Cytorhizophins A and B, benzophenone-hemiterpene adducts from the endophytic fungus Cytospora rhizophorae

Abstract

A pair of novel enantiomeric benzophenone-hemiterpene adducts, (+)-cytorhizophin A (1a) and (−)-cytorhizophin A (1b) as well as cytorhizophin B (2), all of them featuring an unprecedented 6/7/6/7 tetracyclic fused ring system, together with their biosynthetically related precursor cytorhizophin C (3) were isolated from Cytospora rhizophorae A761. Their structures were fully characterized on the basis of extensive spectroscopic analysis, with the absolute configurations of 1 determined by X-ray diffraction and electronic circular dichroism (ECD) calculations. Moreover, compounds 1–3 were evaluated for in vitro antimicrobial activity.