Work

31P NMR Study of P‐Chirogenic Phosphaphenanthrenes with Molecular Flexibility tuned by Amino Acid Substituents

Year: 2025

Type: article

Abstract: Model phosphonamidates derived from 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) with molecular flexibility tuned by amino acid substituents were prepared as pairs of diastereoisomers (DSIs) differing in configuration on phosphorus atom. X‐ray diffraction (XRD) determined absolute configuration on phosphorus and revealed conformational flexibility of six‐membered oxa‐phospha‐cycle. Quantum‐chemical calculations combined with machine learning provided 2–4 representative conformers from each DSI present in solution. 31P chemical shift of RS DSIs was higher compared to the SS ones. Calculated 31P‐1H as well as 31P‐13C J‐couplings followed Karplus dependence of J‐coupling values on dihedral angles between interacting nuclei, showing reasonable match with the literature data. The effect of molecular flexibility quantified by parameter nConf20 on NMR parameters was significant, especially for residual dipolar couplings (RDCs), where Pearson correlation factor R decreased with increasing nConf20 parameter.

Source: Chemistry - A European Journal

DOI: 10.1002/chem.202500330