Study of the m/z [H 1 2 + 13] + Ion in 2-Aminopyranoside Derivatives

The electron impact spectra of 2-N-alkyl, 2-N-acyl-2-N-alkyl and 2-N,N-dialkyl aminosugar derivatives, as well as 2-aminosugar derivatives themselves, all show an [H₁² + 13]⁺ ion.^b In previous work, it was considered that this ion was derived from the [M – OR¹]⁺ ion and was designated as [M – OR¹ − 178]⁺. In the present work, the structure and origin of the [H₁² + 13]⁺ ion is studied in detail, and it is demonstrated that it originates first from the molecular ion, via a primary fragmentation, and second from the [M – OR¹]⁺ ion, in both cases by a [3 + 3] cleavage of the pyranose ring.