The synthesis, crystal structure and Hirshfeld analysis of 4-(3,4-di-methyl-anilino)-N-(3,4-di-methyl-phen-yl)quinoline-3-carboxamide

Mapping Chromone-3-Phenylcarboxamide Pharmacophore: Quid Est Veritas?

Chromone-3-phenylcarboxamides (Crom-1 and Crom-2) were identified as potent, selective, and reversible inhibitors of human monoamine oxidase B (hMAO-B). Since they exhibit some absorption, distribution, metabolism, and excretion (ADME)-toxicity liabilities, new derivatives were synthesized to map the chemical structural features that compose the pharmacophore, a process vital for lead optimization. Structure-activity relationship data, supported by molecular docking studies, provided a rationale for the contribution of the heterocycle's rigidity, the carbonyl group, and the benzopyran heteroatom for hMAO-B inhibitory activity. From the study, N-(3-chlorophenyl)-4H-thiochromone-3-carboxamide (31) (hMAO-B IC₅₀ = 1.52 ± 0.15 nM) emerged as a reversible tight binding inhibitor with an improved pharmacological profile. In in vitro ADME-toxicity studies, compound 31 showed a safe cytotoxicity profile in Caco-2, SH-SY5Y, HUVEC, HEK-293, and MCF-7 cells, did not present cardiotoxic effects, and did not affect P-gp transport activity. Compound 31 also protected SH-SY5Y cells from iron(III)-induced damage. Collectively, these studies highlighted compound 31 as the first-in-class and a suitable candidate for in vivo preclinical investigation.

4-Oxoquinolines and monoamine oxidase: When tautomerism matters

4-Oxoquinoline derivatives have been often used in drug discovery programs due to their pharmacological properties. Inspired on chromone and 4-oxoquinoline chemical structure similarity, a small series of quinoline-based compounds was obtained and screened, for the first time, toward human monoamine oxidases isoforms. The data showed the N-(3,4-dichlorophenyl)-1-methyl-4-oxo-1,4-dihydroquinoline-3-carboxamide 10 was the most potent and selective MAO-B inhibitor (IC₅₀ = 5.30 ± 0.74 nM and SI: ≥1887). The data analysis showed that prototropic tautomerism markedly influences the biological activity. The unequivocal characterisation of the quinoline tautomers was performed to understand the attained data. To our knowledge, there have been no prior reports on the characterisation of quinolone tautomers by 2D NMR techniques, namely by ¹H-¹⁵N HSQC and ¹H-¹⁵N HMBC, which are proposed as expedite tools for medicinal chemistry campaigns. Computational studies on enzyme-ligand complexes, obtained after MM-GBSA calculations and molecular dynamics simulations, supported the experimental data.