Method for purifying estrone

Abstract

The invention belongs to the technical field of steroid drug molecules, and relates to an estrone purification method, which comprises the following steps: adding 1, 4-diazabicyclo [2.2. 2] octane into a solution containing an estrone crude product and a first solvent to obtain a precipitate, dissolving the precipitate in a second solvent, adjusting to be alkaline, filtering, collecting filtrate, adjusting the pH value of the filtrate to be less than or equal to 3, and filtering to obtain the estrone purification product. And extracting with a third solvent to obtain an organic phase, cooling, crystallizing, carrying out suction filtration, and drying to obtain refined estrone. According to the method, the problem of removal of methylation rearrangement impurities generated in the existing preparation technology of the estrone is solved, the methylation rearrangement impurities can be purified from 0.7%-1.5% to less than or equal to 0.10% at a time, the purity of the finally obtained estrone is greater than or equal to 99.8%, and the yield is stable. The method disclosed by the invention is green and environment-friendly, low in cost, less in material loss, good in purification effect and stable in process, and has extremely high industrial application value.

Description

Technical Field

[0001] This invention relates to the field of steroidal drug molecular technology, specifically to a method for purifying estrone, and particularly to a method for removing specific impurities in the preparation of estrone. Background Technology

[0002] Estrone is an important steroidal estrogen drug and a key intermediate in the synthesis of other estrogen drugs such as estradiol and ethinylestradiol. Currently, the method for preparing estrone using 1,4-androstenedione (ADD) as a raw material is simple, inexpensive, and has become the mainstream route for industrial production.

[0003] For example, Chinese patent application CN107602650A discloses a method for preparing estradiol ketone by demethylation aromatization reaction using ADD as a raw material in the presence of organophosphorus reagent and halogen. Compared with traditional processes, this method has improved safety and the reaction conditions are relatively mild, but it still has problems such as more reaction impurities and the need for column chromatography purification of the product, which is not conducive to large-scale industrial application.

[0004] Based on this, Tetrahedron Letters (2023), 117, 154365 reported an improved scheme in which ADD undergoes aromatization with organophosphorus reagents and halogens in the presence of quaternary ammonium salt phase transfer catalysts to obtain estradiol ketone products, which improves the reaction efficiency to a certain extent.

[0005] Furthermore, Chinese patent application CN116640177A introduces an acid-binding agent based on the above literature, which effectively inhibits the occurrence of side reactions and ultimately obtains an estradiol product with a purity of 99.5%, significantly improving the controllability of the process and the quality of the product.

[0006] Although the above methods have improved purity and yield, a common problem remains: when ADD uses the Ph3P·X2 (X is a halogen) system for demethylation aromatization, methylation rearrangement impurities are commonly generated in the reaction system, with HPLC purity typically ranging from 0.7% to 1.5%. These impurities can be effectively removed by column chromatography, but industrial application is limited. Conventional recrystallization is insufficient for effective removal, resulting in the final product failing to meet the stringent impurity limits of international pharmaceutical registration standards (such as ICH Q3A and Q3D). Therefore, it is still necessary to develop a low-cost and effective technique for removing this impurity to improve the purity and quality of estradiol products and meet higher pharmaceutical standards. Summary of the Invention

[0007] To address the problem of impurities in estrone prepared from 1,4-androstenedione (ADD) using existing technologies, particularly the difficulty in effectively removing methylation rearrangement impurities generated during demethylation aromatization using the Ph3P·X2 system, this invention provides an estrone purification method based on co-crystallization technology. This method involves introducing an estrone-DABCO co-crystallization intermediate into the crude estrone raw material, followed by a dissociation step to obtain high-purity estrone, thereby achieving efficient purification of estrone. The structure of the aforementioned methylation rearrangement impurities is as follows: .

[0008] The crude estrone product of the present invention (i.e., the raw material of the method of the present invention) is exemplarily obtained by repeating journal articles. Tetrahedron Letters The method disclosed in (2023), 117, 154365, involves demethylation aromatization of organophosphorus reagents in the presence of halogens (Ph3P·X2).

[0009] In some embodiments, the preparation of crude estrone of the present invention includes the following steps: 1 kg of 1,4-androstenedione is dissolved in 15 L of toluene, purged with an inert gas, 2.7 kg of triphenylphosphine diiodide is added, 1.1 kg of tetrabutylammonium bromide is added, the mixture is heated to reflux, and TLC shows that the raw material is basically completely converted. After about 5 hours of reaction, heating is stopped, the mixture is cooled to room temperature, quenched with sodium sulfite aqueous solution, concentrated under reduced pressure, refluxed with methanol and pulped, and filtered to obtain 850 g of crude estrone, with a weight yield of 85%. The HPLC purity of the sample is 98.63%, and the HPLC purity of methylation rearrangement impurities is 0.97%.

[0010] The crude estrone was dissolved under ethanol reflux, and slowly crystallized by atmospheric distillation. After three refining processes, the impurity removal rate gradually decreased, with methylated rearrangement impurities still remaining at 0.22%. Multiple refining processes resulted in a yield loss of approximately 20% for the finished estrone product, and the impurities still failed to meet the registration standards. The inventors explored a refining method for the crude estrone by precisely developing processes such as solvent selection, temperature control, stirring speed, and the addition of seed crystals. Due to the poor solubility of estrone, conventional methods require a large solvent volume and have limited impurity removal rates, necessitating multiple refining processes to obtain a finished estrone product that meets the standards. The inventors also attempted to derive the crude estrone into a ketal to alter its solubility for refining, but the residual methylated impurities in the finished product still did not meet the registration standard requirement of ≤0.10% impurities.

[0011] To remove or reduce methylation rearrangement impurities in crude estrone, this invention provides an effective technical solution for purifying estrone, which includes the following steps: Crude estrone was dissolved in an appropriate amount of the first solvent and heated until dissolved. An appropriate amount of 1,4-diazabicyclo[2.2.2]octane (DABCO) was added, and the mixture was cooled to room temperature and filtered. The filter cake was dissolved in an appropriate amount of the second solvent, and a strong alkaline aqueous solution was added to adjust the pH to alkalinity. The mixture was stirred for 1-2 hours, filtered, and the filter cake was washed. The filtrate was collected, and acid was added dropwise to adjust the pH to ≤3. The mixture was stirred at a controlled temperature for at least 0.5 hours. The mixture was extracted twice with the third solvent, and the organic phases were combined. The mixture was concentrated under reduced pressure or distilled at normal pressure until a small amount of liquid remained in the container. The mixture was slowly cooled to crystallize, filtered, and dried to obtain purified estrone. The yield was calculated based on the crude estrone product, and the purity was determined by HPLC.

[0012] Furthermore, the first solvent used in the above-mentioned estrone purification method is a good solvent for estrone, selected from one or more of the following solvents, including but not limited to: methanol, ethanol, acetone, tetrahydrofuran (THF), dichloromethane, and ethyl acetate.

[0013] Furthermore, in the above-mentioned estrone purification method, based on the crude estrone product, the solvent ratio is adjusted according to the solubility relationship between estrone and the first solvent. Dissolution can be achieved by stirring at room temperature or by heating and reflux. A suitable ratio should be selected as small as possible to minimize product yield loss, considering the preparation process, energy efficiency, and environmental protection requirements. When 1W of crude estrone product is fed, the first solvent ratio can be 10~60V, preferably 10~30V, including both integer multiples and non-integer multiples within this range. Typical feed ratios for 10-60V include 12V, 15V, 18V, 20V, 22V, 25V, 28V, 31V, 34V, 37V, 40V, 43V, 47V, 50V, 53V, 57V, and 59V; typical feed ratios for 10-30V include 10.5V, 11.5V, 12.5V, 13.5V, 15.5V, 17.5V, 18.5V, 19.5V, 21.5V, 23.5V, 25.5V, 27.5V, and 29.5V. According to the relevant knowledge of those skilled in the art, other feed ratios within this range can be selected to achieve the goal of material dissolution by combining the first solvent with different dissolution temperatures. Note: In this invention, the weight-to-volume ratio refers to W as weight and V as volume. When W is in g, V is in mL; when W is in kg, V is in L.

[0014] Furthermore, the amount of DABCO used in the above-mentioned estrone purification method affects the removal efficiency of methylation rearrangement impurities. When 1W of crude estrone is fed, the amount of DABCO fed according to the weight-volume ratio is selected as 0.1~1.0W, preferably 0.12~0.40W, and more preferably 0.18~0.26W. Typical feed ratios in the 0.1~1.0W range include: 0.10W, 0.15W, 0.18W, 0.20W, 0.25W, 0.30W, 0.35W, 0.40W, 0.45W, 0.50W, 0.55W, 0.65W, 0.70W, 0.75W, 0.80W, 0.85W, 0.95W, etc.; typical feed ratios in the 0.12~0.40W range include: 0.18W, 0.22W, 0.26W, 0.30W, 0.34W, 0.38W. Based on the relevant common knowledge of those skilled in the art, other multiples within this range are also selected.

[0015] Furthermore, the second solvent used in the above-described method for purifying estrone is selected from one or more of the following solvents, including but not limited to: methanol, ethanol, isopropanol, acetone, THF, and toluene.

[0016] Furthermore, in the above-mentioned estrone purification method, the ratio of the second solvent to crude estrone can be 5~30V, preferably 8~20V; typical addition ratios of 5~30V include 6V, 8V, 10V, 12V, 14V, 16V, 18V, 20V, 22V, 14V, 26V, 28V, etc.; typical addition ratios of 8~20V include integer multiples of 9V, 11V, 13V, 15V, 17V, 19V, etc., or other multiples within this range.

[0017] In the dissociation process of the above-mentioned estrone purification method, the alkaline aqueous solution used is preferably an aqueous solution of sodium hydroxide and / or potassium hydroxide, and its concentration is not limited, for example 0.1~10M, 0.5~5M, 0.6~3M, and most preferably 1M.

[0018] Furthermore, hydrochloric acid and sulfuric acid are preferred among the aforementioned acids.

[0019] Furthermore, the third solvent is selected from at least one of the following solvents: dichloromethane, trichloromethane, etc.

[0020] In one embodiment of the present invention, crude estrone obtained according to the above-mentioned literature is used as the starting material to embody the concept of the present invention. Its HPLC purity is 97.9%, and the HPLC purity of methylation rearrangement impurities is 1.28%. Through the alkaline dissociation technology provided by the present invention, crude estrone can be purified to an HPLC purity of 99.9% and an HPLC purity of 0.09% for methylation rearrangement impurities, which can meet the registration standards for active pharmaceutical ingredients, with a weight yield of 89.9%.

[0021] To achieve the above purification objective, in addition to the alkaline dissociation method to obtain purified estrone, an acid dissociation method can also be considered. The specific operation is as follows: Dissolve 1W of crude estrone in an appropriate amount of the first solvent, heat to dissolve completely, add an appropriate amount of 1,4-diazabicyclo[2.2.2]octane (DABCO), cool to room temperature, filter, dissolve the filter cake in an appropriate amount of the second solvent, add a prepared acid aqueous solution to adjust the pH to ≤3, control the temperature at 20~50℃, stir for 1h, filter while hot, slurry the filter cake with water, filter, collect the filter cake, heat the second solvent to dissolve completely, concentrate the solution until a small amount of liquid remains in the container, slowly cool to precipitate crystals, filter, dry, and obtain purified estrone.

[0022] Furthermore, the first solvent in the acid dissociation technique of the above-mentioned estrone purification method is a good solvent for estrone.

[0023] Furthermore, the second solvent in the acid dissociation technique of the above-mentioned estrone purification method is selected from at least one of the following solvents: methanol, ethanol, isopropanol, acetone, THF, and toluene.

[0024] Furthermore, the concentration methods for the filtrate or extract in the above-mentioned estrone purification method include vacuum concentration or atmospheric distillation.

[0025] In one embodiment of the present invention, crude estrone obtained according to the above-mentioned literature is used as the starting material to embody the concept of the present invention. Its HPLC purity is 97.9%, and the HPLC purity of methylation rearrangement impurities is 1.28%. Through the acid dissociation technology of the present invention, crude estrone can be purified to 99.9%, with methylation rearrangement impurities below 0.08% and a weight yield of 88.6%, which can also meet the registration standards for active pharmaceutical ingredients.

[0026] Beneficial effects This invention innovatively introduces an intermediate estrone-DABCO eutectic, which, through base or acid dissociation, completely solves the problem of removing methylation rearrangement impurities generated during the demethylation aromatization reaction of 1,4-androstenedione (ADD) in a Ph3P·X2 system in existing estrone preparation techniques. Methylation rearrangement impurities can be purified from 0.7%~1.5% to no more than 0.10% in a single step, resulting in estrone with a purity ≥99.8% and stable yield. The method of this invention is green and environmentally friendly, low in cost, with minimal material loss, excellent purification effect, and stable process during industrial scale-up, possessing extremely high industrial application value. Attached Figure Description

[0027] Figure 1 This is the HPLC purity chromatogram of crude estrone from Example 1.

[0028] Figure 2This is the HPLC purity chromatogram of estrone purified by alkali dissociation in Example 2.

[0029] Figure 3 This is the HPLC purity chromatogram of estrone purified by alkaline dissociation in Example 3.

[0030] Figure 4 These are HPLC purity chromatograms of crude estrone, the starting material in Examples 4 and 6.

[0031] Figure 5 This is the HPLC purity chromatogram of estrone purified by alkali dissociation in Example 4.

[0032] Figure 6 This is the HPLC purity chromatogram of estrone after acid dissociation and purification in Example 5.

[0033] Figure 7 This is the HPLC purity chromatogram of estrone after acid dissociation and purification in Example 6. Detailed Implementation

[0034] The present invention will be described in more detail below with reference to the embodiments. It should be understood that the implementation of the present invention is not limited to the embodiments below, and any modifications and / or alterations made to the present invention will fall within the protection scope of the present invention.

[0035] In this invention, all equipment and raw materials can be purchased from the market or are commonly used in this industry.

[0036] Example 1 Duplicate journal articles Tetrahedron Letters The crude estradiol ketone obtained by demethylation aromatization reaction of organophosphorus reagent and halogen (Ph3P·X2) disclosed in (2023), 117, 154365.

[0037] 1 kg of 1,4-androstenedione was dissolved in 15 L of toluene, purged with an inert gas, and 2.7 kg of triphenylphosphine diiodide and 1.1 kg of tetrabutylammonium bromide were added. The mixture was heated to reflux, and TLC showed that the starting material was basically completely converted. After about 5 hours of reaction, heating was stopped, and the mixture was cooled to room temperature. The reaction was quenched with sodium sulfite aqueous solution, concentrated under reduced pressure, refluxed with methanol, and filtered to obtain 850 g of crude estrone, with a yield of 85% by weight. The HPLC purity was 98.63%, and the methylation rearrangement impurities had an HPLC purity of 0.97%. Figure 1 ).

[0038] Example 2 100g of the crude estradiol obtained in Example 1 was dissolved in a three-necked flask, 1.5L of THF was added, and the mixture was heated under reflux until dissolved. 20.0g of 1,4-diazabicyclo[2.2.2]octane (DABCO) was added and stirred. The mixture was gradually cooled to room temperature, filtered, and the filter cake was washed with 100mL of THF. The filter cake was collected, 800mL of ethanol was added and stirred, and 800mL of 1M sodium hydroxide aqueous solution was added and stirred for 2 hours. The insoluble matter was filtered off, the filtrate was collected, and 80mL of concentrated hydrochloric acid was added and stirred. Extracted twice with 1.25 L of dichloromethane, the organic phases were combined and washed with 2 L of water. The organic phase was collected, and the remaining 60-100 mL of mother liquor was distilled under normal pressure. Crystallization was slowly precipitated at room temperature, filtered, and the filter cake was washed twice with 200 mL of ethanol. The mixture was then dried under vacuum at 60 °C overnight to obtain 92.7 g of purified estrone, with a yield of 92.7% by weight. The HPLC purity was 99.90%, and the methylation rearrangement impurities were 0.08%. Figure 2 ).

[0039] Example 3 100g of the crude estrone obtained in Example 1 was dissolved in a three-necked flask, 4.5L of acetone was added, and the mixture was heated under reflux until dissolved. 20.0g of 1,4-diazabicyclo[2.2.2]octane (DABCO) was added and stirred. The mixture was gradually cooled to room temperature, filtered, and the filter cake was washed with 100mL of acetone. The filter cake was collected, 800mL of ethanol was added and stirred, and 800mL of 1M sodium hydroxide aqueous solution was added and stirred for 1-2 hours. The insoluble matter was filtered off, the filtrate was collected, and 80mL of concentrated hydrochloric acid was added and stirred for 1 hour. Extracted twice with 1.25 L of dichloromethane, the organic phases were combined and washed with 2 L of water. The organic phase was collected and distilled at atmospheric pressure to about 60-100 mL of mother liquor. The mixture was slowly cooled to room temperature to allow crystals to crystallize. The crystals were filtered, and the filter cake was washed twice with 200 mL of ethanol. The mixture was then dried under vacuum at 60 °C overnight to obtain 89.7 g of purified estrone, with a yield of 89.7% by weight. The HPLC purity was 99.93%, and the methylation rearrangement impurities were 0.07%. Figure 3 ).

[0040] Example 4 Following the method described in Example 1 above, the crude estrone prepared by adding 2.8 kg of triphenylphosphine diiodide and 0.9 kg of tetrabutylammonium bromide had an HPLC purity of 97.9% and a methylation rearrangement impurity HPLC purity of 1.28%. Figure 4Take 100g of the material and dissolve it in a three-necked flask. Add 1.5L of THF, heat and reflux until dissolved, add 24.5g of 1,4-diazabicyclo[2.2.2]octane (DABCO) and stir. Gradually lower the temperature to room temperature, filter, wash the filter cake with 100mL of THF, collect the filter cake, add 1000mL of methanol and stir, add 800mL of 1M sodium hydroxide aqueous solution and stir for 2h. Filter out insoluble matter, collect the filtrate, add 80 mL of concentrated sulfuric acid, stir for 0.5–1 h, extract twice with 1.5 mL of dichloromethane, combine the organic phases, distill under normal pressure to about 60–100 mL of mother liquor, slowly cool to about 25 °C to crystallize, filter, wash the filter cake twice with 200 mL of methanol, dry under vacuum at 60 °C overnight, to obtain 89.9 g of purified estrone, with a yield of 89.9% by weight. HPLC purity was 99.88%, and methylation rearrangement impurities were 0.09%. Figure 5 ).

[0041] Example 5 100g of crude estradiol obtained in Example 1 above was dissolved in a three-necked flask, 1.5L of THF was added, and the mixture was heated under reflux until dissolved. 20.0g of 1,4-diazabicyclo[2.2.2]octane (DABCO) was added and stirred. The room temperature was gradually lowered, and the mixture was filtered. The filter cake was washed with 100mL of THF, and the filter cake was collected. 600mL of ethanol was added and stirred. 300mL of 5% hydrochloric acid aqueous solution was added and the mixture was stirred at a controlled temperature of about 50℃. Filter while hot, rinse the filter cake with water, collect the filter cake, add 700 mL of ethanol and 1.5 L of dichloromethane, stir and dissolve at 60 °C, filter while hot, rinse the filter cake twice with 200 mL of ethanol, distill the filtrate under normal pressure to about 60-100 mL of mother liquor, slowly cool to room temperature to crystallize, filter, rinse the filter cake with 100 mL of ethanol, dry under vacuum, and dry the filter cake at 60 °C for 12 h to obtain 89.7 g of purified estrone, with a yield of 89.7% by weight. HPLC analysis showed a purity of 99.89% and methylation rearrangement impurities of 0.07%. Figure 6 ).

[0042] Example 6 Following the method described in Example 1 above, the crude estrone prepared by adding 2.8 kg of triphenylphosphine diiodide and 0.9 kg of tetrabutylammonium bromide had an HPLC purity of 97.9% and a methylation rearrangement impurity HPLC purity of 1.28%. Figure 4Take 100g of the material and dissolve it in a three-necked flask. Add 1.5L of THF, heat and reflux until dissolved, add 21.0g of 1,4-diazabicyclo[2.2.2]octane (DABCO) and stir. Gradually lower the room temperature, filter, wash the filter cake with 100mL of THF, collect the filter cake, add 600mL of ethanol and stir, add 300mL of 5% sulfuric acid aqueous solution, and stir while maintaining the temperature at 35℃. The mixture was filtered while hot, and the filter cake was rinsed with water. The filter cake was collected, and 700 mL of ethanol and 1.5 L of dichloromethane were added. The mixture was stirred and dissolved at 60 °C. The mixture was filtered while hot, and the filter cake was rinsed twice with 200 mL of ethanol. The filtrate was distilled at atmospheric pressure to about 60-100 mL of mother liquor. The solution was slowly cooled to room temperature to allow crystals to crystallize. The crystals were filtered, and the filter cake was rinsed with 100 mL of ethanol. The solution was dried under vacuum at 60 °C for 12 h to obtain 88.6 g of purified estrone, with a yield of 88.6% by weight. HPLC analysis showed a purity of 99.90% and methylation rearrangement impurities of 0.08%. Figure 7 ).

Claims

1. A method for purifying estrone, characterized in that, It includes the following steps: Add 1,4-diazabicyclo[2.2.2]octane to a solution containing crude estrone and a first solvent to obtain a precipitate. Dissolve the precipitate in a second solvent and adjust the pH to alkaline. Filter and collect the filtrate. Adjust the pH of the filtrate to ≤3, extract with a third solvent to obtain the organic phase, cool to allow crystallization, filter, and dry to obtain purified estrone; wherein: The HPLC purity of methylated rearrangement impurities in the crude estrone product is >0.10%, and the HPLC purity of methylated rearrangement impurities in the purified estrone product is reduced to ≤0.10%. The first solvent is selected from one or more of the following solvents: methanol, ethanol, acetone, tetrahydrofuran, dichloromethane, and ethyl acetate; the second solvent is selected from one or more of the following solvents: methanol, ethanol, isopropanol, acetone, tetrahydrofuran, and toluene; and the methylated rearrangement impurity has the molecular formula C2. 19 H 24 O2, with a molecular weight of 284.4, has the following structural formula: 。 2. A method for purifying estrone, characterized in that, It includes the following steps: Add 1,4-diazabicyclo[2.2.2]octane to the crude estrone solution in the first solvent to obtain a precipitate. Dissolve the precipitate in the second solvent, adjust the pH to ≤3, and obtain a filter cake. Pulp the filter cake with water, filter it, add the filter cake to the first solvent again, heat to dissolve it, concentrate the solution, cool it to crystallize, filter it, and dry it to obtain purified estrone. The HPLC purity of methylated rearrangement impurities in the crude estrone product is >0.10%, and the HPLC purity of methylated rearrangement impurities in the purified estrone product is reduced to ≤0.10%. The first solvent is selected from one or more of the following solvents: methanol, ethanol, acetone, tetrahydrofuran, dichloromethane, and ethyl acetate; the second solvent is selected from one or more of the following solvents: methanol, ethanol, isopropanol, acetone, tetrahydrofuran, and toluene; and the methylated rearrangement impurity has the molecular formula C2. 19 H 24 O2, with a molecular weight of 284.4, has the following structural formula: 。 3. The purification method according to claim 1 or 2, characterized in that, The crude estrone is obtained by demethylation aromatization of 1,4-androstenedione in a Ph3P·X2 system, wherein X refers to a halogen.

4. The purification method according to claim 1, characterized in that, After the precipitate is dissolved in a second solvent, it is adjusted to alkalinity using a strong base, wherein the strong base includes sodium hydroxide and / or potassium hydroxide.

5. The purification method according to claim 1 or 2, characterized in that, Use an acid to adjust the pH to ≤3, wherein the acid includes sulfuric acid and / or hydrochloric acid.

6. The purification method according to claim 1 or 2, characterized in that, The weight-to-volume ratio of the crude estrone to the first solvent and 1,4-diazabicyclo[2.2.2]octane is 1W:10~60V:0.1~1.0W.

7. The purification method according to claim 1 or 2, characterized in that, The weight-to-volume ratio of the crude estrone to the second solvent is 1 W: 5~30 V.

8. The purification method according to claim 1 or 2, characterized in that, The weight-to-volume ratio of the crude estradiol to the second solvent is 1 W: 8~20 V.

9. The purification method according to claim 1 or 2, characterized in that, The third solvent is halomethane.

10. A method for reducing estrone impurities, characterized in that, This includes using the purification method according to any one of claims 1 to 9 as a step.

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