title: Synthesis and biological evaluation of certain 3-beta-D-ribofuranosyl-1,2,4-triazolo[4,3-b)pyridazines related to formycin prepared via ring closure of pyridazine precursors.
abstract: All three amino-substituted 3-beta-D-ribofuranosyl-1,2,4-triazolo[4,3-b]pyridazines (5, 19, and 20) structurally related to formycin A were prepared and tested for their antitumor and antiviral activity in cell culture. Dehydrative coupling of 4-amino-5-chloro-3-hydrazinopyridazine (7) with 3,4,6-tri-O-benzoyl-2,5-anhydro-D-allonic acid (6) in the presence of DCC and subsequent thermal ring closure of the reaction product (8) provided 8-amino-7-chloro-3-(2,3,5-tri-O-benzoyl-beta-D-ribofuranosyl)- triazolo[4,3-b]pyridazine (9). Dehalogenation of 9, followed by debenzoylation, gave the formycin congener 8-amino-3-beta-D-ribofuranosyl-1,2,4- triazolo[4,3-b]pyridazine (5). Similar condensation of 5-amino-4-chloro-3-hydrazinopyridazine (13) with 6 and dehalogenation of the cyclized product (16), followed by debenzoylation, gave the isomeric 7-amino-3-beta-D-ribofuranosyl-1,2,4- triazolo[4,3-b]pyridazine (19). DCC-mediated coupling of 6 with 6-chloro-3-hydrazinopyridazine (12), followed by ammonolysis of the cyclized product (21) with liquid NH3, provided a convenient route to 6-amino-3-beta-D-ribofuranosyl-1,2,4-triazolo[4,3-b]pyridazine (20). The structural assignment of 5 was made by single-crystal X-ray diffraction analysis. Compounds 5, 19, 20, and certain deprotected nucleoside intermediates were evaluated against L1210, WI-L2, and CCRF-CEM tumor cell lines, as well as against DNA and RNA viruses in culture. These compounds did not exhibit any significant antitumor or antiviral activity in vitro.
authors.affiliation: ICN Nucleic Acid Research Institute, Costa Mesa, California 92626.
authors.forename: Y
authors.initials: Y
authors.lastname: Kang
authors.forename: S B
authors.initials: SB
authors.lastname: Larson
authors.forename: R K
authors.initials: RK
authors.lastname: Robins
authors.forename: G R
authors.initials: GR
authors.lastname: Revankar
mesh_terms: D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000138:chemical synthesis; D000998:Antiviral Agents / Q000138:chemical synthesis; D055598:Chemical Phenomena; D002621:Chemistry; D004267:DNA Viruses / Q000187:drug effects; D005573:Formycins / Q000138:chemical synthesis / Q000494:pharmacology*; D006801:Humans; D007939:Leukemia L1210 / Q000473:pathology; D007945:Leukemia, Lymphoid / Q000473:pathology; D051379:Mice; D008968:Molecular Conformation; D011724:Pyridazines / Q000138:chemical synthesis; D012328:RNA Viruses / Q000187:drug effects; D014407:Tumor Cells, Cultured / Q000187:drug effects
chemical_list: D000903:Antibiotics, Antineoplastic; D000970:Antineoplastic Agents; D000998:Antiviral Agents; D005573:Formycins; D011724:Pyridazines