New 4-(heteroanilido)piperidines, structurally related to the pure opioid agonist fentanyl, with agonist and/or antagonist properties

Article abstract of DOI:10.1021/jm00123a028

A research program based on certain heterocyclic modifications (12-50) of the fentanyl (1) molecule has generated a novel class of opioids. In the mouse hot-place test, these compounds were weaker analgesics than 1. Two types of antagonists were observed