EDDA-catalyzed rapid synthetic routes for biologically interesting polycycles bearing citrans and chalcones: the first total synthesis of sumadain A

An efficient and concise synthetic route for biologically interesting polycycles bearing citran and chalcone nuclei was developed starting from a variety of trihydroxybenzenes with substituents on the ring. The key strategies involved an ethylenediamine diacetate-catalyzed cyclization by a domino aldol-type/electrocyclization/H-shift/hetero Diels–Alder reaction of trihydroxybenzenes and citral or trans,trans-farnesal. This methodology was applied successfully to the synthesis of three natural products, desbenzylidenerubramin, rubraine, sumadain A, and their unnatural derivatives.