A new lupin alkaloid, (-)-lusitanine (I), has been isolated from the fresh stems of Maackia amurensis var. buergeri and M. tashiroi (Leguminosae), together with other types of the alkaloids. Its absolute configuration has also been established as (1 R,6R)-5-(E)-aceta-midomethylidenequinolizidine (I) on the basis of chemical transformation into its dihydro-derivatives II ((1R-,5R-,6R-)-( + )-acetamidomethylquinolizidine) and III ((1 R-, 5 S-3,6R-)-(-)-acetami dome thy lquinolizidine) and of their spectral evidence. © 1987, The Pharmaceutical Society of Japan. All rights reserved.