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Synfacts 2008(3): 0230-0230  
DOI: 10.1055/s-2008-1042659
Synthesis of Natural Products and Potential Drugs
© Georg Thieme Verlag Stuttgart · New York

Formal Synthesis of Leucascandrolide A

Contributor(s):Philip Kocienski, Indu Dager
H. H. Jung, J. R. Seiders, II, P. E. Floreancig*
University of Pittsburgh, USA
Oxidative Cleavage in the Construction of Complex Molecules: Synthesis of the Leucascandrolide A Macrolactone
Angew. Chem. Int. Ed.  2007,  46:  8464-8467  
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Publication History

Publication Date:
21 February 2008 (online)

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Key words

electron-transfer-initiated cyclization - oxidative cleavage - acetalization

Significance

Isolated from the sponge Leucascandra caveolata, leucascandrolide is an antifungal macrolide which possesses cytotoxic activity. The key step in the synthesis was an electron-transfer-initiated cyclization (ETIC) of E involving an oxidative cleavage of a benzylic C-C bond to form oxocarbenium ion F followed by cyclization to give a single stereoisomer of G.

Comment

syn Reduction of ketone A, followed by acetalization gave C, which underwent a Lewis acid mediated acetal ring opening to afford D. For conversion of phosphonate H into leucascandrolide A, see: K. R. Hornberger, C. L. Hamblett, J. L. Leighton J. Am. Chem. Soc. 2004, 122, 12894.

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