title: Total synthesis of the quinone epoxide dimer (+)-torreyanic acid: application of a biomimetic oxidation/electrocyclization/Diels-Alder dimerization cascade.
abstract: 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.
authors.affiliation: Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, USA.
authors.forename: Chaomin
authors.initials: C
authors.lastname: Li
authors.forename: Richard P
authors.initials: RP
authors.lastname: Johnson
authors.forename: John A
authors.initials: JA
authors.lastname: Porco
mesh_terms: D040761:Biomimetic Materials / Q000737:chemistry; D003500:Cyclization; D003512:Cyclohexanones / Q000138:chemical synthesis; D019281:Dimerization; D004852:Epoxy Compounds / Q000138:chemical synthesis*; D008958:Models, Molecular; D008968:Molecular Conformation; D010084:Oxidation-Reduction; D011714:Pyrans / Q000138:chemical synthesis; D011809:Quinones / Q000138:chemical synthesis*; D013237:Stereoisomerism
chemical_list: D003512:Cyclohexanones; D004852:Epoxy Compounds; D011714:Pyrans; D011809:Quinones; C429363:ambuic acid; C474396:torreyanic acid