Design, Synthesis, and Evaluation of Opioid Analogues with Non-Peptidic β-Turn Scaffold:  Enkephalin and Endomorphin Mimetics

We have identified a μ-selective opioid receptor agonist without a cationic amino group in the molecule from libraries of bicyclic β-turn peptidomimetics. The biologically active conformation of the lead is proposed to mimic an endomorphin type III 4 → 1 β-turn conformation.