A Convenient High Yield Synthesis of N4-Isobutyryl-2′-O-Methylcytidine and Its Monomer Units For Incorporation into Oligonucleotides

Abstract
We designed an efficient three step procedure for the synthesis of N4-isobutyryl-2′-O-methylcytidine. This protected nucleoside was then used to prepare a methylphosphonamidite monomer for incorporation into oligonucleotides. Transamination at the C4 position of cytidine using ethylenediamine, which has been reported for the N4-benzoyl cytidine, was not observed with N4-isobutyryl protected 2′-O-methylcytidine.