JWH-138
JWH-138 (THC-Octyl, Δ8-THC-C8) is a synthetic cannabinoid first synthesised by John W. Huffman, with a Ki of 8.5nM at the CB1 cannabinoid receptor. Isomers

The Δ3/Δ6a(10a) isomer was synthesised in 1941, but was found to be slightly less active than Δ3-THC itself. The alternate isomer Δ9-THC-C8 has also been synthesised, and both the Δ8 and Δ9 isomers are included within the definition of an "intoxicating cannabinoid" in Colorado under the name tetrahydrocannabioctyl, but it is unclear if it has been identified as a natural product. Tetrahydrocannabioctyl is sometimes referred to as THC-Octyl or THCO, which may cause confusion with THC-O-acetate which is commonly known as THC-O. See also 
 Cannabicyclohexanol
 Parahexyl
 Tetrahydrocannabihexol
 THCP

References 

Xanthenes