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  Home > JCE Print > Journal of Chemical Education > Issues > 2000  > November  >
In the Laboratory
Cyclization of the Monoterpene Citronellal to Isopulegol: A Biomimetic Natural Product Synthesis
Bruce L. Jensen, Ahmed Malkawi, and Vanessa McGowan
Department of Chemistry, University of Maine, Orono, ME 04469
Cover
November 2000
Vol. 77 No. 11
p. 1474
Abstract
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.
Supplement
The full description of this experiment with spectra, structures, and mechanisms is available.
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*  Citation
 Jensen, Bruce L.; Malkawi, Ahmed; McGowan, Vanessa. J. Chem. Educ. 2000 77 1474.
*  Keywords
 IR Spectroscopy; Laboratory Instruction; Natural Products; NMR Spectrometry; Organic Chemistry; Organic Synthesis
*  History
 Created:
Last Updated:		 October 6, 2000
August 31, 2005
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