Differentiation Among the Four Diastereomers of Benzyloxycarbonyl-protected γ-Hydroxyornithine in Negative-ion Fast Atom Bombardment Mass Spectrometry

Article abstract of DOI:10.1002/oms.1210290509

Discrimination among the four γ-hydroxyornithine diastereomers was studied by fast atom bombardment mass spectrometry (FABMS).It is impossible to distinguish among the four diastereomers of this amino acid by positive- and negative-ion FAB and collisionally activated dissociation MS, but benzyloxycarbonyl group protection of the α- and δ-amino groups in γ-hydroxyornithine allows differentiation among the diastereomers in negative-ion FABMS.The negative-ion mass spectra of benzyloxycarbonyl-protected γ-hydroxyornithine diastereomers showed differences among the abundances of the molecule ion (-), the dehydrated ion (-) due to the loss of the γ-hydroxyl group and the fragment ions formed from both (-) and (-) ions.On the other hand, no difference was found between the fragmentations of the benzyloxycarbonyl-protected enantiomers of ornithine in negative-ion FABMS.These results indicate that the orientation of the γ-hydroxyl group and the existence of two benzene rings in the benzyloxycarbonyl group are important factors which are responsible for the fragmentations of the four benzyloxycarbonyl-protected γ-hydroxyornithine diastereomers in negative-ion FABMS.These studies also showed that the negative-ion FABMS for benzyloxycarbonyl-protected γ-hydroxyornithine diastereomers is a useful method for determining the configuration of each diastereomer of γ-hydroxyornithine.