Synthesis The Disaccharide Substrate For Endo-glycosidase

As one of the most important three natural big molecules, Polysaccaride is widely used in medicine, food and some other fields.A class of Endo glycosidases has been found which have a good effection in catalytic synthesis of polysaccharides, for which can identified the oxazoline structure of disccharides.Enzymatic synthesis requires a structure with an oxazoline as its substrate,this thesis synthesize respectively obtain disaccharide glycoside substrate by chemical way.First of all,i protect the-OH of glucose with acetylation, then using bromine replace the 1-OAc to obtain the donor.This monosaccharide easily hydrolyzed, require to keep in low temperature storage, also we should boil away the water inside with toluene before we use it;Then next,when i use the glucosamine hydrochloride as the material of disaccharide acceptor, i should keep other-OH in protecting but 4-OH;So using phthalates in protecting the amino,and the acetyl protecting hydroxy.Introducing the benzyl in the 1 position selectively.Delete the acetyl so i can connect the 4-OH and the 5-OH by benzaldehyde dimethyl acetal,leaving only the 3-OH to protect with benzyl.Utilizing the triethylsilane(Et3SiH) to selectively open the loop to gain the 4-OH disaccharide receptor.Finally,i synthesize the the disaccharide with silver trifluoromethanesulfonate(AgOTf).We also intent to add some function groups acetylenyl at the second position of acceptor.So i use the coupling agent EDC to couple the alkyne acid with NHS. Deprotected disaccharide can use DMC, Et3 N reacting in strong alkaline water.After purificating we obtain the oxazoline disaccharide.Then you can use Endo-A-glucosidase catalytic synthesize polysaccharides.