Novel extracellular diterpenoids with biological activity from the cyanobacterium Nostoc commune

Five novel extracellular metabolites with an unprecedented diterpenoid skeleton and designated comnostins A-D (I-IV, resp.) and E have been isolated from the culture medium of the terrestrial cyanobacterium Nostoc commune by means of bioguided isolation. The structures were detd. by spectroscopic methods, mainly NMR and mass spectrometry. The relative stereochem. of I was confirmed by single-crystal X-ray structure anal. All comnostins showed antibacterial activities. Addnl., cytotoxic and molluscicidal activities were found for II