The first total syntheses of piericidin A1 and B1 are disclosed and unambiguously establish the relative and absolute stereochemistry of the natural products by an approach that will facilitate the synthesis of a series of analogues. Central to the approach is an inverse electron demand Diels-Alder reaction of a N-sulfonyl-1-aza-1,3-butadiene with tetramethoxyethene followed by Lewis acid-promoted