Molecular Design and Highly Efficient Synthesis of Molecular Probes Useful for Investigation of Molecular Recognition Mechanisms of Ligand-Receptor Interaction in Gibberellins

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This study intended to design and synthesize gibberellin (GA)-based molecular probes, fluorescein- and photoaffinity-labeled GAs, useful for investigation of molecular recognition mechanisms of ligand-receptor interaction in a phytohormone, GAs. In order to enhance the chemical stability of GA molecule and seek the position suitable for attaching the spacer-functional site, a variety of GA analogs were synthesized from gibberellic acid (GAィイD23ィエD2), and their biological activities were evaluated by α-amylase induction test using half cut barley seeds. On the basis of these data on the structure-activity relationships, fluorescein- and photoaffinity-labeled GAs were respectively assembled via 17-hydroxy-16β, 17-dihydro-19-deoxoGAィイD21ィエD2 derivative.An experiment on the interaction between the fluorescein-labeled GA with a pyrene moiety as the functional site and protoplasts isolated from the barley aleurone layers suggested that GA receptors might be located at the external face of the aleurone plasma membrane. The photoaffinity-labeled GA with aryl diazirine moiety as the functional site is expected to be used for isolation and identification of GA-binding proteins including GA-receptors.To apply the same synthetic strategies to assembling brassinosteroid (BR)- and jasmonic acid (JA)-based molecular probes, the synthetic modification of BR and JA were also carried out to accumulate the data concerning their structure-activity relationships. During the studies, deuterated-, 5-epi-, 6a-carba- and extra-hydroxylated-brassinolides were synthesized. In addition, a variety of JA derivatives including JA-dexamethasone hybrid ligand were synthesized.