6-Azapurines. Part 2. Crystal and molecular structure of 8,9-dimethyl-6-azapurin-2-one

Abstract

The crystal and molecular structure of 8,9-dimethyl-6-azapurin-2(1H)-one has been determined by single-crystal X-ray diffraction methods and represents the first such study on this novel heterocyclic system. The compound crystallizes in the monoclinic space group P2₁/c in a cell of dimensions a= 6.601(2), b= 10.598(3), c= 10.384(3)Å, β= 99.37(2)°, Z= 4. The structure was solved by direct methods and refined using blocked-cascade full-matrix least-squares calculations, which converged to a final R_w index of 0.044 for 813 (of 941 unique) observed data. The C(11) methyl group exhibited rotational disorder which was accounted for in the refined model. Molecules form an intermolecular hydrogen-bonded chain, connecting H(N1) to N(7) along the c crystallographic axis. The N(1)H tautomer of this 6-azapurine is preferred in the solid state.