Total synthesis of diaporthichalasin by using the intramolecular Diels-Alder reaction of an α,β-unsaturated γ-hydroxylactam in aqueous media.

The first total synthesis of diaporthichalasin has been successfully achieved and complete structure elucidation, including the absolute configuration, was also accomplished. The intramolecular Diels-Alder (IMDA) reaction between the diene side chain on the decalin skeleton and α,β-unsaturated γ-hydroxy-γ-lactam in aqueous media was effectively employed as the key step. From this synthetic study, we found that α,β-unsaturated γ-hydroxy-γ-lactam is an essential precursor for the construction of the diaporthichalasin-type pentacyclic skeleton. This important finding strongly suggests that this route is involved in the biosynthetic pathway for diaporthichalasin.