Method for synthesizing plant-derived 7-dehydrocholesterol from dinorhydrin

Abstract

The invention relates to the technical field of organic synthetic chemistry, in particular to a method for synthesizing plant-derived 7-dehydrocholesterol from dinorhydrin. Comprising the following steps: 1, carrying out sulfonic acid esterification reaction on dinorhydrin to obtain an intermediate 1 or a solution containing the intermediate 1; 2, carrying out first enol esterification or enol etherification on the intermediate 1 to obtain an intermediate 2; 3, carrying out coupling hydrocarbylation on the intermediate 2 to obtain an intermediate 3; 4, carrying out upper debromination and deenolization on the intermediate 3 at the same time to obtain an intermediate 4; 5, carrying out second carbonyl enol esterification on the intermediate 4 to obtain an intermediate 5; and 6, carrying out hydrolysis reduction on the intermediate 5 to obtain the 7-dehydrocholesterol. The botanical 7-dehydrocholesterol is synthesized by taking dinorhydrin as a starting raw material, the total weight yield is 36%, the purity is 98% or above, and industrial synthesis is easy to realize.

Description

Technical Field

[0001] This invention relates to the field of organic synthetic chemistry, specifically to a method for synthesizing plant-derived 7-dehydrocholesterol from dichlorol. Background Technology

[0002] Vitamin D3 has important applications in pharmaceuticals, health products, and feed additives. Currently, the vast majority of 7-dehydrocholesterol, the raw material for producing vitamin D3, comes from animal sources. However, animal-derived cholesterol may contain trace amounts of endogenous harmful proteins, microorganisms, and viruses. Furthermore, the perishable nature of raw materials introduces pathogens, posing unpredictable biological risks, such as the potential presence of prions and streptococci. Primions can cause prions-related diseases like mad cow disease and scrapie, while streptococci can cause serious consequences such as swine fever and anthrax in sheep. In addition, animal-derived vitamin D3 does not align with the dietary habits of certain consumer groups. Therefore, developing plant-derived vitamin D3 is a major trend.

[0003] Dichlornoxin is a very inexpensive and readily available steroidal drug resource that can be produced on a large scale through fermentation. Therefore, developing a process route for the efficient synthesis of 7-dehydrocholesterol from dichlornoxin, enabling the large-scale production of plant-derived 7-dehydrocholesterol for use as a raw material in the production of plant-derived vitamin D3 to meet market demand, is of great significance and represents a huge market need. To date, only two process routes for the synthesis of 7-dehydrocholesterol from dichlornoxin have been reported, documented in Chinese patent CN112608361A and Indian patent IN202221069802A, respectively.

[0004] The process route reported in Chinese patent CN112608361A is as follows: Dichloroethanol first reacts with p-toluenesulfonyl chloride to generate p-toluenesulfonate, then tetrachlorobenzoquinone undergoes dehydrogenation, followed by enol esterification of the ketone carbonyl group, then hydrolysis and reduction of the enol ester, followed by substitution of the benzenesulfonate with bromide ions, and finally coupling to synthesize 7-dehydrocholesterol. The synthetic reaction formula for synthesizing 7-dehydrocholesterol using dichloroethanol as a raw material reported in patent CN112608361A is as follows:

[0005] However, the process route reported by Chinese patent CN112608361A has many defects: (1) The second step reaction requires the dehydrogenation reaction of tetrachlorobenzoquinone. The reduction product of tetrachlorobenzoquinone after hydrogen abstraction is usually very viscous and may even form a polymer, causing serious pollution. Therefore, the post-processing is usually very complicated, the product is difficult to purify, and the product purity is low, especially for scale-up reactions of tens of kilograms or more. Therefore, when conducting large-scale production synthesis, the dehydrogenation reaction of tetrachlorobenzoquinone is generally avoided; (2) Placing the hydrolysis and reduction step of the enol ester before the coupling reaction catalyzed by lithium tetrachlorocopper oxide will lead to the influence of the alkaline environment on the sulfonate group, which will easily lead to its hydrolysis (alcoholization) or replacement by the nucleophile in the reaction system, resulting in a low yield of this step. The yield reported in this patent is only 75%; (3) This process route places the coupling reaction catalyzed by lithium tetrachlorocopper oxide at the end. On the one hand, the yield of this step is generally not very high, especially for large-scale synthesis. The most reasonable route design for an ideal multi-step synthesis process route is to place the reaction step with low yield at the beginning and the reaction step with high yield at the end, which can significantly reduce production costs; on the other hand, such a design is likely to bring the metal residue of the product into the later VD3 product, which may make the VD3 product produced from these 7-dehydrocholesterol raw materials unable to meet the requirements of pharmaceutical products. (4) The overall yield of this process route is also not high, with a mass yield of only about 33% and a molar yield of about 28%.

[0006] The process route described in Indian patent IN202221069802A is as follows: Dichloroethanol first undergoes a dehydrogenation reaction with tetrachlorobenzoquinone, then reacts with p-toluenesulfonyl chloride or methanesulfonyl chloride with a hydroxyl group to generate a sulfonate ester, followed by ketal protection of the ketone carbonyl group, then a side chain coupling reaction, followed by ketal hydrolysis, enol esterification of the ketone carbonyl group, and finally enol ester hydrolysis and reduction, totaling seven steps to synthesize 7-dehydrocholesterol. The synthetic reaction formula for synthesizing 7-dehydrocholesterol using dichloroethanol as a starting material reported in patent IN202221069802 is as follows:

[0007] Although the process route described in Indian patent IN202221069802A scales up the side-chain coupling reaction with a low yield, which helps reduce production costs and avoids the metal residue problem that may exist in VD3 products produced from these 7-dehydrocholesterols, it still has many shortcomings: (1) It still requires the dehydrogenation reaction of tetrachlorobenzoquinone, which causes serious pollution, is very complicated in post-processing, is difficult to purify, and has low product purity, making it unsuitable for large-scale production; (2) It uses ketal for carbonyl protection, and hydrolysis is required to remove the ketal protection in the later stage; (3) The hydrolysis and reduction of the enol ester in the last step is not ideal, and it contains many α-hydroxy isomer byproducts, which are difficult to separate and purify. Column chromatography is required for separation and purification. Only 40-50 grams of product are obtained from 100 grams of feed, that is, the mass yield is only 45-50%, and the purity of the product obtained by column chromatography is only about 96%. Moreover, because column chromatography is required, it is difficult to achieve large-scale industrial production.

[0008] In view of the above problems, the present invention provides a method for synthesizing plant-derived 7-dehydrocholesterol from dichlorol. Summary of the Invention

[0009] The technical problem to be solved by this invention is to provide a method for synthesizing plant-derived 7-dehydrocholesterol from dihydrocholesterol. The aim is to provide a new process route that is more environmentally friendly, has a more rational process design, simplifies synthesis and post-processing, achieves higher product purity and overall yield, and can easily realize large-scale industrial production of high-purity plant-derived 7-dehydrocholesterol.

[0010] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0011] A method for synthesizing plant-derived 7-dehydrocholesterol from dichlorol includes the following steps:

[0012] The first step is to perform a sulfonation reaction on dichlorol to obtain intermediate 1 or a solution containing intermediate 1, the structure of which is shown in Formula 1.

[0013] The second step is to perform a first enol esterification or enol etherification on the ketone carbonyl group in intermediate 1 to obtain intermediate 2, the structure of which is shown in Formula 2.

[0014] The third step is to couple the sulfonate group in intermediate 2 to obtain intermediate 3, the structure of which is shown in Formula 3.

[0015] The fourth step is to perform debromination and deenolization on intermediate 3 to obtain intermediate 4, the structure of which is shown in Formula 4.

[0016] Fifth step, the ketone carbonyl group in intermediate 4 is subjected to a second carbonyl enol esterification to obtain intermediate 5, the structure of which is shown in Formula 5;

[0017] Step 6: Hydrolyze and reduce the enol ester group in intermediate 5 to obtain 7-dehydrocholesterol;

[0018]

[0019] In Equations 2 and 3, R is independently selected from Ac or Et.

[0020] The structural formulas of 7-dehydrocholesterol and vitamin D3 are as follows:

[0021]

[0022] Based on the above technical solution, the present invention can be further improved as follows.

[0023] Furthermore, the first step includes the following specific steps: adding triethylamine, p-methylbenzenesulfonyl chloride and a catalytic amount of 4-dimethylaminopyridine to dichlorol, reacting at room temperature for 6 to 8 hours, and after the reaction is complete, separating, washing and drying are performed sequentially to obtain a solution containing intermediate 1;

[0024] Furthermore, the second step includes the following specific steps: adding isopropyl acetate and p-toluenesulfonic acid to the solution containing intermediate 1, and reacting at 35°C for 5-6 hours to obtain intermediate 2a; intermediate 2a is the formula where R is Ac in formula 2.

[0025] Furthermore, the second step includes the following specific steps: adding triethyl orthoformate to intermediate 1, adding p-toluenesulfonic acid below 0°C, and reacting at room temperature to obtain intermediate 2b; intermediate 2b is Et in formula 2.

[0026] Furthermore, the third step includes the following specific steps: at a temperature not exceeding -40°C, lithium tetrachlorocopper oxide and intermediate 2 are added dropwise to isopentyl magnesium bromide (Gernig's reagent), and then the temperature is slowly raised to room temperature to continue the reaction for 1 to 2 hours to obtain intermediate 3.

[0027] Furthermore, the fourth step includes the following specific steps: dissolving the intermediate 3 in an organic solvent, adding a brominating agent to carry out a bromination reaction, and after the reaction is complete, adding lithium bromide and lithium carbonate to carry out the reaction to obtain intermediate 4.

[0028] Furthermore, the organic solvent mentioned in step four includes at least one of ethyl acetate, N,N-dimethylformamide, and toluene;

[0029] The brominating agent includes at least one of dibromohydantoin and bromosuccinimide;

[0030] The molar ratio of intermediate 3 to the brominated agent dibromohydantoin is 1:0.5-0.6; the molar ratio of intermediate 3 to lithium bromide is 1:1.2-2.5; and the molar ratio of intermediate 3 to lithium carbonate is 1:2.0-4.0.

[0031] The conditions for the bromination reaction are: room temperature reaction for 10 min to 40 min;

[0032] The conditions for the debromination reaction with the addition of lithium bromide and lithium carbonate are: 80±5℃ for 2 to 6 hours.

[0033] Furthermore, the fifth step includes the following specific steps: dissolving the intermediate 4 in an organic solvent, then adding 2,4,6-trimethylpyridine and acetyl chloride as reaction promoters, and refluxing at 125±5℃ for 8 to 16 hours to carry out a second carbonylenol esterification to obtain intermediate 5;

[0034] The organic solvent mentioned in step 5 includes at least one of acetic anhydride and toluene;

[0035] The molar ratio of intermediate 4 to 2,4,6-trimethylpyridine is 1:1.0 to 2.0; and the molar ratio of intermediate 4 to the amount of acetyl chloride is 1:3 to 6.

[0036] Furthermore, the sixth step includes the following specific steps: dissolving the intermediate 5 in an organic solvent, adding calcium chloride and sodium borohydride, carrying out a reduction reaction at room temperature, and then sequentially discharging, washing, drying, pulping and crystallization purification to obtain 7-dehydrocholesterol.

[0037] Furthermore, the organic solvent mentioned in step six includes at least one of tetrahydrofuran and anhydrous ethanol;

[0038] The organic solvent mentioned in step six includes tetrahydrofuran and anhydrous ethanol, wherein the volume ratio of tetrahydrofuran to anhydrous ethanol is 1:2.0 to 4.0;

[0039] The molar ratio of intermediate 5 to the amount of calcium chloride is 1:0.1 to 0.3; the molar ratio of intermediate 5 to the amount of reducing agent sodium borohydride is 1:3.0 to 5.0.

[0040] The beneficial effects of this invention are:

[0041] This invention uses dichlorol as a starting material and proceeds through a six-step reaction: hydroxysulfonation, enol esterification or enol etherification of the carbonyl group, coupling alkylation of the sulfonate ester with a Grignard reagent, debromination and simultaneous deenolization, a second carbonyl enol esterification, and finally, hydrolysis and reduction of the enol ester. The resulting product is plant-derived 7-dehydrocholesterol with a total weight yield of 36%, a purity of over 98%, and is easily synthesized for industrial applications. Attached Figure Description

[0042] Figure 1 For intermediate 1 of the present invention 1 H-NMR spectrum;

[0043] Figure 2 For intermediate 1 of the present invention 13 C-NMR spectrum;

[0044] Figure 3 For intermediate 2a of the present invention 1 H-NMR spectrum;

[0045] Figure 4 For intermediate 2a of the present invention 13 C-NMR spectrum;

[0046] Figure 5 For intermediate 2b of the present invention 1 H-NMR spectrum;

[0047] Figure 6 For intermediate 2b of the present invention 13 C-NMR spectrum;

[0048] Figure 7 For intermediate 3a of the present invention 1 H-NMR spectrum;

[0049] Figure 8 For intermediate 3a of the present invention 13 C-NMR spectrum;

[0050] Figure 9 For intermediate 3b of the present invention 1 H-NMR spectrum;

[0051] Figure 10 For intermediate 3b of the present invention 13 C-NMR spectrum;

[0052] Figure 11 For intermediate 4 of the present invention 1 H-NMR spectrum;

[0053] Figure 12 For intermediate 4 of the present invention 13 C-NMR spectrum;

[0054] Figure 13 intermediate 5 of the present invention 1 H-NMR spectrum;

[0055] Figure 14 intermediate 5 of the present invention 13 C-NMR spectrum;

[0056] Figure 15 The target product of this invention is 7-dehydrocholesterol. 1 H-NMR spectrum;

[0057] Figure 16 The target product of this invention is 7-dehydrocholesterol. 13 C-NMR spectrum;

[0058] Figure 17 This is the HPLC spectrum of the target product of this invention, 7-dehydrocholesterol.

[0059] Figure 18 The HPLC chromatogram of the purchased high-purity 7-dehydrocholesterol is shown. Detailed Implementation

[0060] The principles and features of this invention are described below. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they should be performed according to the techniques or conditions described in the literature in this field, or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased through legitimate channels.

[0061] In this embodiment, the dichlorol first reacts with p-toluenesulfonyl chloride to generate a sulfonate ester, followed by enol esterification or enol etherification of the ketone carbonyl group, then a side chain coupling reaction, followed by an upper debromination reaction, another enol esterification of the ketone carbonyl group, and finally the enol ester hydrolysis and reduction. A total of 6 steps are taken to synthesize 7-dehydrocholesterol.

[0062] This embodiment relates to a method for synthesizing plant-derived 7-dehydrocholesterol from dichlorol, comprising the following steps:

[0063] The first step is to perform a sulfonation reaction on dichlorol to obtain intermediate 1 or a solution containing intermediate 1, the structure of which is shown in Formula 1.

[0064] The second step is to perform a first enol esterification or enol etherification on the ketone carbonyl group in intermediate 1 to obtain intermediate 2, the structure of which is shown in Formula 2.

[0065] The third step is to couple the sulfonate group in intermediate 2 to obtain intermediate 3, the structure of which is shown in Formula 3.

[0066] The fourth step is to perform debromination and deenolization on intermediate 3 to obtain intermediate 4, the structure of which is shown in Formula 4.

[0067] Fifth step, the ketone carbonyl group in intermediate 4 is subjected to a second carbonyl enol esterification to obtain intermediate 5, the structure of which is shown in Formula 5;

[0068] Step 6: Hydrolyze and reduce the enol ester group in intermediate 5 to obtain 7-dehydrocholesterol;

[0069]

[0070] In formulas 2 and 3, R is independently selected from Ac or Et. The synthetic reaction formula for synthesizing plant-derived 7-dehydrocholesterol using dichlorol as a raw material is as follows:

[0071]

[0072] This embodiment also provides specific experimental operation steps:

[0073] The first step involves dissolving dichloromethane in dichloromethane, adding triethylamine, p-toluenesulfonyl chloride, and a catalytic amount of 4-dimethylaminopyridine, reacting at room temperature for 6-8 hours, quenching the reaction with water, separating the layers, washing the organic layer with dilute hydrochloric acid solution, washing with saturated brine, drying with anhydrous sodium sulfate, and filtering to remove the desiccant to obtain a solution containing intermediate 1, which can be directly used for the next step of the reaction.

[0074] In the second step, isopropyl acetate and p-toluenesulfonic acid were added sequentially to the solution containing intermediate 1, and the reaction was carried out at 35°C for 5-6 hours. After the reaction was completed, saturated sodium bicarbonate solution was added and stirred for 10 minutes, followed by extraction with dichloromethane, washing with saturated brine, and drying with anhydrous sodium sulfate. The desiccant was removed by filtration, and the solvent was recovered under reduced pressure. Anhydrous methanol was added and stirred at room temperature, cooled to -5°C, filtered, and dried to obtain colored solid product 2a. The overall molar yield of the two-step reaction was 96%.

[0075] Alternatively, the solution containing intermediate 1 is subjected to reduced pressure to recover dichloromethane, then anhydrous ethanol is added, and the mixture is stirred. Triethyl orthoformate is then added, and the reaction mixture is cooled to below 0°C. Finally, p-toluenesulfonic acid is added as a catalyst, and the mixture is stirred at room temperature. After the reaction is complete, the reaction solution is poured into a cold, saturated sodium bicarbonate solution, stirred thoroughly, and allowed to stand to crystallize. The crystals are filtered, washed twice with distilled water, and then dried under vacuum to obtain the colored solid product 2b. The overall molar yield of the two-step reaction is 92%.

[0076] In the third step, the tetrahydrofuran solution of isopentyl magnesium bromide was cooled to -45°C, and then lithium tetrachlorocopper oxide solution was added dropwise, controlling the temperature of the reaction solution to not exceed -40°C during the addition. Then, anhydrous tetrahydrofuran solution of 2a or 2b was added dropwise, again controlling the temperature of the reaction solution to not exceed -40°C. After the addition was complete, the reaction solution was slowly heated to room temperature and the reaction was stirred for 1–2 hours until TLC monitoring showed complete consumption of the starting material. The reaction mixture was then cooled to below -0°C. An appropriate amount of ethanol solution was added dropwise to decompose the residual Grignard reagent, followed by the addition of ethyl acetate and then ammonium chloride solution. The mixture was stirred until the layers separated. The organic layer was washed with saturated sodium chloride solution and dried over anhydrous sodium sulfate. The mixture was filtered, and the solvent was removed under reduced pressure to obtain the crude coupling product. The molar yield of 3a was approximately 78%, and the molar yield of 3b was approximately 80%. Both crude products 3a and 3b can be used directly in the next reaction step.

[0077] In the fourth step, dissolve 3a or 3b in a mixture of ethyl acetate and N,N-dimethylformamide, and add dibromohydantoin or bromosuccinimide. Initiate the bromination reaction at room temperature. After the bromination is complete, add lithium bromide and lithium carbonate, and react at 80°C. After the reaction is complete, cool the reaction solution to room temperature and quench the reaction with 10% acetic acid solution. Extract with ethyl acetate; wash the organic layer successively with distilled water, saturated sodium bicarbonate solution, and saturated brine; dry with anhydrous sodium sulfate; filter; and recover ethyl acetate under reduced pressure to obtain a pale yellow oily product 4, with a molar yield of 86%. The crude product is used directly in the next reaction step.

[0078] In step five, the coupling product 4 from the previous step was dissolved in acetic anhydride, and reaction promoters 2,4,6-trimethylpyridine and acetyl chloride were added. The mixture was then reacted under reflux conditions. After the reaction was complete, excess acetic anhydride was recovered under reduced pressure. Anhydrous methanol was added to the crude product, and the mixture was stirred and slurried at room temperature for 2 hours. It was then placed at 0°C for 1.5 hours, filtered, and the pale yellow solid product 4 was obtained. The product was dried at 50°C to obtain the final product, with a molar yield of 98%.

[0079] Step 6: Intermediate 5 was dissolved in tetrahydrofuran, anhydrous methanol, anhydrous ethanol, or a mixture thereof. Calcium chloride was added as a catalyst, followed by the addition of sodium borohydride in portions. The reaction was carried out at room temperature. After the reaction was complete, the mixture was cooled to -15°C, acetone was added, and the mixture was stirred for 10 minutes. Then, a saturated oxalic acid solution was added and stirred for 15 minutes. The mixture was extracted with ethyl acetate, and the organic layer was washed successively with distilled water, saturated sodium bicarbonate solution, and saturated brine. The mixture was dried over anhydrous sodium sulfate, filtered, and the ethyl acetate was recovered by rotary evaporation. The remaining species were added to anhydrous methanol and stirred for 2 hours. The mixture was cooled to -5°C to crystallize, filtered, and dried at 50°C to obtain a white solid product, 7-dehydrocholesterol, with a yield of 83%.

[0080] This embodiment also optimizes the final step of the enol ester hydrolysis-reduction reaction. By selecting a suitable mixed reaction solvent and optimizing the reaction temperature, the reaction yield of this step exceeds 85%, and the product purity exceeds 98%, far higher than the 40%-50% yield in patent IN202221069802A. Moreover, the method in patent IN202221069802A requires column chromatography to purify the product to obtain a purity of 96%, which is basically impossible for industrial production. Furthermore, the new process in this embodiment does not require column chromatography separation at any step. The final step only requires simple crystallization to obtain a high-purity product, breaking through the key bottleneck of the process route for large-scale industrial production and easily achieving large-scale production.

[0081] The following description uses specific examples to further illustrate the point.

[0082] Example 1: Preparation of Intermediate 1

[0083] Add 500g of dichloroethanol to a 5L flask, along with 2L of dichloromethane, 400mL of triethylamine, and 10g of 4-dimethylaminopyridine. After stirring to dissolve, cool to approximately 10°C. Add 450g of p-toluenesulfonyl chloride in five portions to the reaction mixture and stir at room temperature for 12 hours. After the reaction is complete, add 1L of distilled water and adjust the pH of the reaction mixture to neutral with concentrated hydrochloric acid. Allow to stand, separate the liquids, collect the organic phase, wash with sodium bicarbonate solution, dry, and filter to obtain the solution containing intermediate 1. Figure 1 and 2 It is used directly in the next reaction.

[0084] Example 2: Preparation of intermediate 2a

[0085] 1.5 L of isopropyl acetate and 25 g of p-toluenesulfonic acid were added sequentially to the solution containing intermediate 1 obtained in Example 1, and the mixture was slowly refluxed at 35 °C for about 8 hours. After the reaction was complete, the mixture was cooled to room temperature, and a saturated sodium bicarbonate solution was added and stirred for 10 minutes. The mixture was extracted with dichloromethane, washed with saturated brine, dried over anhydrous sodium sulfate, filtered, and the solvent was recovered under reduced pressure. Anhydrous methanol was added and the mixture was stirred at room temperature for 2 hours, cooled at 0 °C for 1.5 hours, filtered, and dried to obtain 750 g of white solid product 2a. Figure 3 and 4 The molar yield was 95%.

[0086] Nuclear magnetic resonance structural characterization data of intermediate 2a: 1H NMR (500MHz, CDCl3) δ7.81-7.76(m,2H),7.36-7.33(m,2H),5.68(d,J=2.3Hz,1H),5.38(dd,J=5.3,2.3 Hz,1H),3.97(dd,J=9.3,3.1Hz,1H),3.79(dd,J=9.3,6.5Hz,1H),2.45(s,4H),2.13(s,5H),1.94(dt,J=

[0087] 12.7,3.4Hz,1H),1.83-1.75(m,1H),1.63(s,3H),1.58(d,J=1.2Hz,5H),1.46-1.3 7(m,1H),1.37-1.28(m,1H),1.22-1.14(m,3H),0.99(d,J=6.2Hz,7H),0.66(s,3H).

[0088] 13 C NMR (126MHz, CDCl3) δ169.5,147.2,144.7,139.5,133.3,129.9,128.1,124.0,117.1,75.8,56.6,51.9 ,48.0,42.7,39.5,36.4,35.0,33.9,31.9,31.9,27.6,24.9,24.3,21.8,21.3,21.2,19.0,17.0,12.1.

[0089] Example 3: Preparation of intermediate 2b

[0090] 200g of dichloroethanol, 100mL of dichloromethane, and 160mL of triethylamine were added to a 2L flask. After stirring and dissolving, the mixture was cooled to approximately 10°C. 180g of p-toluenesulfonyl chloride was added to the reaction mixture in three portions, and the mixture was stirred at room temperature for 10 hours. After the reaction was complete, 0.4L of distilled water was added, and the pH of the reaction mixture was adjusted to neutral with concentrated hydrochloric acid. The mixture was allowed to stand and separated, the organic phase was collected, washed with sodium bicarbonate solution, dried, filtered, and concentrated under reduced pressure to obtain 283g of crude product. 3.5L of anhydrous ethanol and 3.5g of p-toluenesulfonic acid were added to the crude product, and 450mL of trimethyl orthoacetate was added dropwise with stirring, maintaining the reaction temperature at 30-40°C. After the reactants had reacted completely, 100mL of saturated sodium bicarbonate solution was added to quench the reaction. The reaction mixture was then poured into 7L of cold water, stirred for 15 minutes, allowed to stand to crystallize, filtered, and dried at 50°C to obtain 299g of compound 2b. Figure 5 and 6 The molar yield was 93%.

[0091] Nuclear magnetic resonance structural characterization data of intermediate 2b: 1H NMR (500MHz, CDCl3) δ7.80-7.74(m,2H),7.33(d,J=8.0Hz,2H),5.20-5.16(m,1H),5.09( d,J=1.9Hz,1H),3.96(dd,J=9.4,3.0Hz,1H),3.80-3.71(m,3H),2.43(s,3H),2.27-1.16 (m,1H),2.15-2.04(m,2H),1.92(dt,J=12.7,3.5Hz,1H),1.79(dd,J=12.6,5.8Hz,1H),1 .69-1.51(m,6H),1.39-1.30(m,1H),1.32-1.12(m,8H),1.02-0.92(m,8H),0.65(s,3H).

[0092] 13 C NMR (126MHz, CDCl3) δ154.5,144.7,141.1,133.2,129.9,128.0,118.0,99.1,75.7,62.2,56.6,51.9, 48.3,42.6,39.5,36.3,35.2,33.9,32.0,31.8,27.6,25.6,24.3,21.7,21.2,19.0,16.9,14.8,12.0.

[0093] Example 4: Preparation of intermediate 2a

[0094] A Grignard reagent was prepared by reacting 50 g of bromoisopentane and 8.2 g of magnesium in anhydrous tetrahydrofuran. The mixture was then cooled to -45°C, and 100 mL of a 0.12 M solution of lithium tetrachlorocopper oxide in tetrahydrofuran was added dropwise, keeping the temperature below -40°C during the addition. Then, 53 g of 2a dissolved in 500 mL of anhydrous tetrahydrofuran was added dropwise, keeping the temperature below -40°C. After the addition was complete, the reaction mixture was slowly heated to room temperature and stirred for 2–3 h until TLC monitoring showed complete consumption of the reactants. The reaction mixture was then cooled to below -0°C. 25 mL of ethanol solution was added dropwise to decompose the residual Grignard reagent, followed by 300 mL of ethyl acetate and then ammonium chloride solution. The mixture was stirred until the layers separated. The aqueous layer was extracted with 300 mL of ethyl acetate, and the organic layers were combined, washed with saturated sodium chloride solution, and dried over anhydrous sodium sulfate. The mixture was filtered, and the solvent was removed under reduced pressure to obtain 33 g of the crude coupling product 3a. Figure 7 and 8 The molar yield was approximately 78%. The crude product 3a can be used directly in the next reaction step.

[0095] Nuclear magnetic resonance structural characterization data of intermediate 3a: 1H NMR (400MHz, CDCl3) δ5.66 (d, J = 2.2Hz, 1H), 5.40-5.35 (m, 1H), 2.43-2.36 (m, 1H), 2.10 (s, 3H), 2.04-1.96 (m, 2H), 1.83-1.78 (m, 2H), 1.63-1.44(m,6H),1.38-1.25(m,6H),1.15-1.07(m,6H),0.98(s,3H),0.90(d,J=6.5Hz,4H),0.85(dd,J=6.7,1.8Hz,8H),0.69(s,3H).

[0096] 13 C NMR (101MHz, CDCl3) δ169.4,147.0,139.4,124.1,117.1,56.9,56.3,48.1,42.5,39.8,39.6,36.3,3 5.9,35.0,33.9,32.0,31.8,28.3,28.1,24.9,24.3,23.9,22.9,22.7,21.3,21.2,18.9,18.8,12.1.

[0097] Example 5: Preparation of intermediate 3b

[0098] Replacing 2a in Example 4 with 52g of 2b, and following the experimental procedure of Example 4, yielded 34g of crude coupling product 3b. Figure 9 and 10 The molar yield was 80%. The crude product 3b can be used directly in the next reaction.

[0099] Nuclear magnetic resonance structural characterization data of intermediate 3b: 1 H NMR (400MHz, CDCl3) δ5.21(dd,J=5.1,2.3Hz,1H),5.11(d,J=1.9Hz,1H),3.85-3.70(m,2H),2.30-1.92(m,1H),2.19-1.99(m,3H),1.83-1.79( m,2H),1.70-1.47(m,5H),1.47-1.20(m,10H),1.19-1.00(m,8H),0.97( s,3H),0.92(d,J=6.6Hz,3H),0.87(dd,J=6.6,1.8Hz,6H),0.70(s,3H).

[0100] 13C NMR (101MHz, CDCl3) δ154.6,141.2,118.3,99.2,62.3,57.1,56.3,48.5,42.6,40.0,39.7,36.4,36 .0,35.3,34.0,32.0,32.0,28.4,28.2,25.7,24.4,24.0,23.0,22.7,21.4,19.1,18.9,14.8,12.1.

[0101] Example 6: Preparation of intermediate 3a

[0102] Weigh 30g of coupling product 3a and dissolve it in 300mL of ethyl acetate / N,N-dimethylformamide (V / V = 1:1). Add 11.8g of dibromohydantoin and react at room temperature for 20min to carry out the bromination reaction. After the reaction is complete, add 9.2g of lithium bromide and 16g of lithium carbonate to the reaction mixture and react at 80℃ for 4 hours. After the reaction is complete, cool to room temperature and quench the reaction with 10% cold acetic acid solution. Separate the layers, extract the aqueous layer with 100mL × 3 ethyl acetate, combine the organic layers, wash with water, wash with saturated sodium bicarbonate solution, wash with saturated brine, dry with anhydrous sodium sulfate, filter, and recover ethyl acetate under reduced pressure to obtain 24g of pale yellow oily product 4( Figure 11 and 12 ), with a molar yield of 95%.

[0103] Nuclear magnetic resonance structural characterization data of intermediate 4: 1 H NMR (400MHz, CDCl3) δ6.15-6.04(m,2H),5.64(d,J=3.4Hz,1H),2.55-2.48(m,1H) ,2.45-2.36(m,1H),2.23-2.12(m,1H),2.08-1.94(m,2H),1.94-1.82(m,1H),1.7 2-1.69(m,2H),1.56-1.44(m,2H),1.44-1.26(m,5H),1.26-1.05(m,12H),1.05-0 .93(m,1H),0.90(dd,J=6.5,2.8Hz,3H),0.85-0.79(m,6H),0.73(d,J=2.8Hz,3H).

[0104] 13C NMR (101MHz, CDCl3) δ199.73,164.10,141.74,127.85,123.57,56.10,53.50,50.76,43.49,39.63,39.57,37. 83,36.20,36.15,35.87,34.05,33.99,28.26,28.09,23.93,23.82,22.92,22.66,20.76,18.75,16.38,11.98.

[0105] Example 7

[0106] Replacing 3a in Example 6 with 30g of 3b, and following the experimental procedure of Example 6, yielded 24.3g of product 4, with a molar yield of 96%.

[0107] Example 8: Preparation of Intermediate 5

[0108] 20 g of compound 4 was dissolved in 150 mL of acetic anhydride, and 8 mL of 2,4,6-trimethylpyridine and 15 mL of acetyl chloride were added. The mixture was refluxed at 135 °C for 10 hours. After solvent recovery under reduced pressure, the mixture was cooled to room temperature, and 100 mL of anhydrous methanol was added and stirred for 1 hour. The mixture was then cooled at 0 °C for 1.5 hours, filtered, and dried at 50 °C to obtain 21 g of pale yellow solid product 5. Figure 13 and 14 ), with a molar yield of 99%.

[0109] Nuclear magnetic resonance structural characterization data of intermediate 5: 1 H NMR (400MHz, CDCl3) δ5.77(d,J=2.3Hz,1H),5.59(d,J=5.8Hz,1H),5.51(dt,J=5.7, 2.7Hz,1H),2.65-2.52(m,1H),2.13(s,4H),2.09-2.06(m,1H),1.96-1.86(m,3H),1. 77-1.65(m,3H),1.65-1.48(m,3H),1.48-1.27(m,6H),1.26-1.10(m,5H),0.99(s,3 H),0.94(d,J=6.5Hz,3H),0.88(d,J=1.9Hz,3H),0.86(d,J=1.9Hz,3H),0.63(s,3H).

[0110] 13C NMR (101MHz, CDCl3) δ169.32,148.55,143.52,137.73,120.34,117.62,116.43,56.03,55.00,44.87,43.03,39.64,39 .16,36.28,36.25,36.14,34.94,28.21,28.15,25.19,24.03,23.18,22.96,22.70,21.24,20.92,18.99,16.30,12.06.

[0111] Example 9

[0112] 20 g of compound 5 was dissolved in 200 mL of a mixed solvent of tetrahydrofuran and anhydrous ethanol (V / V = 1:3). 1.2 g of calcium chloride was added, followed by 8.2 g of sodium borohydride in three portions at 0 °C. The reaction was carried out slowly at room temperature with stirring for 1 hour. After the reaction was complete, the reaction solution was cooled to -15 °C, 15 mL of acetone was added and stirred for 10 minutes, followed by the addition of a saturated oxalic acid solution and stirring for another 10 minutes. The mixture was extracted with ethyl acetate, washed with water, saturated sodium bicarbonate solution, and saturated brine, dried over anhydrous sodium sulfate, filtered, and the ethyl acetate was recovered under reduced pressure. The mixture was then stirred with anhydrous methanol for 2 hours, cooled to -5 °C for 1.5 hours, filtered, and dried at 50 °C to obtain 17.2 g of a white solid product, 7-dehydrocholesterol (…). Figures 15 to 18 The yield was 86%, and the purity was 98%.

[0113] Nuclear magnetic resonance structural characterization data of 7-dehydrocholesterol: 1 H NMR (500MHz, CDCl3) δ5.57(dd,J=5.7,2.6Hz,1H),5.38(dt,J=5.6,2.8Hz,1H),3.63-3.58(m,1H),2.47-2.42(m,1H),2.28-2.20(m,1H),2.09-1.96( m,1H),2.01-1.82(m,6H),1.78-1.44(m,8H),1.44-1.08(m,13H),1.01(q, J=9.2Hz,1H),0.97-0.90(m,7H),0.86(dd,J=6.6,2.3Hz,7H),0.62(s,3H).

[0114] 13C NMR (126MHz, CDCl3) δ141.59,139.90,119.75,116.40,70.60,56.03,54.64,46.38,43.06,40.93,39.65,39.3 4,38.52,37.15,36.29,36.26,32.13,28.24,28.16,24.02,23.17,22.97,22.71,21.26,18.99,16.43,11.97.

[0115] Example 10

[0116] By changing the volume ratio of tetrahydrofuran to anhydrous ethanol to 1:2, with other conditions remaining unchanged, the yield was 82% and the purity was 96%.

[0117] Example 11

[0118] By changing the volume ratio of tetrahydrofuran to anhydrous ethanol to 1:4, with other conditions remaining unchanged, the yield was 80% and the purity was 96%.

[0119] Example 12

[0120] By using pure ethanol as the reaction solvent, with other conditions remaining unchanged, the yield was 72% and the purity was 85%.

[0121] In summary, this invention uses dichlorol as the starting material and proceeds through a six-step reaction: hydroxysulfonation, alcohol esterification or enol etherification of carbonyl olefins, coupling alkylation of the sulfonate ester or enol etherification ester with Grignard reagent, debromination and simultaneous deenolization, a second carbonyl enol esterification, and finally, hydrolysis and reduction of the enol ester. The resulting product is plant-derived 7-dehydrocholesterol with a total weight yield of 36%, a purity of over 98%, and is easily synthesized for industrial applications.

[0122] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for synthesizing plant-derived 7-dehydrocholesterol from dichlorol, characterized in that, Includes the following steps: The first step is to perform a sulfonation reaction on dichlorol to obtain intermediate 1 or a solution containing intermediate 1, the structure of which is shown in Formula 1. The second step is to perform a first enol esterification or enol etherification on the ketone carbonyl group in intermediate 1 to obtain intermediate 2, the structure of which is shown in Formula 2. The third step is to couple the sulfonate group in intermediate 2 to obtain intermediate 3, the structure of which is shown in Formula 3. The fourth step is to perform debromination and deenolization on intermediate 3 to obtain intermediate 4, the structure of which is shown in Formula 4. Fifth step, the ketone carbonyl group in intermediate 4 is subjected to a second carbonyl enol esterification to obtain intermediate 5, the structure of which is shown in Formula 5; Step 6: Hydrolyze and reduce the enol ester group in intermediate 5 to obtain 7-dehydrocholesterol; In Equations 2 and 3, R is independently selected from Ac or Et.

2. The method for synthesizing plant-derived 7-dehydrocholesterol from dichlorol according to claim 1, characterized in that, The first step includes the following specific steps: adding triethylamine, p-methylbenzenesulfonyl chloride and a catalytic amount of 4-dimethylaminopyridine to dichlorol, reacting at room temperature for 6 to 8 hours, and obtaining a solution containing intermediate 1 after the reaction is complete.

3. A method for synthesizing plant-derived 7-dehydrocholesterol from dichlorol according to claim 1 or 2, characterized in that, The second step includes the following specific steps: adding isopropyl acetate and p-toluenesulfonic acid to the solution containing intermediate 1, reacting at 35°C for 5-6 hours, and obtaining intermediate 2a after conventional post-processing.

4. A method for synthesizing plant-derived 7-dehydrocholesterol from dichlorol according to claim 1 or 2, characterized in that, The second step includes the following specific steps: adding triethyl orthoformate to intermediate 1, adding p-toluenesulfonic acid below 0°C, reacting at room temperature, and obtaining intermediate 2b after conventional post-treatment.

5. The method for synthesizing plant-derived 7-dehydrocholesterol from dichlorol according to claim 1, characterized in that, The third step includes the following specific steps: at a temperature not exceeding -45°C, lithium tetrachlorocopper oxide and intermediate 2 are added dropwise to isopentyl magnesium bromide, and then the temperature is slowly raised to room temperature to continue the reaction for 1 to 2 hours to obtain intermediate 3.

6. The method for synthesizing plant-derived 7-dehydrocholesterol from dichlorol according to claim 1, characterized in that, The fourth step includes the following specific steps: dissolving the intermediate 3 in an organic solvent, adding a brominating agent to carry out a bromination reaction, and after the reaction is complete, adding lithium bromide and lithium carbonate to carry out the reaction to obtain intermediate 4.

7. The method for synthesizing plant-derived 7-dehydrocholesterol from dichlorol according to claim 6, characterized in that, The organic solvent mentioned in step four includes at least one of ethyl acetate, toluene, and N,N-dimethylformamide; The brominating agent includes at least one of dibromohydantoin and bromosuccinimide; The molar ratio of intermediate 3 to the brominated agent dibromohydantoin is 1:0.5-0.6; the molar ratio of intermediate 3 to lithium bromide is 1:1.2-2.5; and the molar ratio of intermediate 3 to lithium carbonate is 1:2.0-4.

0. The conditions for the bromination reaction are: room temperature reaction for 10 min to 40 min; The conditions for the debromination reaction with the addition of lithium bromide and lithium carbonate are: 80±5℃ for 2 to 6 hours.

8. The method for synthesizing plant-derived 7-dehydrocholesterol from dichlorol according to claim 1, characterized in that, The fifth step includes the following specific steps: Dissolve the intermediate 4 in an organic solvent, then add 2,4,6-trimethylpyridine and acetyl chloride as reaction promoters, and reflux at 125±5℃ for 8 to 16 hours to carry out a second carbonylenol esterification to obtain intermediate 5; The organic solvent mentioned in step 5 includes at least one of acetic anhydride and toluene; The molar ratio of intermediate 4 to the amount of 2,4,6-trimethylpyridine is 1:1.0 to 2.0; and the molar ratio of intermediate 4 to the amount of acetyl chloride is 1:3.0 to 6.

0.

9. The method for synthesizing plant-derived 7-dehydrocholesterol from dichlorol according to claim 1, characterized in that, The sixth step includes the following specific steps: dissolving the intermediate 5 in an organic solvent, adding calcium chloride and sodium borohydride, carrying out a reduction reaction at 0℃ to room temperature, and then sequentially discharging, washing, drying, pulping and crystallization purification to obtain 7-dehydrocholesterol.

10. The method for synthesizing plant-derived 7-dehydrocholesterol from dichlorol according to claim 9, characterized in that, The organic solvent mentioned in step six includes at least one of tetrahydrofuran and anhydrous ethanol; The organic solvent mentioned in step six includes tetrahydrofuran and anhydrous ethanol, wherein the volume ratio of tetrahydrofuran to anhydrous ethanol is 1:2.0 to 4.0; The molar ratio of intermediate 5 to calcium chloride is 1:0.1 to 0.3; the molar ratio of intermediate 5 to sodium borohydride reducing agent is 1:3.0 to 5.0.

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