Syntheses and analytical characterizations of the research chemical 1‐[1‐(2‐fluorophenyl)‐2‐phenylethyl]pyrrolidine (fluorolintane) and five of its isomers

Summary

Six possible racemic isomers of the research chemical fluorolintane (2-F-DPPy) were synthesized and characterized. The isomers differ by the position of a fluorine substituent on the phenyl or benzyl ring of the 1,2-diarylethylamine structure. Using mass spectrometry, chromatography, nuclear magnetic resonance spectroscopy, and infrared spectroscopy, each isomer was distinguishable. A tandem mass spectrometry method analyzing the [M + H – HF]+ species produced distinct product ions for all six substances, aiding identification of positional isomers that pose challenges for stakeholders confronting new psychoactive substances.

Study at a glance

Abstract

Abstract A number of substances based on the 1,2‐diarylethylamine template have been investigated for various potential clinical applications whereas others have been encountered as research chemicals sold for non‐medical use. Some of these substances have transpired to function as NMDA receptor antagonists that elicit dissociative effects in people who use these substances recreationally. 1‐[1‐(2‐Fluorophenyl)‐2‐phenylethyl]pyrrolidine (fluorolintane, 2‐F‐DPPy) has recently appeared as a research chemical, which users report has dissociative effects. One common difficulty encountered by stakeholders confronting the appearance of new psychoactive substances is the presence of positional isomers. In the case of fluorolintane, the presence of the fluorine substituent on either the phenyl and benzyl moieties of the 1,2‐diarylethylamine structure results in a total number of six possible racemic isomers, namely 2‐F‐, 3‐F‐, and 4‐F‐DPPy (phenyl ring substituents) and 2”‐F‐, 3”‐F‐, and 4”‐F‐DPPy (benzyl ring substituents). The present study reports the chemical syntheses and comprehensive analytical characterizations of the two sets of three positional isomers. These studies included various low‐ and high‐resolution mass spectrometry platforms, gas‐ and liquid chromatography (GC and LC), nuclear magnetic resonance (NMR) spectroscopy and GC‐condensed phase and attenuated total reflection infrared spectroscopy analyses. The differentiation between each set of three isomers was possible under a variety of experimental conditions including GC chemical ionization triple quadrupole tandem mass spectrometric analysis of the [M + H – HF] + species. The latter MS method was particularly helpful as it revealed distinct formations of product ions for each of the six investigated substances.