Biomimetic Syntheses of Analogs of Hongoquercin A and B by Late-Stage Derivatization

The hongoquercins are tetracyclic meroterpenoid natural products with the trans-transoid decalin-dihydrobenzopyran ring system, which display a range of different bioactivities. In this study, the syntheses of a range of hongoquercins using gold-catalyzed enyne cyclization reactions and further derivatization are described. The parent enyne resorcylate precursors were synthesized biomimetically from the corresponding dioxinone keto ester via regioselective acylation, Tsuji-Trost allylic decarboxylative rearrangement, and aromatization. The dioxinone keto ester 12 was prepared in 6 steps from geraniol using allylic functionalization and alkyne synthesis.

Automated summary

This study describes the synthesis of a range of hongoquercins using gold-catalyzed enyne cyclization reactions, and the preparation of the parent enyne resorcylate precursors through several steps including regioselective acylation, Tsuji-Trost allylic decarboxylative rearrangement, and aromatization. The dioxinone keto ester was prepared in 6 steps from geraniol through allylic functionalization and alkyne synthesis.