New 1-Benzyl-4-hydroxypiperidine Derivatives as Non-imidazole Histamine H3 Receptor Antagonists

A series of 1-benzyl-4-(3-aminopropyloxy)piperidine and 1-benzyl-4-(5-aminopentyloxy)piperidine derivatives has been prepared. The 1-benzyl-4-hydroxypiperidine derivatives obtained were evaluated for their affinities at recombinant human histamine H3 receptor, stably expressed in HEK 293T cells. All compounds investigated show moderate to pronounced in-vitro affinities. The most potent antagonists in this series 9b2 (hH3R, pKi = 7.09), 9b1 (hH3R, pKi = 6.78), 9b5 (hH3R, pKi = 6.99), and 9b6 (hH3R, pKi = 6.97) were also tested in vitro as H3 receptor antagonists – the electrically evoked contraction of the guinea-pig jejunum. The histaminergic H1 antagonism of selected compounds 9b1, 9b2, and 9b4–9b6 was established on the isolated guinea-pig ileum by conventional methods; the pA2 values were compared with the potency of pyrilamine. The compounds did not show any H1 antagonistic activity (pA2 < 4; for pyrilamine pA2 = 9.53).