AMINOPYRAZOLONES - NOVEL PHOTOSYSTEM-II INHIBITORS

We have investigated the inhibition of photosynthetic electron flow by the aminopyrazolones, a novel class of photosystem II herbicides. The pattern of substitution in the aryl moiety of these molecules affects the level of inhibition of the Hill reaction. Hydrophobic substituents that are also electron withdrawing favor inhibition. Similarities in the pattern of structure-activity of the aminopyrazolones and the phenylureas indicate that both classes of compounds block electron flow at the acceptor site of photosystem II and also occupy common enzymic space on the 32-kDa herbicide binding protein. © 1990, American Chemical Society. All rights reserved.