N-(Arylcyclopropyl)acetamides and N-(arylvinyl)acetamides or methyl ureas have been prepared as constrained analogues of melatonin. The affinity of these new compounds for chicken brain melatonin receptors and recombinant human MT1 and MT2 receptors was evaluated using 2-[125I]-iodomelatonin as radioligand. Strict ethylenic or cyclopropyl analogues of the commercialized agonist agomelatine (Valdoxan®)