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Fusicoccane-, dolabellane- and rearranged labdane-type diterpenoids from the liverwort Pleurozia gigantea
Phytochemisfry, Vol. 29, No. 8, pp. 2597-2603, 1990. Printedin Great Britain.
0
0031-9422/90 $3.00+0.00 1990 PergamonPressplc
FUSICOCCANE-, DOLABELLANE- AND REARRANGED LABDANE-TYPE DITERPENOIDS FROM THE LIVERWORT PLEUROZIA GZGANTEA* YOSHINORI ASAKAWA,
XUEHUI LIN,
MOTOO
TORI
and
KEIKO
KONDO
Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Yamashiro-cho, Tokushima 770, Japan (Receioed 30 November 1989) Key Word Index-Pleurozia gigantea; Jungermanniales; Hepaticae; fusicogigantones A and B; fusicogigantepoxide; 18-hydroxy-4,8-dolabelladiene; pleuroziol; (-)-3,14-clerodadien-13-01; 14-labden-8,13-dial; fusicoccane-, dolabellane-, rearranged labdane-, clerodane- and labdane-type diterpenoids; chemosystematics; ‘H detected multiple bond connectivity (HMBC)
Abstract-Three new fusicoccane-type diterpenoids, fusicogigantone A, fusicogigantone B and fusicogigantepoxide, a new dolabellane-type diterpenoid, 18-hydroxy-4,8_dolabelladiene and a new rearranged labdane-type diterpenoid, pleurodiol have been isolated from the ether and the methanol extract of the liverwort Pleurozia gigantea together with the previously known (-)-3,14-clerodadien-13-01, 14-labden-8,13-diol, ent-kaurene and spathulenol and their structures elucidated by NMR spectral data and chemical correlation. Pleurozia gigantea is a chemically more advanced species than P. acinosa.
INTRODUCTION
Table I. Distribution of terpenoids in two Heurozia species
Recent chemical studies of the Hepaticae have shown them to be rich sources of terpenoids and lipophilic aromatic compounds [l]. In our earlier work on chemical constituents of the stem-leafy liverwort Plewrozia acinosa we isolated (-)-3,14-clerodadien-13-01 (15) and 14-labden-8,13-diol (16) together with the sesquiterpenoids (Table 1) [2]. In a continuation of chemosystematic studies of the bryophytes, we analysed the chemical constituents of P. gigantea collected in East Malaysia. In this paper we wish to report the isolation and structure characterization of three new fusicoccane-type diterpenoids, named fusicogigantone A (l), fusicogigantone B (2) and fusicogigantepoxide (3), a new dolabellane-type diterpenoid, 18-hydroxy-4,8_dolabelladiene (6) and a new rearranged labdane-type diterpenoid, named pleurodiol (ll), together with the previously known diterpenoids (15-17) and ent-sesquiterpene alcohol (18) [2]. RESULTS AND DISCUSSION
Pleurozia gigantea was extraeted with ether and then methanol and the combined extract was analysed by TLC, GC and GC-MS to detect the presence of kaurene (17), spathulenol (18), campe- stigma- and sitosterols. A combination of silica gel and Sephadex LH column chromatography of the crude extract resulted in the isolation of three new fusicoccane-type diterpenoids fusicogigantone A (I), fusicogigantone B (2) and fusicogigantepoxide (3), a new dolabellane-type diterpenoid, 18hydroxy-4,8-dolabelladiene (6) and a new rearranged labdane-type diterpenoid, pleuroziol (ll), along with the
*Part 38 in the series, ‘Chemosystematics of Bryophytes’ For Part 37 see ref. [ZO].
Terpenoids Monoterpenoids Sesquiterpenoids j?-Elemene Bicyclogermacrene Elemol (+)-Aristol-9-ene ent-Spathulenol (18) Diterpenoids Fusicogigantone A (1) Fusicogigantone B (2) Fusicogigantepoxide (3) 1%Hydroxy-4,8-dolabelladiene (6) Pleuroziol (11) (-)-3,14-Clerodadien-13-01 (15) 14-Labden-8,13-diol (16) ent-Kaurene (17)
previously known diterpenoids, 01(15), 14-labden-8,13-diol(16),
P. gigantea P. acinosa [2] + + + + +
+
-
+ +
-
+ + + + +
+ + -
(-)-3,lCclerodadien-13-
ent-kaurene (17) and entspathulenol (18) [Z]. The molecular formula of 1 was determined to be CzoH,,O, ([Ml’ 304.2402) by high resolution mass spectrometry. The IR spectrum showed the presence of a five-membered ketone group (1745 cm- ‘; 6 213.5, s). The remaining one oxygen was confirmed to be the ether oxygen atom, since no absorption band corresponding to a hydroxyl group was observed in the IR spectrum and two singlet signals (6 70.0 and 70.4) appeared in the ‘%NMR spectrum. The ‘H NMR spectrum (Table 2) contained the signals of one tertiary methyl and four
2597
Y. ASAKAWAet al.
2598
Table 2. ‘H NMR spectral data for compounds 1-3, 6 and 11 (400 MHz, CDCI,, TMS) H
1 1.39 d (14.4) 2.32 d (14.4) 2.73 q (7.1)
1 3
2 1.90d (15.1) 2.03 d (15.1)
2.44 d (18.1) 2.50 d (18.1)
4 2.36 d (18.6) 2.46d (18.6)
5 6
1.59 dd (15.7, 2.9) 1.92 d (15.7)
1.74 m 1.40 m 1.43 m 1.25 m 1.70 m 1.74 m
1.16 m 1.81 m 1.38 m 1.53 m 2.10 m 1.75 m
1.26 in 1.45 m 1.58 m
14 15
1.31 m 1.50 m 1.27 m 1.72 m 2.19 m 1.74 m
2.05 m 1.65 m
16 17 18 19 20
0.88 d (6.4) 0.74 d (6.9) 1.09 d (6.6) 1.16 s 0.89 s
0.88 d (6.8) 0.85 d (6.8) 1.23 d (6.4) 1.43 s 0.90 s
0.88 d (6.7) 0.81 d (6.7) 1.03 d (6.6) 1.63 s 0.98 s
11 12 13
1.10 m
4.82 br dd (7.6, 3.7) 2.07 dd (10.7, 5.0) 2.50 m
1.77 m 1.47 m 1.71 m 1.62 m 1.66 m 2.50 m
IO
1.80 m 2.03 m 3.54 d (2.9)
2.01 m 1.42 m 1.53 m 1.45 m 1.59 m 1.75 m
9
11
1.53 d (15.0) 2.56 d (15.0)
2.21 d (10.3)
7 8
6
3
5.12 br dd (8.8, 5.6) 1.65 dd (14.4, 8.8) 2.19 ddd (14.4, 9.0, 5.6) 1.30 m
*Coupling constants (J in Hz) are given
1.08 s 1.57 s 1.50s 1.28 s 1.26 s
5.90 dd (17.3, 10.7) 5.08 d (10.7) 5.20 d (17.3) 1.25 s 0.75 d (6.6) 0.97 5 0.85 s 0.83 s
in parentheses.
secondary methyls. The 13CNMR spectrum (Table 3) further contained the signals of five methyls, six methylenes, five methines and one quaternary carbon. The above spectral data coupled with the molecular formula indicated that 1 was the four-membered diterpenoid with one ketone and one epoxide group. In order to clarify the partial structures of 1,the ‘H-‘H and “C-‘H 2D COSY NMR spectra were measured and thereby the partial structures A-D were confirmed (Fig. 1). Furthermore, the ‘H detected multiple bond connectivity (HMBC) [3, 41 were examined and the correlation between each methyl group and the other atoms was obtained (Fig. 1 and Table 4). On the basis of the above spectral data, 1 was suggested to be a fusicoccane-type diterpene epoxide, as shown in Fig. 1. This assumption was further confirmed as follow. Treatment of 1 with lithiumdiisopropyl amide (LDA) in tetrahydrofurane gave an a&unsaturated ketone whose spectral data including CD were identical to those of the fusicoccane-type diterpenoid, anadensin (4) isolated from the liverwort Anastrepta orcadensis [SJ. Thus, the absolute stereo structure of fusicogigantone A was established to be 1. Compound 2 had the same molecular formula, C,cH3,02, as that of 1 determined by high resolution mass spectrometry. The IR and 13C NMR spectra showed the presence of a five-membered ketone (1745 cm-‘; 6 210.3. s). Compound 2 gave ‘H and 13C NMR and mass
spectral data similar to those of 1 with the following difference. The ‘H NMR spectrum of 2 lacked the signal of one secondary methyl group. In the 13CNMR spectrum, one methine carbon was observed at the lower field (6 62.4). The above data indicated that 2 possessed the same fusicoccane skeleton as 1 and the ketone was placed at C-5 and the epoxide at C-2/3. This was further confirmed by the ‘H-‘H, ‘3C-1H 2D COSY NMR data as well as HMBC (Table 4). The absolute stereostructure of 2 was suggested by the presence of the NOE (Fig. 1) observed in the NOESY spectrum, along with the occurrence of 1 in the same liverwort. High resolution mass spectrum showed the molecular formula C,,H,,O, (CM]’ 304.2393) for compound 3. The two oxygen atoms were the ether oxygens because neither carbonyl nor hydroxyl absorption band was observed in the IR spectrum. This was confirmed by the presence of four carbon signals at 6 62.4 (s), 66.3 (d), 66.4 (s) and 79.1 (s). The ‘H and 13CNMR spectra of 3 were similar to those of 1, except for the presence of one tertiary methyl group and one proton on a carbon bearing ether oxygen, in place of the ketone, and one secondary methyl group, indicating that 3 also possessed the same fusicoccane skeleton, and that the two epoxy rings were located on a five-membered ring. Consideration of the above data led to two structures of 3 or 5 for fusicogigantepoxide. The structure 5 was excluded, be-
Diterpenoids from Pleurozia Table 3. ‘%NMR
spectral data of compounds 1-3, 6 and 11 (100 MHz, CDCI,, TMS)*
C
1
2
3
6
11
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
42.3 70.4 49.1 213.5 38.4 70.0 31.5 33.6 23.4 48.1 44.3 41.6 20.9 46.0 28.1 23.2 18.6 17.4 9.1 20.5
38.1 61.0 68.6 45.9 210.3 62.4 30.5 34.4 26.4 41.2 43.4 41.1 24.0 47.1 28.3 24.5 20.1 23.7 15.1 23.1
42.0 66.4 62.4 66.3 25.3 79.1 34.7 32.9 20.8 46.8 44.9 42.3 25.2 47.2 28.7 23.7 19.5 18.1 16.9 23.0
47.3 42.3 38.7 133.8 127.8 23.3’ 39.8 134.1 126.0 24.7’ 41.7 53.6 25.6 41.1 24.7 15.8 16.5 72.8 30.1 30.6
22.0 21.6 36.9 38.8 76.7 32.0 26.3 36.4 38.4 40.8 31.3 36.2 73.4 145.0 112.0 27.4 15.9 24.1 24.4 17.6
*All assignments were confirmed by INEPT, 13G1H COSY and long range 13C-‘H 2D COSY spectra. ‘Assignments may be interchangeable.
B
2599
gigantea
cause the correlation between H-4 and C-19 methyl group was observed in the ‘H-‘H and r3C-rH 2D COSY NMR spectra. The structure 3 was further confirmed by HMBC experiments (Table 4). The absolute structure was suggested by consideration of the occurrence of the fusicoccanes (1 and 2). The IR, ‘HNMR and mass spectra of 6, C,,H,,O ([Ml’ 308.2714), showed the presence of a dimethyl carbinol [3620 cm-‘; m/z 59 (lOO%)], three tertiary methyls, two vinyl methyls, two olefinic protons on trisubstituted double bonds (Table 2). The i3CNMR spectrum (Table 3) contained 20 carbon signals; seven methylenes, five methyls, two methines, two trisubstituted double bonds, one quaternary carbon and an additional quaternary carbon bearing hydroxyl group. The above data, coupled with the coexistence of three fusicoccanetype diterpenoids (l-3), suggested that 6 was dolabellanetype diterpenoid with a dimethyl carbinyl group and two non-conjugated double bonds. The ‘H NMR spectrum of 6 was quite similar to that of the previously known 18hydroxydolabelladiene (7) [6], except for the difference of the chemical shifts of H-5, 9, 16 and 17. A similar dolabellane-type diterpenoid (8) has been isolated from brown algae [7]. Lack of identity of the chemical shifts of the olefinic protons and vinyl methyls between 6 and 7 suggested that 6 might be the stereoisomer or 8,9-double bond isomer (e.g. 8) of 7. This assumption was further confirmed by spin decoupling experiments. Irradiation of the double doublet at 6 5.12 (H-9) caused the double
1
-
2
HMBC G&
Fig. 1.
Y. ASAKAWAet al.
2600
i6
6 OAc
AcO
10
9
6 -
HMBC
Fig. 2.
Table
bond connecl-3,6 and (4OOMHz); ‘%NMR (100 MHz), CDCI,, TMS)]
4. ‘H detected
multiple
tivity (HMBC) data for compounds 11 [‘H
Compounds
Me
C 14, 15, 17 14, 15, 16
1
16 17 18 19 20
14, 15, 17 14, 15, 16
2
16 17 18 19 20
14, 15, 17 14, 15, 16
3
16 17 18 19 20
6
15 16 17 19 20
3, 4, 5 7, 8, 9 12, 18, 20 12, 18, 19
16 17 18 19 20
12, 7, 3, 3, 8,
11
6, 7, 8 2, 3, 4 1, 10, 11, 12
6, 7, 8 2, 3, 4 1, 10, 11, 12
doublet at 6 1.65 (H-1Oa) and the triple doublet at 6 2.19 (H-lob) to collapse to the doublet and double doublet, indicating that one methine proton was present at C-l 1. This phenomenon was not explained by the structure (7) with a C-7/C-8 double bond. Furthermore, the presence of the partial structures, -CH,-CH,-C(Me)=CH-CH,-, CH,-CH-CH,-CH = C(Me)- were established by the ‘H-‘H 2D COSY NMR spectral data (Table 5) and the additional partial structures,
were also determined by HMBC (Fig. 2
and Table 4). On the above data, the structure 6 was given for the new dolabellane-type diterpenoid. The geometry of the double bonds and the absolute configuration of 6 remained to be clarified; however, the tentative stereostructure was deduced by consideration of the coexistence
6, 7, 8 2, 3, 4 1, 10, 11, 12 1, 2, 11, 14
13, 14 8, 9 4, 5, 19 4, 5, 18 9, 10, 11
Table 5. ‘H-‘H 2D COSY spectral data for 6 (400 MHz CDCl,, TMS) H
Correlated
3 5 6 9 10
H-2, 3, 16 H-6 H-6, 7 H-10 H-10, 11
H
Diterpenoids
from Pleurozia
of biogenetically correlated fusicoccane-type diterpenoids (1-3). The IR spectrum of 11, C,,H,,O, ([Ml’ 308.2714), showed the presence of a hydroxyl group (3600, 3450 cm- ‘). The ‘H NMR spectrum contained the signals of four tertiary methyls, one secondary methyl and one vinylic group (Table 6). The 13C NMR spectrum (Table 3) indicated the presence of 20 carbons; two of which were assigned to be quaternary carbons (6 73.4, 76.7 each s) bearing hydroxyl group. The above spectral data coupled with the molecular formula indicated that 11 was a bicyclic diterpenoid having two tertiary hydrox-
and ‘H-‘H 2D Table 6. Long range 13C-‘H COSY spectral data for 11 [‘H (400 MHz); 13CNMR (100 MHz), CDCI, - TMS)]
C
Correlated
3 4 8 9 11 12 16 18 19 20
H-18, H-18, H-17 H-20 H-20 H-16 H-16 H-18, H-18, H-20
19 19
H
H
Correlated
3 17 18
H-2, 3 H-8 H-19
H
19 19
17
OH HO $@
19 -
HBMC
18 OH
4”
#
2601
yl groups and one vinyl group. The presence of a 3hydroxy-3-methyl-1-propenyl group in 11 was confirmed by the following chemical reaction. Epoxidation of 11 with meta-chloroperbenzoic acid gave a mono epoxide (12), followed by reduction with lithium aluminium hydride to afford a diol(13), which was oxidized by sodium periodate to furnish a mono ketone (14). Comparison of the ‘H and r3CNMR spectra for 11 and co-occurring (-)-3,lCclerodadien-13-ol(15) [2] showed that the compounds differed with respect to the one vinylic proton, one vinyl methyl and one tertiary hydroxyl group, suggesting 11 to be a labdane- or clerodane-type diterpenoid. In the ’ 3C NMR spectra of labdane-type diterpenoids, C-5 methine and C-10 quaternary carbon signals are observed at a higher field than 45 and 50ppm, respectively. All the carbon signals of 11 appeared at more than 41 ppm, except for the signals of two carbons bearing hydroxyl group, confirming that 11 was not a labdane-type diterpenoid. From the above data, three possible structures (11,19 and 20) were proposed for pleurodiol. The structures (19 and 20) were excluded since the correlation between C,,-Me and C,,-Me was observed in ‘H-‘H 2D COSY (Table 6) and correlations between(i) C-3 and H-18, (ii) C-3 and H19, (iii) C-4 and H-18 and C-4 and H-19 by the i3C-‘H 2D COSY NMR spectra (Table 6). The structure of 11 was further confirmed by the measurement of HMBC spectrum (Fig. 3 and Table 3). The plane structure of 11 was thus determined to be chettaphanin-type (= rearranged labdane-type) diterpene diol [S]. In order to clarify the stereostructure, the difference NOE was measured; however, conclusive evidence was not obtained. Considering the co-occurrence of the clerodane-type diterpenoid
16 OH
gigantea
20 Fig. 3.
Diterpenoids from Pleurozia gigantea (t, C-12), 38.5 (s, C-9), 38.9 (s, C-4), 41.2 (d, C-lo), 76.2 (s, C-5), 209.5 (s, C-13).
Acknowledgements-We thank Prof. J.-P. Frahm (Department of Botany, Duisburg University, F.R.G.) for his collection of the liverwort. We are also indebted to Dr M. Mizutani (Hattori Botanical Laboratory, Nichinan, Japan) for his identification of the specimen.
2603
8. Sato, A., Kurabayashi, M., Nagahori, H., Ogiso, A. and Mishima, H. (1970) Tetrahedron Letters 1095. 9. Ballio, A., Brufani, M., Casinovi, C. G., Cerrini, S., Fedeli, W., Pellicciari, R., Santurbano, B. and Vaciago, A (1968) Experientia 24, 631. 10. Ballio, A., Casinovi, C. G., D’Alessio, V., Grandolini, G., Randazzo, G. and Rossi, C. (1974) Experientia 30, 884. 11. Sass, T. (1972) Agric. Biol. Chem. 36, 2037. 12. Sasa, T. Takahama, A. and Shindo, T. (1975) Agric. Biol. Chem. 39, 1729.
REFERENCES 1. Asakawa, Y. (1982) in Progress in the Chemistry of Organic Natural Products Vol. 42 (Herz, W., Grisebach, H. and
Kirby, G. W., eds), p. 1. Springer, Wien. 2. Wu, C.-L. and Asakawa, Y. (1988) Phytochemistry 27, 940. 3. Bax, A. and Summers, M. F. (1986) .I. Am. Chem. Sot. 108, 2093. 4. Bax, A., Aszalos, A., Dinya, Z. and Sudo, K. (1986) .I. Am. Gem.
Sot. 108,8059.
5. Huneck, S., Baxter, G., Cameron, A. F., Connolly, J. D. and Rycroft, D. S. (1983) Tetrahedron Letters 24, 3787. 6. Amico, V., Currenti, R., Oriente, G., Piattelli, M. and Tringali, C. (1981) Phytochemistry 20, 848. 7. Tringali, C., Piattelli, M. and Nicolosi, G. (1984) Tetrahedron 40. 799.
13. Hashirnoto, T., Tori, M., Taira, Z. and Asakawa, Y. (1985) Tetrahedron Letters 26, 6474.
14. Ireland, C. and Faulkner, D. J. (1977) J. Org. Chem.42,3157. 15. Amico, V., Priente, G., Piattelli, M., Tringali, C, Fattorusso, E., Magna, S. and Mayo], L. (1980) Tetrahedron 47,4129. 16. Tringali, C., Oriente, G., Piattelli, M. and Nicolosi, G. (1984) J. Nat. Prod. 47, 615.
17. Huneck, S., Baxter, G. A., Cameron, A. F., Connolly, J. D., Harrison, L. J., Phillips, W. R., Rycroft, D. S. and Sim, G. A. (1986) J. Chem. Sot. Perkin Trans. I 809. 18. Matsuo, A., Kamio, K., Uohama, K., Yoshida, K., Connolly, J, D. and Sim, G. A. (1988) Phytochemistry 27, 1153. 19. Asakawa, Y., Matsuda, R., Tori, M. and Hashimoto, T. (1988) Phytochemistry 27, 3861. 20. Nagashima, F., Toyota, M. and Asakawa, Y. (1990) Phytochemistry 29, (in press).
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0031-9422/90 $3.00+0.00 1990 PergamonPressplc
FUSICOCCANE-, DOLABELLANE- AND REARRANGED LABDANE-TYPE DITERPENOIDS FROM THE LIVERWORT PLEUROZIA GZGANTEA* YOSHINORI ASAKAWA,
XUEHUI LIN,
MOTOO
TORI
and
KEIKO
KONDO
Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Yamashiro-cho, Tokushima 770, Japan (Receioed 30 November 1989) Key Word Index-Pleurozia gigantea; Jungermanniales; Hepaticae; fusicogigantones A and B; fusicogigantepoxide; 18-hydroxy-4,8-dolabelladiene; pleuroziol; (-)-3,14-clerodadien-13-01; 14-labden-8,13-dial; fusicoccane-, dolabellane-, rearranged labdane-, clerodane- and labdane-type diterpenoids; chemosystematics; ‘H detected multiple bond connectivity (HMBC)
Abstract-Three new fusicoccane-type diterpenoids, fusicogigantone A, fusicogigantone B and fusicogigantepoxide, a new dolabellane-type diterpenoid, 18-hydroxy-4,8_dolabelladiene and a new rearranged labdane-type diterpenoid, pleurodiol have been isolated from the ether and the methanol extract of the liverwort Pleurozia gigantea together with the previously known (-)-3,14-clerodadien-13-01, 14-labden-8,13-diol, ent-kaurene and spathulenol and their structures elucidated by NMR spectral data and chemical correlation. Pleurozia gigantea is a chemically more advanced species than P. acinosa.
INTRODUCTION
Table I. Distribution of terpenoids in two Heurozia species
Recent chemical studies of the Hepaticae have shown them to be rich sources of terpenoids and lipophilic aromatic compounds [l]. In our earlier work on chemical constituents of the stem-leafy liverwort Plewrozia acinosa we isolated (-)-3,14-clerodadien-13-01 (15) and 14-labden-8,13-diol (16) together with the sesquiterpenoids (Table 1) [2]. In a continuation of chemosystematic studies of the bryophytes, we analysed the chemical constituents of P. gigantea collected in East Malaysia. In this paper we wish to report the isolation and structure characterization of three new fusicoccane-type diterpenoids, named fusicogigantone A (l), fusicogigantone B (2) and fusicogigantepoxide (3), a new dolabellane-type diterpenoid, 18-hydroxy-4,8_dolabelladiene (6) and a new rearranged labdane-type diterpenoid, named pleurodiol (ll), together with the previously known diterpenoids (15-17) and ent-sesquiterpene alcohol (18) [2]. RESULTS AND DISCUSSION
Pleurozia gigantea was extraeted with ether and then methanol and the combined extract was analysed by TLC, GC and GC-MS to detect the presence of kaurene (17), spathulenol (18), campe- stigma- and sitosterols. A combination of silica gel and Sephadex LH column chromatography of the crude extract resulted in the isolation of three new fusicoccane-type diterpenoids fusicogigantone A (I), fusicogigantone B (2) and fusicogigantepoxide (3), a new dolabellane-type diterpenoid, 18hydroxy-4,8-dolabelladiene (6) and a new rearranged labdane-type diterpenoid, pleuroziol (ll), along with the
*Part 38 in the series, ‘Chemosystematics of Bryophytes’ For Part 37 see ref. [ZO].
Terpenoids Monoterpenoids Sesquiterpenoids j?-Elemene Bicyclogermacrene Elemol (+)-Aristol-9-ene ent-Spathulenol (18) Diterpenoids Fusicogigantone A (1) Fusicogigantone B (2) Fusicogigantepoxide (3) 1%Hydroxy-4,8-dolabelladiene (6) Pleuroziol (11) (-)-3,14-Clerodadien-13-01 (15) 14-Labden-8,13-diol (16) ent-Kaurene (17)
previously known diterpenoids, 01(15), 14-labden-8,13-diol(16),
P. gigantea P. acinosa [2] + + + + +
+
-
+ +
-
+ + + + +
+ + -
(-)-3,lCclerodadien-13-
ent-kaurene (17) and entspathulenol (18) [Z]. The molecular formula of 1 was determined to be CzoH,,O, ([Ml’ 304.2402) by high resolution mass spectrometry. The IR spectrum showed the presence of a five-membered ketone group (1745 cm- ‘; 6 213.5, s). The remaining one oxygen was confirmed to be the ether oxygen atom, since no absorption band corresponding to a hydroxyl group was observed in the IR spectrum and two singlet signals (6 70.0 and 70.4) appeared in the ‘%NMR spectrum. The ‘H NMR spectrum (Table 2) contained the signals of one tertiary methyl and four
2597
Y. ASAKAWAet al.
2598
Table 2. ‘H NMR spectral data for compounds 1-3, 6 and 11 (400 MHz, CDCI,, TMS) H
1 1.39 d (14.4) 2.32 d (14.4) 2.73 q (7.1)
1 3
2 1.90d (15.1) 2.03 d (15.1)
2.44 d (18.1) 2.50 d (18.1)
4 2.36 d (18.6) 2.46d (18.6)
5 6
1.59 dd (15.7, 2.9) 1.92 d (15.7)
1.74 m 1.40 m 1.43 m 1.25 m 1.70 m 1.74 m
1.16 m 1.81 m 1.38 m 1.53 m 2.10 m 1.75 m
1.26 in 1.45 m 1.58 m
14 15
1.31 m 1.50 m 1.27 m 1.72 m 2.19 m 1.74 m
2.05 m 1.65 m
16 17 18 19 20
0.88 d (6.4) 0.74 d (6.9) 1.09 d (6.6) 1.16 s 0.89 s
0.88 d (6.8) 0.85 d (6.8) 1.23 d (6.4) 1.43 s 0.90 s
0.88 d (6.7) 0.81 d (6.7) 1.03 d (6.6) 1.63 s 0.98 s
11 12 13
1.10 m
4.82 br dd (7.6, 3.7) 2.07 dd (10.7, 5.0) 2.50 m
1.77 m 1.47 m 1.71 m 1.62 m 1.66 m 2.50 m
IO
1.80 m 2.03 m 3.54 d (2.9)
2.01 m 1.42 m 1.53 m 1.45 m 1.59 m 1.75 m
9
11
1.53 d (15.0) 2.56 d (15.0)
2.21 d (10.3)
7 8
6
3
5.12 br dd (8.8, 5.6) 1.65 dd (14.4, 8.8) 2.19 ddd (14.4, 9.0, 5.6) 1.30 m
*Coupling constants (J in Hz) are given
1.08 s 1.57 s 1.50s 1.28 s 1.26 s
5.90 dd (17.3, 10.7) 5.08 d (10.7) 5.20 d (17.3) 1.25 s 0.75 d (6.6) 0.97 5 0.85 s 0.83 s
in parentheses.
secondary methyls. The 13CNMR spectrum (Table 3) further contained the signals of five methyls, six methylenes, five methines and one quaternary carbon. The above spectral data coupled with the molecular formula indicated that 1 was the four-membered diterpenoid with one ketone and one epoxide group. In order to clarify the partial structures of 1,the ‘H-‘H and “C-‘H 2D COSY NMR spectra were measured and thereby the partial structures A-D were confirmed (Fig. 1). Furthermore, the ‘H detected multiple bond connectivity (HMBC) [3, 41 were examined and the correlation between each methyl group and the other atoms was obtained (Fig. 1 and Table 4). On the basis of the above spectral data, 1 was suggested to be a fusicoccane-type diterpene epoxide, as shown in Fig. 1. This assumption was further confirmed as follow. Treatment of 1 with lithiumdiisopropyl amide (LDA) in tetrahydrofurane gave an a&unsaturated ketone whose spectral data including CD were identical to those of the fusicoccane-type diterpenoid, anadensin (4) isolated from the liverwort Anastrepta orcadensis [SJ. Thus, the absolute stereo structure of fusicogigantone A was established to be 1. Compound 2 had the same molecular formula, C,cH3,02, as that of 1 determined by high resolution mass spectrometry. The IR and 13C NMR spectra showed the presence of a five-membered ketone (1745 cm-‘; 6 210.3. s). Compound 2 gave ‘H and 13C NMR and mass
spectral data similar to those of 1 with the following difference. The ‘H NMR spectrum of 2 lacked the signal of one secondary methyl group. In the 13CNMR spectrum, one methine carbon was observed at the lower field (6 62.4). The above data indicated that 2 possessed the same fusicoccane skeleton as 1 and the ketone was placed at C-5 and the epoxide at C-2/3. This was further confirmed by the ‘H-‘H, ‘3C-1H 2D COSY NMR data as well as HMBC (Table 4). The absolute stereostructure of 2 was suggested by the presence of the NOE (Fig. 1) observed in the NOESY spectrum, along with the occurrence of 1 in the same liverwort. High resolution mass spectrum showed the molecular formula C,,H,,O, (CM]’ 304.2393) for compound 3. The two oxygen atoms were the ether oxygens because neither carbonyl nor hydroxyl absorption band was observed in the IR spectrum. This was confirmed by the presence of four carbon signals at 6 62.4 (s), 66.3 (d), 66.4 (s) and 79.1 (s). The ‘H and 13CNMR spectra of 3 were similar to those of 1, except for the presence of one tertiary methyl group and one proton on a carbon bearing ether oxygen, in place of the ketone, and one secondary methyl group, indicating that 3 also possessed the same fusicoccane skeleton, and that the two epoxy rings were located on a five-membered ring. Consideration of the above data led to two structures of 3 or 5 for fusicogigantepoxide. The structure 5 was excluded, be-
Diterpenoids from Pleurozia Table 3. ‘%NMR
spectral data of compounds 1-3, 6 and 11 (100 MHz, CDCI,, TMS)*
C
1
2
3
6
11
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
42.3 70.4 49.1 213.5 38.4 70.0 31.5 33.6 23.4 48.1 44.3 41.6 20.9 46.0 28.1 23.2 18.6 17.4 9.1 20.5
38.1 61.0 68.6 45.9 210.3 62.4 30.5 34.4 26.4 41.2 43.4 41.1 24.0 47.1 28.3 24.5 20.1 23.7 15.1 23.1
42.0 66.4 62.4 66.3 25.3 79.1 34.7 32.9 20.8 46.8 44.9 42.3 25.2 47.2 28.7 23.7 19.5 18.1 16.9 23.0
47.3 42.3 38.7 133.8 127.8 23.3’ 39.8 134.1 126.0 24.7’ 41.7 53.6 25.6 41.1 24.7 15.8 16.5 72.8 30.1 30.6
22.0 21.6 36.9 38.8 76.7 32.0 26.3 36.4 38.4 40.8 31.3 36.2 73.4 145.0 112.0 27.4 15.9 24.1 24.4 17.6
*All assignments were confirmed by INEPT, 13G1H COSY and long range 13C-‘H 2D COSY spectra. ‘Assignments may be interchangeable.
B
2599
gigantea
cause the correlation between H-4 and C-19 methyl group was observed in the ‘H-‘H and r3C-rH 2D COSY NMR spectra. The structure 3 was further confirmed by HMBC experiments (Table 4). The absolute structure was suggested by consideration of the occurrence of the fusicoccanes (1 and 2). The IR, ‘HNMR and mass spectra of 6, C,,H,,O ([Ml’ 308.2714), showed the presence of a dimethyl carbinol [3620 cm-‘; m/z 59 (lOO%)], three tertiary methyls, two vinyl methyls, two olefinic protons on trisubstituted double bonds (Table 2). The i3CNMR spectrum (Table 3) contained 20 carbon signals; seven methylenes, five methyls, two methines, two trisubstituted double bonds, one quaternary carbon and an additional quaternary carbon bearing hydroxyl group. The above data, coupled with the coexistence of three fusicoccanetype diterpenoids (l-3), suggested that 6 was dolabellanetype diterpenoid with a dimethyl carbinyl group and two non-conjugated double bonds. The ‘H NMR spectrum of 6 was quite similar to that of the previously known 18hydroxydolabelladiene (7) [6], except for the difference of the chemical shifts of H-5, 9, 16 and 17. A similar dolabellane-type diterpenoid (8) has been isolated from brown algae [7]. Lack of identity of the chemical shifts of the olefinic protons and vinyl methyls between 6 and 7 suggested that 6 might be the stereoisomer or 8,9-double bond isomer (e.g. 8) of 7. This assumption was further confirmed by spin decoupling experiments. Irradiation of the double doublet at 6 5.12 (H-9) caused the double
1
-
2
HMBC G&
Fig. 1.
Y. ASAKAWAet al.
2600
i6
6 OAc
AcO
10
9
6 -
HMBC
Fig. 2.
Table
bond connecl-3,6 and (4OOMHz); ‘%NMR (100 MHz), CDCI,, TMS)]
4. ‘H detected
multiple
tivity (HMBC) data for compounds 11 [‘H
Compounds
Me
C 14, 15, 17 14, 15, 16
1
16 17 18 19 20
14, 15, 17 14, 15, 16
2
16 17 18 19 20
14, 15, 17 14, 15, 16
3
16 17 18 19 20
6
15 16 17 19 20
3, 4, 5 7, 8, 9 12, 18, 20 12, 18, 19
16 17 18 19 20
12, 7, 3, 3, 8,
11
6, 7, 8 2, 3, 4 1, 10, 11, 12
6, 7, 8 2, 3, 4 1, 10, 11, 12
doublet at 6 1.65 (H-1Oa) and the triple doublet at 6 2.19 (H-lob) to collapse to the doublet and double doublet, indicating that one methine proton was present at C-l 1. This phenomenon was not explained by the structure (7) with a C-7/C-8 double bond. Furthermore, the presence of the partial structures, -CH,-CH,-C(Me)=CH-CH,-, CH,-CH-CH,-CH = C(Me)- were established by the ‘H-‘H 2D COSY NMR spectral data (Table 5) and the additional partial structures,
were also determined by HMBC (Fig. 2
and Table 4). On the above data, the structure 6 was given for the new dolabellane-type diterpenoid. The geometry of the double bonds and the absolute configuration of 6 remained to be clarified; however, the tentative stereostructure was deduced by consideration of the coexistence
6, 7, 8 2, 3, 4 1, 10, 11, 12 1, 2, 11, 14
13, 14 8, 9 4, 5, 19 4, 5, 18 9, 10, 11
Table 5. ‘H-‘H 2D COSY spectral data for 6 (400 MHz CDCl,, TMS) H
Correlated
3 5 6 9 10
H-2, 3, 16 H-6 H-6, 7 H-10 H-10, 11
H
Diterpenoids
from Pleurozia
of biogenetically correlated fusicoccane-type diterpenoids (1-3). The IR spectrum of 11, C,,H,,O, ([Ml’ 308.2714), showed the presence of a hydroxyl group (3600, 3450 cm- ‘). The ‘H NMR spectrum contained the signals of four tertiary methyls, one secondary methyl and one vinylic group (Table 6). The 13C NMR spectrum (Table 3) indicated the presence of 20 carbons; two of which were assigned to be quaternary carbons (6 73.4, 76.7 each s) bearing hydroxyl group. The above spectral data coupled with the molecular formula indicated that 11 was a bicyclic diterpenoid having two tertiary hydrox-
and ‘H-‘H 2D Table 6. Long range 13C-‘H COSY spectral data for 11 [‘H (400 MHz); 13CNMR (100 MHz), CDCI, - TMS)]
C
Correlated
3 4 8 9 11 12 16 18 19 20
H-18, H-18, H-17 H-20 H-20 H-16 H-16 H-18, H-18, H-20
19 19
H
H
Correlated
3 17 18
H-2, 3 H-8 H-19
H
19 19
17
OH HO $@
19 -
HBMC
18 OH
4”
#
2601
yl groups and one vinyl group. The presence of a 3hydroxy-3-methyl-1-propenyl group in 11 was confirmed by the following chemical reaction. Epoxidation of 11 with meta-chloroperbenzoic acid gave a mono epoxide (12), followed by reduction with lithium aluminium hydride to afford a diol(13), which was oxidized by sodium periodate to furnish a mono ketone (14). Comparison of the ‘H and r3CNMR spectra for 11 and co-occurring (-)-3,lCclerodadien-13-ol(15) [2] showed that the compounds differed with respect to the one vinylic proton, one vinyl methyl and one tertiary hydroxyl group, suggesting 11 to be a labdane- or clerodane-type diterpenoid. In the ’ 3C NMR spectra of labdane-type diterpenoids, C-5 methine and C-10 quaternary carbon signals are observed at a higher field than 45 and 50ppm, respectively. All the carbon signals of 11 appeared at more than 41 ppm, except for the signals of two carbons bearing hydroxyl group, confirming that 11 was not a labdane-type diterpenoid. From the above data, three possible structures (11,19 and 20) were proposed for pleurodiol. The structures (19 and 20) were excluded since the correlation between C,,-Me and C,,-Me was observed in ‘H-‘H 2D COSY (Table 6) and correlations between(i) C-3 and H-18, (ii) C-3 and H19, (iii) C-4 and H-18 and C-4 and H-19 by the i3C-‘H 2D COSY NMR spectra (Table 6). The structure of 11 was further confirmed by the measurement of HMBC spectrum (Fig. 3 and Table 3). The plane structure of 11 was thus determined to be chettaphanin-type (= rearranged labdane-type) diterpene diol [S]. In order to clarify the stereostructure, the difference NOE was measured; however, conclusive evidence was not obtained. Considering the co-occurrence of the clerodane-type diterpenoid
16 OH
gigantea
20 Fig. 3.
Diterpenoids from Pleurozia gigantea (t, C-12), 38.5 (s, C-9), 38.9 (s, C-4), 41.2 (d, C-lo), 76.2 (s, C-5), 209.5 (s, C-13).
Acknowledgements-We thank Prof. J.-P. Frahm (Department of Botany, Duisburg University, F.R.G.) for his collection of the liverwort. We are also indebted to Dr M. Mizutani (Hattori Botanical Laboratory, Nichinan, Japan) for his identification of the specimen.
2603
8. Sato, A., Kurabayashi, M., Nagahori, H., Ogiso, A. and Mishima, H. (1970) Tetrahedron Letters 1095. 9. Ballio, A., Brufani, M., Casinovi, C. G., Cerrini, S., Fedeli, W., Pellicciari, R., Santurbano, B. and Vaciago, A (1968) Experientia 24, 631. 10. Ballio, A., Casinovi, C. G., D’Alessio, V., Grandolini, G., Randazzo, G. and Rossi, C. (1974) Experientia 30, 884. 11. Sass, T. (1972) Agric. Biol. Chem. 36, 2037. 12. Sasa, T. Takahama, A. and Shindo, T. (1975) Agric. Biol. Chem. 39, 1729.
REFERENCES 1. Asakawa, Y. (1982) in Progress in the Chemistry of Organic Natural Products Vol. 42 (Herz, W., Grisebach, H. and
Kirby, G. W., eds), p. 1. Springer, Wien. 2. Wu, C.-L. and Asakawa, Y. (1988) Phytochemistry 27, 940. 3. Bax, A. and Summers, M. F. (1986) .I. Am. Chem. Sot. 108, 2093. 4. Bax, A., Aszalos, A., Dinya, Z. and Sudo, K. (1986) .I. Am. Gem.
Sot. 108,8059.
5. Huneck, S., Baxter, G., Cameron, A. F., Connolly, J. D. and Rycroft, D. S. (1983) Tetrahedron Letters 24, 3787. 6. Amico, V., Currenti, R., Oriente, G., Piattelli, M. and Tringali, C. (1981) Phytochemistry 20, 848. 7. Tringali, C., Piattelli, M. and Nicolosi, G. (1984) Tetrahedron 40. 799.
13. Hashirnoto, T., Tori, M., Taira, Z. and Asakawa, Y. (1985) Tetrahedron Letters 26, 6474.
14. Ireland, C. and Faulkner, D. J. (1977) J. Org. Chem.42,3157. 15. Amico, V., Priente, G., Piattelli, M., Tringali, C, Fattorusso, E., Magna, S. and Mayo], L. (1980) Tetrahedron 47,4129. 16. Tringali, C., Oriente, G., Piattelli, M. and Nicolosi, G. (1984) J. Nat. Prod. 47, 615.
17. Huneck, S., Baxter, G. A., Cameron, A. F., Connolly, J. D., Harrison, L. J., Phillips, W. R., Rycroft, D. S. and Sim, G. A. (1986) J. Chem. Sot. Perkin Trans. I 809. 18. Matsuo, A., Kamio, K., Uohama, K., Yoshida, K., Connolly, J, D. and Sim, G. A. (1988) Phytochemistry 27, 1153. 19. Asakawa, Y., Matsuda, R., Tori, M. and Hashimoto, T. (1988) Phytochemistry 27, 3861. 20. Nagashima, F., Toyota, M. and Asakawa, Y. (1990) Phytochemistry 29, (in press).