Total synthesis of viridicatumtoxin B and analogues thereof: strategy evolution, structural revision, and biological evaluation

J Am Chem Soc. 2014 Aug 27;136(34):12137-60. doi: 10.1021/ja506472u. Epub 2014 Aug 15.

Abstract

The details of the total synthesis of viridicatumtoxin B (1) are described. Initial synthetic strategies toward this intriguing tetracycline antibiotic resulted in the development of key alkylation and Lewis acid-mediated spirocyclization reactions to form the hindered EF spirojunction, as well as Michael-Dieckmann reactions to set the A and C rings. The use of an aromatic A-ring substrate, however, was found to be unsuitable for the introduction of the requisite hydroxyl groups at carbons 4a and 12a. Applying these previous tactics, we developed stepwise approaches to oxidize carbons 12a and 4a based on enol- and enolate-based oxidations, respectively, the latter of which was accomplished after systematic investigations that revealed critical reactivity patterns. The herein described synthetic strategy resulted in the total synthesis of viridicatumtoxin B (1), which, in turn, formed the basis for the revision of its originally assigned structure. The developed chemistry facilitated the synthesis of a series of viridicatumtoxin analogues, which were evaluated against Gram-positive and Gram-negative bacterial strains, including drug-resistant pathogens, revealing the first structure-activity relationships within this structural type.

Publication types

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

MeSH terms

  • Alkylation
  • Anti-Bacterial Agents / chemical synthesis*
  • Anti-Bacterial Agents / chemistry
  • Anti-Bacterial Agents / pharmacology
  • Gram-Negative Bacteria / drug effects
  • Gram-Positive Bacteria / drug effects
  • Lewis Acids / chemistry
  • Microbial Sensitivity Tests
  • Molecular Structure
  • Tetracyclines / chemical synthesis*
  • Tetracyclines / chemistry
  • Tetracyclines / pharmacology

Substances

  • Anti-Bacterial Agents
  • Lewis Acids
  • Tetracyclines
  • viridicatumtoxin B