Isolation and stereochemistry of two new alkaloids from Stemona tuberosa

Two new stenine-type alkaloids, neotuberostemonol (3) and neotuberostemoninol (4), along with the known compound neotuberostemonine (2), were isolated from Stemona tuberosa Lour. Their structures were characterized by X-ray crystallography in combination with spectroscopic methods, and their absolute configurations were inferred from the known configuration of tuberostemonine (1). In the crystalline state, weak C-H...O hydrogen bonds play an important role in the molecular packing of 3 and 4. (C) 2002 Elsevier Science Ltd. All rights reserved.