1. Diterpenoids from Isodon eriocalyx var. laxiflora
2. The leaves of I. eriocalyx (Dunn) Hara var. laxiflora Wu and Li were collected in Xishuangbana prefecture, Yunnan Province, People's Republic of China, in November 1999. It was identified by Professor G. D. Tao, Xishuangbana Botanic Garden. A voucher specimen has been deposited in the Herbarium of Kunming Institute of Botany, Chinese Academy of Sciences.
3. Compound 1: Colorless lumpish crystals. Mp 263.5–265.0°C; [α]D13.7 +69.35 (c 0.16, C5H5N); UV (H2O) λmax: no absorption; IR (KBr) νmax: 3411, 2931, 2631, 1742, 1705, 1461, 1287, 1226, 1182, 1128, 1049, 1024, 1001, 986, 950, 911, 843, 805, 726 cm−1; 1H and 13C NMR, data see Table 1; EIMS (70 eV) m/z [M]+ 364 (10), 346 (3), 333 (12), 318 (11), 251 (9), 233 (13), 207 (21), 205 (23), 180 (12), 167 (100), 152 (22), 136 (58), 121 (47), 107 (36), 95 (45), 79 (48), 69 (52), 55 (72); HREIMS m/z [M]+ 364.1859 (calcd for C20H28O6 364.1886). Compound 2: colorless needle crystals. Mp 253.5–255.0°C; [α]D14.7 +68.57 (c 0.18, MeOH); UV (MeOH) λmax: 207 nm; IR (KBr) νmax: 3415, 2964, 2958, 2884, 2805, 1740, 1700, 1631, 1495, 1408, 1368, 1315, 1292, 1247, 1227, 1186, 1128, 1050, 1026, 992, 952, 911, 843, 821 cm−1; 1H and 13C NMR, data see Table 1; EIMS m/z [M]+ 362 (100), 344 (42), 332 (15), 316 (18), 300 (10), 285 (10), 276 (19), 259 (15), 249 (21), 231 (32), 213 (12), 203 (12), 191 (30), 167 (20), 149 (15), 133 (20), 123 (36), 105 (35), 91 (45), 79 (40), 69 (33), 55 (53); HREIMS m/z [M]+ 362.1703 (calcd for C20H26O6 362.1729).
4. X-Ray crystal structure analysis of compound 1: Crystal data: C20H28O6·H2O, M=364.44, orthorhombic system, space group: P212121, a=6.7260(5), b=11.5340(4), c=24.6770(14) Å, V=1914.38(19) Å3, Z=4, d=1.332 g cm−3, Mo Kα radiation, linear absorption coefficient μ=1.0 cm−1. A colorless lumpish crystal of dimensions 0.10×0.10×0.50 mm was used for X-ray measurements on a MAC DIP-2030 diffractometer with a graphite monochromator. The maximum 2θ value was set at 50.0°. The total number of independent reflections measured was 1737, of which 1736 were considered to be observed (|F|2≥8σ|F|2). The structure was solved by the direct method SHELX-866 and expanded using difference Fourier techniques, refined by the program and method NOMCSDP7 and full-matrix least-squares calculations. Hydrogen atoms were fixed at calculated positions. The final indices were Rf=0.073, Rw=0.069 (w=1/σ|F|2), S=7.084, (Δ/σ)max=0.135, (Δρ)min=−0.390 e Å−3, (Δρ)max=0.340 e Å−3.