title: On the conformation of 5-substituted uridines as studied by proton magnetic resonance.
abstract: The proton magnetic resonance (pmr) spectra of 10 basemodified uridine derivatives x5Urd have been measured at 3 degrees, 30 degrees, and 60 degrees C in order to correlate the electronic effects of different substituents with the molecular conformation of the respective nucleosides. The results presented demonstrate the close relation between conformational parameters and the electron-affinity of the substituents as reflected by their Hammett constants. Going from electron-donating to electron-accepting groups, the portion of N-conformer in the ribose N in equilibrium S equilibrium increases from 44% to about 90%. In addition the percentage of gauche-gauche rotamer as measured for the exocyclic groups changes from about 30% in nh52Urd to more than 80% in no52Urd.
mesh_terms: D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008433:Mathematics; D008968:Molecular Conformation; D014529:Uridine / Q000031:analogs & derivatives*
chemical_list: D014529:Uridine