Journal ArticleDOI
Asymmetric synthesis of epicylindrospermopsin via intramolecular nitrone cycloaddition. Assignment of absolute configuration
James D. White,Joshua D. Hansen +1 more
TLDR
Weinreb et al. as mentioned in this paper showed that (-)-epicylindrospermopsin (2) can be synthesized from 4-bromobenzyloxyacetaldehyde.Abstract:
A synthesis of (-)-epicylindrospermopsin (2) was completed that establishes its absolute configuration and corroborates the corrected structural assignment previously made to this toxin by Weinreb et al. The hydroxylamine 3, prepared from 4-bromobenzyloxyacetaldehyde, was condensed with aldehyde 4, obtained in nine steps from (R)-methionine, to give nitrone 16. Intramolecular cycloaddition of 16 proceeded stereoselectively to yield the oxazabicyclo[2.2.1]heptane 17, which after reduction and deprotection afforded piperidine 18. The latter was transformed via cyclic urea 19 to the inverted C12 alcohol 20, and the derived azide 22 was cyclized to produce the guanidine moiety of 25. Final sulfation of the C12 hydroxyl group furnished (-)-2.read more
Citations
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Journal ArticleDOI
Muscarine, imidazole, oxazole, and thiazole alkaloids
TL;DR: A great number of structurally diverse natural products containing five-membered heterocyclic subunits, such as imidazoles, oxazole, thiazole, and their saturated congeners, are abundant in nature and exhibit extensive and pharmacologically important biological activities.
Book ChapterDOI
Pyrimidines and their Benzo Derivatives
TL;DR: The chemistry of pyrimidines and their benzo derivatives, including quinazolines, perimidines, and benzo[gh]perimidine is reviewed in this article, with particular attention paid to work published between 1996 and 2007.
Journal ArticleDOI
Synthesis of the putative structure of 7-deoxycylindrospermopsin: C7 oxygenation is not required for the inhibition of protein synthesis.
Journal ArticleDOI
Total Synthesis of (−)-7-Epicylindrospermopsin, a Toxic Metabolite of the Freshwater Cyanobacterium Aphanizomenon ovalisporum, and Assignment of Its Absolute Configuration
James D. White,Joshua D. Hansen +1 more
TL;DR: Global deprotection, including hydrolysis of the 2,4-dimethyoxypyrimidine appendage to a uracil, and then monosulfation of the resultant diol 60 afforded a substance identical with natural (-)-7-epicylindrospermopsin (1).
Journal ArticleDOI
Synthesis of Dihydrobenzisoxazoles by the [3 + 2] Cycloaddition of Arynes and Oxaziridines
Arif Kivrak,Richard C. Larock +1 more
TL;DR: Dihydrobenzisoxazoles are readily prepared in good yields by the [3 + 2] cycloaddition of oxaziridines and arynes and readily elaborated to more complex products using palladium-catalyzed crossing-coupling processes.
References
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Journal ArticleDOI
Asymmetric 1,3-Dipolar Cycloaddition Reactions
Journal ArticleDOI
Tetrapropylammonium Perruthenate, Pr4N+RuO4-, TPAP: A Catalytic Oxidant for Organic Synthesis
TL;DR: In this paper, a review of the oxidations of a wide range of molecules with tetrapropylammonium perruthenate including examples of both double oxidations and selective oxidations is presented.
Journal ArticleDOI
Cylindrospermopsin: a potent hepatotoxin from the blue-green alga Cylindrospermopsis raciborskii
Journal ArticleDOI
Correlation of configuration and fluorine-19 chemical shifts of .alpha.-methoxy-.alpha.-trifluoromethylphenyl acetate derivatives
Journal ArticleDOI
Electron microscopic studies on experimental poisoning in mice induced by cylindrospermopsin isolated from blue-green alga Umezakia natans.
Kiyoshi Terao,S. Ohmori,Kazuei Igarashi,Ikuko I. Ohtani,Mariyo F. Watanabe,Ken-ichi Harada,Emiko Ito,Masayuki Watanabe +7 more
TL;DR: It was clearly demonstrated that cylindrospermopsin is a potent inhibitor of the protein synthesis and the amount of total P450 was extensively diminished in the toxin treated with hepatic microsomes.