Atsuhito Kuboki

Rational Design of an Auxin Antagonist of the SCFTIR1 Auxin Receptor Complex

The plant hormone auxin is a master regulator of plant growth and development. By regulating rates of cell division and elongation and triggering specific patterning events, indole 3-acetic acid (IAA) regulates almost every aspect of plant development. The perception of auxin involves the formation of a ternary complex consisting of an F-box protein of the TIR1/AFB family of auxin receptors, the auxin molecule, and a member the Aux/IAA family of co-repressor proteins. In this study, we identified a potent auxin antagonist, α-(phenylethyl-2-oxo)-IAA, as a lead compound for TIR1/AFB receptors by in silico virtual screening. This molecule was used as the basis for the development of a more potent TIR1 antagonist, auxinole (α-[2,4-dimethylphenylethyl-2-oxo]-IAA), using a structure-based drug design approach. Auxinole binds TIR1 to block the formation of the TIR1-IAA-Aux/IAA complex and so inhibits auxin-responsive gene expression. Molecular docking analysis indicates that the phenyl ring in auxinole would strongly interact with Phe82 of TIR1, a residue that is crucial for Aux/IAA recognition. Consistent with this predicted mode of action, auxinole competitively inhibits various auxin responses in planta. Additionally, auxinole blocks auxin responses of the moss Physcomitrella patens, suggesting activity over a broad range of species. Our works not only substantiates the utility of chemical tools for plant biology but also demonstrates a new class of small molecule inhibitor of protein-protein interactions common to mechanisms of perception of other plant hormones, such as jasmonate, gibberellin, and abscisic acid.

Total synthesis of sporochnols, fish deterrents from a marine alga

Abstract Sporochnols, fish deterrents from a marine alga, were synthesized, using intramolecular CH insertion of alkylidenecarbene as a key step to construct the chiral quaternary center.

Stereoselective Synthesis of (1S,3R)-1-Aminocyclopentane-1,3-dicarboxylic Acid via C–H Insertion of Alkylidenecarbene

(1S,3R)-1-Aminocyclopentane-1,3-dicarboxylic acid (ACPD), a potent agonist of metabotropic glutamate receptors, was synthesized from L-serine. The chiral quaternary center was constructed by C–H insertion of the alkylidenecarbene, this being generated by the reaction between lithiotrimethylsilyldiazomethane and the corresponding ketone.