TANDEM INTRAMOLECULAR DIELS-ALDER (TIMDA) REACTIONS - BRANCHED SUBSTRATE STUDIES AND NEW SYNTHETIC PATHWAYS

Using a malonic ester route, the first branched tandem intramolecular Diels-Alder (TIMDA) precursor, 3, was synthesized from sorbic acid in seven steps (15% overall yield). Treatment with Lewis acid catalysts ( e.g., boron trifluoride etherate) affects the TIMDA reaction to afford a new fused-tetracyclic, 4, as two diastereomers (1:1). An alternativ e synthetic route to key intermediates used in the synthesis of linear TIMDA precursors has also been achieved.