Free Radical Cyclizations in Alkaloid Total Synthesis: (±)-21-Oxogelsemine and (±)-Gelsemine
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- 作者：Shogo Atarashi ; Joong-Kwon Choi ; Deok-Chan Ha ; David J. Hart ; Daniel Kuzmich ; Chih-Shone Lee ; Subban Ramesh ; and Shung C. Wu
- 刊名：Journal of the American Chemical Society
- 出版年：1997
- 出版时间：July 9, 1997
- 年：1997
- 卷：119
- 期：27
- 页码：6226 - 6241
- 全文大小：746K
- 年卷期：v.119,no.27(July 9, 1997)
- ISSN：1520-5126
文摘
Total syntheses of (±)-21-oxogelsemine (3) and(±)-gelsemine (1) are described. Free radicalcyclizationsplay important roles in constructing the tricyclic core (40
41) and oxindole (93 96)substructures of the targetalkaloids, and an isomerization-cyclization strategy (101 102) was used to complete construction of thegelseminecage. Observations made along the way include intramolecular 1,4-and 1,6-hydrogen atom transfers (64 65and40 47) and a free radicalcyclization-fragmentation sequence (85 86 +87). A retroaldol-aldol strategy foradjusting oxindole stereochemistry in gelsemine-like structures is alsodescribed (72 74 and 86 87).
41) and oxindole (93 96)substructures of the targetalkaloids, and an isomerization-cyclization strategy (101 102) was used to complete construction of thegelseminecage. Observations made along the way include intramolecular 1,4-and 1,6-hydrogen atom transfers (64 65and40 47) and a free radicalcyclization-fragmentation sequence (85 86 +87). A retroaldol-aldol strategy foradjusting oxindole stereochemistry in gelsemine-like structures is alsodescribed (72 74 and 86 87).