DK146539B - METHOD OF ANALOGY FOR THE PREPARATION OF 7ALFA METHOXYCEPHALOSPORINE DERIVATIVES - Google Patents

Description

in 146539

The invention relates to an analogous process for the preparation of novel 7α-methoxycephalosporin derivatives having the general formula (II ') or pharmaceutically acceptable esters thereof as set forth in the preamble of claim 1.

Related 7α-methoxycephalosporins having the same mode of action are known from Danish Patent Application No. 2918/71.

The best of these compounds is the one now commercially sold under the name cefoxitin and having a formula 2 similar to the formula (II ') of claim 1 wherein R is carbamoyloxymethyl but wherein the group R 5 -S- is substituted with a 2-thienyl group.

It will be seen from the following table that the compounds of the invention have substantially better antibacterial activity, especially against Gram-negative bacteria such as E. coli, than cefoxitin. Although there are one or two cases where the minimum inhibitory concentration of compounds of the invention against certain bacteria is the same or slightly higher than that of cefoxitin, the minimum inhibitory concentrations of the compounds of the invention are against E. coli on the whole, substantially lower than the minimal inhibitory concentration of cefoxitin against the same bacterium. Given the essential role played by E. coli in various diseases and the need to find new antibiotics that are more effective against this organism, the compounds of this invention represent a significant advance over those that are set out in Application No. 2918/71.

The process according to the invention is characterized by the characterizing part of claim 1.

r 2 146539 that it does not destroy the cephaline ring during or after the condensation reaction, and provided that it can be readily detached from the cephaline ring. Suitable esters include, for example, alkylsilyl esters such as trimethylsilyl esters, benzyl esters, p-methoxybenzyl esters, benzhydrylic esters, phenacylesters, p-bromophenacyl esters and 2,2,2-trichloroethyl esters. When an esterified carboxyl group, the process of the invention preferably comprises the further step of deesterifying the reaction product.

X is a halogen atom, preferably chlorine or bromine.

The thiol compound of formula (I) may be used as such, or it may preferably be used in the form of a metal salt, e.g. an alkali metal or alkaline earth metal salt such as the sodium, potassium, lithium, calcium or barium salt.

Of these, the sodium, potassium and lithium salts are the preferred ones.

The process of the invention can be easily carried out by simply contacting the 7α-methoxycephalosporin starting compound of formula (III1) with the thiol compound of formula (I) or with a metal salt thereof. Any solvent not participating in the reaction can be used in the process of the invention, including water and many organic solvents. Examples of suitable organic solvents include dialkyl ketones, e.g., acetone or methyl ethyl ketone, halogenated alkanes, e.g. chloroform, methylene chloride or dichloroethane, lower alkanoyls, e.g. methanol or ethanol, and dimethylformamide. Mixtures of two or more solvents may also be used. If the 7α-methoxycephalosporin derivative of formula (III1) has a carboxyl group in position, it is preferred to use a mixture of water and an organic solvent as the reaction medium.

3 146539

The thiol (I) or metal salt thereof should normally be used in an equimolar amount or in a slight excess relative to the 7α-methoxycephalosporin derivative. Thus, for example, the molar ratio of the thiol (I) to the 7α-methoxycephalosporin starting material may be from 1: 1 to 1.1: 1.

Although the reaction will proceed at an approximately neutral pH, it will proceed more smoothly under slightly alkaline conditions. Therefore, if the thiol (I) itself is used, it is preferred to add an alkali to the reaction mixture so that the reaction can be carried out under alkaline conditions.

Suitable alkalies which can be used include sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate and potassium hydrogen carbonate.

The reaction temperature is not critical to the process of the invention, and therefore the reaction is usually carried out at about room temperature, although the reaction will proceed at temperatures higher or lower than room temperature.

The time required for the reaction to be carried out will vary depending on the reaction temperature, the reagents and other conditions, but the reaction will usually be completed within 20 to 30 hours. If X in the 7α-methoxy-cephalosporin starting material is a chlorine atom, the reaction will usually take a relatively long time, i.e. from 10 to 30 hours.

When the reaction is complete, the desired product of formula (II1) can be recovered from the reaction mixture by conventional methods. For example, if a carboxyl group is present in the 4-position of the compound, the reaction mixture is first acidified and if a solvent other than water is used for the reaction, the solvent is removed by distillation and the reaction product is extracted with a suitable solvent (e.g. ethyl acetate) and the extract is washed with water and dried. The solvent is then removed by distillation to give the desired product. If necessary, this can be further purified by conventional means, e.g. by chromatography.

If the compound prepared has an esterified carboxyl group at the 4-position, the reaction medium, as indicated above, is preferably a mixture of water and a water-miscible organic solvent. This organic solvent is first removed from the reaction mixture by distillation, then the residue is extracted with a water-immiscible solvent. The extract is then washed with water and the solvent removed by distillation to give the esterified compound. This compound can be further purified by conventional methods, for example chromatography, but in general it is preferable to subject it directly to a deesterification to obtain the desired compound. The deesterification can be carried out by any conventional method, depending on the nature of the ester.

Suitable deesterification processes include alkaline hydrolysis, acid hydrolysis and reduction with hydrogen. Upon completion of the deesterification, the desired product is recovered from the reaction mixture in the manner described above.

Many of the 7α-methoxycephalosporin derivatives of formula (II ') have valuable antibacterial activity against various pathogenic bacteria. Representative examples of these compounds and their antibacterial activities (expressed as minimal inhibitory concentrations) are given in the following table. For comparison purposes, the minimum inhibitory concentrations against the same bacteria of three known compounds, cefoxitin, 3-carbamoyloxymethyl-7α-methoxy-7β-phenylacetamido-3-cephem-4-carboxylic acid and cephalotinum, are also listed.

5 146539

As will be seen from the table, the most preferred compounds prepared by the process of the invention are those in which are cyanmethyl, 1-cyanethyl and 2-hydroxyethyl 1.

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Thus, the compounds exhibit excellent activity against both Gram-positive and Gram-negative bacteria, especially against Gram-negative bacteria.

The compounds of formula (III ') used as starting materials in the process of the invention are also novel compounds, but these can be readily prepared by known methods. Although inherently having antibacterial activity, they are more valuable as starting materials for the preparation of the compounds of formula (II1) which have much higher antibacterial activities.

The process according to the invention is illustrated in more detail by the following examples. The preparation of certain novel starting materials is also illustrated in the following Preparations 1-4.

EXAMPLE 1 3-Carbamoyloxy) ethyl-7-methoxy-7 [3- (1,3,4-thiadiazol-2-yl-thioacetamido) -3-cephem-4-carboxylic acid

A solution of 117 mg of 7β-bromoacetamido-3-carbamoyloxymethyl-7α-methoxy-3-cephem-4-carboxylic acid in 0.2 ml of 1N sodium hydroxide solution was added to a solution of 23.6 mg of 2-mercapto-1.3, 4-Thiadiazole in 0.2 ml 1N sodium hydroxide solution and the mixture was stirred at room temperature for 2 hours. The pH was then adjusted to 2.5 by the addition of 2N phosphoric acid solution. The solution was then extracted five times, each time with 15 ml of ethyl acetate, and the combined ethyl acetate extracts were dried over sodium sulfate and the solvent was then distilled off to give 69 mg of an amorphous crude product. This was partitioned onto a silica gel plate using a mixture of methanol and chloroform in the 50:50 volume ratio and then extracted with methanol. The solvent was distilled off from the extract to obtain 34 mg of 3-carbamoyloxymethyl-7a-methoxy-78- (1,3,4-thiadiazol-2-yl-thioacetamido) -3-cephem-4-carboxylic acid. form of a powder.

Nuclear Magnetic Resonance Spectrum (CD 2 CN + D 2 O), <SppmJ 9.30 (singlet, H in thiazole) 5.03 (singlet H at 6 position) 4.16 (singlet, S-CH 2 -CO-) 3.46 (singlet, OCH ^ at 7 position).

Ultraviolet absorption spectrum (phosphoric acid buffer, pH 6.86), X nm: 263.

max

Infrared Absorption Spectrum (KBr), cm -1: 1760.

Thin layer chromatography (silica gel): (a) Development agent (n-butanol / acetic acid / water, volume ratio 5: 4: 1): R f value = 0.49.

(b) Development agent (methanol / chloroform, volume ratio 1: 1):

Ry value = 0.29.

May this procedure be repeated, except that 7β-bromoacetamido-3β-carbamoyloxymethyl-7α-methoxy-3-cephem-4-carboxylic acid was replaced with the corresponding 7β-chloroacetamido derivative, similar results were obtained.

Examples of compounds prepared in the same manner as in the preceding examples and their properties are set forth below.

Except where otherwise noted, the physical properties were measured as follows: 9

Magnetic Nuclear Resonance Spectrum (in CD ^ CN + D20), It ppm.

Ultraviolet absorption spectrum (in phosphoric acid buffer with pH 6.86), \ nm. r '4. max

Infrared absorption spectrum (in KBr), Vcm- *.

Thin-layer chromatography (TLC) on silica gel: (a) Rp value obtained using a mixture of n-butanol / acetic acid / water in a 5: 4: 1 volume ratio.

(b) value obtained using a 1: 1 volume ratio of methanol / chloroform.

3-carbamoyloxymethyl-7β-cyanomethylthioacetamido-7α-methoxy-3-cephero-4-carboxylic acid NMR spectrum (DMSO-d ^), δppm: 5.06 (singlet, H at 6 position) 3.58 (singlet UV spectrum, I nm: 246, 265.

v 4. max IR spectrum,: 1720, 1775.

EXAMPLE 2 3-Acetoxymethyl-7a-methoxy-7B- (1,3,4-thiadiazol-2-yl-thioacetamido) -3-cephem-4-carboxylic acid 33 mg 2-mercapto-1,3,4-thiadiazole dissolved in 0.24 ml of 1 N aqueous sodium hydroxide solution and to the resulting solution was added a solution of 0.27 millimoles (100 mg) of 3-acetoxymethyl-7 | 3-chloroacetatamido-7a-methoxy-3-cephem-4-carboxylic acid , 5N sodium bicarbonate solution. The mixture was stirred at room temperature for 3 hours and the pH was then adjusted to 2.3 by the addition of 0.1N phosphoric acid solution. The mixture was then extracted three times with ethyl acetate and the combined ethyl acetate extracts were dried over sodium sulfate. The solvent was distilled off from the dried ethyl acetate solution to give 113 mg of an amorphous crude product. This was partitioned onto a silica gel plate using chloroform containing 40% methanol as solvent and then extracted with methanol. The solvent was distilled off from the extract to give 69 mg of the desired product.

Nuclear Magnetic Resonance Spectrum (CD 2 CN + D 2 O), δ ppm: 9.23 (singlet, H in thiadiazole) 5.00 (singlet, H at 6 position) 4.73 (doubled, CH 2 at 3 position) 4 , 11 (singlet) S-CH 2 -CO-) 3.42 (singlet, OCH 2 at 7-position) 1.98 (singlet, 0-CQ-CH 2).

Ultraviolet Absorption Spectrum (Phosphoric Acid Buffer with pH 6.86), nm: 263 (£ = 8789).

Γ λ. max

Infrared Absorption Spectrum (KBr), V cm -1: 1769.

Thin-layer chromatography (silica gel):

Development agent (methanol / chloroform, volume ratio 1: 1): value: 0.45.

Examples of other compounds prepared in the same manner as in the previous example, together with their properties (determined as described in Example 1), are listed below: 3-acetoxymethyl-7 | 3-cyanmethylthioacetamido-7oi-m ethoxy-3 -cephem-4-carboxylic acid NMR spectrum (CD 3 CN), Jppm: 5.06 (singlet, H at 6 position) 4.76 - 5.06 (quartet, -CH2 OCO- at 3 position) 3, 60 (singlet, NCCH2S or SCH2CO) 3.52 (singlet, OCH ^ at 7 position) 3.42 (singlet, NCCH2S or SCH2CO) 3.32 - 3.55 (quartet, H2 at 2 position) 2.02 (singlet, OCOCH ^).

UV spectrum, δ mgx nm: 247 (δ = 8000) 267 (& - 8400).

IR spectrum, Ycm +: 1775.

Example 3 7a-Methoxy-3- (1-methyl-1H-tetrazol-5-yl) -thiomethyl-7β- (1,3,4-thiadiazol-2-yl-thioacetamido) -3-cephem-4 carboxylic acid 33 mg of 2-mercapto-1,3,4-thiadiazole was dissolved in 0.24 ml of 1N sodium hydroxide solution and to the resulting solution was added a solution of 117 mg (0.27 millimole) of 7β-chloro-acetamido-7a -methoxy-3- (1-methyl-1H-tetrazol-5-yl) thiomethyl-3-cephem-4-carboxylic acid in 0.5N sodium hydrogen carbonate solution. The mixture was stirred at room temperature for 3 hours and the pH was then adjusted to 2.5 by the addition of 0.1N phosphoric acid solution. The mixture was extracted three times with ethyl acetate and the combined extracts were dried over sodium sulfate. The solvent was then distilled off to give 125 mg of an amorphous product. This was partitioned onto a silica gel plate using a mixture of methanol and chloroform in the 50:50 volume ratio and extracted with methanol. The solvent was distilled off from the extract to give 70 mg of the desired product as an amorphous powder.

Magnetic Nuclear Resonance Spectrum (CD 2 CN + D 2 O), δ ppm: 9.28 (singlet, H at 5 position in thiadiazole).

Ultraviolet Absorption Spectrum (Phosphoric Acid Buffer with pH 6.86) V nm: 266 (<? = 9270).

Amax

Infrared Absorption Spectrum (KBr), V cm -1: 1760.

Thin-layer chromatography (silica gel):

Development agent (chloroform / methanol, volume ratio 1: 1)

Rf value = 0.38.

Examples of compounds prepared in the same manner as in the previous example and their properties (measured as described in Example 1) are listed below: 7β-cyanomethylthioacetamido-7α-methoxy-3- (1-methyl-1H-tetrazole -5-yl) thiomethyl-3-cephem-4-carboxylic acid NMR spectrum, <Sppm: 5.10 (singlet, H at 6 position) 4.3 - 4.6 (quartet, CH 2 S at 3 position) 3.98 (singlet, CH 2 at 1 position in tetrazole ring) 3.70 (singlet, -NCCH 2 S or -SCH 2 CO) 3.5 - 3.7 (quartet, H 2 at 2 position) 3.60 (singlet, - NCCH2S or -SCH2CO) 3.50 (singlet, OCH ^ at 7 position).

UV spectrum,! nm: 274 (£ = 9000).

EXAMPLE 4 7 | 3- (2-Hydroxyethylthioacetamido) -7α-methoxy-3- (1-methyl-1H-tetrazol-5-yl) thiomethyl-3-cephem-4-carboxylic acid 434 mg 7β-οίι1θΓ8θβΐ3π -7α-πιβ1Ι · ιοχγ-3- (1-ιηβ11ηγ1-1Η-1εΐΓ3-zol-5-yl) thiomethyl-3-cephem-4-carboxylic acid was dissolved in 20 ml of water containing 84 mg of sodium bicarbonate and 156 mg of thioglycol was added. . The resulting mixture was stirred at room temperature for 3 hours while maintaining the pH at 8.0 - 8.5 by adding one. IN sodium hydroxide solution. The pH was then adjusted to 2.0 - 2.5 by the addition of 1N hydrochloric acid and the mixture was lyophilized. The residue was extracted with methanol and the solvent was distilled off. The resulting residue was then purified by preparative silica gel chromatography using as the developing agent a mixture of n-butanol / acetic acid / water (volume ratio 4: 1: 1) to obtain 360 mg of the desired product as a powder.

Magnetic Nuclear Resonance Spectrum (CD 2 CN + D 2 O), <? Ppm: 5.20 (singlet, 6-position, H) Ύ

so

4.15 - 4.25 (quartet, 3-position, v CH 2 -S-) 3.90 (singlet, 3-position, tetrazole JU '0 ™ 3.44) (singlet, 7-position, S-CH -C-) 3.68 and 2.74 (triplet, 7-position, HO-Ch 2 Ct 2 -S-).

Infrared Absorption Spectrum (KBr), Vcm A 1740, 1675.

146539 14

Ultraviolet absorption spectrum (phosphoric acid buffer, pH 6.86), pH mgx nm: 270 (λ = 9450).

PREPARATION 1 7 | 3-Bromoacetamido-3-carbamoyloxymethyl-7oi-methoxy-3-cephem-4-carboxylic acid In a beaker, 808 mg of bromoacetyl bromide and 1.030 g of bis- (trimethylsilyl) trifluoroacetamide were charged and the resulting mixture was allowed to room temperature for 20 minutes.

Then 5 ml of methylene chloride was added to the mixture followed by a solution of 879 mg of dibenzhydryl-7β- (D-5-t-butoxycarbonylamino-5-carboxyvaleramido (-3-carbamoyloxymethyl-7ct-methoxy-3-cephem-4) The beaker was washed with 10 ml of methylene chloride and the wash solutions combined with the mixture, allowed to stand at room temperature under humid conditions for 2 hours, then 1 g of sodium bicarbonate was added to the reaction mixture with cooling with ice / sodium chloride and then 20 ml of a 5¾ aqueous solution of sodium bicarbonate was added to the reaction mixture, which was stirred for 30 minutes. The methylene chloride phase was combined with the washing solutions obtained by washing the aqueous phase with 10 ml of methylene chloride and the mixture was washed twice with 20 ml of a 20¾ aqueous solution. The organic phase was dried over sodium sulfate and the solvent was distilled off under reduced pressure to give a 1,194 g of crude dibenzhydryl-7 | 3 - [(D-5-t-butoxycarbonylamino-5-carboxyvaleryl) -bromoacetylamino] -3-carbamoyloxymethyl-7α-methoxy-3-cephem-4-carboxylate as a yellow amorphous product .

This yellow product was dissolved in 1 ml of anisole and 2 ml of trifluoroacetic acid and the resulting solution was allowed to stand at room temperature for 5 minutes, after which the solvent was distilled off under reduced pressure; The resulting yellow viscous paste was dissolved in 20 ml of ethyl acetate and 20 ml of a 0.2M phosphoric acid buffer (pH 7.5) and the solution was then transferred to a separatory funnel and shaken well. After phase separation, the pH of the aqueous phase was adjusted to 2.5 with 1N hydrochloric acid and the aqueous phase was extracted five times with 20 ml of ethyl acetate. The extracts were dried over sodium sulfate and the solvent was distilled off under reduced pressure.

300 mg of the desired compound was obtained in the form of a crude amorphous product.

Magnetic Nuclear Resonance Spectrum (CD ^CN + D ^ oij ^ ppm: 5.12 (singlet, H at 6 position) 3.95 (singlet, BrCH 2 CO) 3.53 (singlet, OCH-j at 7 position).

Ultraviolet Absorption Spectrum (CH 2 OH), max max nm: 263.

Infrared Absorption Spectrum (KBr), Vcm 1780, 1700.

Thin layer chromatography (silica gel): (a) Development agent (n-butanol / acetic acid / water, volume ratio 5: 4: 1):

Rp value = 0.53.

(b) Development agent (methanol / chloroform, volume ratio 1: 1): R f value = 0.44.

PREPARATION 2 3-carbamoyloxymethyl-7β-chloroacetamido-7β-methoxy-3-cephem-4-carboxylic acid

The procedure described in Preparation 1 was repeated except that chloroacetyl chloride was used instead of the bromoacetyl bromide. Separation and purification took place as described in Preparation 1 to give the desired compound as a crude amorphous product.

Magnetic Nuclear Resonance Spectrum (CD 2 CN + D 2 O), <$ ppm '5.1 (singlet, H at 6 position) 3.48 (singlet, OCH 2 at 7 position) 4.11 (singlet, C1CH2 CO).

Ultraviolet absorption spectrum (phosphoric acid buffer, pH 6.86), max nm: 264.

Infrared Absorption Spectrum (KBr), V cm -1: 1780, 1700.

Thin-layer chromatography (silica gel):

Development agent (metha'nol / chloroform, volume ratio 1: 1): R value = 0.35).

PREPARATION 3 3-Acetoxymethyl-7β-chloroacetamido-7α-methoxy-3-cephem-4-carboxylic acid 438.5 mg of benzhydryl-3-acetoxymethyl-7β-chloroacetamido-7α-methoxy-3-cephem-4-carboxylate were dissolved in 0.4 ml of anisole and 0.8 ml of trifluoroacetic acid was added to the resulting solution. The mixture was stirred at room temperature for 5 minutes. The reaction mixture was then evaporated to dryness immediately and the residue washed with n-hexane and dissolved in 5 ml of 0.25N phosphoric acid buffer (pH 7.5). The resulting solution was neutralized with a 5 µl aqueous solution of sodium bicarbonate and washed with ethyl acetate. The pH of the aqueous phase was adjusted to 2.0 with 60/0 phosphoric acid and the oily substance which precipitated was extracted with ethyl acetate. The extract was washed with water and dried over anhydrous sodium sulfate, after which the solvent was distilled off to give 276 mg of the desired compound as an amorphous powder.

Magnetic Nuclear Resonance Spectrum (CD 2 CN + D 2 O), <fpppm: 5.08 (singlet, H at 6 position) 4.08 (singlet, C1CH2 CO) 3.55 (singlet, OCH 2 at 7 position).

Thin-layer chromatography (silica gel):

Development agent (chloroform / methanol, 9: 1 by volume):

R value = 0.41).

PREPARATION 4 7 | 3-Chloroacetamido-7ffl-methoxy-3- (1-methyl-1H-tetrazol-5-yl- (thionethyl-3-cephem-4-carboxylic acid) 27.6 g disodium-7β- (D-5 Amino-5-carboxyvaleramido) -3-carbamoyl oxymethyl-7a-methoxy-3-cephem-4-carboxylate was dissolved in 1,090 ml of a 5? aqueous solution of dicalcium phosphate and 715 ml of acetone was added to the resulting solution .

Then 8.1 g of 4-dimethylaminopyridine was added to the solution whose pH was adjusted to 9.5 by the addition of 2.5N aqueous sodium hydroxide solution, then 34.5 ml of t-butoxycarbonylazide was added and the mixture was stirred at room temperature. for 4 hours while maintaining the pH at 9.0 - 9.5. The reaction mixture was allowed to stand at 4 ° C overnight, then 1000 ml of ethyl acetate was added and the mixture was shaken well. The aqueous phase was collected and an additional 1,000 ml of ethyl acetate was added thereto, and the pH of the aqueous phase was adjusted to 2.5 by the addition of concentrated hydrochloric acid while maintaining the temperature at 0-2 ° C. The organic phase was separated and the aqueous phase was further extracted twice with 1200 ml of ethyl acetate. The organic phases were combined and washed with a saturated aqueous solution of sodium chloride until the pH of the wash water reached 4-5, then dried with anhydrous sodium sulfate. Distillation of the solvent from the solution yielded 22.1 g of 7β- (D-5-t-butoxycarbonylamido-5-carboxy-valeramido) -3-carbamoyloxymethyl-7β-methoxy-3-cephem-4-carboxylic acid.

This compound was added to a pH 7.0 phosphoric acid buffer containing 10 g of 5-mercapto-1-methyl-1H-tetrazole, and the mixture was stirred at 95 ° C for 30 minutes, after which the pH was adjusted to 2.5 by addition. of hydrochloric acid under ice-cooling. The reaction mixture was then extracted with ethyl acetate and the extracts were washed with a saturated aqueous solution of sodium chloride until the pH of the wash water reached 4-5, after which the extracts were dried over anhydrous sodium sulfate. A solution of 20 g of diphenyl diazomethane in ether was added to the dried extracts and the mixture was stirred for 2 hours, then washed first with a 20 ά aqueous solution of sodium chloride and then with a 5 ό aqueous solution of sodium hydrogen carbonate. The washed mixture was dried over anhydrous sodium sulfate and the solvents distilled off. The residue was dissolved in chloroform, absorbed on a column packed with silica gel and eluted with chloroform containing 1% by volume of methanol. Distillation of the solvent from the eluate gave dibenzhydryl-7β- (D-5-t-butoxy-carbonylamino-5-carboxyvaleramido) -7β-methoxy-3- (1-methyl-1H-tetrazol-5-yl) thiomethyl-3-cephem -4-carboxylate.

5 millimoles of this compound was dissolved in 50 ml of chloroform, and the solution was added to a mixture of 2.26 g of chloroacetate chloride and 2.26 g of bis (trimethylsilyl) trifluoroacetamide, which had already been allowed to stand at room temperature for 15 minutes. 30 minutes, and the resulting mixture was allowed to stand at 40 ° C for 100 hours. The reaction mixture was then poured into a 5% aqueous solution of sodium hydrogen carbonate and the mixture was stirred for 30 minutes. The organic phase was collected and washed with a 20¾ aqueous solution of sodium chloride and then dried over anhydrous sodium sulfate. The solvent was distilled off from the washed solution and the residue was dissolved in 5 ml of anisole and 10 ml of trifluoroacetic acid. This solution was shaken at room temperature for 3 minutes and then evaporated to dryness under reduced pressure. The residue was dissolved in 1M phosphoric acid buffer (pH 7.5) and extracted with ethyl acetate.

The aqueous phase was collected and its pH adjusted to 2.5 by addition of 1N hydrochloric acid. It was then extracted with ethyl acetate. The extract was dried over anhydrous sodium sulfate and the solvent distilled off to give 7β-chloroacetamido-7α-methoxy-3- (1-methyl-1H-tetrazol-5-yl) thiomethyl-3-cephem-4-carboxylic acid an amorphous powder.

Claims (2)

146539 An analogous process for the preparation of 7α-methoxy-cephalosporin derivatives of the general formula f) CH R -S-CH 2 -CO-NH - <η (II)) -N \> R 2 GT C00H wherein R 1 cyanmethyl, 1-cyanethyl, 2-hydroxyethyl 2 or 1,3,4-thiadiazol-2-yl, and R is acetoxymethyl, carbamoyloxymethyl or (1-methyl-1H-tetrazol-5-yl) thiomethyl, or pharmaceutically acceptable esters thereof, characterized in that a 7α-methoxycephalosporin derivative of the formula OCH3 i / S. X-CH9-CO.NH_.s' \ z I J (III ·) 0> -NV'R2 P