Molecular conformation of 2′-deoxy-3′,5′-di-O-acetyl adenosine. Crystal structure and high resolution proton nuclear magnetic resonance investigations

Abstract

2′-Deoxy-3′,5′-di-O-acetyl adenosine crystallizes in the orthorhombic space group P2₁2₁2₁, and the cell dimensions are a = 7.768(1) Å, b = 12.890(1) Å, c = 15.495(1) Å; Z = 4 molecules per cell. Least-squares refinement converged at R = 0.054 for 1752 observed reflections. The adenine bases are linked via N₆—H … N₁ and N₆—H … N₇ hydrogen bonds, in such a way that infinite one-dimensional chains are formed. Comments are made on the fact that this structure is entirely different from the parallel dimer that was found for 3′,5′-di-O-acetyl thymidine. Furthermore, the conformational preferences of the title compound in aqueous solution have been determined with 300- and 500-MHz ¹H nmr. It is found that the X-ray structure and the solution conformation are essentially similar, except for the C_4′—C_5′ conformation, that is γ⁻ in the solid state, and predominantly γ⁺ in solution.