ChemInform Abstract: Structures of Topostins, DNA Topoisomerase I Inhibitors of Bacterial Origin

The structures of topostins, a novel type of mammalian DNA topoisomerase I inhibitors isolated from the bacterium Flexibacter topostinus sp. nov., have remained unknown. Reexamination of the production of topostins resulted in the isolation of original topostins B (B553 (1) and B567 (2)) and new related compounds named topostins D (D640 (3) and D654 (4)). Their structures, including the absolute stereochemistry, were determined by spectroscopic analyses and chemical degradations. These substances are lipid-containing amino acids and peptides.