Liquid chromatographic and mass spectral methods of identification for regioisomeric dimethoxyamphetamines and brominated dimethoxyamphetamines

The six regioisomeric dimethoxyamphetamines are prepared from the commercially available dimethoxybenzaldehydes. The dimethoxyamphetamines show very similar mass spectra, and chromatographic methods must be used to differentiate the positional isomers. Bromination of the six isomeric dimethoxyamphetamines yields a monobromination product as the major component in all cases except for 3,5-dimethoxyamphetamine, which yields the 2,6-dibrominated species as the major product. Mass spectrometric analysis readily divides the regioisomeric bromodimethoxyamphetamines into two groups of three compounds each. Only those isomers having a bromine substituent "ortho-" to the alkylamine side-chain show a major fragment at m/z 194 from loss of bromine from the molecular ion. The major drug of abuse 4-bromo-2,5-dimethoxyamPhetamine (DOB) is one of three compounds that do not yield the m/z 194 ion. Though the mass spectra for the three "non-m/z 194" isomers show some subtle differences, these compounds are best differentiated by a reversed-phase liquid chromatographic system.