New methotrexate purification method

Abstract

The invention relates to a novel methotrexate purification method. According to the method, the basic ionic liquid is used as the catalyst for the first time and is used in the methotrexate purification process, and the development trend of green chemistry is met. The purification method disclosed by the invention is simple in post-treatment process, does not need complicated post-treatment operation, saves the operation cost and is beneficial to industrial production. The alkaline ionic liquid is simple and easy to obtain, the preparation method is mature, the ionic liquid is easy to separate and can be repeatedly used after being simply activated, the production cost is saved, and industrial production is facilitated. The methotrexate prepared by the purification method disclosed by the invention is high in purity and low in impurity C content, and the total reaction yield is greatly improved compared with the prior art.

Description

Technical Field

[0001] The present invention relates to the field of pharmaceutical chemistry, and particularly relates to a new method for purifying methotrexate. Background Art

[0002] Methotrexate is a folic acid antagonist. It mainly inhibits dihydrofolate reductase, so that dihydrofolic acid cannot be reduced to physiologically active tetrahydrofolic acid, thereby hindering the synthesis of tumor cells and inhibiting the growth and reproduction of tumor cells. In addition, methotrexate can also affect the activities of T cells and B cells, reduce the production of immune mediators, and thus achieve the effects of anti-inflammatory and immunosuppression. Clinically, methotrexate can be used to treat various types of acute leukemia, especially acute lymphoblastic leukemia, malignant lymphoma, non-Hodgkin's lymphoma, and testicular granuloma, multiple myeloma; it can also be used to treat head and neck cancer, lung cancer, various soft tissue sarcomas; as well as breast cancer, ovarian cancer, cervical cancer, malignant mole, choriocarcinoma, testicular cancer, etc. Methotrexate is also a cornerstone drug for the treatment of rheumatoid arthritis, and can also be used to treat juvenile idiopathic arthritis, psoriatic arthritis, systemic lupus erythematosus, vasculitis, inflammatory myopathy, systemic sclerosis, multisystem sarcoidosis, etc.

[0003] According to the regulations of the second part of the Chinese Pharmacopoeia 2020 edition, the purity requirement of methotrexate is: calculated on the anhydrous basis, the content of methotrexate should be 98.0% - 102.0%. Currently, there are mainly two synthetic routes for methotrexate: 1. Patents US4080325, US422446, and US3989703 disclose a three-step synthesis method, in which tetraaminopyrimidine and 1,3-dihydroxyacetone are synthesized into 6-hydroxypteridine, and then after bromination or chlorination, it is docked with p-methylaminobenzoyl-L-glutamic acid to obtain methotrexate, but the yields of these methods are not high; 2. Patent US 4374987 discloses a one-pot synthesis method of methotrexate, in which tetraaminopyrimidine sulfate, p-methylaminobenzoyl-L-glutamic acid, and tribromoacetone are synthesized into methotrexate. After the reaction solution is cooled, it is adjusted to alkaline with ammonia water and filtered. The obtained filtrate needs to be repeatedly adjusted with acid and alkali for many times (acid is adjusted twice continuously, and then alkali and acid are adjusted successively), the obtained filter cake is adjusted to alkaline again and filtered. The obtained filtrate is added with acetone to prepare a high-quality product of methotrexate sodium salt, and then sulfuric acid is added for crystallization to obtain the finished product of methotrexate. The yield and purity of this method are both good, but its post-treatment purification process is extremely cumbersome, and due to the repeated adjustment of acid and alkali, a large amount of ammonia water and a large amount of hydrochloric acid, etc. are required, which has a greater impact on the environment.

[0004] Zhou Bei et al. (Chinese Journal of Pharmaceuticals, 1990, 21(12), 535) disclosed an improvement in the purification process of methotrexate. The methotrexate sample was adjusted to alkaline with ammonia water, filtered, the filtrate was adjusted to acidic for crystallization, filtered, the filter cake was adjusted to alkaline and filtered again, and the obtained filtrate was crystallized with acetone, and the filter cake was crystallized with sulfuric acid to obtain pure methotrexate. This method still uses hydrochloric acid and ammonia water to adjust the acidity and alkalinity, requires a large amount of ammonia water, and causes relatively large environmental pollution. WO2018028496A1 disclosed a purification method of methotrexate. The purification process of this invention controls the pH and temperature of the reaction solution through a pretreatment step of the reaction solution. This pretreatment step of the reaction solution can synergistically control the solubility of methotrexate isomers in the reaction solution, and then filter to remove methotrexate isomers. Although this method reduces the usage amount of ammonia water, it still needs to use a large amount of acetone, and acetone belongs to a controlled substance and is listed as a third-class precursor chemical for drug production. This means that its purchase, use, transportation and other links are strictly supervised and controlled. At the same time, the large amount of acetone used will produce a large amount of wastewater, which is not conducive to environmental protection requirements.

[0005]

[0006] Zhu Haixi et al. (Pharmaceutical and Clinical Research, 2023, 31(2), 136-139) disclosed a synthesis process of methotrexate. By crystallizing (2S)-2-[[4-[[(2,4-diaminopterin-6-yl)methyl]methylamino]benzoyl]amino]pentanedioic acid diethyl ester with an aqueous solution of p-toluenesulfonic acid, its p-toluenesulfonate was obtained. The p-toluenesulfonate was de-ethylated in an aqueous solution of sodium hydroxide to obtain sodium methotrexate, and methotrexate could be precipitated by adjusting the pH. CN114249731A disclosed a purification method of a methotrexate intermediate. After using p-toluenesulfonic acid to salt out the methotrexate intermediate Int1 and then precipitating it, the precursor content of impurity C in the methotrexate precursor was greatly reduced; then the precursor was hydrolyzed to obtain a methotrexate raw material with a lower content of impurity C. The above route can effectively reduce the content of impurity C. However, it is necessary to add a salt formation step for the intermediate, the route becomes longer, and thus the process cost is increased.

[0007]

[0008] Therefore, developing an economical, environmentally friendly and commercially applicable methotrexate purification process has very important economic value and social value. Summary of the Invention

[0009] In order to solve the above technical problems existing in the prior art, the present invention provides a new method for purifying methotrexate. The method of the present invention has mild conditions, the reagents used in the reaction are simple and easily available, the product yield and purity are high, and it is more suitable for industrial production.

[0010] In the first aspect of the present invention, a new method for purifying methotrexate is provided, which is characterized by including the following steps: 1) React compound I and compound II in the presence of a basic ionic liquid to obtain intermediate compound III; 2) Subject intermediate III to an ester hydrolysis reaction under basic conditions to obtain intermediate IV; 3) Adjust the pH value of intermediate IV to obtain the final product V, namely methotrexate; The reaction route is as follows:

[0011] Wherein: X is a halogen, and M is an alkali metal or an alkaline earth metal; The basic ionic liquid in step 1) is [Nbmm]OH, and the structural formula is .

[0012] Preferably, X is bromine; Preferably, M is Na or K; Preferably, the reaction temperature in step 1) is 50°C to 150°C, more preferably 100°C to 120°C.

[0013] Preferably, the reaction time in step 1) is 4 to 24 hours, more preferably 6 to 12 hours, and most preferably 8 to 10 hours.

[0014] Preferably, the molar ratio of compound I to compound II in step 1) is 1:0.8 to 1.5, more preferably 1:1.0 to 1.2.

[0015] Preferably, the mass ratio of compound I to the basic ionic liquid in step 1) is 1:1 to 20, more preferably 1:6 to 12.

[0016] Preferably, the base used under the basic conditions in step 2) is sodium hydroxide or potassium hydroxide.

[0017] Preferably, the reaction temperature in step 2) is room temperature.

[0018] Preferably, the reaction time in step 2) is 1 to 3 hours, more preferably 1.5 to 2 hours.

[0019] Preferably, the acid used in step 3) is hydrochloric acid or sulfuric acid; Preferably, the reaction temperature in step 3) is room temperature.

[0020] Preferably, the steps in step 3) are to dissolve compound IV in water, add an acid, and adjust the pH of the reaction solution to 4.0 to 4.5.

[0021] In recent years, the unique solvent properties of ionic liquids have led to their widespread application in the fields of synthesis and catalysis. The economic and potentially environmentally friendly aspects of ionic liquids have gradually drawn people's attention to their catalytic performance. By modifying the structure of ionic liquids, various functional ionic liquids with specific catalytic properties have been designed. Functional ionic liquids have found considerable applications in the catalytic formation of carbon-nitrogen bonds. The structure of functional ionic liquids usually contains certain functional groups that confer catalytic activity, enabling these specific functional groups to activate reactants in a particular manner. Yetkin GOK et al. (Journal of Catalysis, 2007, 28(6), 489-491) disclosed the use of ionic liquids as solvents / catalysts for the selective alkylation of amines with halogenated hydrocarbons, and studied the selective alkylation of the amino group in amine compounds with various halogenated hydrocarbons in ionic liquids ([bmim]I) and ([bmim]PF6) in the presence of triethylamine.

[0022] Based on this, the present inventors, through extensive research, found that in the presence of the functional ionic liquid of the present invention, the selective alkylation reaction of 6-halomethyl-2,4-pteridinediamine can be achieved under relatively mild conditions, and the yield and purity of the product in this step are both relatively high. Since inorganic bases are not used in this step and water is not generated during the reaction process, hydrolysis of the amino group at the top of the pteridine ring is avoided, thereby significantly reducing the content of impurity C in the finally obtained methotrexate. In addition, in the subsequent purification step, there is no need to carry out a salification reaction on intermediate compound III, reducing the reaction steps, improving the purity of the intermediate, and thus enhancing the product purity and reducing the generation of subsequent impurities. In this process, selecting a suitable ionic liquid is crucial because there is an amino group on the pteridine ring of compound II. If the catalytic activity of the ionic liquid is too high, it may cause the reaction of the halogenated hydrocarbon with the amino group of compound II itself, thereby generating undesired impurities; if the catalytic activity of the ionic liquid is too low, the reaction will be incomplete or even unable to proceed smoothly, thus affecting the yield and purity of the final product.

[0023] Compared with the prior art, the present invention has the following advantages: 1. The present invention for the first time uses a basic ionic liquid as a catalyst in the purification process of methotrexate, which is in line with the development trend of green chemistry.

[0024] 2. The post-treatment process of the purification method of the present invention is simple, without complex post-treatment operations, saving operation costs and being conducive to industrial production.

[0025] 3. The catalyst of the present invention is simple to obtain, the preparation method is mature, and the ionic liquid of the present invention is easy to separate. After simple activation, it can be reused, saving production costs and being conducive to industrial production.

[0026] 4. The methotrexate prepared by the purification method of the present invention has high purity, low content of impurity C, and the total reaction yield is also greatly improved compared with the prior art. Detailed implementation manners

[0027] The content of the present invention will be specifically described below through examples. In the present invention, the following examples are for better elaborating the present invention and are not used to limit the scope of the present invention. The materials, reagents, etc. used in the following examples can be obtained from commercial channels without special instructions.

[0028] Synthesis Example 1 Preparation of basic ionic liquid catalyst The basic ionic liquid adopted in the present invention is [Nbmm]OH, and the structural formula is , and it is prepared by referring to the method of Example 2 of Patent Document CN 109796406 A. The specific steps are as follows: Slowly add 2 mol of n-butyl bromide to a three-necked flask containing 2 mol of N-methylmorpholine, stir and heat to reflux. After reacting for 5 h, place the product obtained by removing unreacted N-methylmorpholine and n-butyl bromide by vacuum filtration in a vacuum drying oven at 70 °C for 24 h to obtain a yellow solid intermediate, N-methyl-N-butylmorpholine bromide. Then dissolve 2 mol of N-methyl-N-butylmorpholine bromide and potassium hydroxide in a certain volume of absolute ethanol, stir and react for 24 h, centrifuge to separate insoluble KBr, and then distill off absolute ethanol from the obtained liquid mixture under reduced pressure. The remaining solid is vacuum dried at 70 °C to constant weight, and recrystallized with absolute ethanol to obtain a white solid, which is the target product, basic ionic liquid [Nbmm]OH.

[0029] Example 1 Step 1): Add 3000 g of basic ionic liquid [Nbmm]OH to the reaction kettle in sequence, heat up with stirring. After the internal temperature rises to 110 °C, add Compound I (336.4 g, 1 mol), continue to stir for 15 min, then add Compound II (255 g, 1.0 mol), and keep the temperature at 110 °C for reaction for 9 h. After the reaction is completed, when the reaction solution cools down to 70 °C, add purified water (8 L) dropwise, stir and crystallize for 1 h, and obtain a brown solid compound III (463.8 g, yield 90.9%) after centrifugal drying. mp 178~179 °C. HPLC purity is 98.43%, and the content of impurity C precursor is 0.08%.

[0030] For the filtrate after suction filtration, most of the water is removed by distillation under reduced pressure, and the residue is dried in an oven to recover the ionic liquid, which can be recycled continuously, or the residue can be filtered, adsorbed and removed impurities with activated carbon, and then recycled.

[0031] Step 2): Add 500 mL of purified water and intermediate 3 (100 g) into the reaction flask in sequence. While stirring, add 250 mL of an aqueous solution of sodium hydroxide (25 g). After the addition is complete, react at room temperature for 1.5 h. After the reaction is completed, filter, collect the filtrate, and add 1500 mL of acetone dropwise while stirring for crystallization. After filtration and drying, a yellow solid compound IV (88.6 g, yield 88.3%) is obtained. The HPLC purity is 99.82%, and the content of impurity C is about 0.02%. 1 1H NMR (400 MHz, CDCl3) δ: 8.59 (s, 1H), 7.80 - 7.83 (t, J = 7.5 Hz, 2H), 6.85 - 6.89 (m, 2H), 4.84 (s, 2H), 4.41 - 4.45 (m, 1H), 3.26 (s, 3H), 2.31 - 2.36 (m, 1H), 2.22 - 2.26 (m, 2H), 2.18 - 2.20 (m, 1H).

[0032] Step 3): Add compound IV (50 g) and 500 mL of purified water into the reaction flask. After stirring until it is dissolved and clear, adjust the pH to 4.0 - 4.5 with an 8% hydrochloric acid solution. After filtration and drying, yellow solid methotrexate (42.2 g, yield 92.5%) is obtained, mp 194 - 195°C, purity 99.79%, and the content of impurity C is 0.01%.

[0033] Example 2 Step 1): Add 4000 g of basic ionic liquid [Nbmm]OH into the reaction kettle and heat it up while stirring. After the internal temperature rises to 120°C, add compound I (336.4 g, 1 mol), continue stirring for 15 min, then add compound II (280.5 g, 1.1 mol), and keep the temperature at 120°C for reaction for 8 h. After the reaction is completed, when the reaction solution cools down to 70°C, add 8 L of purified water dropwise, stir for crystallization for 1 h, and obtain a brown solid compound III (442.7 g, yield 86.7%) after centrifugation and drying, mp 178 - 179°C. The HPLC purity is 98.58%, and the content of impurity C precursor is 0.07%.

[0034] For the filtrate after suction filtration, most of the water is removed by vacuum distillation, and the residue is dried in an oven to recover the ionic liquid, which can be recycled continuously. Or the residue can be filtered, adsorbed with activated carbon to remove impurities, and then recycled.

[0035] Example 3 Step 1): Add 2800 g of basic ionic liquid [Nbmm]OH into the reaction kettle in sequence, heat up with stirring. After the internal temperature rises to 100 °C, add Compound I (336.4 g, 1 mol), continue stirring for 15 min, then add Compound II (280.5 g, 1.1 mol), keep the temperature at 100 °C and react for 10 h. After the reaction is completed, wait for the reaction solution to cool down to 70 °C, then dropwise add purified water (8 L), stir for crystallization for 1 h, and obtain brown solid Compound III (452.3 g, yield 88.6%) after centrifugation and drying, mp 178 - 179 °C. HPLC purity is 97.43%, and the content of impurity C precursor is 0.10%.

[0036] For the filtrate after suction filtration, most of the water is removed by vacuum distillation, and the residue is dried in an oven to recover the ionic liquid, which can be reused continuously, or the residue can be filtered, adsorbed and purified with activated carbon to remove impurities, and then reused.

[0037] Comparative Example 1 Using the same method as in Example 1, the difference is only that 3000 g of basic ionic liquid [Bmim]OH is used instead of the basic ionic liquid in Example 1, and it is found that the target product cannot be obtained.

Claims

1. A new method for purifying methotrexate, characterized in that The steps include: 1) In the presence of an alkaline ionic liquid, compound I and compound II are reacted to obtain an intermediate compound III; 2) Under alkaline conditions, the intermediate III is subjected to ester hydrolysis reaction to obtain the intermediate IV; 3) Adjusting the pH value of the intermediate IV to obtain the final product V, i.e., methotrexate; The reaction route is as follows: Wherein: X is a halogen, M is an alkali metal or an alkaline earth metal; The alkaline ionic liquid in step 1) is [Nbmm]OH, with the structural formula .

2. The novel method for purifying methotrexate according to claim 1, characterized in that: X is bromine; M is Na or K.

3. The novel method for purifying methotrexate according to claim 1 or 2, characterized in that: The reaction temperature of step 1) is 100°C to 120°C.

4. The novel method for purifying methotrexate according to claim 1 or 2, characterized in that: The reaction time of step 1) is 8 to 10 hours.

5. The novel method for purifying methotrexate according to claim 1 or 2, characterized in that: In step 1), the molar ratio of compound I to compound II is 1:0.8-1.5, more preferably 1:1.0-1.

2.

6. The novel method for purifying methotrexate according to claim 1 or 2, characterized in that: In step 1), the mass ratio of carbon tetrachloride to diacidic ionic liquid is 1:6-12.

7. The novel method for purifying methotrexate according to claim 1 or 2, characterized in that: In step 2), the base used in the alkaline condition in step 2) is sodium hydroxide or potassium hydroxide.

8. The novel method for purifying methotrexate according to claim 1 or 2, characterized in that: The reaction temperature of step 2) is room temperature, and the reaction time is 1 to 3 hours.

9. The novel method for purifying methotrexate according to claim 1 or 2, characterized in that: The acid used in step 3) is hydrochloric acid or sulfuric acid.

10. The novel method for purifying methotrexate according to claim 1 or 2, characterized in that: Step 3) is to dissolve compound IV in water, add acid, and adjust the pH of the reaction solution to 4.0-4.5.

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