Mycinamicins, new macrolide antibiotics. IX. Chemical ionization mass spectral studies on mycinamicins.

Chemical ionization (CI) mass spectra of new macrolide ntibiotics, mycinamicins are reported. Protonated molecules (MH+) are observed as base peaks in the CI mass spectra of all components. Fragmentations are mainly restricted to the glycosidic linkages and the resulting aglycone and sugar-derived ions appear regularly in their mass spectra. Moreover, characteristic fragment ions involving carbon-carbon bond fission are found in the CI mass spectra of the epoxyenone-containing components, mycinamicins I (1) and II (2). The mechanism for the formation of the ion species is also discussed.