THC-O.THC-O-acetate (Δ9-tetrahydrocannabinol acetate)

THC-O-acetate is the acetate ester of Δ9-THC, on its phenolic hydroxyl; cannabinoids acylated at the phenol do not occur naturally (EMCDDA 2023). « THC » acetates were described as early as 1940–1945 by Roger Adams's team, but their preparations probably contained mostly the Δ6a,10a isomer; Δ9-THC acetate proper was studied after the isolation of Δ9-THC (Gaoni and Mechoulam, 1966). In rhesus monkeys, the acetates of Δ8- and Δ9-THC at 1 mg/kg intravenously produced effects comparable to those of the parent THCs at lower doses, with a slightly delayed onset, which suggests prodrug action (Edery et al., 1971–1972, cited by the EMCDDA). Human liver microsomes hydrolyse it to Δ9-THC through the carboxylesterases CES1 and CES2 (Zhao et al., 2025). No controlled human study has been published. Under vaping conditions, cannabinoid acetates (including Δ8-THC acetate and a commercial product) formed ketene, a gas toxic to the lungs (Munger et al., 2022), hence a warning about a risk of lung injury similar to EVALI (Benowitz, 2023). In France, the esters of tetrahydrocannabinols have been narcotics since the arrêté of 22 February 1990.

Source

Semi-synthetic (acetate ester of Δ9-THC; does not occur naturally)

No biosynthesis: cannabinoids acylated at the phenol do not occur naturally (EMCDDA 2023). THC-O is the acetate ester of the phenol of Δ9-THC. Human liver microsomes hydrolyse it to Δ9-THC, mainly through the carboxylesterases CES1 and CES2 (Zhao et al., 2025).

European Union

No named listing of the ester in the schedules of the 1971 Convention, which cover Δ9-THC, THC isomers and their stereochemical variants. Verified national examples: Spain, List II, « acetato de tetrahidrocannabinol (THC-O) », defined in the text as Δ8-THC acetate (Orden SND/380/2025, in force on 23 April 2025); Czech Republic, esters of dronabinol listed by regulation 176/2024 Sb. (in force on 1 July 2024). Checked on 19/10/2026.

France

A narcotic since the arrêté of 22 February 1990, which lists « Tétrahydrocannabinols, leurs esters, éthers, sels ainsi que les sels des dérivés précités »; this entry moved from Annex IV to Annex III by the decision of the ANSM Director-General of 6 February 2026. It also falls under the generic class of benzo[c]chromene-nucleus derivatives (ANSM decisions of 22 May and 3 June 2024). Checked on 19/10/2026.

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

Family

Semi-synthetic cannabinoid › Ester or prodrug

Chemistry

C5 side chain · neutral form

Verification

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

Wikipedia (English)

THC-O-acetate (new tab)

Article paired by the molecule's structure (InChIKey), revision read on 19 October 2026. Read as a second opinion, never cited as a source.

1. 1EMCDDA (Ujváry et al.), Hexahydrocannabinol (HHC) and related substances, 2023, §2.6.2 (new tab)
2. 2Zhao S et al. Enzymatic hydrolysis of Δ8-THC-O, Δ9-THC-O, 11-α-HHC-O and 11-β-HHC-O by pooled human liver microsomes. Forensic Toxicol 2025;43:256-265 (new tab)PMID 40153119
3. 3Munger KR, Jensen RP, Strongin RM. Vaping cannabinoid acetates leads to ketene formation. Chem Res Toxicol 2022;35:1202-1205 (new tab)PMID 35801872
4. 4Benowitz NL et al. Vaping THC-O acetate: potential for another EVALI epidemic. J Med Toxicol 2023 (new tab)PMID 36508081
5. 5ANSM, decision of 06/02/2026 amending the list of substances classified as narcotics and the list of psychotropic substances (new tab)
6. 6Orden SND/380/2025, BOE núm. 97 of 22/04/2025 (new tab)

SMILES

CCCCCC1=CC2=C([C@@H]3C=C(CC[C@H]3C(O2)(C)C)C)C(=C1)OC(=O)C

Machine-readable entry (JSON)

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