GC-MS analysis of regioisomeric substituted N-benzyl-4-bromo-2,5-dimethoxyphenethylamines

The six N-(dimethoxybenzyl)-4-bromo-2,5-dimethoxyphenethylamine regioisomers are potential designer compounds related to the common NBOMe drug N-(2-methoxy)benzyl-4-bromo-2,5-dimethoxyphenethylamine (25B-NBOMe). These six compounds represent the incorporation of one additional methoxy-group into the common NBOMe molecular framework. The compounds were prepared from commercially available precursor materials and their electron ionization mass spectra (EI-MS) are quite similar yielding nearly identical fragment ions. The 2',3'-dimethoxybenzyl regioisomer gave a unique fragment ion of significant abundance in the EI-MS at m/z 136. Baseline gas chromatographic resolution of the six regioisomers was achieved using a midpolarity phase of 50% phenyl and 50% dimethyl polysiloxane and the more crowded dimethoxy substitution patterns eluted first under temperature programming conditions. The EI mass spectra for the TFA-derivatives of these six regioisomers gave a molecular ion of significant abundance at m/z 505/507, unlike the parent compounds. Differentiation and specific identification of all six of the regioisomers was possible based on a combination of different base peak ions (m/z 151 or 242/244), unique fragment ions (m/z 136 and m/z 263), along with differences in the relative abundance of ions at m/z 121 and m/z 91.