Fast atom bombardment mass spectrometry of carbobenzyloxy‐protected amino acids and peptides

The positive fast atom bombardment (FAB) mass spectra of 15 N ‐carbobenzyloxy derivatives of α‐amino acids are presented together with those of some synthetic peptides containing other widely employed protecting groups. The data obtained allow a fragmentation pattern to be established for the N ‐carbobenzyloxy moiety and to obtain detailed structural information on the main fragment ions. A study of the ion current ratio vs. time pattern shows that important fragments derive from the parent protonated molecule through FAB‐induced condensed‐phase reactions.