Diamine derivatives containing imidazolidinylidene propanedinitrile as a new class of histamine H(3) receptor antagonists: conformationally restricted derivatives

Novel conformationally restricted diamine derivatives containing imidazolidinylidene propanedinitrile were synthesized and evaluated for human and rat histamine H(3) receptor (H(3)R) binding affinities. Among them, compounds 2b, 2c, 2j, 2k and 2m were found to be potent ligands for both H(3)Rs with K(i) values in the sub-nanomolar range, and showed potent H(3) receptor antagonism.