Synthetic studies of neoclerodane diterpenoids from Salvia splendens and evaluation of Opioid Receptor affinity.

Salvinorin A (1), a neoclerodane diterpene from the hallucinogenic mint Salvia divinorum, is the only known non-nitrogenous and specific kappa-opioid agonist. Several structural congeners of 1 isolated from Salvia splendens (2 - 8) together with a series of semisynthetic derivatives (9 - 24), some of which possess a pyrazoline structural moiety (9, 19 - 22), have been tested for affinity at human mu, delta, and kappa opioid receptors. None of these compounds showed high affinity binding to these receptors. However, 10 showed modest affinity for kappa receptors suggesting other naturally neoclerodanes from different Salvia species may possess opioid affinity.