Application of the bridgehead fragments for the design of conformationally restricted melatonin analogues

Analogues of endogenous hormone melatonin with a side chain incorporated into the bicyclic bridgehead cores were synthesized (left panel). The experimentally determined binding affinity of methoxy-indole derivative fused with exo -N-acetamino-substituted bicyclo[2.2.2]octane confirmed the molecular docking predictions (right panel). ► Bridgehead moieties were used for conformational restriction of melatonin side chain. ► All compounds were synthesized by Fisher indolization of the bridgehead ketones. ► Bicyclo[2.2.2]octane analogue was found to possess nanomolar MT 2 affinity. Conformationally constrained analogues of the hormone melatonin with a side chain incorporated into the bicyclic bridgehead core were synthesized based on the homology modeling and molecular docking studies performed for the MT 2 melatonin receptor. The methoxy-indole derivative fused with exo -N-acetamino-substituted bicyclo[2.2.2]octane was found to possess nanomolar MT 2 receptor affinity.