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Derived from the plant

(9R)-HHC(9R)-Hexahydrocannabinol

The 9R epimer of HHC: a CB1 partial agonist whose affinity matches that of Δ9-THC; the most active form in marketed HHC.

Narcotic: named in schedule
Level of detail

Harm-reduction warning

No characterised human dose: animal / in vitro data only. Effect profile, safety margin and acute toxicity are not documented in human clinical practice. Extremely potent compound: severe effects, seizures and deaths reported in the literature.

C₂₁H₃₂O₂

CAS 36403-90-4

Family
Semi-synthetic cannabinoidHydrogenated
Molar mass
316.50 g/mol

Updated on

In plain terms

(9R)-HHC is one of the two « twin » forms of HHC, which differ only in the orientation of one methyl group. It is the more active one: it binds the CB1 receptor as well as THC does, while its (9S) twin is much less active. Marketed HHC mixes the two in variable proportions; it is classified as a narcotic in France.

Receptors and activity

Target network

CB1Partial agonistKi = 15 nM · human[3H]CP55940 displacement, Chem-1-hCB1 cell lysates; functional EC50 (cAMP) 3.4 nM
  • Activates

The lower the cited value, the closer the target sits to (9R)-HHC: one ring per factor of 100. A target with no measured value stays on the edge.

Where these targets live

Where each target has been found in humans, according to the cited studies. The map shows the target, not an effect of (9R)-HHC.

Brain, side view
Body, front view
Blood

CB1CB1 found in 7 regions of the body

  1. Basal gangliadenseMost dense in basal ganglia outflow nuclei1
  2. CerebellumdenseVery dense in the cerebellum1
  3. HippocampusdenseVery high concentrations in the hippocampus2
  4. AmygdaladenseHigh concentrations in the amygdala2
  5. CortexpresentPresent throughout the neocortex2
  6. Adipose tissuepresentExpressed in adipose tissue3
  7. GutpresentColonic epithelium, smooth muscle and plexus4

Map sources

  1. Herkenham M et al. Cannabinoid receptor localization in brain. Proc Natl Acad Sci U S A, 1990 (new tab)
  2. Glass M et al. Cannabinoid receptors in the human brain: a detailed anatomical and quantitative autoradiographic study in the fetal, neonatal and adult human brain. Neuroscience, 1997 (new tab)
  3. Engeli S et al. Activation of the peripheral endocannabinoid system in human obesity. Diabetes, 2005 (new tab)
  4. Wright K et al. Differential expression of cannabinoid receptors in the human colon: cannabinoids promote epithelial wound healing. Gastroenterology, 2005 (new tab)

Cited values

  1. CB1Partial agonistKi = 15 nM · human64 out of 100

    Nasrallah DJ, Garg NK. Studies Pertaining to the Emerging Cannabinoid Hexahydrocannabinol (HHC). ACS Chem Biol 2023;18:2023-2029 (new tab) · [3H]CP55940 displacement, Chem-1-hCB1 cell lysates; functional EC50 (cAMP) 3.4 nM

  2. CB2Partial agonistKi = 13 nM · human65 out of 100

    Nasrallah DJ, Garg NK. ACS Chem Biol 2023;18:2023-2029 (new tab) · [3H]WIN 55212-2 displacement, CHO-hCB2 cell lysates; functional EC50 (cAMP) 6.2 nM

Bar length follows the measured value (Ki, Kd, EC50 or IC50), on one scale shared by every entry, from 100 µM to 0.1 nM. A target with no cited value has no bar.

Pharmacology

(9R)-HHC is the (6aR,9R,10aR) epimer of hexahydrocannabinol, described as early as 1940 by Roger Adams but which appeared on the market in September 2021 in the United States, then in May 2022 in Europe (WHO 2024). Marketed HHC, obtained from CBD, mixes the (9R) and (9S) epimers, on average in a 1.4:1 ratio (WHO 2024), but from 0.2:1 to 2.4:1 according to the certificates of analysis of more than 60 products (Nasrallah and Garg, 2023). At human receptors, (9R)-HHC binds CB1 with a Ki of 15 nM, like Δ9-THC in the same study, and activates it as a partial agonist, 17 times more potently than (9S)-HHC; in another cell model, its CB1 potency was about five times lower than that of JWH-018 (Persson et al., 2025). In mice, a dose of 10 mg/kg produced cannabinoid-like effects in the tetrad, unlike (9S)-HHC (WHO 2024). Molecular modelling explains this gap by the chair conformation of (9R)-HHC, which places the C9 methyl in an equatorial position in the binding site (Chen et al., 2025). After inhalation of a 50:50 mixture, its serum concentrations exceeded those of (9S)-HHC (mean Cmax: 7.9 versus 2.3 ng/mL). HHC has been classified as a narcotic in France since the ANSM decision of 12 June 2023 and listed in Schedule II of the 1971 Convention since 6 December 2025.

Key sources.

History

Source
Semi-synthetic: the (9R) epimer of market HHC, obtained from CBD; traces of HHC have been reported in cannabis, epimer not specified

Route of preparation

Chemical process

No characterised biosynthesis. Market HHC is obtained from CBD extracted from hemp by cyclisation followed by hydrogenation (Russo et al., 2023); the hydrogenation creates the C9 centre and gives both the (9R) and (9S) epimers, on average in a 1.4:1 ratio (WHO 2024). To explain traces of HHC in cannabis samples, the EMCDDA (2023) proposes a disproportionation of Δ9-THC into HHC epimers and CBN.

Classification

Family, origin and source verification

Family

Semi-synthetic cannabinoid › Hydrogenated

Chemistry

C5 side chain · neutral form

Natural trace reported

Traces of HHC reported in cannabis: the WHO describes it as « found in trace amounts as a phytocannabinoid in certain cannabis strains »; the EMCDDA writes that it « may also co-occur with cannabinol in low amount » and proposes a disproportionation of Δ9-THC into HHC epimers and CBN. No source specifies the epimer; presence possibly artefactual.

WHO ECDD 47, Critical review report: Hexahydrocannabinol, 2024, summary (new tab)

Verification

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

Wikipedia (English)

Hexahydrocannabinol (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.

References

  1. Nasrallah DJ, Garg NK. Studies Pertaining to the Emerging Cannabinoid Hexahydrocannabinol (HHC). ACS Chem Biol 2023;18:2023-2029 (new tab)PMID 37578929
  2. Russo F et al. Synthesis and pharmacological activity of the epimers of hexahydrocannabinol (HHC). Sci Rep 2023;13:11061 (new tab)PMID 37422571
  3. Persson M, Kronstrand R, Evans-Brown M, Green H. In vitro activation of the CB1 receptor by the semi-synthetic cannabinoids HHC, HHC-O and HHC-P. Drug Test Anal 2025;17:487-493 (new tab)PMID 38894658
  4. Chen PP et al. Origin of the Different Binding Affinities of (9R)- and (9S)-Hexahydrocannabinol (HHC) for the CB1 and CB2 Cannabinoid Receptors. ACS Chem Biol 2025;20:2006-2013 (new tab)PMID 40704858
  5. WHO ECDD 47, Critical review report: Hexahydrocannabinol, 2024 (new tab)
  6. Ujváry I. Hexahydrocannabinol and closely related semi-synthetic cannabinoids: A comprehensive review. Drug Test Anal 2024;16:127-161 (new tab)PMID 37269160
  7. ANSM, consolidated list of substances classified as narcotics, updated 26/06/2026 (HHC, annex III: decisions of 12/06/2023 and 16/01/2026; benzo[c]chromene class, annex IV: decisions of 22/05 and 03/06/2024) (new tab)
  8. UNODC, announcement: HHC placed in Schedule II of the 1971 Convention, in force from 6 December 2025 (new tab)

Identifiers

Names

Common name
(9R)-Hexahydrocannabinol
IUPAC name
(6aR,9R,10aR)-6,6,9-trimethyl-3-pentyl-6a,7,8,9,10,10a-hexahydrobenzo[c]chromen-1-ol
Other names
9R-HHC · 9(R)-Hexahydrocannabinol

Identifiers

Formula
C₂₁H₃₂O₂
CAS
36403-90-4
PubChem CID
11067065(new tab)
InChIKey
XKRHRBJLCLXSGE-DJIMGWMZSA-N
SMILES
CCCCCC1=CC(=C2[C@@H]3C[C@@H](CC[C@H]3C(OC2=C1)(C)C)C)O

Machine-readable entry (JSON)

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