Divergent Total Syntheses of (−)‐Daphnilongeranin B and (−)‐Daphenylline
Xiao‐Ming Chen(Shenzhen University), Hai‐Jun Zhang(Shenzhen University), Xinkan Yang(Lanzhou University), Houqiang Lv(Lanzhou University), Xiaoru Shao(Shenzhen University), Tao Cheng(Lanzhou University), Huifei Wang(Shenzhen University), Bin Cheng(Lanzhou University), Yun Li(Lanzhou University), Jingjing Guo(Lanzhou University), Jing Zhang(Shenzhen University), Hongbin Zhai(Shenzhen University)
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Abstract
(-)-Daphnilongeranin B and (-)-daphenylline are two hexacyclic Daphniphyllum alkaloids, each containing a complex cagelike backbone. Described herein are the first asymmetric total synthesis of (-)-daphnilongeranin B and a bioinspired synthesis of (-)-daphenylline with an unusual E ring embedded in a cagelike framework. The key features include an intermolecular [3+2] cycloaddition, a late-stage aldol cyclization to install the F ring of daphnilongeranin B, and a bioinspired cationic rearrangement leading to the tetrasubstituted benzene ring of daphenylline.