Xu Jiaxi, Zuo Gang
Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, Department of Chemical Biology, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.
Rapid Commun Mass Spectrom. 2003;17(14):1651-6. doi: 10.1002/rcm.1097.
The mass spectral behaviour of (S,S)-2-substituted 4,4-diphenyl-3,1-oxazabicyclo[3.3.0]octanes has been studied with the aid of mass-analyzed ion kinetic energy spectrometry and accurate mass measurements under fast atom bombardment (FAB) and electron impact (EI) ionization conditions. Under FAB ionization, all compounds show a tendency to form protonated aldehyde or benzophenone ions and to form protonated 1-azabicyclo[3.1.0]hexane ions, which can further lose an ethylene or cyclopropane from the pyrrolidine ring to produce protonated 1-azabicyclo[1.1.0]butane ions and 3H-azirine ions, respectively. Under EI ionization, a similar fragmentation to that under FAB ionization was observed. The title compounds also show a tendency to yield oxirane ions and oxirenium ions by loss of pyrrolidine and pyrrolidine plus H. Ring contractions of 1,3-oxazolidine by loss of an aldehyde or ketone and of pyrrolidine by loss of an ethylene or cyclopropane were observed under both FAB and EI ionization conditions.
借助质量分析离子动能谱以及在快原子轰击（FAB）和电子轰击（EI）电离条件下的精确质量测量，对（S,S）-2-取代的4,4-二苯基-3,1-恶唑并双环[3.3.0]辛烷的质谱行为进行了研究。在FAB电离条件下，所有化合物都倾向于形成质子化的醛或二苯甲酮离子，以及形成质子化的1-氮杂双环[3.1.0]己烷离子，该离子可进一步从吡咯烷环上失去一个乙烯或环丙烷，分别生成质子化的1-氮杂双环[1.1.0]丁烷离子和3H-氮丙啶离子。在EI电离条件下，观察到了与FAB电离条件下类似的裂解。标题化合物还倾向于通过失去吡咯烷和吡咯烷加H生成环氧乙烷离子和环氧乙鎓离子。在FAB和EI电离条件下，均观察到了通过失去醛或酮使1,3-恶唑烷发生环收缩，以及通过失去乙烯或环丙烷使吡咯烷发生环收缩的现象。
