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Parahexyl
Clinical data
Other names	Synhexyl, n-hexyl-Δ3-THC, (C6)-Δ6a(10a)-THC
Drug class	Cannabinoid
ATC code	none;
Legal status
Legal status	BR: Class F2 (Prohibited psychotropics); CA: Schedule II; DE: Anlage I (Authorized scientific use only); UK: Class B; US: Schedule I; UN: Psychotropic Schedule I;
Identifiers
	IUPAC name 3-n-hexyl- 7,8,9,10-tetrahydro- 6,6,9-trimethyl- 6H-dibenzo(b,d)pyran- 1-ol;
CAS Number	117-51-1 ;
PubChem CID	8334;
ChemSpider	8031 ;
UNII	450N174F9W;
KEGG	C22779;
CompTox Dashboard (EPA)	DTXSID90861748 ;
Chemical and physical data
Formula	C22H32O2
Molar mass	328.496 g·mol−1
3D model (JSmol)	Interactive image;
	SMILES Oc2cc(cc1OC(C\3=C(/c12)CC(CC/3)C)(C)C)CCCCCC;
	InChI InChI=1S/C22H32O2/c1-5-6-7-8-9-16-13-19(23)21-17-12-15(2)10-11-18(17)22(3,4)24-20(21)14-16/h13-15,23H,5-12H2,1-4H3 ; Key:OORFXDSWECAQLI-UHFFFAOYSA-N ;
	(verify)

Parahexyl, also known as synhexyl, is a synthetic homologue of tetrahydrocannabinol (THC) which was invented in 1941 during attempts to elucidate the structure of Δ⁹-THC, one of the active components of cannabis.^[2]^[3]^[4]

Parahexyl is similar in both structure and activity to THC, differing only in the position of one double bond and the lengthening of the 3-pentyl chain by one CH₂ group to n-hexyl.^[5] Parahexyl produces effects typical of other cannabinoid receptor agonists in animals. It has a somewhat higher oral bioavailability than THC itself but is otherwise very similar.^[6] Presumably, it acts as a CB₁ receptor agonist in the same way as THC, but as there has been no research published using parahexyl since the discovery of the CB₁ receptor, this has not been definitively confirmed.

Parahexyl was occasionally used as an anxiolytic in the mid-20th century, the dosage ranging from 5 mg to 90 mg.^[7]^[8]

Parahexyl was made illegal under UN convention in 1971 on the basis of its structural similarity and similar effects profile to THC. Parahexyl was placed into the most restrictive Schedule I^[9] as a compound with no medical use.

Isomerism

At least three isomers of parahexyl have been studied and are known to be active as cannabinoids. Parahexyl itself (i.e. the Δ^6a(10a) isomer) has not had any significant use in scientific research since it was banned internationally in the early 1980s; however, the Δ⁸ and Δ⁹ isomers are both known to be cannabinoid receptor agonists, and Δ⁸-parahexyl has the code number JWH-124,^[10]^[11] while Δ⁹-parahexyl has been isolated from Cannabis plant material and assigned the name tetrahydrocannabihexol (THCH).^[12]

7 double bond isomers of parahexyl and their 30 stereoisomers
Dibenzopyran numbering			Monoterpenoid numbering		Number of stereoisomers	Natural occurrence	Convention on Psychotropic Substances Schedule
Short name	Chiral centers	Full name	Short name	Chiral centers	Number of stereoisomers	Natural occurrence	Convention on Psychotropic Substances Schedule
Δ^6a(7)-parahexyl	9 and 10a	3-hexyl-8,9,10,10a-tetrahydro-6,6,9-trimethyl-6H-dibenzo[b,d]pyran-1-ol	Δ⁴-parahexyl	1 and 3	4	No	unscheduled
Δ⁷-parahexyl	6a, 9 and 10a	3-hexyl-6a,9,10,10a-tetrahydro-6,6,9-trimethyl-6H-dibenzo[b,d]pyran-1-ol	Δ⁵-parahexyl	1, 3 and 4	8	No	unscheduled
Δ⁸-parahexyl	6a and 10a	3-hexyl-6a,7,10,10a-tetrahydro-6,6,9-trimethyl-6H-dibenzo[b,d]pyran-1-ol	Δ⁶-parahexyl	3 and 4	4	No	unscheduled
Δ^9,11-parahexyl	6a and 10a	3-hexyl-6a,7,8,9,10,10a-hexahydro-6,6-dimethyl-9-methylene-6H-dibenzo[b,d]pyran-1-ol	Δ¹⁽⁷⁾-parahexyl	3 and 4	4	No	unscheduled
Δ⁹-parahexyl	6a and 10a	3-hexyl-6a,7,8,10a-tetrahydro-6,6,9-trimethyl-6H-dibenzo[b,d]pyran-1-ol	Δ¹-parahexyl	3 and 4	4	No	unscheduled
Δ¹⁰-parahexyl	6a and 9	3-hexyl-6a,7,8,9-tetrahydro-6,6,9-trimethyl-6H-dibenzo[b,d]pyran-1-ol	Δ²-parahexyl	1 and 4	4	No	unscheduled
Δ^6a(10a)-parahexyl	9	3-hexyl-7,8,9,10-tetrahydro-6,6,9-trimethyl-6H-dibenzo[b,d]pyran-1-ol	Δ³-parahexyl	1	2	No	Schedule I

Note that 6H-dibenzo[b,d]pyran-1-ol is the same as 6H-benzo[c]chromen-1-ol.

References

^ Anvisa (2023-07-24). "RDC Nº 804 - Listas de Substâncias Entorpecentes, Psicotrópicas, Precursoras e Outras sob Controle Especial" [Collegiate Board Resolution No. 804 - Lists of Narcotic, Psychotropic, Precursor, and Other Substances under Special Control] (in Brazilian Portuguese). Diário Oficial da União (published 2023-07-25). Archived from the original on 2023-08-27. Retrieved 2023-08-27.
^ Adams R, Loewe S, Jelinek C, Wolff H (July 1941). "Tetrahydrocannabinol Homologs with Marihuana Activity. IX1". Journal of the American Chemical Society. 63 (7): 1971–1973. doi:10.1021/ja01852a052.
^ Adams R, Harfenist M, Loewe S (1949). "New Analogs of Tetrahydrocannabinol. XIX". Journal of the American Chemical Society. 71 (5): 1624–1628. doi:10.1021/ja01173a023.
^ Ask Dr. Shulgin Online March 7, 2001
^ Ono M, Shimamine M, Takahashi K, Inoue T (1974). "[Studies on hallucinogens. VII Synthesis of parahexyl]". Eisei Shikenjo Hokoku. Bulletin of National Institute of Hygienic Sciences (in Japanese). 49 (92): 46–50. PMID 4477495.
^ Fairchild MD, Jenden DJ, Mickey MR, Yale C (January 1980). "EEG effects of hallucinogens and cannabinoids using sleep-waking behavior as baseline". Pharmacology, Biochemistry, and Behavior. 12 (1): 99–105. doi:10.1016/0091-3057(80)90422-0. PMID 6102770. S2CID 24865915.
^ Supniewski J (1950). Farmakologia. Warsaw: PZWL. p. 89.
^ "Synhexyl page - Supniewski J (1950). Farmakologia. Warsaw: PZWL. P. 89".
^ Report of the Technical Committee on Schedules I, II, III and I at the United Nations Conference for the adoption of a Protocol on Psychotropic Substances. 15 February 1971. E/CONF.58/L.47
^ Martin BR, Jefferson R, Winckler R, Wiley JL, Huffman JW, Crocker PJ, et al. (September 1999). "Manipulation of the tetrahydrocannabinol side chain delineates agonists, partial agonists, and antagonists". The Journal of Pharmacology and Experimental Therapeutics. 290 (3): 1065–79. PMID 10454479.
^ Bow EW, Rimoldi JM (2016). "The Structure-Function Relationships of Classical Cannabinoids: CB1/CB2 Modulation". Perspectives in Medicinal Chemistry. 8: 17–39. doi:10.4137/PMC.S32171. PMC 4927043. PMID 27398024.
^ Linciano P, Citti C, Russo F, Tolomeo F, Laganà A, Capriotti AL, et al. (December 2020). "Identification of a new cannabidiol n-hexyl homolog in a medicinal cannabis variety with an antinociceptive activity in mice: cannabidihexol". Scientific Reports. 10 (1): 22019. Bibcode:2020NatSR..1022019L. doi:10.1038/s41598-020-79042-2. PMC 7744557. PMID 33328530.