Structure of Ethyl Hydrogen P(R), 5′-Anhydro-2′,3′-O-Isopropylidene-Adenosine-8-Phosphonate Hemiethylacetate Solvate

Abstract

The crystal, and molecular structure of the title compound [8,5′-P-cyclo-A(R)] was determined by the X-ray diffraction method. It crystallizes in space group C222₁ with unit-cell dimensions a=14.222(3), b=13.879(4), c=43.612(8) A. There are two 8,5′-P-cyclo-A(R) molecules and one ethyl acetate molecule per asymmetric unit. The two cyclonucleosides have a very similar overall conformation; the glycosidic torsion angle is in the anti range, the hetero-cyclic ring between the base and sugar moieties being in the endo form, while the sugar ring conformation is C(3′)-exo. The two independent cyclo-nucleoside molecules form a hydrogen bonded dimer N(1)—H-N(6) [3.07(2) A] and N(6)-H—O(6)(the free oxygen atom of the phosphonate group) [2.99(2) Å].