Studies of Australian Soft Corals. XLII. Structure Determination of New Briaran Derivatives From Briareum steckei (Coelenterata, Octocorallia, Gorgonacea)

Abstract

The structure and relative stereochemistry of four new metabolites from Briareum steckei has been deduced from 2D-n.m.r. experiments at high field, and confirmed by a single-crystal X-ray determination of a minor metabolite. The new compounds are non-halogenated briaran derivatives: (1R*,2S*,3R*,5Z,7S*,8(17)Z,l0R*, llR *,12S*,14S*)- 3,14-diacetoxy- 11,12-epoxy- 18-oxobriara-5,8(17)-dien-2-yl butanoate (3), its 3-deacetoxy derivative (4), (1R*,2R*,4R*,5Z,7S*,8(17)Z,10R*, 11R *,12S*,14S*)-4,14-diacetoxy-11,12-epoxy-18-oxobriara-5,8(17)-dien-2-yl butanoate (5) and the related 2-propanoate (6). Single-crystal X-ray determinations were performed on (5) and (6).