Synthesis Of Novel Chiral Chelating Extractants And Study On Extraction Resolution Of D/L-phenylalanine

Phenylalanine（α-amino-β-phenylpropionic acid）, can be chemically synthesized to obtainthe racemate. L-phenylalanine have physiological activity, they are used to producesweeteners. D-phenylalanine can enhance the body’s immune function which plays a vitalrole in the produce of AIDS virus inhibitors. So it is necessary to separation the racemate ofPhenylalanine. In this paper, four types of chiral extractants were synthesized: L-tartaric acidoctyl ester, L-phenylalanine n-butyl acetate, L-phenylalanine n-octyl ester, N-butyl-L-phenylalanine methyl ester. The extractants were characterized by infrared spectrum （IR）,nuclear magnetic resonance （1H NMR） and the high performance liquid chromatography（HPLC）, and their purity were determined. Using these four kinds of chiral separationagents of the obtained above, the research of chelating extraction of the Cu（Ⅱ） ion andresolution of the raceme of phenylalanine was conducted. The main contents are as follows:1. Using L-tartaric acid and octyl alcohol as raw materials, toluene as solvent, p-toluenesulfonic acid as the catalyst, L-tartaric acid octyl ester was synthesized, which is whitepowder, and its melting point is41-42℃. L-tartaric acid octyl ester is characterized by1HNMR, the results showed that the purity of the product was over97%. The yield was44%.2. L-phenylalanine methyl ester and n-butanal as the raw material by Schiff base reaction,and the C=N was reduced by hydrogen with Pd-C catalyst, N-butyl-L-phenylalanine methylester was obtained. The product was characterized and the yield was above70%.3. L-Phenylalanine butyl ester was synthesized with L-Phenylalanine, n-butyl alcoholand SOCl₂. L-Phenylalanine ocyl ester was prepared with L-Phenylalanine, n-octyl alcoholand p-toluenesulfonic acid as catalyst. The yields of ester were over84%and53%,respectively.4. The extraction behavior of L-tartaric acid octyl ester, L-phenylalanine n-butyl acetate,L-phenylalanine n-octyl ester, N-butyl-L-phenylalanine methyl ester for copper ion wasinvestigated. We found that L-tartaric acid octyl ester as the chrial extractant, the extractiondistribution ratio is low due to their structure. N-butyl-L-phenylalanine had been found thatit isn’t suitable to act as chiral extractant for its bigger solublity in water. 5. The extraction behavior of Cu （Ⅱ） ion with L-PAnOE and L-PAnBE was investigatedin detail. The effect of various factors on the extraction distribution ratio was investigated.The main contents are as follows:（1） The extraction distribution ratio （D） increase with an increase in the concentration ofNaCl. Copper extraction rate is above99%when the concentration of NaCl in the aqueousphase is up to3.0mol/L. This condition meets the requirements for the extraction ofphenylalanine.（2） The extraction distribution ratio was increased with the increase in the concentrationof extractant. The research shows that the formation of the extraction compound molecule is1:1for Cu²⁺and extractant.（3） The extraction distribution ratio was decreased with the increase in the temperature,which demonstrated that the extraction reaction is exothermic. Raising temperature woulddecrease the reaction.（4） The effect of diluent on the extraction ratio was investigated. The extraction inchloroform system achieves the best, sowe use chloroform as the diluent in the followingstudy.6. Ninhydrin color method was used to detect the content of amino acid in extractedwater phase. The sodium hydroxide method is established to remove Cu（Ⅱ） in the extractedwater phase absolutely, which is a great novelty of this paper.7. The extraction behavior of Phe with PAnOE and PAnBE was investigated. The maincontent was as follows:（1） The extraction distribution ratio had little change with the increasing in theconcentration of phenylalanine, which suggested that the extraction is a simple extractionprocess.（2） With the increase in Cu （Ⅱ） ion, the extraction distribution ratio was increased. If theconcentration of Cu （Ⅱ） ion is too high, it will exceed the load capacity of the organic phase tolead to the formation of the third phase. We can improve the extraction capacity ofD/L-phenylalanine by controlling the amount of Cu （Ⅱ） ion.（3） The extraction capacity of chiral extractants for L-phenylalanine is higher than thatfor D-phenylalanine. The extraction distribution ratio is not high, The separation factor can reached to2.02, which provided an important theoretical and experimental basis for furtherstudy on the separation of D/L-phenylalanine.（4） With the increase in the temperature, the extraction distribution ratio was decreased,which demonstrated that the extraction reaction is exothermic, and high temperature woulddecrease the reaction.