Design, synthesis, and structure–activity relationships of a series of novel N-aryl-2-phenylcyclopropanecarboxamide that are potent and orally active orexin receptor antagonists

Herein we describe the design, synthesis, and structure–activity relationships (SARs) of a novel phenylcyclopropane series represented by 7 and 33b as antagonists of orexin 1 and orexin 2 receptors. With 4 serving as the initial lead for the development of orexin antagonists, exploration of SAR resulted in improved binding affinity for orexin 1 and orexin 2 receptors. Among the synthesized compounds, 33b ((−)-N-(5-cyanopyridin-2-yl)-2-[(3,4-dimethoxyphenyl)oxymethyl]-2-phenylcyclopropanecarboxamide) exhibited potent in vitro activity and oral efficacy in animal sleep measurement experiments. The results of our study suggest that compound 33b may serve as a valuable template for the development of new orexin receptor antagonists.