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Synfacts 2013; 9(1): 0001
DOI: 10.1055/s-0032-1317856
Synthesis of Natural Products and Potential Drugs
© Georg Thieme Verlag Stuttgart · New York

Total Synthesis (±)-Garcibracteatone

Contributor(s):
Erick M. Carreira
,
Stefan Diethelm
Pepper HP, Lam HC, Bloch WM, George JH * University of Adelaide, Australia
Biomimetic Total Synthesis of (±)-Garcibracteatone.

Org. Lett. 2012;
14: 5162-5164
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Publication History

Publication Date:
17 December 2012 (online)

 
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Key words

radical cascade - polyprenylated acylphloroglucinol - biomimetic synthesis

Significance

Garcibracteatone (K) is the structurally most complex polycyclic polyprenylated ­acylphlorogucinol natural product that has so far been isolated. The four-step total synthesis presented makes use of a biomimetic radical cascade reaction to build up four rings in one transformation. Additionally, the previously unknown relative stereochemistry at C-5 was assigned.


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Comment

Precursor F for the key transformation is synthesized from phloroglucinol A in three steps by Friedel–Crafts acylation followed by subsequent diprenylation and alkylation with (±)-lavandulyl iodide (E). Oxidation of F by using Mn(OAc)3–Cu(OAc)2 initiates a radical cascade, which ultimately leads to the formation of the natural product garcibracteatone K (14% yield) along with its C5-epimer L (8% yield). This key transformation constructs four rings and five stereocenters.


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