Asymmetric Synthesis of the Diterpenoid Marine Toxin (+)-Acetoxycrenulide

An enantioselective route to the marine toxin (+)-acetoxycrenulide is described. The early stages of the synthesis feature the conversion of (R)-citronellol into a butenolide whose sole stereogenic center is provided by the terpenic alcohol. Three contiguous chiral carbon atoms are subsequently set...

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Bibliographic Details
Published in:Journal of the American Chemical Society 1996-02, Vol.118 (6), p.1309-1318
Main Authors: Wang, Ting-Zhong, Pinard, Emmanuel, Paquette, Leo A
Format: Article
Language:English
Subjects:
Dictyotaceae
Marine
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Summary:An enantioselective route to the marine toxin (+)-acetoxycrenulide is described. The early stages of the synthesis feature the conversion of (R)-citronellol into a butenolide whose sole stereogenic center is provided by the terpenic alcohol. Three contiguous chiral carbon atoms are subsequently set in the requisite absolute configuration by conjugate addition of an enantiopure allylphosphonamide reagent. The resulting product is transformed during several steps into a primary selenoxide whose thermal activation in dimethylacetamide at 220 °C promotes sequential 1,2-elimination and Claisen rearrangement. The cyclooctenone core of the target is formed in this step. The final stages of the synthesis involve a series of fully stereoselective reactions including Simmons−Smith cyclopropanation and controlled Dibal-H reduction. The naturally occurring dextrorotatory enantiomer of acetoxycrenulide was ultimately acquired.
ISSN:0002-7863
1520-5126
DOI:10.1021/ja9533609