The ODN syntheses were accomplished using phosphoramidites 2a-i, and the linker 2j (Figure ). Among them, 2a-c are standard meDmoc phosphoramidites, and 2j is a standard Dmoc linker. Monomers 2e, 2g-i are known compounds , and they were synthesized in house. The details for the synthesis of 2g-i are provided in the Supporting Information. Monomers 2d and 2f were purchased from commercial sources. The syntheses were carried out under conditions similar to those using standard phosphoramidite chemistry except that capping was achieved using 2-cyanoethyl N,N,N′,N′-tetraisopropylphosphoramidite and the nucleotide at the 5′-end was incorporated using phosphoramidite 2e. At the end of syntheses, the ODNs can be represented by 3 (Figure ), which contained a Tr group (not shown in 3) introduced by 2e. Deprotection and cleavage were achieved in three steps. In the first step, the 2-cyanoethyl groups were removed by washing the CPG with 10% DBU in ACN, which converted 3 to 4. In the second step, the Dmoc and meDmoc groups were oxidized with NaIO 4 converting 4 to 5. In the third step, the oxidized meDmoc and Dmoc groups were cleaved via β-elimination induced by the weak non-nucleophilic base K 2 CO 3 . This gave the fully deprotected ODN with a 5′-Tr group 6 (5′-Tr not shown). All the three steps were convenient to operate because during the first two steps, the ODNs were still on the solid support. Excess reagents and side products could be removed simply by washing. For the third step, the solid support and the ODNs in the supernatant were easy to separate, and the quantity of K 2 CO 3 was minute, which did not require to be removed before HPLC purification of the ODN. In addition, all the deprotection and cleavage reactions were carried out at room temperature, which ensured stability of sensitive groups on the ODNs. The ODNs were purified by precipitation with nBuOH from water to remove small organic molecules resulted from deprotection. The precipitate was then further purified with RP HPLC, which was made possible with the Tr group at the 5′-end of the ODNs. The typical DMTr group was found unstable in the NaIO 4 oxidation step during ODN deprotection and cleavage. The purified Tr-on ODN was then detritylated with 80% AcOH, and purified again with RP HPLC. The purity of the ODNs was evaluated by HPLC and capillary electrophoresis (CE, Figure ) as well as polyacrylamide gel electrophoresis (supporting information). The identity of the ODNs was confirmed with MALDI MS (Figure ).