Synthesis of oligoribonucleotides containing N6-alkyladenosine and 2-methylthio-N6-alkyladenosine.

The N(6)-alkyladenosines and 2-methylthio-N(6)-alkyladenosines are the most common modified adenosine nucleosides, and transfer ribonucleic acids (tRNA) are particularly rich in these modified nucleosides. They are present at position 37 of the anticodon arm, and the contributions of these hypermodified nucleosides to codon-anticodon interactions as well as to translation are significant, although they are not fully understood. This unit describes a new chemical synthesis method for oligoribonucleotides containing N(6)-alkyladenosines and 2-methylthio-N(6)-alkyladenosines via postsynthetic modifications of precursor oligoribonucleotides. To obtain oligoribonucleotides containing N(6)-alkyladenosines, a precursor oligoribonucleotide carrying 6-methylthiopurine riboside residues was used, whereas for the synthesis of oligoribonucleotides containing 2-methylthio-N(6)-alkyladenosines, a precursor oligoribonucleotide carrying the 2-methylthio-6-chloropurine riboside was applied. This allowed synthesis of modified oligoribonucleotides containing naturally occurring modified nucleosides such as N(6)-isopentenyladenosine (i(6)A), N(6)-methyladenosine (m(6)A), 2-methylthio-N(6)-isopentenyladenosine (ms(2)i(6)A), and 2-methylthio-N(6)-methyladenosine (ms(2)m(6)A), as well as several unnaturally modified adenosine derivatives.