Fundamentals of NMR Spectroscopy in Chiral Recognition
摘要
Nuclear Magnetic Resonance (NMR) spectroscopy is a powerful and widely used analytical technique for elucidating the structure, configuration, and dynamics of molecular systems at atomic resolution. With continuous advancements in instrumentation and methodology, NMR has emerged as an important tool for the analysis of chiral compounds. However, a key limitation arises from the fact that enantiomers display identical NMR spectra in achiral, isotropic environments, since their chemical shifts and coupling constants are governed by equivalent electronic and steric environments. As a result, direct enantiomer differentiation is not possible without modifying the NMR environment. Chiral recognition in NMR relies on creating diastereomeric interactions between the analyte and a chiral reference framework, leading to measurable differences in spectral parameters. To achieve this, various strategies have been developed that introduce chirality into the system. The most established approaches include the use of Chiral Solvating Agents (CSAs), Chiral Derivatizing Agents (CDAs), and Chiral Lanthanide Shift Reagents (CLSRs). These methods enhance spectral resolution and enable quantitative and qualitative assessment of enantiomeric composition. This chapter provides a foundational understanding of the principles governing NMR-based chiral discrimination and outlines the theoretical and practical considerations essential for accurate enantiomer analysis.