Differentiation of methylated indole ring regioisomers of JWH-007: GC–MS and GC–IR studies

Abstract

The five regioisomeric methylated indole ring analogues of JWH-018 can be prepared directly from a common set of precursor materials. These five isomers include 2-methyl-1-n-pentyl-3-(1-naphthoyl)-indole (JWH-007) and its four regioisomeric analogues, 4-, 5-, 6- and 7-methyl substituted indoles. The EI-MS spectra show equivalent regioisomeric major fragments resulting from cleavage of the groups attached to the central indole nucleus. The characteristic [M−17]+ fragment ion at m/z 338 resulting from the loss of OH group is significant in the mass spectra of all the studied compounds except Compound 2 (JWH-007) which has two significant fragment ions at m/z 340 and m/z 270. Cations at m/z 298, 284, 228 and 200 result from fragmentation of the naphthoyl and/or n-pentyl groups. GC separations on a trifluoropropylmethyl polysiloxane (Rtx-200) provided excellent resolution of these compounds. The elution order appears to be related to the degree of crowding of indole ring substituents. The vapor phase infrared spectra in the range of 1700–700 cm−1 showed unique and characteristic absorption patterns for each of the five regioisomeric compounds which allowed for discrimination among the isomers in this set of cannabinoid compounds.