25 化学的及び酵素的手法によるシアル酸含有糖鎖の合成研究(口頭発表の部)

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Sialic acid(NeuAc) is a ubiquitous component of glycoconjugates such as glycoprotein and glycosphingolipids. However, stereoselective and efficient introduction of NeuAc has been considered as a difficult task. In order to solve this problem, we developed the strategy depicted in Scheme 1 which takes advantage of the neighbouring group participation by the C-3 substituent (Y). As expected, NeuAc donor 4 gave the α-glycoside in a completely stereoselective manner. This methodology was then successfully applied to the synthesis of disialoganglioside GD3. (Scheme 2) Due to complete stereoselectivity and linkage specificity of glycosyltransferase(GT)-catalyzed reactions, the combined chemical and enzymatic approach is highly promising in oligosaccharide synthesis. Among various GTs, sialyltransferases(STs) are considered to be of particular importance because of the well-recognized difficulty in chemical synthesis of NeuAc glycosides. In order to make ST-assisted strategy practical and widely applicable, the substrate specificities of 2,3-STs were investigated and it was found that some modifications at C-2 position of GalNAc or GlcNAc are acceptable. (Scheme 3) The product derived from 2-O-acyl-lactose derivative 10e was further converted into ganglioside GM3. (Scheme 4) In addition, we developed the novel multienzyme system shown in Scheme 5, which utilizes trans-sialidase in combination with ST. This system was demonstrated to be applicable to the synthesis of NeuAc containing oligosaccharide which is not obtainable by ST alone.
天然有機化合物討論会の論文
1993-09-10

25 化学的及び酵素的手法によるシアル酸含有糖鎖の合成研究(口頭発表の部)

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