C-3 substituted l-alanine amide derivatives, processes for their preparation and use

Abstract

This invention belongs to the fields of biomedicine and carbocyclic compound synthesis technology, specifically relating to a class of C-3 substituted L-alanine amide derivatives, their preparation methods, and applications. The C-3 substituted L-alanine amide derivatives of this invention mostly possess novel chemical structures and exhibit good inhibitory activity against influenza viruses, especially influenza A virus H1N1. Therefore, they can be prepared into anti-influenza A virus drugs, showing promising application prospects in the prevention and / or treatment of influenza virus infections, thus expanding the application value of C-3 substituted L-alanine amide derivatives.

Description

Technical Field

[0001] This invention belongs to the fields of biomedicine and carbocyclic compound synthesis technology. More specifically, it relates to a class of C-3 substituted L-alanine amide derivatives, their preparation methods, and applications. Background Technology

[0002] After influenza A virus infects a host, it can induce a strong systemic inflammatory and immune response, clinically manifesting as symptoms such as fever, headache, and muscle aches. In susceptible populations such as children and the elderly, influenza can easily lead to serious complications such as pneumonia and neurological complications, and even death.

[0003] Currently, based on their mechanisms of action, antiviral drugs for influenza can be mainly divided into the following categories: First, M2 protein ion channel inhibitors (such as amantadine), but due to widespread drug resistance, their routine use is no longer recommended; second, neuraminidase inhibitors (such as oseltamivir), which are currently the mainstream drugs in clinical practice; third, hemagglutinin inhibitors, with the representative drug arbidol mainly exerting its effect by inhibiting hemagglutinin-mediated membrane fusion, and widely used clinically in China and other regions; and fourth, RNA-dependent RNA polymerase inhibitors, including the polymerase acid subunit (PA) inhibitor baloxavir (a new generation of commonly used drugs) and the polymerase basic subunit 1 (PB1) inhibitor favipiravir (a second-line drug), showing promising application prospects. Nevertheless, the currently available antiviral drugs for influenza remain limited and far from meeting clinical needs.

[0004] In the face of the continuous emergence of variant strains of influenza A virus, it is urgent to strengthen the systematic research on conserved potential drug targets in major circulating strains such as H1N1, continuously promote the research and development of broad-spectrum anti-influenza virus drugs, and strive to reserve more candidate drugs, which is of great significance to protecting public health. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings and deficiencies of the limited availability of existing commercially available antiviral drugs for influenza. The primary objective is to provide an application of a class of C-3 substituted L-alanine amide derivatives.

[0006] A second objective of the present invention is to provide a class of C-3 substituted L-alanine amide derivatives having a novel structure.

[0007] A third objective of this invention is to provide a method for preparing the C-3 substituted L-alanine amide derivative.

[0008] The fourth objective of this invention is to provide a drug for treating influenza A virus.

[0009] The above-mentioned objective of this invention is achieved through the following technical solution: This invention protects the use of a class of C-3 substituted L-alanine amide derivatives or pharmaceutically acceptable salts thereof in the preparation of anti-influenza A virus drugs, the structure of which is shown below: ; In the above structure, R is R 1 (m1) Substituted phenyl, R 2 (m2) Substituted biphenyl, heteroaryl or C 3~6 cycloalkyl; The R 1 Whether monosubstituted, polysubstituted, or unsubstituted, m1 represents R on the benzene ring. 1 The number of elements, m1 being any integer from 0 to 5; the R 1 Each is independently selected from hydrogen or benzyloxy groups; The R 2 Whether monosubstituted, polysubstituted, or unsubstituted, m2 represents the R on the benzene ring in the biphenyl group. 2 The number of elements, m2 is any integer from 0 to 9; the R 2 Each is independently selected from hydrogen and C. 1~6 Alkoxy or C 1~6 Halogenated alkyl groups; The heteroaryl group is a 5-6 membered aromatic monocyclic ring containing 1, 2, 3 or 4 heteroatoms independently selected from S, with the remaining ring atoms being carbon.

[0010] Furthermore, R is R 1 (m1) Substituted phenyl, R 2 (m2) Substituted biphenyl, heteroaryl or C 5~6 cycloalkyl; The R 1 Whether monosubstituted or unsubstituted, m1 represents R on the benzene ring. 1 The number of elements, m1 is 0 or 1; the R 1 Each is independently selected from hydrogen or benzyloxy groups; The R 2 Whether monosubstituted or unsubstituted, m2 represents the R on the benzene ring in the biphenyl group. 2 The number of elements, m2 is 0 or 1; the R 2 Each is independently selected from hydrogen and C. 1~3 Alkoxy or C 1~3 Fluorinated alkyl groups; The heteroaryl group is a 5-membered aromatic monocyclic ring containing one heteroatom selected from S, and the remaining ring atoms are carbon.

[0011] Furthermore, R is selected from phenyl, 4-benzyloxyphenyl, 4,4'-biphenyl, (4-methoxy)-4,4'-biphenyl, (4-trifluoromethyl)-4,4'-biphenyl, 2-thienyl or cyclohexyl.

[0012] Furthermore, the influenza A virus is the influenza A H1N1 virus.

[0013] Specifically, the influenza A virus is A / WSN / 33 / H1N1.

[0014] This invention protects a class of C-3 substituted L-alanine amide derivatives or pharmaceutically acceptable salts thereof, the structures of which are shown below: ; In the above structure, R is R 1 (m1) Substituted phenyl, R 2 (m2) Substituted biphenyl, heteroaryl or C 3~6 cycloalkyl; The R 1 Whether it is monosubstituted or polysubstituted, m1 represents R on the benzene ring. 1 The number of R, where m1 is any integer from 1 to 5; 1 Selected from benzyloxy groups; The R 2 Whether monosubstituted, polysubstituted, or unsubstituted, m2 represents the R on the benzene ring in the biphenyl group. 2 The number of elements, m2 is any integer from 0 to 9; the R 2 Each is independently selected from hydrogen and C. 1~6 Alkoxy or C 1~6 Halogenated alkyl groups; The heteroaryl group is a 5-6 membered aromatic monocyclic ring containing 1, 2, 3 or 4 heteroatoms independently selected from S, with the remaining ring atoms being carbon.

[0015] Furthermore, R is R 1 (m1) Substituted phenyl, R 2 (m2) Substituted biphenyl, heteroaryl or C 5~6 cycloalkyl; The R 1 For monosubstituted, m1 represents R on the benzene ring. 1 The number of R, m1 is 1; 1 Selected from benzyloxy groups; The R 2 Whether monosubstituted or unsubstituted, m2 represents the R on the benzene ring in the biphenyl group. 2 The number of elements, m2 is 0 or 1; the R2 Each is independently selected from hydrogen and C. 1~3 Alkoxy or C 1~3 Fluorinated alkyl groups; The heteroaryl group is a 5-membered aromatic monocyclic ring containing one heteroatom selected from S, and the remaining ring atoms are carbon.

[0016] Preferably, R is selected from 4-benzyloxyphenyl, 4,4'-biphenyl, (4-methoxy)-4,4'-biphenyl, (4-trifluoromethyl)-4,4'-biphenyl, 2-thienyl or cyclohexyl.

[0017] The present invention also protects a method for preparing the C-3 substituted L-alanine amide derivative or a pharmaceutically acceptable salt thereof, the preparation of the C-3 substituted L-alanine amide derivative comprising the following steps: S1. Compound 1 and Compound 2 were mixed evenly in a first organic solvent under ice bath conditions, and a condensation reaction was carried out under an inert protective atmosphere and at room temperature to obtain intermediate compound 3. S2. Under normal temperature conditions, the intermediate compound 3 obtained in step S1 is dissolved in a second organic solvent and hydrolyzed in the presence of an alkaline reagent to obtain the L-alanine amide derivative with C-3 as a substituted compound. Wherein, the structure of compound 1 is as follows: The structure of compound 2 is as follows: The structure of the intermediate compound 3 is as follows: .

[0018] Furthermore, compound 1 can be replaced with its pharmaceutically acceptable salt, preferably an acid salt, and preferably a hydrochloride salt.

[0019] Furthermore, the preparation method includes at least one of the following: (1) In step S1, the condensing agent used in the condensation reaction is selected from a combination of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, 1-hydroxybenzotriazole and N-methylmorpholine; (2) In step S1, the first organic solvent is selected from dichloromethane and / or N,N-dimethylformamide; (3) In step S2, the alkaline reagent is selected from at least one of lithium hydroxide, sodium hydroxide, and potassium hydroxide; (4) In step S2, the second organic solvent is selected from at least one of tetrahydrofuran, methanol, and ethanol.

[0020] Further, the molar ratio of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, 1-hydroxybenzotriazole and N-methylmorpholine is 1:(0.8~1.2):(2~2.5), preferably 1:(0.9~1.1):(2.3~2.35).

[0021] Preferably, the first organic solvent is dichloromethane.

[0022] Preferably, the second organic solvent is a combination of tetrahydrofuran and methanol.

[0023] Further, the volume ratio of tetrahydrofuran to methanol is 1:(0.5~1.5), preferably 1:(0.8~1.2), and more preferably 1:(1~1.2).

[0024] Furthermore, the alkaline reagent is preferably lithium hydroxide.

[0025] Further, in step S1, the molar ratio of compound 1 to compound 2 is 1:(1~1.5), preferably 1:(1~1.2).

[0026] Furthermore, in step S1, the gas in the inert protective atmosphere is selected from nitrogen, neon, argon, or helium.

[0027] Further, the molar ratio of compound 1 to condensing agent is 1:(5~6), preferably 1:(5.5~5.7).

[0028] Furthermore, the condensation reaction takes 8 to 20 hours, preferably 12 hours.

[0029] Furthermore, the condensation reaction also includes post-treatment.

[0030] Furthermore, the post-processing includes washing, drying, filtration, solvent removal, and silica gel column chromatography.

[0031] Specifically, the post-processing includes the following steps: the completely reacted mixture is washed sequentially with 1 M hydrochloric acid, saturated sodium bicarbonate solution and saturated sodium chloride solution, the organic phase is dried over anhydrous sodium sulfate solid, filtered, the filtrate is removed by rotary evaporation under reduced pressure to remove the solvent, and finally subjected to silica gel column chromatography to obtain intermediate compound 3.

[0032] Furthermore, the mobile phase for the silica gel column chromatography is a mixed solvent of petroleum ether, ethyl acetate, and dichloromethane.

[0033] Preferably, the volume ratio of petroleum ether, ethyl acetate and dichloromethane is 4:1:1.

[0034] Furthermore, the molar ratio of the intermediate compound 3 to the basic reagent is 1:(4~6), preferably 1:5.

[0035] Furthermore, the hydrolysis reaction takes 0.5 to 1.5 hours, preferably 1 hour.

[0036] Furthermore, the hydrolysis reaction also includes post-treatment.

[0037] Furthermore, the post-processing includes solvent removal, dissolution, pH adjustment, washing, filtration, solvent removal, and silica gel column chromatography.

[0038] Specifically, the post-processing includes the following steps: the solvent in the completely reacted mixture is removed by rotary evaporation under reduced pressure, dissolved in ethyl acetate, the pH is adjusted to acidic with 1M hydrochloric acid, and then the organic phase is washed successively with water and saturated sodium chloride solution, the organic phase is dried with anhydrous sodium sulfate solid, filtered, the filtrate is removed by rotary evaporation under reduced pressure, and finally the target compound is obtained by silica gel column chromatography.

[0039] Furthermore, the mobile phase for the silica gel column chromatography is a mixed solvent of dichloromethane, methanol, and formic acid.

[0040] Preferably, the volume ratio of dichloromethane, methanol, and formic acid is 400:10:1.

[0041] Furthermore, the temperature for vacuum concentration is 30~60 ℃, preferably 37~45 ℃.

[0042] The present invention also protects an anti-influenza A virus drug comprising one or more of the C-3 substituted L-alanine amide derivatives.

[0043] Compared with the prior art, the present invention has the following beneficial effects: The C-3 substituted L-alanine amide derivatives of this invention mostly have novel chemical structures and exhibit good inhibitory activity against influenza viruses, especially influenza A virus H1N1. Therefore, they can be prepared into anti-influenza A virus drugs and have good application prospects in the prevention and / or treatment of influenza virus infection, thus expanding the application value of C-3 substituted L-alanine amide derivatives. Detailed Implementation

[0044] The present invention will be further illustrated below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field.

[0045] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0046] Example 1 Preparation of compound A1 The synthetic route of compound A1 is shown below: ; The main reagents involved in step S1 are as follows: 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl), 1-hydroxybenzotriazole (HOBT), N-methylmorpholine (NMM), and dichloromethane (DCM); the reagents involved in step S2 are as follows: lithium hydroxide (LiOH) and methanol-tetrahydrofuran (MeOH-THF) solution.

[0047] The preparation of compound A1 specifically includes the following steps: S1. Take L-phenylalanine methyl ester hydrochloride (compound 1, 800.00 mg, 3.70 mmol), dissolve it in 20 mL of dry dichloromethane in a 100 mL reaction flask, and add compound 2 (1.48 g, 4.10 mmol), EDC·HCl (924.00 mg, 4.82 mmol), HOBT (651.00 mg, 4.82 mmol) and NMM (1.125 mL, 11.10 mmol) in sequence under ice bath conditions and nitrogen atmosphere, and let it return to room temperature naturally and stir overnight (12 h). Thin-layer chromatography (TLC) was used to detect the reaction until it was complete. The organic phase was washed successively with 1 M hydrochloric acid, saturated sodium bicarbonate solution, and saturated sodium chloride solution using dichloromethane as the organic phase. The organic phase was dried over anhydrous sodium sulfate solid, filtered, and the filtrate was evaporated under reduced pressure (37 °C) to remove the solvent. Finally, the solution was subjected to silica gel column chromatography (the mobile phase was a mixed solvent of petroleum ether, ethyl acetate, and dichloromethane, with a volume ratio of 4:1:1) to give a white solid compound 3 (1.26 g, yield approximately 65.43%).

[0048] S2. Weigh out 600 mg (1.14 mmol) of compound 3 obtained in step S1 and dissolve it in 100 mL of MeOH-THF solution (MeOH and THF volume ratio 1:1) to obtain a mixture. Prepare a 4 M solution of LiOH (137.00 mg, 5.7 mmol) with water and add it dropwise to the obtained mixture. Stir at room temperature for 1 h. Monitor the reaction progress by TLC until complete. Remove methanol and tetrahydrofuran by rotary evaporation under reduced pressure (45 °C). Dissolve the compound in ethyl acetate, adjust the pH to acidic with 1 M hydrochloric acid, and then use ethyl acetate as the organic phase. Wash the organic phase successively with water and saturated sodium chloride solution. Dry the organic phase with anhydrous sodium sulfate solid, filter, and remove the solvent by rotary evaporation under reduced pressure (45 °C) of the filtrate. Finally, the target compound A1 (557.00 mg, yield approximately 96.10%) was obtained by silica gel column chromatography (the mobile phase was a mixed solvent of dichloromethane, methanol and formic acid, with a volume ratio of dichloromethane, methanol and formic acid of 400:10:1).

[0049] Example 2 Preparation of compounds A2-A12 Following the preparation process of the compounds obtained in Example 1 above, only the R substituents in the compounds shown in Formula I were replaced as shown in Table 1 to obtain the corresponding target compounds A2~A12. The appearance, 1H NMR spectrum, and 1C NMR spectrum results of compounds A1~A12 are listed in Table 1. As can be seen from Table 1, the structures of the above compounds are correct, and they are all the compounds shown in the corresponding table below.

[0050]

[0051] Table 1. NMR data of compounds A1~A12

[0052] Example 3: Antiviral activity of compounds A1-A12 against influenza A Using compounds A1-A12 prepared in Example 1 as test subjects, their inhibitory activity against the H1N1 influenza A virus strain (A / WSN / 33 / H1N1) on MDCK cells was tested.

[0053] 1. Toxicity testing methods The test compound needs to be dissolved in 0.1 vol% DMSO before use to prepare a stock solution. MDCK cells are then cultured at 1 × 10⁻⁶ ppm. 5 Cells were seeded at a density of 200 μL / mL in 96-well plates and cultured overnight at 37 °C in a 5% CO2 incubator. Once the cell density reached over 90%, the cells were washed twice with sterile PBS, and the supernatant was discarded. The stock solution of the compound was serially diluted using DMEM maintenance medium without FBS (fetal bovine serum), resulting in nine concentration groups: 0.39, 0.78, 1.5625, 3.125, 6.25, 12.5, 25, 50, and 100 μM. A control group containing 0.1 vol% DMSO was also included. Each group had three replicates, with 200 μL per well. After drug addition, the cells were incubated at 37 °C in a 5% CO2 incubator for 48 h. After terminating the culture, the supernatant was discarded, and 100 μL of CCK-8 working solution diluted 1:20 with DMEM basal maintenance medium was added to each well. The cells were incubated at 37 ℃ in a 5% CO2 incubator for 1 h in the dark. The OD value of each well was measured at 450 nm using a multi-mode microplate reader. Cell viability was calculated as shown in Equation 1. The half-maximal cytotoxic concentration (CMC) of the compound against MDCK cells was calculated using GraphPad Prism 8.0 software. 50 ).

[0054] Formula 1 2. Activity Experiment Methods After the MDCK cells have grown to a confluent monolayer, wash twice with PBS. Dilute the A / WSN / 33 / H1N1 virus to 100 TCID using FBS-free DMEM basal maintenance medium. 50Virus solution was added to each well at 200 μL (except for the cell blank control group), and incubated at 37°C in a 5% CO2 incubator for 1 h for adsorption. After adsorption, the supernatant was discarded, and unadsorbed viruses were washed with PBS. Subsequently, the stock solution of the compound was serially diluted twofold with DMEM basal maintenance medium containing 0.5 μg / mL TPCK-trypsin to set seven concentrations: 0.31, 0.625, 1.25, 2.5, 5, 10, and 20 μM, 200 μL per well. A solvent control group (containing 1 vol% DMSO), a virus control group (virus only, no drug; referred to as the virus group), and a cell blank control group (no virus, no drug; referred to as the blank group) were also set up. The cells were incubated at 37°C in a 5% CO2 incubator for 36–48 h. During this period, the cytopathic effect (CPE) of the virus control group was observed under a microscope. Culture was terminated when significant cytopathic effects (usually ≥80%) were confirmed in the virus control group. Discard the supernatant, add CCK-8 solution diluted 1:20 with DMEM basal maintenance medium to each well, and incubate in a 37 ℃, 5% CO2 incubator in the dark for 1 h. OD values ​​at 450 nm were measured using a multi-mode microplate reader. The inhibition rate (i.e., protection rate) of the above compounds against viral infection was calculated using Equation 2. The half-maximal effective concentration (EC50) of the compounds was calculated using a nonlinear regression function in GraphPad Prism 8.0 software. 50 ).

[0055] Formula 2 The treatment index (SI, or selectivity index) is a key parameter for evaluating drug safety, and it is calculated using formula 3.

[0056] Formula 3 3. Experimental Results Table 2. In vitro anti-A / WSN / 33 (H1N1) activity of compounds A1-A12, their cytotoxicity against MDCK, and SI results.

[0057] Note: NT indicates not measured; the higher the SI value, the better the safety. Generally speaking, when SI>1, the compound can be considered to have good safety.

[0058] As shown in Table 2, compounds A1, A3, and A7-A11 all exhibited excellent inhibitory activity against influenza A virus H1N1 in MDCK cells, and their EC50 values ​​were significantly higher than those of other compounds. 50 All were below 5 μM. Among them, compound A11 showed the most significant activity, with an EC value of [missing value]. 50 Less than 1 μM, and with low toxicity to MDCK cells (CC). 50= 56.18 μM), therefore it has a high selectivity index (SI = CC). 50 / EC 50 >56). Overall, compounds A1, A3, and A7~A11 show good application potential in the preparation of drugs against influenza A virus.

[0059] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. The use of a class of C-3 substituted L-alanine amide derivatives or pharmaceutically acceptable salts thereof in the preparation of drugs against influenza A virus, characterized in that, The structure of the C-3 substituted L-alanine amide derivative is shown below: ； In the above structure, R is R 1 (m1) substituted phenyl, R 2 (m2) substituted biphenyl, heteroaryl or C 3~6 cycloalkyl; The R 1 Whether monosubstituted, polysubstituted, or unsubstituted, m1 represents R on the benzene ring. 1 The number of elements, m1 being any integer from 0 to 5; the R 1 Each is independently selected from hydrogen or benzyloxy groups; The R 2 Whether monosubstituted, polysubstituted, or unsubstituted, m2 represents the R on the benzene ring in the biphenyl group. 2 The number of elements, m2 is any integer from 0 to 9; the R 2 Each is independently selected from hydrogen and C. 1~6 Alkoxy or C 1~6 Halogenated alkyl groups; The heteroaryl group is a 5-6 membered aromatic monocyclic ring containing 1, 2, 3 or 4 heteroatoms independently selected from S, with the remaining ring atoms being carbon.

2. The application according to claim 1, characterized in that, The R is R 1 (m1) Substituted phenyl, R 2 (m2) Substituted biphenyl, heteroaryl or C 5~6 cycloalkyl; The R 1 Whether monosubstituted or unsubstituted, m1 represents R on the benzene ring. 1 The number of elements, m1 is 0 or 1; the R 1 Each is independently selected from hydrogen or benzyloxy groups; The R 2 Whether monosubstituted or unsubstituted, m2 represents the R on the benzene ring in the biphenyl group. 2 The number of elements, m2 is 0 or 1; the R 2 Each is independently selected from hydrogen and C. 1~3 Alkoxy or C 1~3 Fluorinated alkyl groups; The heteroaryl group is a 5-membered aromatic monocyclic ring containing one heteroatom selected from S, and the remaining ring atoms are carbon.

3. The application according to claim 1, characterized in that, The R is selected from phenyl, 4-benzyloxyphenyl, 4,4'-biphenyl, (4-methoxy)-4,4'-biphenyl, (4-trifluoromethyl)-4,4'-biphenyl, 2-thienyl or cyclohexyl.

4. The application according to any one of claims 1 to 3, characterized in that, The influenza A virus mentioned is the H1N1 influenza A virus.

5. A class of C-3 substituted L-alanine amide derivatives or pharmaceutically acceptable salts thereof, characterized in that, The structure of the C-3 substituted L-alanine amide derivative is shown below: ； In the above structure, R is R 1 (m1) Substituted phenyl, R 2 (m2) Substituted biphenyl, heteroaryl or C 3~6 cycloalkyl; The R 1 Whether it is monosubstituted or polysubstituted, m1 represents R on the benzene ring. 1 The number of R, where m1 is any integer from 1 to 5; 1 Selected from benzyloxy groups; The R 2 Whether monosubstituted, polysubstituted, or unsubstituted, m2 represents the R on the benzene ring in the biphenyl group. 2 The number of elements, m2 is any integer from 0 to 9; the R 2 Each is independently selected from hydrogen and C. 1~6 Alkoxy or C 1~6 Halogenated alkyl groups; The heteroaryl group is a 5-6 membered aromatic monocyclic ring containing 1, 2, 3 or 4 heteroatoms independently selected from S, with the remaining ring atoms being carbon.

6. The C-3 substituted L-alanine amide derivative according to claim 5, or a pharmaceutically acceptable salt thereof, characterized in that, The R is R 1 (m1) Substituted phenyl, R 2 (m2) Substituted biphenyl, heteroaryl or C 5~6 cycloalkyl; The R 1 For monosubstituted, m1 represents R on the benzene ring. 1 The number of R, m1 is 1; 1 Selected from benzyloxy groups; The R 2 Whether monosubstituted or unsubstituted, m2 represents the R on the benzene ring in the biphenyl group. 2 The number of elements, m2 is 0 or 1; the R 2 Each is independently selected from hydrogen and C. 1~3 Alkoxy or C 1~3 Fluorinated alkyl groups; The heteroaryl group is a 5-membered aromatic monocyclic ring containing one heteroatom selected from S, and the remaining ring atoms are carbon.

7. The C-3 substituted L-alanine amide derivative according to claim 5, or a pharmaceutically acceptable salt thereof, characterized in that, The R is selected from 4-benzyloxyphenyl, 4,4'-biphenyl, (4-methoxy)-4,4'-biphenyl, (4-trifluoromethyl)-4,4'-biphenyl, 2-thienyl or cyclohexyl.

8. A method for preparing the C-3 substituted L-alanine amide derivative or a pharmaceutically acceptable salt thereof according to any one of claims 5 to 7, characterized in that, The preparation of the C-3 substituted L-alanine amide derivative includes the following steps: S1. Compound 1 and Compound 2 were mixed evenly in a first organic solvent under ice bath conditions, and a condensation reaction was carried out under an inert protective atmosphere and at room temperature to obtain intermediate compound 3. S2. Under normal temperature conditions, the intermediate compound 3 obtained in step S1 is dissolved in a second organic solvent and hydrolyzed in the presence of an alkaline reagent to obtain the L-alanine amide derivative with C-3 as a substituted compound. Wherein, the structure of compound 1 is as follows: The structure of compound 2 is as follows: The structure of the intermediate compound 3 is as follows: .

9. The preparation method according to claim 8, characterized in that, The preparation method includes at least one of the following: (1) In step S1, the condensing agent used in the condensation reaction is selected from a combination of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, 1-hydroxybenzotriazole and N-methylmorpholine; (2) In step S1, the first organic solvent is selected from dichloromethane and / or N,N-dimethylformamide; (3) In step S2, the alkaline reagent is selected from at least one of lithium hydroxide, sodium hydroxide, and potassium hydroxide; (4) In step S2, the second organic solvent is selected from at least one of tetrahydrofuran, methanol, and ethanol.

10. A drug for treating influenza A virus, characterized in that, It includes one or more of the C-3 substituted L-alanine amide derivatives as described in any one of claims 5 to 7.

Images