7-Cyclopropyl-2 `-deoxytubercidin: a carbocyclic side-chain derivative of 7-deaza-2 `-deoxyadenosine

Abstract

The title compound {systematic name: 4-amino-5-cyclopropyl-7-(2-deoxy-beta-D-erythro-pentofuranosyl)-7H-pyrro lo[2,3-d]pyrimidine}, C14H18N4O3, exhibits an anti glycosylic bond conformation, with the torsion angle chi = -108.7 (2)degrees. The furanose group shows a twisted C1'-exo sugar pucker (S-type), with P = 120.0 (2)degrees and tau(m) = 40.4 (1)degrees. The orientation of the exocyclic C4'-C5' bond is -ap (trans), with the torsion angle gamma = -167.1 (2)degrees. The cyclopropyl substituent points away from the nucleobase (anti orientation). Within the three-dimensional extended crystal structure, the individual molecules are stacked and arranged into layers, which are highly ordered and stabilized by hydrogen bonding. The O atom of the exocyclic 5'-hydroxy group of the sugar residue acts as an acceptor, forming a bifurcated hydrogen bond to the amino groups of two different neighbouring molecules. By this means, four neighbouring molecules form a rhomboidal arrangement of two bifurcated hydrogen bonds involving two amino groups and two O5' atoms of the sugar residues.