DETERMINATION OF INTRAMOLECULAR HYDROGEN-BONDS IN AMIKACIN IN WATER SOLUTION BY NMR-SPECTROSCOPY

An NMR investigation has been carried out on amikacin in water solutio n in the physiological pH range. Two-dimenstional heterocorrelated map s provide H-1 NMR chemical shifts from the unambiguous assignment of t he C-13 NMR spectrum. Reorientational dynamics at the molecular level are interpreted in terms of a pseudoisotropic motion with a correlatio n time of 0.17 ns at 300 K, The pH and temperature dependences of C-13 NMR chemical shifts are interpreted to delineate protonation equilibr ia (all pKs are determined) and to assess the occurrence of two interm olecular hydrogen bonds, which are confirmed by molecular modelling.