Synthesis of novel derivatives of 4-amino-3-(2-furyl)-5-mercapto-1,2,4-triazole as potential HIV-1 NNRTIs

4-Phenylcoumarin derivatives as new HIV-1 NNRTIs: Design, synthesis, biological activities, and computational studies

A series of 4-phenylcoumarin derivatives was synthesized and evaluated for their cellular anti-HIV-1 and HIV-2 activities as well as their inhibitory effects against HIV-1 reverse transcriptase (RT). The hydrazone compound 8b and the ethylthiosemicarbazide derivative 4c showed the best inhibition activity against wild-type (WT) HIV-1. The promising compounds were further evaluated against HIV-1 RT and exhibited significant inhibitory activity with compound 8b showing comparable effect to the reference NNRTI Efavirenz (IC50 = 9.01 nM). Structure activity relationship study revealed the importance of 6-chloro and 4-phenyl substituents for optimum activity, as well as the 5-atoms linker (=N-NH-CO-CH2-O-) at position 7 of coumarin scaffold that can support the rotation and flexibility of compound 8b to fit well in the binding pocket. The molecular docking of compound 8b demonstrated a typical seahorse binding mode with better binding interactions that covered more residues when compared to Efavirenz.

Detection of a target protein (GroEl2) in Mycobacterium tuberculosis using a derivative of 1,2,4-triazolethiols

Herein, we identified a potent lead compound RRA2, within a series of 54 derivatives of 1,2,4-triazolethiols (exhibit good potency as an anti-mycobacterial agents) against intracellular Mycobacterium tuberculosis (Mtb). Compound RRA2 showed significant mycobactericidal activity against active stage Mycobacterium bovis BCG and Mtb with minimum inhibitory concentration (MIC) values of 2.3 and 2.0 µg/mL, respectively. At MIC value, RRA2 compound yielded 0.82 log reduction of colony-forming unit (cfu) against non-replicating Mtb. Furthermore, RRA2 compound was selected for further target identification due to the presence of alkyne group, showing higher selectivity index (> 66.66 ± 0.22, in non-replicating stage). Using "click" chemistry, we synthesized the biotin linker-RRA2 conjugate, purified with HPLC method and confirmed the conjugation of biotin linker-RRA2 complex by HR-MS analysis. Furthermore, we successfully pulled down and identified a specific target protein GroEl2, from Mtb whole-cell extract. Furthermore, computational molecular modeling indicated RRA2 could interact with GroEl2, which explains the structure-activity relationship observed in this study. GroEL-2 identified a potent and specific target protein for RRA 2 compound in whole cell extract of Mtb H37Ra.

(R,S)-2-{[4-(4-Methylphenyl)-5-phenyl-4H-1,2,4-triazol-3-yl]thio}-1-phenyl-1-ethanol

4-(4-Methylphenyl)-5-phenyl-4H-1,2,4-triazol-3-thiol (4) was alkylated to 2-{[4-(4-methylphenyl)-5-phenyl-4H-1,2,4-triazol-3-yl]thio}-1-phenylethan-1-one (5) in alkaline conditions using 2-bromo-1-phenylethanone. The alkylated compound (5) was reduced at the carbonyl group to the corresponding racemic secondary alcohol with an asymmetric carbon, (R,S)-2-{[4-(4-methylphenyl)-5-phenyl-4H-1,2,4-triazol-3-yl]thio}-1-phenyl-1-ethanol (6). Both synthesized compounds, ketone (5) and secondary alcohol (6), are new and have not yet been reported in the literature. All the synthesized compounds were characterized by IR, 1D and 2D 1H-1H, 1H-13C and 1H-15N NMR spectroscopy and by elemental analysis.

Two decades of the synthesis of mono- and bis-aminomercapto[1,2,4]triazoles

4-Amino-5-mercapto[1,2,4]triazole and its 3-substituted derivatives have proven to be of biological interest and provide access to a new class of biologically active heterocyclic compounds for biomedical applications. This study will be helpful for scientific researchers interested in the chemistry of bifunctional versatile compounds as it provides a collection of all the methods for the preparation of 3-substituted-4-amino-5-mercapto[1,2,4]triazoles with aliphatic, aromatic, and heterocyclic moieties during the period from 2000 to mid-2020.

A series of 1,3-imidazoles and triazole-3-thiones based thiophene-2-carboxamides as anticancer agents: Synthesis and anticancer activity

By addition of semicarbazide or phenylhydrazine hydrochloride to thienoylisothiocyanate (1) resulted in building of thiosemicarbazide derivative (2), triazole derivative (4) and thiophene-2-carboxamide (5), respectively. Basic cyclization of compound 2 led to formation of oxadiazine (3). Synthesis of thiadiazine derivative (6) was achieved via reaction of compound 5 and maleic anhydride in triethyl amine. Heating of compound 5 with ethyl chloroacetate or sodium ethoxide produced thiadiazine derivative (7) and triazolethione (8), respectively. Thiosemicarbazide derivative 11 was synthesized by addition of nicotinic hydrazide to compound 1. Refluxing of compound 11 with lead acetate afforded triazole (13). Moreover, acid and base mediated cyclizations of compound 11 gave thiadiazole (12) and 1,2,4-triazolethione (14) throughout thiophene intermediate, respectively. Addition of ethyl 2-aminothiophene-3-carboxylate to compound 1 formed thiourea (15) which was refluxed with ethoxide giving thiophene-3-carboxylic acid (16). Lastly, nucleophilic addition of amino phenol or ethylene diamine to compound 1 yielded oxazine structure (18) and imidazole derivative (19), respectively. The yields of the synthesized compounds were 61-95%. The detailed synthesis and spectroscopic data of the new compounds are reported.

Adsorption Mechanism of 4-Amino-5-mercapto-1,2,4-triazole as Flotation Reagent on Chalcopyrite

A novel compound 4-amino-5-mercapto-1,2,4-triazole was first synthesized, and its selective adsorption mechanism on the surface of chalcopyrite was comprehensively investigated using UV-vis spectra, zeta-potential, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy measurements (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and first principles calculations. The experimental and computational results consistently demonstrated that AMT would chemisorb onto the chalcopyrite surface by the formation of a five-membered chelate ring. The first principles periodic calculations further indicated that AMT would prefer to adsorb onto Cu rather than Fe due to the more negative adsorption energy of AMT on Cu in the chalcopyrite (001) surface, which was further confirmed by the coordination reaction energies of AMT-Cu and AMT-Fe based on the simplified cluster models at a higher accuracy level (UB3LYP/Def2-TZVP). The bench-scale results indicated that the selective index improved significantly when using AMT as a chalcopyrite depressant in Cu-Mo flotation separation.

GIAO/DFT studies on 1,2,4-triazole-5-thiones and their propargyl derivatives

Density functional theory (DFT)/Becke-Lee-Yang-Parr (B3LYP) and gauge-including atomic orbital (GIAO) calculations were performed on a number of 1,2,4-triazole derivatives, and the optimized structural parameters were employed to ascertain the nature of their predominant tautomers. (13)C and (15)N NMR chemical shifts of 3-substituted 1,2,4-triazole-5-thiones and their propargylated derivatives were calculated via GIAO/DFT approach at the B3LYP level of theory with geometry optimization using a 6-311++G** basis set. A good agreement between theoretical and experimental (13)C and (15)N NMR chemical shifts could be found for the systems investigated. The data generated were useful in predicting (15)N chemical shifts of all the nitrogen atoms of the triazole ring, some of which could not be obtained in solution state (15)N HMBC/HSQC NMR measurements. The energy profile computed for the dipropargylated derivatives was found to follow the product distribution profile of regioisomers formed during propargylation of 1,2,4-triazole thiones.

Synthesis and anti-human immunodeficiency virus type 1 activity of (E)-N-phenylstyryl-N-alkylacetamide derivatives

A series of (E)-N-phenylstyryl-N-alkylacetamides, 5, were synthesized by direct reduction-acetylation of β-arylnitroolefins, followed by N-alkylation. The title compounds were characterized by ¹H-NMR, EIMS and IR analysis. All the synthesized compounds were assayed as HIV-1 non-nucleoside reverse transcriptase inhibitors. A SAR study revealed that when group R¹ in 5 was ortho-substituted, the resulting compounds showed better inhibitory activities against HIV-1 RT. Among the tested compounds, 5i (R¹ = 2-Br, R² = 3,5-difluorobenzyl) exhibited the highest enzyme activity, with a 88.89% inhibitory ratio against HIV-1 reverse transcriptase at the tested concentration. Further cell-based anti-HIV-1 assays showed that compound 5i exhibited a SI value of 29 with an EC₅₀ value of 4 μM in C8166 cells.

Revealing interaction mode between HIV-1 reverse transcriptase and diaryltriazine analog inhibitor

HIV-1 reverse transcriptase is a key enzyme playing an important role in the HIV-1 life cycle for the replication of the RNA genome into DNA form. Lys103Asn (K103N) mutant frequently is observed in HIV-1 reverse transcriptase. Therefore, a series of novel non-nucleoside reverse transcriptase inhibitors were designed and synthesized. In vitro experimental results show that diaryltriazine analogs have potent anti-HIV activity with moderate to high selectivity. In order to design anti-HIV drug, docking and molecular dynamics simulation were used to investigate the binding mode between ligand and HIV-1 reverse transcriptase. The results suggest that the analogs might have a similar interaction mechanism with HIV-1 reverse transcriptase. Then comparative molecular field analysis and comparative molecular similarity indices analysis were used to construct quantitative structure-activity models. These models were evaluated by eight test set compounds. These models are helpful in making quantitative prediction of their activity for new lead compounds before resorting in vitro and in vivo experimentation.

Structural elucidation of propargylated products of 3-substituted-1,2,4-triazole-5-thiols by NMR techniques

Propargylation of 3-substituted-1,2,4-triazole-5-thiols, which predominantly exist as their thione tautomers, was carried out with the view to synthesize different heterocycles and study their biological activity. Three different products namely, a mono S-propargyl and two S,N-dipropargyl regioisomers, arising from N1/N2 substitution, were isolated and characterized. Unambiguous structural elucidation of the regioisomers of S,N-dipropargyl derivatives was achieved by means of (13)C-(1)H HMBC technique. The proportion of the regioisomers was found to vary with the substituent on the 1,2,4-triazole thiols. No product corresponding to N4 substitution was isolated from any of the reactions carried out.