Crystal structure and conformation of 8-(2-hydroxyethylamino) and 8-(pyrrolidin-1-yl) adenosines

In the course of investigation of 8-alkylamino substituted adenosines, the title compounds were synthesized as potential partial agonists for adenosine receptors. The structure determination of these compounds was carried out with the X-ray crystallography study. Crystals of 8-(2-hydroxyethylamino)adenosine are monoclinic, space group P 2(1); a = 7.0422(2), b = 11.2635(3), c = 8.9215(2) A, beta = 92.261(1) degrees, V = 707.10(3) A3, Z = 2; R-factor is 0.0339. The nucleoside is characterized by the anti conformation; the ribose ring has the C(2')-endo conformation and gauche-gauche form across C(4')-C(5') bond. The molecular structure is stabilized by intramolecular hydrogen bond of N-HO type. Crystals of 8-(pyrrolidin-1-yl)adenosine are monoclinic, space group C 2; a = 19.271(1), b = 7.3572(4), c = 11.0465(7) A, beta = 103.254(2), V = 1524.4(2) degrees A3, Z = 4; R-factor is 0.0498. In this compound, there is syn conformation of the nucleoside; the ribose has the C(2')-endo conformation and gauche -gauche form across C(4')- C(5') bond. The molecular structure is stabilized by intramolecular hydrogen bond of O-HN type. For both compounds, the branching net of intermolecular hydrogen bonds occur in the crystal structures.