Mannose

Summary

Mannose is a sugar monomer of the aldohexose series of carbohydrates. It is a C-2 epimer of glucose. Mannose is important in human metabolism, especially in the glycosylation of certain proteins. Several congenital disorders of glycosylation are associated with mutations in enzymes involved in mannose metabolism. Mannose is not an essential nutrient; it can be produced in the human body from glucose, or converted into glucose. Mannose provides 2–5 kcal/g. It is partially excreted in the urine. Etymology The root of both "mannose" and "mannitol" is manna, which the Bible describes as the food supplied to the Israelites during their journey in the region of Sinai. Several trees and shrubs can produce a substance called manna, such as the "manna tree" (Fraxinus ornus) from whose secretions mannitol was originally isolated. Structure Mannose commonly exists as two different-sized rings, the pyranose (six-membered) form and the furanose (five-membered) form. Each

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https://en.wikipedia.org/wiki/Mannose

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Synthèse de nouveaux inhibiteurs d'A-mannosidases

Eliazar Rodriguez Garcia

DEA2002

Cell surface oligosaccharides control cell adhesion, fertilization, inflammation, the immune response and metastasis. Their biosynthesis implies sequences of reactions catalysed by glycosidases and glycosyltranferases. Inhibitors of these enzymes are therefore potential antiviral, antibacterial, antimetastatic, antidiabetes, antihyperglycemic, antiadhesive or immunostimulatory agents. Carbohydrate mimetics are among the most powerful inhibitors of these enzymes. They are more stable towards endogenous degradative enzymes, they have improved bioavailability and reduced clearances rates, and they have a higher affinity and selectivity for their cognate receptors by taking advantages of interactions that the natural saccharide does not. Besides the polyhydroxylated piperidines, pyrrolidines, indolizidines, pyrrolizidines and nortropanes, important classes of glycomimetics are C-glycosides and aza-C-disaccharides. Aza C-disaccharides are an emergent class of glycomimetics that combine the features of azasugars and C-glycosyl compounds. The first part of this work was devoted to the synthesis of new aza-C(1—>2)-disaccharides. The type of reaction applied to generate the C-C linkage-bond to join the two monosaccharide fragments was an aldol reaction. Reaction of 4,6-O-benzylidene-2-deoxy-α-D-erythro-hexopyranosid-3-ulose and a N-protected pyrrolidine-derived aldehyde generated the corresponding aldol adduct. First assays of aldol coupling gave poor yields. The reaction was improved by realizing the instability of the aldehyde partner, increasing the concentration, decreasing the temperature and by addition of HMPA as stabilizer of the enolate intermediate. From the aldol adduct a first aza-C-disaccharide with a hydroxy group on the methano linker and with D-allose configuration for the pyranose ring was prepared. In order to synthesize branched aza-C-disaccharides without heteroatom on the methano linker, dehydration of the β-hydroxyketone (aldol adduct) was done. Best results for this transformation were obtained using DAST as dehydration agent, in order to avoid secondary reactions. Dehydrated E and Z isomers were thus obtained. Further transformations from these isomers generated two other aza-C(1—>2)-disaccharides with D-allose and D-glucose configuration for the pyranose ring, respectively. In the second part of this work a new and efficient combinatorial methodology has been developed for the design and screening of new inhibitors of α-mannosidases. A family of iminederivatives was formed by mixing amines and aldehydes in a 96-wells microplate. The inhibitory activities against two different mannosidases were measured in situ. On the other hand, isolated imines showed analogous activities to the mixtures prepared in the microplates. The rapid biological screening makes the method a valuable tool. Moreover minutes amounts of products are required. This method can be applied for the discovery of new lead compounds of all classes of enzymes and biopolymers.

EPFL2005

Synthesis of novel pyrrolidine 3,4-diol derivatives as inhibitors of alpha-L-fucosidases

Claudia Bello, Inmaculada Robina, Yolanda Vera-Ayoso, Pierre Vogel

The stereoselective synthesis of new 3,4-dihydroxypyrrolidine derivatives starting from D-mannose, D-ribose and L-fucose is presented. Two synthetic strategies employing organometallic addition to hemiacetalic sugars followed by selective nucleophilic displacement or conjugate addition of ammonia to conjugate aldonic esters as key steps, are used. The new compounds were assayed for their inhibitory activity towards 13 commercially available glycosidases. Compounds that share the absolute configuration at C(2,3,4,5) of L-fucopyranosides and incorporate aromatic moieties are potent and selective inhibitors of alpha-L-fucosidases in the nM range.

2009

EPFL2005