Synthesis of a novel C2/C2′-exo unsaturated pyrrolobenzodiazepine cross-linking agent with remarkable DNA binding affinity and cytotoxicity

A C2/C2′-exo unsaturated pyrrolobenzodiazepine dimer 1 has been synthesised which is cytotoxic at the picomolar level and has remarkable covalent DNA binding affinity, raising the melting temperature of duplex-form calf thymus DNA by 34 °C after 18 h incubation.