A Synthesis of Methyl 3-O-(β-d-Mannopyranosyl)-α-d-mannopyranoside from Sulfonate Intermediates

Abstract

Methyl 3-O-(β-d-mannopyranosyl)-α-d-mannopyranoside was synthesized by the reaction of 3,4,6-tri-O-benzyl-2-O-benzylsulfonyl-1-O-tresyl-d-mannopyranose with methyl 2,4,6-tri-O-benzyl- and 2,4,6-tri-O-(p-bromobenzyl)-α-d-mannopyranoside, followed by deprotection. The corresponding 1-O-(β-tolylsulfonyl)derivative gave better yield and stereoselectivity in the reaction with methanol, but was not sufficiently reactive to couple with a hindered secondary alcohol. The 2-O-benzylsulfonyl group is comparable in β-directing effect to 2-O-methylsulfonyl group, but its stereoselectivity is dependent on the structure of the reactant alcohol. It can be selectively removed by the reaction with sodium amide in N,N-dimethylformamide.

Cross‐reactivity between the mannan of Candida species, Klebsiella K24 polysaccharide and Salmonella C1 and E O‐antigens is mediated by a terminal non‐reducing β‐mannosyl residue

“…Other synthetic saccharides were made as described below. The disaccharides P-D-Manp-( 1+6)-u-~-Manp-l-OMe and p-D-Manp-( 1 +2)-a-~-Manp-l-OMe were respectively synthesized by a silver-zeolite-promoted coupling (Garegg and Ossowski, 1983) between 2,3,4,6-tetra-O-benzyl-a-~-mannopyranosyl bromide (Helander et al, 1992) and either methyl-2,3,4-tri-O-benzyl-a-~-mannopyranoside (BorCn et al, 1972a) or methyl-3-O-benzyl-4,6-O-benzylidene-a-~-mannopyranoside (Awad et al, 1986). The resulting protected disaccharide derivatives were isolated by silica-gel chromatography and subjected to hydrogenolysis over palladium on carbon to give the deprotected target compounds.…”

Strategies of Synthetic Methodologies for Constructing β-Mannosidic Linkage

“…A strategy for the stereoselective synthesis of βmannosides has been developed over the years based on variable introduction of an electronegative group on 2-O of a reactive mannosyl donor [28,29,31,33,[63][64][65]. The electronwithdrawing nature of this group has been considered for inducing the existence of the C-1 in the donor to be intimate ion-pair intermediate during the mannosylation reaction.…”

“…Reaction of 6 8 with silver 2,2,2trifluoroethanesulfonate (tresylate), followed by reaction with 2-[4-(p-toluenesulfonamido) phenyl]ethanol afforded the corresponding β-mannopyranoside 69, which is of great value as precursor for complex oligosaccharides of biological significance (Scheme 18). The 2-O-benzylsulfonyl group on mannosyl donors was found to have a comparable β-directing effect to the 2-Omesyl group and it can be selectively removed by reaction with sodium amide in N,N-dimethylformamide [33], which turned to give excellent β-selectivity when a proper leaving group on 1-C is selected [33,65]. The donor 70 was prepared by the same method used for the corresponding 2-O-mesyl analog.…”

“…Thus, the βanomers 86 and 87 were isolated in 57 and 45% yield, respectively [66]. Deprotection of the 2-O-benzylsulfonyl group was readily performed by the action of sodium amide in DMF at room temperature [31,33] (Scheme 20).…”

“…Reviews on the synthesis of β-mannoglycosides and oligosaccharides have been published [24][25][26][27]. Owing to the importance of this linkage as shown above, it becomes interesting to review the various developed strategies including our work [28][29][30][31][32][33] for constructing the βmannosidic linkage. The different goals are included, however some of them are of limited use, but it may be developed and/or modified to be used in future.…”