tempo and methoxyamine

Most photoinduced DNA cross-link formation by a bifunctional aryl derivative is through a bisquinone methide. DNA cross-linking via a bisarylcarbocation remains a less explored area. We designed and synthesized a series of naphthalene boronates that produce DNA interstrand cross-links via a carbocation upon UV irradiation. A free radical was generated from the naphthalene boronates with 350 nm irradiation and further converted to a carbocation by electron transfer. The activation mechanism was determined using the orthogonal traps, 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) and methoxyamine that react with either the free radical or the carbocation but not both. This represents a novel example of photoinduced DNA cross-link formation via carbocations generated from a bisaryl derivative. This work provides information useful for the design of novel photoactivated DNA cross-linking agents.

Topics: Boronic Acids; Cross-Linking Reagents; Cyclic N-Oxides; DNA; DNA Damage; Electron Transport; Free Radicals; Hydroxylamines; Naphthalenes; Nucleic Acid Conformation; Photochemical Processes; Ultraviolet Rays

UV irradiation of several aryl boronates efficiently produced bifunctional benzyl cations that selectively form guanine-cytosine cross-links in DNA. Photoinduced homolysis of the C-Br bond took place with the aryl boronate bromides 3a and 4a, generating free radicals that were oxidized to benzyl cations via electron transfer. However, photoirradiation of the quaternary ammonium salts 3b and 4b led to heterolysis of C-N bond, directly producing benzyl cations. The electron-donating group in the aromatic ring greatly enhanced cross-linking efficiency.

Topics: Base Sequence; Benzene Derivatives; Boronic Acids; Cations; Cross-Linking Reagents; Cyclic N-Oxides; Cytosine; DNA; DNA Adducts; Guanine; Hydroxylamines; Oxidation-Reduction; Photochemical Processes