Application of the Anomeric Samarium Route for the Convergent Synthesis of the <i>C</i>-Linked Trisaccharide α-<scp>d</scp>-Man-(1→3)-[α-<scp>d</scp>-Man-(1→6)]-<scp>d</scp>-Man and the Disaccharides α-<scp>d</scp>-Man-(1→3)-<scp>d</scp>-Man and α-<scp>d</scp>-Man-(1→6)-<scp>d</scp>-Man
作者:Lise Munch Mikkelsen、Sussie Lerche Krintel、Jesús Jiménez-Barbero、Troels Skrydstrup
DOI:10.1021/jo020339z
日期:2002.9.1
Studies are reported on the assembly of the branched C-trisaccharide, alpha-D-Man-(1-->3)-[alpha-D-Man-(1-->6)]-D-Man, representing the core region of the asparagine-linked oligosaccharides. The key step in this synthesis uses a SmI2-mediated coupling of two mannosylpyridyl sulfones to a C3,C6-diformyl branched monosaccharide unit, thereby assembling all three sugar units in one reaction and with complete stereocontrol at the two anomeric carbon centers. Subsequent tin hydride-based deoxygenation followed by a deprotection step produces the target C-trimer. In contrast to many of the other C-glycosylation methods, this approach employes intact carbohydrate units as C-glycosyl donors and acceptors, which in many instances parallels the well-studied O-glycosylation reactions. The synthesis of the C-disaccharides alpha-D-Man-(1-->3)-D-Man and alpha-D-Man-(1-->6)-D-Man is also described, they being necessary for the following conformational studies of all three carbohydrate analogues both in solution and bound to several mannose-binding proteins.