Studies on transfer ribonucleic acids and related compounds. IX. Ribooligonucleotide synthesis using a photosensitive o-nitrobenzyl protection at the 2'-hydroxyl group

o-Nitrobenzyl group was introduced to the 2'-hydroxyl function of uridine via 2',3'-O-(dibutylstannylene) uridine. The benzylated uridine was protected at the 5'-hydroxyl group with monomethoxytrityl chloride and condensed with 2',3'-O-dibenzoyluridine 5'-phosphate or N,N',2',3'-O-tetrabenzoyladenosine 5'-phosphate using dicyclohexylcarbodiimide (DCC). o-Nitrobenzyl ether linkage of the dinucleotides was removed by UV irradiation with wavelength longer than 320 nm. Deprotected UpU and UpA thus obtained were characterized by RNase A digestion.