Pyrenylboronic acids as a novel entry for photochemical DNA cleavage: diradical-forming pyrene-1,6-diyldiboronic acid mimics the cleavage mechanism of enediyne antitumor antibiotics

Pyren-1-ylboronic acid 4 and pyrene-1,6-diyldiboronic acid 5 are bound to supercoiled double-strand circular DNA plasmid ColE1 (colDNA) and effect its efficient photocleavage under visible light irradiation. Mechanistic studies show that the cleavage occurs according to the radical mechanism. The cleavage activity of monoacid 4 could be suppressed by the addition of D-fructose because of boronic acid–saccharide complexation. Diacid 5 is bound to colDNA more strongly than is monoacid 4 and effects its efficient photocleavage to yield Form III. The results show that diradical-forming diacid 5 is able to cleave DNA at two reaction sites, mimicking the cleavage mechanism of enediyne antitumor antibiotics.