The Diene-Transmissive (4 + 2) Cycloaddition Strategy: Stereoselective Synthesis of Advanced Intermediates to Quassinoids.

Complex intermediates to quassinoids, some optically active and containing many functional groups, were synthesized via a diene-transmissive Diels-Alder strategy. The stereochemistry of the key inter- and intramolecular cycloadditions was controlled by stereodefined groups on the preexisting C ring and on the tether