Gas-Phase Intramolecular Elimination Reaction Studies of Steviol Glycosides in Positive Electrospray and Tandem Mass Spectrometry

Abstract

This paper reports the first study of the gas-phase intramolecular elimination reaction of steviol glycosides in positive electrospray mass spectrometry. The observed glycosylated product ions are proposed to be formed via an intramolecular elimination of sugar units from the parent molecule ion. It was further proven by MS/MS studies and deuterium labeling experiments with one of the steviol glycosides, rebaudioside A. These mass spectrometric results confirmed that the new glycosylated product ions observed are most likely formed by the combination of glucose moieties (Glu) II-IV and Glu I via a gas-phase intramolecular elimination reaction.

“Thermometer” Ions Can Fragment Through an Unexpected Intramolecular Elimination: These Are Not the Fragments You Are Looking For

“…In fact, a fragment with m / z 107 Da was observed in the product ion spectra of all three benzylpyridinium derivatives. We hypothesized that the fragmentation was the result of an intramolecular elimination (E i ) occurring through a pericyclic transition state (TS), which has been previously observed in the gas phase. − However, the geometry of the phenyloxonium side chain in 4a , 4b , and 4c requires the elimination to proceed through a high energy four-membered TS. This is especially perplexing in the case of 4c , which contains a bulky tert -butyl substituent, thus rendering the high-energy pathway unlikely.…”