Mass spectra of 1,6:2,3- and 1,6:3,4-dianhydro-β-D-hexopyranose derivatives: Formation of cluster ions assisted by participation of neighbouring acyloxy groups

Abstract

Chemical ionization and electron impact mass spectra of 1,6:2,3-and 1,6:3,4-dianhydro-β-D-hexopyranose derivatives are reported. The methane and isobutane chemical ionization mass spectra of both positional and configurational isomers differ significantly, while the electron impact mass spectra of stereoisomers are hard to discern. Examination of the isobutane chemical ionization mass spectra indicates that only those isomers containing the acyloxy group and the oxirane ring in the trans position give stable [M+C4H9]+ ions, otherwise these ions are of negligible abundance. This observation is interpreted in terms of participation of the acyloxy group in oxirane ring opening. This feature of the chemical ionization mass spectra can be used for stereochemical assignment.