WO2007054969A2

WO2007054969A2 - Process for the preparation of lercanidipine and amorphous form of lercanidipine hydrochloride

Info

Publication number: WO2007054969A2
Application number: PCT/IN2006/000376
Authority: WO
Inventors: Rao A.V.V. Shrinivas
Original assignee: Torrent Pharmaceuticals Limited
Priority date: 2005-09-21
Filing date: 2006-09-19
Publication date: 2007-05-18
Also published as: EP1963254A2; WO2007054969A3

Abstract

The present invention relates to new, improved and industrially viable process for the preparation of Lercanidipine or its pharmaceutically acceptable salts using novel derivatives of 2,N-dimethyl-N-(3,3-diphenylpropyl)-l -amino compounds and novel polymorphs of Lercanidipine hydrochloride, its process of preparation.

Description

NOVEL PROCESS FOR THE PREPARATION OF LERCANIDIPINE

FIELD OF THE INVENTION:

The present invention relates to new, improved and industrially viable process for the preparation of Lercanidipine or its pharmaceutically acceptable salts using novel derivatives of 2,N-dimethyl-N-(3,3-diphenylpropyl)-l -amino compounds and novel process for the preparation of amorphous Lercanidipine hydrochloride.

BACKGROUND OF THE INVENTION:

Lercanidipine hydrochloride, i.e., 3,5-Pyridinedicarboxylic acid, l,4-dihydro-2,6- dimethyl-4-(3-nitrophenyl)-,2-[(3,3-diphenylpropyl)methylamino]- 1 , 1 -dimethyl ester, hydrochloride having the formula (I)

is an antagonist of type-L calcium channels, and has been found to be very active as an antihypertensive and is an useful agent for the treatment of angina and coronary diseases. Its mechanism of antihypertensive activity is attributed to a direct relaxant effect on vascular smooth muscle, which lowers total peripheral resistance. Lercanidipine hydrochloride (I) is disclosed in US4705797.

The preparation of said compound can be obtained with different synthetic schemes. US4705797 discloses process for the preparation of Lercanidipine Hydrochloride as described according to the following scheme: Scheme - 1

(I)

As per scheme-I crude lercanidipine is obtained as an oily residue that must be purified by flash chromatography using chloroform, containing increasing amounts of acetone, as the eluant. The solvent is then evaporated to dryness and remaining residue is dissolved in methanol adding a small excess of hydrochloric acid in ethanol. After evaporation of the solvent, the hemi-hydrated hydrochloride salt is prepared by treatment with diluted hydrochloric acid in the presence of sodium chloride.

A major disadvantage of the process of preparing lercanidipine, as it is described in US Patent No. 4705797, is that the disclosed cyclization reaction generates several by products, which result s in a lower yield for the desired product. Moreover, the purification and isolation of lercanidipine from the reaction mixture is quite complex, since it requires numerous treatments with different solvents. Finally, the purification and isolation steps are difficult to perform on an industrial scale because of the absolute necessity of purifying the product by column chromatography.

Further, US Patent No. 5912351 describes an alternate process for the preparation of lercanidipine hydrochloride. It involves reaction of 1, 4-dihydro-2, 6-dimethyl-5- methoxycarbonyl-4- (3-nitrophenyl) pyridine-3-carboxylic acid with thionyl chloride in dichloromethane and dimethylformamide at a temperature between -4° and +1⁰ C and subsequent esterification of the obtained acid chloride with 2, N-dimethyl-N- (3, 3 diphenylpropyl)-l-arnino-2-propyl alcohol at a temperature between -10° and O⁰C.

However, the disadvantage of the said process is the use of thionyl chloride as a reactant, which is difficult to handle on an industrial scale because of evolution of sulphur dioxide and hydrochloric gas from the reaction. Moreover it also requires special grade of equipment such as glass-lined reactor etc.

Thus, there is a demand for a simpler, cost-effective, industrially viable process for synthesizing Lercanidipine with higher yields, while reducing number of process steps and avoiding use of harmful reagents, solvents and laborious separation methods such as column chromatography.

The Applicant has found simpler and cost-effective process for synthesizing Lercanidipine, avoiding use of hazardous materials, which is industrially viable and gives better yields.

Further WO/03/014084 discloses novel crystalline form I & II of Lercanidipine Hydrochloride and mixtures of Form I & II having predetermined and reproducible content of Form I & II & optionally other forms of Lercanidipine Hydrochloride such as amorphous. EP 1600441 discloses crystalline form I of Lercanidipine Hydrochloride and a mixture of form I with amorphous and optionally form II. However, these prior art don't describe pure amorphous form (anhydrous or hemihydrate) of Lercanidipine Hydrochloride and its preparation.

Further, WO2006089787A1 discloses process for the preparation of pure amorphous lercanidipine hydrochloride from crystalline lercanidipine hydrochloride.

Thus, the present invention provides obvious benefits with respect to removing both the technical problems associated with prior art as well being simpler and economical, while at the same time achieving high purity and yield of the product with convenience to operate on a commercial scale.

SUMMARY OF THE INVENTION:

The present invention relates to new, improved and industrially viable process for the preparation of Lercanidipine hydrochloride using novel intermediate of amino phenyl derivatives of formula (III) with 1,4-dihydropyridine acid derivative.

( III )

Wherein R is X OrOSO₂R

X = Cl, F, Br or I ; R = alkyl (C₁ to C 4) , phenyl, or 4-methyl phenyl.

OBJECTS OF THE INVENTION

The object of the present invention is to provide a new and improved process for synthesis of Lercanidipine hydrochloride. The second object of the instant invention is to provide a simpler and cost-effective process for synthesis of Lercanidipine hydrochloride.

Another object of the present invention is to provide an industrially viable process for synthesis of Lercanidipine hydrochloride.

Still another object of the present invention is to provide an improved process for synthesis of Lercanidipine hydrochloride, which gives better yield.

Yet another object of the present invention is to provide novel polymorphic forms of Lercanidipine hydrochloride and process for the preparation thereof.

Yet another object of the present invention is to provide novel process for amorphous form of Lercanidipine hydrochloride.

In one general embodiment, the present invention provides a process for the preparation of lercanidipine hydrochloride of formula (I) as described herein below:

Which comprises the steps of:

1) Halogenation of 2,N-Dimethyl-N-(3,3-diphenyl propyl)- l-amino-2- propanol (II)

( M ) in an suitable solvent optionally in presence of a base to obtain derivatives of 2,N- Dimethyl-N-(3,3-diphenyl propyl)-! -amino (III)

2) Reacting 2,6-dimethyl-5-methoxy carbonyl-4-(3-nitrophenyl)-l,4- dihydropyridine-3-carboxylic acid of formula (IV)

in a protic or aprotic solvent with formula III in presence of base; and

3) Isolating resultant lercanidipine or its Pharmaceutically acceptable salts

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:

Fig. 1: This figure indicates X-ray diffraction pattern of amorphous Form Tl of Lercanidipine hydrochloride obtained according to the present invention.

Fig. 2: This figure indicates Infrared Spectrum of amorphous Form Tl Lercanidipine hydrochloride obtained according to the present invention.

Fig. 3: This figure indicates Differential Scaning Calorimetry of amorphous Form Tl Lercanidipine hydrochloride obtained according to the present invention. DETAILED DESCRIPTION:

According to one general aspect of the present invention, there is provided a new, improved and industrially viable process for the preparation of Lercanidipine Hydrochloride, using novel intermediate of amino phenyl compounds of formula III with 1,4-dihydropyridine acid derivative of formula (IV).

According to one aspect of the present invention, there is provided an efficient process for the preparation of Lercanidipine, which provides obvious benefits with respect to economics, generation of minimal effluents, lesser number of process steps, less reactor occupancy, higher purity of the product with convenience to operate on a commercial scale.

According to one another aspect of the present invention there is provided a new, improved and industrially viable process for the preparation of Lercanidipine Hydrochloride, using a novel intermediate of 2-halo amino derivative of formula (III) wherein R=X, with or without insitu formation of Sulphonic acid ester of amino alcohol of formula (III).

The present invention provides an improved process for preparing Lercanidipine Hydrochloride (I) as discussed herein: -

The process of the invention is illustrated by the following reaction scheme.

Reaction-(A)

The 2,N-Dimethyl-N-(3,3-diphenyl propyl)- l-amino-2-propanol Formula ( II ) is prepared according to a procedure known in the prior art (US 4705797)

Reaction-(A)

Reaction-(B)

A process comprising the halogenation of compound of Formula (II) to obtain compound of formula (IIIB), characterized in that:

(a) Reacting 2,N-Dimethyl-N-(3,3-diphenyl propyl)- l-amino-2-propanol Formula ( II ) with Alkyl or aryl or substituted aryl sulphonyl halide in presence of base in suitable solvent or mixture thereof to obtained, compound of formula ( IIIB) via insitu formation of Sulphonic acid ester of N-Dimethyl-N- (3,3-diphenyl propyl)-l- amino-2-propanol compound (IIIA), Wherein R' = alkyl (C_1-4), phenyl, p-tolyl and X = Cl, Br, F, or I or.

( HIB )

Reaction B -(a) (a') Reacting 2,N-Dimethyl-N-(3,3-diphenyl propyl)-l-amino-2-propanol Formula ( II ) with Halogenating agent in suitable solvent or mixture thereof to obtained, of N- Dimethyl-N- (3,3-diphenyl propyl)- l-amino-2-halide compound (IHB) Wherein X = Cl, Br, F, or I. In a preferred embodiment X = chloride, R" = thionyl chloride, Phosphorous oxychloride, Oxaloylchloride, phosphorous trichloride or phosphorous pentachloride.

Reaction B -(a¹)

Reaction-(C): Reacting 2,6-dimethyl-5-methoxy carbonyl-4- (3-nitrophenyl)-l,4- dihydropyridine-3-carboxylic acid of formula (IV)

( I ) Reaction - (C) with halide compound of N-Dimethyl-N-(3,3-diphenyl propyl)- 1 -amino compound ( IIIB ) in presence of base in protic or aprotic solvent mixtures thereof to obtained compound ( I ) optionally purifying the product in alcohol alone or followed by the treatment of the isolated product/residue in a solvent such as ester containing anhydrous Hydrochloric acid.

Reaction B-(a) can be carried out using by methane sulphonyl halide, p-toluene sulphonyl chloride, or benzene sulphonyl chloride using base selected from the group comprising of organic base, inorganic bases. Examples of organic and inorganic bases are triethylamine, pyridine, sodium hydroxide and potassium hydroxide, sodium carbonates, and the like, at temperature ranging from about -15°C. to 60°C, preferably between -5°C. to 25⁰C, more preferably between 5°C. to 2O⁰C, optionally in an inert gas atmosphere. The duration of the esterification reaction may be from 15 minutes to 5 hours depending on reagents used and measuring end point of reaction by analytical method such as TLC, HPLC and the like.

Reaction B-(a') can be carried out by using thionyl chloride, Phosphorous oxichloride, oxalylchloride, phosphorous trichloride or phosphorous pentachloride at temperature ranging from about 15⁰C. to 60°C, preferably between 2O⁰C. to 45°C, more preferably between 25⁰C. to 40°C, optionally in an inert gas atmosphere. The duration of the reaction may be from 15 minutes to 5 hours.

Surprisingly inventor have found that use of methane sulphonyl chloride generates mesylate ester insitu as described herein, but ultimately leads to formation of chloro derivative (Formula HI(B)) instead of mesyl ester of formula III (A) as described herein. The structure elucidation of isolated chloro derivative is supported by the analytical techniques.

Reaction (C) as per the present invention can be carried out using in general by reacting compound (IIIB) with 2,6-dimethyl-5-methoxy carbonyl-4-(3-nitrophenyl)- l,4-dihydropyridine-3-carboxylic acid of formula (IV) using base selected from the group comprising of organic base, inorganic bases. Examples of organic and inorganic bases are triethylamine, pyridine, sodium hydroxide and potassium hydroxide, sodium carbonates, and the like, preferably potassium hydroxide, in a solvent to obtained compound (I) at temperature ranging from about -15⁰C to 90°C, preferably ranging from O⁰C. to 40⁰C, more preferably ranging from 25°C to 30⁰C optionally in an inert gas atmosphere. The duration of the condensation reaction may be from 15 minutes to 5 hours depending on reagents used and measuring end point of reaction by analytical method such as TLC, HPLC and the like.

The suitable solvent used in Reaction B is selected from the group comprising of ethers, esters, aromatic hydrocarbon, chlorinated or non-chlorinated Aprotic solvents or mixtures thereof. The ethers that can be used as solvent are selected from the group comprising of diethyl ether, tetrahydrofuran, petroleum ether (60-80⁰C.) or mixtures thereof. The esters that can be used as solvent are selected from the group comprising of methyl acetate, ethyl acetate, n-butyl acetate, n-propyl acetate or mixtures thereof. The aromatic hydrocarbons that can be used as solvent are selected from the group comprising of benzene, toluene, xylene or mixtures thereof. Chlorinated aprotic solvents that can be used as solvent are selected from the group comprising of Chloroform, chlorobenzene, Dichloromethane, Dichloroethane, 1,1,1-trichloroethane, or any mixture thereof. Non-chlorinated aprotic polar solvent that can be used as solvent are selected from the group comprising of dimethylformatnide, dimethylsulphoxide and dimethyl acetamide or any mixture thereof.

In a preferred embodiment, the solvent used in Reaction B is dichloromethane.

The solvent used in C can be selected from the group comprising of protic or aprotic solvents or mixtures thereof. Protic solvents that can be used as solvent are selected from the group comprising of ethanol, methanol, isopropyl alcohol, and tertbutanol or any mixture thereof. Aprotic solvents that can be used as solvent are selected from the group comprising of chloroform, tetrahydrofuran, and dioxane, dimethylformamide.

In a preferred embodiment, the solvent used in Reaction C is isopropyl alcohol.

In an alternative embodiment, the present invention provides a process for preparing the Lercanidipine Hydrochloride (I) as discussed herein: -

The process of the invention is illustrated by the following reaction scheme.

Reaction-(A)

The 2,N-Dimethyl-N-(3,3-diphenyl propyl)- l-amino-2-propanol Formula( II ) is prepared according to a procedure known in the prior art (US 4705797)

Reaction - (A) Reaction-(B')

Reacting 2,N-Dimethyl-N-(3,3-diphenyl propyl)- l-amino-2-propanol Formula ( II )

( I ) Reaction -(B) with halogenating agent in suitable solvent and then reacting insitu the halogenated compound so obtained with 2,6-dimethyl-5-methoxy carbonyl-4- (3-nitrophenyl)- l,4-dihydropyridine-3-carboxylic acid of formula (IV) without isolation of formula IH(B) to obtained compound (I), optionally purifying the product in alcohol alone or followed by the treatment of the isolated product/residue in a solvent such as ester containing anhydrous Hydrochloric acid. .

In Reaction (B') halogenation can be carried out by using methane sulphonyl chloride, thionyl chloride, Phosphorous oxichloride, oxalylchloride, phosphorous trichloride or phosphorous pentachloride at temperature ranging from about 15°C. to 60°C preferably between 20°C. to 45⁰C, more preferably between 25°C. to 40⁰C, optionally in an inert gas atmosphere. The duration of the reaction may be from 15 minutes to 5 hours. hi a preferred embodiment, reactant used is methane sulphonyl chloride or Thionyl chloride. In a more preferred embodiment, reactant used is methane sulphonyl chloride.

The solvent used in reaction B' is selected from the group comprising of ethers, esters, aromatic hydrocarbon, chlorinated or non-chlorinated aprotic solvents or mixtures thereof. The ethers that can be used as solvent are selected from the group comprising of diethyl ether, tetrahydrofuran, petroleum ether (60-80°C.) or mixtures thereof. The esters that can be used as solvent are selected from the group comprising of methyl acetate, ethyl acetate, n-butyl acetate, n-propyl acetate or mixtures thereof. The aromatic hydrocarbons that can be used as solvent are selected from the group comprising of benzene, toluene, xylene or mixtures thereof. Chlorinated aprotic solvents that can be used as solvent are selected from the group comprising of chloroform, chlorobenzene, dichloromethane, dichloroethane, 1,1,1-trichloroethane, or any mixture thereof. Non-chlorinated aprotic polar solvent that can be used as solvent are selected from the group comprising of dimethylformamide, dimethylsulphoxide and dimethyl acetamide or any mixture thereof.

In a preferred embodiment, the solvent used in Reaction ( B') is dichloromethane. When compound (I) is optionally purified in alcohol followed by treatment in ester in presence of anhydrous hydrochloric acid then the content of hydrochloric acid in ester may vary from about 0.01% w/w to about 0.5%. In a preferred embodiment it may vary from 0.05 to 0.3%. hi a more preferred embodiment it may vary from 0.05% to 0.25%.

In yet another aspect of the present invention there is provided a novel polymorphic form Tl of Lercanidipine hydrochloride e.g. amorphous form.

Due to differing solubility profiles of polymorphs, the identification of pharmaceutical polymorphs is essential for preparing pharmaceutical dosage forms with predictable solubility profiles. Polymorphic forms can be distinguished from each other by various analytical techniques, for example, by x-ray diffraction and infrared spectroscopic techniques.

Among the known polymorph of Lercanidipine Hydrochloride the solubility and thereby its bioavailability is very less. Hence, in an another embodiment of the invention there is provided new amorphous form Tl of Lercanidipine hydrochloride and process of preparation thereof.

In another aspect, the present invention provides a method for preparing amorphous Lercanidipine hydrochloride comprising the steps of: (1) dissolving Lercanidipine hydrochloride in an organic solvent to prepare a solution and optionally distilled out the organic solvent (2) forming precipitates by adding an organic solvent selected from the group consisting of cyclohexane, cyclopentane, n-hexane, and ether; and (3) Isolating amorphous Lercanidipine hydrochloride

The organic solvent of step-1 is used to dissolve Lercanidipine hydrochloride. The suitable solvent used for dissolving Lercanidipine hydrochloride are chlorohydrocarbon such as methylene chloride; alcohol such as methanol, ethanol, isopropyl alcohol and t-butyl alcohol; or a mixture of organic solvent may be used.

In step (2) of the present invention, the addition of another organic solvent may be carried out at 10°C-30°C.

Isolating lercanidipine hydrochloride includes filteration, washing and drying of the isolated product at appropriate condition wherein filtration should preferably be carried out after the formation of precipitates in step (2), more preferably be carried out within about 1-3 hours. Further, drying of the isolated product can be preferably carried out under vacuum at 20 ~ 80°C, preferably at 30 ~ 32°C, for 6 - 12 hours.

Alternative method for preparing amorphous Lercanidipine hydrochloride comprising the steps of: (1) dissolving Lercanidipine hydrochloride in alcohol such as methanol, ethanol, isopropyl alcohol and t-butyl alcohol or MDC or in a mixed organic solvent of methylene chloride and alcohol to form a solution (2) forming precipitates by adding water or by adding solution of step (1) into the water and (3) Isolating amorphous Lercanidipine hydrochloride.

In step (2) of the alternative method, the addition of water may be carried out at 10°C-30°C.

In step (2) of the alternative method, when solution is added into the water, it may optionally contain NaCl or KCl. Addition time may vary from 1 to 3 hour at 0 ~ 5 ⁰C. The present invention provides still another method for preparing amorphous Lercanidipine hydrochloride comprising the steps of: (1) dissolving Lercanidipine hydrochloride in alcohol such as methanol, ethanol, isopropyl alcohol and t-butyl alcohol or MDC or in a mixed organic solvent of methylene chloride and alcohol to form a solution; (2) the solvent removed from the solution by concentrating the solution under reduced pressure or spray drying to obtain amorphous Lercanidipine hydrochloride.

Method and condition of the measurement of X-ray diffraction patterns.

(1) Method of the measurement

X-ray diffraction patterns were measured on each 400 mg of the sample of Lercanidipine hydrochloride by the following condition.

(2) Condition of measurement

While the present invention has been described in term of its specific embodiments, certain modifications & equivalents will be apparent to scope of the instant invention.

In the following section, embodiments are described by way of examples to illustrate the process of invention; however this does not limit the scope of the present invention. Several variants of these examples would be evident to person's skill in the art. PREPARATORY EXAMPLES:

Example -1

Preparation of N-(2-chloro-2-methyIpropyI)-N-(3,3-diphenylpropyl)-N- methylamine.

To a solution of lOOgms of 2,N -Dimethyl-N-(3,3-diphenyl propyl)- l-amino-2- propanol(II), 1.3L of dichloromethane, 44gms of triethyl amine, add solution of Methane sulphonyl chloride in dichloromethane (42.4gm. in 0.2L) at 20°-25°C. in 2- 2.5hrs. .Stir the reaction mass at 20°- 25°C for 4 hours. Check the content of 2,N- Dimethyl-N-(3,3-Diphenylpropyl)-l-Amino-2-Propanol by HPLC. Charge water at 20°-25°C and stir for 20 minutes and separate layers. Wash the Dichloromethane layer with 5 % aq. sodium bicarbonate solution (1.0 L) , water (l.OL) at 25-30°C respectively. Take Dichloromethane layer and charge Na2SO4(10gm) at 25-30°C. Filter the solution through cotton cloth and wash the bed with Dichloromethane. Remove the excess solvent (Dichloromethane) under vacuum below 30°C to give a heavy oil of N-(2-chloro-2-methylpropyl)-N-(3,3-diphenylpropyl)-N-methylamine (Yield: lOOgms; 94%)

IH NMR: 7.330-7.397(8H, m); 7.225-7.284(2H, m); 4.054(1H, t); 2.647(2H, s); 2.548(2H, t); 2.293-2.350(2H, q); 2.462(3H, s); 1.577(6H, s) IR: 1492.8, 1451.3 (Ar.C=C), 1107.1 (C-N stretching), 700.1 (C-Cl stretching) Elemental analysis: Carbon - 75.02%, Nitrogen - 4.07%, Hydrogen - 8.39%

Example - 2

Preparation of 3,5-Pyridinedicarboxylic acid, l,4-dihydro-2,6-dimethyI-4-(3~ nitrophenyl)-,2-[(3,3-diphenylpropyI)methylamino]-l,l-dimethyl ester, hydrochloride [ Lercanidipine hydrochloride) ] (I)

To a stirred solution of 80 gm of 2,6-Dimethyl-5-methoxy carbonyl-4-(3- Nitrophenyl)-l,4-dihydropyridine-3-carboxylicacid, Isopropyl alcohol (0.8L), 20gm of powdered potassium hydroxide, charge solution of N-(2-chloro-2-methylpropyl)- N-(3,3-diphenylpropyl)-N-methylamine in Isopropyl alcohol (lOOgms in 0.2L IPA) under stirring. Stir the reaction mass at 25°-30°C. for 3 hrs. Check the absence of N- (2-Chloro-2-methylpropyl)-N-(3,3-diphenylpropyl)-N-methylamine by TLC. Distill out Isopropyl alcohol completely under vacuum below 50°C. Charge ethyl acetate (2.0L) & Water (1.0L). Stir for 30 min. & separate the layers. Wash the ethyl acetate layer with 1.5 L of 10% Na2CO3 solution in three parts at 25°-30°C followed by washing of organic layer charge with brine solution(0.5L) and 1.5 L of 10% HCL in three separate parts followed by brine solution (0.5L) and finally treatment of NaSO4(20gm) to an organic layer. Filter the solution over cotton cloth and wash the bed with ethylacetate( 0.05 L). Charge 0.01 kg of activated charcoal at 25-30°C. Stir at 25-30°C for 30.0 min. Filter the solution over hyflow bed (0.020 kg of hyflow slurry in 0.150 L of ethylacetate) Distill out ethyl acetate under vacuum below 50⁰C. Charge ethylacetate (l.OL) to the reaction mass at 5O-55°C and stir at 50-55°C for 30 mins. Cool to 25°-30°C and seed the reaction mass with Lercanidipine Hydrochloride crystals. Stir for 16hrs. at 25°-30°C. Filter the reaction mass and wash the cake with Ethylacetate(0.02L). Suck dried and stir the wet material in ethylacetate (0.8L) for 30.0 min. and filter the material. Wash the bed with Ethylacetate (0.02L). Suck dried for 1 hr and dry the material under vaccum at 30-35°C for 8 hrs till constant weight is attained. (Yield: 95 gm; 47%)

Example - 3

Preparation of 3,5-Pyridinedicarboxylic acid, l,4-dihydro-2,6-dimethyl-4-(3- nitrophenyl)-,2-[(3,3-diphenylpropyl)methylamino]-l,l-dimethyl ester, hydrochloride [ Lercanidipine hydrochloride) ] (I)

To a stirred solution of 80 gm of 2,6-Dimethyl-5-methoxy carbonyl-4-(3- Nitrophenyl)-l,4-dihydropyridine-3-carboxylicacid, Isopropyl alcohol (0.8L), 20gm of powdered potassium hydroxide, charge solution of N-(2-chloro-2-methylpropyl)- N-(3,3-diphenylpropyl)-N-methylamine in Isopropyl alcohol (lOOgms in 0.2L IPA) under stirring. Stir the reaction mass at 25°-30°C. for 3 hrs. Check the absence of N- (2-Chloro-2-methylpropyl)-N-(3,3-diphenylpropyl)-N-methylamine by TLC. Distill out Isopropyl alcohol completely under vacuum below 50°C. Charge ethyl acetate (2.0L) & Water (LOL). Stir for 30 min. & separate the layers. Wash the ethyl acetate layer with 1.5 L of 10% Na2CO3 solution followed by washing of organic layer with brine solution(0.5L) and finally treatment of NaSO4(20gm) to an organic layer. Decant the ethylacetate layer and cool the mass to 20°-25°C. Add anhydrous hydrochloric acid in ethyl acetate to adjust the pH of the mass below 2.0 and seed the reaction mass with Lercanidipine Hydrochloride. Stir the reaction mass for 16hrs. at 20°-25°C. Filter the reaction mass and wash the cake with Ethylacetate(0.02L). Suck dried and stir the wet material in ethylacetate (0.8L) for 30.0 min. and filter the material. Wash the bed with Ethylacetate (0.02L). Suck dried for 1 hr and dry the material under vaccum at 30-35⁰C for 8 hrs till constant weight is attained. (Yield: 96 gm; 47%)

Example -4

Purification of crude lercanidipine hydrochloride

Charge Crude Lercanidipine hydrochloride (0.1 Kg) and Absolute Ethanol (0.3L) at 25-30°C. Heat to 75-80 ° C in 20.0 min. and Stir at 75-80 ° C for 5.0 min to get clear solution. Filter the solution over hyflow bed (0.01 Kg hyflow slurry prepared in 0.02 It of absolute Ethanol) and Wash with absolute Ethanol (0.025 L). Cool to 25- 3O⁰C and seed with Lercanidipine hydrochloride (0.0002 Kg) obtained in example 2 above and stir at 25-30⁰C for 16 hrs. Filter the material and wash the bed with Chilled absolute Ethanol (0.025 L, 0-5⁰C) and Suck dry the material for 1 hr. Take the wet material and charge absolute Ethanol (0.3 L) at 25-3O⁰C and Heat up to 75-80° C in 20.0 min. Stir at 75-80° C for 5.0 min to get clear solution. Filter the solution over hyflow bed (0.01 Kg hyflow slurry prepared in 0.02 It of absolute Ethanol). Wash the bed with absolute Ethanol (0.025 L) and Cool to 25-30⁰C and seed with Lercanidipine hydrochloride (0.0002 Kg). Stir at 25-30⁰C for 16 hrs. and Filter the material and wash the bed with Chilled absolute Ethanol ( 0.025 L, 0-5⁰C). Suck dry the material for 1 hr and dry the material in vacuum oven under vacuum at 30- 35⁰C for 8 hrs to get Ethanol below 3000 ppm by residual solvent test. HPLC Purity: ~ 99.9 % Yield: 75 gm (75%)

Example -5

Purification of crude lercanidipine hydrochloride

Charge Crude Lercanidipine hydrochloride (17g) obtained from example 2 in methanol(0.05L) at 25-30⁰C. Heat to 35-40 ° C to get clear solution. Filter the solution over hyflow bed . Distill out the methanol filterate under vacuum. Charge ethyl acetate (0.170L) and anhydrous hydrochloric acid (0.005L; 9.5%w/w in ethylacetate).Stir at 25-30 ° C for five hours. Filter the reaction mass and wash the solid with ethylacetate. HPLC Purity: ~ 99.9 % Yield: 14 gm (-82.4%)

Example -6

Preparation of N-(2-chIoro-2-methylpropyl)-N-(3,3-diphenylpropyl)-N- methylamine (HIB)

To a solution of 3.5gm of 2,N -Dimethyl-N-(3,3-diphenyl propyl)- l-amino-2- propanol(H), prepared as described in US Patent 4705797, is reacted with thionyl chloride in presence of methylenechloride for 5 hrs. at reflux tempearature to get N- (2-chloro-2-methylpropyl)-N-(3,3-diphenylpropyl)-N-methylamine (8.5 gm) (Yield: Example - 7

Preparation of 3,5-PyridinedicarboxyIic acid, l,4-dihydro-2,6-dimethyI-4-(3- nitrophenyl)-,2-[(3,3-diphenylpropyI)methylamino]-l,l-dimethyI ester, hydrochloride [ Lercanidipine hydrochloride) ] (I)

N-(2-chloro-2-methylpropyl)-N-(3,3-diphenylpropyl)-N-methylamine (IIIB)(8.5gm) is reacted with 2,6-Dimethyl-5-methoxy carbonyl-4-(3-Nitrophenyl)-l,4- dihydropyridine-3-carboxylicacid in presence of triethylamine and isopropyl alcohol at 30° to 35° for 2 hr to get Lercanidipine Hydrochloride (8.0gm). (Yield: 47.3%)

Example — 8

Preparation of Amorphous Form of Lercanidipine Hydrochloride

Charge Lercanidipine hydrochloride (10.0 g) in Methanol (30.0 ml) at 25-30°C. and stir for 15.0 min to get clear solution. Filter the solution over hyflow bed(5.0 g of Hyflow is prepared in 30.0 ml of Methanol). Distill out Methanol completely under vacuum at 40-45°C and keep the mass under vacuum at 40-45⁰C for 30.0 min. Charge n-Hexane (50.0 ml) at 25-30°C. and stir for 30.0 min. Filter the solution and wash the bed with 20.0 ml of n-Hexane and finally dry the material under vacuum below 35°C for 8 hrs . (Dry Wt. 9.5 gm; Yield: 95%)

Example -9

Preparation of N-(2-chloro-2-methylpropyl)-N-(3,3-diphenylpropyl)-N- methylamine.

To a solution of lOOgms of 2,N -Dimethyl-N-(3,3-diphenyl propyl)- l-amino-2- propanol(II), 1.3L of dichloromethane, 44.2gms of triethyl amine and cool it to 20-25 °C, add solution of Methane sulphonyl chloride in dichloromethane (46.2gm. in 0.2L) at 20°-25°C in 3-3.5 hrs. .Stir the reaction mass at 20°- 25°C for 4 hours. Check the content of 2,N-Dimethyl-N-(3,3-Diphenylpropyl)-l-Amino-2-Propanol by HPLC. Charge 1.0L water at 20°-25°C and stir for 20 minutes and separate layers. Wash the Dichloromethane layer with 5 % aq. sodium bicarbonate solution (1.0 L) , water (LOL) at 25-3O⁰C respectively. Take Dichloromethane layer and charge Na2SO4 (10gm) at 25-3O⁰C. Filter the solution through cotton cloth and wash the bed with Dichloromethane. Remove the excess solvent (Dichloromethane) under vacuum below 3O⁰C to obtain a heavy oil of N-(2-chloro-2-methylpropyl)-N-(3,3- diphenylpropyl)-N-methylamine (Yield: 102gms; 95.8%).

Example - 10

To a stirred solution of 80 gm of 2,6-Dimethyl-5-methoxy carbonyl-4-(3- Nitrophenyl)-l,4-dihydropyridine-3-carboxylicacid, Isopropyl alcohol (0.4L), 20gm of powdered potassium hydroxide, charge solution of N-(2-chloro-2-methylpropyl)- N-(3,3-diphenylpropyl)-N-methylamine in Isopropyl alcohol (lOOgms in 0.2L IPA) under stirring. Stir the reaction mass at 25°-30°C for 5 hrs. Check TLC for the absence of N-(2-Chloro-2-methylpropyl)-N-(3,3-diphenylpropyl)-N-methylamine. Distill out Isopropyl alcohol completely under vacuum below 55°C. Charge ethyl acetate (2.0L) at 45-55 °C and stir for 15 min at 45-55 ⁰C to get clear solution and cool it to 25-30 °C. Then add water (1.0 L) at 25-30 °C & separate the layers. Wash the ethyl acetate layer with 1.0 L of 5.0% Na2CO3 solution and stir at 25°-30°C for 30 min. and separate the layers. Take the ethyl acetate layer & add water (1.0 L) and stir at 25°-30°C for 30 min. and separate the layers. Followed by washing of organic layer with 0.5 L of 10% HCL and stir at 25°-30°C for 30 min and separate the layers. Take the ethyl acetate layer & add 0.5 L of 10% HCL and stir at 25°-30°C for 30 min. and separate the layers. Followed by treatment with brine solution (0.5L, 25%) and finally treatment of NaSO4 (lOOgm) to an organic layer. Filter the solution over cotton cloth and wash the bed with ethylacetate( 0.2 L). Take ethyl acetate layer and charge 0.01 kg of activated charcoal at 25-3O⁰C & stir at 25-30°C for 30.0 min. Filter the solution over hyflow bed and wash the bed with ethyl acetate (0.05 L). Distill out ethyl acetate under vacuum below 55 °C & again charge 200 ml ethyl acetate and distill out ethyl acetate completely under vacuum below 55 ⁰C. Charge ethyl acetate (1.0L) to the reaction mass at 50-55°C and stir at 50-55⁰C for 30 mins. Cool it to 25°- 30⁰C and seed the reaction mass with Lercanidipine Hydrochloride crystals. Stir for 24 hrs. at 25°-30°C. Filter the reaction mass and wash the cake with Ethyl acetate (0.1 L) and dry the material under vacuum at 40-45⁰C for 8 hrs. (Yield: 105 gm; 51.94%)

Example - 11

Preparation of Amorphous Form of Lercanidipine Hydrochloride

Lercanidipine hydrochloride (10.0 g) is dissolved in methanol (30.0 ml) with stirring for 20 minutes at 25-30⁰C. Filter the solution over hyflow bed and washed hyflow bed with methanol (20.0 ml). Distilled out methanol completely under vacuum below 40-45⁰C and kept the mass with stirring under vacuum at 40-45⁰C for 2 hours. Charge water (100.0 ml) at 25-30⁰C and stirred for 1 hour. Filtered the solution and wash the bed with 30.0 ml of water and finally dried the material under vacuum at 30-32⁰C for 12 hrs. (Dry Wt. 9.5 gm; Yield: 95%).

Example - 12

Preparation of Amorphous Form of Lercanidipine Hydrochloride

Lercanidipine hydrochloride (10.0 g) is dissolved in methanol (50.0 ml) with stirring for 20 minutes at RT. Filter the solution over hyflow bed and washed hyflow bed with methanol (20.0 ml). Distilled out methanol completely under vacuum below 40- 45°C and kept the mass with stirring under vacuum at 40-45°C for 2 hours. Charge diisopropyl ether (100.0 ml) at 25-3O⁰C and stirred for 1 hour. Filtered the solution and wash the bed with 20.0 ml of diisopropyl ether and finally dried the material under vacuum at 30-32°C for 6 hrs. (Dry Wt. 9.4 gm; Yield: 95%).

Example - 13

Preparation of Amorphous Form of Lercanidipine Hydrochloride

NaCl (2.5 g) is dissolved in water (500 ml) at 25-30 °C and cooled the solution at 0-5 °C. Lercanidipine hydrochloride (20.0 g) is dissolved in methanol (35.0 ml) with stirring at 40-45 ⁰C. Filter the solution over hyflow bed and washed hyflow bed with methanol (5.0 ml) and add this filtrate to the NaCl solution at 0-5 °C within 1 hour. Stir the solution at 0-5 ⁰C for 1 hour and filter the solution over hyflow bed and washed hyflow bed with water (50.0 ml). Charge 200 ml water to the wet-cake and keep it under stirring for 30 min. at 25-30 °C and filter the solution over hyflow bed and washed hyflow bed with water (50.0 ml). Finally dried the material under vacuum at 30-32°C for 12 hrs. (Dry Wt. 19 gm; Yield: 95%).

Example — 14

Preparation of Amorphous Form of Lercanidipine Hydrochloride

Lercanidipine hydrochloride (10.0 g) is dissolved in methanol (50.0 ml) with stirring for 20 minutes at RT. Filter the solution over hyflow bed and washed hyflow bed with methanol (20.0 ml). Distilled out methanol completely under vacuum below 40- 45°C and kept the mass with stirring under vacuum at 40-45⁰C for 8 hours. Dried material is taken out from the flask and finally dried the material under vacuum at 30- 32°C for 6 hrs. Example - 15

Preparation of Amorphous Form of Lercanidipine Hydrochloride

Lercanidipine hydrochloride (30.0 g) is dissolved in methanol (450.0 ml) with stirring for 15 minutes at 30-35 °C. Filter the solution over hyflow bed and washed hyflow bed with methanol (50.0 ml). Spray dried the material on spray drier (Input temp: 90 ⁰C, exhaust temp: 67 ⁰C, blanket nitrogen pressure: 1 kg/cm², blanket nitrogen pressure: 1 kg/cm²). Unload the material under nitrogen atmosphere and finally dried the material under vacuum at 30-32°C for 24 hrs. (Dry Wt. 15 gm; Yield: 50%).

Claims

We Claim:

1. A process for the preparation of Lercanidipine of formula (I) or a pharmaceutically acceptable salt thereof,

comprising: a) Halogenating 2,N-Dimethyl-N-(3,3-diphenyl propyl)- l-amino-2-propanol (II)

in a suitable solvent or mixture thereof, optionally in the presence of base to obtain derivatives of 2,N-Dimethyl-N-(3,3-diphenyl propyl)- 1 -amino (UIB)

Wherein X= Cl, F, Br or I b) Reacting 2,6-dimethyl-5 -methoxy carbonyl-4-(3 -nitrophenyl)- 1 ,4- dihydropyridine-3-carboxylic acid of formula (IV)

( IV )

in a protic or aprotic solvent with compound of formula IIIB in presence of base and c) optionally converting into its pharmaceutically acceptable salt.

2. The process according to claim 1, wherein the halogenating agent is methane sulphonyl halide, P-toluene sulphonyl chloride, benzene sulphonyl chloride, thionyl chloride, phosphorous oxychloride, oxalylchloride, phosphorous trichloride or phosphorous pentachloride.

3. The process according to claim 1, wherein suitable solvent used in step a is selected from the group comprising of ethers, ester, aromatic hydrocarbon, chlorinated or nor chlorinated aprotic solvents or mixture thereof.

4. The process according to claim 1, wherein protic or aprotic solvent used in step b is selected from the group comprising of alcohol, chloroform, THF, dioxane and DMF.

5. Amino phenyl derivative of the following formula (III B):

wherein, X = Cl, F, Br or I, or salts thereof.

6. Use of the compound of claim 5 for the manufacture of Lercanidipine or pharmaceutically acceptable salts thereof.

7. Novel amorphous form Tl of Lercanidipine Hydrochloride.

8. The amorphous form according to claim 7, characterized by an X-ray powder diffraction pattern substantially in accordance with Fig-1.

9. A process for the preparation of amorphous Lercanidipine hydrochloride comprising the steps of:

i) dissolving Lercanidipine hydrochloride in an organic solvent selected from alcohol or MDC or in a mixed organic solvent of methylene chloride and alcohol to prepare a solution and optionally distilled out the organic solvent;

ii) a) forming precipitates by adding water or by adding solution of step (i) into the water ; or b) forming precipitate by adding an organic solvent selected from cyclohexane cyclopentane, n-hexane or ether ; or c) the solvent removed from the solution of step (i) by concentrating the solution under reduced pressure or, d) spray drying to obtain a solid substance;

iii) Isolating lercanidipine hydrochloride

10. Process for the preparation of lercanidipine hydrochloride and its amorphous form s herein described, particularly with reference to the foregoing examples.