Enantioselective Biomimetic Total Syntheses of Kiiwanons I and J and Brosimones A and B

摘要

The first enantioselective total syntheses of prenyl-flavonoid Diels-Alder natural products (-)-kuwanon I, (+)-kuwanonJ, (-)-brosimone A, and (-)-brosimone B have been accomplished from a common intermediate based on a concise synthetic strategy. Key elements of the synthesis include a biosynthesis-inspired asymmetric Diels-Alder cyclo-addition mediated by a chiral ligand/boron Lewis acid, as well as a process involving regioselective Schenck ene reaction, reduction, and dehydration to realize a biomimetic dehydro-genation for generation of the required diene precursor. Furthermore, a remarkable tandem inter-Zintramolecular asymmetric Diels-Alder cycloaddition process was applied for the synthesis of (-)-brosimone A.