Identification of (1-pentylindol-3-yl)-(2,2,3,3-tetramethylcyclopropyl)methanone and its 5-pentyl fluorinated analog in herbal incense seized for drug trafficking

Four herbal incense products were seized from suspected drug abusers in Korea. The major ingredients in the herbal incense samples were purified, and their structures were elucidated using gas chromatography–electron ionization–mass spectrometry (GC–EI–MS), liquid chromatography–time-of-flight–mass spectrometry (LC–TOF–MS), and 1D and 2D nuclear magnetic resonance (NMR) spectroscopy. As a result, ingredients in the herbal incense were identified as (1-pentylindol-3-yl)-(2,2,3,3-tetramethylcyclopropyl)methanone and its 5-pentyl fluorinated analog [1-(5-fluoropentyl)indol-3-yl]-(2,2,3,3-tetramethylcyclopropyl)methanone. The former is being sold via the Internet as a "research chemical" named UR-144, and the latter is sold as 5F-UR-144. UR-144 is a selective full agonist of CB₂ cannabinoid receptor, and was first developed by Abbott Laboratories as an analgesic. It exhibits analgesic activity against both neuropathic and inflammatory pain associated mainly with the CB₂ receptor, but shows less psychotropic effects associated with the CB₁ receptor. Fluorination of the N-pentyl side chain of cannabimimetic compounds increases their cannabinoid receptor affinity such as with AM-2201, which shows both increased analgesic and psychotropic effects simultaneously. UR-144 and 5F-UR-144 can be classified as research chemicals based on their analgesic effects, but in practice are abused as psychotropic agents and can cause unexpected toxic effects. Thus, the trade and diversion of these chemicals should be monitored carefully for possible abuse. To our knowledge, this is the first report disclosing cyclopropylcarbonylindoles in herbal products.