Abstract
Glycosyl phosphosaccharides represent a large and important family of complex glycans. Due to the distinct nature of these complex molecules, efficient approaches to access glycosyl phosphosaccharides are still in great demand. Here, we disclose a highly efficient and stereoselective approach to the synthesis of biologically important and complex α-glycosyl phosphosaccharides, employing direct gold(I)-catalyzed glycosylation of the weakly nucleophilic phosphoric acid acceptors. In this work, the broad substrate scope is demonstrated with more than 45 examples, including glucose, xylose, glucuronate, galactose, mannose, rhamnose, fucose, 2-N3-2-deoxymannose, 2-N3-2-deoxyglucose, 2-N3-2-deoxygalactose and unnatural carbohydrates. Here, we show the glycosyl phosphotriester prepared herein was successfully applied to the one-pot synthesis of a phosphosaccharide from Leishmania donovani, and an effective preparation of a trisaccharide diphosphate of phosphosaccharide fragments from Hansenula capsulate via iterative elongation strategy is realized.
Highlights
Glycosyl phosphosaccharides represent a large and important family of complex glycans
Glycosyl phosphosaccharides (GPSs) represent a large and important family of complex glycans, which are ubiquitously distributed in bacteria, yeasts, protozoan parasites and animals, and exhibit numerous bio-functions including bacterial infections, cell adhesive, immunoresponse, and antimicrobial (Fig. 1b)[1,2,3,4,5]
The GPSs consist of anomeric glycosyl phosphates in which the anomeric position of one constituent glycan was linked to another one mainly by α-type phosphodiester linkage (Fig. 1a)
Summary
For the other one equipped with COOMe, the product (3d) can be epimerized to enrich α-anomer (9.7/1) under a higher temperature of 100 °C with a yield of 58% This strategy was extended to a variety of donors including Gal, Man, ManN3, Rha, Fuc, GlcN3, GalN3 and unnatural carbohydrates (Fig. 3). The azido substituted glycosyl phosphates are resistant to epimerization at high temperature, donors of tribenzyl GlcN3 and GalN3 underwent smoothly coupling reactions with good diastereoselective ratios of 8.6/1 (3j) and 7.3/1 (3k) which might find utility in the syntheses of Lipid A or other phosphosaccharides[2,44]. While one-pot glycosylation protocol emerges as versatile strategy to synthesize complex oligo/polysaccharides of which the units are tethered by acetal linkages[49,50,51],
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