Preparation and Crystal Structure of Acetyl Hemerocallin and Structural Revision of Hemerocallin

ObjectiveTo revise the structure of hemerocallin, an active and toxic compound isolated from the roots of Hemerocallis fulva, which was first reported in 1974 based on the chemical and spectral data.MethodsThe structure of acetyl hemerocallin was determined through the acetyl derivative preparing and X-ray diffraction.ResultsThe title compound acetyl hemerocallin (1) has been prepared and structurally characterized by X-ray single-crystal diffraction method. X-ray analysis revealed that the two naphthalene rings in compound 1 were significantly twisted with an average dihedral angle of 44.1°. The two acetate groups in each naphthalene ring adopted anti-parallel conformation. In addition, the π-π stacking interactions were found in the crystal structure, the molecules were linked into a supramolecular network, and the crystal structure was stabilized.ConclusionThe structure of hemerocallin is identified as 2,2′-bi(1,8-dihydroxy-6-methyl-7-acetylnaphthalene) (3).