1H nuclear magnetic resonance study of 2,2′-anhydro-O2-β-D-arabinosyluracil. Four- and five-bond coupling constants in the sugar moiety

A high resolution proton magnetic resonance spectrum for 2,2′-anhydro-O 2 -β- D -arabinosyluracil in aqueous solution at 80 °C is presented. The spectrum provides evidence for the presence of long-range four-bond ( 4 J 1′3′ , 4 J 1′4′ , 4 J 2′4′ ) and five-bond ( 5 J 1′5′ , 5 J 1′5′′ , 5 J 2′5′ , 5 J 2′5′′ ) coupling interactions involving the furanose hydrogens. The 5 J data represent the first reported evidence for the presence of coupling interactions involving the anomeric proton and exocyclic C 5′ protons in a furanose system. The relative signs of the 4 J and 5 J couplings were determined by double resonance methods. The 4 J and 5 J interactions are discussed using crystallographic data and the theory of long-range couplings.