title: Chemical Synthesis of a 5'-Terminal TMG-Capped Triribonucleotide m(3)(2,2,7)G(5)(')pppAmpUmpA of U1 RNA.
abstract: The 5'-terminal TMG-capped triribonucleotide, m(3)(2,2,7)G(5)(')pppAmpUmpA, has been synthesized by condensation of an appropriately protected triribonucleotide derivative of ppAmpUmpA with a new TMG-capping reagent. During this total synthesis, it was found that the regioselective 2'-O-methylation of 3',5'-O-(1,1,3,3-tetraisopropyldisiloxane-1,3-diyl)-N-(4-monomethoxytrityl)adenosine was achieved by use of MeI/Ag(2)O without affecting the base moiety. A new route to 2-N,2-N-dimethylguanosine from guanosine via a three-step reaction has also been developed by reductive methylation using paraformaldehyde and sodium cyanoborohydride. These key intermediates were used as starting materials for the construction of a fully protected derivative of pAmpUmpA and a TMG-capping reagent of Im-pm(3)(2,2,7)G. The target TMG-capped tetramer, m(3)(2,2,7)G(5)(')pppAmpUmpA, was synthesized by condensation of a partially protected triribonucleotide 5'-terminal diphosphate species, ppA(MMTr)mpUmpA, with Im-pm(3)(2,2,7)G followed by treatment with 80% acetic acid. The structure of m(3)(2,2,7)G(5)(')pppAmpUmpA was characterized by (1)H and (31)P NMR spectroscopy as well as enzymatic assay using snake venom phosphodiesterase, calf intestinal phosphatase, and nuclease P1.
authors.affiliation: Institut für Molekularbiologie und Tumorforschung, Philipps-Universität Marburg, Emil-Mannkopff-Strasse 2, D-3550 Marburg, Germany.
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Sekine
authors.forename: Michinori
authors.initials: M
authors.lastname: Kadokura
authors.forename: Takahiko
authors.initials: T
authors.lastname: Satoh
authors.forename: Kohji
authors.initials: K
authors.lastname: Seio
authors.forename: Takeshi
authors.initials: T
authors.lastname: Wada
authors.forename: Utz
authors.initials: U
authors.lastname: Fischer
authors.forename: Vicki
authors.initials: V
authors.lastname: Sumpter
authors.forename: Reinhard
authors.initials: R
authors.lastname: Lührmann