STUDIES OF AUSTRALIAN SOFT CORALS .48. NEW BRIARAN DITERPENOIDS FROM THE GORGONIAN CORAL JUNCEELA-GEMMACEA

The structures of three new briaran based diterpenes are reported from the gor- gonian coral Junceela gemmacea. Their structures were deduced on the basis of extensive one- and two-dimensional high-field n.m.r. experiments. The metabolites were (1R, 2R, 5Z, 7R, 8S, 9R, 10R, 11R, 14R, 17S)-2, 14-diacetoxy-8, 17:1 l, 20-bisepoxy-9-hydroxybriar-5-en- 18-one (3), (1R, 2R, 5Z, 7R, 8S, 9R, 10R, 11R, 14R, 17S)-2, 14-diacetoxy-8, 17-epoxy-9-hydroxybriara- 5.11-dien-18-one (4), and (1R, 2R, 5Z, 7R, 8S, 9R, 10R, 11R, 14R, 17S)-2, 14-diacetoxy-8, 17-epoxy- 9.12-dihydroxybriara-5, 11 (20)-dien-18-one (5). The compounds are closely related to recently reported metabolites from Briareum species of soft corals. © 1990 ASEG.