Site-selected incorporation of 5-carboxymethylaminomethyl(-2-thio)uridine into RNA sequences by phosphoramidite chemistry

5-Carboxymethylaminomethyluridine (cmnm(5)U) and 5-carboxymethylaminomethyl-2-thiouridine (cmnm(5)s(2)U) are located at the wobble position in several cytosolic and mitochondrial tRNA sequences. In this paper, we report the first site-selected incorporation of cmnm(5)U and cmnm(5)s(2)U into RNA sequences by phosphoramidite chemistry on a CPG solid support. Trifluoroacetyl and 2-(trimethylsilyl)ethyl were selected for the protection of the amine and carboxyl functions, respectively.