Sep pak plus c18 environmental cartridge

Syntheses of the ODNs containing B^AEO was performed on an automated DNA synthesizer (Gene Design, nS‐8) at the 0.2 μmol scale. Activator 42® was used as the activator. The coupling time of the standard phosphoramidite coupling protocol was increased from 30 s to 12 min. The B^AEO phosphoramidite 9 was prepared with 0.10 m acetonitrile/THF (v/v, 3:1). The ON synthesis was performed in the DMTr‐on mode. CPG‐supported ODNs were cleaved and the protecting groups of the nucleobases were removed with 50 mm K₂CO₃ in MeOH at RT for 4 h. The DMTr group in ODNs were detritylated and purified with a Sep‐Pak^® Plus C18 Cartridge and Sep‐Pak® Plus C18 Environmental Cartridge (Waters) [washed with 10 % acetonitrile aqueous solution, detritylated with 0.5 % aqueous trifluoroacetic acid solution, and eluted with 35 % aqueous MeOH solution]. ODNs were purified by means of reverse‐phase HPLC on a Waters XBridge^TM OST C18 2.5 μm (10×50 mm) with 0.1 m triethylammonium acetate buffer (pH 7.0) (buffer a) and acetonitrile (buffer b). The purified ODNs were analyzed by means of reverse‐phase HPLC on a Waters XBridge^TM OST C18 2.5 μm (4.6×50 mm) column. The structures of ODNs were determined by means of MALDI‐TOF MS (Bruker Daltonics AutoflexII TOF/TOF mass spectrometer).