The enantioselective synthesis of 2,3-dideoxy-2,2,3,3-tetrafluoro-galactose and 2,3-dideoxy-2,2,3,3-tetrafluoro-glucose

Protein-carbohydrate interactions are at the basis of cell-cell and cell-external agent interactions and therefore play a major role in the biological events in the body. However, protein-carbohydrate interactions are characterized by low binding constants and the scientific community is searching for methods for increasing the rate of binding of carbohydrates to proteins. One proposed method for increasing the binding in protein-carbohydrate interactions is the fluorination of carbohydrates. Pioneering work of DiMagno, who synthesized a racemic hexafluorinated hexose and tested its capacity of transmembrane transport, has shown that the hexafluorinated hexose crosses the erythrocyte membrane ten fold faster than glucose. It was postulated that this is because of the enhanced affinity in the protein-carbohydrate interactions, instilled by the increased hydrophobicity of the carbohydrate. This thesis describes the successful enantioselective synthesis of 2,3-dideoxy-2,2,3,3-tetrafluoro -galactose and 2,3-dideoxy-2,2,3,3-tetrafluoro-glucose and a preliminary investigation of the glycosylation of 2,3-dideoxy-2,2,3,3-tetrafluoro-galactose. A tetrafluorinated building block approach was considered for the synthesis of 2,3-dideoxy-2,2,3,3-tetrafluoro-galactose and 2,3-dideoxy-2,2,3,3-tetrafluoro-glucose. Key steps in the synthesis of galactose and glucose were the β- and α-SAD reactions for the formation of the respective diols and also for introducing the enantioselectivity in the synthesis. The pentose rings were formed by the anionic cyclization reactions, methodology which was previously developed in our group. The glycosylation was achieved via an anomeric alkylation strategy.