Stereoselective synthesis of 2-C-branched (Acetylmethyl) oligosaccahrides and glycoconjugates: Lewis acid-catalyzed glycosylation from 1,2-cyclopropaneacetylated sugars

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DOIResolve DOI: http://doi.org/10.1021/jo1016579
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TypeArticle
Journal titleJournal Of Organic Chemistry
Volume76
Issue4
Pages10451053; # of pages: 9
Abstract1,2-Cyclopropaneacetylated sugars as glycosyl donors reacted with a series of glycosyl acceptors (monosaccharides, amino acids, and other alcohols) in the presence of Lewis acid to produce oligosaccharides and glycoconjugates containing 2-C-acetylmethylsugars. Galactosyl donor gave good to excellent α-selectivities with TMSOTf as a catalyst, whereas galactosyl donor offered moderate to good β-selectivities when BF3·Et2O was used as a catalyst. However, glucosyl donors produced β-exclusive selectivity under both conditions. The stereoselectivities of glycosylation depend on the reactivity of donor sugars and Lewis acid catalyst, which effectively dictated the glycosylation pathways. The evidence suggests that galactosyl donors (e.g., 7) can undergo SN1 pathway with a strong Lewis acid (TMSOTf) and SN2 pathway under BF3·Et2O, whereas the glucosyl donors (e.g., 8 and 10) followed SN2 pathway. The stereoselectivity was also consequential to the formation of a C2′-acetal intermediate formed via the 2-C-acetylmethyl group and the anomeric carbonium intermediate in glycosylation.
Publication date
LanguageEnglish
AffiliationNational Research Council Canada; NRC Institute for Biological Sciences
Peer reviewedYes
NPARC number17364211
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Record identifier371a2d5c-6110-4f73-863d-5c448b3fbf88
Record created2011-03-23
Record modified2016-05-09
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