title: Fragmentation patterns of novel dispirocyclopiperazinium dibromides with strong analgesic activity under electrospray ionization tandem mass spectrometry conditions.
abstract: The fragmentation patterns of a series of dispirocyclopiperazinium dibromides with strong analgesic activity are analyzed by positive ion electrospray ionization mass spectrometry in conjunction with tandem mass spectrometry (ESI-MS(n)). Instead of the parent molecular ions, the fragment ions [M-Br](+) are detected as characteristic double peaks and usually the base peaks. Meanwhile, the fragment ions [M-2Br](2+) are unique for this series of diquaternary ammonium dibromides and show high intensity. Besides the common fragmentation patterns around the carbonyl group, elimination of hydrogen bromide from [M--Br](+) ions is another important pathway. Following the elimination, an interesting rearrangement takes place in the unsaturated spirocyclopiperazine and transforms it into a dihydropyrrole structure, whose fragmentations are similar to its precursor ion in the succeeding steps.
authors.affiliation: School of Pharmaceutical Sciences, Peking University, Beijing 100083, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Wang
authors.forename: Yaowu
authors.initials: Y
authors.lastname: Sha
authors.forename: Runtao
authors.initials: R
authors.lastname: Li
mesh_terms: D000700:Analgesics / Q000032:analysis*; D001965:Bromides; D010879:Piperazines / Q000032:analysis*; D021241:Spectrometry, Mass, Electrospray Ionization; D013141:Spiro Compounds / Q000032:analysis*
chemical_list: D000700:Analgesics; D001965:Bromides; D010879:Piperazines; D013141:Spiro Compounds