Highly efficient chiral extraction of 4-nitro-phenylalanine enantiomers using PFA derivatives with different steric groups

Abstract

This study aimed to develop new and efficient chiral extractants which have good abilities to chiral extract amino acid and/or mandelic acid racemes. PFA, a famous ferrocenyl diphosphine ligand, was employed as a chiral extractant and its extraction properties were investigated. It was found that (S, Sp)-PFA-Pd is a good extractant to enantioseparate 4-nitro-phenylalanine (Nphe) with a separation factor of 1.77. Furthermore, a series of PFA derivatives with different steric groups in central chirality were synthesized and their extraction properties were also investigated. The results show that the separation factors for amino acid and mandelic acid are all improved by structure modification of PFA. (R, Sp)-PFA-4-Pd exhibits the highest separation factor (13.52) for Nphe to date. This work provides a highly efficient chiral extractant to separate Nphe. And the influence rules of the steric groups on extractions also have a great significance to design and structural modify new chiral extractants in future work.