Synthesis and Antiviral Activities of α-Aminophosphonate Derivatives Containing a Pyridazine Moiety

TMV-CP based rational design and discovery of α-Amide phosphate derivatives as anti plant viral agents

The tobacco mosaic virus coat protein (TMV-CP) is indispensable for the virus's replication, movement and transmission, as well as for the host plant's immune system to recognize it. It constitutes the outermost layer of the virus particle, and serves as an essential component of the virus structure. TMV-CP is essential for initiating and extending viral assembly, playing a crucial role in the self-assembly process of Tobacco Mosaic Virus (TMV). This research employed TMV-CP as a primary target for virtual screening, from which a library of 43,417 compounds was sourced and SH-05 was chosen as the lead compound. Consequently, a series of α-amide phosphate derivatives were designed and synthesized, exhibiting remarkable anti-TMV efficacy. The synthesized compounds were found to be beneficial in treating TMV, with compound 3g displaying a slightly better curative effect than Ningnanmycin (NNM) (EC50 = 304.54 µg/mL) at an EC50 of 291.9 µg/mL. Additionally, 3g exhibited comparable inactivation activity (EC50 = 63.2 µg/mL) to NNM (EC50 = 67.5 µg/mL) and similar protective activity (EC50 = 228.9 µg/mL) to NNM (EC50 = 219.7 µg/mL). Microscale thermal analysis revealed that the binding of 3g (Kd = 4.5 ± 1.9 µM) to TMV-CP showed the same level with NNM (Kd = 5.5 ± 2.6 µM). Results from transmission electron microscopy indicated that 3g could disrupt the structure of TMV virus particles. The toxicity prediction indicated that 3g was low toxicity. Molecular docking showed that 3g interacted with TMV-CP through hydrogen bond, attractive charge interaction and π-Cation interaction. This research provided a novel α-amide phosphate structure target TMV-CP, which may help the discovery of new anti-TMV agents in the future.

One-pot synthesis, structure and structure-activity relationship of novel bioactive diphenyl/diethyl (3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazol-5-yl)(arylamino)methylphosphonates

BACKGROUND

N-Pyridylpyrazole derivatives have received continuous attention in agrochemical research during the last decade owing to their remarkable insecticidal or fungicidal potentials. To look for novel heterocyclic agrochemicals for increasing production of agriculture, a series of novel α-aminophosphonate derivatives containing N-pyridylpyrazole moiety were synthesized.

RESULTS

The structures of the title compounds were confirmed via melting point, IR, ¹ H NMR, ¹³ C NMR, ³¹ P NMR, HRMS and elemental analysis. The single crystal structure of diethyl (3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazol-5-yl)(2,6-dimethylphenylamino)methylphosphonate (compound 12b) was first reported. Moreover, the bioassays displayed that the title compounds exhibited modest or weak insecticidal activities against oriental armyworm at 200 μg mL^-1 . The first investigation on the fungicidal potential of chlorantraniliprole showed no significant activities towards the six tested fungi found in this study, however, most of the title compounds displayed apparent in vitro fungicidal activity against some plant fungi, in particular excellent activities towards Physalospora piricola. Compounds 11a and 11b had EC₅₀ values of 18.8 and 17.4 μg mL^-1 , respectively, which were comparable with that of fungicide control triadimefon (EC₅₀  = 24.7 μg mL^-1 ) against Physalospora piricola. In addition, some compounds exhibited modest in vivo control efficacy at 0.5 mg mL^-1 towards Sclerotinia sclerotiorum (11b: 30.1(±1.8)%), Rhizoctonia cerealis (11a: 20.4(±2.1)%; 11b: 30.2(±2.2)%), and Erysiphe graminis (11a: 30.3(±1.8)%; 12d: 40.2(±0.9)%).

CONCLUSION

Compounds 11a, 11b and 12d could be promising new lead structures for the development and discovery of novel fungicides towards Physalospora piricola and Erysiphe graminis. The structure-activity relationship (SAR) analysis provided useful guidance and new understanding for the design of novel pyridylpyrazole-containing agrochemicals. © 2019 Society of Chemical Industry.

in vitro Cytotoxic Evaluation of Some New Synthesized Pyridazine Derivatives

A series of novel pyridazine, pyrazoles, pyrimidines derivatives have been synthesized through the reaction of chloropyridazine (1) with p-phenylenediamine to give compound 2. Diazotization of compound 2 followed by coupling with active methylene compounds namely acetylacetone, ethylcyanoacetate and/or ethylacetoacetate afforded novel hydrazons derivatives (4-6). The resulting hydrazons can have been cyclized using hydrazine hydrate and guanidine gave the corresponding pyrazoles (7-9) and pyimidine (10) derivatives. Reaction of compound 2 with acrylonitrile, aromatic aldehyde, p-chloroacetophenone and phenyl isothiocyanate gave compounds 11, 12a, 12b, 13 and 17, respectively. The latter compounds have been used in synthesis of some heterocyclic compounds. The cytotoxic activity of the most active compounds was assessed in vitro against breast carcinoma cell line (MCF-7), human liver cancer cell line (HEPG2), human colon cancer cell line (HCT). Compounds 4, 8 showed best activity against MCF-7 cell line, compounds 5, 13a showed best activity against HePG2 cell line and compound 10 showed best activity against HCT cell line.

Novel α,β-unsaturated amide derivatives bearing α-amino phosphonate moiety as potential antiviral agents

Based on flexible construction and broad bioactivity of ferulic acid, a series of novel α,β-unsaturated amide derivatives bearing α-aminophosphonate moiety were designed, synthesized and systematically evaluated for their antiviral activity. Bioassay results indicated that some compounds exhibited good antiviral activities against cucumber mosaic virus (CMV) and tobacco mosaic virus (TMV) in vivo. Especially, compound g18 showed excellent curative and protective activities against CMV, with half-maximal effective concentration (EC₅₀) values of 284.67μg/mL and 216.30μg/mL, which were obviously superior to that of Ningnanmycin (352.08μg/mL and 262.53μg/mL). Preliminary structure-activity relationships (SARs) analysis revealed that the introduction of electron-withdrawing group at the 2-position or 4-position of the aromatic ring is favorable for antiviral activity. Present work provides a promising template for development of potential inhibitor of plant virus.

Synthesis of Some New Pyridazine Derivatives for Anti-HAV Evaluation

4-(2-(4-Halophenyl)hydrazinyl)-6-phenylpyridazin-3(2H)-ones 1a,b were prepared and treated with phosphorus oxychloride, phosphorus pentasulphide and ethyl chloroformate to give the corresponding chloropyridazine, pyridazinethione, oxazolopyridazine derivatives 2–4, respectively. Compound 2 reacted with hydrazine hydrate to afford hydrazinylpyridazine 7. The reaction of 4-(2-(4-chlorophenyl)hydrazinyl)-3-hydrazinyl-6-phenylpyridazine (7) with acetic anhydride, p-chlorobenzaldehyde and carbon disulphide gave the corresponding pyridazinotriazine derivatives 8–10. On the other hand, 5-(4-chlorophenylamino)-7-(3,5-dimethoxybenzylidene)-3-phenyl-5H-pyridazino[3,4-b][1,4]thiazin-6(7H)-one (11) was prepared directly from the reaction of compound 3 with chloroacetic acid in presence of p-chlorobenzaldehyde. Compound 11 reacted with nitrogen nucleophiles (hydroxylamine hydrochloride, hydrazine hydrate) and active methylene group-containing reagents (malononitrile, ethyl cyanoacetate) to afford the corresponding fused compounds 12–15, respectively. Pharmacological screening for antiviral activity against hepatitis A virus (HAV) was performed for the new compounds. 4-(4-Chlorophenylamino)-6-phenyl-1,2-dihydropyridazino[4,3-e][1,2,4]triazine-3(4H)-thione (10) showed the highest effect against HAV.

Asymmetric Synthesis and Bioselective Activities of α-Amino-phosphonates Based on the Dufulin Motif

The asymmetric synthesis of enantiomerically pure α-aminophosphonates with high and bioselective activities is a challenge. Here, we report that both enantiomers of α-aminophosphonates bearing the N-benzothiazole moiety can be prepared in high yields (up to 99%) and excellent enantioselectivities (up to 99% ee) by using chiral thiourea organocatalysts. Evaluation of the antiviral activities of our reaction products against cucumber mosaic virus (CMV) led to promising hits with high and selective biological activities, wherein (R)-enantiomers exhibit higher biological activities than the corresponding (S)-enantiomers. Especially, compound (R)-3b with excellent anti-CMV activity (curative activity, 72.3%; protection activity, 56.9%; and inactivation activity, 96.9%) at 500 μg/mL emerged as a potential inhibitor of the plant virus. The difference in the selective bioactivity could be affected by the combination mode of the three-dimensional space between the enantiomers of α-aminophosphonate and cucumber mosaic virus coat protein (CMV-CP) via florescence spectroscopy and molecular docking.

Highly efficient one-pot four-component Kabachnik–Fields synthesis of novel α-amino phosphonates under solvent-free and catalyst-free conditions

A simple and safe one-pot four component synthesis of Kabachnik–Fields synthesis of novel α-amino phosphonates under solvent-free and catalyst-free conditions is reported.

Design, synthesis, and anti-tobacco mosaic virus (TMV) activity of phenanthroindolizidines and their analogues

On the basis of our previous structure-activity relationship (SAR) and antiviral mechanism studies, a series of phenanthroindolizidines and their analogues 3-20 were designed, targeting tobacco mosaic virus (TMV) RNA, synthesized, and systematically evaluated for their antiviral activity against TMV. The bioassay results showed that most of these compounds displayed good anti-TMV activity, and some of them exhibited higher antiviral activity than that of commercial Ningnanmycin (perhaps the most successful registered antiplant viral agent). Especially, (S)-deoxytylophorinine (5) with excellent anti-TMV activity (inactivation activity, 59.8%/500 μg mL(-1) and 40.3%/100 μg mL(-1); curative activity, 65.1%/500 μg mL(-1) and 43.7%/100 μg mL(-1); and protection activity, 70.2%/500 μg mL(-1) and 51.3%/100 μg mL(-1)) emerged as a potential inhibitor of the plant virus. Compound 20 exhibited a strong in vivo protection effect against TMV at 100 μg mL(-1), which indicated that phenanthroindolizidine analogues with a seven-membered D ring have a new and interesting structural scaffold and have great potential for further development as tobacco protection agents.

Design, synthesis, and antiviral activity evaluation of phenanthrene-based antofine derivatives

On the basis of our previous structure-activity relationship (SAR) and antiviral mechanism studies, a series of phenanthrene-based antofine derivatives (1-12 and 18-50) were designed targeting tobacco mosaic virus (TMV) RNA and synthesized and systematically evaluated for their antiviral activity against TMV. The bioassay results showed that most of these compounds exhibited good to excellent in vivo anti-TMV activity, of which compounds 19 and 27 displayed higher activity than commercial Ribavirin, thus emerging as potential inhibitors of plant virus. The novel concise structure provides another new template for antiviral studies.