Asymmetric synthesis of (a)-bissetone via a highly enantioselective hetero-DielsaAlder reaction

We demonstrate a new approach for the asymmetric synthesis of bissetone. The key reaction is the highly enantioselective hetero-DielsaAlder cycloaddition of triene 3 with ethyl glyoxylate catalyzed by readily available BINOLaTi complexes. The HDA cycloadduct 4 was then transformed in five steps into O-protected bissetone (8) and its C5-epimer in good yield.