Highly facile approach to the formal total synthesis of camptothecin

A concise, highly convergent synthesis of camptothecin in good yield from readily accessible building blocks is reported. The key step in this approach is to construct the C ring of camptothecin by coupling two blocks via the Suzuki reaction, followed by a mild one-step, one-pot cyclization, wherein the methoxypyridine nitrogen in the D/E ring block displaces the activated hydroxyl group in the ring A/B block while the methoxy group is cleaved in situ. The key intermediate 12 was obtained in 73% overall yield in three steps.