Chiral-auxiliary-mediated 1,2-cis-glycosylations for the solid-supported synthesis of a biologically important branched alpha-glucan.
Solid-phase oligosaccharide synthesis offers the promise of providing libraries of oligosaccharides for glycomics research. A major stumbling block to solid-phase oligosaccharide synthesis has been a lack of general methods for the stereoselective installation of 1,2-cis-glycosides, and intractable mixtures of compounds are obtained if several such glycosides need to be installed. We have prepared on-resin a biologically important glucoside containing multiple 1,2-cis-glycosidic linkages with complete anomeric control by using glycosyl donors having a participating (S)-(phenylthiomethyl)benzyl chiral auxiliary at C2. A branching point could be installed by using 9-fluorenylmethyloxycarbonyl (Fmoc) and allyloxycarbonyl (Alloc) as a versatile set of orthogonal protecting groups. The synthetic strategy made it possible to achieve partial on-resin deprotection of the completed oligosaccharide, thereby increasing the overall efficiency of the synthesis. The combination of classical and auxiliary-mediated neighbouring-group participation for controlling anomeric selectivity is bringing the promise of routine automated solid-supported oligosaccharide synthesis closer.
Boltje
Thomas J
TJ
Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Road, Athens, GE 30602, USA.
Kim
Jin-Hwan
JH
Park
Jin
J
Boons
Geert-Jan
GJ
D005936:Glucans / Q000138:chemical synthesis* / Q000737:chemistry; D006027:Glycosides / Q000737:chemistry; D006031:Glycosylation; D009682:Magnetic Resonance Spectroscopy; D013237:Stereoisomerism
D005936:Glucans; D006027:Glycosides