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Keywords:

  • Epoxyquinols A, B, C;
  • Epoxytwinol A;
  • Total synthesis;
  • Electrocyclic reactions;
  • Diels–Alder reactions;
  • Density functional calculations

Abstract

The asymmetric total synthesis of epoxyquinols A, B, and C and epoxytwinol A, and computational analysis of the key biomimetic oxidative dimerization procedure are described. In the first-generation synthesis, a HfCl4-mediated diastereoselective Diels–Alder reaction of furan with Corey's chiral auxiliary has been developed. In the second-generation synthesis, a chromatography-free preparation of an iodolactone using acryloyl chloride as the dienophile in the Diels–Alder reaction of furan and a lipase-mediated kinetic resolution of a cyclohexenol derivative have been developed. This second-generation synthesis is suitable for large-scale synthesis. A biomimetic cascade reaction involving oxidation, 6π-electrocyclization, and then Diels–Alder dimerization is the key reaction in the formation of the complex heptacyclic structure of epoxyquinols A, B, and C. Epoxytwinol A is synthesized by the cascade reaction involving oxidation, 6π-electrocyclization, and formal [4+4] cycloaddition reactions. A 2H-pyran, generated by oxidation/6π-electrocyclization, acts as a good diene, reacting with several dienophiles to afford polycyclic compounds in one step. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)