Novel chiral succinate dehydrogenase inhibitor and application thereof

Abstract

The invention discloses a novel chiral succinate dehydrogenase inhibitor and application thereof, and belongs to the field of pesticide chemistry. The compound shown in the formula (I) is obtained by modifying a fluxapyroxad structure, and an aniline group of fluxapyroxad is mainly replaced by a cyclohexylamine group with a chiral structure. The antibacterial activity of the compound is improved, and the compound can play a better role in preventing and controlling fungal diseases of plants, so that the yield and quality of crops are improved, the application amount of pesticides is reduced, environmental pollution and ecological damage are reduced, and the problems of pesticide resistance and the like are solved. # imgabs0 # is represented by formula (I).

Description

Technical Field

[0001] The present invention belongs to the field of pesticide chemistry, and particularly relates to a novel chiral succinate dehydrogenase inhibitor. The present invention also relates to a synthesis method of the chiral succinate dehydrogenase inhibitor and its application in the prevention and control of plant fungal diseases. Background Art

[0002] Crop diseases caused by plant pathogenic fungi account for more than 70% of the total diseases, seriously threatening agricultural production and causing serious economic losses. Pesticides play a crucial role in modern agriculture, mainly used to control pests and improve the yield and quality of crops. However, with the large-scale and intensive development of agricultural production, the application amount of pesticides has increased year by year, and a series of problems such as environmental pollution, ecological damage, food safety and drug resistance have been caused in this process. In this context, the research of pesticides is particularly important. Therefore, exploring new types of environmentally friendly pesticides, such as biological pesticides and targeted pesticides, not only helps to alleviate the problem of drug resistance, but also can significantly reduce the environmental burden and improve food safety, etc., providing important support for improving production efficiency and realizing sustainable agricultural development.

[0003] The action mechanism of succinate dehydrogenase inhibitors (SDHI) mainly inhibits its catalytic reaction by interfering with the binding of the active site of succinate dehydrogenase (SDH). SDH is a key enzyme in the tricarboxylic acid cycle, catalyzing the conversion of succinate to fumarate, and then participating in cell energy metabolism. The inhibitor binds to the active site of the enzyme, hindering the binding of the substrate or affecting the conformational change of the enzyme, thereby reducing its catalytic ability. This inhibitory effect can not only affect the generation of energy, but also may lead to the accumulation of succinate in the cell, inducing oxidative stress and apoptosis.

[0004] As a widely used class of agricultural fungicides, in recent years, the development of SDHI containing chiral centers has attracted extensive attention. Chiral drug molecules usually show significant differences in biological activity, toxicity and environmental impact due to their different stereoisomers. With the continuous development of the field of synthetic chemistry, the synthetic strategies of chiral molecules have been significantly improved. Researchers have begun to try to study the synthesis of chiral SDHI to evaluate its biological activity and agricultural value. The stereoselectivity and biological activity of the fungicides penflufen, fluxapyroxad, sedaxane, benzovindiflupyr, fluxametamide, isopyrazam and cyclopyrimorate have been rationally understood. These compounds show different activity differences due to the differences in their stereoconfigurations. Therefore, the research on the development of novel chiral succinate dehydrogenase inhibitors provides new ideas for improving the efficacy of pesticides and reducing environmental risks. With the progress of synthesis and screening technologies, there will be greater application potential in the development of chiral SDHI in the future. Summary of the Invention

[0005] The object of the present invention is to provide a novel chiral succinate dehydrogenase inhibitor, its preparation method and application. This chiral succinate dehydrogenase inhibitor is modified from the structure of fluxapyroxad, and the main purpose is to improve the antibacterial activity of fluxapyroxad and delay the problem of drug resistance.

[0006] The novel chiral succinate dehydrogenase inhibitor provided by the present invention has the chemical structure shown in formula (I),

[0007]

[0008] In formula (I), R is H or a conventional substituent on the benzene ring, and the conventional substituents include mono- or poly-substituted halogen, alkyl, alkoxy, phenyl, phenoxy, ester group, trifluoromethyl, trimethylsilylethynyl, or benzofuran, benzothiophene;

[0009] The cyclohexylamine group in formula (I) has two chiral centers, which are connected to the amino group and the phenyl group respectively.

[0010] Among them, the stereoconfiguration of the cyclohexylamine group is (1S,2S), (1R,2R), (1S,2R) or (1R,2S).

[0011] Furthermore, when R is para-halogen substituted, the stereoconfiguration of the cyclohexylamine group is (1S,2S) or (1S,2R).

[0012] The preparation method provided by the present invention includes the following steps:

[0013] a. React 3-(difluoromethyl)-1-methyl-1H-pyrazole-4-carboxylic acid with thionyl chloride to generate the intermediate 3-(difluoromethyl)-1-methyl-1H-pyrazole-4-carbonyl chloride;

[0014] b. Through dynamic kinetic asymmetric reductive amination reaction, use an iridium catalyst and a chiral ligand (R) or (S)-DTBM-Segphos to convert a cyclohexanone derivative into a chiral cyclohexylamine intermediate;

[0015] c. Condense the 3-(difluoromethyl)-1-methyl-1H-pyrazole-4-carbonyl chloride in step a with the chiral cyclohexylamine intermediate in step b under alkaline conditions to generate the compound.

[0016] The synthetic route is as follows:

[0017]

[0018] Among them, the iridium catalyst in step b is [Ir(COD)Cl], and the reaction is carried out under a hydrogen pressure of 5 MPa and at 80 °C.

[0019] The above compounds were synthesized and their antibacterial activities were detected. It was found that the inhibitory rates of the synthesized chiral succinate dehydrogenase inhibitors against plant fungi were generally higher than those of the commercialized fluxapyroxad, and they had inhibitory effects on a variety of plant fungi including Gibberella zeae, Botrytis cinerea, Sclerotinia sclerotiorum, Pestalotiopsis spp., Monilinia fructicola, Corynespora cassiicola, and Phytophthora parasitica var. nicotianae, showing a certain broad-spectrum property.

[0020] Further research found that there were significant differences in the inhibition of plant fungi by different isomers of the above compounds, demonstrating the correlation between the chiral structure and antibacterial activity. Taking the compound with a halogen substituent at the para position of the aniline group as an example, the inhibitory effects of the (1S,2S) and (1S,2R) isomers on Gibberella zeae were significantly higher than those of the (1R,2R) and (1R,2S) isomers. Among them, the EC 50 of (1S,2S) against Gibberella zeae was 0.086 μM, and that of (1S,2R) was 0.067 μM, both higher than 0.66 μM of fluxapyroxad.

[0021] The beneficial effects of the present invention are as follows:

[0022] By replacing the aniline group of fluxapyroxad with a chiral cyclohexylamine group, the antibacterial activity of the compound is improved in the present invention, which can better prevent and control plant fungal diseases, thereby increasing the yield and quality of crops, reducing the application amount of pesticides, reducing environmental pollution and ecological damage, and alleviating problems such as pathogen fungal drug resistance. Description of the Drawings

[0023] Figure 1 : Design concept and binding energy prediction results of the novel chiral succinate dehydrogenase inhibitor.

[0024] Figure 2 : EC 50 test results of four isomer compounds and fluxapyroxad against Gibberella zeae. Detailed Embodiments

[0025] The present invention will be described in detail below with reference to specific examples. Unless otherwise specified, the relevant reagents used are from commercial channels, and the experimental methods used are conventional experimental methods in the art. Only several embodiments are listed here. Obviously, the present invention is not limited to the following examples, and modifications or improvements made by those skilled in the art based on the disclosed content of the present invention also fall within the scope of the present invention.

[0026] The compounds synthesized in the present invention are improved based on the fluxapyroxad fungicide, and the main design concept is as follows:

[0027] (1) Fluxapyroxad is a broad-spectrum agricultural fungicide widely used to control various plant diseases. Replacing the aniline group of fluxapyroxad with a cyclohexylamine group may bring the following changes: 1. Environmental stability: Cyclohexylamine will make its compound have higher chemical stability compared with aniline, and the degradation rate in the environment will slow down, thus prolonging its validity period on the soil and plant surface. 2. Toxicity and safety: Aniline compounds sometimes show high toxicity and carcinogenicity. The structural replacement of cyclohexylamine may reduce the toxicity to non-target organisms (such as humans, animals and beneficial insects), thus improving the safety of the compound. 3. Biological activity and selectivity: The replacement of cyclohexylamine may change the hydrophobicity and spatial configuration of the compound, thus improving its selectivity and bactericidal activity against certain specific pathogens. 4. Resistance management: The resistance of pathogens to fungicides has always been a difficult problem restricting the use of pesticides. The change in structure often changes the action mechanism of fungicides, thus slowing down or avoiding the resistance of pathogens to fluxapyroxad drugs. 5. Physicochemical properties: The introduction of cyclohexylamine will change the physicochemical properties of the compound such as solubility, permeability and volatility, which may affect the action mode of the fungicide, formulation development and distribution in plants.

[0028] (2) The unique effect of chiral structure. The introduction of chiral molecules shows a unique action mechanism in the spatial binding mode between drugs and proteins, and there will also be obvious differences between different configurations. Screening drug molecules with high-activity configurations is of great significance. Chiral cyclohexylamine induces different stereochemical properties, which is quite important for improving the selectivity, efficacy and reducing side effects of drugs. It can affect the binding mode between drugs and receptors, thus changing the affinity of drugs. Compared with commercial fluxapyroxad, the isomerized novel chiral succinate dehydrogenase inhibitor has a significant difference in its binding mode, and the binding energy is reduced from -8.3 kcal / mol to -8.4 kcal / mol (using software ChemDraw, AutoDockTool, Figure 1 ). Therefore, the introduction of a chiral cyclohexylamine skeleton may make the succinate dehydrogenase inhibitor have better biological activity.

[0029] Example 1: Synthesis of 3-(difluoromethyl)-1-methyl-N-((1S,2S)-2-phenylcyclohexyl)-1H-pyrazole-4-carboxamide

[0030] Synthesis route:

[0031]

[0032] (1) Step a, synthesis of intermediate II 3-(difluoromethyl)-1-methyl-1H-pyrazole-4-carbonyl chloride:

[0033] The commercially available raw material 3-(difluoromethyl)-1-methyl-1H-pyrazole-4-carboxylic acid (17.6 g, 100 mmol) was added to 50 mL of thionyl chloride solution, and the mixture was heated under reflux for 2 h. The tail gas was absorbed with saturated sodium hydroxide solution. After the reaction was completed, the excess thionyl chloride was removed under reduced pressure. Additionally, the pure compound II was obtained by distillation under reduced pressure and stored in a glove box for later use.

[0034] (2) Step b, synthesis of the intermediate (1S,2S)-2-phenylcyclohexan-1-amine:

[0035] Under a nitrogen atmosphere, metal [Ir(COD)Cl] (0.005 mmol, 1.0 mol%), (R)-DTBM-Segphos (0.0055 mmol, 1.1 mol%) were dissolved in 0.5 mL of anhydrous methanol, and the mixture was stirred for coordination for 30 minutes. The above-mentioned mixed solution was added to a methanol solution containing the raw material 2-phenylcyclohexanone (0.5 mmol, 1.0 eq.), anhydrous ZnCl2 (0.5 mmol, 1.0 eq.) and anhydrous NH4OAc (2.5 mmol, 5.0 eq.), and the volume was made up to 2.5 mL. The reaction flask was placed in a high-pressure reaction kettle, and the gas in the kettle was replaced three times with 0.5 MPa of hydrogen under the state of ventilation startup. After the gas replacement was completed, 5 MPa of hydrogen was slowly introduced into the reaction kettle, and it was placed in an oil bath at 80 °C and stirred for reaction for 36 h. After the reaction was completed, the reaction kettle was slowly cooled to room temperature, the gas in the kettle was slowly released, and the reaction flask was taken out. The excess solvent was removed under reduced pressure to obtain a crude product containing inorganic salts, which was dissolved in ethyl acetate, neutralized with saturated sodium bicarbonate solution, the organic phase was separated, the aqueous phase was extracted three times with ethyl acetate, the combined organic phases were dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure.

[0036] (3) Step c, synthesis of the final product 3-(difluoromethyl)-1-methyl-N-((1S,2S)-2-phenylcyclohexyl)-1H-pyrazole-4-carboxamide:

[0037] Dissolve intermediate Ⅳ (0.5 mmol, 1.0 eq.) in anhydrous dichloromethane, and add dry triethylamine (2.0 mmol, 4.0 eq.). At 0 °C, slowly add a dichloromethane solution of intermediate Ⅱ (1.0 mmol, 2.0 eq.) dropwise to the above mixture. The reaction mixture is slowly warmed to room temperature and stirred overnight. After the reaction is completed, concentrate the reaction solution under reduced pressure, then dilute it with 5 mL of water and 5 mL of ethyl acetate. Separate the organic phase, extract the aqueous phase with ethyl acetate twice, combine the organic phases, dry over anhydrous Na2SO4, filter, collect the filtrate, concentrate under reduced pressure, and purify the crude product by column chromatography to obtain the final product, yield: 93%. The product was analyzed by high performance liquid chromatography (HPLC) to determine its enantiomeric excess (ee): 94% ee (using a Chiralcel OD-3 column, isopropanol / n-hexane = 15 / 85, flow rate = 1.0 mL / min, wavelength = 220 nm); t (1S,2S) (major) = 7.0 min, t (1R,2R) (minor) = 12.7 min.

[0038] 1 H NMR (600 MHz, Chloroform-d) δ 7.75 (s, 1H), 7.24 (t, J = 6.0 Hz, 4H), 7.15 (m, 1H), 6.72 (t, J = 54.0 Hz, 1H), 6.57 (s, 1H), 4.57 (dd, J = 6.0, 3.0 Hz, 1H), 3.83 (s, 3H), 2.98 (dt, J = 12.0, 3.0 Hz, 1H), 2.12–2.08 (m, 1H), 1.96–1.90 (m, 2H), 1.84–1.77 (m, 1H), 1.74–1.69 (m, 1H), 1.67–1.65 (m, 1H), 1.51–1.43 (m, 2H); 13 C NMR (151 MHz, Chloroform-d) δ 160.3, 143.0, 141.9 (t, J = 28.6 Hz), 135.8, 128.3, 127.4, 126.4, 117.2, 112.3 (t, J = 232.5 Hz), 50.3, 45.3, 39.4, 31.4, 26.0, 25.5, 20.5; 19 F NMR (565 MHz, Chloroform-d) δ -106.22 (d, J = 305.1 Hz), -109.80 (d, J = 305.1 Hz).

[0039] Example 2: Synthesis of N-((1S,2S)-2-(4-chlorophenyl)cyclohexyl)-3-(difluoromethyl)-1-methyl-1H-pyrazole-4-carboxamide

[0040] Synthesis route:

[0041]

[0042] (1) Step a, synthesis of intermediate 2-(4-chlorophenyl)cyclohexanone:

[0043] Under a nitrogen atmosphere, Pd(OAc)2 (0.01 eq.), 2-(dicyclohexylphosphino)biphenyl (0.022 eq.), and K3PO4 (2.3 eq.) were added to a Schlenk tube, and then a THF solution of cyclohexanone (1.2 eq.) and 4-bromochlorobenzene (1.0 eq.) was added successively. The mixture was stirred at 85 °C for 48 h. After the reaction was completed, the mixture was cooled to room temperature, and the reaction solution was diluted with ether and washed with water. The organic phase was separated, dried over anhydrous Na2SO4, filtered, and concentrated in vacuo. The crude product was purified by silica gel chromatography to obtain the corresponding compound II with a yield of 63%.

[0044] (2) Step b, synthesis of intermediate (1S,2S)-2-(4-chlorophenyl)cyclohexylamine:

[0045] Under a nitrogen atmosphere, metal [Ir(COD)Cl] (0.005 mmol, 1.0 mol%), (R)-DTBM-Segphos (0.0055 mmol, 1.1 mol%) were dissolved in 0.5 mL of anhydrous methanol, and the mixture was stirred for coordination for 30 minutes. The above mixture was added to a methanol solution containing the raw material 2-(4-chlorophenyl)cyclohexanone (0.5 mmol, 1.0 eq.), anhydrous ZnCl2 (0.5 mmol, 1.0 eq.) and anhydrous NH4OAc (2.5 mmol, 5.0 eq.), and the volume was made up to 2.5 mL. The reaction flask was placed in a high-pressure reactor, and the gas in the reactor was replaced three times with 0.5 MPa of hydrogen under a ventilated start state. After the gas replacement was completed, 5 MPa of hydrogen was slowly introduced into the reactor, and it was placed in an 80 °C oil bath and stirred for reaction for 36 h. After the reaction was completed, the reactor was slowly cooled to room temperature, the gas in the reactor was slowly released, and the reaction flask was taken out. The excess solvent was removed under reduced pressure to obtain a crude product containing inorganic salts, which was dissolved in ethyl acetate, neutralized with saturated sodium bicarbonate solution, the organic phase was separated, the aqueous phase was extracted three times with ethyl acetate, the combined organic phases were dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure to obtain the product.

[0046] (3) Step c, synthesis of the final product N-((1S,2S)-2-(4-chlorophenyl)cyclohexyl)-3-(difluoromethyl)-1-methyl-1H-pyrazole-4-carboxamide:

[0047] Dissolve intermediate III (0.5 mmol, 1.0 eq.) in anhydrous dichloromethane, and add dry triethylamine (2.0 mmol, 4.0 eq.). At 0 °C, slowly add a dichloromethane solution of intermediate 3-(fluoromethyl)-1-methyl-1H-pyrazole-4-carbonyl chloride (1.0 mmol, 2.0 eq.) dropwise to the above mixture. The reaction mixture is slowly restored to room temperature and stirred overnight. After the reaction is completed, concentrate the reaction solution under reduced pressure, then dilute it with 5 mL of water and 5 mL of ethyl acetate, separate the organic phase, extract the aqueous phase twice with ethyl acetate, combine the organic phases, dry over anhydrous Na2SO4, filter, collect the filtrate, and concentrate it under reduced pressure. The crude product is purified by column chromatography to obtain the final product, yield: 91%. This product is analyzed by high performance liquid chromatography (HPLC) to determine its enantiomeric excess (ee): 91% ee (using a Chiralcel OD-3 column, isopropanol / n-hexane = 15 / 85, flow rate = 1.0 mL / min, wavelength = 220 nm); t (1S,2S) (major) = 6.9 min, t (1R,2R) (minor) = 6.5 min.

[0048] 1 H NMR (600 MHz, Chloroform-d) δ 7.73 (s, 1H), 7.18 (d, J = 6.0 Hz, 2H), 7.14 (d, J = 6.0 Hz, 2H), 6.74 (t, J = 54.0 Hz, 1H), 6.65–6.62 (m, 1H), 4.55 (dd, J = 6.0, 3.0 Hz, 1H), 3.79 (s, 3H), 2.93–2.90 (m, 1H), 2.03 (d, J = 12.0 Hz, 1H), 1.93–1.91 (m, 1H), 1.84 (d, J = 12.0 Hz, 1H), 1.76–1.67 (m, 2H), 1.67–1.64 (m, 1H), 1.44 (m, 2H); 13 C NMR (151 MHz, Chloroform-d) δ 160.1, 141.7 (t, J = 30.2 Hz), 141.6, 135.9, 131.9, 128.7, 128.2, 116.8, 112.4 (t, J = 232.5 Hz), 49.7, 44.9, 39.3, 31.4, 25.8, 25.5, 20.3; 1919F NMR (565 MHz, Chloroform-d) δ -106.42 (d, J = 305.1 Hz), -109.00 (d, J = 305.1 Hz).

[0049] Example 3: Synthesis of N-((1R,2R)-2-(4-chlorophenyl)cyclohexyl)-3-(difluoromethyl)-1-methyl-1H-pyrazole-4-carboxamide

[0050] The synthesis strategy is the same as that of Example 2, except that (R)-DTBM-Segphos is replaced by (S)-DTBM-Segphos.

[0051] Example 4: Synthesis of N-((1R,2S)-2-(4-chlorophenyl)cyclohexyl)-3-(difluoromethyl)-1-methyl-1H-pyrazole-4-carboxamide

[0052] Synthetic route:

[0053]

[0054] Step a: The same as step b of Example 2.

[0055] Step b: Under a nitrogen atmosphere, Intermediate II (0.5 mmol, 1.0 eq.), [Ir(dtbbpy)(ppy)2]PF6 (0.01 mmol, 2 mol%), and TIPS-SH (0.5 mmol, 1.0 eq) were dissolved in 2 ml of anhydrous methanol, and reacted with an 18W Blue LED at room temperature for 18 h to synthesize Intermediate III. The reaction mixture was concentrated under reduced pressure and used for the next step without further purification.

[0056] Step c: The same as step c of Example 2, yield: 65%. The product was analyzed by high performance liquid chromatography (HPLC) to determine its enantiomeric excess (ee): 91% ee (using a Chiralcel OD-3 column, isopropanol / n-hexane = 15 / 85, flow rate = 1.0 mL / min, wavelength = 220 nm); t (1S,2S) (major) = 8.5 min, t (1R,2R) (minor) = 17.3 min.

[0057] 11H NMR (600 MHz, Chloroform-d) δ 7.72 (s, 1H), 7.20 (d, J = 6.0, 2H), 7.15 (d, J = 12.0 Hz, 2H), 6.61 (t, J = 54.0 Hz, 1H), 6.04 (s, 1H), 4.18–6.14 (m, 1H), 3.83 (s, 3H), 2.46 (td, J = 12.0, 3.0 Hz, 1H), 2.27–2.24 (m, 1H), 1.93–1.90 (m, 1H), 1.86–1.79 (m, 2H), 1.56–1.48 (m, 2H), 1.40–1.29 (m, 2H); 13 13C NMR (151 MHz, Chloroform-d) δ 160.2, 142.2 (t, J = 28.6 Hz), 142.1, 135.3, 132.1, 128.9, 128.6, 116.9, 111.8 (t, J = 232.5 Hz), 52.5, 50.3, 39.5, 35.3, 33.9, 26.1, 25.3; 19 19F NMR (565 MHz, Chloroform-d) δ -107.41 (d, J = 305.1 Hz), -109.75 (d, J = 305.1 Hz).

[0058] Example 5: Synthesis of N-((1S,2R)-2-(4-chlorophenyl)cyclohexyl)-3-(difluoromethyl)-1-methyl-1H-pyrazole-4-carboxamide

[0059] The synthesis strategy is the same as that in Example 4, except that (R)-DTBM-Segphos is replaced with (S)-DTBM-Segphos.

[0060] The above examples respectively list the synthesis methods of two succinate dehydrogenase inhibitors (i.e., phenylcyclohexyl and chlorophenylcyclohexyl), and the synthesis processes of four chiral isomers of chlorophenylcyclohexyl fluzolamide are described in detail in Examples 2, 3, 4, and 5. On this basis, a series of compounds or their isomers can also be obtained according to the same or similar synthesis principles. Only some compounds synthesized by the applicant are listed below as examples.

[0061]

[0062] The above compounds are numbered 1 - 16 in sequence.

[0063] Example 6 Antibacterial Activity Test

[0064] The plant-derived fungus Fusarium graminearum was inoculated on PDA medium and cultured in a constant temperature incubator at 25 ± 0.1 °C for 4 - 6 days. After the mycelia grew well, they were reserved for use.

[0065] Determination of the inhibition rate of the compound against Fusarium graminearum: The in vitro antibacterial activity was determined by the mycelial growth rate method. The above-provided compound and the commercial drug were formulated into a 20 mM drug solution with dimethyl sulfoxide (DMSO). An appropriate amount of the above drug solution was diluted with PDA medium to prepare a culture solution with a final concentration of 1 μM. The culture solution was spread evenly in a 9 cm Petri dish, and a 0.5 mm mycelial block of Fusarium graminearum was scraped and placed face-down at the center of the medium. After inoculation, it was cultured in a constant temperature incubator at 28 ± 0.1 °C for 4 days. After the colony diameter in the blank control Petri dish reached 7.5 - 8 cm, the colony diameters of the blank group, each treatment group, and the positive control group were measured by the cross method, and the inhibition rate was calculated. There were 3 replicates in each group, and the average value of antibacterial was obtained. DMSO was used as the blank control, and fluxapyroxad was used as the positive control.

[0066] Calculation of the inhibition rate of mycelial growth on the plate: Inhibition rate (%) = [Growth diameter of the blank colony (mm) - Growth diameter of the colony in the drug-containing medium (mm)] / Growth diameter of the blank colony (mm) × 100.

[0067] The inhibition rates of the above-synthesized novel chiral succinate dehydrogenase inhibitors against Fusarium graminearum are shown in Table 1 below.

[0068] Table 1: Inhibitory activity of the compound against Fusarium graminearum

[0069] Compound Inhibition rate Compound Inhibition rate Blank control 0 Compound 8 78.76±1.29 Fluxapyroxad 59.29±2.14 Compound 9 80.41±0.71 Compound 1 79.79±0.71 Compound 10 82.68±0.62 Compound 2 80.21±1.64 Compound 11 78.94±2.52 Compound 3 80.21±0.62 Compound 12 75.17±1.02 Compound 4 79.59±0.62 Compound 13 82.04±1.15 Compound 5 80.62±0.36 Compound 14 72.73±1.76 Compound 6 80.49±2.14 Compound 15 80.62±2.58 Compound 7 77.53±1.43 Compound 16 80.49±1.38

[0070] The above results show that the fluxapyroxad derivatives synthesized in the present invention have outstanding inhibitory effects on Fusarium graminearum, and the inhibition rates are generally higher than those of the commercial fluxapyroxad. The present invention synthesized the α-substituted chiral cyclohexylamine structure by the dynamic kinetic asymmetric reductive amination strategy, and successfully obtained a novel chiral succinate dehydrogenase inhibitor through further condensation. Compared with the commercial fluxapyroxad, the inhibitors of this configuration can effectively improve problems such as the liposolubility and resistance of the compound in plants, and further antibacterial experiments also confirmed that this type of molecule has significant biological activity.

[0071] Example 7 Comparison of antibacterial activities among four isomers

[0072] To compare the differences in antibacterial activities among different isomers, taking the four isomers synthesized in Examples 2 - 5 as an example, the half-maximal effective concentration EC 50Test. An inhibition test with a concentration gradient of Gibberella fujikuroi was carried out. Culture media with six concentration gradients of 1, 0.5, 0.25, 0.125, 0.0625, and 0.03125 μM were set respectively for testing to obtain the half-maximal effective concentration EC 50 . The commercialized fluxapyroxad was used as the positive control, and DMSO was used as the negative control. Each test group and the blank control were repeated three times. The test results are shown in Table 2 below.

[0073] Table 2: EC between four isomers of Compound 2 50 Comparison

[0074] Compounds <![CDATA[EC 50 (μM)]]> (1S,2S) 0.08586 (1R,2R) 2.09 (1R,2S) 1.503 (1S,2R) 0.0668 Fluxapyroxad 0.6594

[0075] According to the above comparison results of the antibacterial activities of the isomers, it was found that there were obvious differences in the inhibitory effects of different isomers on Gibberella fujikuroi. This experiment proved that the chiral structure of this type of novel chiral succinate dehydrogenase inhibitor was closely related to the antibacterial activity.

[0076] Example 8 Antibacterial Activity of Novel Chiral Succinate Dehydrogenase Inhibitor against Other Plant Fungi

[0077] Through the above comparison of the antibacterial activities of the isomers, we successfully screened out two isomers with better activities. Under the condition of 20 μM, the inhibition rates of the two chiral molecules (1S,2S) and (1S,2R) of Compound (2) against other pathogenic fungi such as Botrytis cinerea, Sclerotinia sclerotiorum, Pestalotiopsis, Monilinia fructicola, Corynespora cassiicola, and Black shank were further investigated. The test method was similar to that for Gibberella fujikuroi. The experimental results are shown in Table 3 below.

[0078] Table 3: Antibacterial Activity of Compound 2 against Other Plant Fungi (20 μM)

[0079]

[0080] From the above results, it can be seen that the compound (1S,2R)-(2) synthesized in the present invention has inhibitory effects on a variety of plant fungi and has a certain broad spectrum.

Claims

1. A chiral compound having the structure of formula (I), In formula (I), R is H or a conventional substituent on the benzene ring, and the conventional substituent includes mono- or poly-substituted halogen, alkyl, alkoxy, phenyl, phenoxy, ester group, trifluoromethyl, trimethylsilylethynyl, or benzofuran, benzothiophene; The cyclohexylamine group in formula (I) has two chiral centers, which are connected to the amino group and the phenyl group respectively.

2. The compound according to claim 1, wherein: The stereoconfiguration of the cyclohexylamine group is (1S,2S), (1R,2R), (1S,2R) or (1R,2S).

3. The compound according to claim 1, wherein: When R is para-halogen substituted, the stereoconfiguration of the cyclohexylamine group is (1S,2S) or (1S,2R).

4. The method for synthesizing the compound according to any one of claims 1-3, characterized in that, Comprising the following steps: a. React 3-(difluoromethyl)-1-methyl-1H-pyrazole-4-carboxylic acid with thionyl chloride to generate the intermediate 3-(difluoromethyl)-1-methyl-1H-pyrazole-4-carbonyl chloride; b. Through dynamic kinetic asymmetric reductive amination reaction, use an iridium catalyst and a chiral ligand (R) or (S)-DTBM-Segphos to convert a cyclohexanone derivative into a chiral cyclohexylamine intermediate; c. Condense the 3-(difluoromethyl)-1-methyl-1H-pyrazole-4-carbonyl chloride in step a with the chiral cyclohexylamine intermediate in step b under basic conditions to generate the said compound.

5. The synthesis method according to claim 4, characterized in that, The iridium catalyst in step b is [Ir(COD)Cl], and the reaction is carried out under the conditions of 5 MPa hydrogen and 80 °C.

6. Use of the compound according to any one of claims 1-3 in the preparation of a succinate dehydrogenase inhibitor.

7. The application according to claim 6, characterized in that, The inhibitor is used for preventing and controlling phytopathogenic fungi, and the pathogenic fungi are selected from Gibberella, Botrytis cinerea, Sclerotinia sclerotiorum, Pestalotiopsis, Monilinia fructicola, Corynespora cassiicola or Phytophthora parasitica var. nicotianae.

8. A bactericidal composition, characterized in that, Containing the compound according to any one of claims 1-3 and an agriculturally acceptable carrier.

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