A method for preparing an indole alkaloid

Abstract

This invention belongs to the field of indole alkaloid technology and discloses a method for preparing indole alkaloids. The preparation method of this invention includes the following steps: (1) mixing an organic solvent, L-tryptophan methyl ester hydrochloride, 1-bromo-3-methyl-2-butene and Maruoka catalyst, controlling the temperature to be less than or equal to 10°C, adding an alkaline substance under a protective atmosphere, and then controlling the temperature to be less than or equal to 10°C to carry out a coupling reaction to obtain compound 1; (2) mixing compound 1 with (S) phenyl lactic acid, 1-hydroxybenzotriazole and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride to carry out an addition reaction to obtain indole alkaloids. The preparation method of this invention has a short reaction time, and the coupling reaction can be completed within 3 hours, with an overall reaction time of no more than 6 hours. At the same time, the product yield and purity are high, with a yield greater than 80% and a purity greater than 99%.

Description

Technical Field

[0001] This invention belongs to the field of alkaloid technology, and specifically relates to a method for preparing indole alkaloids. Background Technology

[0002] Indole alkaloid (Misszrtlide A), abbreviated as MZT, has the following structural formula:

[0003]

[0004] The aforementioned indole alkaloids were isolated from sponge-derived Aspergillus. They exhibited strong cytotoxicity against human prostate cancer cell line LNCaP (IC50 = 4.9 μM) and acute myeloid leukemia M3 cell line HL-60 (IC50 = 3.1 μM), and have broad application prospects in the pharmaceutical field.

[0005] In the preparation of the above-mentioned indole alkaloids, the issue of 1-bromo-3-methyl-2-butene coupling selectivity is involved. The traditional process involves an addition reaction between amino and phenyl lactic acid, followed by the addition of tert-butyldimethylchlorosilane (TBSCl) to protect the hydroxyl group, and then coupling with 1-bromo-3-methyl-2-butene. However, this preparation method has the problems of long coupling reaction time (more than 6 hours), many synthesis steps, and low yield (generally in the range of 40-50%).

[0006] Therefore, there is an urgent need to develop a method for preparing indole alkaloids in order to maximize the utilization of raw materials, shorten the coupling reaction time, and improve the yield. Summary of the Invention

[0007] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a method for preparing indole alkaloids, which has a short coupling reaction time (1-3 h), and at the same time produces a high yield (>80%), high purity (>99%), and good reaction stability.

[0008] In a first aspect, this invention provides a method for preparing indole alkaloids, comprising the following steps:

[0009] (1) Mix organic solvent, L-tryptophan methyl ester hydrochloride, 1-bromo-3-methyl-2-butene and Maruoka catalyst, control the temperature to be less than or equal to 10°C, add alkaline substance under protective atmosphere, and then control the temperature to be less than or equal to 10°C to carry out coupling reaction to obtain compound 1.

[0010] (2) The compound 1 was mixed with (S) phenyl lactic acid, 1-hydroxybenzotriazole and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and subjected to an addition reaction to obtain the indole alkaloid.

[0011] The structural formula of compound 1 is shown in formula (Ⅰ):

[0012]

[0013] The structural formula of the indole alkaloid is shown in formula (II) below:

[0014]

[0015] Specifically, this invention utilizes L-tryptophan methyl ester hydrochloride (CAS: 7524-52-9) and 1-bromo-3-methyl-2-butene (CAS: 870-63-3) as reactants, and adds Maruoka catalyst for directional catalytic coupling. By adding alkaline substances and carrying out the coupling reaction at a specific temperature, the high purity and high yield of the product can be ensured, while also having a fast reaction rate, completing the coupling reaction within 3 hours.

[0016] In some embodiments of the present invention, the mass ratio of L-tryptophan methyl ester hydrochloride, 1-bromo-3-methyl-2-butene, basic substance and catalyst is 1:(1.05-1.3):(1.1-1.5):(0.005-0.4).

[0017] In some embodiments of the present invention, the coupling reaction takes 1-3 hours.

[0018] In some embodiments of the present invention, the Maruoka catalyst has the following structural formula (Ⅲ):

[0019] Wherein, the X group is a halogen.

[0020] In some embodiments of the present invention, the Maruoka catalyst has the following structural formula (Ⅳ):

[0021]

[0022] In some embodiments of the present invention, the mass ratio of compound 1, (S) phenyllactic acid, 1-hydroxybenzotriazole (HOBt), and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDCl) is 1:(0.6-0.8):(0.5-0.7):(0.7-0.9).

[0023] In some embodiments of the present invention, the temperature of the addition reaction is 0-10°C.

[0024] In some embodiments of the present invention, the addition reaction takes 1-3 hours.

[0025] In some embodiments of the present invention, the specific preparation process of step (1) includes the following steps:

[0026] An organic solvent, L-tryptophan methyl ester hydrochloride, and 1-bromo-3-methyl-2-butene were mixed and stirred to dissolve. Maruoka catalyst was then added, and the temperature was controlled at 0-10℃. An alkaline substance was then added under a protective atmosphere, and the mixture was kept at this temperature for 1-3 hours to carry out the coupling reaction, thus obtaining the reaction solution.

[0027] The temperature of the reaction solution was controlled at 0-10℃, and the pH of the reaction solution was adjusted to 6-7. After separation, the upper aqueous phase was removed, and the lower product was dried to obtain compound 1.

[0028] In some embodiments of the present invention, the specific preparation process of step (2) includes the following steps:

[0029] Compound 1 was mixed with (S) phenyllactic acid and HOBt, and the temperature was controlled at 0-10℃. Then EDCI was added, and the mixture was kept at this temperature for 1-3 minutes to carry out the addition reaction. After the reaction, the temperature was controlled at 0-10℃, and water was added. After centrifugation, washing and drying, indole alkaloids were obtained.

[0030] In some embodiments of the present invention, the organic solvent includes dichloromethane (DCM) and / or acetonitrile (ACN).

[0031] In some embodiments of the present invention, the alkaline substance includes at least one of sodium hydroxide, potassium hydroxide, and triethylamine.

[0032] In some embodiments of the present invention, the protective atmosphere is a nitrogen or inert gas atmosphere.

[0033] In some embodiments of the present invention, the preparation process of the coupling reaction is represented by the following chemical reaction equations:

[0034]

[0035] In some embodiments of the present invention, the preparation process of the addition reaction is represented by the following chemical reaction equation:

[0036]

[0037] In some embodiments of the present invention, the yield of the indole alkaloid is 83.5-85%.

[0038] In some embodiments of the present invention, the purity of the indole alkaloid is 99.2-99.5%.

[0039] In a second aspect, the present invention provides the application of the preparation method described in the first aspect of the present invention in the preparation of alkaloids.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] (1) The method for preparing indole alkaloids provided by the present invention has a short reaction time, and the coupling reaction can be completed within 3 hours. The overall reaction time does not exceed 6 hours. At the same time, the product yield and purity are high, with a yield greater than 80% and a purity greater than 99%.

[0042] (2) In the preparation process, alkaline substances are added to provide an alkaline environment for the coupling reaction, and Maruoka catalyst is added for directional catalytic coupling to promote the reaction. Moreover, the amount of catalyst used is small, the product purity is high, and the safety is relatively high. Detailed Implementation

[0043] The present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials, reagents, or apparatus used in the embodiments can be obtained from conventional commercial sources or by existing technical methods. Unless otherwise specified, the experimental or testing methods are conventional methods in the art.

[0044] The structural formula of the Maruoka catalyst used in the following examples is shown below:

[0045]

[0046] Example 1: Preparation of indole alkaloids

[0047] The preparation process of indole alkaloids is represented by the following chemical reaction equation:

[0048]

[0049] The preparation method of indole alkaloids (hereinafter referred to as MZT) specifically includes the following steps:

[0050] (1) Add 43.0 kg of acetonitrile (ACN), 10.0 kg of L-tryptophan methyl ester hydrochloride and 11.0 kg of 1-bromo-3-methyl-2-butene to a 200 L reactor. After stirring and dissolving, add 50.0 g of Maruoka catalyst. Control the temperature at 5 °C and add 26.0 kg of 50 wt% potassium hydroxide (KOH) aqueous solution dropwise under nitrogen protection. Then keep the reactor at 5 °C for 2 hours to allow the coupling reaction to occur and obtain the reaction solution.

[0051] (2) Control the temperature at 5℃, add 40.0 kg of water to the reaction vessel in step (1), then add 16.4 kg of 0.5 N hydrochloric acid solution (i.e., 1.1 kg of concentrated hydrochloric acid dissolved in 15.3 kg of water), and adjust the pH of the reaction solution to 7; control the system temperature at 5℃, add 30.0 kg of dichloromethane (DCM) to the reaction vessel, stir the system at 5℃ for 15 min, remove the upper aqueous phase after separation, and add anhydrous magnesium sulfate to the lower product for drying to remove magnesium sulfate and obtain compound 1;

[0052] (3) Add (S)-phenyllactic acid and 1-hydroxybenzotriazole (HOBt) to the reaction vessel in which compound 1 was obtained in step (2), and then add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDCl) at 5°C (wherein the mass ratio of compound 1, (S)-phenyllactic acid, HOBt and EDCl is 1:0.7:0.6:0.8), keep warm for 1 hour, and an addition reaction will occur. After the reaction is completed, control the temperature at 5°C, add 40.0 kg of water to the reaction vessel, and then put the material in the reaction vessel into a centrifuge for centrifugation. Rinse the reaction vessel and wash the filter cake with acetonitrile aqueous solution (wherein the mass ratio of acetonitrile and water is 16.0:41.0), and then wash the filter cake twice with 164.0 kg of water respectively, and filter until there is no effluent and the pH value is 6 (weakly acidic) to obtain MZT wet product;

[0053] (4) Transfer the wet MZT product to an oven and vacuum dry at 40°C for 24 hours to obtain the dry MZT product.

[0054] Example 2: Preparation of indole alkaloids

[0055] The preparation method of indole alkaloids (hereinafter referred to as MZT) specifically includes the following steps:

[0056] (1) Add 43.0 kg of acetonitrile, 10.0 kg of L-tryptophan methyl ester hydrochloride and 11.0 kg of 1-bromo-3-methyl-2-butene to a 200 L reactor. After stirring to dissolve and clarify, add 50.0 g of Maruoka catalyst. Control the temperature at 5 °C and add 12.0 kg of triethylamine dropwise under nitrogen protection. Then keep the reactor at 5 °C for 2 hours to allow the coupling reaction to occur and obtain the reaction solution.

[0057] (2) Control the temperature at 5℃, add 40.0 kg of water to the reaction vessel in step (1), then add 16.4 kg of 0.5 N hydrochloric acid solution (i.e., 1.1 kg of concentrated hydrochloric acid dissolved in 15.3 kg of water), and adjust the pH of the reaction solution to 7; control the system temperature at 5℃, add 30.0 kg of dichloromethane to the reaction vessel, stir the system at 5℃ for 15 min, remove the upper aqueous phase after separation, and add anhydrous magnesium sulfate to the lower product for drying to remove magnesium sulfate and obtain compound 1;

[0058] (3) Add (S) phenyl lactic acid and HOBt to the reaction vessel in which compound 1 was obtained in step (2), and then add EDCl at 5°C (the mass ratio of compound 1, (S) phenyl lactic acid, HOBt and EDCl is 1:0.7:0.6:0.8). Keep warm for 1 hour to allow the addition reaction to occur. After the reaction is complete, control the temperature at 5°C and add 40.0 kg of water to the reaction vessel. Then put the material in the reaction vessel into a centrifuge to centrifuge. Rinse the reaction vessel and wash the filter cake with acetonitrile aqueous solution (the mass ratio of acetonitrile and water is 16.0:41.0). Wash the filter cake twice with 164.0 kg of water and filter until there is no effluent and the pH value is 6 (weakly acidic) to obtain MZT wet product.

[0059] (4) Transfer the wet MZT product to an oven and vacuum dry at 40°C for 24 hours to obtain the dry MZT product.

[0060] Example 3: Preparation of indole alkaloids

[0061] The preparation method of indole alkaloids (hereinafter referred to as MZT) specifically includes the following steps:

[0062] (1) Add 43.0 kg of dichloromethane, 10.0 kg of L-tryptophan methyl ester hydrochloride and 11.0 kg of 1-bromo-3-methyl-2-butene to a 200 L reactor. After stirring to dissolve and clarify, add 50.0 g of Maruoka catalyst. Control the temperature at 5 °C and add 26.0 kg of 50 wt% potassium hydroxide aqueous solution dropwise under nitrogen protection. Then keep the reactor at 5 °C for 2 hours to allow the coupling reaction to occur and obtain the reaction solution.

[0063] (2) Control the temperature at 5℃, add 40.0 kg of water to the reaction vessel in step (1), then add 16.4 kg of 0.5 N hydrochloric acid solution (i.e., 1.1 kg of concentrated hydrochloric acid dissolved in 15.3 kg of water), and adjust the pH of the reaction solution to 7; control the system temperature at 5℃, remove the upper aqueous phase after separation, and add anhydrous magnesium sulfate to the lower product for drying to remove magnesium sulfate and obtain compound 1;

[0064] (3) Add (S) phenyl lactic acid and HOBt to the reaction vessel in which compound 1 was obtained in step (2), and then add EDCl at 5°C (the mass ratio of compound 1, (S) phenyl lactic acid, HOBt and EDCl is 1:0.7:0.6:0.8). Keep warm for 1 hour to allow the addition reaction to occur. After the reaction is complete, control the temperature at 5°C and add 40.0 kg of water to the reaction vessel. Then put the material in the reaction vessel into a centrifuge to centrifuge. Rinse the reaction vessel and wash the filter cake with acetonitrile aqueous solution (the mass ratio of acetonitrile and water is 16.0:41.0). Wash the filter cake twice with 164.0 kg of water and filter until there is no effluent and the pH value is 6 (weakly acidic) to obtain MZT wet product.

[0065] (4) Transfer the wet MZT product to an oven and vacuum dry at 40°C for 24 hours to obtain the dry MZT product.

[0066] Example 4: Preparation of indole alkaloids

[0067] The preparation method of indole alkaloids (hereinafter referred to as MZT) specifically includes the following steps:

[0068] (1) Add 21.5g of dichloromethane, 5g of L-tryptophan methyl ester hydrochloride and 5.5g of 1-bromo-3-methyl-2-butene to a dry 500.0mL three-necked flask. After stirring to dissolve and clarify, add 0.025g of Maruoka catalyst. Control the temperature at 5℃ and add 13g of 50wt% potassium hydroxide aqueous solution dropwise under nitrogen protection. Then keep the reaction vessel at 5℃ for 2 hours to carry out the coupling reaction and obtain the reaction solution.

[0069] (2) Control the temperature to 5℃, add 8g of 0.5N hydrochloric acid solution to the reaction vessel in step (1), and adjust the pH value of the reaction solution to 7; control the system temperature to 5℃, remove the upper aqueous phase after separation, and add anhydrous magnesium sulfate to the lower product for drying to remove magnesium sulfate and obtain compound 1.

[0070] (3) Add (S) phenyl lactic acid and HOBt to the three-necked flask containing compound 1 obtained in step (2), and then add EDCl at 5°C (the mass ratio of compound 1, (S) phenyl lactic acid, HOBt and EDCl is 1:0.7:0.6:0.8). Keep warm for 1 hour to allow the addition reaction to occur. After the reaction is complete, control the temperature at 5°C and add 20g of water to the reactor. Then, put the material in the three-necked flask into a centrifuge and centrifuge. Rinse the reactor and wash the filter cake with acetonitrile aqueous solution (the mass ratio of acetonitrile and water is 16.0:41.0). Wash the filter cake twice with 80g of water and filter until there is no effluent and the pH value is 6 (weakly acidic) to obtain wet MZT.

[0071] (4) Transfer the wet MZT product to an oven and vacuum dry at 40°C for 24 hours to obtain the dry MZT product.

[0072] Comparative Example 1 (The difference from Example 4 is that the temperature was too high when adding the potassium hydroxide aqueous solution in step (1)).

[0073] The preparation method of indole alkaloids (hereinafter referred to as MZT) specifically includes the following steps:

[0074] (1) Add 21.5g of dichloromethane, 5g of L-tryptophan methyl ester hydrochloride, and 5.5g of 1-bromo-3-methyl-2-butene to a dry 500.0mL three-necked flask. After stirring to dissolve and clarify, add 0.025g of Maruoka catalyst. Control the temperature at 15℃ and add 13g of 50wt% potassium hydroxide aqueous solution dropwise under nitrogen protection. Then keep the reaction vessel at 5℃ for 2 hours to carry out the coupling reaction and obtain the reaction solution.

[0075] (2) Control the temperature to 5℃, add 8g of 0.5N hydrochloric acid solution to the reaction vessel in step (1), and adjust the pH value of the reaction solution to 7; control the system temperature to 5℃, remove the upper aqueous phase after separation, and add anhydrous magnesium sulfate to the lower product for drying to remove magnesium sulfate and obtain compound 1.

[0076] (3) Add (S) phenyl lactic acid and HOBt to the three-necked flask containing compound 1 obtained in step (2), and then add EDCl at 5°C (the mass ratio of compound 1, (S) phenyl lactic acid, HOBt and EDCl is 1:0.7:0.6:0.8). Keep warm for 1 hour to allow the addition reaction to occur. After the reaction is complete, control the temperature at 5°C and add 20g of water to the reactor. Then, put the material in the three-necked flask into a centrifuge and centrifuge. Rinse the reactor and wash the filter cake with acetonitrile aqueous solution (the mass ratio of acetonitrile and water is 16.0:41.0). Wash the filter cake twice with 80g of water and filter until there is no effluent and the pH value is 6 (weakly acidic) to obtain wet MZT.

[0077] (4) Transfer the wet MZT product to an oven and vacuum dry at 40°C for 24 hours to obtain the dry MZT product.

[0078] Comparative Example 2 (the difference from Example 4 is that the coupling reaction temperature in step (1) is too high)

[0079] The preparation method of indole alkaloids (hereinafter referred to as MZT) specifically includes the following steps:

[0080] (1) Add 21.5g of dichloromethane, 5g of L-tryptophan methyl ester hydrochloride, and 5.5g of 1-bromo-3-methyl-2-butene to a dry 500.0mL three-necked flask. After stirring to dissolve and clarify, add 0.025g of Maruoka catalyst. Control the temperature at 5℃ and add 13g of 50wt% potassium hydroxide aqueous solution dropwise under nitrogen protection. Then, keep the reaction vessel at 35℃ for 2 hours to carry out the coupling reaction and obtain the reaction solution.

[0081] (2) Control the temperature to 5℃, add 8g of 0.5N hydrochloric acid solution to the reaction vessel in step (1), and adjust the pH value of the reaction solution to 7; control the system temperature to 5℃, remove the upper aqueous phase after separation, and add anhydrous magnesium sulfate to the lower product for drying to remove magnesium sulfate and obtain compound 1.

[0082] (3) Add (S) phenyl lactic acid and HOBt to the three-necked flask containing compound 1 obtained in step (2), and then add EDCl at 5°C (the mass ratio of compound 1, (S) phenyl lactic acid, HOBt and EDCl is 1:0.7:0.6:0.8). Keep warm for 1 hour to allow the addition reaction to occur. After the reaction is complete, control the temperature at 5°C and add 20g of water to the reactor. Then, put the material in the three-necked flask into a centrifuge and centrifuge. Rinse the reactor and wash the filter cake with acetonitrile aqueous solution (the mass ratio of acetonitrile and water is 16.0:41.0). Wash the filter cake twice with 80g of water and filter until there is no effluent and the pH value is 6 (weakly acidic) to obtain wet MZT.

[0083] (4) Transfer the wet MZT product to an oven and vacuum dry at 40°C for 24 hours to obtain the dry MZT product.

[0084] Product yield and purity

[0085] The molar yields of the dried MZT products obtained in Examples 1-4 and Comparative Examples 1-2 were calculated using the following formula:

[0086] The molar yield Y = (M2 / 434.57) / (M1 / 254.71) × 100%.

[0087] Wherein, M1: weight of L-tryptophan methyl ester hydrochloride; M2: weight of dried MZT product.

[0088] The molar yield and purity are shown in Table 1.

[0089] Table 1

[0090] Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 yield 85％ 83.5％ 84％ 82.2％ 71.15％ 67.5％ purity 99.3％ 99.5％ 99.2％ 99.5％ 97.2％ 97.3％

[0091] As can be seen from the table above, the yield and purity of the MZT products obtained in Examples 1-4 of the present invention are significantly higher than those in Comparative Examples 1-2; this indicates that the preparation method of the present invention has good reaction stability and short reaction time, wherein the coupling reaction is 2 hours and the addition reaction is 1 hour.

[0092] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention, and these equivalent modifications or substitutions are all included within the scope defined by the claims of this application.

Claims

1. A method for preparing indole alkaloids, characterized in that, Includes the following steps: (1) Mix organic solvent, L-tryptophan methyl ester hydrochloride, 1-bromo-3-methyl-2-butene and Maruoka catalyst, control the temperature to be less than or equal to 10°C, add alkaline substance under protective atmosphere, and then control the temperature to be less than or equal to 10°C to carry out coupling reaction to obtain compound 1. (2) The compound 1 was mixed with (S) phenyl lactic acid, 1-hydroxybenzotriazole and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and subjected to an addition reaction to obtain the indole alkaloid. The structural formula of compound 1 is shown in formula (Ⅰ): The structural formula of the indole alkaloid is shown in formula (II) below:

2. The preparation method according to claim 1, characterized in that, The mass ratio of L-tryptophan methyl ester hydrochloride, 1-bromo-3-methyl-2-butene, basic substance and catalyst is 1:(1.05-1.3):(1.1-1.5):(0.005-0.4).

3. The preparation method according to claim 1, characterized in that, The coupling reaction takes 1-3 hours.

4. The preparation method according to claim 1, characterized in that, The structural formula of the Maruoka catalyst is shown in formula (Ⅲ) below: Wherein, the X group is a halogen.

5. The preparation method according to claim 1, characterized in that, The mass ratio of compound 1, (S) phenyl lactic acid, 1-hydroxybenzotriazole and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride is 1:(0.6-0.8):(0.5-0.7):(0.7-0.9).

6. The preparation method according to claim 1, characterized in that, The addition reaction is performed at a temperature of 0-10℃.

7. The preparation method according to claim 1, characterized in that, The addition reaction takes 1-3 hours.

8. The preparation method according to claim 1, characterized in that, The organic solvents include dichloromethane and / or acetonitrile.

9. The preparation method according to claim 1, characterized in that, The alkaline substance includes at least one of sodium hydroxide, potassium hydroxide, and triethylamine.

10. The application of the preparation method according to any one of claims 1-9 in the preparation of alkaloids.

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