Muriceanol, a 24(28)-Epoxide Sterol Link in the Carbon Flux Toward Side-Chain Dealkylation of Sterols

4 pages, 2 figures, 1 table, 1 scheme.-- Available online Dec 12, 2005.-- Supporting information (10 pages) available at: http://www.wiley-vch.de/contents/jc_2046/2006/o200500775_s.pdf
Side-chain-oxidized C-28-sterol 1 and one new pregnane metabolite 2 were isolated from eastern Pacific Muricea spp. The C-24(28)-epoxide functionality is a key intermediate in the C-24-dealkylation mechanism of the conversion of phytosterol to cholesterol by phytophagous insects. Certain marine invertebrates share this dealkylation pathway; however, such a key epoxide feature has not yet been found in a naturally occurring sterol from marine invertebrates. The unusual oxidation pattern of the side chain of 1 encourages speculation about its biogenesis and converts this non-zooxanthellate gorgonia into an interesting candidate organism for biosynthetic studies on C-24-dealkylation of phytosterols in octocorals. The (22S)-22-hydroxy group, after 24-dealkylation of 1, may be an advantageous functionalization in the side-chain cleavage to C-21-pregnane steroids in Muricea spp.
This work was supported by the Ministerio de Educación y Ciencia (PPQ2002-02494), and the DGUI of the Canary Islands Government (PI2002/044). M. L. acknowledges MECESUP MAG0002, Chile, for financial support. The STRI provided support and facilities.