Mass spectrometric studies of anomeric glycopyranosyl azides

We studied the mass spectrometric behaviour of peracetylated and underivati zed anomeric hexopyranosyl azides and 5-thioglucopyranosyl azides by means of different mass spectrometric techniques. The unstable molecular ions fra gment predominantly by losing either N-3 radical or N-2 molecule. Loss of N -2 molecule and the protonation of the derived nitrene were characteristic of the studied compounds. The presence of BF3 . Et2O in the ion source is f avorable for producing; the protonated nitrene form. The protonated nitrene shows a new type of ring expansion rearrangement. The abundances of the [M + H - N-2](+) ion makes it possible to identify the anomeric configuration of the azido group. Copyright (C) 2001 John Wiley & Sons, Ltd.