AbstraetCalpurmenin and its 13a-(2'-pyrrolecarboxylic acid) ester, C20H27N304, are alkaloids with a sparteine molecular framework, isolated from the South African Leguminosa, Calpurnia aurea. Crystals of the ester compound are orthorhombic with space group P2~2121 and Z = 4. The lattice dimensions are a = 8.128 (4), b = 12.423 (3) and c = 18.467 (5) A. The structure was solved with direct methods and refined with least squares using 1339 reflexions of which 805 had intensities with I > 2o(1). The keto oxygen atom is bound to C(2), the hydroxyl group is bound to C(12) in a fl axial orientation, the ester moiety is bound to C(13) in an axial orientation. Ring A is a distorted sofa, rings B and D are slightly distorted chairs, while ring C has a nearly ideal boat conformation.