We synthesized oligonucleotide (1) containing 4'-o-nitrobenzyloxythymidine (2), which was prepared by reaction of 4',5'-unsaturated thymidine with m-CPBA followed by Lewis-acid catalyzed addition of o-nitrobenzylalcohol. The duplex stability of 1 with the complementary oligonucleotide was studied by Tm measurement. Photochemical reaction of 1 to generate C4'-oxidized abasic site containing oligonucleotide (3) was studied.