Development of a Unified Enantioselective, Convergent Synthetic Approach Toward the Furanobutenolide-Derived Polycyclic Norcembranoid Diterpenes: Asymmetric Formation of the Polycyclic Norditerpenoid Carbocyclic Core by Tandem Annulation Cascade

J Org Chem. 2018 Apr 6;83(7):3467-3485. doi: 10.1021/acs.joc.7b02825. Epub 2018 Mar 19.

Abstract

An enantioselective and diastereoselective approach toward the synthesis of the tetracyclic scaffold of the furanobutenolide-derived polycyclic norditerpenoids is described. Focusing on synthetic efforts toward ineleganolide, the synthetic approach utilizes a palladium-catalyzed enantioselective allylic alkylation for the construction of the requisite chiral tertiary ether. A diastereoselective cyclopropanation-Cope rearrangement cascade enabled the convergent assembly of the ineleganolide [6,7,5,5]-tetracyclic scaffold. Investigation of substrates for this critical tandem annulation process is discussed along with synthetic manipulations of the [6,7,5,5]-tetracyclic scaffold and the attempted interconversion of the [6,7,5,5]-tetracyclic scaffold of ineleganolide to the isomeric [7,6,5,5]-core of scabrolide A and its naturally occurring isomers. Computational evaluation of ground-state energies of late-stage synthetic intermediates was used to guide synthetic development and aid in the investigation of the conformational rigidity of these highly constrained and compact polycyclic structures.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Diterpenes / chemical synthesis*
  • Diterpenes / chemistry
  • Furans / chemistry*
  • Lactones / chemistry*
  • Molecular Conformation
  • Stereoisomerism

Substances

  • Diterpenes
  • Furans
  • Lactones
  • furanobutenolide