Regioisomeric 4-nitroindazole N-1- and N-2-(beta-D-ribonucleosides)

Abstract

The structures of the isomeric nucleosides 4-nitro-1-(beta-D-ribofuranosyl)-1H- indazole, C12H13N3O6, ( I), and 4-nitro-2( beta-D-ribofuranosyl)-2H-indazole, C12H13N3O6, (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].