開催日: 2017/09/20 - 2017/09/22
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.