Phenanthro[9,10-d]imidazolium quaternary ammonium salt derivatives and their preparation method and antibacterial application

Abstract

The present invention discloses a phenanthro[9,10-d]imidazolium quaternary ammonium salt derivative, its preparation, and antibacterial application. This series of compounds uses phenanthroquinone as a lead compound, and the phenanthroquinone structure is modified to prepare a phenanthro[9,10-d]imidazolium quaternary ammonium salt derivative with novel structure and good antibacterial activity. Its general structural formula is as follows, wherein R is selected from H, C6-C14 alkyl, or C3-C8 olefin group. The phenanthro[9,10-d]imidazolium quaternary ammonium salt derivative prepared by the present invention has a good antibacterial effect on Gram-positive bacteria such as Staphylococcus aureus ATCC 29213 and various clinical methicillin-resistant Staphylococcus aureus (MRSA), while improving water solubility, reducing the biological toxicity of the parent, and having a high yield, and is expected to be further developed into a candidate antibacterial drug in the clinic.

Description

Technical Field

[0001] The present invention belongs to the technical field of phenanthrenequinone derivatives, and particularly relates to phenanthro[9,10-d]imidazolium quaternary ammonium salt derivatives, a preparation method thereof, and antibacterial applications thereof. Background Art

[0002] [9,10-d]Phenanthrenequinone is a type of quinone compound with good biological activities in the medical field, such as antibacterial, anti-tumor, anti-inflammatory, and analgesic properties.

[0003] Phenanthro[9,10-d]imidazole (Phenanthro[9,10-d]imidazole) is composed of a chromophore phenanthroimidazole unit and a bipolar imidazole unit, with a nitrogen-containing heterocyclic structure that has a large conjugated rigid plane. This gives the phenanthroimidazole unit excellent thermodynamic stability and high fluorescence quantum efficiency (A novel bipolar D-π-A type phenanthroimidazole / carbazole hybrid material for high-efficiency nondoped deep-blue organic light-emitting diodes with NTSC CIEy and low efficiency roll-off [J]. Journal of Materials Chemistry C, 2017, 5:11901-11909). Due to its unique chemical structure and properties, it has been widely used in molecular chemistry, organic optoelectronic materials, and has also played a significant role in fluorescent probes.

[0004] In recent years, with the in-depth study of the properties of phenanthroimidazole derivatives, more and more researchers have paid attention to the biological activities of phenanthroimidazole derivatives. Imidazole and its derivatives are an important class of heterocycles, and the introduction of imidazole rings has been widely used in drug discovery. It is reported that various imidazole derivatives have a wide range of biological activities, such as anti-neurodegeneration, anti-inflammatory, anticonvulsant, anti-tumor, anti-tuberculosis, anti-leishmanial, anti-hyperglycemic, anti-aging, antifungal and antibacterial activities (Promising antifungal activity of novel imidazole antifungal drug Luliconazole against Leishmania major: in vitro and in silico studies [J]. Journal of Global Antimicrobial Resistance, 2018, 14: 260-265; Imidazole clubbed 1,3,4-oxadiazole derivatives as potential antifungal agents [J]. Bioorganic & Medicinal Chemistry, 2015, 23 (15): 4172-4180.). However, there are few reports on the antibacterial activity of phenanthroimidazoles, and their water solubility is relatively poor and they have certain biological toxicity. Summary of the Invention

[0005] Purpose of the invention: In response to the above technical problems, the present invention provides a phenanthro[9,10-d]imidazolium quaternary ammonium salt derivative, a preparation method thereof, and an antibacterial application thereof. The phenanthro[9,10-d]imidazolium quaternary ammonium salt derivative has a good antibacterial effect on Gram-positive bacteria such as Staphylococcus aureus ATCC 29213 and various clinically isolated MRSA, and solves the problems of poor water solubility and improved cytotoxicity.

[0006] Technical solution: In order to achieve the above-mentioned purpose of the invention, the technical solution adopted by the present invention is as follows:

[0007] Phenanthro[9,10-d]imidazolium quaternary ammonium salt derivatives, the structural formula of which is shown below:

[0008]

[0009] Wherein, R is selected from H, C6-C14 alkyl or C3-C8 olefin group.

[0010] As a preferred embodiment, the R is selected from H, a C6-C14 single chain alkyl group or a C3-C8 olefin group containing a double bond.

[0011] As a preferred embodiment, the R is selected from H, a C9-C11 single chain alkyl group or a C4-C6 olefin group containing a double bond.

[0012] As the most preferred embodiment, R is selected from the following groups a or b:

[0013]

[0014] The selection of the above groups a and b corresponds to compounds 6a and 6b in the specific embodiment of the present invention, respectively.

[0015] The present invention also provides a method for preparing the phenanthro[9,10-d]imidazolium quaternary ammonium salt derivative, comprising the following steps:

[0016] Step 1: Under acidic conditions, phenanthrenequinone 1 reacts with p-nitrobenzaldehyde 2 to generate intermediate 3;

[0017] Step 2: Intermediate 3 reacts with differently substituted bromoalkanes R-Br under alkaline conditions to generate intermediate 4;

[0018] Step 3, intermediate 4 is reacted with a reducing agent to generate intermediate 5;

[0019] Step 4: Intermediate 5 reacts with iodomethane to obtain the target compound;

[0020]

[0021] Wherein, the R is the same as described above.

[0022] As a specific embodiment, in step 1, the acid in the acidic condition is ammonium acetate, the reaction molar ratio of intermediate 1, p-nitrobenzaldehyde 2 and acid is 1:1:5-1:2:10, the reaction temperature is 90-120°C, and the reaction solvent is acetic acid.

[0023] As a specific embodiment, in step 2, the base in the alkaline conditions is K2CO3, the reaction molar ratio of intermediate 3, bromoalkane R-Br and base is 1:3:3-1:7:7, the reaction temperature is 45-60°C, and the reaction solvent is acetone.

[0024] As a specific embodiment, in step three, the reducing agent is selected from stannous chloride, the reaction molar ratio of the intermediate 4 to the reducing agent is 1:10-1:15, the reaction temperature is 40-78°C, and the reaction solvent is ethyl acetate or ethanol.

[0025] As a specific embodiment, in step 4, the reaction molar ratio of the intermediate 5 to methyl iodide is 1:5-1:10, the reaction temperature is 35-80°C, and the reaction solvent is acetonitrile.

[0026] Finally, the present invention provides the use of the phenanthro[9,10-d]imidazolium quaternary ammonium salt derivatives in the preparation of antimicrobial agents. Preferably, the antimicrobial agent can inhibit Staphylococcus aureus ATCC 29213 and various clinical methicillin-resistant Staphylococcus aureus (MRSA).

[0027] This invention designs and synthesizes phenanthro[9,10-d]imidazolium quaternary ammonium salt derivatives by mimicking the structure and function of antimicrobial peptides. The parent structure in the derivatives acts as a hydrophobic moiety, facilitating insertion of the compound into bacterial phospholipid bilayer membranes. The hydrophilic cationic moiety facilitates interaction with negatively charged bacterial cell membranes. The derivatives can also bind to DNA, disrupting it and causing DNA degradation and damage, leading to bacterial cell death. All target compounds were evaluated for antibacterial activity and demonstrated strong antibacterial activity against Staphylococcus aureus (S. aureus) ATCC 29213 and clinically isolated methicillin-resistant Staphylococcus aureus (MRSA). Their antibacterial values ​​were higher than those of the parent compound, phenanthroquinone, and comparable to the positive control, vancomycin. Their hemolytic activity was also lower than that of the parent compound, phenanthroquinone. The compounds of this invention increase the water solubility of the parent compound, significantly improving toxicity, are less susceptible to drug resistance, and exhibit good stability.

[0028] Technical effect: The phenanthro[9,10-d]imidazole quaternary ammonium salt derivatives prepared by the present invention have good antibacterial effects on Gram-positive bacteria such as Staphylococcus aureus ATCC 29213 and various clinical methicillin-resistant Staphylococcus aureus (MRSA), while also improving water solubility, reducing the biological toxicity of the parent, and having a high yield, and are expected to be further developed into clinical candidate antibacterial drugs. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the dynamic bactericidal curve of compound 6b.

[0030] Figure 2 It is the drug resistance induction of compound 6b.

[0031] Figure 3 The blood routine and blood biochemical indexes of compound 6b in vivo.

[0032] Figure 4 The change of the survival rate of MRSA in the skin of infected mice with compound 6b.

[0033] Figure 5 For compound 6b 1 H-NMR spectrum.

[0034] Figure 6 For compound 6b 13 C-NMR spectrum. DETAILED DESCRIPTION

[0035] The present invention is further described in detail below through examples.

[0036] Example 1 Preparation of Intermediate Compound 3

[0037] In a round-bottom flask, a mixture of phenanthrenequinone 1 and p-nitrobenzaldehyde was dissolved in glacial acetic acid, and an appropriate amount of ammonium acetate was added. After stirring under reflux at 100°C for 1-2 hours, the reaction solution was cooled to room temperature and poured into ice water. The solid was collected by filtration and washed with ice water. The solid was vacuum dried to obtain intermediate 3.

[0038] Example 2 Preparation of Intermediate Compounds 4a and 4b

[0039] In a pear-shaped flask, an acetone solution of intermediate 3 and 1-bromo-n-decane or 1-bromo-3-methyl-2-n-butene was added with KCO and stirred under reflux at 50°C until the reaction was complete. The mixture was spin-dried and extracted with EtOAc. The combined organic phases were dried over anhydrous NaSO, concentrated, and separated by column chromatography to afford intermediates 4a and 4b.

[0040] Example 3 Preparation of Intermediates 5a and 5b

[0041] An appropriate amount of stannous chloride dihydrate was added to an anhydrous ethanol solution of intermediates 4a and 4b in a pear-shaped flask. The mixture was reacted at room temperature and monitored by thin-layer chromatography (TLC) until completion. The solution was then spin-dried, dissolved in a small amount of EtOAc, and the pH was adjusted to neutral with saturated NaHCO₃. The mixture was filtered, extracted with EtOAc, and the organic phases were combined, dried over anhydrous Na₂SO₄, and concentrated to obtain intermediates 5a and 5b.

[0042] Example 4 Preparation of target compounds 6a and 6b

[0043] Intermediates 5a and 5b were weighed separately into a pear-shaped flask, and an appropriate amount of acetonitrile was added to dissolve them. Then, iodomethane was added and the mixture was refluxed at 75°C for 48 h. The reaction was detected by thin layer chromatography (TLC) until completion. The target compounds 6a and 6b were separated by column chromatography.

[0044] Example 5 Compound 6a

[0045] Compound 6a was synthesized using the method described in Example 4. The physicochemical properties of compound 6a are as follows:

[0046] 1) Yellow solid;

[0047] 2) The NMR spectrum of the compound ( 1 H NMR, 400 MHz; 13 C NMR, 100 MHz) characteristics:

[0048] DMSO-d6 was used as solvent, and the peaks were assigned as follows: Yield: 36.4%, yellow solid, 1 H NMR(400MHz DMSO-d6)δ:9.12(d,J=7.6Hz,2H,-Ph),8.77(d,J=4.4Hz,1H,-Ph),8.46(d,J=7.6Hz,1H,- Ph),7.88-7.92(m,4H,-Ph),7.47-7.56(m,2H,-Ph),6.86-6.88(m,2H,-Ph),5.44(s,1H,-C H =CH2),5.30(s,2H,-CH2-),4.28(s3H,N-CH3),1.71(s,3H,-CH3),1.65(s,3H,-CH3); 13 C NMR(100MHz DMSO-d6)δ:152.9,150.8,137.8,132.2,129.1,128.4,127.9,126.4,125.1,124.7,124. 6,122.6,122.5,120.7,120.2,117.8,111.5,105.7,45.3,38.0,25.2,18.1; HRMS(ESI)C 27 H 26 IN3[MI] + calcd=392.2121; found=392.2124.

[0049] Example 6 Compound 6b

[0050] Compound 6b was synthesized using the method described in Example 4. The physicochemical properties of compound 6b are as follows:

[0051] 1) Yellow solid;

[0052] 2) The NMR spectrum of the compound ( 1 H NMR, 400 MHz; 13 C NMR, 100 MHz) characteristics:

[0053] DMSO-d6 was used as solvent, and the peaks were assigned as follows: Yield: 28.3%, yellow solid, 1H NMR (400 MHz DMSO-d6)δ:9.12-9.14(m,2H,-Ph),8.77-8.79(m,1H,-Ph)8.55(d,J=7.6Hz,1 H,-Ph),7.88-7.95(m,4H,-Ph)7.49-7.59(m,2H,-Ph)6.86(d,J=8.8Hz,2H,-P h),6.15(s,2H,-NH2-),4.71(t,J=7.2Hz,2H,-CH2-),4.25(s,3H,N-CH3),1.8 0-1.87(m,2H,-CH2-),1.10-1.23(m,14H,-CH2-),0.81(t,J=7.2Hz,3H,-CH3); 13 C NMR(100MHz DMSO-d6)δ:152.8,150.8,132.2,129.3,129.2,128.7,128.4,127.9,127.8,126.6,124.8,124.7,124.5,122.6,1 22.2,120.8,120.3,113.6,106.0,48.3,37.9,31.2,28.6,28.58,28.5,28.4,28.0,25.1,22.0,13.9; HRMS(ESI)C 32 H 38 IN3[MI] + calcd=464.3060; found=464.3067.

[0054] Application Example 1: In vitro antibacterial activity assay

[0055] 1. Test bacteria:

[0056] Staphylococcus aureus (Staphylococcus aureus ATCC 29213); Escherichia coli (Escherichiacoli ATCC 25922); clinical methicillin-resistant Staphylococcus aureus strains (MRSA 1-10).

[0057] 2. Samples and reagents:

[0058] The samples were: phenanthrenequinone, vancomycin, meropenem, and compounds 6a and 6b prepared in the examples.

[0059] 3. Test method:

[0060] According to the standards of the Clinical Laboratory Standards Institute (CLSI) of the United States, the in vitro antibacterial activities of phenanthrenequinone, compounds 6a and 6b of the present invention, and the clinical antibacterial drug vancomycin were tested using a serial dilution method using a 96-well plate. The drug concentration that produced the smallest completely clear well observed by naked eye was defined as the MIC value.

[0061] Table 1. In vitro antibacterial activity of the phenanthro[9,10-d]imidazolium quaternary ammonium salt derivatives 6a and 6b of the present invention against standard strains (Gram-positive and Gram-negative bacteria) (μg / mL)

[0062]

[0063] Note: 1: phenanthrenequinone, Van: vancomycin, MEM: meropenem, Sa a :Staphylococcus aureus ATCC 29213, M1 d :Micrococcus luteus, Ss c :Streptococcus suis, Ec d :Escherichia coli ATCC 29522, Kp e :Klebsiella pneumoniae 18-227, Kp f : Klebsiella pneumoniae 18-29.

[0064] As can be seen from Table 1: Compounds 6a and 6b both exhibit strong anti-Gram-positive bacteria activity, with MIC values ​​of 0.5-4 μg / mL. They also exhibit good anti-Gram-negative bacteria activity, with MIC values ​​of 8-64 μg / mL. It is noteworthy that compound 6b has the strongest anti-Gram-positive bacteria activity, with an MIC value of 0.5-4 μg / mL. 50 ) to evaluate its toxicity. The results showed that compound 6b exhibited low hemolytic toxicity to sheep erythrocytes, and its HC 50 The selectivity index (SI: HC) was 372.1 μg / mL. 50 The SI (microorganism-specific inhibitory fraction [MICs], for Staphylococcus aureus) is a safe range for determining efficacy. A larger SI indicates a compound's membrane selectivity and a wider safety margin. As shown in Table 1, compound 6b not only exhibits strong antibacterial efficacy but also exhibits good membrane selectivity and safety.

[0065] Table 2. MIC values ​​of phenanthro[9,10-d]imidazolium quaternary ammonium salt derivatives 6a and 6b of the present invention against 10 clinical strains of MRSA

[0066]

[0067] As can be seen from Table 2, compounds 6a and 6b prepared in the present invention exhibited strong anti-MRSA effects, with MIC values ​​of 0.5-2 μg / mL. Compound 6b had the best anti-MRSA effect, with MIC values ​​of 0.5 μg / mL against five clinically isolated MRSA strains. This is comparable to the antibacterial effect of the positive control drug vancomycin, and therefore has the potential to become a clinical antibacterial drug against methicillin-resistant Staphylococcus aureus.

[0068] Application example 2: Time-killing kinetics experiment:

[0069] 1. Test bacteria:

[0070] Staphylococcus aureus ATCC 29213; MRSA-4 (clinical isolate).

[0071] 2. Samples and reagents:

[0072] The samples were: vancomycin and compound 6b prepared in Example.

[0073] 3. Test method:

[0074] The Time-Kill dynamic killing curve of the compound against S. aureus ATCC 29213 and MRSA-4 was determined by the drop plate counting method. Overnight cultured S. aureus and MRSA-4 were diluted 1:10000 into 1 mL of LB medium and cultured (37°C, 200 rpm) until the concentration of the culture reached 1×10 5 CFU / mL. Immediately afterwards, different concentrations of compounds (8×MIC, 4×MIC) and vancomycin (8×MIC) were added to the bacterial solution, and cultured at 37°C, 200rpm. 100 μL of bacterial solution was taken at 0, 0.5, 1, 2, 4, 6, and 8 hours for serial dilution and then counted on MHB agar plates. The bacterial solution was cultured at 37°C for 16-18 hours, the number of colonies was read, and a dynamic killing curve of the logarithm of the number of colonies and time was drawn. The bacterial solution without drug treatment was used as a blank control, and each group was repeated three times. The results are shown in the figure below. Figure 1 shown.

[0075] Figure 1The results showed that at a concentration of 8× the MIC, compound 6b completely killed both S. aureus and MRSA-4 within 0.5-1 hour. The positive control, vancomycin, also showed some bactericidal activity, but only inhibited bacterial growth to a certain extent and failed to completely kill the bacteria. At the same concentration (8× the MIC), compound 6b had a higher bactericidal rate than the positive control, vancomycin. This indicates that 6b has a strong bactericidal effect against both S. aureus ATCC 29213 and MRSA-4, and that the bactericidal effect is concentration-dependent.

[0076] Application Example 3: Drug Resistance Induction Experiment

[0077] 1. Test bacteria:

[0078] Staphylococcus aureus ATCC 29213.

[0079] 2. Samples and reagents:

[0080] The samples were: norfloxacin and compound 9b prepared in Example;

[0081] 3. Test method:

[0082] First, the MIC values ​​of the target compound and the positive control, norfloxacin, were determined using the same testing method as in Application Example 1. Single colonies of Staphylococcus aureus were placed in 1 mL of MHB liquid medium containing a subinhibitory concentration (1 / 2 MIC) of the compound and norfloxacin, and cultured at 200 rpm and 37°C for 3-5 hours. The colonies were then inoculated into LB solid medium containing a subinhibitory concentration (1 / 2 MIC) of the compound and norfloxacin, and cultured in a 37°C incubator for 24 hours. The cultures were cultured for 20 generations, and the MIC changes for each generation were detected.

[0083] Figure 2 The results showed that after culturing Staphylococcus aureus for 20 generations, the MIC value of compound 6b did not change, indicating that 6b is not likely to cause drug resistance in Staphylococcus aureus. In contrast, the positive control drug norfloxacin showed an MIC value increase from 1μg / mL to 128μg / mL at the 15th generation, indicating that norfloxacin can induce bacterial resistance. Application Example 4: In vivo safety evaluation of the compound and in vivo anti-MRSA infection activity test

[0084] 1. Reagents:

[0085] Compound 6b prepared in Example, 0.9% NaCl.

[0086] 2. Test animals

[0087] Healthy SPF-grade KM female mice aged 4-6 weeks, weighing 17-24 g, were purchased from the Experimental Animal Center of Zhengzhou University.

[0088] 3. Test methods

[0089] In vivo acute toxicity experiments are the basis for safety evaluation of compounds in mice. 30 healthy female KM mice aged 4-6 weeks were selected, with 5 mice in each group: blank group (injected with 0.9% NaCl), and drug-treated groups (2.5 mg / kg, 5 mg / kg, 10 mg / kg, 20 mg / kg, 40 mg / kg). The mice were then depilated on their backs, anesthetized 24 hours later, and injected with 60 μL of compound 9b of different concentrations and 0.9% NaCl solution. After 24 hours, the mice were observed to see if they died and if their skin showed abnormalities such as redness, swelling, hardening, and ulcers. The mice in the maximum dose group that did not cause adverse reactions were killed, and blood was collected from the eyeballs, and the skin and tissues of the mice at the drug-treated site were aseptically separated and dissected. Routine blood tests and blood biochemical indicators were performed to evaluate the differences with the blank group. The results are shown in the figure below. Figure 3 shown.

[0090] The results showed that after 24 hours of subcutaneous administration of the compound at different concentrations, the mice were in good mental state and no abnormalities were observed. The survival rate of the mice at different concentrations was 100%. However, at 40 and 20 mg / kg of the compound, the mice had slight redness and swelling on their skin. At 10, 5, and 2.5 mg / kg of the compound, the skin condition was good and no different from the blank group. We sacrificed the mice that received the maximum dose (10 mg / kg) that did not cause adverse reactions, and collected their blood dilutions and serum for routine blood biochemical tests. Figure 2 The results showed that after treatment with 6b (10 mg / kg), all blood biochemical and routine blood count indicators (creatinine, albumin, urea, white blood cells, red blood cells, hematocrit, hemoglobin, mean corpuscular volume, and platelet count) were within normal ranges, virtually identical to those in the blank control group. This suggests that compound 6b has a reasonable in vivo safety profile at ≤10 mg / kg.

[0091] A mouse skin abscess infection model was constructed to evaluate the antibacterial effect of the compound in vivo. 30 KM mice were selected and divided into a blank group (injected with 0.9% NaCl), a control group (injected with MRSA-4 bacterial solution), a high-dose group (injected with MRSA-4 bacterial solution and high-dose compound 6b), a low-dose group (injected with MRSA-4 bacterial solution and low-dose compound 6b), and a positive control group (injected with MRSA-4 bacterial solution and vancomycin). The backs of the mice were depilated. After 24 hours, the mice were anesthetized and MRSA-4 (60 μL, 6×10 8CFU / mL) of bacterial solution was subcutaneously injected into the back of the mice. Two hours later, 60 μL of different concentrations of the compound, vancomycin, and 0.9% NaCl were injected into the infected skin site. Twenty-four hours after administration, the mice were killed by dislocation. The skin tissue of the infected site of the drug-treated mice was dissected and counted using the drop plate count method to evaluate the antibacterial effect of the compound in vivo. Figure 4 shown.

[0092] The results showed that: To further study the in vivo therapeutic effect of 6b, we measured the bacterial survival rate in the skin tissue of infected mice. Figure 4 As shown, the number of MRSA bacteria in the skin of mice was significantly reduced after treatment with vancomycin (2.5 mg / kg) and 6b (2.5 and 5 mg / kg) compared to the control group. Compared with the model, the bacterial survival rate at the infected site of the skin of mice treated with compound 6b (5 mg / kg) was 0.01%. In addition, the bacterial survival rates at the infected site of the skin of mice treated with 6b (2.5 mg / kg) and vancomycin were 0.59% and 8.34%, respectively. It can be seen that the antibacterial effect was more pronounced at a high dose, and both the low-dose and high-dose 6b groups showed more effective in vivo antibacterial effects than vancomycin. These research results indicate that phenanthro[9,10-d]imidazolium quaternary ammonium salt derivatives provide a reference for the development of new antibacterial agents for the treatment of MRSA infections.

Claims

1. Phenanthro[9,10-d]imidazolium quaternary ammonium salt derivatives, the structural formula of which is as follows: in, R is selected from H, C6-C14 monoalkyl or C3-C8 olefin containing one double bond.

2. The phenanthro[9,10-d]imidazolium quaternary ammonium salt derivative according to claim 1, characterized in that The R is selected from H, C9-C11 single chain alkyl or C4-C6 olefin group containing one double bond.

3. The phenanthro[9,10-d]imidazolium quaternary ammonium salt derivative according to claim 1, characterized in that: The R is selected from the following groups a or b:

4. The method for preparing the phenanthro[9,10-d]imidazolium quaternary ammonium salt derivative according to any one of claims 1 to 3, characterized in that: The steps include: Step 1: Under acidic conditions, phenanthrenequinone 1 reacts with p-nitrobenzaldehyde 2 and ammonium acetate to generate intermediate 3; the acid in the acidic conditions is acetic acid; Step 2: Intermediate 3 reacts with differently substituted bromoalkane R-Br under alkaline conditions to generate intermediate 4; the base in the alkaline conditions is K2CO3; Step 3, intermediate 4 is reacted with a reducing agent to generate intermediate 5; the reducing agent is selected from stannous chloride; Step 4: Intermediate 5 reacts with iodomethane to obtain the target compound; Wherein, the R is the same as that described in any one of claims 1-3.

5. The method for preparing a phenanthro[9,10-d]imidazolium quaternary ammonium salt derivative according to claim 4, wherein: In step 1, the reaction molar ratio of the intermediate 1, p-nitrobenzaldehyde 2 and ammonium acetate is 1:1:5-1:2:10, and the reaction temperature is 90-120°C.

6. The method for preparing the phenanthro[9,10-d]imidazolium quaternary ammonium salt derivative according to claim 4, characterized in that: In step 2, the reaction molar ratio of the intermediate 3, the bromoalkane R-Br and the base is 1:3:3-1:7:7, the reaction temperature is 45-60° C., and the reaction solvent is acetone.

7. The method for preparing a phenanthro[9,10-d]imidazolium quaternary ammonium salt derivative according to claim 4, characterized in that: In step 3, the reaction molar ratio of the intermediate 4 to the reducing agent is 1:10-1:15, the reaction temperature is 40-78° C., and the reaction solvent is ethyl acetate or ethanol.

8. The method for preparing a phenanthro[9,10-d]imidazolium quaternary ammonium salt derivative according to claim 4, characterized in that: In step 4, the reaction molar ratio of the intermediate 5 to methyl iodide is 1:5-1:10, the reaction temperature is 35-80° C., and the reaction solvent is acetonitrile.

9. Use of the phenanthro[9,10-d]imidazolium quaternary ammonium salt derivative according to any one of claims 1 to 3 in the preparation of an antibacterial agent.

Images