(+)‐ and (−)‐Xanthostones A–D: Four Pairs of Enantiomeric Cinnamoyl‐β‐Triketone Derivatives from Xanthostemon chrysanthus

Abstract

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.

Xanchryones I−N, Six Unusual Phloroglucinol‐Amino Acid Hybrids from the Leaves of Xanthostemon chrysanthus

“…[1][2][3] Our group has focused on structurally unique and bioactive natural products from Myrtaceae plants. [2][3][4][5][6][7][8][9][10][11][12] In our previous research on the phloroglucinols from Xanthostemon chrysanthus (Myrtaceae), we discovered the first examples of phloroglucinol-amino acid adducts, xanchryones A and B. [12] Meanwhile, xanchryones A and B displayed characteristic even-mass ions in their mass spectra and unique UV absorptions in the range of 200-350 nm.…”