Glycosylation: The Direct Synthesis of 2‐Acetamido‐2‐Deoxy‐Sugar Glycosides

Abstract

Developing methods for the stereoselective synthesis of glycosides, used in the assembly of glycoconjugates or bioactive oligosaccharides, has been essential for making progress in the field of glycosciences. The 2‐acetamido‐2‐deoxy‐glycopyranosyl units are the key motifs of these structures and many innovative methods have been elaborated to incorporate these units by stereoselective chemical glycosylation. Most of these methods introduce additional chemical steps to avoid the presence of the acetamide functional group next to the reacting anomeric center. This microreview details the direct but arduous approaches for the synthesis of glycosides in which the NHAc group is present during the glycosylation reaction. Our focus will be on the methods that have appeared in the last two decades.

Exploratory N‐Protecting Group Manipulation for the Total Synthesis of Zwitterionic Shigella sonnei Oligosaccharides

“…The last two decades have witnessedanumber of reports on the successful step-saver synthesis of 2-acetamido-2-deoxy-glycopyranosides. [35] Yet, directc hemical methods whether in the form of electrophilic routes involving 2-acetamido glycosyl donors or based on the anomeric O-alkylation of 2-acetamido hemiacetalsa re still rarely appliedt oa chieve complex oligosaccharides. In this context, we engaged in as trategy aimed at as uitable AB disaccharide building block in which the 4 Bamino group and 2 B -acetamido group were masked as a4 Bazide and 2 B -trichloroacetamide as previously described.…”

“…The last two decades have witnessed a number of reports on the successful step‐saver synthesis of 2‐acetamido‐2‐deoxy‐glycopyranosides [35] . Yet, direct chemical methods whether in the form of electrophilic routes involving 2‐acetamido glycosyl donors or based on the anomeric O‐alkylation of 2‐acetamido hemiacetals are still rarely applied to achieve complex oligosaccharides.…”

“…acetamido-3-O-benzyl-6-O-tert-butyldiphenylsilyl-2deoxy-4-O-(2-naphthylmethyl)-a-l-altropyranosyl-(1!3)-4-azido-2-trichloroacetamido-2,4,6-trideoxy-b-d-galactopyranoside(35): Ethylenediamine (1.3 mL, 19.3 mmol, 4.0 equiv) was added to disaccharide 34 (6.2 g, 4.8 mmol, 1.0 equiv) in THF/MeOH (1:1, 100 mL) at rt and the reaction mixture was stirred at 50 8Cf or 72 h under an Ar atmosphere. AT LC analysis (Tol/EtOAc 7:3) revealed the absence of the starting 34 (R f 1.0) and the presence of an ew spot (R f 0.55).…”

Comprehensive quali-quantitative profiling of neutral and sialylated O-glycome by mass spectrometry based on oligosaccharide metabolic engineering and isotopic labeling

“…Synthesis of O-glycan precursors were carried out according to a reported procedure with minor modication. [32][33][34] To a solution of glycosamine pentaacetates (200 mg, 0.514 mmol) in dry 1,2dichloroethane (10 mL), anhydrous Cu(OTf) 2 (0.15 equiv.) and d0-benzyl alcohol (4 equiv.)…”

Nitrogen-Centered Radical Mediated Anomeric Specific Cascade Amidoglycosylation of Glycals

“…2,4 Therefore, the stereoselective formation either 1,2-cis or 1,2-trans glycosidic linkage of 2-amino-2-deoxyglycosides is of high signi cance due to its essentiality for oligosaccharide assembly. [5][6][7][8] A variety of synthetic approaches to 2-amino-2-deoxyglycosides have been developed and considerable progresses have been made. [9][10][11][12] Since some of the mono 2-amino-2-deoxysugars are naturally available or easily prepared, they have widely employed in synthesis of 2-amino-2-deoxyglycosides.…”