(A) Ionization of 2 or 2-d leads to ejection of the aminosugar residue and observation of the elimination products 4 or 4-d by HRMS analysis.1b,9 (B) 1, 2: Selected region of the HRMS spectrum of 4, generated by hydrodediazotization of 1 in CH3OH or CH3OD, respectively. 3, 4: Selected region of the HRMS spectrum of 4-d, generated by hydrodediazotization of 1 in CD3OH or CD3OD, respectively. 5, 6: Predicted isotope distribution of 4 and 4-d, respectively.