28 軟サンゴ、オオウミキノコからの新センブラン型ジテルペンの構造(口頭発表の部)

抄録

Sarcophytol A (1a) is a simple monohydroxycembratetraene which we previously isolated from Sarcophyton qlaucum, a ubiquitous soft coral found in the coral reefs of Indo-Pacific coastal waters. Recently, Fujiki and co-workers found that 1a and its derivative sarcophytol B (2a) efficiently inhibit the activity of the powerful tumor-promoter teleocidin in a two-stage carcinogenesis experiment on the mouse dorsal skin. In view of this unique activity of 1a and 2a, the lipid extract of S. glaucum was re-investigated and was found to contain ten new cembranoids, sarcophytol M (5), H (11a), O (15), I (17), G (22a), K (23), P (24a), Q (25), N (26a), and J (28a). The structures of these new compounds were elucidated by means of their spectroscopic data, and most of them were confirmed by chemical correlation. The major component 1a was found to give several secondary products on standing at room temperature. The major products were the dihydrofuran derivative 37 and the novel [9.3.0] bicyclic system 32, the latter being known to occur in a soft coral Cespitularia sp. Compounds 2a, 20 and and 22a were found to give similar bicyclic system, in low yields, indicating this reaction to be characteristic of 14-hydroxy-1,3-diunsaturated cembrane system. Their formation process, involving the initial formation of 3,4-epoxy derivative followed by transannular cyclization,is disscussed.