Effect of alkali metal cationization on the collision‐induced decomposition of alkyl per‐O‐acetyl‐2‐deoxy‐2‐halo‐α‐O‐mannopyranosides

The effect of alkali metal cationization on the collision‐induced decomposition of alkyl per‐O‐acetyl‐2‐deoxy‐2‐bromo‐and‐iodo‐α‐O‐mannopyranosides was studied. The bromo sugars gave fairly abundant MH+, whereas for the iodo sugars the MH+ ions were insignificant. However, both the bromo and the iodo derivatives gave abundant M + alkali metal ion complexes. In contrast to the behaviour of the MH+ ion, the [M + Li]+, [M + Na]+ and [M + K]+ ions of these compounds do not decompose by loss of the C(1) substituent. Elimination of AcOH is the preferred fragmentation pathway of [M + Cat]+. Elimination of HX occurs only after loss of AcOH and CH2CO from MH+, whereas [M + Cat]+ directly loses HX. The elimination of HX is more pronounced from [M + Na]+ and [M + K]+ than from [M + Li]+. Loss of AcOLi is an additional fragmentation route observed in the case of the decomposition of [M + Li]+ ion.