Quassinoids and tetranortriterpenoids from Picrolemm granatensis

Phytochemistry, Vol. 34, No. 2, pp. 501-504, 1993

0031-9422/93 $6.00+0.00 © 1993 Pergamon Press Ltd

Printed in Great Britain.

QUASSINOIDS AND TETRANORTRITERPENOIDS FROM PICROLEMMA GRANATENSIS EDSON RODRIGUES FO., Jo,~o B. FERNANDES, PAULO C. VIEIRA and M. F.~TIMA DAS G. F. DA SILVA Departamento de Quimica, Universidade Federal de S~o Carlos, CP 676, 13565-905 S~o Carlos, SP, Brazil

(Received in revisedform 21 January 1993) Key Word Index--Picrolemma granatensis; Simaroubaceae; stem; stem bark; tetranortriterpenoids; quassinoids.

Abstract--From the stem bark of Picrolemma #ranatensis were isolated two novel tetranortriterpenoids: 7at,21dihydroxy-3-oxo-24,25,26,27-tetranorapotirucall-14,20(22)-dien-21,23-olide and 7~,21-dihydroxy-3-oxo-24,25,26,27tetranorapotirucall-l,14,20(22)-trien-21,23-olide which were identified on the basis of spectroscopic and chemical methods. The triterpene melianodiol, the quassinoids simalikalactone-D, 2'-epi-simalikalactone-D and ailanthinone, the sterols sitosterol, stigmasterol and campesteroi were also identified.

INTRODUCTION

In a previous paper, we reported the isolation and structural elucidation of five canthin-6-one alkaloids from Picrolemma #ranatensis, two of which were novel, 8-hydroxy-9-methoxycanthin-6-one and 9-methoxycanthin-6-one-3N-oxide [1]. During our continued investigation, two new tetranortriterpenoids along with three known quassinoids have been isolated. This appears to be the first record of tetranortriterpenoids with a ~,-hydroxybutenolide side-chain from the Simaroubaceae. They have been reported previously from the Meliaceae and Rutaceae [2]. RESULTS AND DISCUSSION

Further examination of the stem and stem bark led to isolation of six additional compounds and a mixture of sterols. The mixture, obtained from the stem bark, was acetylated with acetic anhydride in pyridine and analysed by GC-mass spectrometry, which established that the sterols were sitosterol, stigmasterol and campesterol. Of the six compounds, two were identified as the known triterpene melianodiol [3] (from stem bark) and the quassinoid ailanthinone [4]. The latter was obtained, from stem, in a mixture with simalikalactone-D and its 2'epi-simalikalactone-D, which was first acetylated and the corresponding acetates purified by preparative TLC. Compound 1 was isolated from stem bark as small needles and exhibited similar spectral data to 21-acetyltosendantriol (5) [5]. The 1H NMR spectrum, instead of signals for a side-chain related to that of 5, showed two broad singlets at 65.92 (H-21) and 6.00 (H-22) for a 7hydroxybutyrolactone. This was corroborated by the 13C N M R spectrum (Table 1) which showed signals for a hemiaketal carbon (698.5, C-21) and an u,fl-unsaturated3,-lactone (6166.6, C-20; 119.6, C-22 and 170.8, C-23). 501 PHYTO 34:2-H

These signals required the presence of a 21-hydroxy20(22)-ene-21,23-7-1actone by comparison with the 1H and I3C NMR data published for isolimocinolide (6) [6]. Moreover, the chemical shifts of the ring A - D carbons were comparable with those reported for 5 [5]. The new natural product is therefore 7ct,21-dihydroxy-3-oxo24,25,26,27-tetranorapotirucall- 14,20(22)-dien-21,23olide (1). A second fraction of the stem bark afforded compound I in addition to a small amount of compound 2 that could not be separated. Additional to the data described above for compound I, detected in the ~H NMR of this mixture was a pair of doublets (65.81, H-2 and 7.09, H-I) that, together with the signals at 6205.1 (C-3), 157.5 (C-I) and 125.7 (C-2) in the ~3C NMR (Table 1), indicated an enone in the A ring as observed for nimbocinol [7]. Thus, the structure of the new tetranortriterpene was characterized as 7~t,21-dihydroxy-3-oxo-24,25,26,27-tetranora potirucall- 1,14,20(22)-trien-21,23-olide (2). Acetylation of 1 and 2 with acetic anhydride in pyridine gave acetates la and 2a which confirmed the presence of a hydroxyl group at C-7 and, by the shift of the vinyl proton H-15, a double bond at C-14 I-8]. A third fraction from stem bark gave an amorphous solid which exhibited similar NMR spectra to simalikalactone-D (3) except for the signals relative to the side chain at C-15. In the ~HNMR, the signals for methyl groups 4' and 5' appeared, respectively, as two triplets and two doublets. The xaC NMR spectrum also showed the presence of double signals for C-5' and C-4'. On acetylation, all the 13C NMR chemical shifts for the side chain (C-1'-C-5') were duplicated (Table 1). In addition, broad signals were obtained for C-14 and C-15. These observations suggest that the amorphous solid is a mixture of two isomers. Thus, they were characterized as simalikalactone-D (3) [4] and 2'-epi-simalikalactone-D.

E. RODRIGUESFO. et al.

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The corresponding C-2' ¢pimer could be an artefact of the isolation procedures. However, the stem examined as above gave both isomers, ailanthinone and no 2'-epiailanthinone. These observations provided conclusive evidence that 2'-epi-simalikalactone-D is a naturally occurring compound and not an artefact. The ~,-hydroxybutenolides may be considered an intermediate stage in the formation of the furan ring or a singlet oxygen oxidation product of the furan present in most of the limonoids isolated [8, 9]. Limonoids, commonly associated with the Meliaceae, Rutaceae and Cneoraceae had not been reported from the Simaroubaceae until recently. However, obacunone and harrisonin have been reported from Harrisonia abyssinica [10, 11] and perforatin from H. perforata [12]. If Harrisonia properly belongs to the Simaroubaceae [13] and if enzymically limonoids can be converted to the y-hydroxybutenolides 1 and 2, further reports of the co-occurrence of quassinoids and limonoids in the Simaroubaceae may be expected.

EXPERIMENTAL General. IR (KBr, BOMEM-FtlR). UV (Perkin Elmer). IH and 13C N M R at 200 and 50 MHz, respectively, TMS as standard. Mp at K6ffler on microscope. MS low resolution on a HP-2576 instrument. Plant material. Picrolemma granatensis was collected in the Colombian Amazon by W. Thomas and a voucher

specimen is deposited at the New York Botanical Garden (W. Thomas 5485). The extraction procedure was described previously [1]. Separation and identification. The CH2CI z extract of the stem bark was chromatographed over silica gel using a CH2CI2-EtOAc-MeOH gradient (column A). The initial fr. (99:1 : 0) yielded, after crystallization on MeOH, an amorphous solid characterized as a mixt. (87 rag) of sitosterol, campesterol and stigmasterol. Elution of column A with CH2CI2-EtOAc-MeOH (94:3:3) gave, after crystallization on MeOH, 29 mg of needles of melianodiol. After continued elution with (94: 3: 3) a fr. (37 mg) was obtained and rechromatographed firstly by silica gel flash CC and then by prep. TLC on neutral alumina, hexane-CHC13-i-PrOH-MeOH (50:45:3:2) with continuous elution over 5.3 hr to yield 11 mg of pure 1 and 3.5 mg of a mixt. of I and 2. After spectroscopic analysis, the sample containing 1 and 2 was allowed to react overnight with an excess of Ac2O in pyridine. Work-up as usual yielded the 7,21diacetates la and 2a (4.3 rag). The ft. eluted with CH2CI2-EtOAc-MeOH (45: 3:2) yielded 58 mg of a crude fr. which was rechromatographed on silica gel flash CC (93:4:3) and then recrystallized in MeOH yielding 45 mg of the epimers simalikalactone-D and 2'-epi-simalikalactone-D. From the stem, the fr. eluted with the same eluent above, (93:4:3) (23 rag) was acylated with Ac20 in pyridine and then sepd by prep. TLC with CHCI3-MeOH (49:1) yielding 9 mg of ailanthinone 1,12,30-triacetate (4a) and 10 mg of simalik-

Constituents of Picrolemma #ranatensis

503

Table L 13CNMR data of compounds 1-3a*

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 28 29 30 1' 2' 3' 4' 5'

1

la

2

2a

38.5t 33.9t 217.4s 46.9s 46.4d 24.9 t 72.1 t 44.4s 41.Od 37.1 s 16.2t 32.9 t 47.7s 160.8s 119.6d 33.3 t 52.6d 15.0q 20.8q 166.6s 98.5 d 119.6d 170.8s 21.1 q 29.7q 27.1 q ------

38.7 33.9 216.4 46.9 42.2 25.9 74.8 46.1 46.9 37.0 16.4 39.9 48.1 158.4 118.6 33.3 52.8 15.1 19.7 166.9 93.3 120.0 169.0 20.9 29.7 27.4 ------

158.3d 125.6d 204.9 s 45.1 s 44.4d 24.3 t 71.6d 44.2s 41.Od 40.1 s 16.2t 32.9 t 47.6s 160.6 s 119.7d 33.3 s 53.7d 15.0q 18.9q 166.6s 98.5 d 119.7d 170.8d 20.9 q 27.6q 26.3 q ------

157.5 125.7 205.1 44.1 38.3 24.2 74.3 46.1 46.1 39.8 16.4 39.8 47.6 158.2 118.8 33.3 52.8 13.6 19.6 166.7 93.3 120.2 169.0 20.6 27.1 27.0 ------

3

81.6d 197.5s 124.2d 163.7s 43.5d 28.2 t 83.1 d 47.7s 42.2d 45.8 s 74.3d 79.1 d 80.5s 52.3d 67.0d 167.8 s -23.0q ll.4q -----22.6q 71.7 t 175.5s 41.0 d 26.6/26.5t 11.6 q 16.6/16.3 q

3a

83.1 190.6 126.0 160.2 43.1 27.6 82.7 45.9 42.1 45.4 78.8 70.7 79.7 52.9 66.3 166.8 -22.7 11.9

-22.4 72.2 175.0 41.0/40.8 26.7/26.3 11.6/11.5 16.6/16.3

*CDCI a, 50 MHz. Multiplicity obtained by DEPT-135 or J-MOD. alactone-D 1,12-diacetate (3a) and 2'-epi-simalikalactone-D 1,12-diacetate. 7ct,21-Dihydroxy-3-oxo-24,25,26,27-tetranorapotirucall-14,20(22)-dien-21,23-olide (1). Amorphous solid, m p 168-172 °. [~t]D+24 ° (CHCI3; c 0.093). UV --max'~EtOHnm (Ioge): 230 (3.51). IR Vm,, KSr c m - l : 3560, 2963, 2924, 2856, 1761, 1702, 1653, 1463, 1392, 1129, 958, 703, 549. MS m/z (rel. int.); 411 [ M - O H ] ÷ (0.I), 378(0.1), 304(3), 302(10), 242(2), 226(1), 216(1), 199(2), 183(3), 175(3), 169(3), 159(4), 149(14), 143(6), 137(6), 131(9), 123(11), 109(15), 105(22), 95(19), 91(31), 83(17), 79(28), 77(21), 69(37), 55(100), 43(95). 1H N M R (CDCIa, 200 MHz): 8 3.97 (H-7, t, J = 2 Hz), 5.55 (H-15, m), 2.80 (H-17, dd, J = 9 , 6Hz), 5.92 (H-21, brs), 6.00 (H-22, br s), 1.22, 1.12, 1.08, 1.03 and 0.99 (Me, s). 13CNMR (&CDC13, 50 MHz): Table 1. 7ct,21-Diacetoxy-3-oxo-24,25,26,27-tetranorapotirucall-14,20(22)-dien-21,23-olide (la). 1H N M R (CDCI3, 200 MHz): 85.35 (H-7, m), 5.23 (H-15, m), 6.85 (H-21, d, J = 1.5 Hz), 5.99 (H-22, br s), 1.23, 1.19, 1.16, 1.05 and 1.01 (Me, s). 7~t,21-Dihydroxy,3-oxo-24,25,26,27-tetranorapotirucall-l,14,20(22)-trien-21,23-olide (2). IR Vm,x Ks, c m - I: 1697. UV 2~t°ffnm (loge): 230 (3.51). 1 H N M R (&CDCI3, 200MHz): 7.09 (H-I, d, J = 1 0 H z ) , 5.81 (H-2, d, J = 10 Hz), 4.00 (H-7, t, J = 2 Hz), 5.57 (H-15, m), 2.86 (H-

17, dd, J = 9, 6 Hz), 5.93 (H-21, br s), 6.01 (H-22, br s), 1.17, 1.16, 1.14, 1.01 and 0.99 (Me, s). 13CNMR (&CDCI3, 50 MHz): Table 1. 7ct,21-Diacetoxy-3-oxo-24,25,26,27-tetranorapotirucall-l,14,20(22)-trien-21,23-olide (2a). 1 H N M R (CDCI3, 200MHz): 87.10 (H-I, d, J = 1 0 H z ) , 5.82 (H-2, d, J = 10 Hz), 5.36 (H-7, m), 5.23 (H-15,.m), 6.84 (H-21, d, J = 1.8 Hz), 5.99 (H-22, br s), 1.46, 1.40, 1.25, 1.24 and 1.25 (Me, s) Simalikalactone D (3)/2'-epi-simalikalactone-D (3'). Amorphous solid (MeOH), m p 230-233 °. [~]D+28 ° (EtOH; c 0.049). UV 2et°ffnm (loge): 239(4.01). IR vm,,Ker_me- 1.. 3442, 2969, 2932, 2876, 1740, 1664, 1543, 1454, 1382, 1262, 1037, 986, 691. MS m/z (rel. int.): 460 [ M - H 2 0 ] ÷ (0.5), 358(3), 301(5), 285(4), 241(4), 225(6), 189(5), 151(12), 142(8), 135(12), 123(17), 109(12), 102(8), 95(27), 91(19), 85(28), 83(12), 79(15), 69(21), 57(100), 55(24), 43(52). 1 H N M R (CDCIa, 200 MHz): 84.16 (H-I, s), 6.10 (H-3, m), 2.94 (H-5, d, J = 12 Hz), 2.31 (H-6~t, m), 1.81 (H6fl, m), 4.67 (H-7, t, J =2.7 Hz), 2.31 (H-9, br s), 4.63 (H-12, m), 6.16 (H-15, d, J = 12 Hz), 3.53 (H-30a, br d, J = 6 Hz), 4.62 (H-30b, br d J = 6 Hz), 1.43 (Me- 18, s), I, 18 (Me- 19, s), 1.96 (Me-29, br s), 2.47 (H-2', m), 1.74 (H-3', m), 0.95 and 0.93 (Me-4', t, J = 7.5 Hz), 1.22 and 1.21 (H-5', d, J = 7 Hz). 13CNMR (CDCI3, 50 MHz): Table 1.

504

E. RODRIGUESFO. et al.

Simalikalactone-D 1,12-diacetate (3a)/2'-epi-simalikalactone-D 1,12-diacetate (3'a). Amorphous solid, mp 248-253 °. UV --max ~EtOn nm (log e): 235(3.98). IR vma xtBr cm-t.. 3516, 2977, 2940, 2878, 1744, 1672, 1635, 1437, 1381, 1048, 954, 820, 625. 1H NMR (CDCI 3, 200 MHz): t55.34 (H-l, s), 6.01 (H-3, m), 3.00 (H-5, d, J = 13 Hz), 4.63 (H-7, m), 2.80 (H-9, m), 4.02 (H-11, brs), 4.63 (H-12, m), 6.01 (H-15, m), 4.62 (H-30a, m), 3.56 (H-30b, d, J = 8 Hz), 1.36 (Me-18, s), 1.28 (Me-19, s), 1.90 (Me-29, br s), 1.20 (Me-4', m) and 0.93 (Me-Y, m). l a C N M R (CDCI3, 50 MHz): Table 1. Ailanthinone 1,12,30-triacetate (4). Oil. [~]D+16 ° (CHC13; c0.039). 1H NMR (CDCl a, 200 MHz): 65.12 (H1, m), 6.00-5.98 (H-3, m), 3.13 (H-5, d, J = 12 Hz), 4.83 (H7, t, 2H), 3.38 (H-9, s), 4.93 (H-12, d, J = 2 Hz), 5.86 (H-15, d, J = l0 Hz), 4.63 (H-30a, d, J = 13 Hz), 3.82 (H-30b, d, J =13 Hz), 1.06 (Me-18, d, J = 7 Hz), 1.38 (Me-19, s), 1.93 (Me-29, s), 0.93 (Me-4', t, J = 8 Hz), 1.15 (Me-Y, d, J = 7 Hz). Acknowledgements--The authors are grateful to Conselho Nacional do Desenvolvimento Cientifico e Tecnol6gico (CNPq), Fundaq~o de Amparo ~i Pesquisa do Estado de $5o Paulo (FAPESP) and Financiadora de Estudos e Projetos (FINEP) for the financial support. REFERENCES

1. Rodrigues Fo., E., Fernandes, J. B., da Silva, M. F. das G. F. and Vieira, P. C. (1992) Phytochemistry 31, 2499.

2. Connoly, J. D. (1983) in Chemistry and Chemical Taxonomy of the Rutales (Waterman, P. G. and Grundon, M. F., eds). Academic Press, London. 3. Merrien, A. and Polonsky, J. (1971) Chem. Commun. 261. 4. Waterman, P. G. and Ampofo, S. A. (1984) Planta Med. 261. 5. Banerji, B. and Nigam, S. K. (1984) Fitoterapia 55, 3. 6. Siddiqui, S., Faizi, S., Mahmool, T. and Siddiqui, B. S. (1986) J. Chem. Soc. Perkin I 1021. 7. Gaikwad, B. R., Mayelvaganan, T., Vyas, B. A. and Bhat, S. V. (1990) Phytochemistry 29, 3963. 8. Connolly, O. J., Labb6, C. and Rycroft, D. S. (1979) d. Chem. Soc. Perkin I 2959. 9. Champagne, D. E., Koul, O., Isman, M. B., Scudder, G. G. E. and Towers, G. H. N. (1992) Phytochemistry 31, 377. 10. Hassanali, A., Bentlley, D. M., Slavin, A. M. Z., Williams, D. J., Shepard, R. N. and Chapya, A. W. (1987) Phytochemistry 26, 573. 11. Kubo, I., Tanis, S. P., Lee, Y. W., Miura, I., Nakanishi, K. and Chapya, A. (1976) Heterocycles 5, 485. 12. Byrne, L. T., Tri, M. V., Phuong, A. M., Sargent, M. V., Skelton, B. W. and White, A. H. (1991) Aust. J. Chem. 44, 165. 13. Engler, S. A. (1964) Syllabus der Pflanzenfamilien. Gerbruder Borntrae, Ger, Berlin.