Synthesis and Antiviral Activities of Chiral Thiourea Derivatives

Green Synthesis of Nitroaryl Thioureas: Towards an Improved Preparation of Guanidinium DNA Binders

We present a general efficient green method for the preparation of nitro N,N'-diaryl thioureas via a one-pot method using cyrene as a solvent with almost quantitative yields. This confirmed the viability of cyrene as a green alternative to THF in the synthesis of thiourea derivatives. After screening different reducing conditions, the nitro N,N'-diaryl thioureas were selectively reduced using Zn dust in the presence of water and acid to the corresponding amino N,N'-diaryl thioureas. These were then used to test the installation of the Boc-protected guanidine group with N,N'-bis-Boc protected pyrazole-1-carboxamidine as a guanidylating reagent not requiring mercury(II) activation. Finally, the TFA salts obtained after Boc-deprotection of two sample compounds were tested for their affinity towards DNA showing no binding.

Kinetics and Pathway Analysis Reveals the Mechanism of a Homogeneous PNP-Iron-Catalyzed Nitrile Hydrogenation

Nitrile hydrogenation via the in situ-generated PNP-Fe^II(H)₂CO (1) catalyst leads to a previously inexplicable loss of mass balance. Reaction kinetics, reaction progress analysis, in situ pressure nuclear magnetic resonance, and X-ray diffraction analyses reveal a mechanism comprising reversible imine self-condensation and amine-imine condensation cascades that yield >95% primary amine. Imine self-condensation has never been reported in a nitrile hydrogenation mechanism. The reaction is first order in catalyst and hydrogen and zero order in benzonitrile when using 2-propanol as the solvent. Variable-temperature analysis revealed values for ΔG_298 K^⧧ (79.6 ± 26.8 kJ mol^-1), ΔH^⧧ (90.7 ± 9.7 kJ mol^-1), and ΔS^⧧ (37 ± 28 J mol^-1 K^-1), consistent with a solvent-mediated proton-shuttled dissociative transition state. This work provides a basis for future catalyst optimization and essential data for the design of continuous reactors with earth-abundant catalysts.

Trifluoromethylpyridine thiourea derivatives: design, synthesis and inhibition of the self-assembly of tobacco mosaic virus particles

BACKGROUND

Devastating plant virus diseases leading to bad harvests and lower quality of crops have made feeding the beyond seven billion population a huge challenge. Nevertheless, growing resistance and cross resistance of crop protection agents have made this challenge harder. Therefore, an efficient crop protection agent with novel structure and mode of action showing higher efficiency and eco-friendly is urgently needed.

RESULTS

The coat protein (CP) of a virus is a potential target for the discovery of new antiviral agents. Antiviral molecules can inhibit infection by obstructing the assembly of virus particles. A series of novel phthalamide-like thiourea derivatives containing trifluoromethylpyridine was designed and synthesized. Most of the compounds exhibited good antiviral activity against tobacco mosaic virus (TMV). Compound 7b showed notable curative, protective and inactivation activities against TMV. Its inactivation half-maximal effective concentration (EC₅₀ ) value (20.5 μg mL^-1 ) was better even than commercial ningnanmycin (23.2 μg mL^-1 ). Compound 7b also had stronger TMV-CP binding ability than ningnanmycin and destroyed the external shape of TMV particles and hindered the self-assembly of TMV-CP and TMV-RNA.

CONCLUSION

These phthalamide-like thiourea derivatives especially compound 7b containing trifluoromethylpyridine are potential lead compounds and inhibitors of TMV particle self-assembly. © 2021 Society of Chemical Industry.

Chiral Thioureas-Preparation and Significance in Asymmetric Synthesis and Medicinal Chemistry

For almost 20 years, thioureas have been experiencing a renaissance of interest with the emerged development of asymmetric organocatalysts. Due to their relatively high acidity and strong hydrogen bond donor capability, they differ significantly from ureas and offer, appropriately modified, great potential as organocatalysts, chelators, drug candidates, etc. The review focuses on the family of chiral thioureas, presenting an overview of the current state of knowledge on their synthesis and selected applications in stereoselective synthesis and drug development.

A new thiourea derivative [2-(3-ethylthioureido)benzoic acid] for cloud point extraction of some trace metals in water, biological and food samples

2-(3-Ethylthioureido)benzoic acid was prepared and characterized by electronic spectrum, elemental analysis, Fourier transform infrared spectroscopy, ¹H nuclear magnetic resonance spectrum and mass spectrum. The produced ligand was applied for the preconcentrative of Fe³⁺, Co²⁺, Cu²⁺ and Zn²⁺ in aqueous samples by cloud point extraction methodology. Triton X-114 was used as extractant. Experimental parameters that may affect the extraction process were examined and optimized; such as pH, ligand and triton concentrations, type of diluting solvent, extraction temperature and ionic strength. The calibration curves were linear upto 500μgL^-1 for Fe³⁺, Cu²⁺ and Zn²⁺ and upto 200μgL^-1 for Co²⁺. The achieved detection limits were 1.5, 0.23, 0.71 and 0.35μgL^-1 for Fe³⁺, Co²⁺, Cu²⁺ and Zn²⁺ respectively. The accuracy was established by analysis of certified reference materials (Seronorm whole blood L2 and ZCS ZC85006 Tomato). The proposed procedure was used for preconcentration of these metal ions in water, biological and food samples prior to their determination by flame atomic absorption spectrometry.

Application of "hydrogen bonding interaction" in new drug development: design, synthesis, antiviral activity, and SARs of thiourea derivatives

A series of simple thiourea derivatives were designed based on the structure of natural product harmine and lead compound and synthesized from amines in one step. The antiviral activity of these thiourea derivatives was evaluated. Most of them exhibited significantly higher anti-TMV activity than commercial plant virucides ribavirin, harmine, and lead compound. The hydrogen bond was found to be important but not the more the better. The optimal compound (R,R)-20 showed the best anti-TMV activity in vitro and in vivo (in vitro activity, 75%/500 μg/mL and 39%/100 μg/mL; inactivation activity, 71%/500 μg/mL and 35%/100 μg/mL; curative activity, 73%/500 μg/mL and 37%/100 μg/mL; protection activity, 69%/500 μg/mL and 33%/100 μg/mL), which is significantly higher than that of Ningnanmycin. The systematic study provides strong evidence that these simple thiourea derivatives could become potential TMV inhibitors.