The fragmentation pathway of the N-phosphoryl hydroxy amino acid and the O-phosphorylamino acid had their resp. characteristics by successive losses of two mols. of CH3CH=CH2 and the HCO2H preferred for the N-DIPP-hydroxy amino acids (DIPP = diisopropyloxyphosphoryl), while for N-DBP-hydroxy amino acids (DBP = di-n-butyloxyphosphoryl) HCOOH was first lost, than one or two mols. of CH3CH2-CH=CH2 and finally H2O. The phosphoryl group N甇 migration product gives the (99)m/z, as the most intensive peak for O-DIPP(DBP)-Ser or Q-DIPP(DBP)甌hr. And the multiple checks for each of the mol. ion M+ and fragment ions F+ were possible through their successive peaks at M+-42(56), M+-84(112), F+-42(56), and F+-84(112).

Key words: AMINO ACID, OLIGOPEPTIDE, PHOSPHORIC ACID ESTER, FAB MASS SPECTROMETRY, PHOSPHORAMIDIC ACID