Bioinspired Total Synthesis of Delitschiapyrone A

A bioinspired seven-step total synthesis of delitschiapyrone A was accomplished in 32% overall yield from commercially available 4-bromo-3,5-dimethoxybenzoic acid. The key step of the synthesis is an exclusively regioselective and diastereoselective reaction cascade consisting of the Diels-Alder reaction, alpha-ketol rearrangement, and cyclic hemiacetalization, achieved by simply stirring a heterogeneous mixture of two Diels Alder substrates (putative biosynthetic intermediates) and water at 35 degrees C, directly furnishing the pentacyclic natural product in 75% yield.