Novel Secondary Metabolites from New Zealand Marine Sponges

Abstract

The isolation and structure elucidation of 12 new compounds from four different genera of marine sponge is described. Continued work with the marine sponge Raspailia topsenti resulted in the isolation of two clerodane diterpenes, raspailodanes F (40) and G (41). Raspailodane F contains a novel tricyclo[5.4.0.0 1.3] undecane scaffold including a cyclopropyl ring. A nonadecanoic acid derivative, petrosianoic acid (123), was isolated from an unknown species of the genus Petrosia. It is believed that 123 is only the third nonadecanoic acid derivative reported from the marine environment. The marine sponge Dendrilla rosea was examined for the presence of new spongian diterpenes. While no new diterpenes were discovered, the acetylenic nitrile dendronitrile (159) was isolated along with two known diterpenes and a known steroid. Dendronitrile is the first acetylenic nitrile discovered from the marine environment and only the third ever reported. Seven new lamellarins and one new dictyodendrin were isolated from Dictyodendrilla dendyi alongside one known lamellarin and two known dictyodendrins. Lamellarins θ (188) and κ (189) are related to known lamellarins. The remaining five lamellarins are sulfated derivatives, lamellarin θ 4",4"'-disulfate (19l), lamellarin O 4"'-sulfate (192), lamellarin O 4",4"'-disulfate (193), lamellarin κ 4"'-sulfate (194), and lamellarin κ 4",4"'-disulfate (195). Dictyodendrin F (196) is a new natural product previously only reported as a semi-synthetic derivative of known dictyodendrins. Lamellarin θ shows moderate cytotoxic activity. The biological activity of the remaining compounds, particularly the sulfated derivatives, is under investigation. The screening protocol used to analyse crude sponge extracts was refined and a number of advances were made towards the automated analysis of the spectra generated. A method was devised to extract peak data from screen HSQC spectra and by combining these data, to produce a software-based mask of known correlations. The application of this mask was demonstrated in three different ways to three different screen HSQC spectra. To aid in the identification of interesting correlations identified by the mask, a database of HSQC correlations was compiled from literature and in-house sources. A new method of describing the chemical environment of a given position was developed to suit the needs of the database. At present, the database contains 91 compounds and represents over 2500 individual HSQC correlations. Development of both the software screening technique and the HSQC correlation database is ongoing.