New diterpene isolated from a sponge of genus Strongylophora

In our quest for discovering new and novel marine natural products, two diterpenes (1 – 2) were isolated from a Hawaiian sponge of the genus Strongylophora, which was collected off the southern coast of Lana'i. New diterpene (1) contains an uncommon naphthyl A, B ring system similar to equilenin [1], one of the active components of the FDA approved drug Premarin, but also unusual oxidation at position 2. The planar structure of (1) was deduced by analysis of 2D NMR spectra (COSY, HMBC, HSQC, ROESY) and high resolution mass spectrometry data. CD spectra of (1) displayed a negative cotton effect in accordance with predictions made using the octant rules [2], suggesting an S configuration of the lone stereocenter. Cinanthrenol A (2) was previously isolated from a sponge of genus Cinachyrella and demonstrated bioactivity against P-388, HeLa cells, and as an estrogen receptor inhibitor [3]. Structural similarities between (1) and (2) suggest (1) may have similar biological activity.

Acknowledgements: Dr. Shugeng Cao is acknowledged for obtaining CD spectra.

Keywords: Sponge metabolite, diterpene, CD.

References:

[1] Girard A, Sandulesco G, Fridenson A, Gaundefroy C, Rutgers JJ. A New Crystalline Sex Hormone. Compt Rend 1932; 195: 981 – 983

[2] Moffitt W, Woodward RB, Moscowitz A, Klyne W, Djerassi C. Structure and the Optical Rotatory Dispersion of Saturated Ketones. J Am Chem Soc 1961; 83: 4013 – 4018

[3] Machida K, Abe T, Arai D, Okamoto M, Shimizu I, de Voogd NJ, Fusetani N, Nakao Y. Cinanthrenol A, an Estrogenic Steroid Containing Phenanthrene Nucleus, from a Marine Sponge Cinachyrella sp. Org Lett 2014; 16: 1539 – 1541

No conflict of interest has been declared by the author(s).