Acetylation of the nucleoside cytidine, which gives the N 4 -acetylcytidine (ac4C, Figure ) epitranscriptomic modification, has been observed in RNAs including tRNAs, rRNAs, mRNAs and various regulatory RNAs. It plays a wide range of roles in biological systems. Errors related to the modification have been found to be associated with many human diseases . More recently, acetylation of deoxycytidine, which gives the N 4 -acetyldeoxycytidine (4acC, Figure ) epigenetic modification, has also been discovered in the DNA of Arabidopsis, rice, maize, mouse, and human. It is mainly located around transcription start sites and positively correlates with gene expression levels . Several studies using synthetic oligodeoxynucleotides (ODNs) and oligoribonucleotides (ORNs) have shown that acetylation of cytosine can increase the UV melting temperature of duplex oligonucleotides (ONs) by 1 -8 °C . The knowledge sheds a light on the mechanisms by which ac4C plays roles such as enhancing protein synthesis efficiency in the biological system . This shows the significance of the synthesis of ONs containing sensitive modifications such as ac4C and 4acC as well as numerous others . However, standard ON synthesis methods requires deprotection and cleavage under strongly basic and nucleophilic conditions, under which ac4C, 4acC and other sensitive groups are unstable. Although several reported methods may be used for the purpose, they have various limitations as discussed earlier . For example, some methods can only synthesize ONs that contain thymidine or uridine only and thus do not need nucleobase protection . Some require UV irradiation for cleavage, which can damage ON . Some are limited to the synthesis of short ONs . Therefore, the development of practically useful methods for sensitive ON synthesis without any sequence limitations and with broad sensitive group scope is highly significant. Our research group recently reported sensitive ODN synthesis using the Dmoc function for linking, and the meDmoc group for the protection of exo-amino groups of the nucleobases cytosine, adenine and guanine. With these protecting and linking strategy, ODN deprotection and cleavage were achieved under non-nucleophilic and weakly basic conditions . The method enabled us to synthesize ODN sequences containing various sensitive groups including 4acC. In this paper, we report the synthesis of ODNs containing up to four 4acC modifications (ODNs 1a-d, Table ), as well as those containing the N 2acetyldeoxyguanosine (2acG, Figure , ODN 1e), N 6 -acetyldeoxyadenosine (6acA, Figure , 1f), and N 4methoxycarbonyldeoxycytidine (4mcC, Figure , ODN 1g) modifications. Unlike ac4C and 4acC, the 6acA, 2acG, and 4mcC as well as ac6A, ac2G and mc4C modifications have not been found in the nature. However, a demonstration of their incorporation into ODNs is expected to facilitate projects with aims such as evaluating their potential for antisense, RNAi, CRISPR, and mRNA therapeutic applications.