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Fast atom bombardment and tandem mass spectrometry of quaternary pyridinium salt‐type tryptophan derivatives
Author(s) -
Prokai Laszlo,
ProkaiTatrai Katalin,
Pop Emil,
Bodor Nicholas,
Lango Jozsef,
Roboz John
Publication year - 1993
Publication title -
organic mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 0030-493X
DOI - 10.1002/oms.1210280610
Subject(s) - pyridinium , chemistry , carbocation , pyridine , protonation , fragmentation (computing) , medicinal chemistry , tryptophan , fast atom bombardment , alkyl , photochemistry , stereochemistry , organic chemistry , ion , amino acid , biochemistry , computer science , operating system
Fast atom bombardment and collision‐induced dissociation tandem mass spectrometry were used to study the fragmentation of quaternary pyridinium salt‐type amides of tryptophan (α‐amino‐3‐indolepropionic acid) esters and their analogs which incorporate the α‐nitrogen into the quaternary pyridinium structure. By cleavage directly at the pyridine nitrogen, the 1‐alkyl‐substituted nicotinamides decompose exclusively to a carbocation, which then becomes the intermediate to further fragments. Rearrangement of the 3‐indolepropionate‐2‐yl carbocations may involve a five‐ to seven‐membered ring expansion, which generates alternative fragmentation pathways; the formation of an even‐electron and a radical cation, respectively. In trigonellyl amide‐type tryptophan derivatives, fragmentation of the pyridinium ion proceeds on multiple pathways induced by the positive charge which may not be localized on the quaternary nitrogen, and isomerization to a dihydropyridinyl structure is probably involved. Besides the formation of protonated nicotinamide and alkene from tryptophan amides that contain methylene or ethylene units between the amino and the quaternary pyridinium nitrogens, a fragmentation route leading to the carbocation identical with that of the 1‐alkyl‐substituted nicotinamides has also been revealed.