Chinese Journal of Chemistry, 2005, 23, 895—897 Full paper

* E-mail: yang_xiaosheng@yahoo.com Received November 4, 2004; revised February 25, 2005; accepted March 28, 2005. Project supported by the Department of the Science and Technology of Guizhou Province.

© 2005 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Two New Oxoaporphine Alkaloids from Thalictrum elegans

LIANG, Zhi-Yuana,b(梁志远) YANG, Xiao-Sheng*,a(杨小生) WANG, Yea(汪冶) HAO, Xiao-Jianga(郝小江)

a Key Laboratory of Chemistry for Natural Products of Guizhou Province and the Chinese Academy of Sciences, Guiyang, Guizhou 550002, China

b Department of Chemistry, Guizhou Educational College, Guiyang, Guizhou 550003, China

Two new oxoaporphine alkaloids, 1,2,3,10-tetramethoxy-9-(2-hydroxy-4,5-dimethoxybenzyloxy)oxoaporphine (1) and 1,2,3,10-tetramethoxy-9-(4,5-dimethoxy-2-formylphenoxy)oxoaporphine (2), were isolated from Thalictrum elegans. Their structures were elucidated based on spectroscopic analysis including 1D, 2D NMR, IR and MS.

Keywords Thalictrum elegans, alkaloid, oxoaporphine

Introduction

The genus of Thalictrum is distributed widely in the southwest of China. In recent decades, the investigation on the genus of Thalictrum was focused on isoquinoline alkaloids with antibacterial, anti-inflammatory, antican-cer, diuretic and blood pressure reducing1-3 bioactivities. In our continuous search for new bioactive compounds, the studies on the chemical constituents of T. elegans were carried out. Two new oxoaporphine alkaloids, 1,2,3,10-tetramethoxy-9-(2-hydroxy-4,5-dimethoxy- benzyloxy)oxoaporphine (1) and 1,2,3,10-tetrameth-oxy-9-(4,5-dimethoxy-2-formylphenoxy)oxoaporphine (2), together with two known compounds, thaliadine (3)4 and 1-(4-methoxybenzyl)-2-methyl-6-hydroxy-5,7- dimetoxy)isoquinoline (4)5 were isolated from the ethanol extract of this plant. Their structures were elu-cidated on the basis of spectroscopic analysis including 1D, 2D NMR, IR and MS. In this paper, the isolation and structure elucidation of these two new compounds 1 and 2 are described.

Figure 1 Structures of compounds 1 and 2.

Results and discussion

Compound 1 was obtained as a white crystal (MeOH). Its molecular formula was established as C29H27NO9 from the HRFABMS 533.1721 (calcd 533.1721). IR spectrum showed the presence of hy-droxyl (3684 cm－1) and carbonyl (1727 cm－1) groups.

The 1H NMR spectrum (Table 1) revealed the sig-nals of six methoxyl groups (δH 3.78, 3.94, 4.11, 4.12, 4.13, 4.19), one methylene group (δH 4.67) attached to oxygen, six aromatic protons in the forms of four singlets (δH 6.59, 7.03, 7.89, 8.85) and a pair of doublets (δH 8.20 and 8.95, J＝5.6 Hz ). The pair of doublets was the characteristic of the cis-double bonds of isoquino-line alkaloids.

The 13C NMR (Table 1) and DEPT spectra showed the signals of six methoxyl groups (δC 56.1, 56.2, 56.3, 61.0, 61.5, 61.8), one oxygen-bearing methylene group (δC 60.8), six methines (δC 104.0, 110.6, 112.2, 116.3, 119.1, 144.6), fifteen quaternary carbons (δC 115.6, 122.5, 126.2, 123.8, 131.2, 131.4, 145.6, 146.1, 146.6, 147.1, 147.2, 148.4, 149.5, 154.6, 155.7) and one car-bonyl (δC 180.9). These data, by comparison with the 1H and 13C NMR spectral data of related compounds in the literatures6-9, suggested that compound 1 possess most probably an oxoaporphine and a benzyloxy skeleton. This was further supported by HMBC spectral evi-dences.

From the HMBC (Table 1) spectrum, the correla-tions between the proton H-8 at δH 7.89 and the carbons at δC 180.9 (C-7), 146.6 (C-9), 154.6 (C-10), 131.4 (C-11a), the proton H-11 at δH 8.85 and the carbons at δC 126.2 (C-7a), 146.6 (C-9), 154.6 (C-10), 115.6 (C-11b), were observed respectively. Thus the para-position of two aromatic protons H-8 and H-11 of ring D of oxoaporphine skeleton was readily assigned. Additionally, the HMBC spectrum showed long range

896 Chin. J. Chem., 2005, Vol. 23, No. 7 LIANG et al.

© 2005 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

correlations between the methylene protons (δH 4.67) and the carbons at δC 123.8 (C-1'), 147.1 (C-2'), 146.6 (C-9), the aromatic proton H-3' at δH 6.59 and the car-bons at δC 123.8 (C-1'), 147.1 (C-2'), 149.5 (C-4'), 146.1 (C-5'), the proton H-6' at δH 7.03 and the carbons at δC 147.1 (C-2'), 149.5 (C-4'), respectively. These data in-dicated that one 2',4',5'-trisubstituted benzyloxy moiety was located at C-9 of the oxoaporphine skeleton, one hydroxyl group and two methoxy groups were respec-tively attached to C-2', C-4' and C-5' of the substituted benzyloxy moiety by further investigation of HMBC spectrum. Therefore, compound 1 was identified as 1,2,3,10-tetramethoxy-9-(2-hydroxy-4,5-dimethoxyben- zoxyl)oxoaporphine.

Compound 2 was obtained as orange yellow amor-phous powder. Its molecular formula C29H25NO9 was

deduced from the HRESI-MS at m/z 532.1613 [M＋H]＋

(calcd 532.1607). IR spectrum showed the presence of carbonyl (1720 cm－1) and formyl groups (1702, 2820 and 2732 cm－1).

Comparing the 1H and 13C NMR data of 2 (Table 2) with those of 1 (Table 1), the two compounds showed close resemblance. The most obvious difference be-tween them was that 2 had the signals of a formyl group (δH 10.4, δC 187.7), and meanwhile the signals of a me-thylene and a hydroxyl group of 1 were absent in 2. It was easily recognized that one formyl group and two methoxy groups were respectively attached to C-2', C-4' and C-5' of a substituted phenoxy moiety through HMBC (Table 2) spectrum. Therefore, compound 2 was identified as 1,2,3,10-tetramethoxy-9-(4,5-dimethoxy-2- formylphenoxy)oxoaporphine.

Table 1 The 1H NMR (CDCl3, 400 MHz) and 13C NMR (CDCl3, 100 MHz) data of 1

Position δC δH (J in Hz) HMBC Position δC δH (J in Hz) HMBC

1 155.7 (s) 11c 122.5 (s)

2 147.2 (s) CH2 60.8 (t) 4.67 C-1', 2', 9

3 148.4 (s) 1' 123 8 (s)

3a 131.2 (s) 2' 147.1 (s)

4 119.1(d) 8. 20 (d, 5.6, 1H) C-3, 11c 3' 104.0 (d) 6.59 (s, 1H) C-1', 2', 4', 5'

5 144.6 (d) 8. 95 (d, 5.6, 1H) C-3a, 4, 6a 4′ 149.5 (s)

6a 145.6 (s) 5' 146.1 (s)

7 180.9 (s) 6' 112.2 (d) 7.03 (s, 1H) C-2', 4', -CH2

7a 126.2 (s) 1-OCH3 61.5 (q) 4.13 (s, 3H) C-1

8 116.3 (d) 7. 89 (s, 1H) C-7, 9, 10, 11a 2-OCH3 61.0 (q) 4.12 (s, 3H) C-2

9 146.6 (s) 3-OCH3 61.8 (q) 4.19 (s, 3H) C-3

10 154.6 (s) 10-OCH3 56.1 (q) 4.11 (s, 3H) C-10

11 110.6 (d) 8. 85 (s, 1H) C-7a, 9, 10, 11b 4'-OCH3 56.2 (q) 3.78 (s, 3H) C-4'

11a 131.4 (s) 5'-OCH3 56.3 (q) 3.94 (s, 3H) C-5'

11b 115.6 (s)

Table 2 The 1H NMR (CDCl3, 400 MHz) and 13C NMR (CDCl3, 100 MHz) data of 2

Position δC δH (J in Hz) HMBC Position δC δH (J in Hz) HMBC

1 156.0 (s) 11c 122.5 (s)

2 147.1 (s) 1' 154.8 (s)

3 148.6 (s) 2' 119.9 (s)

3a 131.0 (s) 3' 110.8 (d) 7.43 (s, 1H) C-1', 4', 5', CHO

4 119.0 (d) 8.21 (d, 5.6, 1H) C-3, 11c 4' 146.2 (s)

5 144.6 (d) 8.96 (d, 5.6, 1H) C-3a, 4, 6a 5' 155.6 (s)

6a 145.4 (s) 6' 102.4 (d) 6.51 (s, 1H) C-1', 2', 4', 5'

7 180.8 (s) 1-OCH3 61.5 (q) 4.15 (s, 3H) C-1

7a 126.2 (s) 2-OCH3 61.1 (q) 4.12 (s, 3H) C-2

8 118.1 (d) 8.05 (s, 1H) C-7, 9, 10, 11a 3-OCH3 61.8 (q) 4.20 (s, 3H) C-3

9 146.4 (s) 10-OCH3 56.1 (q) 4.10 (s, 3H) C-10

10 155.1 (s) 2'-CHO 187.7 (d) 10.40 (s, 1H)

11 110.8 (d) 8.89 (s, 1H) C-7a, 9, 10, 11b 4'-OCH3 56.3 (q) 3.97 (s, 3H) C-4'

11a 132.4 (s) 5'-OCH3 56.4 (q) 3.81 (s, 3H) C-5'

11b 115.1 (s)

Oxoaporphine alkaloids Chin. J. Chem., 2005 Vol. 23 No. 7 897

© 2005 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Experimental

General and experimental procedures

Melting point was measured with an XT-4 apparatus and uncorrected. 1D and 2D NMR spectra were re-corded on an INOVA-400 instrument using TMS as internal standard. ESI-MS was measured with a HP-5973 mass spectrometer. IR spectra were recorded with KBr pellets on a Bruker Victor-22 spectrometer. Silica gel for column chromatography and TLC was the products of Qingdao Haiyang Chemical Factory. D101

resin for column chromatography was made by Tianjin Youchang Industry and Business Limited Company.

Plant material

The whole body of T. elegans was collected from Lijiang County of Yunnan Province, China and identi-fied by MIN, Tian-Lu of the Kunming Institute of Bot-any, the Chinese Academy of Science.

Extraction and isolation

The air-dried and powdered whole body (5 kg) of T. elegans was extracted with 95% ethanol three times and the solvent was evaporated in vacuum. The residue was subjected to D101 resin column chromatography, eluted with H2O, 75% EtOH and CHCl3, respectively, to sepa-rate into three fractions. The CHCl3-eluted fraction (193.4 g) was also separated into six fractions (G1—G6) by column chromatography over silica gel (200—300 mesh), eluting with CHCl3-MeOH (V∶V＝10∶1). The G3 (36 g) was rechromatographed on silica gel column eluting with CHCl3-EtOAc-MeOH (V∶V∶V＝15∶5∶2) to yield five subfractions A—E. The fraction C (6.2 g) was chromatographed repeatedly on silica gel column with eluent CHCl3-acetone from ratio of 10∶1 to 5∶1 to yield pure compounds 1 (9 mg) and 2 (34

mg). 1,2,3,10-Tetramethoxy-9-(2-hydroxy-4,5-dimetho-

xybenzyloxy)oxoaporphine (1): C29H27NO9, white crystals (MeOH), m.p. 140—142 ℃; 1H and 13C NMR (CDCl3) data are shown in Table 1; IR (KBr) ν: 3684 (OH), 1727 (C＝O) cm－1; EI-MS m/z (%): 533 (M＋, 100), 367 (51), 352 (63), 336 (33), 322 (37), 308 (30), 294 (39), 167 (73), 109 (54), 95 (77).

1,2,3,10-Tetramethoxy-9-(4,5-dimethoxy-2-formyl- phenoxy)oxoaporphine (2): C29H25NO9, orange yellow amorphous powder (MeOH), m.p. 136—138 ℃; 1H and 13C NMR data are shown in Table 2; IR (KBr) ν: 1720 (C＝O), 1702 (CHO), 2820 and 2732 (CHO) cm－1; EI-MS m/z (%): 531 (M＋, 100), 500 (5), 351 (40), 336 (25), 180 (22), 83 (22), 69 (32), 351 (41), 336 (26), 180 (23).

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