Process for the preparation of Sodium salt of l-(((l(R)-(3-(2-(7-chloro-2- quinolinyl)-ethenyl)phenyl)-3-(2-(l-hydroxy-l- methylethyl)phenyl)propyl)sulfanyl)methyl)cyclopropaneacetic acid

The subject matter of the invention is a novel method for the preparation of sodium salt of l-(((l(R)-(3-(2-(7-chloro-2-quinolinyl)-ethenyl)ρhenyl)-3-( 2-(l- hydroxy- 1 -methyl ethyl)phenyl)propyl)sulfanyl)methyl)cyclopropaneacetic acid used as an active ingredient in the manufacture of an antiasthmatic medicinal product. l-(((l(R)-(3-(2-(7-chloro-2-quinolinyl)-ethenyl)phenyl)-3-(2 -(l-hydroxy-l- methylethyl)phenyl)propyl)sulfanyl)methyl)cyclopropaneacetic acid known under the international non-proprietary name (INN) of Montelukast is indicated for the treatment of asthmatic and allergic diseases. The Montelucast-acid was disclosed in patent description EP 0 480 717 Bl.

Disclosed methods for the preparation of sodium salt of l-(((l(R)-(3-(2-(7- chloro-2-quinolinyl)-ethenyl)phenyl)-3-(2-(l-hydroxy-l-methy lethyl) phenyl)propyl)sulfanyl)methyl)-cyclopropaneacetic acid consist mainly in the preparation and isolation of crystalline l-(((l(R)-(3-(2-(7-chloro- 2- quinolinyl) - ethenyl) phenyl) 3 (2-(l -hydroxy- 1 -methyl ethyl) phenyl) propyl)sulfanyl)methyl)-cyclopropaneacetic acid and its conversion into the sodium salt. A method for the synthesis of sodium salt of l-(((l(R)-(3-(2-(7-chloro-2- qumolinyl)-ethenyl)phenyl)-3-(2-(l -hydroxy- 1 -methylethyl)phenyl)propyl) sulfanyl)methyl)-cyclopropaneacetic acid involving the isolation of crystalline 2- (2-(3(S)-(3-(2-(7-chloro-2-quinolinyl)-ethenyl)phenyl)-3-(hy droxypropyl) phenyl)- 2-propanol methanesulfonate was disclosed in European patent description EP 0737186 Bl. Furthermore, the crystalline form of sodium salt of l-(((l(R)-(3-(2-(7-

chloro-2-quinolinyl)-ethenyl)phenyl)-3-(2-(l-hydroxy-l-me thylethyl) phenyl)propyl)sulfanyl)methyl)-cyclopropaneacetic acid was disclosed. The disclosed method for the preparation of Montelukast sodium involves the nucleophilic substitution reaction of the methanesulfonyl group in the methanesulfonate using [l-(sulfanylmethyl)cyclopropyl] acetic acid dilithium salt. The dilithium salt is previously obtained through the reaction of two butyllithium equivalents on [l-(sulfanylmethyl)cyclopropyl] acetic acid, and the methylsulfonate forms in the reaction of methanesulfonyl chloride with 2-(2-(3(S)-(3-(2-(7-chloro- 2-quinolinyl)-ethenyl)phenyl)-3-(hydroxypropyl)phenyl)-2-pro panol in the presence of diisopropylethylamine. To isolate the crystalline methanesulfonate, the fact that it is slightly soluble in acetonitrile is exploited, and the waste diisopropylethylamine hydrochloride remains dissolved in methanesulfonate filtrates. The reaction mixture is acidified and Montelukast is extracted to the solvent as an acid to be purified by the crystallization of the dicyclohexylamine salt thereof. The obtained salt is converted back into the Montelucast-acid and the acid subsequently into the crystalline sodium salt.

In the international patent application WO 2006/043846 is disclosed the reaction [l-(sulfanylmethyl)cyclopropyl] acetic acid disodium salt with the methanesulfonate, wherein the disodium salt is formed using sodium tert- butanolate, and Montelukast is isolated as a crystalline tert-butylamine salt. The salt of Montelukast with tert-butylamine may be employed in the preparation of high-purity free 1 -(((1 (R)-(3-(2-(7-chloro-2-quinolinyl)-ethenyl)phenyl)-3-(2-(l - hydroxy- 1 -methylethyl)phenyl)propyl)sulfanyl)methyl)-cyclopropaneacet ic acid and/or sodium salt thereof. According to international patent application WO 2006/043846 the free l-(((l(R)-(3-(2-(7-chloro-2-quinolinyl)-ethenyl)phenyl) -3- (2-(l -hydroxy-1 -methylethyl)phenyl)propyl)sulfanyl)methyl)cyclopropaneaceti c acid is isolated in the crystalline form and may be recrystallised from a lower alcohol if needed.

International publication WO 2005/074935 describes the polymorphic forms of l-(((l(R)-(3-(2-(7-chloro-2-quinolinyl)-ethenyl)phenyl)-3-(2 -(l-hydroxy-l- methyl ethyl)phenyl)propyl)sulfanyl)methyl)cyclopropaneacetic acid.

The issues of the polymorphism of sodium salt of 1 -((( 1 (R)-(3 -(2-(7-chloro-

2-quinolinyl)-ethenyl)phenyl)-3-(2-(l-hydroxy-l-methyleth yl) phenyl)propyl)sulfanyl)methyl) cyclopropaneacetic acid were described in international patent application WO 2005/075427.

The 2-(2-(3(S)-(3-(2-(7-chloro-2-quinolinyl)-ethenyl)phenyl)-3- (hydroxypropyl)phenyl)-2-propanol methanesulfonate described above is very unstable, especially if isolated in the solid form. At temperatures above -10°C and in the presence of the side diisopropylethylamine hydrochloride the resulting methanesulfonate undergoes irreversible intramolecular substitution which yields a cyclic ether. Furthermore, the methanesulfonate must be filtered and stored at very low temperatures, which restricts the application of the crystalline methanesulfonate in the industrial scale. Therefore, it proved advantageous to develop a Montelukast synthesis method in which the crystalline methanesulfonate does not have to be isolated, which is the subject matter of the present invention.

The present invention provides a new method for the preparation of sodium salt of 1 -(((1 (R)-(3 -(2-(7-chloro-2-quinolinyl)-ethenyl)phenyl)-3 -(2-(I -hydroxy- 1 - methylethyl)phenyl)propyl)sulfanyl)methyl)cyclopropaneacetic acid wherein the crystalline forms of methanesulfonate and Montelukast-acid are not isolated, which ensures that the reaction proceeds with high yield and obtain a product with high pharmaceutical purity.

This was accomplished through the preparation of salt of l-(((l(R)-(3-(2-(7- chloro-2-quinolinyl)-ethenyl)phenyl)-3 -(2-( 1 -hydroxy- 1 - methylethyl)phenyl)propyl)sulfanyl)methyl)cyclopropaneacetic acid with tert- butylamine, disclosed in international patent application WO 2006/043846, its purification to achieve pharmaceutical purity and conversion into the amorphous form of Montelukast sodium salt. The following crystalline intermediates are not isolated: 2-(2-(3(S)-(3-(2-(7-chloro-2-quinolinyl)-ethenyl)phenyl)-3-

(hydroxypropyl)phenyl)-2-propanol methanesulfonate (methanesulfonate) and/or free 1 -(((1 (R)-(3 -(2-(7-chloro-2-quinolinyl)-emenyl)phenyl)-3 -(2-(I -hydroxy- 1 - methyl ethyl)phenyl)propyl)sulfanyl)methyl)cyclopropaneacetic acid.

The method according to the present invention consists in that the process for the preparation of l-(((l(R)-(3-(2-(7-chloro-2-quinolinyl)-ethenyl)phenyl)-3-(2 -(l- hydroxy- 1 -methylethyl) phenyl)propyl)sulfanyl)methyl)cyclopropaneacetic acid sodium salt involves the reaction of 2-(2-(3(S)-(3-(2-(7-chloro-2-quinolinyl)- ethenyl)phenyl)-3 -(hydroxypropyl)phenyl)-2-propanol with methanesulfonyl chloride in the presence of a suitable tertiary amine which forms a hydrochloride insoluble in the reaction solvent. The approtiate solvents such as N ₅ N- dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, tetrahydrofurane and N-methylpyrrolidone is used. The mixture after mesylation is filtered to separate the unfavourable tertiary amine hydrochloride, and the filtrate, crude 2-(2- (3(S)-(3-(2-(7-chloro-2-quinolinyl)-ethenyl)phenyl)-3-(hydro xypropyl)phenyl)-2- propanol methanesulfonate solution, is added to the previously prepared [1- (sulfanylmethyl)cyclopropyl]acetic acid disodium salt. Thus, the possibility of the decomposition of the methanesulfonate during the isolation is eliminated, and the yield of Montelukast synthesis remains comparable to those disclosed in the aforementioned patent applications. Subsequently, l-(((l(R)-(3-(2-(7-chloro-2- quinolinyl)-ethenyl)phenyl)-3 -(2-(I -hydroxy- 1 -methylethyl)phenyl)propyl) sulfanyl)methyl)cyclopropaneacetic acid solution is isolated from the reaction mixture. From the solution crystalline salt l-(((l(R)-(3-(2-(7-chloro-2-quinolinyl)- ethenyl)phenyl)-3 -(2-(I -hydroxy- 1 -methyl ethyl)phenyl)propyl)sulfanyl)methyl) cyclopropaneacetic acid with tert-butylamine is isolated. The resulting salt is purified until a salt with high pharmaceutical purity is obtained, which is converted into the amorphous form of sodium salt of l-(((l(R)-(3-(2-(7-chloro-2-quinolinyl)- ethenyl)phenyl)-3 -(2-(I -hydroxy- 1 -methylethyl)phenyl)propyl)sulfanyl)methyl) cyclopropaneacetic acid. As the tertiary amine used is triethylamine. The method for preparing salt of l-(((l(R)-(3-(2-(7-chloro-2-quinolinyl)- ethenyl)phenyl)-3 -(2-( 1 -hydroxy- 1 -methyl ethyl)phenyl)propyl)sulfanyl)methyl)- cyclopropaneacetic acid with tert-butylamine according to the present invention consists in that compound of a 2-(2-(3(S)-(3-(2-(7-chloro-2-quinolinyl)- ethenyl)phenyl)-3 -(hydro xypropyl)phenyl)-2-propanol is reacted with the methanesulfonate chloride in the presence of a tertiary amine. From the resulting

crude 2-(2-(3(S)-(3-(2-(7-chloro-2-quinolinyl)-ethenyl)phenyl)-3-

(hydroxypropyl)phenyl)-2-propanol methanesulfonate solution the precipitated amine hydrochloride is filtered off, after that the solution is directly reacted with [l-(sulfanylmethyl)cyclopropyl] acetic acid disodium salt of Formula 3. From the resulting reaction mixture l-(((l(R)-(3-(2-(7-chloro-2-quinolinyl)-ethenyl)phenyl)- 3-(2-(l -hydroxy- 1 -methylethyl)phenyl)propyl)sulfanyl)methyl) cyclopropaneacetic acid is isolated, from which the crystalline salt l-(((l(R)-(3-(2-(7-chloro-2- quinolinyl)-ethenyl)phenyl)-3-(2-(l-hydroxy-l-methylethyl)ph enyl)propyl)- sulfanyl)methyl)cyclopropaneacetic acid with tert-butylamine is subsequently isolated. The salt is purified to obtain high pharmaceutical purity. As the tertiary amine used is triethylamine.

The method for purifying salt of l-(((l(R)-(3-(2-(7-chloro-2-quinolinyl)- ethenyl)phenyl)-3 -(2-(I -hydroxy- 1 -methylethyl)phenyl)propyl)sulfanyl)methyl)- cyclopropaneacetic acid with tert-butylamine according to the present invention consists in that salt of l-(((l(R)-(3-(2-(7-chloro-2-quinolinyl)-ethenyl)phenyl)-3- (2-(l-hydroxy-l-methylethyl)phenyl)propyl)sulfanyl)methyl)cy clopropaneacetic acid with tert-butylamine is converted into the solution of free l-(((l(R)-(3-(2-(7- chloro-2-quinolinyl)-ethenyl)phenyl)-3 -(2-( 1 -hydroxy- 1 - methylethyl)phenyl)propyl)sulfanyl)methyl)-cyclopropaneaceti c acid using an organic acid in the toluene/methanol/water system; the methanol/water phase, which contains some of the impurities, is discarded, and the solution of free 1- ((( 1 (R)-(3-(2-(7-chloro-2-quinolinyl)-ethenyl)phenyl)-3 -(2-(I -hydroxy- 1 - methylethyl)phenyl)propyl)sulfanyl)methyl)cyclopropaneacetic acid is reacted with tert-butylamine toluene solution and crystallised again as the salt with tert- butylamine.

The method for the preparation of a pharmaceutically acceptable salt of 1- (((l(R)-(3-(2-(7-chloro-2-quinolinyl)-ethenyl)ρhenyl)-3 -(2-(I -hydroxy- 1- methylethyl)phenyl)propyl)sulfanyl)methyl)cyclopropaneacetic acid according to the present invention consists in that a compound of 2-(2-(3(S)-(3-(2-(7-chloro-2-

quinolinyl)-ethenyl)phenyl)-3-(hydroxypropyl)phenyl)-2-pr opanol is reacted with methanesulfonyl chloride in the presence of a tertiary amine.

From the resulting crude 2-(2-(3(S)-(3-(2-(7-chloro-2-quinolinyl)-ethenyl)phenyl)-

3-(hydroxypropyl)phenyl)-2-propanol methanesulfonate solution the precipitated amine hydrochloride is filtered off, and the solution is directly undergone reaction with [l-(sulfanylmethyl)cyclopropyl] acetic acid disodium salt of Formula 3. From the resulting reaction mixture l-(((l(R)-(3-(2-(7-chloro-2-quinolinyl)- ethenyl)phenyl)-3-(2-(l -hydroxy- 1 -methylethyl) phenyl)propyl)sulfanyl)methyl)cyclopropaneacetic acid is isolated, from which the crystalline form of a pharmaceutically acceptable salt of l-(((l(R)-(3-(2-(7-chloro- 2-quinolinyl)-ethenyl)phenyl)-3 -(2-(I -hydroxy- 1 - methylethyl)phenyl)propyl)sulfanyl)methyl)cyclopropaneacetic acid is isolated.

The salt is purified until to obtain high pharmaceutical purity. As the tertiary amine used is triethylamine.

The pharmaceutically acceptable salts are described in Polish patent application

P. 370850.

A prior art for the method for the isolation of crystalline l-(((l(R)-(3-(2-(7- chloro-2-quinolinyl)-ethenyl)phenyl)-3-(2-(l-hydroxy-l-methy lethyl)- phenyl)propyl)sulfanyl)methyl)-cyclopropaneacetic acid and its crystalline sodium salt involves the preparation of high purity tert-butylamine salt thereof. The salt with tert-butylamine is recrystallised from solvents, such as toluene, toluene/acetonitrile, toluene/isopropanol, toluene/ethanol, acetonitrile/water or ethyl acetate. However, the recrystallisation of the salt not always ensures that impurities are efficiently removed and brought to an adequate level.

This has been accomplished by converting Montelukast tert-butylamine salt into the free acid using acetic acid in the toluene/methanol/water system. The methanol/water phase, which contains some of the impurities, is discarded and solution of Montelukast free acid in toluene is treated with tert-butylamine and crystallised again as the tert-butylamine salt. The addition of a lower alcohol yields

higher purity of the salt formed after crystallisation. The above purification procedure is repeated until the salt purity is satisfactory. Purification yield is close to 90%. l-(mercaptomethyl)cyclopropaneacetic acid disodium salt of Formula 3 is obtained in the direct reaction between 1 -(mercaptomethyl)cyclopropaneacetic acid and sodium tert-butanolate in the molar ratio of 1:2. As the solvent selected is N,N-dimethylformamide containing no more than 0.1% water. The same solvent is used in the preparation of methanesulfonate and Montelukast synthesis. The appropriate solvents also include N,N-dimethylformamide, dimethyl sulfoxide, tetrahydrofurane and N-methylpyrrolidone. The same solvent is preferably used both in the mesylation stage and in the coupling of mesylate with mercaptide. To the sodium tert-butanolate solution in N,N-dimethylformamide [1- (sulfanylmethyl)cyclopropyl] acetic acid (solid or in N,N-dimethylformamide solution) is added under nitrogen flow. Exothermic effect of the reaction is observed and the mixture becomes denser. Vigorous mixing of the reaction mixture ensures that the reaction proceeds completely. It was found that the mixing time is to be extended for larger-scale processes.

The methanesulfonate of Formula 2 is formed in the reaction of a diol with methanesulfonyl chloride in N,N-dimethylformamide. Mesyl chloride is added dropwise in the presence of triethylamine while temperature is maintained between -20 and -15°C. The side product, triethylamine hydrochloride, is separated using a pressure filter, and the cooled filtrate (mesylate solution in N ₅ N- dimethylformamide) is added straight to the previously prepared solution of 1- (mercaptomethyl)cyclopropaneacetic acid disodium salt (mercaptide). The coupling of merged solutions of the intermediates (mercaptide with methanesulfonate) proceeds at temperatures between 0 and 25°C under inert gas flow. For the reaction conducted at a temperature of 0-5 ⁰ C complete conversion of the methanesulfonate was observed after 20-25 hours, for a temperature of 10-15°C reaction time was 10-12 hours, and at 20-25°C reaction was completed after only 2-3 hours. It is recommended for the reaction to proceed in lower temperatures; the

higher the temperature, the greater tendency for the formation of unfavourably side products, especially after reaction end. Reaction progress was checked using high- performance liquid chromatography. The molar ratio of 1- (sulfanylmethyl)cyclopropyl]acetic acid to the diol was tested in the range between approximately 0.90:1 to approximately 1.55:1. Lower amounts of 1- (sulfanylmethyl)cyclopropaneacetic acid resulted in reduced yields. Higher molar excess of the acid ensures that the methanesulfonate is completely converted irrespective of the yield of the mesylation stage with greater risk of the formation of unfavourably high concentrations of impurities and reduced process yield. The most favourable molar ratio found was between 1.10:1 and 1.20: 1. After the reaction the mixture is neutralised using citric acid in the water/toluene system. The isolated Montelukast solution in toluene is additionally washed with water. The product is isolated from the solution as a crystalline salt with tert- butylamine. To this end the solution is treated with tert-butylamine and concentrated partially under reduced pressure to remove any residual water and excess of tert-butylamine.

To facilitate crystallisation the concentrated product solution is seeded with crystals of pure Montelukast tert-butylamine salt. Crystallisation time after seeding necessary for complete crystallisation of the salt is at least 24 hours.

The amorphous form of Montelukast sodium is obtained by adding a concentrated Montelukast sodium solution in dichloromethane or toluene dropwise to a non-polar solvent, such as pentane or hexane. The tert-butylamine in the salt molecule is removed by extraction from water using acetic acid or directly using sodium hydroxide solution in methanol.

The high pharmaceutical purity of the amorphous form of sodium salt of 1 - (((l(R)-(3-(2-(7-chloro-2-quinolinyl)-ethenyl)phenyl)-3-(2-( l-hydroxy-l- methylethyl)phenyl)propyl)sulfanyl)methyl)cyclopropaneacetic acid is achieved in the reaction which does not involve the isolation of crystalline Montelukast sodium.

The following examples serve to illustrate the and therefore sould not be take to limit the scope thereof:

Example I. Preparation of l-(((l(R)-(3-(2-(7-chloro-2-quinolinyl)- ethenyl)phenyl)-3 -(2-( 1 -hydroxy- 1 - methylethyl)phenyl)propyl)sulfanyl)methyl)cyclopropaneacetic acid tert- butylamine salt.

Stage 1.

A 1000 mL glass reactor fitted with a mechanical stirrer, thermometer and nitrogen inlet is flushed with nitrogen. 570 mL of N,N-dirnethylformamide and 23.31 g (0.2426 mol) of sodium tert-butanolate is added under nitrogen flow and the content is stirred at 20±5°C until the salt dissolves completely. 17.28 g (0.1182 mol) of solid l-(sulfanylmethyl)cyclopropaneacetic acid is added to the resulting solution with vigorous stirring (exothermic reaction, temperature increase of approx. 10°C). The resulting suspension with a jelly consistency is stirred vigorously under nitrogen flow for at least one hour at >15°C. The content is then cooled to 10-15°C.

Stage 2.

A 250 mL three-necked flask fitted with a stirrer, thermometer and dropping funnel is flushed with nitrogen. 45 g (0.0983 mol) of 2-(2-(3(S)-(3-(2-(7-chloro-2- quinolinyl)-ethenyl)phenyl)-3-(hydroxypropyl)phenyl)-2-propa nol and 120 mL of N,N-dimethylformamide is poured into the flask and stirred until the diol dissolves completely. The content is cooled to between -20 and -15°C in the CO ₂ /acetone bath. After cooling 15.7 mL (11.43 g; 0.1130 mol) of triethylamine is added, the temperature is maintained at -20 to -15°C and 12.38 g (8.4 mL; 0.1081 mol) of methanesulfonyl chloride is added dropwise over 40 minutes. Stage 3.

After the dropping in of the mesyl chloride, the reaction mixture from Stage 2

(mesylate solution) cooled to -20 to -15°C is added through a glass pressure filter to a reactor with the suspension of l-(mercaptomethyl)cyclopropaneacetic acid disodium salt (prepared in Stage 1) using compressed nitrogen. The triethylamine hydrochloride precipitate on the filter is washed with 30 mL of N ₅ N- dimethylformamide. The N,N-dimethylformamide after washing is merged with the resulting reaction mixture.

The reaction mixture is maintained under nitrogen flow at 10-15° for 12 hours. The mixture is thereafter transferred to a 2500 mL glass reactor fitted with a mechanical stirrer and nitrogen inlet, 750 mL of toluene cooled to 0-5°C is added and 750 mL of water cooled to 5°C is added dropwise over one hour while maintaining the reactor temperature at 5-10°C. Subsequently, a solution of 7.2 g (0.0375 mol) of anhydrous citric acid in 76.5 mL of water is added dropwise over 15 minutes at 5-10°C. The content is stirred for 15 minutes and left to enable phase separation. The aqueous phase is discarded. The organic phase with the product is washed with 375 mL of water and then washed with 375 mL of water and 76.5 mL of methanol at 5-10 ⁰ C. 16.8 mL (11.71 g; 0.1601 mol) of tert-butylamine is added to the organic phase and stirred under nitrogen flow for 30 minutes The solution is then concentrated under reduced pressure at 35°C. About 300 mL of the solvent is distilled off including the excess of tert-butylamine. 5.4 mL of isopropanol is added to the solution after distillation along with the seed of the aforementioned Montelukast tert-butylamine salt. The content is stirred under nitrogen flow at 20- 25°C for 22 hours, cooled to 0-5°C and stirred at that temperature for 24 hours. The precipitate formed is filtered using a pressure filter with compressed nitrogen and washed three times with 30 mL portions of cool toluene. The product is dried at 35 ⁰ C under reduced pressure. The yield is 35.5 g of crude tert-butylamine salt (93.6% purity as HPLC tested). Stage 4.

35 g of the tert-butylamine salt (93.6% purity as HPLC tested) is poured into a 1000 mL flask fitted with a stirrer, thermometer, cooler and nitrogen inlet, 175 mL of methanol is added and the content is stirred until the salt dissolves completely.

350 mL of toluene, 2.12 niL of concentrated acetic acid and 175 mL of water is added to the solution. The content is stirred for 30 minutes and left to enable phase separation. The aqueous phase is discarded. 175 mL of toluene and 8.4 mL of tert- butylamine is added to the organic phase and the content is stirred for 20 minutes. Approx. 158 mL of the solvent is distilled off under reduced pressure from the resulting solution at 35°C.

175 mL of methanol, 2.12 mL of concentrated acetic acid and 175 mL of water is added to the solution after distillation. The content is stirred for 30 minutes and left to enable phase separation. The aqueous phase is discarded. 175 mL of toluene and 8.4 mL of tert-butylamine is added to the organic phase and the content is stirred for 20 minutes. Approx. 158 mL of the solvent is distilled off under reduced pressure from the resulting solution at 35 ⁰ C.

17.5 mL of isopropanol is added to the solution after distillation along with the seed of Montelukast tert-butylamine salt. The content is stirred under nitrogen flow at 20-25° for 24 hours. The precipitate formed is filtered using a pressure filter with compressed nitrogen and washed twice with 35 mL portions of toluene. The filtered salt is dried at 35°C under reduced pressure. The yield is 29.7 g of the salt (98.2% purity as HPLC tested).

¹ H NMR (500 MHz, CDCl ₃ ): δ 8.11 (d, IH, J= 8.5 Hz), 8.07 (d, IH, J= 1.7 Hz), 7.73 - 7.65 (m, 4H), 7.50 - 7.09 (m, 9H), 3.99 (t, IH, J= 7.3 Hz), 3.22 - 3.15 (m, IH), 2.91 - 2.84 (m, IH), 2.58 (AB, 2H, J= 12.9 Hz), 2.38 (AB, 2H, J= 15.6 Hz), 2.30 - 2.13 (m, 2H), 1.62, 1.60 (2 x s, 6H), 1.33 (s, 9H), 0.57 - 0.33 (m, 4H).

¹³ C NMR (125,7 MHz, CDCl ₃ ): 177.75, 156.89, 148.42, 145.30, 143.80, 140.28, 136.39, 136.23, 135.59, 135.25, 131,50, 128.91, 128.66, 128.53, 127.91, 127.12, 127.03, 126.66, 126.13, 125.61, 125.55, 125.37, 119.38, 73.60, 50.87, 50.14, 42.65, 40.02, 39.60, 32.26, 31.84, 28.46, 17.23, 12.80, 12.21.

The powder X-ray diffraction pattern is shown in Fig. 1.

To obtain high purity Montelukast tert-butylamine salt the purification step from Stage 4 is repeated. The yield of a single purification stage is 80-90%.

Example II. Preparation of sodium l-(((l(R)-(3-(2-(7-chloro-2-quinolinyl)- ethenyl)phenyl)-3 -(2-(I -hydroxy- 1 - memylethytyphenytypropy^sulfanytymethy^cyclopropaneacetate.

20.5 g of purified Montelukast tert-butylamine salt (99.7% purity as HPLC tested) is poured into a 500 mL flask fitted with a stirrer, thermometer, coller and nitrogen inlet (powder X-ray diffraction pattern shown in Fig. 2). Subsequently, 174 mL of dichloromethane and 1.78 mL of concentrated acetic acid is added. The resulting clear Montelukast solution in dichloromethane is washed twice with 102.5 mL water portions. The aqueous phases after washing are discarded and 13.29 mL of 2.34 M sodium hydroxide methanolic solution is added to the organic phase. 102.5 mL of the solvent is distilled off from the resulting solution under atmospheric pressure; thereafter 82 mL of dichloromethane is added and 102.5 mL of the solvent is distilled off again. The mixture after distillation is filtered warm through filter paper. The filtrate is diluted with 31 mL of dichloromethane and added dropwise to 1025 mL of n-pentane at 15-20°C. The resulting suspension of the product is filtered using a pressure filter with compressed nitrogen. The filtered product is dried at 60-80°C under reduced pressure. The yield is 17.3 g of amorphous Montelukast sodium (99.7% purity as HPLC tested, enantiomeric purity 99.96% as HPLC tested): ¹ H NMR (500 MHz, CD ₃ OD): δ 8.26 (d, IH, J= 8.8 Hz), 7.97 (d, IH, J- 2.0 Hz), 7.88 - 7.70 (m, 4H), 7.57 - 7.05 (m, 9H), 4.91 (s, active H), 4.04 (dd, IH, J= 6.3 Hz), 3.10 (m, IH), 2.83 (m, IH), 2.65 (d, IH, J = 12.7 Hz), 2.52 (d, IH, J = 12.9 Hz), 2.40 (d, IH, J= 14.6 Hz), 2.30 (d, IH, J= 14.6 Hz), 2.29 - 2.10 (m, 2H), 1.53, 1.51 (2 x s, 6H), 0.56 - 0.29 (m, 4H).

¹³ C NMR (125.7 MHz, CD ₃ OD): 180.84, 158.76, 149.29, 147.05, 145.63, 141.31, 138.15, 137.69, 137.40, 136.81, 132.49, 130.48, 130.08, 130.03, 128.77, 128.33, 128.15, 127.90, 127.84, 127.25, 126.89, 126.48, 126.44, 120.81, 73.83, 51.42, 44.75, 41.32, 41.14, 33.47, 31.85, 18.53, 13.35, 12.80.

The powder X-ray diffraction pattern is shown in Fig. 3.