Salvinorin A (SalA) is a potent and selective kappa-opioid receptor agonist, but its chemical instability has hindered medicinal chemistry. Weak bases cause C8 epimerization, which destroys receptor affinity and signaling. Replacing C20 with hydrogen and O6 with CH2 stabilizes the scaffold so completely that epimerization is suppressed. The resulting compound, O6C-20-nor-SalA, retains high potency for kappa-opioid receptor agonism.
Salvinorin A, a plant metabolite, is a potent and selective agonist of the human kappa-opioid receptor, which is being investigated as a target for new painkillers. This review examines analogs of the salvinorin chemotype and how modifications affect their selectivity, affinity, and potency. Extensive modifications to the periphery of the molecule, using isolated salvinorin A, have provided a wealth of structure-activity relationship (SAR) data. Recent advances in chemical synthesis now enable more fundamental changes to the core structure.
Deleting a single carbon atom (C20) from the complex plant metabolite salvinorin A stabilizes its molecular skeleton, simplifies its laboratory synthesis to just 10 steps, and preserves its high affinity and selectivity for the human kappa-opioid receptor. The work also introduces a general workflow for identifying structural changes that keep molecular complexity high while reducing synthetic complexity.