General Access to the Vinca and Tacaman Alkaloids Using a Rh(II)-Catalyzed Cyclization/Cycloaddition Cascade
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- 作者：Dylan B. England ; Albert Padwa
- 刊名：Journal of Organic Chemistry
- 出版年：2008
- 出版时间：April 4, 2008
- 年：2008
- 卷：73
- 期：7
- 页码：2792 - 2802
- 全文大小：226K
- 年卷期：v.73,no.7(April 4, 2008)
- ISSN：1520-6904
文摘
The total synthesis of several members of the vinca and tacaman classes of indole alkaloids has beenaccomplished. The central step in the synthesis consists of an intramolecular [3+2]-cycloaddition reactionof an 
-diazo indoloamide which delivers the pentacyclic skeleton of the natural product in excellentyield. The acid lability of the oxabicyclic structure was exploited to establish the trans-D/E ring fusionof (±)-3H-epivincamine (3). Finally, a base induced keto-amide ring contraction was utilized to generatethe E-ring of the natural product. A variation of the cascade sequence of reactions used to synthesize(±)-3H-epivincamine was also employed for the synthesis of the tacaman alkaloids (±)-tacamonine and(±)-apotacamine.
-diazo indoloamide which delivers the pentacyclic skeleton of the natural product in excellentyield. The acid lability of the oxabicyclic structure was exploited to establish the trans-D/E ring fusionof (±)-3H-epivincamine (3). Finally, a base induced keto-amide ring contraction was utilized to generatethe E-ring of the natural product. A variation of the cascade sequence of reactions used to synthesize(±)-3H-epivincamine was also employed for the synthesis of the tacaman alkaloids (±)-tacamonine and(±)-apotacamine.