Abstract
The synthesis of novel melatonin analogues 3a and 4a-c designed as melatonin receptor ligands is described. Among the newly synthesized ligands, 2-((S)-2-hydroxymethylindolin-1-ylmethyl)-melatonin 4b displayed the highest affinity for MT1 receptors (K-i=9.8 nM) and for MT2 subtype (K-i=7.8 nM), whereas the rigid pentacyclic ligand 3 showed the highest selectivity towards the MT2 receptor subtype ( K-i=319.3 nM for MT1 and K-i=65.2 nM for MT2). (C) 2008 Elsevier Ltd. All rights reserved.