A facile method for the preparation of sugar orthoesters promoted by anhydrous sodium bicarbonate

A facile and eco-friendly method for the preparation of sugar orthoesters by using anhydrous sodium bicarbonate is described. Various sugar orthoesers, including sugar–sugar orthoesters, were synthesized in good-to-excellent yields by the reaction of a protected glycosyl bromide with an alcohol or sugar.

Mirror-image carbohydrates: synthesis of the unnatural enantiomer of a blood group trisaccharide

Methyl D-glucoside and d-glucose pentaacetate are transformed, respectively, into methyl alpha-O-glucuronide 3 and hydroxymethyl beta-C-glucuronide 9, which undergo decarboxylative elimination efficiently to produce 4-deoxypentenoside 4 and L-glucal 10. These unsaturated pyranosides provide an expeditious entry into mirror-image oligosaccharides, as demonstrated in the synthesis of the unnatural enantiomer of the H-type II blood group determinant trisaccharide (D-Fuc-(alpha1-->2)-L-Gal-(beta1-->4)-L-GlcNAc-beta-OMe). This work illustrates that D-glucose, a common starting material in the synthesis of naturally occurring carbohydrates, can also be used to prepare their mirror-image analogues.