Jie Tang

H2SO4-SiO2: Highly Efficient and Reusable Catalyst for per-O-Acetylation of Carbohydrates Under Solvent-Free Conditions

Sulfuric acid immobilized on silica gel (H2SO4-SiO2) was used as an efficient promoter for per-O-acetylation of carbohydrates with acetic anhydride under solvent-free conditions. The substrates include not only monosaccharides and disaccharides, but also glycosides. The catalyst is recyclable and stable at room temperature, and the reaction protocol is simple, is cost-effective, and gives good isolated yield with high purity. The large-scale reactions also proceeded conveniently and in high yields.

A Facile H2SO4-SiO2–Catalyzed Ferrier Rearrangement of 3,4,6-Tri-O-benzyl-d-glucal

Sulfuric acid immobilized on silica gel (H2SO4-SiO2) was used as an efficient and convenient promoter for Ferrier-type rearrangement of 3,4,6-tri-O-benzyl-d-glucal in CH2Cl2, which is a difficult donor for this type of reaction. The acceptors include primary alcohols, secondary alcohols, pentanol, halogenated alcohol, sterols, thiol, and 2-naphthol. Thus, 2,3-unsaturated glycosides were obtained rapidly (<2 h) and efficiently (>62%) in good α-selectivity (α/β>4.2:1) under mild conditions.

FeCl3·6H2O/C: An Efficient and Recyclable Catalyst for the Synthesis of 2,3-Unsaturated O- and S-Glycosides

A novel method for synthesizing 2,3-unsaturated glycosides has been developed using a handy and eco-friendly immobilized catalyst, FeCl3·6H2O/C. A series of 2,3-unsaturated O- and S-glycosides were obtained for bioassay from corresponding 3,4,6-tri-O-acetyl-D-glucal and D-galactal in good to excellent yields (56%–99%) and high anomeric selectivity (α/β = 7:1 to >19:1). Furthermore, the catalyst was efficient on gram-scale reactions and recyclable for at least three times.

Facile TMSOTf-catalyzed preparation of 2-deoxy α-O-aryl-D-glycosides from glycosyl acetates.

Abstract2-Deoxy α-O-aryl glycosides were conveniently obtained by reaction of 2-deoxy-glycosyl acetates with phenols in the presence of TMSOTf as the promoter. The current method provides the O-aryl glycosides with good to excellent yields, and sole alpha selectivity.n Figureu2009

A highly efficient deprotection of the 2,2,2-trichloroethyl group at the anomeric oxygen of carbohydrates.

Commercially available zinc dust in the presence of ammonium chloride in acetonitrile at reflux removes the 2,2,2-trichloroethyl (TCE) group at anomeric centers with excellent yields (>95%) in short reaction times. This present method is easily implemented on substrates containing acyl and benzyl groups and large-scale reactions also proceed in high yield.

Vinyl acetate and sodium carbonate as a fast and efficient catalyst for per-O-acetylation of monosaccharides

Vinyl acetate and sodium carbonate catalysed acetylation of several monosaccharides is an efficient synthesis of per-O-acetylation of carbohydrates and achieve the products in excellent yields and short reaction times. d-Glucose as the substrate in large scale also proceeds in high yield.

4-Nitro­phenyl α-l-rhamnopyran­oside hemihydrate

The absolute configuration of the title compound, C12H15NO7·0.5H2O, was assigned from the synthesis. There are two rhamnoside molecules and one water molecule in the asymmetric unit, displaying O—H⋯O hydrogen bonding. One of the nitro groups does not conjugate efficiently with the benzene ring.

α-Selective synthesis of 2-deoxy-glycosides and disaccharides

GRAPHICAL ABSTRACT ABSTRACT A metal-free catalytic method for the synthesis of 2-deoxy glycosides and disaccharides has been developed using stable 2-deoxy glucosyl and galactosyl acetate donors. They could react with a variety of acceptors in the presence of catalytic amount of TMSOTf at 0°C to form glycosides, glycoconjugates, and disaccharides with excellent α-selectivity (> 19:1) and yields (up to 99%) in a short time (0.5 h). With this expedient method, several new compounds against human K562 and SMMC7721 cell lines were obtained and tested with in vitro antitumor bioactivities.