Tectonaquinones A, B and C: three new naphthoquinone derivatives from the heartwood of Tectona grandis.

Chemical investigation of the chloroform extract of heartwood of Tectona grandis L. f. led to the isolation of three new naphthoquinone derivatives, tectonaquinones A (1), B (2) and C (3), along with six known compounds: barleriaquinone-I (4), tectoquinone (5), tecomaquinone I (6), lapachol (7), obtusifolin (8) and 2-hydroxy-3-methyl anthraquinone (9). The structures of the new compounds were elucidated by spectroscopic methods including 2 D NMR experiments. Tectonaquinone B is the first natural compound that has a hexa-cyclic dinaphthofuran-dione scaffold. Tectonaquinone C has a bicyclic acetal motif that is unusual in nature.