Fragmentation Study of 2-Amino-4H-1,3-oxazines and Octahydro-4-phenyl-2H-pyrano2,3- dpyrimidin-2-ones:Identification of Heterocyclic Six-membered Ring in Three-component Reactions

摘要

The fragmentation behavior of ten 2-amino-4H-1,3-oxazines and seven octahydro-4-phenyl-2H-pyrano[2,3-d]pyrimidin-2-ones was investigated by electrospray ionization tandem mass spectrometry (ESI-MSn).When the precursor ions were protonated oxazines,two predominant fragmentation pathways were observed with elimination of CH2N2 and HCNO,respectively.The product ion [M+H-60]+ could be observed from both pathways.While in the type of pyrimidin-2-ones,only direct loss of 60 Da (urea) could be observed.The fragmentation pathways were investigated by high-resolution mass spectrometry and deuterium-labeling experiments,and the characteristic fragmentations presented here could be convenient for future identification of resembled derivatives,especially in high throughput screening combinatorial chemistry.