Tandem Electrospray Mass Spectrometry of Cyclic N -Substituted Oligo-β-(1→6)-D-glucosamines.

High-resolution electrospray mass spectra (MS and MS/MS CID) of positive ions of a series of protonated, ammoniated, and metallated molecules of cyclic N -substituted oligo-β-(1→6)-D-glucosamines differing in cycle size and N -acyl substituents were registered and interpreted. It was shown that the main type of fragmentation is a cleavage of glycosidic bonds of a cycle, and in some cases fragmentation of amide side chains is possible. If labile fragments in substituents (e.g., carbohydrate chains) are present, a decay of the cycle and an elimination of labile fragments are of comparable possibility. It was found that in some cases rearrangements with loss of an internal carbohydrate residue (IRL), or an internal part of a side chain, are feasible.