Photoirradiation of dibenzoyldiazomethane (DBDM) produced highly electrophilic benzoylketene via Wolff rearrangement. DBDM derivative possessing an aminoalkyl side chain induced a DNA cleavage selectively at guanine (G) residues upon photoirradiation and subsequent piperidine treatment. In order to devise photochemical DNA cleavers that can specifically alkylate a guanine residue proximal to the target sequence of long DNA ...