Mass Spectral Studies on 1-n-pentyl-3-(1-naphthoyl)indole (JWH-018), Three Deuterium-labeled Analogues and the Inverse Isomer 1-naphthoyl-3-n-pentylindole

• NCJ Number: 249446
• Journal: Rapid Communications in Mass Spectrometry Volume: 29 Issue: 9 Dated: May 2015 Pages: 871-877
• Author(s): Amber Thaxton; Tarek S. Belal; Forrest Smith; Jack DeRuiter; Karim M. Abdel-Hay; C. Randall Clark
• Date Published: May 2015
• Length: 7 pages
• Grant Number(s): 2012-DN-BX-K026
• Agencies: NIJ-Sponsored
• Publication Type: Research (Applied/Empirical); Report (Study/Research); Report (Grant Sponsored)
• Award: Forensic Chemistry of Substituted 1-Alkyl-3-Acylindoles: Isomeric Synthetic Cannabinoids.

Annotation

This study compared the electron ionization mass spectrometric (EI-MS) fragmentation of the 1-n-pentyl-3-(1-naphthoyl)indole to its inverse isomer 1-naphthoyl-3-n-pentylindole.

Abstract

These two substances are directly available from indole using identical precursor reagents and similar reaction conditions. Stable isotope deuterium labeling of the three major regions of the JWH-018 molecule allows confirmation of the structures of the major fragment ions. The spectra for the 1-n-pentyl-3-(1-naphthoyl)-d5-indole, 1-n-pentyl-3-(1-d7-naphthoyl)indole and 1-d11-n-pentyl-3-(1-naphthoyl)indole provide significant assistance in elucidating the structures for the major fragment ions in JWH-018. The study found that the EI mass spectra for these isomers show a number of unique ions which allow for the differentiation of the 1-alkyl-3-acylindole compounds from the inverse regioisomeric 1-acyl-3-alkylindoles. The fragment ion [M-17]+ at m/z 324 for JWH-018 was formed by the elimination of a hydroxyl radical and the spectra of the three deuterium-labeled derivatives indicated the loss of hydrogen from the naphthalene ring. Further structural analogues suggest the hydrogen comes from the 8-position of the naphthalene ring. The three deuterium-labeled analogues provide significant assistance in confirming the structures for the major fragment ions in the mass spectrum of the traditional synthetic cannabinoid compound, 1-n-pentyl-3-(1-naphthoyl)indole, JWH-018. The 1-naphthoyl-3-n-pentylindole inverse regioisomer can be easily differentiated from the traditional synthetic cannabinoid compound. (Publisher abstract modified)