rb-64 rb-64 rb-64 is a semi-synthetic derivative of salvinorin a. it is an irreversible agonist, with a reactive thiocyanate group that forms a bond to the κ-opioid receptor (kor), resulting in very high potency. it is functionally selective, activating g proteins more potently than β-arrestin-2. rb-64 has a bias factor of up to 96 and is analgesic with fewer of the side-effects associated with unbiased kor agonists. the analgesia is long-lasting. compared with unbiased agonists, rb-64 evokes considerably less receptor internalization. rb-64legal statuslegal status legal/uncontrolled identifiers iupac name methyl (2s,4ar,6ar,7r,9s,10as,10br)-2-(furan-3-yl)-6a,10b-dimethyl-4,10-dioxo-9-(2-thiocyanatoacetyl)oxy-2,4a,5,6,7,8,9,10a-octahydro-1h-benzoisochromene-7-carboxylate pubchem cid73347341chemspider30812525 ychemblchembl2381583 ychemical and physical dataformulac24h27no8smolar mass489.54 g·mol−13d model (jsmol)interactive image smiles c12cc3c(=o)o(c3(1c(=o)(c2c(=o)oc)oc(=o)csc#n)c)c4=coc=c4 inchi inchi=1s/c24h27no8s/c1-23-6-4-14-22(29)33-17(13-5-7-31-10-13)9-24(14,2)20(23)19(27)16(8-15(23)21(28)30-3)32-18(26)11-34-12-25/h5,7,10,14-17,20h,4,6,8-9,11h2,1-3h3/t14-,15-,16-,17-,20-,23-,24-/m0/s1 ykey:azpuakgnqxurga-zwlnrfidsa-n y