Synthesis of Hybrid Type Polysaccharides

杂合型多糖是植物细胞壁半纤维素的重要组成部分。这些多糖的结构含有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，具有一至三个连接至主链的单糖单元。因此，有必要制备具有规则重复单元的良好精制结构的木葡聚糖，以研究其生物活性，本课题首次利用酶促缩聚法合成了具有完整重复单元的木葡聚糖衍生物和葡甘露聚糖衍生物，并实现了由罗望子木葡聚糖制备三糖的工艺用β1，4-聚糖酶、β-葡萄糖苷酶和异苦木糖产生酶处理天然存在的木葡聚糖，得到O-α-D-吡喃木糖基-（1-6）-β-D-吡喃葡萄糖基-D-吡喃葡萄糖。异头羟基通过乙酰化、溴化、脱乙酰化和脱乙酰化转化为氟原子。在有机溶剂中进行缩聚反应，得到一种新型的支链多糖。本文还设计并制备了一种新的二糖单体（Man-Glc-F），用于酶促缩聚反应，旨在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，为利用生物质生产功能性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.