RCS-4 ortho isomer.

RCS-4 ortho isomer belongs to the benzoylindoles. It is the regioisomer of RCS-4: the methoxy group occupies position 2 of the benzoyl ring instead of position 4. In a membrane potential assay on AtT-20 cells expressing the human receptor, ChEMBL puts its agonist activity at an EC50 of 54 nM at CB1 and 6.9 nM at CB2, a nanomolar potency at both receptors; Banister et al. (2015) report for this series an agonist activity at CB1 and CB2 (EC50 54 to 574 nM at CB1 and 4.5 to 46 nM at CB2). For the class, the synthetic cannabinoids characterised mostly act as full agonists of the CB1 and CB2 receptors, whereas Δ9-THC is only a partial agonist (Fantegrossi et al., 2014); this property was not found for this precise regioisomer, of which only the potency is documented. No clinical study, no human pharmacokinetic data and no case series concern it: human data are lacking, and the published work on RCS-4 itself cannot be transposed to it.

Source

An entirely synthetic molecule, absent from hemp as from any other plant. It belongs to the RCS-4 analogues detected in products intended for human consumption (Banister et al., 2015), and figures in the lists of the EUDA and of UNODC recording the synthetic cannabinoids reported (Zangani et al., 2020). None of this concerns hemp or cannabidiol products.

No biological pathway: this molecule is entirely synthetic, with no plant precursor or enzymatic step. It belongs solely to synthetic chemistry, described here by chemical class only.

European Union

The substance is not listed in the Annex to Council Framework Decision 2004/757/JHA (consolidated version of 12 January 2026), which lists the new psychoactive substances controlled at European Union level; control is a matter for national law. It appears in the lists of the EUDA and of UNODC recording the synthetic cannabinoids reported (Zangani et al., 2020), which is monitoring and not control. It does not appear in the schedules of the 1971 Convention on Psychotropic Substances (green list of the INCB, 35th and 36th editions). France ties it to a generic definition by chemical family in annex IV of its list (see the French status).

France

RCS-4 ortho isomer is not named in any entry of the ANSM consolidated list (updated 16 February 2026), which does however cite RCS-4 (the para isomer) in annex IV. By its structure, it falls under the generic family of « indol-3-yl methanone » of annex IV, which the text of the decree of 31 March 2017 (JORF of 6 April 2017) already contains: a substituent on the indole nitrogen of the alkyl type (here a pentyl) and a group of the phenyl type, substituted or not (here a 2-methoxyphenyl), on the carbon of the methanone bridge. This reading of the structure remains to be confirmed with ANSM. The clause covering tetrahydrocannabinols (annex III since the decision of 6 February 2026) does not apply. Production, possession, supply, transport and use fall under narcotics criminal law.

Sources: EUR-Lex, UNODC, CND, ANSM, IUPHAR/BPS, ChEBI, EUDA. Our method.

Family

Synthetic CB receptor agonist › New psychoactive substance

Class

benzoylindole

Verification

Classification, sources and binding values checked on 20 October 2026; text read against its sources and Wikipedia.

Wikipedia (English)

No dedicated article.

1. 1Banister SD, Stuart J, Conroy T, Longworth M, Manohar M, Beinat C, Wilkinson SM, Kevin RC, Hibbs DE, Glass M, Connor M, McGregor IS, Kassiou M. Structure-activity relationships of synthetic cannabinoid designer drug RCS-4 and its regioisomers and C4 homologues. Forensic Toxicol. 2015;33:355-366 (abstract read: EC50 CB1 54-574 nM, CB2 4.5-46 nM) (new tab)DOI 10.1007/s11419-015-0282-9
2. 2ChEMBL, activities of compound CHEMBL4069848 (EC50 CB1 54 nM, CB2 6.9 nM, document CHEMBL4028847) (new tab)
3. 3Spinelli F et al. Perspectives of Cannabinoid Type 2 Receptor (CB2R) Ligands in Neurodegenerative Disorders: Structure-Affinity Relationship (SAfiR) and Structure-Activity Relationship (SAR) Studies. J Med Chem. 2017;60(24):9913-9931 (source document for the values curated by ChEMBL) (new tab)PMID 28608697
4. 4Hutter M, Kneisel S, Auwärter V, Neukamm MA. Determination of 22 synthetic cannabinoids in human hair by liquid chromatography-tandem mass spectrometry. J Chromatogr B. 2012;903:95-101 (new tab)PMID 22835826
5. 5Florou D, Boumba VA. Hair analysis for New Psychoactive Substances (NPS): Still far from becoming the tool to study NPS spread in the community? Toxicol Rep. 2021;8:1699-1720 (table 3: LOQ 0.5 pg/mg for the RCS-4 ortho isomer, from Hutter 2012) (new tab)PMID 34646750
6. 6Fantegrossi WE, Moran JH, Radominska-Pandya A, Prather PL. Distinct pharmacology and metabolism of K2 synthetic cannabinoids compared to Δ9-THC: mechanism underlying greater toxicity? Life Sci. 2014;97(1):45-54. CLASS datum (full agonism of the synthetic cannabinoids versus partial agonism of THC), not specific to this compound. (new tab)PMID 24084047
7. 7Zangani C et al. The e-Psychonauts' 'Spiced' World: assessment of the synthetic cannabinoids' information available online. Curr Neuropharmacol 2020 (ORTHO-RCS-4 in the UNODC, EUDA and NPSFinder lists) (new tab)PMID 32116194
8. 8ANSM, consolidated list of substances classified as narcotics, updated 16 February 2026 (annex IV, « indol-3-yl methanone » family, RCS-4 cited as an example; the ortho isomer not named) (new tab)
9. 9Order of 31 March 2017 amending the order of 22 February 1990: « indol-3-yl methanone » family of annex IV (Légifrance, JORF of 6 April 2017) (new tab)
10. 10PubChem CID 57507911, RCS-4 ortho isomer: identifiers, synonyms (CAS 1345966-76-8, RCS-2), average mass 321.4 (new tab)

SMILES

CCCCCN1C=C(C2=CC=CC=C21)C(=O)C3=CC=CC=C3OC

Machine-readable entry (JSON)

LLM ingestion format: a structured superset of the entry (identifiers, binding, versioned legal status). Full corpus.