Sulfonylurea (SU) herbicides have been in use for more than thirty years, and they still remain an important class of herbicides widely used in agriculture. In Japan, SU herbicides have been widely used in paddy fields; however, recently several paddy weed species showing resistance to SU herbicides are spreading nationwide. We have focused on discovering a new herbicide and investigated the herbicidal activity of pyrazolesulfonylurea derivatives on SU-resistant weeds. As a result, we found that some pyrazole-5-sulfonylureas showed high levels of herbicidal activity against SU-resistant weeds. Further evaluation of the pyrazolesulfonylurea chemistry led to the discovery of metazosulfuron. It is a new SU herbicide, which shows excellent herbicidal activity against annual and perennial weeds including SU-resistant biotypes in paddy fields. In this presentation, the structure-activity relationships of pyrazolesulfonylurea derivatives as well as the synthesis of metazosulfuron will be discussed.

Discovery of metazosulfuron: A new sulfonylurea herbicide for rice

246th National Meeting (2013)

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