We thus synthesized a new series of transition state analogs of the RNA 2′-O-methylation reaction based on the coupling of a 2′-O-ethyl adenosine to a 5′-amino adenosine. We explored a variety of N-substituted linkers in adenine dinucleosides and their inhibition activity was evaluated against several viral RNA 2′O-MTases as well N7-MTases for specificity purpose. Unexpectedly, none of the N-linked dinucleosides inhibited any 2′O-MTases of flaviviruses or SARS-CoV. However, interestingly some N-nitrobenzenesulfonamide-containing dinucleosides were found to specifically inhibit SARS-CoV N7-MTase nsp14 without inhibiting the cognate human N7-MTase or vaccinia N7-MTase. Such specific inhibition results from a high binding affinity of the most potent inhibitors to N7-MTase nsp14. In addition, computational docking analysis identified some residues of the binding site for the best inhibitor targeting nsp14. As SAM and RNA binding sites of N7-MTase nsp14 are almost completely conserved between SARS-CoV and SARS-CoV-2 (95% sequence homology, Supporting Info Fig. S1) [18], we can forecast that the candidate ligands that are efficient in inhibiting the SARS-CoV functions will be efficient in doing the same for SARS-CoV-2, this emphasizes the interest of the present work.