ABSTRACT: Opioid agonists are among the most commonly used anti-nociceptive xenobiotics for the treatment of pain. Of these xenobiotic agents, morphine, a μ-selective opioid agonist, is perhaps the foremost substrate and most other commercial opiates are either direct analogues or structurally related to morphine. Due to issues associated with side effects and dependence in traditional opiates, there are opportunities to develop new opiate entities based on non-morphine like chemical scaffolds. Salvinorin A, a non-alkaloid diterpenoid bearing opioid activity, has been demonstrated to bear selectivity for the k-opioid receptor. This poses significance as salvinorin A represents a new class of opioid substrates that does not follow the traditional morphine-like scaffold. A semi-synthetic benzyl ester analogue of salvinorin A, herkinorin, has been shown to be a selective substrate to the μ-opioid receptor. Recently at the University of South Australia, a series of novel non-alkaloidal diterpenoid compounds has been isolated from the Northern Kanjuu plant Dodonaea polyandra. Out of these diterpenoid compounds, one was found to possess significant structural similarity to herkinorin and was selected for further development to investigate the compounds potential for opioid activity. The important structure-activity relationships of these compounds will be discussed.