FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
and
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10 and rule 13]
1. Title: Process for preparation of Cephalosporin derivatives.
2. Applicant: Claris Lifesciences Limited,
Claris Corporate Headquarters, Nr.Parimal Crossing, Ellisbridge, Ahmedabad-380006, Gujarat, India.

The following specification particulariy describes the invention and the manner in
which it is to be performed.


DESCRIPTION
Field of Invention:
The present invention relates to a process for preparation of Cephalosporin derivatives, the present invention relates to a process for producing 7-(substituted) amino-3-substituted thiomethyl cephem carboxylic acids.
BACKGROUND OF THE INVENTION
Cephalosporin- Any of a group of broad-spectrum derived from species of fungi of the genus Cephalosporium and is related to the penicillin's in both structure and mode of action but relatively penicillinase-resistant antibiotics. These antibiotics have low toxicity for the host, considering their broad antibacterial spectrum. They have the active nucleus of beta-lac tarn ring, which results in a variety of antibacterial and pharmacological characteristics when modified mainly by substitution at 3 and 7 positions. Their antibacterial activities result from the inhibition of mucopeptide synthesis in the cell wall. They are widely used to treat gonorrhea, meningitis, pneumococcal, staphylococcal and streptococcal infections. The cephalosporin class of antibiotics is usually divided into generations by their antimicrobial properties. Three generations of cephalosporins are recognized and the fourth has been grouped. Each newer generation of cephalosporins has broader range of activity
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against Gram-negative organisms but a narrower range of activity against Gram-positive organisms than the preceding generation.
As to the above-mentioned cephalosporins, the most common method of synthesis is the one, which goes through the chemical transformation 7-amino cephalosporanic acid (here below indicated as 7-ACA), suitably substituted at position 3 and 7.
U.S. Pat. No. 4,317,907 represents the process for the production of Cefazolin uses BF3 or the derivatives thereof in an organic solvent and allows obtaining 3-thiodiazolyl derivatives. The acid Cefazolin is then obtained by acylating, with tetrazolyl acetic acid, the 3-thiodiazolyl derivatives in an organic solvent; the solvent noted as preferred is, usually, a chlorinated solvent such as methylene chloride, the use of which entails however the evaluation of the ecologic impact.
U.S. Pat. No. 3,516,997 is represented by the use of a solution of cephalosporin C, the obtainment of the sodium salt thereof, which is isolated, then of the 3-thiadiazolyl derivative thereof, isolated and used to obtain 3-thiodiazolyl derivatives, then isolated and from which the acid Cefazolin is obtained; such method results in difficulties in isolating the intermediates. A method to obtain Cefazolin is to use 7-ACA obtained enzymatically. The carrying out of such process simplifies the production cycle avoiding the isolation of the cephalosporin C.
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U.S. Pat. No. 3,954,745 utilizes the concept, i.e., formation of \H~ tetrazol-1-acetyl chloride in dimethyl acetamide and coupling the acid chloride with the DMF~solvate of the hydrochloride of 7-aminocephalosporin of the 7-amino-3-2-(5-methyl-l,3,4-thiadiazol-2-yl- thiomethyl) 3-chephem-4-carboxylic acid to yield Cefazolin. However, yields are low. Also, the acylating agent, \H~ tetrazol-1-acetyl chloride, because of its inherent instability, is difficult to isolate and store at room temperature. Another limitation of this process is that acylation is to be carried out in strictly anhydrous conditions.
U.S. Pat. No. 3,502,665 is directed specifically to a method for
accomplishing acylation of 7-aminocephalosporanic acid (7-ACA) or
derivatives of 7-ACA in which the acetoxy function in the 3-position
has been displaced by other well-recognized nucleophiles. By the
definition of the process of this patent, a 7-acylamidocephalosporanic
acid is prepared by acylation of 7-aminocephalosporanic acid or an
acid addition salt thereof by treatment with an acyl halide under
substantially anhydrous conditions and in an inert Lewis base liquid.
Included among those compounds considered as Lewis bases are N,N-
dialkylamides. Those specifically mentioned are N,N-
dimethylformamide, N,N-diethylformamide, N,N-dipropylformamide,
N,N-dibutylformamide, N,N-dimethylacetamide, N,N-diethylacetamide,
N.N-dimethyl valeramide, N,N-dimethylpropionamide, N-
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formylpiperidine, and N-formylmorpholine. It is stated that from this group it is preferred to use N,N-dirnethylacetarnide or N,N-dimethylformamide.
Summary of the invention
The present invention relates to a simple, efficient and commercially feasibie method for the production of Cephalosporin derivatives. The process of the invention involves commercially cheaper and readily available raw materials and reduces reaction time and simple isolation process to obtain Cephalosporin derivatives in pure form.
Object of the present invention is directed to provide a process for the synthesis Cephalosporins derivative by reacting thiol derivatives and tetrazol acetic acid derivative with 7-amino cephalosporanic acid (7-ACA), which would be easy to manufacture.
According to the process of the present invention, the 7-ACA condenses with thiol derivative and tetrazol derivative for synthesis of respective Cephalosporin derivatives.
Detail description of Invention.
As a process for preparing 3 substituted thiol derivative and 7 substituted tetrazol derivative with amino cephalosporanic acid
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compounds. In the present invention the process in which 7-ACA is directly reacted with thiol or its salt and tetrazoi or its salt.
According to the invention, a process for preparing the compound formula I


HO^O
Formula I
Where in R is thiadiazolyl, a triazolyl, a tetrazolyl and a tetrahydrotriazinyi, substituted or not substituted and, preferably, R is a 5-methyl-l,3,4-thiadiazol-2-yl, a l//-l,2,3-triazol-4-yl, a 1-methyl-tetrazol-5-yl, a l,2,5,6-tetrahydro-2-methyl-5,6-dioxo-l,2,4-triazin-3-yl.
Wherein R1 is hydrogen atom and R2 is hydrogen atom, tetrazoi-1-acetyl group.
The process comprising condensation of the compound formula II
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with a thiol derivative of the compound formula III
in presences of condnesing agent (boron trifluoride ethyl etherate) and weak acid; to 3-thiodiazolyl derivatives of 7-ACA of formula-TV. Preferable Weak acid is acetic acid or formic acid.

The process of the invention is carried out in solvent wherein condensing agent acts as solvent, at a temperature of about 0°C to 80°C, and preferably 25°C to 50°C, for a time from about 2hr to lOhr. thereafter adjusting the 2.0pH, followed by stirring the reaction mass
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overnight. The reaction mixture was filtered and washed with water and acetone.
The process according to the present invention 3-thiodiazolyl derivatives of 7-ACA, is acylating with chlorinated tetrazol acetic acid derivative to the cephalosporin intermediate of formula I at temperature of about -65°C to -45°C. Where tetrazol acetic acid derivative is chlorinated with chlorinating agent in presence of catalyst and solvent mixture consisting of chlorinated solvent or amines or mixture there off at temperature of about -45°C to -25°C. The reaction of acylation of 3-thiodiazolyl derivatives of 7-ACA and chlorinated tetrazol acetic acid derivative may be carried out in presence of condensing agent, wherein the condensing agent converts to the salts of 3-thiodiazolyl derivatives of 7-ACA in a liquid phase.
The present invention further discloses a one of compound of formula I, the 7-(l-H-tetrazol-l-yl) acetamide-3-[(5-methyl-l,3,4-thiadiazol-2-yl)-thiomethyl]-cephalosporanic acid i.e (Cefazolin). The process of the invention further can be advantageously used for the preparation of some important cephalosporin derivative, which can be obtained by converting the compounds of formula I, according to known techniques, as above illustrated.
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The process for obtaining Cefazolin described can be illustrated by the following reaction scheme^
Step:-1

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7 - Amino Cephaiosporanic Acid 5-methyl-1,3,4-thiadiazole-2-thio!




10


Cefazolin Acid
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According to the process of the present invention, in the case of Cefazolin, the 7-ACA, is reacted with methylmercaptothiadiazol (MMTD) to obtain the 7-amino-3-[(5-methyl-ll3,4-thiadiazol-2-yl)-thiomethylj-cephalosporanic acid.
In the present embodiment the process for the preparation of cephalosporin derivative, step-2 as above in reaction scheme is to carry out the acylating tetramethylguanidine salt of 7-amino-3-[(5-methyl-l,3,4-thiadiazol-2-yl)-thiomethyl]-cephalosporanic acid with \H -tetrazol-1-ylacetyl chloride to yield 7-(l-//-tetrazol-l-yl) acetamide-3-[(5-methyl-l,3,4-thiadiazol-2-yl)-thiomethyl]-cephalosporanic acid i.e (Cefazolin).
• the process comprising the clorination of l/f-tetrazol-l-ylacetic acid with pivaloyl chloride in presence of catalyst 4-methyl-pyridine. The process of the invention is carried out in chlorinated solvent and amines, at a temperature of about ~65°C to -45°C.
• 7-amino-3-[(5-methyl-l,3,4-thiadiazol-2-yl)-thiomethyl]-cephalosporanic acid from step-1 is reacted with tetramethylguanidine to liquid tetramethylguanidine salt of 7-amino-3-[(5-methyl-l,3,4-thiadiazol-2-yl)-thiomethyl]-cephalosporanic acid. The process of the invention is carried out in chlorinated solvent, at a temperature of about ~35°C to -15°C, for a time from about Ihr to 3hr.
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In the present embodiment the process for the preparation of cephalosporin derivative, in which the tetramethylguanidine salt of 7-amino-3-[(5-methyl-l,3,4-thiadiazol-2-yl)-thiomethyl]-cephalosporanic acid is added dropwise to chlorinated tetrazol acetic acid derivative to 7-(l-H-tetrazol-l-yl)acetamide-3-[(5-methyl-l)3,4-thiadiazol-2-yl)-thiomethyl]-cephalosporanic acid i.e Cefazolin. The process of the invention is carried out in aqueous media, at a temperature of about ~65°C to -45°C, for a time from about 0.5hr to lOhr. add aqueous media and adjust the pH about 6.0 at temperature of about 10°C to 15°C.
Example^ Synthesis of Cefazolin acid.
Step-1 Preparation of 7-amino-3-2-(5-methyl-l,3,4- thiadiazol-2-yl - thiomethyl) 3-cephem -4~carboxylic acid from 7-ACA.
7-ACA (10 gm) was suspended in 70 ml of acetic acid at 28°C.To this reaction mixture was added MMTD(4.85 gm) within 5 minutes followed by addition of 56 ml of BF3 ethyletherate there into. After addition the mixture was stirred at 45-50°C.Immediately after completion of reaction 180 ml of water was added slowly at 35°C.There after sodium hydrosulphite, EDTA and charcoal were charged in reaction mass, which was stirred for 30 minutes followed by micron filtration. The filtrate was adjusted the pH 2.0-2.5 with ammonium solution at 15-20°C followed by stirring over night. Then reaction mass was filtered
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and washed with water and acetone. The product was dried at 45°C under vacuum.
Step-2: Preparation of Cefazolin acid from Step-1
Part (A) :
5.208 g of TAA was suspended in 30.0 ml of dichloromethane at 25-30°C.Then 8.3 ml of triethylamine was added at 0°C slowly. The reaction mixture was further cooled to -15 to -20°C, to which was added 0.02 ml of 4-methyl-pyridine, followed by addition of 5.6 ml of pivaloyl chloride. After stirring for 1 hour at -20 to -25°C, the mixture was further cooled to -55°C to -60°C.
Part (B):
10.0 g of 7-amino-3-2- (5-methyl-l, 3,4 thiadiazol-2yl thiomethyl) 3-cephem-4-carboxylic acid was suspended in 30.0 ml of dichloromethane which was cooled to -30°C to -35°C.To which was added 1.1 mole equal of N,N,N',N'-tetramethyl guanidine, followed by stirring the reaction mixture at the same temperature. The reaction mixture was further cooled to -55°C -60°C.
Part (C):
The solution prepared according to (B) was added dropwise to (A) at about -45° to -50°C. After completion of the reaction temperature of reaction mixture was raised at 10° to 15°C to which was added 150 ml
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Wherein R is as defined above in presences of boron trifiuoride ethyl etherate and acid, at a temperature of about 0°C to 80°C thereby preparing a compound of formula-IV


Formula-IV
Wherein R is as defined above;
(ii)acylation of the tetramethylguanidine salt of compound formula IV with chlorinated tetrazol derivative, in aqueous media, at a temperature of about -65°C to -45°C, for a time from about 0.5hr to lOhr.

2. A process of claim 1, wherein hetrocyclic group represented by R is selected from thiadiazolyl, a triazolyl, a tetrazolyl and a tetrahydrotriazinyl, substituted or not substituted and, preferably, R is a 5-methyl-l,3,4-thiadiazol-2-yl, a lH-l,2,3-triazol-4-yl, a 1-methyl-tetrazol-5-yl. a l,2,5t6-tetrahydro-2-methyl-5,6-dioxo-l,2,4-triazin-3-yl.
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WFI, followed by adjusting the pH 6.0-6.5 with ammonia solution. There after the layers were separated. The aqueous layer was washed with DCM (20ml and 10ml) and the organic layer was washed with 10ml WFI. To the combined aqueous layer was added sodium hydro sulphite, EDTA and charcoal. After treatment the obtained filtrate was cooled to 10°C to 15°C followed by adjusting the pH 1.5-2.0 with HC1. The precipitated material was filtered and washed with water and methanol. The obtained Cefazolin was dried at 45°C under vacuum.
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We Claim,
1. A process for the preparation cephalosporin derivative for formula I

Wherein R is hetrocyclic group
R1 is hydrogen atom
R is hydrogen atom or tetrazol-1-acetyl group
Which comprises the step of
1. condensation of the compound formula II

with the compound of formula III
R-SH Formula III
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3. Process of claim 1, wherein weak acid are acetic acid or formic acid.
4. Process of claim 1, wherein the condensation is performed at a temperature range from 25°C to 50°C.
5. Process of claim 1, wherein salt formation of compound formula IV is carried out preferably with N,N,N'.N'-tetramethylguanidine.
6. Process of claim 5, wherein the solid compound of formula IV is mixed with tetramethylguanidine in presence of chlorinated solvent, at a temperature of about -35°C to -15°C.
7. Process of claim 1, wherein chlorinated tetrazol derivative is clorination of tetrazol acetic acid derivative with pivaloy chloride in presence of catalyst 4-methyl-pyridine, chlorinated solvent and amines, at a temperature of about -15°C to -55°C.
8. Process of claim 7, wherein amines are triethylamines, diethyl
amine, pyridine, N -methyl piperidine.N-methyl morphoHne,N,N-dimethyl aniline, N.N-diisopropyl ethyl amine and mixtures there of.
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9. Process of claim lto 7, wherein chlorinated solvent are dichloromethane, chloroform, dichloroethane, and mixture thereof.
10. Process of claim 1, wherein the compound of formula I is 7-(l~ H-tetrazol-l-yl)acetamide-3-[(5-methy]-l,3,4-thiadiazol-2-yl)-thiomethyl]~cephalosporanic acid i.e (Cefazolin).

DATE and SIGNATURE

Date : 24th January 2009
Signature:

Name : Bhavik Patel
Designation: Patent Agent
(Agent no-1N/PA1379)

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