Design, synthesis, and evaluation of opioid analogues with non-peptidic β-turn scaffold:: Enkephalin and endomorphin mimetics

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