Crystal and solution structure of 5′-O-(guanosine-2′-O-phosphonomethyl)cytidine, an isopolar nonisosteric phosphonate analog of GpC.

X-Ray crystal structure of 5'-O-(guanosine-2'-O-phosphonomethyl)-cytidine (G-p(c)C(2'-5')) was determined. The structural unit involves two molecules cf G-p(c)C(2'-5') differing both in the conformation of the phosphonate internucleotide linkage and in the intramolecular base-plane distances (3.6 Angstrom; 3.3 Angstrom), and fourteen molecules of water. The crystal data of G-p(c)C(2'-5') are discussed along with those. obtained from NMR spectra.