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Head-to-tail bisbenzylisoquinoline alkaloids from Cyclea sutchuenensis
Phytochemiary,Vol. 33, No. 5, pp. 1253-1256, 1993 Printedin Great Britain.
HEAD-TO-TAIL
XIAN-KAI
WANG,
003 1 9422:93 $6.00 + 0.00 CC? . 1993 PergamonPressLtd
BISBENZYLISOQUINOLINE CYCLEA SUTCHUENENSIS
TONG-FANG
ZHAO, SHENG LAI, YOSHIKAZU
ALKALOIDS
SHIZURI*
and
FROM
SHOSUKE YAMAMURA*~
School of Pharmacy, West China University of Medical Sciences, Chengdu 610041, China; *Department of Chemistry, Faculty of Science and Technology, Keio University, Hiyoshi, Yokohama 223, Japan (Received 15 September 1992) Key Word Index-Cyclea
bridged
sutchuenensis; Menispermceae;
bisbenzylisoyuinoline
alkaloids;
7,12’-single
alkaloids.
Abstract-Three new 7,12’-single bridged bisbenzylisoquinoline alkaloids have been isolated from Cyclea sutchuenensis and their structures elucidated on the basis of their spectral data together with some chemical evidence.
INTRODUCTION The
bisbenzylisoquinoline (BBI) alkaloids are dimers built up of two benzylisoquinoline units linked by one or more ether bridges or direct carbon bondings, and they constitute one of the largest and the most important subgroups within the isoquinolines [l-5]. Among over 400 of these dimers, only six head-to-tail single bridged members have been recognized, namely malekulatine (1) [6], efatine (2) [7, 81, ambrimine (3) [7, 81, liensinine (4) [S-l 11, isoliensinine (5) [12] and neferine (6) [13] belonging to the 7,10’- and 7,11’-single bridged subgroups (A and B), respectively. From a biogenetic point of view, 7,12’-single bridged BBI alkaloids of subgroup C are also expected to be found in nature. This prompted us to investigate the BBI alkaloidal contents of Cyclea species (Menispermaceae) known to be rich in head-to-tail BBI alkaloids [14-173. As a result of our study on the alkaloids of C. sutchuenensis, we have isolated the new alkaloids sutchuenenine (7), neosutchuenenine (8) and sutchueneneonine (9) which proved to be the first examples of 7,12’-single bridged BBI alkaloids of subgroup C. RESULTS AND DISCUSSION
Sutchuenenine (7), neosutchuenenine (8) and sutchueneneonine (9) with the same molecular formula, CJ6H4,NZ06, are quite similar to one another. Each gives a UV spectrum with an absorption maximum at 284 nm, suggesting an appreciably conjugated system. A bathochromic shift in basic solution indicated the presence of one or more phenolic hydroxyl groups. Their IR spectra were almost identical, which suggested the presence of one or more hydroxyl groups (3440 cm- ‘), aromatic rings (1610,1595-1590,150 and 83&825 cn-‘)
t Author to whom correspondence
should be addressed.
and ether bonds (1270-1250, 1220-1210 and 112&l 115 cm- ‘). These alkaloids also exhibited essentially the same mass spectrum, showing a weak [M + 11’ at m/z 597 and/or a weak [M]’ at m/z 596 and prominent peaks at m/z 490,489,298,297, 192 (base peak) and 107, immediately suggestive of a single bridged BBI dimer involving head-to-tail coupling [ 181. The prominent ion at m/z 489 ([M - 1071’) resulted from loss of ring C while the dominating or important peaks at m/z 298, 192 and 107 corresponded to rings A, B, C’, rings A’, B’ and ring C, respectively, suggesting the presence of one hydroxyl and one methoxyl group at each moiety of rings A, B, C’ and rings A’, B’, and another hydroxyl group at ring C. The ‘HNMR spectrum of each alkaloid (Table 1) showed signals of two N-methyls C62.22, 2.46 for 7; 62.539, 2.544 for 8; 62.50, 2.55 for 93, two methoxyls cS3.79, 3.88 for 7; 63.84, 3.89 for 8; 63.78, 3.85 for 91 and other characteristic signals for head-to-tail BBI alkaloids [lS, 16, 19-213. Furthermore, their ‘HNMR spectra were quite similar to one another, except for 7 which showed three isolated aromatic protons 166.18,6.49,6.52 (each lH, s)] and two pdisubstituted benzene rings [66.71,6.92(each2H,d,J=8.1 Hz);66.48,6.92(each2H, d, J= 7.7 Hz)], while the others (8 and 9) had four isolated aromatic protons (65.96, 6.30, 6.56,6.68 for 8; 66.17, 6.24, 6.55, 6.62 for 9) and an additional 1,2,4_trisubstituted benzene ring (66.46, 6.75 and 6.78 for S; 66.46, 6.61 and 6.80 for 9). Methylation of each alkaloid yielded a derivative with five methoxyls, three more than for the natural alkaloid, which confirmed the presence of two methoxyl and three phenolic hydroxyl groups in the molecule. On the basis of the above findings, coupled with the 13C NMR spectral data (Table 2), the structures of these alkaloids were unambiguously established as 7, 8 and 9, respectively, wherein the substitution pattern of each alkaloid was determined by complete spin decoupling and NOE experiments (see Experimental). The absolute configuration of the alkaloids have not yet been decided. However, the R-l, R-l’ configuration of
1253
XIAN-KAI WANGet al
1254
C
A
I33
R’ 1 (IS, 1’S) H
R2 OMe
OMe
2 (1 S, 1’S) 3(lS, 1’S)
OMe
H
OH
H
Table
1.
H
OH OMe
‘H NMR
R’ 4 (lR, 1%) OH 5 (lR, 1’R) OMe 6(lR, 1’R) OMe
R2 OMe OH Ok&
spectral data (6) of sutchuenenine (7), neosutchuenenine in CDCl,
7
8
R’ 7 (lR, 1’R) 8 9
OH H H
dd, J=9.8, 2.9 Hz)
3.69 (lH, dd, J=9.3, 3.4 Hz)
3.71 (lH,
t, J=5.9Hz)
3.82 (lH,
dd, J=9.2.
NMe-2 NMe-2 5 5’
2.46 (3H, s) 2 22 (3H. s) 6.49 (lH, s) 6.52 (lH, s)
OMe-6
3.79 (3H, s)
OMe-6
3.88 (3H. s)
3.89 (3H, s)
3.87 (3H, s)
8
._
6.30 (lH, s)
6.24 (lH, s)
8
6 18 (IH. s)
5.96 (1 H, s)
10,14
6.92 (2H,
d, J = 8.1 Hz) 6.71 (2H, d, J=8.1 Hz) 6.92 (1 H, d, J = 7.7 Hz) 6.92 (1H, d, J = 7.7 Hz) 6.48 (lH, d, J=7.7 Hz) 6.48 (I H, d. J = 7.7 Hz)
6.93 (2H,
11’ 13’ -CH,-
2.5-3.4
3.53 (lH,
(12H, complex)
3.70 (lH,
dd. J=9.8, 2.9Hz) 2.544 (3H, s) 2.539 (3H, s) 6.56 (lH, s)
3.72 (1H. t, J=54Hz) 2.55 (3H. s) 2.50 (3H, s) 6.55 (1H. s)
6.68 (lH,
s)
6.62 (1 H. s)
3.84 (3H, s)
3.85 (3H, s)
6.76 6.78 6.46
(9)
9
1’
11.13 10 14
R3 H H OH
(8) and sutchueneneonine
1
40Hz)
R2 H OH H
6.17 (IH, s)
d, J = 8.8 Hz) (2H, d, J = 8.8 Hz) (lH, d, J=2.0 Hz) (1 H,dd, J = 7.8, 2.0 Hz)
6.75 (lH, 2.6-3.5
sutchuenenine (7) is suggested by comparison of its specific rotation ([cl& 147.4”, CHCI,) with those of the R-l, R-l’, head-to-tail single bridged BBI alkaloids, isoliensinine (5) ([a]n 143.3”, CHCl,) [12] and neferine (6) ([cr]n - 37.8”, CHCI,) [13] as well as the S-l, S-l’ head-totail single bridged BBI alkaloids, efatine (2) ([alo +70”, CHCl,) [7] and ambrimine (3) ([~]n + 128”, CHCl,) [7J It should be noted that sutchuenenine (7), neosutchuenenine (8) and sutchueneneonine (9), are a novel subgroup of head-to-tail BBI alkaloids with one ether bridge between C-7 and C-12’ (subgroup C); they are the first examples of single bridged BBI alkaloids from Cyclea species.
d, J=7.8
Hz)
(12H, complex)
6.88 (2H, d, J = 8.8 Hz) 6.65 (2H. d, J = 8.8 Hz) 6.80 (1 H, d, J = 7.8 Hz) 6.46 (1 H, d, J = 2.0 Hz)
6.61 (lH, 2.6-3.5
dd, J=7.8,
2.0 Hz)
(12H. complex)
EXPERIMENTAL
MS were measured with an ionization energy at 70 eV. FABMS were obtained in the positive and negative ionization modes in a glycerol-thioglycerol (1: 1) matrix. Plant material. Cyclea sutchuenensis Gagnep. was collected at Gu Lin country, Sichuan providence, China, in September 1987. A voucher specimen is preserved in the Department of Medicinal Chemistry of Natural Products, West China University of Medical Sciences. Extraction and isolation. Roots (fr. wt, 28.75 kg) were cut into thin slices and extracted with 95% EtOH (dried mart, 9.035 kg). After evapn of solvent, the extract was treated with 2% HCl and filtered. The filtrate was made
Alkaloids from Cyclea sutchuenensis Table 2. 13CNMR spectral data (6) of sutchuenenine (7), neosutchuenenine (8) and sutchueneneonine (9) in CDCl, C
7
1 1’ 3 3 4 4 4a 4a’ 5 5 6 6 7 7 8 8 8a 8s’ 9 9’ 10 10 11 11’ 12 12 13 13’ 14 14 15 15’
60.2(4 64.6(4 43.1 (t) 46.5 (t) 22.8 (t) 24.1 (t) 124.7 (s) 128.1 (s) 108.0 (d) 114.2 (d) 145.6 (s) 146.9 (s) 136.9 (s) 143.3 (s) 138.7 (d) 110.2 (d) 124.4 (s) 124.8 (s) 131.2 (s) 132.7 (s) 130.7 (d) 129.8 (d) 115.4 (d) 114.5 (d) 156.0 (s) 154.8 (s) 115.4 (6) 114.5 (d) 130.7 (d) 129.8 (d) 40.4 (t) 39.6 (t) 42.0 41.9 55.7 56.1
NMe-2 NMe-2 OMe-6 OMe-6
basic
8
(4) (4) (4) (4)
64.3 (d) 65.2 (d) 44.7 (t) 41.3 (t) 22.2 (t) 26.1 (t) 130.2 (s) 129.3 (s) 112.2 (d) 114.5 (d) 148.3 (s) 146.7 (s) 143.8 (s) 143.3 (S) 121.4 (d) 110.8 (d) 127.4 (s) 123.0 (s) 130.2 (s) 130.2 (s) 130.9 (II) 115.7 (d) 116.4 (d) 145.8 (s) 155.6 (s) 143.3 (s) 116.4 (d) 118.2 (d) 130.9 (d) 127.0 (6) 42.1 (t) 37.7 (t)
42.4(4 40.5 (4) 55.8 (4) 56.0 (4)
9
64.1(4 64.6(4 45.4 (t) 47.3 (t) 23.1 (t) 26.3 (t) 130.3 (s) 129.8 (s) 112.3 (d) 114.4 (d) 148.8 (s) 146.2 (s) 144.7 (s) 143.5 (S) 120.3 (d) 110.7 (d) 129.9 (s) 123.7 (s) 130.7 (s) 128.1 (s) 130.7 (d) 145.7 (s) 116.1 (d) 115.7 (d) 155.2 (s) 143.2 (s) 116.1 (d) 125.5 (d) 130.7 (d) 128.3 (d) 41.5 (t) 38.6 (t) 42.6 41.3 55.9 55.9
(4) (4) (4) (4)
@H 9) with NH,OH, affording crude non-quatern-
ary alkaloids, treatment,
which were purified by the above acid-base
furnishing
61 g of non-quaternary alkaloids (0.68% of dry wt). The alkaloids were subjected to CC on silica gel (700 g, Type 60), using a gradient of MeOH-CHCl, (20%, 25%, 50% MeOH in CHCl,, 2800 ml for each). The 25% MeOH-CHCl, eluates were evapd in vacua to afford a dark brown residue, which was sepd by repeated prep. TLC (Kieselgel 60 PF,,J using CsH,-EtOH-NHEt, (4: 5: l), C&H,-Me&O-NHEt, (7:2:1; 5:4:1), CHCl,-MeOH-NHEt, (2O:l:l; 18:l:l) and hexane-Me&O-NHEt, (6:3: l), giving sutchuenenine (7, 12.8 mg) (1.42 x lo-‘% dry wt), neosutchuenenine (8, 13.2 mg) (1.46 x 10w4% dry wt), and sutchueneneonine (9, 11.1 mg) (1.23 x 10e4% dry wt), in addition to the two known head-to-tail BBI alkaloids, insulanoline (ca 0.17% dry wt) [21, 221 and d-isochondodendrine (ca 0.10% dry wt) [19, 23, 241. Sutchuenenine (7). Yellowish powder. [cr]k6 -47.4” (CHCl,; c 0.703). UV #‘EH nm (log E): 210 (4.80), 225sh
1255
(4.67), 284 (3.99); l:;X-E’” nm: 228sh, 298. IR vi: cn-‘: 3440, 1610, 1595, 1510, 1270, 1220, 1115, 830. ‘HNMR (400 MHz, CDCl,) Table 1. Principal NOES were H-l to NMe-2 (0.8%), NMe-2 to H-l (12.6%), OMe-6 to H-5 (13.4%), NMe-2’ to H-l’ (12.0%), OMe-6’ to H-5’ (14.5%). 13CNMR (100 MHz, CDCI,) Table 2. MS m/z (rel. int.): 597 ([M + l]‘, 6), 490 (46), 489 (lOO),298 (6), 297 (6), 192 (36), 107 (5); FAB MS m/z: 597.2948 [M + l]’ (talc. for C,,H,,N,O, m/z: 597.2962). Neosutchuenenine (8). White powder. [a]F + 7.8” (EtOH; c 0.158). UV Ak’H nm (log E): 209 (4.74), 224sh (4.55), 284 (3.95); ~~~X-E’oH nm: 292, 303. IR vEf)l:cm- ‘: 3440 br, 1610, 1590, 1510, 1260, 1220, 1120, 1020, 830. ‘H NMR (400 MHz,, CDCl,) Table 1. Significant NOES were H-l to NMe-2 (6.2%), H-l to H-8 (7.5%), H-l to Hlo,14 (6.3%), H-l to OMe-6 (9.6%), OMe-6 to H-5 (14.4%), H-8 to H-l (5.3%), H-8 to H-10,14 (3.1%), H-8 to H-13’ (8.6%), H-10,14 to H-l (2.7%), H-10,14 to H-8 (2.1%), H-10,14 to H-11,13 (9.3%), H-l’ to NMe-2’ (6.2%), H-l’ to H-8’ (9.6%), H-5’ to OMe-6’ (10.3%), OMe-6’ to H-5’ (lS.O%), H-8’ to H-l’ (4.6%), H-8’ to H-14’ (2.0%), H-14’ to H-10’ (4.2%), H-14’ to H-13’ (10.5%). 13CNMR (100 MHz, CDCl,) Table 2. MS m/z (rel. int.): 490 (4), 489 (12), 298 (94), 297 (8), 192 (lOO), 107 (11); FAB MS m/z: 597.2903 [M +H]+ (talc. for C36H41NZ06 m/z 597.2962). Sutchueneneonine (9). White powder. [a]k6 +6.7” (EtOH; c 0.422). UV l:zH nm (log E): 209 (4.76), (4.56), (3.96); 10,X-E’oHnm: 295, 303. IR v~~cm-‘: 3440 br, 1610, 1595, 1510, 1250, 1210, 1115, 1020, 825. ‘HNMR (400 MHz, CDCl,) Table 1. Significant NOES were NMe-2 to H-l (10.2%), H-5 to OMe-6(11.5%), OMe-6 to H-5 (12.6%), H-8 to H-l (5.4%), H-8 to H-10,14 (4.3%), H-8 to H-l 1’ (5.5%), MNe-2’ to H-l’ (11.4%), OMe-6’ to H-5’ (12.9%), H-8’ to H-l’ (5.8%), H-11’ to H-8 (5.3%). 13C NMR (100 MHz, CDCl,) Table 2. MS m/z (rel. int.): 597 ([M + 1]+,0.7), 596 ([Ml’, 0.1),490(10), 489(32), 298 (40), 297 (ll), 192 (100x 107 (4); FAB MS m/z: 597.2973 [M+H]+ (talc. for C,,H,,N,O, m/z 597.2962); m/z 489.2366 [M- 107]+ (talc. for C,,H,,N,O, m/z 489.2336). 0-Methylation
of sutchuenenine (7). Sutchuenenine (4 mg) in MeOH (1 ml) was treated with CH,N,-Et,0 (0.5 ml) and the soln allowed to stand at room temp. overnight. After evapn, the soln was subjected to prep. TLC [Kieselgel60 PFzs4; C,H,-Me&O-NHEt2 (5 : 4: l)], giving the trimethylated product as a yellowish powder. IR vii’ cm -l: 1605,1580,1505,1210,1015,830. ‘HNMR (400 MHz, CDCl,): 62.41 (3H, s) (NMeG?‘), 2.5-3.5 (12H, complex) (methylene groups), 2.80 (3H, s) (NMe-2), 3.45 (3H, s) (OMe-8), 3.63 (3H, s) (OMe-7’), 3.77 (3H, s) (OMe-12), 3.84 (3H, s) (OMe-6), 3.86 (3H, s) (OMe6’),4.01 (lH, m)(H-1’),4.11 (lH,m)(H-1), 5.86(1H,s)(H8’), 6.57 (lH, s) (H-5), 6.60 (lH, s) (H-5’), 6.73 (2H, d, J =8.3 Hz) (H-11’,13’), 6.77 (2H, d, 5=8.8 Hz) (H-11,13), 7.01(2H,d,J=8.3Hz)(H-10’,14’),7.02(2H,d,J=8.8Hz) (H-10,14). Principal NOES were NMe-2 to H-l (11.7%), OMe-6 to H-5 (14.5%), OMe-8 to H-l (4.5%), OMe-8 to H-11’,13’(4.0%),OMe-12toH-11,13(16.9%),NMe-2’to H-l’ (12.0%), OMe-6’ to H-5’ (lS.O%), OMe-7’ to H-8
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XIAN-KAI WANG et al.
(14.2%). MS m/z (rel. int.): 639 ([M + 1] *, 0.1). 638 ([Ml ‘, O.l), 518(16), 517(49), 312(4), 311 (ll), 206(100). 204(8), 121 (2); FAB MS (+VE) m/z: ([M + 1] +, C,,H,,N,G,). 0-Methylation of neosutchuenenine (8). To a soln of 8 (2.5 mg) in MeOH (2 ml) was added a soln of CH,N,-Et,0 (0.5 ml) and the resulting soln allowed to stand at room temp. overnight. After removal of solvent and excess diazomethane, the residue was subjected to prep. TLC CKieselgel60 PF,,,; hexane--Me,CO-NHEt, (6: 3: I)], affording the trimethyl ether as a yellowish powder (1.5 mg). IR vc’,:: cm -I: 1610, 1580, 1510, 1255, 1255, 1020, 820. ‘HNMR (400 MHz, CDCl,): 62.5-3.5 (14H, H-1,1’ and methylene groups), 2.61 (6H, s) (NMe-2 and NMe-2’) 3.54 (3H, s) (OMe-7’) 3.71 (3H, s) (OMe1 l’), 3.79 (3H, s), (OMe-12), 3.80 (3H, s) (OMe-6). 3.82 (3H, s) (OMe-6’), 5.91 (lH, s) (H-8’), 6.22 (lH, s) (H-8), 6.53 (1H. s) (H-5), 6.54 (lH, d, J==.OHz) (H-10’). 6.66 (2H, d, J =8.5Hz) (H-11,13), 6.66 (lH, s) (H-5’), 6.71 (lH, dd, J =8.3,2.0Hz)(H-l4’),6.82(1H,d,J=8.3Hz)(H-13’),6.89 (2H, d, 5=8.5 Hz) (H-10,14). MS m/z (rel. int.): 639 ([M +I]+, 0.4), 638 ([M-J’-, 0.1). 518 (7), 517 (20), 326 (100). 312 (12), 296 (8), 206 (75) 121 (18): FAB MS (+VE) mjz: 639 (CM + 11’3 C,,H,,N,O,). Acknowledgements----The authors wish to thank the National Natural Science Foundation of China for financial support and the Fujisawa Foundation (Japan) for a scholarship to S.L. They are also indebted to Research Laboratories, Nippon Kayaku Co. Ltd for measurements of FAB MS. REFERENCES
1. Guha, K. P., Mukherjee, B. and Mukherjee, R. (1979) J. Nat. Prod. 42, 1. 2. Schiff, P. L., Jr (1983) J. Nat. Prod. 46, 1. 3. SchilI, P. L., Jr (1987) J. Nut. Prod. 50, 529. 4. Schiff, P. L., Jr (1991) J. Nut. Prod. 54, 645. 5. Bentley, K. W. (1991) Nat. Prod. Rep. 8, 339.
6. Bruneton, J., Shamma, M., Minard, R.D., Freyer, A. J. and Guinaudeau, H. (1983) J. Org. Chem. 48,3957. 7. Chalandre, M. C., Guinaudeau, H. and Bruneton, J. (1985) C. R. Acad. Sci.. Ser. 2 301, 1185. 8. Chalandre, M. C., Bruneton, J., Cabalion, P. and Guinaudeau, H. (1986) Can. J. Chem. 64, 123. 9. Pan, P., Chou, Y.. Sun, T. and Kao, Y. (1962) Sci. Sinica 11, 321. 10. Chao, T., Chou, Y., Yang, P. and Chou, T. (1962) Sci. Sinica 11, 215. 11. Hsieh, Y.. Chen, W. and Kao, Y. (1964) Sci. Sinica 12, 2018. 12. Tomita, M., Furukawa, H., Yang, T. H. and Lin, T. (1964) Tetrahedron Letters 2637. 13. Furukawa, H. (1965) Yakugaku Zasshi 85, 335. 14. Zhu, Z. Y., Feng, Y. X., He, L. Y. and Wang, Y. C. (1983) Acta Pharm. Sinicu 18, 535. 15. Lai. S.. Zhao, T. F. and Wang, X. K. (1988) Acta. Phurm. Sinicu 23, 356. 16. Lai, S.. Zhao, T. F. and Wang, X. K. (1988) West China J. Pharm. Sci. 3, 6. 17. Zhao, T. F., Wan, Q. F., Lai, S. and Wang, X. K. (1988) West China J. Pharm. Sci. 3, 221. 18. Baldas, J., Bick, I. R. C., Ibuka, T., Kapil, R. S. and Porter, Q. N. (1972) J. Chem. Sot., Perkin I 599. 19. Bick. 1. R. C., Harley-Mason, J., Sheppard, N. and Vernengo, M. J. (1961) J. Chem. Sot. 1896. 20. Koike, L., Marsaioli, A. J. and Reis, F. A. M. (1981) J. Org. Chem. 46, 2385. 21. Fang, X. D., Quan, L. J., Shen, P. Z. and Shi, Z. Y. (1985) Zhong Cao Yao 16, 8. 22. Kikuchi, T. and Bessho, K. (1958) Yakugaku Zasshi 78, 1408. 23. Dwuma-Badu, D., Ayim, J. S. K., Mingle, C. A., Tackie, A. N., Slatkin, D. J., Knapp, J. E. and Schiff, P. L., Jr (1975) Phytochemistry 14, 1655. 24. Marsaioli, A. J., Knapp, J. E. and Schiff, P. L., Jr (1978) Phytochemistry 17, 1655.
HEAD-TO-TAIL
XIAN-KAI
WANG,
003 1 9422:93 $6.00 + 0.00 CC? . 1993 PergamonPressLtd
BISBENZYLISOQUINOLINE CYCLEA SUTCHUENENSIS
TONG-FANG
ZHAO, SHENG LAI, YOSHIKAZU
ALKALOIDS
SHIZURI*
and
FROM
SHOSUKE YAMAMURA*~
School of Pharmacy, West China University of Medical Sciences, Chengdu 610041, China; *Department of Chemistry, Faculty of Science and Technology, Keio University, Hiyoshi, Yokohama 223, Japan (Received 15 September 1992) Key Word Index-Cyclea
bridged
sutchuenensis; Menispermceae;
bisbenzylisoyuinoline
alkaloids;
7,12’-single
alkaloids.
Abstract-Three new 7,12’-single bridged bisbenzylisoquinoline alkaloids have been isolated from Cyclea sutchuenensis and their structures elucidated on the basis of their spectral data together with some chemical evidence.
INTRODUCTION The
bisbenzylisoquinoline (BBI) alkaloids are dimers built up of two benzylisoquinoline units linked by one or more ether bridges or direct carbon bondings, and they constitute one of the largest and the most important subgroups within the isoquinolines [l-5]. Among over 400 of these dimers, only six head-to-tail single bridged members have been recognized, namely malekulatine (1) [6], efatine (2) [7, 81, ambrimine (3) [7, 81, liensinine (4) [S-l 11, isoliensinine (5) [12] and neferine (6) [13] belonging to the 7,10’- and 7,11’-single bridged subgroups (A and B), respectively. From a biogenetic point of view, 7,12’-single bridged BBI alkaloids of subgroup C are also expected to be found in nature. This prompted us to investigate the BBI alkaloidal contents of Cyclea species (Menispermaceae) known to be rich in head-to-tail BBI alkaloids [14-173. As a result of our study on the alkaloids of C. sutchuenensis, we have isolated the new alkaloids sutchuenenine (7), neosutchuenenine (8) and sutchueneneonine (9) which proved to be the first examples of 7,12’-single bridged BBI alkaloids of subgroup C. RESULTS AND DISCUSSION
Sutchuenenine (7), neosutchuenenine (8) and sutchueneneonine (9) with the same molecular formula, CJ6H4,NZ06, are quite similar to one another. Each gives a UV spectrum with an absorption maximum at 284 nm, suggesting an appreciably conjugated system. A bathochromic shift in basic solution indicated the presence of one or more phenolic hydroxyl groups. Their IR spectra were almost identical, which suggested the presence of one or more hydroxyl groups (3440 cm- ‘), aromatic rings (1610,1595-1590,150 and 83&825 cn-‘)
t Author to whom correspondence
should be addressed.
and ether bonds (1270-1250, 1220-1210 and 112&l 115 cm- ‘). These alkaloids also exhibited essentially the same mass spectrum, showing a weak [M + 11’ at m/z 597 and/or a weak [M]’ at m/z 596 and prominent peaks at m/z 490,489,298,297, 192 (base peak) and 107, immediately suggestive of a single bridged BBI dimer involving head-to-tail coupling [ 181. The prominent ion at m/z 489 ([M - 1071’) resulted from loss of ring C while the dominating or important peaks at m/z 298, 192 and 107 corresponded to rings A, B, C’, rings A’, B’ and ring C, respectively, suggesting the presence of one hydroxyl and one methoxyl group at each moiety of rings A, B, C’ and rings A’, B’, and another hydroxyl group at ring C. The ‘HNMR spectrum of each alkaloid (Table 1) showed signals of two N-methyls C62.22, 2.46 for 7; 62.539, 2.544 for 8; 62.50, 2.55 for 93, two methoxyls cS3.79, 3.88 for 7; 63.84, 3.89 for 8; 63.78, 3.85 for 91 and other characteristic signals for head-to-tail BBI alkaloids [lS, 16, 19-213. Furthermore, their ‘HNMR spectra were quite similar to one another, except for 7 which showed three isolated aromatic protons 166.18,6.49,6.52 (each lH, s)] and two pdisubstituted benzene rings [66.71,6.92(each2H,d,J=8.1 Hz);66.48,6.92(each2H, d, J= 7.7 Hz)], while the others (8 and 9) had four isolated aromatic protons (65.96, 6.30, 6.56,6.68 for 8; 66.17, 6.24, 6.55, 6.62 for 9) and an additional 1,2,4_trisubstituted benzene ring (66.46, 6.75 and 6.78 for S; 66.46, 6.61 and 6.80 for 9). Methylation of each alkaloid yielded a derivative with five methoxyls, three more than for the natural alkaloid, which confirmed the presence of two methoxyl and three phenolic hydroxyl groups in the molecule. On the basis of the above findings, coupled with the 13C NMR spectral data (Table 2), the structures of these alkaloids were unambiguously established as 7, 8 and 9, respectively, wherein the substitution pattern of each alkaloid was determined by complete spin decoupling and NOE experiments (see Experimental). The absolute configuration of the alkaloids have not yet been decided. However, the R-l, R-l’ configuration of
1253
XIAN-KAI WANGet al
1254
C
A
I33
R’ 1 (IS, 1’S) H
R2 OMe
OMe
2 (1 S, 1’S) 3(lS, 1’S)
OMe
H
OH
H
Table
1.
H
OH OMe
‘H NMR
R’ 4 (lR, 1%) OH 5 (lR, 1’R) OMe 6(lR, 1’R) OMe
R2 OMe OH Ok&
spectral data (6) of sutchuenenine (7), neosutchuenenine in CDCl,
7
8
R’ 7 (lR, 1’R) 8 9
OH H H
dd, J=9.8, 2.9 Hz)
3.69 (lH, dd, J=9.3, 3.4 Hz)
3.71 (lH,
t, J=5.9Hz)
3.82 (lH,
dd, J=9.2.
NMe-2 NMe-2 5 5’
2.46 (3H, s) 2 22 (3H. s) 6.49 (lH, s) 6.52 (lH, s)
OMe-6
3.79 (3H, s)
OMe-6
3.88 (3H. s)
3.89 (3H, s)
3.87 (3H, s)
8
._
6.30 (lH, s)
6.24 (lH, s)
8
6 18 (IH. s)
5.96 (1 H, s)
10,14
6.92 (2H,
d, J = 8.1 Hz) 6.71 (2H, d, J=8.1 Hz) 6.92 (1 H, d, J = 7.7 Hz) 6.92 (1H, d, J = 7.7 Hz) 6.48 (lH, d, J=7.7 Hz) 6.48 (I H, d. J = 7.7 Hz)
6.93 (2H,
11’ 13’ -CH,-
2.5-3.4
3.53 (lH,
(12H, complex)
3.70 (lH,
dd. J=9.8, 2.9Hz) 2.544 (3H, s) 2.539 (3H, s) 6.56 (lH, s)
3.72 (1H. t, J=54Hz) 2.55 (3H. s) 2.50 (3H, s) 6.55 (1H. s)
6.68 (lH,
s)
6.62 (1 H. s)
3.84 (3H, s)
3.85 (3H, s)
6.76 6.78 6.46
(9)
9
1’
11.13 10 14
R3 H H OH
(8) and sutchueneneonine
1
40Hz)
R2 H OH H
6.17 (IH, s)
d, J = 8.8 Hz) (2H, d, J = 8.8 Hz) (lH, d, J=2.0 Hz) (1 H,dd, J = 7.8, 2.0 Hz)
6.75 (lH, 2.6-3.5
sutchuenenine (7) is suggested by comparison of its specific rotation ([cl& 147.4”, CHCI,) with those of the R-l, R-l’, head-to-tail single bridged BBI alkaloids, isoliensinine (5) ([a]n 143.3”, CHCl,) [12] and neferine (6) ([cr]n - 37.8”, CHCI,) [13] as well as the S-l, S-l’ head-totail single bridged BBI alkaloids, efatine (2) ([alo +70”, CHCl,) [7] and ambrimine (3) ([~]n + 128”, CHCl,) [7J It should be noted that sutchuenenine (7), neosutchuenenine (8) and sutchueneneonine (9), are a novel subgroup of head-to-tail BBI alkaloids with one ether bridge between C-7 and C-12’ (subgroup C); they are the first examples of single bridged BBI alkaloids from Cyclea species.
d, J=7.8
Hz)
(12H, complex)
6.88 (2H, d, J = 8.8 Hz) 6.65 (2H. d, J = 8.8 Hz) 6.80 (1 H, d, J = 7.8 Hz) 6.46 (1 H, d, J = 2.0 Hz)
6.61 (lH, 2.6-3.5
dd, J=7.8,
2.0 Hz)
(12H. complex)
EXPERIMENTAL
MS were measured with an ionization energy at 70 eV. FABMS were obtained in the positive and negative ionization modes in a glycerol-thioglycerol (1: 1) matrix. Plant material. Cyclea sutchuenensis Gagnep. was collected at Gu Lin country, Sichuan providence, China, in September 1987. A voucher specimen is preserved in the Department of Medicinal Chemistry of Natural Products, West China University of Medical Sciences. Extraction and isolation. Roots (fr. wt, 28.75 kg) were cut into thin slices and extracted with 95% EtOH (dried mart, 9.035 kg). After evapn of solvent, the extract was treated with 2% HCl and filtered. The filtrate was made
Alkaloids from Cyclea sutchuenensis Table 2. 13CNMR spectral data (6) of sutchuenenine (7), neosutchuenenine (8) and sutchueneneonine (9) in CDCl, C
7
1 1’ 3 3 4 4 4a 4a’ 5 5 6 6 7 7 8 8 8a 8s’ 9 9’ 10 10 11 11’ 12 12 13 13’ 14 14 15 15’
60.2(4 64.6(4 43.1 (t) 46.5 (t) 22.8 (t) 24.1 (t) 124.7 (s) 128.1 (s) 108.0 (d) 114.2 (d) 145.6 (s) 146.9 (s) 136.9 (s) 143.3 (s) 138.7 (d) 110.2 (d) 124.4 (s) 124.8 (s) 131.2 (s) 132.7 (s) 130.7 (d) 129.8 (d) 115.4 (d) 114.5 (d) 156.0 (s) 154.8 (s) 115.4 (6) 114.5 (d) 130.7 (d) 129.8 (d) 40.4 (t) 39.6 (t) 42.0 41.9 55.7 56.1
NMe-2 NMe-2 OMe-6 OMe-6
basic
8
(4) (4) (4) (4)
64.3 (d) 65.2 (d) 44.7 (t) 41.3 (t) 22.2 (t) 26.1 (t) 130.2 (s) 129.3 (s) 112.2 (d) 114.5 (d) 148.3 (s) 146.7 (s) 143.8 (s) 143.3 (S) 121.4 (d) 110.8 (d) 127.4 (s) 123.0 (s) 130.2 (s) 130.2 (s) 130.9 (II) 115.7 (d) 116.4 (d) 145.8 (s) 155.6 (s) 143.3 (s) 116.4 (d) 118.2 (d) 130.9 (d) 127.0 (6) 42.1 (t) 37.7 (t)
42.4(4 40.5 (4) 55.8 (4) 56.0 (4)
9
64.1(4 64.6(4 45.4 (t) 47.3 (t) 23.1 (t) 26.3 (t) 130.3 (s) 129.8 (s) 112.3 (d) 114.4 (d) 148.8 (s) 146.2 (s) 144.7 (s) 143.5 (S) 120.3 (d) 110.7 (d) 129.9 (s) 123.7 (s) 130.7 (s) 128.1 (s) 130.7 (d) 145.7 (s) 116.1 (d) 115.7 (d) 155.2 (s) 143.2 (s) 116.1 (d) 125.5 (d) 130.7 (d) 128.3 (d) 41.5 (t) 38.6 (t) 42.6 41.3 55.9 55.9
(4) (4) (4) (4)
@H 9) with NH,OH, affording crude non-quatern-
ary alkaloids, treatment,
which were purified by the above acid-base
furnishing
61 g of non-quaternary alkaloids (0.68% of dry wt). The alkaloids were subjected to CC on silica gel (700 g, Type 60), using a gradient of MeOH-CHCl, (20%, 25%, 50% MeOH in CHCl,, 2800 ml for each). The 25% MeOH-CHCl, eluates were evapd in vacua to afford a dark brown residue, which was sepd by repeated prep. TLC (Kieselgel 60 PF,,J using CsH,-EtOH-NHEt, (4: 5: l), C&H,-Me&O-NHEt, (7:2:1; 5:4:1), CHCl,-MeOH-NHEt, (2O:l:l; 18:l:l) and hexane-Me&O-NHEt, (6:3: l), giving sutchuenenine (7, 12.8 mg) (1.42 x lo-‘% dry wt), neosutchuenenine (8, 13.2 mg) (1.46 x 10w4% dry wt), and sutchueneneonine (9, 11.1 mg) (1.23 x 10e4% dry wt), in addition to the two known head-to-tail BBI alkaloids, insulanoline (ca 0.17% dry wt) [21, 221 and d-isochondodendrine (ca 0.10% dry wt) [19, 23, 241. Sutchuenenine (7). Yellowish powder. [cr]k6 -47.4” (CHCl,; c 0.703). UV #‘EH nm (log E): 210 (4.80), 225sh
1255
(4.67), 284 (3.99); l:;X-E’” nm: 228sh, 298. IR vi: cn-‘: 3440, 1610, 1595, 1510, 1270, 1220, 1115, 830. ‘HNMR (400 MHz, CDCl,) Table 1. Principal NOES were H-l to NMe-2 (0.8%), NMe-2 to H-l (12.6%), OMe-6 to H-5 (13.4%), NMe-2’ to H-l’ (12.0%), OMe-6’ to H-5’ (14.5%). 13CNMR (100 MHz, CDCI,) Table 2. MS m/z (rel. int.): 597 ([M + l]‘, 6), 490 (46), 489 (lOO),298 (6), 297 (6), 192 (36), 107 (5); FAB MS m/z: 597.2948 [M + l]’ (talc. for C,,H,,N,O, m/z: 597.2962). Neosutchuenenine (8). White powder. [a]F + 7.8” (EtOH; c 0.158). UV Ak’H nm (log E): 209 (4.74), 224sh (4.55), 284 (3.95); ~~~X-E’oH nm: 292, 303. IR vEf)l:cm- ‘: 3440 br, 1610, 1590, 1510, 1260, 1220, 1120, 1020, 830. ‘H NMR (400 MHz,, CDCl,) Table 1. Significant NOES were H-l to NMe-2 (6.2%), H-l to H-8 (7.5%), H-l to Hlo,14 (6.3%), H-l to OMe-6 (9.6%), OMe-6 to H-5 (14.4%), H-8 to H-l (5.3%), H-8 to H-10,14 (3.1%), H-8 to H-13’ (8.6%), H-10,14 to H-l (2.7%), H-10,14 to H-8 (2.1%), H-10,14 to H-11,13 (9.3%), H-l’ to NMe-2’ (6.2%), H-l’ to H-8’ (9.6%), H-5’ to OMe-6’ (10.3%), OMe-6’ to H-5’ (lS.O%), H-8’ to H-l’ (4.6%), H-8’ to H-14’ (2.0%), H-14’ to H-10’ (4.2%), H-14’ to H-13’ (10.5%). 13CNMR (100 MHz, CDCl,) Table 2. MS m/z (rel. int.): 490 (4), 489 (12), 298 (94), 297 (8), 192 (lOO), 107 (11); FAB MS m/z: 597.2903 [M +H]+ (talc. for C36H41NZ06 m/z 597.2962). Sutchueneneonine (9). White powder. [a]k6 +6.7” (EtOH; c 0.422). UV l:zH nm (log E): 209 (4.76), (4.56), (3.96); 10,X-E’oHnm: 295, 303. IR v~~cm-‘: 3440 br, 1610, 1595, 1510, 1250, 1210, 1115, 1020, 825. ‘HNMR (400 MHz, CDCl,) Table 1. Significant NOES were NMe-2 to H-l (10.2%), H-5 to OMe-6(11.5%), OMe-6 to H-5 (12.6%), H-8 to H-l (5.4%), H-8 to H-10,14 (4.3%), H-8 to H-l 1’ (5.5%), MNe-2’ to H-l’ (11.4%), OMe-6’ to H-5’ (12.9%), H-8’ to H-l’ (5.8%), H-11’ to H-8 (5.3%). 13C NMR (100 MHz, CDCl,) Table 2. MS m/z (rel. int.): 597 ([M + 1]+,0.7), 596 ([Ml’, 0.1),490(10), 489(32), 298 (40), 297 (ll), 192 (100x 107 (4); FAB MS m/z: 597.2973 [M+H]+ (talc. for C,,H,,N,O, m/z 597.2962); m/z 489.2366 [M- 107]+ (talc. for C,,H,,N,O, m/z 489.2336). 0-Methylation
of sutchuenenine (7). Sutchuenenine (4 mg) in MeOH (1 ml) was treated with CH,N,-Et,0 (0.5 ml) and the soln allowed to stand at room temp. overnight. After evapn, the soln was subjected to prep. TLC [Kieselgel60 PFzs4; C,H,-Me&O-NHEt2 (5 : 4: l)], giving the trimethylated product as a yellowish powder. IR vii’ cm -l: 1605,1580,1505,1210,1015,830. ‘HNMR (400 MHz, CDCl,): 62.41 (3H, s) (NMeG?‘), 2.5-3.5 (12H, complex) (methylene groups), 2.80 (3H, s) (NMe-2), 3.45 (3H, s) (OMe-8), 3.63 (3H, s) (OMe-7’), 3.77 (3H, s) (OMe-12), 3.84 (3H, s) (OMe-6), 3.86 (3H, s) (OMe6’),4.01 (lH, m)(H-1’),4.11 (lH,m)(H-1), 5.86(1H,s)(H8’), 6.57 (lH, s) (H-5), 6.60 (lH, s) (H-5’), 6.73 (2H, d, J =8.3 Hz) (H-11’,13’), 6.77 (2H, d, 5=8.8 Hz) (H-11,13), 7.01(2H,d,J=8.3Hz)(H-10’,14’),7.02(2H,d,J=8.8Hz) (H-10,14). Principal NOES were NMe-2 to H-l (11.7%), OMe-6 to H-5 (14.5%), OMe-8 to H-l (4.5%), OMe-8 to H-11’,13’(4.0%),OMe-12toH-11,13(16.9%),NMe-2’to H-l’ (12.0%), OMe-6’ to H-5’ (lS.O%), OMe-7’ to H-8
1256
XIAN-KAI WANG et al.
(14.2%). MS m/z (rel. int.): 639 ([M + 1] *, 0.1). 638 ([Ml ‘, O.l), 518(16), 517(49), 312(4), 311 (ll), 206(100). 204(8), 121 (2); FAB MS (+VE) m/z: ([M + 1] +, C,,H,,N,G,). 0-Methylation of neosutchuenenine (8). To a soln of 8 (2.5 mg) in MeOH (2 ml) was added a soln of CH,N,-Et,0 (0.5 ml) and the resulting soln allowed to stand at room temp. overnight. After removal of solvent and excess diazomethane, the residue was subjected to prep. TLC CKieselgel60 PF,,,; hexane--Me,CO-NHEt, (6: 3: I)], affording the trimethyl ether as a yellowish powder (1.5 mg). IR vc’,:: cm -I: 1610, 1580, 1510, 1255, 1255, 1020, 820. ‘HNMR (400 MHz, CDCl,): 62.5-3.5 (14H, H-1,1’ and methylene groups), 2.61 (6H, s) (NMe-2 and NMe-2’) 3.54 (3H, s) (OMe-7’) 3.71 (3H, s) (OMe1 l’), 3.79 (3H, s), (OMe-12), 3.80 (3H, s) (OMe-6). 3.82 (3H, s) (OMe-6’), 5.91 (lH, s) (H-8’), 6.22 (lH, s) (H-8), 6.53 (1H. s) (H-5), 6.54 (lH, d, J==.OHz) (H-10’). 6.66 (2H, d, J =8.5Hz) (H-11,13), 6.66 (lH, s) (H-5’), 6.71 (lH, dd, J =8.3,2.0Hz)(H-l4’),6.82(1H,d,J=8.3Hz)(H-13’),6.89 (2H, d, 5=8.5 Hz) (H-10,14). MS m/z (rel. int.): 639 ([M +I]+, 0.4), 638 ([M-J’-, 0.1). 518 (7), 517 (20), 326 (100). 312 (12), 296 (8), 206 (75) 121 (18): FAB MS (+VE) mjz: 639 (CM + 11’3 C,,H,,N,O,). Acknowledgements----The authors wish to thank the National Natural Science Foundation of China for financial support and the Fujisawa Foundation (Japan) for a scholarship to S.L. They are also indebted to Research Laboratories, Nippon Kayaku Co. Ltd for measurements of FAB MS. REFERENCES
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