Abstract
The asymmetric total synthesis of epoxyquinols A, B, and C, and epoxytwinol A, and computational analysis of the key biomimetic oxidative dimerization, are described. In the first-generation synthesis, the HfCl4-mediated diastereoselective Diels-Alder reaction of furan with chiral acrylate has been 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 have been developed. A biomimetic cascade reaction involving oxidation, 6π-electrocyclization, and Diels-Alder dimerization or formal [4+4] cycloaddition, is the key reaction in the formation of heptacyclic structure of epoxyquinols A, B, and C, and epoxytwinol A. Intermolecular hydrogen-bonding is found to be the key, causing formation of both epoxyquinols A and B. In the dimerization of epoxyquinol monomer, two monomeric 2H-pyrans interact each other to afford pre-associated complexes stabilized by hydrogen-bonding, then Diels-Alder reaction proceeds.
