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2‐Nitroglycals are important synthons for biological active 2‐aminoglycosides, glycoconjugates and natural products synthesis. Herein, we summarized the recent advances of 2‐nitroglycals including its synthetic methods and its applications. Using 2‐nitroglycals, 2‐aminoglycosides, nitro‐polyol derivatives, sugar‐furan derivatives, sugar‐pyrrole molecules, 2,3‐diaminoglycosides and 2‐amino‐1,3‐dithioglycosides were obtained via Michael–type addition, retro‐Henry‐type reaction, C1/C3‐Ferrier rearrangement and [3+2] N‐heterocyclic addition. Most of these conversions are achieved via mild organo‐catalysis glycosylation methods. [ABSTRACT FROM AUTHOR]

Herein, we described the first synthesis of the pentasaccharide and decasaccharide of the A. baumannii ATCC 17961 O‐antigen for developing a synthetic carbohydrate‐based vaccine against A. baumannii infection. The efficient synthesis of the rare sugar 2,3‐diacetamido‐glucuronate was achieved using our recently introduced organocatalytic glycosylation method. We found, for the first time, that long‐range levulinoyl group participation via a hydrogen bond can result in a significantly improved β‐selectivity in glycosylations. This solves the stereoselectivity problem of highly branched galactose acceptors. The proposed mechanism was supported by control experiments and DFT computations. Benefiting from the long‐range levulinoyl group participation strategy, the pentasaccharide donor and acceptor were obtained via an efficient [2+1+2] one‐pot glycosylation method and were used for the target decasaccharide synthesis. [ABSTRACT FROM AUTHOR]

2‐Nitroglycal is a widely used synthon for aminoglycosides synthesis. Herein, we report an efficient method for 2‐nitroglycals synthesis using nBu4NNO3/Tf2O/DTBMP. Using 3‐O‐acetyl‐2‐nitroglycals as donors, a novel method for the construction of challenging 1,2‐cis‐2,3‐diamino‐2,3‐dideoxyglycosidic linkages was established using 4‐pyrrolidinopyridine (PPY) mediated relay glycosylation reaction. The method enjoys many features, including very mild reaction condition, excellent regio‐ and stereoselectivity, good to excellent yields and broad substrate scope. [ABSTRACT FROM AUTHOR]

Herein, we report a novel method for highly efficient and stereoselective construction 1,2-cis-2-amino-2-deoxy-glycosidic linkages using conformation-constrained 2-nitroglycal donors and bifunctional thiourea catalyst. The method enjoys mild reaction conditions, good to excellent stereoselectivity, broad substrate scope, and good to excellent efficiency. [ABSTRACT FROM AUTHOR]

The structural puzzle of amipurimycin, a peptidyl nucleoside antibiotic, is solved by total synthesis and X‐ray diffraction analysis, with the originally proposed configurations at C3′ and C8′ inverted and those at C6′, C2′′, and C3′′ corrected. A similar structural revision of the relevant miharamycins is proposed via chemical transformations and then validated by X‐ray diffraction analysis. The miharamycins bear an unusual trans‐fused dioxabicyclo[4.3.0]nonane sugar scaffold, which was previously assigned as being in the cis configuration. [ABSTRACT FROM AUTHOR]

Abstract: The proposed diastereoisomers (1 a–d) together with their C8′‐epimers (1 e–h) of amipurimycin, a unique antifungal peptidyl nucleoside antibiotic, have been synthesized for the first time. The synthetic approach is efficient and stereodivergent, and features a stereoselective aldol condensation to build the branched C9 sugar amino acid skeleton and a regio‐ and stereocontrolled gold(I)‐catalyzed N‐glycosylation to furnish the purine nucleoside. Analysis of the NMR data suggests that the previously assigned configuration of the tertiary C3′ in amipurimycin should be of opposite configuration. [ABSTRACT FROM AUTHOR]

A novel set of L-gulose and L-guluronic acid building blocks, comprising both monosaccharide and disaccharide synthons, was assembled to investigate how structural changes in these synthons influence the outcome of glycosylation reactions in which they are involved. Our studies corroborate previous reports that identified the gulosyl C4-OH group as a relatively poor nucleophile. We did not find a major influence of the neighboring C5 functionality on the reactivity of the alcohols, and the gulose acceptors did not provide more productive glycosylation reactions than their guluronic acid counterparts. The conformational behavior of the synthons was found to be of prime importance to the outcome of the reactions. [ABSTRACT FROM AUTHOR]

The total synthesis of mixed-sequence alginate oligosaccharides, featuring both β- D-mannuronic acid (M) and α- L-guluronic acid (G), is reported for the first time. A set of GM, GMG, GMGM, GMGMG, GMGMGM, GMGMGMG, and GMGGMG alginates was assembled using GM building blocks, having a guluronic acid acceptor part and a mannuronic acid donor side to allow the fully stereoselective construction of the cis-glycosidic linkages. It was found that the nature of the reducing-end anomeric center, which is ten atoms away from the reacting alcohol group in the key disaccharide acceptor, had a tremendous effect on the efficiency with which the building blocks were united. This chiral center determines the overall shape of the acceptor and it is revealed that the conformational flexibility of the acceptor is an all-important factor in determining the outcome of a glycosylation reaction. [ABSTRACT FROM AUTHOR]

The synthesis of the Staphylococcus aureus strain M capsular polysaccharide repeating unit is reported. A postglycosylation oxidation strategy was utilized for the construction of the α-galactosaminuronic acid linkages, relying on a stereoselective 2-azido-4,6-O-di-tert-butylsilylidene galactopyranoside donor, for which the selectivity was assessed by model glycosylations. The α-fucosamine linkage was installed stereoselectively, using a reactive 2-azidofucosyl donor. An unexpected glycosidic bond cleavage during the TEMPO/PhI(OAc)2-mediated oxidation of a disaccharide intermediate was circumvented by a TEMPO/PhI(OAc)2--Pinnick oxidation protocol. [ABSTRACT FROM AUTHOR]