Pentasaccharides synthesis

For the one-pot pentasaccharide synthesis (Scheme 12), azidoglucosyl donor 29 (RRV, 53.7) was first coupled with disaccharide acceptor 30 (RRV, 18.2) and then a-methyl disaccharide acceptor 31 was added to the reaction mixture. Under these... 

Payre, N., Cottaz, S. and Driguez, H. (1995). Chemoenzymatic synthesis of a modified pentasaccharide as a specific substrate for a sensitive assay of alpha-amylase by fluorescence quenching. Angew. Chem. Int. Ed. Engl. 34, 1239-1241. 

V. K. Rajput and B. Mukhopadhyay, Concise synthesis of a pentasaccharide related to the anti-leishmanial triterpenoid saponin isolated from Maesa balansae, J. Org. Chem., 73 (2008) 6924—6927. 

An intramolecular acetal has also been introduced by the treatment of a mixture of a 1-thio-mannoside, having a methoxybenzyl protecting group at C-2 and an alcohol with DDQ [71] (Scheme 4.4c). Activation of the thioglycoside with methyl triflate gave a P-mannoside as the only anomer. This approach was employed for the synthesis of the core pentasaccharide of N-linked glycoproteins. 

The crown jewel in the application of the sulfoxide method to the assembly of natural products is the synthesis of a pentasaccharide from the antibiotic moeno-mycin A, wherein each glycosidic bond was formed in a stereocontrolled manner by one variant or another by the sulfoxide method (Scheme 4.63) [373],... 

Scheme 4.63 Multiple use of the sulfoxide glycosylation in the synthesis of the moenomycin A pentasaccharide.

With this solid-phase methodology in hand, the synthesis of branched oligosaccharides could be investigated. This led to the preparation of pentasaccharide 15 related to /V-glycan chains (Scheme 4.5).3... 

For this purpose, Ag zeolite and Ag, developed by Garegg25 and Paulsen,26 respectively, have been widely employed (Scheme 7.6). Reactions using these activators have found practical use in synthetic studies on glycoprotein glycans and glycolipids. For instance, Paulsen reported the chemical synthesis of the core pentasaccharide structure 6 common to all types of Asn-linked glycans, using the Ag... 

Scheme 13.16 Synthesis of an Asn-Core pentasaccharide bidding block.

The anticoagulant fondaparinux, a synthetic analogue of the terminal fragment of heparin, is synthesized using multiple protection/deprotection steps that result in a route of up to 50 steps. There is, as yet, no enzymatic system that approaches the capability to make such a molecule." As this modified pentasaccharide is a natural product, it should, in theory, be accessible through a series of biotransformations, but we currently lack the biocatalytic tools to achieve more than a few steps and would stiU need to use some protection steps to avoid multiple products. Enzymatic synthesis in vivo depends largely on the levels and selectivities of glycosylating enzymes to achieve multistep reactions, a situation that has been mimicked in vitro for simpler systems." ... 

Jain, R. K. Matta, K. L., Chemical synthesis of a hexasaccharide comprising the Lewis(x) determinant linked beta-(l->6) to a linear trimannosyl core and the precursor pentasaccharide lacking fucose. Carbohydr. Res. 1996,282, 101-111. 

Sdieme 2. Synthesis of sulfated Trestatin A pentasaccharide substructure 13... 

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