A method for synthesizing apixaban genotoxic impurity I

Abstract

This invention relates to the field of pharmaceutical impurity preparation technology, and discloses a method for synthesizing apixaban genotoxic impurity I. The steps include: S1. performing an addition reaction of compound II in an alkaline system to generate compound III; S2. subjecting the product of S1 to elimination and isomerization reactions under heating, separating the reaction product to obtain apixaban genotoxic impurity I. The synthesis method of this invention has high safety, low raw material cost, and can achieve a one-pot reaction while ensuring yield and product purity (no product separation and purification is required between each reaction step; only one separation and purification is needed after obtaining the final product).

Description

Technical Field

[0001] This invention relates to the field of pharmaceutical impurity preparation technology, and in particular to a method for synthesizing apixaban genotoxic impurity I. Background Technology

[0002] Apixaban is a direct factor Xa inhibitor used as an anticoagulant to reduce the risk of stroke and systemic embolism in patients with nonvalvular atrial fibrillation. It can also be used to prevent deep vein thrombosis (DVT). Its chemical name is 1-(4-methoxyphenyl)-7-oxo-6-[4-(2-oxopiperazin-1-yl)phenyl]-4,5,6,7-tetrahydro-1H-pyrazole[3,4-c]-pyridine-3-carboxamide, and its structural formula is as follows: .

[0003] With the continuous improvement of testing standards both domestically and internationally, higher requirements have been placed on the quality of apixaban. The literature "LC-MS / MS Examination of Genotoxic Impurities in Apixaban" (Cheng Fangjie, Fu Xiaoting, Gao Shuxiao, et al. LC-MS / MS Examination of Genotoxic Impurities in Apixaban [J]. Chinese Journal of New Drugs, 2020, 29(07):816-821.) reports on various genotoxic impurities involved in the synthesis of apixaban and their detection methods, including the following compound I: .

[0004] Currently, there are few reports on the synthesis methods of the aforementioned apixaban genotoxic impurity I. Patent WO2019025426A1 provides a synthetic route: , This method uses highly toxic and volatile oxaloyl chloride monoethyl ester and relatively expensive p-methoxyphenylhydrazine, which poses significant safety risks and high costs during the preparation process. Summary of the Invention

[0005] To address the technical problems of high safety risks and high costs associated with existing methods for synthesizing apixaban genotoxic impurity I, this invention provides a method for synthesizing apixaban genotoxic impurity I. The synthesis method of this invention offers high safety, low raw material costs, and enables a one-pot reaction while ensuring yield and product purity (eliminating the need for product separation and purification between reaction steps, requiring only one separation and purification after obtaining the final product).

[0006] The specific technical solution of this invention is as follows: A method for synthesizing apixaban genotoxic impurity I, comprising: S1. Compound II undergoes an addition reaction in an alkaline system to produce compound III: ; S2. The product of S1 is subjected to elimination and isomerization reactions under heating to separate the reaction products, yielding apixaban genotoxic impurity I: , .

[0007] In the above synthesis process, steps S1 and S2 can be carried out continuously. After the addition reaction in step S1 is completed, there is no need to separate and purify the product. The elimination and isomerization reaction in step S2 can be carried out directly by heating. Thanks to the characteristics of each reaction in the entire reaction route of this invention, this one-pot reaction method can simplify the preparation steps and shorten the preparation process while ensuring the yield and product purity. During this process, the remaining base after step S1 can be used to promote the elimination reaction in step S2 and promote the isomerization of the product of the elimination reaction (compound IV) to form apixaban genotoxic impurity I (for the tautomers of compound IV and impurity I, under acidic conditions, they tend to exist in the form of compound IV, and under alkaline conditions, they tend to exist in the form of impurity I).

[0008] Furthermore, the present invention separates the addition reaction from the elimination and isomerization reaction (after completing the addition reaction in step S1, the elimination and isomerization reaction in step S2 is carried out by heating), which can avoid the reduction in yield caused by the substitution reaction between compound II and alcohols in the reaction solvent after heating.

[0009] Furthermore, this invention uses only two reactants, compound II and a base, to synthesize apixaban genotoxic impurity I without the need for volatile and highly toxic raw materials, and the raw material cost is relatively low.

[0010] As an optional implementation, in step S1, the alkaline system is a mixture containing compound II, a base, and a solvent.

[0011] As an optional implementation, in step S1, the initial pH of the alkaline system is 9-12 (more preferably 11-12).

[0012] Within a certain range, moderately increasing the pH of the alkaline system can promote the addition reaction of compound II, as well as subsequent elimination and isomerization reactions, thereby increasing the yield. However, when the reaction system is too alkaline, the elimination and isomerization reactions under heating will exacerbate the ester hydrolysis side reaction, leading to a decrease in yield. Therefore, this invention controls the initial pH of the alkaline system within the range of 9-12, achieving a relatively high yield. Furthermore, controlling the initial pH at 11-12 can further improve the yield.

[0013] As an optional implementation, in step S1, the alkali is one or more of potassium carbonate, sodium carbonate, potassium bicarbonate, and sodium bicarbonate.

[0014] As an optional implementation, in step S1, the solvent is a mixed solution of alcohol and water, wherein the alcohol content is 20-80% vol.

[0015] As an optional implementation, in step S1, the temperature of the addition reaction is 20~30℃ and the time is 4~8h.

[0016] As an optional implementation, in step S1, the mass ratio of compound II to solvent is 1:7~20.

[0017] As an optional implementation, in step S2, the temperature of the elimination and isomerization reaction is 40~80℃ (more preferably 60~80℃), and the time is 5~6h.

[0018] Elimination reactions require heating; excessively low temperatures can lead to incomplete elimination. While extending the reaction time can improve the degree of reaction to some extent, it also increases the amount of byproducts, affecting the yield and product purity. Conversely, excessively high temperatures can exacerbate ester hydrolysis, also impacting the yield. Therefore, this invention controls the elimination and isomerization reactions at 40–80°C and sets the time to 5–6 hours, which improves the reaction yield and ensures high product purity. Maintaining the temperature at 60–80°C further enhances the yield.

[0019] As an optional implementation, step S2, the process of separating the reaction product includes: filtration, washing with an ethanol-water solution, and then performing silica gel column chromatography.

[0020] Compared with the prior art, the present invention has the following advantages: (1) The present invention adopts the reaction route of addition reaction → elimination reaction → isomerization reaction to synthesize apixaban genotoxic impurity I from compound II. It can achieve one-pot reaction while ensuring yield and product purity (no product separation and purification is required between each step of the reaction, only one separation and purification is required after the final product is obtained), and the raw material cost is low and the safety of the synthesis process is high.

[0021] (2) By performing the addition reaction of compound II and then heating it to carry out the elimination and isomerization reactions, the present invention can carry out the addition reaction and the elimination and isomerization reactions in steps, thereby avoiding the reduction of yield caused by the substitution reaction between compound II and alcohols in the reaction solvent after heating.

[0022] (3) By controlling the initial pH of the reaction system, as well as the temperature and time of the elimination and isomerization reactions within a specific range, the present invention can improve the degree of reaction and reduce the occurrence of ester hydrolysis side reactions, thereby further improving the yield. Attached Figure Description

[0023] Figure 1 The image shows the HPLC chromatogram of the apixaban sample.

[0024] Figure 2 The HPLC chromatogram of apixaban genotoxic impurity I.

[0025] Figure 3 The HPLC chromatogram of an apixaban sample after the addition of apixaban genotoxic impurity I. Detailed Implementation

[0026] The present invention will now be further described.

[0027] A method for synthesizing apixaban genotoxic impurity I, comprising: S1. Compound II undergoes an addition reaction in an alkaline system to produce compound III: ; S2. The product of S1 is subjected to elimination and isomerization reactions under heating to separate the reaction products, yielding apixaban genotoxic impurity I: , .

[0028] In the above synthetic method, an addition reaction → elimination reaction → isomerization reaction is adopted to synthesize apixaban genotoxic impurity I from compound II. The raw materials used are of low cost, the synthesis process is relatively safe, and thanks to the characteristics of each reaction in the entire reaction route, a one-pot reaction can be achieved while ensuring yield and product purity (no product separation and purification is required between each step; only one separation and purification is needed after obtaining the final product). During the process, the residual base after the addition reaction can be used to promote the elimination reaction and the isomerization of the elimination product to form the final target product. Furthermore, in the above synthetic method, by heating after the addition reaction of compound II to carry out the elimination and isomerization reactions, the addition reaction and the elimination and isomerization reactions are carried out stepwise. This also avoids the substitution reaction between compound II and alcohols in the reaction solvent after heating, thereby improving the product yield.

[0029] In some specific embodiments, in step S1, the alkaline system is a mixture containing compound II, a base, and a solvent.

[0030] In some specific embodiments, in step S1, the initial pH of the alkaline system is 9-12. Within this initial pH range, a higher yield can be achieved. However, if the initial pH is too low or too high, the yield of apixaban genotoxic impurity I prepared from compound II will decrease. When the initial pH is too low, it is not conducive to the addition reaction and subsequent elimination and isomerization reactions. When the initial pH is too high, the ester hydrolysis side reaction will be aggravated during the elimination and isomerization reactions under heating.

[0031] In some specific embodiments, in step S1, the alkali is one or more of potassium carbonate, sodium carbonate, potassium bicarbonate, and sodium bicarbonate.

[0032] In some specific embodiments, in step S1, the temperature of the addition reaction is 20~30°C and the time is 4~8h.

[0033] In some specific embodiments, step S1 specifically includes: mixing compound II, base and solvent, and stirring at 20~30°C for 4~8 hours.

[0034] The reaction solvent used in this invention is not particularly limited and can be selected based on the common knowledge of those skilled in the art. In some specific embodiments, in step S1, the solvent is a mixed solution of alcohol and water, wherein the alcohol content is 20-80% vol.

[0035] In some specific embodiments, in step S1, the mass ratio of compound II to solvent is 1:7~20.

[0036] In some specific embodiments, in step S2, the elimination and isomerization reaction is carried out at a temperature of 40-80°C for 5-6 hours. Within the above temperature and time range for the elimination and isomerization reaction, a high yield can be achieved. When the temperature is too low, the elimination reaction will be incomplete. Although extending the reaction time can improve the degree of reaction to some extent, it will also increase the amount of by-products, leading to a decrease in product yield and purity. When the reaction temperature is too high, the ester hydrolysis side reaction is easily aggravated, which will also lead to a decrease in product yield.

[0037] In some specific embodiments, step S2, the process of separating the reaction products includes: filtration, washing with an ethanol aqueous solution with an ethanol content of 20-80% vol, and then performing silica gel column chromatography.

[0038] The present invention will be further described below through specific embodiments and comparative examples. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0039] Example 1: Synthesis of Apixaban Genotoxic Impurity I In this embodiment, the reaction route for synthesizing apixaban genotoxic impurity I is an addition reaction → elimination reaction → isomerization reaction, as detailed below: The specific steps are as follows: In a 1000 mL single-necked flask, 25.69 g of compound II and 500 g of a 20% vol aqueous solution of ethanol were added. Sodium carbonate solid was added to adjust the pH of the mixture to 9. The mixture was stirred at room temperature (20°C) for 8 hours. TLC monitoring (using a 2:1 mixture of ethyl acetate and n-heptane as the developing solvent; iodine staining) showed almost no residue of compound II. The temperature was then raised to 40°C and stirring continued for 5 hours. The mixture was filtered and washed with a 40% vol aqueous solution of ethanol to obtain the crude product. The crude product was subjected to silica gel column chromatography to obtain 9.7 g of apixaban genotoxic impurity I, with a yield of 40.8% and a purity of 97.1%.

[0040] Example 2: Synthesis of Apixaban Genotoxic Impurity I In this embodiment, the reaction route for synthesizing apixaban genotoxic impurity I is an addition reaction → elimination reaction → isomerization reaction, as detailed below: The specific steps are as follows: In a 500 mL single-necked flask, 25.69 g of compound II and 300 g of a 40% vol aqueous ethanol solution were added, along with potassium carbonate solid to adjust the pH of the mixture to 12. The mixture was stirred at room temperature (25°C) for 4 hours. TLC monitoring (using a 2:1 mixture of ethyl acetate and n-heptane as the developing solvent; iodine staining) showed almost no residue of compound II. The temperature was then raised to 60°C and stirring continued for 5 hours. The mixture was filtered and washed with a 40% vol aqueous ethanol solution to obtain the crude product. The crude product was subjected to silica gel column chromatography to obtain 15.2 g of apixaban genotoxic impurity I, with a yield of 63.8% and a purity of 98.7%.

[0041] Example 3: Synthesis of Apixaban Genotoxic Impurity I In this embodiment, the reaction route for synthesizing apixaban genotoxic impurity I is an addition reaction → elimination reaction → isomerization reaction, as detailed below: The specific steps are as follows: In a 500 mL single-necked flask, 25.69 g of compound II and 200 g of an 80% vol aqueous solution of ethanol were added. Sodium bicarbonate solid was added to adjust the pH of the mixture to 10. The mixture was stirred at room temperature (30°C) for 7 hours. TLC monitoring (using a 2:1 mixture of ethyl acetate and n-heptane as the developing solvent; iodine staining) showed almost no residue of compound II. The temperature was then raised to 80°C and stirring continued for 5 hours. The mixture was filtered and washed with an 80% vol aqueous solution of ethanol to obtain the crude product. The crude product was subjected to silica gel column chromatography to obtain 10.6 g of apixaban genotoxic impurity I, with a yield of 44.6% and a purity of 96.7%.

[0042] Example 4: Synthesis of Apixaban Genotoxic Impurity I In this embodiment, the reaction route for synthesizing apixaban genotoxic impurity I is an addition reaction → elimination reaction → isomerization reaction, as detailed below: The specific steps are as follows: In a 1000 mL single-necked flask, 25.69 g of compound II and 500 g of a 20% vol aqueous ethanol solution were added. Sodium carbonate solid was added to adjust the pH of the mixture to 11. The mixture was stirred at room temperature (20°C) for 8 hours. TLC monitoring (using a 2:1 mixture of ethyl acetate and n-heptane as the developing solvent; iodine staining) showed almost no residue of compound II. The temperature was then raised to 40°C and stirring continued for 5 hours. The mixture was filtered and washed with a 40% vol aqueous ethanol solution to obtain the crude product. The crude product was subjected to silica gel column chromatography to obtain 10.3 g of apixaban genotoxic impurity I, with a yield of 43.3% and a purity of 97.2%.

[0043] Example 5: Synthesis of Apixaban Genotoxic Impurity I In this embodiment, the reaction route for synthesizing apixaban genotoxic impurity I is an addition reaction → elimination reaction → isomerization reaction, as detailed below: The specific steps are as follows: In a 1000 mL single-necked flask, 25.69 g of compound II and 500 g of a 20% vol aqueous ethanol solution were added. Sodium carbonate solid was added to adjust the pH of the mixture to 12. The mixture was stirred at room temperature (20°C) for 8 hours. TLC monitoring (using a 2:1 mixture of ethyl acetate and n-heptane as the developing solvent; iodine staining) showed almost no residue of compound II. The temperature was then raised to 40°C and stirring continued for 5 hours. The mixture was filtered and washed with a 40% vol aqueous ethanol solution to obtain the crude product. The crude product was subjected to silica gel column chromatography to obtain 10.9 g of apixaban genotoxic impurity I, with a yield of 45.9% and a purity of 96.8%.

[0044] Example 6: Synthesis of Apixaban Genotoxic Impurity I In this embodiment, the reaction route for synthesizing apixaban genotoxic impurity I is an addition reaction → elimination reaction → isomerization reaction, as detailed below: The specific steps are as follows: In a 1000 mL single-necked flask, 25.69 g of compound II and 500 g of a 20% vol aqueous ethanol solution were added. Sodium carbonate solid was added to adjust the pH of the mixture to 9. The mixture was stirred at room temperature (20°C) for 8 hours. TLC monitoring (using a 2:1 mixture of ethyl acetate and n-heptane as the developing solvent; iodine staining) showed almost no residue of compound II. The temperature was then raised to 60°C and stirring continued for 5 hours. The mixture was filtered and washed with a 40% vol aqueous ethanol solution to obtain the crude product. The crude product was subjected to silica gel column chromatography to obtain 10.8 g of apixaban genotoxic impurity I, with a yield of 45.4% and a purity of 98.3%.

[0045] Example 7: Synthesis of Apixaban Genotoxic Impurity I In this embodiment, the reaction route for synthesizing apixaban genotoxic impurity I is an addition reaction → elimination reaction → isomerization reaction, as detailed below: The specific steps are as follows: In a 1000 mL single-necked flask, 25.69 g of compound II and 500 g of a 20% vol aqueous ethanol solution were added. Sodium carbonate solid was added to adjust the pH of the mixture to 9. The mixture was stirred at room temperature (20°C) for 8 hours. TLC monitoring (using a 2:1 mixture of ethyl acetate and n-heptane as the developing solvent; iodine staining) showed almost no residue of compound II. The temperature was then raised to 80°C and stirring continued for 5 hours. The mixture was filtered and washed with a 40% vol aqueous ethanol solution to obtain the crude product. The crude product was subjected to silica gel column chromatography to obtain 11.3 g of apixaban genotoxic impurity I, with a yield of 47.5% and a purity of 96.9%.

[0046] Comparative Example 1: Synthesis of Apixaban Genotoxic Impurity I The reaction route for synthesizing apixaban genotoxic impurity I in this comparative example is the same as that in Example 1, except that the addition reaction is combined with the elimination and isomerization reactions into one step. Specifically, this comparative example synthesizes apixaban genotoxic impurity I through the following steps: In a 1000 mL single-necked flask, 25.69 g of compound II and 500 g of a 20% vol aqueous solution of ethanol were added. Sodium carbonate solid was added to adjust the pH of the mixture to 9. The mixture was heated to 40°C and stirred for 7 hours. TLC monitoring (using a 2:1 mixture of ethyl acetate and n-heptane as the developing solvent; iodine staining) showed almost no residue of compound II. The mixture was filtered and washed with a 40% vol aqueous solution of ethanol to obtain the crude product. The crude product was subjected to silica gel column chromatography to obtain 8.2 g of apixaban genotoxic impurity I, with a yield of 34.5% and a purity of 92.2%.

[0047] Analysis of experimental results: The yield of Example 1 was significantly higher than that of Comparative Example 1, indicating that by performing the addition reaction and elimination and isomerization reaction stepwise after heating after completing the addition reaction of compound II, the reaction yield can be improved. The reason is that this stepwise reaction method can avoid the substitution reaction of compound II with alcohols in the reaction solvent (such as ethanol used in Example 1 and Comparative Example 1) after heating, which would reduce the yield.

[0048] Comparative Example 2: Synthesis of Apixaban Genotoxic Impurity I The reaction route for synthesizing apixaban genotoxic impurity I in this comparative example is the same as in Example 1, with the only difference being the reduction of the initial pH value of the reaction system. Specifically, this comparative example synthesizes apixaban genotoxic impurity I through the following steps: In a 1000 mL single-necked flask, 25.69 g of compound II and 500 g of a 20% vol aqueous solution of ethanol were added. Sodium carbonate solid was added to adjust the pH of the mixture to 8. The mixture was stirred at room temperature (20°C) for 12 hours. TLC monitoring (using a 2:1 mixture of ethyl acetate and n-heptane as the developing solvent; iodine staining) showed almost no residue of compound II. The temperature was then raised to 40°C and stirring continued for 5 hours. The mixture was filtered and washed with a 40% vol aqueous solution of ethanol to obtain the crude product. The crude product was subjected to silica gel column chromatography to obtain 6.3 g of apixaban genotoxic impurity I, with a yield of 26.5% and a purity of 91.2%.

[0049] Comparative Example 3: Synthesis of Apixaban Genotoxic Impurity I The reaction route for synthesizing apixaban genotoxic impurity I in this comparative example is the same as in Example 1, with the only difference being the increased initial pH of the reaction system. Specifically, this comparative example synthesizes apixaban genotoxic impurity I through the following steps: In a 1000 mL single-necked flask, 25.69 g of compound II and 500 g of a 20% vol aqueous ethanol solution were added. Sodium carbonate and sodium hydroxide solids were added to adjust the pH of the mixture to 13. The mixture was stirred at room temperature (20°C) for 6 hours. TLC monitoring (using a 2:1 mixture of ethyl acetate and n-heptane as the developing solvent; iodine staining) showed almost no residue of compound II. The temperature was then raised to 40°C and stirring continued for 5 hours. The mixture was filtered and washed with a 40% vol aqueous ethanol solution to obtain the crude product. The crude product was subjected to silica gel column chromatography to obtain 5.2 g of apixaban genotoxic impurity I, with a yield of 21.9% and a purity of 90.2%.

[0050] Analysis of experimental results: The yields of Examples 1, 4, and 5 were significantly higher than those of Comparative Examples 2 and 3, indicating that both excessively high and low initial pH of the reaction system would decrease the yield of the preparation of apixaban genotoxic impurity I from compound II. An initial pH of 9-12 effectively improved the yield, with a further preferred initial pH of 11-12. The reason for this is that the addition reaction of compound II requires an alkaline environment, and the elimination reaction of compound III generates HCl. An alkaline environment is conducive to promoting this reaction. For the tautomers of compound IV and impurity I, they tend to exist as compound IV under acidic conditions and as impurity I under alkaline conditions. Therefore, within a certain range, appropriately increasing the initial pH of the reaction system can promote the addition reaction of compound II and subsequent elimination and isomerization reactions, thereby increasing the yield. However, when the alkalinity of the reaction system is too strong, the elimination and isomerization reactions under heating will exacerbate the ester hydrolysis side reaction, leading to a decrease in yield.

[0051] Comparative Example 4: Synthesis of Apixaban Genotoxic Impurity I The reaction route for synthesizing apixaban genotoxic impurity I in this comparative example is the same as in Example 1, with the only difference being the reduced temperature for the elimination and isomerization reactions. Specifically, this comparative example synthesizes apixaban genotoxic impurity I through the following steps: In a 1000 mL single-necked flask, 25.69 g of compound II and 500 g of a 20% vol aqueous solution of ethanol were added. Sodium carbonate solid was added to adjust the pH of the mixture to 9. The mixture was stirred at room temperature (20°C) for 8 hours. TLC monitoring (using a 2:1 mixture of ethyl acetate and n-heptane as the developing solvent; iodine staining) showed almost no residue of compound II. The temperature was then raised to 35°C and stirring continued for 5 hours. The mixture was filtered and washed with a 40% vol aqueous solution of ethanol to obtain the crude product. The crude product was subjected to silica gel column chromatography to obtain 8.1 g of apixaban genotoxic impurity I, with a yield of 34.1% and a purity of 92.1%.

[0052] Comparative Example 5: Synthesis of Apixaban Genotoxic Impurity I The reaction route for synthesizing apixaban genotoxic impurity I in this comparative example is the same as in Example 1, with the only difference being the increased temperature for the elimination and isomerization reactions. Specifically, this comparative example synthesizes apixaban genotoxic impurity I through the following steps: In a 1000 mL single-necked flask, 25.69 g of compound II and 500 g of a 20% vol aqueous solution of ethanol were added. Sodium carbonate solid was added to adjust the pH of the mixture to 9. The mixture was stirred at room temperature (20°C) for 8 hours. TLC monitoring (using a 2:1 mixture of ethyl acetate and n-heptane as the developing solvent; iodine staining) showed almost no residue of compound II. The temperature was then raised to 90°C and stirring continued for 5 hours. The mixture was filtered and washed with a 40% vol aqueous solution of ethanol to obtain the crude product. The crude product was subjected to silica gel column chromatography to obtain 5.2 g of apixaban genotoxic impurity I, with a yield of 21.9% and a purity of 90.5%.

[0053] Analysis of experimental results: The yields of Examples 1, 6, and 7 were significantly higher than those of Comparative Examples 4 and 5, indicating that both excessively high and low reaction temperatures during the elimination and isomerization processes lead to a decrease in reaction yield. Setting the elimination and isomerization reaction temperature to 40–80°C effectively improves the yield, with a further preferred reaction temperature of 60–80°C. The reason for this is that the elimination reaction needs to be carried out under heating conditions; excessively low temperatures result in incomplete elimination, leading to a lower yield; while excessively high reaction temperatures easily exacerbate ester hydrolysis side reactions, thus also causing a decrease in yield.

[0054] Application Example 1: Qualitative Analysis of Genotoxic Impurity I in Apixaban Samples Apixaban was prepared according to the synthesis method in patent WO03049681A2. The chromatogram of the apixaban sample was obtained by HPLC, as shown in [reference needed]. Figure 1 .

[0055] The apixaban genotoxic impurity I obtained in Example 2 was analyzed by HPLC, and its chromatogram is shown below. Figure 2 .

[0056] A small amount of apixaban genotoxic impurity I was added to the apixaban sample, and its chromatogram was obtained by HPLC analysis. (See figure) Figure 3 .

Claims

1. A method for synthesizing apixaban genotoxic impurity I, characterized in that, include: S1. Compound II undergoes an addition reaction in an alkaline system to produce compound III: ； S2. The product of S1 is subjected to elimination and isomerization reactions under heating to separate the reaction products, yielding apixaban genotoxic impurity I: ， 。 2. The synthesis method according to claim 1, characterized in that, In step S1, the alkaline system is a mixture containing compound II, a base, and a solvent.

3. The synthesis method according to claim 1 or 2, characterized in that, In step S1, the initial pH of the alkaline system is 9-12.

4. The synthesis method according to claim 2, characterized in that, In step S1, the alkali is one or more of potassium carbonate, sodium carbonate, potassium bicarbonate, and sodium bicarbonate.

5. The synthesis method according to claim 2, characterized in that, In step S1, the solvent is a mixed solution of alcohol and water, wherein the alcohol content is 20-80% vol.

6. The synthesis method according to claim 1, characterized in that, In step S1, the addition reaction is carried out at a temperature of 20-30°C for 4-8 hours.

7. The synthesis method according to claim 2 or 5, characterized in that, In step S1, the mass ratio of compound II to solvent is 1:7~20.

8. The synthesis method according to claim 1, characterized in that, In step S2, the elimination and isomerization reaction is carried out at a temperature of 40-80°C for 5-6 hours.

9. The synthesis method according to claim 8, characterized in that, In step S2, the temperature of the elimination and isomerization reaction is 60~80℃.

10. The synthesis method according to claim 1, characterized in that, In step S2, the process of separating the reaction products includes: filtration, washing with an ethanol-water solution, and silica gel column chromatography.

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