Acid Catalyzed Transformation of Chamigrane Derivatives

Noboru KAMADA and Junji KIMURA*

Department of Chemistry, College of Science and Engineering, Aoyama Gakuin University; 6-16-1 Chitosedai, Setagaya-ku, Tokyo 157-8572 Japan

The red alga genus Laurencia is a well known source of polyhalogenated sesquiterpenes, some of which possess physiological activities. Structures of typical sesquiterpenes from Laurencia involve mainly bisabolane, chamigrane, and laurane skeletons. Treatment of prepacifenol epoxide(2) with 5% TFA in CCl4 provided new three compounds(7, 8 and 9) together with johnstonol(4) and pacifenediol(5). Also, reaction of 4 with TFA afforded a mixture of 1,6-dibromo-5-chloro-11-hydroxy-5,9,12,12-tetramethyl-2-oxatricyclo[,8]dodecan-10-one(6), 7, 9 and TFA ester of 5(10). Similar treatment of 5 produced only 10. The structures of these compounds were elucidated, and plausible reaction pathway was proposed.

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