution of sodium acid carbonate, diluted to half concentration. The basic aqueous phases were combined, brought to neutrality with 2N hydrochloric acid and extracted twice with 250 cm3 portions of ethyl acetate, which were washed with a saturated solution of sodium chloride. The product was then re-extracted with tetrahydrofuran and washed again. The organic phases were combined, washed with salt water, dried and evaporated under reduced pressure. The gum obtained was triturated with ether, agitated at ambient temperature and vacuum-filtered to give a solid that was rinsed and dried to give 1.020 g of a white powder. M.Pt.=2460C (with decomposition) Rf=0.37 (ethyl acetate-acetic acid water 80:15:5).

Stage C: 3 - carbamoyloxymethyl - 7 - [2 - (2 - amino - 4 - thiazolyl) - 2 (methoxyimino) - acetamido] - ceph - 3 - em - 4 - carboxylic acid, syn isomer 950 mg of the product obtained in Stage B above and 171 mg ofthioureawere introduced into 2 cm3 of distilled water. The mixture formed was placed in an ice bath and 190 mg of potassium bicarbonate were added in several portions. The mixture was allowed to return to ambient temperature and left under agitation for 5 hours 30 minutes, after which formic acid and 6.7 cm3 of water were added until neutrality. Next, the mixture was triturated in an ice bath and vacuum-filtered. The solid was rinsed with 3.8 cm3 of water containing 10% of formic acid, taken up with 5.7 cm3 of water and maintained in an ice bath with the addition of triethylamine so as to ensure good dissolution. 0.6 cm3 of formic acid were added before vacuumfiltration and two subsequent washings with 3.8 cm3 of water containing 10% of formic acid. A dark brown gum was eliminated. The aqueous phases were combined and treated with 10.25 g of ammonium sulphate, and the precipitate formed was recovered by vacuum-filtration, made into a paste with water, then ether, and dried to give a first yield of 470 mg. By saturating the mother liquors with ammonium sulphate a second yield of 52 mg was obtained.

The product was purified as follows: 46 mg of crude product containing formic acid and 0.12 cm3 of absolute ethanol containing 0.1 millimole of pyridine were together agitated for 2 hours. The solid was recovered by vacuum-filtration, rinsed with absolute ethanol and dried to give 32 mg of purified white powder.

NMR (60 MHz (DMSO) p.p.m.: 6.75-proton of the thiazolyl ring, 6.58- OCO NH3.

The 3 - acetoxymethyl - 7 - [2 - (2 - chloracetamido - 4 - thiazolyl) - 2 (methoxyimino) - acetamido] - ceph - 3 - em - 4 - carboxylic acid, syn isomer used at the start of this Example was prepared as follows: Ethyl 2 - (2 - chloracetamido - 4 - thiazolyl) - 2 - (methoxyimino) - acetate, syn isomer 45.8 g of ethyl 2 - (2 - amino - 4 - thiazolyl) - 2 - (methoxyimino) - acetate, syn isomer (prepared as indicated in Example 1) were mixed with 200 cm3 of methylene chloride. 20 em3 of liquor were distilled therefrom to effect drying, and the mixture was cooled to 100C before the addition of 50 cm3 of pyridine. 41 g of monochloracetic anhydride were further added, with slight heating until dissolution, and the mixture was left for six hours at 200C under nitrogen, after which 5 cm3 of water were added. The mixture was agitated, poured into 300 cm3 of chilled 2M hydrochloric acid and then decanted. The product was extracted with methylene chloride, and the extracts were washed with water, sodium bicarbonate and again with water, then dried, passed over active charcoal and concentrated.

300 cm3 of isopropyl ether were added to the residue, and the product crystallised out. The mixture was then concentrated until a thick paste was obtained, chilled and vacuum-filtered. The solid obtained was washed with isopropyl ether and dried to obtain 45.4 g of product. M.Pt.=113 C.

A pure sample was obtained by recrystallisation from a mixture of methylene chloride and isopropyl ether. M.Pt.=118 C.

2 - (2 - chloracetamido - 4 - thiazolyl) - 2 - (methoxyimino) - acetic acid, syn isomer 46 g of the product obtained in the previous stage were introduced into 230 cm3 of absolute ethanol, followed by, at 200C under nitrogen, 30 cm3 of pure sodium hydroxide solution. The product dissolved, the sodium salt began to crystallise out, and the medium congealed into a mass. After sixteen hours a solid was separated by vacuum-filtration and washed with ethanol. The salt thus obtained was dissolved in water and chilled before the addition of 100 cm3 of 2N hydrochloric acid. Next, the formed solution was saturated with sodium chloride and the product was extracted with the ethyl acetate containing 10% ethanol. The extracts were dried, passed over active charcoal, distilled under vacuum, and the water present was entrained with benzene. The residue formed was taken up with methylene chloride, distilled to dryness, taken up again with methylene chloride, chilled and vacuum-filtered. The solid separated was washed with methylene chloride and dried to give 34.5 g of the expected product. M.Pt.=about 200"C. The product was purified by recrystallisation from an acetone-isopropyl ether mixture.

Analysis: C8ll8O4N3ClS=277.68 Calculated: C% 34.60 11% 2.90 N% 15.13 Cl% 12.77 S% 11.55 Found: C% 34.8 H% 2.8 N% 14.8 Cl% 12.6 S% 11.5 3 - acetoxymethyl - 7 - [2 - (2 - chloracetamido - 4 - thiazolyl) - 2 (methoxyimino) - acetamido] - ceph - 3 - em - 4 - carboxylic acid, syn isomer: 15.3 g of the product obtained in the above stage were introduced into 80 cm3 of methylene chloride. At 5"C, 8 cm3 of triethylamine were added, then at OOC and under nitrogen, 3.8 cm3 of thionyl chloride and 26 cm3 of methylene chloride were added. The mixture formed was left for fifteen minutes at OOC and then 7 cm3 of triethylamine were introduced, followed, at OOC under nitrogen, by 13.6 g of 7amino-cephalosporanic acid in 100 cm3 of methylene chloride and 14 cm3 of triethylamine. The temperature was allowed to rise to 200 C, and after one hour's agitation, the solution was distilled to dryness under vacuum at about 335"C.

The residue was dissolved in 250 cm3 of water and passed over active charcoal before the addition of 50 cm3 of 2N hydrochloric acid. A precipitate was formed which was separated by vacuum-filtration and washed with water. The crude product thus obtained was put into a suspension in 80 cm3 of ethanol, and at +50C, 7 cm3 of triethylamine were added, followed by 15 cm3 of 4N sulphuric acid in a single addition, under agitation. The product crystallised out, and after fifteen minutes this was recovered by vacuum-filtration, washed with ethanol by making into a paste, washed with ether and dried under vacuum to give 18.6 g of the expected product. [(r]0=+26"+1" (concentration: 1% in dimethylformamide).

Example 6 Sodium salt of 3-carbamoyloxymethyl-7-[2-(2-amino-4-thiazolyl)-2 (methoxyimino)-acetamido]-ceph-3-em-4-carboxylic acid, syn isomer 92 mg of 3 - carbamoyloxymethyl - 7 - [2 - (2 - amino - 4 - thiazolyl) - 2 (methoxyimino) - acetamido] - ceph - 3 - em - 4 - carboxylic acid, syn isomer, prepared as in Example 5, were introduced into 0.2 cm3 of distilled water. 12 mg of sodium bicarbonate were added in small amounts and a solution was gradually formed before taking up with 2.4 cm3 of acetone and triturating. A gum was formed, which was separated by decanting and taken up with 2.4 cm3 of acetone, before triturating and agitating for 10 minutes at ambient temperature to give fraction A.

2.4 cm3 of acetone were then added to the mother liquors, and the mixture was triturated and agitated for 10 minutes at ambient temperature to give fraction B.

Fractions A and B were combined and made into a paste with, and successively, 0.2 cm3 of ethanol, 0.2 cm3 of isopropyl ether and 0.2 cm3 of acetone. The product was placed in a dissicator until a constant weight was obtained, giving 65 mg of a creamy white powder. M.Pt. > 272 C.

Rf.=0.16 (eluant: ethyl acetate-acetic acid-water: (80:15:5).

Formulation 1 A preparation for injection was prepared of formula: 3 - carbamoyloxymethyl - 7 - [2 - (2 - amino - 4 thiazolyl) - 2 - (methoxyimino) - acetamido] ceph - 3 - em - 4 - carboxylic acid, syn isomer 500 mg Sterile aqueous excipient. . .q.s.v. 5 cm3 Formulation 2 Gelatin capsules were prepared corresponding to the formula: 3 - carbamoyloxymethyl - 7 - [2 - (2 - amino - 4 thiazolyl) - 2 - (methoxyimino) - acetamido] ceph - 3 - em - 4 - carboxylic acid, syn isomer 250 mg Excipient q.s. for one gelatin capsule up to 400 mg Formulation 3 A composition for injection was prepared by the formula: Sodium salt of 3 - carbamoyloxymethyl - 7 - [2 - (2 amino - 4 - thiazolyl) - 2 - (methoxyimino) - acetamido] - ceph - 3 - em - 4 - carboxylic acid, syn isomer 500 mg Sterile aqueous excipient. . .q.s.v. 5 cm3 Formulation 4 Gelatin capsules were prepared corresponding to the formula: Sodium salt of3 - carbamoyloxymethyl - 7 - [2 - (2 amino - 4 - thiazolyl) - 2 - (methoxyimino) - acetamido] - ceph - 3 - em - 4 - carboxylic acid, syn isomer 250 mg Excipient q.s for one gelatin capsule up to 400 mg In the following claims all substituents and formulae are as first defined, unless otherwise stated.

Claims

WHAT WE CLAIM IS:-

1. An oxime derivative of 3 - carbamoyloxymethyl - 7 - amino thiazolyl - acetamido - ceph - 3 - em - 4 - carboxylic acid of the general formula:

(wherein R1 represents a saturated or unsaturated hydrocarbyl radical having from 1 to 4 carbon atoms and A represents either a hydrogen atom, an alkali-metal atom, an equivalent of an alkaline-earth metal atom, an equivalent of a magnesium atom, or a substituted ammonium group) the compound being in the form of the syn isomer.

2. A syn isomer as claimed in Claim 1, wherein A represents a sodium, potassium, lithium, calcium or magnesium atom.

3. A syn isomer as claimed in Claim 1, wherein A represents a substituted ammonium group derived from methylamine, propylamine, diethylamine, trimethylamine, triethylamine, N,N - dimethylethanolamine or tris(hydroxymethyl) - aminomethane.

4. A syn isomer as claimed in Claim 1, wherein R1 represents a methyl radical and A represents a hydrogen atom or a sodium atom.

5. 3 - Carbamoyloxymethyl - 7 - [2 - (2 - amino - 4 - thiazolyl) - 2 (methoxyimino) - acetamido] - ceph - 3 - em - 4 - carboxylic acid, syn isomer.

6. 3 - Carbamoyloxymethyl - 7 - [2 - (2 - amino - 4 - thiazolyl)- 2 (methoxyimino) - acetamido] - ceph - 3 - em - 4 - carboxylic acid, syn isomer, as obtained according to the process described in Example 2.

7. The sodium salt of 3 - carbamoyloxymethyl - 7 - [2 - (2 - amino - 4 thiazolyl) - 2 - (methoxyimino) - acetamido] - ceph - 3 - em - 4 - carboxylic acid syn isomer.

8. An oxime derivative of 3 - carbamoyloxymethyl - 7 - amino - thiazolyl acetamido - ceph - 3 - em - 4 - carboxylic acid of the general formula:

(wherein R' represents a group removable by acid hydrolysis or by hydrogenolysis) the compound being in the form of the syn isomer.

9. A syn isomer as claimed in Claim 8, wherein R' represents a tbutoxycarbonyl, trityl, benzhydryl, trichloroethyl or carbobenzyloxy group.

10. A process for preparing a syn isomer of general formula Ib' wherein A represents a hydrogen atom, in which process an appropriate syn isomer of general formula Ia', wherein A represents a hydrogen atom, is subjected to acid hydrolysis or hydrogenolysis as necessary to remove the substituent R' and so form the desired product of the general formula:

11. A process as claimed in Claim 10, in which the acid hydrolysis is effected with trifluoroacetic acid, formic acid or acetic acid.

12. A process as claimed in Claim 10, in which the hydrogenolysis is effected with a zinc-acetic acid system.

13. A process for preparing the syn isomers of general formula Ia' wherein A represents a hydrogen atom, in which process an appropriate syn isomer of the general formula:

(wherein A' represents an alkali-metal atom or a hydrogen atom and R2 represents a group removable by hydrolysis) is treated with a hydrolysis agent effective at hydrolysing the group R2 and not the group R', and in the case where a basic hydrolysis agent is employed thereafter the hydrolysis product is treated with an acid, to give the desired product of the general formula:

14. A process as claimed in Claim 13, in which the hydrolysis of the svn isomer of general formula II is carried out using aqueous sodium bicarbonate.

15. A process as claimed in Claim 13, in which the hydrolysis of the syn isomer of formula II is carried out using potassium bicarbonate or an alkali-metal carbonate in a medium of water or a water/alcohol mixture.

16. A process as claimed in Claim 14 or Claim 15, in which the hydrolysis product is treated with dilute hydrochloric, sulphuric or phosphoric acid.

17. A process as claimed in any of Claims 13 to 15, in which the substituent R2 is a trichloroethyl, benzyl, p-methoxybenzyl or chlorosulphonyl radical.

18. A process as claimed in any of Claims 13 to 17, in which the syn isomer of general formula II is prepared by reacting an appropriate syn isomer of the general formula:

with an isocyanate of the general formula: R2-N=C=O to give the desired product of general formula II.

19. A process as claimed in Claim 18, in which the reaction is carried out in one or more inert solvents.

20. A process as claimed in Claim 19, in which the reaction is carried out in one or more of methylene chloride, chloroform, dimethylformamide, tetrahydrofuran and pyridine.

21. A process as claimed in any of Claims 18 to 20, in which a syn isomer of general formula III wherein A' represents an alkali-metal atom is prepared by reacting 7-aminocephalosporanic acid of the formula:

with an alkali-metal alcoholate in an alcohol, and treating the formed product with an appropriate syn isomeric acid of the general formula:

or a functional derivative thereof to give the desired product of general formula III.

22. A process as claimed in Claim 21, in which the 7-amino-cephalosporanic acid is reacted with the alkali-metal alcoholate in an alcohol containing from 1 to 3 carbon atoms.

23. A process as claimed in Claim 22, in which the alcoholate is sodium methylate and the reaction is carried out in methanol.

24. A process as claimed in any of Claims 21 to 23, in which the acid of general formula IV is employed as its acid chloride or acid anhydride.

25. A process as claimed in Claim 24, in which the anhydride is formed in situ by the action of isobutyl chloroformate on the free acid.

26. A process as claimed in Claim 24 or Claim 25, in which the reaction is carried out in the presence of a basic agent.

27. A process as claimed in Claim 26, in which the basic agent is an alkalimetal bicarbonate or carbonate, N-methylmorpholine, pyridine or a trialkylamine.

28. A process as claimed in any of claims 18 to 20, in which a syn isomer of general formula III wherein A' represents an alkali-metal atom is prepared by treating an appropriate syn isomer of the general formula:

with an alkali-metal alcoholate in an alcohol to obtain the desired product of general formula III.

29. A process as claimed in Claim 28, in which the alkali-metal alcoholate is sodium methylate, and the alcohol contains from I to 3 carbon atoms.

30. A process as claimed in any of Claims 18 to 20, in which a syn isomer of general formula III wherein A' represents a hydrogen atom is prepared by treating an appropriate syn isomer of the general formula:

with a decetylation enzyme to obtain the desired product of general formula 111.

31. A process as claimed in Claim 30, in which the substituent R' is a tbutoxycarbonyl, trityl, benzyl, benzhydryl, trichloroethyl, carbobenzyloxy or formyl radical or the equivalent of a phthaloyl group.

32. A process as claimed in Claim 30 or Claim 31, in which the enzyme is a wheatgerm enzyme, employed at a temperature of substantially 37"C and at a substantially neutral pK.

33. A process for preparing the syn isomers of general formula Ia, in which the compound of the formula:

is treated with an appropriate acid of general formula IV or with a functional derivative thereof to obtain the desired product of general formula Ia.

34. A process as claimed in Claim 33, in which a functional derivative of the acid of general formula IV as defined in Claim 24 or Claim 25 is employed.

35. A process as claimed in Claim 33 or Claim 34, in which the reaction conditions are as defined in Claim 26 or Claim 27.

36. A process for the preparation of the syn isomers of general formula Ib, as claimed in any of Claims 10 to 12, in which process the syn isomer of general formula Ia' wherein A represents a hydrogen atom is prepared by a process as claimed in any of Claims 13 to 35.

37. A process for preparing the syn isomers of general formula Ib, in which an appropriate syn isomer of the general formula:

is treated with thiourea to obtain the desired product of general formula Ib.

38. A process as claimed in Claim 37, in which the reaction is carried out in a neutral or an acidic medium.

39. A process as claimed in Claim 37 or Claim 38, in which the starting material of general formula VII is prepared by reacting an appropriate syn isomer of the general formula:

with a deacetylation enzyme to obtain the corresponding product of the general formula:

which product of general formula IX is treated with an isocyanate of the general formula: R2-N--C=O to obtain a product of the general formula:

which product is treated with a hydrolysis agent, and in the case when a basic hydrolysis agent has been used thereafter treated with an acid, to obtain the desired product of general formula VII.

40. A process as claimed in Claim 39, in which the substituent group R2 is as defined in Claim 17.

41. A process as claimed in Claim 39 or Claim 40, in which the reaction conditions employed are as defined in Claims 32, 19, 20 and 14 to 16.

42. A process for the preparing the syn isomers of general formula Ia' or Ib' wherein A represents an alkali-metal atom, an equivalent of an alkaline-earth metal atom, an equivalent of magnesium or a substituted ammonium group, in which process an appropriate syn isomer of general formula Ia or Ib is salified by reaction with a suitable base to give the desired product.

43. A process as claimed in Claim 42, in which the salification is carried out in a solvent comprising one or more of water, methanol, ethanol, acetone and dioxan.

44. A process as claimed in Claim 42 or Claim 43, in which the syn isomer of general formula Ia or Ib is prepared by a process as claimed in any of Claims 10 to 41.

45. A process for the preparation of a syn isomer of general formula Ia' or Ib' substantially as described herein with reference to any one of the Examples.

46. A syn isomer of general formula Ia' or Ib', whenever prepared by a process as claimed in any of Claims 10 to 45.

47. A pharmaceutical composition containing as active material one or more syn isomers of general formula Ib', in association with a suitable pharmaceutical vehicle.

48. A composition as claimed in Claim 47, in which the active material is a svn isomer of general formula Ib' wherein R1 represents a methyl radical and A represents a hydrogen or sodium atom.

49. A composition as claimed in Claim 47, in which the active material is: 3 - carbamoyloxymethyl - 7 - [2 - (2 - amino - 4 - thiazolyl) - 2 (methoxyimino) - acetamido] - ceph - 3 - em - 4 - carboxylic acid, syn isomer; 3- carbamoyloxymethyl- 7 - [2 - (2 - amino - 4 - thiazolyl) - 2 (methoxyimino) - acetamido] - ceph - 3 - em - 4 - carboxylic acid, syn isomer, obtained according to the process described in Example 2; or the sodium salt of 3 - carbamoyloxymethyl - 7 - [2 - (2 - amino - 4 thiazolyl) - 2 - (methoxyimino) - acetamido] - ceph - 3 - em - 4 - carboxylic acid, syn isomer.

50. A composition as claimed in any of Claims 47 to 49 and substantially as described herein with reference to any one of the Formulations.

51. The syn isomers of general formula VII.