- Email: [email protected]
Rabdoshikoccins a and B, 8,9-seco-ent-kaurenoids from Rabdosia shikokiana var. occidentalis
Pergamon
Phvtocheraistry, Vol. 35, No. 5, pp. 1289-1291, 1994 Copyright 9 1994 Elsevier Science Ltd Printed in Great Britain. All rights reserved 0031-9422/94 $6.00+0.00
RABDOSHIKOCCINS A A N D B, 8,9-SECO-ENT-KAURENOIDS FROM RABDOSIA SHIKOKIANA VAR. OCCIDENTALIS
YOSHIO TAKEDA,* YUKAKO FUTATSUISHI,'~TAKASHIMATSUMOTO, HIROSHI TERADA,~"and HIDEAKI OTSUKA*:~ Faculty of Integrated Arts and Sciences, The University of Tokushima, Tokushima 770, Japan; "~Facultyof Pharmaceutical Sciences, The University of Tokushima, Tokushima 770, Japan; //Pharmaceutical Institute, Hiroshima University School of Medicine, Minami-ku, Hiroshima 734, Japan
(Received 23 August 1993)
Key Word Index--Rabdosia shikokiana var. occidentalis; Labiatae; 8,9-seco-ent-kaurenoid; rabdoshikoccins A and B.
Abstract--From the aerial parts of Rabdosia shikokiana var. occidentalis, two new 8,9-seco-ent-kaurenoid diterpenes, rabdoshikoccins A and B, were isolated together with the known compounds, shikoccin, shikoccidin and leukamenin E. The structures of the new compounds were elucidated based on the spectroscopic and chemical evidence.
INTRODUCTION
From Rabdosia shikokiana var. occidentalis (Murata) Hara [1], four 8,9-seco-ent-kaurenoid diterpenes, shikoccin, O-methylshikoccin, epoxyshikoccin and O-methylepoxyshikoccin, and three ent-kaurenoid diterpenes, shikoccidin, isodomedin and leukamenin E, were isolated [2]. During the course of our studies on the biologically active substances of the genus Rabdosia (Labiatae), we examined the constituents of the title plant collected in Shimane Prefecture, Japan and isolated two new 8, 9seco-ent-kaurenoid diterpenes, rabdoshikoccins A (1) and B (6) together with the known compounds, shikoccin (3) [2], shikoccidin (9) [2] and leukamenin E (10) [3]. This paper describes the structure elucidation of the new compounds. RESULTS AND DISCUSSION
Rabdoshikoccin A (1) was obtained as an amorphous powder and the molecular formula was determined as C2oH2sO * based on its HRMS and CIMS. It showed an absorption maximum at 242 nm (log e 3.49) in the UV spectrum. The ~H and ~3CNMR spectra suggested the presence of three tertiary methyl groups [fH 1.14 (6H, s) and 1.51 (3H, s); 6c16.8, 17.2 and 29.0 (q)], an exomethylene group conjugated with a carbonyl group [fin 5.40 and 6.22 (each 1H, br s); fc 116.0 (t)], a trisubstituted double bond conjugated with a carbonyl group [f~7.51 (1H, d, J = 3.5 Hz); Jc 147.1 (s) and 159.5 (d)], two secondary carbinyl groups [JH3.49 (1H, dd, J = 11.5 and
*Authors to whom correspondence should be addressed.
'
R=~
~O 18 19
(1) (2) (3) (4) (5) (6) (7) (8)
'~OH
~o AeO
Hb ~a
RI=H ; R2--c(.OH,[}-Ha ; R3=OH R1--H ; R2=a-OAc, ~-H ; R3=OAc RI=H ; Ra=a.H, I~OAC ; R3---OH RI--OAc ; R2==a-H,~OAc ; R3=OH RI=RZ--OH ; R2--H2 RI=Ra=OH ; R2.=a-H,~OAc RI=Rn-.--OAc;R2--rz-H,~OAc RI=R3=H ; R2=H2
(9) ~oN (10) R=H
4.0 Hz) (Ha) and 5.28 (1H, dd, J = 11.5 and 5.0 Hz) (Hb)], 6c77.2 and 64.1 (each t0, and two carbonyl groups in which one is conjugated [6c195.3 (s)] and another is isolated [6c214.6 (s)]. The ~3C NMR spectrum, in addition to the above mentioned signals, further showed the presence of five methylene groups, two methine groups and two quaternary carbon atoms. These spectral data, coupled with the consideration on the structures of diterpenes isolated so far from the genus Rabdosia [4], rabdoshikoccin A (1) is tricyclic and was presumed to have a structure in which two hydroxyl groups are introduced into the basic skeleton, 8. Actually, acetylation of I with a mixture of Ac20 and pyridine gave the diacetate (2). One of the two hydroxyl groups in 1 was presumed to be located at C-7~ by comparing the chemical shift and coupling patterns of a earbinyl proton, Hb and a carbon atom [6 c 64.1 (d)] with those a shikoccin (3) [6u5.10 (1H, dd, J = l l and 5 Hz); 6c 64.3 (d)] [2] and shikodomedin (4) [5] [6n5.13 (1H, dd, J= 11 and 5 Hz);
1289
1290
Y. TAKEDAet al.
6c63.8 (d)]. Another hydroxyl group in 1 was suggested to be located on a carbon between a methylene group and a quaternary carbon atom and takes an equatorial orientation judged from the coupling pattern of the proton on the carbon having the hydroxyl group. The possible position is restricted to C-I~ and C-3~. The location was presumed to be on C-3~ by comparing the chemical shift of the l aC signal of C-10 (~c53.7) in 1 with those (6c 53.0 and 59.6) in 3 and rabdolatifolin (5) [6]. The presumption was further supported by the fact that the signal of C-19 in I suffered an upfield shift like that of C-24 in betulinic acid having a hydroxyl group at C-3 with the same orientation [7]. The aforementioned discussions on the location of the hydroxyl groups were finally confirmed by the NOESY experiments for the diacetate (2). Namely, the signal (~5H1.27) assigned to H-5 crossed peaks with protons [6H4.75 (1H, dd, J = 11.5 and 4 Hz) and 5.91 (IH, dd, d = 12 and 5 Hz)] which are located on carbons having an acetoxyl group. Thus, the structure of rabdshikoccin A has been elucidated as 1. Rabdoshikoccin B (6) was isolated as an amorphous powder and the molecular formula was determined as C22H3oO 6 based on its HRMS. The spectral data (see Table 1 and Experimental) showed the presence of three tertiary methyl groups, an acetoxyl group, an exo-methylene group conjugated with a carbonyl group, trisubstituted double bond conjugated with a carbonyl group two secondary hydroxyl groups and an isolated carbonyl group as partial structures and are very similar to those of shikodomedin (4) [5], except for the fact that the numbers of acetoxyl groups decreased from two in 4 to one in 6 and the proton signal assigned to H-1 [~n4.82 (1H, dd, J = 11.0 and 5.5 Hz)] undergoes an upfield shift by 1.1 ppm compared with that of 4. Acetylation of rabdoshikoccin B (6) gave the diacetate (7) which was identical to shikodomedin monoacetate. Thus, the structure of rabdoshikoccin B was determined as 6 which corresponds to a 1-O-deacetyl derivative of shikodomedin (4). EXPERIMENTAL
General. t H N M R : 200 or 400MHz; 13CNMR: 50 MHz, TMS as int. standard. EIMS: 70 eV; CIMS: isobutane. CC: silica gel 60 (0.05-0.2 ram). TLC and prep. TLC: silica gel 60 F254 (0.25 and 0.5 mm in thickness), respectively. Plant material. Plant material was collected in Kanagi Town, Shimane Prefecture, Japan in early October, 1987 and identified as R. shikokiana var. occidentalis (Murata) Hara by one [H. O.] of the authors. A voucher specimen [87-RSO-Kanagi] is kept in the laboratory of one [H.O.] of the authors. Isolation. Dried aerial parts (305 g) of R. shikokiana var. occidentalis were extracted with MeOH (51) for 2 weeks at room temp. The extraction was repeated once in the same manner. The combined MeOH extract was coned in vacuo. The residue was partitioned between 90% MeOH (330 ml) and n-hexane (300 ml x 3). The 90% MeOH layer was concd in vacuo and then the residue was suspended in H 2 0 (330 ml). The suspension was ex-
Table 1. 13CNMR data (6) of rabdoshikoccins A (1) and B (6) for CsDsN solution Carbon 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Me3CO-
1 32.3 27.4 77.2 41.5 42.6 37.6 64.1 147.1 2t4.6 53.7 31.1 26.1 43.9 159.5 195.3 * 116.0 29.0 17.2f 16.8f
6 67.5 32.0 78.2 38.4 38.4 37.1 64.0 147.1 214.1 59.4 30.6 26.0 42.7 159.5 195.3 * 115.8 27.7 22.1 11.8 20.8, 170.0
*The signal was overlapped with the solvent signals. fMay be reversed.
tracted with EtOAc (300 ml x 3). After washing with H20, the EtOAc extract was dried and evapd in vacuo to give a residue (6.0 g) which was chromatographed over silica gel (200 g) with CHC13-Me2CO as eluant with increasing Me2CO content. CHCI a (2.2 1), CHCIa-Me2CO 19:1 (1.5 1), CHCla-Me2CO 9:1 (1 1), CHCI3-Me2CO 17:3 (1 l) and CHCI3-Me2CO 4:1 (1 l) were passed successively and 100 ml frs were collected. Fr. nos 16-24 gave a residue (1.61 g) which was treated with active charcoal in MeOH to give a residue (750 rag). An aliquot (100 mg) was purified by prep. TLC (solvent: Et20, developed twice) to give shikoccin (3) [2]. Fr. nos 36-38 gave a residue (213 mg) which was sepd by prep. TLC (solvent: Et20, developed twice) it give shikoccin (3, 27.3 mg), shikoccidin (9) [2] (52.8 mg) and leukamenin E (10) [3] (35.9 mg). Fr. nos 54-61 gave a residue (165 rag) which was sepd by repeated prep. TLC (solvent: Et20, developed 3 x and then solvent: Et20 , developed 6 x ) to give rabdoshikoccin A (1, 10.0 mg) and rabdoshikoccin B (6, 4.4 mg). The known compounds were identified by direct comparison with authentic samples. The physical properties of the new compounds are as follows. Rabdoshikoccin A (1). [~t]27 -33.0 ~ (MeOH; c 0.58); UV ~ueoa. .cao3 3425, 1700, 1650 --max 9 242 nm (log ~ 3.49); IR - - - Vrnax and 1620 cm- 1; 1H NMR (CsDsN): ~ 1.14 (6H, s, tert. Me x2), 1.51 (3H, s, tert. Me), 3.49 (1H, dd, J = l l . 5 and 4.0 Hz, H-3), 5.28 (1H, dd, J = 11.5 and 5.0 Hz, H-7), 5.40 and 6.22 (each IH, br s, H2-17) and 7.51 (1H, d, J = 3.5 Hz, H-14); 13CNMR: Table 1; CIMS: m/z 333 [ M + I ] + ; ELMS: m/z 314.1871 [ M - H 2 0 ] § and 296.1798 [M
seco-ent-Kaurenoids from Rabdosia shikokiana - 2 H 2 0 ] +. calcd for C20H2603 and C2oH2402" 314.1882 and 296.1776. Rabdoshikoccin B (6). [~t]27 ~ 0 ~ (MeOH; c 0.64); UV ~Meon. 241 (log e 3.64); IR Vma xcn~ 3425, 1710, 1685, 1640 and 1610 cm-1; 1H NMR (CsDsN): 60.97, 1.16 and 1.35 (each 3H, s, 3 x tert. Me), 2.21 (3H, s, OAc), 4.82 (1H, dd, J = 11.0 and 5.5 Hz, H-l), 5.07 (1H, t, J = 3.0 Hz, H-3), 5.17 (1H, dd, J = 11.5 and 5.5 Hz, H-7), 5.36 and 6.22 (each IH, br s, H2-17 ) and 7.62 (1H, d, J = 3 . 0 Hz, H-14); laC NMR: Table 1; EIMS m/z: 390.2060 [M] +. Calcd for C22H3oO6" 390.2042. Rabdoshikoccin A diacetate (2). Rabdoshikoccin A (1, 6.7 rag) was dissolved in a mixt. of pyridine (0.3 ml) and Ac20 (0.3 ml) and the soln was left at room temp. for 15 hr. After addition of excess MeOH, the solvent was concd in vacuo to give a residue which was purified by prep. TLC (solvent: Et20 ) to give the diacetate (2, 3.6 rag). IR Vma xcHc13". 1720, 1710, 1690, 1240, 1210 and 1200 cm-1; 1HNMR (CsDsN): 61.02, 1.05 and 1.33 (each 3H, s, 3 x tert. Me), 1.27 (1H, m) 2.03 and 2.04 (each 3H, s, 2 x OAc), 4.75 (1H, dd, J= 11.5 and 4.0 Hz), 5.91 (1H, dd, J = 12.0 and 5.0 Hz), 5.45 and 6.22 (each 1H, br s) and 7.32 (1H, d, J = 2 . 8 Hz); CIMS m/z 417 [ M + I ] + ; EIMS m/z 416.2201 [M] +. Calcd for C24H3206;416.2199. Acetylation of rabdoshikoccin B (6). Rabdoshikoccin B (6, 4.1 rag) was acetylated as above to give the diacetate --max
1291
(7) which was identical with shikodomedin monoacetate in all respects.
9
Acknowledgements--The authors thank the staff of the Analytical Centre of Faculty of Pharmaceutical Sciences, The University of Tokushima for measurements of NMR and mass spectra. REFERENCES
1. Hara, H. (1972) J. Jpn Botany 47, 193. 2. Node, M., Ito, N., Uchida, I., Fujita, E. and Fuji, K. (1985) Chem. Pharm. Bull. 33, 1029. 3. Takeda, Y., Fujita, T. and Ueno, A. (1977) Chem. Letters 289. 4. Fujita, E. and Node, M. (1984) in Progress in the Chemistry of Organic Natural Products (Herz, W., Griesebach, H., Kirby, G. W. and Tamm, Ch., eds), Vol. 46, p. 77. Springer, Vienna. 5. Fujita, T., Takeda, Y., Shingu, T., Kido, M. and Taira, Z. (1982) J. Chem. Soc. Chem. Commun. 162. 6. Takeda, Y., Fujita, T. and Ueno, A. (1983) Phytochemistry 22, 2531. 7. Kitajima, J., Shindo, M. and Tanaka, Y. (1990) Chem. Pharm. Bull. 38, 714.
Phvtocheraistry, Vol. 35, No. 5, pp. 1289-1291, 1994 Copyright 9 1994 Elsevier Science Ltd Printed in Great Britain. All rights reserved 0031-9422/94 $6.00+0.00
RABDOSHIKOCCINS A A N D B, 8,9-SECO-ENT-KAURENOIDS FROM RABDOSIA SHIKOKIANA VAR. OCCIDENTALIS
YOSHIO TAKEDA,* YUKAKO FUTATSUISHI,'~TAKASHIMATSUMOTO, HIROSHI TERADA,~"and HIDEAKI OTSUKA*:~ Faculty of Integrated Arts and Sciences, The University of Tokushima, Tokushima 770, Japan; "~Facultyof Pharmaceutical Sciences, The University of Tokushima, Tokushima 770, Japan; //Pharmaceutical Institute, Hiroshima University School of Medicine, Minami-ku, Hiroshima 734, Japan
(Received 23 August 1993)
Key Word Index--Rabdosia shikokiana var. occidentalis; Labiatae; 8,9-seco-ent-kaurenoid; rabdoshikoccins A and B.
Abstract--From the aerial parts of Rabdosia shikokiana var. occidentalis, two new 8,9-seco-ent-kaurenoid diterpenes, rabdoshikoccins A and B, were isolated together with the known compounds, shikoccin, shikoccidin and leukamenin E. The structures of the new compounds were elucidated based on the spectroscopic and chemical evidence.
INTRODUCTION
From Rabdosia shikokiana var. occidentalis (Murata) Hara [1], four 8,9-seco-ent-kaurenoid diterpenes, shikoccin, O-methylshikoccin, epoxyshikoccin and O-methylepoxyshikoccin, and three ent-kaurenoid diterpenes, shikoccidin, isodomedin and leukamenin E, were isolated [2]. During the course of our studies on the biologically active substances of the genus Rabdosia (Labiatae), we examined the constituents of the title plant collected in Shimane Prefecture, Japan and isolated two new 8, 9seco-ent-kaurenoid diterpenes, rabdoshikoccins A (1) and B (6) together with the known compounds, shikoccin (3) [2], shikoccidin (9) [2] and leukamenin E (10) [3]. This paper describes the structure elucidation of the new compounds. RESULTS AND DISCUSSION
Rabdoshikoccin A (1) was obtained as an amorphous powder and the molecular formula was determined as C2oH2sO * based on its HRMS and CIMS. It showed an absorption maximum at 242 nm (log e 3.49) in the UV spectrum. The ~H and ~3CNMR spectra suggested the presence of three tertiary methyl groups [fH 1.14 (6H, s) and 1.51 (3H, s); 6c16.8, 17.2 and 29.0 (q)], an exomethylene group conjugated with a carbonyl group [fin 5.40 and 6.22 (each 1H, br s); fc 116.0 (t)], a trisubstituted double bond conjugated with a carbonyl group [f~7.51 (1H, d, J = 3.5 Hz); Jc 147.1 (s) and 159.5 (d)], two secondary carbinyl groups [JH3.49 (1H, dd, J = 11.5 and
*Authors to whom correspondence should be addressed.
'
R=~
~O 18 19
(1) (2) (3) (4) (5) (6) (7) (8)
'~OH
~o AeO
Hb ~a
RI=H ; R2--c(.OH,[}-Ha ; R3=OH R1--H ; R2=a-OAc, ~-H ; R3=OAc RI=H ; Ra=a.H, I~OAC ; R3---OH RI--OAc ; R2==a-H,~OAc ; R3=OH RI=RZ--OH ; R2--H2 RI=Ra=OH ; R2.=a-H,~OAc RI=Rn-.--OAc;R2--rz-H,~OAc RI=R3=H ; R2=H2
(9) ~oN (10) R=H
4.0 Hz) (Ha) and 5.28 (1H, dd, J = 11.5 and 5.0 Hz) (Hb)], 6c77.2 and 64.1 (each t0, and two carbonyl groups in which one is conjugated [6c195.3 (s)] and another is isolated [6c214.6 (s)]. The ~3C NMR spectrum, in addition to the above mentioned signals, further showed the presence of five methylene groups, two methine groups and two quaternary carbon atoms. These spectral data, coupled with the consideration on the structures of diterpenes isolated so far from the genus Rabdosia [4], rabdoshikoccin A (1) is tricyclic and was presumed to have a structure in which two hydroxyl groups are introduced into the basic skeleton, 8. Actually, acetylation of I with a mixture of Ac20 and pyridine gave the diacetate (2). One of the two hydroxyl groups in 1 was presumed to be located at C-7~ by comparing the chemical shift and coupling patterns of a earbinyl proton, Hb and a carbon atom [6 c 64.1 (d)] with those a shikoccin (3) [6u5.10 (1H, dd, J = l l and 5 Hz); 6c 64.3 (d)] [2] and shikodomedin (4) [5] [6n5.13 (1H, dd, J= 11 and 5 Hz);
1289
1290
Y. TAKEDAet al.
6c63.8 (d)]. Another hydroxyl group in 1 was suggested to be located on a carbon between a methylene group and a quaternary carbon atom and takes an equatorial orientation judged from the coupling pattern of the proton on the carbon having the hydroxyl group. The possible position is restricted to C-I~ and C-3~. The location was presumed to be on C-3~ by comparing the chemical shift of the l aC signal of C-10 (~c53.7) in 1 with those (6c 53.0 and 59.6) in 3 and rabdolatifolin (5) [6]. The presumption was further supported by the fact that the signal of C-19 in I suffered an upfield shift like that of C-24 in betulinic acid having a hydroxyl group at C-3 with the same orientation [7]. The aforementioned discussions on the location of the hydroxyl groups were finally confirmed by the NOESY experiments for the diacetate (2). Namely, the signal (~5H1.27) assigned to H-5 crossed peaks with protons [6H4.75 (1H, dd, J = 11.5 and 4 Hz) and 5.91 (IH, dd, d = 12 and 5 Hz)] which are located on carbons having an acetoxyl group. Thus, the structure of rabdshikoccin A has been elucidated as 1. Rabdoshikoccin B (6) was isolated as an amorphous powder and the molecular formula was determined as C22H3oO 6 based on its HRMS. The spectral data (see Table 1 and Experimental) showed the presence of three tertiary methyl groups, an acetoxyl group, an exo-methylene group conjugated with a carbonyl group, trisubstituted double bond conjugated with a carbonyl group two secondary hydroxyl groups and an isolated carbonyl group as partial structures and are very similar to those of shikodomedin (4) [5], except for the fact that the numbers of acetoxyl groups decreased from two in 4 to one in 6 and the proton signal assigned to H-1 [~n4.82 (1H, dd, J = 11.0 and 5.5 Hz)] undergoes an upfield shift by 1.1 ppm compared with that of 4. Acetylation of rabdoshikoccin B (6) gave the diacetate (7) which was identical to shikodomedin monoacetate. Thus, the structure of rabdoshikoccin B was determined as 6 which corresponds to a 1-O-deacetyl derivative of shikodomedin (4). EXPERIMENTAL
General. t H N M R : 200 or 400MHz; 13CNMR: 50 MHz, TMS as int. standard. EIMS: 70 eV; CIMS: isobutane. CC: silica gel 60 (0.05-0.2 ram). TLC and prep. TLC: silica gel 60 F254 (0.25 and 0.5 mm in thickness), respectively. Plant material. Plant material was collected in Kanagi Town, Shimane Prefecture, Japan in early October, 1987 and identified as R. shikokiana var. occidentalis (Murata) Hara by one [H. O.] of the authors. A voucher specimen [87-RSO-Kanagi] is kept in the laboratory of one [H.O.] of the authors. Isolation. Dried aerial parts (305 g) of R. shikokiana var. occidentalis were extracted with MeOH (51) for 2 weeks at room temp. The extraction was repeated once in the same manner. The combined MeOH extract was coned in vacuo. The residue was partitioned between 90% MeOH (330 ml) and n-hexane (300 ml x 3). The 90% MeOH layer was concd in vacuo and then the residue was suspended in H 2 0 (330 ml). The suspension was ex-
Table 1. 13CNMR data (6) of rabdoshikoccins A (1) and B (6) for CsDsN solution Carbon 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Me3CO-
1 32.3 27.4 77.2 41.5 42.6 37.6 64.1 147.1 2t4.6 53.7 31.1 26.1 43.9 159.5 195.3 * 116.0 29.0 17.2f 16.8f
6 67.5 32.0 78.2 38.4 38.4 37.1 64.0 147.1 214.1 59.4 30.6 26.0 42.7 159.5 195.3 * 115.8 27.7 22.1 11.8 20.8, 170.0
*The signal was overlapped with the solvent signals. fMay be reversed.
tracted with EtOAc (300 ml x 3). After washing with H20, the EtOAc extract was dried and evapd in vacuo to give a residue (6.0 g) which was chromatographed over silica gel (200 g) with CHC13-Me2CO as eluant with increasing Me2CO content. CHCI a (2.2 1), CHCIa-Me2CO 19:1 (1.5 1), CHCla-Me2CO 9:1 (1 1), CHCI3-Me2CO 17:3 (1 l) and CHCI3-Me2CO 4:1 (1 l) were passed successively and 100 ml frs were collected. Fr. nos 16-24 gave a residue (1.61 g) which was treated with active charcoal in MeOH to give a residue (750 rag). An aliquot (100 mg) was purified by prep. TLC (solvent: Et20, developed twice) to give shikoccin (3) [2]. Fr. nos 36-38 gave a residue (213 mg) which was sepd by prep. TLC (solvent: Et20, developed twice) it give shikoccin (3, 27.3 mg), shikoccidin (9) [2] (52.8 mg) and leukamenin E (10) [3] (35.9 mg). Fr. nos 54-61 gave a residue (165 rag) which was sepd by repeated prep. TLC (solvent: Et20, developed 3 x and then solvent: Et20 , developed 6 x ) to give rabdoshikoccin A (1, 10.0 mg) and rabdoshikoccin B (6, 4.4 mg). The known compounds were identified by direct comparison with authentic samples. The physical properties of the new compounds are as follows. Rabdoshikoccin A (1). [~t]27 -33.0 ~ (MeOH; c 0.58); UV ~ueoa. .cao3 3425, 1700, 1650 --max 9 242 nm (log ~ 3.49); IR - - - Vrnax and 1620 cm- 1; 1H NMR (CsDsN): ~ 1.14 (6H, s, tert. Me x2), 1.51 (3H, s, tert. Me), 3.49 (1H, dd, J = l l . 5 and 4.0 Hz, H-3), 5.28 (1H, dd, J = 11.5 and 5.0 Hz, H-7), 5.40 and 6.22 (each IH, br s, H2-17) and 7.51 (1H, d, J = 3.5 Hz, H-14); 13CNMR: Table 1; CIMS: m/z 333 [ M + I ] + ; ELMS: m/z 314.1871 [ M - H 2 0 ] § and 296.1798 [M
seco-ent-Kaurenoids from Rabdosia shikokiana - 2 H 2 0 ] +. calcd for C20H2603 and C2oH2402" 314.1882 and 296.1776. Rabdoshikoccin B (6). [~t]27 ~ 0 ~ (MeOH; c 0.64); UV ~Meon. 241 (log e 3.64); IR Vma xcn~ 3425, 1710, 1685, 1640 and 1610 cm-1; 1H NMR (CsDsN): 60.97, 1.16 and 1.35 (each 3H, s, 3 x tert. Me), 2.21 (3H, s, OAc), 4.82 (1H, dd, J = 11.0 and 5.5 Hz, H-l), 5.07 (1H, t, J = 3.0 Hz, H-3), 5.17 (1H, dd, J = 11.5 and 5.5 Hz, H-7), 5.36 and 6.22 (each IH, br s, H2-17 ) and 7.62 (1H, d, J = 3 . 0 Hz, H-14); laC NMR: Table 1; EIMS m/z: 390.2060 [M] +. Calcd for C22H3oO6" 390.2042. Rabdoshikoccin A diacetate (2). Rabdoshikoccin A (1, 6.7 rag) was dissolved in a mixt. of pyridine (0.3 ml) and Ac20 (0.3 ml) and the soln was left at room temp. for 15 hr. After addition of excess MeOH, the solvent was concd in vacuo to give a residue which was purified by prep. TLC (solvent: Et20 ) to give the diacetate (2, 3.6 rag). IR Vma xcHc13". 1720, 1710, 1690, 1240, 1210 and 1200 cm-1; 1HNMR (CsDsN): 61.02, 1.05 and 1.33 (each 3H, s, 3 x tert. Me), 1.27 (1H, m) 2.03 and 2.04 (each 3H, s, 2 x OAc), 4.75 (1H, dd, J= 11.5 and 4.0 Hz), 5.91 (1H, dd, J = 12.0 and 5.0 Hz), 5.45 and 6.22 (each 1H, br s) and 7.32 (1H, d, J = 2 . 8 Hz); CIMS m/z 417 [ M + I ] + ; EIMS m/z 416.2201 [M] +. Calcd for C24H3206;416.2199. Acetylation of rabdoshikoccin B (6). Rabdoshikoccin B (6, 4.1 rag) was acetylated as above to give the diacetate --max
1291
(7) which was identical with shikodomedin monoacetate in all respects.
9
Acknowledgements--The authors thank the staff of the Analytical Centre of Faculty of Pharmaceutical Sciences, The University of Tokushima for measurements of NMR and mass spectra. REFERENCES
1. Hara, H. (1972) J. Jpn Botany 47, 193. 2. Node, M., Ito, N., Uchida, I., Fujita, E. and Fuji, K. (1985) Chem. Pharm. Bull. 33, 1029. 3. Takeda, Y., Fujita, T. and Ueno, A. (1977) Chem. Letters 289. 4. Fujita, E. and Node, M. (1984) in Progress in the Chemistry of Organic Natural Products (Herz, W., Griesebach, H., Kirby, G. W. and Tamm, Ch., eds), Vol. 46, p. 77. Springer, Vienna. 5. Fujita, T., Takeda, Y., Shingu, T., Kido, M. and Taira, Z. (1982) J. Chem. Soc. Chem. Commun. 162. 6. Takeda, Y., Fujita, T. and Ueno, A. (1983) Phytochemistry 22, 2531. 7. Kitajima, J., Shindo, M. and Tanaka, Y. (1990) Chem. Pharm. Bull. 38, 714.