Design, synthesis, and structure-activity relationships of ω-aryloxy-α-hydroxyalkanoates as selective lateral root inhibitors.

We synthesized a series of ω-aryloxy-α-hydroxyalkanoates and evaluated their effects on Arabidopsis thaliana root architecture. We found that compounds with an odd number of methylene linkers (such as JAX-64) exhibited highly potent overall inhibitory activity for primary root growth and lateral root formation. Structural tuning-such as introducing an ortho-methoxy group or converting the ester to an amide-effectively attenuated the severe primary root inhibition while maintaining sufficient lateral root suppression, yielding highly selective inhibitors. It may be considered that these optimized molecules function in their intact forms. Co-treatment assays with the in vivo indole-3-butyric acid (IBA) generator JAX-44 showed a rightward shift in the lateral root inhibition curve. This suggests that these selective inhibitors putatively target the peroxisomal β-oxidation pathway, which converts IBA to IAA, providing valuable tools for auxin research.