Synthesis, Bioassay, and Molecular Field Topology Analysis of Diverse Vasodilatory Heterocycles

Synthesis & molecular modeling studies of bronchodilatory active indole–pyridine conjugates

Aim: Synthesis of novel bronchodilatory active indole–pyridine conjugates. Results/methodology: Indole–pyridine conjugates (6a–n, 8a–i and 10a–c) were synthesized in a facile pathway through reaction of 2-[(1-alkyl-1H-indol-3-yl)methylene]malononitriles 4a,b with the corresponding ketone-containing compounds (5a–f, 7a–c and 9a,b) in the presence of sodium alkoxide. Single (6l, 8 g) and powder (6k, 8d) x-ray studies supported the structures. Results: Histamine precontracted isolated tracheal rings of guinea pig exhibited the potent bronchodilation properties of 6c (about double-fold potency relative to the standard reference, theophylline). Some of the synthesized conjugates (8d, 6c, 6f and 6e) revealed promising reduction of IL-8 production during lipopolysaccharide-induced airway inflammatory bioassay. Computational studies (3D pharmacophore, 2D-QSAR ‘quantitative structure–activity relationship’) showed high approximations to the bronchodilation properties and explained the parameters controlling biological observations.

Synthesis and 2D-QSAR Study of Active Benzofuran-Based Vasodilators

A new series of 2-alkyloxy-pyridine-3-carbonitrile-benzofuran hybrids (4a–x) was synthesized. All the new derivatives were examined via the standard technique for their vasodilation activity. Some of the investigated compounds exhibited a remarkable activity, with compounds 4w, 4e, 4r, 4s, 4f and 4g believed to be the most active hits in this study with IC₅₀ values 0.223, 0.253, 0.254, 0.268, 0.267 and 0.275 mM, respectively, compared with amiodarone hydrochloride, the reference standard used (IC50 = 0.300 mM). CODESSA PRO was employed to obtain a statistically significant 2-Dimensional Quantitative Structure Activity Relationship (2D-QSAR) model describing the bioactivity of the newly synthesized analogs (N = 24, n = 4, R² = 0.816, R²_cvOO = 0.731, R²_cvMO = 0.772, F = 21.103, s² = 6.191 × 10⁻⁸).

Molecular structure studies of novel bronchodilatory-active 4-azafluorenes

Two 5H-indeno[1,2-b]pyridines, 7a and 7b, were synthesized and characterized by X-ray crystallography. In the molecular packing, molecules of 7a are linked into chains by C–H···N hydrogen bond which, in turn, are connected by H···π, N···π, Cl···π and π···π interactions. In the crystal structure of 7b, molecules are connected by C–H···N and C–H···Cl interactions as well as a set of N···π and Cl···π interactions. The molecular structures were studied by theory using AM1, PM3 and DFT. The basic difference between the theoretical and experimental structures was found in the relative orientation of dichlorophenyl ring attached to the indenopyridine residue, which was revealed to be aligned in nearly opposite orientations. This observation is attributed to the bulky chlorine atom(s) of the phenyl ring that prevent free rotation around the sigma bond attaching this ring with the heterocyclic system. DFT was used to determine the molecular electrostatic potential revealing the nitrile nitrogen to be the most nucleophilic site. A low HOMO-LUMO energy gap indicates high reactivity of 7a and 7b. The synthesized azafluorenes show more potent bronchodilation properties than the standard reference compound (theophylline).

Synthesis, X-ray powder diffraction and DFT calculations of vasorelaxant active 3-(arylmethylidene)pyrrolidine-2,5-diones

Two 3-(arylmethylidene)pyrrolidine-2,5-diones, 12a and 12b, were synthesized and characterized by powder X-ray diffraction utilizing a high-resolution synchrotron X-ray powder technique as well as DFT calculations.