Rhodomyrtials A and B, Two Meroterpenoids with a Triketone-Sesquiterpene-Triketone Skeleton from Rhodomyrtus tomentosa: Structural Elucidation and Biomimetic Synthesis

Rhodomyrtials A and B (1 and 2), two unprecedented triketone-sesquiterpene-triketone adducts, along with five biogenetically related intermediates, rhodomentone A (3) and tomentodiones A-D (4-7), were isolated from the leaves of Rhodomyrtus tomentosa. Their structures and absolute configurations were determined by a combination of NMR spectroscopy, chemical conversion, and X-ray diffraction analysis. Compounds 1 and 2 were biomimetically synthesized via 5 and 4, respectively, rather than 3, revealing their key ordering of biosynthetic events and confirming their structural assignments. Compound 7 exhibited potent metastatic inhibitory activity against DLD-1 cells by suppressing the activation of matrix metalloproteinase (MMP)-2 and MMP-9.