Honokiol derivative with cationic group, preparation method of honokiol derivative and application of honokiol derivative in preparation of anti-infective drugs

Abstract

The invention belongs to the technical field of honokiol derivatives, and particularly discloses a honokiol derivative with a cationic group, a preparation method of the honokiol derivative and application of the honokiol derivative in preparation of anti-infection drugs. The preparation method comprises the following steps: carrying out amide coupling reaction on a compound 1 and a compound 2 to obtain a compound 3; then carrying out hydrolysis reaction on the compound 3 to obtain a compound 4; performing bromination reaction on the compound 4 to obtain a compound 5; and carrying out nucleophilic substitution reaction on the compound 5 and H-R2 to obtain the honokiol derivative with the cationic group. The micromolecular stimulant prepared by the invention can replicate the core physicochemical and biological characteristics of the antibacterial peptide, also can optimize the pharmacological characteristics, and solves many problems existing when the antibacterial peptide is used as an anti-infective drug.

Description

Technical Field

[0001] This invention relates to the field of magnolol derivatives, and more particularly to a magnolol derivative with a cationic group, its preparation method, and its application in the preparation of anti-infective drugs. Background Technology

[0002] Bacterial infections continue to pose a serious challenge to public health, significantly increasing morbidity and mortality. The overuse and overprescription of traditional antibiotics, coupled with the natural adaptive and evolutionary capabilities of bacteria, have jointly driven the emergence of multidrug-resistant strains, weakening the efficacy of many existing treatments. A Lancet report indicates that the severe burden of antimicrobial resistance (AMR) causes approximately 4.95 million deaths globally each year, with 1.27 million of these deaths directly attributable to drug-resistant infections. This death toll exceeds the combined total of HIV / AIDS and malaria. So-called "superbugs," such as methicillin-resistant Staphylococcus aureus (MRSA), carbapenem-resistant Pseudomonas aeruginosa, vancomycin-resistant enterococci, and multidrug-resistant Acinetobacter baumannii, are now prevalent in healthcare settings and community environments, posing a serious threat to immunocompromised individuals and severely ill patients. Therefore, there is an urgent need to continuously explore innovative treatment strategies and novel chemical agents to combat these persistent infections.

[0003] Faced with this pressing challenge, antimicrobial peptides (AMPs) are increasingly being recognized as a promising alternative anti-infective drug class. As key effector molecules of the innate immune system in many organisms, AMPs are typically short-chain, cationic, amphiphilic peptides composed of 20-50 amino acids. Their mechanism of action often involves targeting the microbial cell membrane, leading to membrane disruption and cell death. This membrane-targeting characteristic, coupled with their broad-spectrum activity against bacteria, fungi, and even viruses, makes AMPs ideal candidates for overcoming traditional drug resistance mechanisms. Unlike conventional antibiotics that act on specific intracellular targets, AMPs typically exert their effects by physically disrupting membrane integrity, a mode of action less likely to induce rapid bacterial resistance. Despite their enormous potential, their clinical translation remains constrained by inherent limitations such as proteolytic instability, high production costs, systemic toxicity, and challenges in large-scale synthesis.

[0004] Therefore, how to prepare a class of small molecule mimics that replicate the core physicochemical and biological properties of AMPs, while optimizing their pharmacological properties, and developing next-generation anti-infective drugs is a pressing problem to be solved in this field. Summary of the Invention

[0005] In view of this, the present invention provides a cationic group and a magnolol derivative thereof, a method for preparing the same, and its application in the preparation of anti-infective drugs, thereby solving many drawbacks of antimicrobial peptides as anti-infective drugs.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A honokiol derivative containing a cationic group, wherein the structural formula of the honokiol derivative containing a cationic group is: ; Among them, R 1 Selected from , , , , , , or ; The R 2 Selected from , or .

[0007] Another object of the present invention is to provide a method for preparing a magnolol derivative with a cationic group, comprising the following steps: 1) Compound 1 and compound 2 were subjected to an amide coupling reaction to obtain compound 3; 2) Compound 3 was hydrolyzed to obtain compound 4; 3) Compound 4 was subjected to bromination to obtain compound 5; 4) Compound 5 and HR 2 Nucleophilic substitution reaction was carried out to obtain magnolol derivatives with cationic groups; Wherein, the structural formula of compound 1 is ; The structural formula of compound 2 is as follows: , where R 1 Selected from , , , , , , or ; The structural formula of compound 3 is as follows: ; The structural formula of compound 4 is as follows: ; The structural formula of compound 5 is as follows: ; The HR 2 R in 2 Selected from , or .

[0008] Preferably, the amide coupling reaction in step 1) is carried out by mixing compound 1, compound 2, organic base, peptide coupling reagent and solvent to perform amide coupling reaction.

[0009] Preferably, the molar ratio of compound 1, compound 2, organic base, and peptide coupling reagent is 1:2~2.6:3~6:2~2.6; The amide coupling reaction takes 6-8 hours. The organic base includes one or more of N,N-diisopropylethylamine, triethylamine, and pyridine; The peptide conjugating reagent includes one or more of HATU, TBTU, and BOP.

[0010] Preferably, the hydrolysis reaction in step 2) involves mixing compound 3 with an alkaline solvent, performing a hydrolysis reaction, and then acidifying to obtain compound 4; The hydrolysis reaction is carried out at a temperature of 60-80℃ for 5-10 hours.

[0011] Preferably, the bromination reaction in step 3) is an Appel-type bromination reaction.

[0012] Preferably, compound 5 in step 4) and HR 2 The molar ratio is 1:8~10; The nucleophilic substitution reaction is carried out at a temperature of 80-100°C for 12-24 hours.

[0013] The preparation method of compound 2 includes: Preferably, R 1 It is obtained by substitution reaction of -NH2 and 4-bromobutylacetic acid ester.

[0014] Preferably, the R 1 The molar ratio of -NH2 to 4-bromobutylacetic acid ester is 1:0.8~1.2; The substitution reaction takes 2-4 hours.

[0015] Another object of the present invention is to provide an application of the cationic group-containing magnolol derivative prepared by the above preparation method in the preparation of anti-infective drugs.

[0016] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects: 1. This invention develops an efficient, mild, and scalable synthetic strategy for the preparation of magnolol derivatives. This route employs a modular design, allowing for the flexible introduction of various cationic groups and hydrophobic side chains, thus providing a universal and reliable synthetic platform for constructing a diverse library of derivatives.

[0017] 2. The derivatives synthesized based on the above method have both strong cationic and amphiphilic structural characteristics, and can exhibit significant antibacterial activity against Gram-positive drug-resistant bacteria, showing good application prospects. Detailed Implementation

[0018] This invention provides a honokiol derivative with a cationic group, the structural formula of which is: ; Among them, R 1 Selected from , , , , , or ; The R 2 Selected from , or .

[0019] This invention also provides a method for preparing a magnolol derivative with a cationic group, comprising the following steps: 1) Compound 1 and compound 2 were subjected to an amide coupling reaction to obtain compound 3; 2) Compound 3 was hydrolyzed to obtain compound 4; 3) Compound 4 was subjected to bromination to obtain compound 5; 4) Compound 5 and HR 2 Nucleophilic substitution reaction was carried out to obtain magnolol derivatives with cationic groups.

[0020] In this invention, the amide coupling reaction in step 1) is carried out by mixing compound 1, compound 2, organic base, peptide coupling reagent and solvent to perform amide coupling reaction.

[0021] In this invention, the molar ratio of compound 1, compound 2, organic base, and peptide coupling reagent is 1:2~2.6:3~6:2~2.6.

[0022] In this invention, the amide coupling reaction time is 6-8 hours, specifically 6.2 hours, 6.5 hours, 6.8 hours, 7 hours, 7.2 hours, 7.5 hours, and 7.8 hours.

[0023] In this invention, the organic base includes one or more of N,N-diisopropylethylamine (DIPEA), triethylamine, and pyridine; In this invention, the peptide coupling reagent includes one or more of HATU (O-(7-azabenzotriazol-1-yl)-N,N,N',N'-tetramethylurea hexafluorophosphate), TBTU (1-[bis(dimethylamino)methylene]-1H-benzotriazolium 3-oxide tetrafluoroborate), and BOP (((1H-benzo[d][1,2,3]triazol-1-yl)oxy)tris(dimethylamino)phosphonium hexafluorophosphate).

[0024] In this invention, the solvent for the amide coupling reaction is preferably acetonitrile, and the amount added is sufficient to provide a reaction site for the amide coupling reaction.

[0025] In this invention, the hydrolysis reaction in step 2) involves mixing compound 3 with an alkaline solvent to carry out the hydrolysis reaction, followed by acidification to obtain compound 4.

[0026] In this invention, the alkaline solvent is preferably a methanol / water mixture containing sodium hydroxide.

[0027] In this invention, the temperature of the hydrolysis reaction is 60~80℃, specifically 62℃, 65℃, 68℃, 70℃, 72℃, 75℃, or 78℃; the time is 5~10h, specifically 6h, 7h, 8h, or 9h.

[0028] In this invention, the bromination reaction in step 3) is an Appel-type bromination reaction.

[0029] In this invention, compound 5 described in step 4) and HR 2 The molar ratio is 1:8~10, preferably 1:8.5~9.5, and more preferably 1:9; the HR 2 This is an excessive amount.

[0030] In this invention, the temperature of the nucleophilic substitution reaction is 80~100℃, specifically 85℃, 90℃, or 95℃; the reaction time is 12~24 hours, specifically 14h, 15h, 16h, 18h, 21h, or 22h.

[0031] In this invention, R 1 It is obtained by substitution reaction of -NH2 and 4-bromobutylacetic acid ester.

[0032] In this invention, the R 1 The molar ratio of -NH2 to 4-bromobutylacetic acid ester is 1:0.8~1.2, preferably 1:0.9~1.1, and more preferably 1:1.

[0033] In this invention, the substitution reaction time is 2 to 4 hours, specifically 2.2 hours, 2.5 hours, 2.8 hours, 3 hours, 3.2 hours, 3.5 hours, or 3.8 hours; the reaction temperature is preferably 25°C.

[0034] The present invention also provides the application of the cationic group-containing magnolol derivative prepared by the above preparation method in the preparation of anti-infective drugs.

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] The preparation method of compound 1 used in all embodiments of the present invention is as follows (this preparation method is not considered a limitation of the present invention): ... (5.63 mmol) and potassium carbonate (14.08 mmol) were mixed in anhydrous DMF (8 mL), and excess ethyl bromoacetate (16.89 mmol) was added. The mixture was then stirred at 65 °C for 8 h. After standard post-treatment and rapid chromatographic purification, the product was obtained. (1.93 g, 78%) Will (3.42 mmol) and sodium hydroxide (34.20 mmol) were dissolved in 50 mL of methanol-water mixed solvent and reacted at 60 °C for 5 h. After removing methanol, the solution was acidified to pH 3 with hydrochloric acid, filtered and dried to obtain compound 1 (1.11 g, 85%). .

[0037] Examples 1-24

[0038] The products prepared in Examples 1-24 of this invention are designated as 6A-6X, and their structural formulas are as follows: The reaction process is as follows:

[0039] The specific preparation method is as follows: 27.34 mmol R 1 -NH2 was placed in dry CH2Cl2 (30 ml), then 27.34 mmol of 4-bromobutylacetic acid and 30.07 mmol of triethylamine were added, and the mixture was stirred at 25 °C for 2–4 hours until the reaction was complete. After removing the solvent, the crude product was directly subjected to rapid column chromatography (CH2Cl / MeOH) to give compound 2 in yields ranging from 32% to 66%.

[0040] Based on the R of compound 2 1for , , , , , , , The corresponding compounds are denoted as 2A~2H.

[0041]

[0042] Compounds 2A-2H were subjected to amide coupling reactions with compound 1, respectively, to obtain the corresponding compounds 3A-3H. The specific reactions are as follows: Compound 1 (5 mmol), 2A~2H (11 mmol), DIPEA (25 mmol [1.1][xw1.2]), HATU (11 mmol) and acetonitrile (50 mL) were mixed and reacted at 25 °C for 6~8 hours. After the reaction was complete, the solvent was removed by concentration under reduced pressure. 30 mL of ethyl acetate was added to the residue, and the mixture was extracted successively with dilute hydrochloric acid, 5% sodium bicarbonate and saturated brine. The organic phase was dried over anhydrous sodium sulfate and the solvent was removed by concentration under reduced pressure. The residue was separated by silica gel column chromatography to obtain compounds 3A~3H, with yields of 47%~78%.

[0043]

[0044] 2 mmol of compounds 3A–3H were each mixed with 20 mL of methanol / water solution and 10 mmol of sodium hydroxide, and stirred at 60 °C for 5–10 hours. The mixture was then concentrated to remove methanol, and the pH was adjusted to 3 with hydrochloric acid. The aqueous phase was then extracted with ethyl acetate. The organic extract was dried and concentrated to give crude compounds 4A–4H, which were used directly in the next step.

[0045]

[0046] 1.5 mmol of compounds 4A-4H and 3 mmol of carbon tetrabromide were dissolved in dry dichloromethane (15 ml) and mixed with 3 mmol of triphenylphosphine. The mixture was reacted at 0 °C for 15 min and then at room temperature for 4-6 h. The solvent was removed, and the resulting solid was extracted with ethyl acetate and water. Finally, the solid was purified by silica gel thin-layer chromatography to obtain compounds 5A-5H in yield of 67-85%.

[0047]

[0048] 0.5 mmol of compounds 5A~5H and excess HR were respectively added. 2(5 mmol) was placed in 10 ml of acetonitrile and reacted at 80 °C for 12–24 h. After removing the solvent, the crude product was ground with anhydrous diethyl ether. The resulting solid was filtered to obtain cationic honokiol derivatives with a purity of 55–81%, denoted as 6A–6X.

[0049] 6A~6X of R 1 and R 2 The options are as follows:

[0050] For example, R in 6A 1 for R 2 for ;6E of R 1 for R 2 for .

[0051]

[0052] The 1H NMR data for 6A~6X are as follows:

[0053] The antibacterial properties of 6A-6X were tested according to the Clinical and Laboratory Standards Institute (CLSI) standards, using the microbroth dilution method to determine the minimum inhibitory concentration (MIC) of the derivatives. First, single colonies of activated bacterial strains were picked and inoculated into LB broth, and cultured at 37°C and 200 rpm with shaking for 4 hours. An appropriate amount of bacterial suspension was collected by centrifugation at 3500 rpm and 4°C for 5 minutes. The supernatant was discarded, and the cells were washed three times with sterile PBS buffer, then resuspended in PBS and adjusted to a concentration of approximately 1.0 × 10⁻⁶ using a bacterial turbidimeter. 8 CFU / mL, then diluted to 1.0 × 10⁻⁶ with LB liquid medium. 6CFU / mL was prepared for use. In a clean bench, a 256 μg / mL stock solution of the compound was prepared with sterile water. In a 96-well plate, 200 μL of LB liquid medium was added to the twelfth well as a blank control, and 200 μL of compound dilution or positive control solution was added to the first well, with two replicates per group. Using a two-fold dilution method, 100 μL of solution was transferred from the first well to the second well using a multichannel pipette, mixed, and then serially diluted to the eleventh well, discarding 100 μL from that well. At this point, the compound concentrations in each well were 128, 64, 32, 16, 8, 4, 2, 1, 0.5, and 0.25 μg / mL (DMSO concentration ≤1%). Subsequently, 100 μL of the prepared bacterial culture was added to each well in each of the first to eleventh wells. The 96-well plate was incubated at 37°C for 18 hours, and the results were observed. When the blank control well grows normally, the positive control results meet expectations, and bacterial growth in the sample well is completely inhibited starting from a certain concentration, the corresponding compound concentration of that well is the MIC value.

[0054] The test results are shown in Table 1: Table 1. Antibacterial properties of compounds 6A-6X

[0055] As shown in Table 1, most of the compounds obtained in this invention exhibited significant inhibitory activity against the tested Gram-positive bacteria, including methicillin-sensitive and methicillin-resistant Staphylococcus aureus, Enterococcus faecalis, and vancomycin-resistant Enterococcus faecalis. The MIC values ​​of most compounds were in the μg / mL range. Several lead compounds (6D, 6E, 6P, etc.) showed activity comparable to the positive control drug vancomycin, and even demonstrated superior efficacy against vancomycin-resistant strains (Enterococcus faecalis 51299). Compound 6E exhibited the best antibacterial activity, showing activity against a range of tested Gram-positive strains (including Staphylococcus aureus). 25923, Staphylococcus aureus 43300, Enterococcus faecalis Compound 6E exhibited potent and broad-spectrum activity against *Enterococcus faecalis* 29212, *Enterococcus faecalis* 51299, and *Bacillus subtilis* 9372, with a minimum inhibitory concentration (MIC) range of 1–4 μg / mL. Furthermore, compound 6E also showed moderate activity against Gram-negative bacteria *Acinetobacter baumannii* 19606 (MIC = 8 μg / mL), *Escherichia coli* 25922 (MIC = 16 μg / mL), and *Pseudomonas aeruginosa* 27853 (MIC = 32 μg / mL).

[0056] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0057] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A honokiol derivative with a cationic group, characterized in that, The structural formula of the magnolol derivative containing cationic groups is as follows: ； Among them, R 1 Selected from , , , , , or ; The R 2 Selected from , or .

2. The method for preparing a cationic group and magnolol derivative according to claim 1, characterized in that, Includes the following steps: 1) Compound 1 and compound 2 were subjected to an amide coupling reaction to obtain compound 3; 2) Compound 3 was hydrolyzed to obtain compound 4; 3) Compound 4 was subjected to bromination to obtain compound 5; 4) Compound 5 and HR 2 Nucleophilic substitution reaction was carried out to obtain magnolol derivatives with cationic groups; Wherein, the structural formula of compound 1 is ; The structural formula of compound 2 is as follows: , where R 1 Selected from , , , , , , or ; The structural formula of compound 3 is as follows: ; The structural formula of compound 4 is as follows: ; The structural formula of compound 5 is as follows: ; The HR 2 R in 2 Selected from , or .

3. The method for preparing a cationic group and magnolol derivative according to claim 2, characterized in that, The amide coupling reaction described in step 1) involves mixing compound 1, compound 2, an organic base, a peptide coupling reagent, and a solvent to carry out the amide coupling reaction.

4. The method for preparing a cationic group and magnolol derivative according to claim 3, characterized in that, The molar ratio of compound 1, compound 2, organic base, and peptide coupling reagent is 1:2~2.6:3~6:2~2.6; The amide coupling reaction takes 6-8 hours. The organic base includes one or more of N,N-diisopropylethylamine, triethylamine, and pyridine; The peptide conjugating reagent includes one or more of HATU, TBTU, and BOP.

5. The method for preparing a cationic group and magnolol derivative according to claim 4, characterized in that, The hydrolysis reaction described in step 2) involves mixing compound 3 with an alkaline solvent, carrying out the hydrolysis reaction, and then acidifying to obtain compound 4; The hydrolysis reaction is carried out at a temperature of 60-80℃ for 5-10 hours.

6. The method for preparing a cationic group and magnolol derivative according to claim 5, characterized in that, The bromination reaction described in step 3) is an Appel-type bromination reaction.

7. The method for preparing a cationic group and magnolol derivative according to claim 6, characterized in that, Compound 5 described in step 4) and HR 2 The molar ratio is 1:8~10; The nucleophilic substitution reaction is carried out at a temperature of 80-100°C for 12-24 hours.

8. A method for preparing a magnolol derivative with a cationic group according to any one of claims 2 to 7, characterized in that, The preparation method of compound 2 includes: R 1 It is obtained by substitution reaction of -NH2 and 4-bromobutylacetic acid ester.

9. The method for preparing a cationic group and magnolol derivative according to claim 8, characterized in that, The R 1 The molar ratio of -NH2 to 4-bromobutylacetic acid ester is 1:0.8~1.2; The substitution reaction takes 2-4 hours.

10. The use of the cationic group-containing magnolol derivative prepared by the preparation method according to any one of claims 2 to 9 in the preparation of anti-infective drugs.

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