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Tow New Oplopanol Esters from Ligularia narynensis Xue GAO, Tong SHEN, Wei Dong XIE, Zhong Jian JIA* College of Chemistry and Engineering, State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou 730000 Abstract: Tow new oplopanol esters were isolated from the roots of Ligularia narynensis. Their structures were elucidated by spectroscopic methods, especially 2D-NMR techniques. Keywords: Ligularia narynensis, Compositae, sesquiterpenoids, oplopanol esters. Mainly species of Ligularia have long been used for treatment of fever, inflammation, detoxication, invigorating the circulation of blood and smoothing pain1. So far the opl- opane derivatives were not found in the genus Ligularia. Here we report the structure elucidation of 1, 6-di(methylbutyryloxy)-2, 14-diacetoxy-7-acetoxymethylsenecio- yloxy-11, 12-epoxyloplopa-8(10)-en (1) and 2, 14-diacetoxy-6-methylbutyryloxy-7- methyl-senecioyloxy-11, 12-epoxyloplopa-8(10)-en (2) from the roots of Ligularia narynensis. *E-mail: jiazj@lzu.edu.cn Compound 1, colorless gum, []20 D +100 (c 0.2, CHCl3). The HRESIMS spectrum gave m/z 729.3457 [M+Na]+, in accordance with the molecular formula C37H54O13 (calcd for C37H54O13Na 729.3458). The IR (KBr) showed the presence of ester group (1735 cm-1) and double bond (1656 cm-1). The 1H and 13C NMR (DEPT) spectrum of 1 displayed the signals of two acetoxy, two methylbutyryl and one 4-acetoxy-4- methylsenecioyl2 (see Table 1). In the FABMS spectrum, the fragment peaks at m/z 646.8 [M-HOAc]+, 604.7 [M-HOMebu]+, 534.6 [M-HOMesen-HOAC]+, 330.4 [M- HOMesenOAc-HOMebu-2HOAc]+ and 312.4 [M-HOMesenOAc-2HOMebu-HOAc]+ further confirmed the presence of above groups. The 1H and 13C NMR data of the pent- aester were similar to those of the oplopanol derivative crellisin2. Moreover the 1H-1H COSY spectrum of 1 established the proton connections: H-1/H-2/H-3/ H-4/H-5/H-6/H-7 and H-1/H-9/H-4/H-3/H-14/H-15. In the HMBC spectrum, the correlations of H-10 (H 4.84, 5.24) with C-7 (C 73.2), C-8 (C 137.8), C-9 (C 44.6), and H-13 (H 1.21) with C-5 (C 49.0), C-11 (C 55.1), and C-12 (C 53.0) also proved 1 to be an oplopanol derivative. The positions of the five ester groups were confirmed by the correlations in the HMBC spectrum: H 5.68 (H-1) with C 176.0 (C1 of R1), H 5.55 (H-2) with C 169.8 (C1 of Ac), δH 5.09 (H-6) with C 176.1 (C1 of Mebu), H 5.68 (H-7) with C 164.9 (C1 of R2), and H 5.17 (H-14) with C 170.2 (C1 of Ac). The relative stereochemistry of 1 was deduced by analysis of the 1H-1H coupling constants and the NOE difference spectra. The coupling constants J4,3, J4,5 and J4,9 (10.0 Hz) indicated that H-4 was oriented in an anti-trans-axial direction, with respect to the neighbouring three protons H-3, 5, 9, so that H-4 was arranged in - orientation, and H-3, 5, 9 were in - orientation2. In the NOE difference experiments, irradiation at H-6 produced positive NOE effect on H-4 and H-7, thus H-6, 7 were in - orientation, H-7 in - orientation was also deduced from biogenetic considerations3. On the other hand, irradiation at H-3 produced positive NOE effects on H-1 and H-2. So the relative configuration of 1 was established as figured out. Compound 2, colorless needles, mp: 168 -170 ˚C, []20 D + 167 (c 0.3, CHCl3). Its FABMS spectrum gave [M-H]+ at m/z 547.4. The IR spectrum showed the presence of ester group (1735 cm-1) and double bond bands (1646 cm-1), which with 1H and 13C NMR (DEPT) data were similar to those of 1 (see Table 1). The obvious distinction between 2 and 1 revealed that 2 is a tetraester. A 4-methylsenecioyl instead of a 4- acetoxy-4-methylsenecioyl connected to C-7 and a methylbutyryl at C-1 was absent. The FABMS of 1 showed fragment peaks at m/z 487.9 [M-H-HOAc]+, 446.1[M- HOMebu]+, 434.6 [M-HOMesen]+ and 212.3 [M-HOMesen-HOMebu-2HOAc]+ which further confirmed the presence of the ester groups. Finally 2 was deduced as figured out. Table 1 1H (400MHz), 13C NMR (100MHz), DEPT data of compounds 1 and 2 (CDCl3, TMS, δppm)* No. C 1 H C 2 H 1 71.0 (d) 5.68 brs 33.6 (t) 2.10 m, 1.68 m 2 72.2 (d) 5.55 dd (10.0, 4.2 Hz) 72.9 (d) 5.49 ddd (12.0, 10.0, 3.0 Hz) 3 44.9 (d) 2.73 ddd (10.0, 10.0, 4.5 Hz) 45.3 (d) 2.61 ddd (10.0, 10.0, 4.5 Hz) 4 43.7 (d) 2.00 ddd (12.0, 10.0, 10.0 Hz) 47.4 (d) 1.38 ddd (11.0, 10.0, 10.0 Hz) 5 49.0 (d) 1.77 dd (11.0, 10.0 Hz) 49.0 (d) 1.80 dd (10.8, 10.0 Hz) 6 72.3 (d) 5.09 brd (11.0 Hz) 73.2 (d) 5.10 dd (10.8, 3.0 Hz) 7 73.2 (d) 5.68 brs 72.2 (d) 5.70 d (3.0 Hz) 8 137.8 (s) - 142.9 (s) - 9 10 44.6 (d) 115.2 (t) 2.47 brd (12.0Hz) 41.4 (d) 2.32 brd (11.0 Hz) 5.24 brs, 5.09 brs 112.0 (t) 5.19 brs, 4.91 brs 11 55.1 (s) - 55.1 (s) - 12 53.0 (t) 2.83, 2.76 (each d, 4.0 Hz) 53.0 (t) 2.79, 2.71 (each d, 4.0 Hz) 13 16.2 (q) 1.21 s 16.1 (q) 1.17 s 14 69.7 (d) 5.17 dq (6.8, 4.5 Hz) 70.1 (d) 5.10 dq (6.6, 4.5 Hz) 15 16.2 (q) 1.14 d (6.8 Hz ) 16.1 (q) 1.44 d (6.6 Hz) *assigned by 1H-1H COSY, HMQC and HMBC spectra References and Notes 1. L. S. Chen, Zhong Cao Yao (Chinese Traditional and Herbal Drugs,Chinese), 1987, 18, 421. 2. H. Chen, Z. J. Jia and R. X. Tan, Planta Medica, 1997, 63 (3), 245. 3. F. Bohlmann, C. Zdero, Phytochemistry, 1981, 20 (8), 2024. 4. compound 1: Ac at C-2: H = 2.04, C-1ˊ= 169.8, C-2ˊ= 21.0; Ac at C-3: H = 2.11, C-1 = 170.2, C-2 = 21.2; R1: H-2 = 2.40, H-3 = 1.75, 1.48, H-4 = 0.89, H-5 = 1.14; C-1 = 176.0, C-2 = 41.1, C-3 = 26.3, C-4 = 11.5, C-5 = 16.2; Mebu: H-2 = 2.40, H-3 = 1.75, 1.48, H-4 = 0.97, H-5 = 1.19; C-1 = 176.1, C-2= 41.7, C-3 = 26.5, C-4 = 11.7, C-5 = 17.5; R2: H-2 = 5.82, H-4 = 5.25, H-5 = 1.33, H-6 = 2.08, H-8 = 1.96; C-1 = 164.9, C-2= 114.9, C-3 = 158.0, C-4 = 73.5, C-5 = 19.3, C-6 = 15.4, C-7 = 169.9, C-8 = 19.6; Compound 2: Ac at C-2: H = 2.10, C-1ˊ= 170.6, C-2ˊ= 21.3; Ac at C-3: H = 1.98, C-1 = 170.3, C-2 = 21.0; Mebu: H-2 = 2.37, H-3 = 1.76, 1.40, H-4 = 0.88, H-5 = 1.14; C-1 = 176.1, C-2 = 41.1, C-3 = 26.2, C-4 = 11.5, C-5 = 16.1; R2: H-2 = 5.61, H-4 = 2.14, H-5 = 1.08, H-6 = 2.13; C-1 = 164.5, C-2= 114.0, C-3 = 162.7, C-4 = 33.7, C-5 = 11.7, C-6 = 18.8 [ Last edited by daiqiguang on 2007-5-10 at 18:34 ] |
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