FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
The Patents [Amendment] Rules, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION
A Process For Preparing 7-Amino-3-Vinyl Cephalosporanic Acid (7-Avca)
2. APPLICANT
NAME : Frichem Private Limited
NATIONALITY : IN
ADDRESS : 12, Concord, Bullock Road, Band Stand, Bandra West, Mumbai-400 050, India
3. PREAMBLE TO THE DESCRIPTION
COMPLETE
The following specification particularly describes the invention and the manner in which it is to be performed.


Field of the Invention The present invention relates to a process for preparing 7-amino-3-vinyl cephalosporanic acid (7-AVCA). More particularly, the present invention provides an improved process for preparing highly pure 7-AVCA via salt of 7-(2-phenyl acetamido) vinyl cephalosporanic acid (7-PVCA).
Background of the Invention 7-amino-3-vinyl cephalosporanic acid or vinyl-ACA (7-AVCA) of formula (I) is used as an intermediate in the production of highly active,

oral antibiotics, e.g. cefixime and cefdinir of formulae

(Ill)
According to prior art processes 7-AVCA is produced, for example, by wittig reaction of a corresponding cephalosporin-3-ylide, which has the amine and the carboxylic acid group attached to the ring system protected, with formaldehyde (see e.g. Journal of

Antibiotics, Vol. 38, No. 12, 1739; or EP 503453; or EP 597429). The 7-AVCA so produced is contaminated, e.g. by 7-amino desacetoxy cephalosporanic acid (7-ADCA) impurity. This is consistent with the fact that phosphine alkylenes (ylides) or quaternary phosphonium compounds undergo hydrolysis to form the corresponding alkane and phosphine oxide (see e.g. Houben Weyl, Methoden der organischen Chemic, Phosphorverbindungen I, volume 12/1, especially pages 108 and 119).
As a result, when 7-AVCA is prepared via a wittig reaction, 7-ADCA of formula (IV) or a protected derivative thereof may be formed as a by-product.

Alternatively according to prior art, 7-amino cephalosporanic acid (7-ACA) is produced via fermentative production of cephalosporin C and subsequent conversion to 7-AVCA. The 7-AVCA thus formed may contain 7-ADCA as impurity, because the 7-ADCA-analogous cephalosporin is formed in the course of fermentation, or the raw material is not wholly metabolized to cephalosporin C. Thus, 7-ACA, used for example as a starting material for production of 7-AVCA, may often have an undesired 7-ADCA content, of more than 1%.
However, during the production of active cephalosporins, e.g. cefixime and cefdinir, wherein the intermediate 7-AVCA is used, the 7-ADCA content in 7-AVCA should be as low as possible, because upon appropriate further substitution of 7-AVCA, 7-ADCA could react in the same way as 7-AVCA thereby resulting in contamination of the desired active 7-AVCA compounds, e.g. cefixime or cefdinir, by analoguously substituted 7-ADCA-compounds, which are difficult to separate.

In light of the foregoing discussion, there exists a need to develop an efficient and simple process for producing the 7-AVCA intermediate with minimal 7-ADCA impurity wherein the process eliminates the drawbacks of existing processes.
Summary of the Invention In accordance with a principal object of the present invention, there is provided a process for preparing 7-amino-3-vinyl cephalosporanic acid (7-AVCA), with minimal 7-amino desacetoxy cephalosporanic acid (7-ADCA) impurity.
Another object of the present invention is to provide an efficient process for preparing 7-AVCA with high purity and yield.
In accordance with one preferred embodiment of the present invention there is provided a process for preparing pure 7-amino-3-vinyl cephalosporanic acid (7-AVCA) comprising dissolving 7-(2-phenyl acetamido) vinyl cephalosporanic acid (7-PVCA) in a solvent, adding base or alkali metal salt of weak acid to obtain a precipitate and filtering the resultant to obtain salt of 7-PVCA, treating the resultant salt with enzyme in presence of water and isolating the 7-AVCA.
In accordance with one preferred embodiment of the present invention there is provided a process for preparing pure 7-amino-3-vinyl cephalosporanic acid (7-AVCA), wherein the resultant salt of 7-PVCA is optionally converted into 7-PVCA.
In accordance with one preferred embodiment of the present invention there is provided a process for preparing pure 7-amino-3-vinyl cephalosporanic acid (7-AVCA), wherein the resultant 7-AVCA is characterized by having impurity 7-ADCA (IV) is less than about 0.1%.
Detailed Description of the Invention While this specification concludes with claims particularly pointing out and distinctly claiming that, which is regarded as the invention, it is anticipated that the invention can

be more readily understood through reading the following detailed description of the invention and study of the included examples.
The present invention discloses a process for preparing 7-amino-3-vinyl cephalosporanic acid (7-AVCA), with reduced level of 7-amino desacetoxy cephalosporanic acid (7-ADCA) impurity, wherein the impurity is less than about 0. 1°A
In accordance with a preferred embodiment, the present invention provides a process for preparing 7-AVCA of formula I comprising:
a) dissolving 7-(2-phenylacetamido)vinyl cephalosporanic acid (7-PVCA) of formula (V) in a solvent;
b) adding base or alkali metal salt of weak acid to obtain a precipitate and filtering the resuktanl to obtain salt of 7 -PVC A,
c) treating the resultant salt with enzyme in presence of water; and
d) isolating the 7-AVCA.

According to the process of present invention the resultant salt of 7-PVCA is optionally converted into 7-PVCA.
The solvent employed herein according to the process is selected from the group consisting of acetone, tetrahydrofuran, dioxane, methanol, ethanol, propanol, water and the like or mixture thereof, preferably a mixture of acetone and water.
The alkali metal salt of weak acid employed herein according to the present process is selected from the group consisting of sodium lactate, sodium acetate, sodium 2-ethylhexanoate, potassium acetate and the like, preferably sodium 2-ethylhexanoate.
The base employed herein according to the present process is selected from the group consisting of nitrogen base such as ammonia or an amine for example dicyclohexyl amine, diethyl amine, dimethyl amine, dipropyl amine, methyl ethyl amine, diisopropyl amine, benzhydryl amine, preferably dicyclohexyl amine.
The enzyme used herein is PenG Amidase/Acylase.
According to the process of the present invention the impurity present in 7-PVCA is 3-methyl impurity i.e. 3-methyl-8-oxo-7-(2-phenylacetamido)-5-thia-l-azabicyclo[4.2.0] oct-2-ene-2-carboxylic acid (7-PMCA) (VI) at a concentration of about 0.25-0.5 % in 7-PVCA and acts as a main source of the 7-ADC A (IV) impurity in the final product.
The following examples are for the purpose of illustration of the invention and are not intended in any way to limit the scope of the invention.
Example 1
Preparation of 7-PVCA
7-PVCE i.e. 4-Methoxybenzyl 8-oxo-7-(2-phenylacetamido)-3-vinyl-5-thia-l-azabicyclo [4.2.0]oct-2-ene-2-carboxylate (50 gm) was added to molten phenol (166 ml) at 40° C followed by stirring at 48-50° C. The reaction mixture was cooled to room temperature

and then transferred to a pre-cooled mixture of n-butyl acetate (500ml) and water (400 ml). Subsequently, the pH of the reaction mixture was adjusted to 7.2-7.5 employing sodium bicarbonate solution and stirring. Layers were separated and aqueous layer washed again with n-butyl acetate followed by degassing at 20° C. Water (200 ml) and methanol (150 ml) was added to the reaction mixture, followed by pH adjustment to 3.0 by using 5% HC1. The reaction mixture was then cooled and stirred at 5° C. The solid material obtained was filtered and washed with water. The resultant product was dried under vacuum at 40-45°C to obtain 7-PVCA.
Example 2
Preparation of 7-PVCA dicvlohexyl amine salt
To a solution of 7-PVCA (56 gm) in acetone (150 ml), water (20 ml) was added. Dicyclohexyl amine was added to the reaction mixture followed by stirring at room temperature and cooling at -10°C. The solid obtained was washed with acetone and dried under vacuum at 40-45° C.
Example 3
Preparation of PVCA sodium salt
7-PVCE (4 gm) was added to molten phenol (12.9 gm) at 40°C and stirred. Reaction mixture was cooled to 25°C after 8 hrs. The acetone (266 ml) was added to the above reaction mass. To the resultant reaction mixture water (14 ml) was added followed by the addition of sodium 2-ethyl hexanoate (2.16 gm in acetone) and stirring. The solid obtained was filtered and washed with acetone and then dried under vacuum at 40-45°C.
Example 4
Preparation of highly pure 7-PVCA
A solution of 7-PVCA dicyclohexyl amine salt (42.2 gm) was prepared in water (1000 ml). The pH of the reaction mixture was adjusted to 3.5 by using 5-8 % HC1. The reaction mixture was cooled and stirred at 5°C. The solid obtained was filtered and washed with water (50 ml), followed by drying under vacuum at 40-45° C to obtain pure 7-PVCA. Purity = 99.75 %

7-ADC A content = 0.09%.
Example 5
Preparation of highly pure 7-AVCA from highly pure 7-PVCA
A solution of 7-PVCA (20 gm) and water (500 ml) was prepared. To this solution 10 % sodium bicarbonate solution was added for dissolution. Enzyme (100 gm in water 200 ml) was added to the solution followed by pH adjustment to 8.0-8.2 using 8-10 % sodium carbonate solution. The reaction was observed by HPLC and after completion of the reaction, the reaction mass was filtered and washed with water (2 x 100 ml). To the filtrate EDTA (1 gm) and activated carbon (5 gm) was added and stirred. The reaction mixture was filtered, washed with water and cooled to 3°C. The pH was adjusted again to 3.8-4.0 using 10% HC1 and stirred. Subsequently, the solid obtained was filtered and washed with acetone and water followed by drying under vacuum to obtain highly pure 7-AVCA. Purity = 99.60 % 7-ADCA content = 0.08%.
Example 6
Preparation of highly pure 7-AVCA from 7-PVCA sodium salt
A solution of 7-PVCA sodium salt (1.2 gm) and water (60 ml) was prepared. To this solution Enzyme (5 gm) was added followed by pH adjustment to 7.8-8.0 using 10 % sodium carbonate solution and stirred. The reaction was observed by HPLC and after completion of the reaction, the reaction mass was filtered and washed with water (2 x 100 ml). The pH of the filtrate was adjusted to 6.6-6.8 by acetic acid and cooled. To the filtrate EDTA (0.2 gm) and activated carbon (5%) was added and stirred. The reaction mixture was filtered and washed with water and cooled to 3°C. The pH was adjusted again to 3.8-4.0 using 10% HC1 and stirred. The solid obtained was filtered and washed with acetone and water followed by drying under vacuum to obtain highly pure 7-AVCA. Purity = 99.50 % 7-ADCA content = 0.10%.

While this invention has been described in detail with reference to certain preferred embodiments, it should be appreciated that the present invention is not limited to those precise embodiments rather, in view of the present disclosure, which describes the current best mode for practicing the invention, many modifications and variations, would present themselves to those skilled in the art without departing from the scope and spirit of this invention. This invention is susceptible to considerable variation in its practice within the spirit and scope of the appended claims.

We Claim:
1. A process for preparing pure 7-amino-3-vinyl cephalosporanic acid (7-
AVCA) comprising:
(a) dissolving 7-(2-phenyl acetamido) vinyl cephalosporanic acid (7-
PVCA) in a solvent;
(b) adding base or alkali metal salt of weak acid to obtain a precipitate and filtering the resultant to obtain salt of 7-PVCA;
(c) treating the resultant salt with enzyme in presence of water; and
(d) isolating the 7-AVCA.

2. The process according to claim 1, wherein the resultant 7-AVCA is characterized by having less than 0.1% of 7-amino desacetoxy cephalosporanic acid (7-ADCA) impurity.
3. The process according to claim 1, wherein the 7-PVCA employed contains 0.25-0.5 % of the 3-methyl impurity (7-PMCA).
4. The process according to claim 1, wherein the base used is selected from ammonia or amine.
5. The process according to claim 4, wherein the amine is selected from a group consisting of dicyclohexyl amine, diethyl amine, dimethyl amine, dipropyl amine, methyl ethyl amine, diisopropyl amine and benzhydryl amine.
6. The process according to claim 5, wherein the amine used is dicyclohexyl amine.
7. The process according to claim 1, wherein the salt of weak acid used is selected from sodium lactate, sodium acetate, sodium 2-ethylhexanoate and potassium acetate.

8. The process according to claim 7, wherein the salt of weak acid used is sodium 2-ethylhexnoate.
9. The process according to claim 1, wherein the resultant salt of 7-PVCA is optionally converted into 7-PVCA.
10. The process according to claim 1, wherein the enzyme used is PenG
amidase/acylase.
11. The process according to claim 1, wherein the solvent used is selected from acetone, tetrahydrofuran, dioxane, methanol, ethanol, propanol, water and mixture thereof.
12. The process according to claim 1, wherein the solvent used is a mixture of acetone and water.
MANISHA SINGH NAIR
Agentl for the Applicant [IN/PA-740]
LEX ORB1S
Intellectual Property Practice
709/7 1 0, Tolstoy House,
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