Two‐Phase Electrosynthesis of Dihydroxycoumestans: Discovery of a New Scaffold for Topoisomerase I Poison.

Coumestan represents a biologically relevant structural motif distributed in a number of natural products, and the rapid construction of related derivatives as well as the characterization of targets would accelerate lead compound discovery in medicinal chemistry. In this work, a general and scalable approach to 8,9‐dihydroxycoumestans via two‐electrode constant current electrolysis was developed. The application of a two‐phase (aqueous/organic) system plays a crucial role for success, protecting the sensitive o‐benzoquinone intermediates from over‐oxidation. Based on the structurally diverse products, a primary SAR study on coumestan scaffold was completed, and compound 3 r exhibited potent antiproliferative activities and a robust topoisomerase I (Top1) inhibitory activity. Further mechanism studies demonstrates that compound 3 r was a novel Top1 poison, which might open an avenue for the development of Top1‐targeted antitumor agent. [ABSTRACT FROM AUTHOR]