2.6. 1H NMR studies
Samples for NMR experiments were approximately in 3 mM/MeOD. The samples were purified by RP-HPLC and lyophilised before dissolving in MeOD. The NMR spectra were acquired by a Bruker AVANCE-600 spectrometer at 297 K. The fraction of cis-proline conformer was determined by integrating well-resolved peaks in the one-dimensional 1H NMR spectra.