Design, synthesis and mode of action of novel 3-chloro-6-pyrazolyl picolinate derivatives as herbicide candidates

BACKGROUND: Picolinate/picolinic acid compounds are an important class of synthetic auxin herbicides. To explore the herbicidal activity of 6-pyrazolyl picolinate compounds, a series of 3-chloro-6-pyrazolyl-picolinate derivatives was designed and synthesized. RESULTS: Twenty-five 3-chloro-6-pyrazolyl-picolinate derivatives synthesized were tested for herbicidal activity and the IC50 value of compound c5 to the growth of Arabidopsis thaliana root was 27 times lower than that of the commercial herbicide clopyralid. Compound c5 displayed better post-emergence herbicidal activity and broader (Picloram, Clopyralid, Aminopyralid) herbicidal spectrum at a dosage of 400 g ha(-1) in comparison with clopyralid; it also was safe to wheat and maize at this dosage. Arabidopsis thaliana phenotypes and expression of auxin-response genes demonstrated that compound c5 might be a novel auxin-type herbicide. Molecular docking analyses revealed that compound c5 had stronger binding ability to receptor AFB5 (auxin signaling F-box protein 5) than clopyralid. CONCLUSION: These 6-pyrazolyl picolinate compounds could be used as potential lead structures for the discovery of a novel synthetic auxin herbicide. (c) 2021 Society of Chemical Industry

Automated summary

A series of 3-chloro-6-pyrazolyl-picolinate derivatives were synthesized and tested for herbicidal activity, with compound c5 showing lower IC50 value and broader herbicidal spectrum compared to commercial herbicide clopyralid. Compound c5 may serve as a novel auxin-type herbicide with stronger binding ability to receptor AFB5. These compounds could be potential lead structures for the discovery of new synthetic auxin herbicides.