Synthesis and Pharmacological Characterization of Novel trans-Cyclopropylmethyl-Linked Bivalent Ligands That Exhibit Selectivity and Allosteric Pharmacology at the Dopamine D₃ Receptor (D₃R)

The development of bitopic ligands directed toward D 2 -like receptors has proven to be of particular interest to improve the selectivity and/or affinity of these ligands and as an approach to modulate and bias their efficacies. The structural similarities between dopamine D 3 receptor (D 3 R)-selective molecules that display bitopic or allosteric pharmacology and those that are simply competitive antagonists are subtle and intriguing. Herein we synthesized a series of molecules in which the primary and secondary pharmacophores were derived from the D 3 R-selective antagonists SB269,652 ( 1 ) and SB277011A ( 2 ) whose structural similarity and pharmacological disparity provided the perfect templates for SAR investigation. Incorporating a trans -cyclopropylmethyl linker between pharmacophores and manipulating linker length resulted in the identification of two bivalent noncompetitive D 3 R-selective antagonists, 18a and 25a, which further delineates SAR associated with allosterism at D 3 R and provides leads toward novel drug development.