D-36 ブラシノステロイドの構造展開 : [25, 26, 27-^2H_7]ブラシノライド並びに5-エピ-ブラシノライドの合成

概要

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In the investigation of brassinosteroids (BRs), the isotopically labeled BRs are powerful tools to elucidate the biosynthesis, metabolism, mode of action at the molecular level. Since nowadays some natural BRs are commercially available. we planned a general approach to labeled BRs from the parent BRs, which included three basic steps, C-25 h droxylation, dehydration to introduce a Δ^<25>^<(26)>-double bond and catalytic deuteriogenation or tritiation or the double bond. By following this strategy, [25, 26, 27-^2H_n] brassinolide (BL) was synthesized from BL with 5 steps, where the catalytic deuteriogenation of Δ^<25>^<(26)>-BL using 5% palladium-on-charcoal resulted in abundant incorporation of deuterium atoms to give [25, 26, 27-^2H_7] BL with 60% isotopic purity. In addition, during this work, we found that BL easily epimerized at C-5 by treatment with sodium methoxide in refluxing methanol to give 5-epi-BL. The prepared 5-epi-BL had neitheragonistic nor antagonistic effect on the rice lamina inclination test, providing the first experimental proof that A/B trans fused ring junction of BRs is an essential structural factor not only for the higt BR activity, but also for interacting with the binding site of the BR receptor.
植物化学調節学会の論文
1998-10-01