Juglone-amino-acid ester derivative, synthetic method thereof and application of juglone-amino-acid ester derivative in biological antibacterial agent

Abstract

The invention discloses juglone-amino-acid ester derivatives, a synthetic method thereof and application of the juglone-amino-acid ester derivatives in biological antibacterial agents, the synthetic method comprises the following steps: taking natural amino acid as a raw material, preparing a series of amino acid methyl esters through esterification and deacidification reaction, and then carrying out double-bond reaction on the amino acid methyl esters and 5-hydroxynaphthalene-1, 4-diketone (juglone) to obtain the juglone-amino-acid ester derivatives. And preparing different juglone-amino-acid ester derivatives. In addition, the invention also provides an application of the juglone-amino-acid ester derivative in an antibacterial agent, the juglone derivatives of valine methyl ester, leucine methyl ester and threonine methyl ester have certain antibacterial activity on escherichia coli and staphylococcus aureus, and the growth inhibition effect on the staphylococcus aureus is more prominent.

Description

Technical Field

[0001] The invention relates to the field of biotechnology, and in particular to a juglone-amino acid ester derivative and a synthesis method thereof and application of the derivative in a biological antibacterial agent. Background Art

[0002] Antimicrobial agents play an important role in clinical treatment, but due to the widespread and irrational use of antimicrobial agents, many pathogens are becoming increasingly resistant to various antimicrobial agents. At present, the resistance of pathogens to antimicrobial agents seriously threatens human health and has become a severe challenge worldwide. The problem of bacterial resistance needs to be solved urgently, and it is particularly important to develop new and efficient antimicrobial agents.

[0003] Juglone is considered an important candidate drug for the treatment of cancer and has been shown to have inhibitory effects on prostate cancer, cervical cancer, breast cancer, etc. Juglone has also been found to have inhibitory effects on fungi such as Candida albicans, Penicillium, Aspergillus, and Carlsberg yeast. Based on label-free quantitative proteomics, researchers analyzed the differential proteins of Escherichia coli treated with juglone, and the study showed that juglone effectively restricted energy production, blocked RNA formation, and ribosome assembly. In addition, juglone can lyse Staphylococcus aureus by inhibiting protein synthesis, tricarboxylic acid cycle, and nucleic acid synthesis pathways.

[0004] In the exploration of antibacterial drugs, non-protein amino acids of natural or synthetic origin and their derivatives constitute an important group of drugs or drug candidates. These properly designed compounds can be strong inhibitors of enzymes involved in protein amino acid metabolism. There are also a large number of enzymes involved in the biochemical pathways of other microorganisms. These enzymes have been confirmed or are waiting to be verified as molecular targets of amino acid antibacterial agents. This fully demonstrates the antibacterial potential of amino acid compounds. Summary of the invention

[0005] One of the purposes of the present invention is to provide an antibacterial agent, which is a juglone-amino acid ester derivative and is a novel antibacterial agent synthesized for the first time. The synthesis method is simple in process, and the product purity and synthesis yield are both high. Secondly, the present invention is to provide an application of the above antibacterial agent in inhibiting bacteria, especially having a strong antibacterial effect on Staphylococcus aureus.

[0006] In order to solve the problems of the prior art, the technical solution adopted by the present invention is:

[0007] A juglone-amino acid ester derivative, the structural formula of the juglone-amino acid ester derivative is wherein R is CH(CH3)2, CH2CH(CH3)2, CH(CH3)CH2CH3, CH2OH, or CH(CH3)OH.

[0008] The above-mentioned method for synthesizing juglone-amino acid ester derivatives is characterized in that it comprises the following steps: Step 1, 1,5-dihydroxynaphthalene, a catalyst C4H 18 Cl 15 After FeN2O3 and acetonitrile are dissolved, hydrogen peroxide is added dropwise in an ice water bath, stirred for 30 minutes, and reacted at room temperature of 25°C to synthesize 5-hydroxynaphthalene-1,4-dione (juglone); step 2, natural amino acid and methanol are stirred into a suspension at room temperature, hydrochloric acid is slowly added dropwise, refluxed at 80°C, amino acid methyl ester hydrochloride is synthesized, chloroform is added and stirred evenly at room temperature, triethylamine is slowly added dropwise, stirred at room temperature, and then the reaction system is transferred to 60°C for reflux reaction to synthesize amino acid methyl ester; step 3, 5-hydroxynaphthalene-1,4-dione, cerium trichloride and ethanol are mixed, stirred at room temperature, and an ethanol solution of amino acid methyl ester is added dropwise, and stirring is continued to obtain the product juglone-amino acid ester derivative.

[0009] The reaction formula of the above preparation method is as follows:

[0010]

[0011] As an improvement, the natural amino acid is L-valine, L-leucine, L-isoleucine, L-serine, L-threonine, D-valine, or D-leucine.

[0012] As an improvement, the concentration of the hydrochloric acid in step 2 is 35% to 38%.

[0013] As an improvement, the amount of catalyst C4H8Cl5FeN2O3 used is 10 mol% of the amount of 1,5-dihydroxynaphthalene used.

[0014] As an improvement, the catalyst C4H8Cl5FeN2O3 uses the nitrogen-containing heterocyclic compound anhydrous piperazine, the metal salt FeCl3 and a 30% HCl aqueous solution as raw materials, synthesizes the complex by a hydrothermal method, and obtains a pure compound by single crystal cultivation.

[0015] As an improvement, the molar ratio of carbamate to juglone is 2:1.

[0016] Application of the above juglone-amino acid ester derivatives in the preparation of biological antibacterial agents.

[0017] Beneficial effects:

[0018] Compared with the prior art, the invention discloses a juglone-amino acid ester derivative and a synthesis method thereof and an application thereof in a biological antibacterial agent. A series of amino acid methyl esters are prepared by esterification and deacidification reaction using natural amino acids as starting materials. Subsequently, under the catalysis of cerium trichloride, 5-hydroxynaphthalene-1,4-dione (juglone) prepared by oxidation reaction of 1,5-dihydroxynaphthalene with hydrogen peroxide reacts with amino acid methyl ester to undergo double bond reaction to prepare different juglone-amino acid ester derivatives. The synthesis method has simple process, simple equipment, convenient operation, high product purity and high product yield. Moreover, the substance is synthesized for the first time and no relevant patents or literature reports are found. The antibacterial agent can be used for antibacterial activity, especially has strong antibacterial activity against Staphylococcus aureus. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 , Figure 3 , Figure 5 , Figure 7 , Fig. 9 , Fig.11 , Fig.13 , Fig.15 , Fig.17 , Fig.19 , Fig.21 , Fig.23 , Fig.25 , Fig. 27 They are respectively the H NMR spectra of products 3aa, 3ab, 3ac, 3ad, 3ae, 3af, 3ag, 3ah, 3ai, 3aj, 3ak, 3al, 3am and 3an in Examples 1-7.

[0020] Figure 2 , Figure 4 , Figure 6 , Figure 8 , Fig.10 , Fig.12 , Fig.14 , Fig.16 , Fig.18 , Fig. 20 , Fig. 22 , Fig.24 , Fig.26 , Fig.28 This is the NMR carbon spectra of products 3aa, 3ab, 3ac, 3ad, 3ae, 3af, 3ag, 3ah, 3ai, 3aj, 3ak, 3al, 3am, and 3an in Examples 1-7.

[0021] Fig.29 This is the inhibition zone diagram of Escherichia coli antibacterial culture medium.

[0022] Fig.30 This is the inhibition zone diagram of Staphylococcus aureus antibacterial culture medium.

[0023] Fig.31This is the absorbance diagram of the inhibition of Escherichia coli.

[0024] Fig.32 This is the absorbance diagram of Staphylococcus aureus inhibition. DETAILED DESCRIPTION

[0025] The following examples will enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0026] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0027] Preparation of raw materials:

[0028] 1. Preparation of amino acid methyl esters

[0029]

[0030] Add amino acid (37.41mmol) to the bottle, add methanol (100mL), and stir at room temperature to form a suspension. Slowly add concentrated HCl (35%, 3.5mL) to the reaction system, and observe that the reaction liquid gradually changes from a suspension state to a colorless and transparent state. Continue to reflux the reaction system at 80℃ for 5 hours. When the reaction is complete, cool it down. The solvent is removed by a rotary evaporator, and the remaining uncolored oil residue is dried under vacuum to obtain amino acid methyl ester hydrochloride.

[0031] Amino acid methyl ester hydrochloride (30mmol) and chloroform (10mL) were stirred at room temperature for 5min. Triethylamine (4.17mL, 30mmol) was slowly added dropwise to the reaction system and stirred at room temperature for 5 hours. Subsequently, the reaction system was transferred to 60°C for reflux reaction for 1 hour. After the reaction was complete, the temperature was cooled. The solvent was removed by a rotary evaporator to obtain a white solid compound. The white solid was extracted with ethyl acetate (3×25mL) and filtered under reduced pressure. The ethyl acetate was removed to obtain pure amino acid methyl ester.

[0032] 2.5-Hydroxynaphthalene-1,4-dione (juglone), the reaction formula is as follows:

[0033]

[0034] 1,5-Dihydroxynaphthalene (1 mmol, 160.1 mg), catalyst C4H 18Cl5FeN2O3 (0.1mmol, (1) 37.5mg) and 10mL acetonitrile were stirred at room temperature for 15min. The reaction system was then transferred to an ice bath and H2O2 (30%, 10mmol, 1.020mL) was added dropwise. After stirring in an ice bath for 30min, the reaction system was stirred at room temperature. After the reaction was completed, the reaction solution was added dropwise to 100mL distilled water and extracted with ethyl acetate. The organic phase was collected and washed twice with saturated brine, and the organic phase was dried over anhydrous sodium sulfate, filtered, and concentrated. Finally, it was separated and purified by column chromatography (petroleum ether: ethyl acetate = 20:1).

[0035] Example 1 Juglone-L-valine methyl ester derivatives (3aa, 3ab)

[0036]

[0037] 5-Hydroxynaphthalene-1,4-dione (174.0 mg, 1.0 mmol), cerium trichloride (24.5 mg, 0.1 mmol) and ethanol (10 mL) were added to a 25 mL eggplant-shaped bottle and stirred at room temperature for 1 hour. L-valine methyl ester (262.2 mg, 2.0 mmol) was weighed, diluted with ethanol (3 mL), and added dropwise to the reaction solution. The reaction system continued to stir at room temperature until 5-hydroxynaphthalene-1,4-dione was completely consumed, which took about 6 hours. After the reaction was complete, the solvent was removed by a rotary evaporator and separated and purified on a column chromatography to obtain product 3aa (less polar, 103.1 mg, 34%) and product 3ab (more polar, 160.6 mg, 53%), with a total yield of 87%.

[0038] (5-Hydroxy-1,4-dioxo-1,4-dihydronaphthalen-2-yl)-L-valine methyl ester (3aa): black oil. 1 H NMR(400MHz,Chloroform-d)δ12.86(s,1H),7.56(dd,J=7.5,1.0Hz,1H),7.48–7.39(m,1H),7.20(dd,J=8.4,0.9Hz,1H),6.46(d, J=8.4Hz,1H),5.56(s,1H),3.88(dd,J=8.6,5.4Hz,1H),3.77(s,3H),2.28(dt,J=12.4,6.8Hz,1H),1.02(dd,J=22.6,6.9Hz,6H). 13C NMR(101MHz,CHLOROFORM-D)δ189.28,180.62,170.79,161.09,147.98,134.22,130.42,125 .96,119.26,114.69,100.89,60.63,52.64,31.29,18.88,18.54.HRMS(ESI-TOF)m / z:[M+H] + calcd.forC 16 H 17 NO5304.1180,Found304.1188.

[0039] (8-Hydroxy-1,4-dioxo-1,4-dihydronaphthalen-2-yl)-L-valine methyl ester (3ab): black oil. 1 HNMR(400MHz,Chloroform-d)δ11.49(s,1H),7.62–7.52(m,2H),7.11(dd,J=6.9,2.7Hz,1H),6.30(d,J=8.4Hz ,1H),5.64(s,1H),3.87(dd,J=8.5,5.3Hz,1H),3.77(s,3H),2.36–2.20(m,1H),1.02(dd,J=23.4,6.9Hz,6H). 13 CNMR(101MHz,CHLOROFORM-D)δ185.65,182.51,171.05,161.77,147.08,137.76,133.20,12 2.55,118.83,114.05,102.56,60.54,52.62,31.24,18.90,18.57.HRMS(ESI-TOF)m / z:[M+H] + calcd.forC 16 H 17 NO5304.1180, found304.1184.

[0040] Example 2 Juglone-D-valine methyl ester derivatives (3ac, 3ad)

[0041]

[0042] 5-Hydroxynaphthalene-1,4-dione (174.0 mg, 1.0 mmol), cerium trichloride (24.5 mg, 0.1 mmol) and ethanol (10 mL) were added to a 25 mL eggplant-shaped bottle and stirred at room temperature for 1 hour. D-valine methyl ester (262.2 mg, 2.0 mmol) was weighed, diluted with ethanol (3 mL), and added dropwise to the reaction solution. The reaction system continued to stir at room temperature until 5-hydroxynaphthalene-1,4-dione was completely consumed, which took about 6 hours. After the reaction was complete, the solvent was removed by rotary evaporator and separated and purified on column chromatography to obtain product 3ac (97.1 mg, 32%) and product 3ad (145.6 mg, 48%), with a total yield of 90%.

[0043] (5-Hydroxy-1,4-dioxo-1,4-dihydronaphthalen-2-yl)-D-valine methyl ester (3ac): black oil. 1 HNMR(400MHz,Chloroform-d)δ12.88(s,1H),7.60(d,J=7.4Hz,1H),7.47(t,J=7.9Hz,1H),7.23(d,J=8.4Hz,1H),6.47(d,J=8 .4Hz,1H),5.58(s,1H),3.89(dd,J=8.6,5.4Hz,1H),3.78(s,3H),2.29(dq,J=13.6,6.8Hz,1H),1.03(dd,J=22.2,6.9Hz,6H). 13 CNMR(101MHz,CHLOROFORM-D)δ189.39,180.74,170.85,161.18,148.06,134.31,130.52,125.9 5,119.39,114.79,100.94,60.71,52.68,31.38,31.33,18.95,18.59.HRMS(ESI-TOF)m / z:[M+H ]+ calcd.forC 16 H 17 NO5304.1180, found304.1187.

[0044] (8-Hydroxy-1,4-dioxo-1,4-dihydronaphthalen-2-yl)-D-valine methyl ester (3ad): black oil. 1HNMR(400MHz,Chloroform-d)δ11.47(s,1H),7.55(q,J=6.7,5.9Hz,2H),7.09(dd,J=7.3,2.0Hz,1H),6.29(d,J=8.3 Hz,1H),5.62(s,1H),3.87(d,J=5.3Hz,1H),3.76(s,3H),2.26(dq,J=13.3,6.7Hz,1H),1.01(dd,J=23.7,6.8Hz,6H). 13 CNMR(101MHz,CHLOROFORM-D)δ185.59,182.44,171.01,161.70,147.04,137.70,133.14,12 2.43,118.76,113.99,102.48,60.50,52.56,31.20,18.85,18.54.HRMS(ESI-TOF)m / z:[M+H] + calcd.forC 16 H 17 NO5304.1180, found304.1185.

[0045] Example 3 Juglone-L-leucine methyl ester derivatives (3ae, 3af)

[0046]

[0047] 5-Hydroxynaphthalene-1,4-dione (174.0 mg, 1.0 mmol), cerium trichloride (24.5 mg, 0.1 mmol) and ethanol (10 mL) were added to a 25 mL eggplant-shaped bottle and stirred at room temperature for 1 hour. L-leucine methyl ester (290.4 mg, 2.0 mmol) was weighed, diluted with ethanol (3 mL), and added dropwise to the reaction solution. The reaction system continued to stir at room temperature until 5-hydroxynaphthalene-1,4-dione was completely consumed, which took about 6 hours. After the reaction was complete, the solvent was removed by rotary evaporator and separated and purified on column chromatography to obtain product 3ae (104.7 mg, 33%) and product 3af (136.5 mg, 43%), with a total yield of 76%.

[0048] (5-Hydroxy-1,4-dioxo-1,4-dihydronaphthalen-2-yl)-L-leucine methyl ester (3ae): black oil. 1HNMR(400MHz,Chloroform-d)δ12.87(s,1H),7.58(dd,J=7.5,1.0Hz,1H),7.46(t,J=7.9Hz,1H),7.22(dd,J=8.4,0.9Hz,1H),6.29 (d,J=8.1Hz,1H),5.58(s,1H),4.06(q,J=7.9Hz,1H),3.77(s,3H),1.87–1.51(m,3H),0.98(d,J=6.3Hz,3H),0.93(d,J=6.3Hz,3H). 13 CNMR(101MHz,CHLOROFORM-D)δ189.38,180.75,171.82,161.19,147.82,134.31,130.50,126.0 5,119.33,114.78,100.99,53.81,52.86,40.95,25.05,22.70,22.16.HRMS(ESI-TOF)m / z:[M+H] + calcd.for C17H 19 NO5318.1336, found318.1342.

[0049] (8-Hydroxy-1,4-dioxo-1,4-dihydronaphthalen-2-yl)-L-leucine methyl ester (3af): black oil. 1 HNMR(400MHz,Chloroform-d)δ11.49(s,1H),7.58(q,J=3.8,3.2Hz,2H),7.12(dd,J=6.1,3.5Hz,1H),6.12(d,J=8.1Hz ,1H),5.65(s,1H),4.05(d,J=6.5Hz,1H),3.76(s,3H),1.86–1.65(m,3H),0.98(d,J=6.2Hz,3H),0.93(d,J=6.2Hz,3H). 13 CNMR(101MHz,CHLOROFORM-D)δ185.68,182.59,172.03,161.79,146.89,137.79,133.22,122.6 0,118.89,114.09,102.61,53.68,52.79,40.95,25.05,22.67,22.15.HRMS(ESI-TOF)m / z:[M+H] + calcd.forC 17 H 19 NO5318.1336, found318.1339.

[0050] Example 4 Juglone-D-leucine methyl ester derivatives (3ag, 3ah)

[0051]

[0052] 5-Hydroxynaphthalene-1,4-dione (174.0 mg, 1.0 mmol), cerium trichloride (24.5 mg, 0.1 mmol) and ethanol (10 mL) were added to a 25 mmL eggplant-shaped bottle and stirred at room temperature for 1 hour. D-leucine methyl ester (290.4 mg, 2.0 mmol) was weighed, diluted with ethanol (3 mL), and added dropwise to the reaction solution. The reaction system continued to stir at room temperature until 5-hydroxynaphthalene-1,4-dione was completely consumed, which took about 6 hours. After the reaction was complete, the solvent was removed by rotary evaporator and separated and purified on column chromatography to obtain product 3ag (95.2 mg, 30%) and product 3ah (161.8 mg, 51%), with a total yield of 81%.

[0053] (5-Hydroxy-1,4-dioxo-1,4-dihydronaphthalen-2-yl)-D-leucine methyl ester (3ag): black oil. 1 HNMR(400MHz,Chloroform-d)δ11.49(s,1H),7.63–7.54(m,2H),7.12(dd,J=6.1,3.5Hz,1H),6.12(d,J=8. 1Hz,1H),5.65(s,1H),4.05(d,J=6.5Hz,1H),3.76(s,3H),1.83–1.71(m,3H),0.95(dd,J=21.8,6.2Hz,6H). 13 CNMR(101MHz,CHLOROFORM-D)δ189.37,180.74,171.82,161.18,147.82,134.36,130.50,125.9 0,119.39,114.78,100.93,53.81,52.82,40.94,25.17,22.69,22.15.HRMS(ESI-TOF)m / z:[M+H] + calcd.forC 17 H 19 NO5318.1336, found318.1341.

[0054] (8-Hydroxy-1,4-dioxo-1,4-dihydronaphthalen-2-yl)-D-leucine methyl ester (3ah): black oil. 1HNMR(400MHz,Chloroform-d)δ11.43(s,1H),7.60–7.50(m,2H),7.07(dd,J=6.8,2.8Hz,1H),6.13(d,J=8. 1Hz,1H),5.62(s,1H),4.03(q,J=7.7Hz,1H),3.74(s,3H),1.82–1.63(m,3H),0.93(dd,J=21.1,6.3Hz,6H). 13 CNMR(101MHz,CHLOROFORM-D)δ185.62,182.44,172.00,161.68,146.85,137.69,133.13,122.6 0,118.78,113.99,102.48,53.63,52.70,40.84,24.90,22.63,22.10.HRMS(ESI-TOF)m / z:[M+H] + calcd.forC 17 H 19 NO5318.1336, found318.1338.

[0055] Example 5 Juglonequinone-L-isoleucine methyl ester derivatives (3ai, 3aj)

[0056]

[0057] 5-Hydroxynaphthalene-1,4-dione (174.0 mg, 1.0 mmol), cerium trichloride (24.5 mg, 0.1 mmol) and ethanol (10 mL) were added to a 25 mL eggplant-shaped bottle and stirred at room temperature for 1 hour. D-leucine methyl ester (290.4 mg, 2.0 mmol) was weighed, diluted with ethanol (3 mL), and added dropwise to the reaction solution. The reaction system continued to stir at room temperature until 5-hydroxynaphthalene-1,4-dione was completely consumed, which took about 6 hours. After the reaction was complete, the solvent was removed by rotary evaporator and separated and purified on column chromatography to obtain product 3ai (85.7 mg, 27%) and product 3aj (168.2 mg, 53%), with a total yield of 80%.

[0058] (5-Hydroxy-1,4-dioxo-1,4-dihydronaphthalen-2-yl)-L-isoleucine methyl ester (3ai): black oil. 1HNMR(400MHz,Chloroform-d)δ12.86(s,1H),7.58–7.52(m,1H),7.43(t,J=7.9Hz,1H),7.19(d,J=8.4Hz,1H),6.49(d,J=8.4Hz,1H),5.55 (s,1H),3.99–3.91(m,1H),3.76(s,3H),2.06–1.94(m,1H),1.88–1.64(m,1H),1.55(ddd,J=14.8,7.3,3.7Hz,1H),0.95(t,J=7.6Hz,6H). 13 CNMR(101MHz,CHLOROFORM-D)δ189.25,180.64,170.72,161.11,147.77,134.21,130.44,125.9 6,119.25,114.71,100.76,59.51,52.58,37.59,25.72,15.43,11.60.HRMS(ESI-TOF)m / z:[M+H] + calcd.forC 17 H 19 NO5318.1336, found318.1342.

[0059] (8-Hydroxy-1,4-dioxo-1,4-dihydronaphthalen-2-yl)-L-isoleucine methyl ester (3aj): black oil. 1 HNMR(400MHz,Chloroform-d)δ11.50(s,1H),7.65–7.54(m,2H),7.12(dd,J=6.3,3.3Hz,1H),6.33(d,J=8.3Hz,1H),5.64(s,1H),3.95(dd, J=8.4,5.3Hz,1H),3.77(s,3H),2.00(ddt,J=9.9,7.0,5.2Hz,1H),1.85(dd,J=12.4,6.2Hz,1H),1.59–1.53(m,1H),0.96(d,J=7.2Hz,6H). 13 CNMR(101MHz,CHLOROFORM-D)δ185.75,182.60,171.04,161.86,146.96,137.85,133.31,122.6 2,118.92,114.15,102.49,59.50,52.63,37.62,25.81,15.52,11.69.HRMS(ESI-TOF)m / z:[M+H] + calcd.forC17 H 19 NO5318.1336, found318.1338.

[0060] Example 6 Juglonequinone-L-serine methyl ester derivatives (3ak, 3al)

[0061]

[0062] 5-Hydroxynaphthalene-1,4-dione (174.0 mg, 1.0 mmol), cerium trichloride (24.5 mg, 0.1 mmol) and ethanol (10 mL) were added to a 25 mL eggplant-shaped bottle and stirred at room temperature for 1 hour. L-serine methyl ester (238.2 mg, 2.0 mmol) was weighed, diluted with ethanol (3 mL), and added dropwise to the reaction solution. The reaction system continued to stir at room temperature until 5-hydroxynaphthalene-1,4-dione was completely consumed, which took about 6 hours. After the reaction was complete, the solvent was removed by a rotary evaporator and separated and purified on a column chromatography to obtain product 3ak (55.3 mg, 19%) and product 3al (107.8 mg, 37%), with a total yield of 56%.

[0063] (5-Hydroxy-1,4-dioxo-1,4-dihydronaphthalen-2-yl)-L-serine methyl ester (3ak): black oil. 1 HNMR(400MHz,DMSO-d6)δ13.13(s,1H),7.65–7.59(m,1H),7.56(dd,J=7.5,1.3Hz,1H),7.43–7.27(m, 2H),5.76(s,1H),5.33(t,J=6.0Hz,1H),4.50(dt,J=7.9,3.8Hz,1H),3.94–3.79(m,2H),3.71(s,3H). 13 CNMR(101MHz,DMSO-D6)δ188.60,180.54,169.76,160.24,148.62,134.70,130.29 ,125.49,118.83,114.15,100.15,60.54,56.97,52.51.HRMS(ESI-TOF)m / z:[M+H] + calcd.for C14H13NO6292.0816,found292.0821.

[0064] (8-Hydroxy-1,4-dioxo-1,4-dihydronaphthalen-2-yl)-L-serine methyl ester (3al): black oil. 1HNMR (400MHz, DMSO-d6) δ11.35(s,1H),7.71(t,J=7.9Hz,1H),7.45(d,J=7.4Hz,1H),7.22(d,J=8.4Hz,1H),7.00(d, J=8.2Hz,1H),5.73(s,1H),5.34(t,J=5.8Hz,1H),4.43(dt,J=7.5,3.4Hz,1H),3.86(t,J=12.1Hz,2H),3.71(s,3H). 13 CNMR(101MHz,DMSO-D6)δ184.91,181.31,170.04,160.48,147.35,137.74,133.09 ,122.27,117.87,114.09,101.64,60.52,56.78,52.47.HRMS(ESI-TOF)m / z:[M+H] + calcd.forC 14 H 13 NO6292.0816, found292.0821.

[0065] Example 7 Juglone-L-threonine methyl ester derivatives (3am, 3an)

[0066]

[0067] 5-Hydroxynaphthalene-1,4-dione (174.0 mg, 1.0 mmol), cerium trichloride (24.5 mg, 0.1 mmol) and ethanol (10 mL) were added to a 25 mL eggplant-shaped bottle and stirred at room temperature for 1 hour. L-threonine methyl ester (266.3 mg, 2.0 mmol) was weighed, diluted with ethanol (3 mL), and added dropwise to the reaction solution. The reaction system continued to stir at room temperature until 5-hydroxynaphthalene-1,4-dione was completely consumed, which took about 6 hours. After the reaction was complete, the solvent was removed by rotary evaporator and separated and purified on column chromatography to obtain product 3am (58.0 mg, 19%) and product 3an (125.2 mg, 41%), with a total yield of 60%.

[0068] (2S)-3-hydroxy-2-((5-hydroxy-1,4-dioxo-1,4-dihydronaphthalen-2-yl)amino)butanoic acid methyl ester (3am): black oil. 1HNMR(400MHz,Chloroform-d)δ12.80(s,1H),7.58(d,J=6.8Hz,1H),7.46(t,J=7.9Hz,1H),7.22(d,J=7.8Hz,1H),6.74(d,J=8.7 Hz,1H),5.62(s,1H),4.45(dd,J=6.2,2.3Hz,1H),3.99(dd,J=8.8,2.4Hz,1H),3.80(s,3H),2.85(s,1H),1.30(d,J=6.4Hz,3H). 13 CNMR(101MHz,CHLOROFORM-D)δ189.53,180.62,170.37,161.08,148.72,134.46,130.52 ,125.87,119.53,114.71,101.19,67.62,60.25,53.09,20.27.HRMS(ESI-TOF)m / z:[M+H] + calcd.forC 15 H 15 NO6306.0973, found306.0978.

[0069] (2S)-3-hydroxy-2-((8-hydroxy-1,4-dioxo-1,4-dihydronaphthalen-2-yl)amino)butanoic acid methyl ester (3-dn): black oil. 1 HNMR(400MHz,Chloroform-d)δ11.47(s,1H),7.61–7.50(m,2H),7.10(dd,J=8.0,1.3Hz,1H),6.65(d,J=8.7Hz,1H),5 .68(s,1H),4.44(dd,J=6.2,2.8Hz,1H),3.98(dd,J=8.7,2.9Hz,1H),3.78(s,3H),3.46(s,1H),1.31(d,J=6.4Hz,3H). 13 CNMR(101MHz,CHLOROFORM-D)δ185.44,182.98,170.51,161.81,147.93,137.78,133.10 ,122.75,118.88,114.00,102.52,67.70,60.38,53.04,20.26.HRMS(ESI-TOF)m / z:[M+H] + calcd.forC 15 H 15 NO6306.0973, found306.0978.

[0070] The antibacterial activity of the compounds synthesized in the above examples against Escherichia coli and Staphylococcus aureus was tested by the inhibition zone method. The determination method and results are as follows:

[0071] Escherichia coli and Staphylococcus aureus strains stored at low temperature below 4°C were cultured in sterile liquid culture medium (LB Broth 25 g / L) at 37°C for 24 hours. The cultured bacterial suspension was diluted to a biomass of 10 using a sterile liquid culture medium by turbidimetry. 8 CFU / mL of the suspension for use in the next step.

[0072] Use LBBroth (25g / L) and agar powder (15g / L) to prepare solid culture medium, and pour it into the culture dish while hot to a depth of 3-4 mm. The prepared solid culture dish is cooled and solidified in the clean bench at room temperature. Juglone-amino acid ester derivatives are prepared into sample solutions of different concentrations (1mM, 0.5mM, 0.25mM, 0.125mM, 0.0625mM, 0.03125mM) with acetone.

[0073] Take 100 μL of pre-diluted bacterial solution and drop it into a solid culture dish. Use a glass coating rod to spread the bacterial solution evenly. The coated solid culture medium is divided into 6 areas and punched (6 mm in diameter). Add sample solutions of different concentrations to different punched areas, and use acetone as a negative control. Pre-incubate the plate at room temperature for 1 hour and incubate at 37°C for 24 hours to test the antibacterial activity.

[0074] After 24 hours of culture, the E. coli culture medium Fig.29 As shown:

[0075] Inconspicuous inhibition zones were observed for compounds 3aa, 3ab, 3ae, 3af, 3ag, and 3an, but no inhibition zones were observed for compounds 3ac, 3ad, 3aj, and 3ah.

[0076] After 24 hours of culture, the Staphylococcus aureus culture medium was Fig.30 As shown:

[0077] Obvious inhibition zones were observed for all the above 11 compounds. At the same time, it can be observed that the inhibition zones of 3ab, 3ad, 3af, and 3ah have larger radii than those of 3aa, 3ac, 3ae, and 3ag. 3ab, 3ae, 3aj, 3al, and 3an all have larger inhibition ranges.

[0078] In order to accurately analyze the biological activity of juglone-amino acid ester derivatives against Escherichia coli, the absorbance method was used for quantitative analysis, and the antibacterial rate of the compound against Escherichia coli was further determined. The determination method and results are as follows:

[0079] Escherichia coli and Staphylococcus aureus strains stored at low temperature below 4°C were cultured in sterile liquid culture medium (LB Broth 25 g / L) at 37°C for 24 hours. The cultured bacterial suspension was diluted to a biomass of 10 using a sterile liquid culture medium by turbidimetry. 6 CFU / mL suspension for use in the next step. Juglone-amino acid ester derivatives were prepared into sample solutions of different concentrations (1mM, 0.5mM, 0.25mM, 0.125mM, 0.0625mM, 0.03125mM, 0.015623mM, 0.007813mM, 0.003906mM, 0.001953mM) with acetone. 2mL of liquid culture medium (25g / L) was added to each test tube, and the diluted bacterial suspension (200μL) was placed in the test tube. The final bacterial solution concentration was 10 4 -10 5 CFU / mL, add different concentrations of sample solution (200μL) to the suspension, so that the final concentration of the compound in the system is 0.1mM, 0.05mM, 0.025mM, 0.0125mM, 0.00625mM, 0.003125mM, 0.0015623mM, 0.0007813mM, 0.0003906mM, 0.0001953mM, and use acetone as a negative control (200μL). The mixed suspension was cultured on a culture shaker for 20 hours, and the absorbance value of the bacterial solution in each test tube was measured in turn. Repeat the test three times. The bacterial survival rate was calculated according to the formula:

[0080] R=Si / S0×100%

[0081] Where R is the survival rate of bacteria, S0 is the absorbance of the negative control group, and Si is the absorbance of the positive control group and each experimental group. The inhibition rate is (1-R)×100%.

[0082] E. coli test results Fig.31 As shown:

[0083] Compounds 3aa, 3ab, 3ae, 3af, and 3ag have a strong inhibitory effect on Escherichia coli. When the concentration of 3ae and 3af is in the range of 0.0001953mM to 0.1mM, only <50% of Escherichia coli survive. When the concentration of 3aa, 3ab, and 3ag is in the range of 0.00625mM to 0.1mM, only <50% of Escherichia coli survive. However, 3ac, 3ad, and 3ah have no obvious inhibitory effect on the growth of Escherichia coli. It is worth noting that compound 3ad has a promoting effect on the growth of Escherichia coli at higher concentrations (>0.0125mM). As the concentration decreases, this promoting effect turns into an inhibitory effect. At a concentration of 0.0001953mM, only about 65% of Escherichia coli survived. Compounds 3ab, 3af, and 3an at position 3 have an inhibitory effect on E. coli, and the inhibitory effect becomes stronger with increasing compound concentrations. When the concentration is > 0.025 mM, only about 25% of E. coli growth is observed. Compounds 3aj and 3al promote the growth of E. coli at all concentrations.

[0084] Staphylococcus aureus results Fig.32 As shown:

[0085] Compounds 3ab, 3ad, 3af, and 3ah have strong inhibitory effects on Staphylococcus aureus. When the concentration of compounds 3da, 3ab, 3ad, 3ae, 3af, and 3ah is in the range of 0.0001953mM to 0.1mM, the survival rate of Staphylococcus aureus is <50%. When the concentration of 3ab, 3ad, and 3ah is in the range of 0.025mMmM to 0.1mM, only <10% of Escherichia coli survives. The growth inhibitory effects of all the above compounds on Staphylococcus aureus are more obvious at high concentrations (0.1mM) (survival rate <50%), but as the concentration of the compounds in the culture system decreases, their growth inhibitory effects gradually weaken. The substituted compound No. 3 has a certain inhibitory effect on Staphylococcus aureus at all concentrations, and the inhibitory effect becomes stronger as the concentration of the compound increases. At concentrations > 0.00625 mM, all compounds showed > 70% inhibition of Staphylococcus aureus growth, with compounds 3ad and 3ah showing an inhibition of more than 80% in this concentration range. These results demonstrate that the D-configuration juglone-amino acid methyl ester derivatives substituted at position 3 have a greater antibacterial potential against Staphylococcus aureus.

[0086] In summary, the synthetic method of the synthetic antibacterial agent of the present invention has simple process, simple equipment, convenient operation and high product purity. The substance can be used for antibacterial, especially has strong antibacterial activity against Staphylococcus aureus.

[0087] The embodiments described above are part of the embodiments of the present invention, rather than all of the embodiments. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Claims

1. A juglone-amino acid ester derivative, characterized in that: The structural formula of the juglone-amino acid ester derivative is wherein R is CH(CH3)2, CH2CH(CH3)2, CH(CH3)CH2CH3, CH2OH, or CH(CH3)OH.

2. A method for synthesizing a juglone-amino acid ester derivative according to claim 1, characterized in that: The following steps are involved: Step 1: 1,5-dihydroxynaphthalene, catalyst C4H 18 Cl 15 After FeN2O3 and acetonitrile are dissolved, hydrogen peroxide is added dropwise in an ice water bath, stirred for 30 minutes, and reacted at room temperature of 25°C to synthesize 5-hydroxynaphthalene-1,4-dione; step 2, natural amino acid and methanol are stirred into a suspension at room temperature, hydrochloric acid is slowly added dropwise, refluxed at 80°C, amino acid methyl ester hydrochloride is synthesized, chloroform is added and stirred evenly at room temperature, triethylamine is slowly added dropwise, stirred at room temperature, and then the reaction system is transferred to 60°C for reflux reaction to synthesize amino acid methyl ester; step 3, 5-hydroxynaphthalene-1,4-dione, cerium trichloride and ethanol are mixed, stirred at room temperature, and an ethanol solution of amino acid methyl ester is added dropwise, and stirring is continued to obtain the product juglone-amino acid ester derivative.

3. The method for synthesizing a juglone-amino acid ester derivative according to claim 2, characterized in that: The natural amino acid is L-valine, L-leucine, L-isoleucine, L-serine, L-threonine, D-valine, or D-leucine.

4. The method for synthesizing a juglone-amino acid ester derivative according to claim 2, characterized in that: The concentration of the hydrochloric acid in step 2 is 35% to 38%.

5. The method for synthesizing a juglone-amino acid ester derivative according to claim 2, characterized in that: The amount of catalyst C4H8Cl5FeN2O3 used is 10 mol% of that used for 1,5-dihydroxynaphthalene.

6. The method for synthesizing a juglone-amino acid ester derivative according to claim 2, characterized in that: The catalyst C4H8Cl5FeN2O3 uses anhydrous piperazine, a nitrogen-containing heterocyclic compound, a metal salt FeCl3 and a 30% HCl aqueous solution as raw materials, synthesizes the complex through a hydrothermal method, and obtains a pure compound through single crystal cultivation.

7. The method for synthesizing a juglone-amino acid ester derivative according to claim 2, characterized in that: The molar ratio of carbamate to juglone is 2:

1.

8. Use of the juglone-amino acid ester derivative according to claim 1 in the preparation of biological antibacterial agents.

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