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Keywords:

  • Diels–Alder reaction;
  • Cyclization;
  • Methyl calendulate;
  • Methyl α-eleostearate;
  • Maleic anhydride;
  • Renewable feedstock

Abstract

The thermal, solvent-free addition of maleic anhydride to methyl calendulate (methyl 8,10-trans,12-cis-octadecatrienoate) (1a) occurs with very high regio- and stereoselectivity at C-8 and C-11 of the fatty compound giving the endo-Diels–Alder adduct 4 with retention of the cis-configured double bond. Analogously, the Diels–Alder addition of maleic anhydride to methyl α-eleostearate (methyl 9-cis,11,13-trans-octadecatrienoate) (2a) takes place regio- and stereoselectively at C-11 and C-14 yielding the endo-product 5 which was hydrolyzed to give the respective tricarboxylic acid 6. X-ray diffraction analyses of compounds 4 and 6 clearly show the regio- and stereoselectivity of the Diels–Alder addition reactions.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)