Jatrowediol, a lathyrane diterpene from Jatropha weddelliana

Short Report

Jatrowediol, a Lathyrane Diterpene from Jatropha weddelliana

Rosenei L. Bruma^*, Alberto J. Cavalheiro^b, Franco D. Monache^c and Ivo Vencato^d

^a Departamento de Química / CCET, Universidade Federal de Mato Grosso do Sul, C. P. 549, 79070-900 Campo Grande - MS, Brazil

^b Instituto de Química, Universidade Estadual Paulista de Araraquara, 14801-970 Araraquara - SP, Brazil

^c Centro Chimica dei Recettori del C. N. R., Istituto di Chimica, U.C.S.C., Largo Francesco Vito 1, 00168, Roma, Italy

^d Departamento de Física, Universidade Federal de Goiás, 74001-970 Goiânia - GO, Brazil

A partir das raízes de Jatropha weddelliana foram isolados os diterpenóides jatrogrossidiona, 4Z-jatrogrossidentadiona, 15-epi-4Z-jatrogrossidentadiona, 4E-jatrogrossidentadiona,15-epi-4E-jatrogrossidentadiona, 2-hidroxiisojatrogrossidiona, 2-epi-hidroxiisojatrogrossidiona e jatrowediol. A elucidação da estrutura do jatrowediol, um novo diterpenóide latirânico, foi realizada por meio de análises por técnicas de RMN e de difração de raios-X.

Jatrogrossidion, 4Z-jatrogrossidentadion, 15-epi-4Z-jatrogrossidentadion, 4E-jatrogrossidentadion,15-epi-4E-jatrogrossidentadion, 2-hydroxyisojatrogrossidion, 2-epi-hydroxyisojatrogrossidion and jatrowediol have been isolated from the stems of Jatropha weddelliana. The elucidation of the structure of the latter, a novel lathyrane, was accomplished by detailed NMR investigation and X-ray diffraction analysis.

Keywords: Jatropha weddelliana, Euphorbiaceae, diterpene, lathyrane, jatrowediol, Pantanal, X-ray diffraction analysis

Introduction

Jatropha weddelliana is a shrub found in calcimorphic and dry soils of the highlands of the bearing the pantanal of Mato Grosso do Sul, Brazil¹.

In this work we describe the chemical studies with the dichloromethane extract of the stems of J. weddelliana, that yielded a novel lathyrane diterpene, jatrowediol (1), and other seven known diterpenes: jatrogrossidion (2)², 4Z-jatrogrossidentadion (3)², 15-epi-4Z-jatrogrossidentadion (4)², 4E-jatrogrossidentadion (5)², 15-epi-4E-jatrogrossiden-tadion (6)^2,3, 2-hydroxyisojatrogrossidion (7)², and 2-epi-hydroxyisojatrogrossidion (8)².

Experimental

General experimental procedures

¹H, ¹³C NMR, DEPT, HETCOR, NOE and INEPT experiments: Bruker AM 300 and Varian Gemini 300 spectrometers; UV spectra: Hitachi U 3000 spectrometer; FT-IR spectra: BOMEN MB spectrometer; EI/MS and ES/MS Mass spectra: FISONS VG Plataform II spectrometer, 70 eV.

Extraction and isolation

The powdered stems (2.3 kg) were exhaustively extracted with cold hexane and CH₂Cl₂. Repeated CC (silica gel; hexane with increasing amounts of Me₂CO) of the CH₂Cl₂ extract (73.4 g) afforded 1 (166.2 mg), 2 (8.7 mg), 3 (34 mg), 4 (10 mg), 5 (16 mg), 6 (92 mg), a mixture of 7 and 8 (140 mg) and 8 (20.5 mg).

Jatrowediol (1): white, amorphous powder, subl. at 220 ^oC. [a]_D²⁰ +52.7 (c 2.0, CHCl₃); UV, l_max /nm (CHCl₃): 239.5; IR (n_max/cm^-1): 3518-3407 (OH), 1716 (C=O) (KBr); ESMS (m/z) : 334 [M]⁺ (0), 333 [M - H]⁺ (14), 335 [M + H]⁺ (17.5), 357 [M + Na]⁺ (9.0), 373 [M + K]⁺ (8.9), 352 [M + H₂O]⁺ (5.7), 316 [M - H₂O]⁺ (17.8), 299 [M - 2H₂O + H]⁺ (26); ¹H NMR (C₅D₅N) and ¹³C NMR (C₅D₅N) : see Table 1.

Jatrogrossidion (2): colourless crystals, subl. at 230^oC. ESMS (m/z) : 332 [M]⁺ (0), 333 [M + H]⁺ (100), 355 [M+Na]⁺ (25.3), 371 [M+ K]⁺ (18.4), 315 [M- H₂O + H]⁺ (95.1), 297 [M- 2H₂O + H]⁺ (53.6). ¹H- and ¹³C NMR data identical to the literature².

4Z-Jatrogrossidentadion (3): colourless crystals, m.p. 167-168 ^oC; UV l_max /nm (CHCl₃): 239; IR (n_max/cm^-1): 3409 (OH), 1710, 1676, 1632 (C=O, C=C-C=O) (KBr); EIMS (m/z) : 332 [M]⁺ (0), 314 [M- H₂O]⁺ (3.6), 271 (9.3), 163 (41.1), 69 (86.9), 67 (100); ¹³C NMR (CDCl₃): d 153,8 (C-1), 146.7 (C-2), 196.4 (C-3), 134.6 (C-4), 149.0 (C-5), 73.9 (C-6), 43.5 (C-7), 18.9 (C-8), 24.8 (C-9), 16.8 (C-10), 22.0 (C-11), 28.3 (C-12), 37,2 (C-13), 210,8 (C-14), 84.1 (C-15), 10.8 (C-16), 29.0 (C-17), 28.6 (C-18), 15.4 (C-19), 19.4 (C-20). The assignments for C-1 and C-5 have been revised with respect to the literature².

15-epi-4Z-Jatrogrossidetadion (4): yellow solid; IR (n_max/cm^-1): 3426 (OH), 1698, 1653 (C=O, C=C-C=O) (CHCl₃ film); ESMS (m/z): 332 [M]⁺ (0), 355 [M + Na]⁺ (6.7), 371 [M+ K]⁺ (7.8), 297 [M- 2H₂O + H]⁺ (9.5); ¹H- and ¹³C NMR data identical to the literature².

4-E-Jatrogrossidentadione (5): colourless crystals, m.p. 181-182 ^oC; UV l_max /nm (CHCl₃): 243; IR (n_max/cm^-1): 3488 (OH), 1709, 1697, 1645 (C=O, C=C-C=O) (KBr); ¹³C NMR (CDCl₃) : d 150.7 (C-1), 145.3 (C-2), 195.8 (C-3), 132.3 (C-4), 149.0 (C-5), 73.5 (C-6), 38.7 (C-7), 18.0 (C-8), 27.4 (C-9), 17.8 (C-10), 20.0 (C-11), 29.9 (C-12), 43.6 (C-13), 213.5 (C-14), 85.1 (C-15), 10.7 (C-16), 28.6 (C-17), 29.1 (C-18), 15.0 (C-19), 16.7 (C-20). The assignements for the pairs C-2 and C-5, C-7, C-13, Me-17 and Me-18, have been revised with respect to the literature².

15-epi-4E-Jatrogrossidentadione (6): colourless crystals, m.p. 173-174 ^oC; UV l_max /nm (CHCl₃): 259; IR (n_max/cm^-1): 3320 (OH), 1722, 1699, 1647, 1629 (C=O, C=C-C=O) (KBr); ESMS (m/z): 332 [M]⁺ (0), 333 [M + H]⁺ (27.6), 355 [M + Na] ⁺ (44), 371 [M + K]⁺ (9.8), 315 [M-H₂O + H]⁺ (100), 297 [M- 2H₂O + H]⁺ (38.9); ¹H- and ¹³C NMR data identical to the literature^2,3.

2- Hydroxyisojatrogrossidion (7): yellow solid material. ESMS (m/z) : 332 [M]+. I IR (n_max/cm^-1): 3407 (OH), 1721 (C=O) (CHCl₃); ¹H- and ¹³C NMR data identical to the literature².

2-epi-Hydroxyisojatrogrossidion (8): white, amorphous powder, m.p. 181-182^oC; UV l_max /nm (CHCl₃): 250; IR (n_max/cm^-1): 3482 (OH), 1721, 1698 (C=O, C=C-C=O) (KBr); ESMS (m/z) : 332 [M]⁺ (0), 333 [M + H]⁺ (43.8), 315 [M- H₂O+ H]⁺ (100), 297 [M - 2H₂O + H]⁺ (28.9) 355 [M + Na]⁺ (10.9), 371 [M + K]⁺ (6.8); ¹H- and ¹³C NMR data identical to the literature².

X-ray crystal structure analysis of 1

A colourless plate single crystal (0.50 x 0.33 x 0.07 mm) of 1 (C₂₀H₃₀O₄) was mounted on an Enraf-Nonius CAD-4 diffractometer with graphite-monochromated Mo Ka radiation and w-2q scan-technique. The unit cell and the orientation matrix for the data collection were obtained by a least-squares fit of 25 centered reflections (8.69 < q < 14.1^o). The intensities of three standard reflections were measured every 60 min and varied about 1.0% throughout the experiment. The intensity data were corrected for Lorentz and polarization effects, but not absorption corrections [m(Mo-Ka = 0.080 mm^-1]. The number of measured reflections was 4930 in the range -10£ h£10, -9£k£12, 0£l£46, with 3530 unique reflections, and 2529 with the condition I ³2s(I) were considered observed. Equivalent reflections were merged with R_int = 3.27%. Crystal data: orthorhombic, P2₁2₁2₁ (no.19), a = 8.833 (2), b = 10.749(2), c = 39.837(8) A°, Z = 8, with two independent molecules in the asymmetric unit. The structure was solved by means of direct methods using SHELXS97 computer program⁴ and refined by full-matrix least-squares techniques on F² with SHELXL97 computer program⁵. H atoms were placed geometrically except those on the hydroxyl groups. The final refinement gave R (on F) factor of 0.055, wR (on F²) = 0.152 for 446 refined parameters.

Results and Discussion

Jatrowediol (1) was obtained from the dichloromethane extract of the stems of J. weddelliana as a dextrorotatory powder. The molecular formula C₂₀H₃₀O₄ was deduced from the NMR data and the molecular ion ([M+1] at m/z 335) from the Electron Spray Mass Spectrum. The IR spectrum indicated the presence of carbonyl (1716 cm^-1) and hydroxyl groups (3495 cm^-1). The UV spectrum in CHCl₃ afforded a l_max at 239.5 nm (-C=C-C=O). The ¹³C NMR and DEPT spectra presented twenty carbon signals, including characteristic signals due to a trisubstituted double bond (d_C 154.3 and 140.4), two carbonyls (d_C 210.5 and 213.3), two carbinols hydroxyls (d_C 71.5 and 85.9), five methyls, four methylenes, four methines and a quaternary carbon. Triplets at d_H 0.34 (t, 1H) and 0.79 (lt, 1H) in the ¹H NMR spectrum suggested the presence of a cyclopropane moiety in the molecule. The unambiguous assignment of the protonated carbons was obtained by the HETCOR measurements (Table 1) and decoupling experiments, while that of quaternary carbons came from the long-range HETCOR spectrum and selective INEPT experiments (Table 2). Together, the above data suggested a lathyrane gross structure for 1.

The relative stereochemistry of methyl groups and of carbons C-6 to C-15 was confirmed by a series of difference NOE experiments (Table 3). However, the stereochemistry of cyclopentanone ring junction with the macrocycle could not be confirmed. The signal at d_H 8.0 could not be unambiguously assigned as refering to the hydroxyl on C-15 or on C-6 or both. The absolute configuration of 1 was determined by single a crystal X-ray analysis (Figure 1). The two independent molecules of the asymmetric unit have the same absolute configuration.

Compounds 2-8^2-3 were also isolated from the dichloromethane extract of the stems and identified by 2D NMR experiments. In particular, some assignments of the carbon signals for compounds 3 and 5 have been revised.

Acknowledgments

The authors are indebted to CNPq, PROPP / UFMS, PRONEX and also to the Chemistry Department of UFSC for the X-ray single crystal data collection.

Supplementary Material

Crystallographic data (excluding structure factors) for the structures in this paper have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication no CCDC 15883. Copies of the data can be obtained, free of charge, on application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK, (fax: [phone] or e-mail: [e-mail]).

Received: December 09, 1999

Published on the web: February 21, 2001

FAPESP helped in meeting the publication costs of this article.

• 1 Pott, A.; Pott, V. J. Plantas do Pantanal EMBRAPA, Corumbá, 1994
• 2. Schmeda-Hirschmann, G.; Tsichritzis, F.; Jakupovic, J. Phytochemistry 1992, 31, 1731.
• 3. Aiyelaagbe, O. O.; Gloer, J. B.; Adesogan, E. K.; Ekundayo, O. Fitoterapia 1998, 69, 381.
• 4. Sheldrick, G. M. SHELXS97. Program for the Solution of Crystal Structures. University of Göttingen, Germany, 1990
• 5. Sheldrick, G. M. SHELXL97. Program for the Refinement of Crystal Structures University of Göttingen, Germany, 1997
• 6. Zsolnai, L.; Pritzkow, H. & Huttner, G. ZORTEP University of Heidelberg, Germany, 1996

Publication Dates

• Publication in this collection
  02 July 2001
• Date of issue
  Apr 2001

History

• Received
  12 Sept 1999