Enantioselective Organocatalyzed Bromolactonizations: Applications in Natural Product Synthesis

Asymmetric bromolactonization reactions of δ-unsaturated carboxylic acids have been investigated in the presence of 10 chiral squaramide hydrogen-bonding organocatalysts. The best catalyst enabled the cyclization of several 5-arylhex-5-enoic acids into the corresponding bromolactones with up to 96%...

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Bibliographic Details
Published in:Journal of organic chemistry 2016-09, Vol.81 (18), p.8287-8295
Main Authors: Aursnes, Marius, Tungen, Jørn E, Hansen, Trond V
Format: Article
Language:English
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Summary:Asymmetric bromolactonization reactions of δ-unsaturated carboxylic acids have been investigated in the presence of 10 chiral squaramide hydrogen-bonding organocatalysts. The best catalyst enabled the cyclization of several 5-arylhex-5-enoic acids into the corresponding bromolactones with up to 96% ee and in high to excellent chemical yields. The reported catalysts are prepared in a straightforward manner in two steps from dimethyl squarate. The utility of the developed protocol was demonstrated in highly enantioselective syntheses of the sesquiterpenoids (−)-gossoronol and (−)-boivinianin B. Both natural products were obtained in ≥99% enantiomeric excess.
ISSN:0022-3263
1520-6904
DOI:10.1021/acs.joc.6b01375