Short Reports REFERENCES 1. Merxmuller, H., Leins, P. and Roesseler, H. (1977) in The Biology and Chemistry qf Compositae (Heywood, J. B., Harborne, J. B. and Turner, B. L., eds). pp. 590. Academic Press, New York. 2. Leins, P. (1971) Bot.Jahrh. 91, 91. 3. Pascual, Teresa, J., Barrero, A. F., San Feliciano, A.. Grande, M., and Medarde, M. (1978) Tetrahedron Letters 43, 4141. 4. Pascual Teresa, J., Barrero, A. F., San Feliciano, A. and Medarde, M. (1980) Phytochemistry 19, 2155. 5. Ahmed, A. A., Jakupovic, J., Eid, F. and Ali, A. A. (1989) Phytochemistry (in press). 6. Tatum, J. H. and Berry, R. E. (1972) Phytochemistry 11,2283. 7. Row, L. R. and Sastry, G. (1963) Indian J. Gem. 1, 207. 667 8. Joseph-Nathan, P., Abramo-Bruno and Torres Ma. M. (1981), Phytochemistry 20, 313. 9. Buschi, C. A., Pomilio, A. B. and Gros, E. G. (1981) Phytochemistry 20, 1179. 10. Rodrigues, E., Carman, N. J. and Mabry, T. J. (1972) Phytochemistry 11, 409. 11. Rodrigues, E., Carman, N. J., Velde, G. V., McReynols, J. H., Mabry, T. J., Irwin, M. A. and Geissman, T. A. (1972) Phytochemistry 11, 3509. 12. Harborne, J. B. and Mabry, T. J. (1982) The Flauonoids, Advances in Research. Chapman & Hall, London. 13. Mabry, T. J., Markham, K. R. and Thomas, N. B. (1970) The Systematic Identification ojFlauonoids. Springer, New York. Phytochemistry, Vol. 28, No. 2, pp. 667 670. 1989. Printed in Great Britain. 0 ALKALOIDS ABDALLAH CHERIF, GEORCES MASSIOT, OF ALSTONIA LOUISETTE 003l-9422/89$3.00+ 0.00 1989Pergamon Press plc. CORIACEA LE MEN-OLIVIER, JACQUES PUSSET and STPPHANE LABARRE Faculte de Pharmacie (U.A. au C.N.R.S. N” 492), 51 rue Cognacq-jay, 51096 Reims Cedex, France;t Laboratoire des Plantes Medicinales du C.N.R.S. B.P. 643, Noumea, New Caledonia, France; Institut de Chimie des Substances Naturelles du CNRS 91198 Gif sur Yvette-Cedex, France (Received in revisedform 8 June 1988) Key Word Index- Alstonia coriacea; Apocynaceae; indole alkaloids; quinoline alkaloids; ‘H and 13CNMR. Abstract-Seven alkaloids have been identified from the stem bark of Alstonia coriacea from New Caledonia. They are gentianine, lo-methoxy deplancheine, vincamajine, desmethylquaternine, lo-methoxy-3-epi-a-yohimbine, corialstonine and cabucraline. Corialstonine is a novel member of the little represented quinoline alkaloid series. INTRODUCTION Panther ex S. Moore is a shrub from which sometimes is mistaken for A. fenormandii [l]. After studying the alkaloid content of this latter species [2], we herein report our results on the alkaloids of the stem bark of A. coriacea collected by two of us (J. P. and S. L.) in the southern part of the island. Alkaloids were extracted in the standard fashion and from 3.3 kg of dried milled stem bark, there was obtained 17 g of alkaloids (yield 5.2 g/kg); some alkaloids were also isolated from the leaves but their low yield discouraged us from pursuing investigation. Alstonia coriacea New Caledonia, RESULTS AND DISCUSSION From the crude alkaloid mixture, seven alkaloids were isolated in a pure state and identified. They are gentianine, 1 (0.6% of alkaloid mixture (AM)), lo-methoxy deplancheine, 2 (1.5% AM), vincamajine, 3 (6.5% AM), Part 125 in the series ‘Plants from New Caledonia’. For part 124, see Ettouati, L., Ahond, A., Convert, O., Poupat. C. and Potier, P. (1988) Bull. Sot. Chim. Fr., (in press). desmethylquaternine 4 (56% AM), lo-methoxy-3-epi-ayohimbine 5 (0.9% AM), corialstonine 6 (0.5% AM) and cabucraline, 7 (0.8% AM). Among these, alkaloids 1-3 and 7 are known compounds, available for direct comparison from the study of other Alstonia species. Alkaloid 4, previously isolated from A. legouixae, was identified here by comparison of spectra [3]. To the best of our knowledge, alkaloids 5 and 6 are new; the structural elucidation of 6 has been reported in a preliminary note [4] and will not be detailed here. The novel isolation of 2-4 and 7 has provided the opportunity of obtaining by means of complete ‘H and ’ 3C NMR assignments 2D NMR experiments. Deplancheine and lo-methoxydeplancheine 2 are rare alkaloids, isolated from A. deplanchei [S], A. undulata [6] and A. lanceolifera [7]. Previous structural assignment of 2 was based on comparison of the ‘H NMR spectra of 2 and of the corresponding fully synthetic 19,20-dihydro derivative. This is now done using 13C NMR, to establish the gross structure of 2 and to settle the aromatic substitution, and ‘HNMR. Both spectra were assigned using 6-6 correlation experiments and the chemical shifts of the aromatic carbons were found to be close to the values reported for lo-methoxy indoles by Verpoorte et al. [S]. Ring junction H-3 was observed as a broad Short Reports 668 H CO&e m N :I Me0 TH \---H>e \ 7 Me0 doublet with J= 10.9 Hz at S=3.38 ppm, indicating a trans quinolizidine arrangement. Among correlations observed on the COSY spectrum, a few unusual modulations due to long-range couplings deserve comments since the deplancheine unit is part of many more elaborate alkaloids; they are observed between H-21 axial and H-15 axial, H-21 equatorial and H-15 equatorial, H-18 and H-21 axial, H-19 and H-21 axial and H-15 axial. Not surprisingly, allylic and homoallylic couplings are found to have a larger value in the case of axial protons whose CH bonds are orthogonal to the plane of the olefin. It is also worthy of note that none of the couplings observed between allylic and vinylic groups allows establishment of the double bond configuration. This point is settled after the C-21 chemical shift (54.8 ppm) which favours a E configuration. Vincamajine 3 and cabucraline 7 are ubiquitous AIstonia alkaloids; their ‘H and ‘“C NMR spectra have been assigned using 2D-techniques (see Table 1 for 13C and Experimental for ‘H). With regard to the original assignment of 7 [9], three pairs of carbons are interchanged; CH,:5 and 21, 6 and 14 and CH:3 and 16. Similar changes will probably have to be made on the spectra of molecules containing cabucraline or derivatives thereof; this point is currently under investigation in our laboratory. The ‘HNMR spectrum of cabucraline was completely analysed by means of 2D spectroscopy and the only observed unexpected chemical shifts are those of H-2 (abnormally shielded at 6 2.56 ppm) and of H-15 (deshielded at 63.62 ppm). Whereas connectivities were not easily demonstrated using double resonance, there is no difficulty in following a path from H-2 to H-16 via H-3, H-14 and H-15. Some couplings such as J,, 3 are Heteronuclear long range couplings -C-2 - H- 3 (‘J) -C- 5 - H-21 PJ) -C-20 - H-16 (‘J) -C- 2 - H- 5 c3J) -C-20 - H-21 (‘J) -C- 8 - H-6 CJ) -C-20- H-l? t3J) -C- 8 - H -12 c3J) -C-20- H-15 (‘J) -C-13- H-9 c3J) 669 Short Reports of alkaloids 2-7 (75 MHz, CDCI,; central line of Table 1. ‘%NMR CDCI, used as intl standard 6 =77. ppm). In ref. [4], 13C data for compound 4 have unfortunately been exchanged for those of the N (1) methylated derivative. C 8 9 10 11 12 13 14 15 16 17 18 19 20 21 Ar-OMe CO,Me co N-Me better seen when delays (0.1 set) are sequence before and after the mixing conditions, one observes correlations matic narrow doublet (6 = 6.18 ppm) and N-methyl groups; this experiment 2 3 4 5 6 7 135.5 59.8 52.9 21.4 107.7 127.6 100.5 153.7 110.7 111.1 130.9 30.6 33.7 74.7 53.2 61.8 35.3 56.8 130.0 124.5 119.2 129.5 109.2 154.3 21.8 30.1 59.6 74.6 12.8 117 136.2 55.5 107 52.1 87.5 40.6 52.1 128.2 110.2 141.5 145.4 96.5 149.4 26.1 31 52.2 132.4 53.9 51.0 16.6 107.6 127.9 100.3 154.1 111.3 111.8 130.9 24.0 32.3 54.0 65.8 33.3 23.7 35.6 49.6 55.9 89.7 73.4 146.9 115.2 146.5 122.2 107.9 152.0 148.9 105.8 148.0 31.4 40.2 59.4 78.2 47.6 50.2 29.9 42.1 132.4 121.3 103.6 159.9 97.4 154.1 32.3 33.8 52.6 12.9 119.5 135.8 53.1 55.9 55.7 50.8 169.2 13.1 121.8 135.1 54.3 55.3 12.6 118.6 133.6 54.8 55.7 51.6 173.1 34.3 12.7 120.1 138.4 46.4 56.9 56.1 51.4 172.7 introduced in the pulse. Under these between the aroand the methoxy represents a simple means of locating a methoxy on a N-methyl indole derivative. The same results are deduced from a NOESY experiment using a 900 msec mixing time (for a 300 MHz field); in the NOESY spectrum a meaningful throughspace correlation is found between H-2 and H-16, thus allowing the configurations of the C-2 and C-16 stereocentres to be determined. N (1) Desmethyl quaternine 4 is the major alkaloid from the plant, obtained here in a crystalline form with mp 197” (from diethyl ether). Its IR, UV and mass spectra are superimposable with the corresponding spectra of the alkaloid from A. legouixae, kindly provided by Prof. Poisson [3]. High field ‘H and “C data were fully assigned as described above and we wish to analyse here some of the observations deduced from a Kessler experiment optimized for J= 10 Hz. As noticed by others ‘J have smaller values than 3J especially in the aromatic area; 3J have a Karplus-type angular dependance and are useful in the assignment of proton configurations. Thus, C-13 resonance is modulated by H-9 frequency but not by H-12; correlations between C-8 and H-12 on one hand and H-6 on the other allow the establishment of a link between ring A and C through two quaternary carbon atoms. Other unexpected correlations are observed between C-2 and H-5, C-S and H-21, through oxygen and nitrogen heteroatoms, respectively. The first novel compound from the plant, alkaloid 5 is 51.8 174.6 51.6 172.5 33.2 lo-methoxy-3-epi-cr-yohimbine. According to its mass spectrum, it is an isomer of quaternatine (= 1 l-methoxy3-epi-a-yohimbine) from A. qunternata [lo]. Comparison of the high field parts of the 13C NMR spectra of 5 and of the series of yohimbinoids described by Wenkert et al. [l 1] allows identification of the configurations of the asymmetric centres of 5 and its assignment to the 3-epi-ccseries. Confirmation of the stereochemistry of 5 is obtained, in part, from the analysis of the high field ‘H NMR spectrum, where several important protons are observable: H3 (br s) at S 4.41 ppm thus indicating a cis quinolizidine ringjunction, H-l 7 (doublet of triplets, J = 4.511 Hz) at 6 4.08 ppm showing that H-17 and H-16 are trans diaxially oriented and H-16 (doublet of doublets, J = 3.5, 10.4 Hz) at 62.43 ppm which is cis related to H-15. The H-21 are a br d (6 = 2.5 ppm, J = 12.4 Hz) and a doublet of d (6 = 3.02 ppm, J = 12.4,4.2 Hz) and this proves that H-20 is equatorial in ring D and thus is c(. Location of the aromatic methoxy substituent is based on r3C increments and comparison with literature data [8]. Corialstonine 6 is a minor alkaloid from A. coriacea and it remains one of the rare members of the quinoleine alkaloids family. As many other quinoline alkaloids, it might be formed by oxidation and rearrangement of an indole precursor Alstonia coriacea shares with the varieties of A. lenormandii the feature of producing large amounts of alkaloids with the lO,ll-dimethoxy picraline skeleton; they differ however in the nature of their minor bases (indo loquinolizidines in A. coriacea and anilinoacrylic esters in A. lenormandii). 670 Short Reports The crude alkaloid mixture was assayed for pharmacological activities in the central nervous system domain and for cardiovascular, antibiotic and anti-inflammatory activities; no significant properties were observed. EXPERIMENTAL General. Plant material was collected at ‘For&t Cachte’ in ‘Plaine des Lacs’. A herbarium specimen is deposited at the Herbarium of Orstom Centre in NoumCa. ‘H and 13CNMR were measured at 300 and 75 MHz, respectively. Extraction and isolation of alkaloids. Dried, powdered stem bark of A. coriacea (3.3 kg) was wetted with 50% NH,OH and lixiviated with 60 1 of EtOAc. The lixiviate was extracted with 2% H,SO, and the aq. phase made alkaline with NH,OH and extracted with CHCI,. The CHCI, layers were dried (Na,SO,) and evapd in vacua to give 17 g of crude alkaloid mixt. (yield 5.2 g/kg). Alkaloid 4 was obtained by crystallization of the crude AM from Et,0 (yield 9.5 g). The mother liquors ofcrystallization were placed on a silica gel column packed in CHCl, and eluted with CHCI, (600 ml, fractions l-5). CHCI,-MeOH (49: 1; 5OOml Fr. 6-15), CHCI,-MeOH (19:l; SOOml, Fr. l&31), CHCI,-MeOH (9: 1; 500 ml, Fr. 32-38). CHCl,-MeOH (17:3; 250 ml, Fr. 39-55) and CHCI,-MeOH (4: 1; 200 ml, Fr. 56-69). Gentianine 1 was in Fr. l-5; alkaloids 3, 5, 6, were in Fr. 631; alkaloid 2 was in Fr. 32-38 and alkaloid 7 in Fr. 32-55. Description ofnew alkaloids. lo-Methoxy-3-epi-a-yohimhine 5, (ceric sulphate TLC (CR) pale green): [alo - 66” CHCI,; c 1; UV: I:$‘” nm: 227, 285, 310, 335: IR: ~~~~‘~crn-‘: 3380, 1720, 1620, 1590, 1480, 1460, 1430, 1305, 1210; MS m/z (rel. int.): 384 ([Ml’; C,,H,,N,O,, 100). 383 (95), 369 (IO), 353 (lo), 325 (5), 258 (15), 222 (20), 214 (20), 200 (15), 199 (12), 174 (10); ‘HNMR (300 MHz, CDCI,): 6 7.21 (d, J=8.7 Hz, H-12), 6.93 (d, J =2.3 Hz, H-9), 6.82 (dd, J=8.7 2.3 Hz, H-11), 4.41 (br s, W, =4 Hz, H-3),4.08(dt,J=4.5,11 Hz, H-17), 3.86(s,ArOMe),3.84 (s, CO,Me), 3.23 (m, 2H, H-5), 3.02 (dd, J= 12.4, 4.2 HZ, H-21), 2.94 (m, H-6), 2.5 (br d, J = 12.4 Hz, H-21), 2.48 (m, H-6), 2.43 (dd, 5=10.4, 3.5 Hz, H-16), 2.16 (br s, H-15), 2.14(m, H-14), 2.13 (m, H-19),2.1 (m,H-18), 1.69(m,H-14), 1.55(m,H-20),2,35(m,H-19X 1.28 (m, H-18). Corialstonine 6. [aID + 102” (CHCI,; c l), UV I.!$‘” nm; 218, 238, 317, 330; (MeOH +HCI)=220, 246, 354; IR vzyF13 cm-‘: (1745, 1620, 1580, 1500, 1480, 1430, 1345, 1250, 1160, MS: m/z (rel. int.): 424 ([M + 14,5]+], 410 ([Ml’, C2,H,,N,0,, 30), 258 (lo), 188 (12), 135 (25), 122 (40), 121 (100); ‘HNMR (300 MHz, CDCI,):68.65(d,J=4.8 Hz, H-5), 8.32(s,H-12), 7.4(s,H-9), 7.08 (d,J=4.8Hz,H-6),5.4(hrq,J=7Hz,H-l9),4.7(d,J=6.7Hz, H-5’), 4.35 (d, J=6.7 Hz, H-5’), 4.3 (d, J=4.1 Hz, H-3), 4.02 (s, 3H, ArOMe), 4.0 (s, 3H, ArOMe), 3.95 (dq, J= 16.5, 2.4 Hz, H21), 3.65 (br s, H-15), 3.45 (s, 3H, CO,Me), 3.2 (br d, J= 16.5 Hz, H-21),2.85(d,J=5.1 Hz,H-16),2,5(d,J=l3,2Hz,H-14),2.l(dt, J= 13.2, 4.1 Hz, H-14). 1.5 (dd, 3H, J=7, 2.4 Hz, Me-18). Complementary data for known alkaloids. IO-Methoxy deplancheine 2. ‘H NMR (300 MHz, CDCl,) 6: 7.85 (br s, NH), 7.18 (d, J=8.5Hz, H-12), 6.92 (d, J=2.6Hz, H-9), 6.78 (dd, J =8.5, 2.6 Hz, H-II), 5.35 (br q, J=6.8 Hz, H-19), 3.85 (s, 3H, OMe), 3.8 (br d, J = 12.4 Hz, H-21), 3.38 (d, J = 10.9 Hz, H-3), 3.15(dd,J = 10.6,6 Hz, H-5),2.98(dddd,J= 2.2,5.8, IO, 12 Hz, H.6), 2.77 (d, J= 12.4 Hz, H-21), 2.7 (dd, J= 10.6, 6 Hz, H-5), 2.68 (m, H-6), 2.38 (br d, J = 13.4 Hz, H-15), 2.25 (br t, J = 13.4 Hz, Hl5), 2.1 (ddt, J= 12.3, 2.5, 1.4 Hz, H-14), 1.67 (d, J=6.8 Hz, Mel8), 1.62 (dq, J=4.5, 13.4 Hz, H-14). Vincamajine3. ‘HNMR(300 MHz, CDCI,)6: 7.18 (dt, J=7.1, 1.1 Hz,H-11),7.15(brd,J=7.5Hz,H-9),6.8(dt,J=7.5, I.1 Hz, H-10), 6.66 (br d, J=7.1 Hz, H-12), 5.27 (br q, J=7 Hz, H-19), 4.24 (br s, H-17), 3.7 (s, 3H, CO,Me), 3.56 (m, H-3), 3.51 (m, H-5), 3.5 (m, 2H, H-21), 3.42 (br s, H-15). 3.24 (d, J =4.6 Hz, H-2), 2.64 (s, N-Me), 2.62 (dd. J = I I, 4.5 Hz, H-6). 2.45 (dd, J = 14.5 Hz, Hl4), 2.1 (br s, OH), 1.75 (d, J = 1 I Hz. H-6), 1.6 (dt, J= 7, 1.5 Hz, Me-l8), 1.54 (dd, J= 14, 9.5 Hz, H-14). Desmethylquaternine 4. CR green then pink; mp 197-200” (Et,O); [a], -19” (CHCI,; c 1); UV$$!j”‘nm: 210, 235, 300, IR \,I;;;” cm- 1: 3340.1735, 1615, 1495,1130,1070,990,865,815; MS:m/z (ret. int.): 398 (100). 383 (20), 380 (20), 339 (30), 299 (70), 262 (55), 254 (20). 204 (15), 190 (15). 136 (30). ‘H NMR (300 MHz, CDCI,)G:6.78(s.H-9),6.4(s,H-12),5.41 (brq,J=6,7Hz,H-19). 4.83 (d, J = 2.1 Hz, H-5), 3.81 (s. OMe). 3.76 (s, Me), 3.75 (m, H21),3.66(s,Me),3.57(d,J=4.6Hz,H-3),3.36(d,J=13.6H~,H6), 3.28 (br s, H-5), 3.08 (d. J = 17.6 Hz, H-21), 2.42 (d, J = 3.6 Hz, H-16), 2.24 (dd, J= 13.6, 2.4 Hz, H-6). 2.14 (dt, J= 13.0, 3.9 Hz, H-14),1.85(dd,J=13,2Hz,H-14),1.48(dd,J=7,2Hz,Me-18). Cabucraline 7. ‘H NMR (300 MHz. CDCI,) 6: 6.8 (d. J = 7.9 Hz, H-9), 6.2 (dd, J=7.9, 2.2. Hz, H-10), 6.18 (d, J=2.2 Hz, H-12), 5.46 (br q, J = 7 Hz, H-19), 4.28 (d, J = 4.8 Hz, H-3), 4.05 (hr d, J = 15.7 Hz, H-21), 3.83 (dr, J=5.4, 13.5 Hz, H-5), 3.77 (s, OMe), 3.73 (s, ArOMe), 3.62 (br s, H-15). 3.12 (dt, J =6.6, 13.5 Hz, H-6), 3.03 (d, J= 15. Hz, H-21), 2.92 (d, J-3.9 Hz. H-16), 2.71 (dd, J =6.6, 13.5 Hz, H-5). 2.64 (s, N-Me), 2.56 (s, H-2), 2.35 (ddd, J = 2.9, 4.8, 14.2 Hz, H-14), 1.63 (hr dd. J = 14.2, 2 Hz, H-14), 1.48 (dd, J = 7.2 Hz, Me-l 8). Acknowledgements--The authors are indebeted to Dr T. Sivenet for selecting plant material and to Sanofi-Recherche (Montpellier) for performing the biological testing. REFERENCES 1. Boiteau, P., Allorge, L. and Stvenet, T. (1977) Adansonia 16, 465. 2. Legseir, B., Chkrif. A. Richard, B., Pusset, J., Labarre, S., Massiot, G. and Le Men-Olivier. L. (1986) Phytochemistry 25, 1735. 3. Lewin, G., Tamini, 0.. Cabalion, P. and Poisson. J. (1981) Ann. Pharm. Fr. 39, 273. 4. Cherif, A., Massiot, G. and Le Men-Olivier. L. 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