Study of Structure and Interactions of Biologically Active Molecules by NMR Spectroscopy

This thesis combines experimental NMR spectroscopy with quantum-chemical calculations and machine-learning predictions to advance the structural analysis of organic and biologically relevant molecules in both solution and solid state. In solution, long-range fluorine-carbon J-couplings were investigated in a series of monodeoxyfluorinated disaccharides. Formal six- to seven-bond F-C couplings were observed experimentally and rationalised by DFT calculations in model studies, which confirmed the distance and orientation dependence of the coupling. In the saccharides, these couplings were shown to arise predominantly through-space and correlated with molecular conformation, establishing them as valuable geometry-sensitive probes. Solid-state studies focused on amino acids, combining experimental 13C and 1H CP-MAS spectra with periodic DFT calculations. These calculations reproduced experimental chemical shifts with reasonable accuracy, and a single-molecule correction approach further improved the agreement. This enabled additional signal assignments and distinction between crystallographically non-equivalent molecules and polymorphic forms. Nitrogen solid-state NMR was applied to a series of natural products to characterise local nitrogen environments by measuring both 15N and quadrupolar 14N...