Low Molecular Weight Modifications of Anthracycline Antibiotics. Part II. Reactions by Other Positions (A Review)

This review continues the discussion of known chemical transformations of anthracyclines, with a primary focus on daunorubicin and doxorubicin. In the first part, various modifications involving the amino group in the amino sugar moiety were explored. The second part shifts attention to modifications occurring at other sites within the anthracycline molecule. These include alterations at the C-13 keto group of the aglycone, such as deoxygenation and imine formation, as well as reactions involving the hydroxy groups at the C-9 and C-14 positions. Additionally, modifications to the A, B, C, and D rings of the anthraquinone nucleus are discussed in detail. Separate consideration is given to anthracyclines with non-classical structures, such as nogalomycin. For each modified anthracycline, data are provided regarding changes in biological activity, particularly with respect to antitumor efficacy and the cardiotoxicity commonly associated with anthracyclines.