Bis-benzylisoquinoline alkaloids from Abuta pahni

zyx zyxwvutsrqponmlk zyxwvutsrqponm zyxwvutsrq zyxw 0031 -9422/87 %3.00+0.00 P h ~ ~ f ~ ~ VOI. h i 26, i ~ NO. y , 7, pp. 2136-2137, 1987. Printed in Great Britain. 0 1987 Pcrgamon Journals Ltd. BIS-BENZYLISOQUINOLINE ALKALOIDS FROM ABUTA P A H N I zyxwv zyxwvutsrqp PASCALE D u T ~J,E A N - F R É D ~ R I C WEBER, ALAINFOURNET*, ADRIENCAvÉt and JEANBRUNETONS Laboratoire de Pharmacognosie, Centre d'Etudes des Plantes Médicinales, Faculté de Pharmacie, 16 bd Daviers, 49000 Angers, France; *O.R.S.T.O.M.-I.B.B.A., CP 824, La Paz, Bolivia; tC.C.I.P.E., BP 5055, 34033 Montpellier Cedex, France (Reoised received 1 October 1986) Key Word Iadex-Abutcl pultni; Menispermaceae; bis-benzylisoquinoline alkaloids; 2'-N-nordaurisoline; 2-Nmethyllindoldhamiiie; 2'-N-methyllindoldhnmine. ,. Abstract-From the stems of Abicta pcthrii, eight isoquinoline alkaloids were isolated and identified by spectroscopic methods and chemical correlations. Three of the bis-benzylisoquinoline alkaloids are new and were assigned the structures 2'-N-nordaurisoline, 2-N-methyllindoldhamine and 2'-N-methyllindoldhamine. The other known alkaloids were coclaurine, daurisoline, lindoldhamine, dimethyllindoldhamine, stepharine and thalifoline. INTRODUC'IION The genus Abuta (Menispermaceae, Anomospermae) spreads widely throughout tropical America. Out of its 30 species [l] only a few have been studied from a chemical point of view. They all contain isoquinoline alkaloids of several types, namely bis-benzylisoquinolines [2, 31, oxoaporphines [4,5], amfluoranthenes [5], tropoloisoquinolines [6] and isoquinolobenzazepines [7]. As A. pahni [SI is part of Amazonian curare mixtures, we thought it worthwhile carrying out the analysis of the alkaloidal composition of this species. and of the N-Me. Irradiation of the N-Me singlet induces a 4 increase of the signal at 3.61 ppm; when this last signal is irradiated, increases of 2 % on the H-8 signal (at 6.31 ppm) and of 1.2 on the doublet of the X proton of the ABX system in the ring C (H-10 at 6.49 ppm)can be observed. Therefore, the nitrogen in position 2 carries the methyl group and alkaloid 2 is assigned the structure 2'N-nordaurisoline. Alkaloids 4 and 5 exhibit the same molecular formula C35133~N206,[MI" tn/z 582. Like 2, they both carry a secondary amino function, which o n methylation (HCHO-NaBH,) gives one product only, the ( - ) - N , N dimethyllindoldhamine 6 ( = guattegaumerine [lo]), identified by comparison with authentic samples [1I]. As above, the respective positions of the secondary amino and tertiary amino groups in alkaloid 4 are determined through N O E measurements (cf. values in the Experimental). It can then be given the structure 2-Nmethyllindoldllamine. Consequently alkaloid 5 corresponds to 2-N-methyllindoldhamine. Like (-)-daurisoline 1 and (-)-lindoldhamine 3 the three new alkaloids have a 1RJ'R configuration as establishcd by the superimposability of their CD curves. Thus, A . palmi displays a n array of isoquinoline alkaloids close in composition to other Abuta species. Yet zyxwvutz RESULTS AND DISCUSSION Extraction and separation of the non-quaternary alkaloids, according t o a conventional process, led to the isolation, and characterization of eight alkaloids. Five of them are known, a n isoquinolone, thalifoline, a benzylisoquinoline, (+)-coclaurine, a proaporphine, ( +)stepharine and two bis-benzylisoquinolines, (-)daurisoline 1 and (-)-lindoldhamine 3. The three remaining alkaloids are new. They are all of the single bridged bis-benzylisoquinoline type, a s suggested by mass spectroscopy by the very low intensity of the [ M l * peak [9]. The ' H NMR spectra (360 MHz, FT) (cf. Table 1) display much analogy. There appears, in particular, the constant presence of an ABX system, and of an A2B2 system, respectively, assigned to the protons in the 10,13,14 and 10',11',13',14' positions, a characteristic feature of the 11,12' single bridged bis-coclaurine [2, 31. Each of the three spectra also shows only one singlet assignable to a N-methyl group at ca 2.5 ppm. The other nitrogen atom is therefore engaged in a secondary amino function as established by the very strong deshielding of the 1- or l'-proton (CU 4.1-4.2 ppm). Alkaloid 2, C36H40NZ06,[MI* m/z 596, presents a 'H N M R spectrum that differs little from that of daurisoline 1. Methylation of 2 (HCHO-NaBH4) N o r d s a compound identical in every respect to 1. The use of NOES helps establish the respective positions of the N-H on i' q lT tc a( Pi m B; in Pf C fu bJ ar zyxwvu PS wi CO [3 di: da O O C 21 31 1 R1 = Me, RZ = Me, R3 = Me 2 It' = Me, Ri = H , R3 = Me 3 It' = I l , IIz = I I , R3 = H 4 RI = Me, R2 = H , R3 = H 5 R' = H, R2 = Me. R3 = H o1 H rv 11 2137 Short Reports zyxwvutsrq zyxwvu zyxwvutsrqp zyxwvuts zyxwvuts Table 1. 'H NMR chemical shifts of compounds 1-6 (6 ppm, 360 MHz, CDC13, TMS as internal standard) 2-N-CH3 T-N-CH3 H-1 H-1' H-5 H-5' H-8 H-8' H-10 H-13 H-14 H-IO' and 14' H-11' and 13' CH30-6 Clj30-6' CH30-7 1 2 2.47 s 2.53 s 3.62 dd 3.77 dd 6.46 s 6.57 s 6.34 s 6.14 s 6.53 d 6.90 d 6.84 dd 7.03 d 6.81 d 3.80* s 3.83* s 3.62 s 2.43 s 4 3 - - 3.61 dd 4.15 dd 6.45 s 6.60 s 6.32 s 6.69 s 6.49 d 6.90 d 6.84 dd 7.16 d 6.83 d 3.81~s 3.861- s 3.84 s 4.05 dd 4.15 dd 6.51 s 6.58 s 6.69 s 6.69 s 6.66 d 6.89 d 6.91 dd 7.17 d 6.87 d 3.86~s 3.85~s - 6 5 2.46 s - 3.61 dd 4.11 dd 6.45 s 6.57 s 6.30 s 6.77 s 6.48 d 6.87 d 6.84 dd 7.14 d 6.82 d 3.859 s 3.819: s - - 2.47 s 4.16 dd 3.61 dd 6.45 s 6.62 s 6.66 s 6.35 s 6.48 d 6.90 d 6.85 dd 7.17 d 6.84 d 3.8511 s 3.8111 s - 2.50 s 2.45 s 3.62 dd 3.72 dd 6.48 s 6.54 s 6.24 s 6.32 s 6.61 d 6.87 d 6.76 dd 7.02 d 6.82 d 3.8511s 3 . 8 4 ~s - * t $ §IIl[Assignments with the same superscript are interchangeable for a given compound. only A. candicans and A . yrisebachii contain bisquaternary alkaloids which could be responsible for a muscle relaxant activity and therefore for a curare-like toxicity. Due t o the lack of detailed investigations on the activity of tertiary bis-benzylisoquinolines on muscle, the part played by the other Abuta species in the arrow poison mixtures still reinains unclcar. N-Methylation reactions. 37% formalin (1 ml) was added slowly into samples of 2,4 and 5 (10 mg) in MeOH (5 mi) and the s o h stirred under reflux for 45 min, thencooled. NaBH4 (50 mg) was then added and the s o h stirred under reflux for another 45 min. After cooling, HoAc was added to decompose excess reagent and the mixtures made alkaline with NH, and then extd with CHCI,. Solvent was removed in vacuum, and the rcsiducs purified by prep. TLC. EXPERIMENTAL Plant niaterial. Stems of Abicta pahtii (Martius) KrukoF and Barneby (1.5 kg) were collected in August 1984by one of us (A.F.) in Alto-Beni, Marimono, Bolivia, at 850 m altitude. Extraction and chrotnatoyrap/iy. After removal of lipids with petrol, the stem powder was made alkaline and extracted with CHzCIz in a Soxhlet apparatus. The alkaloidal mixture was further purified by the usual acid-base treatment, then separated by EC on Merck 60 silica gel or by TLC on Merck 60 H silica gel and by prep. TLC on Merck HFZ5,, silica gel. Identijication ofcotnpoutids. Data ('H NMR, MS, UV, comparative TLC) of the known compounds were in total accordance with those published. For thalifoline refer to [12], for (+)coclaurine and (+)-stepharinc to [13], for (-)-daurisoline 1 to [3], for (-)-lindoldhamine 3 to [2] and for N,Ndimcthyllindoldhamine 6 to [ll] (cxcept 360 MHz 'HNMR data of 1, 3 and 6 cfi Table 1). 2'-N-NordaurisoIine 2. [alD: negative. MS ni/z (rel. int.): 596 [MIt (cl), 192 (100). 360 MHz ' H N M R cfi Table 1. Main observed NOEs: 2-N-CH3 on H-1: + 4 % (reciprocal); H-1 on H-8: + 2 % (reciprocal); H-1 on H-10 + 1.2% (reciprocal). 2-N-Metliy~~iiidoldhurtiiite 4. [a]" = - 185" (MeOH; c = 0.10). UV (EtOH) X,,, nm (log): 213 (4.965), 225 sh (4.829), 285 (4.364). MS rn/z (rcl. int.): 582 [MIS(< I), 192 (loo), 178 (20). 360 MHz 'II NMR: cfi Table 1. Main observed NOEs: 2-N-Q13 on H-10+ 1.5 "/, (reciprocal); H-1' on H-8': f 5 "/, (reciprocal); H-1' on H-10',14':+2.5%, (reciprocal). 2'-N-Metliyllitidold/iuitiiiie 5. [a] = -47' (McOH; c = 0.17). MS ni/z (rcl. int.): 582 [MI' (< l), 192 (47), 178 (100) 360 MHz ' H N M R cfi Table 1. REFERENCES 1. Hegnauer, R. (1964) Clrernotaxoiiornie der Pflanzen 3, Birkhaüser, Basel. 2. Guha, K. P., Mukherjee, B. and Mukherjee, R. (1979) J. Nut. Prod. 42, 1. 3. Schi& P., Jr. (1983) J . Nat. Prod. 46, 1. 4. Guinaudeau, H., Lebccuf, M. and Cavé, A. (1979) J . Nat. Prod. 42, 325. 5. Guinaudeau, H., Lebocuf, M. and Cavé, A. (1983) J . Nat. Prod. 46, 761. '6. Menachery, M. D. and Cava, M. P. (1980) Heterocycles 14, 943. 7. Hocquemiller, R.,Cavé, A. and Fournct, A. (1984) J. Nat. Prod. 41, 539. 8. Barneby, R. C. and Krukoff, B. A. (1971) Mein. N.Y. Bot. Gard. 22, 1. 9. Baldas, J., Bick, I. R. C., Ibuka, T., Capil, R. S . and Porter, Q. N. (1972) J. Chan. Soc, Perkin 1592. 10. Dehaussy, H., Tits, M. and Angenot, L. (1983) PIarita Med. 49, 25. 11. Jossang, A., Lcbccuf, M., Cabalion, P. and Cavé, A. (1983) Plurita Med. 49, 20. 12. Bick, 1. R. C., Sbvcncl, T., Sinchai, W., Skclton, B. W. and White, A. 1-1. (1981) Arrsf. J . Cltern. 34, 195. 13. Kametani, T. (1969)The Clicrnisrry oflsoquitroline Alkaloids, Tokyo Hyrokawa, Amsterdam. zyxwvutsrq zyxwvutsrqpo zyxwvutsrq