Synthesis of 3-aminoimidazo[4,5-c]pyrazole nucleoside via the N-N bond formation strategy as a [5:5] fused analog of adenosine

Tun Cheng Chien, David A. Berry, John C. Drach, Leroy B. Townsend

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□ 3-Amino-6-(β-D-ribofuranosyl)imidazo[4,5-c]pyrazole (2) was synthesized via an N-N bond formation strategy by a mononuclear heterocyclic rearrangement (MHR). A series of 5-amino-1-(5-O-tert-butyldimethylsilyl-2,3-O- isopropylidene-β-D-ribofuranosyl)-4-(1,2,4-oxadiazol-3-yl)imidazoles (6a-d), with different substituents at the 5-imposition of the 1,2,4-oxadiazole, were synthesized from 5-amino-1-(β-D-ribofuranosyl)imidazole-4-carboxamide (AICA Ribose, 3). It was found that 5-amino-1-(5-O-tert-butyldimethylsilyl-2,3- O-isopropylidene-ß-D-ribofuranosyl)-4-(5-methyl-l, 2,4-oxadiazol-3-yl) imidazole (6a) underwent the MHR with sodium hydride in DMF or DMSO to afford the corresponding 3-acetamidoimidazo[4,5-c]pyrazole nucleoside(s) (7b and/or 7a) in good yields. A direct removal of the acetyl group from 3-acetamidoimidazo[4, 5-c]pyrazoles under numerous conditions was unsuccessful. Subsequent protecting group manipulations afforded the desired 3-amino-6-(β-D-ribofuranosyl) imidazo[4,5-c]pyrazole (2) as a 5:5 fused analog of adenosine (1)

Original languageEnglish
Pages (from-to)1971-1996
Number of pages26
JournalNucleosides, Nucleotides and Nucleic Acids
Issue number10-12
Publication statusPublished - 2005 Sep 1



  • AICA riboside
  • Adenosine analog
  • Boulton-Katritzky rearrangement
  • Imidazo[4,5-c]pyrazole
  • Mononuclear heterocyclic rearrangements

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Medicine
  • Genetics

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