Synthesis of Bitopic Ligands as Potent Dopamine D2 Receptor Agonists

In this study, we designed and synthesized twelve bitopic ligands as dopamine D₂ receptor (D₂R) agonists. The forskolin-induced cAMP accumulation assay revealed that all the finial compounds are able to activate D₂R. Furthermore, bitopic ligand N-((trans)-4-(((2,3-dihydro-1H-inden-2-yl)(propyl)amino)methyl)cyclo-hexyl)-1H-pyrrolo[2,3-b]pyridine-2-carboxamide ( 11 b ) showed 21-fold higher potency than lead compound propyl aminoindane ( 2 ) and 17-fold higher subtype selectivity for D₂R over D₄R, indicating that the optimal length of spacer affects the D₂R functionality. Molecular modeling study exhibited that 11 b formed an electrostatic interaction and two H-bonds with amino acid Asp114, which contributes significantly to the D₂R functional activity. Taken together, we discovered a bitopic ligand 11 b as potent D₂R agonist, which may be used as a tool compound for further study.