WO2005070881A1

WO2005070881A1 - An efficient process for the manufacture of (e)-entacapone polymorphic form a

Info

Publication number: WO2005070881A1
Application number: PCT/IB2003/006176
Authority: WO
Inventors: Siddiqui Mohammed Jaweed Mukarram; Rashid Abdul Rehman Khan; Ram Prasad Yavad
Original assignee: Wockhardt Limited
Priority date: 2003-12-24
Filing date: 2003-12-24
Publication date: 2005-08-04
Also published as: EP1701936A1; EP1701936A4; AU2003296838A1; US20070004935A1

Abstract

The present invention describes an improved process for the manufacture of (E)-N, N-Diethyl-2-cyano-3-(3, 4-dihydroxy-5-nitrophenyl) acrylamide (Entacapone) polymorphic Form A, which is an excellent inhibitor of Catechol-O-methyltransferase (COMT) enzyme. 3, 4-Dihydroxy-5-nitrobenzaldehyde is condensed with N, N-Diethylcyanoacetamide in presence of a base in alcoholic solution to get the Entacapone. After the disappearance of reactants the crude reaction mixture is poured into aqueous ethyl acetate solution followed by adjusting pH between 3.5 to 4.0 with acetic acid. Simple extraction process provides 99.7% HPLC pure (E)- isomer of Entacapone Form A.

Description

AN EFFICIENT PROCESS FOR THE MANUFACTURE OF (EVENT ACAPONE POLYMRPHIC FORM A

FIELD OF THE INVENTION

The present invention relates to a simple and efficient process for the preparation of stable and crystallographically pure polymorphic Form A of (E)-N,N-Diethyl-2-cyano-3-(3,4- dihydroxy-5-nitrophenyl)acrylamide (Entacapone) having Formula I,

which is an excellent potent inhibitor of Catechol-O-methyl-transferase (COMT) enzyme. The required geometrical (E)-isomer with excellent crystalline purity is obtained during the simple extraction procedure with ethyl acetate solvent once the reaction is over.

BACKGROUND OF THE INVENTION

The chemical name of Entacapone is N,N-Diethyl-2-cyano-3-(3,4-dihydroxy-5- nitrophenyl)acrylamide. British patent application No. 8,727,854 describes Entacapone as a potent inhibitor of catechol-O-methyl-transferase (COMT) enzyme. The product is indicated for the treatment of Parkinson's disease. Catechol-O-methyltransferase (COMT) enzyme catalyzes the methyl group from S-adenosyl-L-methionine to a number of compounds with catechol structures. This enzyme is important in the extraneuronal inactivation of catecholamines and drugs with catechol structures. COMT is one of the most important enzyme involved in the metabolism of catecholamines. It is present in the most tissues, both in periphery and the central nervous system. The highest activities are found in the liver, intestine and kidney.

US Patent No. 4,963,590 describes a process for the preparation of crude N,N-Diethyl-2- cyano-3-(3,4-dihydroxy-5-nitrophenyl)acrylamide (Formula I). The synthetic process disclosed in US patent "590" comprises the condensation of 3,4-Dihydroxy-5-nitrobenzal- dehyde (Formula II) and N,N-Diethylcyano acetamide (Formula III) in anhydrous ethanol as shown below: Formula (II) Formula (III) Formula (IV)

Entacapone (E)- & (Z)- Isomers

Piperidine acetate was used as catalyst in the process described above. Entacapone thus synthesized was obtained in 73 % yield having a mixture of two geometrical isomeric forms, i.e., (E)- and (Z). About the separation of these isomers no techniques is discussed so for in US Patent No. 4,963,590.

On the other hand US Patent No. 5,131,950 discloses about the (E)- and (Z)- isomers having the structural formula:

E-isomer Z-isomer m.p.162-163 ^cC m.p. 148-151 °C

are obtained as mixture in the ratio of about 70-80 % to about 30-20 %, respectively. As revealed by X-Ray crystallography, (E)-N,N-Diethyl-2-cyano-3-(3,4-dihydroxy-5- nitrophenyl)acrylamide may exist at least in two polymorphic forms A and B. The (Z)-isomer as well as polymorphic form B of the (E)-isomer have been shown to be unstable under the influence of heat or acids. Similarly, the polymoφhic form B of the (E)-isomer isomerizes slowly to the polymoφhic form A on standing at room temperature. US Patent 4,963,590 teaches that crude synthesized Entacapone from conventional solvent such as hydrocarbons, alcohols or esters, e.g., benzene, toluene, methanol, ethanol, ethyl acetate, isopropyl acetate, etc. a very complicated mixture of different geometric isomers and/or polymoφhic forms are generally obtained that interfere with the characterization and standardization of the drug substance. The bioavailability of the drug may be also influenced by polymoφhism and geometrical isomerism.

US Patent 5,135,950 discloses that crystallographically essentially pure and stable polymoφhic form A of (E)-N,N-Diethyl-2-cyano-3-(3,4-dihydroxy-5-nitrophenyl)acrylamide may be obtained in good yield, when the crude product of synthesis is re-crystallized from lower aliphatic carboxylic acids such as formic acid or acetic acid with a catalytic amount of hydrochloric or hydrobromic acid as shown below:

(E)- and (Z)-isomers of Entacapone (E)-isomer of Entacapone

The said method allows large scale production of homogeneous and crystallographically essentially pure polymoφhic pure form A of (E)-N,N-Diethyl-2-cyano-3-(3,4-dihydroxy-5- nitrophenyl)acrylamide. In this context "Crystallographically essentially pure" means the polymoφhic form A of (E)-N,N-Diethyl-2-cyano-3-(3,4-dihydroxy-5-nitrophenyl)acrylamide containing a maximum of 3 % and preferably a maximum of 2 % of other polymoφhic forms or the Z-isomer.

The main drawbacks of the above invention are: a) it requires isolation of crude mixture and their further treatment with formic acid or acetic acid in the presence of hydrochloric acid or hydrobromic acid to get isomerically pure (E)-N,N-Diethyl-2-cyano-3-(3,4-dihydroxy-5-nitrophenyl)- acrylamide. b) it uses hazards and corrosive acids as a solvent for re-crystallization. c) removal of residual solvent used in the crystallization process may be problematic at large scale operations and; d) product so obtained becomes contaminated with unwanted (Z)-isomer (at least up to 2 %). It is therefore an object of the present invention to provide an economical and industrially advantageous manufacturing method of (E)-N,N-Diethyl-2-cyano-3-(3,4- dihydroxy-5-nitrophenyl)acrylamide having free of (Z)- isomer.

SUMMARY OF THE INVENTION

The present invention relates to a simple and efficient process for the manufacture of stable and crystallographically pure polymoφhic Form A of (E)-N,N-Diethyl-2-cyano-3-(3,4- dihydroxy-5-nitrophenyl)acrylamide (Entacapone) having Formula I,

which is an excellent potent inhibitor of Catechol-O-methyl-transferase (COMT) enzyme.

In one embodiment a process is provided for the manufacture of (E)-N,N-Diethyl-2- cyano-3 -(3 ,4-dihydroxy-5 -nitrophenyl)acrylamide. 3,4-Dihydroxy-5 -nitrobenzaldehyde is condensed with N,N-Diethylcyanoacetamide in presence of a base in alcoholic solution. Here the required geometrical (E)-isomer with excellent polymoφhic crystalline purity is obtained after simple extraction process. The crude (E)-entacapone having both geometrical isomers, (E)- and (Z)- is simply extracted by ethyl acetate in acidic medium preferably pH between about 3.5 to about 4.0. Thus, isolated product yields desired (E)- isomer in more than 99.6 % HPLC purity.

DETAILED DESCRIPTION OF THE INVENTION

(E)-Isomer of N,N-Diethyl-2-cyano-3-(3,4-dihydroxy-5-nitrophenyl)acrylamide being a potent inhibitor of Catechol-O-methyl transferase (COMT) enzyme, a systematic study for its large scale production with high purity product is under taken. This resulted in incoφorat- ing an extra step for crystallization of crude isomer of (E)- and (Z)- in lower aliphatic acid, e.g., formic acid or acetic acid in the presence of hydrochloric acid or hydrobromic acid. The present invention is directed towards a method by which the stable polymoφhic form A of (E)-N,N-Diethyl-2-cyano-3-(3,4-dihydroxy-5-nitrophenyl)acrylamide may be obtained in high purity without isolating crude solid isomeric mixture of N,N-Diethyl-2- cyano-3-(3,4-dihydroxy-5-nitrophenyl)acrylamide. The pictorial diagram of the synthetic process of crude Entacapone is shown below:

F o rm u la II Formula III Formula IV

(E)- and (Z)- isomers of Entacapone

The synthesis is suitably carried out by condensing 3,4-Dihydroxy-5-nitrobenzaldehyde (Formula II) with N,N-Diethyl cyanoacetamide (Formula III) in alcohol such as methanol, ethanol, isopropanol, isobutanol, n-butanol etc., preferably isopropanol at reflux temperature in the presence of suitable organic base such as piperidine, N-methylmoφholine, pyridine, piperazine, etc. Preferably the reaction is carried out using piperidine base. After completion of the reaction, mixture is poured in to a mixture of chilled water and ethyl acetate. pH of the solution is adjusted between 3.5 to 4.0 by adding acid. The preferable acid used for acidification is acetic acid. Ethyl acetate layer is separated, washed properly with water and concentrated to obtain pure (E)- isomer of polymoφhic form A, essentially without (Z)- isomer contamination.

On the other hand the Entacapone is not isolated in its crude form, it is rather extracted with ethyl acetate which after partial concentration affords the desired product with excellent purity. Other aliphatic esters like methyl acetate, propyl acetate or n-butyl acetate affords similar result.

The present invention is quite interesting since the US Patent No. 5,135,950 emphasizes that crude mixture can not afford desired purity using lower aliphatic alcohols, esters or hydrocarbons, e.g. ethanol, 2-propanol, ethyl acetate, benzene or toluene and a very complicated mixture of different geometrical isomers and/or polymoφhic forms are generally obtained.

But suφrisingly, we get desired pure product by very simple operation. HPLC purity of the product of present invention, i.e., (E)-Entacapone is more than 99 % while (Z)-isomer is found in less than 0.1 %.

The specification of HPLC profile of the present invention is mentioned below:

Coluriin HICHROM HIRPB (250 x 4.6 m, 5 μ) Wavelength 210 nm Flow rate 1.0 ml /minute Temperature Ambient Buffer 1 ml H₃PO₄ in 1000 ml distilled water

Mobile phase Buffer (65) : Acetonitrile (35) Sample preparation ,0.5 mg/ml in mobile phase Retention Time (E)-Isomer = 11.5 minutes, Z-Isomer = 10.3 minutes

The developed HPLC method of analysis clearly resolves both the reactants as well as (Z)- and (E)- isomers of Entacapone.

Infra Red spectrum of polymoφhic form A of (E)-N,N-Diethyl-2-cyano-3-(3,4- dihydroxy-5-nitrophenyl)acrylamide is characterized by the following peaks at about 3330, 3083, 3059, 3032, 2979, 2935, 2216, 1628, 1606, 1580, 1541,1512, 1440, 1379, 1296, 1280, 1209, 1165, 1150, 800, 777, 742 and cm^"1.

X-Ray powder diffraction of the present invention is characterized by the following peaks (2Θ) at about 9.080, 11.700, 11.880, 13.600, 14.140, 15.860, 16.400, 18.240, 18.600, 18.800, 19.040, 20.080, 20.460, 21.200, 21.980, 22.600, 23.040, 23.440, 23.960, 26.160, 26.920, 27.500, 28.000, 28.580, 29.140, 30.200, 30.740, 32.060, 32.580 and 33.320°.

The salient merits of the present invention over existing process are as follows: a) single step process giving highly pure (E)-N,N-Diethyl-2-cyano-3-(3,4- dihydroxy-5-nitrophenyl)acrylamide without isolation of crude mixtures of isomers and re-crystallizations process; b) purity is ascertained by HPLC analysis and getting unknown impurity in less than 0.1%; and c) developed process is robust and adoptable at kilogram to multi kilogram level.

The example discussed below illustrates the invention, but is not limiting thereof:

EXAMPLE 1

(E)-N,N-Diethyl-2-cyano-3-(3,4-dihydroxy-5-nitrophenyl)acrylamide

3,4-Dihydroxy-5-nitrobenzaldehyde (5.0 gm, 27.3 mmol), N,N-Diethyl cyanoacetamide (7.65 gm, 54.57 mmol) and piperidine (7.50 gm, 85.15 mmol) is charged to isopropanol (50 ml). The reaction mixture is refluxed for 10 to 15 hours till the disappearance of stating material. After the reaction is over it is cooled to room temperature. The reaction mixture is poured slowly into a mixture of cold water and ethyl acetate followed by adjusting pH between about 3.5 to about 4.0 with acetic acid. Organic layer is separated, charcohzed and concentrated to afford crystalline (E)-N,N-Diethyl-2-cyano-3-(3,4-dihydroxy-5-nitrophenyl) acrylamide. The title product is filtered and dried to get the desired product in 99.7 % HPLC purity. Mass spectra = (m + 1) 306 (100 %). (Z)-Εntacapone is observed in less than 0.1 %.

Claims

We Claim:

1 A compound having the Formula I

Formula I

substantially free from (Z)-isomer.

2 A pharmaceutical composition comprising compound of claim 1.

3 A process for the manufacturing a compound of Formula (I)

the said method comprising:

(a) reacting 3,4-Dihydroxy-5-nitrobenzaldehyde with N,N-Diethylcyanoacetamide to form a mixture of (E)- and (Z)- isomers of N,N-Diethyl-2-cyano-3-(3,4-dihydroxy-5-nitro- phenyl)acrylamide; and

(b) isolating the (E)- isomer of N,N-Diethyl-2-cyano-3-(3,4-dihydroxy-5-nitrophenyl)- acrylamide Form A.

4 The process of claim 3, wherein step (a) is carried out in organic solvent.

5 The process of claim 4, wherein solvents are protic.

6 The process of claim 5, wherein protic solvents selected are methanol, ethanol, isopropanol, isobutanol or n-butanol.

7 The process of claim 5-6, wherein more preferable solvent is isopropanol.

8 The process of claim 3, wherein step (a) is carried out in presence of a base.

9 The process of claim 8, wherein base is selected from piperidine, N-methylmoφholine, pyridine or piperazine.

10 The process of claim 8-9, wherein more particularly base is piperidine. The process of claim 3, wherein heating in step (a) is conducted at reflux temperature. The process of claim 3, wherein reaction time in step (a) is between about 5 to about 20 hours. The process of claim 12, wherein more preferably reaction time is between about 5 to about 15 hours. The process of claim 3, wherein reaction mixture in step (b) is poured into aqueous ester. The process of claim 14, wherein said ester is methyl acetate, ethyl acetate, n-propyl acetate or n-butyl acetate. The process of claim 15-16, wherein more preferably ester is ethyl acetate. The process of claim 14, wherein reaction mixture is acidified. The process of claim 17, wherein acidifying agent is aliphatic acid. The process of claim 18, wherein said acid is acetic acid. The process of claim 3, wherein isolated (E)- N,N-Diethyl-2-cyano-3-(3,4-dihydroxy-5- nitrophenyl)acrylamide in step (b) has more than 99.6 % HPLC purity. The process of claim 3, wherein (Z)-N,N-Diethyl-2-cyano-3-(3,4-dihydroxy-5- nitrophenyl)acrylamide is present in less than 0.1 %. The process of claim 3, wherein isolated (E)-N,N-Diethyl-2-cyano-3-(3,4-dihydroxy-5- nitrophenyl)acrylamide is polymoφh A.