Fast atom bombardment mass spectrometry of some anthracycline and bisanthracycline derivatives

Fast atom bombardment (FAB) mass spectra of daunomycin (1), four of its derivatives (2–5), seven bisanthracyclines (6–12) and three mixed‐functional daunomycin‐acridine derivatives (13–15) are reported. These anthracyclines all exhibited their expected [MH]+ ions and peaks corresponding to the fragmentations which are characteristic of the anthracycline moiety, and in addition the spectra showed enhanced [MH + n]+ (n = 1–4) ions which were attributed to reductive processes occurring in the liquid matrix under FAB conditions. Daunomycin was also observed to form a dimeric cluster ion [M2H]+ together with associated reduced ions under FAB conditions. We have found that FAB mass spectrometry is an ideal method for the qualitative analysis of large, non‐volatile derivatives of anthracyclines.