Chem. Pharm. Bull. 53(1) 11—14 (2005)

one species of endemic plants in Taiwan. It contains essential oil (more than 6%) in its heartwood. Because of its antifungal and decay-resistant characteristics as well as beautiful yellowish-red color with distinct purplish-pink streaks, it is an important building material with high value. Previously, we investigated the chemical components of the heartwood and bark of this plant. a-Cadinol, a major component in the heartwood, shows selectively for human colon tumor cell lines. It also has potent activity against wood-decay fungi. Because of interesting structures in addition to those conferring biological activities, we were encouraged to study the diterpene constituents of its roots. We report here four new diterpenes, 3-oxosaprorthoquinone (1), 3-oxomicrostegiol (2), 3-oxoisotaxodione (3), and taiwaninal (4), together with the two known compounds 3-oxosaprorthoquinone (5) and 6-dehydrohinokiol (6). 3-Oxosaprorthoquinone (1) was isolated as red crystal needles; its molecular formula of C20H24O3 was established through C-NMR and high-resolution impact mass spectral (HR-EI-MS) data. The index of hydrogen deficiency (IHD) of 1 is 9. The IR and UV spectra of 1 confirmed to the presence of an orthonaphthoquinone group (nmax 1664, 1637, 1571 cm , lmax 260, 353, 432 nm) and an isolated ketone (1712 cm ). The H-NMR spectrum (Table 1) exhibited signals for two isopropyl groups [d 1.11 (6H, d, J 7.2 Hz, H18, -19), 2.69 (1H, sep, J 7.2 Hz, H-4), 1.14 (6H, d, J 6.8 Hz, H-16, -17), 2.99 (1H, sep, J 6.8 Hz, H-15)], one aromatic methyl group (d 2.34, s, H-20), and two methylene groups [d 3.21 (2H, dd, J 9.2, 6.8 Hz, H-1) and 2.63—2.72 (2H, m, H-2, overlapping with H-4)] linked between carbonyl and aromatic groups. In addition, there were signals for three aromatic protons at d 7.06 (1H, s, H-14), 7.04, and 7.35 (each 1H, d, J 7.6 Hz, H-7, -6). Twenty C-NMR signals (Table 2) included three carbonyl signals at d 213.9 (C3), 182.3 (C-11), and 181.2 (C-12). The former is an isolated ketone, and latter two are orthonaphthoquinone carbonyls. The red color and UV absorption together with eight aromatic signals indicate that 1 is an orthonaphthquinone derivative. Three methyl signals at d 18.3 (2 CH3), 21.4 (2 CH3), and 19.8 (C-20) were assigned as two isopropyl and one aromatic methyl groups. Comparison of the all physical data with those of aethiopinone (7) showed that the difference is a side chain of orthonaphthoquinone. The heteronuclear multiple-bond correlation spectroscopy (HMBC) (see structure 8) spectrum confirmed the assigned structure, and the nuclear Overhause enhancement exchange spectroscopy (NOESY) spectrum (see structure 9) clarified the January 2005 Chem. Pharm. Bull. 53(1) 11—14 (2005) 11