Atalaphylline

The title acridone alkaloid [systematic name: 1,3,5-trihydroxy-2,4-bis(3-methylbut-2-enyl)acridin-9(10H)-one], C(23)H(25)NO(4\), known as atalaphylline, was isolated from Atalantia monophylla Correa, a mangrove plant. The molecule contains three fused planar rings with an r.m.s. deviation of 0.026 (2) angstrom. Both 3-methylbut-2-enyl substituents are in a (-)anticlinal conformation. An intramolecular N-H center dot center dot center dot O hydrogen bond generates an S(5) ring motif, while an intramolecular O-H center dot center dot center dot O hydrogen bond generates an S( 6) ring motif. In the crystal structure, the molecules are linked into screw chains along [010] by intermolecular O-H center dot center dot center dot O hydrogen bonds. These chains are stacked along the a axis by pi-pi interactions with centroid-centroid distances of 3.6695 (13) and 3.6696 (13) angstrom.