Fine-tuning alkyne cycloadditions: Insights into photochemistry responsible for the double-strand DNA cleavage via structural perturbations in diaryl alkyne conjugates

• Wang-Yong Yang,
• Samantha A. Marrone,
• Nalisha Minors,
• Diego A. R. Zorio and
• Igor V. Alabugin

Beilstein J. Org. Chem. 2011, 7, 813–823, doi:10.3762/bjoc.7.93

• cytotoxicity) value of 1.49 × 10−7 M. Keywords: cancer cell proliferation assay; DNA alkylation; lysine conjugate; photocycloaddition; photo-DNA cleavage; plasmid relaxation assay; triplet excitation; Introduction Triggering chemical processes with light offers numerous practical advantages. Not only does

• -membered product, a benzoxazine. The formation of benzoxazines has been previously reported by Roberts and coworkers, who suggested cyclization via triplet excitation following hydration [59][60][61][62]. The presence of vinyl peaks at 6.2 and 5.9 ppm in the reaction mixture and their quick disappearance

• hydroxyl radical scavengers, glycerol and DMSO, protected DNA from the cleavage by 33 and 26%, respectively, whereas NaN3 showed ~43% protection. The large protecting effect of NaN3, the singlet oxygen scavenger, is consistent with the efficient photoaddition reaction of its chromophore via triplet