Synthesis and Functional Characterization of 2-(2,5-Dimethoxyphenyl)-N-(2-fluorobenzyl)ethanamine (25H-NBF) Positional Isomers

Abstract

Serotonergic psychedelics, substances exerting their pharmacological action through activation of the serotonin 2A receptor (5-HT 2A R), have continuously comprised a substantial fraction of the over 1000 reported New Psychoactive Substances (NPS) so far. Within this category, N-benzyl derived phenethylamines, such as NBOMes and NBFs, have shown to be of particular relevance. As these substances remain incompletely characterized, this study aimed at synthesizing positional isomers of 25H-NBF, with two methoxy groups placed on different positions of the phenyl group of the phenethylamine moiety. These isomers were then functionally characterized in an in vitro bioassay monitoring the recruitment of β-arrestin 2 to the 5-HT 2A R through luminescent readout via the NanoBiT technology. The obtained results provide insight into the optimal substitution pattern of the phenyl group of the phenethylamine moiety of Nbenzyl derived substances, a feature so far mostly explored in the phenethylamines underived at the N-position. In the employed bioassay, the most potent substances were 24H-NBF (EC 50 value of 158 nM), 26H-NBF (397 nM), and 25H-NBF (448 nM), with 23H-NBF, 35H-NBF, and 34H-NBF yielding μM EC 50 values. A similar ranking was obtained for the compounds' efficacy: taking as a reference LSD (lysergic acid diethylamide), 24H-, 26H-, and 25H-NBF had an efficacy of 106−107%, followed by 23H-NBF (96.1%), 34H-NBF (75.2%), and 35H-NBF (58.9%). The stronger activity of 24H-, 25H-, and 26H-NBF emphasizes the important role of the methoxy group at position 2 of the phenethylamine moiety for the in vitro functionality of NBF substances.

Potential of chromatography and mass spectrometry for the differentiation of three series of positional isomers of 2‐(dimethoxyphenyl)‐N‐(2‐halogenobenzyl)ethanamines

“…This fact is supported by the data that we have published earlier 25,26 and also published by Jensen et al 27 Within the NBF group itself, all positional isomers exhibit high affinity to the 5‐HT 2A receptor (24H‐ ≈ 25H‐ ≈ 26H‐ ≥ 23H‐ ≥ 35H‐ and 34H‐NBF; Table 1). 26 …”

“…In vitro study of some groups of N ‐(2‐substituted benzyl)phenethylamines showed that the affinity to the 5‐HT 2A receptor decreases in the row: NBOMe ≈ NBOH > NBMD > NBF 19–24 . This fact is supported by the data that we have published earlier 25,26 and also published by Jensen et al 27 Within the NBF group itself, all positional isomers exhibit high affinity to the 5‐HT 2A receptor (24H‐ ≈ 25H‐ ≈ 26H‐ ≥ 23H‐ ≥ 35H‐ and 34H‐NBF; Table 1). 26 …”

“…[18][19][20] In vitro study of some groups of N-(2-substituted benzyl)phenethylamines showed that the affinity to the 5-HT 2A receptor decreases in the row: NBOMe ≈ NBOH > NBMD > NBF. [19][20][21][22][23][24] This fact is supported by the data that we have published earlier 25,26 and also published by Jensen et al 27 Within the NBF group itself, all positional isomers exhibit high affinity to the 5-HT 2A receptor (24H-≈ 25H-≈ 26H-≥ 23H-≥ 35H-and 34H-NBF; Table 1). 26 Some compounds of the NBF group containing methoxy groups at 2 and 5 positions and various lipophilic substituents at 4 position of the phenylethyl fragment of the molecule exhibit a powerful psychotomimetic effect, similar to the compounds of the NBOMe group, and have a high toxicity, 28 which leads to their legislative prohibition in many countries such as Sweden, Japan, and Russia.…”

“…The synthesis and analytical data of target compounds 8 – 12 , 14 – 18 , and intermediate products are presented in supporting information. The synthesis of compounds 2 – 6 was described earlier by us 26 …”

“…The most known method 5,18,23,46 of the synthesis of N ‐(2‐substituted benzyl)phenethylamines consists in modification of the “classical” phenethylamines of the 2C family 47 by their reductive amination with the corresponding aldehydes. Synthesis of legally non‐controlled positional isomers of the NBOMe and NBF series was carried out according to a similar method from the corresponding phenethylamines with positional arrangement of methoxy groups different from 2,5‐ and was described earlier by our group 17,26 …”