Unusual Transannular Cyclization Products of Sarcophytoxide, a 14-Membered Marine Cembranoid:  Anomalous Stereochemistry of Epoxide−Ketone Rearrangement

Nii, Keiji; Tagami, Keiko; Matsuoka, K.; Munakata, Tatsuo; Ooi, Takashi; Kusumi, Takenori

doi:10.1021/ol0608404

Cited by 10 publications

(8 citation statements)

References 15 publications

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“…Fortunately, the minor ketone (À)-5 was crystallized and the crystal was subjected to X-ray analysis, determining the structure to be 5 (relative). 8 The X-ray crystallography also revealed that the crystal applied to the analysis was racemic, that is, a racemate crystallized out from (À)-5. The smaller ½ D absolute value (67) of (À)-5 than that of (+)-5 (75) suggests that this material is enantiomerically impure [enantiomeric excess (ee) of (À)-5: 79% based on the ½ D value of (+) -5].…”

Section: Resultsmentioning

confidence: 99%

Acid-Catalyzed Reactions of Sarcophytoxide, a Marine Cembranoid: An Apparently Enantio-Directive Reaction, Unusual Products and Stereochemical Reconsideration of Epoxide–Ketone Rearrangement

Nii¹,

Tagami²,

Kijima³

et al. 2008

Bulletin of the Chemical Society of Japan

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Perchloric acid treatment of sarcophytoxide, a marine cembranoid possessing an epoxide, brought about epoxideketone rearrangement affording ketones. When the reaction time was long (22 h), a minor ketone that was antipodal to the ketone obtained in a short-time (10 min) reaction was formed. These puzzling findings, considering that the starting epoxide had three asymmetric carbons, were interpreted by surveying the structures of other ketonic products. The stereochemistry of a major ketone, which had been wrongly assigned, was corrected by extensive analyses of NMR spectra. The correct stereochemistry indicated that the epoxide-ketone rearrangement took a course via a cationic intermediate.

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Section: Resultsmentioning

confidence: 99%

Acid-Catalyzed Reactions of Sarcophytoxide, a Marine Cembranoid: An Apparently Enantio-Directive Reaction, Unusual Products and Stereochemical Reconsideration of Epoxide–Ketone Rearrangement

Nii¹,

Tagami²,

Kijima³

et al. 2008

Bulletin of the Chemical Society of Japan

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“…C-17). Based on the physicochemical analyses, including IR, 1D NMR, MS, and their comparisons with data from the literature, the isolated compound was determined to be a known cembranoid typediterpene, (2S,7S,8S)-sarcophytoxide (Bowden, Coll, Heaton, Konig & Scheuer, 1987;Nii et al, 2006;Pollastro et al, 2016).…”

Section: Resultsmentioning

confidence: 99%

Bioassay-Guided Isolation of an Antibacterial Compound from the Indonesian Soft Coral

Putra¹,

Saparhadi²,

Karim³

et al. 2017

Squalen Bull. Marine Fisheries Postharvest Biotech.

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W ith the aim of searching for new antibacterial compound from marine soft corals, the investigation had been conducted on antibacterial activity of an extract from soft corals Sarcophyton trocheliophorum in the n-hexane, ethyl acetate, n-butanol, and aqueous fractions. The antibacterial activity was tested against two Gram-positive bacteria, viz. Bacillus subtilis (ATCC 6633) and Staphylococcus aureus (ATCC 25923), and two Gram-negative bacteria, viz. Escherichia coli (ATCC 25922) and Vibrio cholerae (ATCC 14035) using the agar disc diffusion assay. Among them, the n-hexane fraction was the most active against three tested bacteria, viz. Bacillus subtilis, Staphylococcus aureus and Vibrio cholerae at the concentration 125 µg/ml, with inhibition zone 14.2, 18.2, 13.8 mm, respectively. Isolation and purification of the active component from the n-hexane fraction led to a known cembran oid-type diterpene, sarcophytoxide. The chemical structure of the isolated compound was determined by IR, MS and NMR, as well as compared to data from the literature. Sarcophytoxide showed moderate activity against B. subtilis, S. aureus and V. cholerae, with a minimum inhibitory concentration (MIC) of 125, 100, 125 mg/ml, respectively.

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“…46 Several tetrasubstituted cyclopentanes (51) can be prepared in four steps from cyclopentadiene in good overall yield (30%) by the acid-catalysed rearrangement of epoxide (49) followed by a regio-and stereo-selective nucleophilic attack, with control of the relative configuration of four contigous stereogenic centres in a single operation (Scheme 14). 54 The concomitant opening of the epoxide ring in (61) creates flexibility, thereby permitting intermolecular ring closure. The Lewis acid-promoted rearrangement of 2,2,3,3-tetrasubstituted de 2,3-epoxyalcohol derivatives, which have only a slight difference in stability of carbocation at the C(2) or C(3) positions, proceeds through the C(3) carbocation.…”

Section: Cationic Rearrangementsmentioning

confidence: 99%

Molecular Rearrangements: Part 2. Other Reactions

Brandi

Gensini

2010

Organic Reaction Mechanisms · 2006

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The formation of α-phenyl-β-halovinyl cation, β-phenyl-α-halovinyl cation, and also the halogen-bridged and the spirocyclic phenyl-bridged cations, as intermediates of protonation of phenylethynyl halides, or of halogen addition to phenylethynes, has been evaluated by DFT at the B3LYP/6-31+G(d) level and, for comparison in representative cases, by B3LYP/6-311++G(d,p). 1 Structural and mechanistic studies of the lithium diisopropylamide (LDA)-mediated anionic Fries rearrangements of aryl carbamates have been described. 2 Substituents at the meta position of the arene (H, OMe, F) and the dialkylamino moiety of the carbamate (Me 2 N, Et 2 N, and i-Pr 2 N) markedly influence the relative rates of ortholithiation and subsequent Fries rearrangement. The mechanism of the Fries rearrangement of aryl formates promoted by boron trichloride has been studied by means of 1 H, 2 H, and 11 B NMR spectroscopy and DFT calculations. 3 After the formation of a 1:1 substrate -Lewis acid adduct, the rearrangement proceeds in two steps, beginning with the cleavage of the ester bond and the release of formyl chloride in situ, which, in turn, acts as a formylating agent, introducing 451

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Unusual Transannular Cyclization Products of Sarcophytoxide, a 14-Membered Marine Cembranoid: Anomalous Stereochemistry of Epoxide−Ketone Rearrangement

Cited by 10 publications

References 15 publications

Acid-Catalyzed Reactions of Sarcophytoxide, a Marine Cembranoid: An Apparently Enantio-Directive Reaction, Unusual Products and Stereochemical Reconsideration of Epoxide–Ketone Rearrangement

Acid-Catalyzed Reactions of Sarcophytoxide, a Marine Cembranoid: An Apparently Enantio-Directive Reaction, Unusual Products and Stereochemical Reconsideration of Epoxide–Ketone Rearrangement

Bioassay-Guided Isolation of an Antibacterial Compound from the Indonesian Soft Coral

Molecular Rearrangements: Part 2. Other Reactions

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