Efficient Synthesis of 2’-O-Cyanoethylated Imidazole C-Ribonucleoside Phosphoramidite:A Practical Building Block for Probing the Catalytic Mechanism of Ribozymes

A high-yielding synthetic route leading to new 2'-O-cyanoethylated imidazole C-ribonucleoside phosphoramidite (PA) 1 has been developed (41% overall yield in ten steps). This has resulted in a marked improvement of yield compared to unstable 2'-O-TBDMS PA 2. The new synthon PA 1 enables the imidazole moiety to be incorporated into any RNA sequence in principle, and has been used as a practical building block for probing the catalytic mechanism of a ribozyme.