Cytisine-like alkaloids from Ormosia hosiei Hemsl. & E.H. Wilson.

Four alkaloids named hosieines A-D were isolated from the root and stem of Ormosia hosiei. Their flat structures were established by mass spectrometry and by a combination of NMR experiments. These molecules probably share a common biosynthetic origin with the lupin alkaloids but they differ in the formation of the last ring, being here part of a rare 2-azabicyclo[3.2.1]octane system. Their absolute configuration was determined by X-ray crystallography using CuKα radiation. As has been described for cytisine, they display a remarkable affinity towards neuronal nicotinic acetylcholine α4β2 receptor.