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Relative stereochemical determination and synthesis of the C17-C25 δ-lactone fragment of hemicalide.

Authors
  • Fleury, Etienne
  • Sorin, Geoffroy
  • Prost, Elise
  • Pancrazi, Ange
  • Sautel, François
  • Massiot, Georges
  • Lannou, Marie-Isabelle
  • Ardisson, Janick
Type
Published Article
Journal
The Journal of Organic Chemistry
Publisher
American Chemical Society
Publication Date
Feb 01, 2013
Volume
78
Issue
3
Pages
855–864
Identifiers
DOI: 10.1021/jo302440a
PMID: 23301639
Source
Medline
License
Unknown

Abstract

Hemicalide is a novel marine metabolite polyketide distinguished by a unique mechanism of action. Because of insufficient quantities of purified material, this natural product has evaded complete stereochemical assignments. Recently, we have determined the relative stereochemistry of the C8-C13 hexad by synthesizing the C1-C13 fragment. Presently, we report the assignment of the C17-C25 δ-lactone fragment. NMR analysis of authentic hemicalide along with a computational conformation study allowed us to reduce the number of putative relative isomers from 16 to 4. Concise syntheses of the four candidate diastereomers were achieved using a common strategy based on a Dias aldehyde allylation reaction, an intramolecular Horner-Wadsworth-Emmons olefination, and a dihydroxylation reaction. Finally, thorough NMR comparisons enabled us to deduce the relative stereochemistry of the C1-C17 fragment with high certainty.

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