A Novel Approach to the Pyridoacridine Ring System: Synthesis of the Topoisomerase Inhibitor 13‐Deazaascididemin

A novel approach to the pyridoacridine ring system of the ascididemin‐type marine alkaloids is presented. This approach allows for the introduction of the ring A of the alkaloids by using a simple aromatic aldehyde building block. The viability of this approach is demonstrated with the synthesis of AK37, a bioactive deaza analogue of the alkaloid ascididemin. Starting from 3‐cyano‐4‐methylquinoline, a sequence of regioselective homolytic benzoylation, annulation of a bromopyridine ring, and radical cyclization leads to the pentacyclic ring system.