著者

廣田 洋 棚橋 善昭 高橋 武美

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.19, pp.54-61, 1975-10-01

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Structure elucidation of LB, one of the volatile components of "San-shion" (Ligularia species), was accomplished in the following way. LB, C_<15>H_<26>O, was assumed to be a saturated guaiane-type sesquiterpene ether from its spectra and the dehydrogenation reaction. INDOR experiments on LB and 1-epiguaioxide(13) showed that LB is one of the eight stereoisomers of guaioxide(10). As six compounds of them are already known, the structure of LB must be represented by either 14 or 16. The reaction of LB with NBS in CCl_4 gave 4-bromo-LB(22) in 8〜18% yield. The compound(22) was dehydrobrominated into 23, which reacted with diborane to give 27. The oxidation of 27 with Jones' reagent gave the ketone(29), which then isomerized to 26. The structure of 22, 23, 26, 27, and 29 were confirmed by their spectral data, obtained by double resonance and lanthanide-induced shift techniques in PMR. The absolute structure of 29 was determined by the ORD and CD experiments. The hydrogenation of 23 gave 4-epi-LB. The compound(14) obtained by tosylation of 27 followed by reduction with LiAlH_4, was identical with 4-epi-LB. Therefore, the structure of LB was determined to be 16, including the absolute configuration.