Studies of Australian Soft Corals. XLVI. New Diterpenes From a Briareum Species (Anthozoa, Octocorallia, Gorgonacea)

Bowden, BF; Coll, John C.; Vasilescu, Ioana M.

doi:10.1071/ch9891705

Cited by 45 publications

(47 citation statements)

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“…As a matter of interest, the compounds formulated as 10 and 12 in this investigation appear to be spectroscopically identical to a pair of natural products isolated by Bowden et al from an Australian Briareum species for which structures 13 and 14 were assigned. 15 , respectively, indicating that both congeneric pairs are enantiomeric. As there are noticeable structural differences between the proposed molecular formulas for 10 and 13 (and 12 and 14), it seems conceivable that structures 13 and 14 were misformulated and that these compounds' structural assignments require revision.…”

Section: Resultsmentioning

confidence: 99%

Briarellins J−P and Polyanthellin A: New Eunicellin-Based Diterpenes from the Gorgonian Coral Briareum polyanthes and Their Antimalarial Activity

Ospina¹,

Rodrı́guez²,

Ortega-Barrı́a³

et al. 2003

J. Nat. Prod.

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A new chemical study of the hexane extract of the gorgonian Briareum polyanthes collected in Puerto Rico afforded 10 new diterpenes of the eunicellin class, briarellins 1-9 and polyanthellin A (10), along with the known diterpene briarellin D (11). The structures and relative stereochemistry of metabolites 1-10 were assigned on the basis of NMR studies, chemical methods, and comparisons to the spectral properties of 11. A reassessment of prior structural assignment for briarellin A and two known sclerophytin-type diterpenes, 13 and 14, is proposed. Antimalarial tests on 1-6 and 8-12 indicated that they were active against Plasmodium falciparum.The considerable structural diversity of the terpene metabolites produced by Caribbean gorgonian octocorals is widely recognized by both natural products and synthetic chemists alike. Specifically, specimens from this region belonging to the genus Briareum (syn: Solenopodium, order Gorgonacea, phylum Cnidaria, family Briareidae) have been the subject of several chemical investigations which thus far have led to the isolation of two related classes of 2,11-cyclized cembranoids. 1 Of these, the asbestinins are the most abundant, whereas the eunicellins (briarellins) constitute a significantly smaller group. 2,3 Briarellin-type diterpenoids have also been isolated from the Taiwanese soft coral Pachyclavularia violacea. 4 The unique and complex architecture of these two groups of natural products has made them irresistible targets for total synthesis. 5 Recently, we have focused our attention on the gorgonian Briareum polyanthes (Duchassaing & Michelotti) collected on the southwest coast of Puerto Rico. Two previous investigations of this gorgonian from Bermudian and Puerto Rican waters had led largely to complex mixtures of chlorinated and nonchlorinated 3,8-cyclized cembranoids known as briareins (briantheins and briareolides). 6,7 From this soft coral, we now wish to report the isolation and structural elucidation of 10 new eunicellintype diterpenes (also known as cladiellins and sclerophytins), briarellins J-P (1-9) and polyanthellin A (10). The known compound briarellin D (11), previously isolated by us from the gorgonian octocoral Briareum asbestinum, was also isolated in the course of this investigation. 3a This is the first time that diterpenes based on this type of carbon skeleton are reported in B. polyanthes. Results and DiscussionHealthy and robust specimens of B. polyanthes were collected by hand using scuba at -10 m in Cabo Rojo, Puerto Rico. The animal specimens were frozen, freezedried, cut in small pieces, and homogenized exhaustively using a mixture of CHCl 3 -MeOH (1:1) to obtain, after in vacuo concentration, an extract that was fractionated using our standard partitioning procedure into several fractions of differing polarity. 8 The hexane fraction was purified by size-exclusion chromatography on a Bio-Beads SX-2 column with toluene followed by repeated chromatography on Si gel flash columns to give pure compounds 1-11. Briarellin D (11), a minor compone...

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Section: Resultsmentioning

confidence: 99%

Briarellins J−P and Polyanthellin A: New Eunicellin-Based Diterpenes from the Gorgonian Coral Briareum polyanthes and Their Antimalarial Activity

Ospina¹,

Rodrı́guez²,

Ortega-Barrı́a³

et al. 2003

J. Nat. Prod.

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“…Its 13 C NMR spectrum indicated that a γ-lactone and an ester were present, as carbonyl resonances were observed δ C 172.6 and 167.4, respectively ( Table 4 ). The 1 H NMR spectrum also indicated the presence of an acetate methyl (δ H 2.23, 3H × s) ( Table 4 ), and its NMR data were found to be similar to those of a known briarane analogue, (1 S *,2 S *,5 Z ,7 S *,8 S *,9 S *,10 S *,11 R *,12 R *,13 Z ,17 R *)-2,12-diacetoxy-8,17-epoxy-9-hydroxybriara-5,13-dien-18-one ( 6 ) ( Figure 1 ) [ 9 , 10 ], with the exception that the 12-acetoxy group in 6 was replaced by a hydroxy group in 4 . Based on HMBC correlations, an acetate group was concluded to be attached to C-2 in 4 , as an acetate carbonyl and an oxygen-bearing methine proton were observed at δ C 167.4 and δ H 4.83, respectively ( Table 4 ).…”

Section: Resultsmentioning

confidence: 88%

“…Additionally, the stereogenic centers of 4 were found to be the same as those of 6 , as the 1 H and 13 C NMR chemical shifts, proton-proton coupling data, and NOESY correlations of 4 and 6 matched. However, the optical rotation value of 4 ([α]

+22 ( c 0.01, CHCl 3 )) was substantially different from that of 6 ([α]

–44.9 ( c 0.31) [ 9 ]; [α]

–42 ( c 0.3, CHCl 3 ) [ 10 ]), indicating that 4 was found to be the enantiomer of the 12-deacetoxy-12-hydroxy derivative of 6 .…”

Section: Resultsmentioning

confidence: 99%

Briaviolides K–N, New Briarane-Type Diterpenoids from Cultured Octocoral Briareum violaceum

Lai

et al. 2018

Marine Drugs

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Four new briarane diterpenoids, briaviolides K–N (1–4), have been obtained from the cultured-type octocoral Briareum violaceum. Using a spectroscopic approach, the structures of briaranes 1–4 were identified. This study employed an in vitro model of lipopolysaccharide (LPS)-induced inflammation in the murine macrophage RAW 264.7 cell line, and found that among the four briaranes, briarane 2 possessed anti-inflammatory activity against inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) protein expressions in cells. In addition, principal component analysis using the chemical global positioning system (ChemGPS) for natural products (ChemGPS-NP) was employed in order to analyze the structure-activity relationship (SAR), and the results indicated that the ring conformation of the compound has a leading role in suppressing the expressions of pro-inflammatory iNOS and COX-2 proteins in macrophages.

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“…Polyanthellin A has been isolated as both the dextro-and levorotatory forms from the west Pacific ocean near Australia and the Caribbean off the coast of Puerto Rico, respectively. 13,14 To our knowledge, it is the only cladiellin diterpene to carry this distinction. (-)-Polyanthellin A is reported to be an antimalarial agent.…”

Section: Scheme 1 Approaches To the Cladiellin Core Using Oxocarbeniumentioning

confidence: 99%

Enantioselective Synthesis of (+)-Polyanthellin A via Cyclopropane-Aldehyde (3+2)-Annulation

Campbell¹,

Johnson²

2010

Synthesis

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The asymmetric synthesis of the cladiellin diterpene natural product (+)-polyanthellin A is described. The core tetrahydrofuran was constructed using a stereospecific and stereoselective (3+2)-annulation of a donor-acceptor cyclopropane and a labile bsilyloxy aldehyde. These particular reactants necessitated the application of a new Lewis acid, MADNTf 2 [(ArO) 2 AlNTf 2 ], to avoid competitive elimination. Ring-closing metathesis was employed to form the oxonane ring at C3-C4 and give a functional group handle that could be elaborated to the natural product.

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Studies of Australian Soft Corals. XLVI. New Diterpenes From a Briareum Species (Anthozoa, Octocorallia, Gorgonacea)

Cited by 45 publications

References 0 publications

Briarellins J−P and Polyanthellin A: New Eunicellin-Based Diterpenes from the Gorgonian Coral Briareum polyanthes and Their Antimalarial Activity

Briarellins J−P and Polyanthellin A: New Eunicellin-Based Diterpenes from the Gorgonian Coral Briareum polyanthes and Their Antimalarial Activity

Briaviolides K–N, New Briarane-Type Diterpenoids from Cultured Octocoral Briareum violaceum

Enantioselective Synthesis of (+)-Polyanthellin A via Cyclopropane-Aldehyde (3+2)-Annulation

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