2,6-diamino-9-(carboxymethyl)purine ethyl ester

In the crystal structure of the title compound (as its hemihydrate, C9H12N6O2 . 0.5H(2)O), a potential intermediate for the synthesis of peptidic nucleic acids containing 2,6-diaminopurine, the asymmetric unit contains two molecules, one ordered and the other with twofold positional disorder about a pivot point near the 6-amino group, together with one water molecule. The side chain emerges at N9 with C8-N9-C10-C11 torsion angles of 93.0(2) and 50.8(6)/-97.0(6)degrees, respectively.