Mannosides

Mannosides are difficult to obtain since here a 2-O-acyl group blocks the -position. 2-O-Benzyl-a-mannosyl bromides give, however, high yields of pure -glycosides with a heterogeneous silver silicate catalyst preventing anomerization and SnI reaction of the bromide H. Paulsen, 1981 B, Q. 

D-Methyl mannoside with 2 M KSCN at pH 7.5 in potassium phosphate buffer... 

Methyl a-D-mannopyranoside was treated in succession with p-toluene-sulfonyl chloride, carbonyl chloride, and benzoyl chloride, and, without isolating the intermediates, there was obtained in 37% yield methyl 4-0-l enzoyl-2,3-O-carbony 1-6-0-(p-tolylsulfonyl ) -D-mannoside. The tos-yloxyl group of the latter was replaced by iodine, and hydrogenation of the 6-iodo derivative in the presence of a nickel boride catalyst gave methyl 4-0-benzoyl-2,3-0-carbonyl-6-deoxy- -D-mannoside. Treatment of the latter with hydrogen bromide in acetic acid gave crystalline 4-0-benzoyl-2,3-0-carbonyl-6-deoxy-a-D-mannosyl bromide (8) (16). The... 

Structure and Reactivity of Anhydro-sugars. Part I. Branched-chain Sugars. Part I. Action of Di-ethylmagnesium on Methyl 2 3-Anhydro-4 6-0-benzylidene-a-D-mannoside, A. B. Foster, W. G. Overend, M. Stacey, and G. Vaughan,/. Chem. Soc., (1953) 3308-3313. 

Acidification with trichloracetic acid catalyses oxidation , the fractional increase in the rate coefficient per mole of acid added, viz. Ak/ko)/[sicid], being of the order of two. Strong catalysis by alkali metal acetates has been observed for several oxidations, e.g. of m-cyclohexane-l,2-diol °, formic acid , methyl mannoside and galactoside and several a-hydroxycarboxylic acids °. 

J. J. Grimaldi, B. D. Sykes 1975, (Con-canavalin A a stopped flow nuclear magnetic resonance study of conformational changes induced by Mn++, Ca++, and alpha-methyl-D-mannoside),/. Biol. Chem. 250, 1618. 

Carbon atom D-Gulose Me a-D-guIoside D-Mannose Me a-D-mannoside... 

The methyl 2,3,4-trimethyl-a-D-mannuronoside (XLI) was synthesized from methyl 2,3,4-trimethyl-a-D-mannoside by the method pre-... 

Three routes to the synthesis of D-mannuronic acid (XLIII) are now known. The first42 was based on the original method of Fischer and Piloty48 and involved the reduction of D-mannosaccharodilactone (XLII) with sodium amalgam. The second44 utilized methyl 2,3-isopropyli-dene-a-D-mannoside (XLIV) which was oxidized at C6 with alkaline potassium permanganate to methyl isopropylidene-a-D-mannuronoside ... 

R. Roy, D. Page, S. F. Perez, and V. V. Bencomo, Effect of shape, size, and valency of multivalent mannosides on their binding properties to phytohemagglutinins, Glycoconj. J., 15 (1998) 251-263. 

FIG. 3. Early mannoside clusters used as ligands for E. coli FimH.61 62... 

In this context, Lindhorst et al. proposed biological investigations of pentaerythri-tol-based mannoside clusters to test their capacity to block the binding of E. coli to yeast mannan in vitro.75 In all of the proposed structures, and according to a rational approach, pentaerythritol itself, as well as the included C3 spacers, were used as structural components for substituting the inner regions of the monosaccharide moieties (Scheme 4). The tetravalent cluster 27 has been efficiently synthesized according... 

Further, dendritic growths with new multiarmed clusters having more flexibility and various geometries have also been considered by the authors. Thus, the hexato-sylated dipentaerythritol 39 was converted into hexaazide 40, which upon treatment with propargylated mannoside 29 under standard conditions of click chemistry and subsequent O-deacetylation afforded the hexavalent cluster 42 in good (61%) yield over two steps (Scheme 6). 

Recently, Gouin et al. have designed a tetravalent cluster (60)84 based on a potent E. coli FimH ligand heptyl x-D-mannoside (59)85 that has been preliminarily recognized as a strong binder to FimH, with a KD of 5 nM, as determined by SPR measurements (Fig. 5). Furthermore, this derivative inhibited both adhesion of... 

Con A by the mannoside cluster at concentrations slightly above the nanomolar range, according to a mannose-dependent and partially reversible process. Finally, these results suggested that, rather than an increased avidity for Con A, the unusual potency of these molecular glycoasterisks was due to an efficient and kinetically controlled macromolecular assembly that strongly amplified the effect of these low-valency ligands. 

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