Transannular [6 + 4] and Ambimodal Cycloaddition in the Biosynthesis of Heronamide A.
The transannular [6 + 4] cycloaddition proposed as a step in the biosynthesis of heronamide A has been modeled using density functional theory. The proposed cycloaddition is highly stereoselective, affording a single product. The reaction proceeds through an ambimodal transition state that directly...
| Publicado en: | Journal of the American Chemical Society Vol. 137; no. 42; pp. 13518 - 13524 |
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| Autores principales: | , , |
| Formato: | Artículo |
| Publicado: |
American Chemical Society
10/28/2015
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| Materias: | |
| Acceso en línea: | Ver este registro en EBSCOhost |
| Sumario: | The transannular [6 + 4] cycloaddition proposed as a step in the biosynthesis of heronamide A has been modeled using density functional theory. The proposed cycloaddition is highly stereoselective, affording a single product. The reaction proceeds through an ambimodal transition state that directly leads to a [4 + 2] adduct in addition to the observed [6 + 4] adduct. Interconversion of these adducts is possible via a facile Cope rearrangement. The [6 + 4] adduct is thermodynamically more stable than the [4 + 2] adduct by 5.2 kcal mol due to a combination of the ring and steric strain in the [4 + 2] product. The results strongly support the plausibility of the proposed transannular [6 + 4] cycloaddition in the biogenesis of heronamide A and may provide insights to designing substrates that selectively undergo [6 + 4] cycloaddition to form unbridged 10-membered rings. |
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