Published on Aug. 5, 2003 in Helvetica Chimica Acta volume .
The synthesis of various N-methylated nucleosides (m6A, m3C, m4C, m3U) is described. These minor nucleosides can be obtained by simple methylation with diazomethane of [2-(4-nitrophenyl)ethoxy]carbonyl(npeoc)-protected nucleosides. These methylated compounds are easily further derivatized to fit into the scheme of the [2-(dansyl)ethoxy]carbonyl (dnseoc) approach for RNA synthesis (dansyl=[5-(dimethylamino)naphthalen-1-yl]sulfonyl). Various oligoribonucleotides containing N6-methyladenosine were synthesized, underlining the usefulness of the dnseoc approach, especially for the synthesis of natural tRNA-derived oligoribonucleotide sequences.