Indian Patents. 254818:AN IMPROVED PROCESS FOR THE PREPARATION OF MONTELUKAST AND ITS PHARMACEUTICALLY ACCEPTABLE SALTS

Title of Invention	AN IMPROVED PROCESS FOR THE PREPARATION OF MONTELUKAST AND ITS PHARMACEUTICALLY ACCEPTABLE SALTS
Abstract	Title of the invention: An improved process for the preparation of Montelukast and its pharmaceutically acceptable salts Montelukast sodium (Formula-I) illustrated as below

Full Text	An improved process for the preparation of Montelukast and its pharmaceutically acceptable salts Field of the Invention The present invention relates to an improved process for the preparation of [R- Formula (I). Montelukast sodium is a leukotriene antagonist and is useful in the treatment of Asthma and as well as other conditions mediated by leukotrienes, such as inflammation and allergies. Background of the Invention pyran with Methyl l-(acetylthiomethyl) cyclopropane acetate in presence of hydrazine, cesium carbonate in acetonitrile as solvent to get methyl ester of Montelukast in pyran protected form. The protected compound is further reacted with pyridinium p-toluene sulfonate, sodium hydroxide in a mixture of methanol and tetrahydrofuran as a solvent to afford Montelukast sodium of Formula (I). US 5,614,632 discloses the preparation of l-(mercapto methyl) cyclopropane acetic acid, which is a key intermediate for the preparation of Montelukast sodium. The said patent claimed an improved process for the preparation of Montelukast sodium including the process for the preparation of its key intermediates. The process comprises, the generation of dilithium dianion of l-(mercaptomethyl) cyclopropaneacetic acid and then 3-hydroxy propyl) benzoate with methyl magnesium chloride to give diol, which is further converted to mesylated alcohol on reaction with methanol sulfonyl chloride. The process for the preparation of above described benzoate is disclosed in EP 480717 (example 146, step-2), which involves the usage of (-)B-chloro diisopinocamphenylborane as achiral reducing agent. The said patent also claims the process for the preparation of crystalline Montelukast sodium salt. Many other related patents discloses the process for the preparation of Montelukast and its intermediates but none of those patents are related to the process of the present invention. The prior art procedures involves more number of steps which includes the protection and further deprotection of diol intermediate, the usage of hazardous and costly raw materials such as n-butyl lithium in typical rections i.e., at very low temperatures (-25°C). The processes of the prior art references involve tedious workup to isolate the required product and thus results in excess time cycle, which in turn rendering the process more costly and less eco friendly thus the process is not recommendable for commercial scale up. As the Montelukast sodium of Formula (I), which is useful in the treatment of Asthma, hence, it is important to have a cost effective and commercially viable process for preparing the compound of Formula (I). Therefore, the main objective of the present invention is to prepare Montelukast sodium in an improved method, which is cost-effective, commercially viable and non-hazardous. The Montelukast sodium is prepared in the present invention; in an improved process that is cost effective and the Montelukast sodium obtained in this process is suitable for pharmaceutical formulations. Disadvantages of the prior art processes • Usage of n-Butyl lithium is leading to increase the cost of the product and which is highly flammable and dangerous, it needs special equipment to handle the reagent, needs personal attention throughout the process. • Usage of sodium hydroxide for the preparation of Montelukast sodium (formula-I) from Montelukast produces water as by product it leads to formation of gummy material so removal of water is essential this leads to prolonged process. • Prior art processes teaches conversion of Montelukast amine salt to Montelukast free acid then converting to its sodium salt needs more time. Summary of the Invention The present invention provides an improved process for the preparation of Montelukast and its pharmaceutically acceptable salts, preferably sodium salt. The improved process of the present invention comprises; Reacting (S) Benzenepropanol α-[3-[2-(7-chloro-2-quinolinyl) ethenyl]phenyl]-2-(l-hydroxy-1-methyl ethyl)-α-methane sulfonate compound of formula (II) with 1-(mercapto methyl) cyclo propane acetic acid compound of formula (III) in presence of alkali or alkaline carbonates like cesium carbonate or strong base like alkali or alkaline earth metal alkoxide i.e,. potassium tertiary butoxide, sodium methoxide, sodium ethoxide, in a suitable polar aprotic solvent with or without combination of C1-C4 alcoholic solvents like methanol, ethnaol, preferably methanol and then treating with an organic amine of general formula R-NH2 in a suitable solvent selected from keto solvents like acetone, butanone or ester solvents like ethyl acetate, propyl acetate, preferably acetone and ethylacetate gives corresponding amine salt of Montelukast compound of formula (IV) and then converting compound of corresponding amine salt of Montelukast into its sodium salt of Formula (I) (Montelukast sodium) using sodium source in methanol. Advantages over prior art processes • The object of the present invention is to provide an improved process for the preparation of Montelukast sodium using a simple base like sodium methoxide or potassium tertiary butoxide in place of n-butyl lithium which is easy to handle it does not need any special equipment. • Usage of sodium methoxide for the preparation of Montelukast sodium (formula-I) from Montelukast produces methanol as by product and removal of methanol is very easy and it gives the free flow powder. • Present invention provides process for the preparation of Montelukast sodium without conversion of Montelukast amine salt to Montelukast free acid, it leads to reduction of cycle time. • Highest yield obtained while using cesium carbonate. • Introducing the toluene/hexanes washings after completion of the condensation reaction to remove impurities, which avoids purification at organic amine salt stage. • Cost effective process, and reduction of cycle time. • Environment friendly and easy scalable process. Brief description of the Invention The present invention provides an improved process for the preparation of Montelukast and its pharmaceutically acceptable salts, preferably sodium salt. The improved process of the present invention comprises the following steps; 1. 2. Quenching the reaction mixture with water and adding sodium hydroxide and washing the reaction mixture with water immiscible solvents like hydrocarbon solvents, ester solvents, chloro solvents, preferably hydrocarbon solvents, more preferably toluene. 3. Lowering the pH of the reaction mixture by adding acetic acid to the reaction mixture and extracting the Montelukast with a suitable solvent selected from ester solvents, chloro solvents, preferably ester solvents, more preferably ethylacetate. 4. Treating the product obtained from step 3 with an organic amine compound of general formula R-NH2 (wherein R is dicyclohexyl amine, tertiary butyl amine, isopropyl amine) in a suitable solvent selected from keto solvents like acetone, butanone or ester solvents like ethyl acetate, propyl acetate, preferably acetone and ethylacetate gives corresponding Montelukast amine salt compound of formula (IV). 5. Optionally purifying the corresponding amine salt of Montelukast using hydrocarbon solvents like toluene, hexanes, heptane or keto solvents like acetone or mixture of them. Another aspect of the present invention is to provide an improved process for the preparation of Montelukast sodium compound of formula (I) without converting the organic amine salt of Montelukast compound of formula (IV) to Montelukast free acid. Accordingly the present invention provides an improved process for the preparation of Montelukast sodium compound of formula (I) which comprises of following steps a) Reacting the organic amine salt of Montelukast compound of formula (IV) with a sodium source in methanol. b) Removing the organic amine by extracting the mass with solvents which are immiscible with methanol like hexanes, heptane, and concentrating the methanol. c) Dissolving the product obtained from step b. in toluene and saturating the toluene with heptane to give Montelukast sodium compound of formula (I). Another aspect of the present invention is to provide an improved process for the preparation of Montelukast sodium which comprises of following steps. 1. Reacting (S) Benzenepropanol α-[3-[2-(7-chloro-2-quinolinyl) ethenyl]phenyl]-2-(l-hydroxy-1-methyl ethyl)-α-methane sulfonate compound of formula (II) with 1-(mercapto methyl) cyclopropane methyl ester compound of formula (V) or 1-(mercapto methyl) cyclopropane acetonitrile compound of formula (VII) in presence of polar aprotic solvent with without combination of C1-C4 alcohol and strong base like alkali or alkaline earth metal alkoxides i.e,. potassium tertiary butoxide, sodium methoxide, sodium ethoxide preferably sodium methoxide in DMSO/Methanol. 2. Optionally isolating the compound of formula (VI)/compound of formula (VIII) or in situ hydrolyzing with inorganic base like alkali metal hydroxide in a suitable solvent selected from hydrocarbon solvents, preferably toluene. 3. Treating the product obtained from step 2 with an organic amine compound of general formula R-NH2 (wherein R is dicyclohexyl amine, tertiary butyl amine, isopropyl amine) in a suitable solvent selected from keto solvents like acetone, butanone or ester solvents like ethyl acetate, propyl acetate, preferably acetone and ethylacetate gives corresponding Montelukast amine salt compound of formula (IV). 4. Optionally purifying the corresponding amine salt of Montelukast using hydrocarbon solvents like toluene, hexanes, heptane or keto solvents like acetone or mixture of them. 5. Converting the Organic amine salt of Montelukast compound of formula (IV) into its sodium salt of Formula (I) using sodium source in methanol. Yet another aspect of the present invention is to provide an improved process for the preparation of Montelukast sodium which comprises of the following steps; 1. Reacting (S) Benzenepropanol α-[3-[2-(7-chloro-2-quinolinyl) ethenyl]phenyl]-2-(l-hydroxy-1-methyl ethyl)-α-methane sulfonate compound of formula (II) with 1-(mercapto methyl) cyclo propane acetic acid compound of formula (III) or 1-(mercapto methyl) cyclo propane acetic acid methyl ester or l-(mercapto methyl) cyclo propane acetonitile in presence of polar aprotic solvent with or without combination of C1-C4 alcohol and alkali or alkaline carbonates like cesium carbonate, preferably cesium carbonate in presence of dimethylsulfoxide and methanol. 2. Quenching the reaction mixture with water and adding sodium hydroxide and washing the reaction mixture with water immiscible solvents like hydrocarbon solvents, ester solvents, chloro solvents, preferably hydrocarbon solvents, more preferably toluene. 3. Lowering the pH of the reaction mixture by adding acetic acid to the reaction mixture and extracting the Montelukast with a suitable solvent selected from ester solvents, chloro solvents, preferably ester solvents, more preferably ethylacetate. 4. Treating the product obtained from step 3 with an organic amine compound of general formula R-NH2 (wherein R is dicyclohexyl amine, tertiary butyl amine, isopropyl amine) in a suitable solvent selected from keto solvents like acetone, butanone or ester solvents like ethyl acetate, propyl acetate, preferably acetone and ethylacetate gives corresponding Montelukast amine salt compound of formula (IV). 5. Optionally purifying the corresponding amine salt of Montelukast using hydrocarbon solvents like toluene, hexanes, heptanes or keto solvents like acetone or mixture of both. 6. Converting the Organic amine salt of Montelukast compound of formula (IV) into its sodium salt of Formula (I) using sodium source in methanol. The present invention schematically represents as follows : Detailed description of the present Invention The present invention provides an improved process for the preparation of Montelukast and its pharmaceutically acceptable salts, preferably sodium salt. The improved process of the present invention comprises of; a) Reacting (S) Benzenepropanol α-[3-[2-(7-chloro-2-quinolinyl) ethenyl]phenyl]-2-(l-hydroxy-1-methyl ethyl)-α-methane sulfonate compound of formula (II) with 1-(mercapto methyl) cyclo propane acetic acid compound of formula (III) in presence of polar aprotic solvents like dimethylsulfoxide, dimethyl acetamide with or without combination of C1-C4 alcoholic solvents like methanol, ethanol, propanol, butanol, and strong base like alkali or alkaline earth metal alkoxides i.e,. potassium tertiary butoxide, sodium methoxide, sodium ethoxide, preferably sodium methoxide in a mixture of methanol and DMSO (dimethylsulfoxide) at a temperature of-20 to 0°C for 5 to 20 hours, preferably at a temperature of about -5 to 5°C for 8-10 hours. b) Quenching the reaction mixture with water and adding sodium hydroxide solution to the reaction mixture, and then extracting with water immiscible solvents like hydrocarbon solvents, chloro solvents, ester solvents, preferably hydrocarbon solvents more preferably toluene. c) Lowering pH of the reaction mixture with acetic acid then extracting the Montelukast with ester solvents, chloro solvents, preferably ester solvents more preferably ethylacetate. Concentrating the solvent and dilluting with a suitable solvent selected from keto solvents like acetone, butanone or ester solvents like ethylacetate, propyl acetate, preferably acetone and ethylacetate. d) Treating the product obtained from step c. with an organic amine having general formula R-NH2 (i.e,. organic amine like cyclic amines such as cyclo propyl amine, cyclo pentyl amine, cyclo hexyl amine, dicyclohexyl amine, pyrrolidine or morpholine or alkyl amines such as methyl amine, isopropyl amine, disiopropyl amine, tert-butyl amine, n-octyl glucamine or aryl amines such as phenyl ethyl amine, phenyl propyl amine) in a suitable solvent selected from keto solvents like acetone, butanone or ester solvents like ethyl acetate, propyl acetate, preferably acetone and ethylacetate at a temperature of 20-40°C for 5-15 hours, preferably at a temperature of about 25-35°C for 8-10 hours under inert atmosphere to give a respective salt of compound of formula (IV). e) Optionally purifying the corresponding amine salt of Montelukast using hydrocarbon solvents like toluene, hexanes, heptane or keto solvents like acetone or mixture of them. f) Converting the Organic amine salt of Montelukast compound of formula (IV) into its sodium salt of Formula (I) using sodium methoxide in methanol using sodium methoxide in methanol at a temperature of 20-40°C for 1-2 hours, preferably at a temperature of 25-35°C for 45 minutes under inert atmosphere. Another aspect of the present invention is to provide an improved process for the preparation of Montelukast sodium compound of formula (I) which comprises the following steps a) Reacting the organic amine salt of Montelukast compound of formula (IV) with a sodium source like sodium methoxide or sodium hydroxide in methanol. b) Removing the organic amine by extracting the mass with solvents which are immiscible with methanol like hexanes, heptane, and concentrating the methanol. c) Dissolving the product obtained from step b. in toluene and saturating the toluene with heptane to give Montelukast sodium compound of formula (I). Another aspect of the present invention is to provide an improved process for the preparation of Montelukast sodium compound of formula (I) which comprises the following steps. 1. Reacting (S) Benzenepropanol α-[3-[2-(7-chloro-2-quinolinyl) ethenyl]phenyl]-2-(l-hydroxy-1-methyl ethyl)-α-methane sulfonate compound of formula (II) with 1-mercapto methyl cyclopropane methyl ester compound of formula (V) or 1-mercapto methyl cyclopropane acetonitrile compound of formula (VII) in presence of polar aprotic solvent like dimethylsulfoxide, dimethyl acetamide with or without combination of C1-C4 alcoholic solvents like methanol, ethanol, propanol, butanol, and strong base like alkali or alkaline earth metal alkoxides i.e,. potassium tertiary butoxide, sodium methoxide, sodium ethoxide, preferably sodium methoxide in a mixture of methanol and DMSO (dimethylsulfoxide) at a temperature of-20 to 0°C for 5 to 20 hours, preferably at a temperature of about -5 to 5°C for 8-10 hours. 2. Optionally isolating the compounds of formula (VI)/compound of formula (VIII) or in situ hydrolyzing with inorganic base like alkali metal hydroxide in a suitable solvent selected from hydrocarbon solvents like toluene, xylene, preferably toluene at a temperature of 10-70°C for 10-20 hours, preferably at a temperature of 40-50°C for 15 hours. 3. Treating the product obtained from step 2 with an organic amine compound of general formula R-NH2 (wherein R is dicyclohexyl amine, tertiary butyl amine, isopropyl amine) in a suitable solvent selected from keto solvents like acetone, butanone or ester solvents like ethyl acetate, propyl acetate, preferably acetone and ethylacetate at a temperature of 20-40°C for 5-15 hours, preferably at a temperature of about 25-35°C for 8-10 hours under inert atmosphere to give a respective salt of compound of formula (IV). 4. Optionally purifying the corresponding amine salt of Montelukast using hydrocarbon solvents like toluene, hexanes, heptane or keto solvents like acetone or mixture of them. 5. Converting the Organic amine salt of Montelukast compound of formula (IV) into its sodium salt of Formula (I) using sodium methoxide in methanol at a temperature of 20-40°C for 1-2 hours, preferably at a temperature of 25-35°C for 60 minutes under inert atmosphere. Yet another aspect of the present invention is to provide an improved process for the preparation of Montelukast sodium which comprises of the following steps; 1. Reacting (S) Benzenepropanol α-[3-[2-(7-chloro-2-quinolinyl) ethenyl]phenyl]-2-(l-hydroxy-1-methyl ethyl)-α-methane sulfonate compound of formula (II) with 1- (mercapto methyl) cyclo propane acetic acid compound of formula (III) or 1-(mercapto methyl) cyclo propane acetic acid methyl ester or 1-(mercapto methyl) cyclo propane acetonitrile in presence of polar aprotic solvent like dimethyl sulfoxide, dimethyl acetamide with or without combination of C1-C4 alcohol and alkali or alkaline carbonates like cesium carbonate at a temperature of-20 to 0°C for 5 to 20 hours, preferably at a temperature of about -5 to 5°C for 8-10 hours. 2. Quenching the reaction mixture with water and adding sodium hydroxide and washing the reaction mixture with water immiscible solvents like hydrocarbon solvents, ester solvents, chloro solvents, preferably hydrocarbon solvents, more preferably toluene. 3. Lowering the pH of the reaction mixture by adding acetic acid to the reaction mixture and extracting the Montelukast with a suitable solvent selected from ester solvents, chloro solvents, preferably ester solvents, more preferably ethylacetate. 4. Treating the product obtained from step 3 with an organic amine compound of general formula R-NH2 (wherein R is dicyclohexyl amine, tertiary butyl amine, isopropyl amine) in a suitable solvent selected from keto solvents like acetone, butanone or ester solvents like ethyl acetate, propyl acetate, preferably acetone and ethylacetate at a temperature of 20-40°C for 5-15 hours, preferably at a temperature of about 25-35°C for 8-10 hours under inert atmosphere to give a respective salt of compound of formula (IV). 5. Optionally purifying the corresponding amine salt of Montelukast using hydrocarbon solvents like toluene, hexanes, heptane or keto solvents like acetone or mixture of them. 6. Converting the Organic amine salt of Montelukast compound of formula (IV) into its sodium salt of Formula (I) using sodium methoxide in methanol at a temperature of 20-40°C for 1-2 hours, preferably at a temperature of 25-35°C for 60 minutes under inert atmosphere. The processes described in the present invention were demonstrated in examples illustrated below. These examples are provided as illustration only and therefore should not be construed as limitation of the scope of the invention. Examples A solution of dimethylsulfoxide (400 ml) and sodium methoxide solution (200 ml) in methanol is cooled to -5 to 0°C under nitrogen atmosphere. Added l-(mercapto methyl) cyclo propane acetic acid (35 gr) compound of formula (III) under nitrogen atmosphere. Stirred the reaction mixture for 60 minutes at -5 to 0°C. Added 100 gr of (S) Benzenepropanol α-[3-[2-(7-chloro-2-quinolinyl) ethenyl]phenyl]-2-(l-hydroxy-1-methyl ethyl)-α-methane sulfonate compound of formula (II) to the reaction mixture at -5-0°C. Stirred the reaction mixture at -5 to 5°C for 10 hours. Added the reaction mixture to 3000 ml of chilled Water. Stirred the reaction mixture at 10-20°C for 30 minutes. Slowly added sodium hydroxide solution at 10-20°C. Washed the reaction mixture with toluene and removed the toluene layer. Cooled the aqueous layer to 10-20°C and slowly added 50% acetic acid solution. Extracted the reaction mixture with ethylacetate, washed the total organic layer with water and concentrated the organic layer at below 55°C under reduced pressure. Added 500 ml of ethylacetate to the above obtained crude at 25-35°C and stirred for 45 minutes under nitrogen atmosphere. Added 55 ml of dicyclohexylamine at 25-35°C. Stirred the reaction mixture for 10 hours. Filtered the solid and washed with ethylacetate under nitrogen atmosphere. Wet material taken into a mixture of 500 ml of toluene and 500 ml of hexenes and heated to 55-65°C, stirred for 60 minutes. Cooled the mass to 25-35°C and stirred for 8 hours. Separated the solid by filtration. Dried the compound at 40-60°C to get title compound. Yield : 80 gr. A solution of dimethylsulfoxide (400 ml) and sodium methoxide solution (200 ml) in methanol is cooled to -5 to 0°C under nitrogen atmosphere. Added l-(mercapto methyl) cyclo propane acetic acid (35 gr) compound of formula (III) under nitrogen atmosphere. Stirred the reaction mixture for 60 minutes at -5 to 0°C. Added 100 gr of (S) Benzenepropanol α-[3-[2-(7-chloro-2-quinolinyl) ethenyl]phenyl]-2-(l-hydroxy-1-methyl ethyl)-α-methane sulfonate compound of formula (II) to the reaction mixture at -5-0°C. Stirred the reaction mixture at -5 to 5°C for 10 hours. Added the reaction mixture to 3000 ml of chilled Water. Stirred the reaction mixture at 10-20°C for 30 minutes. Slowly added sodium hydroxide solution at 10-20°C. Washed the reaction mixture with toluene and removed the toluene layer. Cooled the aqueous layer to 10-20°C and slowly added 50% acetic acid solution. Extracted the reaction mixture with ethylacetate, washed the total organic layer with water and concentrated the organic layer at below 55°C under reduced pressure. Added 500 ml of acetone to the above obtained crude at 25-35°C and stirred for 45 minutes under nitrogen atmosphere. Added 55 ml of dicyclohexylamine at 25-35°C. Stirred the reaction mixture for 10 hours. Filtered the solid and washed with acetone under nitrogen atmosphere. Dried the compound at 40-60°C to get title compound. Yield : 80 gr. A solution of dimethylsulfoxide (400 ml) and sodium methoxide solution (200 ml) in methanol is cooled to -5 to 0°C under nitrogen atmosphere. Added l-(mercapto methyl) cyclo propane acetic acid (35 gr) compound of formula (III) under nitrogen atmosphere. Stirred the reaction mixture for 60 minutes at -5 to 0°C. Added 100 gr of (S) Benzenepropanol α-[3-[2-(7-chloro-2-quinolinyl) ethenyl]phenyl]-2-(l-hydroxy-1-methyl ethyl)-α-methane sulfonate compound of formula (II) to the reaction mixture at -5-0°C. Stirred the reaction mixture at -5 to 5°C for 10 hours. Added the reaction mixture to 3000 ml of chilled Water. Stirred the reaction mixture at 10-20°C for 30 minutes. Slowly added sodium hydroxide solution at 10-20°C. Washed the reaction mixture with toluene and removed the toluene layer. Cooled the aqueous layer to 10-20°C and slowly added 50% acetic acid solution. Extracted the reaction mixture with ethylacetate, washed the total organic layer with water and concentrated the organic layer at below 55°C under reduced pressure. Added 500 ml of acetone to the above obtained crude at 25-3 5°C and stirred for 45 minutes under nitrogen atmosphere. Added 15 gr of tertiary butyl amine at 25-35°C. Stirred the reaction mixture for 10 hours. Filtered the solid and washed with acetone under nitrogen atmosphere. Dried the compound at 40-60°C to get title compound. Yield : 70 gr. A solution of dimethylsulfoxide (400 ml) and sodium methoxide solution (200 ml) in methanol is cooled to -5 to 0°C under nitrogen atmosphere. Added l-(mercapto methyl) cyclo propane acetic acid methyl ester compound of formula (V) (45 gr) compound of formula (III) under nitrogen atmosphere. Stirred the reaction mixture for 60 minutes at -5 to 0°C. Added 100 gr of (S) Benzenepropanol α-[3-[2-(7-chloro-2-quinolinyl) ethenyl]phenyl]-2-(l-hydroxy-1 -methyl ethyl)-α-methane sulfonate compound of formula (II) in DMSO (dimethyl sulfoxide) to the reaction mixture at -5-0°C. Stirred the reaction mixture at -5 to 5°C for 10 hours. Added the reaction mixture to 1000 ml of chilled Water. Stirred the reaction mixture at 10-20°C for 30 minutes. Extracted the reaction mixture with toluene. Concentrated the toluene layer completely and added toluene to the residue. Added sodium hydroxide solution and stirred at a temperature of about 40 to 50°C for 15 hours. Washed the reaction mixture with toluene and removed the toluene layer. Cooled the aqueous layer to 10-20°C and slowly added 50% acetic acid solution. Extracted the reaction mixture with ethylacetate, washed the total organic layer with water and concentrated the organic layer at below 55°C under reduced pressure. Added 500 ml of acetone to the above obtained crude at 25-35°C and stirred for 45 minutes under nitrogen atmosphere. Added 55 ml of dicyclohexylamine at 25-35°C. Stirred the reaction mixture for 10 hours. Filtered the solid and washed with acetone under nitrogen atmosphere. Dried the compound at 40-60°C to get title compound. Yield : 80 gr. A solution of dimethylsulfoxide (400 ml) and sodium methoxide solution (200 ml) in methanol is cooled to -5 to 0°C under nitrogen atmosphere. Added l-(mercapto methyl) cyclo propane acetonitrile compound of formula (VII) (25 gr) compound of formula (III) under nitrogen atmosphere. Stirred the reaction mixture for 60 minutes at -5 to 0°C. Added 100 gr of (S) Benzenepropanol α-[3-[2-(7-chloro-2-quinolinyl) ethenyl]phenyl]-2-(l-hydroxy-1-methyl ethyl)-α-methane sulfonate compound of formula (II) in DMSO (dimethyl sulfoxide) to the reaction mixture at -5-0°C. Stirred the reaction mixture at -5 to 5°C for 10 hours. Added the reaction mixture to 1000 ml of chilled Water. Stirred the reaction mixture at 10-20°C for 30 minutes. Extracted the reaction mixture with toluene. Concentrated the toluene layer completely and added toluene to the residue. Added caustic lye solution and stirred at a temperature of 125°C for 15 hours. Washed the reaction mixture with toluene and removed the toluene layer. Cooled the aqueous layer to 10-20°C and slowly added 50% acetic acid solution. Extracted the reaction mixture with ethylacetate, washed the total organic layer with water and concentrated the organic layer at below 55°C under reduced pressure. Added 500 ml of acetone to the above obtained crude at 25-35°C and stirred for 45 minutes under nitrogen atmosphere. Added 55 ml of dicyclohexylamine at 25-35°C. Stirred the reaction mixture for 10 hours. Filtered the solid and washed with acetone under nitrogen atmosphere. Dried the compound at 40-60°C to get title compound. Yield : 65 gr. A solution of dimethylsulfoxide (400 ml) and cesium carbonate (120 gr) in methanol (200 ml) is cooled to -5 to 0°C under nitrogen atmosphere. Added l-(mercapto methyl) cyclo propane acetic acid (35 gr) compound of formula (III) under nitrogen atmosphere. Stirred the reaction mixture for 60 minutes at -5 to 0°C. Added 100 gr of (S) Benzenepropanol, α-[3-[2-(7-chloro-2-quinolinyl) ethenyl]phenyl]-2-(l -hydroxy-1-methyl ethyl)-, α-methane sulfonate compound of formula (II) to the reaction mixture at -5-0°C. Stirred the reaction mixture at -5 to 5°C for 10 hours. Added the reaction mixture to 3000 ml of chilled Water. Stirred the reaction mixture at 10-20°C for 30 minutes. Slowly added sodium hydroxide solution at 10-20°C. Washed the reaction mixture with toluene and removed the toluene layer. Cooled the aqueous layer to 10-20°C and slowly added 50% acetic acid solution. Extracted the reaction mixture with ethylacetate, washed the total organic layer with water and concentrated the organic layer at below 55°C under reduced pressure. Added 500 ml of acetone to the above obtained crude at 25-3 5°C and stirred for 45 minutes under nitrogen atmosphere. Added 55 ml of dicyclohexylamine at 25-35°C. Stirred the reaction mixture for 10 hours. Filtered the solid and washed with acetone under nitrogen atmosphere. Dried the compound at 40-60°C to get title compound. Yield : 100 gr. Added dicyclohexyl amine salt of [R-(E)-l[[[l-[3-[2-[7-chloro-2-quinolinyl]ethenyl]phenyl]-3-[2-( 1 -hydroxy-1 - methylethyl)phenyl]propyl]thio]methyl]cyclopropaneacetic acid compound of formula (IV) (100 gr) prepared as per the procedures given in examples 1,2,4,5 & 6 to a solution of sodium methoxide (23 gr) and methanol (210 ml) at 25-35°C. Stirred for 60 minutes at 25-35°C. Washed the reaction mixture with hexanes. Distilled the solvent completely under reduced pressure at below 55°C. Added toluene to the crude and slowly added the toluene layer to heptane at 25-35°C under nitrogen atmosphere. Stirred the mass for 45 minutes under nitrogen atmosphere. Separated the solid by filtration and washed with heptane. Dried the compound at 60-70°C under reduced pressure to get title compound. Yield 70 gr. Added tertiary butyl amine salt of [R-(E)-l[[[l-[3-[2-[7-chloro-2-quinolinyl]ethenyl]phenyl]-3-[2-(l-hydroxy-l- methylethyl)phenyl]propyl]thio]methyl]cyclopropaneacetic acid compound of formula (IV) (100 gr) prepared as per the procedures given in examples 3, to a solution of sodium methoxide (22 gr) and methanol (210 ml) at 25-35°C. Stirred for 60 minutes at 25-35°C. Washed the reaction mixture with hexanes. Distilled the solvent completely under reduced pressure at below 55°C. Added toluene to the crude and slowly added the toluene layer to heptane at 25-35°C under nitrogen atmosphere. Stirred the mass for 45 minutes under nitrogen atmosphere. Separated the solid by filtration and washed with heptane. Dried the compound at 60-70°C under reduced pressure to get title compound. Yield 70 gr. We Claim : 1. Process for the preparation of Montelukast sodium compound of formula (I) Which comprises of; a) Reacting (S) Benzenepropanol a -[3-[2-(7-chloro-2-quinolinyl) ethenyl]phenyl]-2-(l-hydroxy-1-methyl ethyl)-a-methane sulfonate compound of formula (II) with 1-(Mercapto methyl) cyclo propane acetic acid compound of formula (III) in presence of polar aprotic solvents like dimethylsulfoxide/dimethyl formamide,dimethyl acetamide and strong base like alkali or alkaline earth metal alkoxides i.e,. potassium tertiary butoxide, sodium methoxide, sodium ethoxide in a suitable solvent or mixture of solvents selected from C1-C4 alcoholic solvents like methanol, ethanol, propanol, butanol, preferably sodium methoxide in a mixture of methanol and DMSO (dimethylsulfoxide) at a temperature of -20 to 0°C for 5 to 20 hours, preferably at a temperature of about -5 to 5°C for 8-10 hours, b) Quenching the reaction mixture with water and adding sodium hydroxide solution to the reaction mixture and then extracting with water immiscible solvents like hydrocarbon solvents, chloro solvents, ester solvents, preferably hydrocarbon solvents more preferably toluene to remove impurities, c) Lowering pH of the reaction mixture with acetic acid then extracting the Montelukast with ester solvents, chloro solvents preferably ester solvents more preferably ethylacetate. Concentrating the solvent and diluting with a suitable solvent selected from keto solvents like acetone, butanone or ester solvents like ethylacetate, propyl acetate, preferably acetone and ethylacetate, d) Treating the product obtained from step c. with an organic amine having general formula R-NH2 (i.e,. organic amine like cyclic amines such as cyclo propyl amine, cyclo pentyl amine, cyclo hexyl amine, dicyclohexyl amine, pyrrolidine or morpholine or alkyl amines such as methyl amine, isopropyl amine, disiopropyl amine, tert-butyl amine, n-octyl glucamine or aryl amines such as phenyl ethyl amine, phenyl propyl amine) at a temperature of 20-40°C for 5-15 hours, preferably at a temperature of about 25-35°C for 8-10 hours under inert atmosphere to give a respective salt of compound of formula (IV), e) Optionally purifying the corresponding amine salt of Montelukast using hydrocarbon solvents like toluene, hexanes, heptane or keto solvents like acetone or mixture of them, f) Converting the Organic amine salt of Montelukast compound of formula (IV) into its sodium salt of Formula (I) using sodium methoxide in methanol at a temperature of 20-40°C for 1-2 hours, preferably at a temperature of 25-35°C for 60 minutes under inert atmosphere. Which comprises of; a) Reacting the organic amine salt of Montelukast compound of formula (IV) with a sodium source in methanol. b) Removing the organic amine by extracting the mass with solvents which are immiscible with methanol like hexanes, heptane and concentrating the methanol. c) Dissolving the product obtained from step b. in toluene and saturating the toluene with heptane to give Montelukast sodium compound of formula (I). Which comprises of; a) Reacting (S) Benzenepropanol, a -[3-[2-(7-chloro-2-quinolinyl) ethenyl]phenyl]- 2-(l-hydroxy-1-methyl ethyl)-, a -methane sulfonate compound of formula (II) with 1-mercapto methyl cyclopropane methyl ester compound of formula (V) or 1-mercapto methyl cyclopropane acetonitrile compound of formula (VII) in presence of polar aprotic solvent and strong base like alkali or alkaline earth metal alkoxides i.e,. potassium tertiary butoxide, sodium methoxide, sodium ethoxide in a suitable solvent or mixture of solvents like C1-C4 alcohol preferably sodium methoxide in DMSO/Methanol at a temperature of -20 to 0°C for 5 to 20 hours, preferably at a temperature of about -5 to 5°C for 8-10 hours, b) Optionally isolating the compounds of formula (VI)/compound of formula (VIII) or in situ hydrolyzing the compound with inorganic base like alkali metal hydroxide in a suitable solvent selected from C1-C4 alcohol, preferably methanol at a temperature of 10-70°C for 10-20 hours, preferably at a temperature of 40- 50°C for 15 hours, c) Treating the product obtained from step b. with an organic amine compound of general formula R-NH2 (wherein R is dicyclohexyl amine, tertiary butyl amine, isopropyl amine) in a suitable solvent selected from keto solvents like acetone, butanone or ester solvents like ethyl acetate, propyl acetate, preferably acetone and ethylacetate gives corresponding Montelukast amine salt compound of formula (IV) at a temperature of 20-40°C for 5-15 hours, preferably at a temperature of about 25-35°C for 8-10 hours under inert atmosphere to give a respective salt of compound of formula (IV), d) Optionally purifying the corresponding amine salt of Montelukast using hydrocarbon solvents like toluene, hexanes, heptane or keto solvents like acetone or mixture of them, e) Converting the Organic amine salt of Montelukast compound of formula (IV) into its sodium salt of Formula (I) using sodium methoxide in methanol at a temperature of 20-40°C for 1-2 hours, preferably at a temperature of 25-35°C for 60 minutes under inert atmosphere. Which comprises of; a) Reacting (S)Benzenepropanol a -[3-[2-(7-chloro-2-quinolinyl) ethenyl]phenyl]-2-(l-hydroxy-1-methyl ethyl)-a-methane sulfonate compound of formula (II) with 1-(mercapto methyl) cyclopropane acetic acid compound of formula (III) or 1-(mercapto methyl) cyclopropane acetic acid methyl ester compound of formula (V) or 1 -(mercapto methyl) cyclopropane acetonitrlle compound of formula (VII) in presence of polar aprotic solvent and cesuim carbonate in a suitable solvent or mixture of solvents like C1-C4 alcohol preferably cesuim carbonate in DMSO/Methanol at a temperature of -20 to 0°C for 5 to 20 hours, preferably at a temperature of about -5 to 5°C for 8-10 hours, b) Quenching the reaction mixture with water and adding sodium hydroxide solution to the reaction mixture and then extracting with water immiscible solvents like hydrocarbon solvents, chloro solvents, ester solvents, preferably hydrocarbon solvents more preferably toluene to remove impurities, c) Lowering pH of the reaction mixture with acetic acid then extracting the Montelukast with ester solvents, chloro solvents preferably ester solvents more preferably ethylacetate. Concentrating the solvent and diluting with a suitable solvent selected from keto solvents like acetone, butanone or ester solvents like ethylacetate, propyl acetate, preferably acetone and ethylacetate, d) Treating the product obtained from step c. with an organic amine compound of general formula R-NH2 (wherein R is dicyclohexyl amine, tertiary butyl amine, isopropyl amine) in a suitable solvent selected from keto solvents like acetone, butanone or ester solvents like ethyl acetate, propyl acetate, preferably acetone and ethylacetate gives corresponding Montelukast amine salt compound of formula (IV) at a temperature of 20-40°C for 5-15 hours, preferably at a temperature of about 25-35°C for 8-10 hours under inert atmosphere to give a respective salt of compound of formula (IV), e) Optionally purifying the corresponding amine salt of Montelukast using hydrocarbon solvents like toluene, hexanes, heptane or keto solvents like acetone or mixture of them, f) Converting the Organic amine salt of Montelukast compound of formula (IV) into its sodium salt of Formula (I) using sodium methoxide in methanol at a temperature of 20-40°C for 1-2 hours, preferably at a temperature of 25-35°C for 60 minutes under inert atmosphere. 5. Usage of polar aprotic solvents like dimethyl sulfoxide, dimethylacetamide, with strong base like alkali or alkaline earth metal alkoxide i.e, sodium methoxide, potassium tertiary butoxide, sodium ethoxide according to claim la) and 3 a) with or without combination of C1-C4 alcoholic solvents, for the reaction of (S) Benzenepropanol a -[3-[2-(7-chloro-2-quinolinyl) ethenyl]phenyl]-2-(l-hydroxy-1- methyl ethyl)-a-methane sulfonate with l-(mercapto methyl) cyclopropane acetic acid or l-(mercapto methyl) cyclopropane acetic acid methyl ester or l-(mercapto methyl) cyclopropane acetonitrile. 6. Water immiscible solvent used for extracting the reaction mixture to remove impurities according to claim 1 b) is toluene. 7. Water immiscible solvent used for extracting the reaction mixture to remove impurities according to claim 1 b) is heptane. 8. Sodium source for the convertion of organic amine salt of Montelukast compound of formula (IV) to Montelukast sodium compound of formula (I) according to claim 2 a) is sodium methoxide. 9. Removing the organic amine salt by extracting the reaction mixture with methanol immiscible solvent according to claim 2 b) is hexanes. 10.Usage of alkali or alkaline carbonate like cesium carbonate with polar aprotic solvent like dimethyl sulfoxide, dimethyl acetamide with or without combination of C1-C4 alcoholic solvents according to claim 4 a) for the reaction of (S) Benzenepropanol a -[3-[2-(7-chloro-2-quinolinyl) ethenyl]phenyl]-2-(l-hydroxy-1-methyl ethyl)-a-methane sulfonate with l-(mercapto methyl) cyclopropane acetic acid or l-(mercapto methyl) cyclopropane acetic acid methyl ester or l-(mercapto methyl) cyclopropane acetonitrile.

Full Text

An improved process for the preparation of Montelukast and its pharmaceutically acceptable
salts

Field of the Invention
The present invention relates to an improved process for the preparation of [R-

Formula (I).

Montelukast sodium is a leukotriene antagonist and is useful in the treatment of Asthma and as well as other conditions mediated by leukotrienes, such as inflammation and allergies.

Background of the Invention

pyran with Methyl l-(acetylthiomethyl) cyclopropane acetate in presence of hydrazine, cesium carbonate in acetonitrile as solvent to get methyl ester of Montelukast in pyran protected form. The protected compound is further reacted with pyridinium p-toluene sulfonate, sodium hydroxide in a mixture of methanol and tetrahydrofuran as a solvent to afford Montelukast sodium of Formula (I).
US 5,614,632 discloses the preparation of l-(mercapto methyl) cyclopropane acetic acid, which is a key intermediate for the preparation of Montelukast sodium. The said patent claimed an improved process for the preparation of Montelukast sodium including the process for the preparation of its key intermediates. The process comprises, the generation of dilithium dianion of l-(mercaptomethyl) cyclopropaneacetic acid and then

3-hydroxy propyl) benzoate with methyl magnesium chloride to give diol, which is further converted to mesylated alcohol on reaction with methanol sulfonyl chloride. The process for the preparation of above described benzoate is disclosed in EP 480717 (example 146, step-2), which involves the usage of (-)B-chloro diisopinocamphenylborane as achiral reducing agent. The said patent also claims the process for the preparation of crystalline Montelukast sodium salt.

Many other related patents discloses the process for the preparation of Montelukast and its intermediates but none of those patents are related to the process of the present invention. The prior art procedures involves more number of steps which includes the protection and further deprotection of diol intermediate, the usage of hazardous and costly raw materials such as n-butyl lithium in typical rections i.e., at very low temperatures (-25°C). The processes of the prior art references involve tedious workup to isolate the required product and thus results in excess time cycle, which in turn rendering the process more costly and less eco friendly thus the process is not recommendable for commercial scale up.
As the Montelukast sodium of Formula (I), which is useful in the treatment of Asthma, hence, it is important to have a cost effective and commercially viable process for preparing the compound of Formula (I).
Therefore, the main objective of the present invention is to prepare Montelukast sodium in an improved method, which is cost-effective, commercially viable and non-hazardous. The Montelukast sodium is prepared in the present invention; in an improved process that is cost effective and the Montelukast sodium obtained in this process is suitable for pharmaceutical formulations.
Disadvantages of the prior art processes
• Usage of n-Butyl lithium is leading to increase the cost of the product and which is highly flammable and dangerous, it needs special equipment to handle the reagent, needs personal attention throughout the process.
• Usage of sodium hydroxide for the preparation of Montelukast sodium (formula-I) from Montelukast produces water as by product it leads to formation of gummy material so removal of water is essential this leads to prolonged process.
• Prior art processes teaches conversion of Montelukast amine salt to Montelukast free acid then converting to its sodium salt needs more time.

Summary of the Invention
The present invention provides an improved process for the preparation of Montelukast and its pharmaceutically acceptable salts, preferably sodium salt. The improved process of the present invention comprises;
Reacting (S) Benzenepropanol α-[3-[2-(7-chloro-2-quinolinyl) ethenyl]phenyl]-2-(l-hydroxy-1-methyl ethyl)-α-methane sulfonate compound of formula (II) with 1-(mercapto methyl) cyclo propane acetic acid compound of formula (III) in presence of alkali or alkaline carbonates like cesium carbonate or strong base like alkali or alkaline earth metal alkoxide i.e,. potassium tertiary butoxide, sodium methoxide, sodium ethoxide, in a suitable polar aprotic solvent with or without combination of C1-C4 alcoholic solvents like methanol, ethnaol, preferably methanol and then treating with an organic amine of general formula R-NH2 in a suitable solvent selected from keto solvents like acetone, butanone or ester solvents like ethyl acetate, propyl acetate, preferably acetone and ethylacetate gives corresponding amine salt of Montelukast compound of formula (IV) and then converting compound of corresponding amine salt of Montelukast into its sodium salt of Formula (I) (Montelukast sodium) using sodium source in methanol.
Advantages over prior art processes
• The object of the present invention is to provide an improved process for the preparation of Montelukast sodium using a simple base like sodium methoxide or potassium tertiary butoxide in place of n-butyl lithium which is easy to handle it does not need any special equipment.
• Usage of sodium methoxide for the preparation of Montelukast sodium (formula-I) from Montelukast produces methanol as by product and removal of methanol is very easy and it gives the free flow powder.

• Present invention provides process for the preparation of Montelukast sodium
without conversion of Montelukast amine salt to Montelukast free acid, it leads to
reduction of cycle time.
• Highest yield obtained while using cesium carbonate.
• Introducing the toluene/hexanes washings after completion of the condensation
reaction to remove impurities, which avoids purification at organic amine salt stage.
• Cost effective process, and reduction of cycle time.
• Environment friendly and easy scalable process.
Brief description of the Invention
The present invention provides an improved process for the preparation of Montelukast and its pharmaceutically acceptable salts, preferably sodium salt. The improved process of the present invention comprises the following steps;
1.
2. Quenching the reaction mixture with water and adding sodium hydroxide and
washing the reaction mixture with water immiscible solvents like hydrocarbon
solvents, ester solvents, chloro solvents, preferably hydrocarbon solvents, more
preferably toluene.
3. Lowering the pH of the reaction mixture by adding acetic acid to the reaction mixture
and extracting the Montelukast with a suitable solvent selected from ester solvents,
chloro solvents, preferably ester solvents, more preferably ethylacetate.
4. Treating the product obtained from step 3 with an organic amine compound of
general formula R-NH2 (wherein R is dicyclohexyl amine, tertiary butyl amine,

isopropyl amine) in a suitable solvent selected from keto solvents like acetone, butanone or ester solvents like ethyl acetate, propyl acetate, preferably acetone and ethylacetate gives corresponding Montelukast amine salt compound of formula (IV). 5. Optionally purifying the corresponding amine salt of Montelukast using hydrocarbon solvents like toluene, hexanes, heptane or keto solvents like acetone or mixture of them.

Another aspect of the present invention is to provide an improved process for the preparation of Montelukast sodium compound of formula (I) without converting the organic amine salt of Montelukast compound of formula (IV) to Montelukast free acid. Accordingly the present invention provides an improved process for the preparation of Montelukast sodium compound of formula (I) which comprises of following steps
a) Reacting the organic amine salt of Montelukast compound of formula (IV) with a
sodium source in methanol.
b) Removing the organic amine by extracting the mass with solvents which are
immiscible with methanol like hexanes, heptane, and concentrating the methanol.
c) Dissolving the product obtained from step b. in toluene and saturating the toluene
with heptane to give Montelukast sodium compound of formula (I).
Another aspect of the present invention is to provide an improved process for the preparation of Montelukast sodium which comprises of following steps.
1. Reacting (S) Benzenepropanol α-[3-[2-(7-chloro-2-quinolinyl) ethenyl]phenyl]-2-(l-hydroxy-1-methyl ethyl)-α-methane sulfonate compound of formula (II) with 1-(mercapto methyl) cyclopropane methyl ester compound of formula (V) or 1-(mercapto methyl) cyclopropane acetonitrile compound of formula (VII) in presence of polar aprotic solvent with without combination of C1-C4 alcohol and strong base

like alkali or alkaline earth metal alkoxides i.e,. potassium tertiary butoxide, sodium methoxide, sodium ethoxide preferably sodium methoxide in DMSO/Methanol.
2. Optionally isolating the compound of formula (VI)/compound of formula (VIII) or in situ hydrolyzing with inorganic base like alkali metal hydroxide in a suitable solvent selected from hydrocarbon solvents, preferably toluene.
3. Treating the product obtained from step 2 with an organic amine compound of general formula R-NH2 (wherein R is dicyclohexyl amine, tertiary butyl amine, isopropyl amine) in a suitable solvent selected from keto solvents like acetone, butanone or ester solvents like ethyl acetate, propyl acetate, preferably acetone and ethylacetate gives corresponding Montelukast amine salt compound of formula (IV).
4. Optionally purifying the corresponding amine salt of Montelukast using hydrocarbon solvents like toluene, hexanes, heptane or keto solvents like acetone or mixture of them.
5. Converting the Organic amine salt of Montelukast compound of formula (IV) into its sodium salt of Formula (I) using sodium source in methanol.
Yet another aspect of the present invention is to provide an improved process for the preparation of Montelukast sodium which comprises of the following steps;
1. Reacting (S) Benzenepropanol α-[3-[2-(7-chloro-2-quinolinyl) ethenyl]phenyl]-2-(l-hydroxy-1-methyl ethyl)-α-methane sulfonate compound of formula (II) with 1-(mercapto methyl) cyclo propane acetic acid compound of formula (III) or 1-(mercapto methyl) cyclo propane acetic acid methyl ester or l-(mercapto methyl) cyclo propane acetonitile in presence of polar aprotic solvent with or without combination of C1-C4 alcohol and alkali or alkaline carbonates like cesium carbonate, preferably cesium carbonate in presence of dimethylsulfoxide and methanol.
2. Quenching the reaction mixture with water and adding sodium hydroxide and washing the reaction mixture with water immiscible solvents like hydrocarbon

solvents, ester solvents, chloro solvents, preferably hydrocarbon solvents, more preferably toluene.
3. Lowering the pH of the reaction mixture by adding acetic acid to the reaction mixture and extracting the Montelukast with a suitable solvent selected from ester solvents, chloro solvents, preferably ester solvents, more preferably ethylacetate.
4. Treating the product obtained from step 3 with an organic amine compound of general formula R-NH2 (wherein R is dicyclohexyl amine, tertiary butyl amine, isopropyl amine) in a suitable solvent selected from keto solvents like acetone, butanone or ester solvents like ethyl acetate, propyl acetate, preferably acetone and ethylacetate gives corresponding Montelukast amine salt compound of formula (IV).
5. Optionally purifying the corresponding amine salt of Montelukast using hydrocarbon solvents like toluene, hexanes, heptanes or keto solvents like acetone or mixture of both.
6. Converting the Organic amine salt of Montelukast compound of formula (IV) into its sodium salt of Formula (I) using sodium source in methanol.
The present invention schematically represents as follows :

Detailed description of the present Invention
The present invention provides an improved process for the preparation of Montelukast and its pharmaceutically acceptable salts, preferably sodium salt. The improved process of the present invention comprises of;
a) Reacting (S) Benzenepropanol α-[3-[2-(7-chloro-2-quinolinyl) ethenyl]phenyl]-2-(l-hydroxy-1-methyl ethyl)-α-methane sulfonate compound of formula (II) with 1-(mercapto methyl) cyclo propane acetic acid compound of formula (III) in presence of polar aprotic solvents like dimethylsulfoxide, dimethyl acetamide with or without combination of C1-C4 alcoholic solvents like methanol, ethanol, propanol, butanol, and strong base like alkali or alkaline earth metal alkoxides i.e,. potassium tertiary butoxide, sodium methoxide, sodium ethoxide, preferably sodium methoxide in a mixture of methanol and DMSO (dimethylsulfoxide) at a temperature of-20 to 0°C for 5 to 20 hours, preferably at a temperature of about -5 to 5°C for 8-10 hours.
b) Quenching the reaction mixture with water and adding sodium hydroxide solution to the reaction mixture, and then extracting with water immiscible solvents like hydrocarbon solvents, chloro solvents, ester solvents, preferably hydrocarbon solvents more preferably toluene.
c) Lowering pH of the reaction mixture with acetic acid then extracting the Montelukast with ester solvents, chloro solvents, preferably ester solvents more preferably ethylacetate. Concentrating the solvent and dilluting with a suitable solvent selected from keto solvents like acetone, butanone or ester solvents like ethylacetate, propyl acetate, preferably acetone and ethylacetate.
d) Treating the product obtained from step c. with an organic amine having general formula R-NH2 (i.e,. organic amine like cyclic amines such as cyclo propyl amine, cyclo pentyl amine, cyclo hexyl amine, dicyclohexyl amine, pyrrolidine or morpholine or alkyl amines such as methyl amine, isopropyl amine, disiopropyl amine, tert-butyl amine, n-octyl glucamine or aryl amines such as phenyl ethyl amine, phenyl propyl amine) in a suitable solvent selected from keto solvents like acetone, butanone or ester solvents like ethyl acetate, propyl acetate, preferably acetone and

ethylacetate at a temperature of 20-40°C for 5-15 hours, preferably at a temperature of about 25-35°C for 8-10 hours under inert atmosphere to give a respective salt of compound of formula (IV).
e) Optionally purifying the corresponding amine salt of Montelukast using hydrocarbon solvents like toluene, hexanes, heptane or keto solvents like acetone or mixture of them.
f) Converting the Organic amine salt of Montelukast compound of formula (IV) into its sodium salt of Formula (I) using sodium methoxide in methanol using sodium methoxide in methanol at a temperature of 20-40°C for 1-2 hours, preferably at a temperature of 25-35°C for 45 minutes under inert atmosphere.
Another aspect of the present invention is to provide an improved process for the preparation of Montelukast sodium compound of formula (I) which comprises the following steps
a) Reacting the organic amine salt of Montelukast compound of formula (IV) with a sodium source like sodium methoxide or sodium hydroxide in methanol.
b) Removing the organic amine by extracting the mass with solvents which are immiscible with methanol like hexanes, heptane, and concentrating the methanol.
c) Dissolving the product obtained from step b. in toluene and saturating the toluene with heptane to give Montelukast sodium compound of formula (I).
Another aspect of the present invention is to provide an improved process for the preparation of Montelukast sodium compound of formula (I) which comprises the following steps.
1. Reacting (S) Benzenepropanol α-[3-[2-(7-chloro-2-quinolinyl) ethenyl]phenyl]-2-(l-hydroxy-1-methyl ethyl)-α-methane sulfonate compound of formula (II) with 1-mercapto methyl cyclopropane methyl ester compound of formula (V) or 1-mercapto methyl cyclopropane acetonitrile compound of formula (VII) in presence of polar aprotic solvent like dimethylsulfoxide, dimethyl acetamide with or without

combination of C1-C4 alcoholic solvents like methanol, ethanol, propanol, butanol, and strong base like alkali or alkaline earth metal alkoxides i.e,. potassium tertiary butoxide, sodium methoxide, sodium ethoxide, preferably sodium methoxide in a mixture of methanol and DMSO (dimethylsulfoxide) at a temperature of-20 to 0°C for 5 to 20 hours, preferably at a temperature of about -5 to 5°C for 8-10 hours.
2. Optionally isolating the compounds of formula (VI)/compound of formula (VIII) or in situ hydrolyzing with inorganic base like alkali metal hydroxide in a suitable solvent selected from hydrocarbon solvents like toluene, xylene, preferably toluene at a temperature of 10-70°C for 10-20 hours, preferably at a temperature of 40-50°C for 15 hours.
3. Treating the product obtained from step 2 with an organic amine compound of general formula R-NH2 (wherein R is dicyclohexyl amine, tertiary butyl amine, isopropyl amine) in a suitable solvent selected from keto solvents like acetone, butanone or ester solvents like ethyl acetate, propyl acetate, preferably acetone and ethylacetate at a temperature of 20-40°C for 5-15 hours, preferably at a temperature of about 25-35°C for 8-10 hours under inert atmosphere to give a respective salt of compound of formula (IV).
4. Optionally purifying the corresponding amine salt of Montelukast using hydrocarbon solvents like toluene, hexanes, heptane or keto solvents like acetone or mixture of them.
5. Converting the Organic amine salt of Montelukast compound of formula (IV) into its sodium salt of Formula (I) using sodium methoxide in methanol at a temperature of 20-40°C for 1-2 hours, preferably at a temperature of 25-35°C for 60 minutes under inert atmosphere.
Yet another aspect of the present invention is to provide an improved process for the preparation of Montelukast sodium which comprises of the following steps;
1. Reacting (S) Benzenepropanol α-[3-[2-(7-chloro-2-quinolinyl) ethenyl]phenyl]-2-(l-hydroxy-1-methyl ethyl)-α-methane sulfonate compound of formula (II) with 1-

(mercapto methyl) cyclo propane acetic acid compound of formula (III) or 1-(mercapto methyl) cyclo propane acetic acid methyl ester or 1-(mercapto methyl) cyclo propane acetonitrile in presence of polar aprotic solvent like dimethyl sulfoxide, dimethyl acetamide with or without combination of C1-C4 alcohol and alkali or alkaline carbonates like cesium carbonate at a temperature of-20 to 0°C for 5 to 20 hours, preferably at a temperature of about -5 to 5°C for 8-10 hours.
2. Quenching the reaction mixture with water and adding sodium hydroxide and washing the reaction mixture with water immiscible solvents like hydrocarbon solvents, ester solvents, chloro solvents, preferably hydrocarbon solvents, more preferably toluene.
3. Lowering the pH of the reaction mixture by adding acetic acid to the reaction mixture and extracting the Montelukast with a suitable solvent selected from ester solvents, chloro solvents, preferably ester solvents, more preferably ethylacetate.
4. Treating the product obtained from step 3 with an organic amine compound of general formula R-NH2 (wherein R is dicyclohexyl amine, tertiary butyl amine, isopropyl amine) in a suitable solvent selected from keto solvents like acetone, butanone or ester solvents like ethyl acetate, propyl acetate, preferably acetone and ethylacetate at a temperature of 20-40°C for 5-15 hours, preferably at a temperature of about 25-35°C for 8-10 hours under inert atmosphere to give a respective salt of compound of formula (IV).
5. Optionally purifying the corresponding amine salt of Montelukast using hydrocarbon solvents like toluene, hexanes, heptane or keto solvents like acetone or mixture of them.
6. Converting the Organic amine salt of Montelukast compound of formula (IV) into its sodium salt of Formula (I) using sodium methoxide in methanol at a temperature of 20-40°C for 1-2 hours, preferably at a temperature of 25-35°C for 60 minutes under inert atmosphere.

The processes described in the present invention were demonstrated in examples illustrated below. These examples are provided as illustration only and therefore should not be construed as limitation of the scope of the invention. Examples

A solution of dimethylsulfoxide (400 ml) and sodium methoxide solution (200 ml) in methanol is cooled to -5 to 0°C under nitrogen atmosphere. Added l-(mercapto methyl) cyclo propane acetic acid (35 gr) compound of formula (III) under nitrogen atmosphere. Stirred the reaction mixture for 60 minutes at -5 to 0°C. Added 100 gr of (S) Benzenepropanol α-[3-[2-(7-chloro-2-quinolinyl) ethenyl]phenyl]-2-(l-hydroxy-1-methyl ethyl)-α-methane sulfonate compound of formula (II) to the reaction mixture at -5-0°C. Stirred the reaction mixture at -5 to 5°C for 10 hours. Added the reaction mixture to 3000 ml of chilled Water. Stirred the reaction mixture at 10-20°C for 30 minutes. Slowly added sodium hydroxide solution at 10-20°C. Washed the reaction mixture with toluene and removed the toluene layer. Cooled the aqueous layer to 10-20°C and slowly added 50% acetic acid solution. Extracted the reaction mixture with ethylacetate, washed the total organic layer with water and concentrated the organic layer at below 55°C under reduced pressure. Added 500 ml of ethylacetate to the above obtained crude at 25-35°C and stirred for 45 minutes under nitrogen atmosphere. Added 55 ml of dicyclohexylamine at 25-35°C. Stirred the reaction mixture for 10 hours. Filtered the solid and washed with ethylacetate under nitrogen atmosphere. Wet material taken into a mixture of 500 ml of toluene and 500 ml of hexenes and heated to 55-65°C, stirred for 60 minutes. Cooled the mass to 25-35°C and stirred for 8 hours. Separated the solid by filtration. Dried the compound at 40-60°C to get title compound. Yield : 80 gr.

A solution of dimethylsulfoxide (400 ml) and sodium methoxide solution (200 ml) in methanol is cooled to -5 to 0°C under nitrogen atmosphere. Added l-(mercapto methyl) cyclo propane acetic acid (35 gr) compound of formula (III) under nitrogen atmosphere. Stirred the reaction mixture for 60 minutes at -5 to 0°C. Added 100 gr of (S) Benzenepropanol α-[3-[2-(7-chloro-2-quinolinyl) ethenyl]phenyl]-2-(l-hydroxy-1-methyl ethyl)-α-methane sulfonate compound of formula (II) to the reaction mixture at -5-0°C. Stirred the reaction mixture at -5 to 5°C for 10 hours. Added the reaction mixture to 3000 ml of chilled Water. Stirred the reaction mixture at 10-20°C for 30 minutes. Slowly added sodium hydroxide solution at 10-20°C. Washed the reaction mixture with toluene and removed the toluene layer. Cooled the aqueous layer to 10-20°C and slowly added 50% acetic acid solution. Extracted the reaction mixture with ethylacetate, washed the total organic layer with water and concentrated the organic layer at below 55°C under reduced pressure. Added 500 ml of acetone to the above obtained crude at 25-35°C and stirred for 45 minutes under nitrogen atmosphere. Added 55 ml of dicyclohexylamine at 25-35°C. Stirred the reaction mixture for 10 hours. Filtered the solid and washed with acetone under nitrogen atmosphere. Dried the compound at 40-60°C to get title compound. Yield : 80 gr.

A solution of dimethylsulfoxide (400 ml) and sodium methoxide solution (200 ml) in methanol is cooled to -5 to 0°C under nitrogen atmosphere. Added l-(mercapto methyl) cyclo propane acetic acid (35 gr) compound of formula (III) under nitrogen atmosphere. Stirred the reaction mixture for 60 minutes at -5 to 0°C. Added 100 gr of (S) Benzenepropanol α-[3-[2-(7-chloro-2-quinolinyl) ethenyl]phenyl]-2-(l-hydroxy-1-methyl ethyl)-α-methane sulfonate compound of formula (II) to the reaction mixture at -5-0°C. Stirred the reaction mixture at -5 to 5°C for 10 hours. Added the reaction mixture to 3000 ml of chilled Water. Stirred the reaction mixture at 10-20°C for 30 minutes. Slowly added sodium hydroxide solution at 10-20°C. Washed the reaction mixture with toluene and removed the toluene layer. Cooled the aqueous layer to 10-20°C and slowly added 50% acetic acid solution. Extracted the reaction mixture with ethylacetate, washed the total organic layer with water and concentrated the organic layer at below 55°C under reduced pressure. Added 500 ml of acetone to the above obtained crude at 25-3 5°C and stirred for 45 minutes under nitrogen atmosphere. Added 15 gr of tertiary butyl amine at 25-35°C. Stirred the reaction mixture for 10 hours. Filtered the solid and washed with acetone under nitrogen atmosphere. Dried the compound at 40-60°C to get title compound. Yield : 70 gr.

A solution of dimethylsulfoxide (400 ml) and sodium methoxide solution (200 ml) in methanol is cooled to -5 to 0°C under nitrogen atmosphere. Added l-(mercapto methyl) cyclo propane acetic acid methyl ester compound of formula (V) (45 gr) compound of formula (III) under nitrogen atmosphere. Stirred the reaction mixture for 60 minutes at -5 to 0°C. Added 100 gr of (S) Benzenepropanol α-[3-[2-(7-chloro-2-quinolinyl) ethenyl]phenyl]-2-(l-hydroxy-1 -methyl ethyl)-α-methane sulfonate compound of formula (II) in DMSO (dimethyl sulfoxide) to the reaction mixture at -5-0°C. Stirred the reaction mixture at -5 to 5°C for 10 hours. Added the reaction mixture to 1000 ml of chilled Water. Stirred the reaction mixture at 10-20°C for 30 minutes. Extracted the reaction mixture with toluene. Concentrated the toluene layer completely and added toluene to the residue. Added sodium hydroxide solution and stirred at a temperature of about 40 to 50°C for 15 hours. Washed the reaction mixture with toluene and removed the toluene layer. Cooled the aqueous layer to 10-20°C and slowly added 50% acetic acid solution. Extracted the reaction mixture with ethylacetate, washed the total organic layer with water and concentrated the organic layer at below 55°C under reduced pressure. Added 500 ml of acetone to the above obtained crude at 25-35°C and stirred for 45 minutes under nitrogen atmosphere. Added 55 ml of dicyclohexylamine at 25-35°C. Stirred the reaction mixture for 10 hours. Filtered the solid and washed with acetone under nitrogen atmosphere. Dried the compound at 40-60°C to get title compound. Yield : 80 gr.

A solution of dimethylsulfoxide (400 ml) and sodium methoxide solution (200 ml) in methanol is cooled to -5 to 0°C under nitrogen atmosphere. Added l-(mercapto methyl) cyclo propane acetonitrile compound of formula (VII) (25 gr) compound of formula (III) under nitrogen atmosphere. Stirred the reaction mixture for 60 minutes at -5 to 0°C. Added 100 gr of (S) Benzenepropanol α-[3-[2-(7-chloro-2-quinolinyl) ethenyl]phenyl]-2-(l-hydroxy-1-methyl ethyl)-α-methane sulfonate compound of formula (II) in DMSO (dimethyl sulfoxide) to the reaction mixture at -5-0°C. Stirred the reaction mixture at -5 to 5°C for 10 hours. Added the reaction mixture to 1000 ml of chilled Water. Stirred the reaction mixture at 10-20°C for 30 minutes. Extracted the reaction mixture with toluene. Concentrated the toluene layer completely and added toluene to the residue. Added caustic lye solution and stirred at a temperature of 125°C for 15 hours. Washed the reaction mixture with toluene and removed the toluene layer. Cooled the aqueous layer to 10-20°C and slowly added 50% acetic acid solution. Extracted the reaction mixture with ethylacetate, washed the total organic layer with water and concentrated the organic layer at below 55°C under reduced pressure. Added 500 ml of acetone to the above obtained crude at 25-35°C and stirred for 45 minutes under nitrogen atmosphere. Added 55 ml of dicyclohexylamine at 25-35°C. Stirred the reaction mixture for 10 hours. Filtered the solid and washed with acetone under nitrogen atmosphere. Dried the compound at 40-60°C to get title compound. Yield : 65 gr.

A solution of dimethylsulfoxide (400 ml) and cesium carbonate (120 gr) in methanol (200 ml) is cooled to -5 to 0°C under nitrogen atmosphere. Added l-(mercapto methyl) cyclo propane acetic acid (35 gr) compound of formula (III) under nitrogen atmosphere. Stirred the reaction mixture for 60 minutes at -5 to 0°C. Added 100 gr of (S) Benzenepropanol, α-[3-[2-(7-chloro-2-quinolinyl) ethenyl]phenyl]-2-(l -hydroxy-1-methyl ethyl)-, α-methane sulfonate compound of formula (II) to the reaction mixture at -5-0°C. Stirred the reaction mixture at -5 to 5°C for 10 hours. Added the reaction mixture to 3000 ml of chilled Water. Stirred the reaction mixture at 10-20°C for 30 minutes. Slowly added sodium hydroxide solution at 10-20°C. Washed the reaction mixture with toluene and removed the toluene layer. Cooled the aqueous layer to 10-20°C and slowly added 50% acetic acid solution. Extracted the reaction mixture with ethylacetate, washed the total organic layer with water and concentrated the organic layer at below 55°C under reduced pressure. Added 500 ml of acetone to the above obtained crude at 25-3 5°C and stirred for 45 minutes under nitrogen atmosphere. Added 55 ml of dicyclohexylamine at 25-35°C. Stirred the reaction mixture for 10 hours. Filtered the solid and washed with acetone under nitrogen atmosphere. Dried the compound at 40-60°C to get title compound. Yield : 100 gr.

Added dicyclohexyl amine salt of [R-(E)-l[[[l-[3-[2-[7-chloro-2-quinolinyl]ethenyl]phenyl]-3-[2-( 1 -hydroxy-1 -
methylethyl)phenyl]propyl]thio]methyl]cyclopropaneacetic acid compound of formula (IV) (100 gr) prepared as per the procedures given in examples 1,2,4,5 & 6 to a solution of sodium methoxide (23 gr) and methanol (210 ml) at 25-35°C. Stirred for 60 minutes at 25-35°C. Washed the reaction mixture with hexanes. Distilled the solvent completely under reduced pressure at below 55°C. Added toluene to the crude and slowly added the toluene layer to heptane at 25-35°C under nitrogen atmosphere. Stirred the mass for 45 minutes under nitrogen atmosphere. Separated the solid by filtration and washed with heptane. Dried the compound at 60-70°C under reduced pressure to get title compound. Yield 70 gr.

Added tertiary butyl amine salt of [R-(E)-l[[[l-[3-[2-[7-chloro-2-quinolinyl]ethenyl]phenyl]-3-[2-(l-hydroxy-l-
methylethyl)phenyl]propyl]thio]methyl]cyclopropaneacetic acid compound of formula (IV) (100 gr) prepared as per the procedures given in examples 3, to a solution of sodium methoxide (22 gr) and methanol (210 ml) at 25-35°C. Stirred for 60 minutes at 25-35°C. Washed the reaction mixture with hexanes. Distilled the solvent completely under reduced pressure at below 55°C. Added toluene to the crude and slowly added the toluene layer to heptane at 25-35°C under nitrogen atmosphere. Stirred the mass for 45 minutes under nitrogen atmosphere. Separated the solid by filtration and washed with heptane. Dried the compound at 60-70°C under reduced pressure to get title compound. Yield 70
gr.

We Claim :
1. Process for the preparation of Montelukast sodium compound of formula (I)

Which comprises of;
a) Reacting (S) Benzenepropanol a -[3-[2-(7-chloro-2-quinolinyl) ethenyl]phenyl]-2-(l-hydroxy-1-methyl ethyl)-a-methane sulfonate compound of formula (II) with 1-(Mercapto methyl) cyclo propane acetic acid compound of formula (III) in presence of polar aprotic solvents like dimethylsulfoxide/dimethyl formamide,dimethyl acetamide and strong base like alkali or alkaline earth metal alkoxides i.e,. potassium tertiary butoxide, sodium methoxide, sodium ethoxide in a suitable solvent or mixture of solvents selected from C1-C4 alcoholic solvents like methanol, ethanol, propanol, butanol, preferably sodium methoxide in a mixture of methanol and DMSO (dimethylsulfoxide) at a temperature of -20 to 0°C for 5 to 20 hours, preferably at a temperature of about -5 to 5°C for 8-10 hours,
b) Quenching the reaction mixture with water and adding sodium hydroxide solution to the reaction mixture and then extracting with water immiscible solvents like hydrocarbon solvents, chloro solvents, ester solvents, preferably hydrocarbon solvents more preferably toluene to remove impurities,
c) Lowering pH of the reaction mixture with acetic acid then extracting the Montelukast with ester solvents, chloro solvents preferably ester solvents more preferably ethylacetate. Concentrating the solvent and diluting with a suitable solvent selected from keto solvents like acetone, butanone or ester solvents like ethylacetate, propyl acetate, preferably acetone and ethylacetate,

d) Treating the product obtained from step c. with an organic amine having general
formula R-NH2 (i.e,. organic amine like cyclic amines such as cyclo propyl amine,
cyclo pentyl amine, cyclo hexyl amine, dicyclohexyl amine, pyrrolidine or
morpholine or alkyl amines such as methyl amine, isopropyl amine, disiopropyl
amine, tert-butyl amine, n-octyl glucamine or aryl amines such as phenyl ethyl amine,
phenyl propyl amine) at a temperature of 20-40°C for 5-15 hours, preferably at a
temperature of about 25-35°C for 8-10 hours under inert atmosphere to give a
respective salt of compound of formula (IV),
e) Optionally purifying the corresponding amine salt of Montelukast using hydrocarbon
solvents like toluene, hexanes, heptane or keto solvents like acetone or mixture of
them,
f) Converting the Organic amine salt of Montelukast compound of formula (IV) into its
sodium salt of Formula (I) using sodium methoxide in methanol at a temperature of
20-40°C for 1-2 hours, preferably at a temperature of 25-35°C for 60 minutes under
inert atmosphere.

Which comprises of;
a) Reacting the organic amine salt of Montelukast compound of formula (IV) with a sodium source in methanol.

b) Removing the organic amine by extracting the mass with solvents which are
immiscible with methanol like hexanes, heptane and concentrating the methanol.
c) Dissolving the product obtained from step b. in toluene and saturating the toluene
with heptane to give Montelukast sodium compound of formula (I).

Which comprises of;
a) Reacting (S) Benzenepropanol, a -[3-[2-(7-chloro-2-quinolinyl) ethenyl]phenyl]-
2-(l-hydroxy-1-methyl ethyl)-, a -methane sulfonate compound of formula (II)
with 1-mercapto methyl cyclopropane methyl ester compound of formula (V) or
1-mercapto methyl cyclopropane acetonitrile compound of formula (VII) in
presence of polar aprotic solvent and strong base like alkali or alkaline earth metal
alkoxides i.e,. potassium tertiary butoxide, sodium methoxide, sodium ethoxide in
a suitable solvent or mixture of solvents like C1-C4 alcohol preferably sodium
methoxide in DMSO/Methanol at a temperature of -20 to 0°C for 5 to 20 hours,
preferably at a temperature of about -5 to 5°C for 8-10 hours,
b) Optionally isolating the compounds of formula (VI)/compound of formula (VIII)
or in situ hydrolyzing the compound with inorganic base like alkali metal
hydroxide in a suitable solvent selected from C1-C4 alcohol, preferably methanol
at a temperature of 10-70°C for 10-20 hours, preferably at a temperature of 40-
50°C for 15 hours,

c) Treating the product obtained from step b. with an organic amine compound of general formula R-NH2 (wherein R is dicyclohexyl amine, tertiary butyl amine, isopropyl amine) in a suitable solvent selected from keto solvents like acetone, butanone or ester solvents like ethyl acetate, propyl acetate, preferably acetone and ethylacetate gives corresponding Montelukast amine salt compound of formula (IV) at a temperature of 20-40°C for 5-15 hours, preferably at a temperature of about 25-35°C for 8-10 hours under inert atmosphere to give a respective salt of compound of formula (IV),
d) Optionally purifying the corresponding amine salt of Montelukast using hydrocarbon solvents like toluene, hexanes, heptane or keto solvents like acetone or mixture of them,
e) Converting the Organic amine salt of Montelukast compound of formula (IV) into
its sodium salt of Formula (I) using sodium methoxide in methanol at a
temperature of 20-40°C for 1-2 hours, preferably at a temperature of 25-35°C for
60 minutes under inert atmosphere.

Which comprises of;
a) Reacting (S)Benzenepropanol a -[3-[2-(7-chloro-2-quinolinyl) ethenyl]phenyl]-2-(l-hydroxy-1-methyl ethyl)-a-methane sulfonate compound of formula (II) with 1-(mercapto methyl) cyclopropane acetic acid compound of formula (III) or 1-(mercapto methyl) cyclopropane acetic acid methyl ester compound of formula (V) or

1 -(mercapto methyl) cyclopropane acetonitrlle compound of formula (VII) in presence of polar aprotic solvent and cesuim carbonate in a suitable solvent or mixture of solvents like C1-C4 alcohol preferably cesuim carbonate in DMSO/Methanol at a temperature of -20 to 0°C for 5 to 20 hours, preferably at a temperature of about -5 to 5°C for 8-10 hours,
b) Quenching the reaction mixture with water and adding sodium hydroxide solution to the reaction mixture and then extracting with water immiscible solvents like hydrocarbon solvents, chloro solvents, ester solvents, preferably hydrocarbon solvents more preferably toluene to remove impurities,
c) Lowering pH of the reaction mixture with acetic acid then extracting the Montelukast with ester solvents, chloro solvents preferably ester solvents more preferably ethylacetate. Concentrating the solvent and diluting with a suitable solvent selected from keto solvents like acetone, butanone or ester solvents like ethylacetate, propyl acetate, preferably acetone and ethylacetate,
d) Treating the product obtained from step c. with an organic amine compound of general formula R-NH2 (wherein R is dicyclohexyl amine, tertiary butyl amine, isopropyl amine) in a suitable solvent selected from keto solvents like acetone, butanone or ester solvents like ethyl acetate, propyl acetate, preferably acetone and ethylacetate gives corresponding Montelukast amine salt compound of formula (IV) at a temperature of 20-40°C for 5-15 hours, preferably at a temperature of about 25-35°C for 8-10 hours under inert atmosphere to give a respective salt of compound of formula (IV),
e) Optionally purifying the corresponding amine salt of Montelukast using hydrocarbon solvents like toluene, hexanes, heptane or keto solvents like acetone or mixture of them,
f) Converting the Organic amine salt of Montelukast compound of formula (IV) into its sodium salt of Formula (I) using sodium methoxide in methanol at a temperature of 20-40°C for 1-2 hours, preferably at a temperature of 25-35°C for 60 minutes under inert atmosphere.

5. Usage of polar aprotic solvents like dimethyl sulfoxide, dimethylacetamide, with
strong base like alkali or alkaline earth metal alkoxide i.e, sodium methoxide,
potassium tertiary butoxide, sodium ethoxide according to claim la) and 3 a) with or
without combination of C1-C4 alcoholic solvents, for the reaction of (S)
Benzenepropanol a -[3-[2-(7-chloro-2-quinolinyl) ethenyl]phenyl]-2-(l-hydroxy-1-
methyl ethyl)-a-methane sulfonate with l-(mercapto methyl) cyclopropane acetic
acid or l-(mercapto methyl) cyclopropane acetic acid methyl ester or l-(mercapto
methyl) cyclopropane acetonitrile.
6. Water immiscible solvent used for extracting the reaction mixture to remove impurities according to claim 1 b) is toluene.
7. Water immiscible solvent used for extracting the reaction mixture to remove impurities according to claim 1 b) is heptane.
8. Sodium source for the convertion of organic amine salt of Montelukast compound of
formula (IV) to Montelukast sodium compound of formula (I) according to claim 2 a)
is sodium methoxide.
9. Removing the organic amine salt by extracting the reaction mixture with methanol
immiscible solvent according to claim 2 b) is hexanes.
10.Usage of alkali or alkaline carbonate like cesium carbonate with polar aprotic solvent like dimethyl sulfoxide, dimethyl acetamide with or without combination of C1-C4 alcoholic solvents according to claim 4 a) for the reaction of (S) Benzenepropanol a -[3-[2-(7-chloro-2-quinolinyl) ethenyl]phenyl]-2-(l-hydroxy-1-methyl ethyl)-a-methane sulfonate with l-(mercapto methyl) cyclopropane acetic acid or l-(mercapto methyl) cyclopropane acetic acid methyl ester or l-(mercapto methyl) cyclopropane acetonitrile.

Documents:

1818-CHE-2005 AMENDED CLAIMS 09-11-2011.pdf

1818-CHE-2005 AMENDED PAGES OF SPECIFICATION 09-11-2011.pdf

1818-CHE-2005 FORM-3 09-11-2011.pdf

1818-CHE-2005 FORM-3 17-08-2012.pdf

1818-CHE-2005 CORRESPONDENCE OTHERS 17-08-2012.pdf

1818-CHE-2005 EXAMINATION REPORT REPLY RECEIVED 09-11-2011.pdf

1818-che-2005-abstract.pdf

1818-che-2005-claims.pdf

1818-che-2005-correspondnece-others.pdf

1818-che-2005-description(complete).pdf

1818-che-2005-form 1.pdf

1818-che-2005-form 3.pdf

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Patent Number

254818

Indian Patent Application Number

1818/CHE/2005

PG Journal Number

52/2012

Publication Date

28-Dec-2012

Grant Date

21-Dec-2012

Date of Filing

13-Dec-2005

Name of Patentee

MSN LABORATORIES LIMITED

Applicant Address

MSN LABORATORIES LIMITED FACTORY SY NO 317 & 323 RUDRARAM VIL PATANCHERU MDL MEDAK DIST ANDHRA PRADESH 502329

Inventors:

#	Inventor's Name	Inventor's Address
1	DR MANNE SATYANARAYANA REDDY	DR MANNE SATYANARAYANA REDDY CHAIRMAN AND MANAGING DIRECTOR MSN LABORATORIES LIMITED FACTORY SY NO 317 & 323 RUDRARAM VIL PATANCHERU MDL MEDAK DIST ANDHRA PRADESH 502329
2	MUPPA KISHORE KUMAR	MUPPA KISHORE KUMAR LIG 34 DHARMAREDDY COLONY PHASE 1 NEAR JNTUC HYDERABAD 500072 ANDHRA PRADESH
3	SRINIVASAN THIRUMALAI RAJAN	SRINIVASAN THIRUMALAI RAJAN PLOT NO 12&13 LAKE VIEW ENCLAVE MIYAPUR HYDERABAD 500 049
4	KARAMAL RAMA SUBBA REDDY	KARAMALA RAMA SUBBA REDDY REDDIPALLI V VELLATUR POST PENDLIMARRI MONDAL KADAPA DIST 516216 ANDHRA PRADESH

PCT International Classification Number

A61K 31/47

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA