Synthesis Of Novel Macrocyclic Oligosaccharides Based On Lactose /Galactose Via The Click Reaction

Cyclodextrins are formed from D-glucose units connected by ?-1,4-glycosidic bonds,which is widely used as natural macrocyclic oligosaccharides.It can be used as the host to form the complex with the small guest molecule,because of its structure of hydrophilic surface and hydrophobic cavity.However,due to the presence of disadvantage like a certain size with relatively rigid structure,a single type of sugar and so on,CDs can not meet the requirement of including all kind of the guest molecule.So,synthetic macrocyclic oligosaccharides was needed and significant.Thus we put forward our project that synthesis of lactose 1,3'-,1,4'-and galactose 1,3-triazolyl linkage macrocyclic oligosaccharide.We started with lactose/galactose and introduced azide group and alkynyl directly at corresponding hydroxy.Then we got lactose 1,3'-,galactose 1,3-and lactose 1,4'-triazolyl linkage macrocyclic oligosaccharide from the monomer by click reaction.The monomer was obtained from lactose,which linked azide at 1-OH and alkynyl at 3'-OH.Then though the click reaction,lactose 1,3'-triazolyl linkage macrocyclic oligosaccharide was got.Comparing with cyclodextrins,this macrocyclic structure is more flexible and changeable.The structure simulation of the macrocyclic revealed that it is a long and narrow structure by Gaussian 09.The length is about 7 ? and the width is about 3.4-4 ?.We selected the small molecular like propargyl alcohol,n-propanol,ethylene diamine as the guest to take the inclusion experiment.Though the study of capacity of inclusion of the host,it shown the host and guest were forming 1:1 complex.The result matched with computer simulation data.The association constant of macrocyclic with prop4 argyl alcohol and n-propanol are 29.74 ± 1.6 M-1 and 8.66 ± 0.29 M-1.Then galactose 1,3-triazolyl linkage macrocyclic oligosaccharide was got using galactose instead of lactose.The result shown it was a tetramer,whose flexible cavity diameter was about 8.5 ? by structure simulation.So the bigger molecules were chosen as the guest like benzyl alcohol,methyl gallate and p-toluenesulfonic acid.Then the computer simulation of the inclusion experiment showed one macrocyclic could include two benzyl alcohol and just one methyl gallate.We continued to synthesizing the lactose 1,4'-triazolyl linkage macrocyclic.These three macrocyclic had different structure but interrelated which greatly enriched categories of macrocyclic oligosaccharides by the click reaction.Though the click reaction,we synthesized lactose 1,3'-and galactose 1,3-triazolyl linkage macrocyclic oligosaccharide.The synthetic route had less steps and was simple,which was very significance in carbohydrate synthesis.