Synthesis and ESI-MS/MS fragmentation study of two new isomeric oxazolidin-2-one derivatives

Abstract

Two new isomeric oxazolidin-2-one derivatives have been synthesized through reaction of (E)-3-styrylquinoxalin-2-one with bis-dichloroethylamine hydrochloride in presence of potassium carbonate. The structures of the formed products were established by NMR and mass spectroscopy. The fragmentation patterns of the two novel synthesized oxazolidin-2-ones (1, 2), possessing the same backbone structure, were investigated using electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (MS/MS) techniques. A simple methodology, based on the use of ESI (positive ion mode) and by increasing the declustering potential in the atmospheric pressure/vacuum interface, collision induced dissociation (CID), was used to enhance the formation of the fragment ions. In general, the novel synthetic oxazolidin-2-one derivatives afforded, in the gas phase, protonated molecules leading to the confirmation of the molecular masses and chemical structures of the studied compounds. The breakdown routes of the protonated molecules were rationalized by conducting low-energy collision CID-MS/MS analyses (product ion scans) using. The structural similarity between the two studied oxazolidin-2-ones explains the similarity observed in their CID-MS/MS spectra and their fragmentation pathways. ESI-MS/MS recorded with increased collision energy values permits us to observe different product ions and allow us to differentiate the two studied isomers. ESI-MS and CID-MS/MS analyses have thus proven to be a specific and very sensitive method for the structural investigation of the two novel synthesized oxazolidin-2-one derivatives.