Method for chemical synthesis of citicoline

Abstract

FIELD: chemical and pharmaceutical industry.SUBSTANCE: method for the chemical synthesis of citicoline. The method involves the reaction of converting cytidine-5'-monophosphate morpholidate (5'-CMP) and phosphorylcholine into citicoline. The method is distinguished in that the conversion reaction involves the interaction of phosphorylcholine with hydrogen chloride and a magnesium salt in a methanol medium and the addition of the resulting reaction mixture to a methanol solution of 5'-CMP morpholidate. The invention also relates to a variant of the said embodiment.EFFECT: reduction of the consumption of phosphorylcholine, decrease of the yield of the by-product - 5'-CMP methyl ester, as well as the amount of waste.11 cl, 9 ex

Description

[0001] FIELD OF TECHNOLOGY

[0002] The invention relates to the field of the chemical-pharmaceutical industry, namely to the chemical synthesis of citicoline, the salts of which, for example, sodium citicoline, have pharmaceutical activity.

[0003] STATE OF THE ART

[0004] Citicoline (formula 1) is a complex organic molecule that participates in the synthesis of cell membrane phospholipids, the synthesis of acetylcholine, and neurotransmitter transmission processes. Endogenous production of citicoline limits the rate of synthesis of phosphatidylcholine, the main membrane phospholipid. Exogenous citicoline helps conserve choline reserves in the body, inhibit the breakdown of membrane phospholipids, and improve nerve impulse transmission (Bezdetko N.V., Citicoline: New on the Known / / International Neurological Journal; MNJ. 2015. No. 4 (74)).

[0005]

[0006] Known methods for producing citicoline include chemical synthesis, enzymatic production, and microbial transformation. The state of the art for producing citicoline by chemical synthesis is described in two of the most common variants.

[0007] From DE 2059429 C2 (23.10.1986) a method for producing citicoline is known, in which 1 equivalent of cytidine-5'-monophosphate (5'-CMP, formula 2) in the presence of 1.6 equivalents of N,N-dicyclohexylcarbodiimide (DCC, formula 3) first reacts at 50°C with 2.8 equivalents of morpholine (formula 4) or other amines in an alcoholic medium, in particular, in methanol, to form 5'-CMP morpholidate (formula 5) or another phosphamide.

[0008]

[0009]

[0010] Next, a methanol solution of morpholidate (amide) is slowly added to a methanol solution of 2.5 equivalents of phosphorylcholine calcium chloride (formula 6) acidified with hydrochloric acid.

[0011]

[0012] The reaction to form citicoline is completed within a few hours at 50°C. Citicoline is isolated by precipitation in isopropanol, dissolution of the resulting precipitate in water, and final purification on an anion exchanger with a yield of 90%.

[0013] A second method for producing citicoline is known from US 3666748 A (30.05.1972), in which, instead of 5'-CMP amidate (formula 5), ​​phosphorylcholine amidate (in a particular case, morpholidate, formula 7) is used in the form of its salt with N-substituted guanidine, which, in turn, is obtained by the reaction of 1 equivalent of zwitterphosphorylcholine hydrochloride (formula 8) with an amine in the presence of 2.9 equivalents of N,N-dicyclohexylcarbodiimide in an n-butanol-water medium. Purification of the salt (formula 7) is carried out using ether and ethanol.

[0014]

[0015]

[0016] Citicoline is synthesized by reacting guanidine phosphorylcholine amidate chloride (formula 7) with 1.4 equivalents of 5'-CMP salt and an amine (e.g., tri-n-butylamine) in o-chlorophenol at 100°C for 18 hours with a yield of 95%. Purification is carried out on activated carbon.

[0017] Other patents, such as US2009286284, IN3279MUM2012, WO2013128393, CN 105732752, mainly vary the methods for purifying and isolating citicoline, or the methods for synthesizing amidates.

[0018] Thus, there are two main routes to chemical synthesis of citicoline.

[0019] The first method involves the interaction of 5'-CMP in the form of its amidate (in particular, morpholidate) with phosphorylcholine in the form of its calcium chloride salt in methanol acidified with hydrogen chloride at a temperature below the boiling point of methanol.

[0020] The second method involves the interaction of phosphorylcholine in the form of its amidate (in particular, morpholidate) with 5-CMP in the form of its salts, which have relatively good solubility (for example, with tri-n-butylamine) in a high-boiling solvent (for example, o-chlorophenol) at a temperature of 100°C and above.

[0021] The first method, specifically known from DE 2059429 C2 (23.10.1986), is the closest analogue (prototype) to the present invention. It is more cost-effective than the second method, as it synthesizes both 5'-CMP morpholidate and citicoline itself in a single solvent (methanol) at a relatively low temperature. Synthesis by the second method occurs under more stringent conditions and requires a wider range of raw materials, including high-temperature solvents. Consequently, the load on the regeneration system and the volume of waste in the second method are greater.

[0022] However, the synthesis according to the first method, in particular the one known from DE 2059429 C2 (23.10.1986), has a clear drawback: to achieve acceptable yields of citicoline (90% or more), it is necessary to use at least a two-fold excess of phosphorylcholine in the form of its calcium chloride salt (Example 1) compared to the theoretical one. Obviously, such an excess of the key intermediate causes a high load on the citicoline purification systems and the solvent and reagent regeneration system, a large volume of waste, and a negative impact on the economic performance of citicoline production. A second disadvantage of the first method is the formation of significant (up to 15 mol%) quantities of a by-product - 5'-CMP methyl ester (formula 9), which further increases the load on the citicoline purification system and significantly increases the volume of production waste.

[0023]

[0024] SUMMARY OF THE INVENTION

[0025] The aim of the present invention is to create a cost-effective method for synthesizing citicoline that fully satisfies the requirements of “green chemistry”.

[0026] The task is to change the qualitative composition of the reaction mass at the stage of transformation (condensation) of 5'-CMP morpholidate and phosphorylcholine into citicoline in order to significantly improve the economic and environmental performance of the citicoline production process as a whole.

[0027] In one aspect, a method for chemically synthesizing citicoline is provided, which includes a reaction of converting 5'-CMP morpholidate and phosphorylcholine into citicoline, wherein the conversion reaction is carried out by reacting phosphorylcholine with hydrogen chloride and a magnesium salt, adding the resulting reaction mixture to cytidine-5'-monophosphate morpholidate.

[0028] In a preferred embodiment, the magnesium salt has catalytic activity for the reaction of converting 5'-CMP morpholidate and phosphorylcholine into citicoline.

[0029] In a preferred embodiment, the magnesium salt is magnesium chloride.

[0030] In a preferred embodiment, magnesium chloride is obtained directly in the reaction mass by adding to it any suitable substance, the interaction of which with hydrogen chloride present in the reaction mass leads to the formation of magnesium chloride.

[0031] In another aspect, a method for the chemical synthesis of citicoline is provided, which includes a reaction of converting 5'-CMP morpholidate and phosphorylcholine into citicoline, wherein the reaction activator (catalyst) of said conversion is a magnesium salt.

[0032] In a preferred embodiment of the method, the conversion reaction is carried out in methanol.

[0033] In a preferred embodiment of the method, the magnesium salt is magnesium salt of phosphorylcholine chloride or magnesium chloride.

[0034] In a preferred embodiment of the method, the magnesium salt is a phosphorylcholine chloride salt.

[0035] In a preferred embodiment of the method, the magnesium salt is magnesium chloride.

[0036] In a preferred embodiment of the method, the magnesium salt is a magnesium salt of phosphorylcholine chloride, and the conversion reaction comprises dissolving the magnesium salt of phosphorylcholine chloride in a methanol solution of hydrogen chloride, adding the resulting reaction mixture to 5'-CMP morpholidate.

[0037] In a preferred embodiment of the method, the magnesium salt is magnesium chloride, and the conversion reaction involves reacting phosphorylcholine with hydrogen chloride and magnesium chloride in a methanol medium, adding the resulting reaction mixture to a methanol solution of 5'-CMP morpholidate.

[0038] In a preferred embodiment of the method, magnesium chloride is obtained directly in the reaction mass by reacting the hydrogen chloride present in it with any magnesium compounds suitable for this purpose, for example, with magnesium oxide, magnesium hydroxide, magnesium carbonate and others, or directly with magnesium.

[0039] In a preferred embodiment of the method, phosphorylcholine is in the zwitterionic form or in the form of its hydrochloride.

[0040] In another aspect, the use of a magnesium salt as an activator of the reaction (catalyst) for converting 5'-CMP morpholidate and phosphorylcholine into citicoline is proposed.

[0041] In a preferred embodiment, the magnesium salt is magnesium salt of phosphorylcholine chloride or magnesium chloride.

[0042] In a preferred embodiment, the magnesium salt is magnesium chloride.

[0043] In a preferred embodiment, the magnesium salt is magnesium salt of phosphorylcholine chloride.

[0044] The technical result of the proposed solution is a nearly twofold reduction in the consumption of phosphorylcholine, which is a key intermediate in the synthesis of citicoline, a several-fold reduction in the yield of the by-product - 5'-CMP methyl ester, and a reduction in the volume of waste from the production of citicoline.

[0045] To find technical solutions to achieve this goal, the authors conducted a series of experiments (Examples 2-4) in which phosphorylcholine, hydrogen chloride, and calcium chloride were separately added to a reaction mixture containing 5'-CMP morpholidate. The results obtained clearly demonstrate that Ca ions 2+They are not an inert component (ballast) of the reaction mixture, entering it along with phosphorylcholine chloride as a counterion, increasing the solubility of phosphorylcholine chloride. Calcium ions are an active participant in the chemical transformation—a catalyst for the condensation of the phosphate groups of the two individual starting molecules into the diphosphate group of the citicoline molecule.

[0046] It is known that the key activator of the synthesis and conversion of adenosine diphosphate (ADP) and adenosine triphosphate (ATP) are Mg ions 2+ In the work of J. E. Wilson, A. Chin., Chelation of divalent cations by ATP, studied by titration calorimetry / / Analytical Biochemistry, 1991 Feb 15; 193(1), p. 16, the binding of Mg ions is described 2+ , Sa 2+ and Sr 2+ with ATP. It has been shown that the binding constants (K b ) of these ions with ATP in a 1:1 ratio are 9554, 3722, and 1381, respectively. These values ​​of K bantibatically correlate with the ionic radii of the metals: 86, 114, and 132 pm (for a coordination number of 6). The binding constants of singly charged alkali metal cations are significantly lower than those of alkaline earth metals, but also decrease with increasing radius (the maximum value of K b observed in Li + ). In all cases, the process of complex formation is endothermic, i.e. the driver of the reaction is the increase in entropy, which is confirmed by the increase in K b with increasing temperature. The increase in entropy may be due to the release of solvent molecules from the solvated ATP ion during complexation with divalent metal cations.

[0047] Based on the analogy described above, a test was carried out to check the activation of the citicoline synthesis process by other metal cations, in particular, Mg ions, which are the most active in relation to adenosine phosphates. 2+ The results of the experiments are reflected in Examples 5 - 6.

[0048] Unexpectedly, the inventors of the present invention have discovered that, compared to calcium chloride, magnesium chloride is indeed a more effective activator (catalyst) of the reaction converting 5'-CMP morpholidate and phosphorylcholine into citicoline, enabling the achievement of virtually quantitative yields of citicoline with a small (20%) excess of phosphorylcholine. It can be assumed that this unexpected effect is achieved due to the fact that magnesium ions more effectively coordinate the phosphate groups of 5'-CMP morpholidate and phosphorylcholine molecules into a transition complex necessary for citicoline formation. A side effect of this complexation may be the displacement of methanol molecules from the solvation shell of the initial reagent molecules by magnesium ions, which blocks the reaction of forming the byproduct - 5'-CMP methyl ester.

[0049] A further illustration of the conclusions reached is provided by a comparison of Example 6 with Example 7, where the reaction mixtures differ only in the metal cations, with the concentrations and molar ratios of all reaction mixture components being fully preserved. A comparison of Example 6, which illustrates the proposed approach, with the prior art (patent DE 2059429 C2 and Example 1), which illustrates the generally accepted approach to citicoline synthesis, reveals a twofold reduction in phosphorylcholine consumption by replacing calcium salts with magnesium salts.

[0050] Example 8 shows that replacing the separate dosing of a mixture of free phosphorylcholine, magnesium chloride and hydrogen chloride into the reaction mass with dosing of an acidified solution of magnesium salt of phosphorylcholine chloride into the reaction mass at the same ratios of 5'-CMP morpholidate and phosphorylcholine gives practically the same result - the quantitative yield of citicoline.

[0051] Example 9 demonstrates the result of the invention on an industrial scale.

[0052] Thus, the stated goal - a more cost-effective and industrial method for synthesizing citicoline that best meets the requirements of “green chemistry” - is achieved by changing the composition of the reaction mass at the stage of conversion (condensation) of 5'-CMP morpholidate and phosphorylcholine into citicoline, namely by introducing soluble magnesium salts into the reaction mass.

[0053] Although the present invention admits of various modifications and alternative forms, a specific embodiment thereof will be described in detail below. It should be understood that the invention is not intended to be limited to the specific examples disclosed, but rather that the invention is intended to encompass all modifications, equivalents, and alternatives falling within the scope of legal protection defined by the claims.

[0054] Citicoline obtained by the method of the present invention can be easily isolated and purified using known and standard purification methods. For example, the resulting reaction mixture is evaporated, and a citicoline-precipitating solvent, such as isopropanol, is added to the residue. The precipitated citicoline is dissolved in water and purified using activated carbon and ion-exchange resins.

[0055] Furthermore, purified citicoline can be used by known methods to obtain sodium citicoline, for example, by treating an aqueous solution of citicoline with sodium hydroxide. Anhydrous sodium citicoline is obtained by adding precipitating solvents, such as acetone, to its aqueous solution and drying the resulting precipitate of wet sodium citicoline at elevated temperature under vacuum.

[0056] EXAMPLES

[0057] Example 1.

[0058] 33.7 g of a methanol solution of cytidine-5'-monophosphate (5'-CMP) morpholidate with the following characteristics was placed in a flask: morpholidate concentration 0.371 mmol / g, total morpholidate 12.5 mmol (1 equivalent), impurity content of 5'-CMP methyl ester 4.2 mol%. The solution was heated to 55 °C.

[0059] 8.3 g (25 mmol, 2 equivalents) of calcium phosphorylcholine chloride tetrahydrate were dissolved in 15.6 g of 11.7% hydrogen chloride solution (50 mmol, 4 equivalents) in methanol. Maintaining the reaction temperature at approximately 55°C, the resulting solution was added dropwise to a solution of 5'-CMP morpholidate over 15 minutes. After 10 minutes, the reaction mixture turned into a suspension. The reaction mixture was left for 180 minutes.

[0060] According to the results of the analysis (HPLC) of the reaction mass diluted with water to obtain a homogeneous solution, all 5'-CMP morpholidate was consumed, the content of 5'-CMP methyl ester impurity increased to 14.5%.

[0061] Citicoline yield 11.2 mmol, 89.6%.

[0062] Example 2.

[0063] A flask was charged with 33.7 g of a methanol solution of 5'-CMP morpholidate with a concentration of 0.371 mmol / g, total 5-CMP morpholidate 12.5 mmol. The solution was heated to 55 °C.

[0064] In a beaker, 11.9 g of a solution of free phosphorylcholine (zwitterionic form) in methanol (concentration 2.10 mmol / g, total 25 mmol) and 15.6 g of a solution of hydrogen chloride in methanol (concentration 11.7%, total 50 mmol) were mixed. Maintaining the reaction temperature at approximately 55°C, the resulting solution was added dropwise to a solution of 5-CMP morpholidate over 15 minutes. The reaction mixture was left for 180 minutes.

[0065] According to the results of the analysis (HPLC) of the reaction mass, all 5-CMP morpholidate was consumed, the content of 5'-CMP methyl ester impurity was 35.6%.

[0066] Citicoline yield 6.17 mmol, 49.4%.

[0067] Example 3.

[0068] Same as in Example 2, but 25 mmol of hydrogen chloride was used. Analysis of the reaction mixture (HPLC) showed that 5'-CMP morpholidate was not completely consumed; the impurity content of 5'-CMP methyl ester was 22.3%.

[0069] Citicoline yield 4.19 mmol, 33.5%.

[0070] Example 4.

[0071] 33.7 g of a methanol solution of 5'-CMP morpholidate with a concentration of 0.371 mmol / g (12.5 mmol) was placed in a flask. The solution was heated to 55 °C.

[0072] 11.9 g of a solution of free phosphorylcholine (zwitterionic form) in methanol (concentration 2.10 mmol / g, total 25 mmol), 7.80 g of a solution of hydrogen chloride in methanol (concentration 11.7%, total 25 mmol), and a solution of 2.78 g (25 mmol) of calcium chloride in 12.5 ml of methanol were mixed in a beaker. Maintaining the temperature of the reaction mixture at about 55°C, the resulting solution was added dropwise to a solution of 5'-CMP morpholidate over 15 minutes. After 10 minutes, the reaction mixture turned into a suspension. The mixture was left for 180 minutes.

[0073] According to the results of the analysis (HPLC) of the reaction mass diluted with water to obtain a solution, all 5'-CMP morpholidate was consumed, the content of 5'-CMP methyl ester impurity was 9.8%.

[0074] Citicoline yield 11.1 mmol, 88.8%.

[0075] Example 5.

[0076] A flask was charged with 33.7 g of a methanol solution of 5'-CMP morpholidate with a concentration of 0.371 mmol / g (12.5 mmol, 1 equivalent). The solution was heated to 55 °C.

[0077] 11.9 g of a solution of free phosphorylcholine (zwitterionic form) in methanol (concentration 2.10 mmol / g, total 25 mmol, 2 equivalents), 7.80 g of a solution of hydrogen chloride in methanol (concentration 11.7%, total 25 mmol, 2 equivalents) and a solution of 2.38 g (25 mmol, 2 equivalents) of magnesium chloride in 12.5 ml of methanol were mixed in a beaker. Maintaining the temperature of the reaction mixture at about 55 °C, the resulting solution was added dropwise to a solution of 5'-CMP morpholidate over 15 minutes. The mixture was left for 180 minutes.

[0078] According to the results of the analysis (HPLC) of the reaction mass (clear solution), all 5-CMP morpholidate was consumed, the content of 5'-CMP methyl ester impurity was 4.5%.

[0079] Citicoline yield 12.3 mmol, 98.4%.

[0080] Example 6.

[0081] 33.7 g of a methanol solution of 5'-CMP morpholidate with the following characteristics was placed in a flask: morpholidate concentration 0.371 mmol / g, total morpholidate 12.5 mmol (1 equivalent), impurity content of 5'-CMP methyl ester 4.2%. The solution was heated to 55 °C.

[0082] 7.14 g of a solution of free phosphorylcholine (zwitterionic form) in methanol (concentration 2.10 mmol / g, total 15 mmol, 1.2 equivalents), 6.65 g of a solution of hydrogen chloride in methanol (concentration 11.7%, total 21.3 mmol, 1.7 equivalents) and a solution of 1.43 g (15 mmol, 1.2 equivalents) of magnesium chloride in 10 ml of methanol were mixed in a beaker. Maintaining the temperature of the reaction mixture at about 55 °C, the resulting solution was added dropwise to a solution of 5'-CMP morpholidate over 15 minutes. The mixture was left for 180 minutes.

[0083] According to the results of the analysis (HPLC) of the reaction mass (clear solution), all 5'-CMP morpholidate was consumed, the content of 5'-CMP methyl ester impurity remained unchanged (4.2%).

[0084] Citicoline yield 12.4 mmol, 99.2%.

[0085] Example 7.

[0086] Same as Example 6, but 15 mmol of calcium chloride was used instead of 15 mmol of magnesium chloride. The reaction mixture quickly turned into a suspension.

[0087] After the exposure time, water was added to the reaction mixture until it was completely dissolved.

[0088] Citicoline yield (HPLC) 9.36 mmol, 74.9%, the content of 5'-CMP methyl ester impurity increased to 25%.

[0089] Example 8.

[0090] 33.7 g of a methanol solution of 5'-CMP morpholidate with the following characteristics was placed in a flask: morpholidate concentration 0.371 mmol / g, total morpholidate 12.5 mmol (1 equivalent), impurity content of methyl ester of cytidine-5'-monophosphate (5'-CMP) 4.2 mol%. The solution was heated to 55 °C.

[0091] 4.71 g (15 mmol, 1.2 equivalents) of magnesium salt of phosphorylcholine chloride in the form of its tetrahydrate were dissolved in a glass in 10.9 g of 11.7% hydrogen chloride solution (35 mmol, 2.8 equivalents) in methanol.

[0092] Maintaining the reaction temperature at approximately 55°C, the resulting acidified solution was added dropwise to the 5'-CMP morpholidate solution over 15 minutes. The reaction was held for 180 minutes.

[0093] According to the results of the analysis (HPLC) of the reaction mass (transparent solution), all 5'-CMP morpholidate was consumed, the content of 5´-CMP methyl ester impurity remained unchanged (4.2 mol%).

[0094] Citicoline yield 12.3 mmol, 98.4%.

[0095] Example 9.

[0096] 5.54 kg (151.8 mol) of hydrogen chloride were dissolved in 40 L of methanol in a 100 L reactor at 0-5°C with vigorous stirring. Titration of the sample yielded a 14.8% methanolic solution of hydrogen chloride. 1.80 kg (44.4 mol) of magnesium oxide were added to the resulting hydrogen chloride solution. The mixture was stirred at room temperature until the oxide was completely dissolved (2 hours), after which 25.6 kg of a 45.3% (51.9 mol) methanolic solution of phosphorylcholine in methanol was added to the reaction mixture.

[0097] A 200 L reactor was charged with 99 kg of a methanol solution of 5'-CMP morpholidate, obtained from 12.5 kg (38.5 mol) of 5'-CMP. The reagent mixture from a 100 L reactor was fed to the 5'-CMP morpholidate solution heated to 55°C over 30 minutes so that the temperature remained in the range of 50-55°C. After dosing was complete, stirring was continued at a reaction mixture temperature of 53-55°C until the reaction was complete (210 minutes): the residual content of 5'-CMP morpholidate was 0.5%, the yield of citicoline was 98.5%.

[0098] 82 kg (103 L) of methanol were distilled from the resulting clear reaction mixture. 82 L of acetone were added to the concentrate with stirring. The resulting precipitate was filtered and dried. 32.1 kg of dry intermediate product was obtained, containing approximately 53.9% citicoline, calculated as citicolinic acid (35.4 mol).

[0099] From the semi-finished product, after undergoing standard purification and isolation stages, 17.6 kg of pharmacopoeial grade sodium citicoline was obtained.

Claims

1. A method for the chemical synthesis of citicoline, including a reaction of converting 5'-CMP morpholidate and phosphorylcholine into citicoline, characterized in that the conversion reaction involves the interaction of phosphorylcholine with hydrogen chloride and a magnesium salt in a methanol medium, adding the resulting reaction mixture to a methanol solution of cytidine-5'-monophosphate (5'-CMP) morpholidate.

2. The method according to claim 1, characterized in that the magnesium salt has catalytic activity in the reaction of converting 5'-CMP morpholidate and phosphorylcholine into citicoline.

3. The method according to claim 2, characterized in that the magnesium salt is magnesium chloride.

4. The method according to paragraph 3, characterized in that magnesium chloride is obtained directly in the reaction mass by adding to it any suitable substance, the interaction of which with hydrogen chloride present in the reaction mass leads to the formation of magnesium chloride.

5. A method for the chemical synthesis of citicoline, including the reaction of converting cytidine-5'-monophosphate morpholidate and phosphorylcholine into citicoline, characterized in that the conversion reaction is carried out in the presence of hydrogen chloride and methanol, and the catalyst is a magnesium salt.

6. The method according to claim 5, characterized in that the magnesium salt is a magnesium salt of phosphorylcholine chloride.

7. The method according to claim 5, characterized in that the magnesium salt is magnesium chloride.

8. The method according to claim 6, characterized in that the conversion reaction includes dissolving the magnesium salt of phosphorylcholine chloride in a methanol solution of hydrogen chloride, adding the resulting reaction mixture to a methanol solution of 5'-CMP morpholidate.

9. The method according to claim 7, characterized in that the conversion reaction includes the interaction of phosphorylcholine with hydrogen chloride and magnesium chloride in a methanol medium, adding the resulting reaction mixture to a methanol solution of 5'-CMP morpholidate.

10. The method according to claim 9, characterized in that magnesium chloride is obtained directly in the reaction mass by adding to it any suitable substance, the interaction of which with hydrogen chloride present in the reaction mass leads to the formation of magnesium chloride.

11. The method according to any one of paragraphs 5-10, characterized in that the phosphorylcholine is in the zwitterionic form or in the form of its hydrochloride.

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