Integrastatins are naturally occurring heterotetracyclic compounds with a broad spectrum of biological activity. A number of new structural analogues of integrastatins 2a-u have been synthesized using a novel one-step method [1], but a systematic theoretical study of their structural features and biological activity has not been realized. This study aimed to in silico investigate physicochemical and bioactivity properties for a series of 21 new synthetic analogues of natural integrastatins. Global chemical reactivity descriptors was assessed using DFT B3LYP 6-311++G(d, p) CPCM (solvent — water) calculations. High ionization potential IP in the range from 5.9 to 7.1 eV and electron affinity EA at the level of 2.1 to 3.2 eV were shown, which together with a sufficiently large energy gap DEgap from 3.8 to 4.6 eV indicates the hard nature of the compounds 2a-u. Antiviral activity and inhibitory potential as CYP2C19 inducers were identified using the PASSOnline resource. According to the results of molecular docking studies Human immunodeficiency virus HIV-1 reverse transcriptase protein (PDB ID: 3V81) and protein of the RNA-dependent RNA polymerase of the SARS-CoV-2 (PDB ID: 7AAP) can serve as a likely biological target for the compounds 2a-u. Potentially high oral efficacy and a promising safety profile for the therapeutic use were showed using ADMETlab 3.0 online portal. Further experimental in vitro and in vivo studies of the pharmaceutical potential of compounds 2a-u is need for more accurate evaluation the assumptions made on the basis of in silico approach.

Quantum chemical studies of the protolytic ability of some dicarboxylic acids are carried out. The geometric and kinetic parameters of the dimeric molecules of maleic, succinic, tartaric, oxalic, and adipic acids are in-vestigated. The dimerization energies of these substances are determined by considering the basis set super-position error (BSSE). The effect of the presence of a carbon skeleton, unsaturated bonds, and hydroxy sub-stituents on the dicarboxylic acids kinetic parameters is confirmed. The frontier molecular orbitals of the studied dimeric acids molecules are considered and the HOMO-LUMO energy gap is determined. The ob-tained values of the energy gaps show an increase in the stability of a number of cyclic compounds formed by the participation of two hydrogen bonds. The ability of the acids to form complexes with the 3,6-di-tert-butyl-2-hydroxyphenoxyl semiquinone radical is studied. The effect of the nature of the solvent on the activation barrier of the complexation reaction of the semiquinone radical — dicarboxylic acid system is analyzed using the CPCM and IEFPCM models. The dependence of the energy parameter on the solvent polarity is estab-lished using the examples of toluene, tetrahydrofuran, and nitrobenzene. The DFT method at the B3LYP lev-el, together with the 6-31+G (d, p) basis set, is used to optimize molecular structures. The calculations are carried out using the Gaussian 16 Revision A.03 WIN64.

Terpyridines are well-known ligands in coordination chemistry due to their conforma-tional flexibility and strong metal-binding properties; therefore, they serve as attractive platforms for the design and synthesis of new functional derivatives. This study focused on the synthesis and comprehensive investigation of a new class of bis-oxazolo[5,4-b]pyridine derivatives, designed based on their structural similarity to terpyridines. Four novel compounds 4a–d were synthesized by cyclization of amide de-rivatives of 3-aminopyridin-2(1H)-ones using pyridine-2,6-dicarboxylic acid and its di-chloride as key acidic components. Their structures and purity were confirmed by melt-ing point analysis, high-resolution mass spectrometry, and detailed 1H NMR spectros-copy. Photophysical studies in chloroform, dichloromethane, and acetonitrile revealed that compounds 4a–c exhibit intense blue to deep blue fluorescence (л_max 323–347 nm) with high quantum yields (φi ≈ 0.32–0.84), attributed to р–π* transitions within the con-jugated ring system. These findings suggest their potential as air-stable phosphors for organic electronics. Computational modeling of 4a–c molecules provided insight into their electronic structures, conformational stability, and predicted optical behavior. The most stable conformers (4a–II, 4b–II, 4c–II′) showed decreasing HOMO–LUMO gaps and photoactivity from 4a to 4c, with 4a–II emerging as the most promising fluorophore due to its high symmetry and consistent emission. Overall, this study lays the foundation for future studies of bis(oxazolo[5,4-b]pyridine) derivatives in coordination chemistry and optoelectronic materials development.

Herein, we report an unexpected pseudo-multicomponent transformation discovered during attempts to selectively nitrate the pyridine core of 3-acetyl-2,4,6-trimethylpyridine (3). Despite employing standard nitration conditions, including KNO₃–H₂SO₄ and HNO₃–H₂SO₄ mixtures, electrophilic substitution of the aromatic ring did not occur. Instead, the reaction sequence promoted an in situ nitrozation, dehydration to nitrile oxide intermediates, and subsequent [3+2]-cycloaddition involving two substrate molecules. This process yielded a novel, highly functionalized furoxan derivative, precisely identified as 3,4-bis(2,4,6-trimethylnicotinoyl)-1,2,5-oxadiazole 2-oxide (5). The molecular architecture of compound 5 was established by ¹H and ¹³C NMR spectroscopy, mass spectrometry, elemental analysis, and single-crystal X-ray diffraction (XRD) analysis. To elucidate the stereochemical and electronic features governing compound 5, DFT calculations were performed at the ωB97X-D/6-311++G(d,p) level of theory. The experimental crystallographic disorder of the N-oxide oxygen atom was computationally rationalized by the thermodynamic near-degeneracy (ΔG < 0.63 kcal/mol) of two orientational isomers (5a and 5b). Furthermore, frontier molecular orbital analysis within the framework of perturbation theory accounted for the head-to-tail regioselectivity during cyclization, while wide energy gaps (ΔE = 8.13–8.27 eV) and high chemical hardness (η = 4.07–4.14 eV) underscored the kinetic stability of the heterocycle. Phenotypic and target-specific in silico profiling using PASS Online identified Matrix Metalloproteinase-9 (MMP-9) as a relevant target for potential hemorheological and cardioprotective applications. Validated molecular docking simulations across three human MMP-9 crystallographic domains (PDB: 8K5Y, 6ESM, 4XCT) demonstrated competitive binding affinities and balanced Ligand Efficiency metrics (LE = 0.26–0.29 kcal/mol/heavy atom), anchoring compound 5 within the catalytic pocket via conventional hydrogen bonds and π-mediated interactions. Finally, in vitro evaluations using a blood hyperviscosity model confirmed significant hemorheological efficacy, as compound 5 effectively prevented the rise in blood viscosity, outperforming the reference drug pentoxifylline. The convergence of computational insights and experimental functional activity establishes this novel bis(nicotinoyl)furoxan framework as a promising candidate for further hemorheological and cardioprotective applications.

Terpyridines are well-known ligands in coordination chemistry, are valued for their conformational flexibility and strong metal-binding properties, and are also of interest as fluorophores. This study focused on the synthesis and comprehensive investigation of a new class of bis-oxazolo[5,4-b]pyridine derivatives, designed based on their structural similarity to terpyridines. Four novel compounds, 4a–d, were synthesized by cyclization of amide derivatives of 3-aminopyridin-2(1H)-ones using pyridine-2,6-dicarboxylic acid and its dichloride as key acidic components. Their structures and purity were confirmed by melting point analysis, high-resolution mass spectrometry, and ¹H, ¹³C NMR spectroscopy. Compounds 4a–c exhibit UV absorption at 323–357 nm and intense blue to deep-blue fluorescence (357–474 nm, цi ≈ 0.32–0.84) in chloroform, dichloromethane, and acetonitrile, attributed to p–p* transitions within the conjugated ring system. These findings suggest their potential as phosphors for organic electronics. Computational modeling of 4a–c molecules provided insight into their electronic structures, conformational stability, and predicted optical behavior. The most stable conformers (4a–II, 4b–II, 4c–II′) exhibited a progressive decrease in the HOMO–LUMO gap from 4a to 4c, correlated with the enhancement of photoactivity. Among them, compound 4a stands out as the most promising luminophore, displaying the most intense and narrow luminescence band, owing to its high molecular symmetry and stable emission characteristics. Overall, this study lays the foundation for future studies of bis(oxazolo[5,4-b]pyridine) derivatives in coordination chemistry and optoelectronic materials development.