Acid-Catalyzed E-Ring Expansion and Isomerization of 3-Acetylbetulin: Synthesis of Cytotoxic Anhydrobetulin Saponins

22(17 → 28)abeo-Lupene derivatives 5a and 6a were obtained after the acid-catalyzed E-ring expansion of 3-acetylbetulin (1a). Glycosylation of these dehydrated triterpenoids using Schmidt's trichloroacetimidate sugar donors in the presence of trimethylsilyl trifluoromethanesulfonate (TMSOTf) pr...

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Bibliographic Details
Published in:Synthetic communications 2010-01, Vol.40 (2), p.213-221
Main Authors: Thibeault, Dominic, Legault, Jean, Gauthier, Charles, Lavoie, Serge, Bouchard, Jimmy, Pichette, André
Format: Article
Language:English
Subjects:
Acid-catalyzed isomerization
Acids
anhydrobetulin saponins
betulin
cytotoxicity
E-ring expansion
triterpenoids
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Summary:22(17 → 28)abeo-Lupene derivatives 5a and 6a were obtained after the acid-catalyzed E-ring expansion of 3-acetylbetulin (1a). Glycosylation of these dehydrated triterpenoids using Schmidt's trichloroacetimidate sugar donors in the presence of trimethylsilyl trifluoromethanesulfonate (TMSOTf) provided the new anhydrobetulin saponins 7b-7e in which the terminal olefin C-20(29) isomerizes to form a C-19 tetrasubstituted alkene. The preliminary cytotoxic evaluation revealed that saponins 7b-7d exhibited a moderate cytotoxic activity against A549, DLD-1, and WS1 human cell lines with IC 50 ranging from 22 to 49 μM.
ISSN:0039-7911
1532-2432
DOI:10.1080/00397910902962886