Unmodified nucleoside phosphoramidites

Chemicals were obtained from Aldrich Chemical Company (St. Louis, MO, USA) and were used without further purification unless otherwise stated. Unmodified nucleoside phosphoramidites and 5′-dimethoxytrityl-2′-propargyluridine 3′-O-(N,N-diisopropyl-2-cyanoethyl) phosphoramidite were purchased from ChemGenes Corporation (Wilmington, MA, USA). [(3,3′-Iron-1,2,1′,2′-dicarbollide)(−1)]ate cesium salt was bought from Katchem (Režn/Prague, Czech Republic). Flash chromatography was performed on silica gel 60 (230–400 mesh, Aldrich Chemical Company). R_f values refer to analytical thin layer chromatography (TLC) performed using pre-coated silica gel 60 F₂₅₄ plates purchased from Sigma-Aldrich (Steinheim, Germany) and developed in the solvent system indicated. Compounds were visualized with UV light (at λ_max = 254 nm). The yields are not optimized.

Unmodified nucleoside phosphoramidites and 5’-dimethoxytrityl-2’-propargyluridine 3’-O-(N,N-diisopropyl-2-cyanoethyl) phosphoramidite were purchased from ChemGenes Corporation (Wilmington, MA, USA). [(3,3’-Iron-1,2,1’,2’-dicarbollide)(−1)]ate (-1) cesium salt (ferra(III) bis(dicarbollide), FESAN) was purchased from Katchem (Režn/Prague, Czech Republic). Radio-labeled adenosine 5’-triphosphate ([γ-³²P]-ATP) was purchased from Hartmann-Analytik (Braunschweig, Germany), and T4 polynucleotide kinase and kinase buffer were purchased from BioLabs (New England, MA, USA). Autoradiography double-coated films were purchased from Carestream Medical X-ray blue (MXBE film, Rochester, NY, USA). The developer reagent and fixer reagent were from Kodak Processing Chemicals (Sigma Aldrich, St. Louis, MO, USA). The snake venom phosphodiesterase I from Crotalus atrox Western Diamondback Rattlesnake was purchased from Sigma-Aldrich (USA).