2,8-dihydroxy-1-(3-methylbut-2-enyl)9H-carbazole-3-carbaldehyde

The title naturally occurring carbazole compound, C18H17NO3, known as hepta-zoline, was isolated from Micromelum minutum. The carbazole ring system is essentially planar. The hydr-oxy and aldehyde substituent groups lie in the plane of the benzene ring, while the 3-methyl-2-butenyl group is anti-clinal, with a dihedral angle of 70.26 (7)° between it and the mean plane of the carbazole. In the crystal structure, an intra-molecular O - H⋯O inter-action generates an S(6) ring motif, while an inter-molecular O - H⋯O inter-action forms dimers that link into chains along the [401] direction. The structure is further stabilized by weak intra-molecular C - H⋯O inter-actions and π-π inter-actions [centroid-to-centroid distances 3.5901 (8) and 3.5899 (8) Å]. © International Union of Crystallography 2007.