Design, Synthesis And Bioactivity Assay Of Auxin-type Herbicide Molecular Probes

Herbicides block the physiological processes of plant mainly through inhibiting the specific targets, affect the normal growth and kill the plant ultimately. However, among the more than270kinds of commercial herbicides, there are only17targets that are known. Large numbers of herbicides’targets are ambiguity. Thus, identifying the targets of these herbicides and developing the strageties for the design and synthesis of new lead compunds based on the structures of these targets have a primary importance. The strategies using chemical small molecule probes have been proven to be effective methods in the study of drug targets and the mode of action. Generally, molecular probes are derived from drug molecules, and used to trace the target distribution in organisms and identify their targets. Indoleacetic acid (IAA), naphthylacetic acid (NAA), and picolinate are plant auxin hormones, and their targets are the focus of recent researches. In this thesis, the hormone molecules, including IAA, NAA and picolinate, are used as parents and derived to afford new auxin-type herbicide probes, and their interaction with the targets in plant is preliminarily explored. The main work contains the following aspects:1. The outline of the function and mechanism of auxin is briefly presented; the characteristics and research status of IAA, NAA, and picolinate derivatives are disclosed. The methods and applications of chemical small molecular probes in target research are also described.2. Starting with IAA and NAA, alkyl or alkoxy group chains are introduced at the a positions of carboxyl group to construct a series of auxin inhibitors. The structures of these compounds are confirmed and their biological activities are tested against the growth of Arabidopsis thaliana. Experimental results show that when the alkyl or alkyloxy chain with six or more carbon atoms, the compounds display auxin-type inhibital activities, demonstrating they are potential auxin-type herbicides. Among these compounds,4c,5c and lla have higher auxin-type inhibital activities. By coupling with fluorescein and co-culture with Arabidopsis thaliana, the probe6is inverstigated for its distribution in the root of the plant.3. Based on the herbicides3,6-dichloropyridine-2-carboxylic acid and4-Amino-3,5,6-trichloro-2-picolinic acid, a series of alkoxy chain-containing derivatives are obtained via esterification and amidation of the carboxyl group. Meanwhile,3,6-dichloropyridine-2-carboxylic acid is used, and4-alkylamino and4-polyetherethyl-amino groups are introduced at position4to yield a series of4-amino-3,6-dichloro-2-picolinic acid derivatives. The structures of these compounds are confirmed by1H NMR, MS, IR, X-Ray (21b) etc. and their biological activities tested against the growth of the plant Arabidopsis thaliana. Experimental results show that the esterified products of picolinate and the position-4derivatives exhibit similar inhibicidal phenotype before and after the structural modifications, which can inhibit the growth of primary and lateral roots, demonstrating they are potential auxin-type herbicides. Among these compounds,14,17,21e and22d have higher auxin-type inhibital activities.