A Novel Eleven-Membered-Ring Triterpene Dilactone, Pseudolarolide F and A Related Compound, Pseudolarolide E, fromPseudolarix Kaempferi

A novel eleven-membered-ring triterpene dilactone, pseudolarolide F (1), and a related compound, pseudolarolide E (2), were isolated from the seeds of Pseudolarix kaempferi, a plant indigenous to eastern China. Their structures and stereochemistry were established by spectroscopic studies, which included UV, IR, HREIMS, 2D NMR correlation methods (1H-1H COSY, 13C-H COSY, NOESY, HMQC, and HMBC), and single-crystal X-ray analysis.