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Abstract
The fascinating benzenoid and troponoid Cephalotaxus diterpenoids are highly related biosynthetically, both of which are popular targets for total synthesis. Herein, we describe a unified strategy for the concise synthesis of cephanolide A and harringtonolide in 14 and 16 steps respectively. Palladium catalyzed Csp2-Csp3 cross-coupling followed by doubly electron-deficient intramolecular Diels-Alder reaction secure the rapid construction of the Cephalotaxus carbon framework. Late-stage benzenoid-to-troponoid ring expansion was accomplished employing Büchner-Curtius-Schlotterbeck (BCS) reaction, furnishing harringtonolide in two steps from cephanolide A. This work shed light on the chemical synthetic connection between benzenoid and troponoid Cephalotaxus diterpenoids.
