Structure–activity relationships of synthetic cannabinoid designer drug RCS-4 and its regioisomers and C4 homologues

Samuel D. Banister, Jordyn Stuart, Trent Conroy, Mitchell Longworth, Madhura Manohar, Corinne Beinat, Shane M. Wilkinson, Richard C. Kevin, David E. Hibbs, Michelle Glass, Mark Connor, Iain S. McGregor, Michael Kassiou*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

21 Citations (Scopus)


RCS-4 [(4-methoxyphenyl)-1-yl-(1-pentyl-1H-indol-3-yl)methanone] represents the first of several N-alkyl-3-(methoxybenzoyl)indoles identified by forensic scientists as synthetic cannabinoid (SC) designer drugs. Despite the detection of RCS-4 and several analogues (RCS-2, RCS-3, RCS-2-C4, RCS-3-C4, and RCS-4-C4) in products intended for human consumption, relatively little is known about this class of cannabinoids. The synthesis of all regioisomers of RCS-4 and their C4 homologues is described. This study also systematically explored the structure–activity relationships of this class of SCs at human CB1 and CB2 receptors using an in vitro fluorometric imaging plate reader membrane potential assay. All compounds demonstrated agonist activity at CB1 (EC50 = 54–574 nM) and CB2 (EC50 = 4.5–46 nM) receptors, with the C4 homologues showing a preference for CB2 receptors over CB1 receptors (31–42 times). Since most of the analogues (RCS-2, RCS-3, RCS-2-C4, RCS-3-C4 and RCS-4-C4) are not subject to regulation in much of the world, despite their activities towards CB1 and CB2 receptors, there is a possibility that these analogues will emerge on the black market.

Original languageEnglish
Pages (from-to)355-366
Number of pages12
JournalForensic Toxicology
Issue number2
Publication statusPublished - 23 Jul 2015

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