Juncins G and H: new briarane diterpenoids of the Indian Ocean gorgonian Junceella juncea Pallas

Abstract

Chemical examination of the Indian Ocean gorgonian, Junceella juncea furnishes two new diterpenoids of the briarane skeleton, juncin G, 1 and juncin H, 3 along with the antipodal derivatives of known gemmacolides A, 4 and B, 2. The structures of juncin H and G are shown to be (1S,2S,6S,8R,9S,10S ,11R,12R,14R,17R)-6-chloro-11, 20-epoxy-14-(3-methylbutanoyl)-2,9,12-triacetoxy-8-hydroxybriar-5(16)-e n-18,7-olide and (1S,2S,6S,9S,10S,12R ,13R,14R)-6-chloro-13-(3-methylbutanoyl)-2,9,12, 14-tetraacetoxybriaran-4,8(17)-dien-18,7-olide, respectively, by a comparative study of their spectral data. For the first time, three polyhydroxy sterols 6–8 are also isolated from this species.