Using the Dmoc method, ODNs 1a-g (Table ) were synthesized. Among them, 1a-d contain one to four 4acC modifications, respectively. As shown in Figures , the acetylated ODNs showed a major peak in RP HPLC profiles. Unfortunately, besides the major ODN peak, the peak for 1a had a shoulder before the major peak, and in the profiles of 1b-d, a smaller peak appeared at ~10 minutes. However, we believe that these were caused by non-ODN materials from the HPLC system because CE analysis of the samples gave single sharp peaks (Figures ). In addition, the samples all gave single sharp peaks in MALDI MS with predicted molecular mass (Figures ), and gel electrophoresis analysis also gave single bands (supporting information). The MS data indicates that the 4acC modification was stable under the Dmoc ODN synthesis, deprotection and cleavage conditions. It is well known that 4acC and ac4C are highly sensitive modifications. It is remarkable that the ODN 1d, which contained four 4acC modifications densely packed in a short sequence, could be synthesized. The ODNs 1e-f contain a 2acG and 6acA modification, respectively. As shown in Figures , a major peak corresponding to the ODNs was observed although the peak of 1e had a shoulder after the major peak. Again, we believe that it was caused by our HPLC system because both samples gave a single sharp peak in CE profiles (Figures ), and MALDI MS gave a single sharp peak with predicted molecular mass (Figure ). In addition, gel electrophoresis analysis gave single bands (supporting information). The 2acG and 6acA modifications have not been found in nature. However, it is possible that they behave similarly as 4acC and ac4C, and may increase ON cellular stability, duplex stability, and mRNA translational efficiency. The success of their incorporation into ODN is expected to facilitate the study of these and other biophysical properties of such ODNs. It is noted that among the ODNs containing the 4acC, 2acG, and 6acA modifications, the ODN containing 2acG is most labile. The success in synthesizing ODN 1e, and purifying and analyzing it indicates that 2acG, like 4acC and 6acA, is stable enough for applications such as antisense, RNAi, CRISPR, and mRNA therapeutic development.