Mitsuru Shoji
2007
Citations
0
Influential Citations
10
Citations
Journal
Bulletin of the Chemical Society of Japan
Abstract
Asymmetric total synthesis of epoxyquinonoid natural products, such as epoxyquinols A, B, and C, epoxytwinol A, and EI-1941-1, -2, and -3, are described. In the first-generation synthesis of epoxyquinols, the HfCl 4 -mediated diastereoselective Diels-Alder reaction of furan with a chiral acrylate ester was developed. In the second-generation synthesis, a chromatography-free preparation of an iodolactone by using acryloyl chloride as the dienophile in the Diels-Alder reaction of furan, and the lipase-mediated kinetic resolution of a cyclohexenol derivative were developed. This second-generation synthesis is suitable for large-scale preparation. A biomimetic cascade reaction involving oxidation, 67π-electrocyclization, then Diels-Alder dimerization, is the key reaction in the formation of epoxyquinols A-C. Epoxytwinol A was synthesized by the cascade reaction composed of oxidation, 6π-electrocyclization, and formal [4 + 4] cycloaddition. A 2H-pyran, generated by oxidation/67r-electrocyclization, acts as a good diene, reacting with several dienophiles to afford polycyclic compounds in one step. The asymmetric total synthesis of EI-1941s was accomplished, starting from a chiral epoxy iodoquinone, a key intermediate in the total synthesis of epoxyquinols. They were diastereoselectively synthesized via an intramolecular carboxypalladation in a 6-endo cyclization mode, followed by β-hydride elimination, as the key steps.