ELECTROSPRAY-IONIZATION MASS-SPECTROMETRY .3. ACID-CATALYZED ISOMERIZATION OF N,N'-BIS [(E)-3-(4-HYDROXYPHENYL)PROP-2-ENOYL]SPERMIDINES BY THE ZIP REACTION

The electrospray tandem mass spectra (ESI-MS/MS) of the three is[(E)-3 -(4-hydroxyphenyl)prop-2-enoyl]spermidines 1-3 displayed the same frag ment-ion signals. These isomers could not be differentiated by ESI-MS/ MS, since their fragmentation patterns are similar. -(butane-1,4-diyl) bis[prop-2-enamide]([N-15(1)]-1) was synthesized in order to get furth er information about the fragmentation mechanisms. The comparison of t he ESI-MS/MS of 1 and [N-15(1)]-1 revealed a transamidation, the Zip r eaction, under mass-spectral conditions of the [1 + H](+) ions. Becaus e of this reaction, the three isomers 1-3 could not be distinguished.