Vulgarisin A, a New Diterpenoid with a Rare 5/6/4/5 Ring Skeleton from the Chinese Medicinal Plant Prunella vulgaris
摘要:
Vulgarisin A (1), a new diterpenoid with an unprecedented 5/6/4/5 fused tetracyclic ring skeleton, has been isolated from the medicinal plant Prunella vulgaris Linn. Its structure was characterized by extensive spectroscopic methods, and the absolute configuration was secured by single crystal X-ray diffraction analysis. Compound 1 showed weak cytotoxicity against human lung carcinoma A549 cells with an IC50 value of 57.0 mu M.
The asymmetric total syntheses of (+)-vulgarisins A–E, which share a rare [5-6-4-5] tetracyclic core structure, have been achieved for the first time in a divergent manner. Key features of the strategy involve a catalytic asymmetric intramolecular cyclopropanation, a one-pot borylation/conjugate addition process, a Wolff ringcontraction and a stereocontrolled pinacol cyclization.