Chemical reagents, including fully protected 2'-O-methyladenosine phosphoramidite were purchased from commercial sources. P-Imidazolide of N7-methylguanosine 5′-diphosphate Geng 13
(im-m 7 GDP), fully protected of 2′-O,N 6 -dimethyladenosine phosphoramidite and N2isobutyryl-2′,3′-isopropylidene-guanosine were synthesized according to the previously described protocols (Kowalska et al. 2008; Eisenführ et al. 2003; Sikorski et al. 2020) .
(im-m 7 GDP), fully protected of 2′-O,N 6 -dimethyladenosine phosphoramidite and N2isobutyryl-2′,3′-isopropylidene-guanosine were synthesized according to the previously described protocols (Kowalska et al. 2008; Eisenführ et al. 2003; Sikorski et al. 2020) .
