Novel naphthalimide hydroperoxide photonucleases: the role of thiocyclic-fused area and the difference in spectra, photochemistry and photobiological activity.

Novel five- and six-membered thiocyclic-fused naphthalimide hydroperoxides (7, 8) as photonucleases were designed, synthesized via unusual isomerization in Pschorr cyclization and photooxygenation. The five-membered 7 was able to induce single-strand nicks in duplex DNA pH independently (7.0-8.5) at 0.5 microM under 366 nm, while the six-membered 8 could photonick the duplex DNA pH dependently (7.0-8.5) at 5 microM under 450 nm and showed 'time-controlled' photo-bioactivity. Their thiocycles and the angular conjugated plane have contributions to their binding affinity with DNA and photocleaving efficiency.