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| Other names | 2,5-Dimethoxy-4-hexylamphetamine; 2,5-Dimethoxy-4-n-hexylamphetamine; 4-Hexyl-2,5-dimethoxyamphetamine; DOHx; DOHX; DOHE |
| Drug class | Serotonin5-HT2 receptormodulator;Serotonin receptor antagonist |
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| Chemical and physical data | |
| Formula | C17H29NO2 |
| Molar mass | 279.424 g·mol−1 |
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2,5-Dimethoxy-4-hexylamphetamine (DOHx orDOHE) is a non-hallucinogenicserotonin receptormodulator of thephenethylamine,amphetamine, andDOx families.[1][2][3][4]
DOHx has shown the highestaffinity for theserotonin5-HT2A and5-HT2C receptors of any other assessed DOx drug in multiple studies.[2][3][5][6] In one study, its affinities for the human serotonin5-HT2 receptors were 0.1 nM for the 5-HT2A receptor, 30 nM for the5-HT2B receptor, and 0.7 nM for 5-HT2C receptor.[3][4][5] In the case of the serotonin 5-HT2A receptor, this was 6- to 14-fold higher thanDOB,DOI, andDOC and was 9-fold higher thanDOPR.[3][5] In another study, DOHx showed 25-fold higher affinity for the serotonin 5-HT2A receptor thanDOM orDOET, 23- to 28-fold higher affinity than DOPR and DOBU, and 2.8-fold higher affinity than DOAM.[6] Conversely, it showed only slightly higher or roughly the same affinity for the receptor relative to DOCT (2.5 nM vs. 3.0 nM, respectively).[6]
In contrast to many other DOx drugs, DOHx, as well as related drugs like DOCT, have been found to act as serotonin 5-HT2 receptorantagonists rather than as anagonists, and hence would not be expected to beserotonergic psychedelics.[1][2] In accordance, DOHx, DOCT, and other related drugs do not produce DOM-like effects in rodentdrug discrimination tests.[2] DOHx has also been assessed and found to act as asilent antagonist of the serotonin 5-HT2B receptor (EmaxTooltip maximal efficacy = 0%).[7]
DOHx is part of the series of 4-alkylated DOx drugs that includesDOM (methyl),DOET (ethyl),DOPR (propyl),DOBU (butyl), andDOAM (amyl/pentyl), with DOHx having ahexylsubstitution and hence the longest alkylchain of the preceding drugs.[1][3][4] Following DOHx in the series areDOHP (heptyl) and thenDOCT (octyl).[2][6]
DOHx was first described in thescientific literature by at least 1989.[8]
DOHx is acontrolled substance inCanada under phenethylamine blanket-ban language.[9]
Due to the incredibly large number of possible analogues, it is common to simply refer to this as the DOX series wherein the aryl 2,5-dimethoxy groups have been retained and the 4-position substituent has been varied. For example, DOHX is DOX where the 4-position substituent is an n-hexyl group. [...] A large number of DOX-related phenylalkylamines was examined and structure−activity and QSAR studies were conducted.51,144 Although 5-HT2 receptor affinity could be accounted for by the lipophilic and electronic character of the 4-position substituent of DOX compounds, affinity and agonist action were not synonymous. That is, some high-affinity DOX analogues with sterically large/extended 4-position substituents unexpectedly resulted in antagonist action. For example, where the X substituent was benzyl (DOBZ, Ki = 7 nM), n-hexyl (DOHX, Ki = 2.5 nM), or n-octyl (Ki = 3 nM)] the compounds acted as antagonists, whereas DOM (4), DOET (5), DOPR (6), DOB (7), and DOI (1) displayed agonist action in a 5-HT2-mediated inositol phosphate assay.51,145 It would appear that there is a "sweet spot" for agonist action with compounds such as DOI and DOB (as well as DOET and DOPR) bearing 4-position substituents being among the optimal. In contrast, DOPP (11; Figure 4) is a high-affinity 5- HT2A receptor antagonist,51 and the 2,5-dimethoxy substitution pattern of DOX compounds was not required for high affinity.
Novel lipophilic derivatives, predicted to bind with Ki values of between 1 and 15 nM, were subsequently prepared and evaluated. For example, the 4-hexyl and 4-octyl derivatives DOHX and DOCT (Ki = 2.5 and 3 nM, respectively) bind with greater affinity than DOM (Ki = 100 nM) and represent some of the highest affinity [phenylalkylamines (PAAs)] reported to date. Discordant with these findings, however, is that neither DOHX nor DOCT (nor several other related agents) produce DOM-like stimulus effects in DOM-trained animals. [Figure 1 shows the relationship between the chain length of several 4-alkyl-substituted derivatives and both their 5-HT2 affinity and relative potency in the drug discrimination assay using 1 mg/kg of DOM as the training drug. Note that the derivatives where the chain length is 5, 6 (DOHX), and 8 (DOCT) carbon atoms lack agonist activity.] Because these highly lipophilic high-affinity agents lack agonist activity, the possibility existed that they constitute a novel class of 5-HT2 antagonists; several have now been shown to antagonize the contractile effects of 5-HT in the rat aorta preparation (Seggel et al., 1990).
Using [125I]DOI labeled human receptor data, the highest binding affinity at 5-HT2A receptors was found for the 4-n-hexyl analogue DOHx (21, Ki=0.1 nm), followed by the 4-benzyl analogue DOBz (22, Ki=0.4 nm), DOB (16, Ki=0.6 nm), DOI (17, Ki=0.7 nm), and the 4-n-propyl analogue DOPR (23, Ki=0.9 nm).[63]
Similarly, based on compounds 2C-C, 2C-B, and 2C-I, the introduction of an α-methyl group to the aminoalkyl chain resulted in a novel series of compounds known as DOXs (Figure 11B), including DOC (88), DOB (89), and DOI (90). These compounds are among the most potent phenethylamines at the 5-HT2AR (Ki = 1.4, 0.6, and 0.7 nM, respectively; [ 125I]-DOI).172 Replacing the halogen on the 4-position with a methyl group led to significantly reduced activity (91, DOM, Ki = 100 nM), but the activity could be restored with longer linear alkyl chains and the benzyl group, such as compounds DOPR (92, Ki = 0.9 nM), DOHx (93, Ki = 0.1 nM), and DOBz (94, Ki = 0.4 nM).172 Interestingly, these DOXs compounds also exhibited some selectivity against the 5- HT2BR and 5-HT2CR.172 [...] Besides 25CN-NBOH, a small number of other abovementioned 5-HT2AR agonists have also been reported to be subtype-selective for 5-HT2AR, which are summarized in Table 3. [...] DOHx and DOBz also have high binding selectivity for 5-HT2AR against 5- HT2BR (303-fold and 87.5-fold, respectively). However, because the degree of sequence identity between 5-HT2AR and 5-HT2CR is extremely high, achieving 5-HT2AR versus 5-HT2CR selectivity is more challenging.