A series of l and dl forms of O-phosphorylated amino acids (serine, threonine, tyrosine) have been studied by using solid-state multinuclear NMR spectroscopy and ab initio calculations. Principal elements of the (13)C and (31)P chemical shielding tensors have been measured and discussed in relation to zwitterionic structures and intermolecular contacts. DFT calculations have been compared with experimental data showing their ability to reproduce experimentally obtained tensor values in this challenging class of compounds. The changes of orientation of (31)P chemical shielding tensor with respect to the molecular frame in the presence of hydrogen bonds have been revealed and discussed on the ground of theoretical calculations. The measurements of internuclear P...P distances, based on Zeeman magnetization exchange between (31)P spins with differing chemical shielding tensor orientations, were exploited for a clear distinction between enantiomers and racemates.
Homo-and heteronuclear correlated spectroscopy in the liquid phase and the PASS-2D NMR technique in the solid state were applied to the identification and structural studies of the flavanone 2-(3Ј,4Ј-dihydroxyphenyl)-7-β-glucopyranos-1-O-yl-8-hydroxychroman-4-one 1. The principal elements of the 13 C chemical shift tensor were established and verified by DFT GIAO calculations. Analysis of the 13 C δ ii and comparison with the theoretical shielding parameters calculated for different conformers of 1 in a vacuum were carried out to choose the most reliable geometry in the solid state.
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