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-O2-β-D-arabinosyluracil in aqueous solution at 80 °C is presented. The spectrum provides evidence for the presence of long-range four-bond (4J1′3′, 4J1′4′, 4J2′4′) and five-bond (5J1′5′, 5J1′5′′, 5J2′5′, 5J2′5′′) coupling interactions involving the furanose hydrogens. The 5J data represent the first reported evidence for the presence of coupling interactions involving the anomeric proton and exocyclic C5′ protons in a furanose system. The relative signs of the 4J and 5J couplings were determined by double resonance methods. The 4J and 5J interactions are discussed using crystallographic data and the theory of long-range couplings.