Efficient Route to 2-Deoxy β-O-Aryl-d-Glycosides via Direct Displacement of Glycosyl Iodides

Glycosyl iodides. History and recent advances

The use of glycosyl iodides as an effective method for the preparation of glycosides has had a recent resurgence in carbohydrate chemistry, despite its early roots in which these species were believed to be of limited use. Renewed interest in these species as glycosylating agents has been spurred by their demonstrated utility in the stereoselective preparation of O-glycosides, and other glycosylic compounds. This review provides a brief historical account followed by an examination of the use of glycosyl iodides in the synthesis of oligosaccharides and other glycomimetics, including C-glycosylic compounds, glycosyl azides and N-glycosides.

Direct and stereoselective synthesis of alpha-linked 2-deoxyglycosides

alpha-Linked 2-deoxyglycosides were conveniently obtained by employing a glycosyl donor having a participating ( S)-(phenylthiomethyl)benzyl moiety at C-6, whereas 2,6-dideoxy-alpha-glycosides could be prepared by BF 3.Et 2O-promoted activation of allyl glycosyl donors.

Stereoselective synthesis of sugar nucleotides using neighboring group participation

A straightforward, efficient method for the chemical synthesis of sugar nucleotides derived from D-mannose and L-fucose precursors is described. This synthetic strategy involves the coupling of acylated glycosyl bromides with nucleoside 5'-diphosphates, which enables the exploitation of neighboring group participation to exclusively prepare diastereomerically pure sugar nucleotides of desired 1,2-trans anomeric configuration. This is the first stereoselective direct coupling approach to sugar nucleotide synthesis. Following deprotection using triethylamine and purification via C18 reversed-phase ion-pair chromatography, UDP- and GDP-alpha-D-mannose as well as UDP- and GDP-beta-L-fucose were obtained in good yield in only four synthetic steps from D-mannose and L-fucose.

Stereo- and regioselective glycosylations to the bis-C-arylglycoside of kidamycin

In explorations toward the total synthesis of the antitumor anthrapyran natural product kidamycin, the regioselective introduction of aminosugars angolosamine and vancosamine as C-arylglycosides has been accomplished onto hydroxylated anthrapyran aglycones. Specifically, the 9,11-dihydroxylated anthrapyran A undergoes sequential glycosylations with angolosamine synthon B and vancosamine synthon C to regio- and stereoselectively afford bis-C-glycoside D corresponding to the C-glycoside pattern of kidamycin.

Synthesis of aryl-2-deoxy-d-lyxo/arabino-hexopyranosides from 2-deoxy-1-thioglycosides

The synthesis of either anomers of aryl 2-deoxy-D-glycopyranosides from 2-deoxy-1-thioglycosides is reported. The alpha-anomers form as the major product when thioglycosides react with differently substituted phenols and naphthols, in the presence of N-iodosuccinimide/triflic acid. On the other hand, reaction of the thioglycosides with bromine initially, followed by reaction with aryloxy anions lead to aryl 2-deoxy-beta-D-glycosides with high specificities.