Solvent-Dependent Conformational Diversity of Polysaccharide-Based Chiral Selectors

Area of Science:

• Analytical Chemistry
• Physical Chemistry
• Materials Science

Background:

• Chiral separations are crucial in the pharmaceutical industry.
• Polysaccharide derivatives are widely used as chiral stationary phases (CSPs) for enantiomer separation.
• Accurate structural and dynamic information of CSPs is needed to optimize separation efficiency.

Purpose of the Study:

• To investigate the structure and dynamics of two representative polysaccharide-based chiral selectors: amylose tris(3,5-dimethylphenylcarbamate) and cellulose tris(3,5-dimethylphenylcarbamate).
• To assess the conformational flexibility of these selectors under conditions relevant to reversed-phase liquid chromatography (RPLC).

Main Methods:

• Explicit solvent molecular dynamics simulations were employed.
• Analysis of conformational ensembles and flexibility was performed.
• Compatibility with existing Nuclear Overhauser Effect Spectroscopy (NOESY) data was evaluated.

Main Results:

• The study revealed a significantly more disordered conformational ensemble for the chiral selectors than previously assumed.
• Existing NOESY data is consistent with an equilibrium between two major conformations.
• Considerable conformational flexibility was observed, particularly in polar solvent mixtures simulating RPLC conditions.

Conclusions:

• The conformational freedom of polysaccharide-based selectors is substantial and must be considered.
• Future studies predicting enantioselectivity should explicitly account for this conformational flexibility.
• This research provides critical insights for the rational design of advanced chiral stationary phases.