Process for the preparation of a derivative of indole alkaloids and uses thereof

Abstract

The application discloses a synthesis method and application of an indole alkaloid derivative. The method uses 5-aminoindole or 6-aminoindole as a substrate, reacts with acyl chloride or carboxylic acid to obtain an intermediate, and then reacts with Hydroxyclavatol to obtain a Penindolone (PND) derivative of the application. The method has the advantages of easy availability of raw materials, short reaction time, few steps involved, simple post-treatment and the like. The indole alkaloid PND derivative prepared by the method has good anti-influenza virus activity and wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of pharmaceutical chemical synthesis technology, and relates to the structure and synthesis method of an indole alkaloid derivative. Background Technology

[0002] Amide bonds frequently appear in many natural products and drug molecules, serving as important functional groups in biomolecules and drugs, possessing unique physical properties and application value in compounds. A novel indole alkaloid compound, Penindolone (PND), exhibits inhibitory activity against influenza A virus. To enhance the antiviral activity and drug-likeness of PND derivatives, this invention introduces amide bonds as connecting bonds between the indole benzene ring and substituents in PND. These results provide a certain reference for the development of this indole alkaloid compound. Summary of the Invention

[0003] The primary objective of this invention is to provide a novel PND derivative containing an amide bond that exhibits good inhibitory effects against influenza viruses.

[0004] The second objective of this invention is to provide a simple synthetic method for preparing PND derivatives that achieve the first objective.

[0005] To achieve the first objective of the invention, the indole at the 5- or 6-position of the PND derivative structure is linked to a 3,4,5-trimethoxyphenyl substituent via an amide bond, and its structure I and structure II are respectively: Alternatively, it can be formed by linking an amide bond to a (4-methyl-piperazinyl)ethyl group at the 5- or 6-position of the indole in PND, with structures III and IV being: The technical solution for achieving the second objective of the invention is a method for preparing indole alkaloid derivatives. This method prepares PND derivatives that achieve the first objective of the invention. The method includes the following preparation steps:

[0006] 5-Nitroindole or 6-nitroindole is reacted with hydrogen to give indoles with amino substitutions at the 5- and 6-positions. The 5-aminoindole or 6-aminoindole is then placed in a round-bottom flask, dissolved completely in solvent, and then a substituted acyl chloride or a substituted carboxylic acid is slowly added. The reaction continues at room temperature until complete, after which it is quenched. The product is purified by column chromatography to obtain an intermediate product, which is then used as one of the reactants with Hydroxyclavatol (…). Figure 1 The reaction generates PND derivatives.

[0007] As a preferred technical solution, the specific synthetic route of the above-mentioned synthetic method is shown below: As a preferred technical solution, the general chemical formula of different substituted acyl chlorides is RCOCl, and the general chemical formula of different substituted carboxylic acids is RCOOH, wherein the R structure is selected from any substituted or unsubstituted C. 1-5 Alkyl, C 3-7 One of cycloalkyl, benzyl, and aryl, wherein the substituent group includes halogen.

[0008] As a preferred technical solution, the solvents include methanol, dichloromethane, N,N-dimethylformamide, and toluene.

[0009] As a preferred technical solution, the quenching agent used for quenching is water or saturated saline solution.

[0010] As a preferred technical solution, the molar ratio of different substituted acyl chlorides or different substituted carboxylic acids to amino-substituted indole is 1.5:1.

[0011] As a preferred technical solution, the molar ratio of the intermediate product of the reaction of different substituted acyl chlorides or different substituted carboxylic acids with amino-substituted indole to Hydroxyclavatol is 1:2.

[0012] Then, the activity against PR8 (H1N1) influenza virus was detected using a cytopathic effect inhibition assay, with the antiviral drug oseltamivir as the positive control. The prepared PND derivatives I-IV were compared and verified with PND. The verification results are shown in the table below:

[0013] Table 1. Results of anti-influenza virus test

[0014]

[0015] As can be seen from Table 1, the four PND derivatives (structural formulas I-IV) prepared by the method provided in this invention all exhibit good anti-influenza virus activity, superior to PND and the positive control drug oseltamivir, while also demonstrating good safety. Figure 2 ).

[0016] This invention uses easily prepared 5-aminoindole or 6-aminoindole as substrates, reacting them with different substituted acyl chlorides or different substituted carboxylic acids at room temperature. After the reaction is complete, the reaction is quenched and purified by column chromatography to obtain an intermediate product, which is then reacted with Hydroxyclavatol as one of the reactants to generate PND derivatives. Therefore, this invention provides a method for synthesizing indole alkaloid PND derivatives. This method uses readily available raw materials, has a short reaction time, and simple post-processing, showing broad application prospects. Furthermore, the indole alkaloid PND derivatives prepared by the method provided in this invention exhibit good anti-influenza virus activity and have significant application value in the preparation of anti-influenza virus drugs. Detailed Implementation

[0017] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. However, it should be understood that these embodiments are only used to illustrate the disclosure of the present invention to help understand the present invention, and are not intended to limit the scope of the present invention. The protection scope of the present invention is not limited to the following embodiments.

[0018] The present invention does not impose any particular restrictions on the source of raw materials in the following embodiments; they can be prepared by methods known to those skilled in the art or purchased commercially.

[0019] In this embodiment of the invention, the nuclear magnetic resonance spectrum of the compound ( 1 H NMR, 13 C10 NMR was determined by a Bruker AVANCE 400 and a JEOLJN M-ECP 600 in deuterated dimethyl sulfoxide. Chemical shift δ Quoted in ppm, with tetramethylsilane as an internal standard, multiplicity is as follows: s = singlet, d = doublet, t = triplet, q = quartet, m = multiplicity. High-resolution mass spectrometry (HRMS) was performed using a Thermo Scientific LTQ Orbitrap XL.

[0020] Example 1:

[0021] Synthetic methods for indole alkaloid PND derivatives (compounds shown in Formulas I and II):

[0022] In a 50 mL round-bottom flask, 5.0 mmol of 5-nitroindole or 6-nitroindole was dissolved in 15 mL of methanol, followed by the addition of 10% (w / w) palladium on carbon. The mixture was then stirred at 40 °C for 2 h under hydrogen atmosphere, and the reaction was monitored by TLC until complete. The residual palladium on carbon was filtered off with diatomaceous earth, and the mixture was concentrated under reduced pressure and purified by silica gel column chromatography (petroleum ether: ethyl acetate = 1:1) to obtain 5-aminoindole and 6-aminoindole. 0.68 mmol of 5-aminoindole or 6-aminoindole was dissolved in dichloromethane (DCM, 6 mL), and then 1.02 mmol of 3,4,5-trimethoxybenzoyl chloride and 1.36 mmol of triethylamine (TEA) were slowly added. The mixture was stirred at room temperature for 0.5 h, and the reaction was monitored by TLC until complete. The reaction solution was extracted twice with DCM, the organic phases were combined, washed three times with saturated brine, and the organic layer was dried with anhydrous Na₂SO₄. The organic phase was concentrated under reduced pressure, and the sample was purified by silica gel column chromatography (petroleum ether:ethyl acetate = 20:1 to 1:1) to obtain the intermediate product. The intermediate product (0.5 mmol) was reacted with Hydroxyclavatol (1.0 mmol) in toluene solution in a one-step Michael addition reaction, stirred at 110 °C for 3–6 h. After the reaction was complete, the solid precipitated was directly filtered to obtain the product. The solution without precipitated solid was concentrated under reduced pressure and recrystallized from ethyl acetate and petroleum ether. The product with a purity still below 95% was purified by silica gel column chromatography. The structure of the compound shown in Formula I is as follows: N-(2,3-bis(3-acetyl-2,6-dihydroxy-5-methylbenzyl)-1H-indol-5-yl)-3,4,5- trimethoxybenzamide. Yellow solid, yield 28.7%, melting point: 200–201 °C. 1 H NMR (400 MHz, DMSO- d 6): δ 13.08 (s, 1H), 13.05 (s, 1H), 9.84 (s, 1H), 9.75 (s, 1H), 9.66(s, 1H), 9.44 (s, 1H), 7.74 (s, 1H), 7.63 (s, 1H), 7.53 (s, 1H), 7.28 (s,2H), 7.17 (d, J = 8.6 Hz, 1H), 7.05 (dd, J = 8.6, 2.0 Hz, 1H), 4.22 (s, 2H), 4.09 (s, 2H), 3.86 (s, 6H), 3.73 (s, 3H), 2.56 (s, 3H), 2.51 (s, 3H), 2.19(s, 3H), 2.16 (s, 3H);13 C NMR (100 MHz, DMSO- d 6): δ 203.67, 203.59, 164.71, 161.25, 161.17, 161.17, 161.12, 153.00, 152.99, 152.99, 140.28, 135.87, 132.99, 131.90, 131.20, 131.06, 129.84, 128.38, 116.44, 116.20, 115.42, 113.37, 113.10, 113.03, 112.83, 110.65, 109.16, 105.50, 105.50, 60.56, 56.47,56.47, 26.69, 26.69, 20.23, 18.20, 16.92, 16.87. HRMS: calcd for C 38 H 39 N2O 10 [M+ H] + , 683.2599; found, 683.2579. The structure of the compound shown in Formula II is: N-(2,3-bis(3-acetyl-2,6-dihydroxy-5-methylbenzyl)-1H-indol-6-yl)-3,4,5- trimethoxybenzamide. White solid, yield 35.7%, melting point: 188–190 °C. 1 H NMR (400 MHz, DMSO- d 6): δ 13.09 (s, 1H), 13.04 (s, 1H), 9.87 (s, 2H), 9.64 (s, 1H), 9.52(s, 1H), 7.76 (s, 1H), 7.62 (s, 1H), 7.55 (s, 1H), 7.35 (d, J = 8.3 Hz, 1H), 7.22 (s, 2H), 6.95 (d, J = 8.6 Hz, 1H), 4.24 (s, 2H), 4.09 (s, 2H), 3.84 (s,6H), 3.71 (s, 4H), 2.55 (s, 3H), 2.53 (s, 3H), 2.19 (s, 3H), 2.17 (s, 3H); 13 CNMR (100 MHz, DMSO- d 6): δ203.76, 203.63, 164.85, 161.23, 161.20, 161.19, 161.08, 153.00, 153.00, 153.00, 140.37, 135.44, 135.21, 132.10, 131.81, 131.23, 131.18, 125.46, 118.28, 116.45, 116.27, 115.58, 113.54, 113.31, 113.03, 112.82, 108.95, 105.58, 104.27, 60.55, 56.50, 56.50, 26.67, 26.67,20.25, 18.29, 16.90, 16.89. HRMS: calcd for C 38 H 39 N2O 10 [M + H] + , 683.2599;found, 683.2584. Example

[0023] Synthetic methods for indole alkaloid PND derivatives (compounds shown in formulas III and IV):

[0024] 5-Aminoindole or 6-aminoindole (0.68 mmol) was dissolved in dichloromethane (DCM, 6 mL), followed by the slow addition of 4-methyl-1-piperazinacetic acid (1.02 mmol), then 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDCI, 0.82 mmol) and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (HOBt, 0.82 mmol). The mixture was stirred at room temperature for 3–6 h, and TLC was monitored until the starting material showed no further change. The reaction was quenched with water, and the mixture was extracted twice with DCM. The organic phases were combined, dried over anhydrous Na₂SO₄, and concentrated under reduced pressure. The mixture was then separated by silica gel column chromatography using eluent (dichloromethane:methanol = 40:1 to 10:1) to obtain the intermediate. The intermediate (0.5 mmol) was reacted with Hydroxyclavatol (1.0 mmol) in toluene solution via a one-step Michael addition reaction, stirred at 110 °C for 3–6 h. After the reaction was complete, the precipitated solid was directly filtered to obtain the product. The solution without precipitated solid was concentrated under reduced pressure and recrystallized from ethyl acetate and petroleum ether. The product with a purity still below 95% was purified by silica gel column chromatography.

[0025] The structure of the compound shown in Formula III is as follows: N-(2,3-bis(3-acetyl-2,6-dihydroxy-5-methylbenzyl)-1H-indol-5-yl)-2-(4- methylpiperazin-1-yl)acetamide.White solid, yield 35.8%, melting point: 171–173 °C. 1 H NMR (400 MHz, DMSO-) d 6): δ 13.09 (s, 1H), 13.03 (s, 1H), 9.73 (s, 1H), 9.68 (s,1H), 9.60 (s, 1H), 9.44 (s, 1H), 7.69 (d, J = 1.9 Hz, 1H), 7.62 (s, 1H), 7.53(s, 1H), 7.12 (d, J = 8.6 Hz, 1H), 7.04 (dd, J = 8.6, 2.0 Hz, 1H), 4.21 (s, 2H), 4.06 (s, 2H), 3.46 (s, 2H), 3.24 (s, 8H), 2.83 (s, 3H), 2.55 (s, 3H), 2.53 (s, 4H), 2.19 (s, 3H), 2.15 (s, 3H); 13 C NMR (100 MHz, DMSO- d 6): δ 203.69, 203.62, 161.32, 161.26, 161.22, 161.15, 160.97, 136.06, 132.80, 131.90, 131.26, 129.49, 128.37, 116.44, 116.20, 115.47, 114.56, 113.91, 113.37, 113.01, 112.82, 110.77, 109.14, 52.39, 52.36, 51.96, 49.74, 49.66, 40.90, 26.74, 26.70, 20.21, 18.12, 16.87, 16.87. HRMS: calcd for C 35 H 41 N4O7 [M+ H] + , 629.2970; found, 629.2982.

[0026] The structure of the compound shown in Formula IV is as follows: N-(2,3-bis(3-acetyl-2,6-dihydroxy-5-methylbenzyl)-1H-indol-5-yl)-2-(4- methylpiperazin-1-yl)acetamide. Pale yellow solid, yield 27.7%, melting point: 165–167 °C. 1HNMR (400 MHz, DMSO- d 6): δ 13.09 (s, 1H), 13.04 (s, 1H), 10.03 (s, 1H), 9.87 (s, 1H), 9.67 (d, J = 72.5 Hz, 2H), 7.70 (d, J = 2.0 Hz, 1H), 7.61 (s, 1H), 7.54 (s, 1H), 7.35 (d, J = 8.4 Hz, 1H), 6.86 (d, J = 8.4 Hz, 1H), 4.24 (s,2H), 4.08 (s, 2H), 3.83 (s, 2H), 3.65 – 3.17 (m, 8H), 2.85 (s, 3H), 2.55 (s,3H), 2.53 (s, 3H), 2.20 (s, 3H), 2.17 (s, 3H); 13 C NMR (100 MHz, DMSO- d 6): δ 203.75, 203.62, 164.14, 161.24, 161.17, 161.13, 161.09, 135.40, 131.81, 131.24, 125.50, 118.57, 117.84, 116.48, 116.28, 115.55, 114.94, 113.51, 113.00, 112.79, 111.83, 108.99, 102.90, 58.39, 51.10, 49.33, 49.33, 49.04, 42.52, 26.66, 26.66, 20.20, 18.23, 16.86, 16.86. HRMS: calcd for C 35 H 41 N4O7 [M+ H] + , 629.2970; found, 629.2980.

[0027] Experimental Example 1:

[0028] Antiviral activity assay

[0029] Test method: MDCK cells were first infected with H1N1 / PR8 (MOI = 0.1). After removing the viral inoculum, different concentrations of the compound were administered, with three replicates per group. After 48 h of culture, when the virus control group showed obvious cytopathic effects, the cells were fixed with 4% paraformaldehyde for 20 min at room temperature. The paraformaldehyde was then removed, and the cells were stained with 0.1% crystal violet for 30 min. After washing and drying, the absorbance of each well was measured at 570 nm. The toxicity of the PND derivative to MDCK cells was also detected by the MTT assay. Cell viability (%) = (OD value of experimental group - OD value of blank control group) / (OD value of negative control group - OD value of blank control group) × 100%. The above experiments were repeated three times.

[0030] The indole alkaloid PND derivatives prepared in Examples 1 and 2 were subjected to the above tests, and the results are shown in Table 1 and 2. Figure 2 As shown.

[0031] The conventional techniques described in the above embodiments are existing technologies known to those skilled in the art, and therefore will not be described in detail here.

[0032] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims. Attached Figure Description

[0033] Figure 1 Chemical synthesis method of compound Hydroxyclavatol.

[0034] Figure 2 The cytotoxic effects of compounds shown in formulas I, II, III and IV on MDCK cells.

Claims

1. Compounds of formula I, II, III and IV, or pharmaceutically acceptable salts thereof. .

2. A method for chemically synthesizing the compound of claim 1, comprising: Synthetic methods for the compounds shown in Formulas I and II: In a 50 mL round-bottom flask, 5.0 mmol of 5-nitroindole or 6-nitroindole was dissolved in 15 mL of methanol. Then, 10% palladium on carbon was added. The mixture was stirred at 40 °C for 2 h under hydrogen protection. The reaction was monitored by TLC until complete. Residual palladium on carbon was filtered off with diatomaceous earth, and the mixture was concentrated under reduced pressure. The sample was purified by silica gel column chromatography using petroleum ether:ethyl acetate = 1:1 eluent to obtain 5-aminoindole and 6-aminoindole. 0.68 mmol of 5-aminoindole or 6-aminoindole was dissolved in 6 mL of dichloromethane. Then, 1.02 mmol of 3,4,5-trimethoxybenzoyl chloride and 1.36 mmol of triethylamine were slowly added, and the mixture was stirred at room temperature for 0.5 h. The reaction was monitored by TLC until complete. The reaction solution was extracted twice with DCM, the organic phases were combined, washed three times with saturated brine, and the organic layer was dried with anhydrous Na2SO4. The organic phase was concentrated under reduced pressure and separated by silica gel column chromatography with petroleum ether:ethyl acetate = 20:1 to 1:1 to obtain the intermediate product. 0.5 mmol of the intermediate product was reacted with 1.0 mmol of Hydroxyclavatol in toluene solution to carry out a one-step Michael addition reaction. The mixture was stirred at 110 °C for 3-6 h. After the reaction was completed, the product was obtained by direct filtration if a solid precipitated. If no solid precipitated, the solution was concentrated under reduced pressure and recrystallized with ethyl acetate and petroleum ether. The product with a purity still below 95% was purified by silica gel column chromatography. Synthetic methods for the compounds shown in Formulas III and IV: 0.68 mmol of 5-aminoindole or 6-aminoindole was dissolved in 6 mL of dichloromethane, followed by the slow addition of 1.02 mmol of 4-methyl-1-piperazinic acid, then 0.82 mmol of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 0.82 mmol of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride. The mixture was stirred at room temperature for 3–6 h, and TLC was monitored until the starting material showed no further change. The reaction was quenched with water, and the mixture was extracted twice with DCM. The organic phases were combined and dried over anhydrous Na₂SO₄, concentrated under reduced pressure, and separated by silica gel column chromatography with dichloromethane:methanol at a ratio of 40:1 to 10:1 to obtain an intermediate. 0.5 mmol of the intermediate was reacted with 1.0 mmol of Hydroxyclavatol in toluene solution in a one-step Michael addition reaction, and stirred at 110 °C for 3–6 h. h. After the reaction is complete, the product is obtained by direct filtration if a solid is precipitated. If no solid is precipitated, the solution is concentrated under reduced pressure and recrystallized with ethyl acetate and petroleum ether. The product with a purity still below 95% is purified by silica gel column chromatography.

3. Use of the compound of claim 1 in the preparation of antiviral drugs.

Images