Synthesis and photochemical behaviour of a T-T dimer containing an amide linkage

A T-T dimer characterized by an amide linkage to replace the phosphodiester backbone has been synthesized using a modified radical strategy. The new synthetic approach makes use of a thymidin-3'-yl phosphorodithioate derivative as a precursor of 3'-allyl-3'-deoxythymidine. Standard chemical transformations of this derivative led to the desired T-T dimer incorporating an amide bond. The latter was irradiated with 254 nm wavelength light to yield mainly cyclobutane and [6-4] photoadducts.