We aimed to discover a novel type of transient receptor potential vanilloid 1 (TRPV1) antagonist because such antagonists are possible drug candidates for treating various disorders. We modified the structure of hit compound 7 (human TRPV1 IC50= 411nM) and converted its pyrrolidino group to a (hydroxyethyl) methylamino group, which substantially improved inhibitory activity (15d; human TRPV1 IC50= 33nM). In addition, 15d ...