Regioselective polymethylation of α-(1 → 4)-linked mannopyranose oligosaccharides
1Alberta Glycomics Centre and Department of Chemistry, University of Alberta, Gunning-Lemieux Chemistry Centre, Edmonton, AB T6G 2G2, Canada.
Abstract:
An approach has been developed of the regioselective methylation of α-(1 → 4)-linked mannopyranose oligosaccharides via a four-step methodology. The key reaction involved n-Bu2SnCl2-mediated activation of cis-diols. By tuning protecting groups on the substrates, multiple cis-diols in the substrates were functionalized in a consistent and regioselective manner. Using optimized substrates and reaction conditions, regioselective methylation of di-, tri-, and tetrasaccharide substrates proceeded in isolated yields per cis-diol of 95, 88 and 79%, respectively. The methodology was also applied to functionalize trans-diols in α-cyclodextrin.
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