The utility of glycoside copper chelates for effecting regioselective glycosidation

Boronic Acid-Catalyzed Regioselective Koenigs-Knorr-Type Glycosylation

Boronic acid-catalyzed regioselective Koenigs-Knorr-type glycosylation is presented. The reaction of an unprotected or partially protected glycosyl acceptor with a glycosyl halide donor in the presence of silver oxide and a low catalytic amount of imidazole-containing boronic acid was found to proceed smoothly, which enables construction of a 1,2-trans glycosidic linkage with high regioselectivities. This is the first example of the use of a boronic acid catalyst to initiate regioselective glycosylation via the activation of cis-vicinal diols in glycosyl acceptors.

Stereo- and regioselective glycosylation with protection-less sugar derivatives: an alluring strategy to access glycans and natural products

This review delivers insights for dedicated chemists into the development of efficient methods in accessing carbohydrates at a lower cost.

Efficient synthesis of methyl lycotetraoside, the tetrasaccharide constituent of the tomato defence glycoalkaloid α-tomatine

Branched oligosaccharide lycotetraose, beta-D-glucopyranosyl-(1-->2)-[beta-D-xylopyranosyl-(1-->3)]-beta-D-glucopyranosyl-(1-->4)-beta-D-galactopyranose, is a key constituent of many steroidal saponins, including glycoalkaloid alpha-tomatine, which is involved in protection of plants from invading pathogens. A new synthesis of the methyl beta-lycotetraoside () is described. Key steps of the synthesis include two successive glycosylation reactions of disaccharide acceptor methyl (4,6-O-benzylidene-3-O-p-methoxybenzyl-beta-D-glucopyranosyl)-(1-->4)-2,3,6-tri-O-benzyl-beta-D-galactopyranoside with readily available benzoylated trichloroacetimidates of alpha-D-glucopyranose and alpha,beta-D-xylopyranose. This scheme allows sequential glycosylation in one-pot on account of the convenient in situ removal of a p-methoxybenzyl protecting group under the acid conditions of the first glycosylation step. Following deprotection, tetrasaccharide was obtained in 19% yield over eight steps.