Alternative spiroketalization methods toward purpuromycin: a diketone approach to prevent benzofuran formation |
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Authors: | Lowell Andrew N Fennie Michael W Kozlowski Marisa C |
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Institution: | Roy and Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, USA. |
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Abstract: | 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. |
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