The structure-activity relationships of the anthracycline-related antibiotics of the tetracenomycin C/elloramycin-type were investigated by derivatization of elloramycin (1) and elloramycinone (2). During hydrolysis experiments a unique transglycosylation reaction was discovered, converting elloramycin (1) into isoelloramycin (10) by treatment with anhydrous trifluoroacetic acid. Following the proposed structure-activity relationship concept, 8-O-methylelloramycinone (14) was synthesized from elloramycinone (2), and was shown to be the most active derivative according to the proliferation inhibition assay against murine L1210 leukemia cells.