Structure Elucidation of Glykenin, Glycosidic Antibiotics from Basidiomycetes sp. VII. Structure Elucidation of the GK Components Using Tandem Mass Spectrometry

Abstract

The exact positions of the acetyl groups in the sugar moieties of the glycosidic antibiotics, the glykenin (GK) components, were elucidated using MS/MS technique under high energy collision conditions, because the frit-FAB LC/MS technique that was described in a preceding paper and other techniques were insufficient for the purpose. In the negative product ion spectra of (M-H)^-, a charge-remote fragmentation based on a terminal carboxylic acid of the aglycone was observed, whereas many cleavage ions were observed in the positive product ion spectra of (M+Li)⁺. The diagnostic ions were selected from the cleavage ions of two bonds within the glycosidic ring in the product ion spectra of the (M+Li)⁺ and (M-H)^-. The positions of the acetyl groups for each component could be determined by the presence or absence of these diagnostic ions, which enabled us to determine the structure of each of the GK components.