Cyclization of the Monoterpene Citronellal to Isopulegol:: A Biomimetic Natural Product Synthesis

• Bruce L. Jensen ^[1] ; Ahmed Malkawi ^[1] ; Vanessa McGowan ^[1]
  1. [1] University of Maine

     University of Maine

     Town of Orono, Estados Unidos

     
• Localización: Journal of chemical education, ISSN 0021-9584, Vol. 77, Nº 11 (November), 2000, págs. 1474-1474
• Idioma: inglés
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• Resumen

  • Cyclization of the monoterpene (S)-(--)-citronellal takes place rapidly in the presence of tin(IV) chloride in methylene chloride at 0 °C, affording the cyclic monoterpene isopulegol in a yield of 85%. The experiment reported here mimics the reaction found in the biosynthetic pathway leading to another well-known natural product, menthol. The starting material and final product display easily interpreted infrared and proton-NMR spectra. Coupling patterns and constants produced by the C-3 methine proton establish the all-equatorial substitution pattern of the cyclohexane ring system found in the product. Either a carbocation process or an ene reaction can be used to describe the mechanistic details of this reaction.