Abstract
Two novel series of melatonin-derived compounds have been synthesized and pharmacologically evaluated at the MT1 and MT2 subtypes of melatonin receptors. Compounds 12b-c are non-selective high-affinity MT1 and MT2 receptor ligands (K-i = 7-11 nM). Compound 12b had little intrinsic activity at the MT1 receptor and no intrinsic activity at the MT2 receptor. Compound 20d displayed the highest MT2 binding affinity (K-i = 2 nM) and moderate selectivity toward the MT2 subtype (K-i MT1/MT2 ratio = 8) behaving as MT2 antagonist and MT1 agonist (IC50 = 112 pM). The findings help define SARs around the positions 1 and 2 of melatonin with respect to binding affinity, MT2 selectivity, and intrinsic activity. (C) 2009 Elsevier Ltd. All rights reserved.