Process for the preparation of 19-nordehydroepiandrosterone and intermediates thereof

Abstract

The application provides a preparation method of 19-nordehydroepiandrosterone and an intermediate thereof, and relates to the technical field of medicine intermediate preparation, and comprises the following steps: performing a hydrolysis reaction on a compound of formula (II) and an acid, and performing purification treatment to prepare 19-nordehydroepiandrosterone, wherein the compound of formula (II) is prepared from 19-nor-4-androstene-3, 17-dione through esterification reaction, ketalization reaction and reduction reaction. The application provides a new synthesis route for the preparation of 19-nordehydroepiandrosterone, and compared with the prior art, the reaction steps are greatly shortened; meanwhile, the synthesis route provided by the application can improve the yield of the target product, the total yield is up to 70% or more, the purity of the product is more than 99%, and the method is suitable for industrial production.

Description

Technical Field

[0001] This invention relates to the field of pharmaceutical intermediate preparation technology, and in particular to a method for preparing 19-nordehydroepiandrosterone and its intermediates. Background Technology

[0002] 19-Noredohydroepiandrosterone is a steroid hormone with the structural formula shown in Formula I: 19-Noredohydroepiandrosterone (19-Nordedohydroepiandrosterone) is an important raw material for the manufacture of steroidal hormones and contraceptives. German patent DE2037296 reports a synthetic route for 19-Nordedohydroepiandrosterone, using nandrolone as a starting material, and preparing 19-Nordedohydroepiandrosterone through six steps: diesterization, reduction, hydroxyl protection, hydrolysis, oxidation, and deprotection. The specific synthetic route is shown below:

[0003]

[0004] However, the above-mentioned synthetic route for 19-nordehydroepiandrosterone has the problems of long synthetic steps and low yield. At the same time, the starting material nandrolone for this route needs to be obtained from the acid dehydrogenase (i.e., compound 19-norde-4-androstene-3,17-dione) through four steps of cyanation, ketalization, hydrolysis and reduction, which makes the production cost of nandrolone higher than that of the acid dehydrogenase, thus increasing the preparation cost. Summary of the Invention

[0005] In view of this, the present invention proposes a method for preparing 19-nordehydroepiandrosterone and its intermediates, in order to solve the problems of complex preparation routes, high preparation costs and low preparation yields of 19-nordehydroepiandrosterone in the prior art.

[0006] The technical solution of this invention is achieved as follows: On one hand, this invention provides a method for preparing 19-nordehydroepiandrosterone, comprising the following steps:

[0007] 19-nordehydroepiandrosterone was prepared by hydrolysis of compound (II) with acid and subsequent purification. The structural formula of compound (II) is as follows:

[0008]

[0009] The structural formula of the 19-nordehydroepiandrosterone is shown in formula (Ⅰ).

[0010]

[0011] The preparation of 19-nordehydroepiandrosterone from compound (II) via hydrolysis can reduce the number of synthetic steps, the preparation and purification of intermediates, and simplify the process. At the same time, the production cost of compound (II) is relatively low, thereby reducing production costs.

[0012] Based on the above technical solutions, preferably, the compound of formula (II) is prepared by a reduction reaction of the compound of formula (III) and a borohydride, wherein the borohydride includes sodium borohydride, potassium borohydride, or calcium borohydride, and the calcium borohydride is obtained by reacting sodium borohydride with calcium chloride.

[0013] The structural formula of the compound of formula (III) is as follows:

[0014]

[0015] Based on the above technical solutions, preferably, the compound of formula (III) is obtained by reacting the compound of formula (IV) with triethyl orthoformate, p-toluenesulfonic acid, and ethylene glycol in a ketal reaction.

[0016] The structural formula of compound (Ⅳ) is as follows:

[0017]

[0018] Based on the above technical solutions, preferably, the compound of formula (Ⅳ) is obtained by esterification reaction of the compound of formula (Ⅴ) with isopropyl acetate and p-toluenesulfonic acid.

[0019] The structural formula of the compound of formula (V) is:

[0020]

[0021] More preferably, the synthetic route for preparing 19-nordehydroepiandrosterone using compound (V) (19-nor-4-androstene-3,17-dione) as the starting material is shown below:

[0022]

[0023] In this invention, 19-nordehydroepiandrosterone is prepared from compound (19-nor-4-androstene-3,17-dione) as the starting material through a four-step reaction involving esterification, ketalization, reduction, and hydrolysis. Compared with existing technologies, this method shortens the reaction steps. Furthermore, the synthetic route provided by this invention can improve the yield of the target product, with an overall yield of up to 70% and a product purity of over 99%, making it suitable for industrial production.

[0024] Based on the above technical solutions, preferably, the molar ratio of compound (V), isopropyl acetate, and p-toluenesulfonic acid in the esterification reaction is 1:(2.3-2.7):(0.12-0.16). More preferably, the molar ratio of compound (V), isopropyl acetate, and p-toluenesulfonic acid is 1:2.5:0.14.

[0025] Specifically, using dichloromethane as a solvent, and under the catalysis of p-toluenesulfonic acid, compound (V) undergoes an esterification reaction with isopropyl acetate at a reaction temperature of 30–50°C for 2–4 h; more preferably, the reaction temperature is 40–45°C for 3–4 h. In this reaction, excess isopropyl acetate acts as the esterification reagent, which helps to push the equilibrium towards the esterified product, thereby increasing the yield; p-toluenesulfonic acid acts as a catalyst, accelerating the reaction rate.

[0026] Based on the above technical solutions, preferably, the purification process of the esterification reaction includes: dispersing the crude product of formula (Ⅳ) compound in a solvent, stirring at 25-27℃ for 2-3 hours, cooling to 0-10℃, stirring for 1-2 hours, filtering, and drying; the ratio of the crude product of formula (Ⅳ) compound to the solvent is 1W:(1-4)V, where W represents weight and V represents volume. When W is in g, V is in ml; when W is in kg, V is in L.

[0027] Specifically, the crude product of compound (IV) is dispersed in a solvent and stirred at 25–27°C for 2–3 h, then cooled to 0–10°C and stirred for 1–2 h. After filtration and drying, the purified compound (IV) is obtained. The solvent used in the purification process is any one of ethyl acetate, isopropyl acetate, and butyl acetate. More preferably, ethyl acetate is used as the solvent. The ratio of the crude product of compound (IV) to the solvent is 1 W: (1–4) V; more preferably, the ratio is 1 W: (1–2); and even more preferably, the ratio is 1 W: 1.5 V.

[0028] In the esterification reaction, the 17th site of the compound of formula (Ⅳ) will undergo further esterification, resulting in a small amount of impurity as shown in formula (Ⅵ) in the esterification product. This may introduce impurity as shown in formula (Ⅶ) into the final product. Purification treatment can reduce the content of impurity as shown in formula (Ⅵ) in step S1, thereby reducing the content of impurity as shown in formula (Ⅶ) in the final product. The chemical structural formula of the compound shown in formula (Ⅵ) is as follows:

[0029]

[0030] The chemical structural formula of the compound shown in formula (VII) is:

[0031]

[0032] Based on the above technical solutions, preferably, in the ketal reaction, the molar ratio of the compound of formula (IV), p-toluenesulfonic acid, and triethyl orthoformate is 1:(0.02-0.08):(2.5-3.5); the solvent for the ketal reaction includes any one of dichloromethane, ethyl acetate, toluene, and ethylene glycol; the reaction temperature is 40-60℃; and the reaction time is 3-5h. More preferably, the reaction temperature is 45-50℃; and the reaction time is 3-3.5h. When ethylene glycol is used only as the ketal reagent, the molar ratio of ethylene glycol to the compound of formula (IV) is (2-4):1; when ethylene glycol is used as both the ketal reagent and the reaction solvent, the mass-volume ratio of the compound of formula (IV) to ethylene glycol is 1g:(4-5)ml.

[0033] Based on the above technical solutions, preferably, the purification process of the ketal reaction includes: dispersing the crude product of compound (III) in a solvent, stirring at 25-27°C for 2-3 hours, cooling to 0-10°C, stirring for 1-2 hours, filtering, and drying; the ratio of the crude product of compound (III) to the solvent is 1W:(1-4)V, where W represents weight and V represents volume. When W is in g, V is in ml; when W is in kg, V is in L.

[0034] In the ketal reaction, the crude product of compound (III) obtained by the ketal reaction is dispersed in a solvent and stirred at 25-27°C for 2-3 hours. The temperature is then lowered to 0-10°C and stirred for 1-2 hours. After filtration and drying, the purified compound (III) is obtained. The solvent in the purification process is a lower alcohol solvent or a mixture of a lower alcohol solvent and water. Preferably, the solvent is any one of methanol, ethanol and isopropanol. More preferably, the solvent is ethanol.

[0035] During the ketal reaction, since the ketal reaction is reversible, a small amount of compound (Ⅳ) cannot react completely, resulting in compound (Ⅳ) remaining in the product and forming impurities. This may introduce impurities such as compound (Ⅶ) into the final product. By purifying the crude product of compound (Ⅲ) obtained from the ketal reaction, the residue of compound (Ⅳ) in the product can be reduced, thereby reducing the impurity content of compound (Ⅶ) in the final product.

[0036] Based on the above technical solutions, preferably, in the reduction reaction, the solvent includes one or more of tetrahydrofuran, methanol, and ethanol; more preferably, the solvent is a mixture of tetrahydrofuran and methanol, with a volume ratio of tetrahydrofuran to methanol of (0.5–3):1; even more preferably, the volume ratio of tetrahydrofuran to methanol is 1:1. The reaction temperature is 20–40°C, and the reaction time is 1–3 h; more preferably, the reaction temperature is 35–40°C, and the reaction time is 2–3 h.

[0037] Based on the above technical solutions, preferably, in the reduction reaction, the reactants also include calcium chloride, and the molar ratio of the compound of formula (III), calcium chloride and sodium borohydride is 1:(0.16~0.65):(2~2.5). More preferably, the molar ratio of the compound of formula (III), calcium chloride and sodium borohydride is 1:0.32:2.2.

[0038] Specifically, in the reduction reaction, in the presence of calcium chloride in a solvent, compound (III) is reduced by sodium borohydride. During the reduction reaction, while generating the target product compound (II), isomer impurities as shown in compound (IX) are also generated, which may introduce impurities as shown in compound (X) into the final product. In the reduction reaction, directly using sodium borohydride as a reducing agent to reduce compound (III) results in incomplete reaction of the raw materials, leading to a low product yield. In this invention, sodium borohydride and calcium chloride are reacted together to generate calcium borohydride in situ for reduction, which can promote the conversion of the raw materials to the product, improve the reaction conversion rate, and thus improve the product yield. In the reduction reaction, compared to directly separating the isomers of the reduction product and then carrying out the next hydrolysis reaction, it is easier to purify the isomer impurities in the hydrolysis product. Therefore, the crude product compound (II) is not purified and is directly used for the next hydrolysis reaction.

[0039] The chemical structural formula of the compound shown in formula (IX) is:

[0040]

[0041] The chemical structural formula of the compound shown in formula (X) is,

[0042]

[0043] Based on the above technical solutions, preferably, in the hydrolysis reaction, the acid is dilute hydrochloric acid or dilute sulfuric acid; more preferably, the acid is dilute hydrochloric acid; the hydrolysis reaction temperature is 30–50°C, and the hydrolysis reaction time is 2–4 h. Even more preferably, the reaction temperature is 40–45°C, and the reaction time is 2.5–3 h.

[0044] Based on the above technical solutions, preferably, in the hydrolysis reaction, the molar ratio of compound (II) to acid is 1:(0.5~1.0).

[0045] Based on the above technical solution, preferably, the purification process in the hydrolysis reaction includes: dispersing the crude product of compound (I) in an alcohol solvent, heating to reflux to dissolve the crude product, cooling to 30-40°C, and stirring for 1-4 hours, preferably 3-4 hours; cooling to 0-10°C, and stirring for 1-4 hours, preferably 3-4 hours; filtering and drying to obtain the purified compound (I). Preferably, the alcohol solvent includes one or more of methanol, ethanol, and isopropanol; more preferably, the alcohol solvent is ethanol.

[0046] Specifically, in the hydrolysis reaction, tetrahydrofuran is used as the solvent. Under acidic conditions, compound (II) undergoes a hydrolysis reaction to generate crude compound (I). The main impurities in the crude product are compounds shown in formula (X). Using lower alcohols as solvents in the purification process can effectively remove impurities of compounds shown in formula (X). During the recrystallization process, by controlling the cooling rate, the crystals of compound (I) are slowly precipitated from the system, thereby improving the purity of the final product.

[0047] On the other hand, the present invention also provides an intermediate for the synthesis of 19-nordehydroepiandrosterone, characterized in that: the intermediate is a compound of formula (II), the structural formula of which is

[0048]

[0049] The method for preparing 19-nordehydroepiandrosterone and its intermediates according to the present invention have the following advantages over the prior art:

[0050] (1) 19-nordehydroepiandrosterone can be prepared directly by hydrolysis of the compound of formula (II), while the compound of formula (II) can be obtained directly by esterification, ketalization and reduction of the acid-degraded product 19-norde-4-androstene-3,17-dione. This invention provides a new synthetic route for the preparation of 19-nordehydroepiandrosterone, which greatly shortens the reaction steps compared with the prior art. At the same time, the synthetic route provided by this invention can improve the yield of the target product, with a total yield of over 70% and a product purity of over 99%, which is suitable for industrial production.

[0051] (2) By purifying the products of esterification, ketalization and hydrolysis, the impurity content in the preparation process can be further reduced, and the purity and yield of the final product can be improved. Compound (II) has low purification efficiency and low yield due to the presence of isomers in the preparation process. By directly hydrolyzing the crude product of compound (II) obtained by reduction reaction and purifying the hydrolysis product, the purity and yield of 19-nordehydroepiandrosterone can be improved. In addition, the purification efficiency of the product can be further improved by controlling the cooling rate during the purification process.

[0052] (3) In the reduction reaction, the present invention further improves the reaction conversion rate by reacting sodium borohydride and calcium chloride together to generate calcium borohydride in situ, thereby avoiding the incomplete reaction of raw materials and affecting the product yield. Attached Figure Description

[0053] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0054] Figure 1 The HPLC chromatogram of the compound of formula (Ⅳ) prepared in step S1 of Example 1 of this invention;

[0055] Figure 2 The HPLC chromatogram of the compound of formula (Ⅲ) prepared in step S2 of Example 1 of this invention;

[0056] Figure 3 The HPLC chromatogram of compound (II) prepared in step S3 of Example 1 of this invention;

[0057] Figure 4 The compound of formula (II) prepared in step S3 of Example 1 of this invention. 1 H NMR spectrum;

[0058] Figure 5 The compound of formula (II) prepared in step S3 of Example 1 of this invention. 13 C NMR spectrum

[0059] Figure 6 The HPLC chromatogram of the compound of formula (Ⅰ) prepared in step S4 of Example 1 of this invention;

[0060] Figure 7 The HPLC chromatogram of the purified compound of formula (Ⅰ) obtained in step S5 of Example 1 of this invention;

[0061] Figure 8 The purified compound of formula (Ⅰ) obtained in step S5 of Example 1 of this invention. 1 H NMR spectrum;

[0062] Figure 9 The HPLC chromatogram of the crude compound of formula (II) obtained in step S3 of Example 2 of this invention. Detailed Implementation

[0063] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0064] To enable those skilled in the art to better understand the technical solution of this application, the technical solution of this application will be described in detail below with reference to specific embodiments. Unless otherwise specified, experimental conditions are generally as per conventional conditions or the conditions recommended by the reagent company. The reagents, consumables, etc., used in the following embodiments can be obtained commercially unless otherwise specified.

[0065] Example 1

[0066] This embodiment provides a method for preparing 19-nordehydroepiandrosterone, specifically including the following steps:

[0067]

[0068] S1. Add compound (V) (100g, 0.37mol), isopropyl acetate (92g, 0.92mol), p-toluenesulfonic acid (10g, 0.058mol), and 300mL dichloromethane to a 1L reaction flask. Under nitrogen purging protection, reflux at 45℃ for 3 hours. TLC (PE:EA = 3:1, vanillin / 254nm) shows complete conversion of the starting material. Cool to 25℃, adjust pH to neutral with triethylamine, and concentrate under reduced pressure at 40℃ to obtain a yellow viscous substance, which is the crude product of compound (IV). Add 150mL of ethyl acetate to the crude product of compound (IV), stir at 25℃ for 2 hours, cool in an ice-water bath at 0-10℃ and continue stirring for 1 hour. Filter, wash the filter cake with glacial ethyl acetate, and dry in a forced-air environment at 50℃ for 6 hours to obtain 102.38g of compound (IV), with a yield of 88%. Figure 1 The HPLC chromatogram of compound (Ⅳ) is shown. HPLC analysis shows that compound (Ⅳ) accounts for 99.1%, while diester impurities (i.e., compound (Ⅵ)) account for 0.60%.

[0069] HPLC detection method: Column: InfinityLab Poroshell 120EC-C18 (4.6×150mm, 4Micron), Agilent; Mobile phase: water and acetonitrile gradient; Flow rate: 1ml / min; Detector: UV detector (VWD), signal polarity: positive, dual wavelengths 254nm & 210nm; Column oven temperature: 30℃; Injection volume: 10ul; Acquisition time: 20min; Sample preparation solvent: acetonitrile (1mg / ml).

[0070] S2. Add 400 mL of ethylene glycol, 100 g (0.32 mol) of compound (IV), and 3 g (0.017 mol) of p-toluenesulfonic acid to a 2 L reaction flask. Stir until homogeneous. Under nitrogen protection, add 141 g (0.95 mol) of triethyl orthoformate dropwise. After the addition is complete, maintain the temperature at 45 °C for 3 h. When TLC (PE:EA = 3:1, vanillin / 254 nm) shows that the starting material is basically completely converted, cool to 25 °C, add triethylamine to quench the reaction, add 500 mL of water, stir at 25 °C for 1 h, filter, wash the filter cake with water, and dry under vacuum to obtain crude compound (III). Add 300 mL of ethanol to the crude compound (III), stir at 25 °C for 2 h, stir in an ice-water bath at 0–10 °C for 1 h, filter, wash the filter cake with ice-cold ethanol, and dry under forced air at 50 °C to obtain 105.54 g of compound (III), yield 92%. Figure 2 The HPLC chromatogram of compound (III) is shown. HPLC detection shows that compound (III) accounts for 97.62%, esterified impurities (i.e. compound (IV)) account for 0.46%, and diester impurities were not detected. The HPLC detection method is the same as in step S1.

[0071] S3. Add 400 mL of tetrahydrofuran, 400 mL of methanol, and 10 g of anhydrous calcium chloride (0.09 mol) to a 2 L reaction flask and stir to dissolve. Cool to -10 °C, add sodium borohydride (23.3 g, 0.62 mol), and add compound (III) (100 g, 0.28 mol) in portions. React at room temperature for 2 h until TLC (PE:EA = 2:1, vanillin) shows that the starting material is basically completely converted. Slowly add 50% glacial acid aqueous solution to the reaction solution to quench the reaction, and then slowly pour it into 1000 mL of ice water. A large amount of solid precipitates out. Filter, rinse the filter cake with water, dry under vacuum, and dry in a forced-air dryer at 50 °C for 3 h to obtain 84.71 g of crude compound (II), with a yield of 95% and a purity of 87.56%.

[0072] HPLC detection method: Column: InfinityLab Poroshell 120EC-C18 (4.6×150mm, 4Micron), Agilent; Mobile phase: water and acetonitrile gradient; Flow rate: 1ml / min; Detector: UV detector (VWD), signal polarity: positive, wavelength 210nm; Column oven temperature: 30℃; Injection volume: 10ul; Acquisition time: 20min; Sample preparation solvent: acetonitrile (1mg / ml).

[0073] Figure 3 The HPLC chromatogram of the crude compound of formula (II) is shown. HPLC analysis shows that the compound of formula (II) accounts for 88.69%, and the isomer (i.e., the compound of formula (IX)) accounts for 8.8%.

[0074] Figure 4 The compound of formula (II) is shown. 1 H NMR spectrum, 1 ¹H NMR detection showed: ¹H NMR (600MHz, CDCl₃) δ 5.45 (s, ¹H), 3.97–3.82 (m, ¹H), 3.72 (d, J = 2.4Hz, ¹H), 3.57–3.48 (m, ¹H), 2.49 (d, J = 12.0Hz, ¹H), 2.15–2.05 (m, ¹H), 2.04–1.86 ( m,6H),1.84–1.75(m,1H),1.71–1.51(m,4H),1.42(dd,J=20.7,10.1Hz,2H),1.34– 1.22(m,3H),1.17(ddd,J=16.7,13.7,3.9Hz,1H),0.87(s,3H),0.85–0.75(m,1H).

[0075] Figure 5 The compound of formula (II) is shown. 13 C NMR spectrum, 13 C NMR analysis showed: 13 C NMR (151MHz, CDCl3) δ137.29,121.47,119.52,71.08,65.20,64.56,49.68,46.01,45.3 3,44.94,42.76,36.82,35.41,35.34,34.16,30.50,30.30,30.12,26.69,22.51,14.22.

[0076] S4. Add 100g (0.31mol) of crude compound (II), 500mL of tetrahydrofuran, 500mL of water, and 20mL (0.24mol) of concentrated hydrochloric acid to a 2L reaction flask. Heat to 45℃ and react for 2 hours. TLC (PE:EA = 2:1, vanillin) shows that the starting material is basically completely converted. Cool the reaction solution to 25℃, adjust the pH to neutral with sodium bicarbonate, concentrate under reduced pressure at 45℃ to remove tetrahydrofuran, add 500mL of water, stir at 25℃ for 1 hour, filter, wash the filter cake with 200mL of water, dry under vacuum, and dry in a forced-air environment at 50℃ for 3 hours to obtain 85.06g of crude compound (I), with a yield of 100%. Figure 6 The HPLC chromatogram of the crude compound of formula (I) is shown. HPLC detection shows that compound (I) accounts for 89.54% and the 3α-hydroxy isomer (i.e., compound (X)) accounts for 8.41%. The HPLC detection method is the same as in step S3.

[0077] S5. Take 100 g (0.36 mol) of crude compound (I), add 200 mL of ethanol, heat to reflux until dissolved, slowly cool to 25 °C, stir to precipitate crystals for 3 h, stir to precipitate crystals in an ice-water bath at 0-10 °C for 3 h, filter, wash the filter cake with ice-cold ethanol, and dry under vacuum; repeat purification with ethanol once, dry at 50 °C to constant weight, to obtain 88.5 g of compound (I), purification yield 88.5%.

[0078] Figure 7 The HPLC chromatogram of the purified compound (I) is shown. HPLC analysis shows that compound (I) accounts for 99.85%, and the 3α-hydroxy isomer (i.e., compound (X)) accounts for 0.07%. The HPLC detection method is the same as in step S3. LCMS analysis shows that LCMS: MS(ESI) m / z = 257.2 [M-H2O+H]

[0079] Figure 8 The purified compound of formula (Ⅰ) is shown. 1 H NMR spectrum, 1 HNMR analysis showed that: 1 H NMR (600MHz, CDCl3) δ5.51 (d, J=5.3Hz, 1H), 3.56 (td, J=10.7, 5.2Hz, 1H), 2.58-2.40 (m, 2H), 2.09 (ddd, J=31.2, 20.2, 10.6Hz, 4H), 2.0 1-1.90(m,3H),1.83(d,J=12.8Hz,1H),1.68(s,3H),1.52(dddd,J=21.5,15.0,11.4,3.5Hz,2H),1.38-1.22(m,4H),0.96-0.81(m,5H).

[0080] Example 2

[0081] This embodiment provides a method for preparing 19-nordehydroepiandrosterone. The operation steps are the same as in Example 1, except that in step S3, calcium chloride is not added to the reactants, that is, only sodium borohydride is used for the reduction reaction. Figure 9 The HPLC chromatogram of the crude product of formula (II) obtained in step S3 is shown. As can be seen from the figure, HPLC detection shows that the product of formula (II) accounts for 19.19%, the isomer (i.e., the product of formula (IX)) accounts for 2.01%, and the raw material of formula (III) accounts for 77.26%.

[0082] Example 3

[0083] This embodiment provides a method for preparing 19-nordehydroepiandrosterone. The operation steps are the same as in Example 2, except that in step S3, the crude product of formula (II) is purified by adding 300 mL of methanol to the crude product of formula (II), stirring at 25°C for 2 h, stirring in an ice-water bath at 0-10°C for 1 h, filtering, washing the filter cake with ice-cold ethanol, and drying in a forced-air oven at 50°C. The isomer (i.e., formula (IX)) is reduced from 8% to 4%. The purification process is repeated twice, and the isomer (i.e., formula (IX)) is reduced to 1.17%. However, after a total of 3 purification processes, the yield of formula (II) is reduced to 70%.

[0084] Example 4

[0085] This embodiment provides a method for preparing 19-nordehydroepiandrosterone. The specific operation steps are the same as in Example 2, except that in step S5, 100g (0.36mol) of crude compound (I) is taken, 200mL of ethanol is added, the mixture is heated to reflux and dissolved, cooled to an ice-water bath at 0-10℃ and stirred to crystallize for 6h, filtered, the filter cake is washed with ice-cold ethanol and dried under vacuum; the purification is repeated once with ethanol, and the mixture is dried at 50℃ to constant weight to obtain 76.2g of compound (I), with a purification yield of 76.%. HPLC analysis shows that compound (I) accounts for 99.08%, and the 3α-hydroxy isomer (i.e., compound (X)) accounts for 0.76%. It can be seen that if the cooling rate is not controlled during the purification process, the removal effect of the 3α-hydroxy isomer in the final product will be affected.

[0086] Example 5

[0087] This embodiment provides a method for preparing 19-nordehydroepiandrosterone, specifically including the following steps:

[0088]

[0089] S1. Add compound (V) (100g, 0.37mol), isopropyl acetate (85g, 0.85mol), p-toluenesulfonic acid (7.65g, 0.044mol), and 300mL of dichloromethane to a 1L reaction flask. Under nitrogen purging protection, reflux at 40℃ for 2h. TLC (PE:EA = 3:1, vanillin / 254nm) shows complete conversion of the starting material. Cool to 25℃, adjust pH to neutral with triethylamine, and concentrate under reduced pressure at 40℃ to obtain a yellow viscous substance, which is the crude product of compound (IV). Add 150mL of ethyl acetate to the crude product of compound (IV), stir at 25℃ for 2.5h, cool in an ice-water bath at 0-10℃ and continue stirring for 1.5h. Filter, wash the filter cake with glacial ethyl acetate, and dry in a forced-air dryer at 50℃ for 6h to obtain 95.41g of compound (IV), with a yield of 82.01% and a purity of 99.04%.

[0090] S2. Add 200 mL of ethylene glycol, 200 mL of dichloromethane, 100 g (0.32 mol) of compound (IV) and 1.1 g (0.006 mol) of p-toluenesulfonic acid to a 2 L reaction flask, stir well, and under nitrogen protection, add 118.56 g (0.80 mol) of triethyl orthoformate dropwise. After the addition is complete, keep the temperature at 40 °C for 4 h, until TLC (PE:EA = 3:1, vanillin / 254 nm) shows that the starting material is basically completely converted. Cool to 25 °C, add triethylamine to quench the reaction, add 500 mL of water, stir at 25 °C for 1 h, filter, wash the filter cake with water, dry under vacuum, and obtain the crude product of compound (III). Add 300 mL of ethanol to the crude product of compound (III), stir at 25 °C for 2.5 h, stir in an ice-water bath at 0–10 °C for 1.5 h, filter, wash the filter cake with ice-cold ethanol, and dry in a forced-air environment at 50 °C to obtain 101.64 g of compound (III), with a yield of 88.61% and a purity of 99.12%.

[0091] S3. Add 270 mL of tetrahydrofuran, 530 mL of methanol, and anhydrous calcium chloride (4.97 g, 0.045 mol) to a 2 L reaction flask and stir to dissolve. Cool to -10 °C, add sodium borohydride (21.18 g, 0.56 mol), and add compound (III) (100 g, 0.28 mol) in portions. React at 30 °C for 1 h until TLC (PE:EA = 2:1, vanillin) shows that the starting material is basically completely converted. Slowly add 50% glacial acid aqueous solution to the reaction solution to quench the reaction, and then slowly pour it into 1000 mL of ice water. A large amount of solid precipitates out. Filter, wash the filter cake with water, dry under vacuum, and dry in a forced-air dryer at 50 °C for 3 h to obtain 78.12 g of crude compound (II), with a yield of 87.61% and a purity of 85.19%.

[0092] S4. Add 100g (0.31mol) of crude compound (II), 500mL of tetrahydrofuran, 500mL of water, and 26mL (0.31mol) of concentrated hydrochloric acid to a 2L reaction flask. Heat to 30℃ and react for 3h. TLC (PE:EA = 2:1, vanillin) shows that the starting material is basically completely converted. Cool the reaction solution to 25℃, adjust the pH to neutral with sodium bicarbonate, concentrate under reduced pressure at 45℃ to remove tetrahydrofuran, add 500mL of water, stir at 25℃ for 1h, filter, wash the filter cake with 200mL of water, dry under vacuum, and dry in a forced-air environment at 50℃ for 3h to obtain 81.96g of crude compound (I), yield 96.36%, purity 87.24%, 3α-hydroxy isomer (i.e., compound (X)) accounts for 8.37%.

[0093] S5. Take 100 g (0.36 mol) of crude compound (I), add 200 mL of ethanol, heat to reflux until dissolved, slowly cool to 30 °C, stir to crystallize for 1 h, stir to crystallize in an ice-water bath at 0-10 °C for 1 h, filter, wash the filter cake with ice-cold ethanol, and dry under vacuum; repeat purification with ethanol once, dry at 50 °C to constant weight, to obtain 78.49 g of compound (I), purification yield 78.49%, purity 99.53%.

[0094] Example 6

[0095] This embodiment provides a method for preparing 19-nordehydroepiandrosterone, specifically including the following steps:

[0096]

[0097] S1. Add compound (V) (100g, 0.37mol), isopropyl acetate (100.01g, 1.00mol), p-toluenesulfonic acid (8.95g, 0.052mol), and 300mL of dichloromethane to a 1L reaction flask. Under nitrogen purging protection, reflux at 50℃ for 4 hours. TLC (PE:EA = 3:1, vanillin / 254nm) shows complete conversion of the starting material. Cool to 25℃, adjust pH to neutral with triethylamine, and concentrate under reduced pressure at 40℃ to obtain a yellow viscous substance, which is the crude product of compound (IV). Add 150 mL of ethyl acetate to the crude compound of formula (IV), stir at 25 °C for 3 h, cool in an ice-water bath at 0–10 °C and continue stirring for 2 h, filter, wash the filter cake with glacial ethyl acetate, and dry in a forced-air dryer at 50 °C for 6 h to obtain 103.56 g of compound of formula (IV), with a yield of 89.01% and a purity of 99.16%.

[0098] S2. Add 300 mL of ethylene glycol, 100 mL of dichloromethane, 100 g (0.32 mol) of compound (IV) and 4.48 g (0.026 mol) of p-toluenesulfonic acid to a 2 L reaction flask, stir well, and under nitrogen protection, add 165.98 g (1.12 mol) of triethyl orthoformate dropwise. After the addition is complete, keep the temperature at 60 °C for 5 h, until TLC (PE:EA = 3:1, vanillin / 254 nm) shows that the starting material is basically completely converted. Cool to 25 °C, add triethylamine to quench the reaction, add 500 mL of water, stir at 25 °C for 1 h, filter, wash the filter cake with water, dry under vacuum, and obtain the crude product of compound (III). Add 300 mL of ethanol to the crude product of compound (III), stir at 25 °C for 3 h, stir in an ice-water bath at 0–10 °C for 2 h, filter, wash the filter cake with ice-cold ethanol, and dry in a forced-air environment at 50 °C to obtain 104.98 g of compound (III), with a yield of 91.52% and a purity of 99.54%.

[0099] S3. Add 600 mL of tetrahydrofuran, 200 mL of methanol, and anhydrous calcium chloride (19.98 g, 0.18 mol) to a 2 L reaction flask and stir to dissolve. Cool to -10 °C, add sodium borohydride (26.48 g, 0.70 mol), and add compound (III) (100 g, 0.28 mol) in portions. React at 40 °C for 3 h until TLC (PE:EA = 2:1, vanillin) shows that the starting material is basically completely converted. Slowly add 50% glacial acid aqueous solution to the reaction solution to quench the reaction, and then slowly pour it into 1000 mL of ice water. A large amount of solid precipitates out. Filter, rinse the filter cake with water, dry under vacuum, and dry in a forced-air dryer at 50 °C for 3 h to obtain 85.16 g of crude compound (II), with a yield of 95.50% and a purity of 88.62%.

[0100] S4. Add 100g (0.31mol) of crude compound (II), 500mL of tetrahydrofuran, 500mL of water, and 13mL (0.16mol) of concentrated hydrochloric acid to a 2L reaction flask. Heat to 50℃ and react for 4h. TLC (PE:EA = 2:1, vanillin) shows that the starting material is basically completely converted. Cool the reaction solution to 25℃, adjust the pH to neutral with sodium bicarbonate, concentrate under reduced pressure at 45℃ to remove tetrahydrofuran, add 500mL of water, stir at 25℃ for 1h, filter, wash the filter cake with 200mL of water, dry under vacuum, and dry in a forced-air environment at 50℃ for 3h to obtain 85.01g of crude compound (I), with a yield of 99.94% and a purity of 90.05%. The 3α-hydroxy isomer (i.e., compound (X)) accounts for 8.21%.

[0101] S5. Take 100 g (0.36 mol) of crude compound (I), add 200 mL of methanol, heat to reflux until dissolved, slowly cool to 40 °C, stir to precipitate crystals for 4 h, stir to precipitate crystals in an ice-water bath at 0-10 °C for 4 h, filter, wash the filter cake with ice-cold ethanol, and dry under vacuum; repeat purification with ethanol once, dry at 50 °C to constant weight, to obtain 80.15 g of compound (I), purification yield 80.15%, purity 99.53%.

[0102] Comparing Examples 1 and 2, it is evident that using calcium chloride as a Lewis acid to form a complex with sodium borohydride for the reduction reaction can improve the conversion rate. Comparing Examples 1 and 3, it is evident that the purification of isomers in the reduction product of step S3 is not effective, requiring multiple purification processes with low yields. Comparing Examples 1 and 4, it is evident that controlling the cooling rate in step S5 to promote slow crystal precipitation ensures the purity of the precipitated product. Comparing Examples 1 and Examples 5 and 6, it is evident that variations in raw material ratios, reaction time, reaction temperature, and post-treatment parameters in the preparation process can all affect the reaction conversion rate.

[0103] 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 within the protection scope of the present invention.

Claims

1. A method for preparing 19-nordehydroepiandrosterone, characterized in that: 19-nordehydroepiandrosterone was prepared by hydrolysis of compound (II) with acid and subsequent purification. The structural formula of compound (II) is as follows: ； The structural formula of 19-nordehydroepiandrosterone is shown in formula (Ⅰ): ； The compound of formula (II) is prepared by a reduction reaction of the compound of formula (III) with a borohydride, wherein the borohydride includes sodium borohydride, potassium borohydride, or calcium borohydride, and the calcium borohydride is obtained by reacting sodium borohydride with calcium chloride. The structural formula of the compound of formula (III) is: ； The compound of formula (III) is obtained by a ketal reaction of the compound of formula (IV) with triethyl orthoformate, p-toluenesulfonic acid, and ethylene glycol. The structural formula of the compound of formula (IV) is as follows: ； The compound of formula (IV) is obtained by esterification of the compound of formula (V) with isopropyl acetate and p-toluenesulfonic acid, and the structural formula of the compound of formula (V) is: ； The purification process after hydrolysis includes: dispersing the crude product of compound (I) in an alcohol solvent, heating and refluxing until the crude product is dissolved, cooling to 30-40°C, stirring for 1-4 hours, cooling to 0-10°C, stirring for 1-4 hours, filtering and drying to obtain the purified compound (I). The alcohol solvent includes one or more of methanol, ethanol and isopropanol.

2. The method for preparing 19-nordehydroepiandrosterone as described in claim 1, characterized in that: In the hydrolysis reaction, the acid is dilute hydrochloric acid or dilute sulfuric acid, the reaction temperature is 30~50℃, the reaction time is 2~4h, and the molar ratio of compound (II) to acid is 1:(0.5~1.0).

3. The method for preparing 19-nordehydroepiandrosterone as described in claim 1, characterized in that: In the reduction reaction, the molar ratio of the compound of formula (III), calcium chloride and sodium borohydride is 1:(0.16~0.65):(2~2.5); the solvent for the reduction reaction includes one or more of tetrahydrofuran, methanol and ethanol, the reaction temperature is 20~40℃, and the reaction time is 1~3h.

4. The method for preparing 19-nordehydroepiandrosterone as described in claim 1, characterized in that: In the ketal reaction, the molar ratio of the compound of formula (IV), p-toluenesulfonic acid and triethyl orthoformate is 1:(0.02~0.08):(2.5~3.5); the solvent for the ketal reaction includes any one of dichloromethane, ethyl acetate, toluene and ethylene glycol, the reaction temperature is 40~60℃, and the reaction time is 3~5h.

5. The method for preparing 19-nordehydroepiandrosterone as described in claim 1, characterized in that: The molar ratio of compound (V), isopropyl acetate, and p-toluenesulfonic acid is 1:(2.3~2.7):(0.12~0.16).

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