31 ECD スペクトルの加成性に基づいた新規骨格を有するセスキテルペンの構造解析 (口頭発表の部)

抄録

Marine sponges are known to be rich sources of biologically active and structurally unique compounds. A large number of marine natural products have been discovered from the order of Dictyoceratida, which is well known as a rich source of structurally highly diverse terpenes including sesterterpenes, norsesterterpenes, sesquiterpene quinones, and furan-containing terpenes. In our search for the novel metabolites from marine sponges, four new sesquiterpenes (1–4) together with a known sesquiterpene, O-methyl nakafuran-8 lactone (5), were obtained from the marine sponge, Lamellodysidea herbacea, collected in Indonesia. Their planar structures were elucidated by analyses of spectroscopic data. Compounds 1 and 2 were structurally unique bridged polycyclic furanosesquiterpenes. Although several polycyclic furanosesquiterpenes were isolated from the marine sponges to date, the skeletons of 1 and 2 were the first compounds containing the unprecedented frameworks. Compounds 3 and 4 were obtained as an inseparable mixture in the ratio of 1:1 and shown to be 11-epimers. We determined the absolute configurations of 1–4 by interpretation of the calculated ECD spectra using the additivity relations of chromophores. The biosynthesis of 1–5 from farnesyl pyrophosphate were proposed.