Kajihara Yasuhiro, Yoshihara Akiko, Hirano Kiriko, Yamamoto Naoki
International Graduate School of Arts and Sciences, Yokohama City University, 22-2, Seto, Yokohama 236-0027, Japan.
Carbohydr Res. 2006 Jul 24;341(10):1333-40. doi: 10.1016/j.carres.2006.04.037. Epub 2006 May 15.
Access to glycopeptides with C-terminal thioester functionality is essential for the synthesis of large glycopeptides and glycoproteins through the use of native chemical ligation. Toward that end, we have developed a concise method for the synthesis of a glycopeptide thioester having an intact complex-type dibranched disialyl-oligosaccharide. The synthesis employed a coupling reaction between benzylthiol and a free carboxylic acid at the C-terminus of a glycopeptide in which the peptide side chains are protected. After construction of glycopeptide on the HMPB-PEGA resin through the Fmoc-strategy, the protected glycopeptide was released upon treatment with acetic acid/trifluoroethanol and then the C-terminal carboxylic acid was coupled with benzylthiol at -20 degrees C in DMF. For this coupling, PyBOP/DIPEA was found to be the best for the formation of the thioester, while avoiding racemization. Finally, the protecting groups were removed in good yield with 95% TFA, thus affording a glycopeptide-thioester having an intact and homogeneous complex-type disialyl-oligosaccharide.
通过使用天然化学连接法合成大型糖肽和糖蛋白时，获得具有C端硫酯功能的糖肽至关重要。为此，我们开发了一种简洁的方法来合成具有完整复合型二分支二唾液酸寡糖的糖肽硫酯。该合成方法采用苄硫醇与糖肽C端游离羧酸之间的偶联反应，其中肽侧链受到保护。通过Fmoc策略在HMPB-PEGA树脂上构建糖肽后，用乙酸/三氟乙醇处理使受保护的糖肽释放，然后在-20℃下于DMF中将C端羧酸与苄硫醇偶联。对于这种偶联反应，发现PyBOP/DIPEA最适合硫酯的形成，同时避免消旋化。最后，用95%的三氟乙酸以良好的产率除去保护基团，从而得到具有完整且均一的复合型二唾液酸寡糖的糖肽硫酯。
