Single crystals of the phenylcoumarin named mammeigin (or mammea A/AA cycle D) [systematic name: 5-hydroxy-8,8-dimethyl-6-(3-methylbutanoyl)-4-phenyl-2H,8H-pyrano[2,3-f]chromen-2-one], C25H24O5, were obtained in the course of a chemotaxonomic study of the Guttiferae family. Mammeigin was extracted from the fruits of Kilmeyera pumila. The structure reveals an infinite three-dimensional network stabilized by non-classical intermolecular hydrogen bonds.