Photocycloaddition of cytosine to 5-methoxyuracil in dinucleotide model compound

Abstract

The intramolecular photocycloaddition of cytosine (Cyt) to 5-methoxyuracil (mo5U) in Cyt-(CH2)3-mo5Ura, a dinucleotide model compound, occurs upon irradiation with near ultraviolet light (λ > 300 nm) with the formation of an unstable cyclobutane dimer. The dimer undergoes spontaneous dark deamination with a rate constant k = 9.0 × 10−5 s−1 and t1/2 = 128 min, to give a related uracil derivative.