A toyocamycin analogue with the sugar moiety in a syn conformation

Abstract

The title compound [systematic name: 4-amino-5-cyano-1-(beta-d-ribofuranosyl)-7H-pyrrolo[2,3-d] pyrimidine hemihydrate], C12H13N5O4 center dot 0.5H(2)O, is a regioisomer of toyocamycin with the ribofuranosyl residue attached to the pyrimidine moiety of the heterocycle. This analogue exhibits a syn glycosylic bond conformation with a chi torsion angle of 57.51 (17)degrees. The ribofuranose moiety shows an envelope C2'-endo (2 E) sugar conformation (S-type), with P = 161.6 (2)degrees and tau(m) = 41.3 (1)degrees. The conformation at the exocyclic C4'-C5' bond is sc (gauche, gauche), with a chi torsion angle of 54.4 (2)degrees. The crystal packing is stabilized by intermolecular O-H center dot center dot center dot O, N-H center dot center dot center dot N and O-H center dot center dot center dot N hydrogen bonds; water molecules, located on crystallographic twofold axes, participate in interactions. An intramolecular O-H center dot center dot center dot N hydrogen bond stabilizes the syn conformation of the nucleoside.