Cajuputones A–C, β ‐Triketone Flavanone Hybrids from the Branches and Leaves of Melaleuca cajuputi

Three new β ‐triketone flavanone hybrids, cajuputones A–C were obtained from Melaleuca cajuputi (the Australian ‘tea tree’). The structures of cajuputones A–C were elucidated by 1D/2D NMR spectroscopy and HR‐ESI‐MS analyses; and their absolute configurations were established by electric circular dichroism (ECD) calculations using TDDFT method. Structurally, cajuputones A–C feature a rare 6/6/6/6 oxatetracyclic ring system fused between an acylphloroglucinol‐derived β ‐triketone and a pinocembrin or strobopinin moiety via an angle‐type pyran‐like motif. DFT‐based conformational optimization in chloroform explained the similarity of the 1D NMR data of cajuputones B and C (C‐2 epimers).