N-phosphoryl amino acids and peptides. Part II: Fast atom bombardment mass spectrometry of N-di-isopropyloxyphosphoryl and N-dibutyloxyphosphoryl amino acids

The positive ion fast atom bombardment mass spectra of N-di-isopropyloxyphosphoryl (Dipp) and N-dibutyloxyphosphoryl (Dbp) amino acids or amino acid methyl esters are presented; and according to the observation of the metastable ions and the high-resolution accurate mass measurement their fragmentation patterns are postulated. Both types of compounds were found to undergo similar fragmentations to produce (HO)₂P(O)N?CH? R + H⁺, in most cases as the most abundant fragment ion of structural significance. An intrinsical difference between the two types of compounds is that N-Dippamino acids appear to favour the successive losses of two molecules of propylene, while the loss of HCOOH seems to be preferred by the Dbp amino acids. For those compounds containing an extra functional group on the side chain of amino acids such as serine or glutamic acid some other type of fragmentation was observed besides the normal phenomenon.