Marine Terpenes and Terpenoids. VIII

The major cembranoid, sarcophytol A (1a), from the soft coral Sarcophyton glaucum was found to be converted to a bicyclo[9.3.0]tetradecene derivative (3a), on standing in CHCl3 solution at room temperature. Two unstable epoxides (7a and 8), obtained by autoxidation of 1a, were shown to afford 3a on further storage in CHCl3. The acetate 7b, in contrast, is stable under the same conditions and gave the dihydrofuran (9) and triol monoacetate (11) derivatives on mild alkaline and acid treatment, respectively. Five minor cembranoids of S. glaucum, having the 1, 3-diene system, were examined for the cyclization reaction by dissolving them in CHCl3. The 1, 3, 7, 11-tetraenes (2, 14, 16) gave similar bicyclotetradecene derivatives (12, 15, 17), while the 7-hydroxy 1, 3, 8(19), 11-tetraenes (18, 20) gabe the 3, 7-oxide derivatives (19, 21) in low yields.