Tris-mannoside

Figure 5.20 Tris-mannoside structure identified from acyl hydrazone DCL targeting Con A.

M. Touaibia, T. C. Shiao, A. Papadopoulos, J. Vaucher, Q. Wang, K. Benhamioud, and R. Roy, Tri- and hexavalent mannoside clusters as potential inhibitors of type 1 fimbriated bacteria using pentaerythritol and triazole linkages, Chem. Commun. (2007) 380-382. 

Starting from methyl glucoside 39, the 2,4-triflate intermediate 55 could be produced as well (Scheme 16). The 4-triflate of this intermediate was subsequently inversed to the corresponding 4-0-acetyl intermediates 56 by substitution with tetrabutylammonium acetate, followed by inversion of the 2-position by tetrabutylammonium nitrite, to yield methyl 3,4,6-tri-O-acetyl mannoside 58. When the intermediates 55 were first inversed to the corresponding 4-hydroxyl groups intermediates 57 via the use of tetrabutylammonium nitrite, directly followed by inversion of the 2-position by tetrabutylammonium acetate, methyl 2,3,6-tri-O-acetyl mannoside 59 was efficiently produced. 

An intermediate in Hudson s synthesis4 of D-rhamnose (24) is methyl 2,3,4-tri-0-benzoyl-6-deoxy-a-D-mannoside (25). Frequently, direct replacement of the methoxyl group at C-l of O-acylated hexopyranosides by halide proceeds with difficulty (or not at all) however, treatment of (25) with hydrogen bromide in acetic acid resulted in the slow replacement of the methoxyl group by bromide ion, to give the desired 2,3,4-tri-O-... 

Ault, Haworth and Hirst47 first synthesized the methyl a-D-glycoside methyl ester of 2,3,4-tri-O-methyl-D-mannuronic acid by successive treatment of potassium (methyl a-D-mannopyranosid)uronate with dimethyl sulfate and sodium hydroxide, and then methyl iodide and silver oxide. Although no crystalline derivatives were isolated, there is little doubt about its structure, since the authors48 subsequently proved the presence of a pyranose ring in the starting material for the synthesis, methyl 2,3-O-isopropylidene-a-D-mannoside. The uronic acid has also been synthesized by Smith, Stacey and Wilson,28 who oxidized methyl... 

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