Regioselective Carbohydrate Protection And Fabrication Of The Three Dimensional Function Carbohydrate Sensor Chips

Carbohydrates play key roles in intercellular processes, including recognition fertilization and development, regulation of signaling and so on. Abnormal changes in the carbohydrate composition will lead to diseases, for example tumor, autoimmune disease, infection or other major diseases. In cells, sugar chain is mostly composed of mannose, galactose, N-acetyl glucosamine and other carbohydrates. In order to clarify the mechanisms and develop new therapeutics, chemical synthesis of carbohydrates is indispensable. Firstly,syntheses of the sugar chain conclude two key issues: the first is how to simplify connecting ways of all kinds of sugar blocks to synthesize the oligosaccharide efficiently; the second is how to economically synthesize all kinds of target sugar blocks. Therefore, efficient synthesis of target sugar block based on protection and selectively protection strategy has always been the key issue of carbohydrate chemistry research, and the selective protection of carbohydrate hydroxyl group is still a serious challenge. Secondly, following genomics and proteomics, to study the structure and function of carbohydrates, especially the biological mechanisms of carbohydrates plays an important role and it has become a hot spot in life science. The glycomics research emphasizes developing a rapid, efficient and high throughput method to determine the cell surface carbohydrate structures and functions. Meanwhile, carbohydrate microarray technology, a novel tool emerging at the frontier of glycomics and glycobiology, having the advantages of small amount of sample needed, high specificity and high throughput, is of great significance to the study of carbohydrate-protein interactions and the development of the functional glycomics. This paper have mainly studied in several contents and described as follows:1. Based on the alkali catalyzed regioselectivity of protection carbohydrateThis paper discussed the carbohydrate hydroxyl steric hindrance and stereo electronic effect, and used the alkali as catalyst development a novel efficient regioselective protection carbohydrate strategy. Firstly, a novel method for an efficient regioselective acetylation of carbohydrates and diols in aqueous solution is described. Treatment of substrates with 1-acetylimidazole, tetramethyl-ammonium hydroxide(TMAH) in water under mild conditions gave highly regioselective acetylation for primary hydroxyl groups. This discovery provides an eco-friendly way for selective acetylation of non-protected glycosides and diols in water, avoiding the use of toxic organic solvents and the necessity of pre-protection of secondary hydroxyl groups. Secondly, the metal-free organobase-catalyzed regioselective benzoylation of diols and carbohydrates has been developed. Treatment of diol and carbohydrate substrates with 1.2 equiv. of 1-benzoylimidazole and 0.2 equiv. of 1,8-Diazabicyclo[5.4.0]undec-7-ene(DBU) in Me CN under mild conditions gave highly regioselective benzoylation for primary hydroxyl group. Importantly, comparing with the most used of 6-OH protecting bulky groups, the 6-OH protecting benzoyl group supplied a new protection strategy.2. Preparation of the three-dimensional(3D) carbohydrate chipIn this paper, 4-Azido-2,3,5,6-tetrafluorobenzoic acid(PFPA) is inserted onto Quartz Crystal Microbalance(QCM) sensor chip with the motivation of ultraviolet(UV) light to fabricate the carboxyl chip,and then through the amidation reaction three-dimensional tree molecular is immobilized on the chip. At the same time, we use the click reaction to immobilize azide carbohydrate on the prepared 3D-carbohydrate chip. We synthesize 3D matrices by using an efficient azide-alkyne click reaction to fabricate 3D chip for gaining the sugar cluster effect on amplification of the weak interactions of carbohydrate – protein; develop a new method for the efficient syntheses of a variety of derivatives of monosaccharides only one steps by using the hexafluorophosphate. And this method provides an efficient and universal way in fabrication of carbohydrate microarrays.