NO753255L - - Google Patents

Description

Intermediate products for use in the manufacture of

' 7-amino-cephalosporanic acid.

The present invention relates to intermediate products for . use in the production of 7-amino-cephalosporanic acid, and the intermediate products have the general formula:

where R' is C 1 -C 8 alkyl, alkenyl or alkynyl; halogen C 1 -C 8 alkyl, alkenyl, alkynyl;

Y .is oxygen, sulfur, or a carbon-to-carbon-.

bond,

n is an integer from 0 - 3 and is at least 1. when Y is oxygen or sulfur;

Z is oxygen, sulfur or

m is an integer from 1 to 3; °S

R" is an amino-protecting group.

The cephalosporins are a well-known group of antibiotics that are widely used for the treatment of various diseases.- In the chemical modification of various compounds, in this group it is often desirable to cleave the '7-carboxamido group to produce a free amino group in the 7-position. This reaction is particularly important for removing the amino-adipoyl side chain in cephalosporin C to produce 7-amino-cephalosporaninic acid (7-ACA).

A known method for cleaving the amido group to produce the free amine is described by Lander, J. Chem. Soc. 83,320 (1903). According to this method, the amide is treated with a halogenating agent to convert the amido group into an iminohalide, after which this is treated with an alcohol to produce the iminoether, which is then hydrolyzed

to the free amine. The use of this method for cleaving cephalosporin C to 7-ACA is described in Canadian Patent No. 770,125 and British Patent No. 1,041,985.

In order to be able to apply the above reactions to cephalosporins with practical benefit, it is first necessary to protect the carboxyl groups in the molecule. It is particularly important to protect the carboxyl group in the 4-position of the cephalosporin core. Until now, these carboxyl groups have usually been protected by a conversion • to esters. With the exception of silyl esters, these esters are usually stable to the reaction conditions used, and the ester product must be subjected to a further treatment to obtain the free acid. Such a treatment includes a more powerful acid or base hydrolysis, ■ or in certain cases a hydrogenolysis. These additional processing steps increase costs, and in certain cases where a strong acid hydrolysis is used, some hydrolysis occurs. also of the acetoxy group at the .C^ methyl group, whereby desacetyl-cephalosporins are produced, and in connection with base hydrolysis there is always a certain risk of isomerisation of the double bond in the ring.

Furthermore, it can be mentioned that numerous methods for the production of carbon esters lead to isomerization of the double bond in the nucleus, whereby an A 2 product (isocephalosporin) is produced. Silyl esters are more sensitive to traces of moisture, and are consequently far less stable" than carbon esters during the reaction. In reality, in most cases, they can be removed too easily. The reagents used

• in the production of the silyl esters are also relatively expensive

and are usually not readily available in large commercial quantities.

The present invention provides new intermediates which are useful for use in the process according to Norwegian patent no (application 4303/70), which process is an improved method for cleaving 7-carboxamido groups from cephalosporins.

It is understood that when the cephalosporin contains an amino, hydroxy or mercapto group, such a group must be blocked prior to the cleavage reaction. Amino, hydroxy and mercapto blocking groups are well known from the literature and various patents. If the group is present in the 7-side chain so that it will be lost during the cleavage reaction, it does not matter whether the blocking group is one that can be easily removed or not. As an amino-protecting group, mention may be made of alkanoyl, aroyl, alkyloxycarbonyl or aryloxycarbonyl, and similar groups substituted with halogen, nitro or alkoxy groups. Specific examples of amino protecting groups include acetyl, formyl, chloroacetyl, benzoyl, p-nitrobenzoyl, phthaloyl, p-tosyl, 2,4-dinitropheny 1,. t-butyloxycarbonyl and benzyloxycarbonyl. Hydroxyl groups are usually protected by the formation of esters, and then especially by the formation of formyl esters. Mercapto groups are protected by conversion to sulphides, such as benzyl, benzhydryl, trityl or t-butyl sulphides, by formation of disulphides, by formation of thioesters or as the thiocarbamyl group or the S-acetamido-methyl group. It is understood that the above list of blocking groups is intended as examples only, and that many other amino, hydroxy and mercapto protecting groups may be used.

According to the above method, the carboxyl groups become

in the cephalosporin molecule protected by a conversion to mixed anhydrides. Specific examples of suitable mixed anhydrides include those derived from acetic acid, chloroacetic acid, propionic acid, valeric acid, crotonic acid, propiolic acid, 3-chloro-2-pentenoic acid, 4-bromo-2-butynoic acid, phenylacetic acid, phenoxyacetic acid, benzoic acid, furylacetic acid and thienylacetic acid. It is preferred to use the mixed anhydrides of acetic acid and propionic acid because these can be easily prepared. It is further understood that you can use other mixed anhydrides such as

are equivalent to those mentioned above.

Methods for the preparation of mixed anhydrides are well known, and any known method can be used in this regard. The particular method mari uses for the production of the anhydride is not critical. Particularly good results have been achieved by treating the cephalosporin with an acid halide,

then especially acid chlorides, in the presence of a hydrogen halide acceptor such as a tertiary amine. The mixed acetic anhydride has also been prepared by treating the cephalosporin with the ketene. The production of mixed anhydrides will be indicated in the following examples.-

This new blocked cephalosporin can be treated with a halogenating agent as described previously to convert the 7-amido group to an iminohalide. The iminohalide can then be converted into an iminoether by reaction with an alcohol or a phenol. The imino bond in the iminoether can be easily cleaved by weak acid or basic hydrolysis or alcoholysis.

The advantage of these intermediates is that carboxyl protection is achieved by the formation of mixed anhydrides and by using the method in Norwegian patent no. it is often in connection with many esters, and the carboxyl blocking group will be removed during the hydrolysis of the imino ether. The product from the hydrolysis in the method in the above-mentioned patent is thus a free 7-amino-cephalosporin acid. No further carboxyl deblocking step is required.

The following examples illustrate the application of the present invention.

Example 1

To a suspension of 3.6 g (4.9 mmol, 87.5% pure) of the monoquinoline salt of N-chloroacetyl-cephalosporin C monohydrate in 38 ml of freshly distilled chloroform was added 2.08 g (17.1 mmol) of N ,N-dimethylaniline, 1.72 g (22 mmol) acetyl chloride and 4 drops of dimethylformamide. The mixture was stirred at room temperature for 45 minutes. The starting material dissolved within 20 minutes and the solution had a deep yellow color. The mixture was cooled in a carbon tetrachloride-dry ice bath for approx. 10 minutes, after which a further 2.08 g (17.1 mmol) of N,N-dimethylaniline and 2.4 g (11.6 mmol) of phosphorus pentachloride were added. The mixture was stirred in the cold for 2 hours, after which 12 ml of n-propanol was added. The mixture was then stirred for an additional .2 hours. 20 ml of water was added and the mixture was warmed to room temperature over 30 min. The chloroform phase and the aqueous phase separated, and the chloroform phase was washed twice with 5 ml of water each time. The aqueous phase and washing solutions were combined and washed first with chloroform and then with ethyl acetate. The pH of the aqueous phase was adjusted to 3.6 with concentrated ammonium hydroxide, after which the mixture was cooled in a refrigerator overnight. The 7-ACA that had crystallized was collected by filtration and dried for 24 hours in a vacuum. The yield of 7-ACA was 1.075 g. The filtrate contained some additional 7-ACA, which could be detected by thin layer chromatography.

Example 2

Example 1 was repeated except that 2.2 g of quinoline

instead of dimethylaniline was added together with phosphorus pentachloride, and by using a 25% sodium hydroxide solution instead of said ammonium hydroxide to adjust the pH in the aqueous phase. The yield of 7-ACA was 1.14 g.

Example 5

To a suspension of 3.3 g (4.9 mmol, 94.7% - pure) of the monoquinoline salt of N-chloroacetyl-cephalosporin C monohydrate in 38 ml of freshly distilled chloroform was added 2.55 g (17.1 mmol) of N,N -diethylaniline, 1.72 g (22 mmol) acetyl chloride and 4 drops of dimethylformamide. The mixture was stirred at room temperature for 45 min. and then cooled in an ice-salt bath to -5 to -10°C. To the cold mixture was added 2.55 g (17.1 mmol) of diethylaniline and 2.4 g (11.6 mmol) of phosphorus pentachloride. The mixture was stirred in the cold for 30 min., after which 12 ml of cold methanol was added and stirring continued for a further 30 min. 20 ml of cold water was added, the cooling bath removed and vigorous stirring maintained for 10 min. The aqueous layer was separated, washed with chloroform, after which the pH was adjusted to 3.6 in the cold by adding a saturated ammonium bicarbonate solution. The precipitated 7-ACA was filtered after 30 min., washed with cold acetone and then dried in vacuum at 50°C. The yield of 7-ACA was 1.12 g.

• Example 4

The procedure of Example 1 was repeated using 2.04 g of propionyl chloride in place of the acetyl chloride." The yield of 7-ACA was 1.07 g.

Example 5

The procedure from example 1 was repeated by using 2.48 g of chloroacetyl chloride instead of the acetyl chloride. The yield of 7-ACA was 700 mg.

Example 6

Example 1 was repeated using methylene chloride as solvent instead of chloroform. The yield of 7-ACA was 1.01 g.

Example 7

Example 6 was repeated using N,N-dimethylbenzylamine instead of dimethylformamide. The yield of 7-ACA was 1.02 g.

Example 8

Example 2 was repeated by using 2.2 g of freshly distilled quinoline instead of N,N-dimethylaniline for the preparation of the mixed acetic anhydride. The yield of 7-ACA was 790 mg.

Example 9

Example 1 was repeated except that said N,N-dimethylaniline was replaced by dry pyridine in each of the steps. The yield of 7-ACA was 300 mg.

Example 10

Example 1 was repeated by using 3.4 g of phenyl acetyl chloride instead of the acetyl chloride. The yield of 7-ACA was 584 mg.

■ E xample1 11

Example 1 was repeated using 3.0 g of phenoxyacetyl chloride instead of the acetyl chloride. The yield of 7-ACA was 310 mg.

Example 12

Example 1 was repeated using 2.8 g of thiophene-2-acetyl chloride instead of the acetyl chloride. The yield of 7-ACA was 210 mg.

Example 13

Example 1 was repeated using 2.4 g of N-p-toluenesulfonyl-cephalosporin C instead of N-chloro-acetylcephalosporin C monoquinoline salt monohydrate. The yield of 7-ACA was 200 mg.

Example 14

To a suspension of 3.3 g (4.9 mmol, 94.7% pure) of the monoquinoline salt of N-chloroacetyl-cephalosporin C monohydrate in 80 ml of freshly distilled chloroform was added 8 drops of dimethylacetamide. The ketene was passed through the stirred mixture at room temperature for 35 minutes, and the starting material was then completely dissolved. A stream of nitrogen was then passed through the reaction mixture to drive off the excess ketene. The mixture was cooled to -20°C, after which 2.07 g (17.1 mmol) of N,N-dimethylaniline and 2.4 g (11.5 mmol) of phosphorus pentachloride were added. The mixture was stirred at -20°C for 2 hours, then treated with 12 ml of n-propanol and stirred for a further 2 hours at -20°C. 20 ml of water was added, the cooling bath removed and the mixture stirred for 15 minutes. The aqueous layer was separated, washed with .chloroform, after which the pH was adjusted to 3.6 in the cold. The precipitated 7-ACA was collected by filtration and dried in vacuo at 50°C. The yield was 1.01 g.

■ Oak sempe l 15

Example 1 was repeated using heptanoyl chloride instead of acetyl chloride. The presence of 7-ACA in the aqueous extract was detected by thin layer chromatography.

Example 16

Example 1 was repeated using pivaloyl chloride instead of acetyl chloride. The presence of 7-ACA in the aqueous extract was detected by thin-layer chromatography and. bioautography.

Example 17

To a suspension of 2.4 g (5 mmol) of the monoacetic acid salt of cephalosporin C in 38 ml of methylene chloride was added 3.26 g (27 mmol) of N,N-dimethylaniline, 1.73 g (22 mmol) of acetyl chloride and six drops of dimethylformamide. The mixture was stirred at room temperature until complete dissolution was obtained, which occurred after about 2 hours. The solution was then cooled to -20°C and treated with 2.07 g (17.1 mmol) of N,N-dimethylaniline and 2.4 g (11.5 mmol) of phosphorus pentachloride. The mixture was stirred at -20°C for 2 hours, after which 12 ml of n-propanol was added. Stirring and cooling were continued

for another 2 hours. 10 ml of water was added, and the mixture stirred for approx. 10 minutes The aqueous layer was separated, washed with chloroform, after which the pH was adjusted to 3.6 with concentrated ammonium hydroxide in the cold. The yield of 7-ACA was 600 mg.

Example 18

A suspension of 2.4 g (5 mmol) of the monoacetic acid salt of cephalosporin C in 40 ml of freshly distilled chloroform was treated with a stream of ketene for 1 hour at room temperature. Excess ketene was removed by applying a stream of dry nitrogen. The reaction mixture was then cooled to approx. -20°C for an addition of 2.07 g (17.1 mmol).N,N-dimethylaniline and 2.4 g (11.5 mmol) phosphorus pentachloride. The mixture was stirred in the cold for 2 hours, after which 12 ml of n-propanol was added and the stirring continued for 2 hours. The hydrolysis was carried out by adding 20 ml of water and allowing the mixture to slowly warm up to room temperature. The aqueous phase was separated, washed with chloroform and pH adjusted to 3.6. The crystalline product, namely 7-ACA, weighed 758 mg after drying for 3 hours at 50°C in vacuum.

Examples 17 and 18 show simultaneous blocking of the carboxyl groups and the free amino group. In both examples, the carboxyl groups were converted to mixed acetic anhydrides while the amino group was simultaneously acetylated.

The mixed anhydride-blocked cephalosporins obtained as intermediates are new compounds that have not been reported so far. Thus, it can be mentioned that the mixed anhydride-blocked cephalosporin C is one with the formula:

where R' has the meaning given above and R" is an amino protecting group.

Since the preferred mixed anhydrides are acetic acid and propionic acid mixed anhydrides, the preferred values for R' are methyl and ethyl. The particular amino protecting group used is not critical and is not a new feature of the present compounds. Amino protecting groups are well known and described above. A preferred amino protecting group is the chloroacetyl group.

Claims (3)

1. Intermediates for use in the production of 7-amino-cephalosporanic acid compounds, characterized by the general formula: where R' is C 1 -C 8 alkyl, alkenyl or alkynyl, halogen C^ -Cg alkyl, aikenyl, alkynyl,. Y is oxygen, sulfur or a carbon-to-carbon bond, n is a number from 0 - 3, and at least 1 when Y is oxygen or sulphur, Z is oxygen, sulfur or m is a number from 1 - 3, and R" is an amino protecting group. 2. Intermediate according to claim 1, characterized in that R' is methyl or ethyl. 3. Intermediate product according to claim 1 or 2, characterized in that R" is chloroacetyl.