title: Synthesis, NMR conformational analysis and pharmacological evaluation of 7,7a,13,14-tetrahydro-6H-cyclobuta[b]pyrimido[1,2-a:3,4-a']diindole analogues as melatonin receptor ligands.
abstract: A structure for the self-condensation product of 2-(1H-indol-2-yl)ethyl tosylate 2a, previously proposed as 6,7,14,15-tetrahydro-15aH-azocino[1,2-a:6,5-b]diindole 3a, was revised based on the (13)C-2D-INADEQUATE experiment, and proved to be 7,7a,13,14-tetrahydro-6H-cyclobuta[b]pyrimido[1,2-a:3,4-a']diindole 4a. A mechanism for the unexpected formation of this novel hexacyclic heterocycle was proposed and its NMR solution structure was elucidated. Five derivatives of the title ring skeleton 12-16 designed as melatonin receptor ligands were synthesized and their affinities for the human MT(1) and MT(2) receptors were determined. Both butyramides 13 and 15, as well as the non-methoxy acetamide 12 exhibited micromolar binding affinities for both receptors being slightly MT(2) selective. The methoxy acetamide 14 showed the best pharmacological profile exhibiting a five times higher affinity for MT(1) (K(i) = 49 nM) than for MT(2) (K(i) = 246 nM) receptor.
authors.affiliation: Pharmaceutical Institute, University of Würzburg, Am Hubland, 97074, Würzburg, Germany.
authors.forename: Mohamed I
authors.initials: MI
authors.lastname: Attia
authors.forename: Deniz
authors.initials: D
authors.lastname: Güclü
authors.forename: Barbara
authors.initials: B
authors.lastname: Hertlein
authors.forename: Justin
authors.initials: J
authors.lastname: Julius
authors.forename: Paula A
authors.initials: PA
authors.lastname: Witt-Enderby
authors.forename: Darius P
authors.initials: DP
authors.lastname: Zlotos
mesh_terms: D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D006801:Humans; D007211:Indoles / Q000737:chemistry* / Q000494:pharmacology; D020128:Inhibitory Concentration 50; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008550:Melatonin / Q000737:chemistry; D008958:Models, Molecular; D008968:Molecular Conformation; D011743:Pyrimidines / Q000737:chemistry* / Q000494:pharmacology; D044122:Receptor, Melatonin, MT1 / Q000378:metabolism*; D044123:Receptor, Melatonin, MT2 / Q000378:metabolism*
chemical_list: C522355:7,7a,13,14-tetrahydro-6H-cyclobuta(b)pyrimido(1,2-a-3,4-a')diindole; D007211:Indoles; D008024:Ligands; D011743:Pyrimidines; D044122:Receptor, Melatonin, MT1; D044123:Receptor, Melatonin, MT2; D008550:Melatonin