A chalcone derivative containing a benzoxazole structure, and its preparation method and application

Abstract

The present invention discloses a chalcone derivative containing a benzoxazole structure, a preparation method thereof, and an application thereof, and belongs to the field of chemical technology. The present invention uses 1-(4-(3-bromopropyloxy)phenyl)-3-(substituted aromatic)-2-propylene-1-one or 1-(4-(4-bromobutyloxy)phenyl)-3-(substituted aromatic)-2-propylene-1-one to undergo an etherification reaction with benzo[d]oxazole-2-thiol to generate a chalcone derivative containing a benzoxazole structure, the structural formula of which is as follows, wherein n is 3 or 4, and R is any one of a phenyl, a substituted phenyl, a thienyl, or a furyl group. Experimental testing has shown that the derivative has good inhibitory activity against plant bacteria such as rice bacterial blight, melon wilt, and potato soft rot, and can be used as a potential agent for inhibiting plant bacteria.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical industry, in particular to a chalcone derivative containing a benzoxazole structure and a preparation method and application thereof. Background Art

[0002] Plant diseases caused by plant bacteria have long had a severe impact on global food production and quality, resulting in enormous economic losses. For example, rice bacterial leaf blight (BLB), caused by Xanthomonas oryzae pv. oryzae (Xoo), is one of the most serious bacterial diseases, resulting in rice yield losses of up to 50%. Potato soft rot infection causes approximately 15% of potato damage, resulting in severe economic losses. Therefore, scientists have been committed to developing new fungicides with excellent antibacterial activity, low toxicity, and environmental friendliness. Chalcones are an extremely important class of natural products, widely found in plants such as licorice, safflower, and hops. Chalcones and their derivatives have a variety of biological activities, including antibacterial, antiviral, antioxidant, insecticidal, and anticancer activities, and are highly favored by scientific researchers. In recent years, chalcones and their derivatives have been widely used in the field of pesticides.

[0003] In 2019, Xia et al. synthesized a series of quinoxaline-containing chalcone derivatives and tested the bioactivity of all target compounds. The results showed that some of the compounds exhibited excellent antibacterial activity against X. citri (Xac), R. solanacearum (Rs), and X. oryzae (Xoo), significantly outperforming the control agents chlorothalonil and thiophanate-methyl.

[0004] In 2019, Chen et al. synthesized a series of thioether triazole-containing chalcone derivatives through active splicing and tested the bioactivity of all target compounds. The results showed that some of the compounds exhibited excellent antibacterial activity against Xac, significantly outperforming their control agents, chlorothiazolinone and thiophanate-methyl.

[0005] In 2023, Hu et al. synthesized a series of indole-containing chalcone derivatives through active splicing and tested the bioactivity of all target compounds. The results showed that some of the compounds had good antibacterial activity against Xanthomonas oryzae (Xoo) and Xanthomonas citri (Xac), significantly outperforming the control agent, thiophanate-methyl.

[0006] To date, there has been no report on introducing benzoxazole structures into chalcone derivatives and testing their antibacterial activity against plants. Summary of the Invention

[0007] The purpose of the present invention is to provide a chalcone derivative containing a benzoxazole structure and its preparation method and application to solve the problems existing in the above-mentioned prior art. The derivative has good inhibitory activity against various bacteria and is a potential compound for preparing antibacterial preparations for plants.

[0008] To achieve the above object, the present invention provides the following solutions:

[0009] The present invention provides a chalcone derivative containing a benzoxazole structure, the structural formula of which is shown below:

[0010]

[0011] wherein n is 3 or 4, and R is any one of phenyl, substituted phenyl, thienyl or furyl.

[0012] Preferably, when R is a substituted phenyl group, the position at the meta or para position of the bond to the benzene ring is a substituent group, and the substituent group includes any one of a methyl group, a methoxy group, a nitro group or a halogen atom, and the halogen atom is fluorine, chlorine or bromine.

[0013] The present invention also provides a method for preparing the chalcone derivatives containing a benzoxazole structure, comprising the following steps:

[0014] Using ethanol as solvent, under alkaline conditions, 4-hydroxyacetophenone and substituted formaldehyde undergo aldol condensation reaction to prepare 1-(4-hydroxyphenyl)-3-(substituted aromatic)-2-propen-1-one;

[0015]

[0016] Under the conditions of K2CO3 as an acid-binding agent and acetonitrile as a solvent, the 1-(4-hydroxyphenyl)-3-(substituted aromatic)-2-propene-1-one reacts with 1,3-dibromopropane or 1,4-dibromobutane to prepare 1-(4-(3-bromopropoxy)phenyl)-3-(substituted aromatic)-2-propene-1-one or 1-(4-(4-bromobutoxy)phenyl)-3-(substituted aromatic)-2-propene-1-one;

[0017]

[0018] Benzo[d]oxazole-2-thiol was prepared by the reaction of 2-aminophenol with CS2 in the presence of KOH as an acid-binding agent and ethanol as a solvent.

[0019]

[0020] Under the conditions of K2CO3 as an acid binding agent and acetonitrile as a solvent, the 1-(4-(3-bromopropyloxy)phenyl)-3-(substituted aromatic)-2-propene-1-one or the 1-(4-(4-bromobutyloxy)phenyl)-3-(substituted aromatic)-2-propene-1-one and the benzo[d]oxazole-2-thiol undergo an etherification reaction to generate a chalcone derivative containing a benzoxazole structure;

[0021]

[0022] Preferably, the molar ratio of the 4-hydroxyacetophenone to the substituted formaldehyde is (4-20):(5-20), the ratio of the 4-hydroxyacetophenone to the ethanol is (4-20) mmol:(30-80) mL; and the aldol condensation reaction time is 10-12 h.

[0023] Preferably, the molar ratio of the 1-(4-hydroxyphenyl)-3-(substituted aromatic)-2-propene-1-one to the 1,3-dibromopropane, or the molar ratio of the 1-(4-hydroxyphenyl)-3-(substituted aromatic)-2-propene-1-one to the 1,4-dibromobutane is (2-10):(5-20);

[0024] The ratio of the 1-(4-hydroxyphenyl)-3-(substituted aromatic)-2-propen-1-one, the K2CO3 and the acetonitrile is (2-10) mmol: (6-20) mmol: (25-50) mL;

[0025] The reaction temperature of the 1-(4-hydroxyphenyl)-3-(substituted aromatic)-2-propene-1-one and the 1,3-dibromopropane or the 1,4-dibromobutane is 75-85° C., and the reaction time is 5-6 hours.

[0026] Preferably, the molar ratio of the 2-aminophenol to the CS2 is (30-60) mmol: (20-70) mmol; the ratio of the 2-aminophenol, the KOH and the ethanol is (30-60) mmol: (20-100) mmol: (20-50) mL;

[0027] The reaction conditions of the 2-aminophenol and the CS2 are: 60° C. for 4 to 6 hours.

[0028] Preferably, the molar ratio of the 1-(4-(3-bromopropoxy)phenyl)-3-(substituted aromatic)-2-propene-1-one to the benzo[d]oxazole-2-thiol is (2.5-10):(1-10);

[0029] The molar ratio of the 1-(4-(4-bromobutyloxy)phenyl)-3-(substituted aromatic)-2-propene-1-one to the benzo[d]oxazole-2-thiol is (2 to 10):(1 to 10);

[0030] The ratio of the benzo[d]oxazole-2-thiol, the K2CO3 and the acetonitrile is (1-10) mmol: (5-20) mmol: (20-50) mL;

[0031] The etherification reaction conditions are: reaction at room temperature for 18 hours.

[0032] The present invention also provides the use of the chalcone derivatives containing a benzoxazole structure in inhibiting plant bacteria or preparing a preparation for inhibiting bacteria.

[0033] Preferably, the bacteria include Xanthomonas citri, Xanthomonas oryzae, Xanthomonas kiwifruit, Fusarium wilt of melon, Psoralea corylifolia of tobacco, Soft rot of potato or Xanthomonas angularis leaf spot of mango.

[0034] The present invention also provides a preparation for inhibiting bacteria, which contains the chalcone derivatives containing a benzoxazole structure, and the bacteria include citrus canker, rice bacterial blight, kiwifruit canker, melon wilt, tobacco bacterial wilt, potato soft rot or mango bacterial leaf spot.

[0035] The present invention discloses the following technical effects:

[0036] The present invention reacts 1-(4-(3-bromopropyloxy)phenyl)-3-(substituted aromatic)-2-propene-1-one or 1-(4-(4-bromobutyloxy)phenyl)-3-(substituted aromatic)-2-propene-1-one with benzo[d]oxazole-2-thiol having excellent biological activity to generate chalcone derivatives containing a benzoxazole structure. The present invention uses 4-hydroxyacetophenone, various substituted formaldehydes, 2-aminophenol, CS2, and the like as raw materials to first prepare the above-mentioned compounds. In the preparation of the chalcone derivatives containing a benzoxazole structure, the raw materials and reagents used in the entire preparation process are all common organic reagents and solvents that are readily available. Furthermore, the reaction conditions used in the preparation process are relatively mild, post-processing is simple, and the yield is high, ranging from 30% to 95%.

[0037] The chalcone derivatives containing a benzoxazole structure prepared by the present invention have been experimentally verified to have an inhibitory activity against plant bacteria at a concentration of 100 μg / mL. The results show that at the above concentration, the derivatives have good inhibitory activity against various bacteria. In particular, some target compounds have obvious inhibitory activity against citrus canker, rice bacterial blight, kiwifruit canker, melon wilt, tobacco bacterial wilt, potato soft rot, and mango bacterial angular leaf spot, and can be used as potential agents for inhibiting plant bacteria. DETAILED DESCRIPTION

[0038] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0039] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the stated range, is also encompassed within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0040] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0041] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be illustrative only.

[0042] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0043] Example 1

[0044] The synthesis of (E)-1-(4-(3-(benzo[d]oxazol-2-yl-thio)propoxy)phenyl)-3-phenyl-2-propene-1-one (compound number Z1) comprises the following steps:

[0045] (1) Synthesis of 1-(4-hydroxyphenyl)-3-phenyl-2-propen-1-one: 4-Hydroxyacetophenone (3.00 g), benzaldehyde (2.58 g), and 50 mL of ethanol were added to a round-bottom flask. 20-30 mL of 10% sodium hydroxide solution was slowly added dropwise under an ice bath and stirred for approximately 10-12 hours. After the reaction was completed, the mixed solution was poured into a 1000 mL beaker containing 400 mL of ice water. The pH was adjusted to 5-6 with 5% dilute hydrochloric acid solution. A large amount of light yellow solid precipitated. The solid was filtered under reduced pressure and finally recrystallized from an ethanol / water system to obtain a light yellow solid with a yield of 94%.

[0046] (2) Synthesis of 1-(4-(3-bromopropoxy)phenyl)-3-phenyl-2-propen-1-one: 1-(4-hydroxyphenyl)-3-phenyl-2-propen-1-one (1.5 g), K2CO3 (2.6 g), and 40 mL of acetonitrile were added to a 100 mL round-bottom flask. The temperature was controlled at approximately 80°C and the mixture was stirred under electromagnetic stirring for 30 to 60 min. Then, 2.0 mL of 1,3-dibromopropane was slowly added dropwise and heated to react for 5 to 6 h. After the reaction was completed, the system was transferred to a beaker containing 50 mL of ice water and stirred until a white solid precipitated. The solid was filtered under reduced pressure and the filter cake was washed with petroleum ether to obtain a white solid with a yield of 85%.

[0047] (3) Synthesis of benzo[d]oxazole-2-thiol: 2-Aminophenol (3.00 g), KOH (3.08 g), and 40 mL of ethanol were placed in a 100 mL round-bottom flask and stirred at room temperature for 15 min. CS2 (3.49 mL) was then slowly added dropwise to the reaction system. The temperature was raised to 60°C and the reaction was allowed to proceed for 4-6 h. After the reaction was completed, the system was cooled to room temperature and transferred to a 1000 mL beaker containing ice water. The pH of the system was adjusted to 1-2 with 5% HCl solution. The mixture was filtered under reduced pressure and the filter cake was washed with petroleum ether to obtain a white solid with a yield of 89%.

[0048] (4) Synthesis of (E)-1-(4-(3-(Benzo[d]oxazol-2-yl-thio)propoxy)phenyl)-3-phenyl-2-propene-1-one: Benzo[d]oxazole-2-thiol (0.38 g), K2CO3 (1.20 g) and 40 mL of CH3CN were added to a 100 mL round-bottom flask. After stirring at room temperature for 30 min, 1-(4-(3-bromopropoxy)phenyl)-3-phenyl-2-propene-1-one (1.00 g) was added to the reaction system. The reaction was continued at room temperature for 18 h. The reaction system was concentrated under reduced pressure to remove part of the solvent and then poured into 300 mL of ice water and stirred until a large amount of white solid precipitated. The reaction mixture was allowed to stand, filtered, and recrystallized from anhydrous ethanol to obtain a crude product, which was purified by column chromatography (petroleum ether:ethyl acetate = 2:1, v / v) to obtain (E)-1-(4-(3-(benzo[d]oxazol-2-yl-thio)propoxy)phenyl)-3-phenyl-2-propene-1-one as a yellow solid in a yield of 53%.

[0049] Example 2

[0050] The synthesis of (E)-1-(4-(4-(Benzo[d]oxazol-2-yl-thio)butoxy)phenyl)-3-phenyl-2-propene-1-one (compound number Z2) comprises the following steps:

[0051] (1) Synthesis of 1-(4-hydroxyphenyl)-3-phenyl-2-propene-1-one: Same as (1) in Example 1.

[0052] (2) Synthesis of 1-(4-(4-bromobutoxy)phenyl)-3-phenyl-2-propene-1-one: Compared with (2) of Example 1, the difference is that 1-(4-hydroxyphenyl)-3-phenyl-2-propene-1-one and 1,4-dibromobutane are used as raw materials; the other steps are the same.

[0053] (3) Synthesis of benzo[d]oxazole-2-thiol: Same as (3) in Example 1.

[0054] (4) Synthesis of (E)-1-(4-(4-benzo[d]oxazol-2-yl-thio)phenyl)-3-phenylpropyl-2-ene-1-one: Compared with (4) in Example 1, the difference is that 1-(4-(4-bromobutoxy)phenyl)-3-phenyl-2-propene-1-one is used as the raw material; the other steps are the same.

[0055] Example 3

[0056] The synthesis of (E)-1-(4-(3-(benzo[d]oxazol-2-yl-thio)propoxy)phenyl)-3-(4-methylphenyl)-2-propene-1-one (compound number Z3) includes the following steps:

[0057] (1) Synthesis of 1-(4-hydroxyphenyl)-4-(4-methylphenyl)-2-propene-1-one: Compared with (1) of Example 1, the difference is that 4-methylbenzaldehyde is used as the raw material; the other steps are the same.

[0058] (2) Synthesis of 1-(4-(3-bromopropyloxy)phenyl)-4-(4-methylphenyl)-2-propene-1-one: Compared with (2) of Example 1, the difference is that 1-(4-hydroxyphenyl)-4-p-methylphenyl-2-propene-1-one is used as the raw material; the other steps are the same.

[0059] (3) Synthesis of benzo[d]oxazole-2-thiol: Same as (3) in Example 1.

[0060] (4) (E)-1-(4-(3-(Benzo[d]oxazol-2-yl-thio)propoxy)phenyl)-3-(4-methylphenyl)-2-propene-1-one: Compared with (4) in Example 1, the difference is that 1-(4-(3-bromopropoxy)phenyl)-4-(4-methylphenyl)-2-propene-1-one is used as the raw material; the other steps are the same.

[0061] Example 4

[0062] The synthesis of (E)-1-(4-(4-(Benzo[d]oxazol-2-yl-thio)butoxy)phenyl)-3-(4-methylphenyl)-2-propene-1-one (compound number Z4) comprises the following steps:

[0063] (1) Synthesis of (E)-1-(4-hydroxyphenyl)-3-(4-methylphenyl)-2-propene-1-one: Compared with (1) of Example 1, the difference is that 4-methylbenzaldehyde is used as the raw material; the other steps are the same.

[0064] (2) Synthesis of 1-(4-(4-bromobutoxy)phenyl)-3-(4-methylphenyl)-2-propene-1-one: Compared with (2) of Example 1, the difference is that 1-(4-hydroxyphenyl)-3-(4-methylphenyl)-2-propene-1-one is used as the raw material; the other steps are the same.

[0065] (3) Synthesis of benzo[d]oxazole-2-thiol: Same as (3) in Example 1.

[0066] (4) Synthesis of (E)-1-(4-(4-(Benzo[d]oxazol-2-yl-thio)butoxy)phenyl)-3-(4-methylphenyl)-2-propene-1-one: Compared with (4) in Example 1, the difference is that 1-(4-(4-bromobutoxy)phenyl)-3-(4-methylphenyl)-2-propene-1-one is used as the raw material; the other steps are the same.

[0067] Example 5

[0068] The synthesis of (E)-1-(4-(3-(benzo[d]oxazol-2-yl-thio)propoxy)phenyl)-3-(4-methoxyphenyl)-2-propen-1-one (compound number Z5) comprises the following steps:

[0069] (1) Synthesis of 1-(4-hydroxyphenyl)-3-(4-methoxyphenyl)-2-propen-1-one: Compared with (1) of Example 1, the difference is that 4-methoxybenzaldehyde is used as the raw material; the other steps are the same.

[0070] (2) Synthesis of 1-(4-(3-bromopropyloxy)phenyl)-3-(4-methoxyphenyl)-2-propene-1-one: Compared with (2) of Example 1, the difference is that 1-(4-hydroxyphenyl)-3-(4-methoxyphenyl)-2-propene-1-one is used as the raw material; the other steps are the same.

[0071] (3) Synthesis of benzo[d]oxazole-2-thiol: Same as (3) in Example 1.

[0072] (4) Synthesis of (E)-1-(4-(3-(Benzo[d]oxazol-2-yl-thio)propoxy)phenyl)-3-(4-methoxyphenyl)-2-propene-1-one: Compared with (4) of Example 1, the difference is that 1-(4-(3-bromopropoxy)phenyl)-3-(4-methoxyphenyl)-2-propene-1-one is used as the raw material; the other steps are the same.

[0073] Example 6

[0074] The synthesis of (E)-1-(4-(3-(benzo[d]oxazol-2-yl-thio)propoxy)phenyl)-3-(4-fluorophenyl)-2-propen-1-one (compound number Z6) comprises the following steps:

[0075] (1) Synthesis of 1-(4-hydroxyphenyl)-3-(4-fluorophenyl)-2-propen-1-one: Compared with (1) of Example 1, the difference is that 4-fluorobenzaldehyde is used as the raw material; the other steps are the same.

[0076] (2) Synthesis of 1-(4-(3-bromopropyloxy)phenyl)-3-(4-fluorophenyl)-2-propene-1-one: Compared with (2) of Example 1, the difference is that 1-(4-hydroxyphenyl)-3-(4-fluorophenyl)-2-propene-1-one is used as the raw material; the other steps are the same.

[0077] (3) Synthesis of benzo[d]oxazole-2-thiol: Same as (3) in Example 1.

[0078] (4) Synthesis of (E)-1-(4-(3-(Benzo[d]oxazol-2-yl-thio)propoxy)phenyl)-3-(4-fluorophenyl)-2-propene-1-one: as in step (4) of Example 1, except that 1-(4-(3-bromopropoxy)phenyl)-3-(4-fluorophenyl)-2-propene-1-one was used as the raw material; the other steps were the same.

[0079] Example 7

[0080] The synthesis of (E)-1-(4-(4-(Benzo[d]oxazol-2-yl-thio)butoxy)phenyl)-3-(4-fluorophenyl)-2-propen-1-one (compound number Z7) comprises the following steps:

[0081] (1) Synthesis of (E)-3-(4-fluorophenyl)-1-(4-hydroxyphenyl)-2-propen-1-one: Compared with (1) of Example 1, the difference is that 4-fluorobenzaldehyde is used as the raw material; the other steps are the same.

[0082] (2) Synthesis of 1-(4-(4-bromobutoxy)phenyl)-3-(4-fluorophenyl)-2-propene-1-one: Compared with (2) of Example 1, the difference is that (E)-3-(4-fluorophenyl)-1-(4-hydroxyphenyl)-2-propene-1-one and 1,4-dibromobutane are used as raw materials; the other steps are the same.

[0083] (3) Synthesis of benzo[d]oxazole-2-thiol: Same as (3) in Example 1.

[0084] (4) Synthesis of (E)-1-(4-(4-(Benzo[d]oxazol-2-yl-thio)butoxy)phenyl)-3-(4-fluorophenyl)-2-propene-1-one: as in step (4) of Example 1, except that 1-(4-(4-bromobutoxy)phenyl)-3-(4-fluorophenyl)-2-propene-1-one was used as the raw material.

[0085] Example 8

[0086] The synthesis of (E)-1-(4-(3-(benzo[d]oxazol-2-yl-thio)propoxy)phenyl)-3-(4-bromophenyl)-2-propen-1-one (compound number Z8) comprises the following steps:

[0087] (1) Synthesis of 1-(4-hydroxyphenyl)-3-(4-bromophenyl)-2-propen-1-one: Compared with (1) of Example 1, the difference is that 4-bromobenzaldehyde is used as the raw material; the other steps are the same.

[0088] (2) Synthesis of 1-(4-(3-bromopropyloxy)phenyl)-3-(4-bromophenyl)-2-propene-1-one: Compared with (2) of Example 1, the difference is that 1-(4-hydroxyphenyl)-3-(4-bromophenyl)-2-propene-1-one is used as the raw material; the other steps are the same.

[0089] (3) Synthesis of benzo[d]oxazole-2-thiol: Same as (3) in Example 1.

[0090] (4) Synthesis of (E)-1-(4-(3-(Benzo[d]oxazol-2-yl-thio)propoxy)phenyl)-3-(4-bromophenyl)-2-propene-1-one: Compared with (4) in Example 1, the difference is that 1-(4-(3-bromopropoxy)phenyl)-3-(4-bromophenyl)-2-propene-1-one is used as the raw material; the other steps are the same.

[0091] Example 9

[0092] The synthesis of (E)-1-(4-(3-(Benzo[d]oxazol-2-yl-thio)propoxy)phenyl)-3-(3-methylphenyl)-2-propene-1-one (compound number Z9) comprises the following steps:

[0093] (1) Synthesis of 1-(4-hydroxyphenyl)-3-(3-methylphenyl)-2-propene-1-one: Compared with (1) of Example 1, the difference is that 3-methylbenzaldehyde is used as the raw material; the other steps are the same.

[0094] (2) Synthesis of 1-(4-(3-bromopropyloxy)phenyl)-3-(3-methylphenyl)-2-propene-1-one: Compared with (2) of Example 1, the difference is that 1-(4-hydroxyphenyl)-3-(3-methylphenyl)-2-propene-1-one is used as the raw material; the other steps are the same.

[0095] (3) Synthesis of benzo[d]oxazole-2-thiol: Same as (3) in Example 1.

[0096] (4) Synthesis of (E)-1-(4-(3-(Benzo[d]oxazol-2-yl-thio)propoxy)phenyl)-3-(3-methylphenyl)-2-propene-1-one: Compared with (4) of Example 1, the difference is that 1-(4-(3-bromopropoxy)phenyl)-3-(3-methylphenyl)-2-propene-1-one is used as the raw material; the other steps are the same.

[0097] Example 10

[0098] The synthesis of (E)-1-(4-(4-(Benzo[d]oxazol-2-yl-thio)butoxy)phenyl)-3-(3-methylphenyl)-2-propen-1-one (Compound No. Z10) comprises the following steps:

[0099] (1) Synthesis of 1-(4-hydroxyphenyl)-3-(3-methylphenyl)-2-propene-1-one: Compared with (1) of Example 1, the difference is that 3-methylbenzaldehyde is used as the raw material; the other steps are the same.

[0100] (2) Synthesis of 1-(4-(4-bromobutoxy)phenyl)-3-(3-methylphenyl)-2-propene-1-one: Compared with (2) of Example 1, the difference is that 1-(4-hydroxyphenyl)-3-(3-methylphenyl)-2-propene-1-one and 1,4-dibromobutane are used as raw materials; the other steps are the same.

[0101] (3) Synthesis of benzo[d]oxazole-2-thiol: Same as (3) in Example 1.

[0102] (4) Synthesis of (E)-1-(4-(4-(Benzo[d]oxazol-2-yl-thio)butoxy)phenyl)-3-(3-methylphenyl)-2-propene-1-one: Compared with (4) in Example 1, the difference is that 1-(4-(4-bromobutoxy)phenyl)-3-(3-methylphenyl)-2-propene-1-one is used as the raw material; the other steps are the same.

[0103] Example 11

[0104] The synthesis of (E)-1-(4-(3-(benzo[d]oxazol-2-yl-thio)propoxy)phenyl)-3-(3-methoxyphenyl)-2-propen-1-one (compound number Z11) comprises the following steps:

[0105] (1) Synthesis of 1-(4-hydroxyphenyl)-3-methoxyphenyl-2-propene-1-one: Compared with (1) of Example 1, the difference is that 3-methoxybenzaldehyde is used as the raw material; the other steps are the same.

[0106] (2) Synthesis of 1-(4-(3-bromopropyloxy)phenyl)-3-(3-methoxyphenyl)-2-propene-1-one: Compared with (2) of Example 1, the difference is that 1-(4-hydroxyphenyl)-3-(3-methoxyphenyl)-2-propene-1-one is used as the raw material; the other steps are the same.

[0107] (3) Synthesis of benzo[d]oxazole-2-thiol: Same as (3) in Example 1.

[0108] (4) Synthesis of (E)-1-(4-(3-(Benzo[d]oxazol-2-yl-thio)propoxy)phenyl)-3-(3-methoxyphenyl)-2-propene-1-one: as in step (4) of Example 1, except that 1-(4-(3-bromopropoxy)phenyl)-3-(3-methoxyphenyl)-2-propene-1-one was used as the raw material; the other steps were the same.

[0109] Example 12

[0110] The synthesis of (E)-1-(4-(4-(Benzo[d]oxazol-2-yl-thio)butoxy)phenyl)-3-(3-methoxyphenyl)-2-propen-1-one (Compound No. Z12) comprises the following steps:

[0111] (1) Synthesis of 1-(4-hydroxyphenyl)-3-(3-methoxyphenyl)-2-propen-1-one: Compared with (1) of Example 1, the difference is that 3-methoxybenzaldehyde is used as the raw material; the other steps are the same.

[0112] (2) Synthesis of 1-(4-(4-bromobutoxy)phenyl)-3-(3-methoxyphenyl)-2-propene-1-one: Compared with (2) of Example 1, the difference is that 1-(4-hydroxyphenyl)-3-(3-methoxyphenyl)-2-propene-1-one and 1,4-dibromobutane are used as raw materials.

[0113] (3) Synthesis of benzo[d]oxazole-2-thiol: as in step (3) of Example 1

[0114] (4) Synthesis of (E)-1-(4-(4-(Benzo[d]oxazol-2-yl-thio)butoxy)phenyl)-3-(3-methoxyphenyl)-2-propene-1-one: Compared with (4) in Example 1, the difference is that 1-(4-(4-bromobutoxy)phenyl)-3-methoxyphenyl-2-propene-1-one is used as the raw material; the other steps are the same.

[0115] Example 13

[0116] The synthesis of (E)-1-(4-(4-(Benzo[d]oxazol-2-yl-thio)butoxy)phenyl)-3-(3-fluorophenyl)-2-propen-1-one (Compound No. Z13) comprises the following steps:

[0117] (1) Synthesis of 1-(4-hydroxyphenyl)-3-(3-fluorophenyl)-2-propen-1-one: Same as (1) in Example 1, except that 3-fluorobenzaldehyde is used as the raw material.

[0118] (2) Synthesis of 1-(4-(4-bromobutoxy)phenyl)-3-(3-fluorophenyl)-2-propene-1-one: Compared with (2) of Example 1, the difference is that 1-(4-hydroxyphenyl)-3-(3-fluorophenyl)-2-propene-1-one and 1,4-dibromobutane are used as raw materials; the other steps are the same.

[0119] (3) Synthesis of benzo[d]oxazole-2-thiol: Same as (3) in Example 1.

[0120] (4) Synthesis of (E)-1-(4-(4-(Benzo[d]oxazol-2-yl-thio)butoxy)phenyl)-3-(3-fluorophenyl)-2-propene-1-one: Compared with (4) in Example 1, the difference is that 1-(4-(4-bromobutoxy)phenyl)-3-(3-fluorophenyl)-2-propene-1-one is used as the raw material; the other steps are the same.

[0121] Example 14

[0122] The synthesis of (E)-1-(4-(4-(Benzo[d]oxazol-2-yl-thio)butoxy)phenyl)-3-(3-nitrophenyl)-2-propen-1-one (Compound No. Z14) comprises the following steps:

[0123] (1) Synthesis of 1-(4-hydroxyphenyl)-3-nitrophenyl-2-propene-1-one: Compared with (1) of Example 1, the difference is that 3-nitrobenzaldehyde is used as the raw material; the other steps are the same.

[0124] (2) Synthesis of 1-(4-(4-bromobutoxy)phenyl)-3-(3-nitrophenyl)-2-propene-1-one: Compared with (2) of Example 1, the difference is that 1-(4-hydroxyphenyl)-3-(3-nitrophenyl)-2-propene-1-one and 1,4-dibromobutane are used as raw materials; the other steps are the same.

[0125] (3) Synthesis of benzo[d]oxazole-2-thiol: Same as (3) in Example 1.

[0126] (4) Synthesis of (E)-1-(4-(4-(Benzo[d]oxazol-2-yl-thio)butoxy)phenyl)-3-(3-nitrophenyl)-2-propene-1-one: Compared with (4) of Example 1, the difference is that 1-(4-(4-bromobutoxy)phenyl)-3-(3-nitrophenyl)-2-propene-1-one is used as the raw material; the other steps are the same.

[0127] Example 15

[0128] The synthesis of (E)-1-(4-(3-(benzo[d]oxazol-2-yl-thio)propoxy)phenyl)-3-(3-chlorophenyl)-2-propen-1-one (compound number Z15) comprises the following steps:

[0129] (1) Synthesis of 1-(4-hydroxyphenyl)-3-(3-chlorophenyl)-2-propen-1-one: Compared with (1) of Example 1, the difference is that 3-chlorobenzaldehyde is used as the raw material; the other steps are the same.

[0130] (2) Synthesis of 1-(4-(3-bromopropyloxy)phenyl)-3-(3-chlorophenyl)-2-propene-1-one: Compared with (2) of Example 1, the difference is that 1-(4-hydroxyphenyl)-3-(3-chlorophenyl)-2-propene-1-one is used as the raw material; the other steps are the same.

[0131] (3) Synthesis of benzo[d]oxazole-2-thiol: Same as (3) in Example 1.

[0132] (4) Synthesis of (E)-1-(4-(3-(Benzo[d]oxazol-2-yl-thio)propoxy)phenyl)-3-(3-chlorophenyl)-2-propene-1-one: Compared with (4) of Example 1, the difference is that 1-(4-(3-bromopropoxy)phenyl)-3-(3-chlorophenyl)-2-propene-1-one is used as the raw material; the other steps are the same.

[0133] Example 16

[0134] The synthesis of (E)-1-(4-(4-(Benzo[d]oxazol-2-yl-thio)butoxy)phenyl)-3-(3-chlorophenyl)-2-propen-1-one (Compound No. Z16) comprises the following steps:

[0135] (1) Synthesis of 1-(4-hydroxyphenyl)-3-(3-chlorophenyl)-2-propen-1-one: Compared with (1) of Example 1, the difference is that 3-chlorobenzaldehyde is used as the raw material; the other steps are the same.

[0136] (2) Synthesis of 1-(4-(4-bromobutoxy)phenyl)-3-(3-chlorophenyl)-2-propene-1-one: Compared with (2) of Example 1, the difference is that 1-(4-hydroxyphenyl)-3-(3-chlorophenyl)-2-propene-1-one and 1,4-dibromobutane are used as raw materials; the other steps are the same.

[0137] (3) Synthesis of benzo[d]oxazole-2-thiol: Same as (3) in Example 1.

[0138] (4) Synthesis of (E)-1-(4-(4-(Benzo[d]oxazol-2-yl-thio)butoxy)phenyl)-3-(3-chlorophenyl)-2-propene-1-one: Compared with (4) in Example 1, the difference is that 1-(4-(4-bromobutoxy)phenyl)-3-(3-chlorophenyl)-2-propene-1-one is used as the raw material; the other steps are the same.

[0139] Example 17

[0140] The synthesis of (E)-1-(4-(3-(benzo[d]oxazol-2-yl-thio)propoxy)phenyl)-3-(3-bromophenyl)-2-propen-1-one (compound number Z17) comprises the following steps:

[0141] (1) Synthesis of 1-(4-hydroxyphenyl)-3-(3-bromophenyl)-2-propen-1-one: Compared with (1) of Example 1, the difference is that 3-bromobenzaldehyde is used as the raw material; the other steps are the same.

[0142] (2) Synthesis of 1-(4-(3-bromopropyloxy)phenyl)-3-bromophenyl-2-propene-1-one: Compared with (2) of Example 1, the difference is that 1-(4-hydroxyphenyl)-3-(3-bromophenyl)-2-propene-1-one is used as the raw material; the other steps are the same.

[0143] (3) Synthesis of benzo[d]oxazole-2-thiol: Same as (3) in Example 1.

[0144] (4) Synthesis of (E)-1-(4-(3-(Benzo[d]oxazol-2-yl-thio)propoxy)phenyl)-3-(3-bromophenyl)-2-propene-1-one: Compared with (4) of Example 1, the difference is that 1-(4-(3-bromopropoxy)phenyl)-3-(3-bromophenyl)-2-propene-1-one is used as the raw material; the other steps are the same.

[0145] Example 18

[0146] The synthesis of (E)-1-(4-(4-(Benzo[d]oxazol-2-yl-thio)butoxy)phenyl)-3-(3-bromophenyl)-2-propen-1-one (Compound No. Z18) comprises the following steps:

[0147] (1) Synthesis of 1-(4-hydroxyphenyl)-3-(3-bromophenyl)-2-propen-1-one: Compared with (1) of Example 1, the difference is that 3-bromobenzaldehyde is used as the raw material; the other steps are the same.

[0148] (2) Synthesis of 1-(4-(4-bromobutoxy)phenyl)-3-bromophenyl-2-propene-1-one: Compared with (2) of Example 1, the difference is that 1-(4-hydroxyphenyl)-3-(3-bromophenyl)-2-propene-1-one and 1,4-dibromobutane are used as raw materials; the other steps are the same.

[0149] (3) Synthesis of benzo[d]oxazole-2-thiol: Same as (3) in Example 1.

[0150] (4) Synthesis of (E)-1-(4-(4-(Benzo[d]oxazol-2-yl-thio)butoxy)phenyl)-3-(3-bromophenyl)-2-propene-1-one: Compared with (4) in Example 1, the difference is that 1-(4-(4-bromobutoxy)phenyl)-3-(3-bromophenyl)-2-propene-1-one is used as the raw material; the other steps are the same.

[0151] Example 19

[0152] The synthesis of (E)-1-(4-(3-(Benzo[d]oxazol-2-yl-thio)propoxy)phenyl)-3-(2-methylphenyl)-2-propene-1-one (compound number Z19) comprises the following steps:

[0153] (1) Synthesis of 1-(4-hydroxyphenyl)-3-(2-methylphenyl)-2-propene-1-one: Compared with (1) of Example 1, the difference is that 2-methylbenzaldehyde is used as the raw material; the other steps are the same.

[0154] (2) Synthesis of 1-(4-(3-bromopropyloxy)phenyl)-3-(2-methylphenyl)-2-propene-1-one: Compared with (2) of Example 1, the difference is that 1-(4-hydroxyphenyl)-3-(2-methylphenyl)-2-propene-1-one is used as the raw material; the other steps are the same.

[0155] (3) Synthesis of benzo[d]oxazole-2-thiol: Same as (3) in Example 1.

[0156] (4) Synthesis of (E)-1-(4-(3-(Benzo[d]oxazol-2-yl-thio)propoxy)phenyl)-3-(2-methylphenyl)-2-propene-1-one: Compared with (4) of Example 1, the difference is that 1-(4-(3-bromopropoxy)phenyl)-3-(2-methylphenyl)-2-propene-1-one is used as the raw material; the other steps are the same.

[0157] Example 20

[0158] The synthesis of (E)-1-(4-(4-(Benzo[d]oxazol-2-yl-thio)butoxy)phenyl)-3-(2-methylphenyl)-2-propene-1-one (Compound No. Z20) comprises the following steps:

[0159] (1) Synthesis of 1-(4-hydroxyphenyl)-3-(2-methylphenyl)-2-propene-1-one: Compared with (1) of Example 1, the difference is that 2-methylbenzaldehyde is used as the raw material; the other steps are the same.

[0160] (2) Synthesis of 1-(4-(4-bromobutoxy)phenyl)-3-(2-methylphenyl)-2-propene-1-one: Compared with (2) of Example 1, the difference is that 1-(4-hydroxyphenyl)-3-(2-methylphenyl)-2-propene-1-one and 1,4-dibromobutane are used as raw materials; the other steps are the same.

[0161] (3) Synthesis of benzo[d]oxazole-2-thiol: Same as (3) in Example 1.

[0162] (4) Synthesis of (E)-1-(4-(4-(Benzo[d]oxazol-2-yl-thio)butoxy)phenyl)-3-(2-methylphenyl)-2-propene-1-one: Compared with (4) in Example 1, the difference is that 1-(4-(4-bromobutyloxy)phenyl)-3-(2-methylphenyl)-2-propene-1-one is used as the raw material; the other steps are the same.

[0163] Example 21

[0164] The synthesis of (E)-1-(4-(3-(Benzo[d]oxazol-2-yl-thio)propoxy)phenyl)-3-(2-furyl)-2-propen-1-one (Compound No. Z21) comprises the following steps:

[0165] (1) Synthesis of 1-(4-hydroxyphenyl)-3-(2-furyl)-2-propene-1-one: Compared with (1) of Example 1, the difference is that 2-furan benzaldehyde is used as the raw material; the other steps are the same.

[0166] (2) Synthesis of 1-(4-(3-bromopropyloxy)phenyl)-3-(2-furyl)-2-propene-1-one: Compared with (2) of Example 1, the difference is that 1-(4-hydroxyphenyl)-3-(2-furyl)-2-propene-1-one is used as the raw material; the other steps are the same.

[0167] (3) Synthesis of benzo[d]oxazole-2-thiol: Same as (3) in Example 1.

[0168] (4) Synthesis of (E)-1-(4-(3-(benzo[d]oxazol-2-yl-thio)propoxy)phenyl)-3-(2-furyl)-2-propene-1-one: Compared with (4) of Example 1, the difference is that 1-(4-(3-bromopropoxy)phenyl)-3-(2-furyl)-2-propene-1-one is used as the raw material.

[0169] Example 22

[0170] The synthesis of (E)-1-(4-(4-(Benzo[d]oxazol-2-yl-thio)butoxy)phenyl)-3-(2-furyl)-2-propen-1-one (Compound No. Z22) comprises the following steps:

[0171] (1) Synthesis of 1-(4-hydroxyphenyl)-3-(2-furyl)-2-propene-1-one: Compared with (1) of Example 1, the difference is that 2-furan carboxaldehyde is used as the raw material; the other steps are the same.

[0172] (2) Synthesis of 1-(4-(4-bromobutoxy)phenyl)-3-(2-furyl)-2-propene-1-one: Compared with (2) of Example 1, the difference is that 1-(4-hydroxyphenyl)-3-(2-furyl)-2-propene-1-one and 1,4-dibromobutane are used as raw materials; the other steps are the same.

[0173] (3) Synthesis of benzo[d]oxazole-2-thiol: Same as (3) in Example 1.

[0174] (4) Synthesis of (E)-1-(4-(4-(benzo[d]oxazol-2-yl-thio)butoxy)phenyl)-3-(2-furyl)-2-propene-1-one: Compared with (4) in Example 1, the difference is that 1-(4-(4-bromobutoxy)phenyl)-3-(2-furyl)-2-propene-1-one is used as the raw material; the other steps are the same.

[0175] The physicochemical properties and mass spectrometry data of the synthesized chalcone derivatives containing benzoxazole structure are shown in Table 1. 1 H NMR) and carbon spectroscopy ( 13 C NMR) data are shown in Table 2.

[0176] Table 1 Physicochemical properties of target compounds and their mass spectrometry analysis data

[0177] Compound Yield (%) Traits Melting point (℃) HRMS, m / z (calcd.) Z1 53 Yellow solid 79.2-80.9 <![CDATA[416.13149(416.13065[M+H] + )]]> Z2 57 White solid 96.6-98.2 <![CDATA[430.14714(430.14655[M+H] + )]]> Z3 62 White solid 85.7-87.1 <![CDATA[430.14714(430.20483[M+H] + )]]> Z4 74 White solid 104.8-106.2 <![CDATA[444.16279(444.16107[M+H] + )]]> Z5 33 White solid 85.2-86.8 <![CDATA[446.23619(446.14206[M+H] + )]]> Z6 63 Yellow solid 110.3-112.1 <![CDATA[434.12207(432.12189[M+H] + )]]> Z7 67 Yellow solid 127.2-128.5 <![CDATA[448.13772(448.13635[M+H] + )]]> Z8 65 Yellow solid 92.6-93.9 <![CDATA[494.04200(494.04205[M+H] + )]]> Z9 50 Yellow solid 59.4-61.1 <![CDATA[430.14714(430.14597[M+H] + )]]> Z10 56 Yellow solid 72.6-74.1 <![CDATA[444.16279(444.16116[M+H] + )]]> Z11 82 Yellow solid 88.8-90.6 <![CDATA[445.13423(445.14804[M+H] + )]]> Z12 78 White solid 80.7-82.4 <![CDATA[460.15771(460.15570[M+H] + )]]> Z13 71 Yellow solid 78.4-79.6 <![CDATA[448.13772(448.13608.[M+H] + )]]> Z14 93 Red solid 133.1-134.9 <![CDATA[475.13222(475.13184[M+H] + )]]> Z15 71 Yellow solid 80.1-80.5 <![CDATA[450.09252(450.09204[M+H] + )]]> Z16 85 Yellow solid 98.1-99.7 <![CDATA[464.10817(464.10773[M+H] + )]]> Z17 72 Yellow solid 85.2-87.1 <![CDATA[494.04200(494.04156[M+H] + )]]> Z18 62 Yellow solid 93.9-95.1 <![CDATA[508.05765(508.05719.[M+H] + )]]> Z19 48 White solid 82.5-84.2 <![CDATA[430.14714(430.14670[M+H] + )]]> Z20 47 White solid 112.3-113.6 <![CDATA[444.16279(444.16223[M+H] + )]]> Z21 64 brown solid 81.6-82.8 <![CDATA[406.11076(406.10913[M+H] + )]]> Z22 85 brown solid 94.9-96.8 <![CDATA[420.12641(420.12601[M+H] + )]]>

[0178] Table 2 H NMR and C NMR data of target compounds

[0179]

[0180]

[0181]

[0182]

[0183]

[0184] Activity test example: Plant bacterial inhibition activity test

[0185] 1. Test method

[0186] Refer to the Peng Feng method (Peng, F., Liu, TT, Wang, QF, Liu, F., Cao, X., Yang, JS, Liu, LW, Xie, CW, Xue, W.. J. Agric. Food Chem., 2021, 69: 11085-11094.). The turbidity method was used to test the inhibitory activity of all synthesized chalcone derivatives against citrus canker (Xac), rice bacterial blight (Xoo), kiwifruit canker (Psa), melon wilt (Ac), tobacco bacterial wilt (Rs), potato soft rot (Pcb), and mango bacterial leaf spot (Xcm). The commercial agent thiophanate-methyl (TC) was used as a control drug. The operation steps are as follows:

[0187] 1.1 Preparation of culture medium

[0188] (1) Preparation of NB medium: To a 5000 mL beaker, add 3000 mL of distilled water, 3 g of yeast powder, 30 g of glucose, 15 g of peptone, and 9 g of beef extract in that order. After weighing, stir evenly, and then adjust the pH of the medium to 7.2 ± 0.2 with sodium hydroxide solution. Place six clean test tubes in a test tube rack. Use a pipette to add 4 mL of NB medium to each test tube. Insert a rubber stopper and wrap the tubes in newspaper.

[0189] (2) Preparation of NA medium: Take a 250 mL conical flask, add 3.6 g agar powder and 200 mL NB medium, shake and mix evenly, and seal with a breathable sealing film.

[0190] (3) High-temperature sterilization: Sterilize the packaged NB and NA culture media in a high-pressure steam sterilizer at 120°C for 20 min and set aside.

[0191] 1.2 Bacterial culture

[0192] In a clean bench, pour approximately 10-15 mL of sterile NA medium into each sterile culture dish and sterilize under UV light for 30 minutes. Use a sterile inoculation loop to contact a single pathogenic bacterium and inoculate it by streaking. Seal the dish with parafilm and place it in a 28°C incubator for activation. Once activation is complete, use a sterile inoculation loop to streak a small piece of the culture medium containing the colony into a conical flask containing sterile NB medium. Seal the dish with parafilm and incubate the dish in a shaker until the logarithmic growth phase.

[0193] 1.3 Treatment of the drug

[0194] Weigh 15.0 mg of compound or commercial thiophanate-methyl and dissolve it in 300 μL DMSO. Pipette 40 μL of the solution into sterile centrifuge tubes. Add 4 mL of sterile deionized water (containing 0.1% Tween-20) to each centrifuge tube. Use 40 μL of DMSO and 4 mL of 0.1% Tween-20 as a blank control group.

[0195] 1.4 Antibacterial activity experimental operation

[0196] Sterilize in a UV clean bench for 0.5-1 hour. Add 1 mL of the solution prepared in step 3 to the sterilized NB medium test tube. Shake the test tube and take 200 μL of the solution to a 96-well plate. Measure and record the OD value. Then, inoculate 40 μL of the bacteria into each test tube and culture in a shaker (180-240 rpm, 24-48 hours). When the bacteria grow to the logarithmic period (OD 595 =0.6-0.8), calculate the inhibition rate of all compounds. The inhibition rate formula is as follows:

[0197] Corrected OD value = OD value of bacteria-containing culture medium - OD value of sterile culture medium

[0198]

[0199] Table 3 Antibacterial activity of target compounds against seven plant bacteria

[0200]

[0201] a: Average of three parallel tests. b: The inhibitory activity of the commercial agent thiophanate-methyl was used as a positive control.

[0202] The turbidity method was used, with the commercial agent thiophanate-methyl as the control, to test the inhibitory activity of the target compounds Z1-Z22 against seven plant bacteria, Xac, Xoo, Psa, Ac, Rs, Pcb, and Xcm (see Table 3) at a concentration of 100 μg / mL. The test results showed that some of the target compounds had certain inhibitory activity against the seven plant bacteria. At a concentration of 100 μg / mL, the inhibition rates of Z1 and Z2 on Xac were 72.3% and 68.2%, respectively, which were better than the control agent thiophanate-methyl (64.2%); the inhibition rate of Z2 on Xoo was 93.0%, which was better than the control agent thiophanate-methyl (90.7%); the inhibition rates of Z1, Z3, Z4, Z6, Z7, and Z10 on Ac were 86.2%, 78.5%, 81.2%, 75.5%, 73.0%, and 81.6%, respectively, which were better than the control agent thiophanate-methyl (47.4%); the inhibition rates of Z2, Z6, Z7, Z12, Z17, and Z20 on Rs were 79.9%, 81.2%, 81.6 ... .5%, 72.9%, 73.5%, 72.9%, 70.9%, 78.5%, which are better than the control agent thiophanate-methyl (43.5%); the inhibition rates of Z2, Z3, Z4, and Z7 on Pcb were 84.6%, 77.1%, 72.2%, and 75.9%, respectively, which are better than the control agent thiophanate-methyl (63.0%); the inhibition rates of Z2, Z10, Z11, Z17, Z19, and Z20 on Xcm were 66.4%, 65.7%, 64.0%, 63.3%, 78.6%, 68.8%, and 61.0%, respectively, which are better than the control agent thiophanate-methyl (40.9%).

[0203] The above experimental activity data show that chalcone derivatives containing benzoxazole structure have certain inhibitory effects on some plant bacteria. Among them, some target compounds show excellent activity against plant-inhibiting bacteria and can be used as potential plant-inhibiting bacteria drugs with good application prospects.

[0204] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the scope of protection determined by the claims of the present invention.

Claims

1. Use of chalcone derivatives containing a benzoxazole structure in inhibiting plant bacteria or preparing antibacterial preparations, characterized in that: The structural formula of the chalcone derivative containing a benzoxazole structure is shown below: ； wherein n is 3 or 4, and R is any one of phenyl, substituted phenyl, thienyl or furyl; The bacteria are citrus canker, rice bacterial blight, kiwifruit canker, melon wilt, tobacco bacterial wilt, potato soft rot or mango bacterial leaf spot; When R is a substituted phenyl group, the position at the meta or para position to the benzene ring connection bond is a substituent group, and the substituent group is any one of methyl, methoxy, nitro or halogen atom, and the halogen atom is fluorine, chlorine or bromine.

2. A method for preparing the chalcone derivatives containing a benzoxazole structure as claimed in claim 1, characterized in that: The following steps are involved: Using ethanol as solvent and under the alkaline condition of NaOH, 4-hydroxyacetophenone and substituted formaldehyde undergo aldol condensation reaction to prepare 1-(4-hydroxyphenyl)-3-(substituted aromatic)-2-propen-1-one; Under the conditions of K2CO3 as an acid-binding agent and acetonitrile as a solvent, the 1-(4-hydroxyphenyl)-3-(substituted aromatic)-2-propene-1-one reacts with 1,3-dibromopropane or 1,4-dibromobutane to prepare 1-(4-(3-bromopropoxy)phenyl)-3-(substituted aromatic)-2-propene-1-one or 1-(4-(4-bromobutoxy)phenyl)-3-(substituted aromatic)-2-propene-1-one; Benzo[d]oxazole-2-thiol was prepared by the reaction of 2-aminophenol with CS2 in the presence of KOH as an acid-binding agent and ethanol as a solvent. Under the conditions of K2CO3 as an acid binding agent and acetonitrile as a solvent, the 1-(4-(3-bromopropyloxy)phenyl)-3-(substituted aromatic)-2-propene-1-one or the 1-(4-(4-bromobutyloxy)phenyl)-3-(substituted aromatic)-2-propene-1-one and the benzo[d]oxazole-2-thiol undergo an etherification reaction to generate a chalcone derivative containing a benzoxazole structure; 。 3. The preparation method according to claim 2, wherein The molar ratio of the 4-hydroxyacetophenone to the substituted formaldehyde is (4-20) mmol: (5-20) mmol, and the ratio of the 4-hydroxyacetophenone to the ethanol is (4-20) mmol: (30-80) mL; the aldol condensation reaction time is 10-12 h.

4. The preparation method according to claim 2, wherein The molar ratio of the 1-(4-hydroxyphenyl)-3-(substituted aromatic)-2-propene-1-one to the 1,3-dibromopropane, or the 1-(4-hydroxyphenyl)-3-(substituted aromatic)-2-propene-1-one to the 1,4-dibromobutane is (2-10):(5-20); The ratio of the 1-(4-hydroxyphenyl)-3-(substituted aromatic)-2-propen-1-one, the K2CO3 and the acetonitrile is (2-10) mmol: (6-20) mmol: (25-50) mL; The reaction temperature of the 1-(4-hydroxyphenyl)-3-(substituted aromatic)-2-propene-1-one and the 1,3-dibromopropane or the 1,4-dibromobutane is 75-85° C., and the reaction time is 5-6 h.

5. The preparation method according to claim 2, wherein The molar ratio of the 2-aminophenol to the CS2 is (30-60) mmol: (20-70) mmol; the ratio of the 2-aminophenol, the KOH, and the ethanol is (30-60) mmol: (20-100) mmol: (20-50) mL; The reaction conditions of the 2-aminophenol and the CS2 are: 60° C. for 4 to 6 hours.

6. The preparation method according to claim 2, wherein The molar ratio of the 1-(4-(3-bromopropoxy)phenyl)-3-(substituted aromatic)-2-propene-1-one to the benzo[d]oxazole-2-thiol is (2.5-10) mmol: (1-10) mmol; The molar ratio of the 1-(4-(4-bromobutyloxy)phenyl)-3-(substituted aromatic)-2-propene-1-one to the benzo[d]oxazole-2-thiol is (2-10) mmol: (1-10) mmol; The ratio of the benzo[d]oxazole-2-thiol, the K2CO3 and the acetonitrile is (1-10) mmol: (5-20) mmol: (20-50) mL; The etherification reaction conditions are: reaction at room temperature for 18 h.

7. A bacteriostatic preparation, characterized in that: The chalcone derivative containing the benzoxazole structure as claimed in claim 1, wherein the bacterium is citrus canker, rice bacterial blight, kiwifruit canker, melon wilt, tobacco bacterial wilt, potato soft rot or mango bacterial angular leaf spot.

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