Crystallographic and1H nuclear magnetic resonance studies of 5′-deoxy-5′-adenosineacetic acid; a model nucleotide of adenosine-5′-monophosphate

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Abstract
In order to elucidate the substrate specificity of adenosine-5′-monophosphate utilizing enzymes, the spatial conformation of 5′-deoxy-5′-adenosineacetic acid has been studied by X-ray crystallography and 1H n.m.r. spectroscopy, and the results compared with those for adenosine-5′-monophosphate. In the crystal, the conformation about the glycosyl bond is anti with the torsion angle χ[O(1′)–C(1′)–N(9)–C(8)] equal to 50.7(9)°. The puckering of the ribose ring is C(3′)-exo(3E). The significant conformational discrepancy between 5′-deoxy-5′-adenosineacetic acid and adenosine-5′-monophosphate was in the orientations of their exocyclic C(4′)–C(5′) bonds: gauche-trans for the former and gauche-gauche for the latter. These conformational characteristics were also observed in 2H2O solution by 1H n.m.r. spectroscopy. The intermolecular hydrogen bonding mode between the carboxyl group and the adenine ring found in the crystal would constitute a good model for the specific interaction between the acidic amino-acid and the nucleic acid base adenine.