Keywords: Diels-Alder reaction / Cyclization / Methyl calendulate / Methyl α-eleostearate / Maleic anhydride / Renewable feedstockThe 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-DielsAlder 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