Exploring the Original Proposed Biosynthesis of (+)-Symbioimine: Remote Exocyclic Stereocontrol in a Type I IMDA Reaction

The originally proposed biosynthesis of (+)-symbioimine was explored, resulting in the successful intramolecular Diels−Alder (IMDA) cyclization of an appropriate (E,E,E)-1,7,9-decatrien-3-one. In contrast to the originally proposed biosynthesis, the IMDA reaction appears to proceed via an endo transition state. Remarkably, a single exocyclic stereogenic center effectively controls the π-facial selectivity affording a highly diastereoselective cycloaddition.