Nitration versus nitrosation chemistry of menthofuran: remarkable fragmentation and dimerization pathways and expeditious entry into dehydromenthofurolactone

J Org Chem. 2007 Dec 21;72(26):10123-9. doi: 10.1021/jo701992r. Epub 2007 Nov 29.

Abstract

The reaction chemistry of menthofuran (1), a toxic furan terpenoid from various mint oils, with nitric acid and nitrous acid has been investigated. Treatment of 1 with nitric acid afforded a 1:1 mixture of the bisfuran derivatives 5 and 6, resulting from the unexpected cleavage of the furan into two carbonyl fragments (3-methylcyclohexanone and hydroxyacetone) and their subsequent trapping by unreacted 1. Under conditions of high dilution, the nitrofuran derivative 7 was formed instead as the major reaction product. During investigation of this chemistry, it was found that oxidation of 1 with DDQ led to the important fragrant monoterpenoid 4 [dehydromenthofurolactone (anhydro Woodward-Eastman lactone)] in 44% yield. Exposure of 1 to nitrite ions at pH 3 afforded a completely different type of products, encompassing the known lactone 14, the lactam 15, and the remarkable dimer 16, bearing a N-hydroxy-2-pyrrolinone moiety linked to a nitrooximinofuran unit by an oxygen bridge. By using a combined spectroscopic and DFT approach, the constitution and configuration of 16 could be determined. These results fill a gap in the chemistry of furan compounds and describe routes to menthofuran-derived scaffolds of potential synthetic and biomedical relevance.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 4-Butyrolactone / analogs & derivatives*
  • 4-Butyrolactone / chemical synthesis
  • 4-Butyrolactone / chemistry
  • Dimerization
  • Magnetic Resonance Spectroscopy / methods
  • Magnetic Resonance Spectroscopy / standards
  • Models, Chemical
  • Molecular Structure
  • Monoterpenes / chemical synthesis*
  • Monoterpenes / chemistry*
  • Nitric Acid / chemistry*
  • Nitrosation
  • Nitrous Acid / chemistry*
  • Reference Standards
  • Stereoisomerism

Substances

  • Monoterpenes
  • dehydromenthofurolactone
  • Nitric Acid
  • menthofuran
  • 4-Butyrolactone
  • Nitrous Acid