Different routes to the spiro[2.4]hepta-4,6-dien-1-yl esters 5, 6, 7, 26, and 28 are described and their intramolecular Diels–Alder reactivity examined. A sidechain oxygen substituent is essential for cyclization although its exact role in the cycloaddition remains obscure. The trienes 5, 6, and 28 cyclize to the tetracyclo[5.4.01.7.04.6.06.10]undecenes 9, 10, and 30 which are useful synthetic intermediates for the preparation of sesquiterpenes.
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