Binuclear macrocyclic metronidazole metal complex as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of organic compounds, and particularly relates to a binuclear macrocyclic metronidazole metal complex as well as a preparation method and application thereof. The preparation method comprises the following steps: (1) carrying out reflux reaction on 2-pyridine formylhydrazine, potassium hydroxide and carbon disulfide to prepare 5-(pyridine-2-yl)-1, 3, 4-oxadiazole-2-thiol; (2) respectively carrying out primary reflux on metronidazole, triethylamine and p-toluenesulfonyl chloride, and then carrying out secondary reflux on metronidazole and potassium iodide, so as to prepare 1-(2-iodoethyl)-2-methyl-5-nitro-1H-imidazole; and (3) carrying out reflux reaction on products prepared in the steps (1) and (2), and dissolving in an organic solvent containing silver salt to prepare the binuclear macrocyclic metronidazole metal complex. According to the binuclear macrocyclic metronidazole metal complex disclosed by the invention, the antibacterial effect of the current metronidazole metal complex can be further improved; the preparation method is simple and easy to implement, purification is convenient, and the prepared product is good in stability in air.

Description

Technical Field

[0001] The invention belongs to the technical field of organic compounds, and specifically relates to a binuclear macrocyclic metronidazole metal complex and a preparation method and application thereof. Background Art

[0002] Due to its unique chemical configuration and functional properties, the binuclear macrocyclic structure has shown significant advantages in the antibacterial field. First, the synergistic effect of the bimetallic center can enhance its binding ability with biological targets. For example, binuclear metal complexes of transition metals such as copper can destroy bacterial membrane structures or interfere with nucleic acid metabolism through antiferromagnetic coupling effects or redox activity. Secondly, the geometric configuration of the macrocyclic skeleton is characterized by high stability, which provides better molecular design for the overall complex and allows the directional modification of functional groups (such as sulfide bridges and sulfone groups). For example, the sulfone derivatives formed by oxidation of the sulfide-bridged Schiff base macrocycle have significantly improved antibacterial activity compared to the unmodified structure. In addition, some binuclear macrocyclic metal complexes exhibit broad-spectrum inhibition against standard strains of Gram-positive and Gram-negative bacteria. For example, some binuclear macrocyclic zinc complexes have an inhibition zone of 17 mm against Escherichia coli in the paper diffusion method. These characteristics make this type of binuclear macrocyclic zinc complexes potential in the treatment of biofilms and bacterial infections. These research cases show that in the field of antibacterial drugs, researchers can further explore the synergistic mechanism of metal types and functional groups in binuclear macrocyclic structures in the future to develop highly effective and low-toxic antibacterial drugs. Aziza, S.; Hadariah, B.; Bibi, S.;, Anila, A.; Sajjad, B.; Yatimah, AMJM2023, 19(3), 333-347; Liu Huan, Liu Yu, Zhang Xuemei, Pan Zhiquan, Gao Juan. Synthesis, properties and antibacterial activity of asymmetric macrocyclic binuclear copper complexes [J]. Chemical Research and Application, 2019, 31: 314; Wang Yishou. Preparation and post-modification reaction of nitrogen heterocyclic metal carbene macrocycles and molecular cages [D]. Northwest University, 2021. The above three documents disclose the application research of binuclear macrocyclic structures in the fields of antibacterial and medicine.

[0003] 1,3,4-oxadiazole is a five-membered heterocyclic compound with a wide range of applications in the medical field, such as antibacterial, anti-inflammatory and anti-tumor. On the basis of maintaining the integrity of the metronidazole skeleton, the side chain alcohol hydroxyl group of metronidazole was modified using 1,3,4-oxadiazole to successfully synthesize a binuclear macrocyclic metronidazole derivative. Compared with metronidazole, the antibacterial activity of this derivative is significantly improved. Mohsin, M.; Nadia, H. Iran J Med Sci.2023,48,167-175; Sylvia, AS;Neli, E.; Maya, G.; Svetlana, F.; Emilia, G. Scr. Sci. Pharm.2021,8(2),38-44, the above documents disclose the application research of metronidazole derivatives in the antibacterial and medical fields.

[0004] Metal ions maintain a complex and delicate dynamic balance in the body and participate in regulating various physiological processes. Silver ions have become a commonly used bactericide due to their unique bactericidal mechanism and wide application fields. Existing studies have coordinated metronidazole derivatives with metal ions to form binary complexes, and used the synergistic effect of metal ions to enhance their antibacterial activity. For example, Rolf, B.; Arne, B.; Bianka, K.; Mark, B.; Till, S.; Ingo, OJ Biol. Inorg. Chem. 2024, 29, 511-518, which discloses the application research of metronidazole metal complexes in the medical field.

[0005] However, existing binuclear macrocyclic metal complexes still have many shortcomings in antibacterial properties. Bacteria often excrete drugs through efflux pumps or degrade drug molecules through enzymes. If binuclear macrocyclic complexes lack designs to counteract such mechanisms, the biofilm formed by bacteria can hinder the penetration of the complexes. Existing studies rarely involve how to improve permeability through structural modification. In addition, there is a lack of multi-target action design. Existing studies mostly focus on a single action mechanism (such as membrane destruction or DNA binding), while bacteria can escape through multiple pathways. If binuclear complexes do not integrate multi-target synergy, they are easily adapted by bacteria.

[0006] Based on the above shortcomings, in response to the increasingly serious problem of antibiotic resistance, more new antibacterial drugs based on metal complexes need to be developed to meet the challenges of bacterial infections. Summary of the invention

[0007] The purpose of the present invention is to provide a binuclear macrocyclic metronidazole metal complex to further enhance the antibacterial effect of current metronidazole metal complexes; the present invention also provides a preparation method and application, the preparation method is easy to obtain and easy to purify, and the prepared binuclear macrocyclic metronidazole metal complex has good stability in the air.

[0008] To achieve the above object, the technical solution adopted by the present invention is: The binuclear macrocyclic metronidazole metal complex of the present invention has the following structural formula: .

[0009] Where: X1 = SbF6 - When X2=CH2Cl2; or X1=NO3 - When X2=0; or X1=OSO2CF3 - , X2=0.

[0010] The method for preparing the binuclear macrocyclic metronidazole metal complex of the present invention comprises the following steps: (1) dissolving 2-pyridinecarboxylic acid hydrazide and potassium hydroxide in an organic solvent, adding liquid carbon disulfide dropwise for reflux reaction, removing the organic solvent after the reaction, adding water for filtration to obtain a filtrate, and acidifying the filtrate to obtain 5-(pyridin-2-yl)-1,3,4-oxadiazole-2-thiol; (2) dissolving metronidazole, triethylamine and p-toluenesulfonyl chloride in an organic solvent, mixing and then subjecting to reflux reaction. After the reaction is completed, filtering and washing to obtain 4-(3-(2-methyl-5-nitro-1H-imidazol-1-yl)propyl)benzenesulfonate; (3) Dissolving 4-(3-(2-methyl-5-nitro-1H-imidazol-1-yl)propyl)benzenesulfonate and potassium iodide in an organic solvent respectively, and after being uniformly dissolved, performing a reflux reaction, filtering and concentrating to obtain 1-(2-iodoethyl)-2-methyl-5-nitro-1H-imidazole; (4) Mix 5-(pyridin-2-yl)-1,3,4-oxadiazole-2-thiol with potassium hydroxide, an organic solvent, and 1-(2-iodoethyl)-2-methyl-5-nitro-1H-imidazole, perform reflux reaction, and filter to obtain 2-((2-(2-methyl-5-nitro-1H-imidazole-1-yl)ethyl)thio)-5-(pyridin-2-yl)-1,3,4-oxadiazole; (5) Dissolve 2-((2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)thio)-5-(pyridin-2-yl)-1,3,4-oxadiazole in solvent A, and dissolve a silver salt in solvent B. Mix the two solutions and keep them in the dark to obtain a binuclear macrocyclic metronidazole metal complex; wherein the silver salt is one of silver nitrate, silver hexafluoroantimonate or silver trifluoromethanesulfonate.

[0011] in: In the step (1), the organic solvent is methanol, and the dosage ratio of 2-pyridinecarboxylic acid hydrazide, potassium hydroxide, carbon disulfide, and organic solvent is 1:1.5:10:7, wherein 2-pyridinecarboxylic acid hydrazide, potassium hydroxide, and carbon disulfide are measured in mmol, and the organic solvent is measured in mL.

[0012] In the step (1), the reflux reaction time is 5 to 7 hours; the addition time of liquid carbon disulfide is 15 to 20 minutes; and the pH of the acidified filtrate is 3 to 5.

[0013] In the step (2), the organic solvent is dichloromethane, and the dosage ratio of metronidazole, triethylamine, p-toluenesulfonyl chloride and the organic solvent is 1:1.2:1.2:(1-1.3), wherein the metronidazole, triethylamine and p-toluenesulfonyl chloride are measured in mmol, and the organic solvent is measured in mL.

[0014] In the step (3), the organic solvent is acetone, and the dosage ratio of 4-(3-(2-methyl-5-nitro-1H-imidazol-1-yl)propyl)benzenesulfonate, potassium iodide and organic solvent is 1:1.5:(2.5-3), wherein 4-(3-(2-methyl-5-nitro-1H-imidazol-1-yl)propyl)benzenesulfonate and potassium iodide are measured in mmol, and the organic solvent is measured in mL.

[0015] In the step (4), the organic solvent is methanol, and the amount ratio of 5-(pyridin-2-yl)-1,3,4-oxadiazole-2-thiol, potassium hydroxide, 1-(2-iodoethyl)-2-methyl-5-nitro-1H-imidazole and the organic solvent is 1:1:2:(4-5), wherein 5-(pyridin-2-yl)-1,3,4-oxadiazole-2-thiol, potassium hydroxide and 1-(2-iodoethyl)-2-methyl-5-nitro-1H-imidazole are measured in mmol, and the organic solvent is measured in mL.

[0016] In the step (5), solvent A is dichloromethane, solvent B is methanol; the usage ratio of 2-((2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)thio)-5-(pyridin-2-yl)-1,3,4-oxadiazole, silver salt, solvent A, and solvent B is 1:(1-2):100:100, wherein 2-((2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)thio)-5-(pyridin-2-yl)-1,3,4-oxadiazole and silver salt are in mmol, and solvent A and solvent B are in mL; and the standing time is 5-7 days.

[0017] In the step (2), the reflux reaction time is 20-26 hours, and the reflux reaction temperature is 39-40°C; in the step (3), the reflux reaction time is 20-25 hours, and the reflux reaction temperature is 52-56°C; in the step (4), the reflux reaction time is 20-24 hours, and the reflux reaction temperature is 76-84°C.

[0018] Application of the binuclear macrocyclic metronidazole metal complex of the present invention: using it in the preparation of antibacterial drugs.

[0019] Reaction equation of the present invention is as follows: ; Where: X1 = SbF6 - , X2=CH2Cl2; or X1=NO3 - , X2=0; or X1=OSO2CF3 - , X2=0.

[0020] The beneficial effects of the present invention are as follows: (1) Through nucleophilic substitution reaction, two rigid groups of metronidazole and oxadiazole are spliced ​​to obtain a semi-rigid metronidazole spliced ​​oxadiazole derivative 2-((2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)thio)-5-(pyridin-2-yl)-1,3,4-oxadiazole, which has multiple strong coordination sites and is easy for metal ions to undergo self-assembly reactions. The semi-rigid structure of the molecule is easy to form cyclic compounds. The nucleophilic substitution reaction is easy to operate, has a low incidence of side reactions, and has a high yield.

[0021] (2) Metronidazole is clinically used for gingivitis, periodontitis, acute pericoronitis, bacterial vaginitis, peritonitis and other diseases caused by anaerobic bacteria, but its antibacterial effect on aerobic bacteria or facultative anaerobes is difficult to meet the antibacterial needs after bacterial infection; 5-(pyridin-2-yl)-1,3,4-oxadiazole-2-thiol has poor antibacterial activity. Examples 1 to 3 have no effect on Gram-positive bacteria (such as Staphylococcus aureus, S. aureus ), Gram-negative bacteria (such as Escherichia coli, E. coli ) showed good antibacterial activity, IC 50 The value range is 8.01~13.7µg / mL, which brings more possibilities for designing new antibacterial drugs to overcome bacterial resistance.

[0022] (3) The binuclear central silver ions in Examples 1 to 3 exert antibacterial effects by disrupting bacterial DNA replication and transcription. The binuclear macrocyclic structure enhances the biocompatibility of silver ions, making it easy for them to enter the bacteria and exert antibacterial effects. The antibacterial activities of the three examples are better than those of the positive control group. E. coli , Example IC 50The value is about 40~50% of the positive control group. S. aureus , Example IC 50 The value was approximately 57~65% of the positive control group.

[0023] (4) The preparation method of the binuclear macrocyclic metronidazole metal complex described in the present invention is simple and easy, convenient for purification, and has good stability in air.

[0024] (5) 2-((2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)thio)-5-(pyridin-2-yl)-1,3,4-oxadiazole is subjected to self-assembly reaction with silver nitrate, silver hexafluoroantimonate, and silver trifluoromethanesulfonate in a mixed solvent system of dichloromethane and methanol to obtain a macrocyclic binuclear structure. The present invention synthesizes a binuclear macrocyclic metronidazole metal complex by bridging a metal silver ion with an oxadiazole-modified metronidazole derivative in the form of a thioether bond, and utilizes the synergistic effect of binuclear metal silver, metronidazole derivatives, and macrocyclic structure: The binuclear macrocyclic structure has a higher degree of conformational freedom. This flexibility allows the nitroimidazole core of metronidazole to adjust its conformation and precisely insert into the DNA base pairs through binuclear multi-target binding, forming a stable embedding effect, inhibiting the bacterial DNA repair mechanism (such as SOS response) or target mutation (such as DNA helix conformation change) escape effect.

[0025] The introduction of thioether bonds will change the polarity of the molecule and reduce the recognition of traditional drugs such as metronidazole and silver metal by bacterial efflux pumps (such as AcrB-TolC), thereby inhibiting the efflux effect and effectively killing bacteria.

[0026] The thioether bond bridge form allows the active structure of metronidazole, the nitroimidazole structure, to be retained. Its nitro group (-NO2) can be activated by bacterial nitroreductase in an anaerobic environment to generate free radicals to attack DNA, maintaining a specific killing effect on anaerobic bacteria. The synergy with silver ions enables the drug to have both broad-spectrum (aerobic bacteria) and specific (anaerobic bacteria) antibacterial capabilities.

[0027] (6) Through the unique binuclear macrocyclic framework of the present invention, through semi-rigid geometric constraints and electronic effect transmission, it cooperates with binuclear silver metal: Under the premise of the thioether bond providing spatial conformational freedom, the ring skeleton fixes two Ag groups through the coplanar arrangement of the oxadiazole ring and the pyridine group. + The spacing of the ions is stabilized within a plane spacing (Examples 1-3), close to the hydrophobic core thickness of the bacterial membrane phospholipid bilayer, thereby optimizing the membrane insertion ability and maximizing the dual-core Ag + The macrocyclic framework forces the two Ag +The antiparallel spin arrangement is formed through the sulfur bridge (-S-), and the antiferromagnetic coupling effect is higher than that of the traditional flexible binuclear macrocyclic metal complex system. The antiferromagnetic coupling transfers electrons through the π-conjugated system (oxadiazole ring) of the macrocycle, thereby increasing the superoxide radical (O2· - ) generation rate. Superoxide radicals attack bacterial cell membrane lipids, triggering lipid peroxidation, and synergistically disrupt bacterial DNA replication and transcription with binuclear Ag⁺, covering multiple targets and accelerating the destruction of cell membrane integrity.

[0028] The conjugated system of the oxadiazole ring can interact with the phospholipid layer of the bacterial membrane through π-π stacking, thereby improving the transmembrane permeation efficiency of the complex. At the same time, the N and O heteroatoms of the oxadiazole ring provide additional coordination sites to bind Ag. + Form a stable five-membered chelate ring, enhance the electron density of the metal center, and promote Ag + The synergistic effect of the two allows the drug to quickly pass through the target on the surface of the bacterial membrane and penetrate across the membrane, minimizing the release window of hydrolases such as β-lactamase, an enzyme associated with bacterial resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the infrared spectrum of the binuclear macrocyclic metronidazole metal complex of Example 1; Figure 2 This is the infrared spectrum of the binuclear macrocyclic metronidazole metal complex of Example 2; Figure 3 This is the infrared spectrum of the binuclear macrocyclic metronidazole metal complex of Example 3. DETAILED DESCRIPTION

[0030] The present invention is specifically described and illustrated below in conjunction with embodiments.

[0031] The instruments used for detection in the examples are: Perkin-Elmer 240C elemental analyzer, Nicolet iS50 Fourier transform infrared spectrometer, Bruker Smart Apex CCD single crystal diffractometer and BioRad 550 microplate reader, etc.

[0032] Example 1 The preparation method of 2-((2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)thio)-5-(pyridin-2-yl)-1,3,4-oxadiazole silver nitrate is as follows: (1) Dissolve 2-pyridinecarboxylic acid hydrazide (1.38 g, 10 mmol) and KOH (0.84 g, 15 mmol) in 70 ml of methanol and stir evenly. Cool the suspension to 0 °C and add liquid carbon disulfide (6.04 mL, 100 mmol) dropwise for 15 min. After the addition is complete, heat and reflux for 6 h. Cool to room temperature overnight and remove the solvent under reduced pressure. Add an appropriate amount of ice water and filter. Add dilute hydrochloric acid to the filtrate to adjust the pH to 5. Filter and obtain 1.56 g of white powder 5-(pyridin-2-yl)-1,3,4-oxadiazole-2-thiol. Analysis showed that the structure was correct and the yield was 87.05%.

[0033] (2) Metronidazole (8.557 g, 50 mmol), triethylamine (8.34 mL, 60 mmol), and p-toluenesulfonyl chloride (11.439 g, 60 mmol) were added to a round-bottom flask, and 50 mL of dichloromethane was added. The mixture was heated to 39°C and refluxed for 24 h. A white precipitate was precipitated. The precipitate was filtered and the residual triethylamine was washed off with dilute hydrochloric acid. The residual p-toluenesulfonyl chloride was washed off with ethanol. Finally, 12.67 g of a white solid compound 4-(3-(2-methyl-5-nitro-1H-imidazol-1-yl)propyl)benzenesulfonate was obtained. Analysis showed that the structure was correct and the yield was 78.13%.

[0034] (3) 4-(3-(2-methyl-5-nitro-1H-imidazol-1-yl)propyl)benzenesulfonate (6.505 g, 20 mmol) and potassium iodide (4.98 g, 30 mmol) were added to a round-bottom flask, and 50 ml of acetone was added as a solvent. The mixture was heated at 56°C for 24 h and then refluxed. After the reaction was completed, the insoluble potassium iodide was filtered out, the solvent was concentrated, and the product 1-(2-iodoethyl)-2-methyl-5-nitro-1H-imidazole (4.55 g) was obtained. The analysis showed that the structure was correct and the yield was 80.95%.

[0035] (4) 5-(Pyridin-2-yl)-1,3,4-oxadiazole-2-thiol (0.895 g, 5 mmol) and potassium hydroxide (0.28 g, 5 mmol) were added to a round-bottom flask, 25 mL of methanol was added to dissolve the raw materials, and then 1-(2-iodoethyl)-2-methyl-5-nitro-1H-imidazole (2.8 g, 10 mmol) was added. The mixture was heated to reflux at 80°C for 24 h. After the reaction was completed, the precipitate was filtered to obtain the final product, 2-((2-(2-methyl-5-nitro-1H-imidazole-1-yl)ethyl)thio)-5-(pyridin-2-yl)-1,3,4-oxadiazole, 1.26 g, as a yellow solid. Analysis showed that the structure was correct and the yield was 75.82%.

[0036] (5) Silver nitrate (0.0085 g, 0.05 mmol) was dissolved in 5 ml of methanol solution, and then slowly dripped into 5 ml of dichloromethane solution containing 2-((2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)thio)-5-(pyridin-2-yl)-1,3,4-oxadiazole (0.0166 g, 0.05 mmol). The solution was kept at room temperature for 7 days away from light. 17.36 mg of colorless crystals appeared. The crystals were filtered and washed three times with dichloromethane. The crystals were dried in an anhydrous calcium chloride desiccator to obtain a binuclear macrocyclic metronidazole metal complex with a yield of 69.13%. The results of infrared and elemental analysis showed that the structure was correct. The data are as follows: Infrared (KBr, cm -1 ): 3640, 3457, 3110, 3065, 3023, 1740, 1638, 1608, 1551, 1475, 1429, 1378, 1327, 1266, 1190, 1160, 1120, 1090, 1037, 1016, 971, 879, 830, 796, 743, 717, 702, 659, 574, 505; infrared spectrum as shown Figure 1 shown.

[0037] Elemental analysis results: calculated value (%): C, 31.06; H, 2.42; N, 19.50; S, 6.41 Found value (%): C, 31.09; H, 2.41; N, 19.52; S, 6.38.

[0038] The structural formula of 2-((2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)thio)-5-(pyridin-2-yl)-1,3,4-oxadiazole silver nitrate is as follows: The molecular formula, properties, yield and other properties of the above complexes are shown in Table 1.

[0039] Example 2 The preparation method of 2-((2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)thio)-5-(pyridin-2-yl)-1,3,4-oxadiazole silver hexafluoroantimonate is as follows: In step (1), the liquid carbon disulfide is added for 18 minutes, and after the dropwise addition is completed, the mixture is heated to reflux for 5 hours, and dilute hydrochloric acid is added to the filtrate to adjust the pH to 3; in step (2), the dichloromethane is 60 mL, the reflux reaction time is 26 hours, and the reflux reaction temperature is 39° C.; in step (3), the acetone is 60 mL, the reflux reaction time is 25 hours, and the reflux reaction temperature is 52° C.; in step (4), the methanol is 24 mL, the reflux reaction time is 20 hours, and the reflux reaction temperature is 76° C.; the remaining steps are the same as in Example 1.

[0040] (5) Silver hexafluoroantimonate (0.0172 g, 0.05 mmol) was dissolved in 5 ml of methanol solution, and then slowly dripped into 5 ml of dichloromethane solution containing 2-((2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)thio)-5-(pyridin-2-yl)-1,3,4-oxadiazole (0.0166 g, 0.05 mmol). The solution was kept away from light for 6 days, and 21.6 mg of colorless crystals appeared. The crystals were filtered, washed three times with dichloromethane, and dried in an anhydrous calcium chloride desiccator to obtain a binuclear macrocyclic metronidazole metal complex with a yield of 61.96%. The results of infrared and elemental analysis showed that the structure was correct. The data are as follows: Infrared (KBr, cm -1 ): 3566, 3163, 2940, 2832, 1611, 1553, 1513, 1465, 1428, 1389, 1369, 1294, 1268, 1190, 1156, 1124, 1089, 1023, 870, 831, 795, 742, 704, 659; infrared spectrum as shown Figure 2 shown.

[0041] Elemental analysis results: calculated value (%): C, 22.49; H, 1.88; N, 12.09; S, 4.63; found value (%): C, 22.83; H, 1.81; N, 12.05; S, 4.6.

[0042] The structural formula of 2-((2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)thio)-5-(pyridin-2-yl)-1,3,4-oxadiazole silver hexafluoroantimonate is as follows: The molecular formula, properties, yield and other properties of the above complexes are shown in Table 1.

[0043] Example 3 The preparation method of 2-((2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)thio)-5-(pyridin-2-yl)-1,3,4-oxadiazole trifluoromethanesulfonate silver is as follows: In step (1), the liquid carbon disulfide is added for 20 minutes, and after the dropwise addition is completed, the mixture is heated to reflux for 7 hours, and dilute hydrochloric acid is added to the filtrate to adjust the pH to 4; in step (2), the dichloromethane is 65 mL, the reflux reaction time is 20 hours, and the reflux reaction temperature is 40° C.; in step (3), the acetone is 55 mL, the reflux reaction time is 20 hours, and the reflux reaction temperature is 54° C.; in step (4), the methanol is 20 mL, the reflux reaction time is 22 hours, and the reflux reaction temperature is 84° C.; the remaining steps are the same as in Example 1.

[0044] (5) Silver trifluoromethanesulfonate (0.0257 g, 0.1 mmol) was dissolved in 5 ml of methanol solution, and then slowly dripped into 5 ml of dichloromethane solution containing 2-((2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)thio)-5-(pyridin-2-yl)-1,3,4-oxadiazole (0.0166 g, 0.05 mmol). The solution was kept away from light for 5 days, and 19.75 mg of colorless crystals appeared. The crystals were filtered, washed three times with dichloromethane, and dried in an anhydrous calcium chloride desiccator to obtain a binuclear macrocyclic metronidazole metal complex with a yield of 67.03%. The results of infrared and elemental analysis showed that the structure was correct. The data are as follows: Infrared (KBr, cm -1 ): 3523, 3142, 3083, 2987, 2945, 1608, 1550, 1462, 1428, 1371, 1253, 1224, 1190, 1163, 1122, 1090, 1027, 885, 830, 795, 742, 704, 676, 635, 572, 517; infrared spectrum as shown Figure 3 shown.

[0045] Elemental analysis results: calculated value (%): C, 28.51; H, 2.07; N, 14.25; S, 10.9; found value (%): C, 28.54; H, 2.05; N, 14.26; S, 10.88.

[0046] The structural formula of 2-((2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)thio)-5-(pyridin-2-yl)-1,3,4-oxadiazole silver trifluoromethanesulfonate is as follows: The molecular formula, properties, yield and other properties of the above complexes are shown in Table 1.

[0047]

[0048] Next, the binuclear macrocyclic metronidazole metal complex obtained in Example 1-3 was characterized: Single crystal diffraction experiment: Mo-Ka (λ=0.071073nm) rays were used in ω / 2θ scanning mode at 25℃. The data were obtained through SAINT correction, Lorentz correction and elimination of polarization effects. Absorption correction was supplemented by Bruker's SADABS. The molecular structure was directly solved using SHELXL-97. The positions of metal atoms and the atoms connected to them were measured using the direct E-maps method, and the fine structures of other non-hydrogen atoms were gradually determined through Fourier transformation and least squares correction. The hydrogen atoms were finally determined at the calculated positions and had a unified U isoThe test results are shown in Table 2.

[0049]

[0050] a R1=S||C|-|F c || / SF o |. b wR2=[Sw(F o 2 -F c 2 ) 2 / Sw(F o 2 )] 1 / 2 .

[0051] Comparative Example 1 Metronidazole was used to replace the binuclear macrocyclic metronidazole metal complex prepared in Example 1. Metronidazole was used in antibacterial experiments. The results are shown in Table 3.

[0052] Comparative Example 2 The 5-(pyridin-2-yl)-1,3,4-oxadiazole-2-thiol in the present invention is replaced with 4-amino-5-(p-tolyl)-4H-1,2,4-triazole-3-thiol to synthesize 3-((2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)thio)-5-(p-tolyl)-4H-1,2,4-triazole-4-amine. The structural formula of 4-amino-5-(p-tolyl)-4H-1,2,4-triazole-3-thiol is as follows: , The remaining steps and raw materials were the same as those in Example 1 to obtain a product, which was used in antibacterial experiments. The results are shown in Table 3.

[0053] Comparative Example 3 2-((2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)thio)-5-(pyridin-2-yl)-1,3,4-oxadiazole was synthesized according to steps (1) to (4) of Example 1, without performing step (5). The final product was used for antibacterial experiments. The results are shown in Table 3.

[0054] The present invention uses infrared, elemental analysis (C, H, N, S), and X-ray single crystal diffraction to characterize and confirm the structure of the binuclear macrocyclic metronidazole metal complex. The binuclear macrocyclic metronidazole metal complex of the present invention has strong antibacterial activity, and the half inhibition concentration IC 50 The values ​​are shown in Table 3.

[0055] The binuclear macrocyclic metronidazole metal complexes obtained in Examples 1 to 3 were subjected to IC 50 Value determination experiment.

[0056] Test methods and steps: Add 6 mL of LB liquid culture medium to a 12 mL shake tube, then use a pipette to accurately aspirate 100 µL of bacterial solution and inoculate it into the shake tube. Then place them together in a constant temperature shaking incubator, set the culture conditions to 37°C and 200 rpm, and continue culturing until the bacterial solution reaches the logarithmic growth phase. The resulting bacterial solution can be used for subsequent experiments.

[0057] The experiment was divided into an experimental group (examples and comparative examples), a negative control group and a positive control group, and 6 concentration gradients were set for each example and comparative example in the experimental group and the positive control group, and 20 μL of bacterial solution and 160 μL of LB culture medium were added to the experimental group, the negative control group and the positive control group, respectively.

[0058] Afterwards, 20 µL of sterile distilled water was added to the negative control group; kanamycin was added to the positive control group, and the total liquid volume less than 200 µL was made up with sterile distilled water to a final kanamycin concentration of 30 µg / mL, 20 µg / mL, 10 µg / mL, 3 µg / mL, 2 µg / mL, and 1 µg / mL; the solutions of the prepared products were added to the 6 concentration gradients of each embodiment and comparative example, and the total liquid volume less than 200 µL was made up with sterile distilled water to a final product concentration of 30 µg / mL, 20 µg / mL, 10 µg / mL, 3 µg / mL, 2 µg / mL, and 1 µg / mL, and cultured at 37 ° C in a constant temperature incubator for 6 hours, and the OD value was detected by an enzyme reader at a wavelength of 600 nm, and the IC was calculated using graphpad nonlinear fitting. 50 value.

[0059]

[0060] From Table 3, we can see that E. coli and S. aureus Two bacteria, Example 1, prepared IC of binuclear macrocyclic metronidazole metal complex 50 The value is smaller than that of the comparative example and the positive control group, indicating that the binuclear macrocyclic metronidazole metal complex of the present invention has better antibacterial activity than metronidazole (Comparative Example 1), non-oxadiazole modified metronidazole derivatives (Comparative Example 2) and non-binuclear macrocyclic structure compounds (Comparative Example 3).

Claims

1. A binuclear macrocyclic metronidazole metal complex, characterized in that: The structural formula is as follows: ； Where: X1 = SbF6 - When X2=CH2Cl2; or X1=NO3 - When X2=0; or X1=OSO2CF3 - , X2=0.

2. A method for preparing the binuclear macrocyclic metronidazole metal complex according to claim 1, characterized in that: The following steps are involved: (1) dissolving 2-pyridinecarboxylic acid hydrazide and potassium hydroxide in an organic solvent, adding liquid carbon disulfide dropwise for reflux reaction, removing the organic solvent after the reaction, adding water for filtration to obtain a filtrate, and acidifying the filtrate to obtain 5-(pyridin-2-yl)-1,3,4-oxadiazole-2-thiol; (2) dissolving metronidazole, triethylamine and p-toluenesulfonyl chloride in an organic solvent, mixing and then subjecting to reflux reaction. After the reaction is completed, filtering and washing to obtain 4-(3-(2-methyl-5-nitro-1H-imidazol-1-yl)propyl)benzenesulfonate; (3) Dissolving 4-(3-(2-methyl-5-nitro-1H-imidazol-1-yl)propyl)benzenesulfonate and potassium iodide in an organic solvent respectively, and after being uniformly dissolved, performing a reflux reaction, filtering and concentrating to obtain 1-(2-iodoethyl)-2-methyl-5-nitro-1H-imidazole; (4) Mix 5-(pyridin-2-yl)-1,3,4-oxadiazole-2-thiol with potassium hydroxide, an organic solvent, and 1-(2-iodoethyl)-2-methyl-5-nitro-1H-imidazole, perform reflux reaction, and filter to obtain 2-((2-(2-methyl-5-nitro-1H-imidazole-1-yl)ethyl)thio)-5-(pyridin-2-yl)-1,3,4-oxadiazole; (5) Dissolve 2-((2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)thio)-5-(pyridin-2-yl)-1,3,4-oxadiazole in solvent A, and dissolve a silver salt in solvent B. Mix the two solutions and keep them in the dark to obtain a binuclear macrocyclic metronidazole metal complex; wherein the silver salt is one of silver nitrate, silver hexafluoroantimonate or silver trifluoromethanesulfonate.

3. The method for preparing the binuclear macrocyclic metronidazole metal complex according to claim 2, characterized in that: In step (1), the organic solvent is methanol, and the dosage ratio of 2-pyridinecarboxylic acid hydrazide, potassium hydroxide, carbon disulfide and organic solvent is 1:1.5:10:7, wherein 2-pyridinecarboxylic acid hydrazide, potassium hydroxide and carbon disulfide are measured in mmol, and the organic solvent is measured in mL.

4. The method for preparing the binuclear macrocyclic metronidazole metal complex according to claim 2, characterized in that: In step (1), the reflux reaction time is 5 to 7 hours; the addition time of liquid carbon disulfide is 15 to 20 minutes; and the pH of the acidified filtrate is 3 to 5.

5. The method for preparing the binuclear macrocyclic metronidazole metal complex according to claim 2, characterized in that: In step (2), the organic solvent is dichloromethane, and the dosage ratio of metronidazole, triethylamine, p-toluenesulfonyl chloride and the organic solvent is 1:1.2:1.2:(1-1.3), wherein the metronidazole, triethylamine and p-toluenesulfonyl chloride are measured in mmol, and the organic solvent is measured in mL.

6. The method for preparing the binuclear macrocyclic metronidazole metal complex according to claim 2, characterized in that: In step (3), the organic solvent is acetone, and the amount ratio of 4-(3-(2-methyl-5-nitro-1H-imidazol-1-yl)propyl)benzenesulfonate, potassium iodide and organic solvent is 1:1.5:(2.5-3), wherein 4-(3-(2-methyl-5-nitro-1H-imidazol-1-yl)propyl)benzenesulfonate and potassium iodide are measured in mmol, and the organic solvent is measured in mL.

7. The method for preparing the binuclear macrocyclic metronidazole metal complex according to claim 2, characterized in that: In step (4), the organic solvent is methanol, and the amount ratio of 5-(pyridin-2-yl)-1,3,4-oxadiazole-2-thiol, potassium hydroxide, 1-(2-iodoethyl)-2-methyl-5-nitro-1H-imidazole and the organic solvent is 1:1:2:(4~5), wherein 5-(pyridin-2-yl)-1,3,4-oxadiazole-2-thiol, potassium hydroxide and 1-(2-iodoethyl)-2-methyl-5-nitro-1H-imidazole are measured in mmol, and the organic solvent is measured in mL.

8. The method for preparing the binuclear macrocyclic metronidazole metal complex according to claim 2, characterized in that: In step (5), solvent A is dichloromethane, solvent B is methanol; the amount ratio of 2-((2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)thio)-5-(pyridin-2-yl)-1,3,4-oxadiazole, silver salt, solvent A, and solvent B is 1:(1-2):100:100, wherein 2-((2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)thio)-5-(pyridin-2-yl)-1,3,4-oxadiazole and silver salt are measured in mmol, and solvent A and solvent B are measured in mL; and the standing time is 5-7 days.

9. The method for preparing the binuclear macrocyclic metronidazole metal complex according to claim 2, characterized in that: In step (2), the reflux reaction time is 20-26 h, and the reflux reaction temperature is 39-40° C.; in step (3), the reflux reaction time is 20-25 h, and the reflux reaction temperature is 52-56° C.; in step (4), the reflux reaction time is 20-24 h, and the reflux reaction temperature is 76-84° C.

10. Use of the binuclear macrocyclic metronidazole metal complex according to claim 1, characterized in that: Used in the preparation of antibacterial drugs.

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