Solid-phase synthesis of sialylglycopeptides through selective esterification of the sialic acid residues of an Asn-linked complex-type sialyloligosaccharide
Solid-phase synthesis of sialylglycopeptides through selective esterification of the sialic acid residues of an Asn-linked complex-type sialyloligosaccharide
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DOI：
10.1002/anie.200250572
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发表时间：
2003-01-01
影响因子：
16.6
通讯作者：
Kajihara, Y
中科院分区：
文献类型：
--
作者：
Yamamoto, N;Ohmori, Y;Kajihara, Y
糖蛋白和糖肽在其肽骨架上含有O-或N-连接的寡糖，并在几种生物事件中发挥核心作用。[1]因此，能够合成糖蛋白和糖肽用作探针以研究其生物学作用是必不可少的。[2-4]已经报道了一种基于肽的固相化学合成和通过糖苷内切酶Endo M将唾液酸寡糖酶促连接到肽上的化学酶促方法用于合成N-连接唾液酸糖肽。[3a然而，由于所用的酶不是商业上可获得的，并且由于酶促方法通常需要底物特异性，[5]化学合成对于制备纯唾液酸低聚糖是必不可少的。迄今为止，还没有固相化学合成具有N-连接复合型双触角唾液酸低聚糖结构的糖肽，这种结构在报道的糖蛋白中常见，因为关于这些化合物的固相合成存在两个主要问题，第一个问题是糖肽的唾液酸键在95%三氟乙酸（TFA）存在下发生酸催化水解的趋势，在固相糖肽合成的最后裂解步骤中。[6]α-2，6和α-2，3唾液酸键都非常不稳定，但前者尤其如此。如果α-2，6唾液酸低聚糖要抵抗酸水解，则应使用吸电子基团如乙酰基作为保护基团。[3g]避免唾液酸键水解的另一种方法是使用复杂的接头，如HYCRON，其可以在温和条件下裂解。[7]第二个问题是所需复合型唾液酸低聚糖的量。如果IOmg十肽（MW ca. 1000）连接到复合型双触角唾液酸低聚糖（MW约1000）上。2000）通过固相肽合成，必须使用至少20 mg的寡糖。
Glycoproteins and glycopeptides contain O-or N-linked oligosaccharides on their peptide backbones and play a central role in several biological events.[1] Thus, it is essential to be able to synthesize glycoproteins and glycopeptides for use as probes to study their biological roles.[2–4] A chemoenzymatic method based on the solid-phase chemical synthesis of peptides and the enzymatic attachment of a sialyloligosaccharide to the peptide by the endoglycosidase enzyme Endo M has been reported for the synthesis of N-linked sialylglycopeptides.[3a, 4] However, as the enzyme used is not commercially available and as the enzymatic method often requires substrate specificity,[5] chemical synthesis is essential for the preparation of pure sialyloligosaccharides. To date there has been no solid-phase chemical synthesis of glycopeptides with the N-linked complex-type biantennary sialyloligosaccharide structure that is commonly found on glycoproteins reported, as there are two major problems concerning the solid-phase synthesis of these compounds.The first of these problems is the tendency of the sialyl linkage of glycopeptides to undergo acid-catalyzed hydrolysis in the presence of 95% trifluoroacetic acid (TFA) during the final cleavage step in solid-phase glycopeptide synthesis.[6] Both α-2, 6 and α-2, 3 sialyl linkages are very labile, but particularly the former. If α-2, 6 sialyloligosaccharides are to resist acid hydrolysis, an electron-withdrawing group such as an acetyl group should be used as a protecting group.[3g] Another way to avoid hydrolysis of the sialyl linkage is to use a sophisticated linker such as HYCRON, which can be cleaved under mild conditions.[7] The second problem is the quantity of complex-type sialyloligosaccharide required. If 10mg of a decapeptide (MW ca. 1000) is to be attached to a complex-type biantennary sialyloligosaccharide (MW ca. 2000) by solid-phase peptide synthesis, at least 20 mg of the oligosaccharide must be used.