Study On The Crystallization And Chiral Resolution Of Aspartic Acid

In addition to glycine,the other natural amino acids have chiral alpha carbon atoms with D-and L-type enantiomers.In the achiral environment,the two enantiomers have similar physical and chemical properties,while they often exhibit different properties in the chiral environment,especially in pharmacological and physiological effects.Therefore,the preparation of single chiral amino acids has attracted extensive attention,and the chiral resolution of racemes has always been a research hotspot.Like most other amino acids,DL-aspartic acid?Asp?crystallizes as a racemic compound under natural conditions in aqueous solution,so obtaining the mixture crystals?D crystal+L crystal?is an important step in chiral separation.In this paper,the crystalline form of aspartic acid was affected by changing the solvent.The racemic DL-aspartic acid was resolved by using additives or L-cysteine self-assembled monolayers in ethanol-water mixed solvents,and pure D-aspartic acid crystals were obtained.The specific research contents and results are as follows:?1?The ethanol solvent was added to change the crystalline form of aspartic acid.Ethanol was rapidly added into saturated racemic aspartic acid aqueous solution,and the crystal state of aspartic acid was observed in different volume ratio VEtOH/VH₂O ethanol-water mixed solvents.The experimental results show that when VEtOH/VH₂O reaches 3:2,mixture crystals of aspartic acid are obtained,and the transformation from racemic compound DL crystal in aqueous solution to mixture crystals?D Crystal+L crystal?cin water-ethanol solution is realized.?2?The addition of additive L-Phenylalanine?Phe?in ethanol-water mixed solvent inhibited the crystallization of L-aspartic acid,and a mixture crystal of excess D-aspartic acid was obtained.Using a series recrystallization,the obtained crystal was formulated into the next crystallization solution,and 5 mol%of L-Phe was also added and crystallized in a mixed solvent of VEtOH:VH₂O=1.5:1.The mixture crystal of larger ee was obtained.After several recrystallization,the pure D-aspartic acid was finally obtained.?3?L-Cys SAMs can chirally recognize D-/L-aspartic acid in ethanol-water mixed solvents,and D-aspartic acid was excessive in the crystals of the mixture crystal obtained on the membrane.Similarly,pure D-aspartic acid was obtained on SAMs by series enrichment recrystallization in a mixed solvent of VEtOH:VH₂O=2:1,and DL-aspartic acid was successfully resolved.