X-ray crystallographic study of several 2'-deoxy-beta-D-ribonucleosides with 1-deazapurine-derived aglycones.
The 2'-deoxy-beta-D-ribonucleosides of 1,3-deazapurine (benzimidazole (1)), 1-deazapurine (both 1H-imidazo[4,5-b]pyridine (2) and 3H-imidazo[4,5-b]pyridine (3)), and 6-benzoylamino-1-deazapurine (7-benzoylamino-3H-imidazo[4,5-b]pyridine (4)) have been prepared and structurally characterized by X-ray crystallography. Especially compounds 1-3 can serve as artificial nucleosides that may substitute 2'-deoxy adenosine because they lack the exocyclic amino group and one or two of the endocyclic nitrogen atoms and hence have a much smaller potential to engage in hydrogen bonds. In the latter respect, they are candidates for nucleosides in metal-ion mediated base pairs. The unit cell of compound 3 contains two crystallographically independent molecules. Compound 4 was crystallized from methanol and water, respectively, giving rise to two different solvates. Despite the closely related aglycones, the sugar conformations in 1-4 are found to be highly variable (1: (2)T(1); 2: (3)T(2); 3: (3)E and E(4); 4: (2)E and (2)T(3)). The structures reported here confirm that there is no simple correlation between the sugar conformation and the character of the nucleoside, and they will hopefully contribute to a better understanding of the complex interplay of different effects that are in control of the conformational equilibrium.
Müller
Jens
J
University of Dortmund, Department of Chemistry, Otto-Hahn-Strasse 6, D-44227 Dortmund, Germany. jens.mueller@uni-dortmund.de
Polonius
Fabian-Alexander
FA
Freisinger
Eva
E
Gil Bardají
Elisa
E
D018360:Crystallography, X-Ray; D003853:Deoxyribonucleosides / Q000737:chemistry*; D015394:Molecular Structure; D011687:Purines
D003853:Deoxyribonucleosides; D011687:Purines