RCS-8, or 1-(2-cyclohexylethyl)-3-(2-methoxyphenylacetyl)indole, is a synthetic cannabinoid also known as SR-18 or BTM-8 that has been found as an ingredient of "herbal" synthetic cannabis blends. It can be described as an analogue of JWH-250 with the 1-pentyl group replaced by 1-(2-cyclohexylethyl), and can be expected to be less potent than JWH-250 (cf. JWH-007 and its cyclohexylethyl analogue). Despite not having been reported in the scientific or patent literature as yet, reputed recreational use of RCS-8 in the United States has led to it being specifically listed in a proposed 2011 amendment to the Controlled Substances Act, aiming to add a number of synthetic drugs into Schedule I.
^Huffman, J. W.; Dai, D.; Martin, B. R.; Compton, D. R. (1994). "Design, Synthesis and Pharmacology of Cannabimimetic Indoles". Bioorganic & Medicinal Chemistry Letters. 4 (4): 563. doi:10.1016/S0960-894X(01)80155-4.