Synthesis method of diterpene natural product przewalskin B

Abstract

The invention relates to a method for quickly constructing a reaction precursor by utilizing an intermolecular SN2'reaction, realizing a [5 + 2] cycloaddition reaction of intramolecular alpha-hydroxyl o-benzoquinone and a carbon-oxygen double bond for the first time, and quickly constructing a [5, 5] fused ring structure with a high oxidation state to obtain a natural product przewalskin B. The previous synthesis method often needs complex steps to construct a ring system and introduce an oxidation state. The key to solve the problem is that 1, a chiral center can be effectively introduced by utilizing an SN2'reaction among molecules to finish asymmetric synthesis of przewalskin B molecules, and 2, [5 + 2] cycloaddition reaction of alpha-hydroxyl o-benzoquinone and carbon-oxygen double bonds is realized.

Description

Technical Field

[0001] The invention relates to the technical field of synthetic chemistry, and in particular to a method for synthesizing a diterpene natural product przewalskin B. Background Art

[0002] Salvia Przewalskii is a plant of the subgenus Salvia of the genus Salvia of the family Lamiaceae. It is also known as purple salvia, plateau salvia, red qinjiao, etc. It is widely distributed in western Gansu, western Sichuan, northwestern Yunnan and Tibet in my country. It is one of the famous Tibetan medicines. The Jingzhu Materia Medica records that this medicine has the effect of "clearing liver heat and treating oral diseases". In May 1995, the Gansu Provincial Health Department officially included it in the Gansu Provincial Local Standard and promulgated it for trial implementation. In the 1980s, this medicinal material was included in the Yunnan Provincial Local Standard. Because its roots and stems have similar pharmacological activities to salvia miltiorrhiza, it is widely used as a high-quality substitute for salvia miltiorrhiza in China. As the demand for salvia miltiorrhiza increases year by year, it has the trend of becoming a mainstream commodity.

[0003] With the continuous deepening of research on Salvia miltiorrhiza, people have a deeper understanding of its phytochemical components and pharmacological effects. This type of plant contains a variety of components, including polysaccharides, sesquiterpenes, diterpenes, triterpenes, flavonoids and polyphenols, which have anti-inflammatory, antibacterial, antioxidant, anti-cardiovascular and cerebrovascular disease biological activities. Among them, tanshinone II A (tanshinone IIA) and salvianolic acid B (salvianolic acid B) are the main components of tanshinone II-sulfonate injection and salvianolic acid injection, respectively, and have excellent therapeutic effects in the treatment of coronary heart disease, angina pectoris and myocardial infarction.

[0004] Przewalskin B is a diterpenoid natural product isolated from dried sage, which has certain anti-HIV activity (EC50 = 30 μg / mL) and can be used as an important source for further structural modification and activity research. However, the isolation of przewalskin B from plants is currently inefficient, the steps are complicated, and it is difficult to obtain a large amount for subsequent modification and improvement research. Therefore, large-scale preparation through rapid and efficient chemical synthesis has become an important means to solve this problem. However, the current synthetic routes for przewalskin B are faced with problems such as long steps, low total yield, and high cost, which are not suitable as its batch synthesis strategy. Summary of the invention

[0005] In view of this, the present invention provides an efficient and economical method for synthesizing a diterpenoid compound przewalskin B. Compared with the prior art, the method has the advantages of low cost, short production cycle, high production efficiency, etc.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] A method for synthesizing a diterpenoid compound przewalskin B, the compound has the following structural formula:

[0008]

[0009] The synthesis path is as follows:

[0010] Synthesis of fragment 4:

[0011]

[0012] Synthesis of fragment 8:

[0013]

[0014] Fragment docking:

[0015]

[0016] The specific steps are as follows:

[0017] (1) Compound 1 was dissolved in anhydrous pyridine, iodine was added at room temperature, and the mixture was stirred at this temperature for 1 hour. The reaction was then quenched with a 1 mol / L hydrochloric acid aqueous solution, extracted with ethyl acetate, washed with a saturated sodium chloride aqueous solution, dried over anhydrous sodium sulfate, filtered under reduced pressure, and concentrated under reduced pressure to obtain a crude product. The crude product was purified by silica gel column chromatography to obtain compound 2;

[0018] (2) Dissolve (S)-2-methyl-CBS-oxazaborolidine in anhydrous dichloromethane, add borane dimethyl sulfide solution at 0°C, react at this temperature for 30 minutes, then slowly add a dichloromethane solution of compound 2 dropwise, and continue to react for 2 hours. Quench the reaction at 0°C with H2O, extract with ethyl acetate, wash with saturated sodium chloride aqueous solution, dry with anhydrous sodium sulfate, filter under reduced pressure, and concentrate under reduced pressure to obtain a crude product, which is purified by silica gel column chromatography to obtain compound 3;

[0019] (3) Compound 3 was dissolved in anhydrous dichloromethane, imidazole was added at 0°C, and then redistilled triethyl chlorophosphate was added. The reaction was detected by TLC. After about 1 hour, H2O was added to quench the reaction. The mixture was extracted with ethyl acetate, washed with saturated sodium chloride aqueous solution, dried over anhydrous sodium sulfate, filtered under reduced pressure, and concentrated under reduced pressure to obtain a crude product. The crude product was purified by silica gel column chromatography to obtain compound 4;

[0020] (4) Compound 5 was dissolved in anhydrous dichloromethane, 1,1-dichloromethyl ether was added at 0°C, and SnCl4 was slowly added dropwise. The mixture was returned to room temperature and stirred for 1 hour. The reaction was quenched with a 1 mol / L aqueous hydrochloric acid solution at 0°C, and then extracted with ethyl acetate, washed with a saturated aqueous sodium chloride solution, dried over anhydrous sodium sulfate, filtered under reduced pressure, and concentrated under reduced pressure to obtain a crude product. The crude product was purified by silica gel column chromatography to obtain compound 6;

[0021] (5) Dissolve triphenylmethylphosphonium bromide in anhydrous tetrahydrofuran, add dropwise 2.4 mol / L n-butyllithium solution at 0°C, continue stirring at this temperature for 30 minutes, then add the tetrahydrofuran solution of compound 6, return to room temperature and react for 10 minutes. Quench the reaction with saturated aqueous ammonium chloride at 0°C, extract with ethyl acetate, wash with saturated aqueous sodium chloride, dry with anhydrous sodium sulfate, filter under reduced pressure, and concentrate under reduced pressure to obtain a crude product, which is purified by silica gel column chromatography to obtain compound 7;

[0022] (6) Compound 7 was dissolved in anhydrous tetrahydrofuran, and 1 mol / L zirconium hydride tetrahydrofuran solution was added dropwise at 0°C. Stirring was continued at this temperature for 30 minutes, and then iodine was added and stirring was continued for 30 minutes. The reaction was quenched with a saturated aqueous ammonium chloride solution at 0°C, and then extracted with ethyl acetate, washed with a saturated aqueous sodium chloride solution, dried over anhydrous sodium sulfate, filtered under reduced pressure, and concentrated under reduced pressure to obtain a crude product. The crude product was purified by silica gel column chromatography to obtain compound 8;

[0023] (7) Compound 8 was dissolved in anhydrous tetrahydrofuran, and a 2.4 mol / L tert-butyl lithium solution was added dropwise at -78°C. Stirring was continued at this temperature for 30 minutes, and then a tetrahydrofuran solution of cuprous cyanide was added and stirring was continued for 30 minutes. Then, a tetrahydrofuran solution of 4 was slowly added dropwise, and the temperature was naturally raised to room temperature (about 2 hours). The reaction was quenched with a saturated aqueous ammonium chloride solution at 0°C, and then extracted with ethyl acetate, washed with a saturated aqueous sodium chloride solution, dried over anhydrous sodium sulfate, filtered under reduced pressure, and concentrated under reduced pressure under vacuum to obtain a crude product. The crude product was purified by silica gel column chromatography to obtain compound 9;

[0024] (8) Compound 9 was dissolved in anhydrous tetrahydrofuran, and 2.4 mol / L tert-butyl lithium solution was added dropwise at -78°C. The mixture was stirred for 30 minutes at this temperature, and then a formylation agent was added. The reaction was quenched with a saturated aqueous ammonium chloride solution at 0°C, and then extracted with ethyl acetate, washed with a saturated aqueous sodium chloride solution, dried over anhydrous sodium sulfate, filtered under reduced pressure, and concentrated under reduced pressure to obtain a crude product. The crude product was purified by silica gel column chromatography to obtain compound 10;

[0025] (9) Compound 10 was dissolved in anhydrous dichloromethane and boron tribromide was added at -78°C. The mixture was returned to room temperature and stirred for 1 hour. The reaction was quenched with H2O at 0°C, extracted with ethyl acetate, washed with saturated sodium chloride aqueous solution, dried over anhydrous sodium sulfate, filtered under reduced pressure, and concentrated under reduced pressure to obtain a crude product. The crude product was purified by silica gel column chromatography to obtain compound 11;

[0026] (10) Compound 11 was dissolved in anhydrous tetrahydrofuran, potassium ferrocyanide was added dropwise at room temperature, and then triethylamine was added, and the reaction was carried out at room temperature for 30 minutes. The reaction was quenched with H2O at 0°C, and then extracted with ethyl acetate, washed with saturated sodium chloride aqueous solution, dried over anhydrous sodium sulfate, filtered under reduced pressure, and concentrated under reduced pressure to obtain a crude product, which was purified by silica gel column chromatography to obtain przewalskin B;

[0027] The advantages of the present invention are:

[0028] 1. Most of the reagents used in the present invention are commercially available and inexpensive, and no special treatment is required.

[0029] 2. The present invention is easy to operate and post-process, which greatly reduces the cost of product separation.

[0030] 3. The present invention utilizes asymmetric reduction to obtain chiral alcohols, thereby inducing the generation of subsequent chiral centers and being able to efficiently obtain optically pure products.

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0032] Figure 1 The accompanying drawing is a hydrogen spectrum of compound 8 prepared in the present invention;

[0033] Figure 2 The attached figure is a carbon spectrum of compound 8 prepared by the present invention;

[0034] Figure 3 The accompanying drawing is a hydrogen spectrum of compound 9 prepared in the present invention;

[0035] Figure 4 The attached figure is a carbon spectrum of compound 9 prepared by the present invention;

[0036] Figure 5 The attached figure is a hydrogen spectrum of compound 10 prepared in the present invention;

[0037] Figure 6 The attached figure is a carbon spectrum of compound 10 prepared in the present invention;

[0038] Figure 7 The attached figure is a hydrogen spectrum of compound 11 prepared in the present invention;

[0039] Figure 8 The attached figure is a carbon spectrum of compound 11 prepared in the present invention;

[0040] Fig. 9 The accompanying drawing is a hydrogen spectrum of the compound przewalskin B prepared in the present invention;

[0041] Fig.10 The accompanying drawing is a carbon spectrum of the compound przewalskin B prepared in accordance with the present invention; Specific implementation methods

[0043] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] Embodiment 1:

[0045]

[0046] Compound 8 (2 mmol) was dissolved in 10 ml of anhydrous tetrahydrofuran, and 1.6 ml of 2.4 mol / L (4 mmol) of tert-butyl lithium solution was added dropwise at -78°C, and stirring was continued at this temperature (400 rpm) for 30 minutes, and then 5 ml of tetrahydrofuran solution of cuprous cyanide (2 mmol) was added, and stirring was continued (400 rpm) for 30 minutes. Then, a tetrahydrofuran solution of 4 (0.6 mmol) was slowly added dropwise, and the mixture was naturally warmed to room temperature (about 2 hours), and the reaction was quenched with 10 ml of saturated ammonium chloride aqueous solution at 0°C, and then extracted with 5 ml of ethyl acetate and washed with 10 ml of saturated sodium chloride aqueous solution, dried over anhydrous sodium sulfate, filtered under reduced pressure, and concentrated under reduced pressure under vacuum to obtain a crude product, which was purified by silica gel column chromatography to obtain compound 9 (232 mg, yield 82%).

[0047] The detection data of compound 9 are as follows:

[0048] 1H NMR (400MHz, Chloroform-d) δ6.78 (s, 1H), 6.30 (t, J = 3.8Hz, 1H), 3.90 (s, 3H), 3.88 (s, 3H), 3.84 (s, 3H), 3.34-3.15 (m, 1H), 2.62 (dddd, J = 33.8, 13 .0, 11.0, 5.9Hz, 2H), 2.15-2.01(m, 3H), 1.90-1.69(m, 2H), 1.62-1.50(m , 1H), 1.30-1.24 (m, 1H), 1.21 (d, J=6.9Hz, 6H), 1.06 (s, 3H), 1.01 (s, 3H).

[0049] 13 C NMR (400MHz, Chloroform-d) δ149.7, 149.4, 146.1, 137.4, 136.4, 131.3, 121.4, 10 5.3, 61.3, 61.2, 60.7, 56.2, 35.3, 33.6, 30.7, 30.3, 28.1, 27.7, 27.2, 26.9, 23.8.

[0050] HRMS (m / z): [M+H] + Calculate for C 22 H 34 IO3 + 473.1553, found 473.1546.

[0051] Embodiment 2:

[0052]

[0053] (1) Compound 9 (0.49 mmol) was dissolved in 5 ml of anhydrous tetrahydrofuran, and 0.3 ml of 2.4 mol / L (0.73 mmol) of tert-butyl lithium solution was added dropwise at -78°C. The mixture was stirred at 400 rpm for 30 minutes. Then, a formylation agent (0.83 mmol) was added and stirred at 400 rpm for 30 minutes. The mixture was naturally heated to room temperature (about 2 hours), and the reaction was quenched with 10 ml of saturated aqueous ammonium chloride solution at 0°C. The mixture was extracted with 5 ml of ethyl acetate and washed with 10 ml of saturated aqueous sodium chloride solution, dried over anhydrous sodium sulfate, filtered under reduced pressure, and concentrated under reduced pressure to obtain a crude product. The crude product was purified by silica gel column chromatography to obtain compound 10 (130 mg, yield 71%).

[0054] (2) Compound 10 (0.35 mmol) was dissolved in 3.5 ml of anhydrous dichloromethane, and boron tribromide (1.75 mmol) was added dropwise at -78°C. The mixture was stirred at 400 rpm for 30 minutes, and then the temperature was raised to 0°C and stirred at 400 rpm for 30 minutes. The reaction was quenched with 10 ml of H2O at 0°C, extracted with 5 ml of ethyl acetate, washed with 10 ml of saturated sodium chloride aqueous solution, dried over anhydrous sodium sulfate, filtered under reduced pressure, and concentrated under reduced pressure to obtain a crude product, which was purified by silica gel column chromatography to obtain compound 11 (93 mg, yield 81%).

[0055] (3) Compound 11 (0.28 mmol) was dissolved in 2 ml of anhydrous tetrahydrofuran, triethylamine (1.12 mmol) was added dropwise at 25°C, and potassium ferrocyanide (0.56 mmol) was then added at the same temperature, and stirring (400 rpm) was continued for 30 minutes. Solid impurities were filtered through diatomaceous earth, and the mixture was concentrated under reduced pressure to obtain a crude product, which was purified by silica gel column chromatography to obtain compound przewalskin B (60 mg, yield 65%).

[0056] The detection data of compound 10 are as follows:

[0057] 1 H NMR (400MHz, Chloroform-d) δ9.51 (s, 1H), 6.75 (t, J = 3.6Hz, 1H), 6.67 (s, 1 H), 3.88 (s, 3H), 3.82 (s, 3H), 3.81 (s, 3H), 3.32-3.14 (m, 1H), 2.52 (dtd, J=3 5.5, 13.2, 5.1Hz, 2H), 2.41-2.28 (m, 2H), 1.82-1.61 (m, 2H), 1.32 (ddd, J=31 .3, 13.3, 6.9Hz, 3H), 1.18 (dd, J=6.9, 1.8Hz, 6H), 1.07 (s, 3H), 0.82 (s, 3H).

[0058] 13 C NMR (400MHz, Chloroform-d) δ194.6, 150.3, 149.5, 149.3, 146.1, 145.9, 137.2, 131.7 , 121.2, 61.2, 61.0, 60.6, 41.3, 34.3, 32.0, 30.7, 30.5, 28.1, 26.9, 26.9, 24.7, 23.7.

[0059] HRMS (m / z): [M+H] + Calculate for C 23 H 35 O4+ 375.2535, found 375.2529.

[0060] The detection data of compound 11 are as follows:

[0061] 1 H NMR (400MHz, Chloroform-d) δ9.42 (s, 1H), 7.19 (s, 1H), 6.84 (t, J = 3.8Hz, 1H), 6.41 (s, 1H), 5.56 (s, 1H), 5.22 (s, 1H), 3.38-3.03 (m, 1H), 2.62 (ddd, J=9.9, 6.2, 4.0Hz, 2H), 2.39 (qd, J= 9.6, 8.4, 3.2Hz, 2H), 2.04 (t, J=4.7Hz, 1H), 1.82 (dtd, J=12.9, 8.9, 3.6Hz, 1H), 1.56 (ddd, J =13.7, 9.7, 7.0Hz, 1H), 1.35-1.26 (m, 2H), 1.20 (t, J = 6.6Hz, 6H), 0.88 (s, 3H), 0.77 (s, 3H).

[0062] 13 C NMR (400MHz, Chloroform-d) δ197.1, 153.9, 146.8, 139.8, 139.7, 132.2, 127.1, 119.6, 117.1, 41.5, 34.3, 31.9, 30.8, 30.5, 27.4, 27.0, 26.6, 25.2, 23.0, 22.9.

[0063] HRMS(m / z):[MH]-calcd for C 20 H 27 O4 - 331.1909, found 331.1917.

[0064] The test data of compound przewalskin B are as follows:

[0065] 1H NMR(400MHz,Chloroform-d)δ7.10(d,J=1.4Hz,1H),5.80(q,J=4.0,3.3Hz,1H),4.79(q,J=2.6Hz,1H),3.66(s,1H),2.63(pd,J=6.9,1.4Hz,1H),2.15-1.95(m,2H),1.87-1.66(m,3H),1.62-1.48(m,2H),1.42(ddd,J=13.1,8.9,6.2Hz,1H),1.30-1.18(m,1H),1.14(d,J=6.8Hz,3H),1.09(d,J=6.9Hz,3H),0.95(s,3H),0.89(s,3H).

[0066] 13 C NMR(400MHz,Chloroform-d)δ200.5,173.2,158.5,149.2,136.0,121.3,82.3,54.4,45.1,32.5,31.4,29.6,27.7,26.5,25.4,25.3,22.5,20.7,20.6.

[0067] HRMS(m / z):[M+NH4] + calcd for C 20 H 30 NO4 - 348.2175found 348.2170.

Claims

1. An efficient synthesis method of a diterpene natural product przewalskin B, the structure of which is:

2. A method for synthesizing przewalskin B as claimed in claim 1, characterized in that: The steps include: Dissolve compound 8 in anhydrous tetrahydrofuran, add tert-butyl lithium solution, continue stirring at this temperature for 30 minutes, then add tetrahydrofuran solution of cuprous cyanide, continue stirring for 30 minutes. Then slowly add tetrahydrofuran solution of 4, naturally warm to room temperature, and quench the reaction with saturated ammonium chloride aqueous solution at 0°C; The quenched reaction product was extracted with ethyl acetate, washed with saturated sodium chloride aqueous solution, dried over anhydrous sodium sulfate, filtered under reduced pressure, and concentrated under reduced pressure to obtain a crude product. The crude product was purified by silica gel column chromatography to obtain compound 9.

3. The method for synthesizing compound 9 according to claim 2, characterized in that: The concentration of the solution after adding tetrahydrofuran in the step is 0.1-0.2 mol / L; the concentration of the added tert-butyl lithium is 1.0-2.4 mol / L, and the volume ratio of the tetrahydrofuran solution of cuprous cyanide to the substrate solution is 1:2-1:

1. The stirring reaction temperature is -78 to 20°C, the time is 0.5 to 1 hour, and the rotation speed is 100 to 1000 rpm; The quenching reaction temperature is -20 to 0°C and the time is 20 to 30 minutes: The concentration process is reduced pressure concentration, and the vacuum degree is 50-600 mbar.

4. A method for synthesizing przewalskin B as claimed in claim 1, characterized in that: The steps include: Compound 9 was dissolved in anhydrous tetrahydrofuran, and tert-butyl lithium solution was added dropwise. The mixture was stirred for 30 minutes at this temperature, and then a formylating agent was added. The reaction was quenched with a saturated aqueous ammonium chloride solution. The residue was then extracted with ethyl acetate, washed with saturated aqueous sodium chloride solution, dried over anhydrous sodium sulfate, filtered under reduced pressure, and concentrated under reduced pressure to obtain a crude product. The crude product was purified by silica gel column chromatography to obtain compound 10.

5. The method for synthesizing compound 10 according to claim 2, characterized in that: After adding tetrahydrofuran, the concentration of the solution is 0.05-0.4 mol / L; the concentration of the added tert-butyl lithium is 1.0-2.4 mol / L, and the ratio of the formylating agent to the compound 9 is 1.8:1-2:

1. The stirring reaction temperature is -78 to -50°C, the time is 0.5 to 6 hours, and the speed is 100 to 1000 rpm; The quenching reaction temperature is -78 to -50°C and the time is 1 to 3 minutes; The concentration process is reduced pressure concentration, and the vacuum degree is 50-600 mbar.

6. A method for synthesizing przewalskin B as claimed in claim 1, characterized in that: The steps include:

7. The method for synthesizing the compound przewalskin B according to claim 2, characterized in that: After adding tetrahydrofuran, the solution concentration is 0.05-0.4 mol / L; the ratio of the added triethylamine to the compound 11 is 3:1-6:1, and the ratio of the added potassium ferrocyanide to the compound 11 is 2:1-4:

1. The stirring reaction temperature is 15-50°C, the time is 0.5-6h, and the speed is 100-1000rpm; The quenching reaction temperature is 15 to 50°C and the time is 1 to 3 minutes; The concentration process is reduced pressure concentration, and the vacuum degree is 50-600 mbar.

Images