Total synthesis of giffonin H by fluoride-catalyzed macrocyclization

The first total synthesis of giffonin H, a highly strained 15-membered macrocyclic diaryl ether, has been achieved in eight linear steps with 10% overall yield. Key steps include Ullmann cross coupling, (Z)-selective Julia-Kocienski olefination, and fluoride-mediated macrocyclization of TMS-alkyne and aldehyde. In particular, the strategy used for macrocyclization is an unprecedented and unique synthetic approach for cyclic diarylheptanoids. The fluoride-mediated macrocyclization strategy should be applicable to the synthesis of giffonin congeners under mild reaction conditions without affecting the integrity of subtle diene moieties.