1990 Volume 38 Issue 3 Pages 664-668
Acid-catalyzed transannular cyclization of 11, 12-epoxycembranolide (1), isolated from the soft coral Sinularia mayi, was studied. The major product was the trans-fused bicyclo[8.4.0]tetradecene derivative 2, and the maximum yield was 89% with boron trifluoride in benzane at 0°C. When treated with p-toluenesulfonic acid in benzene at 55°C, 1 gave a bicyclo[9.3.0]tetradecene derivative 11 in 36% yield. Its immediate precursor was shown to be the allylic alcohol 4, which was converted to 11 on treatment with p-toluenesulfonic acid. The stereochemistries of the cyclization products indicated that the reaction takes place throught a conformation in which the dispositions of 11, 12- and 12, 13-bonds are crossed, with respect to the 7, 8- and 3, 4-double bonds, respectively.
