Thymol derivative as well as preparation method and application thereof

Abstract

The invention relates to the technical field of medicinal chemistry, and discloses a thymol derivative as well as a preparation method and application thereof. The thymol ethyl, propyl, butyl azole and piperazine derivative provided by the invention is used as a bacteriostatic agent for resisting phytopathogen and is used for preparing pesticides; the prepared pesticide can be used for preventing and treating plant diseases such as cucumber damping-off, rice damping-off, cotton damping-off, watermelon damping-off, sclerotinia rot of colza, botrytis cinerea, cucumber gray mold, grape gray mold, wheat scab, rice blast, wheat sharp eyespot, wheat stem rot, sweet potato soft rot and lily wilt.

Description

Technical Field

[0001] This application belongs to the field of medicinal chemistry technology, specifically relating to a thymol derivative and its preparation method and application. Background Technology

[0002] Thymol, also known as thymol, is a common natural product derived from the volatile oil of plants in the genus thyme. Its structure is very simple, obtained by introducing isopropyl and methyl groups at the 2 and 5 positions of phenol, respectively. As a natural product, it has a wide range of uses. In the pharmaceutical field, it can be used as a topical medication to treat prickly heat, herpes, and pruritus; in agriculture, it can be used as an insecticide and antifungal agent to control plant diseases and pests; in animal husbandry, it can also be used as a feed additive to reduce animal diarrhea and enhance fertility and lactation performance.

[0003] Rhizoctonia solani ( Rhizoctonia solani ) belongs to the genus Rhizoctonia, a type of deuteromycete. Rhizoctonia The fungus is the main cause of stripe leaf blight and sheath blight, and is the reason for the reduction in the yield of high-quality maize worldwide. It is an invasive soil-borne semi-living nutritional pathogen that causes devastating diseases to other important economic crops worldwide, such as rice, wheat, potatoes, soybeans, tomatoes, sugar beets, and cabbage, in addition to maize.

[0004] Sclerotium sclerotiorum ( Sclerotinia sclerotiorum ) belongs to the genus *Sclerotium* of the ascomycetes class ( Sclerotinia Fungi are a type of plant pathogenic fungi with a wide host range. They can infect more than 600 kinds of plants, including important crops such as rapeseed, potato, cotton, tomato, and soybean. They can cause stem rot and lead to necrosis of plant tissues.

[0005] Botrytis cinerea ( Botrytis cinerea ) belongs to the genus *Botrytis cinerea* of the ascomycetes class. Botrytis Botrytis cinerea, also known as gray botrytis, is a broad-host fungus that can cause damping-off, leaf drop, flower rot, fruit rot, and cellar rot in a variety of plant seedlings, fruits, and storage organs. It also poses a significant threat to ornamental plants in gardens. Its infection range is wide, affecting more than 470 plant species, including those in the Solanaceae, Cucurbitaceae, and Rosaceae families.

[0006] wheat scab (Fusarium head blight) Fusarium asiaticum ) and Fusarium graminearum, an ascomycete belonging to the genus Fusarium ( FusariumFusarium head blight is the main pathogen causing wheat scab, a significant disease affecting cereal crops. It occurs in all wheat-producing regions worldwide, but is most severe in warm, humid areas. In my country, scab has consistently been one of the most important wheat diseases in the southwestern winter wheat region, the northeastern spring wheat region, and the Yangtze-Huaihe River basin.

[0007] Rice blast fungus ( Magnaporthe oryzae ) belongs to the genus *Gyropoda* of the ascomycetes ( Magnaporthe Rice blast, caused by fungi, is one of the most important diseases in rice production. It is characterized by high frequency of occurrence, wide range, and strong infectivity. It infects rice throughout its entire growth period. Rice blast causes at least 10% of the yield loss in my country's rice production every year, and in severe cases, the yield reduction can be as high as 40% to 50%.

[0008] Rhizoctonia cerealis, a fungus belonging to the genus Rhizoctonia in the class Deuteromycetes, is the main pathogen causing wheat sheath blight. It is a soil-borne fungal disease widely distributed in temperate wheat-growing regions worldwide. With the replacement of wheat varieties and the promotion of high-yield cultivation practices (such as early sowing, dense planting, and high fertilization), this disease has become widespread in winter wheat-growing areas of my country and has now become an important disease in the wheat-growing areas of the Yangtze River Basin and the Huang-Huai Plain.

[0009] The fungus *Fusarium pseudograminearum* is responsible for wheat stem rot. Ascomycetes Fusarium fungi are important pathogens causing wheat stem rot. It is a global disease that occurs in wheat-producing areas around the world, including Asia, Africa, North America, South America, and Oceania. It mainly infects the leaf sheaths and stems of the basal 1-2 nodes of wheat, causing lodging and premature death of wheat. It generally reduces yield by 5-10%, but in severe cases, it can reduce yield by more than 50% or even cause total crop failure.

[0010] Alternaria solani is a deuteromycete. Alternaria Alternaria fungi are important pathogens causing early blight in potatoes and tomatoes. They are multi-cycle fungal diseases caused by Alternaria solanacea, which are soil-borne and air-borne. Under high temperature and humidity conditions, multiple reinfections can occur throughout the growing season, leading to large-scale outbreaks. This disease has occurred in all major potato-producing areas in my country, seriously restricting the development of the potato industry.

[0011] creeping roots Mold Rhizopus stolonifer is a fungus belonging to the genus Rhizopus in the zygomycetes family. It is one of the main pathogens in the postharvest storage and logistics of more than 100 kinds of fruits such as strawberries, tomatoes, and melons. It can be spread through the air and grows rapidly in humid environments, causing fruit rot.

[0012] Fusarium oxysporum ( Fusarium oxysporum ) belongs to the genus Fusarium of the class Deuteromycetes ( Fusarium Fungi are the main pathogens that cause wilt disease in plants, and can cause wilt disease in more than 150 kinds of plants, including cotton, tomatoes, bananas, watermelons, strawberries, cabbage, chickpeas, peas, alfalfa, lilies and so on.

[0013] Currently, the control of plant diseases caused by the above pathogens mainly falls into two categories: biological control and chemical control. Biological control generally utilizes microorganisms (bacteria, fungi, or actinomycetes) that can produce antibiotics to inhibit the growth of pathogens. Although biological control has made some progress, it has largely not been scaled up, mainly due to unstable control effects in the field, lack of broad-spectrum efficacy, strict requirements for product production and storage, slower and less effective results compared to chemical agents, and higher prices. Under current circumstances, chemical control remains the primary strategy for controlling pathogens. Chemical control mainly uses pesticides such as azoles, methyl esters, and amides. However, overall, the control effects of currently used chemical pesticides are not ideal, they easily lead to resistance, long-term use can cause soil acidification and heavy metal contamination, and they are also relatively expensive. Therefore, it is essential to develop new, highly effective, low-toxicity, and inexpensive pesticides to combat plant pathogens.

[0014] In the process of realizing this invention, the inventors discovered that thymol has significant activity against various plant pathogens, but it still lags behind existing antibacterial agents. Summary of the Invention

[0015] The purpose of this application is to provide a thymol derivative, its preparation method and application, in order to solve the problem of poor antibacterial activity of thymol against various plant pathogens.

[0016] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows: In a first aspect, this application provides thymol derivatives and their salts, the chemical structural formula of which is shown in formula (1): Equation (1), The structure of R1 is at least one of the following 1a to 1c: .

[0017] In one alternative implementation, the structure of R1 is as shown in 1a below: .

[0018] Secondly, this application provides a method for preparing the above-mentioned thymol derivative, comprising the following steps: Thymol was subjected to a substitution reaction with dibromoethane in the presence of a base to give thymol oxyethyl bromide; The thymol oxyethyl bromide is refluxed with 2-aminobenzimidazole, 1-(4-trifluoromethylbenzyl)piperazine, or 4,4'-difluorobenzylpiperazine in the presence of carbonate.

[0019] Thirdly, this application provides applications of the above-mentioned thymol derivatives and their salts, the applications including at least one of the following: Application in the preparation of antimicrobial agents against plant pathogens, including those resistant to Rhizoctonia solani (…). Rhizoctoniasolani ), Sclerotinia sclerotiorum ( Sclerotiniasclerotiorum ), gray mold ( Botrytiscinerea ), wheat scab ( Fusariumasiaticum ), rice blast fungus ( Magnaportheoryzae ), Trichophyton tritici ( Rhizoctoniacerealis ), wheat stem rot fungus ( Fusariumpseudograminearum Fusarium graminearum ( ), Fusarium graminearum ( Fusariumgraminearum Alternaria solanacearum ( Alternariasolani ), creeping rhizomycetes ( Rhizopusstolonifer ) and Fusarium oxysporum ( Fusariumoxysporum At least one of the following: ; preferably, the plant pathogenic fungus includes at least one of Rhizoctonia solani, Sclerotinia sclerotiorum, Botrytis cinerea, Wheat rhizoctonia solani, Wheat stem rot fungus, Fusarium graminearum, Alternaria alternata, and Fusarium oxysporum. Application in the preparation of pesticides for the control of plant diseases, wherein the plant diseases include at least one of cucumber damping-off, rice damping-off, cotton damping-off, watermelon damping-off, rapeseed sclerotinia stem rot, tomato gray mold, cucumber gray mold, grape gray mold, wheat scab, rice blast, wheat sheath blight, wheat stem base rot, sweet potato soft rot, and lily wilt.

[0020] Fourthly, this application provides a thymol derivative and its salt, the chemical structural formula of which is shown in formula (2): Equation (2), Wherein, R2 is at least one of the following 2a to 2c: .

[0021] Fifthly, this application provides a method for preparing the above-mentioned thymol derivative, comprising the following steps: Thymol was subjected to a substitution reaction with dibromopropane in the presence of a base to give thymol oxypropyl bromide; The thymoloxypropyl bromide is refluxed with 2-aminobenzimidazole, 3-mercapto-1,2,4-triazole or 1-(4-trifluoromethylbenzyl)piperazine in the presence of carbonate.

[0022] Sixthly, this application provides applications of the above-mentioned thymol derivatives and their salts, said applications including at least one of the following: Application in the preparation of antimicrobial agents against plant pathogens, including those resistant to Rhizoctonia solani (…). Rhizoctoniasolani ), Sclerotinia sclerotiorum ( Sclerotiniasclerotiorum ), gray mold ( Botrytiscinerea ), wheat scab ( Fusariumasiaticum ), rice blast fungus ( Magnaportheoryzae ), Trichophyton tritici ( Rhizoctoniacerealis ), wheat stem rot fungus ( Fusariumpseudograminearum Fusarium graminearum ( ), Fusarium graminearum ( Fusariumgraminearum Alternaria solanacearum ( Alternariasolani ), creeping rhizomycetes ( Rhizopusstolonifer ) and Fusarium oxysporum ( Fusariumoxysporum At least one of the following: ; preferably, the plant pathogenic fungus includes at least one of Sclerotinia sclerotiorum, Botrytis cinerea, wheat sheath blight fungus, wheat stem rot fungus, Fusarium graminearum, Alternaria alternata, Rhizopus spp., and Fusarium oxysporum. Application in the preparation of pesticides for the control of plant diseases, wherein the plant diseases include at least one of cucumber damping-off, rice damping-off, cotton damping-off, watermelon damping-off, rapeseed sclerotinia stem rot, tomato gray mold, cucumber gray mold, grape gray mold, wheat scab, rice blast, wheat sheath blight, wheat stem base rot, sweet potato soft rot, and lily wilt.

[0023] In a seventh aspect, this application provides a thymol derivative and its salt, the chemical structural formula of which is shown in formula (3): Equation (3), Wherein, R3 is at least one of the following 3a to 3d: .

[0024] Eighthly, this application provides a method for preparing the above-mentioned thymol derivative, comprising the following steps: Thymol was subjected to a substitution reaction with dibromobutane in the presence of a base to give thymol oxybutyl bromide; The thymoloxybutyl bromide is subjected to a reflux reaction with 2-aminobenzimidazole, 3-mercapto-1,2,4-triazole, 1-(4-trifluoromethylbenzyl)piperazine, or 4,4'-difluorobenzylpiperazine in the presence of carbonate.

[0025] Ninthly, this application provides applications of the above-mentioned thymol derivatives and their salts, said applications including at least one of the following: Application in the preparation of antimicrobial agents against plant pathogens, including those resistant to Rhizoctonia solani (…). Rhizoctoniasolani ), Sclerotinia sclerotiorum ( Sclerotiniasclerotiorum ), gray mold ( Botrytiscinerea ), wheat scab ( Fusariumasiaticum ), rice blast fungus ( Magnaportheoryzae ), Trichophyton tritici ( Rhizoctoniacerealis ), wheat stem rot fungus ( Fusariumpseudograminearum Fusarium graminearum ( ), Fusarium graminearum ( Fusariumgraminearum Alternaria solanacearum ( Alternariasolani ), creeping rhizomycetes ( Rhizopusstolonifer ) and Fusarium oxysporum ( Fusariumoxysporum At least one of the following: ; preferably, the plant pathogenic fungus includes at least one of Sclerotinia sclerotiorum, Botrytis cinerea, wheat stem rot fungus, Fusarium graminearum, Alternaria alternata, and Rhizopus stolonifera; Application in the preparation of pesticides for the control of plant diseases, wherein the plant diseases include at least one of cucumber damping-off, rice damping-off, cotton damping-off, watermelon damping-off, rapeseed sclerotinia stem rot, tomato gray mold, cucumber gray mold, grape gray mold, wheat scab, rice blast, wheat sheath blight, wheat stem base rot, sweet potato soft rot, and lily wilt.

[0026] Based on the above technical solution, this application has at least the following beneficial effects: The thymol ethyl, propyl, butylazole, and piperazine derivatives provided in this application are used as antibacterial agents against plant pathogens and for the preparation of pesticides. The prepared pesticides can be used to control plant diseases such as cucumber damping-off, rice damping-off, cotton damping-off, watermelon damping-off, rapeseed sclerotinia stem rot, tomato gray mold, cucumber gray mold, grape gray mold, wheat scab, rice blast, wheat sheath blight, wheat stem base rot, sweet potato soft rot, and lily wilt.

[0027] Specifically, the thymol ethyl, propyl, butylazole, and piperazine derivatives provided in this application have the following advantages: In in vitro bioactivity tests, the thymol ethyl, propyl, butylazole, and piperazine derivatives provided in this application exhibit inhibitory activity against various plant pathogens. Among them, compound 1a shows high inhibitory activity against various plant pathogens and is a novel compound with broad-spectrum antibacterial activity. Specifically, it exhibits EC50 activity against *Botrytis cinerea*, *Bacillus oryzae*, *Rhizoctonia solani*, and *Bacillus thuringiensis*. 50 All were less than 10 μg / mL (their EC50) 50 Compound 1b exhibits high inhibitory activity against Alternaria solanacearum and Rhizopus stolonifer, with an EC50 value ranging from 6.53 to 9.13 μg / mL. 50The values ​​were 16.57 μg / mL and 10.97 μg / mL, respectively; compound 2a showed inhibitory activity against various plant pathogens, but its activity was somewhat lower than that of compound 1a; compound 2b showed certain inhibitory activity against various plant pathogens, especially against Rhizopus stolonifer, where its inhibitory activity was almost 100%, and its EC50 value was 16.57 μg / mL. 50 The value reached 1.78 μg / mL; compound 3a showed significantly higher inhibitory activity against *Sclerotinia sclerotiorum*, *Wheat stem rot*, *Fusarium graminearum*, and *Alternaria alternata* than thymol; compound 3b exhibited inhibitory activity against various plant pathogens, with inhibition rates all greater than 60%, among which the EC50 against *Botrytis cinerea* was significantly higher. 50 The concentration reached 2.57 μg / mL; compound 3c showed much higher inhibitory activity against Sclerotinia sclerotiorum than thymol, with an inhibition rate of 91.47%; compound 3d showed significantly higher inhibitory activity against Sclerotinia sclerotiorum than thymol. Detailed Implementation

[0028] To further illustrate the technical means and results adopted by this application to achieve the intended inventive purpose, the following preferred embodiments are used to describe in detail the specific implementation methods, technical solutions, and features according to this application. Specific features, structures, or characteristics in the various embodiments described below can be combined in any suitable form.

[0029] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0030] The present application will be further described in detail below with reference to specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in this application.

[0031] Example 1 Compound 1 (compounds 1a, 1b, and 1c) was prepared according to the following method: ; The structural formulas of compounds 9a, 9b, and 9c are shown below: ; The groups R1 in compounds 1a, 1b, and 1c are shown below: .

[0032] The specific steps are as follows: (1) Add thymol (10g, 67mmol) to a 500mL three-necked flask, then slowly add 150mL of pure water to the flask and stir. Then add sodium hydroxide (NaOH, 4g, 100mmol), tetrabutylammonium bromide (TBAB, 2.2g, 6.7mmol), and potassium iodide (KI, 1.1g, 6.7mmol) in sequence and heat until completely dissolved. When the temperature reaches 90℃, slowly add 1,2-dibromoethane (12mL, 134mmol) to the reaction solution and keep the temperature at around 100℃. Continue stirring for 12h. The reaction was monitored by thin-layer chromatography (TLC). After the reaction was completed, the mixture was filtered and the oily liquid was collected. The mixture was then washed three times with 2% NaOH aqueous solution and saturated saline solution, respectively. Finally, it was extracted with ethyl acetate. The collected organic layer solution was dried with anhydrous sodium sulfate. The filtrate was concentrated and separated by silica gel column chromatography with petroleum ether / ethyl acetate (V / V=40 / 1) as the eluent to obtain compound 6 (thymol oxyethyl bromide). (2) Add compound 6 (thymol oxyethyl bromide, 500 mg, 2.07 mmol) prepared in step (1) to a 50 mL reaction flask, then add 25 mL of acetonitrile, stir, add potassium carbonate (572 mg, 4.14 mmol), and finally add compound 9 (9a, 9b, or 9c, 3.12 mmol). Heat under reflux at 80 °C for 12 h. After the reaction is completed by thin-layer chromatography (TLC), filter the precipitate, wash the precipitate three times with 50 mL of acetonitrile, concentrate the filtrate under reduced pressure, and then separate and purify it by silica gel column chromatography with petroleum ether / ethyl acetate (V / V=1 / 1) as the eluent to obtain the target product compounds 1a-1c.

[0033] The physicochemical data of the compounds synthesized in this embodiment are as follows: Compound 6, a colorless oily liquid. 1 H NMR (600 MHz, CDCl3) δ 7.13 (d, J = 7.7 Hz, 1H), 6.80 (d, J = 7.6 Hz, 1H), 6.65 (s, 1H), 4.30 (t, J = 6.1 Hz, 2H), 3.68 (t, J = 6.1Hz, 2H), 3.33 (m, 1H), 2.34 (s, 3H), 1.24 (d, J = 6.9 Hz, 6H).

[0034] Compound 1a, a white powdery solid. 1 H NMR (600 MHz, CDCl3) δ 7.45 (d,J = 7.8 Hz,1H), 7.17 – 7.12 (m, 2H), 7.11 – 7.07 (m, 2H), 6.79 (d, J = 7.7 Hz, 1H), 6.61(s, 1H), 4.38 (t, J = 4.9 Hz, 2H), 4.30 (t, J = 4.9 Hz, 2H), 3.15 (m, 1H), 2.28(s, 3H), 1.13 (d, J = 6.9 Hz, 6H). 13 C NMR (150 MHz, CDCl3) δ 155.2, 154.6,141.9, 136.9, 134.3, 126.3, 122.9, 122.1, 120.3, 116.8, 113.4, 107.7, 67.7,43.0, 26.7, 23.2, 21.5.

[0035] Compound 1b, a white, blocky solid. 1 H NMR (600 MHz, CDCl3) δ 7.57 (d, J = 8.1 Hz, 2H), 7.46 (d, J = 8.0 Hz, 2H), 7.09 (d, J = 7.7 Hz, 1H), 6.75 (d, J = 7.7 Hz, 1H), 6.66 (s, 1H), 4.10 (t, J = 5.8 Hz, 2H), 3.56 (s, 2H), 3.27 (m, 1H), 2.85 (t, J =5.8 Hz, 2H), 2.58 (d, J = 87.1 Hz, 8H), 2.31 (s, 3H), 1.19 (d, J = 6.9 Hz, 6H). 13 CNMR (150 MHz, CDCl3) δ 156.1, 142.9, 136.6, 134.4, 129.8, 129.6, 126.2,125.5, 123.7, 121.6, 112.7, 66.7, 62.8, 57.7, 54.0, 53.5, 26.9, 23.2, 21.7.

[0036] Compound 1c, a white, blocky solid. 1 H NMR (600 MHz, CDCl3) δ 7.37 – 7.32 (m, 4H),7.08 (d, J = 7.7 Hz, 1H), 6.97 (t, J = 8.6 Hz, 4H), 6.74 (d, J = 7.6 Hz, 1H), 6.65(s, 1H), 4.22 (s, 1H), 4.09 (t, J = 5.8 Hz, 2H), 3.25 (m, 1H), 2.85 (t, J = 5.7Hz, 2H), 2.64 (s, 4H), 2.41 (s, 4H), 2.30 (s, 3H), 1.18 (d, J = 6.9 Hz, 6H). 13 CNMR (150 MHz, CDCl3) δ 162.7, 161.0, 155.9, 138.3, 136.3, 134.2, 129.3,125.9, 121.3, 115.5, 112.4, 74.5, 66.3, 57.3, 53.9, 51.8, 26.5, 22.8, 21.3.

[0037] Example 2 Compound 2 (compounds 2a, 2b, and 2c) was prepared according to the following method: ;

[0038] The structural formulas of compounds 10a, 10b, and 10c are shown below: ;

[0039] The R2 group in compounds 2a, 2b, and 2c is shown below: .

[0040] The specific steps are as follows: (1) Add thymol (10g, 67mmol) to a 500mL three-necked flask, then slowly add 150mL of pure water to the flask, stir, and then add sodium hydroxide (NaOH, 4g, 100mmol), tetrabutylammonium bromide (TBAB, 2.2g, 6.7mmol), and potassium iodide (KI, 1.1g, 6.7mmol) in sequence. Heat to dissolve completely. When the temperature reaches 90℃, slowly add 1,3-dibromopropane (134mmol) to the reaction solution and keep the temperature at about 100℃. Continue stirring for 12h. Monitor the reaction by thin-layer chromatography (TLC). After the reaction is complete, filter and collect the oily liquid. Then wash three times with 2% NaOH aqueous solution and saturated saline solution respectively. Finally, extract with ethyl acetate. Dry the collected organic layer solution with anhydrous sodium sulfate. After the filtrate is concentrated, separate it by silica gel column chromatography with petroleum ether / ethyl acetate (V / V=40 / 1) as the eluent to obtain compound 7 (thymoloxypropyl bromide). (2) Add compound 7 (thymoloxypropyl bromide, 2.07 mmol) prepared in step (1) to a 50 mL reaction flask, then add 25 mL of acetonitrile, stir, add potassium carbonate (572 mg, 4.14 mmol), and finally add compound 10 (10a, 10b, or 10c, 3.12 mmol). Heat under reflux at 80 °C for 12 h. After the reaction is completed by thin-layer chromatography (TLC), filter the precipitate, wash the precipitate three times with 50 mL of acetonitrile, concentrate the filtrate under reduced pressure, and then purify it by silica gel column chromatography with petroleum ether / ethyl acetate (V / V=1 / 1) as the eluent to obtain the target product compounds 2a-2c.

[0041] The physicochemical data of the compounds synthesized in this embodiment are as follows: Compound 7, a colorless oily liquid. 1 H NMR (600 MHz, CDCl3) δ 7.11 (d, J = 7.7 Hz, 1H), 6.77 (d, J = 8.1 Hz, 1H), 6.70 (s, 1H), 4.11 (t, J = 5.7 Hz, 2H), 3.65 (t, J = 6.5Hz, 2H), 3.28 (m, 1H), 2.38 – 2.35 (m, 2H), 2.34 (s, 3H), 1.22 (d, J = 7.0 Hz, 6H).

[0042] Compound 2a, a white powdery solid. 1H NMR (600 MHz, CDCl3) δ 7.41 (d, J = 7.8 Hz, 1H), 7.14 (d, J = 7.8 Hz, 2H), 7.12 (d, J = 2.2 Hz, 1H), 7.09 – 7.06 (m, 1H), 6.80 (d, J = 7.7 Hz, 1H), 6.62 (s, 1H), 4.22 (t, J = 6.4 Hz, 2H), 3.98 – 3.96 (m,2H), 3.38 – 3.34 (m, 1H), 2.29 (s, 3H), 2.26 (dd, J = 12.3, 6.3 Hz, 2H), 1.28(d, J = 6.9 Hz, 6H). 13 C NMR (150 MHz, CDCl3) δ 155.1, 154.2, 141.9, 136.7,133.9, 126.2, 122.1, 121.6, 119.8, 116.3, 112.8, 107.5, 63.9, 39.0, 28.8,26.7, 23.1, 21.3.

[0043] Compound 2b is a white powdery solid. 1 H NMR (600 MHz, CDCl3) δ 8.13 (s, 1H), 7.09(d, J = 7.7 Hz, 1H), 6.74 (d, J = 7.8 Hz, 1H), 6.65 (s, 1H), 4.08 (t, J = 5.8 Hz, 2H), 3.38 (t, J = 7.0 Hz, 2H), 3.27 (m, 1H), 2.30 (s, 3H), 2.24 (t, J = 6.8 Hz, 2H), 1.19 (d, J = 6.9 Hz, 6H). 13 C NMR (150 MHz, CDCl3) δ 155.7, 136.4, 134.5,134.1, 125.9, 121.4, 112.3, 110.0, 65.7, 29.6, 26.6, 22.8, 21.3, 20.8.

[0044] Compound 2c is a white powdery solid. 1 H NMR (600 MHz, CDCl3) δ 7.57 (d, J = 8.0 Hz, 2H), 7.45 (d, J = 8.0 Hz, 2H), 7.08 (d, J = 7.7 Hz, 1H), 6.73 (d, J = 7.3 Hz, 1H), 6.65 (s, 1H), 4.00 (t, J = 6.1 Hz, 2H), 3.56 (s, 2H), 3.28 – 3.24 (m, 1H), 2.57(s, 2H), 2.46 (d, J = 60.5 Hz, 8H), 2.31 (s, 3H), 2.01 – 1.97 (m, 2H), 1.19 (d, J = 6.9 Hz, 6H). 13 C NMR (150 MHz, CDCl3) δ 156.1, 142.6, 136.3, 134.0, 129.2,127.0, 125.9, 125.2, 125.1, 123.4, 121.0, 112.2, 66.1, 62.5, 55.5, 53.3, 27.0, 26.7, 22.8, 21.4.

[0045] Example 3 Compound 3 (compounds 3a, 3b, 3c, and 3d) was prepared according to the following method: ;

[0046] The structural formulas of compounds 11a, 11b, 11c, and 11d are shown below: ;

[0047] The R3 group in compounds 3a, 3b, 3c, and 3d are shown below: .

[0048] The specific steps are as follows: (1) Add thymol (10g, 67mmol) to a 500mL three-necked flask, then slowly add 150mL of pure water to the flask, stir, and then add sodium hydroxide (NaOH, 4g, 100mmol), tetrabutylammonium bromide (TBAB, 2.2g, 6.7mmol), and potassium iodide (KI, 1.1g, 6.7mmol) in sequence. Heat to dissolve completely. When the temperature reaches 90℃, slowly add 1,4-dibromobutane (134mmol) to the reaction solution and keep the temperature at about 100℃. Continue stirring for 12h. Monitor the reaction by thin-layer chromatography (TLC). After the reaction is complete, filter and collect the oily liquid. Then wash three times with 2% NaOH aqueous solution and saturated saline solution respectively. Finally, extract with ethyl acetate. Dry the collected organic layer solution with anhydrous sodium sulfate. After the filtrate is concentrated, separate it by silica gel column chromatography with petroleum ether / ethyl acetate (V / V=40 / 1) as the eluent to obtain compound 8 (thymol oxybutyl bromide). (2) Add compound 8 (thymol oxybutyl bromide, 2.07 mmol) prepared in step (1) to a 50 mL reaction flask, then add 25 mL of acetonitrile, stir, add potassium carbonate (572 mg, 4.14 mmol), and finally add compound 11 (11a, 11b, 11c or 11d, 3.12 mmol). Heat under reflux at 80 °C for 12 h. After the reaction is completed by thin-layer chromatography (TLC), filter the precipitate, wash the precipitate three times with 50 mL of acetonitrile, concentrate the filtrate under reduced pressure, and then separate and purify it by silica gel column chromatography with petroleum ether / ethyl acetate (V / V=1 / 1) as the eluent to obtain the target product compounds 3a-3d.

[0049] The physicochemical data of the compounds synthesized in this embodiment are as follows: Compound 8, a colorless oily liquid. 1 H NMR (600 MHz, CDCl3) δ 7.10 (d, J = 7.7 Hz, 1H), 6.75 (d, J = 7.5 Hz, 1H), 6.66 (s, 1H), 4.00 (t, J = 6.0 Hz, 2H), 3.52 (t, J = 6.6Hz, 2H), 3.28 (m, 1H), 2.33 (s, 3H), 2.11 (p, J = 6.8 Hz, 2H), 1.98 (dt, J =12.5, 6.1 Hz, 2H), 1.21 (d, J = 6.9 Hz, 6H).

[0050] Compound 3a, a white powdery solid. 1 H NMR (600 MHz, CDCl3) δ 7.42 (d, J = 7.8 Hz, 1H), 7.13 (dd, J = 7.4, 6.2 Hz, 1H), 7.11 (d, J = 3.9 Hz, 1H), 7.09 (d, J = 1.9 Hz,1H), 7.08 – 7.05 (m, 1H), 6.76 (d, J = 7.7 Hz, 1H), 6.63 (s, 1H), 4.04 (t, J =7.2 Hz, 2H), 3.97 (t, J = 5.9 Hz, 2H), 3.25 (m, 1H), 2.31 (s, 3H), 2.06 – 2.02(m, 2H), 1.89 – 1.85 (m, 2H), 1.19 (d, J = 6.9 Hz, 6H). 13 C NMR (150 MHz, CDCl3)δ 155.7, 153.4, 141.7, 136.4, 134.1, 126.0, 121.5, 121.5, 119.8, 116.3,112.5, 107.8, 67.5, 42.5, 26.7, 26.5, 26.1, 22.9, 21.3.

[0051] Compound 3b is a white powdery solid. 1 H NMR (600 MHz, CDCl3) δ 8.14 (s, 1H), 7.08(d, J = 7.7 Hz, 1H), 6.73 (d, J = 8.0 Hz, 1H), 6.63 (s, 1H), 3.96 (d, J = 5.6 Hz, 2H), 3.26 (t, J = 6.0 Hz, 2H), 3.25 – 3.20 (m, 1H), 2.30 (s, 3H), 1.95 (dq, J =6.5, 3.1 Hz, 4H), 1.17 (d, J = 6.9 Hz, 6H). 13C NMR (150 MHz, CDCl3) δ 156.2,136.6, 134.3, 133.7, 126.2, 121.4, 112.5, 110.2, 67.4, 50.9, 32.8, 28.7,26.9, 26.8, 23.1, 21.7.

[0052] Compound 3c is a colorless, oily liquid. 1 H NMR (600 MHz, CDCl3) δ 7.57 (d, J = 8.0 Hz, 2H), 7.45 (d, J = 8.0 Hz, 2H), 7.08 (d, J = 7.7 Hz, 1H), 6.73 (d, J = 7.6 Hz, 1H), 6.64 (s, 1H), 3.96 (t, J = 6.2 Hz, 2H), 3.56 (s, 2H), 3.28 (m, 1H), 2.50 (s,6H), 2.47 – 2.41 (m, 4H), 2.31 (s, 3H), 1.84 – 1.80 (m, 2H), 1.72 – 1.68 (m,2H), 1.19 (d, J = 6.9 Hz, 6H). 13 C NMR (150 MHz, CDCl3) δ 156.1, 142.6, 136.2,134.0, 129.2, 127.0, 125.8, 125.2, 123.4, 121.0, 112.2, 67.6, 62.5, 58.3,53.2, 27.6, 26.6, 23.7, 22.8, 21.4.

[0053] Compound 3d is a yellow, oily liquid. 1 H NMR (600 MHz, CDCl3) δ 7.35 (ddd, J = 8.4, 5.2,2.5 Hz, 4H), 7.08 (d, J = 7.7 Hz, 1H), 7.00 – 6.94 (m, 4H), 6.73 (d, J = 7.7 Hz,1H), 6.64 (s, 1H), 4.22 (s, 1H), 3.96 (t, J= 6.2 Hz, 2H), 3.27 (m, 1H), 2.60 –2.32 (m, 10H), 2.31 (s, 3H), 1.84 – 1.79 (m, 2H), 1.69 (q, J = 8.0 Hz, 2H), 1.19 (d, J = 6.9 Hz, 6H). 13 C NMR (150 MHz, CDCl3) δ 162.6, 161.0, 156.1, 138.3,136.2, 134.0, 129.3, 125.8, 121.0, 115.4, 112.2, 74.6, 67.7, 58.3, 53.5,51.8, 27.6, 26.6, 23.7, 22.8, 21.4.

[0054] Test case The anti-plant pathogen activity of compounds 1, 2, and 3 was determined using the mycelial inhibition rate method.

[0055] (1) Test strains Rhizoctonia solani ( Rhizoctoniasolani ), Sclerotinia sclerotiorum ( Sclerotiniasclerotiorum ), gray mold ( Botrytiscinerea ), wheat scab ( Fusariumasiaticum ), rice blast fungus ( Magnaportheoryzae Wheat sheath blight pathogen ( Rhizoctoniacerealis ), wheat stem rot fungus ( Fusariumpseudograminearum Fusarium graminearum ( ), Fusarium graminearum ( Fusariumgraminearum Alternaria solanacearum ( Alternariasolani ), creeping rhizomycetes ( Rhizopusstolonifer ) and Fusarium oxysporum ( Fusariumoxysporum All of them are kept in Laboratory 407 of the School of Life Sciences and Engineering, Lanzhou University of Technology.

[0056] (2) Preparation of culture medium PDA Flat Solid Culture Medium: Weigh 200g of potatoes, wash, peel, and cut into small pieces. Add to 1500mL of water, boil for 30 minutes, and filter through eight layers of gauze to obtain 1000mL of potato extract. After cooling, add 20.00g each of glucose and agar, and stir to dissolve evenly. Dispense the solution into 100mL Erlenmeyer flasks, seal with sealing film, and place in an autoclave along with glass petri dishes. Sterilize at 121℃ for 30 minutes, then remove and place on a clean bench. When the temperature drops to approximately 60℃-70℃, add the prepared sample to the culture medium, shake well, pour into glass petri dishes, and allow the culture medium to cool before use.

[0057] Potato Composite Agar (CPDA): Weigh 10.00g potato extract powder, 20.00g glucose, 3.00g dipotassium hydrogen phosphate, 1.50g magnesium sulfate heptahydrate, 0.008g thiamine, and 15.00-20.00g agar. Add 1000mL of hot water and stir until dissolved. Dispense the dissolved medium into 50mL Erlenmeyer flasks, seal with sealing film, and place in an autoclave along with glass petri dishes. Sterilize at 121℃ for 30 minutes, then remove and place on a clean bench. Once the temperature has dropped to approximately 60℃-70℃, add the prepared sample to the medium, shake well, pour into glass petri dishes, and allow to cool completely before use.

[0058] (3) Preparation of the sample solution to be tested Accurately weigh 2 mg of sample, add 100 μL of DMSO to dissolve completely, and then add 1900 μL of sterile water to obtain a 1 mg / mL sample solution.

[0059] (4) Preparation of positive drug solution Accurately weigh 2 mg of the positive control agent (azoxystrobin), add 100 μL of DMSO to dissolve completely, and then add 1900 μL of sterile water to obtain a 1 mg / mL positive control agent solution.

[0060] (5) Measurement method Add 10 mL of the diluted sample solution to 90 mL of PDA (60-70℃) medium. After the medium cools and solidifies, use a 5 mm diameter sterile punch to collect mycelial cells of the plant pathogen that have grown for 5-6 days. Inoculate the 5 mm mycelial cells into the center of the PDA medium containing the sample solution; this is the sample treatment group. Use PDA medium without the sample solution as the blank control group. After inoculation, incubate at 30℃ for 4-5 days, measure the colony diameter, and calculate the inhibition rate. Except for *Alternaria solanacearum*, which is cultured on CPDA medium, all other pathogens are cultured on PDA medium. The inhibition rate is calculated using the following formula: ; Wherein, dc: colony diameter of the blank control group; d0: diameter of the bacterial pellet; ds: colony diameter of the sample treatment group.

[0061] EC 50 Determination method: Select strains whose crude extract at a sample concentration of 50 µg / mL showed an inhibition rate of greater than 70% on the growth of the test strains, and perform EC assays. 50Determination. The sample to be tested was dissolved in a certain amount of DMSO and then added to sterile PDA medium. It was then diluted 2-fold sequentially to a final concentration of 50µg / mL, 25µg / mL, 10µg / mL, 5µg / mL, and 2.5µg / mL. Each concentration was poured into three parallel plates. After cooling, the pathogenic mycelial discs (5mm) were inoculated onto the PDA medium, sealed, and incubated in a 26℃ incubator. After the mycelia of the blank control group had fully grown in the culture dish, the colony diameter was measured, and the inhibition rate was calculated using the above formula.

[0062] (6) Results of the anti-plant pathogen activity of compounds 1, 2 and 3 Data on the anti-plant pathogenic activity of compounds 1, 2, 3 and thymol (compound 4) and EC50 data. 50 The data results are shown in Tables 1 and 2.

[0063] Table 1. Antimicrobial activity data of compounds 1, 2, 3 and thymol (4) against plant pathogens (50 µg / mL)

[0064] Continued from Table 1.

[0065] Table 2. EC50 of compounds 1, 2, 3 and thymol (compound 4) against plant pathogens 50 data

[0066] Continued from Table 2.

[0067] The above description is merely a preferred embodiment of this application; however, the scope of protection of this application is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in this application, based on the technical solution and its improved concept, should be included within the scope of protection of this application.

Claims

1. A thymol derivative and salts thereof, characterized by, The chemical structural formula of the thymol derivative is shown in formula (1): Formula (1), The structure of R1 is at least one of the following 1a to 1c: 。 2. The thymol derivative and salts thereof according to claim 1, characterized by, The structure of R1 is shown in 1a below: 。 3. The method of preparing a thymol derivative according to claim 1 or 2, characterized in that, Includes the following steps: Thymol was subjected to a substitution reaction with dibromoethane in the presence of a base to give thymol oxyethyl bromide; The thymol oxyethyl bromide is refluxed with 2-aminobenzimidazole, 1-(4-trifluoromethylbenzyl)piperazine, or 4,4'-difluorobenzylpiperazine in the presence of carbonate.

4. The application of the thymol derivative and its salt as described in claim 1 or 2, characterized in that, The application includes at least one of the following: Application in the preparation of antimicrobial agents against plant pathogens, wherein the plant pathogens include at least one of the following: Rhizoctonia solani, Sclerotinia sclerotiorum, Botrytiscinerea, Fusarium asiaticum, Magnaphorthe oryzae, Rhizoctonia cerealis, Fusarium pseudograminearum, Fusarium graminearum, Alternaria solani, Rhizopusstolonifer, and Fusarium oxysporum; Application in the preparation of pesticides for the control of plant diseases, wherein the plant diseases include at least one of cucumber damping-off, rice damping-off, cotton damping-off, watermelon damping-off, rapeseed sclerotinia stem rot, tomato gray mold, cucumber gray mold, grape gray mold, wheat scab, rice blast, wheat sheath blight, wheat stem base rot, sweet potato soft rot, and lily wilt.

5. A thymol derivative and its salt, characterized in that, The chemical structural formula of the thymol derivative is shown in formula (2): Equation (2), Wherein, R2 is at least one of the following 2a to 2c: 。 6. The method for preparing the thymol derivative according to claim 5, characterized in that, Includes the following steps: Thymol was subjected to a substitution reaction with dibromopropane in the presence of a base to give thymol oxypropyl bromide; The thymoloxypropyl bromide is refluxed with 2-aminobenzimidazole, 3-mercapto-1,2,4-triazole or 1-(4-trifluoromethylbenzyl)piperazine in the presence of carbonate.

7. The application of the thymol derivative and its salt according to claim 5, characterized in that, The application includes at least one of the following: Application in the preparation of antimicrobial agents against plant pathogens, wherein the plant pathogens include at least one of the following: Rhizoctonia solani, Sclerotinia sclerotiorum, Botrytiscinerea, Fusarium asiaticum, Magnaphorthe oryzae, Rhizoctonia cerealis, Fusarium pseudograminearum, Fusarium graminearum, Alternaria solani, Rhizopusstolonifer, and Fusarium oxysporum; Application in the preparation of pesticides for the control of plant diseases, wherein the plant diseases include at least one of cucumber damping-off, rice damping-off, cotton damping-off, watermelon damping-off, rapeseed sclerotinia stem rot, tomato gray mold, cucumber gray mold, grape gray mold, wheat scab, rice blast, wheat sheath blight, wheat stem base rot, sweet potato soft rot, and lily wilt.

8. A thymol derivative and its salt, characterized in that, The chemical structural formula of the thymol derivative is shown in formula (3): Equation (3), Wherein, R3 is at least one of the following 3a to 3d: 。 9. The method for preparing the thymol derivative according to claim 8, characterized in that, Includes the following steps: Thymol was subjected to a substitution reaction with dibromobutane in the presence of a base to give thymol oxybutyl bromide; The thymoloxybutyl bromide is subjected to a reflux reaction with 2-aminobenzimidazole, 3-mercapto-1,2,4-triazole, 1-(4-trifluoromethylbenzyl)piperazine, or 4,4'-difluorobenzylpiperazine in the presence of carbonate.

10. The application of the thymol derivative and its salt according to claim 8, characterized in that, The application includes at least one of the following: Application in the preparation of antimicrobial agents against plant pathogens, wherein the plant pathogens include at least one of the following: Rhizoctonia solani, Sclerotinia sclerotiorum, Botrytiscinerea, Fusarium asiaticum, Magnaphorthe oryzae, Rhizoctonia cerealis, Fusarium pseudograminearum, Fusarium graminearum, Alternaria solani, Rhizopusstolonifer, and Fusarium oxysporum; Application in the preparation of pesticides for the control of plant diseases, wherein the plant diseases include at least one of cucumber damping-off, rice damping-off, cotton damping-off, watermelon damping-off, rapeseed sclerotinia stem rot, tomato gray mold, cucumber gray mold, grape gray mold, wheat scab, rice blast, wheat sheath blight, wheat stem base rot, sweet potato soft rot, and lily wilt.

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