Two diterpenes from Euphorbia sieboldiana

Short Reports

atmosphere. A soln of TBHP (0.2 ml, 70%) in dry CH,CI, (3 ml) was added dropwise. The colour of the reaction mixture changed to brown. It was further stirred for 15 min at the same tempera-

ture, diluted with H,O, extracted with CH,CI,, washed with H,O and dried (Na,SO,). Evapn of the solvent under red. pres. gave a crystalline compound (5, 0.8 g) mp 164” identical in all respects to the natural product (5). Reaction ofisotelekin with PBA. A soln of isotelekin (1, 0.4 g) was reacted with an excess of PBA soln in CHCI,. The reaction mixture was kept at 0” overnight. After usual work-up, evapn of the solvent afforded a mixture of two components (0.38 g) separated by chromatography. Elution of the column with petrol--Et,0 (1: 1) yielded a pure crystalline compound (2, 0.26 g). mp 180” identical in all respects to the natural product (2, IR, NMR and mmp). Further elution of the column with the same solvent yielded a solid crystalline compound (3,O.lO g), mp 160”. IR Y,,, cn- I: 3490,1750,1660,1450,1370,1130,1050,960 and 810. (Found C: 68.09; H: 7.57; C,,H,,O, requires C: 68.16; H: 7.62%). Reaction of isotelekin with TBHP/VO(acac),. To a soln of isotelekin (1, 0.25 g) in CH,Cl, (7 ml) was added VO (acac)z (10 mg) and the green reaction mixture was stirred at room temp. under an inert atmosphere. A soln of TBHP (0.35 ml, 70%) in dry CH,Cl, (3 ml) was added dropwise. After usual work-up, evapn of the solvent under red. pres. afforded a pure white crystalline compound (0.23 g) mp 180” identical IR, NMR and mp with compound 2.

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Acetylation ofisotelekin oxide. Isotelekin oxide (2,0.15 g) was treated with pyridine (2 ml) and Ac,O (1.0 ml). After 2 hr at room temp. it was diluted with H,O and extracted with Et,O. The Et20 extracts were washed with dilute HCI, H,O and dried (Na,SO,). Evaporation of the solvent afforded a single liquid compound (8, 0.14 g) which showed IR v,,, cm-’ 1765, 1735, 1660,1450,1370,1240,1150,1030,950 and 810. ‘HNMR: 60.97 (s, 3H), 2.06 (s, 3H), 2.70 and 2.83 (d, 1H each, J=5 Hz), 4.56 (m, lH), 4.63 (br s, IH) and 5.65 and 6.20 (s, 1H each). Acknowledgement-One of us (RG) Research Centre, Trombay, (India) support.

thanks Bhabha Atomic for providing financial

REFERENCES

1. Tsuada, K, Tanabe, K, Iwai; I. and Funakoshi, K (1957). J. Am. Chem. Sot. 19, 5721. 2. Miller, R. B. and Nash R. D. (1974) Tetrahedron 30, 2961. 3. Kaur, B. and Kalsi, P. S. (1985) Phytochemistry 24, 2007. 4. Kalsi, P. S., Goyal, R; Talwar, K. K. and Chhabra, B. R. (1988) Phytochemistry 27, 2079. 5. Kalsi, P. S., Goyal, R., Talwar, K. K. and Chhabra, B. R. (1989) Phytochemistry 28, 2093. 6. Sharpless, K. B. and Verhoeven, T. R. (1979) Aldrichima Acta 12, 4.

Phytochemistry,Vol. 29, No. 7, pp. 2343-2345, 1990 Printedin Great Britain.

0

0031&9422/90 $3.00+0.00 1990 PergamonPressplc

TWO DITERPENES FROM EUPHORBIA SIEBOLDIANA ZHONG-JIAN

Institute

JIA,* YI-LI

of Organic

DING,

Chemistry,

QI-GUANG

Lanzhou

WANG

University,

and

Yu-TING

Lanzhou-730000,

LIU~ China

(Received 26 October 1989) Key Word Index-Euphorbia

sieboldiana; Euphorbiaceae;

diterpenes;

em-atis-16-ene

derivatives

Abstract-From the acetone extract of roots of Euphorbia sieboldiana, two new diterpenes have been isolated and their structures determined as ent-13R-hydroxy-atis-16-en-3,14-dione and ent-13,3/?-dihydroxy-14-oxo-atis-16-ene on the basis of chemical and spectral evidence together with X-ray diffraction studies.

INTRODUCTION

Recently, a number of biological active diterpenes lated from the Euphorbiaceae have attracted interest

iso[ 11.

*Author to whom correspondence should be addressed. tPresent address: Chemistry Department of XingJiang University, Wulumuqi, China.

Euphorbia sieboldiana, a perennial herb, is widely distributed in northwestern China and is used as an insecticide and a local analgensic. Its chemical constituents have not previously been investigated. From the acetone extract of the dried roots of this plant, we have isolated two new atis-16-ene type diterpenes (1, 2). In this communication we report the isolation and structure elucidation of these compounds.

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Short Reports

RJ 1

R1 =

-"-O,R 2=

H

2 R1 = OH. Ra = H 3 R1 = "--'-O.R a = Ac

RESULTS AND DISCUSSION

C o m p o u n d 1, molecular formular C20H2803 (elemental analysis and mass spectrum) exhibited in its IR spectrum signals for two carbonyl groups (1726 and 1696.9 cm-1), an hydroxy group (3432.6 cm-1) and an exocyclic methylene group (3070.2, 1665.5 and 848.5 cm-1). In its 1H N M R spectrum signals were exhibited for three tertiary methyl groups (6 1.09, 1.01 and 0.85 each 3H s), an exocyclic methylene group (6 5.02, d, 1H and 4.86, d, 1H, J = 0 . 8 Hz) and a proton on the methine carbon atom bearing an oxygen atom (6 3.88, d, 1H, J = 2.9 Hz). It was shown to contain three Me, seven CH2, four C H and six C by means of 13C N M R and D E P T spectra (Table 1). All the above data may be accommodated most readily, albeit not exclusively, in a tetracyclic, mono-olefinic, diterpenic structure of the ent-kaur- 16-ene or ent-atis- 16ene type with a carbonyl group on C-3 [2, 3]. However, the 1H N M R signal pattern, demonstrated by the exocyclic methylene group (see above), would be expected for a C-15 hydroxylated (or esterified) ent-kaur-16-ene compound [4]. Nevertheless, these signals are normal in all ent-atis-16-ene derivatives [-5] and the signal exhibited at 6 3.88 (d, J = 2.9 Hz) suggested that the hydroxy group was not located at C-15, and we could eliminate the first skeleton. After acetylation of 1, the chemical shifts exhibited by a carbonyl carbon and a methine carbon in the 13C N M R spectrum had changed (from 6 218.32 to 211.76 and from 6 44.79 to 43.00, see Table 1), indicating that the hydroxy group in 1 was adjacent to a carbonyl group and a CH, and that the hydroxy group was located at C-I 3 and the carbonyl group was located at C-14 [6]. Considering these facts,

Table C

1

1 36.68 2 34.06 3 216.23 4 47.29 5 55.07 6 19.93 7 30.39 8 47.48 9 51.07 10 37.54 MeCO

2

C

36.45 29.90 78.87 CH 38.70 54.06 18.84 30.83 47.43 52.02 37,84

1.

we presumed the structure to be ent-13-hydroxy-atis-16en-3,14-dione. This structure was confirmed by X-ray diffraction which also showed that the hydroxy group was in the R configuration. C o m p o u n d 2, molecular formular C2oH3oO 3 (elemental analysis and mass spectrum), exhibited in its IR spectrum signals for a carbonyl group (1714.9 cm-1), a hydroxy group (3495.5 and 3393.8 c m - 1) and an exocyclic methylene group (3069.9, 1656.1 and 895.4 c m - 1). In its 1H N M R spectrum signals were exhibited for three tertiary methyl groups (60.99, 0.76 and 0.65 each 3H, s), for an exocyclic methylene group (64.996, 1H, d, and 4.835, 1H, d, J = 1.2 Hz) and for two protons on methine carbon atoms bearing an oxygen atom (3 3.85, 1H, d, J = 3 Hz and 3.21, 1H, dd, J = 11.6, 4.4 Hz). Its 13C N M R and D E P T spectra suggested that it contained three Me, seven C H 2, five C H and five C (Table 1). Accordingly, 2 was also a tetracyclic diterpene, and was an ent-atis-16ene rather than a ent-kaur-16-ene as deduced from the characteristic splitting of the tH N M R signals due to the exomethylene group (see above) I-7]. By comparing the 13C and 1H N M R spectra with those of 1, we deduced that there was an hydroxy group located at C-3 whilst the rest of the structure was as for 1. F r o m the 1H N M R signal exhibited at 63.21 (1H, dd, J = l l . 6 , 4.4 Hz), we determined that the hydroxy group at C-3 was in the fl configuration [8]. Thus, we identified 2 as ent-13R,3fldihydroxy-14-oxo-atis-16-ene. C o m p o u n d 1 and 2 belong to a small group of nitrogen-free natural substances with this hydrocarbon skeleton [9, 10]. EXPERIMENTAL

Mps: uncorr.; 1H and 13CNMR: 400 and 100.16MHz respectively, CDC13 with TMS as int. standard. MS: direct inlet, 70 eV. Plant material was collected in August of 1988, at Lanzhou city, Gansu. Plants were identified by Professor Runeng Zhao, and a voucher specimen is deposited in the Herbarium of the Biology Department, Lanzhou University. Extraction and isolation. Air-dried roots (10 kg) were extracted (×4) with MezCO. The extract was concd and 50% of the fraction chromatographed on a silica gel column eluted with a gradient of petrol and M%CO to produce four fractions. Fraction 3 was rechromatographed on a silica gel column, eluted with petrol-MezCO-MeCO2Et-Et20 (20:1 : 1 : 1 l : 1 : ! :1) to give 1 (30 mg) and 2 (15 mg).

13C NMR spectral data for compounds 3 36.96 33.96 215.84 47.43 55.17 19.76 30.65 47.62 50.78 37.75

CH 2 CH 2 C C CH CH 2 CH 2 C CH C

1-3"

C

1

2

3

11 12 13 14 15 16 17 18 19 20

25.34 44.79 75.08 218.32 43.63 142.20 111.07 26.15 21.87 13.67

25.31 44.91 75.12 218.23 43.94 142.76 110.75 28.45 15.61 14.07

25.38 43.00 74.62 211.76 42.92 141.55 110.56 25.97 21.78 13.35 170.15 20.73

CH 2 CH CH C CH 2 C CH 2 Me Me Me C Me

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Short Reports

1

Fig. 1. Stereoscopic view of the molecule showing the atom labelling scheme of 1.

=CH,), 3495.5, 3393.8 (two OH). ‘H NMR (CDCI,): see text. ‘“C NMR: see Table 1. Anal. calcd for C,,H,,O,, C 75.47%, H 9.43, found: C 75.22%, H 9.39%. X-Ray data of compound 1. A crystal of dimensions 0.8 x 0.8 x0.6mm was mounted on an Enraf-Nonius CAD4 diffractometer equipped with MO radiation (A= 0.71073 A) and a graphite monochromater. Crystal data: C,,H,sO, MeOH, M,= 346.47, orthorhombic space group: P2,2,&, a=7.4605 (6), b= 12.3552 (6), C=20.5662 (3) A; V=4895.7/j3; Z=4; D,=1.214gcme3; T= 298 K. Data collection: 2” < 20 < 50” p(Mo)=0.77mm-‘; w-28 scan technique; 1950 total reflection, 1684 reflection with 12 30(I) and were corrected for background, Lorentz and polarization effects. This structure was solved by direct methods, using MULTAN-82 and Fourier techniques, refined by full-matrix least-squares. Nonhydrogen atoms were anistropic. A difference Fourier synthesis upon convergence permitted location of 28 hydrogen atoms. In subsequent cycles of refinement the H atoms were assigened fixed isotropic thermal parameters. In the final cycle of refinement R = 0.054, R, = 0.052, and the largest residul electron density was 0.184 eA_j. Acknowledgement-This work was supported by the National Natural Science Foundation of China. REFERENCES

Compound 1. Plates, mp 162-163”, [a]k”=42”, (CHCI,; c 0.52),

EIMS m/z (rel. int.): 316 CM]’ (lOO),301 [M-Me]+ (2%), 298 [M-H,01 + (2), 288 [M-CO]+ (3), 273 (8), 255 (6). IR vkf; cm-‘: 1726, 1696.9 (two C=O), 1665.6, 848.3 (C=CH,), 3432.6 (OH). ‘H NMR (CDCl,): see text; 13C NMR: see Table 1. Anal: calcd for C 20H 280 3, C 75.95%, H 8.86%, found: C 76.16%, H 8.89%. Acetylation of compound 1. A mixture of 15 mg 1 and 1 ml Ac,O-pyridine (1: 1) was allowed to stand at room temp. overnight. After the usual work-up, the crystalline product 3 was obtained. Mp 125-126”, [a]i’=51.5”, (CHCI,; cO.18), EIMS m/z: 358 [M]’ (lo), 330 [M-CO]+ (8), 315 [M-AC]+ (3), 254(15), 43 (100). IR vii; cm-‘: 1746.7,1059.6 (AcO), 1727.3,1696.7 (two C=O), 1657.9, 890.8 (C=CHI). ‘H NMR (CDCI,): 60.91 (3H, s), 1.01 (3H, s), 1.08 (3H, s), 2.11 (3H, s), 5.02 (lH, d, J=2.9 Hz); 4.93 (lH, d, 5=0.7 Hz), 4.82 (lH, d, J=O.7 Hz); 13C NMR: see Table 1. Compound 2. Needles, mp 208-209”, [a];” = 34.9”, (CHCl,; cO.17),EIMS m/z: 318 [M]’ (lOO),300 [M-H,O]+ (15), 285 [M -Me-H,O]+ (12), 275 [M-CO-Me]+ (14), 273 (13), 257 (20); IR v:f: cm- ‘: 1714.9 (C=O), 3069.9, 1656.1, 895.4 (C

1. Yamamura, S., Kosemura, S., Ohba, S., Ito, M. and Saito, Y. (1981) Tetrahedron Letters 5315. 2. Hanson, J. R., Sivems, M., Piozzi, F. and Savona, G. (1976) J. Chem. Sot. Perkin 1. 114, 3. Chalmers, A. A., Gorst-Allman, C. P. and Piacenza, L. P. L. (1977) Tetrahedron Letters 1665. 4. Cannon, J. R., Jefferies, P. R. and Meehan, G. V. (1966) Aust. J. Chem. 19, 861. 5. Kapadi, A. H., Sobti, R. R. and Dev, S. (1965) Tetrahedron Letters 2729. 6. Rodriguez, B., Alemany, A. and Pinar, M. (1978) Tetrahedron Letters 3069. 7. Herz, W., Kulanthaivel, P. and Watanabe, K. (1983) Phyto-

chemistry 22, 2021. 8. Schmitz, F. J., Vanderah, D. J., Hollenbeak, K. H., Enwall, C. E. L. and Gopichand, Y. (1983) J. Org. Chem. 48, 3941. 9. Ayer, W. A., Ball, J-A. H., Rodriguez, B. and Valverde, S. (1974) Can. J. Chem. 52, 2792. 10. Carrascal, I., Rodriguez, B., Valverde, S. and Fayos, J. (1975) Chem. Commun. 815.