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A sesquiterpene polyol ester from Euonymus sachalinensis
P~y~~c~e~iscry, Vol. 33, No. 2, pp. 503-505, 1993 Printedin Great Britain.
A SESQUITERPENE
003 I-9422,‘93 $6.00 + 0.00 @ 1993 PergamonPress Ltd
POLYOL ESTER FROM EUONYlMUS SACHALlRrENSIS JUDIT HOHMANN,
GABOR NAGY,
GABOR GUNTHER*
Department of Pharmacognosy, Albert Szent-Gyiirgyi Medical University, H-6720 E6tv6s u. 6., Szeged, Hungary; *Department of Pharmaceutical Chemistry, Albert Szent-Gy6rgyi Medical University, Szeged, Hungary (Received in revisedform 9 September 1992)
Key Word Ibex-Euonymus
sachali~~~;
Celastraceae; dihydro-~-agarofuran;
sesquiterpene.
Abstract-A new sesquiterpene ester, euosachalidin-A, was isolated from the fruits of Euonymus sachalinensis, and its structure was elucidated on the basis of spectral analysis. Complete assignment of all ‘H and 13C NMR chemical shifts was achieved via ‘H-‘HCOSY, 1H-‘3CCOSY, NOESY and COLOC experiments.
INTRODUCTION
Sesquiterpenes with a dihydro-&agarofuran skeleton are found in nature in various oxygenated forms and these polyol esters mostly occur in members of the Celastraceae [I]. Some of these compounds exhibit insecticidal, insect antifeedant and cytotoxic activity [2-41. In a search for this type of compound, we have studied the chemical composition of Euonymus sachalinensis fruits. The present paper reports the isolation and structure elucidation of a new sesquiterpene ester, which was named euosach~id~A.
OCOCH, CH_COO
I
oco OCOCH,
RESULTS AND DISCUSSION
The cyclohexene fraction of a methanolic extract of the fruits of Euo~ymus sac~l~ne~sis (F. Schmidt) Maxim (syn. E. pla~i~es Koehne) was subjected to repeated chromatography to afford compound 1. The IR spectrum of 1 contained an ester carbonyl band at 1740 cm-l. Its UV spectrum showed the presence of benzoate moieties. The mass spectrum exhibited peaks due to the loss of acetic and benzoic acid units: m/z 529 [(M +H)+ HOAcJ E33and 467 [(M + H)+ -C$H,COOH] [I]. The ‘HNMR and 13CNMR spectra (Table 1) indicated the presence of five ester groups (ester carbonyls 6165.6-170.7): four acetate (‘HNMR: 62.16, 2.11, 2.02, 1.53; 13CNMR: 622.0,21.7, 21.3,20.4) and one benz,oate ester (‘H NMR: 67.96 d, 7.45 Y, 7.57 ‘t’; 13C NMR: 6130.1, 130.5, 129.3, 134.2). In addition, the ‘%NMR
spectrum showed signals attributed to three methyls (631.2, 25.6, 18.6), two methylenes (661.0, 31.7), five methines (665.8-80.4) and four quaternary carbons (6 198.7,92.4, 84.1, 52.7). In the ‘H NMR spectrum, three methyl proton peaks (S1.52, 1.47, 1.28), four signals (66.36, 5.89, 5.64, 5.49) attributed to hydrogens attached to the carbon atoms bearing the secondary ester groups and an AI3 quartet (65.12,4.66) assigned to the hydrogens in the methylene attached to the carbon atoms bearing primary ester groups were observed. These data sugges-
1
ted that 1 is a sesquiterpene based on the ~hydroagarofuran skeleton [2,5,6’J substituted with five ester groups. On the basis of the multiplicity and the ‘H-‘HCOSY spectrum, the signals at 65.89, 5.49, 6.36, 5.64, 5.12 and 4.66 in the ‘H NMR spectrum of 1 were assigned to H-l, H-2, H-6, H-9 and H,-15, respectively. The shifts of H-3 and H-4, whose signals overlapped in the ‘HNMR spectrum, were ascertained on the basis of the correlation with H-2 and H-14, respectively. Weak 4J couplings were also observed between H-7 and H-12, H-7 and H-13, and H-l and H-9 in the “H-‘H COSY spectrum. The carbon signal at 6198.7 indicated a keto group, which was located on C-8 according to the chemical shifts of H-7 (S3.06) and C-7 (665.8) [2]. It was concluded that 1 is an ester of 8-oxo-1,2,6,9,15-pentahydroxydihydro+-agarofuran. The relative configuration of 1 was confirmed via the NOESY spectrum. The methylene proton signal at 64.66 was correlated with the proton signals at 66.36 (H-6) and 6 1.28 (H-14), and therefore H-6 and the methyl group on C-4 have axial stereochemistry. The cross-peaks between H-l and H-3,,, H-l and H-9, and H-9 and H-12 proved the axial orientation of H-l and H-9, The appearance of a 503
Short Reports
504
Table 1. ‘H (400 MHz) and 13C (100 MHz) NMR spectral data of compound 1 (CD&
TMS as
internal standard) ‘H-‘H COSY correlated with
NOESY correlated with
5.89 d (3.5) 5.49 q (3.2) 2.44 ddd (14.8,6.3, 3.4) &, 1.95 dd (14.8, 2.4) H,, 2.49 m
H-2, H-9 H-l, H-3.,, H-3, H-2 H-2 H-14 -
H-3,,, H-2, H-9 H-3,,, H-3, H-l, H-2, H-3, H-2, H-3,, H-4 H-3, -
6.36 d (0.7) 3.06 d (0.7) -
H-7 H-6, H-12, H-13
H-15b, H-7, H-14 H-6, H-12, H-13 -
Atom
6, (J Hz)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15a lfb Bz 1’ 2:6’ 3,s 4
-
5.64 s 1.41 s 1.52 s 1.28 d (7.5) 5.12 4.66 ABq (12.9)
-
H-12 H-9, H-7 H-7 H-6, H-1Sb H-2,6’, H-15b H-6, H-14, H-t5a
H-4
7.96 br d (7.8) 7.45 Y (7.8) 1.57 9 (7.4)
2-COMe 6-COMe 9-COMe 15-COMe
2.11 2.16 1.53 2.02
I-CO 2x0 &CO 9-co IS-CO
-
H-3, H-5 H-2’, H-6, H-4 H-2’, H-6’, H-3’, H-5
s s s s
high-field acetate methyl singlet at 61.53 suggested an equatorially oriented aromatic ester on C-l and an acetoxy group on C-9, or conversely [3, 5-j. This was substantiated by the correlation between the methyl (6 1.53) and orrko-benzoyl protons (67.96) in the NOESY spectrum. The positions of ester groups were established unambiguously by using 1H-*3C long-range correlation (COLOC) spectroscopy. Cross-peaks were observed between the carbonyl carbon at 6 165.6 and H-l, and thus the benzoyl group must be located on C-l. The longrange couplings of the carbonyl signals at 6169.7, 169.9 and 170.7 with the proton signals at 66.36,5.63 and 5.12 and the acetyl methyl signals at 62.16, 1.53 and 2.02 indicated the presence of acetyl groups on C-6, C-9 and C-15. The fourth acetyl group (‘HNMR: 62.11; ’ 3C NMR: S 170.2 and 22.0) had to be situated on C-2. The full 13C NMR chemical shift assignments were made by means of ‘H-’ 3C COSY spectral analysis, the data are listed in Table 1.
H-l 5% H-9 OAc
H-2’. H-6
76.2 70.7 31.7 342 92.4 75s 65.8 198.7 80.4 52.7 84.1 25.6 31.2 18.6 61.0
130.1 130.5 129.3 134.2 22.0 21.7 20.4 21.3 165.6 170.2 169.7 169.9 170.7
Considering all of the above data for 1 the structure was elucidated to be 8-oxo-l/.%enzoyloxy-2#J,6e,9/3,15tetraacetoxy-dihydro-&agarofuran. Esters of 8-0x01,2,6,9,15-pentahydroxydihydro-j?-agarofuran were known previously [7’J, but derivatives having H-l,,, H-2,,, H-6,, and H-9,, stereochemistry have not been reported earlier, EXPERIMENTAL
Plant material.
The fruits of Euonymus sachalinensis were collected in Sept. 1989 in the Nursery-Garden of Parks and Gardens, Tahi, Budapest, Hungary. A voucher specimen has been deposited in the Herbarium of the Museum of Natural Science, Budapest. Isolation. Fresh fruits (4.8 kg) were extracted with MeOH. The crude extract was concentrated in uacuo to give a residue (125 g) which was partitioned between cyclohexene and HzO. The cyciohexene tayer was chromatograph~ on a polyamide (Woelm) column. Fractions
Short
eluted with MeOH-H,O 3 : 2 were subjected to silica gel CC with mixtures of cyclohexene-EtOAc. The fractions from cyclohexene-EtOAc 4 : 1 yielded 1 (20 mg). Euosachalidin-A (1). Mp 160-162.5” (from MeOHk [ol]~‘+O.~ (CHCl,, ~1.13); UV ET” nm (log 6): 232 (4.641), 269 (3.512), 276 (3.537), 282 (3.479); IR v!%cm-‘: 1740, 1380, 1270, 1220, 1100, 710; ‘H and l ‘C NMR data are given in Table 1; FABMS ( + ve) m/z [origin] (rel. int.): 589 [M + H] + (4), 611 [M + Na] + (18), 547 [(M + H)+ - CH,CO] (l), 529 [(M + H)+ -HOAc] (3), 467 [(M + H)] + - CsH,C02H] (1), 105 [C,H,CO+] (loo). ._a
Acknowledgements-This investigation was subsidized by the National Scientific Research Fund, Project No. F5128. We are grateful to J. Vajda (Central Research Institute for Chemistry, The Hungarian Academy of Sciences, Budapest, Hungary) for the mass spectroscopic measurements.
505
Reports REFERENCES
1. Bruning, R. and Wagner, H. (1978) Phytochemistry 17, 1821. 2. Vichnewski, W., Prasad, J. S. and Herz, W. (1984) Phytochemistry 23, 1655. 3. Tu, Y. Q., Wu, D. G., Zhoy J., Chen, Y. Z. and Pan, X. F. (1990) J. Nat. Prod. 53,603. 4. Kuo, Y. H., Chen, C. H., Kuo, L. M. Y., King, M. L., Wu, T. S., Haruna, M. and Lee, K. H. (1990) J. Nut. Prod. 53,422. 5. Tu, Y. Q. (1990) J. Nat. Prod. 53, 915. 6. R6zsa, Zs. and Pelczer, I. (1989) 1. C&m. Sot., Perkin Trans I 1089. 7 Gonzalez, A. G., Nunez, M. P., Ravelo, A. G., Luis, ’ J. G., Jimenez, I. A., Vzizquez, J. T. and Munoz, 0. M. (1989) Heterocycles 29, 2287.
A SESQUITERPENE
003 I-9422,‘93 $6.00 + 0.00 @ 1993 PergamonPress Ltd
POLYOL ESTER FROM EUONYlMUS SACHALlRrENSIS JUDIT HOHMANN,
GABOR NAGY,
GABOR GUNTHER*
Department of Pharmacognosy, Albert Szent-Gyiirgyi Medical University, H-6720 E6tv6s u. 6., Szeged, Hungary; *Department of Pharmaceutical Chemistry, Albert Szent-Gy6rgyi Medical University, Szeged, Hungary (Received in revisedform 9 September 1992)
Key Word Ibex-Euonymus
sachali~~~;
Celastraceae; dihydro-~-agarofuran;
sesquiterpene.
Abstract-A new sesquiterpene ester, euosachalidin-A, was isolated from the fruits of Euonymus sachalinensis, and its structure was elucidated on the basis of spectral analysis. Complete assignment of all ‘H and 13C NMR chemical shifts was achieved via ‘H-‘HCOSY, 1H-‘3CCOSY, NOESY and COLOC experiments.
INTRODUCTION
Sesquiterpenes with a dihydro-&agarofuran skeleton are found in nature in various oxygenated forms and these polyol esters mostly occur in members of the Celastraceae [I]. Some of these compounds exhibit insecticidal, insect antifeedant and cytotoxic activity [2-41. In a search for this type of compound, we have studied the chemical composition of Euonymus sachalinensis fruits. The present paper reports the isolation and structure elucidation of a new sesquiterpene ester, which was named euosach~id~A.
OCOCH, CH_COO
I
oco OCOCH,
RESULTS AND DISCUSSION
The cyclohexene fraction of a methanolic extract of the fruits of Euo~ymus sac~l~ne~sis (F. Schmidt) Maxim (syn. E. pla~i~es Koehne) was subjected to repeated chromatography to afford compound 1. The IR spectrum of 1 contained an ester carbonyl band at 1740 cm-l. Its UV spectrum showed the presence of benzoate moieties. The mass spectrum exhibited peaks due to the loss of acetic and benzoic acid units: m/z 529 [(M +H)+ HOAcJ E33and 467 [(M + H)+ -C$H,COOH] [I]. The ‘HNMR and 13CNMR spectra (Table 1) indicated the presence of five ester groups (ester carbonyls 6165.6-170.7): four acetate (‘HNMR: 62.16, 2.11, 2.02, 1.53; 13CNMR: 622.0,21.7, 21.3,20.4) and one benz,oate ester (‘H NMR: 67.96 d, 7.45 Y, 7.57 ‘t’; 13C NMR: 6130.1, 130.5, 129.3, 134.2). In addition, the ‘%NMR
spectrum showed signals attributed to three methyls (631.2, 25.6, 18.6), two methylenes (661.0, 31.7), five methines (665.8-80.4) and four quaternary carbons (6 198.7,92.4, 84.1, 52.7). In the ‘H NMR spectrum, three methyl proton peaks (S1.52, 1.47, 1.28), four signals (66.36, 5.89, 5.64, 5.49) attributed to hydrogens attached to the carbon atoms bearing the secondary ester groups and an AI3 quartet (65.12,4.66) assigned to the hydrogens in the methylene attached to the carbon atoms bearing primary ester groups were observed. These data sugges-
1
ted that 1 is a sesquiterpene based on the ~hydroagarofuran skeleton [2,5,6’J substituted with five ester groups. On the basis of the multiplicity and the ‘H-‘HCOSY spectrum, the signals at 65.89, 5.49, 6.36, 5.64, 5.12 and 4.66 in the ‘H NMR spectrum of 1 were assigned to H-l, H-2, H-6, H-9 and H,-15, respectively. The shifts of H-3 and H-4, whose signals overlapped in the ‘HNMR spectrum, were ascertained on the basis of the correlation with H-2 and H-14, respectively. Weak 4J couplings were also observed between H-7 and H-12, H-7 and H-13, and H-l and H-9 in the “H-‘H COSY spectrum. The carbon signal at 6198.7 indicated a keto group, which was located on C-8 according to the chemical shifts of H-7 (S3.06) and C-7 (665.8) [2]. It was concluded that 1 is an ester of 8-oxo-1,2,6,9,15-pentahydroxydihydro+-agarofuran. The relative configuration of 1 was confirmed via the NOESY spectrum. The methylene proton signal at 64.66 was correlated with the proton signals at 66.36 (H-6) and 6 1.28 (H-14), and therefore H-6 and the methyl group on C-4 have axial stereochemistry. The cross-peaks between H-l and H-3,,, H-l and H-9, and H-9 and H-12 proved the axial orientation of H-l and H-9, The appearance of a 503
Short Reports
504
Table 1. ‘H (400 MHz) and 13C (100 MHz) NMR spectral data of compound 1 (CD&
TMS as
internal standard) ‘H-‘H COSY correlated with
NOESY correlated with
5.89 d (3.5) 5.49 q (3.2) 2.44 ddd (14.8,6.3, 3.4) &, 1.95 dd (14.8, 2.4) H,, 2.49 m
H-2, H-9 H-l, H-3.,, H-3, H-2 H-2 H-14 -
H-3,,, H-2, H-9 H-3,,, H-3, H-l, H-2, H-3, H-2, H-3,, H-4 H-3, -
6.36 d (0.7) 3.06 d (0.7) -
H-7 H-6, H-12, H-13
H-15b, H-7, H-14 H-6, H-12, H-13 -
Atom
6, (J Hz)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15a lfb Bz 1’ 2:6’ 3,s 4
-
5.64 s 1.41 s 1.52 s 1.28 d (7.5) 5.12 4.66 ABq (12.9)
-
H-12 H-9, H-7 H-7 H-6, H-1Sb H-2,6’, H-15b H-6, H-14, H-t5a
H-4
7.96 br d (7.8) 7.45 Y (7.8) 1.57 9 (7.4)
2-COMe 6-COMe 9-COMe 15-COMe
2.11 2.16 1.53 2.02
I-CO 2x0 &CO 9-co IS-CO
-
H-3, H-5 H-2’, H-6, H-4 H-2’, H-6’, H-3’, H-5
s s s s
high-field acetate methyl singlet at 61.53 suggested an equatorially oriented aromatic ester on C-l and an acetoxy group on C-9, or conversely [3, 5-j. This was substantiated by the correlation between the methyl (6 1.53) and orrko-benzoyl protons (67.96) in the NOESY spectrum. The positions of ester groups were established unambiguously by using 1H-*3C long-range correlation (COLOC) spectroscopy. Cross-peaks were observed between the carbonyl carbon at 6 165.6 and H-l, and thus the benzoyl group must be located on C-l. The longrange couplings of the carbonyl signals at 6169.7, 169.9 and 170.7 with the proton signals at 66.36,5.63 and 5.12 and the acetyl methyl signals at 62.16, 1.53 and 2.02 indicated the presence of acetyl groups on C-6, C-9 and C-15. The fourth acetyl group (‘HNMR: 62.11; ’ 3C NMR: S 170.2 and 22.0) had to be situated on C-2. The full 13C NMR chemical shift assignments were made by means of ‘H-’ 3C COSY spectral analysis, the data are listed in Table 1.
H-l 5% H-9 OAc
H-2’. H-6
76.2 70.7 31.7 342 92.4 75s 65.8 198.7 80.4 52.7 84.1 25.6 31.2 18.6 61.0
130.1 130.5 129.3 134.2 22.0 21.7 20.4 21.3 165.6 170.2 169.7 169.9 170.7
Considering all of the above data for 1 the structure was elucidated to be 8-oxo-l/.%enzoyloxy-2#J,6e,9/3,15tetraacetoxy-dihydro-&agarofuran. Esters of 8-0x01,2,6,9,15-pentahydroxydihydro-j?-agarofuran were known previously [7’J, but derivatives having H-l,,, H-2,,, H-6,, and H-9,, stereochemistry have not been reported earlier, EXPERIMENTAL
Plant material.
The fruits of Euonymus sachalinensis were collected in Sept. 1989 in the Nursery-Garden of Parks and Gardens, Tahi, Budapest, Hungary. A voucher specimen has been deposited in the Herbarium of the Museum of Natural Science, Budapest. Isolation. Fresh fruits (4.8 kg) were extracted with MeOH. The crude extract was concentrated in uacuo to give a residue (125 g) which was partitioned between cyclohexene and HzO. The cyciohexene tayer was chromatograph~ on a polyamide (Woelm) column. Fractions
Short
eluted with MeOH-H,O 3 : 2 were subjected to silica gel CC with mixtures of cyclohexene-EtOAc. The fractions from cyclohexene-EtOAc 4 : 1 yielded 1 (20 mg). Euosachalidin-A (1). Mp 160-162.5” (from MeOHk [ol]~‘+O.~ (CHCl,, ~1.13); UV ET” nm (log 6): 232 (4.641), 269 (3.512), 276 (3.537), 282 (3.479); IR v!%cm-‘: 1740, 1380, 1270, 1220, 1100, 710; ‘H and l ‘C NMR data are given in Table 1; FABMS ( + ve) m/z [origin] (rel. int.): 589 [M + H] + (4), 611 [M + Na] + (18), 547 [(M + H)+ - CH,CO] (l), 529 [(M + H)+ -HOAc] (3), 467 [(M + H)] + - CsH,C02H] (1), 105 [C,H,CO+] (loo). ._a
Acknowledgements-This investigation was subsidized by the National Scientific Research Fund, Project No. F5128. We are grateful to J. Vajda (Central Research Institute for Chemistry, The Hungarian Academy of Sciences, Budapest, Hungary) for the mass spectroscopic measurements.
505
Reports REFERENCES
1. Bruning, R. and Wagner, H. (1978) Phytochemistry 17, 1821. 2. Vichnewski, W., Prasad, J. S. and Herz, W. (1984) Phytochemistry 23, 1655. 3. Tu, Y. Q., Wu, D. G., Zhoy J., Chen, Y. Z. and Pan, X. F. (1990) J. Nat. Prod. 53,603. 4. Kuo, Y. H., Chen, C. H., Kuo, L. M. Y., King, M. L., Wu, T. S., Haruna, M. and Lee, K. H. (1990) J. Nut. Prod. 53,422. 5. Tu, Y. Q. (1990) J. Nat. Prod. 53, 915. 6. R6zsa, Zs. and Pelczer, I. (1989) 1. C&m. Sot., Perkin Trans I 1089. 7 Gonzalez, A. G., Nunez, M. P., Ravelo, A. G., Luis, ’ J. G., Jimenez, I. A., Vzizquez, J. T. and Munoz, 0. M. (1989) Heterocycles 29, 2287.