Regioselective Synthesis of Indazole N1‐ and N2‐(β‐d‐Ribonucleosides)
摘要:
The regioselective synthesis of 4-nitroindazole N-1- and N-2- (beta-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-(beta-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.
Regioselective Synthesis of Indazole <i>N</i> <sup>1</sup>‐ and <i>N</i> <sup>2</sup>‐(<i>β</i>‐<scp>d</scp>‐Ribonucleosides)
作者:Frank Seela、Xiaohua Peng
DOI:10.1081/ncn-120027830
日期:2004.1.1
The regioselective synthesis of 4-nitroindazole N-1- and N-2- (beta-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-(beta-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.