Studies on the minor constituents of the Caribbean gorgonian octocoral Briareum asbestinum Pallas. Isolation and structure determination of the eunicellin-based diterpenoids briarellins E-I.
ABSTRACT Five new eunicellin-type diterpenoids, briarellins E-I, along with several known diterpenoids of the asbestinane, briarane and eunicellane classes, were isolated from the Caribbean gorgonian octocoral Briareum asbestinum collected in Puerto Rico. The structures of these compounds were established on the basis of spectroscopic evidence.
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ABSTRACT: Enantioselective total syntheses of briarellin E (12) and briarellin F (13), as well as the structure originally proposed for the cladiellin diterpene alcyonin (10), have been realized. Comparison of the spectral data for synthetic 10, natural alcyonin, cladiellisin (33), and cladiellaperoxide (34), as well as chemical transformations of 10 and natural alcyonin, suggest that the structure of this coral metabolite is allylic peroxide 11. The unified approach detailed herein can be used to access both C4-deoxygenated and C4-oxygenated cladiellins and briarellins. The central step in these syntheses is acid-promoted condensation of (Z)-alpha,beta-unsaturated aldehydes 17 with cyclohexadienyl diols 18 to form intermediates 16 incorporating the hexahydroisobenzofuran core and five stereocenters of these marine diterpenes (Scheme 1 ).The Journal of Organic Chemistry 07/2009; 74(15):5458-70. · 4.56 Impact Factor
Article: Marine natural products.[show abstract] [hide abstract]
ABSTRACT: Covering: 2010. Previous review: Nat. Prod. Rep., 2011, 28, 196. This review covers the literature published in 2010 for marine natural products, with 895 citations (590 for the period January to December 2010) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1003 for 2010), together with the relevant biological activities, source organisms and country of origin. Biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.Natural Product Reports 02/2012; 29(2):144-222. · 10.18 Impact Factor
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ABSTRACT: Two new eunicellin-based diterpenes, seco-briarellinone (1) and briarellin S (2), and a known seco-asbestinin (3) have been isolated from the methanolic extract of the common octocoral Briareum asbestinum collected in Bocas del Toro, Caribbean of Panama. The structures and relative stereochemistry of the compounds were defined using extensive spectroscopic analysis including 1D, 2D-nuclear magnetic resonance (NMR) and high-resolution mass spectrometry (HRMS). Compounds 1 and 2 displayed anti-inflammatory properties inhibiting nitric oxide (NO) production induced by lipopolisacharide (LPS) in macrophages with an Inhibitory concentration 50% (IC(50)) of 4.7 μM and 20.3 μM, respectively. This is the first report of briarellin diterpenes containing a ketone group at C-12.Marine Drugs 11/2012; Mar. Drugs(10):2608-2617. · 3.98 Impact Factor