Practical synthesis of N-(di-n-butylamino)methylene-protected 2-aminopurine riboside phosphoramidite for RNA solid-phase synthesis

Synthesis of N4-acetylated 3-methylcytidine phosphoramidites for RNA solid-phase synthesis

The growing interest in 3-methylcytidine (m³C) originates from the recent discoveries of m³C modified tRNAs in humans as well as its intensively debated occurrence in mRNA. Moreover, m³C formation can be catalyzed by RNA without the assistance of proteins as has been demonstrated for a naturally occurring riboswitch fold using the methylated form of its cognate ligand as cofactor. Additionally, new RNA sequencing methods have been developed to detect this modification in transcriptome-wide manner. For all these reasons, an increasing demand for synthetic m³C containing oligoribonucleotides is emerging. Their chemical synthesis relies on RNA solid-phase synthesis using phosphoramidite building blocks. Here, we describe a facile synthetic path towards N⁴-acetylated 2′-O-TBDMS- and 2′-O-TOM m³C phosphoramidites to provide an optimal toolbox for solid-phase synthesis of m³C containing RNA.