Assembly Of Tetrameric Mannan Phosphate And Trimer Acetylglucosamine Phosphate By Ionic Liquid-supported Oligosaccharide Synthesis

Phosphoglycan is a natural polysaccharide composed of multiple glycosyl phosphate repeating units.It is an important part of the cell wall and capsular polysaccharide of many pathogenic microorganisms.It is also an important virulence factor of pathogenic microorganisms.It has immunological activity and can therefore be used as antigenic determinants are used to develop glycoconjugate vaccines to prevent microbial infections.The cell wall polysaccharides of yeast Saccharomyces cerevisiae and Kloeckera brevis are composed of mannans with a-(1?6)phosphodiester linkages.This polysaccharide has an important regulatory effect on the body's immune system.Neisseria meningitidis is a gram-negative diplococcus,which is the main cause of global bacterial meningitis and sepsis.The capsular polysaccharide on the surface of Neisseria meningitides X(Men X)is composed of acetylglucan linked by a-(1?4)phosphodiester bond,which is a potential immune antigen molecule.It is of great significance to develop fast and efficient synthetic methods to prepare polysaccharide antigens for vaccine research.In this paper,Ionic liquids(IL)-loaded oligosaccharide synthesis strategies are developed,which are used for a-(1?6)phosphodiester linkage of manntetraose 1 and a-(1?4)phosphodiester linkage of acetylglucosamine 14.This paper first designed a new benzyl-type IL carrier containing 5-aminopentanol linking arm,which can be prepared by four-step reaction.Subsequently,mannose and glucosamine were used as starting materials to obtain ?-mannose phosphite 3 and ?-2-azide glucose phosphite 16 through 4-step and 10-step reactions.The ionic liquid carrier and intermediate 3 undergo five steps of H-phosphite chemical condensation,oxidation,purification,deprotection and purification to achieve the growth of sugar chains on the ionic liquid.This process was repeated four times to synthesize the mannotetraose 2 with a-(1?6)phosphodiester linkage in 45 h and 18 steps with a yield of 29.80%.Using the same strategy,the ionic liquid carrier and intermediate 16 were repeated three times to synthesize the acetylglucosamine 15 with a-(1?4)phosphodiester linkage in 81 h and 22 steps with a yield of 14.60%.After each step of the reaction,the "dissolution-precipitation" method is used to quickly purify the target product,without the need for time-consuming and laborious silica gel column chromatography.Finally,after removing the protective group of compounds 2 and 15,the benzyl protecting group,benzyloxycarbonyl group and ionic liquid carrier are removed in one step by hydrogenolysis method catalyzed by palladium-carbon.We get oligosaccharide antigens tetrameric mannan phosphate and trimer acetylglucosamine phosphate with aminopentanol structure.The antigen can be further linked to the carrier protein for immunological research.