Synthesis of Multi Amino Acid Chiral Polymeric Microparticles for Enantioselective Chemistry

Chiral polymeric particles have emerged as a new and exciting field of research and in the last years due to their possible use for many applications in chiral chemistry. In this article, an important question is focused upon that has not been explored in detail in the field of chiral polymeric particles. The main question is whether the chiral composition of the polymeric particles affects their chiral recognition. The hypothesis is that chiral polymeric particles with a variety of different chiral groups will improve chiral recognition and improve their use of enantioselectivity crystallization. Consequently, chiral microparticles based on one up to three different amino acids based monomers are prepared by precipitation polymerization. The chiral microspheres are characterized by dynamic light scattering, scanning electron microscope (SEM), mass spectrometry (MS), and nuclear magnetic resonance (NMR) and display a narrow size distribution in the range of 1-2 mu m. The chiral discrimination ability of these chiral microspheres for enantioselective crystallization is studied in the crystallization of DL-leucine crystallization, as a model system. Time-resolved polarimetry, X-ray diffraction (XRD), and differential scanning calorimetry (DSC) are used to provide evidence for enantioselective crystallization. Surprisingly the results show that only particles composed of one amino acids monomers show the best results for enantioselective crystallization.