Synthesis based on cyclohexadienes. Part 34. A tandem cationic rearrangement–ene cyclisation route to 2-pupukeanone

Biju, Purakkattle; Kaliappan, Krishna P.; Laxmisha, M. S.; Rao, G. Sasibhushana

doi:10.1039/b003409f

Cited by 7 publications

(5 citation statements)

References 23 publications

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“…The isotwistyl skeleton and the substituent positions and configurations in 13 were confirmed by 2-D NMR spectroscopy. Dibrominated isotwistanes may be useful as starting materials in natural product syntheses …”

Section: Discussionmentioning

confidence: 99%

“…Dibrominated isotwistanes may be useful as starting materials in natural product syntheses. 132 The multistep mechanism proposed for this transformation (Scheme 8) takes the following into account: (1) an organicsoluble phosphonium ion that activates oxetane 2 into cation 36, (2) the thwarting of direct S N 2 displacement of the C−O bonds of 36 by bromide nucleophiles due to the extensive phosphoranyl pendant group, (3) the facilitation of C−O bond cleavage within 36 due to opportune anchimeric assistance from a properly aligned C−C bond within it, (4) the somewhat energetically favored skeletal rearrangement observed in the product, (5) the completely stereoselective S N 1 formation of the first C−Br bond at the newly vacated site that is farther from the still-controlling phosphoranyloxy group (Scheme 9), and (6) the possible stereospecificity for the second bromide substitution via S N 2 or S N 2′ leading to the favorable departure of the neutral Ph 3 PO nucleofuge and formation of dibromo compound 13. ■ EXPERIMENTAL SECTION Computational Methods.…”

Section: ■ Conclusionmentioning

confidence: 99%

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Bromination and Accompanying Rearrangement of the Polycyclic Oxetane 2,4-Oxytwistane

et al. 2014

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Bromination of the polycyclic oxetane 2,4-oxytwistane (rac-(1R,3S,4R,7S,9R,11S)-2-oxatetracyclo[5.3.1.0(3,11).0(4,9)]undecane) was undertaken in order to form 2,4-dibromotwistane. The oxetane was subjected to the mild reagent combination CBr4/Ph3P in a fashion similar to that for the Appel and Corey-Fuchs reactions. NMR spectroscopy revealed that the isomeric dibromo compound 2,8-dibromoisotwistane (2,8-dibromotricyclo[4.3.1.0(3,7)]decane) was inadvertently formed. The conversion was prevented by migration of a C-C bond within the geometrically stressed C10 framework. Computational chemistry was used to model the structure of the polycyclic oxetane and to assess the component of total ring strain energy due to the four-membered heterocycle. Mechanistic aspects behind the skeletal rearrangement are also discussed.

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Section: Discussionmentioning

confidence: 99%

Section: ■ Conclusionmentioning

confidence: 99%

Bromination and Accompanying Rearrangement of the Polycyclic Oxetane 2,4-Oxytwistane

et al. 2014

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“…A new route has been used in a synthesis of 2-pupukeanone. 393 The eight stereoisomers of the germination stimulant strigol have been synthesized. 394 A racemic synthesis of orobanchol and strigol has been described.…”

Section: Miscellaneous Sesquiterpenoidsmentioning

confidence: 99%

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2001

Nat. Prod. Rep.

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“…They are all characterized by 3-alkyl pyridinium units, connected via long alkyl chains. Sometimes the alkyl chains show unsaturation, as in the niphatoxins A and B (54,55), isolated from the sponge Niphates sp. 94 Cyclic versions have also been isolated, such as the dimeric cyclostellettamines A-F (56-61) reported 95 from the sponge Stelletta maxima * and the trimeric version of 58, viscosamine (62) 97 from the Arctic sponge Haliclona viscosa.…”

Section: Polymeric Alkyl-pyridinium Saltsmentioning

confidence: 99%

Isolation of New Secondary Metabolites from New Zealand Marine Invertebrates

Wojnar¹

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<p>This study describes the isolation and structure elucidation of several known and 13 new compounds from New Zealand marine organisms. Furthermore, it describes the development of a digital mask program for the analysis of HSQC spectra of crude sponge extracts. This was used as a screening tool to identify secondary metabolite producers that warranted further analysis. As reports of metabolites from New Zealand nudibranchs are poorly represented in the literature, a study of five New Zealand nudibranch species was undertaken. These coloured and seemingly undefended nudibranchs are known to concentrate or sequester toxic metabolites from their prey, facilitating rapid isolation and structure elucidation of these metabolites. This study resulted in the isolation of a variety of metabolite classes; two new compounds, 13alpha- acetoxypukalide diol (30) and lopholide diol (31) from the nudibranch Tritonia incerta, are described. Examination of the sponge Raspailia agminata resulted in the isolation of a novel family of partially acetylated glycolipids which contain up to six glucose residues. The chromatographic separation of these compounds was a challenge due to the similarity of the congeners and their lack of a chromophore. MSguided isolation eventually led to the purification of agminosides A-E (145-149). An unidentified sponge of the order Dictyoceratida was found to contain a new isomer (186) of the known sesterterpene variabilin. As variabilin-type compounds are predominantly found from sponges of the family Irciniidae, the unidentified sponge is most likely an irciniid. In addition, the sponge contained two prenylated quinones, one of which, 189, is a new isomer of a known sponge metabolite. The sponge Darwinella oxeata contained four new nitrogenous diterpenes of the aplysulphurane (rearranged spongian) skeleton, oxeatamide A (214), isooxeatamide A (215), oxeatamide A 23-methyl ester (216) and oxeatamide B (217).</p>

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Synthesis based on cyclohexadienes. Part 34. A tandem cationic rearrangement–ene cyclisation route to 2-pupukeanone

Cited by 7 publications

References 23 publications

Bromination and Accompanying Rearrangement of the Polycyclic Oxetane 2,4-Oxytwistane

Bromination and Accompanying Rearrangement of the Polycyclic Oxetane 2,4-Oxytwistane

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Isolation of New Secondary Metabolites from New Zealand Marine Invertebrates

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