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Total Synthesis of the Quinone Epoxide Dimer (+)-Torreyanic Acid: Application of a Biomimetic Oxidation/Electrocyclization/Diels−Alder Dimerization Cascade 1

2003; American Chemical Society; Volume: 125; Issue: 17 Linguagem: Inglês

10.1021/ja021396c

1943-2984

Chaomin Li, Richard P. Johnson, John A. Porco,

Synthetic Organic Chemistry Methods

An asymmetric synthesis of the quinone epoxide dimer (+)-torreyanic acid (48) has been accomplished employing [4 + 2] dimerization of diastereomeric 2H-pyran monomers. Synthesis of the related monomeric natural product (+)-ambuic acid (2) has also been achieved which establishes the biosynthetic relationship between these two natural products. A tartrate-mediated nucleophilic epoxidation involving hydroxyl group direction facilitated the asymmetric synthesis of a key chiral quinone monoepoxide intermediate. Thermolysis experiments have also been conducted on a model dimer based on the torreyanic acid core structure and facile retro Diels−Alder reaction processes and equilibration of diastereomeric 2H-pyrans have been observed. Theoretical calculations of Diels−Alder transition states have been performed to evaluate alternative transition states for Diels−Alder dimerization of 2H-pyran quinone epoxide monomers and provide insight into the stereocontrol elements for these reactions.