4-Allyl-5-pyridin-4-yl-2,4-dihydro-3H-1,2,4-triazole-3-thione: synthesis, experimental and theoretical characterization

In silico design, synthesis and antitubercular activity of novel 2-acylhydrazono-5-arylmethylene-4-thiazolidinones as enoyl-acyl carrier protein reductase inhibitors

Mycobacteria regulate the synthesis of mycolic acid through the fatty acid synthase system type 1 (FAS I) and the fatty acid synthase system type-2 (FAS-II). Because mammalian cells exclusively utilize the FAS-I enzyme system for fatty acid production, targeting the FAS-II enzyme system could serve as a specific approach for developing selective antimycobacterial drugs. Enoyl-acyl carrier protein reductase enzyme (MtInhA), part of the FAS-II enzyme system, contains the NADH cofactor in its active site and reduces the intermediate. Molecular docking studies were performed on an in-house database (∼2200 compounds). For this study, five different crystal structures of MtInhA (PDB Code: 4TZK, 4BQP, 4D0S, 4BGE, 4BII) were used due to rotamer difference, mutation and the presence of cofactors. Molecular dynamics simulations (250 ns) were performed for the novel 2-acylhydrazono-5-arylmethylene-4-thiazolidinones derivatives selected by molecular docking studies. Twenty-three compounds selected by in silico methods were synthesized. Antitubercular activity and MtInhA enzyme inhibition studies were performed for compounds whose structures were elucidated by IR,1H-NMR,13C-NMR, HSQC, HMBC, MS and elemental analysis.Communicated by Ramaswamy H. Sarma.

Synthesis, structural, spectral, antioxidant, bioactivity and molecular docking investigations of a novel triazole derivative

The structural, spectroscopic and electronic properties of 4-(4-nitrophenyl)-5-(pyridin-3-yl)-2,4-dihydro-3H-1,2,4-triazole-3-thione have been analyzed by using single crystal X-ray diffraction (SCXRD), ¹H and ¹³C NMR chemical shifts and FT-IR spectroscopic methods both theoretically and experimentally. The tautomeric (thiol and thione) energetic analysis results, structural optimization parameters (bond lengths and angles), vibrational wavenumbers, proton and carbon NMR chemical shifts, UV-Vis. parameters, the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) analyses and Molecular Electrostatic Potential (MEP) surface have been calculated by using DFT/B3LYP quantum chemical method with 6-311++G(2d,2p) basis set to compare with the experimental results. The computed geometry parameters, vibrational wavenumbers, and NMR chemical shifts have been in good agreement with the experimental results. It should be noted that the radical scavenging activities of the title compound have been evaluated by using different test methods i.e. 2,2-Diphenyl-1-picrylhydrazyl (DPPH), N,N-dimethyl-p-phenylenediamine (DMPD) and 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS). According to obtained results, the title compound displayed DPPH (SC₅₀ 19.42 ± 0.11 μg/mL), DMPD (SC₅₀ 21.13 ± 0.08 μg/mL) and ABTS (SC₅₀ 38.17 ± 0.25 μg/mL) scavenging activities. Also, these results have been compared with Butylated hydroxyanisole (BHA), Rutin (RUT) and Trolox (TRO) used as standard compounds. The physicochemical, pharmacokinetic, and toxicity features of the compound have been determined by using drug-likeness and in silico ADMET investigations. The interaction results with SARS-CoV-2 main protease (M^pro) of the title ligand compound have been analyzed via the help of molecular docking study.Communicated by Ramaswamy H. Sarma.

Interaction of carbonic anhydrase isozymes I, II, and IX with some pyridine and phenol hydrazinecarbothioamide derivatives

A series of hydrazinecarbothioamide derivatives incorporating ethyl, phenyl, tolyl, benzyl, and allyl moieties were prepared and tested as possible inhibitors of three members of the pH regulatory enzyme family, carbonic anhydrase (CA; EC 4.2.1.1). The inhibitory and activatory potencies of the compounds against the cytosolic human isoforms hCA I and hCA II and the transmembrane, tumor-associated hCA IX were analyzed by a hydrase assay with CO2 as substrate, and the inhibition constants (KI) were calculated. Most compounds investigated here exhibited nanomolar or low micromolar inhibition constants against the three isoenzymes. KI values were in the range of 34.1-871 nM for hCA I and compounds 5-10 showed interesting activation of the hCA II with KA value of 0.81-12.5 μM. Compounds 11-16 exhibited moderate inhibition effects on hCA IX in the range of 0.317-1.245 μM but they were less effective for hCA II. Tested compounds were also investigated using in silico applications at the binding pockets of these three targets. The different mechanisms of inhibition by these tested compounds as compared to sulfonamides, and their diverse inhibition profile for these mammalian isozymes, makes this class of derivatives of great interest for the design of novel CA inhibitors.

Normal coordinate analysis, molecular structure, vibrational, electronic spectra and NMR investigation of 4-Amino-3-phenyl-1H-1,2,4-triazole-5(4H)-thione by ab initio HF and DFT method

In the present work, the characterization of 4-Amino-3-phenyl-1H-1,2,4-triazole-5(4H)-thione (APTT) molecule was carried out by quantum chemical method and vibrational spectral techniques. The FT-IR (4000-400 cm(-1)) and FT-Raman (4000-100 cm(-1)) spectra of APTT were recorded in solid phase. The UV-Vis absorption spectrum of the APTT was recorded in the range of 200-400 nm. The molecular geometry, harmonic vibrational frequencies and bonding features of APTT in the ground state have been calculated by HF and DFT methods using 6-311++G(d,p) basis set. The complete vibrational frequency assignments were made by normal coordinate analysis (NCA) following the scaled quantum mechanical force field methodology (SQMF). The molecular stability and bond strength were investigated by applying the natural bond orbital analysis (NBO) and natural localized molecular orbital (NLMO) analysis. The electronic properties, such as excitation energies, absorption wavelength, HOMO and LUMO energies were performed by time depended DFT (TD-DFT) approach. The (1)H and (13)C nuclear magnetic resonance chemical shift of the molecule were calculated using the gauge-including atomic orbital (GIAO) method and compared with experimental results. Finally, the calculation results were analyzed to simulate infrared, FT-Raman and UV spectra of the title compound which shows better agreement with observed spectra.

6-Phenyl-3-(4-pyridyl)-1,2,4-triazolo-[3,4-b][1,3,4]thiadiazole: synthesis, experimental, theoretical characterization and biological activities

The molecular geometry, vibrational frequencies, and gauge including atomic orbital (GIAO) (1)H and (13)C NMR chemical shift values of the title compound in the ground state have been calculated using the Hartree-Fock (HF) and density functional theory (DFT) methods with 6-31G(d) basis sets, and compared with the experimental data. The calculated results show that the optimized geometries can well reproduce the crystal structural parameters and the theoretical vibrational frequencies, and (1)H and (13)C NMR chemical shift values show good agreement with experimental data. To determine conformational flexibility, molecular energy profile of the title compound was obtained by HF/6-31G(d) and (DFT/B3LYP) calculations with respect to selected degree of torsional freedom, which was varied from -180° to +180° in steps of 10°. The energetic behavior of the title compound in solvent media was examined using the B3LYP method with the 6-31G(d) basis set by applying the Onsager and the polarizable continuum model (PCM). The results obtained with these methods reveal that the PCM method provided more stable structure than Onsager's method. The title compound has been tested in vitro for biological effects.

3-Amino-1,2,4-triazolium ion in [24(3at)]Cl and [24(3at)]₂SnCl6·H₂O. Comparative X-ray, vibrational and theoretical studies

Crystal structures of 3-amino-1,2,4-triazolium chloride and bis(3-amino-1,2,4-triazolium) hexachloridostannate monohydrate were determined by means of X-ray single crystal diffraction. The route of protonation of organic molecule and tautomer equilibrium constants for the cationic forms were calculated using B3LYP/6-31G* method. The most stable protonated species is 2,4-H(2)-3-amino-1,2,4-triazolium ion, 24(3at)(+). Very good agreement between theoretical and experimental frequencies was achieved due to very weak interactions existing in studied compounds. Significantly weaker intermolecular interactions are found in [24(3at)](2)SnCl(6)·H(2)O than in [24(3at)]Cl. The differences in strength of interactions are manifested in red and blue shifts for stretching and bending motions, respectively. PED calculations show that for 24(3at)(+) ion the stretching type of motion of two N(ring)H bonds is independent, whereas bending is coupled.