Design And Synthesis Of Carbohydrate-Derived Chiral Catalysts And Their Apphcation In Asymmetric Catalysis

This thesis mainly focused on the design, synthesis and application of chiral carbohydrate-derived chiral catalysts s. We reviewed systematically the concept of chirality, the history of development and the strategy of asymmetric synthesis and their application in the synthesis of chiral drugs and natural products. We also summarized the reactions of asymmetric synthesis which were related to our subject recent years, especially, the rections and methods of asymmetric synthesis using carbohydrates as the chiral reagents, chiral auxiliaries, organocatalysts and chiral ligands. The research results are summarized below:1. A series of novel carbohydrate-derived phosphine ligands have been synthesized and been applied in the palladium-catalyzed asymmetric allylic alkylation. The advantage of these chiral ligands is that they can be easily prepared from inexpensive crude material, be stable in air and be prepared in high yields. The effects of solvents, temperature, the structure of ligands etc. for the asymmetric allylic alkylation are investigated, which has the advantages of high yields and high enantioselectivity, some coordination styles and catalytic mechanisms were also discussed.2. We have developed a new type of carbohydrate-derived prolinamide organocatalysts, which is capable of catalyzing asymmetric aldol reaction. The parameters including solvents, temprature, additives and the structure of substrates were systematically examined, a remarkably better catalytic performance was provided by the reactions in terms of productivity, diastereoselectivity enantioselectivity in water. The recycling of the catalytic system essentially retained its catalytic activity, and only slightly decrease in enantioselectivity was observed after five cycles. We also advised a possible mechanism of reaction and a transition state for the aldol reaction.3. We have described the first application of carbohydrate-based amino alcohols as organocatalysts in the enantioselective aldol reactions of ketones with isatins and its derivatives. A variety of isatins were used as substrates and the corresponding aldol products were obtained in high yields and with moderate enantioselectivities. The influence of the D-glucosamine moiety on the enantiose-lectivity of the product of the aldol reaction was studied by modifying the size of the alkyl group at the anomeric position. The mechanism for reaction catalyzed by chiral amino alcohols was also proposed.