Structure activity relationship exploration of 5-hydroxy-2-(3-phenylpropyl)chromones as a unique 5-HT receptor antagonist scaffold.

Antagonists for the serotonin receptor 2B (5-HT) have clinical applications towards migraine, anxiety, irritable bowl syndrome, and MDMA abuse; however, few selective 5-HT antagonists have been identified. Previous studies from these labs identified a natural product, 5-hydroxy-2-(2-phenylethyl)chromone (5-HPEC, 2) as the first non-nitrogenous ligand for the 5-HT receptor. Studies on 5-HPEC optimization led to the identification of 5-hydroxy-2-(3-phenylpropyl)chromone (5-HPPC, 3), which showed a tenfold improvement in binding affinity over 2 at 5-HT. This study aimed to further improve receptor pharmacology of this unique scaffold. Guided by molecular modeling studies modifications at the C-3' and C-4' positions of 3 were made to probe their effects on ligand binding affinity and efficacy. Among the derivatives synthesized 5-hydroxy-2-(3-(3-cyanophenyl)propyl)chromone (5-HCPC, 3d) showed the most promise with a multifold improvement in binding affinity (pK = 7.1 ± 0.07) over 3 with retained antagonism.