Trifluoroethylsulfonate protected monosaccharides in glycosylation reactions

A variety of sulfo-protected monosaccharide donors and acceptors were investigated in glycosylation reactions. Trifluoroethylsulfonate (SO3TFE) group was compatible with a wide range of activation conditions commonly used with fluoride, imidate, and sulfide donors. In addition, the influence of a SO3TFE group, at the critical 2-position in glycosyl donor, on the stereoselectivity of the glycosylation reaction was studied. 2004 Elsevier Ltd. All rights reserved. Glycosaminoglycans (GAGs) are linear, polydisperse acidic polysaccharides that occur ubiquitously in animal tissues, membranes, intracellularly in secretory granules or extracellularly in the matrix. GAGs contain repeating units of hexosamine, either glucosamine (GlcNp) or galactosamine (GalNp), and uronic acid, either glucuronic acid (GlcAp) or iduronic acid (IdoAp). The biological significance of these sulfated oligosaccharides have made them the object of numerous studies for synthetic carbohydrate chemists for several decades. However, due to their structural complexity, GAG synthesis has remained an important challenge. Recent advances in oligosaccharide preparation, such as automated solid phase synthesis, have shown promising results, allowing faster access to the molecules of interest. Nevertheless, these approaches still require preparation of suitably designed monomers. Positions that will ultimately contain sulfo groups must be masked with temporary protecting groups, deprotected after assembly of the oligosaccharide and sulfonated. Thus, such strategies require long multi-step synthetic sequences and intensive protecting group manipulation. Additionally, sulfonation reactions can be troublesome and often sluggish at the higher 0040-4039/$ see front matter 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.tetlet.2004.06.131