Abstract
4,5′,8-Trimethylpsoralen was attached to the C8- position of deoxyadenosine via a sulfur atom and a five carbon atom linker. The modified deoxyadenosine was then converted to a protected phosphoramidite and used as usual as a building block for solid phase oligodeoxyribonucleotide synthesis. The efficiency of the photoreaction of a psoralen-modified oligonucleotide to a complementary matrix strand reached more than 90% within a 1hour irradiation time at a wavelength of 345 nm.