Synthesis, biological activity, and molecular modeling studies of selective 5-HT2C/2B receptor antagonists

The synthesis and biological activity are reported for a series of analogues of the previously published indole urea 2 (SB-206553), designed to probe the 5-HT2C receptor binding site. Small molecule modeling studies have been used to define a region in space which is allowed at the 5-HT2C receptor but disallowed at the 5-HT2A receptor. In a complementary approach, docking of 2 into our model of the 5-HT2C receptor has allowed us to propose a novel primary binding interaction for this series of diaryl ureas, involving a potential double hydrogen-bonding interaction between the urea carbonyl oxygen of the ligand and two serine residues in the receptor. The difference of two valine residues in the 5-HT2C receptor for leucine residues in the 5-HT2A receptor is believed to account for the observed 5-HT2C/5-HT2A selectivity with 2.