Free Radical Cyclizations in Alkaloid Total Synthesis: (±)-21-Oxogelsemine and (±)-Gelsemine
作者:Shogo Atarashi、Joong-Kwon Choi、Deok-Chan Ha、David J. Hart、Daniel Kuzmich、Chih-Shone Lee、Subban Ramesh、Shung C. Wu
DOI:10.1021/ja970089h
日期:1997.7.1
Free radical cyclizations play important roles in constructing the tricyclic core (40 → 41) and oxindole (93 → 96) substructures of the target alkaloids, and an isomerization−cyclization strategy (101 → 102) was used to complete construction of the gelsemine cage. Observations made along the way include intramolecular 1,4- and 1,6-hydrogen atom transfers (64 → 65 and 40 → 47) and a free radical cyc
描述了 (±)-21-oxogelsemine (3) 和 (±)-gelsemine (1) 的全合成。自由基环化在构建目标生物碱的三环核 (40 → 41) 和羟吲哚 (93 → 96) 亚结构中起重要作用,并采用异构化-环化策略 (101 → 102) 完成了明胶笼的构建。沿途观察包括分子内 1,4- 和 1,6- 氢原子转移(64 → 65 和 40 → 47)和自由基环化 - 断裂序列(85 → 86 + 87)。还描述了一种用于调节gelsemine样结构中oxindole立体化学的retroaldol-aldol策略(72→74和86→87)。