The structurally diverse nature of the 1,2‐diphenylethylamine template provides access to a range of substances for drug discovery work but some have attracted attention as ‘research chemicals’. The most recent examples include diphenidine, i.e. 1‐(1,2‐diphenylethyl)piperidine and 2‐methoxydiphenidine, i.e. 1‐[1‐(2‐methoxyphenyl)‐2‐phenylethyl]piperidine (MXP, methoxyphenidine, 2‐MXP) that have been associated with uncompetitive N‐methyl‐D‐aspartate (NMDA) receptor antagonist activity. Analytical challenges encountered during chemical analysis include the presence of positional isomers. Three powdered samples suspected to contain 2‐MXP were obtained from three Internet retailers in the United Kingdom and subjected to analytical characterization by gas chromatography (GC) and high performance liquid chromatography (HPLC) coupled to various forms of mass spectrometry (MS). Nuclear magnetic resonance spectroscopy, infrared spectroscopy and thin layer chromatography were also employed. This was supported by the synthesis of all three isomers (2‐, 3‐ and 4‐MXP) by two different synthetic routes. The analytical data obtained for the three purchased samples were consistent with the synthesized 2‐MXP standard and the differentiation between the isomers was possible. Distinct stability differences were observed for all three isomers during in‐source collision‐induced dissociation of the protonated molecule when employing detection under HPLC selected‐ion monitoring detection, which added to the ability to differentiate between them. Furthermore, the analysis of a 2‐MXP tablet by matrix assisted inlet ionization Orbitrap mass spectrometry confirmed that it was possible to detect the protonated molecule of 2‐MXP directly from the tablet surface following addition of 3‐nitrobenzonitrile as the matrix. Copyright © 2015 John Wiley & Sons, Ltd.

The recent occurrence of deaths associated with the psychostimulant cis-4,4′-dimethylaminorex (4,4′-DMAR) in Europe indicated the presence of a newly emerged psychoactive substance on the market. Subsequently, the existence of 3,4-methylenedioxy-4-methylaminorex (MDMAR) has come to the authors’ attention and this study describes the synthesis of cis- and trans-MDMAR followed by extensive characterization by chromatographic, spectroscopic, mass spectrometric platforms and crystal structure analysis. MDMAR obtained from an online vendor was subsequently identified as predominantly the cis-isomer (90%). Exposure of the cis-isomer to the mobile phase conditions (acetonitrile/water 1:1 with 0.1% formic acid) employed for high performance liquid chromatography analysis showed an artificially induced conversion to the trans-isomer, which was not observed when characterized by gas chromatography. Monoamine release activities of both MDMAR isomers were compared with the non-selective monoamine releasing agent (+)-3,4-methylenedioxymethamphetamine (MDMA) as a standard reference compound. For additional comparison, both cis- and trans-4,4′-DMAR, were assessed under identical conditions. cis-MDMAR, trans-MDMAR, cis-4,4′-DMAR and trans-4,4′-DMAR were more potent than MDMA in their ability to function as efficacious substrate-type releasers at the dopamine (DAT) and norepinephrine (NET) transporters in rat brain tissue. While cis-4,4′-DMAR, cis-MDMAR and trans-MDMAR were fully efficacious releasing agents at the serotonin transporter (SERT), trans-4,4′-DMAR acted as a fully efficacious uptake blocker. Currently, little information is available about the presence of MDMAR on the market but the high potency of ring-substituted methylaminorex analogues at all three monoamine transporters investigated here might be relevant when assessing the potential for serious side-effects after high dose exposure.

Substances with the diphenylethylamine nucleus represent a recent addition to the product catalog of dissociative agents sold as ‘research chemicals’ on the Internet. Diphenidine, i.e. 1‐(1,2‐diphenylethyl)piperidine (1,2‐DEP), is such an example but detailed analytical data are less abundant. The present study describes the synthesis of diphenidine and its most obvious isomer, 1‐(2,2‐diphenylethyl)piperidine (2,2‐DEP), in order to assess the ability to differentiate between them. Preparation and characterization were also extended to the two corresponding pyrrolidine analogues 1‐(1,2‐diphenylethyl)‐ and 1‐(2,2‐diphenylethyl)pyrrolidine, respectively. Analytical characterizations included high‐resolution electrospray mass spectrometry (HR‐ESI‐MS), liquid chromatography ESI‐MS/MS, gas chromatography ion trap electron and chemical ionization MS, nuclear magnetic resonance spectroscopy (NMR) and infrared spectroscopy. Differentiation between the two isomeric pairs was possible under GC‐(EI/CI)‐MS conditions and included the formation of distinct iminium ions, such as m/z 174 for 1,2‐DEP and m/z 98 for 2,2‐DEP, respectively. The pyrrolidine counterparts demonstrated similar phenomena including the expected mass difference of 14 Da due to the lack of one methylene unit in the ring. Two samples obtained from an Internet vendor provided confirmation that diphenidine was present in both samples, concurring with the product label. Finally, it was confirmed that diphenidine (30 μM) reduced N‐methyl‐D‐aspartate‐mediated field excitatory postsynaptic potentials (NMDA‐fEPSPs) to a similar extent to that of ketamine (30 μM) when using rat hippocampal slices. The appearance of 1,2‐ diphenylethylamines appears to reflect the exploration of alternatives to arylcyclohexylamine‐type substances, such as methoxetamine, PCP and PCPy‐based analogues that also show NMDA receptor activity as demonstrated here for diphenidine. Copyright © 2014 John Wiley & Sons, Ltd.

5-(2-Aminopropyl)benzofuran (5-APB), a 'research chemical' that was first reported by UK authorities to the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) in 2010, is anecdotally reported to produce a combination of stimulant and entactogenic effects. More recently, in 2011, 6-(2-aminopropyl)benzofuran (6-APB) was identified by Hungarian authorities. To confirm positional isomer identity in Internet purchased products, 4- 5- 6- and 7-APBs were synthesized and found to be separable by gas chromatography (as heptafluorobutyramide derivatives) and liquid chromatography. The analyses of products purchased from online vendors of 'research chemicals' identified the presence of 5- or 6-APBs. These findings were further confirmed by liquid chromatography-mass spectrometry and (1) H nuclear magnetic resonance spectroscopy. In products containing 6-APB, the 4- positional isomer was also identified and this may have arisen during the manufacturing process.

The knowledge captured in patent and scientific research literature stimulates new ideas and fosters new drug development efforts. Manufacturers and entrepreneurs dedicated to the sale of ‘research chemicals’ and/or new psychoactive substances (NPS) also make use of access to information to identify, prepare, and launch a range of new substances. One of the most recent compounds to appear on the NPS market is the phenmetrazine analog 3‐fluorophenmetrazine (3‐FPM) which represents one of many phenylmorpholines designed to explore treatment options in areas such as obesity and drug dependence. The anorectic drug analogs phenmetrazine and phendimetrazine, used as prescription medicines before they were withdrawn, feature amphetamine‐like properties associated with monoamine release. Available data on 3‐FPM suggest that the effects might show mechanistic overlaps. This study describes the synthesis and extensive analytical characterization of 3‐FPM and its differentiation from synthesized ortho‐ and para‐ substituted isomers, 2‐FPM and 4‐FPM, respectively. This study was triggered by the purchase of five powdered samples advertised as 3‐FPM by five different Internet vendors based in the United Kingdom. The analytical data obtained for the vendor samples were consistent with the synthesized 3‐FPM standard and differentiation between all three isomers was possible. The presence of positional isomers and the absence of suitable reference material can cause difficulties in the day‐to‐day operation of forensic work and given the rate at which many of the newly emerging NPS appear on the market, a comprehensive approach is needed when attempting to decipher the identity of NPS arriving onto the drug market. Copyright © 2016 John Wiley & Sons, Ltd.