The structure-activity relationship in herbicidal monosubstituted sulfonylureas

Area of Science:

• Agricultural Chemistry
• Organic Chemistry
• Biochemistry

Background:

• Sulfonylurea (SU) herbicides are globally significant due to their low mammalian toxicity and ultralow dosage application.
• Established structure-activity relationship (SAR) guidelines by G. Levitt guided SU design for high bioactivity.
• A novel approach to SU molecular design has been developed, challenging existing paradigms.

Purpose of the Study:

• To explore novel sulfonylurea (SU) structures for enhanced herbicidal activity.
• To revise existing SU structure-activity relationship (SAR) guidelines based on new findings.
• To investigate the mode of action of newly developed SU herbicides.

Main Methods:

• X-ray diffraction analysis of numerous SU products.
• Greenhouse herbicidal screening of 900 novel SU structures.
• Systematic structural study of substrate-target complexes for new SU molecules.

Main Results:

• Several SU structures with a monosubstituted pyrimidine moiety exhibited excellent herbicidal characteristics.
• The findings necessitated a partial revision of the original Levitt SAR guidelines for SU design.
• Two novel SU herbicides, monosulfuron and monosulfuron-ester, were developed and approved.

Conclusions:

• Monosulfuron and monosulfuron-ester herbicides are approved for field use in millet and wheat in China.
• A new mode of action for these novel SU herbicides has been postulated.
• The study contributes to the advancement of herbicide design and application.