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Synfacts 2013; 9(2): 0121
DOI: 10.1055/s-0032-1317999
Synthesis of Natural Products and Potential Drugs
© Georg Thieme Verlag Stuttgart · New York

Total Synthesis of (±)-Alstilobanine A

Contributor(s):
Erick M. Carreira
,
Simon Breitler
Feng Y, Majireck MM, Weinreb SM * The Pennsylvania State University, University Park, USA
Total Synthesis of the Unusual Monoterpenoid Indole Alkaloid (±)-Alstilobanine A.

Angew. Chem. Int. Ed. 2012;
51: 12846-12849
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Further Information

Publication History

Publication Date:
18 January 2013 (online)

 
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Key words

alstilobanine A - nitrosoalkenes - [2+2] cycloaddition - alkaloids - β-lactones

Significance

Monoterpene indole alkaloids usually consist of a tryptamine residue attached to a monoterpenoid unit. (±)-Alstilobanine A, however, features an intriguing rearranged skeleton. The authors based their concise synthesis on the conjugate addition of ester enolate F to an in situ-generated nitrosoalkene and the formation of β-lactam L via an intramolecular formal ketene–ketone [2+2] cycloaddition developed by Romo and co-workers (Org. Lett. 2006, 8, 4363).


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Comment

The intermolecular conjugate addition of ester enolate F onto nitrosoalkene G, generated in situ from α-chlorooxime E, proceeded efficiently to give H. This transformation highlights an interesting method to construct 1,4-dicarbonyl frameworks. Both C16-diastereomers could be used to access I, which then underwent a formal [2+2] cycloaddition to afford the desired syn-2-azadecalin L in excellent yield and diastereoselectivity. The synthesis was completed in eight steps from L to generate the natural product in an impressive 14% overall yield.


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