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Synthesis 2003(1): 0117-0123
DOI: 10.1055/s-2003-36253
PAPER
© Georg Thieme Verlag Stuttgart · New York

Total Synthesis of Himachalene Sesquiterpenes of Aphthona and Phyllotreta Flea Beetles

Robert J. Bartelt*, David Weisleder, Frank A. Momany
USDA-ARS, National Center for Agricultural Utilization Research, 1815 N. University St., Peoria, Illinois 61604, USA
Fax: +1(309)6816686; e-Mail: BartelRJ@NCAUR.USDA.gov;
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Publication History

Received 10 September 2002
Publication Date:
18 December 2002 (online)

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Abstract

A total synthesis is presented for himachalene-related norsesquiterpene ketone 1 (racemic), based on the Robinson annulation and other standard reactions. The route involved five steps from cycloheptanone. A favorable result was that the desired dia­stereomer of 1 was obtained preferentially (97:3) over the unwanted one. Molecular modeling (ab initio calculations) aided in confirming the assignment of relative stereochemistry of 1 and in rationalizing the observed ratio of diastereomers. Three related sesquiterpene hydrocarbons and two alcohols were subsequently produced from 1. The six compounds occur naturally in several flea beetle species and likely serve a pheromonal function.

Key words

himachalene - terpenoids - pheromones - annulations - stereoselective synthesis - natural products