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Asymmetric Total Syntheses of Kopsia Indole Alkaloids
Author(s) -
Leng Lingying,
Zhou Xiaohan,
Liao Qi,
Wang Falu,
Song Hao,
Zhang Dan,
Liu XiaoYu,
Qin Yong
Publication year - 2017
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201700831
Subject(s) - chemistry , cyclopropanation , stereochemistry , total synthesis , decarboxylation , intramolecular force , indole test , asymmetric carbon , carbon skeleton , medicinal chemistry , organic chemistry , catalysis , optically active
The asymmetric total syntheses of a group of structurally complex Kopsia alkaloids, (−)‐kopsine, (−)‐isokopsine, (+)‐methyl chanofruticosinate, (−)‐fruticosine, and (−)‐kopsanone, has been achieved. The key strategies for the construction of the molecular complexity in the targets included an asymmetric Tsuji–Trost rearrangement to set the first quaternary carbon center at C20, an intramolecular cyclopropanation by diazo decomposition to install the second and third quaternary carbon centers at C2 and C7, respectively, and a SmI 2 ‐promoted acyloin condensation to assemble the isokopsine core. A radical decarboxylation of an isokopsine‐type intermediate results in a thermodynamic partial rearrangement to give N‐decarbomethoxyisokopsine and N‐decarbomethoxykopsine, two key intermediates for the syntheses of Kopsia alkaloids with different subtype core structures.