exo-THC.exo-Tetrahydrocannabinol

Exo-THC, or Δ9(11)-THC, carries its double bond outside the terpene ring, on a methylene group at C9, where Δ9-THC and Δ8-THC keep it inside the ring. It is still recognised by the CB1 receptor: it displaces [3H]CP-55,940 from rat brain membranes with an IC50 of 334 nM, versus 218 nM for Δ9-THC (Compton 1991). In mice it reproduced the cannabinoid tetrad (reduced locomotor activity, hypothermia, antinociception, immobility) at doses 4 to 40 times higher than those of Δ9-THC. Drug-discrimination results diverge: no substitution up to 30 mg/kg in rats in the 1991 study, full but less potent substitution in rats and rhesus monkeys in that of Wiley et al. (1993), who concluded it lacks antagonist properties in this paradigm. In rhesus monkeys, Beardsley et al. (1987) had not observed the ptosis, sedation or ataxia produced by Δ9-THC. The intravenous LD50 in mice is 93 mg/kg, double that of Δ9-THC. No human data are published.

Source

Exo-THC has not been described as a constituent of hemp and no plant biosynthetic route is known; the FDA laboratory classes it among the "unnatural" THC isomers. It is met in two settings. In pharmacy, the United States Pharmacopeia (USP) distributes an "exo-tetrahydrocannabinol" reference standard used in the dronabinol monograph. On the market, the FDA's Forensic Chemistry Center identified it in THC vaping liquids analysed after the 2019 EVALI outbreak, together with Δ8-THC, Δ6a,10a-THC and Δ10-THC; the authors attribute these isomers to the chemical and thermal treatments undergone by the source materials, cannabis concentrates or converted hemp.

No known biosynthetic route in hemp. Exo-THC is a product of chemical synthesis, described as early as 1971, and an isomerisation by-product found in cannabis or hemp products subjected to chemical and thermal treatments (Ciolino 2021).

European Union

Internationally, exo-THC is one of the six tetrahydrocannabinol isomers listed by name in Schedule I of the 1971 Convention on Psychotropic Substances, as (6aR,10aR)-6a,7,8,9,10,10a-hexahydro-6,6-dimethyl-9-methylene-3-pentyl-6H-dibenzo[b,d]pyran-1-ol. The WHO Expert Committee on Drug Dependence reviewed these isomers at its 41st meeting, in 2018. The European Union keeps no list of its own: each Member State applies the Convention in national law, and no EU-specific control measure targets this isomer.

France

In France, exo-THC is not listed by name. It falls under the generic entry "Tetrahydrocannabinols, their esters, ethers, salts as well as the salts of the aforementioned derivatives" of the narcotics list (decree of 22 February 1990), an entry moved from annex IV to annex III by the ANSM decision of 6 February 2026. This is a family classification, not an individual listing: production, possession, transfer and use are prohibited, and a consumer product containing it is unlawful, whatever its CBD content.

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

Family

Semi-synthetic cannabinoid › Isomer or by-product

Chemistry

C5 side chain · neutral form

Verification

Every fact on this entry was checked against its primary sources on 20 October 2026.

Wikipedia (English)

No dedicated article.

1. 1Wildes JW, Martin NH, Pitt CG, Wall ME. The synthesis of (-)-delta-9(11)-trans-tetrahydrocannabinol. J Org Chem 1971;36:721-723 (new tab)PMID 5545571
2. 2Beardsley PM, Scimeca JA, Martin BR. Studies on the agonistic activity of delta 9-11-tetrahydrocannabinol in mice, dogs and rhesus monkeys and its interactions with delta 9-tetrahydrocannabinol. J Pharmacol Exp Ther 1987;241:521-526 (new tab)PMID 3033218
3. 3Compton DR, Prescott WR Jr, Martin BR, Siegel C, Gordon PM, Razdan RK. Synthesis and pharmacological evaluation of ether and related analogues of delta 8-, delta 9-, and delta 9,11-tetrahydrocannabinol. J Med Chem 1991;34:3310-3316 (new tab)PMID 1659638
4. 4Wiley JL, Barrett RL, Britt DT, Balster RL, Martin BR. Discriminative stimulus effects of delta 9-tetrahydrocannabinol and delta 9-11-tetrahydrocannabinol in rats and rhesus monkeys. Neuropharmacology 1993;32:359-365 (new tab)PMID 8388551
5. 5WHO, Expert Committee on Drug Dependence. Isomers of THC: Critical Review Report, 41st meeting, 2018 (new tab)
6. 6Ciolino LA, Ranieri TL, Brueggemeyer JL, Taylor AM, Mohrhaus AS. EVALI Vaping Liquids Part 1: GC-MS Cannabinoids Profiles and Identification of Unnatural THC Isomers. Front Chem 2021;9:746479 (new tab)PMID 34631667
7. 7USP–NF, Dronabinol monograph (USP reference standards Delta-9-Tetrahydrocannabinol RS and Exo-tetrahydrocannabinol RS) (new tab)
8. 8ANSM, decision of 6 February 2026 amending the list of substances classified as narcotics and the list of psychotropic substances (new tab)
9. 9ANSM, consolidated list of substances classified as narcotics, updated 16 February 2026 (new tab)
10. 10PubChem, Delta(9-11)-Tetrahydrocannabinol, CID 167577 (new tab)

SMILES

CCCCCC1=CC(=C2[C@@H]3CC(=C)CC[C@H]3C(OC2=C1)(C)C)O

Machine-readable entry (JSON)

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