Fast atom bombardment mass spectrometry in the characterization of some enantiomerically pure fluorinated β-phenylserines

The fast atom bombardment-induced mass spectrometric behaviour of six enantiomerically pure and fluoro-substituted β-phenylserines was studied in detail with the aid of metastable ion data. Results show mainly that the formation of the imminium cations, a decomposition pathway characteristic of non-fluorinated analogs, is strongly reduced, while water loss becomes the preferred primary decomposition route. Fluorine-containing substituents are also active in promoting the formation of polycyclic product ions which allow the characterization of the various isomers to be performed.