Synthesis of 2-(4-biphenylyl)quinoline-4-carboxylate and carboxamide analogs. New human neurokinin-3 (hNK-3) receptor antagonists

The 2-phenylquinoline-4-carboxamide 1 (Chart[TH]1) has been found to possess moderate affinity for human neurokinin-3 (hNK-3) receptor. In the present work, and in a trial to investigate the effect of the lipophilic moiety at C-2 of the quinoline ring on the antagonistic activity, an enlargement of the aromatic area at this position was suggested. In this respect, two series of 2-(4-biphenylyl)quinoline-4-carboxylates and carboxamides have been synthesized with certain modifications at the quinoline-2 and 4-position in order to study their effect on the anticipated hNK-3 receptor antagonistic activity. Fifteen compounds were screened for such activity using guinea-pig isolated ileum longitudinal muscle preparation and senktide as selective hNK-3 receptor agonist. Some compounds showed considerable antagonistic effect. Compound 7b, 6-bromo-2-(4-biphenylyl)quinoline-4-carboxylic acid, was the most prominent hNK-3 receptor antagonist in this study. Unexpectedly, some compounds were agonists.