GB1600723A - Cephalosporin derivatives their preparation and compositions containing them - Google Patents

Description

(54) NEW CEPHALOSPORIN DERIVATIVES, THEIR PREPARATION AND COMPOSITIONS CONTAINING THEM (71) We, RHONE-POULENC INDUSTRIES, a French Body Corporate of 22 Avenue Montaigne, Paris 8 eme, 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 cephalosporins, their production and their use.

The present invention provides, as new compounds, the cephalosporin derivatives of the formula:

in which R represents a carboxyl radical or a radical of the general formula:

in which R, represents a hydrogen atom or an alkyl radical containing 1 to 4 carbon atoms and R2 represents a straight- or branched-chain alkyl radical containing I to 4 carbon atoms, or a cyclohexyl radical, the radical

being a radical which is easily removable by an enzymatic route, such as the pivaloyloxymethyl radical, in their diastereoisomeric forms and their mixtures, and their acid addition salts and, when R is carboxyl, their metal salts and their addition salts with organic nitrogen-containing bases.

The products of the formula (I) are derived from the D. L and DL forms of the aminoacid of the formula:

and the diastereoisomeric forms of the products of the formula (I) which thus result, and their mixtures. are all within the scope of the present invention.

According to a feature of the invention, the compounds otthe general formula (I) are obtained by the action of the acid of the formula (IV), in racemic or optically active form, and in which the amine function has been protected beforehand, or a reactive derivative of this acid, on a cephalosporin of the general formula:

in which R is as hereinbefore defined or is a protected carboxyl group, and then removing the protecting groups.

a) When the acid of the formula (IV) is used, the amino group is protected by any method known for blocking an amine function without affecting the rest of the molecule. It is necessary to use for this purpose an easily removable group such as the tert.-butoxycarbonyl or 2,2,2 - trichloroethoxycarbonyl group. It is particularly advantageous to use the tert.-butoxycarbonyl group which can be introduced bv the action of di-tert.-butyl dicarbonate, tert.-butyl azidoformate, tert.-butyl chloroformate or the mixed tert.-butyl/p - nitrophenyl carbonate.

It is also possible to protect the amino radical in the form of an enamine of the general formula:

in which the sumbol R3 represents an alkyl radical containing 1 to 4 carbon atoms and the symbol R4 represents an alkyl radical containing 1 to 4 carbon atoms, an alkoxy radical in which the alkyl part contains 1 to 4 carbon atoms, or a phenyl radical.

The enamine of the general formula (VI) can be prepared in accordance with the method described by E. Dane et al., Chem. Ber., 98, 789 (1965).

a) When R represents a carboxyl radical, the product of the formula (IV), in which the acid function is free and the amine function has been protected beforehand, is generally condensed with 7 - amino - 3 deacetoxycephalosporanic acid in which the acid function has been protected beforehand by an easily removable group such as the benzhydryl, tert.-butyl or 2,2,2 - trichloroethyl radical.

The condensation is generally carried out in an organic solvent such as dimethylformamide, acetonitrile, tetrahydrofurane or chloroform, in the presence of a condensation agent such as carbodiimide (e.g. dicyclohexylcarbodiimide) or N,N' - carbonyldiimidazole and at a temperature of between 0 and 40 C. and the protective groups of the amine and acid functions are then removed. This removal can be carried out in a single stage or in two stages, depending on the nature of the protective groups. When the protective group of the amine function is a tert.butoxycarbonyl radical, then, depending on the nature of the protective group of the acid function, the removal may be carried out: (i) in a single phase by treatment in an acid medium, when the acid function is protected by a tert.-butyl or benzhydryl group. Preferably, trifluoroacetic acid is used, the reaction being carried out at a temperature between 0 and 20"C (and in the case of the benzhydryl radical, in the presence of anisole). or para - toluenesulphonic acid is used. Under these conditions, the product of the general formula (I) is obtained in the form of the trifluoroacetate or para toluenesulphonate salt from which the amine can be liberated by any method known for obtaining an amine from one of its salts without affecting the rest of the molecule. The reaction may be carried out, in particular, by bringing the salt into contact with an ion exchange resin (e.g. a polystyrene-amine resin such as that sold under the Registered Trade Mark Amberlite IR-45) in its basic form or by the action of an organic base.

(ii) by treatment with zinc in acetic acid and then replacement of the tert.butoxycarbonyl radical by treatment in an acid medium, when the acid function is protected by the 2,2.2 - trichloroethyl radical. The treatment in an acid medium is carried out using trifluoroacetic acid: under these conditions, the product of the general formula (I) is obtained in the form of the trifluoroacetate salt and the free amine can be liberated from this salt in the manner described previously.

When the protective group of the amine function is a 2,2,2trichloroethoxycarbonyl radical, then, depending on the nature of the protective group of the acid function, the removal may be carried out: (i) by treatment with zinc in acetic acid and then treatment in an acid medium, preferably by the action of trifluoroacetic acid, when the protective group of the acid function is a tert.-butyl or benzhydryl radical, or (ii) by treatment with zinc in acetic acid, when the protective group of the acid function is a 2,2,2 - trichloroethyl radical.

When the amine function is protected in the form of an enamine, then, depending on the nature of the protective group of the acid function, the removal may be carried out: (i) by hydrolysis in a dilute acid medium, e.g. in the presence of hydrochloric acid, and then treatment with trifluoroacetic acid, when the protective group of the acid function is a tert.-butyl or benzhydryl radical, or (ii) by hydrolysis in an acid medium, e.g. in the presence of hydrochloric acid, and then treatment with zinc in acetic acid, when the protective group of the acid function is a 2,2,2 - trichloroethyl radical.

p) When R represents a radical of the general formula (II), as defined previously, the acid of the formula (IV) is generally condensed with the derivative of the general formula (V) in an organic solvent such as dimethylformamide or chloroform, in the presence of a condensation agent such as a carbodiimide (e.g.

dicyclohexylcarbodiimide) or N,N' - carbonyldiimidazole and at a temperature of between 0 and 40"C, and the protective group of the amine function is then removed under the conditions described above.

b) When a reactive derivative of the acid of the formula (IV) is used, it is advantageous to employ the anhydride, a mixed anhydride or a reactive ester of the general formula:

in which Rs represents a succinimido, benzotriazol - 1 - yl or 2,4 - dinitrophenyl radical and in which the amine function has been protected beforehand; it is also advantageous to employ the acid chloride by reacting the hydrochloride of the chloride of the acid of the formula (IV) with the cephalosporin of the general formula (V). It is also possible to use the Leuchs' anhydride.

When employing the anhydride, a mixed anhydride, the Leuchs' anhydride or the acid chloride (which can all be prepared in situ), the condensation is carried out in an organic solvent such as tetrahydrofuran, chloroform or methylene chloride, in the presence of an acid acceptor such as an organic nitrogencontaining base like pyridine or triethylamine, or in an aqueous-organic medium in the presence of an alkaline condensation agent such as sodium bicarbonate. the reaction being carried out at a temperature of between -40 and +40 C. and the protective group of the amine function is then optionally replaced by a hydrogen atom. In the case where R represents a carboxyl radical, it is not necessary to protect the acid function.

When employing a reactive ester of the general formula (VII). the reaction is generally carried out in the prsence of-triethylamine in an organic solvent such as dimethylformamide. at a temperature of between 0 and 40"C, and the protective group of the amine function is then replaced by a hydrogen atom. In the case where R represents a carboxyl radical, it is not necessary to protect the acid function.

The acid of the formula (IV) can be obtained: a) either by deformylating a - formylamino(l,3 - dithiin - 5 - yl)acetic acid.

The reaction is generally carried out in an aqueous acid medium at a temperature of between 0 and 100"C. A mineral acid, such as a solution of hydrochloric acid in water, is preferably used, at a temperature of about 100"C.

a-formylamino(l.3 - dithiin - 5 - yl)acetic acid can be obtained bv saponifying the corresponding ester of the general formula:

in which R6 represents an alkyl radical containing 1 to 4 carbon atoms, the reaction being carried out under conditions which make it possible to saponify the ester to give the corresponding acid without affecting the rest of the molecule. The ester to be saponified is generally treated with an alkali metal hydroxide in an aqueousalcoholic medium at a temperature of between 0 and 50"C. Preferably, the methyl or ethyl ester is used and the saponification is carried out in an aqueous-methanolic or aqueous-ethanolic medium at a temperature of about 5"C.

The ester of the general formula (VIII) can be obtained by the action of an isocyanoacetate of the general formula: CN-CH2-COOR6 (IX) in which R6 is defined as previously, on 1,3 - dithiacyclohexan - 5 - one. The reaction is generally carried out in an anhydrous organic solvent such as tetrahydrofuran, in the presence of an alkaline condensation agent such as potassium tert.-butylate and at a temperature of between 70 and 0 C.

The isocyanoacetate of the general formula (IX) can be prepared in accordance with the method described by U. Schollkopf et al., Chem. Ber., 108.

1580 (1975).

1,3 - dithiacyclohexan - 5 - one can be prepared in accordance with the method described by E. G. Howard and R. V. Lindsey, J. Amer. Chem. Soc., 8^, 158 (1960).

The optically active forms of the acid of the formula (IV) can be obtained from the racemate by applying physico-chemical methods or by an enzymatic route.

b) or by saponifying the ester of the general formula:

in which R, represents an alkyl radical containing I to 4 carbon atoms, followed by the removal of the protective group of the amine function. The saponification is advantageously carried out in an aqueous-alcoholic medium by treatment with an alkali metal hydroxide at a temperature of between 0 and 50"C. Preferably, sodium hydroxide is used and the methyl or ethyl ester is treated in an aqueous-methanolic or aqueous-ethanolic medium at a temperature of about 20"C.

When it is desired to obtain a product of the formula (IV) in which the amine function is free, the protective group is generally removed in the presence of trifluoroacetic acid at a temperature of between 0 and 30"C.

When it is desired to obtain the D or L forms of the acid of the formula (IV), it can be advantageous to separate the optically active forms before removing the protective group of the amine function. For example, it is possible to treat the racemic form with quinine in a solvent such as methyl ethyl ketone.

The salts of the D and L forms are purified by crystallisation: the free D and acids are isolated from these salts and the protective group of the amine function is then removed in order to obtain the D and L forms of the aminoacid of the formula (lv).

The aminoacid of the formula (IV) and its derivatives in which the amine function is protected by a tert.-butoxycarbonyl or 2,2,2 - tri chloroethoxycarbonyl radical, in the D, L and D,L forms and their preparation by deformylating a formylamino - (1.3 - dithiin - 5 - yl)acetic acid and optionally introducing a said protective radical, or by saponifying an ester of the formula (X) and optionally separating the optionally active forms of the acid obtained and optionally removing the protective tert.-butoxycarbonyl groups of the amine function, are described and claimed in our copending Application No. 23558/78, Serial No. 1600724.

The ester of the general formula (X) can be obtained by the action of potassium tert.-butylate on a product of the general formula:

in which R7 is defined as previously. The reaction is generally carried out in an organic solvent such as tetrahydrofuran at a temperature of between -78 and 0 C.

The product of the general formula (XI) can be obtained by the action of an alkyl (e.g. ethyl) isothiocyanatoacetate on 1,3 - dithiacyclohexan - 5 - one, in the presence of potassium tert.-butylate, followed by the action of di-tert.-butyl dicarbonate. The reaction is generally carried out in a solvent such as tetrahydrofuran at a temperature of between -78 and 0 C.

The product of the general formula (V) in which R represents the carboxyl radical is 7 - amino - 3 - deacetoxycephalosporanic acid (or 7-ADCA); it can be obtained either from a penicillin in accordance with the process which forms the subject of Belgian Patent 747,382, or by deacetoxylating 7 - aminocephalosporanic acid (or 7-ACA) in accordance with the process which forms the subject of Belgian Patent 779,034.

The product of the general formula (V) in which R represents a radical of the general formula (II), in which R1 and R2 are defined as previously, can be prepared from 7 - amino - 3 - deacetoxycephalosporanic acid by any method which is in itself known for preparing an ester from an acid without affecting the rest of the molecule. In general, an alkali metal salt or a tertiary amine salt of 7 - amino - 3 deacetoxycephalosporanic acid is reacted with a halide of the general formula:

in which R, and R2 are defined as previously and Z represents a halogen atom, in an inert solvent such as dimethylformamide and at a temperature of between 0 and 30"C.

The products of the general formula (XII) can be prepared in accordance with the method described in German Patent Application 2,350.230.

According to a further feature of the invention, the products of the general formula (I) in which R represents a radical of the general formula (II) in which R1 and R2 are defined as previously, and acid addition salts thereof can also be obtained by esterifying a product of the general formula (I), in which R represents a carboxyl radical and in which the amine function has been protected beforehand.

by any method which is in itself known for preparing an ester from an acid without affecting the rest of the molecule and then removing the protective group of the amine function and optionally converting the product obtained into an acid addition salt. By "method which is in itself known" is meant any method heretofore used or described in the chemical literature.

In general, an alkali metal salt or a tertiary amine salt of a product of the general formula (I) as defined above, in which the amine function has been protected beforehand. is reacted with a halide of the general formula (XII) in which R,. R2 and Z are defined as previously. The reaction is preferably carried out in an inert solvent such as dimethylformamide at a temperature of between 0 and 30"C, and the protective group of the amine function is then removed by any method which is in itself known.

The diastereoisomeric forms of the products of the general formula (I) and salts thereof can also be obtained from their mixture by separating, by physical methods, a mixture of the diastereoisomers, in which the amine and acid functions are optionally protected, and then removing the protective groups, and optionally converting a diastereoisomer obtained into an acid addition salt or, when R represents carboxyl, into a salt with a metal or an organic nitrogen-containing base.

It is possible to carry out this separation at the various stages of the synthesis. For example, a product of the general formula (I), in which the amine and acid functions are protected, can be separated by chromatography on a suitable support. The diastereoisomers of the products of the general formula (I) are then isolated after removal of the protective groups under the usual conditions.

The new products according to the invention can optionally be purified by physical methods such as crystallisation or chromatography.

The new products according to the invention can be converted into addition salts with acids. In accordance with the processes of the present invention, the products are generally obtained in the form of the trifluoroacetate or para toluenesulphonate. The products of the general formula (I) which are obtained in the form of these salts can be liberated and converted into salts of other acids in accordance with the usual methods.

The products of the general formula (I) in which R represents the carboxyl radical can also be converted into metal salts or into addition salts with organic nitrogen-containing bases in accordance with methods which are in themselves known, These salts can be obtained by the action of a metal base (e.g. an alkali metal or alkaline earth metal base) or an amine on a product of the general formula (I) in an appropriate solvent such as an alcohol, an ether or water, or by an exchange reaction with a salt of an organic acid. The salt which has formed precipitates, after concentration, if necessary, of its solution, and is separated off by filtration or decantation.

When used for pharmaceutical purposes the acid addition salts, and salts with metals and nitrogen-containing organic bases of the compounds of formula I above referred to, should contain non-toxic anions and cations respectively, i.e. they should be derived from acids, metals and nitrogen-containing bases which are not sufficiently toxic to interfere with the valuable properties of the compound of formula I.

The cephalosporin derivatives of formula I and their salts as aforesaid exhibit particularly valuable antibacterial properties. They show a remarkable in vitro and in vivo activity against Gram-positive and Gram-negative germs. In vitro, the products according to the invention have shown themselves to be active at a concentration of between 2 and 15 ,ug/cc against Staphylococcus strains which are sensitive to penicillin G (Staphylococcus aureus Smith), at a concentration of between 10 and 150 ,ug/cc against Staphylococcus strains which are resistant to penicillin G (Staphylococcus aureus MB 9), at a concentration of between 0.125 and 1.5 ,ug/cc against Streptococcus pyogenes Dig 7, at a concentration of between 2 and 30 ,ug/cc against Escherichia coli, Monod strain, at a concentration of between 4 and 30 ,ag/cc against Klebsiella pneumoniae, at a concentration of between I and 8 ,ug/cc against Salmonella typhi, at a concentration of between 1 and 8 ,ug/cc against Shigellaflexneri and at a concentration of between 5 and 20 yg/cc against Proteus mirabilis.

In vivo, the products have shown themselves to be active against experimental infections in mice with Staphylococcus aureus Smith (sensitive to penicillin G) at a dose of between 0.05 and 0.6 mg/kg, administered orally or subcutaneously, and with Escherichia coli at a dose of between I and 6 mg/kg, administered orally or subcutaneously.

When administered subcutaneously, the products have been shown to be nontoxic at a dose of 2.5 g/kg in mice.

The products of the general formula (I) in which R represents a carboxyl radical, and especially the products in which the aminoacid bonded to the cephalosporin nucleus is in the D form, are of very particular value.

The following Examples illustrate the invention.

EXAMPLE I Triethylamine (6.25 cc) is added, whilst stirring, to a solution of D,L - (r tert. - butoxycarbonylamino( 1,3 - dithiin - 5 - yl)acetic acid (13 g) in tetrahydrofuran (160 cc). The mixture is cooled to --100C and isobutyl chloroformate (5.8 cc) is added dropwise. The reaction mixture is stirred for 10 minutes at --100C and a solution of 7 - amino - 2 - carboxy - 3 - methyl - 8 oxo - 5 - thia - 1 - azabicyclo[4.2.Oioct - 2 - ene (9.54 g) in a mixture of tetrahydrofuran (140 cc), water (140 cc) and triethylamine (6.25 cc) is then added.

The reaction mixture is stirred at 0 C for 30 minutes and then at 200C for 90 minutes. The solvents are evaporated under reduced pressure (20 mm Hg) at 30"C.

Water (300 cc) and a saturated aqueous solution of sodium bicarbonate (50 cc) are added and extraction is then carried out with ethyl acetate (500 cc). The aqueous phase is separated and acidified to pH=2.0 by adding 4N hydrochloric acid in the presence of ethyl acetate (500 cc). The organic phase is separated off and the aqueous layer is re-extracted with ethyl acetate (200 cc). The last two organic phases are combined and washed with a saturated aqueous solution of sodium chloride (150 cc) and then dried over sodium sulphate and filtered in the presence of decolorising charcoal. The filtrate is concentrated to dryness under reduced pressure (20 mm Hg) at 30"C to obtain 7- [D, - a - tert. butyxocarbonylamino(l,3 - dithin - 5 - yl)acetamidol - 2 - carboxy - 3 methyl - 8 - oxo - 5 - thia - 1 - azabicyclol4.2.0]oct - 2 - ene (I 8.7 g) in the form of a hard white foam.

7 - [D,L - a - tert. - butoxycarbonylamino( 1,3 - dithiin - 5 - yl)acetamidoi - 2 - carboxy - 3 - methyl - 8 - oxo - 5 - thia - I - azabicyclo[4.2.0]oct - 2 - ene (2.7 g) is dissolved in anisole (3 cc) and trifluoroacetic acid (15 cc). The solution obtained is stirred for 15 minutes at 20"C. It is concentrated to dryness under reduced pressure (0.5 mm Hg) at 300 C. The residue is taken up with ethyl acetate (15 cc), and isopropyl ether (100 cc) is then added. A white precipitate appears which is filtered off. Crude 7 - [D,L - a - amino(l,3 - dithiin - 5 - yl)acetamido] 2 - carboxy - 3 - methyl - 8 - oxo - 5 - thia - 1 - azabicyclo[4.2.0]oct - 2 - ene trifluoroacetate (2.4 g) is thus obtained in the form of a white solid.

A solution of 7 - [D,L - aamino(1,3 - dithiin - 5 - yl)acetamido] - 2 carboxy - 3 - methyl - 8 - oxo - 5 - thia - 1 - azabicyclo[4.2.0]oct - 2 - ene trifluoroacetate (11.9 g) in distilled water (500 cc) is extracted with ethyl acetate (3x 100 cc). The aqueous phase is treated with moist Amberlite IR-45 resin (OH0) (50 cc) until the pH has stabilised at approximately 5.25 (about one hour). The resin is filtered off. The aqueous phase is lyophilised. 7 - [D,L - a - amino(l,3 dithiin - 5 - yl)acetamido] - 2 - carboxy - 3 - methyl - 8 - oxo - 5 - thia - 1 azabicyclo[4.2.0]oct - 2 - ene (5.7 g) is thus obtained and has the following characteristics: [a]2 =+131.2+2 (c=0.98; water) Elementary analysis: calculated C 43.39 H 4.42 N 10.84 0 16.52 S 24.83 4 found 42.6 3.8 10.7 24.6 IR spectrum: characteristic bands 33002200 cm-' (NH of amide and NH3) 1755 cm-': carbonyl of the p-lactam 1685 cm1: CONH- 1575 cm1: -COOH D,L - a - tert. - butoxycarbonylamino(1,3 - dithiin - 5 - yl)acetic acid can be prepared in the following manner: Sodium carbonate (10.6 g) and then a solution of di - tert. - butyl dicarbonate (24 g) in dioxane (130 cc) are added successively to a suspension of D,L - a amino(l,3 - dithiin - 5 - yl)acetic acid (19.1 g) in a mixture of dioxane (130 cc) and water (130 cc). This suspension is stirred for 18 hours at 200C. The solvents are evaporated off under reduced pressure (20 mm Hg) at 40"C. Water (200 cc) and a saturated aqueous solution of sodium bicarbonate (50 cc) are added. The mixture is washed with ethyl acetate (3x300 cc). The aqueous phase is acidified to pH=1.5 with 4N hydrochloric acid. Extraction is carried out with ethyl acetate (2x250 cc).

The combined organic extracts are washed with a saturated solution of sodium chloride (150 cc) and dried over sodium sulphate. The solution is treated with decolorising charcoal and then filtered and concentrated to dryness under reduced pressure (20 mm Hg) at 300C. D,L - c- tert. - butoxycarbonylamino(1,3 dithiin - 5 - yl)acetic acid (26 g) is obtained in the form of a hard white foam.

D.L - a - amino(l.3 - dithiin - 5 - yl)acetic acid can be prepared in the following manner: A suspension of D,L - a - formylamino(l,3 - dithiin - 5 - yl)acetic acid (63 g) in 4N hydrochloric acid (320 cc) is heated at 900C until the solid has completely dissolved. The solution is cooled to 200C and treated with decolorising charcoal.

The solution is filtered and then brought to pH=4.5 by adding 4N sodium hydroxide. The precipitate which has appeared is filtered off. D,L - (l amino(l,3 - dithiin - 5 - yl)acetic acid (41 g) is thus obtained in the form of a white solid which melts at about 270"C with decomposition.

D,L - a - formylamino(l,3 - dithiin - 5 - yl)acetic acid can be prepared in the following manner: A suspension of an equilibrium mixture (72 g) of ethyl a - formylamino(4,5 dihydro - 1,3 - dithiin - 5 - ylidene)acetate and ethyl D,L - a - formylamino(l.3 dithiin - 5 - yl)acetate in ethanol (720 cc) and water (200 cc) is cooled to 5"C. 4N sodium hydroxide (80 cc) is added. The reaction mixture is stirred for 90 minutes at 5"C. It is concentrated to a volume of 100 cc under reduced pressure (20 mm Hg).

The solution obtained is cooled in an ice-bath and acidified to pH=2.0 by adding 4N hydrochloric acid. The precipitate which has appeared is filtered off. Crude D,L - a - formylamino(l,3 - dithiin - 5 - yl)acetic acid (67 g) is thus obtained in the form of a white solid.

The mixture of ethyl a - formylamino(4,5 - dihvdro - 1.3 - dithiin - 5 ylidene)acetate and ethyl D,L - a - formylamino(l.3 - dithiin - 5 - yl)acetate can be prepared in the following manner: A solution of potassium tert. - butylate (27.2 g) in tetrahydrofurane (200 cc) is cooled to 05C. A solution of ethyl isocyanoacetate (25 g) in tetrahydrofurane (150 cc) is added dropwise. The mixture is stirred for a further one hour at OOC and a solution of 1,3 - dithiacyclohexan - 5 - one (29.6 g) in tetrahydrofurane (375 cc) is then added. The reaction mixture is stirred for a further 90 minutes at 0 C. Acetic acid (50 cc) is added and the precipitate is filtered off. The solvents are evaporated off under reduced pressure (20 mm Hg) at 300 C. The residue is taken up with methylene chloride (2500 cc). Extraction is carried out with a mixture of water (500 cc) and a saturated aqueous solution dissolved in methanol (1770 cc) at 35"C. Dicyclohexylamine (145 cc) and then acetone (1770 cc) are added, The mixture is allowed to stand for 90 minutes at OOC and the crystals are then filtered off and dried under reduced pressure ( I mm Hg) at 20 C. The dicyclohexylamine salt of 7 - [D - a - tert. butoxycarbonylamino(1,3 - dithiin - 5 - yl)acetamidoi - 2 - carboxy - 3 methyl - 8 - oxo - 5 - thia - I - azabicyclo[4.2.0]oct - 2 - ene (326.4 g) is thus obtained in the form of white crystals.

A suspension in water (300 cc) of the salt (29.5 g) thus obtaned is acidifed to pH=2 by adding 4N hydrochloric acid in the presence of ethyl acetate (300 cc). The organic phase is separated off and a further two extractions are carried out with ethyl acetate (150 cc in total). The organic phases are combined, washed with a saturated aqueous solution of sodium chloride (150 cc), dried over sodium sulphate, filtered and concentrated to dryness under reduced pressure (20 mm Hg) at 30"C. 7 - [D - a - tert. - butoxycarbonylamino(l,3 - dithiin - 5 yl)acetamidol - 2 - carboxy - 3 - methyl - 8 - oxo - 5 - thia - I azabicyclo[4.2.Oloct - 2 - ene (21.5 g) is thus obtained in the form of a white solid.

IR spectrum (KBr): characteristic bands 3320 cm-1 (NH of amide and carbamate) 1770 cm-' (carbonyl of the p-lactam) 1700 cm-' (carbonyl of the acid and carbamate) 1680 cm-1 (carbonyl of the amide) 1390 and 1365 cm-' (tert.-butyl).

A solution of 7 - [D - a - tert. - butoxycarbonylamino(l,3 - dithiin - 5 yl)acetamido] - 2 - carboxy - 3 - methyl - 8 - oxo - 5 - thia - 1 - azabicyclo[4.2.Oloct - 2 - ene (20.3 g) in trifluoroacetic acid (200 cc) is stirred for 20 minutes at about 20 C. This solution is added, in the course of 30 minutes and whilst stirring, to ethyl ether (1000 cc) at OOC. The precipitate is filtered off and dried under reduced pressure (I mm Hg) at 200C. 7 - [D - a - amino(l,3 dithiin - 5 - yl)acetamido] - 2 - carboxy - 3 - methyl - 8 - oxo - 5 - thia - 1 azabicyclo[4.2.0]oct - 2 - ene trifluoroacetate.(l5.7 g) is thus obtained and is dissolved in acetone (750 cc). Triethylamine (3.2 cc) is then added in order to obtain a pH of 4.8. The precipitate is filtered off and washed with ethyl ether (400 cc). 7 - [D - a - amino(l,3 - diithin - 5 - yl)acetamido] - 2 - carboxy - 3 methyl - 8 - oxo - 5 - thia - I - azabicyclo[4.2.0]oct - 2 - ene (10.6 g) is thus obtained in the form of a beige solid.

The 7 - [D - a - amino(l,3 - dithiin - 5 - yl)acetamido] - 2 - carboxy - 3 methyl - 8 - oxo - 5 - thia - 1 - azabicyclo[4.2.0]oct - 2 - ene (14.45 g) prepared in this way is dissolved in water (750 cc) and acetonitrile (750 cc) is then added.

After one hour, the crystals are filtered off and dried under reduced pressure (1 mm Hg) at 200C. 7 - [D - a - amino(l,3 - dithiin - 5 - yl)acetamido] - 2 - carboxy 3 - methyl - 8 - oxo - 5 - thia - 1 - azabicyclo[4.2.0]oct - 2 - ene (9.8 g) is thus obtained in the form of white crystals.

[(u1,20=+137+2" (c=l, 0.1N sodium bicarbonate) Elementary analysis: O calculated C 43.39 H 4.42 N 10.84 0 16.52 S 24.83 Oo found 43.9 4.9 10.3 16.6 23.5 D - a - tert. - butoxycarbonylamino(l,3 - dithiin - 5 - yl)acetic acid can be obtained in the following manner: A solution of D,L - a - tert. - butoxycarbonylamino(l,3 - dithiin - 5 yl)acetic acid (212 g) and quinine (236 g) in methyl ethyl ketone (4300 cc) is heated under reflux. It is allowed to cool and left for 3 hours, whilst stirring, and white crystals (169 g) are filtered off and discarded. The filtrate is stirred for 16 hours at ambient temperature. White crystals (150 g) can be isolated by filtration.

A suspension in methyl ethyl ketone (3750 cc) of the crystals (375 g) thus obtained is heated at 80"C until the solid has completely dissolved. The solution is allowed to cool and the crystals obtained are then filtered off. The quinine salt of D - a - tert. - butoxycarbonylamino( 1,3 - dithiin - 5 - yl)acetic acid (187 g) is thus obtained in the form of white crystals.

The quinine salt of D - a - tert. - butoxycarbonylamino(l,3 - dithiin - 5 yl)acetic acid (98.5 g) is added to a stirred mixture of water (2 litres) and ethyl ether (2 litres), keeping the pH at 11 by adding 4N sodium hydroxide. After the solid has dissolved, the aqueous phase is decanted and acidified to pH=l by adding 4N hydrochloric acid in the presence of ethyl ether (one litre). The organic phase is decanted and a further extraction is carried out with ethyl ether (one litre). The organic extracts are combined and dried over magnesium sulphate. They are concentrated to dryness under reduced pressure (20 mm Hg) at 30"C. D - a tert. - butoxycarbonylamino(l,3 - dithiin - 5 - yl)acetic acid (41.7 g) is thus obtained in the form of a yellow oil. The acid (5 g) thus obtained is dissolved in a mixture of isopropyl ether (10 cc) and cyclohexane (25 cc) under reflux. After cooling, the crystals are filtered off. D - a - tert. - butoxycarbonylamino( 1,3 dithiin - 5 - yl)acetic acid (4 g) is thus obtained in the form of white crystals which melt at 1100C (Kofler instantaneous m.p.).

[a] 20=121 +2 (c=l, dimethylformamide).

D,L - a - tert. - butoxycarbonylamino(l,3 - dithiin - 5 - yl)acetic acid can be obtained in the following manner: A suspension of ethyl a - tert. - butoxycarbonylamino - 4,5 - dihydro - 1,3 dithiin - 5 - ylidene)acetate (0.96 g) in ethanol (7 cc) and N sodium hydroxide (3.3 cc) is stirred for 90 minutes at 200C. It is concentrated to a volume of 5 cc under reduced pressure (20 mm Hg) at 300 C. The solution obtained is acidified to pH=2.0 by adding N hydrochloric acid in the presence of ethyl ether (25 cc). The organic phase is decanted and dried over sodium sulphate. The solution is filtered and concentrated to dryness under reduced pressure (20 mm Hg) at 300 C. D,L - a tert. - butoxycarbonylamino(l,3 - dithiin - 5 - yl)acetic acid (0.85 g) is thus obtained and has the following characteristics: Elementary analysis: % calculated C 45.34 H 5.88 N 4.80 0 21.97 S 22.01 % found 44.8 5.7 4.7 Ethyl a - tert. - butoxycarbonylamino(4,5 - dihydro - 1,3 - dithiin - 5 ylidene)acetate can be prepared in the following manner: A solution of potassium tert. - butylate (5.35 g) in tetrahydrofurane (40 cc) is cooled to70 C. A solution of 3 - tert. - butoxycarbonyl - 4 - ethoxycarbonyl 2- thioxo- 1 - oxa- 7,9 - dithia- 3 - azaspiro[4.5]decane (9 g) in tetrahydrofurane (40 cc) is added dropwise. The mixture is stirred for a further 3 hours, acetic acid (2.9 g) is then added and the reaction mixture is allowed to warm up to 200C. The tetrahydrofurane is evaporated off under reduced pressure (20 mm Hg) at 30"C. The residue is dissolved in ethyl acetate (25 cc). The solution is washed with water (25 cc) and then dried over sodium sulphate. The solution is filtered and the filtrate is concentrated to dryness under reduced pressure (20 mm Hg). A solid residue is obtained and treated with petroleum ether (100 cc). The precipitate is filtered off and dried under reduced pressure. Ethyl a - tert. butoxycarbonylamino(4,5 - dihydro - 1,3 - d.thiin - 5 - ylidene)acetate (5.3 g) is thus obtained in the form of a beige solid which melts at 1 540C (Kofier instantaneous m.p.).

3 - tert. - butoxycarbonyl - 4 - ethoxycarbonyl - 2 - thioxo - I - oxa - 7,9 dithia - 3 - azaspiro[4.5]decane can be prepared in the following manner: A solution of potassium tert. - butylate (4.6 g) in tetrahydrofurane (40 cc) is cooled to --700C A solution of ethyl isothiocyanatoacetate (5.8 g) and 1,3 dithiacyclohexan - 5 - one (5.4 g) in tetrahydrofurane (80 cc) is added dropwise.

After 40 minutes, the solution is heated 50 about 0 C and a solution of di - tert. butyl dicarbonate (8.75 g) in tetrahydrofurane (10 cc) is added. The mixture is stirred for a further 12 hours at about 20"C and then concentrated to dryness under reduced pressure (20 mm Hg) at 30"C. The residue is dissolved in methylene chloride (150 cc), acetic acid (3 cc) is added and the insoluble material is filtered off. The filtrate is concentrated to dryness under reduced pressure (20 mm Hg) at 30"C. The residue is crystallised from ethyl ether (100 cc) and then filtered off and dried under reduced pressure (I mm Hg) at 20"C. 3 - tert. - butoxycarbonyl - 4 ethoxycarbonyl - 2 - thioxo - 1 - oxa - 7,9 - dithia - 3 - azaspiro[4.5ldecane (9.8 g) is thus obtained in the form of white crystals which melt at 1250C (Kofler instantaneous m.p.).

Ethyl isothiocyanatoacetate can be prepared according to D. Hoppe and R.

Follmann, Chem. Ber., 109, 3047 (1976).

EXAMPLE 3 7 - [D - a - tert. - butoxycarbonylamino(I,3 - dithiin - 5 - yl)acetamidol - 2 - carboxy - 3 - methyl - 8 - oxo - 5 - thia - I - azabicyclo[4.2.0]oct - 2 - ene (24 g), obtained under the conditions described in Example 2, is dissolved in acetonitrile (750 cc). p - toluenesulphonic acid (18.7 g) is added and the reaction is allowed to proceed at 20"C for about 20 hours. Water (40 cc) is added and the mixture is treated with decolorising charcoal. The solution is filtered and triethylamine (17.2 cc) is added slowly until a pH of 4.8 is obtained. The crystals are filtered off and dried under reduced pressure (1 mm Hg) at 20"C. 7 - [D - a amino(l,3 - dithiin - 5 - yl)acetamidoi - 2 - carboxy - 3 - methyl - 8 - oxo - 5 thia - 1 - azabicyclo[4.2.0loct - 2 - ene (17.7 g) is thus obtained and has identical characterististics to those of the product obtained in Example 2.

EXAMPLE 4 7 - D,L - a - tert. - butoxycarbonylamino(l,3 - dithiin - 5 - yl)acetamido] 2 - carboxy - 3 - methyl - 8 - oxo - 5 - thia - I - azabicyclo[4.2.0]oct - 2 - ene (18.7 g), prepared in accordance with Example 1, is dissolved in tetrahydrofurane (200 cc) and a solution of diphenyldiazomethane (7.45 g) in tetrahydrofurane (50 cc) is then added. The mixture is stirred for 16 hours at 20"C. It is then evaporated to dryness under reduced pressure (20 mm Hg) at 300 C. The residue is taken up with ethyl acetate (350 cc). The organic layer is washed with a saturated aqueous solution of sodium bicarbonate (100 cc) and then dried over sodium sulphate. The solution is treated with decolorising charcoal and filtered. The filtrate is concentrated to dryness under reduced pressure (20 mm Hg) at 30"C. The residue is purified by chromatography on a column (diameter: 4.5 cm; height: 54 cm) containing silica (400 g). Elution is carried out successively with mixtures of ethyl acetate and cyclohexane of increasing ethyl acetate concentration (10/90 by volume, 1000 cc; 20/80 by volume, 1000 cc; 25/75 by volume, 1000 cc). Fractions of 100 cc are taken and portions 35--45 are concentrated to dryness under reduced pressure (20 mm Hg) at 300C. 7 - [D,L - a - tert. - butoxycarbonylamino(l,3 dithiin - 5 - yl)acetamido] - 2 - benzhydryloxycarbonyl - 3 - methyl - 8 - oxo 5 - thia - 1 - azabicyclo[4.2.0]oct - 2 - ene (10 g) is thus obtained in the form of a hard white foam.

The crude product resulting from the esterification of 7 - [D,L - a - tert. butoxycarbonylamino(l,3 - dithiin - 5 - yl)acetamido] - 2 - carboxy - 3 methyl - 8 - oxo - 5 - thia - 1 - azabicyclo[4.2.Oioct - 2 - ene (13.6 g) with diphenyldiazomethane is chromatographed on a column (diameter: 6.6 cm; height: 73 cm) containing silica gel (1200 g). Elution is carried out successively with a mixture of cyclohexane and ethyl acetate (90/10 by volume) (1500 cc), a mixture of cyclohexane and ethyl acetate (85/15 by volume) (1500 cc), a mixture of cyclohexane and ethyl acetate (75/25 by volume) (1500 cc), a mixture of cyclohexane and ethyl acetate (70/30 by volume) (1500 cc) and a mixture of cyclohexane and ethyl acetate (65/35 by volume (5000 cc), 250 cc fractions being collected.

Fractions 35 to 37 [elution with the mixture of cyclohexane and ethyl acetate (65/35 by volume yield 7 - ID - tr - tert. - butoxycarbonylamino(l,3 - dithiin 5 - yl)acetamidol - 2 - benzhydryloxycarbonyl - 3 - methyl - 8 - oxo - 5 - thia I - azabicyclo[4.2.0]oct - 2 - ene (1.83 g) after evaporation. After recrystallisation from methanol (165 cc), this product (1.19 g) is obtained in the form of white crystals.

Fractions 38 to 40 yield a mixture (3.09 g) of the D and L forms.

After evaporation, fractions 41 to 45 yield a product (3.09 g) which is recrystallised from ethanol (150 cc).7 - [L - -tert. - butoxycarbonylamino(l,3 dithiin - 5 - yl)acetamidol - 2 - benzhydryloxycarbonyl - 3 - methyl - 8 - oxo 5 - thia - I - azabicyclo[4.2.0loct - 2 - ene (2.01 g) is thus obtained in the form of white crystals.

7 - [D - a - tert. - butoxycarbonylamino(l,3 - dithiin - 5 - yl)acetamidoi 2- benzhydryloxycarbonyl - 3 - methyl - 8 - oxo - 5 - thia - 1 - azabicyclo[4.2.0]oct - 2- ene (1.09 g) is dissolved in anisole (1.3 cc) and trifluoroacetic acid (50 cc). The solution obtained is stirred for 15 minutes at 200C and then concentrated to dryness under reduced pressure (0.5 mm Hg) at 300 C.

The residue is dissolved in ethyl acetate (5 cc). The solution obtained is poured into isopropyl ether (40 cc). The precipitate obtained is filtered off. A white powder (0.94 g) is thus obtained and dissolved in water (20 cc) and 0.1N hydrochloric acid (10 cc). The aqueous phase is washed with ethyl acetate (2tis cc) and then treated, whilst stirring, with moist Amberlite IR-45 resin (OHB) (15 cc) until the pH has stabilised at about 5.0. The resin is filtered off and the filtrate is lyophilised. 7 ID - α - amino(1,3 - dithiin - 5 - yl)acetamidol - 2 - carboxy - 3 - methyl - 8 - oxo - 5 - thia - 1 - azabicyclo[4.2.0]oct - 2 - ene (0.33 g) is thus obtained.

[α]D20=+ 128#4 (c=1.020, water) Elementary analysis: ,0calculated C 43.39 H 4.42 N 10.84 016.52 S '4.83 found 39.7 3.5 10.0 22.1 Proton NMR spectrum: os (ppm) (CF3COOH): 2.40 (s, CH3 in the 3-position, 3H): 3.46 (s, -CH2-S of cephem, 2H): 3.55 (s, -CH2-S- of dithiine, 2H); 4.06 (s, -S-CH2 S-, 2H): 5.15 (s,

IH); 5.26 (d, J=5 Hz, H in the 6-position); 5.80 (d, J=5 Hz, H in the 7-position): 7.06 (s, -CH=, IHO.

This product has a minimum bacteriostatic concentration of 2 g/cc against Staphylococcus aureus Smith and 15 ,ug/cc against Staphylococcus aureus M B 9, Escherichia coli and Klebsiella pneumoniae.

By following the same procedure, 7 - [L - a - amino(l,3 - dithiin - 5 yl)acetamido] - 2- carboxy - 3 - methyl - 8- oxo - 5 - thia - 1 - azabicyclo[4.2.0]oct - 2 - ene (0.57 g) is obtained starting from 7 - [L - α - tert. butoxycarbonylamino(1,3 - dithiin - 5 - yl)acetamidol - 2 benzhydryloxycarbonyl - 3 - methyl - 8 - oxo - 5 - thia - I azabicyclo[4.2.0]oct - 2 - ene (1.99 g).

[α]D20=+120#2 (c=1.012, water) Elementary analysis: %calculated C43.39 114.42 N 10.84 016.52 S24.83 %found 42.7 3.8 11.1 24.5 Proton NMR spectrum: a (ppm) (CF3COOH): 2.43 (s, C113- in the 3-position, 3H); 3.43 (s, -CH2- S- of cephem, 2H); 3.55 (s, HzS of dithiine, 2H); 4.06 (s, -S CH,S-, 2H); 5.13 (s,

1H); 5.26 (d, J=5 Hz, H in the 6-position); 5.70 (d, J=5 Hz, H in the 7 position); 7.03 (s, -CH=, 1H).

EXAMPLE 5 7 - amino - 3 - methyl - 8 - oxo - 2 - pivaloyloxymethoxycarbonyl - 5 thia - 1 - azabicyclo[4.2.0]oct - 2 - ene (11.3 g) and dicyclohexylcarbodiimide (7.1 g) are added to a solution of D - a - tuft. - butoxycarbonylamino(l,3 - dithiin 5 - yl)acetic acid (10 g) in dimethylformamide (100 cc). The reaction mixture is stirred for 2 hours and then filtered. The filtrate is diluted with ethyl acetate (300 cc) and water (500 cc). The organic phase is decanted and washed with water (100 cc) and then with a saturated aqueous solution of sodium bicarbonate (100 cc) and is then dried over sodium sulphate and filtered in the presence of decolorising charcoal. The filtrate is concentrated to dryness under reduced pressure (20 mm Hg) at 30 C. The residue is chromatographed on a column (diameter 3.5 cm, height 35 cm) containing silica(l50 g). Elution is carried out successively with mixtures of ethyl acetate and cyclohexane of increasing ethyl acetate concentration (10/90 by volume, 500 cc; 20/80 by volume, 500 cc; 30/70 by volume, 500 cc; 40/60 by volume, 2000 cc). 200 cc fractions are collected. Fractions 14 to 21 are concentrated to dryness under reduced pressure (20 mm Hg) at 300C. 7 - [D - a - tert. butoxycarbonylamino( 1,3 - dithiin - 5 - yl)acetamidol - 3 - methyl - 8 - oxo - ' - pivaloyloxymethoxycarbonyl - 5 - thia - 1 - azabicyclo[4.2.0]oct - 2 - ene (8 g) is thus obtained in the form of a hard orange foam.

The product thus prepared is dissolved in trifluoroacetic acid (50 cc) and stirred for 15 minutes at 20"C. The mixture is concentrated to dryness under reduced pressure (0.5 mm Hg) at 300C. The residue is dissolved in water (200 cc).

The solution is washed with ether (100 cc). The aqueous phase is covered with ethyl acetate (250 cc) and stirred. A saturated aqueous solution of sodium bicarbonate (100 cc) is added, whilst stirring. The organic phase is decanted, dried over sodium sulphate and filtered in the presence of decolorising charcoal. The filtrate is concentrated to 15 cc under reduced pressure (20 mm Hg) at 300C. Ethyl ether (100 cc) is added and a 2.7N solution (10 cc) of anhydrous hydrochloric acid in ether is then added dropwise. The mixture is stirred for 10 minutes and the precipitate is then filtered off.7 - [D - a - amino(l,3 - dithiin - 5 - yl)acetamido] - 3 - methyl 2 - pivaloyloxymethoxycarbonyl - 8 - oxo - 5 - thia - I - azabicyclo[4.2.0]oct 2 - ene hydrochloride (4.8 g) is thus obtained in the form of a white powder.

Elementary analysis: %calculated C44.64 H5.24 Cl 6.59 N7.81 0 17.84 S 17.88 %'found C45.3 115.4 Cl 6.7 N7.9 S 17.7 7 - amino - 3 - methyl - 8 - oxo - 2 - pivaloyloxymethoxycarbonyl - 5 thia - 1 - azabicyclo[4.2.0]oct - 2 - ene can be prepared in accordance with the method described in German Patent 1,951,012.

The present invention also provides pharmaceutical compositions which can be used in therapy and which contain, as an active ingredient, at least one compound of the formula (I) or a non-toxic salt thereof (as previously defined) in association with one or more compatible, pharmaceutically acceptable diluents or adjuvants. These compositions can be used by oral, parenteral or rectal administration.

Solid compositions for oral administration can be tablets, pills, powders or granules. In these compositions, the active product according to the invention is mixed with one or more inert diluents or adjutants, such as sucrose, lactose or starch. These compositions can also comprise substances other than diluents, e.g. a lubricant such as magnesium stearate.

Liquid compositions for oral administration can be solutions, suspensions, syrups, elixirs containing inert diluents such as water or paraffin oil, and pharmaceutically acceptable emulsions. These compositions can also comprise substances other than diluents, e.g. wetting products, sweetening agents or flavourings.

The compositions for parenteral administration can be suspensions, emulsions or aqueous or non-aqueous sterile solutions. Propylene glycol, polyethylene glycol, vegetable oils, in particular olive oil, and injectable organic esters, e.g. ethyl oleate, can be employed as solvent or vehicle. These compositions can also contain adjuvants, in particular wetting agents, emulsifiers or dispersing agents.

Sterilisation can be carried out in several ways, e.g. with the aid of a bacteriological filter, by incorporating sterilising agents into the composition, by irradiation or by heating. The compositions can also be prepared in the form of sterile solid compositions which can be dissolved at the time of use in sterile water or in any other injectable sterile medium.

The compositions for rectal administration are suppositories which can contain, in addition to the active product, excipients such as cacao butter or suppository wax.

In human therapy, the compositions . according to the invention are particularly useful in the treatment of infections of bacterial origin. In general, the physician will decide the posology which he considers to be most appropriate as a function of the age, weight, degree of infection and other factors which are peculiar to the subject to be treated. For an adult, the doses are generally between 1 and 12 g of active product per day, administered orally, intramuscularly or intravenously.

The following Examples illustrate compositions according to the invention.

EXAMPLE A An injectable solution having the following composition is prepared: 7 - ID - a - amino(l,3 - dithiin - 5 - y1)acetamidoi - 2 carboxy - 3 - methyl - 8 - oxo - 5 - thia - 1 - azabicyclo[4.2.0]oct - 2 - ene 250 mg Sodium chloride 1.5 mg Injectable solvent 2 cc EXAMPLE B Tablets having the following composition are prepared in accordance with the usual method: mg 7 - ID,L - a - amino(l,3 dithiin - 5 - yl)acetamidol - 3 methyl - 2 - carboxy - 8 - oxo - 5 - thia - I azabicyclo[4.2.0]oct - 2 - ene 500 Starch 200 Precipitated silica 45 Magnesium stearate 5 WHAT WE CLAIM IS:- 1. A cephalosporin derivative of the formula:

in which R represents carboxyl or a radical of the formula:

in which RX represents hydrogen or alkyl of 1 to 4 carbon atoms and R2 represents straight- or branched-chain alkyl of I to 4 carbon atoms, or cyclohexyl, the radical

being easily removable enzymatically, in its diastereoisomeric forms and their mixtures, and its acid addition salts and, when R is carboxyl, its metal salts and its addition salts with organic nitrogen-containing bases.

2. 7 - [D,L - a - amino(l,3 - dithiin - 5 - yl)acetamido] - 2 - carboxy - 3 methyl - 8 - oxo - 5 - thia - I - azabicyclo[4.2.0]oct - 2 - ene and its salts with non-toxic acids, non-toxic metals and non-toxic organic nitrogen-containing bases.

3. 7 - [D - a - amino(l,3 - dithiin - 5 - yl)acetamidoi - 2 - carboxy - 3 methyl - 8 - oxo - 5 - thia - 1 - azabicyclo[4.2.0]oct - 2 - ene and salts with nontoxic acids, non-toxic metals and non-toxic organic nitrogen-containing bases.

4. 7 - [D - cr- amino(l,3 - dithiin - 5 - yl)acetamido] - 3 - methyl - 2 pivaloyloxymethoxycarbonyl - 8 - oxo - 5 - thia - 1 - azabicyclo[4.2.0]oct - 2 ene and its salts with non-toxic acids.

5. A process for the preparation of a cephalosporin derivative or salt thereof as defined in Claim 1, which comprises reacting the acid of the formula:

in racemic or optically active form, and in which the amine function has been protected beforehand, or a reactive derivative of this acid, with a cephalosporin of the formula:

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

Claims (13)

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

   EXAMPLE B Tablets having the following composition are prepared in accordance with the usual method: mg 7 - ID,L - a - amino(l,3 dithiin - 5 - yl)acetamidol - 3 methyl - 2 - carboxy - 8 - oxo - 5 - thia - I azabicyclo[4.2.0]oct - 2 - ene 500 Starch 200 Precipitated silica 45 Magnesium stearate 5 WHAT WE CLAIM IS:- 1. A cephalosporin derivative of the formula:

   in which R represents carboxyl or a radical of the formula:

   in which RX represents hydrogen or alkyl of 1 to 4 carbon atoms and R2 represents straight- or branched-chain alkyl of I to 4 carbon atoms, or cyclohexyl, the radical

   being easily removable enzymatically, in its diastereoisomeric forms and their mixtures, and its acid addition salts and, when R is carboxyl, its metal salts and its addition salts with organic nitrogen-containing bases.
2. 2. 7 - [D,L - a - amino(l,3 - dithiin - 5 - yl)acetamido] - 2 - carboxy - 3 methyl - 8 - oxo - 5 - thia - I - azabicyclo[4.2.0]oct - 2 - ene and its salts with non-toxic acids, non-toxic metals and non-toxic organic nitrogen-containing bases.
3. 3. 7 - [D - a - amino(l,3 - dithiin - 5 - yl)acetamidoi - 2 - carboxy - 3 methyl - 8 - oxo - 5 - thia - 1 - azabicyclo[4.2.0]oct - 2 - ene and salts with nontoxic acids, non-toxic metals and non-toxic organic nitrogen-containing bases.
4. 4. 7 - [D - cr- amino(l,3 - dithiin - 5 - yl)acetamido] - 3 - methyl - 2 pivaloyloxymethoxycarbonyl - 8 - oxo - 5 - thia - 1 - azabicyclo[4.2.0]oct - 2 ene and its salts with non-toxic acids.
5. 5. A process for the preparation of a cephalosporin derivative or salt thereof as defined in Claim 1, which comprises reacting the acid of the formula:

   in racemic or optically active form, and in which the amine function has been protected beforehand, or a reactive derivative of this acid, with a cephalosporin of the formula:

   in which R is defined as in Claim 1 or is a protected carboxyl group, and then removing the protecting groups, and optionally converting the product obtained into an acid addition salt or, when R represents carboxyl into a metal salt or an addition salt with an organic nitrogen-containing base.
6. 6. A process for the preparation of a cephalosporin derivative as defined in Claim 1, in which R represents a radical of the formula:

   wherein R, and R2 are defined as in Claim 1, or an acid addition salt thereof which comprises esterifying a cephalosporin derivative as defined in Claim 1, in which R represents carboxyl and the amine function has been protected beforehand, by any method which is in itself known for preparing an ester from an acid without affecting the rest of the molecule, and then removing the protective group of the amine function and optionally converting the product obtained into an acid addition salt.
7. 7. A process for the preparation of a diastereoisomer of a cephalosporin derivative or salt thereof as defined in Claim I, which comprises separating, by physical methods, a mixture of diastereoisomers according to Claim 1, in which the amine and acid functions are optionally protected, and then removing the protective groups, and optionally converting a diastereoisomer obtained into an acid addition salt or, when R represents carboxyl, into a salt with a metal or an organic nitrogen-containing base.
8. 8. Process according to Claim 5 in which the amine function of the said acid is protected, with a t - butoxycarbonyl group.
9. 9. Process according to Claim 5 substantially as described in Example 1, 2 or 5.
10. 10. Process according to Claim 7 substantially as described in Example 4.
11. 11. A compound as claimed in Claim 1 when prepared by a process as claimed in any one of Claims 5 to 10.
12. 12. A pharmaceutical composition which comprises at least one cephalosporin derivative or non-toxic salt thereof as claimed in any one of Claims 1 to 4 and 11 in association with one or more compatible, pharmaceutically acceptable diluents or adjuvants.
13. 13. A composition as claimed in Claim 12 substantially as hereinbefore described.