A Rare Mass Spectrometric Neutral Loss of 48 u

Abstract

Fast atom bombardment and thermospray mass spectrometry results are consistent with the 2-deoxyfluoromethine derivative of the nucleoside (cytidine) shown below and designated 2DFC. However, a mass loss of 48 u from [M+H]+ (m/z 258) was observed forming an abundant fragment ion at m/z 210. The loss seemed peculiar since a 48 u neutral is more often associated with H3CSH or H3SiOH, which are not possible neutrals to be eliminated from 2DFC. Accurate mass measurement of m/z 210 indicated the 48 u neutral lost had the molecular formula CH4O2. Constant neutral loss (48 u) linked scan experiments showed the fragmentation (depicted below) is concerted within the microsecond time frame of the mass spectrometer. Other structurally homologous nucleosides, such as cytidine, do not exhibit this prominent fragmentation. Computerized molecular modeling was used to propose why the marked elimination occurs with 2DFC. © 1997 by John Wiley & Sons, Ltd.