A-Mannopyranosides

Klein D, Braekman JC, Daloze D, Hoffmann L, Demoulin V (1997) Lyngbyaloside, a Novel 2,3,4-Tri-0-methyl-6-deoxy-a-mannopyranoside Macrolide from Lyngbya bouillo-nii (Cyanobacteria). J Nat Prod 60 1057... 

Molecular recognition experiments were carried out with a racemic mixture of phenyl-a-mannopyranoside 2 (Fig. 2) in a heterogeneous phase as well as in a homogeneous phase depending on the solubility of the microgel in the... 

The regiochemistries of reactions on dibutylstannylene acetals of a-mannopyranosides having only the c/s-l,2-diol on 0-2 and 0-3 free are much more complicated than those just discussed. By far the greatest extent... 

Pietraszkiewicz, M., Kozbial, M., Pietraszkiewicz, O. (1997). Chiral recognition of amino acids by diaza crown ethers and crowns incorporating a mannopyranoside unit, immobilized in a supported liquid membrane. Enantiomer, 2, 319-25. 

Figure 2.9 Predicted H1-H2 dihedral angles for [3- and oc-glucopyranosides (top) and P- and a-mannopyranosides (bottom).

Carbohydrate-binding studies indicate a specificity similar to Con A the pea lectin binds mannose, glucose, fructose and L-sorbose with methyl a-mannopyranoside being the most potent inhibitor of phosphomannan-lectin precipitation [88]. 

Klein, D., Braekman, J. C., Daloze, D., Hoffmann, L., and Demoulin, V. (1997). Lyngbyaloside, a novel 2,3,4-tri-0-methyl-6-deoxy-a-mannopyranoside macrolide from Lyngbya bouillonii (Cyanobacteria). J. Nat. Prod. 60, 1057-1059. 

The syntheses of sucrose 6 -phosphate, methyl a-mannopyranoside 4- and 6-phosphates, and 3-deoxy-3-fluoro-D-glucose 1- and 6-phosphates [ (57) and (58) ] have been described. Neither (57) nor (58) was a substrate for UDPGlc-pyrophosphorylase or phosphoglucomutase, although (58) was a poor substrate for glucose 6-phosphate dehydrogenase. ... 

Z. Yang, H. Cao, J. Hu, R. Shan, and B. Yu, 1 ->2 Migation and concurrent glycosylation of phenyl 1-thio-a-mannopyranosides via 2,3-O-cyclic dioxonium intermediates, Tetrahedron, 59... 

Schlaf and co-workers have studied the regiochemical outcomes of palladium- and iridium-catalyzed silylations of pyranosides [106,107]. Similar distributions ofbis-or tris-silylated regioisomers were obtained using heterogeneous (palladium (0) nanoparticles) or homogeneous (iridium(I) phosphine complex) catalysis, as exemplified by the results obtained for methyl a-mannopyranoside (Scheme 30). fii general, these catalyst systems resulted in silylation of the most sterically accessible OH group(s). 

Azidophenyl-a- -mannopyranoside, 85 4-Azidophenylphosphoric acid, 652 4-Azido-/3-D-xylopyranoside, 86 Azidopurines, 79 Azidopsrriniidines, 79 Azidoquinones, 99 Aziiidinum ion, 578... 

P-selectivities in the anomeric 0-alkylation of tetraacetylgluco- (23) and -gal-actopyranose (24), and of heptaacetyllactopyranose (25) with decyl triflate at room temperature [9], This procedure is applicable to the synthesis of P-lactosyl ceramide. Klotz and Schmidt converted heptaacetyllactose (25) with the triflate and nonaflate(nonafluorobutane-sulfonate) of azidosphingosine (31 and 32) into P-lactosyl ceramide (33) in 49 and 42% yield, respectively (Scheme 8). In contrast, tetraacetylmannopyranose (26) was converted to decyl a-mannopyranoside (20) stereoselectively at —40 °C as shown in Scheme 7. This a-selectivity arises as a result of steric and electronic effects of the nucleophile and the reduced reactivity of the p-... 

Glycosylation of 3,4,6-tri-O-benzylglucopyranose (42) via stannylene acetal with methyl iodide resulted in the production of the 2-0-methyl ether (70%) and a-methyl glycoside (30%) [20], presumably as a result of the formation of stannylene acetal on axial 0-1 and equatorial 0-2, The equatorial 0-2 is more reactive during stannylene complexation, which leads the 2-0-methyl ether. Thus stannylene-mediated alkylation of 6-0-tritylmannose and methyl a-mannopyranoside afforded 3-0-alkylated products because of the greater reactivity of the equatorial oxygen at the 3-position [20]. The reaction mechanism is discussed in detail in Section 8.3.4. 

Activation of 54 with NIS and a catalytic amount of TMSOTf gave the bridged a-mannopyranoside 55 in 54yo yield (Scheme 16). 

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