Shaa Zhou

Research on controllable degradation of sulfonylurea herbicides

In order to seek ecologically safer and environmentally benign sulfonylurea herbicides (SU), insight into the structure/bioassay/soil degradation tri-factor relationship was first established. With the introduction of various groups (alkyl, nitro, halogen, cyano etc.) at the 5th position of its benzene ring, structural derivatives of chlorsulfuron were designed, synthesized, and evaluated for their herbicidal activity. The structures of the title compounds were confirmed by infrared spectroscopy, ultraviolet spectroscopy, 1H and 13C NMR, mass spectrometry, elemental analysis and X-ray diffraction. Bioassay results confirmed that most derivatives retained their superior herbicidal activities in comparison with chlorsulfuron. After investigating the soil degradation behavior of each molecule under set conditions, it was found that structures with electron-withdrawing substituents at the 5th position of the benzene ring retained their long degradation half-lives, yet the introduction of electron-donating substituents accelerated the degradation rate. These results will provide a valuable clue to further explore the potential controllable degradation of SU and other herbicides, and to discover novel herbicides that are favorable for environmentally and ecologically sustainable development.

Design, synthesis and herbicidal activity study of aryl 2,6-disubstituted sulfonylureas as potent acetohydroxyacid synthase inhibitors

A series of sulfonylurea derivatives containing a 2,6-disubstituted aryl moiety were designed, synthesized and evaluated for their herbicidal activities. Most of these compounds showed excellent inhibitory rates against both monocotyledonous and dicotyledonous weeds, especially 10a, 10h and 10i. They exhibited equivalent or superior herbicidal efficiency than commercial chlorsulfuron at the dosage of 15g/ha and the preliminary SAR was summarized. In order to illuminate the molecular mechanism of several potent compounds, their apparent inhibition constant (Kiapp) of Arabidopsis thaliana acetohydroxyacid synthase (AHAS) were determined and the results confirmed that these compounds were all potent AHAS inhibitors. 10i have a Kiapp of 11.5nM, which is about 4 times as potent as chlorsulfuron (52.4nM).

Research on Controllable Degradation of Novel Sulfonylurea Herbicides in Acidic and Alkaline Soils

The degradation issue of sulfonylurea (SU) has become one of the biggest challenges that hamper the development and application of this class of herbicides, especially in the alkaline soils of northern China. On the basis of the previous discovery that some substituents on the fifth position of the benzene ring in Chlorsulfuron could hasten its degradation rate, apparently in acidic soil, this work on Metsulfuron-methyl showed more convincing results. Two novel compounds (I-1 and I-2) were designed and synthesized, and they still retained potent herbicidal activity in tests against both dicotyledons and monocotyledons. The half-lives of degradation (DT50) assay revealed that I-1 showed an accelerated degradation rate in acidic soil (pH 5.59). Moreover, we delighted to find that the degradation rate of I-1 was 9-10-fold faster than that of Metsulfuron-methyl and Chlorsulfuron when in alkaline soil (pH 8.46), which has more practical value. This research suggests that a modified structure that has potent herbicidal activity as well as accelerated degradation rate could be realized and this approach may provide a way to improve the residue problem of SUs in farmlands with alkaline soil.