Abstract: The present invention relates to the field of oncology. laboratory tools and methods, and especially anti-tumor DNA crosslinking agents. Most patients with advanced solid tumors develop resistance to chemotherapy due to the ability of cancer cells to repair or tolerate sustained DNA damages. The inventors showed that the compounds according to the present invention allow the detection and visualization of alkylated DNA damages induced by PBDs without altering their DNA crosslinking ability. This enables the study of the effect and properties of PBDs. In particular, the present invention relates new derivates of PBD molecules and their synthesis. The present invention also relates to a method for visualizing DNA crosslinking: to a method for assessing the resistance of a tumor to a crosslinking agent and to a method for identifying a molecule or treatment for improving the efficiency of a crosslinking agent.