Previously 2'-O-(o-nitrobenzyl) uridine was synthesized via 2', 3'-O-(stannylene) uridine and used in the synthesis of UpA and UpU. 2'-O-(o-Nitrobenzyl) derivatives of cytidine and adenosine were synthesized with o-nitrobenzyl bromide in the presence of sodium hydride. 3'-O-(o-Nitrobenzyl) cytidine was also isolated. Using these 2'-protected nucleosides, partially protected trinucleoside diphosphates, CpA (o-nitrobenzyl)-pA and CpCpA (o-nitrobenzyl) were synthesized using a diester method or a triester method. These oligomers are candidates as suitable substrates of ribonucleic acid (RNA) ligase. Removal of the o-nitrobenzyl group was effected by irradiation with ultraviolet spectrum (UV) light (wavelength longer than 280 nm) and the completely deblocked oligonucleotides were characterized by enzymatic hydrolysis.