Synthesis of a hairpin pyrrole–imidazole polyamide conjugate containing a quinone methide precursor and vinyl linking group

Standard procedures for elaborating a quinone methide precursor for conjugation to a DNA ligand was not compatible with the presence of a vinyl group. Instead, an acrylate linker was attached by Heck coupling subsequent to o-substitution of the phenolic precursor. This transformation required protection of the phenolic group and use of ethyl acrylate rather than acrylic acid. The presence of the vinyl group also rendered the quinone methide precursor more labile to alkaline conditions than its equivalent saturated derivative and required mild conditions for coupling to the pyrrole–imidazole polyamide.