Method for preparing high-purity estetrol

Abstract

The invention discloses a method for preparing high-purity estra-1, 3, 5 (10)-triene-3, 15 alpha, 16 alpha, 17 beta-tetrol (abbreviated as estratrol), which is characterized in that 3-hydroxy-17 beta-hydroxyestra-1, 3, 5 (10), 15-tetraene is used as a raw material, and the estratrol is prepared by three steps of phenolic hydroxyl group protection, asymmetric dihydroxylation and hydrolysis. According to the preparation method, 3-hydroxy-17beta-hydroxyestra-1, 3, 5 (10), 15-tetraene is taken as a raw material, 3-hydroxyl is protected by alkoxy-substituted benzoyl, asymmetric dihydroxyl reaction is carried out through catalytic oxidation of potassium osmate, double alpha-hydroxyl is introduced to 15, 16-positions, chemical reagents and catalysts with high cost are not needed in the preparation method, and the preparation method is simple and easy to implement. The dihydroxylation has the advantages of high stereoselectivity, easiness in purification and separation, mild reaction conditions and simplicity and convenience in operation, and high-efficiency preparation of high-purity estetrol (more than or equal to 99.5%) can be realized.

Description

Technical Field

[0001] The invention belongs to the technical field of organic compound preparation and relates to a method for preparing high-purity estetrol. Background Art

[0002] As a female hormone, estetrol is produced only by the liver of the baby during pregnancy. Clinical studies have shown that estetrol can be used for hormone replacement therapy and female oral contraceptives. In addition, estetrol has important applications in the treatment of autoimmune diseases, prevention and treatment of breast and colon tumors, osteoporosis, skin care and wound healing (WO02 / 094276, WO02 / 094279, WO02 / 094278, WO02 / 094275, WO03 / 041718 and WO03 / 018026).

[0003] The chemical name of estratetrol is estradiol-1,3,5(10)-triene-3,15α,16α,17β-tetrol, and its structure is shown in Formula 1. The main characteristic structural part is 15α,16α,17β-triol.

[0004]

[0005] Early methods for synthesizing estetrol mainly used 3,17-diacetyl-protected estrone-1,3,5(10),15-tetraene-3,17β-diol to undergo asymmetric dihydroxylation with osmium tetroxide (J.Org.Chem.1968,33,3133-3135; Steroids,1976,27,111-121; Steroids,1995,60,277-284). Using estrone as the starting material, the total yield of estetrol was 7-8%, the yield of the asymmetric dihydroxylation reaction was 46-47%, and the ratio of dihydroxylated product / isomer was 74 / 26, i.e., the ratio of 15α,16α- / 15β,16β- was 74 / 26. Unfortunately, the purity of the product estetrol was not reported. The reaction route is shown in Scheme 1.

[0006]

[0007] When acetyl is used as the protecting group for 3-phenolic hydroxyl group, not only is the protecting group unstable in the reaction, but also when the intermediate product is purified by crystallization, once a protic solvent such as methanol is used, the generation of by-products will increase.

[0008] In 2004, patent WO 2004 / 041839 synthesized estetrol from estrone as the starting material by protecting the 3-hydroxyl group with benzyl and the 17-hydroxyl group with acetyl. The total yield of the reaction was 10.8%. The carbonyl reduction step used the NaBH4 / CeCl3 system. The key asymmetric dihydroxylation step also used osmium tetroxide as an oxidant. Starting from compound K, dihydroxylation was performed to obtain compound L. The crude yield was 84%. After three recrystallizations, the purity of compound L was 98.7%, and the refined yield was 43%. The purity of the final product estetrol was not reported, as shown in Scheme 2.

[0009]

[0010] The same scheme was repeated in patent WO 2013 / 012328, where osmium tetroxide was replaced with PVP-osmium tetroxide. The data for dihydroxylation were consistent. After deprotection by catalytic hydrogenation (92% yield) and alkaline hydrolysis (92.5% yield), the purity of the obtained estetrol was 99.5%. The total impurities of the estetrol process reported in the patent did not exceed 1%, but the content information of a single impurity was not provided.

[0011] Patent WO 2013 / 012328 also reports a method for preparing estetrol by asymmetric dihydroxylation reaction with different protecting groups protecting the 3-hydroxyl group and the 17-hydroxyl group being unprotected. The 3-hydroxyl group is protected as benzyl ether, benzoyloxy, alkyl ether, silyl ether, etc. The asymmetric dihydroxylation was carried out using PVP-osmium tetroxide, and the ratio of 15α, 16α- / and 15β, 16β- was 90 / 10, but the refining yield of the asymmetric dihydroxylation was not reported. As a control experiment, the patent also reported the results of the direct asymmetric dihydroxylation reaction without protecting the 3-hydroxyl group, with a low yield (62%), and the generated estetrol was wrapped with impurities, with a poor solid form and difficult to purify.

[0012] In 2013, patent WO 2013 / 034780 reported the limitation of 3-phenolic hydroxyl protecting groups. As shown in Formula 2, R is limited to benzoyl, acetyl, and benzyl.

[0013]

[0014]

[0015] Patent CN 103890001 (related patent number WO 2013050553) in 2014 also reported the limitation of the 3-phenolic hydroxyl protecting group, wherein it was reported that P1 was a protecting group selected from R1CO-, and R1 was a group selected from C1-C6 alkyl or C3-C6 cycloalkyl, as shown in Formula 3.

[0016]

[0017] 3-Hydroxy-17β-hydroxyestra-1,3,5(10),15-tetraene as a starting material can be synthesized according to the literature [J. Org. Chem. 1968, 33, 3133-3135; Steroids, 1976, 27, 111-121; Steroids, 1995, 60, 277-284].

[0018] In all the above patents publicly reporting asymmetric dihydroxylation, the 3-phenolic hydroxyl group is mainly protected by an ester group or an ether bond. The main problem is that after dihydroxylation, the presence of isomers and impurities makes purification difficult, and repeated purification is required to obtain a high-purity dihydroxylation product with a low yield.

[0019] Regarding how to effectively purify the dihydroxylated product, the 2022 patent CN 114514237 and patent CN114302889 (related patent WO 2021044302) reported that the three hydroxyl groups at positions 15, 16, and 17 were first formed into ester derivatives and then purified and separated, as shown in Scheme 3. After preparing compound III, it was recrystallized with methanol, and the refining yield was 69.8%, and compound III with a purity of 99.2% could be obtained, but the material loss was large. After purification, after two steps of hydrogenation debenzylation and hydrolysis, the final purity of estratetrol can reach 99.67%, isomers <0.04%, and all impurities <0.10%, but the route of this derivatization method is long, the refining yield is low, and the loss is large.

[0020]

[0021] In summary, it is a very challenging task to purify the asymmetric dihydroxylation product directly after the asymmetric dihydroxylation without derivatization or repeated purification, and to ensure that the purity of estetrol after hydrolysis is ≥99.5%, and that the single impurity is <0.04% and the total impurity is <0.1%. Summary of the invention

[0022] The technical problem to be solved by the present invention is how to provide a method for preparing high-purity estetrol. The present invention proposes to protect the 3-phenolic hydroxyl group by using an alkoxy-substituted benzoyl group through the optimization screening of the 3-hydroxyl protecting functional group. In addition to being able to increase the ratio of dihydroxylation (from 93:7 to 95:5), more importantly, the physical properties (melting point, solubility, solid crystal form, etc.) of the dihydroxylated product are changed, so that the advantageous product structure (15α, 16α, 17β-) is easier to be effectively separated from impurities and isomers (15β, 16β, 17β-). Through a simple solvent refining, a dihydroxylated product with a purity (≥98.5%) can be obtained, and then through the later hydrolysis and deprotection, the preparation of high-purity estetrol (≥99.5%) can be achieved.

[0023] The present invention uses 3-hydroxy-17β-hydroxyestra-1,3,5(10),15-tetraene as a raw material, and utilizes an alkoxy-substituted benzoyl group to protect the 3-phenolic hydroxyl group, so that the subsequent dihydroxylation yield, stereoselectivity and product purification are effectively solved. The alkoxy-containing benzoyl group provides a larger steric hindrance, so that the dihydroxylation has a higher stereoselectivity, and at the same time increases the solubility of the product after the dihydroxylation, which has a greater advantage in the subsequent purification treatment of the material. Compared with the benzoyl or ether protective group introduced without a substituent reported in the prior art, it has a better separation and purification effect, the advantage of a higher dihydroxylation ratio, avoids cumbersome post-processing and a reduction in yield, and improves the preparation yield of high-purity estetrol.

[0024] In the preparation method of the present invention, 3-hydroxy-17β-hydroxyestra-1,3,5(10),15-tetraene is used as a raw material, and estetrol is prepared through three steps of phenolic hydroxyl protection, dihydroxylation and hydrolysis.

[0025] The reaction process of the above-mentioned preparation method of the present invention is shown in reaction formula (I):

[0026]

[0027] Wherein, R is an alkoxy group, and the position of R is at the ortho position, meta position or para position of the aromatic ring.

[0028] Wherein, the R group is located at one or more of the ortho, meta or para positions of the benzene ring; preferably, at the para position.

[0029] The R group on the benzene ring is an alkoxy group containing a C1-C6 alkane, which is one or more of methoxy, ethoxy, isopropoxy, tert-butoxy, etc.; preferably, it is methoxy.

[0030] The method of the present invention comprises the following steps:

[0031] Step 1, 3-phenolic hydroxyl protection: In a first solvent, the compound of formula (1) and a hydroxyl-protecting aromatic reagent are subjected to a hydroxyl protection reaction in the presence of a base to obtain a compound of formula (2); the reaction process is shown in reaction formula (A):

[0032]

[0033] Step 2, asymmetric dihydroxylation reaction: dissolving the compound of formula (2) obtained in step 1 in a second solvent, and reacting under temperature control in the presence of a catalyst and an oxidant to obtain a compound of formula (3); the reaction process is shown in reaction formula (B):

[0034]

[0035] Step 3, hydrolysis reaction: the compound of formula (3) obtained in step 2 is dissolved in a third solvent, and deprotected under alkaline conditions to obtain the target product estetrol; the reaction process is shown in reaction formula (C):

[0036]

[0037] In step 1 of the present invention, the 3-phenolic hydroxyl protection reaction is specifically as follows: the compound of formula (1) reacts with an aromatic reagent for protecting the hydroxyl group in the first solvent under the action of a base to obtain a compound of formula (2).

[0038] The aromatic reagent for protecting the hydroxyl group is selected from one or more of p-methoxybenzoyl chloride, o-methoxybenzoyl chloride, p-ethoxybenzoyl chloride, p-isopropoxybenzoyl chloride, p-tert-butoxybenzoyl chloride, etc.; preferably, p-methoxybenzoyl chloride.

[0039] Wherein, the base is selected from one or more of triethylamine, diisopropylethylamine, imidazole, pyridine, DMAP, etc.; preferably, it is pyridine.

[0040] Wherein, the first solvent is selected from one or more of ethyl acetate, dichloromethane, chloroform, DMF, toluene, tetrahydrofuran, 2-methyltetrahydrofuran, etc.; preferably, it is dichloromethane.

[0041] The molar ratio of the compound of formula (1), the hydroxyl-protecting aromatic reagent and the base is 1:(1-4):(0.05-5); preferably, it is 1:1.1:1.1.

[0042] Wherein, the reaction temperature is 0-50°C; preferably, 25°C.

[0043] Wherein, the reaction time is 2 to 24 hours; preferably, 3 hours.

[0044] In step 2, the second solvent is selected from one or more of dichloromethane, chloroform, acetone, toluene, ethyl acetate, methanol, ethanol, tetrahydrofuran, 2-methyltetrahydrofuran, etc.; preferably, it is acetone.

[0045] In step 2, the oxidant is selected from one or more of N-methylmorpholine oxide (NMO), trimethylamine N-oxide, etc.; preferably, it is N-methylmorpholine oxide (NMO).

[0046] In step 2, the catalyst is selected from one or more of osmium tetroxide, potassium osmate, etc.; preferably, it is potassium osmate.

[0047] In step 2, the mass ratio of the compound of formula (3), the oxidant and the catalyst is 1:(1-2):(0.001-0.01); preferably, it is 1:1.2:0.005.

[0048] In step 2, the temperature of the oxidation reaction is 0°C-50°C; preferably, 50°C.

[0049] In step 2, the oxidation reaction time is 6-12 hours; preferably, 6 hours.

[0050] In step 3, the hydrolysis reaction is specifically as follows: the compound of formula (2) undergoes a hydrolysis reaction in the third solvent under the action of a base to obtain estetrol.

[0051] Wherein, the base is selected from one or more of LiOH, KOH, NaOH, t-BuOK, K2CO3, etc.; preferably, it is NaOH.

[0052] Wherein, the molar ratio of the compound of formula (3) to the base is 1:(0.5-2); preferably, 1:2.

[0053] Wherein, the third solvent is selected from one or two of water, methanol, ethanol, etc.; preferably, it is methanol.

[0054] Wherein, the temperature of the hydrolysis reaction is 10-75°C; preferably, 65°C.

[0055] Wherein, the hydrolysis reaction time is 0.5 to 12 hours; preferably, 6 hours.

[0056] In the present invention, the phenolic hydroxyl group at the 3-position is protected by an alkoxy-containing benzoyl group, which has a large steric hindrance, changes the physical properties of the dihydroxylated product, and has good fat solubility. A high-purity dihydroxylated product (purity ≥ 98.5%) can be obtained by one-time refining, and then deprotected by hydrolysis to efficiently prepare high-purity estetrol (purity ≥ 99.5%). In the reaction process of the present invention, whether it is 3α-hydroxyl protection, dihydroxylation and hydrolysis reaction, the reaction conditions are safe and mild, and no strong base or strong acid system is involved, which will not affect the configuration of 15α, 16α-hydroxyl and 17β-hydroxyl, and its unique stereo configuration is maintained, which has the advantage of efficient separation.

[0057] The beneficial effects of the present invention are as follows: 3-hydroxy-17β-hydroxyestra-1,3,5(10),15-tetraene is used as a raw material, a benzoyl group containing an alkoxy group is used to protect the 3-hydroxyl group, a dihydroxyl reaction is carried out by catalytic oxidation with potassium osmate, and a di-α-hydroxyl group is introduced at the 15,16-positions; the preparation method does not require the use of chemical reagents and catalysts with high costs; the dihydroxylization reaction has the characteristics of high stereoselectivity, easy purification and separation, mild reaction conditions, and simple and convenient operation, and can realize the efficient preparation of high-purity estetrol. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 This is the HPLC spectrum of high-purity estetrol in Example 12 of the present invention.

[0059] Figure 2 The high-purity estetrol in Example 12 of the present invention 1 HNMR spectrum. DETAILED DESCRIPTION

[0060] The invention is further described in detail in conjunction with the following specific examples. The process, conditions, experimental methods, etc. for implementing the present invention, except for the contents specifically mentioned below, are all common knowledge and common common sense in the art, and the present invention has no particular limitations. (The results shown in the embodiments are all obtained under optimized experimental conditions and have potential application value).

[0061] Example 1 (protection of p-methoxybenzoyl)

[0062]

[0063] In a 1L dry three-necked flask, add 54.0g (0.2mol) of the compound of formula (1), 540ml of dichloromethane, and 17.5g (0.22mol) of pyridine, stir and adjust the temperature to 25°C; add 37.4g (0.22mol) of p-methoxybenzoyl chloride dropwise at 25°C to control the temperature of the reaction system not higher than 25°C; after the addition, keep stirring at 25°C for 3 hours, add 100ml of 1mol / L sodium carbonate solution after the reaction is completed, stir for 30 minutes, let stand, separate the water phase, add 100ml of water to the organic phase, stir for 15 minutes, let stand, separate the water phase; dry the organic phase with anhydrous sodium sulfate for 2 hours, filter, concentrate to dry dichloromethane, add 150g of methanol and stir at 10°C for 2h; filter and dry to obtain 80.0g of the compound of formula (2), purity: 99.5%, molar yield: 99.0%.

[0064] Example 2 (protection of p-methoxybenzoyl)

[0065]

[0066] In a 1L three-necked flask, add 80.0g (0.198mol) of the compound of formula (2), 400ml of acetone, and 32g (0.236mol) of NMO monohydrate, and stir evenly; add 362mg (1mmol) of potassium osmate dihydrate, and stir at 50℃ for 6h; after the reaction, drop the internal temperature to 10℃ and add 300ml of NaHSO3 (15%) dropwise, and control the internal temperature to 25℃ due to heat release during the addition. Stir for 1 hour after the addition is completed, add 400ml of dichloromethane and stir again for 0.5 hour; stand for stratification, separate the water phase; wash the organic phase with 300ml of water; stand for stratification, add 300ml of methanol after concentrating the organic phase, stir at 25℃ for 2 hours, and filter, and dry the filter cake to obtain 63.5g of the compound of formula (3). Purity: 98.5%, molar yield: 73.2%.

[0067] Example 3 (protection of p-methoxybenzoyl, THF as solvent)

[0068]

[0069] In a 1L three-necked flask, add 80.0g (0.198mol) of the compound of formula (2), 400ml of tetrahydrofuran, and 32g (0.236mol) of NMO monohydrate, and stir evenly; add 362mg (1mmol) of potassium osmate dihydrate, and stir at 50℃ for 6h; after the reaction, drop the internal temperature to 10℃ and add 300ml of NaHSO3 (15%) dropwise, and control the internal temperature to 25℃ due to heat release during the addition. Stir for 1 hour after the addition is completed, add 400ml of dichloromethane and stir again for 0.5 hour; stand for stratification, separate the water phase; wash the organic phase with 300ml of water; stand for stratification, add 300ml of methanol after the organic phase is concentrated, stir at 25℃ for 2 hours, and filter, and dry the filter cake to obtain 62.4g of the compound of formula (3). Purity: 98.3%, molar yield: 71.9%.

[0070] Example 4 (protection of p-methoxybenzoyl using trimethylamine N-oxide as oxidant)

[0071]

[0072] In a 1L three-necked flask, add 80.0g (0.198mol) of the compound of formula (2), 400ml of acetone, and 17.7g (0.236mol) of trimethylamine N-oxide, and stir evenly; add 362mg (1mmol) of potassium osmate dihydrate, and stir at 50℃ for 6h; after the reaction, drop the internal temperature to 10℃ and add 300ml of NaHSO3 (15%) dropwise, and control the internal temperature to 25℃ due to heat release during the addition. Stir for 1 hour after the addition is completed, add 400ml of dichloromethane and stir again for 0.5 hour; let stand to separate, and separate the water phase; wash the organic phase with 300ml of water; let stand to separate, and add 300ml of methanol after the organic phase is concentrated, and stir at 25℃ for 2 hours, and filter, and dry the filter cake to obtain 61.8g of the compound of formula (3). Purity: 98.1%, molar yield: 71.2%.

[0073] Example 5 (protection of p-methoxybenzoyl)

[0074]

[0075] In a 1L three-necked flask, add 63.5g (0.145mol) of the compound of formula (3) and 600ml of methanol, stir evenly at 25°C; add 11.6g (0.29mol) of sodium hydroxide in batches, stir under reflux at 65°C for 6 hours; after the reaction, neutralize the pH to neutral with acetic acid; concentrate to remove most of the methanol; add 300ml of purified water, stir at room temperature for 2 hours, filter and wash with purified water, and dry the filter cake to obtain 33.1g of estetrol. Purity ≥ 99.5%, molar yield: 75.0%.

[0076] Example 6 (protection of p-methoxybenzoyl, base is lithium hydroxide)

[0077]

[0078] In a 1L three-necked flask, add 63.5g (0.145mol) of the compound of formula (3) and 600ml of methanol, stir evenly at 25°C; add 12.2g (0.29mol) of lithium hydroxide monohydrate in batches, stir under reflux at 65°C for 6 hours; after the reaction, neutralize the pH to neutral with acetic acid; concentrate to remove most of the methanol; add 300ml of purified water, stir at room temperature for 2 hours, filter and wash with purified water, and dry the filter cake to obtain 32.9g of estetrol. Purity ≥ 99.5%, molar yield: 74.5%.

[0079] Example 7 (o-Anisyl Protection)

[0080]

[0081] In a 1L dry three-necked flask, add 54.0g (0.2mol) of the compound of formula (1), 540ml of dichloromethane, and 17.5g (0.22mol) of pyridine, stir and adjust the temperature to 25°C; add 37.4g (0.22mol) of o-anisyl chloride dropwise at 25°C to control the temperature of the reaction system not higher than 25°C; after the addition, keep stirring at 25°C for 3 hours, add 100ml of 1mol / L sodium carbonate solution after the reaction is completed, stir for 30 minutes, let stand, separate the water phase, add 100ml of water to the organic phase, stir for 15 minutes, let stand, separate the water phase; dry the organic phase with anhydrous sodium sulfate for 2 hours, filter, concentrate to dry dichloromethane, add 150g of methanol and stir at 10°C for 2h; filter and dry to obtain 78.4g of the compound of formula (2), purity: 99.2%, molar yield: 97.0%.

[0082] Example 8 (o-Anisyl Protection)

[0083]

[0084] In a 1L three-necked flask, add 80.0g (0.198mol) of the compound of formula (2), 400ml of acetone, and 32g (0.236mol) of NMO monohydrate, and stir evenly; add 362mg (1mmol) of potassium osmate dihydrate, and stir at 50℃ for 6h; after the reaction, drop the internal temperature to 10℃ and add 300ml of NaHSO3 (15%) dropwise, and control the internal temperature to 25℃ due to heat release during the addition. Stir for 1 hour after the addition is completed, add 400ml of dichloromethane and stir again for 0.5 hour; let stand to separate, and separate the water phase; wash the organic phase with 300ml of water; let stand to separate, and add 300ml of methanol after concentrating the organic phase, and stir at 25℃ for 2 hours, and filter, and dry the filter cake to obtain 62.9g of the compound of formula (3). Purity: 98.3%, molar yield: 72.5%.

[0085] Example 9 (o-Anisyl Protection)

[0086]

[0087] In a 1L three-necked flask, add 63.5g (0.145mol) of the compound of formula (3) and 600ml of methanol, stir evenly at 25°C; add 11.6g (0.29mol) of sodium hydroxide in batches, stir under reflux at 65°C for 6 hours; after the reaction, neutralize the pH to neutral with acetic acid; concentrate to remove most of the methanol; add 300ml of purified water, stir at room temperature for 2 hours, filter and wash with purified water, and dry the filter cake to obtain 32.5g of estetrol. Purity ≥ 99.4%, molar yield: 73.3%.

[0088] Example 10 (Protection of isopropoxybenzoyl)

[0089]

[0090] In a 1L dry three-necked flask, add 54.0g (0.2mol) of the compound of formula (1), 540ml of dichloromethane, and 17.5g (0.22mol) of pyridine, stir and adjust the temperature to 25°C; add 43.6g (0.22mol) of p-isopropoxybenzoyl chloride dropwise at 25°C to control the temperature inside the reaction system to be no higher than 25°C; after the addition, keep stirring at 25°C for 3 hours; after the reaction is completed, add 100ml of 1mol / L sodium carbonate solution, stir for 30 minutes, let stand, separate the water phase, add 100ml of water to the organic phase, stir for 15 minutes, let stand, separate the water phase; dry the organic phase with anhydrous sodium sulfate for 2 hours, filter, concentrate to dry dichloromethane, add 150g of methanol, stir at 10°C for 2h; filter with suction and dry to obtain 84.6g of the compound of formula (2), purity: 99.2%, molar yield: 98.0%.

[0091] Example 11 (Protection of p-isopropoxybenzoyl)

[0092]

[0093] In a 1L three-necked flask, add 85.5g (0.198mol) of the compound of formula (2), 400ml of acetone, and 32g (0.236mol) of NMO monohydrate, and stir evenly; add 362mg (1mmol) of potassium osmate dihydrate, and stir at 50℃ for 6h; after the reaction, drop the internal temperature to 10℃ and add 300ml of NaHSO3 (15%) dropwise, and control the internal temperature to 25℃ due to heat release during the addition. Stir for 1 hour after the addition is completed, add 400ml of dichloromethane and stir again for 0.5 hour; let stand to separate, and separate the water phase; wash the organic phase with 300ml of water; let stand to separate, and add 300ml of methanol after the organic phase is concentrated, and stir at 25℃ for 2 hours, and filter, and dry the filter cake to obtain 65.7g of the compound of formula (3). Purity: 98.7%, molar yield: 71.2%.

[0094] Example 12 (Protection of isopropoxybenzoyl)

[0095]

[0096] In a 1L three-necked flask, add 67.6g (0.145mol) of the compound of formula (3) and 600ml of methanol, stir evenly at 25°C; add 11.6g (0.29mol) of sodium hydroxide in batches, stir under reflux at 65°C for 6 hours; after the reaction, neutralize the pH to neutral with acetic acid; concentrate to remove most of the methanol; add 300ml of purified water, stir at room temperature for 2 hours, filter and wash with purified water, and dry the filter cake to obtain 32.6g of estetrol. Purity ≥ 99.5%, molar yield: 74%.

[0097] 1 H NMR (400MHz, CD3OD) δ7.09 (d, J = 8.0 Hz, 1H), 6.50-6.57 (m, 2H), 3.86-3.93 (m, 1H), 3.44 (d, J = 4.0 Hz,2H),2.75-2.89(m,2H),2.17-2.34(m,3H),1.90-1.93(m,1H),1.18-1.65(m,5H),0.81(s,3H).

[0098] Example 13 (Control Experiment, Benzoyl Protection)

[0099]

[0100] In a 1L three-necked flask, add 74.1g (0.198mol) of the compound of formula (2), 400ml of acetone, and 32g (0.236mol) of NMO monohydrate, and stir evenly; add 362mg (1mmol) of potassium osmate dihydrate, and stir at 50°C for 6h; after the reaction is completed, lower the internal temperature to 10°C and add 300ml of NaHSO3 (15%) dropwise, and exotherm is generated during the addition to control the internal temperature to 25°C. After the addition is completed, stir for 1 hour, add 400ml of dichloromethane and stir again for 0.5 hour; let stand to separate, and remove the aqueous phase; wash the organic phase with 300ml of water; let stand to separate, and after the organic phase is concentrated, add 300ml of methanol, stir at 25°C for 2 hours, and filter, and dry the filter cake to obtain 58.1g of the compound of formula (3).

[0101] Purity: 96.7%, molar yield: 72%.

[0102]

[0103] In a 1L three-necked flask, add 59.2g (0.145mol) of the compound of formula (3) and 600ml of methanol, stir evenly at 25°C; add 11.6g (0.29mol) of sodium hydroxide in batches, stir under reflux at 65°C for 6 hours; after the reaction, neutralize the pH to neutral with acetic acid; concentrate to remove most of the methanol; add 300ml of purified water, stir at room temperature for 2 hours, filter and wash with purified water, and dry the filter cake to obtain 32.2g of estetrol. Purity: 97.6%, molar yield: 73%.

[0104] The protection content of the present invention is not limited to the above embodiments. Without departing from the spirit and scope of the inventive concept, changes and advantages that can be thought of by those skilled in the art are included in the present invention and are protected by the attached claims.

Claims

1. A method for preparing high-purity estetrol, characterized in that: The reaction process of the method is shown in reaction formula (I): Reaction formula (I): Wherein, R is an alkoxy group, and the position of R is at the ortho, meta or para position of the aromatic ring; The method comprises the following steps: Step 1, 3-phenolic hydroxyl protection: In a first solvent, the compound of formula (1) reacts with an aromatic reagent for protecting the hydroxyl group in the presence of a base to obtain a compound of formula (2); the reaction process is shown in reaction formula (A): Reaction formula (A): Step 2, asymmetric dihydroxylation reaction: dissolving the compound of formula (2) obtained in step 1 in a second solvent, and reacting under temperature control in the presence of a catalyst and an oxidant to obtain a compound of formula (3); the reaction process is shown in reaction formula (B): Reaction formula (B): Step 3, hydrolysis reaction: the compound of formula (3) obtained in step 2 is dissolved in a third solvent, and deprotected under alkaline conditions to obtain the target product estetrol; the reaction process is shown in reaction formula (C): Reaction formula (C).

2. The method according to claim 1, characterized in that The R group on the benzene ring is located at one or more of the ortho, meta or para positions of the benzene ring.

3. The method according to claim 1, characterized in that The R group on the benzene ring is an alkoxy group with a chain length of C1-C6, selected from one or more of methoxy, ethoxy, isopropoxy and tert-butoxy.

4. The method according to claim 1, characterized in that In step 1, the aromatic reagent for protecting the hydroxyl group is selected from one or more of p-methoxybenzoyl chloride, o-methoxybenzoyl chloride, p-ethoxybenzoyl chloride, p-isopropoxybenzoyl chloride, and p-tert-butoxybenzoyl chloride; and / or, the first solvent is selected from one or more of ethyl acetate, dichloromethane, chloroform, DMF, toluene, tetrahydrofuran, and 2-methyltetrahydrofuran; and / or, the base is selected from one or more of triethylamine, diisopropylethylamine, imidazole, pyridine, and DMAP.

5. The method according to claim 1, characterized in that In step 1, the molar ratio of the compound of formula (1), the hydroxyl-protecting aromatic reagent, and the base is 1:(1-4):(0.05-5); and / or the reaction temperature is 0-50° C.; and / or the reaction time is 2-24 h.

6. The method according to claim 1, characterized in that In step 2, the second solvent is selected from one or more of dichloromethane, chloroform, acetone, toluene, ethyl acetate, methanol, ethanol, tetrahydrofuran, and 2-methyltetrahydrofuran; and / or, the oxidant is selected from one or both of N-methylmorpholine oxide NMO and trimethylamine N-oxide; and / or, the catalyst is selected from one or both of osmium tetroxide and potassium osmate.

7. The method according to claim 1, characterized in that In step 2, the mass ratio of the compound of formula (2), the oxidant and the catalyst is 1:(1-2):(0.001-0.01); and / or the temperature of the oxidation reaction is 0°C-50°C; and / or the time of the oxidation reaction is 6-12h.

8. The method according to claim 1, characterized in that In step 3, the hydrolysis reaction is specifically as follows: the compound of formula (3) undergoes a hydrolysis reaction in the third solvent under the action of a base to obtain estetrol.

9. The method according to claim 8, characterized in that The base is selected from one or more of LiOH, KOH, NaOH, t-BuOK, K2CO3; and / or the molar ratio of the compound of formula (3) to the base is 1:(0.5-2); and / or the third solvent is selected from one or two of water, methanol, and ethanol.

10. The method according to claim 8, characterized in that The temperature of the hydrolysis reaction is 10 to 75° C.; and / or the time of the hydrolysis reaction is 0.5 to 12 hours.

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