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Regioisomeric 4-nitroindazole N1- and N2-(beta-D-ribonucleosides)
Frank Seela1, Xiaohua Peng, Henning Eickmeier
1Laboratorium für Organische und Bioorganische Chemie, Institut für Chemie, Universität Osnabrück, Barbarastrasse 7, 49069 Osnabrück, Germany. frank.seela@uni-osnabrueck.de
Abstract:
The structures of the isomeric nucleosides 4-nitro-1-(beta-D-ribofuranosyl)-1H-indazole, C(12)H(13)N(3)O(6), (I), and 4-nitro-2-(beta-D-ribofuranosyl)-2H-indazole, C(12)H(13)N(3)O(6), (II), have been determined. For compound (I), the conformation of the glycosylic bond is anti [chi = -93.6 (6) degrees ] and the sugar puckering is C2'-exo-C3'-endo. Compound (II) shows two conformations in the crystalline state which differ mainly in the sugar pucker; type 1 adopts the C2'-endo-C3'-exo sugar puckering associated with a syn base orientation [chi = 43.7 (6) degrees ] and type 2 shows C2'-exo-C3'-endo sugar puckering accompanied by a somewhat different syn base orientation [chi = 13.8 (6) degrees ].