Visible‐Light‐Triggered Cross‐Linking of DNA Duplexes by Reversible [2+2] Photocycloaddition of Styrylpyrene

Reversible photo-cross-linking of a DNA duplex through the [2+2] photocycloaddition of styrylpyrene is reported. Styrylpyrene moieties on d-threoninol linkers were introduced into complementary positions on DNA strands. Irradiation of the styrylpyrene pair in the duplex with visible light at λ=455 nm induced a [2+2] photocycloaddition between styrylpyrenes that cross-linked the two strands of the duplex. Two diastereomers were formed after [2+2] photocycloaddition as a result of rotation of the styrylpyrene residues. Also, the cycloreversion reaction was induced by UV light at λ=340 nm, which reversibly yielded the uncross-linked strands.