Isolation, Structural Analysis and Biological Activity Assays of Biselisabethoxanes A and B: Two Dissymmetric <i>Bis</i>-Diterpenes from the Southwestern Caribbean Sea Gorgonian Coral <i>Pseudopterogorgia elisabethae</i>

Abstract

Two novel dissymmetric diterpenoids, biselisabethoxanes A and B (1 and 2), were isolated from the hexane extracts of the gorgonian coral Pseudopterogorgia elisabethae. Biselisabethoxane A (1) represents the first example of a marine-derived C40 dimer made of two distinct diterpene fragments, whereas biselisabethoxane B (2) is a fused heterodimer stemming from coupling of two amphilectane-based fragments. The structures of 1 and 2 were elucidated based on 1D and 2D NMR spectral data analysis. The molecular structure of 1 was subsequently confirmed by X-ray crystallographic analysis. When evaluated for their inhibitory effects in a series of well-established biological activity assays the isolated compounds were shown to moderately inhibit the growth of Mycobacterium tuberculosis.

Keywords

• <i>Pseudopterogorgia elisabethae</i>
• biselisabethoxanes
• hetero-Diels-Alder reaction
• <i>bis</i>-diterpenes
• diterpene dimers
• gorgonian octocoral