Sequence-Selective Cleavage of Oligoribonucleotides by 3d Transition Metal Complexes of 1,5,9-TriazacyclododecaneFunctionalized 2-O-Methyl Oligoribonucleotides

2ʹ-O-Methyl oligoribonucleotides bearing a 3ʹ-[2,6-dioxo-3,7-diaza-10-(1,5,9-triazacyclododec-3-yl)decyl phospate conjugate group have been shown to cleave in slight excess of Zn^2+ ions complementary oligoribonucleotides at the 5ʹ-side of the last base-paired nucleotide. The cleavage obeys first-order kinetics and exhibits turnover. The acceleration compared to the monomeric Zn^2+ 1,5,9-triazacyclododecane chelate is more than 100-fold. In addition, 2ʹ-O-methyl oligoribonucleotides having the 1,5,9-triazacyclododec-3-yl group tethered to the anomeric carbon of an intrachain 2-deoxy-(beta)-D-erythropentofuranosyl group via a 2-oxo-3-azahexyl, 2,6-dioxo-3,7-diazadecyl, or 2,9-dioxo-3,10-diazatridecyl linker have been studied as cleaving agents. These cleave as zinc chelates a tri- and pentaadenyl bulge opposite to the conjugate group approximately 50 times as fast as the monomeric chelate and show turnover. The cleavage rate is rather insensitive to the length of linker. Interestingly, a triuridyl bulge remains virtually intact in striking contrast to a triadenyl bulge. Evidently binding of the zinc chelate to a uracil base prevents its catalytic action. Replacement of Zn^2+ with Cu^2+ or Ni^2+ retards the cleaving activity of all the cleaving agents tested.