Liquid Chromatographic and Mass Spectral Methods of Identification for the Regioisomeric 2,3- and 3,4-Methylenedioxyphenalkylamines

Abstract

A series of ring and side-chain regioisomers of 3,4-methylenedioxymethamphetamine are compared by chromatographic and spectroscopic methods. Regioisomerism at the aromatic ring and the alkyl side-chain in the methylenedioxyphenalkylamines produces a variety of compounds that have very similar analytical properties. The specific identification of one of these compounds in a forensic drug sample depends on the analyst's ability to eliminate other regioisomers as possible interfering substances. The 2,3- and 3,4-regioisomers of methylenedioxymethamphetamine, N-ethyl-methylenedioxyamphetamine, 1-methylenedioxyphenyl-2-butanamine, and N-methyM-methylenedioxyphenyl-2-butanamine are synthesized from commercially available precursor chemicals. The mass spectra for the underivatized amines are very similar and do not provide sufficient information to differentiate among the side-chain or ring regioisomers. Preparation of the pentafluoropropionamides of the amines produces derivatives that show mass spectral fragmentation identifying the substituent attached to nitrogen and the number of carbons attached directly to the aromatic ring. The regioisomeric amines are well-resolved in a reversed-phase chromatographic system using a Hypersil-Elite C18 stationary phase and acidic hydroorganic mobile phases.