Toward Biophysical Probes for the 5-HT₃ Receptor: Structure−Activity Relationship Study of Granisetron Derivatives

This report describes the synthesis and biological characterization of novel granisetron derivatives that are antagonists of the human serotonin (5-HT₃A) receptor. Some of these substituted granisetron derivatives showed low nanomolar binding affinity and allowed the identification of positions on the granisetron core that might be used as attachment points for biophysical tags. A BODIPY fluorophore was appended to one such position and specifically bound to 5-HT₃A receptors in mammalian cells