Synthesis of Sensitive Oligodeoxynucleotides Containing Acylated Cytosine, Adenine, and Guanine Nucleobases

The synthesis of oligodeoxynucleotides (ODNs) containing the base-labile <i>N</i> ⁶-acetyladenosine (6acA), <i>N</i> ²-acetylguanosine (2acG), and <i>N</i>4-methyoxycarbonyldeoxycytidine (4mcC), as well as up to four <i>N</i> ⁴-acetyldeoxycytidine (4acC) modifications is described. The 1,3-dithian-2-yl-methoxycarbonyl (Dmoc) group was used as the linker for solid phase synthesis, and the methyl Dmoc (meDmoc) group was used for the protection of the <i>exo</i>-amino groups of nucleobases. Deprotection and cleavage were achieved under non-nucleophilic conditions, under which the highly sensitive 4acC, 6acA, 2acG, and 4mcC were found completely stable. Among the modified nucleotides, 4acC has been found in nature, and proven beneficial to DNA duplex stability. Although 6acA, 2acG and 4mcC have not been found in nature, a synthetic route to ODNs containing them is expected to facilitate projects aimed at studying their biophysical properties as well as potential for antisense, RNAi, CRISPR, and mRNA therapeutic applications.