title: Synthesis of novel C4-linked C2-imidazole ribonucleoside phosphoramidite and its application to probing the catalytic mechanism of a ribozyme.
abstract: The synthesis of a novel C4-linked C2-imidazole ribonucleoside phosphoramidite (ICN-C2-PA 1) with a two-carbon linker between imidazole and ribose moieties is described. In the phosphoramidite, POM and 2-cyanoethyl groups were selected to protect the endocyclic amine function of imidazole and the 2'-hydroxyl function of D-ribose, respectively. The C2-imidazole nucleoside, a flexible structural mimic of a purine nucleobase, was successfully incorporated using ICN-C2-PA 1 into position 638 of the VS ribozyme through 2'-TBDMS chemistry to study the role of G638 in general acid-base catalysis. The modified VS ribozyme (G638C2Imz) exhibited significantly greater catalytic activity than observed with the C0-imidazole that has no carbon atoms linking the ribose and the C4-imidazole. Imidazole nucleoside analogues with variable spacer lengths could provide a valuable general methodology for exploring the catalytic mechanisms of ribozymes.
authors.affiliation: Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka 569-1094, Japan.
authors.forename: Lisa
authors.initials: L
authors.lastname: Araki
authors.forename: Keiji
authors.initials: K
authors.lastname: Morita
authors.forename: Maho
authors.initials: M
authors.lastname: Yamaguchi
authors.forename: Zheng-yun
authors.initials: ZY
authors.lastname: Zhao
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Wilson
authors.forename: David M J
authors.initials: DM
authors.lastname: Lilley
authors.forename: Shinya
authors.initials: S
authors.lastname: Harusawa
mesh_terms: D002384:Catalysis; D007093:Imidazoles / Q000138:chemical synthesis; D009943:Organophosphorus Compounds / Q000138:chemical synthesis*; D016337:RNA, Catalytic / Q000737:chemistry*; D012263:Ribonucleosides / Q000138:chemical synthesis*
chemical_list: D007093:Imidazoles; D009943:Organophosphorus Compounds; D016337:RNA, Catalytic; D012263:Ribonucleosides; C434331:phosphoramidite