Synthesis, characterization and monoamine transporter activity of the new psychoactive substance mexedrone and its N‐methoxy positional isomer, N‐methoxymephedrone

Abstract

3-Methoxy-2-(methylamino)-1-(4-methylphenyl)propan-1-one (mexedrone) appeared in 2015 and was advertised by UK Internet retailers as a non-controlled mephedrone derivative (2-(methylamino)-1-(4-methylphenyl)propan-1-one), which was of particular interest to countries who operate generic drugs legislation. This study describes the synthesis and analytical characterization of mexedrone and the differentiation from its isomer, N-methoxymephedrone, which was predicted to be a suitable candidate before the identity of mexedrone was revealed. A full analytical characterization is described using various chromatographic, spectroscopic and mass spectrometric platforms and X-ray crystal structure analysis. The analytical data obtained for a vendor sample were consistent with the synthesized mexedrone reference standard and analytical differentiation between the mexedrone and N-methoxymephedrone positional isomers was achieved. Furthermore, α-chloromethylmephedrone was identified as a by-product during mexedrone synthesis. All three substances were also studied for their uptake and releasing properties at dopamine transporters (DAT), norepinephrine transporters (NET) and serotonin transporters (SERT) using in vitro monoamine transporter assays in rat brain synaptosomes and compared to mephedrone. Mexedrone was a weak non-selective uptake blocker with IC50 values in the low μM range. It was also devoid of releasing activity at DAT and NET but displayed weak releasing activity at SERT (EC50= 2.5 μM). The isomer N-methoxymephedrone was found to be a weak uptake blocker at DAT, NET and SERT, as well as a fully efficacious substrate-type releasing agent across all three transporters with EC50 values in the low micromolar range. The synthesis by-product α-chloromethylmephedrone was inactive in all assays.

Hazard Characterization of Synthetic Cathinones Using Viability, Monoamine Reuptake, and Neuronal Activity Assays

“…Our results confirm previous reports on the potent inhibitory effects of cathinones on monoamine transporters hDAT and hNET, and the less potent inhibition of hSERT [ Table 1; for review see Hondebrink et al (2018); also see Baumann et al, 2013;Eshleman et al, 2013;Simmler et al, 2013;Kolanos et al, 2015;Saha et al, 2015;McLaughlin et al, 2017]. The magnitude of the hSERT IC 50 values for the cathinones without pyrrolidine structure or lengthened alkyl chain (3-MMC, 4-MMC, 4-MEC, and methylone) showed some deviations compared to literature.…”

Spectroscopic characterization and crystal structures of four hydrochloride cathinones: N-ethyl-2-amino-1-phenylhexan-1-one (hexen, NEH), N-methyl-2-amino-1-(4-methylphenyl)-3-methoxypropan-1-one (mexedrone), N-ethyl-2-amino-1-(3,4-methylenedioxyphenyl)pentan-1-one (ephylone) and N-butyl-2-amino-1-(4-chlorophenyl)propan-1-one (4-chlorobutylcathinone)

“…Torsion angles C7C8N1C9 were identical in both enantiomers (178.56 o ). Discussion concerning interactions in the crystal can be found in [1]. Interactions in the molecule of this compound were of C-H•••π type (3.008 Å).…”

“…Deuterated dimethyl sulfoxide (DMSO-d 6 ) was purchased from Sigma-Aldrich (Poznań, Poland). N-Ethyl-2-amino-1-phenylhexan-1-one hydrochloride (1), N-methyl-2amino-1-(4-methylphenyl)-3-methoxypropan-1-one hydrochloride (2), N-ethyl-2-amino-1-(3,4-methylenedioxyphenyl)pentan-1-one hydrochloride (3) and N-butyl-2-amino-1-(4-chlorophenyl)propan-1-one hydrochloride (4) salts were provided in pure form by drug enforcement agencies as materials seized on the illicit drug market.…”

“…1 have been distributed on the illegal drug market in Poland. During the preparation of this manuscript, the crystallographic structures of two designer drugs, 2 (The Cambridge Crystallographic Data Centre, CCDC 1452166) [1] and 3 (CCDC1504573) [2] were reported. We show here data obtained in our laboratories in order to compare the results of examining differently sourced crystals of the same designer drug; the results unequivocally showed that we dealt with the same compounds of the same enantiomeric compositions.…”

Addressing the challenges in forensic drug chemistry

“…Interestingly, N ‐methoxymephedrone was shown to act as a weak uptake blocker at DAT, NET, and SERT, as well as a fully efficacious substrate‐type releasing agent across all three transporters. The synthesis by‐product α‐chloromethylmephedrone was inactive in all assays …”