Several monocyclic derivatives structurally related to the μ-opioid agonist 3-cinnamyl-8 propionyl-3,8-diazabicyclo[3.2. 1]octane have been synthesized and tested in binding studies using the μ-selective 3H-DAMGO as ligand. Modeling studies have been performed on the same compounds in order to explain the observed lack of affinity towards μ-opioid receptors