Total Synthesis of the Natural Pyridocoumarins Goniothaline A and B

In this paper, we report the first total synthesis of goniothaline A and B, which are rare natural pyridocoumarins isolated from Goniothalamus australis . The key feature of the synthesis of goniothaline A is high-yielding silver-catalyzed cycloisomerization to afford the pyridine moiety. In addition, goniothaline B, a natural 8-hydroxyquinoline derivative, is readily synthesized by the regioselective demethylation of goniothaline A.