Development of automated synthesis of oligosaccharides based on solid-phase methodology

为了发展低聚糖的自动化合成，对低聚糖的固相合成进行了研究。固相低聚糖合成中最基本的问题是聚合物载体的异质性，导致固体载体上糖基化作用不足。本研究开发了两种高效固相合成低聚糖的新方法：一种是利用特定反应对产物进行捕获和释放分离的新方法；通过叠氮基与聚合物支载的膦之间的简单反应，从粗混合物中选择性地分离出具有4-叠氮基-3-氯苯基的所需化合物。该方法成功地应用于低聚糖激发子的固相合成。Glcβ1-3Glcβ1-3(Glcβ1-6)Glcβ1-3Glc是通过固体载体上糖链的延长、被保护的低聚糖从树脂上断裂、捕捉释放分离和最终脱保护而合成的；另一种是利用载体上具有炔基功能的糖基受体与载体上的碘苯甲酰胺发生Sonogashira偶联反应来选择聚合物载体上的反应区。以炔基甲基苷或炔基酯为连接物。用CO_2(CO)_8和TFA处理后，这些连接子被切割。后者的连接子在碱性条件下也被切割。糖基化反应在载体的选定区域顺利进行，以定量的方式得到所需的糖苷。利用市售多用途合成器实现了寡糖的自动化合成。

Solid-phase synthesis of oligosaccharides was investigated in order to develop automated synthesis of oligosaccharides. The most fundamental problem in solid-phase oligosaccharide synthesis is heterogeneity of polymer supports that causes insufficient glycosylation on solid support. Two new methods were developed for efficient solid-phase synthesis of oligosaccharides in the present study.The one is a new catch-and-release method of isolation for products using a specific reaction. Desired compounds possessing the 4-azido-3-chlorobenzyl group were selectively isolated from a crude mixture by means of the facile reaction between the azido group and polymer-supported phosphine. This method was successfully applied to the solid-phase synthesis of an oligosaccharide elicitor. Glcβ1-3Glcβ1-3 (Glcβ1-6)Glcβ1-3Glc was synthesized via elongation of saccharide chain on solid-support, cleavage of the protected oligosaccharide from the resin, catch-and-release isolation, and final deprotection.The other is selection of reactive region on polymer supports by using Sonogashira coupling reaction of glycosyl acceptors having an alkyne function with iodobenzamide on supports. Alkynylmethyl glycoside or alkyne ester was used as linker parts. These linkers were cleaved by treatment of Co_2(CO)_8 and TFA. The latter linker was also cleaved under basic conditions. The glycosylation reaction smoothly proceeded on the selected area of the supports to give the desired glycosides in quantitative yields.Automated synthesis of oligosaccharides was carried out by using commercially available multipurpose synthesizer.