Methylating agents are common carcinogens which function by methylation of nucleobases in DNA. Cellular polynucleotides are alkylated by endogenous components, such as S-adenosylmethionine. Chemically, SN1 agents such as alkylnitrosourea and N-alkyl-N-nitro-N-nitrosoguanidine will react with the N7 position of guanine, N3 of adenine, O6 of guanine, O2 or O4 of pyrimidines, and the non-phosphodiester oxygen atoms of the phosphate backbone. In contrast, SN2 chemical agents such as methyl methanesulfonate and dimethyl sulfate react primarily with the N1 position of adenine (1-Methyl-2'-deoxyadenosine) and N3 of cytosine. To examine some of these resulting mutagenic effects, the methylated products O6-Me-dG- CE Phosphoramidite, N6-Me-dA-CE Phosphoramidite, and O4-Me-dT-CE Phosphoramidite can be incorporated in oligonucleotides. To avoid chain branching during synthesis when using DCI as activator, N6-Me-dA is offered with acetyl protection. O6-Me-dG- CE Phosphoramidite has classic iBu protection.