Synthesis of Hybrid Type Polysaccharides

杂交型多糖是植物细胞壁中最重要的半纤维素成分。这些多糖的结构包含一个β-1，4连接的D-吡喃葡萄糖残基和各种单糖，如甘露糖和木糖。木葡聚糖是一种杂多糖，主链上连接着一到三个单糖单元。本课题首次通过糖基氟化物单体的酶促缩聚反应合成了具有完美重复单元的木聚糖衍生物和葡甘聚糖衍生物。以天然生成的罗望子木葡聚糖为原料，用O-α-D-xylopyranosyl-(1-6)-β-D-glucopyranosyl-D-glucopyranose.-1、4-葡聚糖酶、β-葡糖苷酶和异丙米韦糖产酶处理木葡聚糖制备三糖。异构羟基通过乙酰化、溴化、氟化和脱乙酰化转化为氟原子。在有机溶剂中进行缩聚反应，得到了一种新型的支链多糖。还设计并制备了一种新的双糖单体(Man-GLC-F)用于酶促缩聚，用于合成人工葡甘露聚糖衍生物。在此基础上，提出了“糖化学循环系统”这一概念，为生物质生产功能多糖材料提供了新的思路。

Hybrid type polysaccharides are the most important components of hemicellulose in plant cell walls. The structure of these polysaccharides contains a β-1, 4 linked D-glucopyranose residue with various monosaccharides such as mannose and xylose. Xyloglucan is a heteropolysaccharide with one to three monosaccharides units linked to the main chain. It is, therefore, necessary to prepare a xyloglucans having a well-refined structure with a regular repeating unit in order to investigate its biological activities, physical and chemical properties.The present project deals with the first synthesis of xyloglucan derivatives and glucomannan derivatives with a perfect repeating unit by the enzymatic polycondensation of glycosyl fluoride monomers.Preparation of trisaccharide from xyloglucan from Tamarindus has been achieved by treating naturally occurring xyloglucan with β1, 4-glycanase, β-glucosidase, and isoprimeverose producing enzyme, affording O-α-D-xylopyranosyl-(1-6)-β-D-glucopyranosyl-D-glucopyranose. The anomeric hydroxy group was converted to the fluorine atom via acetylation, bromination, fluorination, and deacetylation. The polycondensation was carried out in an aqueous organic solvent, giving rise to a novel branched polysaccharides. A new disaccharide monomer (Man-Glc-F) has also been designed and prepared for the enzymatic polycondensation, aiming at the synthesis of artificial glucomannan derivatives. Based on these results, a term "Glycochemisty Cycle System" has been proposed as a new concept for production of functional polysaccharide materials from biomasses.