Desorption chemical ionization mass spectrometry of anthracyclines and of trisaccharides related to aclacinomycin A and marcellomycin.

Desorption chemical ionization mass spectrometry with ammonia as the reagent gas was used to obtain positive ion spectra of twelve alkyl-anthraquinones, seven anthracyclinones, eleven anthracycline antibiotics and nine oligosaccharides (di- and trisaccharides). Ions corresponding to the intact molecules (M) were present in all spectra as pseudo-molecular ions [M + H]+ and/or [M + NH]+. However, the most significant results were obtained in the case of anthracyclines and oligosaccharides. With anthracyclines, in addition to the preceding ions, spectra exhibited characteristic fragment ions due to the aglycon or to the sugar moiety while ions corresponding to the sequential loss of monosaccharide units were observed with oligosaccharides. All these fragment ions can be readily explained by an initial site of protonation located at the oxygen atom of the glycosidic linkages.