Design, synthesis, and bioactivity of the first nonsteroidal mimetics of brassinolide.
Ten novel compounds, each consisting of two subunits and a linker, were designed with the aid of molecular modeling to resemble the natural steroidal phytohormone brassinolide. The mimetics were synthesized and subjected to the rice leaf lamina inclination bioassay to test for brassinosteroid activity. Most of the mimetics displayed very weak or no bioactivity, but two were strongly active when coapplied with the auxin indole-3-acetic acid (IAA), which synergizes the activity of brassinosteroids. Thus, 1-(4,6 alpha,7 alpha-trihydroxy-5,6,7,8-tetrahydronaphthyl)-2-(6 alpha',7 alpha'-dihydroxy-5',6',7',8'-tetrahydronaphthyl)ethyne (4) and (E)-1,2-bis[trans-(4a alpha,8a beta)-4-oxo-6 alpha,7 alpha-dihydroxy-4a,5,6,7,8,8a-hexahydro-(3H)-naphthyl]ethylene (11) showed exceptional activity at doses as low as 0.01 ng and 0.001 ng/plant, respectively. These compounds are the first biologically active nonsteroidal brassinolide mimetics.
Andersen
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Department of Chemistry and Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada, T2N 1N4.
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Janzen
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Michalak
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Pharis
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Sung
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D060406:Brassinosteroids; D002777:Cholestanols / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D015195:Drug Design; D004357:Drug Synergism; D007210:Indoleacetic Acids / Q000494:pharmacology; D008958:Models, Molecular; D018716:Molecular Mimicry; D015394:Molecular Structure; D012275:Oryza / Q000187:drug effects; D010937:Plant Growth Regulators / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology*; D018515:Plant Leaves / Q000187:drug effects; D013260:Steroids, Heterocyclic / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D013329:Structure-Activity Relationship
D060406:Brassinosteroids; D002777:Cholestanols; D007210:Indoleacetic Acids; D010937:Plant Growth Regulators; D013260:Steroids, Heterocyclic; C030737:indoleacetic acid; C023623:brassinolide