Synthesis and opioid receptor affinity of bivalent ligands derived from 3,8-diazabicyclo(3.2.1)octanes

A new series of bivalent ligands (2a-d), derived from the previously reported analgesic 3-cinnamyl-8-propionyl-3,8-diazabicyclo(3.2.1)octane (1a), has been synthesized and tested in vitro for their affinity towards opioid receptors and in vivo for their analgesic potency. None of the new compounds showed either appreciable affinity for opioid receptors or analgesic activity comparable to that of the model 1a.