Salvinorin B ethoxymethyl ether
Salvinorin B ethoxymethyl ether, also known as 2-O-ethoxymethylsalvinorin B or as symmetry, is a semi-synthetic analogue of the natural product salvinorin A, with a longer duration of action of around 3hours, and increased affinity and intrinsic activity at the κ-opioid receptor. Like the related compound herkinorin, 2-EMSB is made from salvinorin B, which is most conveniently made from salvinorin A by deacetylation, as while both salvinorin A and salvinorin B are found in the plant Salvia divinorum, salvinorin A is present in larger quantities.
2-EMSB has an affinity of 0.32nM at the κ-opioid receptor, and around 3,000 times selectivity over the μ- and δ-opioid receptors, making it one of the most potent and selective κ-opioid receptor agonists yet discovered. In animal studies it fully substituted for salvinorin A and the synthetic κ-opioid receptor agonist U-69593, and was active at doses as low as 0.005mg/kg. Human bioassays found the compound to be active at 50 μg smoked.
It has been sold online as an analytical standard.