Glycyrrhizic Acid Based Self-assembled Helical Nanostructures As Scaffolds For Asymmetric Diels-alder Reaction

Gels are common ingredients in everyday life,such as hair gels,contact lenses,lithium grease,and jelly gel-like desserts.In nature,gels belong to the category of colloids because gels disperse gelling agent molecules(solid,continuous phase)in solvents(liquid,dispersed phase).More attention is now being paid to a different type of gel,the supramolecular gels,which are fibrous aggregates of small molecules that are not covalently bonded.Supramolecular gels,mainly by small molecular gelling agents through the synergistic non-covalent bond force in the solvent medium self-assembly formed by the formation of cross-linked three-dimensional network structure.These non-covalent bond interactions usually include hydrogen bond interactions,hydrophilic and hydrophobic solvent interactions,electrostatic interactions,subject and object interactions,?-? interactions,coordination effects,and so on.The spiral structure is one of the most interesting chiral structures in nature.In biological systems,helical structures are ubiquitous,such as double-stranded DNA1 and alpha-helical proteins,all of which are involved in a variety of physiologically active functions in organisms.It has become possible to artificially synthesize a spiral structure,but artificial synthesis has been faced with many shortcomings such as complicated synthesis steps,low product rate,and high cost.There are many natural macromolecules in nature that form a regular helical structure under the action of supramolecular chemistry.In this paper,glycyrrhizic acid was used as the helical molecular skeleton studied in this paper.Glycyrrhizic acid(GA),a traditional herbal medicine,can self-assemble into spiral nanofibers in water.The resulting helical nanostructures can be used as scaffolds to catalyze asymmetric Diels-Alder reactions.By co-assembly with a series of achiral copper ligands,the chirality of the GA helix nanostructures can be transferred to the catalytic sites and the resulting assembly exhibits catalytic enantioselectivity for the Diels-Alder reaction.In this paper,the morphology and catalytic properties of glycyrrhizic acid were studied from two aspects.1.In this paper,some achiral copper ligands were synthesized and assembled with glycyrrhizic acid to study their assembly morphology.2.Asymmetric catalytic Diels-Alder study by two assembly methods.As shown in the paper,the assembly morphology of glycyrrhizic acid hydrogel and the catalytic asymmetric catalytic reaction were investigated by two assembly methods.It was found that the ligand was assembled at a low concentration(1 mol%-5 mol%)with glycyrrhizic acid.It can be kept in a good spiral fiber structure.When using this as a catalyst,two different results can be obtained in two ways.A catalyst can obtain a faster reaction rate,but the enantioselectivity is lower than only 29%ee value.The higher enantiomer selection can be obtained by the reaction of catalyst B.The sex has a 61%ee value,but the reaction rate is reduced.The possibility of using supramolecular helical structure as asymmetric catalytic framework is discussed.For the next step of the work to lay a good foundation and accumulated experience.