2-Amino-8-methyladenosine 5'-Monophosphate Dihydrate. A Nucleotide with Syn C4'-Exo Conformation and ''Triple-Stranded'' Packing

Article abstract of DOI:10.1021/ja00368a028

The preparation and crystal structure of 2-amino-8-methyladenosine 5'-monophosphate dihydrate, C11H14N6O7P*2H2O, are described.The space group is R3, with a = 20.192 (1) Angstroem and c = 11.0849 (7) Angstroem.The final R factor was 2.3percent, using counter data corrected for absorption and extinction, and the resulting esd's are the smallest yet reported for an X-ray structure of a nucleotide.The nucleotide molecules adopt the unusual syn C4'-exo conformation, and the extensively hydrogen-bonded components of the crystals are organized into crystallographic helices which, in turn form triangular groupings reminiscent of the early Pauling and Corey model for the nucleic acids.The extensive involvment of water bridges in the packing is of interest.The observation of the syn C4'-exo conformation is relevant to modeling studies of polynucleotides and may indicate that the allowable ranges of sugar conformation are broader than previously suspected.