Application of the anomeric samarium route for the convergent synthesis of the C-linked trisaccharide alpha-D-Man-(1-->3)-[alpha-D-Man-(1-->6)]-D-Man and the disaccharides alpha-D-Man-(1-->3)-D-Man and alpha-D-Man-(1-->6)-D-Man.
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 SmI(2)-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.
Department of Chemistry, University of Aarhus, Langelandsgade 140, 8000 Aarhus C, Denmark.
Lise Munch
LM
Mikkelsen
Sussie Lerche
SL
Krintel
Jesús
J
Jiménez-Barbero
Troels
T
Skrydstrup
D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D002384:Catalysis; D020650:Combinatorial Chemistry Techniques; D004187:Disaccharides / Q000138:chemical synthesis*; D006027:Glycosides / Q000138:chemical synthesis / Q000737:chemistry; D006031:Glycosylation; D037601:Mannose-Binding Lectin / Q000737:chemistry; D008362:Mannosides / Q000138:chemical synthesis*; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods; D025942:Oligosaccharides, Branched-Chain / Q000737:chemistry; D012493:Samarium / Q000737:chemistry*; D013237:Stereoisomerism; D014312:Trisaccharides / Q000138:chemical synthesis*
D004187:Disaccharides; D006027:Glycosides; C472424:Man-(1-3)-(Man-(1-6))-Man; D037601:Mannose-Binding Lectin; D008362:Mannosides; D025942:Oligosaccharides, Branched-Chain; D014312:Trisaccharides; C472425:alpha-D-Man-(1-3)-D-Man; C472426:alpha-D-Man-(1-6)-D-Man; D012493:Samarium