Abstract
The conformation of the 7-bromo- and 7-iodo-substituted 8-aza-7-deazapurine nucleosides 1 and 2 in the solid state and in aqueous solution was studied by single-crystal X-ray analyses and by 1H-NMR spectroscopy. In the solid state, both compounds display a high-anti conformation around the glycosylic bond, and their 2′-deoxy-β-D-ribofuranose moieties adopt an N-type sugar puckering. The orientation of the exocyclic C(4′)−C(5′) bond was found to be ap in both cases. In D2O solution, both compounds display i) an 8 – 10% higher N-conformer population than 2′-deoxyguanosine and ii) a preference of the −sc conformation about the C(4′)−C(5′) bond. A comparative study on the influence of modified bases on the sugar structure of nucleosides is made.
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