Abstract
The regioselective synthesis of 4‐nitroindazole N 1‐ and N 2‐(β‐d‐ribonucleosides) (8, 9, 1b and 2b) is described. The N 1‐regioisomers are formed under thermodynamic control of the glycosylation reaction [fusion reaction or Silyl Hilbert‐Johnson glycosylation for 48 h (66%)], while the kinetic control (Silyl Hilbert‐Johnson glycosylation for 5 h) afforded only the N 2‐isomer (64%). The structures of the nucleosides 1b and 2b were assigned by single crystal X‐ray analyses. The 4‐amino‐N 1‐(β‐d‐ribofuranosyl)‐1H‐indazole (3b) was obtained from the nitro nucleoside 1b by catalytic hydrogenation. Compound 3b shows fluorescence while the 4‐nitroindazole nucleosides 1b and 2b do not possess this property.
†In honor and celebration of the 70th birthday of Professor Leroy B. Townsend.
Acknowledgments
The authors thank Dr. H. Rosemeyer and Dr. Y. He for the measurement of the 1H‐ and 13C‐NMR spectra. We gratefully acknowledge financial support by the European Community (grant no.: QLRT‐2001‐00506, “Flavitherapeutics”).
Notes
†In honor and celebration of the 70th birthday of Professor Leroy B. Townsend.