PT  - JOURNAL ARTICLE
AU  - Andreas Fredenhagen
AU  - Jürgen Kühnöl
AU  - Matthias Kittelmann
AU  - Lukas Oberer
TI  - Gas-Phase Rearrangement of the <em>O</em>-Glucuronide of Vildagliptin Forms Product-Ion Fragments Suggesting Wrongly an <em>N</em>-Glucuronide
AID  - 10.1124/dmd.118.085597
DP  - 2019 Mar 01
TA  - Drug Metabolism and Disposition
PG  - 189--193
VI  - 47
IP  - 3
4099  - http://dmd.aspetjournals.org/content/47/3/189.short
4100  - http://dmd.aspetjournals.org/content/47/3/189.full
SO  - Drug Metab Dispos2019 Mar 01; 47
AB  - The O-glucuronide of vildagliptin, a dipeptidyl peptidase 4 inhibitor, is a major metabolite in monkeys and a minor metabolite in humans, rats, and dogs. Its product ion spectrum shows fragments that can be explained only by an N-glucuronide. Biotransformation using rat liver yielded milligram amounts of the O-glucuronide, and its structure was assigned unambiguously by nuclear magnetic resonance. The tandem mass spectra (MS/MS) of this compound was investigated in detail using MSn and accurate mass spectrometers and was identical to the animal metabolite. Thus, the MS/MS fragments suggesting an N-glucuronide had to be formed by gas-phase rearrangement. This gas-phase rearrangement can be observed on quadrupole time-of-flight and ion-trap mass instruments. The literature on gas-phase rearrangements is reviewed.