Das unterschiedliche massenspektrometrische Fragmentierungsverhalten von Lysinmethylester und dessen N , N ′‐Diacetylderivat . 27. Mitteilung über das massenspektrometrische Verhalten von Stickstoffverbindungen

The Different Behaviour of Lysine Methyl Ester and its N , N ′‐Diacetyl Derivative under Electron Impact The base peak in the spectrum of lysine methyl ester is due to the fragment ion C 5 H 10 N ( m / e 84), for which the cyclic structure g ( Scheme 1 ) is deduced. During its formation from the [ M ‐COOCH 3 ]‐ion an equilibration of both nitrogen atoms takes place (ion c , Scheme 1 ). The cyclic nature of ion m / e 84 is in agreement with the intensity of the corresponding ions in the spectra of homologues of lysine methyl ester (Fig. 1). Although in comparison with lysine methyl ester ( 1 ) N , N ′‐diacetyl‐lysine methyl ester ( 7 ) shows the same general fragmentation pathway with formation of the ions [ M ‐COOCH 3 ] and [ M ‐COOCH 3 ‐H 2 NCOCH 3 ] ( m / e 126), the exact fragmentation mechanism proves to the different. Two mechanisms are discussed for the formation of the ion m / e 126 from 7 ( Schemes 2 and 3 ). The results are based on the spectra of labelled derivatives.