Synthesis and PASS-assisted evaluation of new heterocyclic compounds containing hydroquinoline scaffolds

Currently, there is a growing interest in the synthesis of heterocyclic compounds containing hydroquinoline fragments. This surge can be attributed to the broad range of pharmaceutical and industrial applications that these compounds possess. In this study, the synthesis of both linear and fused heterocyclic systems that incorporate hydroquinoline fragments was described. Furthermore, the pharmacological activity spectra of the synthesized compounds were predicted using the in silico method, employing the Prediction of Activity Spectra of Substances (PASS) program. Hydroquinolines containing the nitrile functionality 7 and 8 were synthesized through the reaction of the corresponding hydroquinolinecarbaldehyde 5a, 6b with hydroxylamine hydrochloride and iodine in aqueous ammonia under ambient conditions, respectively. 2-Phenyl-1,3-oxazol-5(4 H)-ones 9a, b and 10a, b were synthesized via the condensation of compounds 5a, b and 6a, b with hippuric acid in acetic acid in 30–60% yield. When the methyl activated 7-methylazolopyrimidines 11a, b were reacted with N-alkyl-2,2,4-trimethyl-1,2,3,4-tetrahydroquinoline-6-carbaldehydes 6a, b, 60–70% yield of triazolo/pyrazolo[1,5-a]pyrimidin-6-yl carboxylic acids 12a, b were obtained. The condensation of 7-hydroxy-1,2,3,4-tetramethyl-1,2-dihydroquinoline 3 h with dimethylacetylenedicarboxylate (DMAD) and ethyl acetoacetate afforded cyclic products 16 and 17, respectively. The condensation reaction of 6-formyl-7-hydroxy-1,2,2,4-tetramethyl-1,2-dihydroquinoline 5e with methylene-active compounds such as ethyl cyanoacetate/dimethyl-3-oxopentanedioate/ethyl acetoacetate/diethylmalonate/Meldrum’s acid afforded 3-substituted coumarins 19 and 21 containing dihydroquinoline moiety. The pentacyclic coumarin 22 was obtained via the tandom condensation reaction of malononitrile with 5e in the presence of a catalytic amount of piperidine in ethanol. The biological activities of the synthesized compounds were predicted using the PASS program. Based on the prognosis, compounds 13a, b, and 14 exhibited a high likelihood of being active as inhibitors of gluconate 2-dehydrogenase, as well as possessing antiallergic, antiasthmatic, and antiarthritic properties, with a probability value (Pa) ranging from 0.849 to 0.870. Furthermore, it was discovered that compounds 7 and 8 tended to act as effective progesterone antagonists and displayed antiallergic, antiasthmatic, and antiarthritic effects (Pa = 0.276–0.827). Among the hydroquinolines containing coumarin moieties, compounds 17, 19a, and 19c were predicted to be potent progesterone antagonists, with Pa values of 0.710, 0.630, and 0.615, respectively.

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