Process for preparing high-purity estetrol

Abstract

The present invention proposes a process for preparing high-purity estetrol, which uses (17β)-3-(phenylmethoxy)-estra-1,3,5(10),15-tetraen-17-ol acetate as a raw material, introduces hydroxyl groups at positions 15 and 16 through a dihydroxylation reaction, protects the hydroxyl groups at positions 15 and 16 through a ketal reaction, separates isomers, and then sequentially removes the benzyl protecting group, the acyl group, and the ketal protecting group. Finally, the process is purified to obtain a compound of formula (I) #imgabs0#. The present invention uses a ketal method to protect the hydroxyl groups at positions 15 and 16, and then separates the isomers, thereby achieving a satisfactory isomer removal effect and refining yield. Moreover, the process is convenient, and the ketal reaction only requires the use of an organic ketone reagent and a catalytic amount of acid. The organic ketone reagent can be completely recovered and reused, and almost no waste is generated.

Description

Technical Field

[0001] The present invention relates to the technical field of organic chemical synthesis and preparation, and in particular to a process for preparing high-purity estetrol. Background Art

[0002] Estetrol is a pharmacologically active pharmaceutical ingredient (API) that can be used for hormone replacement therapy (HRT) in female contraception or for the treatment of autoimmune dysfunction associated with hormone imbalance. The structural formula of estetrol is shown in Formula I:

[0003]

[0004] In publicly reported estetrol production processes, the introduction of the 15α,16α-dihydroxyl group is typically achieved through the dihydroxylation of 15,16-ene. For example, in Chinese patent CN100343269C, estetrol is prepared by introducing the 15,16-dihydroxyl group through a dihydroxylation reaction. However, during the dihydroxylation reaction, a 15β,16β-dihydroxylation reaction inevitably occurs, resulting in the production of the following estetrol isomers (15β,16β,17β-estetrol, whose structural formula is shown in Formula VI). The concentration of these isomers in estetrol must be reduced to within a safe limit (e.g., 0.15%) before it can be used in pharmaceutical formulations. In this patent, the estetrol isomer content is reduced to below 0.5% after beating with heptane / ethyl acetate (1:1) and then recrystallizing three times with heptane / ethyl acetate / ethanol (2:1:1). This results in a refined yield of only 43%.

[0005] In order to more effectively purify and remove estetrol isomers (15β, 16β, 17β-estetrol), several new estetrol purification methods have been disclosed in recent years, including protecting multiple hydroxyl groups in the estetrol molecular structure before purification.

[0006] In Chinese patent CN114302889A, when (15ξ,16ξ,17β)-estra-1,3,5(10)-triene-3,15,16,17-tetrol 3-benzyl ether was directly refined with methanol, the content of 15β,16β,17β-isomers could only be reduced from 10% to 6%. However, after the three hydroxyl groups at positions 15,16,17 in the molecular structure were protected with acetic anhydride and then refined twice with methanol, the content of 15β,16β,17β-isomers was significantly reduced to 0.14%.

[0007] Chinese patent CN114514237A also employs an acylation method to protect the three hydroxyl groups at positions 15, 16, and 17 of (15ξ, 16ξ, 17β)-estra-1,3,5(10)-triene-3,15,16,17-tetrol 3-benzyl ether, followed by purification. After one purification step with methanol, the content of the 15β, 16β, 17β-isomers decreased from 1.6% to 0.18%, with a yield of 84.5%. After further purification with methanol beating, the content of the 15β, 16β, 17β-isomers decreased to 0.07%, with a yield of 94%.

[0008] It can be seen that protecting the 15, 16, and 17-hydroxyl groups of estetrol before refining can significantly improve the refining efficiency, remove impurities more thoroughly, and achieve a higher refining yield. However, in the above technical solution, in order to improve the refining and impurity removal effect, an acylation reaction must be added. The acylation reaction usually uses dichloromethane as a solvent, DMAP as a catalyst, triethylamine as an acid-binding agent, and acetic anhydride as an acylation agent. After the reaction is completed, it must be neutralized with an alkaline solution, and then separated, extracted, washed with water, and concentrated. Finally, it can be refined with a solvent to achieve the refining and impurity removal effect. The whole process is not only cumbersome, but also consumes a large amount of reagent raw materials, increases costs, and generates a large amount of waste and wastewater. Summary of the Invention

[0009] In view of this, the present invention proposes a process for preparing high-purity estetrol, in which the hydroxyl groups at positions 15 and 16 are first protected by a ketal method, and then the product is refined and impurity-removed to prepare high-purity estetrol, so as to solve the technical problems of the existing technology of estetrol preparation being complicated, costly, and containing many pollutants.

[0010] The technical solution of the present invention is achieved as follows: The present invention provides a process for preparing high-purity estetrol, comprising the following steps:

[0011] Step 1: Using the compound (17β)-3-(phenylmethoxy)-estra-1,3,5(10),15-tetraene-17-ol acetate of formula (II) as the starting material, a dihydroxylation reaction is carried out with an oxidant and an inert solvent at 35-60°C for 12-18 hours to obtain the compound (17β)-3-(phenylmethoxy)-estra-1,3,5(10)-triene-15,16,17-triol 17-acetate of formula (III).

[0012]

[0013] It should be noted that Bn represents a benzyl group, and the configurations of carbon atoms 15 and 16 of the steroid skeleton of the compound of formula (III) are not fixed.

[0014] In step 1, a dihydroxylation reaction is carried out using the compound of formula (II) as a starting material. However, since the dihydroxylation reaction is not completely stereoselective, the compound of formula (III) is a mixture of two isomers having configurations (15α, 16α, 17β) and (15β, 16β, 17β). The compound of formula (III) obtained by the dihydroxylation reaction can be a solid product separated by crystallization after the reaction, or preferably a concentrate that is not separated by crystallization. By omitting the post-reaction purification operation, the loss of part of the product during post-processing can be avoided, thereby ensuring a higher product yield.

[0015] Step 2: The compound of formula (III) is subjected to a ketal reaction with an organic ketone reagent in the presence of a catalyst to obtain a compound of formula (IV'); the compound of formula (IV') is subjected to an isomer separation operation to obtain a compound of formula (IV) (15α, 16α, 17β)-3-(phenylmethoxy)-estra-1,3,5(10)-triene-15,16,17-triol 17-acetate, 15,16-dihydroxyketal;

[0016]

[0017] wherein R1 and R2 are selected from hydrogen, a C1-C6 saturated alkyl group, or R1 and R2 together form a cyclohexyl group or a cyclopentyl group;

[0018] In step 2, the compound of formula (III) can be the solid product separated by crystallization after the reaction in step 1, or preferably the concentrate that has not been separated by crystallization. The ketal reaction produces a compound of formula (IV') composed of a mixture of isomers with a predominant amount of 15α, 16α, 17β and a minor amount of 15β, 16β, 17β. The isomer content can then be controlled to below 0.1% by an isomer separation operation, wherein the isomers are separated by a recrystallization purification method. In the present invention, the ketal reaction and recrystallization purification can achieve effective removal of the isomers.

[0019] Step 3: The compound of formula (IV) is subjected to catalytic hydrogenation to obtain the compound of formula (V) (15α,16α,17β)-1,3,5(10)-triene-3,15,16,17-estratetrol 17-acetate, 15,16-dihydroxyketal;

[0020]

[0021] wherein R1 and R2 are selected from hydrogen, a C1-C6 saturated alkyl group, or R1 and R2 together form a cyclohexyl group or a cyclopentyl group;

[0022] It should be noted that the compound of formula (V) obtained after the catalytic hydrogenation reaction in step 3 is directly used in the next reaction without the need for post-processing operations such as crystallization, separation, and purification;

[0023] Step 4: The compound of formula (V) is subjected to alkaline hydrolysis reaction with a base or alkaline salt to obtain the compound of formula (VI) (15α,16α,17β)-1,3,5(10)-triene-3,15,16,17-estratetrol, 15,16-dihydroxyketal,

[0024]

[0025] In step 4, the compound of formula (V) is the solid product separated by crystallization after the reaction in step 3, or preferably, the concentrate that has not been separated by crystallization. More preferably, the compound of formula (V) is the reaction liquid that is not separated from the reaction system after the reaction in step 3. Specifically, after the catalytic hydrogenation reaction in step 3 is completed and the palladium-carbon catalyst is removed by filtration, a base or a basic salt is directly added to the hydrogenation reaction liquid to carry out the alkaline hydrolysis reaction in step 4. The above technical solution can ensure a higher product yield.

[0026] Step 5: The compound of formula (VI) is subjected to acidic hydrolysis to obtain crude estratetrol, which is then purified to obtain the compound of formula (I).

[0027]

[0028] Based on the above technical solution, preferably, the oxidant in step 1 includes a main oxidant and a co-oxidant, the main oxidant is osmium tetroxide (OsO4) or osmate, and the co-oxidant is an organic amine N-oxide; more preferably, the organic amine N-oxide is trimethylamine N-oxide dihydrate or N-methylmorpholine N-oxide. The solvent for the dihydroxylation reaction in step 1 is a solvent inert to osmium derivatives, including tetrahydrofuran, acetone, or butanone, or a mixture of acetonitrile, isopropanol, or tert-butanol and water. The solvent for the dihydroxylation reaction is preferably acetone. The temperature for the dihydroxylation reaction is 30-40°C, and the reaction time is 8-10 hours.

[0029] On the basis of the above technical solution, preferably, in the step 1, the molar ratio of the compound of formula (II) to the main oxidant and the co-oxidant is 1: (0.008-0.012): (1.5-2.5).

[0030] Based on the above technical solution, preferably, in the step 2, the molar ratio of the compound of formula (III), the organic ketone reagent and the catalyst is 1: (0.15-0.25), and the amount of the organic ketone reagent added is 8.5-9.5 times the mass of the compound of formula (III).

[0031] Based on the above technical solution, preferably, the organic ketone reagent in step 2 is selected from a linear or branched saturated alkyl ketone, a cyclic ketone, and a substituted product thereof containing 11 or fewer carbon atoms, and the catalyst is an organic acid or an inorganic acid catalyst. The reaction temperature in step 2 is 20-30° C., and the reaction time is 3-4 hours.

[0032] More preferably, the organic ketone reagent is selected from acetone, methyl isobutyl ketone, cyclohexanone or cyclopentanone, and the catalyst is perchloric acid or p-toluenesulfonic acid.

[0033] On the basis of the above technical solution, preferably, the step 2 of separating the isomers of the compound of formula (IV') to obtain the compound of formula (IV) specifically comprises the following steps:

[0034] Dissolving the compound of formula (IV') in a solvent and refluxing at 78-80°C for 30-60 minutes to obtain a mixture, wherein the solvent is a linear or branched C1-C6 fatty alcohol solvent;

[0035] The mixture is continuously stirred at 0-40° C. for 1-8 hours, and then filtered and dried to obtain the compound of formula (IV).

[0036] Specifically, the temperature during stirring is 20-30° C., and the stirring time is 2-4 hours; the reflux solvent is methanol, ethanol or propanol, and more preferably ethanol.

[0037] Based on the above technical solution, preferably, the conditions for the catalytic hydrogenation reaction in step three are: 5-10% by weight of palladium on carbon as a catalyst, the amount of the catalyst added is 8-12% by weight of the compound of formula (IV); a straight-chain or branched C1-C6 fatty alcohol is used as a solvent, the hydrogen pressure is 1-5 bar, and the reaction is carried out at 50-60°C for 14-18 hours.

[0038] Based on the above technical solution, preferably, the solvent for the alkaline hydrolysis reaction in step 4 is a linear or branched C1-C6 fatty alcohol or water, the alkaline salt is preferably potassium carbonate, and the amount of the base or alkaline salt added is 1.5 to 2.5 times the amount of the compound of formula (IV).

[0039] Based on the above technical solution, preferably, the acidic hydrolysis reaction in step 5 uses hydrochloric acid, sulfuric acid, methanesulfonic acid or perchloric acid, and the solvent is a mixture of one or more of methanol, ethanol, isopropanol or water. More preferably, the acidic hydrolysis reaction uses sulfuric acid or methanesulfonic acid, and the solvent is a mixture of methanol and water.

[0040] On the basis of the above technical solution, preferably, the purification treatment in step 5 includes the following steps:

[0041] reflux the crude estratetol in a solvent for 30 to 60 minutes, wherein the solvent is one or more of tetrahydrofuran, methanol, and acetonitrile, and the reflux temperature is 65 to 80° C.;

[0042] The refluxed estetrol crude solution is cooled to 20-30° C., stirred for 50-70 min, filtered, and dried to obtain the compound of formula (I).

[0043] The process for preparing high-purity estetrol of the present invention has the following beneficial effects compared with the prior art:

[0044] (1) The present invention uses (17β)-3-(phenylmethoxy)-estra-1,3,5(10),15-tetraene-17-ol acetate as a raw material, introduces hydroxyl groups at positions 15,16 by a dihydroxylation reaction, protects the hydroxyl groups at positions 15,16 by a ketal reaction, and then separates the isomers to obtain a compound of formula (IV) (15α,16α,17β)-3-(phenylmethoxy)-estra-1,3,5(10)-triene-15,16,17-triol 17-acetate and 15,16-dihydroxyketal, and then removes the benzyl protecting group, the acyl group, and the ketal protecting group in sequence, thereby achieving a satisfactory isomer removal effect and a refining yield. Moreover, the process is convenient, and the ketal reaction only requires the use of an organic ketone reagent and a catalytic amount of acid. The organic ketone reagent can be completely recovered and reused, and almost no waste is generated.

[0045] (2) In the present invention, isomer removal is achieved through ketal reaction and recrystallization purification in step 2, which can improve the isomer removal effect and avoid increasing the acylation reaction, thereby simplifying the reaction steps, reducing costs, and improving product yield, which is conducive to industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0047] Figure 1 is a high performance liquid chromatogram of the compound of formula (III) in step (1) of Example 1 of the present invention;

[0048] Figure 2 is a high performance liquid chromatogram of the compound of formula (IV') in step (2) of Example 1 of the present invention;

[0049] Figure 3 is a high performance liquid chromatogram of the compound of formula (IV) in step (2) of Example 1 of the present invention;

[0050] Figure 4 is the hydrogen nuclear magnetic resonance spectrum of the compound of formula (IV) in step (2) of Example 1 of the present invention;

[0051] Figure 5 is a high performance liquid chromatogram of the compound of formula (V) in step (3) of Example 1 of the present invention;

[0052] Figure 6 is the hydrogen nuclear magnetic resonance spectrum of the compound of formula (V) in step (3) of Example 1 of the present invention;

[0053] Figure 7 is a high performance liquid chromatogram of the crude estratetrol product of step (5) in Example 1 of the present invention;

[0054] Figure 8 is a high performance liquid chromatogram of the compound of formula (I) in step (5) of Example 1 of the present invention;

[0055] Figure 9 This is a high performance liquid chromatogram of the compound of formula (III) after purification in step (1) of Example 4 of the present invention. DETAILED DESCRIPTION

[0056] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0057] In order to enable those skilled in the art to more clearly understand the technical solution of the present application, the technical solution of the present application will be described in detail below with reference to specific examples. If the specific experimental conditions are not specified in the examples, they are usually based on conventional conditions or the conditions recommended by the reagent company: the reagents, consumables, etc. used in the following examples, unless otherwise specified, can be obtained through commercial channels.

[0058] Example 1

[0059] This embodiment provides a process for preparing high-purity estetrol, which specifically comprises the following steps:

[0060]

[0061] (1) Add 87.8g (0.22mol) of the compound of formula (II), 0.8g (0.0022mol) of potassium osmate dihydrate, 48.48g (0.44mol) of trimethylamine dihydrate, and 878mL of acetone to a reaction flask. The hydrogen pressure is 3 bar, and the mixture is heated to 35°C and stirred for 8 hours. The reaction endpoint is confirmed by TLC monitoring. After the reaction, the temperature is lowered to below 30°C, and 54g (0.22mol) of sodium thiosulfate is added and stirred for 0.5 hours. The reaction solution is concentrated, and 878mL of ethyl acetate is added to dissolve the solution. The solution is washed once with 400mL of water and saturated brine. The organic phase is dried and concentrated to obtain 98g of the compound of formula (III), which is directly used in the next step. HPLC analysis shows that the target product 15α,16α,17β-triol accounts for 73.25% and the isomer 15β,16β,17β-triol accounts for 7.85%.

[0062] (2) 98 g (0.22 mol) of the compound of formula (III), 8.30 g (0.044 mol) of p-toluenesulfonic acid, and 880 mL of acetone were added to a 2 L reaction flask, and the reaction was stirred at room temperature (25°C) for 4 h. The reaction endpoint was confirmed by TLC monitoring. After the reaction was completed, the temperature was lowered and the reaction solution was concentrated under reduced pressure to obtain the compound of formula (IV'). HPLC analysis showed that the target product had a 15α, 16α, 17β-configuration accounting for 81.95%, and the isomer 15β, 16β, 17β-configuration accounted for 7.93%, which was basically consistent with the isomer ratio of the dihydroxylation product in step (1).

[0063] 880 mL of ethanol was added to the compound of formula (IV'), and the mixture was refluxed at 78-80°C to dissolve the mixture, stirred for 1 h, slowly cooled, and slurried at room temperature (25°C) and stirred for 3 h. The mixture was filtered, dried, and the filter cake was air-dried at 50±5°C to constant weight to obtain 73.3 g of compound of formula (IV) (purity: 100.0%). HPLC analysis showed that the target product had a 15α, 16α, 17β-configuration of almost 100%, and the isomers 15β, 16β, 17β-configuration were almost completely eliminated. The H NMR spectrum showed: 1H NMR (600MHz, CDCl3) δ7.43(d,J=7.20Hz,2H),7.38(t,J=7.50Hz,2H),7.32(t,J=7.20Hz,1H),7.18 (d,J=9.00Hz,1H),6.78(dd,J=8.4,2.4Hz,1H),6.73(s,1H),5.04(s,2H),4.94(d,J=4.2Hz,1H),4. 65(dd,J=7.80,4.80Hz,1H),4.46(t,J=8.10Hz,1H),2.90–2.86(m,2H),2.27(t,J=8.0Hz,2H),2.1 2–2.09(m,4H),1.75-1.73(m,1H),1.64–1.52(m,7H),1.43–1.37(m,1H),1.33(s,3H),0.89(s,3H);

[0064] (3) 73.3 g (0.15 mol) of the compound of formula (IV), 7.3 g of 10% wet palladium carbon, and 1400 mL of methanol were added to a 2 L hydrogenation reaction vessel, and the gas was replaced with hydrogen three times. The reaction was carried out at 50-60° C. under a hydrogen atmosphere for 16 h. After the reaction was completed by TLC, the palladium carbon was filtered off to obtain a methanol solution of the compound of formula (V); the H NMR spectrum showed: 1 H NMR(600MHz,DMSO-d6)δ8.96(s,1H),6.96(d,J=8.4Hz,1H),6.45(d,J=8.4Hz,1H),6.3 9(s,1H),4.72(d,J=4.8Hz,1H),4.56(t,J=6.3Hz,1H),4.38(t,J=8.1Hz,1H),2.73–2.6 3(m,2H),2.14–2.07(m,2H),2.02(s,3H),1.93–1.89(m,1H),1.34(d,J=12.6Hz,1H),1 .44-1.40(m,2H),1.38–1.35(m,4H),1.32–1.25(m,1H),1.21–1.50(m,4H),0.78(s,3H)

[0065] (4) To a methanol solution of the compound of formula (V) was added 17.3 g (0.3 mol) of potassium carbonate, and the mixture was reacted under nitrogen for 5 hours. The mixture was filtered and the filtrate was concentrated to obtain 52 g of the compound of formula (VI);

[0066] (5) Add 52 g (0.15 mol) of the compound of formula (VI) and 520 mL of 30% sulfuric acid to a 1 L reaction flask, heat to 78-80 ° C for 8 h, and react until the reaction is complete by TLC. Cool to room temperature (25 ° C), add 520 mL of water to dilute, and beat at room temperature for 1-2 h. Filter, wash the filter cake twice with 200 mL of water, and air dry to obtain 45.6 g of off-white estetrol crude product with a yield of 100%; add 45.6 g of estetrol crude product and 90 mL of methanol to a 1 L reaction flask, heat to 65-80 ° C for dissolution and reflux for 45 min, concentrate until the solution has 30 mL (1 V), add 270 mL (9 V) of acetonitrile, stir under reflux for 0.5 h, then cool to 20-25 ° C for 1 h, and filter. The filter cake was dried at 50° C. for 6 to 10 h to obtain 37.98 g of compound (I) with a yield of 83.3%. HPLC analysis showed that the target product estratetrol accounted for almost 100%, and the isomers 15β, 16β, 17β-configuration and other impurities were almost completely removed.

[0067] Example 2

[0068] (1) Add 87.8g (0.22mol) of the compound of formula (II), 0.65g (0.0018mol) of potassium osmate dihydrate, 36.68g (0.33mol) of trimethylamine dioxide dihydrate, and 878mL of acetone to a reaction flask, heat to 35°C, stir and react for 8h, and confirm the reaction endpoint by TLC plate monitoring; after the reaction, cool to below 30°C, add 54g (0.22mol) of sodium thiosulfate and stir for 0.5h. The reaction solution is concentrated, 878mL of ethyl acetate is added to dissolve the clear solution, and the solution is washed once with 400mL of water and saturated brine. The organic phase is dried and concentrated to obtain 90g of the compound of formula (III), which is directly used in the next step of the reaction;

[0069] (2) Add 90 g (0.21 mol) of the compound of formula (III), 5.51 g (0.032 mol) of p-toluenesulfonic acid, and 765 mL of acetone to a 2 L reaction flask, stir at room temperature (25°C) for 4 h, and confirm the reaction endpoint by TLC monitoring; after the reaction is completed, cool the reaction solution and concentrate it under reduced pressure to obtain the compound of formula (IV');

[0070] 765 mL of ethanol was added to the compound of formula (IV'), refluxed at 78-80°C to dissolve the solution, stirred for 1 h, slowly cooled, slurried at room temperature and stirred for 3 h, filtered, dried, and the filter cake was air-dried at 50±5°C to constant weight to obtain 63.5 g of compound of formula (IV) (purity: 100.0%);

[0071] (3) Add 63.5 g (0.13 mol) of the compound of formula (IV), 5.1 g of 5% wet palladium carbon, and 1200 mL of methanol to a 2 L hydrogenation reactor, replace the gas with hydrogen three times, and react at 50-60° C. under a hydrogen atmosphere for 16 h. After the reaction is complete by TLC detection, the palladium carbon is filtered off to obtain a methanol solution of the compound of formula (V).

[0072] (4) To a methanol solution of the compound of formula (V) was added 17.3 g (0.3 mol) of potassium carbonate, and the mixture was reacted under nitrogen for 5 hours. The mixture was filtered and the filtrate was concentrated to obtain 40.8 g of the compound of formula (VI);

[0073] (5) Add 40.8 g (0.12 mol) of the compound of formula (VI) and 408 mL of 30% sulfuric acid to a 1 L reaction flask, heat to 78-80 ° C for 8 h, and react until the reaction is complete by TLC. Cool to room temperature (25 ° C), add 390 mL of water for dilution, and beat at room temperature for 1-2 h. Filter, wash the filter cake twice with 200 mL of water, and air dry to obtain 33.58 g of off-white crude estratetrol with a yield of 92%. Add 33.58 g of crude estratetrol and 90 mL of methanol to a 1 L reaction flask, heat to 65-80 ° C for dissolution, concentrate to a solution with 30 mL (1 V), add 180 mL (6 V) of acetonitrile, stir under reflux for 0.5 h, then cool to 20-25 ° C for 1 h, and filter. The filter cake was dried at 50°C for 6-10 h to obtain 27.47 g of compound of formula (I) with a yield of 81.80%.

[0074] Example 3

[0075] (1) Add 87.8g (0.22mol) of the compound of formula (II), 0.97g (0.0026mol) of potassium osmate dihydrate, 61.13g (0.55mol) of trimethylamine dihydrate, and 878mL of acetone to a reaction flask, heat to 35°C, stir and react for 8h, and confirm the reaction endpoint by TLC plate monitoring; after the reaction, cool to below 30°C, add 54g (0.22mol) of sodium thiosulfate and stir for 0.5h. The reaction solution is concentrated, 878mL of ethyl acetate is added to dissolve the clear solution, and the solution is washed once with 400mL of water and saturated brine. The organic phase is dried and concentrated to obtain 98.4g of the compound of formula (III), which is directly used in the next step of the reaction;

[0076] (2) Add 98.4 g (0.23 mol) of the compound of formula (III), 10.0 g (0.058 mol) of p-toluenesulfonic acid, and 935 mL of acetone to a 2 L reaction flask, stir at room temperature (25°C) for 4 h, and confirm the reaction endpoint by TLC monitoring; after the reaction is completed, cool the reaction solution and concentrate it under reduced pressure to obtain the compound of formula (IV');

[0077] 880 mL of ethanol was added to the compound of formula (IV'), refluxed at 78-80°C to dissolve the solution, stirred for 1 h, slowly cooled, slurried at room temperature and stirred for 3 h, filtered, dried, and the filter cake was air-dried at 50±5°C to constant weight to obtain 74 g of compound of formula (IV) (purity: 100.0%);

[0078] (3) Add 74 g (0.16 mol) of the compound of formula (IV), 8.88 g of 8% wet palladium carbon, and 1480 mL of methanol to a 2 L hydrogenation reactor, replace the gas with hydrogen three times, and react at 50-60° C. under a hydrogen atmosphere for 16 h. After the reaction is complete by TLC, the palladium carbon is filtered off to obtain a methanol solution of the compound of formula (V);

[0079] (4) To a methanol solution of the compound of formula (V) was added 17.3 g (0.32 mol) of potassium carbonate, and the mixture was reacted under nitrogen for 5 hours. The mixture was filtered and the filtrate was concentrated to obtain 54 g of the compound of formula (VI);

[0080] (5) Add 54 g (0.16 mol) of the compound of formula (VI) and 540 mL of 30% sulfuric acid to a 1 L reaction flask, heat to 78-80 ° C for 8 h, and react until the reaction is complete by TLC. Cool to room temperature (25 ° C), add 610 mL of water for dilution, and beat at room temperature for 1-2 h. Filter, wash the filter cake twice with 200 mL of water, and air dry to obtain 48.12 g of off-white crude estetrol with a yield of 98.89%. Add 45 g of crude estetrol and 90 mL of methanol to a 1 L reaction flask, heat to 65-80 ° C for dissolution, concentrate until the solution remains 30 mL (1 V), add 360 mL (12 V) of acetonitrile, stir under reflux for 0.5 h, then cool to 20-25 ° C for 1 h, and filter. Dry the filter cake at 50 ° C for 6-10 h to obtain 39.92 g of the compound of formula (I) with a yield of 82.96%.

[0081] Example 4

[0082] This embodiment provides a process for preparing high-purity estetrol. The specific operating steps are the same as those in Example 1, except that, in step (2), 98 g (0.22 mol) of the compound of formula (III), 5.68 g (0.033 mol) of p-toluenesulfonic acid, and 880 mL of acetone are added to a 2 L reaction flask, and the reaction is stirred at room temperature (25° C.) for 4 h. The reaction endpoint is confirmed by TLC monitoring. After the reaction is completed, the temperature is lowered, and the reaction solution is concentrated under reduced pressure to obtain a compound of formula (IV′).

[0083] 880 mL of ethanol was added to the compound of formula (IV'), refluxed at 78-80°C to dissolve the mixture, stirred for 1 h, slowly cooled, slurried at room temperature (25°C) and stirred for 3 h, filtered, dried, and the filter cake was air-dried at 50±5°C to constant weight to obtain 67.2 g (purity 100.0%) of the compound of formula (IV). HPLC analysis showed that the target product 15α, 16α, 17β-configuration accounted for almost 100%, and the isomer 15β, 16β, 17β-configuration was almost completely eliminated.

[0084] Example 5

[0085] This embodiment provides a process for preparing high-purity estetrol. The specific operating steps are the same as those in Example 1, except that, in step (2), 98 g (0.22 mol) of the compound of formula (III), 9.46 g (0.055 mol) of p-toluenesulfonic acid, and 880 mL of acetone are added to a 2 L reaction flask, and the reaction is stirred at room temperature (25° C.) for 4 h. The reaction endpoint is confirmed by TLC monitoring. After the reaction is completed, the temperature is lowered, and the reaction solution is concentrated under reduced pressure to obtain a compound of formula (IV′).

[0086] 880 mL of ethanol was added to the compound of formula (IV'), refluxed at 78-80°C to dissolve the mixture, stirred for 1 h, slowly cooled, slurried at room temperature (25°C) and stirred for 3 h, filtered, dried, and the filter cake was air-dried at 50±5°C to constant weight to obtain 72.6 g (purity: 100.0%) of the compound of formula (IV). HPLC analysis showed that the target product 15α, 16α, 17β-configuration accounted for almost 100%, and the isomer 15β, 16β, 17β-configuration was almost completely eliminated.

[0087] Comparative Example 1

[0088] This embodiment provides a process for preparing high-purity estetrol. The specific operating steps are the same as those in Example 1, except that, in step (1), the compound of formula (III) obtained by the reaction is purified, and then the purified compound of formula (III) is used in the next step. The purification process is as follows: in step (1), after the reaction is completed, 50 g of the compound of formula (III) is taken, 150 mL of a solvent of n-heptane and ethyl acetate (1:1) is added, the mixture is slurried at room temperature for 1 hour, filtered, and dried. The filter cake is dried at 50° C. with forced air to constant weight to obtain 35.4 g of a white solid, with a combined yield of 72.5% for the dihydroxylation reaction and purification. HPLC detection showed that the target product 15α,16α,17β-configuration accounted for 95.58%, and the isomer 15β,16β,17β-configuration accounted for 1.98%. It can be seen that when the dihydroxy product was directly refined once, the isomer content decreased from 7.63% to 1.98%. Even with further refinement, it is not easy to reach below the desired limit. The efficiency of direct refining isomer removal is not high.

[0089] By comparing Example 1 with Comparative Example 1, it can be seen that directly applying the compound of formula (III) obtained in step (1) to the reaction of step (2) without purification can ensure a higher product yield and does not affect the efficiency of isomer removal. By comparing Example 1 with Examples 2 and 3, it can be seen that the yield and purity of estetrol prepared in Example 1 are the best; by comparing Example 1 with Examples 4-5, it can be seen that the amount of catalyst added in step (2) can affect the yield of the ketal reaction. When the molar ratio of the compound of formula (III) to the catalyst is 1:0.02, the ketal reaction yield is better, that is, the yield of the compound of formula (IV) is better.

[0090] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A process for preparing high-purity estetrol, characterized in that: The following steps are involved: Step 1: Using the compound of formula (II) as the starting material, carry out an oxidation reaction with an oxidant and an inert solvent at 35-60°C for 12-18 hours to obtain a compound of formula (III). ； Step 2: The compound of formula (III) is subjected to a ketal reaction with an organic ketone reagent in the presence of a catalyst to obtain a compound of formula (IV'); the compound of formula (IV') is subjected to an isomer separation operation to obtain a compound of formula (IV). ， Wherein, R1 and R2 are selected from hydrogen, C1~C6 saturated alkyl, or R1 and R2 together form cyclohexyl or cyclopentyl; Step 3: The compound of formula (IV) is subjected to catalytic hydrogenation to obtain the compound of formula (V), ； Step 4: The compound of formula (V) is subjected to alkaline hydrolysis reaction with a base or a basic salt to obtain a compound of formula (VI). ； Step 5: The compound of formula (VI) is subjected to acidic hydrolysis to obtain crude estratetrol, which is then purified to obtain the compound of formula (I). ； In the step 2, the organic ketone reagent is selected from acetone, methyl isobutyl ketone, cyclohexanone or cyclopentanone, and the catalyst is perchloric acid or p-toluenesulfonic acid; In the step 2, the compound of formula (IV') is subjected to isomer separation operation to obtain the compound of formula (IV) specifically comprising the following steps: Dissolving the compound of formula (IV') in a solvent and refluxing at 78-80°C for 30-60 minutes to obtain a mixture, wherein the solvent is a linear or branched C1-C6 fatty alcohol solvent; The mixture is continuously stirred at 0-40° C. for 1-8 hours, and then filtered and dried to obtain the compound of formula (IV).

2. A process for preparing high-purity estetrol according to claim 1, characterized in that: The oxidant in step 1 includes a main oxidant and a co-oxidant, the main oxidant is osmium tetroxide or osmate, and the co-oxidant is an organic amine N-oxide.

3. A process for preparing high-purity estetrol according to claim 2, characterized in that: In the step 1, the molar ratio of the compound of formula (II) to the main oxidant and the co-oxidant is 1: (0.008-0.012): (1.5-2.5).

4. A process for preparing high-purity estetrol according to claim 1, characterized in that: In the step 2, the molar ratio of the compound of formula (III) to the catalyst is 1:(0.15-0.25), and the amount of the organic ketone reagent added is 8.5-9.5 times the mass of the compound of formula (III).

5. A process for preparing high-purity estetrol according to claim 1, characterized in that: The conditions for the catalytic hydrogenation reaction in step 3 are as follows: using 5-10% by weight of palladium on carbon as a catalyst, the amount of the catalyst added is 8-12% by weight of the compound of formula (IV); using a linear or branched C1-C6 fatty alcohol as a solvent, a hydrogen pressure of 1-5 bar, and reacting at 50-60° C. for 14-18 hours.

6. A process for preparing high-purity estetrol according to claim 1, characterized in that: In the step 5, the acidic hydrolysis reaction adopts hydrochloric acid, sulfuric acid, methanesulfonic acid or perchloric acid, and the solvent is a mixture of one or more of methanol, ethanol, isopropanol and water.

7. A process for preparing high-purity estetrol according to claim 1, characterized in that: The purification process in step 5 comprises the following steps: reflux the crude estratetol in a solvent for 30 to 60 minutes at a temperature of 65 to 80° C., wherein the solvent is one or more of tetrahydrofuran, methanol, and acetonitrile; The refluxed estetrol crude solution is cooled to 20-30° C., stirred for 50-70 min, filtered, and dried to obtain the compound of formula (I).

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