Preparation and characterization of the ‘research chemical’ diphenidine, its pyrrolidine analogue, and their 2,2‐diphenylethyl isomers
Jason Wallach, Pierce V. Kavanagh, Gavin McLaughlin, Noreen Morris, John D. Power, Simon Elliott, Marion Mercier, David Lodge, Hamilton Morris, Nicola M. Dempster, Simon D. Brandt
Drug Testing and Analysis July 15, 2014 DOI: 10.1002/dta.1689 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Laboratory study Peer reviewed |
|---|---|
| Population | Rat hippocampal slices |
| Interventions | Diphenidine Ketamine |
| Dose | 30 μM |
| Keywords | Pyrrolidine Piperidine Methylene Electrospray ionization Mass spectrometry Iminium Stereochemistry Medicinal chemistry Organic chemistry Chromatography Radical photochemical reactions |
| Citations | 26 |
| Key points | Diphenidine (30 μM) reduced NMDA-mediated field excitatory postsynaptic potentials to a similar extent as ketamine (30 μM) in rat hippocampal slices. |
Abstract
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.