5-Amino-1-(2',3'--iso-propyl-idene-d-ribit-yl)-1-imidazole-4-carboxamide: a crystal structure with ' = 4.

The title compound, CHNO, crystallizes in the monoclinic space group 2, with four crystallographically independent mol-ecules in the asymmetric unit. The four mol-ecules have a very similar conformation that is basically determined by the formation of two intra-molecular hydrogen bonds between the amino NH donors and the carbonyl and ring O-atom acceptors, forming, respectively, (6) and (7) ring motifs.. In the crystal, inter-molecular hydrogen bonding leads to the formation of (10) ring patterns, involving one amide CONH donor and an imidazole N-atom acceptor. The cluster of the four independent mol-ecules has approximate non-crystallographic point symmetry. The structural analysis also shows that during the synthesis of the title compound, the reductive cleavage of the d-ribose ring of the inosine precursor proceeds stereoselectively, with retention of configuration.