Structure Revision of Circumdatins A and B, Benzodiazepine Alkaloids Produced by Marine Fungus <i>Aspergillus ostianus</i>, by X-ray Crystallography

The structures of circumdatins A and B, pentacyclic alkaloids produced by Aspergillus ostianus, were revised from the previously reported betaine structures to unique oxepin ones by X-ray crystallography. The co-occurring known alkaloids, circumdatins D, E, and H, and a new compound reported here, circumdatin J, have a common framework.