Structure of 3-isoadenosine.

3-beta-D-Ribofuranosyladenine, C10H13N5O4, Mr = 267.25, orthorhombic, P2(1)2(1)2(1), a = 13.470 (4), b = 16.054 (6), c = 5.141 (2) A, V = 1111.8 (7) A3, Z = 4, Dx = 1.596 g cm-3, lambda(Mo K alpha) = 0.71073 A, mu = 1.18 cm-1, F(000) = 560, T = 298 K, R = 0.043, wR = 0.042 for 1136 reflections. The tautomeric form present in the crystal is 6-NH2. The adenine moiety is nearly planar and the torsional angle of the glycosidic linkage O(4')-C(1')-N(3)-C(4) is -161.5 degrees. All N and O atoms except N(3) and O(4') participate in a three-dimensional hydrogen-bonding system.