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Synfacts 2007(5): 0451-0451  
DOI: 10.1055/s-2007-968386
Synthesis of Natural Products and Potential Drugs
© Georg Thieme Verlag Stuttgart · New York

Synthesis of (±)-11-O-Debenzoyltashironin

Contributor(s):Philip Kocienski
S. P. Cook, A. Polara, S. J. Danishefsky*
Columbia University and Sloan-Kettering Institute for Cancer Research, New York, USA
The Total Synthesis of (±)-11-O-Debenzoyltashironin
J. Am. Chem. Soc.  2006,  128:  16440-16441  
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Publication History

Publication Date:
24 April 2007 (online)

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Key words

intramolecular Diels-Alder reaction - biomimetic cascade - oxidative dearomatization

Significance

11-O-Debenzoyltashironin, a metabolite of Illicium merrillanium, induces neurite outgrowth in fetal rat cortical neurons. The key step in this biomimetic synthesis is an oxidative dearomatization leading to quinone monoketal B, which underwent an intramolecular Diels-Alder reaction to create all four rings of the target.

Comment

Reduction of the ketone in C proceeded with a dr > 9:1. After homogeneous hydro­genation of the exo-methylene in D, the epoxide was reductively cleaved with a large excess of ­lithium triethylborohydride at 100 °C in a sealed tube. Under these conditions, the enol tosylate was also reductively cleaved but surprisingly, the product was the secondary alcohol rather than the ketone.

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