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Eur. J. Mass Spectrom.
10, 673–681 (2004)
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| N-methyl-N-trimethylsilyltrifluoroacetamide-promoted synthesis and mass spectrometric characterization of deuterated ephedrines | ||
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Mario Thevis,* Georg Opfermann and Wilhelm Schänzer |
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| ABSTRACT: | ||
| Synthesis and mass spectrometric characterization of drugs or metabolites labeled by stable isotopes has been of great interest in fields of clinical, forensic and doping control analysis. Deuterated ephedrine and p-hydroxypseudoephedrine were prepared from corresponding amines by a novel procedure utilizing N-methyl-N-trimethylsilyltrifluoroacetamide and deuterated iodomethane. The mechanism of methylation was studied by mass spectrometry using phenylethylamine as a model compound, and a rearrangement based on an intermediate six-membered ring structure with a trimethylsilyl- enol-ether is proposed giving rise to a leaving group of trimethyliodosilane and the desired monomethylated product. Deuterated analogues to frequently quantitated ephedrines were readily synthesized with purities >90%, and mass spectra recorded under different ionization and dissociation conditions presented distinct fragmentation processes including eliminations of water and methylamine as well as the generation of a benzyl cation. | ||
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Keywords: MSTFA, alkylation, labeling, isotope dilution mass spectrometry, collision-induced dissociation, fragmentation |
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