Amide-to-chloroalkene substitution for overcoming intramolecular acyl transfer challenges in hexapeptidic neuromedin U receptor 2 agonists.

CPN-116 is a peptidic agonist that activates human neuromedin U receptor type 2 (NMUR2) but suffers from chemical instability due to inherent backbone isomerization on the Dap residue. To address this, a Leu-Dap-type ()-chloroalkene dipeptide isostere was synthesized diastereoselectively as a surrogate of the Leu-Dap peptide bond to develop a ()-chloroalkene analogue of CPN-116. The synthesized CPN-116 analogue is stable in 1.0 M phosphate buffer (pH 7.4) without backbone isomerization and can activate NMUR2 with similar potency to CPN-116 at nM concentrations (EC = 1.0 nM).