Sequence determination of permethylated oligosaccharides by chemical ionization mass spectrometry

Abstract

Chemical ionization mass spectra of several permethylated oligosaccharides were studied using isobutane and ammonia as reagent gases. In the molecular ion region, protonated molecule [MH]" or ammonium adduct ion [M-NHJ were observed. Fragmentations were mainly restricted to the cleavages of the glycosidic bonds between the glycosidic oxygen and the anomeric carbon atoms. Resulting fragment ions were classified into oxonium type ions and their counterpart ions with hydrogen or methyl transfer, which were very useful for determining the sequence of the constituent saccharide units. These ions were confirmed by shift techniques with pertrideuteromethyl derivatives, deuterated reagent gases, i-C,ZH,, and N'H,, and 15NH3. Finally, these results were applied successfully to the structural characterization of the unknown trisaccharides, viridotriose A (6), B (7) and C (8).

Structural Characterization of Abscisic Acid and Related Metabolites by Chemical Ionization Mass Spectrometry

“…The fraction with 20% acetone gave 94mg (39%) of the tetraacetate of 5. (12). Acetyl groups were removed with esterase from seeds of Helinanthus annuus.…”

“…288 (100) 268 (8) 244 (4) 268 (8) 224 ( (9) 260 (4) MePA (2b) I 317 (100) 297 (*) 297 (*) 277 (18) DPA (3a) epi-DPA (4a) 3 3 307 (100) 307 (100) 287 (16) 287 (33) 267 (12) 267 (37) 263 (5) 263 (6) 243 (5) 243 (3) 287 (16) 287 (33) 267 (12) 267 (37) 247 (*) 247 (*) 243 (3) 243 (3) 223 (8) 223 (4) DPA (3b) epi-MeDPA (4b) 2 2 320 (100) 320 (100) 300 (12) 300 (22) 300 (12) 300 (22) 280 (16) 280 (37) Ions marked by an asterisk were ambiguously observed.…”