Naphthalene derivatives from Diospyros kaki

A detailed chemical investigation of the extractives of the blackened heartwood of Diospyros kaki was carried out to understand their chemical characteristics and to obtain chemotaxonomic information. Three novel naphthalene derivatives were isolated, i.e., 4-hydroxy-5,6-dimethoxy-2-naphthaldehyde (1), 5,6,8-trimethoxy-3-methyl-1-naphthol (2), and 4,8-dihydroxy-5-methoxy-2-naphthaldehyde (3), in addition to two previously reported 2-naphthaldehydes: 4-hydroxy-5,8-dimethoxy-2-naphthaldehyde (4) and 4-hydroxy-5-methoxy-2-naphthaldehyde (5) Their structures were identified by 1D and 2D nuclear magnetic resonance spectroscopy, as well as by high-resolution mass spectrometry.