title: Stereochemical diversity-oriented conformational restriction strategy. Development of potent histamine H3 and/or H4 receptor antagonists with an imidazolylcyclopropane structure.
abstract: The stereochemical diversity-oriented conformational restriction strategy can be an efficient method for developing specific ligands for drug target proteins, especially in cases where neither the bioactive conformation nor the pharmacophore is known. To develop potent H3 and H4 receptor antagonists, a series of conformationally restricted analogues of histamine with a chiral cis- or trans-cyclopropane structure were designed on the basis of this strategy. These target compounds with stereochemical diversity were synthesized from the versatile chiral cyclopropane units (1S,2R)- and (1R,2R)-2-(tert-butyldiphenylsilyloxy)methyl-1-formylcyclopropane (6 and 7, respectively) or their enantiomers ent-6 and ent-7. Pharmacological profiles of these conformationally restricted analogues were shown to be different depending on the cyclopropane backbones. Among the analogues, (1R,2S)-2-[2-(4-chlorobenzylamino)ethyl]-1-(1H-imidazol-4-yl)cyclopropane (11a) with the (1R)-trans-cyclopropane structure has remarkable antagonistic activity to both the H3 (Ki = 8.4 nM) and H4 (Ki = 7.6 nM) receptors. The enantiomer of 11a, i.e., ent-11a, with the (1S)-trans-cyclopropane structure turned out to be a highly potent and selective H3 receptor antagonist with a Ki of 3.6 nM. Conversely, (1R,2R)-2-[(4-chlorobenzylamino)methyl]-1-(1H-imidazol-4-yl)cyclopropane (10a) with the (1R)-trans structure was selective for the H4 receptor (Ki = 118 nM) compared to the H3 receptor (Ki > 10(3) nM). Thus, a variety of compounds with different pharmacological profiles have been developed. These results show that when the structure of the target protein is unknown, the stereochemical diversity-oriented approach can be a powerful strategy in medicinal chemical studies.
authors.affiliation: Graduate School of Pharmaceutical Sciences, Hokkaido University, Kita-ku, Sapporo 060-0812, Japan.
authors.forename: Mizuki
authors.initials: M
authors.lastname: Watanabe
authors.forename: Yuji
authors.initials: Y
authors.lastname: Kazuta
authors.forename: Hideki
authors.initials: H
authors.lastname: Hayashi
authors.forename: Shizuo
authors.initials: S
authors.lastname: Yamada
authors.forename: Akira
authors.initials: A
authors.lastname: Matsuda
authors.forename: Satoshi
authors.initials: S
authors.lastname: Shuto
mesh_terms: D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D003521:Cyclopropanes / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D017442:Histamine Agonists / Q000737:chemistry; D006633:Histamine Antagonists / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D006634:Histamine H1 Antagonists / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D006801:Humans; D007093:Imidazoles / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D008968:Molecular Conformation; D011869:Radioligand Assay; D043562:Receptors, G-Protein-Coupled / Q000187:drug effects*; D011968:Receptors, Histamine / Q000187:drug effects*; D011969:Receptors, Histamine H1 / Q000187:drug effects*; D018100:Receptors, Histamine H3 / Q000187:drug effects*; D000074040:Receptors, Histamine H4; D013237:Stereoisomerism; D013329:Structure-Activity Relationship
chemical_list: D003521:Cyclopropanes; C418607:HRH4 protein, human; D017442:Histamine Agonists; D006633:Histamine Antagonists; D006634:Histamine H1 Antagonists; D007093:Imidazoles; D043562:Receptors, G-Protein-Coupled; D011968:Receptors, Histamine; D011969:Receptors, Histamine H1; D018100:Receptors, Histamine H3; D000074040:Receptors, Histamine H4