著者

竹内 純 甲斐 建次 片岡 太一 横山 峰幸 渡辺 修治

出版者

天然有機化合物討論会

雑誌

天然有機化合物討論会講演要旨集

巻号頁・発行日

no.50, pp.439-444, 2008-09-01

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In the course of screening for endogenous flowering inducer, α-ketol of octadecadienoic acid (KODA, Figure1) was isolated from Lenma paucicostata. KODA showed the activity after reacting with norepinephrine (NE) under the basic conditions. Further investigations have revealed that FN1 is a major active compound, which is expected to be formed by cycloaddition between 12-olefin of KODA and α, β-unsaturated carbonyl of noradrenochrome, an oxygenated form of NE. However, the mechanism of flower-induction of FN has not been examined. In present study, we carried out the structure-activity relationship study of the fatty acid moiety of FN for flowering in L. paucicostata by using series of KODA analogs shown in Figure 2. Firstly, we synthesized nine fatty acid analogs, where single or combinative alterations have been made to the structural components of KODA and tested for their ability to induce flowering. With the exception of compounds 8, 10, 12, all these analogs proved to have a flowering activity after reacting with NE. Compound 4, in which 15-olefinic bond is saturated, displayed high activity of same magnitude as KODA. This suggested that olefinic bond at 15-position in KODA in not important for activity. Compounds 7 and 9 displayed a significant activity but less in magnitude as the parent KODA. This implied that 9-hydroxy group may not be involved in primary recognition of the target whereas the presence is favorable to show high activity. Compounds 5 and 6, in which their alkyl chains are shortened, displayed flowering activity at a concentration of more than 1μM. In addition to this, the biological result obtained with methyl ester 11 indicated that recognition of the aliphatic chain and terminal carboxy group in FNs is relatively obscure. On the other hand, compounds 8, 10, and, 12, changing of β, γ-unsaturated carbonyl moiety led to complete loss of activity in L. paucicostata. This result showed that cycloaddition of fatty acid with NE is inevitable process to induce flowering in L. paucicostata. Furthermore, to obtain clearly insight in the structural requirements of FN1 for flower inducing activity, we prepared FN derivatives from corresponding fatty acid analogs and evaluated their activity.