Irreversibly Binding Photosynthetic Electron Transport Inhibitors II. Halogen-Substituted 1,4-Naphthoquinones and Halogenmethyl-1,4-quinones

Several halogen-substituted 1,4-naphthoquinones have been synthesized and found to be effective photosystem II inhibitors. Due to their properties as vinylogous acid halides they can react with nucleophiles under formation of a covalent linkage. In their presence other photosystem II herbicides show a decreased binding affinity. This decrease is dependent from the preincubation time. Halogenmethyl-1,4-quinones also turned out to be efficient photosystem II inhibitors and. in addition, possessed herbicidal in vivo activity. They function as “bioreductive alkylating agents” in a way that after reduction they can split off hydrogen halide under formation of a o-quinonemethide. This quinonemethide can react with nucleophilic groups in proteins.