Alternative Spiroketalization Methods toward Purpuromycin: A Diketone Approach To Prevent Benzofuran Formation

The central portion of purpuromycin has been assembled via a classical spiroketalization reaction. Key to promoting this reaction mode versus benzofuran formation was the oxidation state of the spiroketal core. With a higher oxidation state, even the electron-deficient isocoumarin found in purpuromy...

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Veröffentlicht in:Journal of organic chemistry 2011-08, Vol.76 (16), p.6488-6502
Hauptverfasser: Lowell, Andrew N, Fennie, Michael W, Kozlowski, Marisa C
Format: Artikel
Sprache:eng
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Zusammenfassung:The central portion of purpuromycin has been assembled via a classical spiroketalization reaction. Key to promoting this reaction mode versus benzofuran formation was the oxidation state of the spiroketal core. With a higher oxidation state, even the electron-deficient isocoumarin found in purpuromycin could be employed directly in the spiroketalization. The two halves of the spiroketalization precursor were joined via a nitrile oxide/styrene 1,3-dipolar cycloaddition. A very mild selenium dioxide oxidation was used to introduce the required oxidation state of the spiroketal core.
ISSN:0022-3263
1520-6904
DOI:10.1021/jo200399z