Rameswaralide, a novel diterpenoid from the soft coral Sinularia dissecta

Ramesh, P.; Reddy, N. Srinivasa; Venkateswarlu, Y.; Reddy, M. Venkata Rami; Faulkner, D. John

doi:10.1016/s0040-4039(98)01879-6

Cited by 62 publications

(49 citation statements)

References 8 publications

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“…The 1 H-and 13 C-NMR data of 12 were similar to that of dihydrorameswaralide, 25) except for the presence of a ketone and an oxygenated quaternary carbon in 12 instead of an oxymethine and a methine carbons in dihydrorameswaralide. The HMBC correlations between H-2 (δ H 2.38, 3.13) and C-1 (δ C 48.1)/C-3 (δ C 203.3)/C-4 (δ C 80.5) and H-5 (δ H 4.06) and C-3 (δ C 203.3)/C-4 (δ C 80.5)/C-6 (δ C 207.7)/C-18 (δ C 170.9) indicated the location of a ketone at C-3 and an oxygenated quaternary carbon at C-4.…”

Section: Resultsmentioning

confidence: 70%

Diterpenoids from the Soft Coral <i>Sinularia maxima</i> and Their Inhibitory Effects on Lipopolysaccharide-Stimulated Production of Pro-inflammatory Cytokines in Bone Marrow-Derived Dendritic Cells

et al. 2012

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Section: Resultsmentioning

confidence: 70%

Diterpenoids from the Soft Coral <i>Sinularia maxima</i> and Their Inhibitory Effects on Lipopolysaccharide-Stimulated Production of Pro-inflammatory Cytokines in Bone Marrow-Derived Dendritic Cells

et al. 2012

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“…It also shows antifouling activity against cyprid larvae of bernacle Balanus amphitrite with a MIC value of 0.1 ppm. This activity is higher than that of CuSO 4 and TBTO (bis(tributyltin) oxide), which is one of the most effective antifoulants. Compound 4 has a minor antifouling activity against the blue mussel Mytilus edulis [20].…”

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confidence: 86%

Furanocembranoids from the Soft Corals Sinularia asterolobata and Litophyton arboreum

Grote

Dahse

Seifert

2008

Chemistry & Biodiversity

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The new cembranoid diterpene danielid (1) along with 3alpha-ethoxyfuranocembranoid 2, pukalide (3), 13alpha-acetoxypukalide (4), furanocembranoid 5, and furanosesquiterpene 6 have been isolated from the soft coral Sinularia asterolobata. The furanocembranoid diterpene 11beta,12beta-epoxypukalide (7) and the sesquiterpene (-)-bicyclogermacrene (8) have been obtained from the soft coral Litophyton arboreum. The structures were elucidated primarily by NMR spectroscopy. The furanocembranoids 2, 4, and 5 show good antiproliferative activities against the cell lines L-929 and K-562, and weak cytotoxic effects on HeLa cells.

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“…1 Its relative stereochemistry was determined by analysis of 1 H NMR coupling constants and NOESY correlations. The structure of 1 was further confirmed by selective reduction of the enolic group with NaBH 4 to form the corresponding dihydrorameswaralide ( 2 ).…”

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confidence: 99%

Synthesis of a tricyclic core of rameswaralide

Trost

Nguyen

Koradin

2010

Tetrahedron Letters

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A tricyclic core containing a 5,7-fused bicyclic unit of rameswaralide was prepared starting from a 1,6-enyne. The synthetic sequence involved (i) ruthenium-catalyzed [5+2]-cycloaddition of 1,6-enyne, (ii) an acyl radical based approach to construct the lactone, and (iii) a regioselective installation of the conjugated double bond by a concomitant sulfenylation-dehydrosulfenylation sequence. KeywordsRuthenium; Cycloaddition; The fused bicyclic system; Reductive radical cyclization; Total synthesis Rameswaralide (1), a novel diterpene with a tetracyclic ring skeleton, was isolated from the soft coral Sinularia dissecta near the Mandapam coast of India in 1998 (Figure 1). 1 Its relative stereochemistry was determined by analysis of 1 H NMR coupling constants and NOESY correlations. The structure of 1 was further confirmed by selective reduction of the enolic group with NaBH 4 to form the corresponding dihydrorameswaralide (2). It was reported that rameswaralide (1), and its derivatives, could function as effective anti-inflamatory agents for the treatment of a variety of inflammatory disorders, including arthritis, psoriasis and inflammatory bowel disease. 2 Rameswaralide (1) is a highly oxygenated natural product containing a variety of functional groups, including a tertiary hydroxyl group, a carbonyl moiety, a fully enolized β-ketoester, a γ-lactone, and an isopropylidene group (Figure 1). Furthermore, it contains cis-fusions at the AB-and BC-ring junctions. Due to its complex features and biological importance, rameswaralide (1) is a good target for total synthesis. To date, the total synthesis of 1 has not been reported, but several reported approaches have appeared. 3 Herein, we report the synthesis of the tricyclic core 3 containing a 5,7-fused bicyclic (AB-ring) unit of rameswaralide (1) (Figure 2).Retrosynthetically, the tricyclic compound 3 (Figure 2) could be accessed from chemoselective epoxidation of vinylsilane 4. In turn, the five-membered γ-lactone in 4 could be derived from the alkoxycarbonyl radical cyclization of acylselenium 5 onto the exocyclic cis-disubstituted olefin with retention of the alkene functionality. 4 The 5,7-fused bicyclic skeleton 6 could be © 2010 Elsevier Ltd. All rights reserved. * Corresponding author. Tel.: +1-650-723-3385; fax: +1-650-725-0002; bmtrost@stanford.edu.Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Supplementary dataSupplementary data associated with this article can be found, in the online version, at doi: 10.1016/j.tetlet. formed by ruthenium-catalyzed [5+2] intramolecular cycloaddition of the 1,6-enyne 7 de...

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Rameswaralide, a novel diterpenoid from the soft coral Sinularia dissecta

Cited by 62 publications

References 8 publications

Diterpenoids from the Soft Coral <i>Sinularia maxima</i> and Their Inhibitory Effects on Lipopolysaccharide-Stimulated Production of Pro-inflammatory Cytokines in Bone Marrow-Derived Dendritic Cells

Diterpenoids from the Soft Coral <i>Sinularia maxima</i> and Their Inhibitory Effects on Lipopolysaccharide-Stimulated Production of Pro-inflammatory Cytokines in Bone Marrow-Derived Dendritic Cells

Furanocembranoids from the Soft Corals Sinularia asterolobata and Litophyton arboreum

Synthesis of a tricyclic core of rameswaralide

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