Oligosaccharides biological synthesis

Loewus, F. (1965) Inositol Metabolism and Cell Wall Formation in Plants , Federation Proceedings of the Federation of American Societies for Experimental Biology, 24, 855-62 Lotan, R. (1980) Effects of Vitamin A and its Analogs (Retinoids) on Normal and Neoplastic Cells , Biochimica et Biophysica Acta, 605, 33-91 Lowden, J.A O Brien, J.S. (1979) Sialidosis a Review of Human Neurominidase Deficiency , American Journal of Human Genetics, 31, 1-18 Lucas, J.J., Waechter, C.J. Lennarz, W.J. (1975) The Participation of Lipid-linked Oligosaccharide in Synthesis of Membrane Glycoproteins , Journal of Biological Chemistry, 250,1992-2002... 

VIII. Synthesis of Biologically Active Carba-oligosaccharides. 74... 

The chemical synthesis of oligosaccharides is also more complicated than the synthesis of other biopolymers, because the construction of each individual oligosaccharide poses a new challenge, requiring a knowledge of methods, together with experience and experimental skill. Thus, there are no universal methods available neither for biological in vivo nor for chemical in vitro syntheses. 

Example 5 Hayakawa and Noyori group in their studies on new activators for phosphoroamidite coupling reactions have applied the most effective member of the group of acid/azole complexes AT-(phenyl)imidazolium tri-flate (N-PhIMT) in the efficient synthesis of biologically important compounds [20j]. A noteworthy example is synthesis of cytidine-5 -monophos-pho-AT-acetylneuraminic acid. This compound is a source of sialic acid in the sialyltransferase-catalysed biosynthesis of sialyl oligosaccharides [25]. 

The sulfated oligosaccharides discussed above were highly, but not completely, sulfated so that mixtures of compounds with a slightly different sulfation pattern resulted. An attempt to understand which sulfation site was important for the biological activity of tetrasaccharide 15 was made by the synthesis of mono-and oligodeoxygenated analogues of 15. These tetrasaccharides were prepared in a block synAesis approach comparable to Ae synthesis of 15, and the deoxy Anctions were essentially mtroduced on the di- or tetrasaccharide level. A representative synAetic example is depicted in Scheme 4 [44]. 

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