The structure of the title compound, C21H23N3O7, has been determined a
t 193 K, The equivalent DNA-backbone torsion angles delta (O6'-C6'-C5'
-C8') and gamma (C6'-C5'-C8'-O8') are 157.3(4) and 67.5(5)degrees, res
pectively. An intramolecular hydrogen bond involving the hydroxy O8' a
nd carbonyl O2 atoms helps fix the molecule in an extended arrangement
with the torsion angle between the bicycle and pyrimidinyl moieties (
C5'-O1-C1-N1) being 159.9(4)degrees.