4-Phenoxypiperidines:: Potent, conformationally restricted, non-imidazole histamine H3 antagonists

Two new series of 4-(1-alkyl-piperidin-4-yloxy)-benzonitriles and 4-(1-isopropyl-piperidin-4-yloxy)-benzylamines have been prepared. In vitro activity was determined at the recombinant human H-3 receptor and several members of these new series were found to be potent H3 antagonists. The present compounds contain a 4-phenoxypiperidine core, which behaves as a conformationally restricted version of the 3-amino-1-propanol moiety common to the many previously described non-imidazole histamine H-3 ligands. One selected member of the new series, 4-[4-(l-isopropyl-piperidin-4-yloxy)-benzyl]-morpholine (13g), was found to be a potent, highly selective H3 receptor antagonist with in vivo efficacy in a rat EEG model of wakefulness at doses as low as 1 mg/kg sc.