Synthesis of the tetracyclic core of chlorospermines

Chlorospermines A and B are biologically interesting acridone natural products and recently isolated from Glycosmis chlorosperma. We report here a convergent approach to construct the tetracyclic core of the natural products. The two fragments are assembled together through Sonogashira coupling, and a cis-triene intermediate was prepared by using hydrosilylation/desilylation. A 6π-electrocyclization/aromatization sequence served as the key step of the synthesis, which formed the tetrasubstituted arene motif in one pot.

Graphical abstractThe tetracyclic core of chlorospermines A and B, two acridone alkaloids isolated from Glycosmis chlorosperma, have been constructed through a 6π electrocyclization/aromatization sequence.Figure optionsDownload full-size imageDownload as PowerPoint slide