WO2020207397A1 - Method for purifying pemetrexed intermediate - Google Patents

Abstract

Provided in the present invention is a method for purifying a pemetrexed intermediate. The method comprises the following steps: A) dissolving a crude product, a pemetrexed intermediate, in a solvent to obtain a pemetrexed intermediate crude product solution; and B) mixing the pemetrexed intermediate crude product solution with trifluoroacetic acid to obtain a trifluoroacetate of the pemetrexed intermediate. In the present invention, by adding an appropriate acid under a certain solvent and temperature to form a salt with the intermediate, the aim of purifying the pemetrexed intermediate can be achieved, the content of impurities in the intermediate can be reduced, and a high-purity pemetrexed intermediate can be obtained. Use of the intermediate for preparing a pemetrexed disodium raw material medicine can effectively reduce impurity residues in the raw material medicine, thereby obtaining a high-purity pemetrexed disodium raw material medicine that meets medicine standards. The preparation method provided in the present invention is simple to operate and suitable for industrial production. In addition, the trifluoroacetic acid used does not introduce any genotoxic impurity, resulting in higher safety.

Description

Method for purifying pemetrexed intermediate

This application claims the priority of a Chinese patent application filed with the Chinese Patent Office, the application number is 201910290215.4, and the invention title is "a purification method of pemetrexed intermediate" on April 11, 2019, the entire content of which is incorporated by reference In this application.

Technical field

The invention relates to the technical field of medicinal chemistry, in particular to a method for purifying pemetrexed intermediates.

Background technique

Pemetrexed (Pemetrexed), the chemical name is N-(4-[2-(2-amino-4,7-dihydro-4-oxo-1H-pyrrolo[2,3-d]pyrimidine-5 -Yl)ethyl]benzoyl)-L-glutamic acid, its disodium salt molecular formula is C ₂₀ H ₁₉ N ₅ Na ₂ O ₆ , CAS number is 150399-23-8, and has the structure shown in formula I .

Pemetrexed disodium is a multi-target folate antagonist that acts on multiple targets and can inhibit thymidylate synthase (TS), dihydrofolate reductase (DHFR) and glycinamide ribonucleotides Many folate-dependent enzymes such as formyl transferase (GARFT) reduce the possibility of drug resistance, and there is less cross-resistance with other antifolate drugs. Pemetrexed disodium was developed by Eli Lilly. Clinical trials have shown that it is effective against a variety of solid tumors. It was approved by the FDA in February 2004 in combination with cisplatin for use in malignant pleural mesothelium that is not suitable for surgical resection. The treatment of inpatients with tumor (MPM) is the first drug approved by the FDA for the treatment of malignant pleural mesothelioma. At present, the drug has been marketed in the United States, the European Union, China and other countries and regions for the first-line treatment of malignant pleural mesothelioma and the second-line treatment for locally advanced and metastatic non-small cell lung cancer.

The structure compound shown in the following formula II is a key intermediate in the preparation process of pemetrexed disodium. The various preparation processes of pemetrexed disodium will pass this intermediate to prepare the finished pemetrexed disodium. For example, the preparation method of pemetrexed disclosed in The Journal of Organic Chemistry, 1993, 58(7): 1696-1701.

It is found through experiments that in the process of preparing pemetrexed diester, the intermediate compound II, more by-products are produced. If the by-products in this step cannot be minimized during the preparation process, they will remain in the final product pemetrexed disodium, which will increase the difficulty of purification of pemetrexed disodium, affect the purity of the product, and possibly As a result, the final product does not meet the medical standards due to excessive impurities. None of the existing purification methods can make the pemetrexed diester achieve high purity, making the final product pemetrexed disodium chromaticity not up to the standard, and at the same time it will cause a greater degree of waste in the purification process, which is not conducive to industrialization produce.

Drugs are special commodities, and the purity of raw materials directly affects the efficacy of the drug and the magnitude of its side effects. Improving the purity of raw materials can greatly reduce the side effects of drugs. Therefore, in the preparation process of pemetrexed, the purification process of intermediates is improved, and the purity of pemetrexed intermediates is improved, so as to simplify the purification method of the raw material drug pemetrexed disodium and improve its purity, which is helpful for obtaining high-purity pemetrexed. It is of great significance to improve the quality of the raw material of trexedine disodium.

Summary of the invention

In view of this, the technical problem to be solved by the present invention is to provide a purification method of pemetrexed intermediate, which has a higher yield and purity.

In order to solve the above technical problems, the present invention provides a purification method of pemetrexed intermediate, which includes the following steps:

A) Dissolve the crude pemetrexed intermediate in a solvent to obtain a crude pemetrexed intermediate solution;

B) Mixing the crude solution of pemetrexed intermediate with trifluoroacetic acid to obtain the trifluoroacetate salt of pemetrexed intermediate;

The pemetrexed intermediate has the structure shown in formula II:

Among them, R is CH ₃ or CH ₂ CH ₃ .

The purification method provided by the present invention can effectively remove impurities and improve the purity of the pemetrexed intermediate compound represented by the structure of formula II, thereby simplifying the purification difficulty of the crude drug pemetrexed disodium and obtaining high purity that meets pharmaceutical standards Pemetrexed disodium crude drug.

In the present invention, the source of the crude pemetrexed intermediate is not particularly limited, and it can be generally commercially available or prepared according to methods well known to those skilled in the art.

In some specific embodiments of the present invention, 4-[2-(2-amino-4,7-dihydro-4-oxo-1H-pyrrolo[2,3-d]pyrimidin-5-yl)ethyl Benzoic acid and L-glutamic acid dimethyl ester as raw materials to prepare the crude pemetrexed intermediate. During the reaction, it is preferable to use N-methylmorpholine as an acid binding agent and 2-chloro-4,6-dimethoxy-1,3,5-triazine as a condensing agent.

The route of the above reaction is as follows:

The present invention first dissolves the crude pemetrexed intermediate in a solvent to obtain the crude pemetrexed intermediate solution.

Specifically, the crude pemetrexed intermediate is mixed with the first solvent and the second solvent, stirred and dissolved to obtain a crude pemetrexed intermediate solution.

The first solvent is preferably methanol or ethanol.

The second solvent is preferably acetonitrile or acetone.

In some specific embodiments of the present invention, the first solvent is methanol and the second solvent is acetonitrile.

In some other specific embodiments of the present invention, the first solvent is ethanol, and the second solvent is acetone.

Preferably, in the present invention, the crude pemetrexed intermediate is first mixed with the first solvent, then mixed with the second solvent, and stirred to dissolve it, which is beneficial to the better dissolution of the crude pemetrexed intermediate.

Preferably in the present invention, the stirring and dissolving is carried out under the protection of inert gas. In some specific embodiments of the present invention, the inert gas is nitrogen.

Preferably in the present invention, the temperature for stirring and dissolving is 10-20°C.

The dosage ratio of the crude pemetrexed intermediate to the first solvent is preferably 1 g: (3-10) mL.

The amount ratio of the crude pemetrexed intermediate to the second solvent is preferably 1 g: (5-15) mL.

Then, the crude solution of the pemetrexed intermediate is mixed with trifluoroacetic acid to form a salt to obtain the trifluoroacetate salt of the pemetrexed intermediate.

The present invention does not specifically limit the way of adding the trifluoroacetic acid, and preferably, the way of dropping is adopted.

In some specific embodiments of the present invention, the trifluoroacetic acid is dissolved in the above-mentioned second solvent to form a trifluoroacetic acid solution, and then added dropwise to the crude pemetrexed intermediate solution.

The dropping is preferably carried out under the protection of inert gas. The present invention does not specifically limit the inert gas, and may be an inert gas well known to those skilled in the art. In some specific embodiments of the present invention, the inert gas is nitrogen.

The temperature of the dropwise addition is preferably 5-25°C.

The molar ratio of the crude pemetrexed intermediate to trifluoroacetic acid is preferably 1: (1 to 1.5).

After the addition of trifluoroacetic acid was completed, the system was stirred and a solid was precipitated. The stirring temperature is preferably 0 to 5°C, and the stirring time is preferably 1 to 3 hours.

The crude solution of the pemetrexed intermediate is mixed and reacted with trifluoroacetic acid, and after the salt is formed, the precipitated solid is filtered to obtain the pure trifluoroacetate salt of the pemetrexed intermediate.

The present invention does not specifically limit the filtering method, and it may be a method well known to those skilled in the art, such as funnel filtration or suction filtration.

Then the obtained solid is washed, and the above solid is preferably washed with a second solvent, and then dried under reduced pressure to obtain the pure trifluoroacetate salt of pemetrexed intermediate.

The temperature of the vacuum drying is preferably 35-45°C.

In the present invention, the purification method of pemetrexed intermediate obtained by studying the above-mentioned purified solvent, dosage ratio, test temperature, etc., and using a specific acid, can prepare a culture with a structure of formula II with an HPLC content greater than 99.2%. The trifluoroacetate salt of the intermediate compound of metroxide.

After the above-mentioned pemetrexed intermediate is purified, pemetrexed disodium can be prepared according to methods well known to those skilled in the art. The HPLC purity of the prepared pemetrexed disodium bulk drug reaches more than 99.9%, and the color of the finished solution also meets the pharmaceutical standards.

Preferably, the present invention provides a method for preparing pemetrexed disodium, which comprises the following steps:

S1) Purifying the crude pemetrexed intermediate by using the above purification method to obtain the pemetrexed intermediate;

S2) Using the pemetrexed intermediate obtained in step S1) as a raw material, prepare pemetrexed disodium.

The present invention does not specifically limit the above-mentioned method for preparing pemetrexed disodium, and it can be a general method well known to those skilled in the art.

In some specific embodiments of the present invention, the preparation method is specifically:

The obtained pemetrexed intermediate trifluoroacetate is mixed and reacted with sodium hydroxide to obtain pemetrexed diacid, and then reacted with sodium hydroxide under alkaline conditions to obtain pemetrexed disodium .

Compared with the prior art, the present invention provides a purification method of pemetrexed intermediate, which comprises the following steps: A) dissolving the crude pemetrexed intermediate in a solvent to obtain the crude pemetrexed intermediate Solution; B) mixing the crude solution of the pemetrexed intermediate with trifluoroacetic acid to obtain the trifluoroacetate salt of the pemetrexed intermediate. The invention achieves the purpose of purifying the pemetrexed intermediate by adding an appropriate acid under a certain solvent and temperature to form a salt with the intermediate, reducing the impurity content in the intermediate, and obtaining high-purity pemetrexed intermediate body. The use of the intermediate to prepare pemetrexed disodium bulk medicine can effectively reduce the residual impurities in the bulk medicine, and obtain high-purity pemetrexed disodium bulk medicine that meets the pharmaceutical standards. The preparation method provided by the invention has simple operation and is suitable for industrialized production. At the same time, the trifluoroacetic acid used does not introduce genotoxic impurities and is safer.

Description of the drawings

Figure 1 is an HPLC chart of the trifluoroacetate salt of the compound having the structure of formula (II-A) prepared in Example 2 of the present invention;

2 is an HPLC chart of the trifluoroacetate salt of the compound having the structure of formula (II-A) prepared in Example 3 of the present invention;

Fig. 3 is an HPLC chart of pemetrexed disodium prepared in Example 4 of the present invention.

detailed description

In order to further illustrate the present invention, the purification method of pemetrexed intermediate provided by the present invention will be described in detail below in conjunction with examples.

Example 1 Preparation of crude pemetrexed intermediate (Formula II-A)

Add 756mL saturated sodium bicarbonate, 130.2g L-glutamate dimethyl hydrochloride to the beaker, stir at 25±5℃ for 30 minutes, add dichloromethane for extraction three times, collect the organic phase to obtain free L-glutamate Dimethyl carboxylate dissolved in dichloromethane for use.

Add 4-[2-(2-amino-4,7-dihydro-4-oxo-1H-pyrrolo[2,3-d]pyrimidin-5-yl)ethyl]benzoic acid, DMF in sequence in a three-necked flask , N-methylmorpholine, argon protection, stirring at 25±5℃. Under the protection of argon gas, 2-chloro-4,6-dimethoxy-1,3,5-triazine was added to the reaction solution and stirred for 30 minutes. Keep the internal temperature at 25±5°C, and quickly drop the methylene chloride solution of L-glutamic acid dimethyl prepared above. After dripping, the reaction was stirred at 25±5°C for 1 hour and then detected by HPLC. After the reaction was completed, purified water was added to quench the reaction, transferred to a separatory funnel, extracted, and the organic layer was collected. The aqueous layer was washed once with dichloromethane, the organic phases were combined, and the organic layer was washed twice with purified water. The organic layer was collected and concentrated under reduced pressure at 35-40°C until there was no distillate. Remove the single-neck bottle, add dropwise acetone to crystallize at 25±5°C, after dropping, lower to 5-10°C and stir to crystallize for 1 hour, filter with suction, and dry to obtain the pemetrexed represented by formula (II-A) Crude intermediate.

Example 2 Purification of the compound of formula (II-A)

Weigh 10 grams of the crude compound of formula (II-A) into a three-neck flask, add 50 mL of methanol, and then add 80 mL of acetonitrile, and stir to clear under nitrogen protection at 15°C. After the solution is clear, add 1.7 mL of trifluoroacetic acid to 20 mL of acetonitrile Add slowly under the protection of nitrogen at 20℃, after dripping, cool to 0～5℃ and stir for 2 hours, filter with suction, wash the filter cake with 10mL acetonitrile, and dry the filter cake under reduced pressure at 40±5℃ to get white to off-white The solid is the trifluoroacetic acid salt of the compound represented by formula (II-A), with a yield of 89.5% and a purity of 99.55% as determined by HPLC. The HPLC chart is shown in FIG. 1.

Example 3 Purification of the compound of formula (II-A)

Weigh 10 grams of the crude compound of formula (II-A) into a three-neck flask, add 70 mL of ethanol, and then add 100 mL of acetone, and stir to clear under nitrogen protection at 10°C. After the solution is clear, add 1.5 mL of trifluoroacetic acid to 15 mL of acetone Add slowly under the protection of nitrogen at 10℃, after dripping, cool to 0～5℃ and stir for 2 hours, filter with suction, wash the filter cake with 20mL acetone, and dry the filter cake under reduced pressure at 40±5℃ to get white to off-white The solid is the trifluoroacetate salt of the compound represented by formula (II-A), with a yield of 90.2% and a purity of 99.53% as determined by HPLC. The HPLC chart is shown in FIG. 2.

Example 4 Preparation of Pemetrexed Disodium from Pure Compound (II-A)

Weigh 8.2 grams of the purified trifluoroacetate of the compound of formula (II-A) prepared in Example 3 into a three-necked flask, and add 70 mL of ethanol and 50 mL of aqueous sodium hydroxide, and stir at 25±5°C 30min; then 15.2g solid sodium acetate trihydrate was added, and the reaction was stirred; after the reaction was detected by HPLC, hydrochloric acid was added dropwise to adjust the pH to 7-8, and the mixture was stirred for crystallization at 25±5°C for 1 hour. Suction filtration, washing the filter cake with ethanol, and drying to constant weight.

Put the obtained crude product into the flask, add 80mL sterile water for injection, stir at 25±5℃ until completely dissolved, adjust the pH of the reaction solution to 9.5-10 with the concentration of 0.02M hydrochloric acid/0.01M sodium hydroxide, and stir for 30min . Filter with a sand core funnel, transfer the filtrate to a three-necked flask, add absolute ethanol dropwise with stirring, and stir to crystallize for 2 hours. After suction filtration, the filter cake was washed twice with absolute ethanol and dried in vacuum to obtain a finished product of pemetrexed disodium. The purity of pemetrexed disodium was determined by HPLC to be 99.92%. The HPLC chart is shown in FIG. 3.

Comparative example 1

Take the crude compound of formula (II-A) prepared according to the method of Example 1, and dissolve it with ethanol according to the purification method disclosed in the example of patent application CN105531276A, add p-toluenesulfonic acid, stir at 50°C, then cool and filter, and use The filter cake was washed with ethanol and dried in vacuum to obtain the p-toluenesulfonate salt of the compound of formula (II-A) with a purity of 98.9% as determined by HPLC.

The prepared p-toluenesulfonate of the compound of formula (II-A) was prepared according to the method described in Example 4 to prepare pemetrexed disodium, and the purity of the finished product was 99.87% by HPLC.

Comparative example 2

Weigh 10 grams of the crude compound of formula (II-A) into a three-neck flask, add 100 mL of ethanol, and then add 120 mL of acetone, and stir to clear under nitrogen protection at 20°C. After the solution is clear, add 1.2 mL of hydrochloric acid to 10 mL of acetone. Slowly add dropwise under the protection of nitrogen at 20°C. After dropping, cool to 0～5°C and stir for 1.5 hours. A solid precipitates out. The Buchner funnel is used for suction filtration, but the suction filtration is basically impossible, and the solvent is wrapped in the solid. The solid was separated by centrifugation with a centrifuge, washed with 20 mL of acetone, and then dried under reduced pressure at 40±5°C to obtain the solid, which was the hydrochloride salt of the compound represented by formula (II-A), with a yield of 84.5%. The purity was tested by HPLC Is 97.70%.

Comparative example 3

Take the prescribed amount of the test product (0.56g, pharmacopoeia standard), add water to dissolve it, place it in a 25mL Nessler colorimetric tube, and dilute to 10mL with water. Take another 10 mL of the standard colorimetric solution of the specified color tone and color number, and place it in a Nessler colorimetric tube. The two tubes are placed in front of a white background, and the color is observed by looking up. The disodium pemetrexed prepared in Example 4 and Comparative Example 1 were taken as test samples to test the color of the solution of pemetrexed disodium. The results are shown in Table 1.

Table 1 Comparison of solution colors of pemetrexed disodium prepared in the examples of the application and the comparative examples

Test sample	Solution color number
Pemetrexed disodium of Example 4	GY4
Pemetrexed disodium of Comparative Example 1	GY2

From the comparison in Table 1, it can be seen that the purification method of pemetrexed disodium intermediate provided by the present invention can prepare intermediate compounds with HPLC purity higher than 99.2%, and the pemetrexed disodium prepared thereby has higher HPLC purity 99.9%, and the color of the finished product solution is far better than the finished product prepared in the comparative example.

It can be seen from the above-mentioned examples and comparative examples that the above-mentioned preparation method provided by the present invention is simple to operate, and at the same time obtains a higher yield and purity, and further improves the purity of pemetrexed disodium bulk drug.

The description of the above embodiments is only used to help understand the method and core idea of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims (10)

1. A purification method of pemetrexed intermediate is characterized in that it comprises the following steps:

   A) Dissolve the crude pemetrexed intermediate in a solvent to obtain a crude pemetrexed intermediate solution;

   B) Mixing the crude solution of pemetrexed intermediate with trifluoroacetic acid to obtain the trifluoroacetate salt of pemetrexed intermediate;

   The pemetrexed intermediate has the structure shown in formula II:

   

   Among them, R is CH ₃ or CH ₂ CH ₃ .
2. The purification method according to claim 1, wherein the step A) is specifically:

   Mixing the crude pemetrexed intermediate with the first solvent and the second solvent, stirring and dissolving to obtain a crude pemetrexed intermediate solution;

   The first solvent is methanol or ethanol;

   The second solvent is acetonitrile or acetone.
3. The purification method according to claim 2, wherein the stirring and dissolving is carried out under the protection of inert gas.
4. The purification method according to claim 2, wherein the temperature of the stirring and dissolving is 10-20°C.
5. The purification method of claim 2, wherein the first solvent is methanol, and the second solvent is acetonitrile;

   Alternatively, the first solvent is ethanol, and the second solvent is acetone.
6. The purification method according to claim 2, wherein the ratio of the crude pemetrexed intermediate to the first solvent is 1g: (3-10) mL; the crude pemetrexed intermediate is The amount ratio of the second solvent is 1 g: (5-15) mL.
7. The purification method of claim 1, wherein the molar ratio of the crude pemetrexed intermediate to trifluoroacetic acid is 1: (1 to 1.5).
8. The purification method according to claim 1, wherein the trifluoroacetic acid is added dropwise to the crude solution of pemetrexed intermediate under the protection of inert gas; the temperature of the dropwise addition is 5~ 25°C.
9. The purification method according to claim 1, wherein the step B) is specifically:

   The crude pemetrexed intermediate solution is mixed with trifluoroacetic acid, reacted, and the precipitated solid is filtered to obtain the pure trifluoroacetate salt of the pemetrexed intermediate.
10. A method for preparing pemetrexed disodium, which is characterized in that it comprises the following steps:

    S1) Purifying the crude pemetrexed intermediate by using the purification method of any one of claims 1-9 to obtain the pemetrexed intermediate;

    S2) Using the pemetrexed intermediate obtained in step S1) as a raw material, prepare pemetrexed disodium.

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