β-Glycosylations with 2-Deoxy-2-(2,4-dinitrobenzenesulfonyl)-amino-glucosyl/galactosyl Selenoglycosides: Assembly of Partially N-Acetylated β-(1 → 6)-Oligoglucosaminosides

Abstract

An efficient protocol has been established for βglycosylations with 2-deoxy-2-(2,4-dinitrobenzenesulfonyl)amino (2dDNsNH)-glucopyranosyl/galactopyranosyl selenoglycosides using PhSeCl/AgOTf as an activating system. The reaction features highly β-selective glycosylation with a wide range of alcohol acceptors that are either sterically hindered or poorly nucleophilic. Thioglycoside-and selenoglycoside-based alcohols prove to be viable nucleophiles, opening up new opportunities for one-pot construction of oligosaccharides. The power of this approach is highlighted by the efficient assembly of tri-, hexa-, and nonasaccharides composed of β-(1 → 6)-glucosaminosyl residues based on one-pot preparation of a triglucosaminosyl thioglycoside with DNs, phthaloyl, and 2,2,2-trichloroethoxycarbonyl as the protecting groups of amino groups. These glycans are potential antigens for developing glycoconjugate vaccines against microbial infections.

A comprehensive synthetic library of poly-N-acetyl glucosamines enabled vaccine against lethal challenges of Staphylococcus aureus

“…While several PNAG structures have been synthesized before 16 – 20 , a general method for the expeditious construction of a comprehensive PNAG pentasaccharide library is lacking. To accelerate the library synthesis, rather than starting from monosaccharide building blocks for each targeted pentasaccharide, we envisioned the overall efficiency can be significantly enhanced with a divergent strategy.…”

Synthesis of L-Hexopyranosyl Fluorides Enabled by Radical Decarboxylative Fluorination: Assembly of a Pentasaccharide Repeating Unit Corresponding to Extracellular Polysaccharide S-88

“…We therefore embarked on the preparation of uronic acid-based disaccharide 14 . As outlined in Scheme 5b, BF 3 •Et 2 O-catalyzed glycosylation of26 [30] with27 [31] supplied 77% of disaccharide14 in CH 2 Cl 2 in the presence of 4 Å MS. At this stage, the coupling reaction of 14 and13 was explored. As tabulated in Table 1, we were disappointed to find that the reaction under the promotion of NIS with either TfOH or Lewis acids such as AgOTf and TBSOTf supplied the desired tetrasaccharide 10 in the best yield up to 23% (Table 1, entries 1-5).…”

Iodosylbenzene-Promoted Glycosylation with Selenoglycosides: Application in One-Pot Glycosylation

“…One critical step in the assembly of oligosaccharides is glycosidic bond formation. , At present, the family of general glycosylation donors includes acetimidates, , glycosyl halides, , thioglycosides, − phosphates, glycals, , and alkynyl donors. , In recent years, selenoglycosides have increasingly been used as glycosyl donors for oligosaccharide synthesis. Activation conditions similar to those of thioglycosides are generally used for selenoglycosides (Scheme A), − but the activity of selenoglycosides is higher than that of thioglycosides, which makes selenoglycosides more attractive in certain forms of carbohydrate chemistry. In addition, selenoglycosides can also be activated to afford O -glycosides by photoinduced reactions (Scheme B) with a limited substrate scope.…”