Abstract
Selenoglycosides are used as reactive glycosyl donors in the syntheses of oligosaccharides. In addition, such heavy atom analogs of natural glycosides are useful tools for structure determination of their lectin receptors using X-ray crystallography. Some lectins, e.g., members of the tectonin family, only bind to carbohydrate epitopes with O-alkylated ring hydroxy groups. In this context, we report the first synthesis of an O-methylated selenoglycoside, specifically methyl 2-O-methyl-L-selenofucopyranoside, a ligand of the lectin tectonin-2 from the mushroom Laccaria bicolor. The synthetic route required a strategic revision and further optimization due to the intrinsic lability of alkyl selenoglycosides, in particular for the labile fucose. Here, we describe a successful synthetic access to methyl 2-O-methyl-L-selenofucopyranoside in 9 linear steps and 26% overall yield starting from allyl L-fucopyranoside.
Highlights
Since the discovery of seleno mercaptan by Siemens in 1847 [1], organoselenium compounds have attracted high attention
The first synthetic approach towards O-methylated selenofucoside 3 was based on the reported syntheses of unmodified methyl α-L-selenofucoside (1) [23] and of the reported tectonin ligand allyl 2-O-methyl-α-L-fucoside (2) [28]
The obtained crude methyl β-selenofucoside was anomerized under Lewis acid catalysis to give the anomeric mixture in a ratio of α/β = 2:1
Summary
Since the discovery of seleno mercaptan by Siemens in 1847 [1], organoselenium compounds have attracted high attention. The co-crystallization of a protein in complex with selenium-containing ligands can enable the phase determination without the need for recombinant incorporation of amino acid analogues. After the introduction of the seleno aglycon, a subsequent selective methylation was expected to lead to the desired derivative 3.
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