Molecular structure of tuberostemonone

A newstemona alkaloid, tuberostemonone (C22H31NO6), has been isolated from the roots ofstemona tuberosa Lour, and its molecular structure determined by MS, IR, NMR spectra and X-ray crystallography (R=0.046 for 1746 observed Mo-Kα data). Besides retaining the characteristicstemona skeleton, which is composed of anα-methyl-γ-lactone and anN-methylene azepine ring linked at the γ-position of this lactone, the tuberostemonone molecule possesses a nine-membered azacycle which is hitherto not found in other knownstemona alkaloids.