Negative ion mass spectra of some unsaturated C-glycosides following keV ion bombardment

A series of anomeric unsaturated C-glycosides were studied by negative ion mass spectrometry following keV ion bombardment The compounds bearing an acidic hydrogen show a prominent [M ? H]^? peak; in the other cases, the [M ? H]^? peak is of very low intensity. A retro-Diels–Alder fragmentation and the abstraction of a hydrogen atom from the aglycon residue are observed in all cases.