Studies On Design And Preparation Of Chiral Functionalized Hydrotalcite And Its Application In Enantioseparation

The biological activity,metabolism and toxicity of different enantiomers of chiral drugs are often quite different,making enantioseparation a focus in the production of chiral drugs.However,since the enantiomers of chiral compounds have the identical or similar physical and chemical properties,chiral separation is challenging.Layered double hydroxides（LDH）with unique two-dimensional structures,interlayer anion exchangeability,tunability of interlayer space,and good biocompatibility can provide a new tool for chiral separation.On the one hand,chiral functional recognition molecules can be modified on LDH substrates to separate chiral compounds by the exchangability of anions between LDH layers.On the other hand,the advantages of LDH can provide abundant recognition sites for the recognition of molecules,such as large specific surface area,easy functionalization,ect.Therefore,this paper focuses on the construction of chiral recognition functionalized hydrotalcite and its application in chiral separation.The main research work is as follows:（1）Designing chiral adsorption separation material with high enantioselectivity and stability is an important route to realize the enantioselective recognition and separation of racemic molecules.Here,we designed and synthesized camphor sulfonic acid derivatives（CSA）as a chiral resolving agent,and modified it on Mg/Al layered double hydroxide（Mg/Al-LDH）through electrostatic self-assembly to construct functionalized chiral adsorption separation material（CSA@LDH）,It could be served as an adsorbent for enantioselective recognition and separation of propranolol enantiomers（R,S-PRO）.The layered structure of CSA@LDH maintains the advantage of limited chiral space of CSA to achieve the selective enrichment of R-PRO,and the e.e.%value of single separation could reach 19.5%.Meanwhile,density functional theory（DFT）calculations showed that chiral recognition and separation were ascribed to the discrepancy in affinities stemming from the difference ofπ-πinteraction force and hydrogen bonding capacity of CSA with R,S-PRO.Hence,considering the superior ability of hydrogen bond coordination and stereocontrol of camphor sulfonic acid derivatives,this strategy is expected to provide useful reference for the other similar the development and application of other similar chiral resolution agents.（2）A novel biocatalysis system（LAAO@LDH）for efficient stereoconversion of tryptophan was constructed by modifying L-amino acid oxidase（LAAO）on LDH by electrostatic self-assembly.LAAO could specifically oxidize the amide group in L-tryptophan to produce imino acid,and the intermediate product could be continuously reduced to D and L-tryptophan by the reducing agent NH₃·BH₃.The reaction process was repeated to achieve the purpose of cyclic preparation of D-tryptophan,with ultra-high conversion rate（89%）and e.e.%（over 99%）.In addition,the ZnMgAl-LDH with large-scale lamellar structure not only overcame the limitation of the substrate size,but also the mesoporous structure of LDH materials was beneficial to reduce the mass transfer resistance in catalytic reactions to improve the catalytic activity.In view of this,the constructed chiral reactor is expected to achieve the synthesis and transformation of a series of pure D-amino acid enantiomers.