Studies On The Novel Glycosylations

Part 1:Study on the glycosylation of glycosyl N-tosyl benzimidate donorOligosaccharide and glycoconjugate are applied to the connection of various of biological activity intramolecularly and intermolecularly. The glycosylation plays an important role in the synthesis of oligosaccharide and glycoconjugate. The glycosyl donor have great influence on stereoselectivity and yield of glycosylation product, so different glycosyl donors ared developed. For example, trichloroacetimidate donor, N-phenyl trifluoroacetimidates donor (PTFAI). Their instability lead that they cannot become the ideal glycosyl donor. So developing a new glycosyl donor owned wider application, better activity, better stereoselectivity is in demand.N-sulphonyl imidates as an prodrug or nucleophile react with imine. However, there have not the report about the preparation of N-tosyl glycosyl donor and its application in the glycosylation reaction which is the content of the paper.The paper reports the synthesis of imine chloride and then it has reactions with the glycosyl hemiacetal to get eight new N-tosyl ester glycosyl donors in existence of anhydrous K2CO3 with a high rate. In order to investigate its applicability, we use them to have cross glycosylation reactions with glycosyl receptor possessing different steric hindrance and electronic effect in the action of TMSOTf promoter. We synthesis nineteen glycoside products, among them, the number of the products which have the yield of above 90% is nine; the number of good stereoselectivity products is eighteen; single configuration are nine. Therefore, new N-tosyl ester glycosyl donor has advantages of simple operation, good stability, good activity, wide range, high yield and mild reaction conditions. It not only enriches the existing glycosylation method and synthetic strategy, but also expands the application of imidate donor in the synthesis of Carbohydrate Chemistry.Part 2:Study on the synthesis of the β-Mannoside(3-D-Mannoside and Mannuronic acid are the common composition of diverse bioactivity natural products. They are difficult to synthesize, because the unfavorable anomer effect and the steric hindrance effect in the C2 place. At present, there are numerous reports about the methods of synthesis of β-Mannoside, but their applications are limited owing to the harsh reaction condition and complicated operation and so on. Recently, a large number of reports about gold catalyst has caused the attention of scientific researchers, we are no exception. Therefore, the primary content of the paper is also include the selective synthesis of β-Mannoside with the golden catalytic promoter.The paper reports o-iodine benzoic acid as the starting compound to synthesis o-hexynebenzoic acid through three simple steps of methylation, alkynylation and hydrolysis reaction. We use Mannose as the starting compound to synthesis 2,3-O-benzyl-4,6-O-benzylidene Mannose benzoate and Mannuronic benzoate through a series of protection operation. Then we get the 2,3-O-phenyl-4,6-O-benzilidene Mannoside benzene sulfonic acid ester donor and Mannuronic acid benzene sulfonic acid ester donor with the o-hexynebenzoic acid under the action of condensation reaction. Next, they have cross glycosylation with a series of glycosyl receptor in the action of gold catalyst (4-MeOPh)3PAuB(C6F5)4 to investigate the β selectivity of the donor and the golden catalyst. We synthesis tweentyseven glycoside compounds, among them, the number of the products which have the yield of above 80% and β configuration are sixteen. Therefore, Mannose benzoate donors have good β selectivity under the action of golden catalyst. This method also has merits of mild reaction conditions, simple operation, high yield and provides methodology basis for the synthesis of β-Mannose derivatives.