ABSTRACT
Compared with the racemate of chiral drugs, enantiopure chiral drugs have been the hot spot of drug research because of their higher selectivity and lower side-effects. Although remarkable progress of asymmetric synthesis has been achieved in the last decades, chiral resolution is regarded as an important approach to obtain chiral drugs. Recent research advancements in the field of chiral resolution of racemic drugs and intermediates are reviewed here. It is clear that combination of chiral separation and racemization to improve the resolution efficiency has become a trend of chiral resolution. In addition, we also introduce some novel resolution methods, such as chiral extraction, membrane resolution, and resolution using nanoparticles.
ABSTRACT
Production of chiral amines and unnatural amino-acid using ω-transaminase can be achieved by kinetic resolution and asymmetric synthesis, thus ω-transaminase is of great importance in the synthesis of pharmaceutical intermediates. By genomic data mining, a putative ω-transaminase gene hbp was found in Burkholderia phytofirmans PsJN. The gene was cloned and over-expressed in Escherichia coli BL21 (DE3). The recombinant enzyme (HBP) was purified by Ni-NTA column and its catalytic properties and substrate profile were studied. HBP showed high relative activity (33.80 U/mg) and enantioselectivity toward β-phenylalanine (β-Phe). The optimal reaction temperature and pH were 40 ℃ and 8.0-8.5, respectively. We also established a simpler and more effective method to detect the deamination reaction of β-Phe by UV absorption method using microplate reader, and demonstrated the thermodynamic property of this reaction. The substrate profiling showed that HBP was specific to β-Phe and its derivatives as the amino donor. HBP catalyzed the resolution of rac-β-Phe and its derivatives, the products (R)-amino acids were obtained with about 50% conversions and 99% ee.