Previously, we have reported the isolation and structure determination of six novel anthracycline antitumor antibiotics from the bohemic acid complex 1-6 (Figure 1) (1-3). We now report the isolation and structure determination of schaunardimycin 7. During the course of large scale fermentation for the production of marcellomycin (1), one fermentation produced moderate amounts of a new antibiotic which eluted closely behind 1 on silica gel chromatography. The presence of this new component greatly complicated large-scale chromatography using CH₂Cl₂-MeOH-NH₃ based systems on silica gel as described earlier (2). Separation of 7 from 1 was attempted using this system, only partial resolution was observed. Substitution of CHCl₃ for toluene-MeOH led to resolution of two major components of the mixture as well as several minor ones. Essentially, pure 7 was obtained from the second major fraction. Application of the method on a preparative scale gave pure marcellomycin (1) needed for clinical trials. The structure of schaunardimycin was determined by nmr studies. The cmr chemical shifts for 7 were very similar to those of musettamycin except for those arising from the carbon atoms in the vicinity of the nitrogen atom on the amino sugar. Strong upfield shifts were observed for C-3' (61.8 ppm to 54.8 ppm) and the N-methyl groups (42.7 ppm to 33.2 ppm) with lesser downfield shifts for C-2' (29.2 ppm to 31.8 ppm) and C-4' (73.6 ppm to 77.7 ppm). The pmr spectrum was very similar to that of musettamycin except that the N-methyl signal integrated for only three protons and had moved downfield from 2.22 to 2.35. Biologically, schaunardimycin appears to have about a tenth of the potency of musettamycin and around one twentieth that of marcellomycin (cf. Table 1).