Synthesis, Structure Revision, and Anti-inflammatory Activity Investigation of Putative Blumeatin

Blumeatin, reported herein, bearing two hydroxyl groups at C3' and C5' of ring B, is isolated from the traditional Chinese medicine Blumea balsamifera. But the isolation procedure of blumeatin from plants has limitations of prolonged duration and high cost. A procedure featuring Lewis acid-catalyzed ring closure and chiral resolution via Schiff base intermediates is provided here to prepare optically pure blumeatin and its R-isomer efficiently. Furthermore, the structure revision of putative blumeatin based on a logically synthetic procedure and NMR spectroscopic analysis was conducted. The 1D and 2D NMR data analysis unambiguously confirmed our proposal that the reported blumeatin structure has been misassigned as it corresponds to sterubin, which contains two hydroxyl groups at C3' and C4' of ring B. Finally, the results of the ear-swelling test exhibited that synthetic (±)-blumeatin and (±)-sterubin had moderate anti-inflammatory activity which was less than that of (-)-sterubin.