Enantioselective Total Syntheses of Various Amphilectane and Serrulatane Diterpenoids via Cope Rearrangements

J Am Chem Soc. 2016 May 18;138(19):6261-70. doi: 10.1021/jacs.6b02624. Epub 2016 May 10.

Abstract

Ampilectane and serrulatane natural products are structurally and stereochemically complex compounds that display various potent pharmacological activities ranging from anti-inflammatory to antituberculosis. A general synthetic route toward this family of natural products has been developed, which accomplished a number of amphilectane and serrulatane natural products. The key step employed a stereoselective Cope rearrangement either promoted by gold catalysis or thermal conditions, while a regioselective gold-catalyzed 6-endo-dig cyclization was optimized to afford a precursor. The preparation of the chiral β-ketoester as a starting material was established via an optimized asymmetric 1,4-addition followed by trapping with Mander's reagent, and this initially installed stereogenic center provided good control in the subsequent introduction of all the other stereocenters. A rarely investigated one-pot conversion of α-pyrone into phenol was also examined to enable the syntheses. DFT calculations explain the high stereoselectivity of the Cope rearrangement of the intermediate that eventually led to amphilectolide and caribenol A.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biological Products / chemistry
  • Catalysis
  • Cyclization
  • Cycloaddition Reaction
  • Diterpenes / chemical synthesis*
  • Gold / chemistry
  • Indicators and Reagents
  • Stereoisomerism

Substances

  • Biological Products
  • Diterpenes
  • Indicators and Reagents
  • amphilectolide
  • serrulatic acid
  • Gold