title: Synthesis and cytokinin activity of fluorescent 7-Phenylethynylimidazo[4,5-b]pyridine and its riboside.
abstract: 7-Phenylethynylimidazo[4,5-b]pyridine and its riboside have been newly developed as fluorescent carbon-substituted cytokinin analogues. Palladium-catalyzed coupling of 7-iodo-3-(tri-O-acetyl-beta-D-ribofuranosyl)imidazo[4,5-b]pyridine with phenylacetylene followed by ammonolysis afforded the 7-phenylethynyl riboside via its tri-O-acetate. Acid hydrolysis of the riboside provided its free base, which showed a marked enhancement in fluorescence intensity in an aqueous alkaline solution. The free base and its riboside were more active than the corresponding 6-phenylethynylpurine and its riboside, respectively, in Amaranthus betacyanin and tobacco callus bioassays. Surprisingly, the imidazo[4,5-b]pyridine base exhibited strong cytokinin activity comparable to that of N(6)-benzyladenine in the tobacco callus bioassay. This compound would be useful for studying localization and transport of cytokinins in cells or tissues of plants.
authors.affiliation: Department of Bioscience, Mie University, Tsu, Japan. nisikawa@bio.mie-u.ac.jp
authors.forename: S
authors.initials: S
authors.lastname: Nishikawa
authors.forename: M
authors.initials: M
authors.lastname: Kurono
authors.forename: K
authors.initials: K
authors.lastname: Shibayama
authors.forename: S
authors.initials: S
authors.lastname: Okuno
authors.forename: M
authors.initials: M
authors.lastname: Inagaki
authors.forename: N
authors.initials: N
authors.lastname: Kashimura
mesh_terms: D003583:Cytokinins / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D007093:Imidazoles / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D008968:Molecular Conformation; D009705:Nucleosides / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D010944:Plants / Q000187:drug effects* / Q000378:metabolism; D011725:Pyridines / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D013050:Spectrometry, Fluorescence; D013329:Structure-Activity Relationship
chemical_list: C412473:7-phenylethynylimidazo(4,5-b)pyridine; D003583:Cytokinins; D007093:Imidazoles; D009705:Nucleosides; D011725:Pyridines