Enantioselective Crystallization on Chiral Polymeric Microspheres

Abstract

In this article, a new approach to chiral resolution based on enantioselective crystallization on chiral polymeric microspheres is presented. To demonstrate the approach, a new synthetic method is developed for the preparation of porous and hollow chiral polymeric microspheres. Chiral microspheres based on poly(N‐vinyl α‐L‐phenylalanine) (PV‐L‐Phe) are synthesized from uniform polystyrene (PS) microsphere templates by a single‐step swelling process. The chiral microspheres display a narrow size distribution, and their properties, especially the porosity, can be controlled by varying the synthesis conditions. The chiral discrimination ability of these chiral microspheres is studied for DL‐valine crystallization, as a model system for chiral racemic crystallization. X‐ray diffraction (XRD) and differential scanning calorimetry (DSC) provide evidence for the crystallization of enantiopure crystals on the chiral polymeric microspheres. Optical rotation measurements during crystallization show an enatiomeric excess of ca. 25 % for L‐valine in the chiral microspheres. Although this excess is not yet very high, the basic principle of chiral discrimination by enantioselective crystallization on chiral microspheres is demonstrated.

Chiral Task-Specific Solvents for Mandelic Acid and Their Impact on Solution Thermodynamics and Crystallization Kinetics

“…In our studies, obviously the rule of reversal is not obeyed because the S -configured chiral solvent inhibits nucleation of the R -enantiomer of mandelic acid. This unusual effect was also reported recently by Medina et al for the enantioselective crystallization in the presence of chiral polymeric microspheres . However, the obtained nucleation behavior correlates with the presence of more stable ( R )-mandelic acid−( S )- n -propyl mandelate adducts in the solution phase.…”

Growth of Hybrid Inorganic/Organic Chiral Thin Films by Sequenced Vapor Deposition

“…In order to support our findings and to further demonstrate the enantioselective nature of the thin films, we focus on chiral recrystallization 43,44 of racemic solution over the as-prepared thin films. The chiral thin films have served as selective chiral agents during the crystallization process of supersaturated racemic solutions.…”

Particles of polyacetylene and its derivatives: preparation and applications

“…Optically active particles can be used as unique chiral additives in enantiomer crystallization, in which only one enantiomer is preferentially induced to crystallize. [112][113][114][115][116] This hypothesis was convincingly conrmed by the work of Deng and co-workers, 46 in which optically active particles derived from substituted polyacetylene successfully acted as chiral inducers. From (R)and (S)-acetylenic monomers, Chen et al prepared hollow particles denoted as (R)-and (S)-PSA particles, respectively.…”