The structures of new antitumor antibiotics elsamicins A (la) and B (lb), produced by an unidentified actinomycete strain 5907-21, have been established by a combination of chemical degradation, spectral analysis, and X-ray diffraction. They are structurally similar to chartreusin containing chartarin as an aglycon, but differ to each other in sugar moieties. Elsamicin A possesses two novel sugars, 2-amino-2, 6-dideoxy-3-O-methyl-~ galactose ...
