L-tryptophan amide salt tobacco root-knot nematode inhibitor

Abstract

The invention relates to the technical field of pest repellents, and discloses an L-tryptophan amide salt tobacco root-knot nematode inhibitor. The structural formula of the active ingredient of the L-tryptophan amide salt tobacco root-knot nematode inhibitor provided by the invention is # imgabs0 #. The L-tryptophan amide salt tobacco root-knot nematode inhibitor provided by the invention has a good inhibition effect on tobacco root-knot nematode, and can effectively block a parasitic channel of the root-knot nematode and restore normal growth of plants; the L-tryptophan amide salt type tobacco root-knot nematode inhibitor provided by the invention has relatively high biological safety.

Description

Technical Field

[0001] The present invention relates to the technical field of pest repellents, and more particularly to an L-tryptophan amide salt tobacco root-knot nematode inhibitor. Background Art

[0002] Tobacco root-knot nematode disease is one of the important diseases that endanger tobacco production. After the root-knot nematode invades the roots of tobacco, it will stimulate the proliferation of root cells, forming root knots of different sizes, seriously affecting the absorption of water and nutrients by the tobacco root system, resulting in weak growth of tobacco plants, yellowing of leaves, reduction in yield, and decline in quality. Therefore, the research and development of tobacco root-knot nematode inhibitors is of great significance for tobacco cultivation. Summary of the Invention

[0003] The object of the present invention is to provide an L-tryptophan amide salt tobacco root-knot nematode inhibitor, which has a good inhibitory effect on tobacco root-knot nematodes and can effectively block the parasitic channels of root-knot nematodes and restore the normal growth of plants.

[0004] To achieve the above object, the present invention provides the following technical solutions: One of the technical solutions of the present invention: An L-tryptophan amide salt tobacco root-knot nematode inhibitor, the structural formula of its active ingredient is: ; In the formula, R1 is selected from one of H and C1-C5 alkyl; In the formula, R2 is selected from one of C1-C6 alkyl, C2-C4 acyl, C6-C9 phenyl, halogenated phenyl, C1-C3 alkoxyphenyl, and nitrophenyl.

[0005] Preferably, R1 is selected from one of -H, -CH3, and -CH(CH3)2.

[0006] Preferably, R2 is selected from -CH3, , -COCH3, , , , , , and one of them.

[0007] Furthermore, the synthesis method of the active ingredient includes the following steps: 1) First, put L-tryptophan and R1CHO in an organic solvent, add a catalytic amount of trifluoromethanesulfonic acid, and then drop triethylsilane into the mixed solution of L-tryptophan and R1CHO, react, and purify to obtain intermediate A; Among them, the structural formula of intermediate A is ; 2) Place the intermediate A obtained in step 1) in thionyl chloride, add a catalytic amount of N,N-dimethylformamide, carry out chlorination, and purification to obtain a chlorinated product. Then place the chlorinated product in an organic solvent, and dropwise add a tetrahydrofuran solution of ammonia to the solution of the chlorinated product, react, and purify to obtain intermediate B; Among them, the structural formula of intermediate B is ; 3) Place the intermediate B obtained in step 2) in an organic solvent, add a catalytic amount of potassium carbonate, and then dropwise add R2X to the solution of intermediate B, react, and purify to obtain intermediate C; Among them, the structural formula of intermediate C is ; 4) Place the intermediate C obtained in step 3) in a nitrating reagent, carry out nitration to obtain a nitrated product. Then mix the nitrated product, tin chloride, and hydrochloric acid, and carry out reduction to obtain intermediate D; Among them, the structural formula of intermediate D is ; 5) Place the intermediate D obtained in step 4) in hydrochloric acid, and successively dropwise add sodium nitrite and fluoroboric acid to the solution of intermediate D, react to obtain a diazotized product. Then add a catalytic amount of silica to the diazotized product and carry out thermal decomposition to obtain the active ingredient of the L-tryptophan amide salt tobacco root-knot nematode inhibitor.

[0008] Furthermore, in step 1), the organic solvent is trifluoroacetic acid or dichloroethane.

[0009] Furthermore, in step 1), the molar ratio of L-tryptophan, R1CHO, and triethylsilane is 1∶(1.1 - 1.3)∶(1.1 - 1.3).

[0010] Furthermore, in step 1), the reaction is specifically: react at 0 °C, monitor by thin-layer chromatography until the L-tryptophan reaction is complete.

[0011] Furthermore, in step 2), the molar ratio of the intermediate A and thionyl chloride is 1∶(1.1 - 1.3).

[0012] Furthermore, in step 2), the chlorination is specifically: carry out chlorination at room temperature, monitor by thin-layer chromatography until the intermediate A reaction is complete.

[0013] Furthermore, in step 2), the molar ratio of the chlorinated product and ammonia is 1∶(1.1 - 1.3).

[0014] Further, in step 2), the organic solvent is tetrahydrofuran or diethyl ether.

[0015] Further, in step 2), the reaction is specifically as follows: reacting at 0 °C and monitoring by thin-layer chromatography until the chlorinated product completely reacts.

[0016] Further, in step 3), the organic solvent is N,N-dimethylformamide or dimethyl sulfoxide.

[0017] Further, in step 3), the molar ratio of the intermediate product B to R2X is 1:(2.2 - 2.4).

[0018] Further, in step 3), the reaction is specifically as follows: reacting at 0 °C and monitoring by thin-layer chromatography until the intermediate product B completely reacts.

[0019] Further, in step 4), the nitrating reagent is composed of concentrated sulfuric acid and concentrated nitric acid mixed in a volume ratio of 2:1.

[0020] Further, in step 4), the molar ratio of the intermediate product C to the nitrating reagent is 1:(1.1 - 1.3).

[0021] Further, in step 4), the nitration is specifically as follows: nitrating at room temperature for 1 - 1.5 h.

[0022] Further, in step 4), the molar ratio of the nitrated product, tin chloride, and hydrochloric acid is 1:(3 - 4):(6 - 8).

[0023] Further, in step 4), the reduction is specifically as follows: reducing at room temperature and monitoring by thin-layer chromatography until the nitro group disappears.

[0024] Further, in step 5), the molar ratio of the intermediate product D, sodium nitrite, and fluoboric acid is 1:(1.1 - 1.3):(1.1 - 1.3).

[0025] Further, in step 5), the reaction is specifically as follows: reacting at 0 °C for 30 - 40 min.

[0026] Further, in step 5), the temperature of the thermal decomposition is 60 - 90 °C.

[0027] The synthesis steps of the active ingredient of the L-tryptophan amide salt tobacco root-knot nematode inhibitor of the present invention are as follows: 。

[0028] The second technical solution of the present invention: The preparation method of the above-mentioned L-tryptophan amide salt tobacco root-knot nematode inhibitor includes the following steps: Mix the active ingredient, chitosan and water, and stir to obtain the L-tryptophan amide salt tobacco root-knot nematode inhibitor.

[0029] Furthermore, the mass ratio of the active ingredient, chitosan and water is (5-15):(20-30):(40-60).

[0030] Furthermore, the stirring is specifically: stirring at room temperature for 1-3 h.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows: When the L-tryptophan amide salt tobacco root-knot nematode inhibitor provided by the present invention directly acts on the second-stage larvae of tobacco root-knot nematodes, the mortality rate of the second-stage larvae of tobacco root-knot nematodes can reach 78% at 24 h and 86% at 48 h. Compared with the common insecticide abamectin, the L-tryptophan amide salt tobacco root-knot nematode inhibitor provided by the present invention has a better direct killing effect on tobacco root-knot nematodes; After the L-tryptophan amide salt tobacco root-knot nematode inhibitor provided by the present invention is applied by root irrigation, the root-knot index can reach 1, the nematode reduction rate can reach 77%, and the SPAD value can reach 44. This shows that the L-tryptophan amide salt tobacco root-knot nematode inhibitor provided by the present invention has a good inhibitory effect on tobacco root-knot nematodes and can effectively block the parasitic channels of root-knot nematodes and restore the normal growth of plants; When the L-tryptophan amide salt tobacco root-knot nematode inhibitor provided by the present invention is directly sprayed on the surface of K326 tobacco leaves, there are no symptoms such as leaf burning and deformity, and it has a low contact toxicity to bees. This shows that the L-tryptophan amide salt tobacco root-knot nematode inhibitor provided by the present invention has high biological safety. Detailed implementation manners

[0032] Now, various exemplary implementation manners of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics and implementation manners of the present invention. It should be understood that the terms described in the present invention are only for describing specific implementation manners and are not used to limit the present invention.

[0033] In addition, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0034] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although only preferred methods and materials are described in this invention, any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of this invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0035] Without departing from the scope or spirit of the present invention, various modifications and variations can be made to the specific embodiments of the description of the present invention, which are obvious to those skilled in the art. Other embodiments obtained from the description of the present invention are obvious to those skilled in the art. The description and examples of the present invention are merely exemplary.

[0036] Regarding the use of "comprising", "including", "having", "containing", etc. in this article, they are all open-ended terms, meaning including but not limited to.

[0037] In the following examples, the synthesis method of the active ingredient of the L-tryptophanamide salt tobacco root-knot nematode inhibitor comprises the following steps: 1) According to the molar ratio of L-tryptophan, R1CHO and triethylsilane of 1∶(1.1~1.3)∶(1.1~1.3), first place L-tryptophan and R1CHO in trifluoroacetic acid or dichloroethane, add a catalytic amount of trifluoromethanesulfonic acid, and then control the dropping rate at 30 d / min, dropwise add triethylsilane to the mixed solution of L-tryptophan and R1CHO, react at 0 °C, monitor by thin-layer chromatography until L-tryptophan reacts completely, and purify by column chromatography to obtain intermediate A; 2) According to the molar ratio of intermediate A and thionyl chloride of 1∶(1.1~1.3), place the intermediate A obtained in step 1) in thionyl chloride, add a catalytic amount of N,N-dimethylformamide, chlorinate at room temperature, monitor by thin-layer chromatography until intermediate A reacts completely, purify by column chromatography to obtain the chlorinated product, and then according to the molar ratio of the chlorinated product and ammonia of 1∶(1.1~1.3), place the chlorinated product in tetrahydrofuran or diethyl ether, and at 0 °C, control the dropping rate at 30 d / min, dropwise add the tetrahydrofuran solution of ammonia to the solution of the chlorinated product, monitor by thin-layer chromatography until the chlorinated product reacts completely, filter, and purify by column chromatography to obtain intermediate B; 3) According to the molar ratio of intermediate B to R2X being 1∶(2.2 - 2.4), place the intermediate B obtained in step 2) in N,N-dimethylformamide or dimethyl sulfoxide, add a catalytic amount of potassium carbonate, then control the dropping rate at 30 d / min, dropwise add R2X to the solution of intermediate B, react at 0 °C, monitor by thin-layer chromatography until the reaction of intermediate B is complete, filter, and purify by column chromatography to obtain intermediate C; 4) According to the volume ratio of concentrated sulfuric acid to concentrated nitric acid being 2∶1, mix concentrated sulfuric acid (98%) and concentrated nitric acid (68%) to obtain a nitrating reagent. Then, according to the molar ratio of intermediate C to the nitrating reagent being 1∶(1.1 - 1.3), place the intermediate C obtained in step 3) in the nitrating reagent, nitrify at room temperature for 1 - 1.5 h to obtain a nitrated product. Then, according to the molar ratio of the nitrated product, stannous chloride, and hydrochloric acid being 1∶(3 - 4)∶(6 - 8), mix the nitrated product, stannous chloride, and hydrochloric acid, reduce at room temperature, monitor by thin-layer chromatography until the nitro point disappears, separate the liquid, and rotary evaporate to obtain intermediate D; 5) According to the molar ratio of intermediate D, sodium nitrite, and fluoboric acid being 1∶(1.1 - 1.3)∶(1.1 - 1.3), place the intermediate D obtained in step 4) in hydrochloric acid (10%), and at 0 °C, control the dropping rate at 30 d / min, successively dropwise add sodium nitrite (15% aqueous solution) and fluoboric acid (40% aqueous solution) to the solution of intermediate D, react for 30 - 40 min to obtain a diazotized product. Then, add a catalytic amount of silica to the diazotized product and thermally decompose at 60 - 90 °C to obtain the active ingredient of the L-tryptophan amide salt tobacco root-knot nematode inhibitor.

[0038] Example 1 An active ingredient of an L-tryptophan amide salt tobacco root-knot nematode inhibitor In this example, the synthesis of the active ingredient was carried out with reference to the following synthetic route: ; 1) According to the molar ratio of L-tryptophan, HCHO, and triethylsilane being 1∶1.2∶1.2, first place L-tryptophan and HCHO in trifluoroacetic acid or dichloroethane, add a catalytic amount of trifluoromethanesulfonic acid, then control the dropping rate at 30 d / min, dropwise add triethylsilane to the mixed solution of L-tryptophan and HCHO, react at 0 °C, monitor by thin-layer chromatography until the reaction of L-tryptophan is complete, and purify by column chromatography to obtain intermediate A; 2) According to the molar ratio of intermediate A to thionyl chloride being 1∶1.2, place the intermediate A obtained in step 1) into thionyl chloride, add a catalytic amount of N,N-dimethylformamide, carry out chlorination at room temperature, monitor by thin-layer chromatography until the reaction of intermediate A is complete, purify by column chromatography to obtain the chlorinated product. Then, according to the molar ratio of the chlorinated product to ammonia being 1∶1.2, place the chlorinated product into tetrahydrofuran or diethyl ether, and at 0 °C, control the dropping rate to be 30 d / min, dropwise add the tetrahydrofuran solution of ammonia to the solution of the chlorinated product, monitor by thin-layer chromatography until the reaction of the chlorinated product is complete, filter, and purify by column chromatography to obtain intermediate B; 3) According to the molar ratio of intermediate B to CH3Cl being 1∶2.4, place the intermediate B obtained in step 2) into N,N-dimethylformamide or dimethyl sulfoxide, add a catalytic amount of potassium carbonate, then control the dropping rate to be 30 d / min, dropwise add CH3Cl to the solution of intermediate B, react at 0 °C, monitor by thin-layer chromatography until the reaction of intermediate B is complete, filter, and purify by column chromatography to obtain intermediate C; 4) According to the volume ratio of concentrated sulfuric acid to concentrated nitric acid being 2∶1, mix concentrated sulfuric acid (98%) and concentrated nitric acid (68%) to obtain the nitrating reagent. Then, according to the molar ratio of intermediate C to the nitrating reagent being 1∶1.2, place the intermediate C obtained in step 3) into the nitrating reagent, carry out nitration at room temperature for 1.2 h to obtain the nitrated product. Then, according to the molar ratio of the nitrated product, stannous chloride, and hydrochloric acid being 1∶4∶8, mix the nitrated product, stannous chloride, and hydrochloric acid, carry out reduction at room temperature, monitor by thin-layer chromatography until the nitro point disappears, separate the liquid, and carry out rotary evaporation to obtain intermediate D; 5) According to the molar ratio of intermediate D, sodium nitrite, and fluoboric acid being 1∶1.2∶1.2, place the intermediate D obtained in step 4) into hydrochloric acid (10%), and at 0 °C, control the dropping rate to be 30 d / min, successively dropwise add sodium nitrite (15% aqueous solution) and fluoboric acid (40% aqueous solution) to the solution of intermediate D, react for 35 min to obtain the diazotized product. Then, add a catalytic amount of silica to the diazotized product, carry out thermal decomposition at 70 °C to obtain the active ingredient of the L-tryptophan amide salt tobacco root-knot nematode inhibitor.

[0039] Example 2 An active ingredient of L-tryptophan amide salt tobacco root-knot nematode inhibitor Same as Example 1, the difference is only that HCHO in step 1) is replaced by CH3CHO, and CH3Cl in step 3) is replaced by ; The specific synthetic route is as follows: .

[0040] Example 3 An active ingredient of L-tryptophan amide salt for inhibiting tobacco root-knot nematodes Same as Example 1, except that CH3Cl in step 3) is replaced by CH3COCl; The specific synthesis route is as follows: 。

[0041] Example 4 An active ingredient of L-tryptophan amide salt for inhibiting tobacco root-knot nematodes Same as Example 1, except that HCHO in step 1) is replaced by CH3CHO, and CH3Cl in step 3) is replaced by ; The specific synthesis route is as follows: 。

[0042] Example 5 An active ingredient of L-tryptophan amide salt for inhibiting tobacco root-knot nematodes Same as Example 1, except that HCHO in step 1) is replaced by (CH3)2CHCHO, and CH3Cl in step 3) is replaced by ; The specific synthesis route is as follows: 。

[0043] Example 6 An active ingredient of L-tryptophan amide salt for inhibiting tobacco root-knot nematodes Same as Example 1, except that HCHO in step 1) is replaced by CH3CHO, and CH3Cl in step 3) is replaced by ; The specific synthesis route is as follows: 。

[0044] Example 7 An active ingredient of L-tryptophan amide salt for inhibiting tobacco root-knot nematodes Same as Example 1, except that CH3Cl in step 3) is replaced by ; The specific synthesis route is as follows: 。

[0045] Example 8 An active ingredient of L-tryptophan amide salt for inhibiting tobacco root-knot nematodes Same as Example 1, except that HCHO in step 1) is replaced by (CH3)2CHCHO, and CH3Cl in step 3) is replaced by ; The specific synthesis route is as follows: 。

[0046] Example 9 An active ingredient of L-tryptophan amide salt tobacco root-knot nematode inhibitor Same as Example 1, except that HCHO in step 1) is replaced by (CH3)2CHCHO, and CH3Cl in step 3) is replaced by ; The specific synthesis route is as follows: 。

[0047] Example 10 An active ingredient of L-tryptophan amide salt tobacco root-knot nematode inhibitor Same as Example 1, except that CH3Cl in step 3) is replaced by ; The specific synthesis route is as follows: 。

[0048] Using the compounds synthesized in Examples 1 to 10 as the active ingredients of L-tryptophan amide salt tobacco root-knot nematode inhibitors to prepare L-tryptophan amide salt tobacco root-knot nematode inhibitors, which specifically include the following steps: According to the mass ratio of the active ingredient, chitosan and water of 10:25:50, mix the active ingredient, chitosan and water, and stir at room temperature for 1 to 3 h to obtain the L-tryptophan amide salt tobacco root-knot nematode inhibitor.

[0049] Effect verification I. Laboratory in vitro activity test Isolate the second-stage larvae (J2) of tobacco root-knot nematodes from infected tobacco root knots and suspend them in sterile water; Add 1 mL of the reagent to be tested (L-tryptophan amide salt tobacco root-knot nematode inhibitor prepared with the compounds synthesized in Examples 1 to 10 as the active ingredient, with a concentration of 100 ppm) and 100 J2 larvae to each well of the multi-well plate, culture in the dark at 25 °C, and perform microscopic examination at 24 h and 48 h respectively to calculate the mortality rate (rigid immobility is regarded as death). The calculation results of the mortality rate are shown in Table 1; Table 1 Mortality rate (%)

[0050] As can be seen from the data in Table 1, when a tobacco root-knot nematode inhibitor of L-tryptophan amide salt provided by the present invention directly acts on the second-stage larvae of tobacco root-knot nematodes, the mortality rate of the second-stage larvae of tobacco root-knot nematodes can reach 78% at 24 h and 86% at 48 h. Compared with the common insecticide abamectin, the tobacco root-knot nematode inhibitor of L-tryptophan amide salt provided by the present invention has a better direct killing effect on tobacco root-knot nematodes.

[0051] II. Pot experiment Sow K326 tobacco in cultivation pots (sowing 5 plants in each cultivation pot). After 2 weeks of sowing, inoculate 1000 J2 larvae in each cultivation pot. 24 h after inoculation, apply medicine by drenching the roots at 50 mL / plant (using the L-tryptophan amide salt tobacco root-knot nematode inhibitor prepared with the compounds synthesized in Examples 1-10 as the active ingredient, with a concentration of 100 ppm; abamectin, with a concentration of 50 ppm; clear water). 3 weeks after the end of medicine application, detect the nematode quantity and plant growth indexes. The detection results of the pot experiment are shown in Table 2; Table 2 Detection results of pot experiment

[0052] As can be seen from the data in Table 2, when a tobacco root-knot nematode inhibitor of L-tryptophan amide salt provided by the present invention is applied by drenching the roots, the root-knot index can reach 1, the nematode reduction rate can reach 77%, and the SPAD value can reach 44. This shows that the tobacco root-knot nematode inhibitor of L-tryptophan amide salt provided by the present invention has a good inhibitory effect on tobacco root-knot nematodes, and can effectively block the parasitic channels of root-knot nematodes and restore the normal growth of plants.

[0053] III. Biosafety detection Conduct biosafety detection on the L-tryptophan amide salt tobacco root-knot nematode inhibitor prepared in Example 7. After detection, when the L-tryptophan amide salt tobacco root-knot nematode inhibitor with a concentration of 1000 ppm is sprayed on the surface of K326 tobacco leaves, there are no symptoms such as leaf burns and deformities; After detection, after bees contact the L-tryptophan amide salt tobacco root-knot nematode inhibitor with a concentration of 1000 ppm, the mortality rate at 48 h is only 26%, showing low contact toxicity to bees.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: still modifications or equivalent substitutions can be made to the specific embodiments of the present invention, and any modification or equivalent substitution that does not depart from the spirit and scope of the present invention should be covered by the protection scope of the claims of the present invention.

Claims

1. An L-tryptophan amide salt tobacco root-knot nematode inhibitor, characterized in that, The structural formula of the active ingredient of the L-tryptophan amide salt tobacco root-knot nematode inhibitor is as follows: ； In the formula, R1 is selected from one of H and C1-C5 alkyl; In the formula, R2 is selected from one of C1-C6 alkyl, C2-C4 acyl, C6-C9 phenyl, halogenated phenyl, C1-C3 alkoxyphenyl and nitrophenyl.

2. The L-tryptophan amide salt tobacco root-knot nematode inhibitor according to claim 1, wherein The synthesis method of the active ingredient includes the following steps: 1) First, put L-tryptophan and R1CHO into an organic solvent, add a catalytic amount of trifluoromethanesulfonic acid, and then dropwise add triethylsilane to the mixed solution of L-tryptophan and R1CHO, react and purify to obtain intermediate A; Among them, the structural formula of intermediate A is ; 2) Put the intermediate A obtained in step 1) into thionyl chloride, add a catalytic amount of N,N-dimethylformamide, chlorinate and purify to obtain a chlorinated product. Then put the chlorinated product into an organic solvent, and dropwise add a tetrahydrofuran solution of ammonia to the solution of the chlorinated product, react and purify to obtain intermediate B; Among them, the structural formula of intermediate B is ; 3) Put the intermediate B obtained in step 2) into an organic solvent, add a catalytic amount of potassium carbonate, and then dropwise add R2X to the solution of intermediate B, react and purify to obtain intermediate C; Among them, the structural formula of intermediate C is ; 4) Put the intermediate C obtained in step 3) into a nitrating reagent, nitrate to obtain a nitrated product. Then mix the nitrated product, stannous chloride and hydrochloric acid, and reduce to obtain intermediate D; Among them, the structural formula of the intermediate D is ; 5) Put the intermediate D obtained in step 4) into hydrochloric acid, and dropwise add sodium nitrite and fluoroboric acid to the solution of intermediate D in sequence, react to obtain a diazotized product. Then add a catalytic amount of silica to the diazotized product and thermally decompose to obtain the active ingredient of the L-tryptophan amide salt tobacco root-knot nematode inhibitor.

3. The L-tryptophan amide salt tobacco root-knot nematode inhibitor according to claim 2, characterized in that, In step 1), the organic solvent is trifluoroacetic acid or dichloroethane; the molar ratio of L-tryptophan, R1CHO and triethylsilane is 1∶(1.1-1.3)∶(1.1-1.3); the specific reaction is: react at 0 °C and monitor by thin-layer chromatography until L-tryptophan reacts completely.

4. The L-tryptophan amide salt tobacco root-knot nematode inhibitor according to claim 2, wherein In step 2), the molar ratio of intermediate A and thionyl chloride is 1∶(1.1-1.3); the specific chlorination is: chlorinate at room temperature and monitor by thin-layer chromatography until intermediate A reacts completely; the molar ratio of the chlorinated product and ammonia is 1∶(1.1-1.3); the organic solvent is tetrahydrofuran or ether; the specific reaction is: react at 0 °C and monitor by thin-layer chromatography until the chlorinated product reacts completely.

5. The L-tryptophan amide salt tobacco root-knot nematode inhibitor according to claim 2, characterized in that, In step 3), the organic solvent is N,N-dimethylformamide or dimethyl sulfoxide; the molar ratio of intermediate B and R2X is 1∶(2.2-2.4); the specific reaction is: react at 0 °C and monitor by thin-layer chromatography until intermediate B reacts completely.

6. The L-tryptophan amide salt tobacco root-knot nematode inhibitor according to claim 2, wherein In step 4), the nitrating reagent is formed by mixing concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 2:1; the molar ratio of the intermediate product C to the nitrating reagent is 1:(1.1 - 1.3); the nitration is specifically as follows: nitration is carried out at room temperature for 1 - 1.5 h; the molar ratio of the nitration product, tin chloride and hydrochloric acid is 1:(3 - 4):(6 - 8); the reduction is specifically as follows: reduction is carried out at room temperature and monitored by thin-layer chromatography until the nitro group point disappears.

7. The L-tryptophan amide salt tobacco root-knot nematode inhibitor according to claim 2, characterized in that, In step 5), the molar ratio of the intermediate product D, sodium nitrite and fluoboric acid is 1:(1.1 - 1.3):(1.1 - 1.3); the reaction is specifically as follows: the reaction is carried out at 0 °C for 30 - 40 min; in step 5), the temperature of the thermal decomposition is 60 - 90 °C.

8. A preparation method of an L-tryptophan amide salt tobacco root-knot nematode inhibitor as described in any one of claims 1 to 7, characterized in that, It includes the following steps: Mix the active ingredient, chitosan and water, and stir to obtain the L-tryptophan amide salt tobacco root-knot nematode inhibitor.

9. The preparation method according to claim 8, characterized in that, The mass ratio of the active ingredient, chitosan and water is (5 - 15):(20 - 30):(40 - 60).

10. The preparation method according to claim 8, characterized in that, The stirring is specifically as follows: stirring is carried out at room temperature for 1 - 3 h.

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