Speradines B-D, oxygenated cyclopiazonic acid alkaloids from the sponge-derived fungus Aspergillus flavus MXH-X104

Abstract Two new highly oxygenated hexacyclic cyclopiazonic acid (CPA) alkaloids, speradines B and C ( 1 and 2 ), together with one new related tetracyclic oxindole alkaloid, speradine D ( 3 ), were isolated from the sponge derived fungus Aspergillus flavus MXH-X104. Among them, speradine C ( 2 ) possesses unprecedented 6/5/6/5/5/6 hexacyclic ring system and 4-oxo-1, 3-oxazinane ring. The structures including absolute configurations of 1 – 3 were deduced from the spectroscopic data, X-ray diffraction analysis and the computational method including the calculation of the chemical shifts and the electronic circular dichroism (ECD) spectra.