Tuning Diketodioxinone Reactivity: Biomimetic Synthesis of the Resorcylate Antibiotic Fungal Metabolites <i>ent</i>-W1278A, -B, and -C, Using Iterative Aromatization Reactions
作者:Ismael Navarro、Christoph Pöverlein、Gerhard Schlingmann、Anthony G. M. Barrett
DOI:10.1021/jo9015858
日期:2009.11.6
The onset temperature of the retro-Diels-Alder reactions of diketo-1,3-dioxin-2-ones to generate alpha,gamma,epsilon-triketo-ketenes was found to be significantly reduced with 2-phenyl substitution. These ketenes, generated at 78 degrees C, were trapped with alcohols to provide resorcylate esters following aromatization by sequential reaction with cesium acetate and trifluoroacetic acid. The methodology was applied iteratively to the total synthesis of the resorcylate antibiotics W1278A, -B, and -C. It is noteworthy that in this process the linking of the monomer units occurs during construction of the aromatic ring.
The Effects of a Remote Stereogenic Center in the Lewis Base Catalyzed Aldol Additions of Chiral Trichlorosilyl Enolates
作者:Scott E. Denmark、Shinji Fujimori
DOI:10.1021/ol026594n
日期:2002.10.1
Chiral trichlorosilylenolates bearing a remote stereogenic center were employed in the phosphoramide-catalyzed aldol reaction. The additions of the methyl ketoneenolates proceeded with only moderate diastereoselectivities. The addition of the Z-enolate to various aldehydes selectively produced the syn relative diastereomers. In both cases, the effect of the beta-silyloxy stereogenic center was modest