Recent advances of intermolecular Diels-Alder reaction in bio-inspired synthesis of natural products

The Diels-Alder (D-A) reaction is one of the most powerful reactions in organic synthesis. The intermolecular D-A reaction attracts much less attentions than its intramolecular counterpart in natural product synthesis, possibly due to the issues of reactivity and selectivity. In the past decade, the intermolecular D-A reaction has been increasingly utilized in the total synthesis of structurally complex natural products. In this article, we present a few examples for the elegant applications of the intermolecular D-A reaction that are inspired by biosynthetic hypotheses of the target natural products. These examples demonstrate that D-A reaction is not only useful for preparing building blocks but also powerful for coupling structurally complicated and sterically demanding segments in a highly chemo- and stereo-controlled fashion, which may inspire further developments of intermolecular D-A reaction from both strategy and methodology perspectives.