Microwave-assisted Claisen rearrangement/Diels-Alder cascade reaction for the synthesis of caged Garcinia natural products and analogues

摘要

A microwave-assisted Claisen rearrangement/Diels-Alder cascade reaction was used to synthesise caged Garcinia natural products and analogues containing the unique 4-oxa-tricyclo[4.3.1.0~(3,7)]decan-2-one scaffold from xanthonebased and chromone-based substrates. Forbesione and cluvenone as well as two new and six known caged analogues were obtained. Compared with the traditional thermal method, the reaction time was reduced dramatically and the yield was greatly improved under microwave irradiation. In addition, the regioselectivity observed in the cascade reaction has also been rationalised. Garcinia have long been used in folk medicines for their healing, antibacterial, and cytotoxic activities.