Binuclear macrocyclic metronidazole metal complex and its preparation method and application

Abstract

The present invention belongs to the technical field of organic compounds, and specifically relates to a binuclear macrocyclic metronidazole metal complex and its preparation method and application. The preparation method: (1) 2-Pyridinecarboxylic hydrazide, potassium hydroxide and carbon disulfide are subjected to a reflux reaction to obtain 5-(pyridin-2-yl)-1,3,4-oxadiazole-2-thiol; (2) Metronidazole is subjected to a first reflux with triethylamine and p-toluenesulfonyl chloride respectively, and then subjected to a second reflux with potassium iodide to obtain 1-(2-iodoethyl)-2-methyl-5-nitro-1H-imidazole; (3) The products obtained in (1) and (2) are subjected to a reflux reaction, and then dissolved in an organic solvent containing a silver salt to obtain a binuclear macrocyclic metronidazole metal complex. The binuclear macrocyclic metronidazole metal complex of the present invention can further improve the antibacterial effect of the current metronidazole metal complex; and the preparation method is simple and easy to operate, convenient for purification, and the obtained product has good stability in the air.

Description

Technical Field

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

[0002] Due to its unique chemical configuration and functional characteristics, the binuclear macrocyclic structure has shown significant advantages in the antibacterial field. First, the synergistic effect of the bimetallic centers can enhance its binding ability to biological targets. For example, binuclear metal complexes of transition metals such as copper can disrupt the bacterial membrane structure or interfere with nucleic acid metabolism through antiferromagnetic coupling effects or redox activities. Second, the geometric configuration of the macrocyclic skeleton has the characteristic of high stability, providing better molecular designability for the overall complex and allowing for the directed modification of functional groups (such as sulfur bridges, sulfone groups). For example, the antibacterial activity of sulfone derivatives formed by the oxidation of sulfur-bridged Schiff base macrocycles is significantly improved compared to the unmodified structure. In addition, some binuclear macrocyclic metal complexes show broad-spectrum inhibition against standard strains of Gram-positive and Gram-negative bacteria. For example, the inhibition zone of some binuclear macrocyclic zinc complexes against Escherichia coli reaches 17 mm in the disk diffusion method. These characteristics make such binuclear macrocyclic zinc complexes have potential in the treatment of anti-biofilm and bacterial infections. These research cases show that in the field of antibacterial drugs, researchers can further explore the synergistic action mechanism of metal types and functional groups in the binuclear macrocyclic structure in the future to develop antibacterial drugs with high efficiency and low toxicity. Aziza, S.; Hadariah, B.; Bibi, S.;, Anila, A.; Sajjad, B.; Yatimah, A.M. J.M. 2023, 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 research of azacyclic metal carbene macrocycles and molecular cages [D]. Northwest University, 2021. The above three literatures disclose the application research of binuclear macrocyclic structures in the antibacterial and pharmaceutical fields.

[0003] 1,3,4-oxadiazole is a five-membered heterocyclic compound with extensive applications in the medical field, such as antibacterial, anti-inflammatory, and anti-tumor effects. On the basis of maintaining the integrity of the metronidazole skeleton, 1,3,4-oxadiazole was used to modify the alcohol hydroxyl group of the metronidazole side chain, and a binuclear macrocyclic metronidazole derivative was successfully synthesized. Compared with metronidazole, the antibacterial activity of this derivative was significantly improved. Mohsin, M.; Nadia, H. Iran J Med Sci. 2023, 48, 167-175; Sylvia, A. S.; Neli, E.; Maya, G.; Svetlana, F.; Emilia, G. Scr. Sci. Pharm. 2021, 8(2), 38-44. The above-mentioned literature discloses 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 the regulation of various physiological processes. Silver ions have become commonly used bactericides due to their unique bactericidal mechanism and extensive application fields. Existing studies have coordinated metronidazole derivatives with metal ions to form binary complexes and enhanced their antibacterial activity through the synergistic effect of metal ions. For example, Rolf, B.; Arne, B.; Bianka, K.; Mark, B.; Till, S.; Ingo, O. J. Biol. Inorg. Chem. 2024, 29, 511-518. This literature discloses the application research of metronidazole metal complexes in the medical field.

[0005] However, there are still many drawbacks in the antibacterial properties of existing binuclear macrocyclic metal complexes. Bacteria often expel drugs through efflux pumps or degrade drug molecules through enzymes. If the binuclear macrocyclic complexes lack designs to counter such mechanisms, the biofilms formed by bacteria can hinder the penetration of the complexes, and existing research rarely involves how to improve penetration through structural modification; in addition, there is a lack of multi-target action design. Existing research mainly focuses on a single mechanism of action (such as membrane disruption or DNA binding), while bacteria can escape through multiple pathways. If the binuclear complexes do not integrate multi-target synergistic effects, they are easily adapted by bacteria.

[0006] Based on the above-mentioned many drawbacks and in response to the increasingly serious problem of antibiotic resistance, it is necessary to develop more novel antibacterial drugs based on metal complexes to address the challenges of bacterial infections. Summary of the Invention

[0007] The object of the present invention is to provide a binuclear macrocyclic metronidazole metal complex to further enhance the antibacterial effect of the current metronidazole metal complex; the present invention also provides a preparation method and application, the conditions of the preparation method are easy to obtain and convenient for purification, 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:

[0009] The binuclear macrocyclic metronidazole metal complex described in the present invention has the following structural formula:

[0010] 。

[0011] Wherein: when X1 = SbF6 - , X2 = CH2Cl2; or when X1 = NO3 - , X2 = 0; or when X1 = OSO2CF3 - , X2 = 0.

[0012] The preparation method of the binuclear macrocyclic metronidazole metal complex described in the present invention includes the following steps:

[0013] (1) Dissolve 2-pyridinecarboxylic hydrazide and potassium hydroxide in an organic solvent, dropwise add liquid carbon disulfide for reflux reaction, after the reaction is completed, remove the organic solvent, add water and filter to obtain a filtrate, acidify the filtrate to obtain 5-(pyridin-2-yl)-1,3,4-oxadiazole-2-thiol;

[0014] (2) Dissolve metronidazole, triethylamine, and p-toluenesulfonyl chloride in an organic solvent, mix well and carry out a reflux reaction, after the reaction is completed, filter and wash to obtain 4-(3-(2-methyl-5-nitro-1H-imidazol-1-yl)propyl)benzenesulfonate;

[0015] (3) Dissolve 4-(3-(2-methyl-5-nitro-1H-imidazol-1-yl)propyl)benzenesulfonate and potassium iodide in an organic solvent respectively, after dissolving evenly, carry out a reflux reaction, filter and concentrate to obtain 1-(2-iodoethyl)-2-methyl-5-nitro-1H-imidazole;

[0016] (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, carry out a reflux reaction, and filter to obtain 2-((2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)thio)-5-(pyridin-2-yl)-1,3,4-oxadiazole;

[0017] (5) Dissolve 2 - ((2 - (2 - methyl - 5 - nitro - 1H - imidazol - 1 - yl)ethyl)sulfanyl)-5-(pyridin - 2 - yl)-1,3,4 - oxadiazole in solvent A, dissolve the silver salt in solvent B, mix the above two solutions and let stand in the dark to obtain the binuclear macrocyclic metronidazole metal complex; the silver salt is one of silver nitrate, silver hexafluoroantimonate or silver trifluoromethanesulfonate.

[0018] Among them:

[0019] In the step (1), the organic solvent is methanol, and the dosage ratio of 2 - pyridinecarboxylic hydrazide, potassium hydroxide, carbon disulfide and the organic solvent is 1:1.5:10:7, where 2 - pyridinecarboxylic hydrazide, potassium hydroxide and carbon disulfide are in mmol, and the organic solvent is in mL.

[0020] In the step (1), the reflux reaction time is 5 - 7 h; the addition time of liquid carbon disulfide is 15 - 20 min; the pH of the filtrate acidification is 3 - 5.

[0021] 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), where metronidazole, triethylamine and p - toluenesulfonyl chloride are in mmol, and the organic solvent is in mL.

[0022] 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 the organic solvent is 1:1.5:(2.5 - 3), where 4-(3-(2 - methyl - 5 - nitro - 1H - imidazol - 1 - yl)propyl)benzenesulfonate and potassium iodide are in mmol, and the organic solvent is in mL.

[0023] In the step (4), the organic solvent is methanol, and the dosage 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), where 5-(pyridin - 2 - yl)-1,3,4 - oxadiazole - 2 - thiol, potassium hydroxide and 1-(2 - iodoethyl)-2 - methyl - 5 - nitro - 1H - imidazole are in mmol, and the organic solvent is in mL.

[0024] In the step (5), the solvent A is dichloromethane and the solvent B is methanol; the dosage 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; the standing time is 5-7 days.

[0025] In the step (2), the reflux reaction time is 20-26 h and the reflux reaction temperature is 39-40 °C; in the step (3), the reflux reaction time is 20-25 h and the reflux reaction temperature is 52-56 °C; in the step (4), the reflux reaction time is 20-24 h and the reflux reaction temperature is 76-84 °C.

[0026] The application of the binuclear macrocyclic metronidazole metal complex of the present invention: It is used for the preparation of antibacterial drugs.

[0027] The reaction equation of the present invention is as follows:

[0028] ;

[0029] Wherein: X1 = SbF6 - , X2 = CH2Cl2; or X1 = NO3 - , X2 = 0; or X1 = OSO2CF3 - , X2 = 0.

[0030] The beneficial effects of the present invention are as follows:

[0031] (1) Through nucleophilic substitution reaction, two rigid groups 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 ligand sites, is easy for metal ions to carry out self-assembly reaction, and due to the semi-rigid structure of the molecule, it is easy to form cyclic compounds. The nucleophilic substitution reaction is easy to operate, the incidence of side reactions is low, and the yield is high.

[0032] (2) Metronidazole is clinically used for diseases such as gingivitis, periodontitis, acute pericoronitis, bacterial vaginitis, peritonitis, etc. caused by anaerobic bacteria, but the antibacterial effect against aerobic or facultative anaerobic bacteria is difficult to meet the antibacterial requirements after bacterial infection; the antibacterial activity of 5-(pyridin-2-yl)-1,3,4-oxadiazole-2-thiol is poor. Examples 1-3 have good antibacterial effects against Gram-positive bacteria (such as Staphylococcus aureus, S. aureus), Gram-negative bacteria (such as Escherichia coli, E. coli ) all showed good antibacterial activity, and the IC 50 values ranged from 8.01 to 13.7 μg / mL, bringing more possibilities for designing new antibacterial drugs to overcome bacterial drug resistance.

[0033] (3) The dinuclear center silver ions in Examples 1 to 3 exerted antibacterial effects by disrupting bacterial DNA replication and transcription. The dinuclear macrocyclic structure enhanced the biocompatibility of silver ions, making it easy to enter bacteria to exert antibacterial effects. The antibacterial activities of the three examples were all superior to the positive control group. For E. coli , the IC 50 value of the example was about 40-50% of the positive control group. For S. aureus , the IC 50 value of the example was about 57-65% of the positive control group.

[0034] (4) The preparation method of the dinuclear macrocyclic metronidazole metal complex described in the present invention is simple and easy to implement, convenient for purification, and has good stability in the air.

[0035] (5) 2-((2-(2-Methyl-5-nitro-1H-imidazol-1-yl)ethyl)thio)-5-(pyridin-2-yl)-1,3,4-oxadiazole undergoes self-assembly reactions with silver nitrate, silver hexafluoroantimonate, and silver trifluoromethanesulfonate in a dichloromethane and methanol mixed solvent system to obtain a macrocyclic dinuclear structure. In the present invention, metal silver ions and metronidazole derivatives modified with oxadiazole are synthesized into a dinuclear macrocyclic metronidazole metal complex in the form of a thioether bond bridge. Utilizing the synergistic effects of dinuclear metal silver, metronidazole derivatives, and the macrocyclic structure:

[0036] The dinuclear macrocyclic structure has a higher conformational freedom. This flexibility allows the nitroimidazole core of metronidazole to adjust its conformation, and through the dinuclear multi-target binding method, it can accurately insert between DNA base pairs to form a stable intercalation effect, inhibiting the DNA repair mechanism (such as SOS response) or target mutation (such as DNA helix conformation change) escape effect of bacteria.

[0037] The introduction of the thioether bond will change the molecular polarity, 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.

[0038] The thioether bond bridge form enables the retention of the active structure nitroimidazole structure of metronidazole. Its nitro group (-NO2) can be activated by bacterial nitroreductase in an anaerobic environment to generate free radicals to attack DNA, maintaining the specific killing effect on anaerobic bacteria. The synergy with silver ions endows the drug with both broad-spectrum (aerobic bacteria) and specific (anaerobic bacteria) antibacterial capabilities.

[0039] (6) Through the unique binuclear macrocyclic skeleton of the present invention, through semi-rigid geometric constraints and electron effect transfer, and in synergy with binuclear silver metal:

[0040] On the premise that the thioether bond provides conformational freedom, the ring skeleton fixes the two Ag ions through the coplanar arrangement of the oxadiazole ring and the pyridine group + The spacing of the ions is stabilized within a planar spacing (Examples 1 to 3), approaching the hydrophobic core thickness of the bacterial membrane phospholipid bilayer, thereby optimizing the membrane insertion ability and maximizing the synergistic oxidation effect of binuclear Ag + The macrocyclic skeleton forces the two Ag + to form an anti-parallel spin arrangement through a 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, increasing the generation rate of superoxide radicals (O2· - ). Superoxide radicals attack the lipids of the bacterial cell membrane, triggering lipid peroxidation, and synergize with the destruction of bacterial DNA replication and transcription by binuclear Ag⁺ to cover multiple targets and accelerate the destruction of cell membrane integrity.

[0041] The conjugated system of the oxadiazole ring can interact with the bacterial membrane phospholipid layer through π-π stacking, improving the transmembrane penetration efficiency of the complex. At the same time, the N and O heteroatoms of the oxadiazole ring provide additional coordination sites, forming a stable five-membered chelate ring with Ag + to enhance the electron density of the metal center and promote the electron transfer of Ag + to the bacterial target. The two work together, enabling the drug to quickly respond to the targets on the bacterial membrane surface and penetrate across the membrane, minimizing the release window of bacterial resistance-related enzymes such as β-lactamase. Description of the Drawings

[0042] Figure 1 It is the infrared spectrum of the binuclear macrocyclic metronidazole metal complex in Example 1;

[0043] Figure 2 It is the infrared spectrum of the binuclear macrocyclic metronidazole metal complex in Example 2;

[0044] Figure 3 It is the infrared spectrum of the binuclear macrocyclic metronidazole metal complex in Example 3. Detailed Embodiments

[0045] The present invention will be specifically described and illustrated below with reference to the examples.

[0046] 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, BioRad 550 microplate reader, etc.

[0047] Example 1

[0048] The preparation method of silver nitrate complex of 2-((2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)thio)-5-(pyridin-2-yl)-1,3,4-oxadiazole is as follows:

[0049] (1) Dissolve 2-pyridinecarboxylic hydrazide (1.38 g, 10 mmol) and KOH (0.84 g, 15 mmol) in 70 ml of methanol, stir evenly, cool the suspension to 0 °C, dropwise add liquid carbon disulfide (6.04 mL, 100 mmol) over 15 min, heat under reflux for 6 h after dropping, cool to room temperature overnight, remove the solvent under reduced pressure, add an appropriate amount of ice water, filter, adjust the pH of the filtrate to 5 with dilute hydrochloric acid, and filter to obtain 1.56 g of white powder 5-(pyridin-2-yl)-1,3,4-oxadiazole-2-thiol. Analysis shows that the structure is correct and the yield is 87.05%.

[0050] (2) Add metronidazole (8.557 g, 50 mmol), triethylamine (8.34 mL, 60 mmol), and p-toluenesulfonyl chloride (11.439 g, 60 mmol) to a round-bottom flask, add 50 mL of dichloromethane, heat to reflux at 39 °C for 24 h, a white precipitate will form, filter the precipitate, wash away the residual triethylamine with dilute hydrochloric acid, and then wash away the residual p-toluenesulfonyl chloride with ethanol. Finally, 12.67 g of white solid compound 4-(3-(2-methyl-5-nitro-1H-imidazol-1-yl)propyl)benzenesulfonate is obtained. Analysis shows that the structure is correct and the yield is 78.13%.

[0051] (3) Add 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) to a round-bottom flask, add 50 ml of acetone as the solvent, then heat under reflux at 56 °C for 24 h. After completion, filter out the insoluble potassium iodide, concentrate the solvent, and filter to obtain 4.55 g of product 1-(2-iodoethyl)-2-methyl-5-nitro-1H-imidazole. Analysis shows that the structure is correct and the yield is 80.95%.

[0052] (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 under reflux at 80 °C for 24 h. After the reaction was completed, the precipitate was filtered, and finally 1.26 g of the final product, yellow solid 2-((2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)thio)-5-(pyridin-2-yl)-1,3,4-oxadiazole, was obtained. Analysis showed that the structure was correct, and the yield was 75.82%.

[0053] (5) Silver nitrate (0.0085 g, 0.05 mmol) was dissolved in 5 mL of methanol solution, and then it was slowly added dropwise to 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 mixture was allowed to stand in the dark at room temperature for 7 days, and 17.36 mg of colorless crystals appeared. The crystals were filtered and washed three times with dichloromethane, and then dried in a desiccator containing anhydrous calcium chloride to obtain the binuclear macrocyclic metronidazole metal complex, with a yield of 69.13%. It was verified by infrared and elemental analysis. The results showed that the structure was correct, and the data were as follows:

[0054] 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; The infrared spectrum was as Figure 1 shown.

[0055] Elemental analysis results: Calculated values (%): C, 31.06; H, 2.42; N, 19.50; S, 6.41. Measured values (%): C, 31.09; H, 2.41; N, 19.52; S, 6.38.

[0056] The structural formula of silver nitrate complex of 2-((2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)thio)-5-(pyridin-2-yl)-1,3,4-oxadiazole is as follows:

[0057]

[0058] The properties such as the molecular formula, properties, and yield of the above complex are shown in Table 1.

[0059] Example 2

[0060] The preparation method of silver hexafluoroantimonate complex with 2 - ((2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)thio)-5-(pyridin-2-yl)-1,3,4-oxadiazole is as follows:

[0061] In step (1), the addition time of liquid carbon disulfide is 18 min. After dropping, heat under reflux for 5 h, and adjust the pH of the filtrate to 3 with dilute hydrochloric acid; in step (2), dichloromethane is 60 mL, the reflux reaction time is 26 h, and the reflux reaction temperature is 39 °C; in step (3), acetone is 60 mL, the reflux reaction time is 25 h, and the reflux reaction temperature is 52 °C; in step (4), methanol is 24 mL, the reflux reaction time is 20 h, and the reflux reaction temperature is 76 °C; the remaining steps are the same as in Example 1.

[0062] (5) Dissolve silver hexafluoroantimonate (0.0172 g, 0.05 mmol) in 5 ml of methanol solution, and then slowly drop it into a 5 mL 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). Let it stand in the dark for 6 days. 21.6 mg of colorless crystals appear. Filter and wash with dichloromethane three times. Place it in a desiccator with anhydrous calcium chloride for drying to obtain the binuclear macrocyclic metronidazole metal complex, with a yield of 61.96%. It was verified by infrared and elemental analysis. The results show that the structure is correct, and the data are as follows:

[0063] 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; The infrared spectrum is as Figure 2 shown.

[0064] Elemental analysis results: Calculated values (%) : C, 22.49; H, 1.88; N, 12.09; S, 4.63; Measured values (%) : C, 22.83; H, 1.81; N, 12.05; S, 4.6.

[0065] The structural formula of silver hexafluoroantimonate complex with 2 - ((2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)thio)-5-(pyridin-2-yl)-1,3,4-oxadiazole is as follows:

[0066]

[0067] The properties such as the molecular formula, physical properties, and yield of the above complex are shown in Table 1.

[0068] Example 3

[0069] The preparation method of silver trifluoromethanesulfonate complex with 2-((2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)thio)-5-(pyridin-2-yl)-1,3,4-oxadiazole is as follows:

[0070] In step (1), the addition time of liquid carbon disulfide is 20 min. After the dropping is completed, heat under reflux for 7 h, and adjust the pH of the filtrate to 4 with dilute hydrochloric acid; in step (2), 65 mL of dichloromethane is used, the reflux reaction time is 20 h, and the reflux reaction temperature is 40 °C; in step (3), 55 mL of acetone is used, the reflux reaction time is 20 h, and the reflux reaction temperature is 54 °C; in step (4), 20 mL of methanol is used, the reflux reaction time is 22 h, and the reflux reaction temperature is 84 °C; the remaining steps are the same as in Example 1.

[0071] (5) Dissolve silver trifluoromethanesulfonate (0.0257 g, 0.1 mmol) in 5 mL of methanol solution, and then slowly drop it into a 5 mL 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). Let it stand in the dark for 5 days. 19.75 mg of colorless crystals appear. Filter and wash three times with dichloromethane, and dry it in a desiccator containing anhydrous calcium chloride to obtain the binuclear macrocyclic metronidazole metal complex with a yield of 67.03%. It was verified by infrared and elemental analysis. The results show that the structure is correct, and the data are as follows:

[0072] 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; The infrared spectrum is as Figure 3 shown.

[0073] Elemental analysis results: Calculated values (%) : C, 28.51; H, 2.07; N, 14.25; S, 10.9; Measured values (%) : C, 28.54; H, 2.05; N, 14.26; S, 10.88.

[0074] The structural formula of silver trifluoromethanesulfonate complex with 2-((2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)thio)-5-(pyridin-2-yl)-1,3,4-oxadiazole is as follows:

[0075]

[0076] Properties such as the molecular formula, properties, and yield of the above complex are shown in Table 1.

[0077]

[0078] Next, the binuclear macrocyclic metronidazole metal complexes prepared in Examples 1-3 were characterized:

[0079] Single crystal diffraction experiment: Using Mo-Kα (λ = 0.071073nm) radiation, the test was carried out in the ω / 2θ scanning mode at 25°C. The data was corrected by SAINT, Lorentz correction, and elimination of polarization effects. The absorption correction was supplemented by SADABS of Bruker. The molecular structure was solved directly by SHELXL-97. The positions of the metal atoms and the atoms connected around them were measured by the method of direct E-maps, and the fine structures of other non-hydrogen atoms were gradually determined by Fourier transform and least squares refinement. The hydrogen atoms were finally determined at the calculated positions and had a unified U iso value. The detection results are shown in Table 2.

[0080]

[0081] a R1 = S||C|-|F c || / SF o |. b wR2 = [Sw(F o 2 -F c 2 ) 2 / Sw(F o 2 )] 1 / 2 .

[0082] Comparative Example 1

[0083] Using metronidazole instead of the binuclear macrocyclic metronidazole metal complex prepared in Example 1, metronidazole was used in the antibacterial experiment, and the results are shown in Table 3.

[0084] Comparative Example 2

[0085] Replace 5-(pyridin-2-yl)-1,3,4-oxadiazole-2-thiol in the present invention 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-triazol-4-amine. The structural formula of 4-amino-5-(p-tolyl)-4H-1,2,4-triazole-3-thiol is shown as follows:

[0086] , The remaining steps and raw materials are the same as those in Example 1 to obtain the product. The product is used in the antibacterial experiment, and the results are shown in Table 3.

[0087] Comparative Example 3

[0088] Synthesize 2-((2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)thio)-5-(pyridin-2-yl)-1,3,4-oxadiazole according to the steps (1) to (4) of Example 1 without performing step (5). The obtained final product is used in the antibacterial experiment, and the results are shown in Table 3.

[0089] The present invention characterized and confirmed the structure of the binuclear macrocyclic metronidazole metal complex by infrared, elemental analysis (C, H, N, S), and X-ray single crystal diffraction. The binuclear macrocyclic metronidazole metal complex of the present invention has strong antibacterial activity, and the half inhibitory concentration IC 50 value is shown in Table 3.

[0090] Perform the IC 50 value determination experiment on the binuclear macrocyclic metronidazole metal complexes prepared in Examples 1 to 3.

[0091] Test methods and steps:

[0092] Add 6 mL of LB liquid medium to a 12 mL shaking flask, then accurately pipette 100 μL of the bacterial solution into the shaking flask with a pipette gun. Then place them together in a constant temperature shaking incubator, set the culture conditions to 37 °C and 200 rpm, and continuously culture until the bacterial solution reaches the logarithmic growth phase. The obtained bacterial solution can be used for subsequent experiments.

[0093] Divide the experiment into experimental groups (Examples and Comparative Examples), negative control group, and positive control group. Set 6 concentration gradients for each Example, Comparative Example, and positive control group in the experimental group, and add 20 μL of the bacterial solution and 160 μL of LB medium to the experimental group, negative control group, and positive control group respectively.

[0094] After that, 20 μL of sterilized distilled water was added to the negative control group; kanamycin was added to the positive control group, and the total volume of the liquid was made up to 200 μL with sterilized distilled water if it was less than 200 μL, so that the final concentration of kanamycin was 30 μg / mL, 20 μg / mL, 10 μg / mL, 3 μg / mL, 2 μg / mL, 1 μg / mL; for each of the 6 concentration gradients of each example and comparative example, the solution of the prepared product was added, and the total volume of the liquid was made up to 200 μL with sterilized distilled water if it was less than 200 μL, so that the final concentration of the product was 30 μg / mL, 20 μg / mL, 10 μg / mL, 3 μg / mL, 2 μg / mL, 1 μg / mL. It was cultured in an incubator at 37 °C for 6 hours, and the OD value was measured with a microplate reader at a wavelength of 600 nm, and the IC 50 value was calculated using graphpad non-linear fitting.

[0095]

[0096] As can be seen from Table 3, for E. coli and S. aureus the two bacteria, the IC 50 value of the binuclear macrocyclic metronidazole metal complex prepared in the example was less 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 does not exist; or X1=OSO2CF3 - , X2 does not exist.

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 for the preparation of antibacterial drugs, which are used to inhibit the reproduction of Staphylococcus aureus and Escherichia coli.

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