MOLECULAR-CONFORMATION OF 2'-DEOXY-3',5'-DI-O-ACETYL ADENOSINE - CRYSTAL-STRUCTURE AND HIGH-RESOLUTION PROTON NUCLEAR-MAGNETIC-RESONANCE INVESTIGATIONS

2′-Deoxy-3′,5′-di-0-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-HN1 and N6-HN7 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-0-acetyl thymidine. Furthermore, the conformational preferences of the title compound in aqueous solution have been determined with 300- and 500-MHz 'H nmr. It is found that the X-ray structure and the solution conformation are essentially similar, except for the C4′-C5′, conformation, that is γ- in the solid state, and predominantly γ+ + in solution.