A method for refining pharmaceutical-grade adenine

Abstract

The present application provides a method for refining pharmaceutical-grade adenine, which relates to the pharmaceutical field. The method for refining pharmaceutical-grade adenine comprises: adding a refined solvent to a crude adenine product, adding a purification reagent after heating and stirring, stirring, concentrating or filtering to obtain an adenine complex; adding an organic solvent to the adenine complex, heating and stirring for refining, cooling to room temperature, and filtering to obtain a refined adenine complex; neutralizing the refined adenine complex with an alkali in purified water, crystallizing, filtering, and drying to obtain the pharmaceutical-grade adenine. The method for refining pharmaceutical-grade adenine provided in the present application can purify the impurities such as ammonium salts in the crude adenine product to almost undetectable levels, effectively improving the purity of the product, meeting pharmaceutical requirements, and solving the problem of excessive impurities in the ammonium salts of commercially available industrial-grade adenine.

Description

Technical Field

[0001] The present invention relates to the field of pharmaceutical technology, and more particularly to a method for refining pharmaceutical-grade adenine. Background Art

[0002] Adenine, also known as 6-aminopurine (Compound I) in Chinese, has a melting point of 360-365°C and sublimes at 220°C. It is sparingly soluble in water, soluble in boiling water, slightly soluble in ethanol, and insoluble in ether and chloroform. It is an important pharmaceutical raw material and intermediate. Its phosphate, commonly known as vitamin B4, is a component of nucleic acids and participates in the synthesis of genetic material. It can promote leukocyte proliferation and increase white blood cell count. It is used to prevent and treat leukopenia caused by various causes, particularly leukopenia caused by cancer chemotherapy. It is also used for acute granulocytopenia.

[0003] Adenine, as a biological product, has begun to be widely used in medicine, microbiology, and organic synthesis. It has the effect of stimulating leukocyte proliferation and is therefore used to treat leukopenia caused by various reasons, especially leukopenia caused by tumor chemotherapy, radiotherapy, and benzene poisoning. Adenine is an active ingredient in nucleic acids and some coenzymes. Therefore, it is also an important intermediate for purine drugs such as 6-benzylaminopurine, kinetin, isopentenyl adenine, benzylpyranoadenine, ATP, nucleosides, etc. It also has the physiological effects of cytokines and is widely used in biochemical research. Adenine is also an essential raw material for the preparation of the anti-hepatitis B drugs adefovir dipivoxil and tenofovir disoproxil fumarate (also known as "tenofovir disoproxil").

[0004] According to CN200710071182.1, the production of adenine utilizes the inherent acid-base catalytic properties of high-temperature liquid water and its ability to dissolve organic matter to hydrolyze adenosine to produce adenine. Patent CN201110282021.3 discloses a process in which hypoxanthine or acetylhypoxanthine reacts with phosphorus oxychloride to produce 6-chloropurine, which is then aminated to produce crude adenine. This route utilizes readily available raw materials, but is long, highly polluting, and has poor atom economy. The crude adenine produced by this process contains impurities such as hypoxanthine, tertiary amine hydrochloride, phosphate, and metal ions, requiring purification to obtain high-purity adenine. The current mainstream production process involves acetylation of adenosine to produce acetyladenine, which is then hydrolyzed in sodium hydroxide solution to directly produce adenine. This process is simple, easy, and offers high yields, making it a green and environmentally friendly process suitable for industrial production. The product primarily contains impurities such as hypoxanthine and contains a large amount of ammonium salts.

[0005] This application uses purchased industrial-grade adenine and a special refining method to solve the technical problem of unqualified industrial-grade adenine ammonium salt.

[0006] Patent CN201210229904.2 reports a method for refining adenine: crude adenine is dissolved in water, adjusted to a pH of 3-5 with an inorganic acid, and then activated carbon is added and heated for refining. However, ammonium salts in the product are difficult to remove. Traditionally, the adenine refining process involves adding 40-60 times the amount of water and an appropriate amount of activated carbon to the crude adenine product, heating to a boil, maintaining the temperature, filtering while hot, cooling for a long time to crystallize, filtering, and drying. This method uses a lot of water, and ammonium salts are often difficult to remove after refining. Hunan Erkang Pharmaceutical Co., Ltd. has optimized this refining method in patent CN201310000056.2, where industrial-grade crude adenine is boiled in water, maintained for 5 minutes, centrifuged, and the solid washed with hot water until the washing liquid no longer reacts with chloride ions. After centrifugation, the solid is dissolved in water, and an organic acid is added to adjust the pH to 2-3. Then, medicinal activated carbon and EDTA are added, and the mixture is heated to 90°C. After the reaction is kept warm, the mixture is filtered while hot and then ultrafiltered. After the filtrate is cooled, the pH is adjusted to 7-8 with an inorganic alkaline substance. After stirring evenly, the mixture is filtered. The filter cake is washed with cold water and dried to obtain pure adenine. This method introduces impurities such as EDTA, and ammonium salts are difficult to remove.

[0007] Because ammonium salts are difficult to remove, this application provides a new refining method to refine industrial-grade products to meet pharmaceutical-grade requirements. Summary of the Invention

[0008] The purpose of this application is to provide a method for refining pharmaceutical-grade adenine to solve the above problems.

[0009] To achieve the above objectives, this application adopts the following technical solutions:

[0010] A method for refining pharmaceutical-grade adenine, comprising:

[0011] Adding a refined solvent to the crude adenine, heating and stirring, then adding a purification reagent, stirring, concentrating or filtering to obtain an adenine complex;

[0012] adding an organic solvent to the adenine complex, heating and stirring for purification, cooling to room temperature, and filtering to obtain a purified adenine complex;

[0013] The purified adenine complex is neutralized with alkali in purified water, crystallized, filtered, and dried to obtain the pharmaceutical grade adenine.

[0014] Preferably, the refined solvent includes one or more of purified water, ethanol, methanol, isopropanol, and acetone, and the mass volume ratio of the crude adenine to the refined solvent is 1g:(1-5)ml, preferably 1g:3ml.

[0015] Optionally, the mass volume ratio of the crude adenine to the refined solvent can be 1g:1ml, 1g:2ml, 1g:3ml, 1g:4ml, 1g:5ml, 1g:6ml, 1g:7ml, 1g:8ml, 1g:9ml, 1g:10ml or any value between 1g:(1-10)ml.

[0016] Preferably, the purification reagent comprises hydrochloric acid and / or glacial acetic acid, and the amount used is 0.8-1.2 times, preferably 1 times, the molar amount of the crude adenine.

[0017] Optionally, the purification reagent includes hydrochloric acid and / or glacial acetic acid, and the amount used can be 0.8 times, 0.9 times, 1.0 times, 1.1 times, 1.2 times or any value between 0.8 and 1.2 times the molar amount of the crude adenine.

[0018] Preferably, the organic solvent comprises one or more of ethanol, methanol, and isopropanol, and the mass volume ratio of the crude adenine to the organic solvent is 1 g: (1-10) ml.

[0019] Optionally, the mass volume ratio of the crude adenine to the organic solvent can be 1g:1ml, 1g:2ml, 1g:3ml, 1g:4ml, 1g:5ml, 1g:6ml, 1g:7ml, 1g:8ml, 1g:9ml, 1g:10ml or any value between 1g:(1-10)ml.

[0020] Preferably, the refining temperature is 30-80°C and the time is 0.5-24h.

[0021] Optionally, the refining temperature can be 30, 40, 50, 60, 70, 80 or any value between 30-80°C, and the refining time can be 0.5h, 1h, 2h, 4h, 6h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h, 24h or any value between 0.5-24h.

[0022] Preferably, the base includes one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate.

[0023] Preferably, the neutralization endpoint pH is 7-9.

[0024] Optionally, the neutralization endpoint pH may be 7, 8, 9 or any value between 7 and 9.

[0025] Preferably, the mass volume ratio of the refined adenine complex to the purified water is 1 g: (1-15) ml.

[0026] Preferably, the mass volume ratio of the refined adenine complex to the purified water is 1 g:5 ml.

[0027] Optionally, the mass volume ratio of the refined adenine complex to the purified water can be 1g:1ml, 1g:2ml, 1g:3ml, 1g:4ml, 1g:5ml, 1g:6ml, 1g:7ml, 1g:8ml, 1g:9ml, 1g:10ml, 1g:11ml, 1g:12ml, 1g:13ml, 1g:14ml, 1g:15ml or any value between 1g:(1-15)ml.

[0028] Preferably, the material is sterile filtered before the neutralization.

[0029] Compared with the prior art, the advantages of this application include:

[0030] The present application provides a method for refining adenine, which comprises the following steps: subjecting a crude adenine product to a complexing salt using a complexing agent under the action of a solvent heating; refining the complex salt in a specific refining solvent; utilizing the difference in solubility of related impurity ammonium salts and adenine complexes in the solvent system and the difference in the crystal seed generation process to achieve the refining effect of removing ammonium salts, thereby improving the purity of the product; the refined adenine complex salt is freed to finally obtain pharmaceutical-grade adenine, and finally the ammonium salt impurities in the crude adenine product are refined to almost undetectable levels, meeting pharmaceutical requirements. DETAILED DESCRIPTION

[0031] The embodiments of the present application will be described in detail below in conjunction with specific examples, but it will be understood by those skilled in the art that the following examples are merely illustrative of the present application and should not be considered as limiting the scope of the present application. In the examples, if specific conditions are not specified, the conditions are carried out according to conventional conditions or manufacturer recommendations. The reagents or instruments used are not specified by the manufacturer and are conventional products that can be purchased commercially.

[0032] The raw material information and sources used in the following specific examples are shown in Table 1:

[0033] Table 1 Reagents and sources

[0034]

[0035] Example 1

[0036] 500g of adenine was added to a 3000ml three-necked flask, 1000ml of purified water was added, the temperature was raised to 50±3°C, the mixture was stirred thoroughly and kept warm for 30min, 222g of glacial acetic acid was added, and the mixture was stirred until dissolved. The reaction solution was concentrated to obtain an adenine complex; the adenine complex salt was added to 1500ml of ethanol, transferred to a 3000ml three-necked flask, heated to 77°C and stirred under reflux for 1h, cooled to room temperature, and filtered to obtain a refined salt. The refined salt was transferred to a 10000ml three-necked flask, 5000ml of purified water was added, stirred at 50°C, sterilized and filtered, the filtrate was adjusted to pH 8-9 with 30% sodium hydroxide solution, stirred for 1h, and then filtered and rinsed with 500ml of purified water in portions to obtain a refined product. The refined product was vacuum dried at 60°C for 6h to obtain 458.6g of pharmaceutical-grade adenine, with a yield of 91.72%, a content of 99.8%, and an ammonium salt ≤0.0002%.

[0037] Example 2

[0038] 500g of adenine was added to a 3000ml three-necked flask, and 1000ml of ethanol was added. The temperature was raised to 50±3℃ and stirred thoroughly for 30min. 375.2g of 36% hydrochloric acid was added and stirred for about 30min. The temperature was lowered to 0-5℃ and filtered to obtain adenine complex salt. The adenine complex salt was added to 2000ml of methanol and transferred to a 3000ml three-necked flask. The temperature was raised to 60℃ and stirred for 1h. The temperature was lowered to room temperature and filtered to obtain a refined product. Salt, transfer the refined salt to a 10000ml three-necked flask, add 8000ml of purified water, stir at 80℃, sterilize and filter, adjust the pH of the filtrate to 8-9 with 30% potassium hydroxide solution, stir for 1h and filter, rinse with 500ml of purified water in batches to obtain a refined product, which is vacuum dried at 55℃ for 8h to obtain 425.3g of pharmaceutical grade adenine, with a yield of 85.06%, a content of 99.8%, and ammonium salt ≤0.0005%.

[0039] Example 3

[0040] 500g of adenine was added to a 3000ml three-necked flask, 1000ml of isopropanol was added, the temperature was raised to 50±3°C, the mixture was stirred thoroughly and kept warm for 30min, 375.2g of 36% hydrochloric acid was added, stirred for about 30min, and concentrated to obtain an adenine complex salt; the adenine complex salt was added to 2000ml of ethanol, transferred to a 3000ml three-necked flask, heated to 70°C and stirred for 1h, cooled to room temperature, and filtered to obtain a refined salt. The refined salt was transferred to a 10000ml three-necked flask, 3000ml of purified water was added, stirred at 80°C, sterilized and filtered, the filtrate was adjusted to pH 8-9 with 30% potassium hydroxide solution, stirred for 1h, and then filtered. The purified product was rinsed with 500ml of purified water in portions to obtain a refined product. The refined product was vacuum dried at 58°C for 7h to obtain 471.1g of pharmaceutical-grade adenine with a yield of 94.22%. Content 100.1%, ammonium salt ≤ 0.0005%

[0041] It is noteworthy that in the embodiments of the present application, industrial-grade adenine is subjected to solvent heating, and crude adenine is subjected to solvent heating, and a complexing agent is used to complex the adenine to form a salt. The complex salt is refined in a specific refined solvent, and the difference in solubility of related impurity ammonium salts and adenine complexes in the solvent system and the difference in the crystal seed production process are utilized to achieve the refining effect of removing ammonium salts, thereby improving the purity of the product. The refined adenine complex salt is freed to finally obtain pharmaceutical-grade adenine, and the ammonium salt impurities in the crude adenine are finally refined to almost undetectable levels, meeting pharmaceutical requirements.

[0042] The pharmaceutical grade quality standards of adenine are shown in Table 2 below:

[0043] Table 2 Adenine pharmaceutical grade quality standards

[0044]

[0045]

[0046] To further confirm the validity of this patent, experiments were designed to test whether adenine complex salt was purified or not purified, and the results were similar to those of Example 4 and Example 5.

[0047] Example 5

[0048] 500g of adenine was added to a 3000ml three-necked flask, followed by 1000ml of purified water. The mixture was heated to 100°C and stirred for 1 hour. The mixture was cooled to room temperature and filtered to obtain the refined salt. The refined salt was vacuum dried at 58°C for 7 hours to obtain 485.6g of refined adenine, with a yield of 97.12%. The content was 98.4%, and the ammonium salt content was >0.001%, which was unacceptable.

[0049] Example 6

[0050] 500g of adenine was added to a 3000ml three-necked flask, followed by 1000ml of anhydrous ethanol. The temperature was raised to 50±3°C and stirred thoroughly for 30 minutes. 222g of glacial acetic acid was added and stirred for approximately 30 minutes. The adenine complex salt was then concentrated to obtain the adenine complex salt. The adenine complex salt was transferred to a 10000ml three-necked flask, 3000ml of purified water was added, and the mixture was stirred at 80°C. The mixture was sterile filtered and the pH of the filtrate was adjusted to 8-9 with 30% potassium hydroxide solution. The mixture was stirred for 1 hour and then filtered. The mixture was rinsed with 500ml of purified water in portions to obtain a refined product. The refined product was vacuum dried at 58°C for 7 hours to obtain 482.3g of pharmaceutical-grade adenine, with a yield of 96.46%. The content was 99.1%, and the ammonium salt content was >0.001%, which was unacceptable.

[0051] Experiments without refining adenine complex salts or without refining adenine complex salts have shown that traditional adenine refining methods are ineffective in removing ammonium salts and that only special refining methods can be effective. The present invention has successfully developed an effective method for refining pharmaceutical-grade adenine ammonium salts.

[0052] Although some specific embodiments of the present invention have been described in detail by way of examples, it should be understood by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the present invention. It should be understood by those skilled in the art that modifications may be made to the above embodiments without departing from the scope and spirit of the present invention. The scope of the present invention is defined by the appended claims.

Claims

1. A method for refining pharmaceutical grade adenine, characterized in that: include: Adding a refined solvent to the crude adenine, heating and stirring, then adding a purification reagent, stirring, concentrating or filtering to obtain an adenine complex; adding an organic solvent to the adenine complex, heating and stirring for purification, cooling to room temperature, and filtering to obtain a purified adenine complex; The purified adenine complex is neutralized with alkali in purified water, crystallized, filtered, and dried to obtain the pharmaceutical grade adenine; the mass volume ratio of the purified adenine complex to the purified water is 1 g: (1-15) ml; The refining solvent is selected from one or more of purified water, ethanol, methanol, isopropanol, and acetone, and the mass volume ratio of the crude adenine to the refining solvent is 1 g: (1-10) ml; The purification reagent is selected from hydrochloric acid and / or glacial acetic acid, and the amount used is 0.8-1.2 times the molar amount of the crude adenine; The organic solvent is selected from one or more of ethanol, methanol, and isopropanol, and the mass volume ratio of the crude adenine to the organic solvent is 1 g: (1-10) ml; The refining temperature is 30-80°C and the time is 0.5-24h; The base is selected from one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate; The neutralization end point pH is 7-9.

2. The method for refining pharmaceutical grade adenine according to claim 1, wherein During the neutralization, the mass volume ratio of the purified adenine complex to the purified water is 1 g:5 ml.

3. The method for purifying pharmaceutical grade adenine according to claim 1 or 2, wherein: Prior to the neutralization, the material was sterile filtered.

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