Design and synthesis of 3,5-disubstituted benzamide analogues of DNK333 as dual NK1/NK2 receptor probes

N-[(R,R)-(E)-(3,4-dichlorobenzyl)-3-(2-oxoazepan-3-yl)carbamoyl]allyl-N-methyl-3,5-bis(trifluoromethyl)benzamide (DNK333, 1b) has been reported to be a potent and balanced dual neurokinin (tachykinin) receptor antagonist. A recent clinical trial using DNK333 has shown that it blocks the NKA-induced bronchoconstriction in patients with asthma. A series of six analogues 3–8 derived from modification of 3,5-bis(trifluoromethyl)benzamide moiety of DNK333 has been synthesized to serve as the dual NK1/NK2 receptor probes. The 3,5-dinitro substituted benzamide compound 3 was found to possess potent and balanced dual NK1/NK2 receptor antagonist activities (pKb = 8.4 for the NK1 receptors, pKb = 7.87 for the NK2 receptors) in the functional assay using guinea pig trachea. Furthermore, SAR analysis suggests that steric, electronic, and lipophilic characteristics of substituents in the benzamide region of DNK333 have a crucial effect on both the NK1 and NK2 receptor antagonist activities.