Total synthesis of aldehyde-containing Garcinia natural products isomorellin and gaudichaudione A

The natural products, isomorellin and gaudichaudione A, with a 4-oxa-tricyclo[4.3.1.0^3,7] dec-8-en-2-one scaffold were synthesized for the first time using an efficient method. The key improvement of this method was the simultaneous bisalkylation of 5,6-dihydroxyxanthone with the bulky 2-methylbutyne group. This method obviously shortened the synthetic route and enhanced the total yield. Four analogues named forbesione, desoxymorellin, desoxygaudichaudione A, and gambogin containing the same caged structure were prepared using this method.