2-(4-Tolylsulfonyl)ethoxymethyl (TEM)—a new 2′-OH protecting group for solid-supported RNA synthesis

The 2-(4-tolylsulfonyl)ethoxymethyl (TEM) as a new 2′-OH protecting group is reported for solid-supported RNA synthesis using phosphoramidite chemistry. The usefulness of the 2′-O-TEM group is exemplified by the synthesis of 12 different oligo-RNAs of various sizes (14–38 nucleotides long). The stepwise coupling yield varied from 97–99% with an optimized coupling time of 120 s. The synthesis of all four pure phosphoramidite building blocks is also described. Two new reliable parameters, δ_C2′ − δ_C3′ and δ_H2′ − δ_H3′, have been suggested for the characterization of isomeric 2′-O-TEM and 3′-O-TEM as well as other isomeric mono 2′/3′-protected ribonucleoside derivatives. The most striking feature of this strategy is that the crude RNA prepared using our 2′-O-TEM strategy is sufficiently pure (>90%) for molecular biology research without any additional purification step, thereby making oligo-RNAs easily available at a relatively low cost, saving both time and lab resources.