Nor-sesterterpenes from the North Adriatic sponge Ircinia oros

Together with the previously described ircinin 1 and ircinin 2, two new isomeric linear difurano-norsestectepenes 1 and 3 have been isolated from the sponge Ircinia oros, collected in the Northern Adriatic Sea. The structural elucidation and biological activity of these compounds are reported.