Four pairs of cinnamoyl‐β‐triketone derivative enantiomers, (+)‐ and (−)‐xanthostones A–D ((+)‐ and (−)‐1–4), were isolated from Xanthostemon chrysanthus. Compounds 1 and 2 feature a new rearranged cinnamoyl‐phloroglucinol scaffold fused with a cinnamyl‐β‐triketone framework. Compounds 1, 3, and 4 are the first examples of natural products with a peculiar phenethyl‐pyranone acid unit. Their structures with absolute configurations were determined by spectroscopic data, X‐ray diffraction analysis and electronic circular dichroism (ECD) calculation. Interestingly, these novel compounds showed a tautomeric behavior in solution, which was revealed by NMR spectroscopy and density functional theory calculation. A plausible biosynthetic pathway toward xanthostones A–D was proposed. Additionally, the anti‐inflammatory and antibacterial activities of xanthostones A–D were evaluated.

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Six new phloroglucinol derivatives, xanchryones IÀ N (1 -6), were isolated from the leaves of Xanthostemon chrysanthus. Compounds 1 -6 are unusual phloroglucinol-amino acid hybrids constructed through C 2 À N and OÀ C 1 ' bonds forming a peculiar oxazole ring. The structures and absolute configurations of compounds 1-6 were determined by MS, NMR, and single-crystal X-ray diffraction. Moreover, the anti-inflammatory and antibacterial activities of these compounds were evaluated.