FAST-ATOM-BOMBARDMENT MASS AND TANDEM MASS-SPECTRA OF PROTONATED AND ALKALI CATIONIZED ALDOBIOURONIC AND PSEUDOALDOBIOURONIC ACID PER-O-METHYL DERIVATIVES

The positive-ion fast atom bombardment mass spectra of permethylated a ldo- and pseudoaldobiouronic acids can be used to distinguish these cl asses of compounds. The collisional-induced dissociation spectra of th e [M + H](+) ions show fragment ions resulting from glycosidic bond cl eavage and successive losses of methanol molecules. These spectra toge ther with those of the [M + H - MeOH](+) oxonium ions allow the identi fication of the type of interglycosidic linkage. Collisional activatio n of the relatively stable [M + Na](+) ions show many fragmentations w hich are common to alkali cationized permethylated saccharides. Moreov er, fragment ions resulting from two-bond ring cleavage processes yiel d additional information with respect to the linkage between the hexos e and uronic acid units.