GC and Mass Spectral Studies on Acylated Side Chain Regioisomers of 3-Methoxy-4-methyl-phenethylamine and 4-Methoxy-3-methyl-phenethylamine

The side chain regioiomers of the 3-methoxy-4-methylphenethylamines and 4-methoxy-3-methyl-phenethylamines have mass spectra essentially equivalent to the controlled drug substance 3,4-methylenedioxymethamphetamine (3,4-MDMA), all have molecular weight of 193 and major fragment ions in their electron ionization mass spectra at m/z 58 and 135/136. Furthermore, the compounds in this study have ring substitutions in the same relative positions as 3,4-MDMA. The nonequivalence of the substituents (methoxy and methyl) yields two sets of compounds, 3-methoxy-4-methyl- and 4-methoxy-3-methylphenethylamines. The perfluoroacyl derivatives (pentafluoropropionylamides and heptafluorobutrylamides) of the primary and secondary regioisomeric amines were prepared and evaluated in gas chromatography-mass spectrometry studies. The mass spectra for these derivatives are significantly individualized and the resulting unique fragment ions allow for specific side chain identification. The heptafluorobutrylamide derivatives offer more fragment ions than the pentafluoropropionylamides for molecular individualization among these regioisomeric substances. These acylated derivatives show excellent resolution on a dimethyl polysiloxane stationary phase such as Rtx-1.