Conformation of nucleosides: The comparison of an X-ray diffraction and proton nmr study of 5′,2-O-cyclo, 2′,3′-O-Isopropylidene uridine
| Autor: | Philip C. Manor, D.B Davies, K Jankowski, Wolfram Saenger, A. Rabczenko |
|---|---|
| Rok vydání: | 1974 |
| Předmět: |
chemistry.chemical_classification
Carbon Isotopes Magnetic Resonance Spectroscopy Double bond Chemistry Ribose Molecular Conformation Nuclear magnetic resonance spectroscopy Crystal structure Dihedral angle Deuterium Biochemistry Genetics and Molecular Biology (miscellaneous) Models Structural Bond length Crystallography X-Ray Diffraction Cyclization Evaluation Studies as Topic X-ray crystallography Methods Proton NMR Uridine Monoclinic crystal system |
| Zdroj: | Biochimica et Biophysica Acta (BBA) - Nucleic Acids and Protein Synthesis. 340:472-483 |
| ISSN: | 0005-2787 |
| Popis: | The title compound crystallizes in the monoclinic space group P21 with unit cell dimensions, a = 9.091 A , b = 6.404 A , c = 10.395 A , β = 93.6°, and there are two molecules per unit cell. The crystal structure has been determined on the basis of 828 diffraction intensities measured with a four-circle diffractometer, Cu radiation, and refined by the method of least squares to a residual index of R = 0.049. The uracil residue shows the features typical for O(2) cyclic derivatives: the C(2)-N(3) bond length, 1.283 A, is characteristic of a double bond. The ribofuranose conformation is an envelope with O(1′) 0.524 A exo, and the base is oriented syn with respect to the sugar with dihedral angles C(2)-N(1)-C(1′)-O(1′) = 71.2° and C(2)-N(1)-C(1′)-C(2′) = −47.6° which results in the positioning of O(2) almost over the center of the ribose ring. The spin-coupling constants of the proton magnetic resonance spectrum of this cyclic nucleoside derivative measured in C2HCl3 solution confirm the conformation found in the solid state by X-ray methods. There are substantial differences between the experimentally observed coupling constants for the bridged nucleoside and those predicted from the X-ray structure using modified Karplus type relations derived from less strained molecules. |
| Databáze: | OpenAIRE |
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