Concise synthesis of (±)-fortuneicyclidins and (±)-cephalotine B enabled by Pd-catalyzed dearomative spirocyclization

Total syntheses of C11-oxygenated Cephalotaxus alkaloids, fortuneicyclidins A and B, and cephalotine B, were achieved. The key for the synthesis is a Pd-catalyzed dearomative spirocyclization of bromofurans with N-tosylhydrazones, followed by acid-mediated tandem transformation to construct the tetracyclic skeleton with the C11-oxygen functional group. Chemo-selective and catalytic functional group conversions of the tetracyclic intermediate completed the synthesis of fortuneicyclidins and cephalotine B in 8 and 9 steps, respectively.