Salvinorin B ethoxymethyl ether, also known as 2-O-ethoxymethylsalvinorin B (2-EMSB) or as symmetry, is a semi-synthetic analogue of the natural product salvinorin A, with a longer duration of action of around 3hours (compared to less than 30minutes for salvinorin A), and increased affinity and intrinsic activity at the ú-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 (K<sub>i</sub>) of 0.32nM at the ú-opioid receptor, and around 3,000 times selectivity over the ü- and ô-opioid receptors, making it one of the most potent and selective ú-opioid receptor agonists yet discovered. In animal studies it fully substituted for salvinorin A and the synthetic ú-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 üg smoked.
It has been sold online as an analytical standard.