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

为开发低聚糖的自动合成技术，对低聚糖的固相合成进行了研究。固相低聚糖合成中最根本的问题是聚合物载体的非均质性，导致固体载体上的糖基化不足。本研究开发了两种高效固相合成低聚糖的新方法。一是利用特定反应分离产物的一种新的捕获-释放方法。通过叠氮基与聚合物负载的膦之间的易反应，从粗混合物中选择性地分离出含有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。葡萄糖β1- 3glc β1- 3glc （Glcβ1-6）通过固体载体上的糖链延伸，从树脂上裂解受保护的低聚糖，分离并释放，最后脱保护，合成了葡萄糖β1- 3glc。二是利用具有炔基功能的糖基受体与碘苯酰胺在载体上的Sonogashira偶联反应选择聚合物载体上的反应区。连接部位采用炔基甲基糖苷或炔酯。用Co_2(CO)_8和TFA处理这些连接体。后一连接体在基本条件下也发生了裂解。糖基化反应在载体的选定区域顺利进行，以定量产率得到所需的糖苷。利用市售的多功能合成器进行了低聚糖的自动合成。

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.