A method for preparing an alpha isomer of decitabine

Abstract

This invention provides a method for preparing decitabine by converting the α-isomer. The method mainly involves reacting the decitabine isomer with a silanizing agent to obtain compound III. After the reaction is complete, a pyridine-Lewis acid complex is added. After high-temperature reaction, the mixture is washed with alkali, deprotected, and recrystallized to obtain decitabine. The method provided by this invention utilizes the α-isomer, a byproduct of decitabine production, to prepare decitabine, achieving material recycling and saving energy. This method can achieve a decitabine isomer conversion rate of over 75%, with high yield and low loss.

Description

Technical Field

[0001] This invention belongs to the technical field of medicinal chemistry, specifically relating to a method for preparing decitabine using the α-isomer. Background Technology

[0002] Decitabine, chemically named 4-amino-1-(2-deoxy-β-D-erythro-furanose)-1,3,5-triazine-2(1H)-one, has the following structure:

[0003]

[0004] The synthetic route of decitabine is mostly to couple protected 2-deoxy-D-ribose with protected 5-azacytosine, remove the protecting group, and then purify it to obtain decitabine.

[0005]

[0006] When preparing decitabine via the above route, the formation of the α-isomer during glycosylation cannot be avoided even if the conditions such as the protecting group, catalyst, and solvent are changed due to the oxonium cation process. However, some technical means can be used to make decitabine the dominant configuration product.

[0007] Chen Jijun, Synthetic Study of Anticancer Drug Decitabine [D], Zhejiang University of Technology, 2010. This paper summarizes the synthetic methods of decitabine and conducts a detailed study on the factors affecting the configuration of glycosylation products. It also proposes the reaction mechanism. The results show that the proportion of β-products can be increased by increasing the volume of the protecting group, but a large number of isomers are still generated when the reaction time is prolonged and the reaction temperature is increased.

[0008] This demonstrates that the β-configuration glycosylation product is a kinetic product, while its isomers are thermodynamic products, further illustrating the inevitability of isomers. The isomers mixed in the product can be separated by recrystallization; after multiple resolutions, the purity of decitabine can reach over 99.9%, but the yield of each resolution is only around 80% at most. When the content of the α-isomer in the mother liquor is too high, it is difficult to obtain pure decitabine. Therefore, this method not only wastes decitabine but also renders a large number of isomers unusable.

[0009] Although researchers have explored further extraction methods and configuration conversion mechanisms for low-purity decitabine mixtures to achieve the recycling of α-configuration isomers—for example, patent CN200910056111 uses decitabine α-configuration intermediates as raw materials, converting them into β-configuration intermediates under the action of Lewis acids, with a β to α molar ratio of 3:2 in the product, thus initially achieving isomer conversion—this method suffers from problems such as complex processes, high costs, and low conversion efficiency.

[0010] Therefore, there is an urgent need for a low-cost, simple-to-operate, and high-conversion-rate method for recovering decitabine isomers. Summary of the Invention

[0011] This invention addresses the problems existing in the prior art by providing a method for converting decitabine α isomer into decitabine, which has the advantages of simple operation, high conversion rate and low cost.

[0012] This invention provides a method for preparing decitabine by conversion of α isomer. Its main technical features include: in an organic solvent, decitabine α isomer, namely compound II, reacts with a silanizing agent to obtain compound III. After the reaction is completed, a pyridine-Lewis acid complex is added. After the reaction is completed at high temperature, deprotection is carried out by alkali washing and recrystallization to obtain decitabine.

[0013]

[0014] The technical solution adopted includes the following steps:

[0015] Step a: In organic solvent A, compound II, an acid-binding agent, and a silanizing agent are added to obtain compound III. Then, a pyridine-Lewis acid complex is added to react and compound IV is obtained.

[0016] Step b: Compound IV was dissolved in anhydrous methanol, the protecting group was removed, and high-purity decitabine was obtained by recrystallization.

[0017] Preferably, the silanizing agent in step a is selected from one of trimethylchlorosilane, trimethylbromosilane, and hexamethyldisilazane; more preferably, it is trimethylchlorosilane.

[0018] Preferably, the molar ratio of compound II to the silanizing agent in step a is 1:3-3.5; more preferably 1:3.1.

[0019] Preferably, the acid-binding agent in step a is selected from imidazole, triethylamine, methylamine, N,N-diisopropylethylamine (DIPEA); imidazole is preferred.

[0020] Preferably, the molar ratio of compound II to the acid-binding agent in step a is 1:3-3.5; more preferably 1:3.1.

[0021] Preferably, the Lewis acid in the pyridine-Lewis acid complex in step a is selected from one of tin tetrachloride, boron trifluoride, aluminum chloride, zinc chloride, and trimethylsilyl trifluoromethanesulfonate; more preferably, it is trimethylsilyl trifluoromethanesulfonate.

[0022] Preferably, in step a, the molar ratio of pyridine to Lewis acid in the pyridine-Lewis acid complex is 1:0.9-1.1; more preferably, it is 1:1.

[0023] Preferably, the amount of pyridine-Lewis acid complex used in step a is such that the molar ratio of compound II to the pyridine-Lewis acid complex is 1:1.1-1.3; more preferably 1:1.2.

[0024] Preferably, the reaction temperature in step a is 40-60°C; more preferably, it is 55°C.

[0025] Preferably, the reaction time in step a is 1-20 hours; more preferably, it is 6-8 hours.

[0026] Preferably, the organic solvent A in step a is selected from one or a mixture of two or more of dichloromethane, chloroform, ethyl acetate, and toluene; preferably, it is chloroform.

[0027] Preferably, the amount of organic solvent A used in step a is such that the mass-to-volume ratio of compound II to organic solvent A is 1:10-20, where the mass is in g and the volume is in ml; more preferably, it is 1:15.

[0028] More preferably, step a is as follows: In organic solvent A, compound II and an acid-binding agent are added, and a silanizing reagent is added dropwise. After the addition is complete, the mixture is stirred to react. After the reaction is complete, compound III, which has not been separated, is obtained. A pyridine-Lewis acid complex is added to the reaction solution, and the mixture is reacted at high temperature for 6-8 hours. The temperature is then lowered to room temperature, and a saturated sodium bicarbonate aqueous solution is added. The mixture is separated, and the organic phase is evaporated to dryness under reduced pressure to obtain a white solid compound IV.

[0029] Preferably, the amount of anhydrous methanol used in step b is such that the mass-to-volume ratio of compound IV to anhydrous methanol is 1:10-20, expressed in g / mL; more preferably, it is 1:10.

[0030] Preferably, the deprotecting agent in step b is a methanol solution of an acidic reagent or a fluorine-containing neutral reagent, wherein the acidic reagent is selected from hydrochloric acid, sulfuric acid, and formic acid, and the fluorine-containing reagent is selected from sodium fluoride, potassium fluoride, and tetrabutylammonium fluoride; preferably, it is a methanol solution of hydrochloric acid.

[0031] Preferably, the amount of hydrochloric acid and methanol used in step b, in g / g, is 1:0.05-0.2 in mass ratio of compound IV to hydrochloric acid and methanol; more preferably, it is 1:0.1.

[0032] Preferably, the recrystallization in step b involves dissolving compound IV in a certain amount of methanol, cooling and crystallizing to obtain high-purity decitabine; wherein the ratio of compound IV to methanol is preferably 1:70, in g / mL.

[0033] More preferably, step b is as follows: compound IV is added to anhydrous methanol, stirred to dissolve, hydrochloric acid methanol solution is added dropwise, and after the addition is complete, the mixture is stirred until the reaction is complete. Sodium bicarbonate solid is added to quench the reaction, and the reaction solution is evaporated to dryness under reduced pressure and recrystallized to obtain white solid compound I.

[0034] Preferably, the hydrochloric acid in the methanol hydrochloric acid of step b has a mass fraction of 0.1%-1%, more preferably 0.1%.

[0035] Preferably, in step b, the molar ratio of sodium bicarbonate to hydrochloric acid is 1:0.8-1; more preferably, it is 1:1.

[0036] Compared with the prior art, the technical effects achieved by the present invention are as follows:

[0037] 1. The method provided by this invention utilizes the α-isomer, a byproduct of decitabine production, to prepare decitabine, thereby achieving material recycling and saving energy consumption.

[0038] 2. The method provided by this invention can achieve a conversion rate of over 75% for decitabine α isomers, with high yield and low loss. Attached Figure Description

[0039] Figure 1 Example 1: HPLC chromatogram of compound IV Detailed Implementation

[0040] The present invention will be further illustrated by the following embodiments. It should be understood that the embodiments of the present invention are merely for illustrating the present invention and are not intended to limit the present invention. Therefore, any simple improvements to the present invention under the premise of the method of the present invention are within the scope of protection claimed by the present invention.

[0041] Example 1

[0042] At room temperature, 50 g of compound II (purity 98.65%), 750 mL of chloroform, and 45.6 g of imidazole were added to a reaction flask. 74 g of trimethylchlorosilane was added dropwise. After the addition was complete, the mixture was stirred for 2 h. 79 g of a complex of pyridine and trimethylsilyl trifluoromethanesulfonate (molar ratio 1:1) was added dropwise. After the addition was complete, the mixture was heated to 55 °C and stirred for 6-8 h. Heating was stopped, and the mixture was allowed to cool naturally to room temperature. 750 mL of saturated sodium bicarbonate solution was added to the reaction mixture, and the mixture was stirred for 5 min. The mixture was allowed to stand and separated. The organic phase was dried over anhydrous sodium sulfate and concentrated under reduced pressure to obtain 70 g of white solid compound IV, β:α = 4.7:1.

[0043] Compound IV 70g was dissolved in 700mL of anhydrous methanol, and 7g of 0.1% hydrochloric acid methanol solution was added dropwise. After the addition was complete, the mixture was stirred and reacted overnight. 3mg of sodium bicarbonate solid was added, and the reaction was continued to be stirred for 0.5h. The reaction solution was evaporated to dryness under reduced pressure to obtain a white solid. 4.9L of anhydrous methanol was added to the white solid, and the mixture was heated to reflux. 2g of activated carbon was added, and the mixture was refluxed for 0.5h. The mixture was filtered, and the filtrate was allowed to stand at room temperature for 24h to crystallize. After filtration and drying, 32g of decitabine was obtained; HPLC purity 98.9%.

[0044] Example 2

[0045] At room temperature, 50 g of compound II (purity 98.65%), 500 mL of chloroform, and 44.2 g of imidazole were added to a reaction flask. 71.6 g of trimethylchlorosilane was added dropwise. After the addition was complete, the mixture was stirred for 2 h. Then, 83.3 g of a complex of pyridine and trimethylsilyl trifluoromethanesulfonate (molar ratio 0.9:1) was added dropwise. After the addition was complete, the mixture was heated to 55 °C and stirred for 6-8 h. Heating was stopped, and the mixture was allowed to cool naturally to room temperature. 500 mL of saturated sodium bicarbonate solution was added to the reaction mixture, and the mixture was stirred for 5 min. The mixture was allowed to stand and separated. The organic phase was dried over anhydrous sodium sulfate and concentrated under reduced pressure to obtain 68.35 g of white solid compound IV, β:α = 4.6:1.

[0046] Compound IV 68.35 g was dissolved in 700 mL of anhydrous methanol, and 3.5 g of 0.1% hydrochloric acid methanol solution was added dropwise. After the addition was complete, the mixture was stirred and reacted overnight. 1.5 mg of sodium bicarbonate solid was added, and the reaction was continued to be stirred for 0.5 h. The reaction solution was evaporated to dryness under reduced pressure to obtain a white solid. 4.9 L of anhydrous methanol was added to the white solid, and the mixture was heated to reflux. 2 g of activated carbon was added, and the mixture was refluxed for 0.5 h. The mixture was filtered, and the filtrate was allowed to stand at room temperature for 24 h to crystallize. After filtration and drying, 30.8 g of decitabine was obtained; the HPLC purity was 98.7%.

[0047] Example 3

[0048] At room temperature, 50 g of compound II (purity 98.65%), 1000 mL of chloroform, and 51.7 g of imidazole were added to a reaction flask. 83.5 g of trimethylchlorosilane was added dropwise. After the addition was complete, the mixture was stirred for 2 h. Then, 77.7 g of a complex of pyridine and trimethylsilyl trifluoromethanesulfonate (molar ratio 1:1.1) was added dropwise. After the addition was complete, the mixture was heated to 60 °C and stirred for 6-8 h. Heating was stopped, and the mixture was allowed to cool naturally to room temperature. 750 mL of saturated sodium bicarbonate solution was added to the reaction mixture, and the mixture was stirred for 5 min. The mixture was allowed to stand and separated. The organic phase was dried over anhydrous sodium sulfate and concentrated under reduced pressure to obtain 68.4 g of white solid compound IV, β:α = 4.7:1.

[0049] Compound IV 68.4 g was dissolved in 700 mL of anhydrous methanol, and 14 g of 0.1% hydrochloric acid methanol solution was added dropwise. After the addition was complete, the mixture was stirred and reacted overnight. 6 mg of sodium bicarbonate solid was added, and the reaction was continued to be stirred for 0.5 h. The reaction solution was evaporated to dryness under reduced pressure to obtain a white solid. 4.9 L of anhydrous methanol was added to the white solid, and the mixture was heated to reflux. 2 g of activated carbon was added, and the mixture was refluxed for 0.5 h. The mixture was filtered, and the filtrate was allowed to stand at room temperature for 24 h to crystallize. After filtration and drying, 30.44 g of decitabine was obtained; the HPLC purity was 98.8%.

[0050] Example 4

[0051] At room temperature, 50 g of compound II (purity 98.65%), 750 mL of ethyl acetate, and 67.8 g of triethylamine were added to a reaction flask. 74 g of trimethylchlorosilane was added dropwise. After the addition was complete, the mixture was stirred for 2 h. 90 g of a complex of pyridine and tin tetrachloride (molar ratio 1:1) was added dropwise. The mixture was heated to 55 °C and stirred for 6-8 h. Heating was stopped, and the mixture was allowed to cool naturally to room temperature. 750 mL of saturated sodium bicarbonate solution was added to the reaction mixture, and the mixture was stirred for 5 min. The mixture was allowed to stand and separated. The organic phase was dried over anhydrous sodium sulfate and concentrated under reduced pressure to obtain 63.4 g of white solid compound IV, β:α = 4:1.

[0052] Compound IV 63.4 g was dissolved in 700 mL of anhydrous methanol, and 7 g of 0.1% hydrochloric acid methanol solution was added dropwise. After the addition was complete, the mixture was stirred and reacted overnight. 3 mg of sodium bicarbonate solid was added, and the reaction was continued to be stirred for 0.5 h. The reaction solution was evaporated to dryness under reduced pressure to obtain a white solid. 4.9 L of anhydrous methanol was added to the white solid, and the mixture was heated to reflux. 2 g of activated carbon was added, and the mixture was refluxed for 0.5 h. The mixture was filtered, and the filtrate was allowed to stand at room temperature for 24 h to crystallize. After filtration and drying, 27.2 g of decitabine was obtained; the HPLC purity was 98.2%.

[0053] Example 5

[0054] At room temperature, 50 g of compound II (purity 98.65%), 750 mL of toluene, and 64.8 g of triethylamine were added to a reaction flask. 104.3 g of trimethylbromosilane was added dropwise. After the addition was complete, the mixture was stirred for 2 h. Then, 38.72 g of a complex of pyridine and boron trifluoride (molar ratio 1:1) was added dropwise. After the addition was complete, the mixture was heated to 60 °C and stirred for 10 h. Heating was stopped, and the mixture was allowed to cool naturally to room temperature. 750 mL of saturated sodium bicarbonate solution was added to the reaction mixture, and the mixture was stirred for 5 min. The mixture was allowed to stand and separated. The organic phase was dried over anhydrous sodium sulfate and concentrated under reduced pressure to obtain 61.8 g of white solid compound IV, β:α = 4:1.

[0055] Compound IV 61.8 g was dissolved in 620 mL of anhydrous methanol, and 7 g of 0.1% hydrochloric acid methanol solution was added dropwise. After the addition was complete, the mixture was stirred and reacted overnight. 3 mg of sodium bicarbonate solid was added, and the reaction was continued to be stirred for 0.5 h. The reaction solution was evaporated to dryness under reduced pressure to obtain a white solid. 4.9 L of anhydrous methanol was added to the white solid, and the mixture was heated to reflux. 2 g of activated carbon was added, and the mixture was refluxed for 0.5 h. The mixture was filtered, and the filtrate was allowed to stand at room temperature for 24 h to crystallize. After filtration and drying, 26.7 g of decitabine was obtained; the HPLC purity was 98.3%.

[0056] Example 6

[0057] At room temperature, 50 g of compound II (purity 98.65%), 750 mL of chloroform, and 58.8 g of imidazole were added to a reaction flask. 95.5 g of trimethylchlorosilane was added dropwise. After the addition was complete, the mixture was stirred for 2 h. Then, 90.9 g of a complex of pyridine and trimethylsilyl trifluoromethanesulfonate (molar ratio 0.7:1) was added dropwise. After the addition was complete, the mixture was heated to 60 °C and stirred for 12 h. Heating was stopped, and the mixture was allowed to cool naturally to room temperature. 750 mL of saturated sodium bicarbonate solution was added to the reaction mixture, and the mixture was stirred for 5 min. After standing and separating the liquids, the organic phase was dried over anhydrous sodium sulfate and concentrated under reduced pressure to obtain 55.2 g of white solid compound IV, β:α = 3:1.

[0058] Compound IV 55.2 g was dissolved in 600 mL of anhydrous methanol, and 7 g of 0.1% hydrochloric acid methanol solution was added dropwise. After the addition was complete, the mixture was stirred and reacted overnight. 3 mg of sodium bicarbonate solid was added, and the reaction was continued to be stirred for 0.5 h. The reaction solution was evaporated to dryness under reduced pressure to obtain a white solid. 4.9 L of anhydrous methanol was added to the white solid, and the mixture was heated to reflux. 2 g of activated carbon was added, and the mixture was refluxed for 0.5 h. The mixture was filtered, and the filtrate was allowed to stand at room temperature for 24 h to crystallize. After filtration and drying, 23.1 g of decitabine was obtained; the HPLC purity was 97.8%.

[0059] Example 7

[0060] At room temperature, 50 g of compound II (purity 98.65%), 750 mL of chloroform, and 53 g of pyridine were added to a reaction flask. 74 g of trimethylchlorosilane was added dropwise. After the addition was complete, the mixture was stirred for 2 h. 116 g of trimethylsilyl trifluoromethanesulfonate was added dropwise. After the addition was complete, the mixture was heated to 60 °C and stirred for 10 h. Heating was stopped, and the mixture was allowed to cool naturally to room temperature. 750 mL of saturated sodium bicarbonate solution was added to the reaction mixture, and the mixture was stirred for 5 min. The mixture was allowed to stand and separated. The organic phase was dried over anhydrous sodium sulfate and concentrated under reduced pressure to obtain 35.4 g of white solid compound IV, with a β:α ratio of 2:1.

[0061] Compound IV 35.4 g was dissolved in 400 mL of anhydrous methanol, and 7 g of 0.1% hydrochloric acid methanol solution was added dropwise. After the addition was complete, the mixture was stirred and reacted overnight. 3 mg of sodium bicarbonate solid was added, and the reaction was continued to be stirred for 0.5 h. The reaction solution was evaporated to dryness under reduced pressure to obtain a white solid. 4 L of anhydrous methanol was added to the white solid, and the mixture was heated to reflux. 2 g of activated carbon was added, and the mixture was refluxed for 0.5 h. The mixture was filtered, and the filtrate was allowed to stand at room temperature for 24 h to crystallize. After filtration and drying, 12 g of decitabine was obtained; HPLC purity 97.5%.

[0062] Example 8

[0063] At room temperature, 50 g of compound II (98.65% purity), 750 mL of chloroform, and 53 g of pyridine were added to a reaction flask. 74 g of trimethylchlorosilane was added dropwise. After the addition was complete, the mixture was stirred for 2 h. 44.3 g of boron trifluoride was added dropwise. The mixture was heated to 60 °C and stirred for 10 h. Heating was stopped, and the mixture was allowed to cool naturally to room temperature. 750 mL of saturated sodium bicarbonate solution was added to the reaction mixture, and the mixture was stirred for 5 min. The mixture was allowed to stand and separated. The organic phase was dried over anhydrous sodium sulfate and concentrated under reduced pressure to obtain 32.1 g of white solid compound IV, with a β:α ratio of 2:1.

[0064] Compound IV 32.1 g was dissolved in 400 mL of anhydrous methanol, and 7 g of 0.1% hydrochloric acid methanol solution was added dropwise. After the addition was complete, the mixture was stirred and reacted overnight. 3 mg of sodium bicarbonate solid was added, and the reaction was continued to be stirred for 0.5 h. The reaction solution was evaporated to dryness under reduced pressure to obtain a white solid. 4 L of anhydrous methanol was added to the white solid, and the mixture was heated to reflux. 2 g of activated carbon was added, and the mixture was refluxed for 0.5 h. The mixture was filtered, and the filtrate was allowed to stand at room temperature for 24 h to crystallize. After filtration and drying, 10.5 g of decitabine was obtained; the HPLC purity was 97.2%.

Claims

1. A method for preparing decitabine by conversion of the α-isomer, characterized in that, The method includes the following steps: ， Specifically, the steps include the following: Step a: In organic solvent A, compound II, an acid-binding agent, and a silanizing agent are added to obtain compound III. Then, a pyridine-Lewis acid complex is added to react and compound IV is obtained. Step b: Compound IV was dissolved in anhydrous methanol, the protecting group was removed, and high-purity decitabine was obtained by recrystallization.

2. The preparation method according to claim 1, characterized in that, The silanizing agent in step a is selected from one of trimethylchlorosilane, trimethylbromosilane, and hexamethyldisilazane.

3. The preparation method according to claim 1, characterized in that, The acid-binding agent is selected from imidazole, triethylamine, methylamine, or N,N-diisopropylethylamine.

4. The preparation method according to claim 1, characterized in that, The Lewis acid mentioned in step a is selected from one of tin tetrachloride, boron trifluoride, aluminum chloride, zinc chloride, and trimethylsilyl trifluoromethanesulfonate.

5. The preparation method according to claim 1, characterized in that, The pyridine-Lewis acid complex described in step a has a molar ratio of pyridine to Lewis acid of 1:0.9-1.

1.

6. The preparation method according to claim 1, characterized in that, The amount of pyridine-Lewis acid complex used in step a is such that the molar ratio of compound II to the pyridine-Lewis acid complex is 1:1.1-1.

3.

7. The preparation method according to claim 1, characterized in that, The organic solvent A mentioned in step a is selected from one or more of dichloromethane, trichloromethane, ethyl acetate, and toluene.

8. The preparation method according to claim 1, characterized in that, The deprotecting agent mentioned in step b is a methanol solution of an acidic reagent or a fluorine-containing neutral reagent. The acidic reagent is selected from hydrochloric acid, sulfuric acid, and formic acid, and the fluorine-containing reagent is selected from sodium fluoride, potassium fluoride, and tetrabutylammonium fluoride.

9. The preparation method according to claim 1, characterized in that, The recrystallization in step b involves dissolving compound IV in a certain amount of methanol, cooling it, and then crystallizing it to obtain high-purity decitabine; wherein the ratio of compound IV to methanol is 1:70, expressed in g / mL.

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