The fungal antibiotic botrydial (1) and related compounds constitute an important group of metabolites whose biological activity was not previously known in depth. The isolation, in addition to known compounds, of three new epimer metabolites with the botryane structure has allowed us to study the structure-activity relationships. The results suggest that, in addition to the presence of the dialdehyde functionality, the antibiotic, phytotoxic and cytostatic activities shown by some of these compounds are strongly correlated with the stereochemistry of the C-1/C-8 dialdehyde moieties. The relative configuration (S) of the C-1 substituent seems to play a critical role in the binding of the substrate to the chemoreceptor.