Synthesis, testing and structure-activity studies on a library of 5-HT₄ ligands

Several indole derivatives and analogues comprising a range of related structural classes were designed, synthesized and tested as ligands for the 5-HT₄ receptor. Within each series, binding experiments showed compounds with good affinity demonstrating high percentage displacement values at 1 µM. The most potent of these (20) had a pKi of 8.54 demonstrating very good affinity. These indole analogues were combined with 55 ligands that were previously produced in our laboratory to explore the structure-activity relationships of these 5-HT₄ ligands. A CoMFA (Comparative Molecular Field Analysis) analysis was used to extend an earlier simple pharmacophore to suggest two new molecular features beyond the primary amino binding site. The pharmacophore confirmed that a newly described tetrahydroquinoline analogue was able to match the basic requirements of the model and the pharmacology of this molecule is provided in more detail.