Synthesis of the tetracyclic core of chlorospermines

Chlorospermines A and B are biologically interesting acridone natural products and recently isolated from Glycosmis chlorosperrna. 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 6 pi-electrocyclization/aromatization sequence served as the key step of the synthesis, which formed the tetrasubstituted arene motif in one pot. (C) 2015 Hua Liu and Ang Li. Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. All rights reserved.