Pyrroloquinoxaline Derivatives as High-Affinity and Selective 5-HT<sub>3</sub> Receptor Agonists: Synthesis, Further Structure−Activity Relationships, and Biological Studies
[(3)H]zacopride binding. The SAR studies detailed herein delineated a number of structural features required for improving affinity. Some of the ligands were employed as "molecular yardsticks" to probe the spatial dimensions of the lipophilic pockets L1, L2, and L3 in the 5-HT(3) receptor cleft, while the 7-OH pyrroloquinoxaline analogue was designed to investigate hydrogen bonding with a putative receptor site