Study of selected ions in the ammonia desorption chemical ionization mass spectra of peracetylated gentiobiose and two isotopically labelled peracetylated gentiobioses

✍ Scribed by John M. Peltier; Richard W. Smith; David B. Maclean; Walter A. Szarek

• Publisher: John Wiley and Sons
• Year: 1992
• Tongue: English
• Weight: 583 KB
• Volume: 27
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/oms.1210270108

✦ Synopsis

Abstract

The ammonia desorption chemical ionization (NH~3~‐DCI) mass spectra of peracetylated gentiobiose (1) and two isotopically labelled gentiobioses (2 and 3) were examined. Compound 2 is labelled with trideuteroacetyl groups in the non‐reducing moiety and 3 with trideuteroacetyl groups in the reducing moiety. It is shown that the [M + NH~4~ – 42]^+^ ion is not formed direct from [M + NH~4~]^+^ by loss of ketene but appears to be formed by way of a nucleophilic acyl substitution reaction resulting in a neutral species which complexes with NH~4~^+^. The disaccharides undergo cleavage at either side of the glycosidic oxygen joining the two sugar residues, a process which is accompanied by addition of H or CH~3~CO to afford neutral species which complex with NH~4~^+^. The structures of the ions resulting from H transfer have been inferred by comparison of their mass‐analysed ion kinetic energy (MIKE) spectra with MIKE spectra of the [M + NH~4~]^+^ ions of compounds of established structure. A ring fragmentation reaction of 1, 2 and 3 is reported.