Methylated aldobiouronic acids, mass

Methanolysis and acetylation to give partially methylated aldobiouronic acid derivatives ( ) - m/e values are shown for characteristic fragment ions in the mass spectrum... 

Fig. 8. The mechanisms of fragmentation that lead to the key fragments observed in the mass spectrum of the fully methylated derivative of a l->4 linked aldobiouronic acid that possesses a furanosidic hexuronic acid unit. The simultaneous occurrence of the fragments of mass 319 and 161 is typical of the l->4 linkage, and the fragment at m/e 333 is characteristic for the hexofuranosyluronic acid structure.

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