z zyxwvutsr zyxwvutsrqponml View Article Online / Journal Homepage / Table of Contents for this issue zyxwvuts zyx J. C H E M . SOC. PERKIN TRANS. i 663 1992 Ophiorrhizine, a New Quaternary lndole Alkaloid Related to Cinchonamine, from Ophiorrhiza major Ridl. Published on 01 January 1992. Downloaded by McMaster University on 23/10/2014 20:24:05. Dayar Arbain,*naLindsay T. Byrne,b Deddi Prima Putra,b Melvyn V. Sargent,*Sb Brian W. Skeltonb and Allan H. Whiteb a Department of Pharmacy, FMIPA, University of Andalas, Padang, West Sumatra, Indonesia Department of Chemistry, University of Western Australia, Nedlands, Western Australia, 6009 zyx Extraction of the aerial parts of Ophiorrhiza major Ridl. has yielded a n e w C,, pentacyclic quaternary indole alkaloid, ophiorrhizine. The structure was established as 1 on the grounds of its spectral properties (optical rotation) and its X-ray molecular structure. Its biosynthetic relationship to the Cinchona alkaloids is discussed. ’ In continuation of our phytochemical survey of West Sumatra we have examined an extract of the fresh aerial parts of Opliiorrliiza major Ridl. (Rubiaceae), which gave a positive field test for alkaloids using the Culvenor-Fitzgerald method.’ 0. major is a small shrub, ca. 20 cm high, which although rare, is used by traditional healers in West Sumatra as a component of a poultice used for skin disorders, especially eczema. After a small amount of tertiary alkaloids had been removed from the extract, the remaining aqueous phase was extracted with butanol. After chromatography, a low yield of a quaternary chloride was obtained which crystallized from methanolethyl acetate. We suggest the trivial name ophiorrhizine for this new alkaloid. The FABMS exhibited a molecular ion at m / ; 297 which in conjunction with the I3C and ‘H NMR spectra allowed the molecular formula C,,H2,N,0 to be advanced for the cation. The electronic spectrum of ophiorrhizine was typical of an indole c h r ~ m o p h o r eThe . ~ 13C (75.5 MHz) and the ‘H (500 MHz) NMR spectra were determined in deuteriomethanol (see Table 1) and were analysed by the help of proton-proton decoupling, and by the double quantum filtered COSY, HETCOR protonsarbon correlation, TOCSY and DEPT techniques. These spectra, particularly the 3C ~ p e c t r u m , ~ allowed the identification of the eight carbon atoms of an 11hydroxyindole system and the connections between C-5 and C-6; (2-18, C- 19, C-20 and C-21; C-3 and C-14 and also between C- 17, C- 16 and C- 15 (see structure 1). Long-range coupling was observed between 3-H and the protons attached to C-6. Owing to the overlap of key proton resonances and the lack of strong evidence for coupling between 15-Hand 20-H the structure of ophiorrhizine 1 could not be advanced with certainty from the available spectroscopic data. Recourse was therefore taken to the X-ray method which gave structure 1 (see Fig. 1) and defined the relative stereochemistry at C-3, C-15 and C-20. Both dihydrocorynantheol3, readily available from dihydrocorynantheine 4, and dihydrocinchonamine 5, readily available I3C (75.5 MHz) and ‘ H (500 MHz) NMR data for ophiorrhizine 1 in deuteriomethanol Table 1 Carbon no. 6, 2 3 5 6 7 8 9 10 11 12 13 14 6,, multiplicity, coupling constants (Hz) 127.72 62.48 Obscured by OH (4.90,* br t, J3.,4a= J3.,46 61.29 3.54, ddd, J51.5D 12.5, J5a.6D 12, J5u.6u5 3.58, dd, J58.5512.5, J58.6D 6.5 18.25 2.96, br d, JsU.6 18 3-10, dddd,J,p.6,, 18, J6&5n 12, J6B.5D 6.5 J68.3m 2-5 105.37 120.71 119.72 7.28, d, JQ, o 8.4 111.05 6.64,dd, 7,-,., 8.4, J,,,,, 2.1 155.22 97.96 6.79, d, J,,.,, 2.1 139.98 26.82 1.9, overlaps with 16-H (1.79,* dd, J14.14 13.5, J14.3 9) 2.71, ddd, J I 4 . , , 13.5, J14.3 9, J I 4 . , ,4 25.12 2.24, m 26.26 1.9Ck1.98,m 49.17 3.28, m 3.67, m 12.00 1.04, t, J,,.,, 7.5 27.97 1.70, AB of ABM,X 38.12 2.15, m 65.23 3.25, m 3.83,dd, J,,,,, 12.5, J,,,,, 10.5 9.21 * 10.98 * = 9) - zyxwvut ’ D Fig. 1 Projection of a single cation of 1. 20% Thermal ellipsoids are shown for the non-hydrogen atoms; hydrogen atoms have arbitrary radii of 0.I A. 15 16 17 18 19 20 21 NH OH * These values determined at 300 MHz in deuteriodimethyl sulfoxide. from cinchonamine 6, and of known absolute configuration,’ undergo 0-tosylation on treatment with tosyl chloride and pyridine. The resultant tosylates when boiled in N,N-dimethylformamide yield the quaternary tosylate 2. Dihydroantirhine 7 also yields the tosyl salt 2 on similar treatment.8 The sign and magnitude of the specific rotation of ophiorrhizine ( [ 5 ~ ] 2 6 ) -60 ( c 0.001, MeOH))? are similar to those of the tosylate 2 { [ a ] D-67 (90% MeOH)) so that it is likely that both possess the same absolute configuration. The biosynthesis of the Cinchona alkaloids involves cleavage of ring C of corynantheal 8 to produce cinchonaminal9,’ and further transformations. Cinchonamine 6 is, therefore, likely to be derived from cinchonaminal9, so that ophiorrhizine 1 would be derived from a hydroxylated strictosidine by a similar pathway. t [%ID Values are recorded in lo-’ deg cm2 g-’. zyxwv zy z View Article Online 664 J. CHEM. SOC. PERKIN TRANS. 1 Published on 01 January 1992. Downloaded by McMaster University on 23/10/2014 20:24:05. 1; R = O H , X = C I 2; R = H , X = T s 3 5; R = Et Structure Determination.-A unique diffractometer data set was measured at ca. 295 K within the limit 28,,, = 50" [monochromatic Mo-Ka radiation, I. = 0.7107, A; 1839 independent reflections of which 1113 with I > 3 4 0 were considered 'observed']. The structure was solved by direct methods and refined by full matrix least-squares with anisotropic thermal parameters for C,N,O; hydrogen atoms were included, constrained in (x, y , z , Uiso),the hydroxy hydrogen being located in a difference map. Conventional residuals R , R , on IE;1 at convergence were 0.057,0.058 (both hands) [statistical weights, derivative of a2(1) = a2(ldiff)+ 0.0004~*(Idiff>].The chirality adopted follows from the chemistry; neutral atom complex scattering factors were employed. Computation used the XTAL 3.0 program system" implemented by S. R. Hall. Pertinent results are given in Fig. l.* zyxwv zy zyxwvuts z zyxwvutsr z OH ' H 4 1992 H 6; R=CH=CHz Crystal Data.-[C,,H,,N,O] +C1--H20, M = 350.8. No. 19), a = Orthorhombic, space group P2,2,2, 15.610(10), b = 15.079(6), c = 7.689(3) A, U = 1810 A3. D,(Z = 4) = 1.29 g cm-,. F(000) = 752. pMo= 1.8 cm-'; specimen = 0.07 x 0.29 x 0.37 mm (no correction). Molecular geometries are substantially as expected. Hydrogen-bonding interactions are found from the anion to the 0 (2, hydrogen atoms of independent water molecules [Cl 3 + y, 3 - z ; 3 + x, 3 - y , d ) , 3.073(7), 3.037(8) A] and to the N(l), 3.177(6) A]; a further N(1) hydrogen of the cation [Cl hydrogen bond is found between the phenol moiety and the O(11) (3 + x, 3 - y , z ) , 2.613(8) A]. water oxygen atom [O 9 \CHO 8 7 Acknowledgements ' H H 9 The support of this work by the International Foundation for Science (Stockholm), the Network for the Chemistry of Biologically Important Natural Products and the Australian Research Council is gratefully acknowledged. We thank Professor L. Mander for the NMR spectra at 500 MHz, Dr. J. Macleod for the mass spectra, and Dr. Soedarsono Riswas and Ms. Afristiani for identifying the plant material. * Supplementary data: see section 5.6.3 of Instructions for Authors (1992), J . Chem. SOC.,Perkin Trans. 1 , 1992, Issue 1. Atom co-ordinates, Experimenta1 General directions have been given previously." Extraction of Ophiorrhiza major.-The botanical material was collected in November 1989 in Anai Reserved Forest, West Sumatra. Herbarium specimens (DA840) are deposited in Herbarium Bogoriense (BO) and Herbarium Biology, Universitas Andalas (AND). The chopped fresh aerial parts of the plant (3 kg) were covered with methanol (10 dm3) and allowed to stand for 2 d and then filtered. The process was repeated twice more and the combined filtrates were concentrated under reduced pressure. The concentrate (400cm3) was diluted with sulfuric acid (10%; 50 cm3) and set aside for 12 h. The acidic solution was decanted and extracted with chloroform (3 x 100 cm3) and next basified with ammonia and extracted with chloroform (4 x 500 cm3). Work-up of the extract yielded a small amount of crude tertiary alkaloids which was reserved for further study. The aqueous phase, which gave a strong Mayer's test, was extracted with butanol(4 x 500 cm3) and the extract was evaporated to dryness under diminished pressure to afford a dark brown gum (12.5 g). This was chromatographed over silica gel with increasing proportions of methanol in butanol as eluent. Those fractions which gave a positive Dragendorff test were combined and evaporated and the residue was crystallized from methanol-ethyl acetate to give ophiorrhizine 1 as plates (45 mg), m.p. 162-164 "C (decomp.); [z];' -60 ( c 0.001, MeOH); A,,,/nm 220, 260sh, 270 and 295 ( E 18,000,4000,4100 and 5700 respectively). thermal parameters, molecular non-H geometry tables have been deposited at the Cambridge Crystallographic Data Centre. References 1 D. Arbain, R. Djamal, Wiryani and M. V. Sargent, Aust. J . Chem., 1991,44, 1013. 2 C. C . J. Culvenor and J. S. Fitzgerald, J. Pharm. Sci., 1963,52,303. 3 A. I. Scott, Interpretation of the Ultraviolet Spectra of Natural Products, Pergamon, Oxford, 1964, p. 297. 4 L. Braunschweiler and R. R. Ernst, J . Magn. Reson., 1983,53, 521. 5 R. Verpoorte, T. A. van Beek, R. L. M. Riegman, P. J. Hylands and N. G. Bisset, Org. Mag. Res., 1984,22,328. 6 This biogenetic numbering system is that of J. Le Men and W. I. Taylor, Experientia, 1965, 21, 508. 7 E. Wenkert and N. V. Bringi, J . Am. Chem. SOC.,1958,80,3484; 1959, 81, 1474,6535. 8 S. R. Johns, J. A. Lamberton and J. L. Occolowitz, Aust. J. Chem., 1967,20,1463. 9 A. R. Battersby and R. J. Parry, J. Chem. SOC.,Chem. Commun., 1971, 31. 10 D. Arbain, A. A. Birkbeck, L. T. Byrne, M. V. Sargent, B. W. Skelton and A. H. White, J. Chem. SOC.,Perkin Trans. 1 , 1991,1863. 11 J. A. Ibers and W. C. Hamilton, eds., International Tables for X-ray Crystallography,vol. 4, The Kynoch Press, Birmingham, 1974. 12 S . R. Hall and J. M. Stewart, eds., The XTAL Users Manual - Version 3.0, Universities of Western Australia and Maryland, 1990. zyxwvuts Paper 1/06420G Received 23rd December 1991 Accepted 20th January 1992