Five new diterpenoids from the wood of Cunninghamia konishii

Article abstract of DOI:10.1021/np980074c

Five new diterpenes, 3β-acetoxyabieta-8,11,13-trien-12-ol (1), 8α- hydroxy-13(16),14-labdadien-19-al (2), 16-hydroxy-19-oxomanoyl oxide (3), 15- nor-14-oxo-8(17),12-labdadiene-18-ol (4), and 15,16-bisnor-13-oxo-8(17),11- labdadien-18-ol (5), were isolated from the wood of Cunninghamia konishii. Their structures were elucidated by 2D NMR spectroscopy and by chemical methods.

Full text of DOI:10.1021/np980074c

J . Nat. Prod. 1998, 61, 997-1000
997
F ive New Diter p en oid s fr om th e Wood of Cu n n in gh a m ia kon ish ii
Yen-Cheng Li† and Yueh-Hsiung Kuo*,†,‡
Department of Chemistry, National Taiwan University, and National Research Institute of Chinese Medicine,
Taipei, Taiwan, Republic of China
Received March 4, 1998
Five new diterpenes, 3â-acetoxyabieta-8,11,13-trien-12-ol (1), 8R-hydroxy-13(16),14-labdadien-
19-al (2), 16-hydroxy-19-oxomanoyl oxide (3), 15-nor-14-oxo-8(17),12-labdadiene-18-ol (4), and
15,16-bisnor-13-oxo-8(17),11-labdadien-18-ol (5), were isolated from the wood of Cunninghamia
konishii. Their structures were elucidated by 2D NMR spectroscopy and by chemical methods.
Only two species of Cunninghamia (Taxodiaceae)
grow in Taiwan. Cunninghamia konishii Hayata is a
coniferous tree, distributed in the northern and central
parts of Taiwan at altitudes of 1300-2700 m. The wood
of this tree is one of the best building materials available
in Taiwan. In previous investigations on the chemical
composition, the essential oils of the wood1,2 and the
milled bark3 were reported. We now describe the
compounds obtained from the wood. The methanol
extract of the wood of C. konishii was concentrated to
give a residue that was suspended in water and parti-
tioned with n-hexane, ethyl acetate, and n-BuOH,
successively. Repeated chromatography of the ethyl
acetate extract over silica gel and by HPLC yielded five
new compounds (1-5).
Resu lts a n d Discu ssion
Compound 1 showed a molecular formula C22H32O3
by high-resolution mass spectrometry. Absorptions in
the IR spectrum were attributable to a hydroxyl (3413
cm-1), an ester carbonyl (1737 cm-1), and a benzene ring
1
(1615 and 1495 cm-1). Observed H NMR signals were
attributable to a phenyl group (δ 6.81 and 6.58), a
phenolic proton (δ 5.03, disappeared upon addition of
D2O), an acetoxy group (δ 2.05), an isopropyl group [δ
3.09 (1H, sept), 1.21 and 1.20 (3H each, d)], and three
singlet methyl groups (δ 1.18, 0.94, and 0.92). A typical
Hâ-1 signal of a dehydroabietane diterpene was observed
at δ 2.17 (1H, ddd, J ) 13.2, 3.3, 3.3 Hz).4,5 Comparison
1
of the H and 13C NMR (Table 1) spectral data 1 and
hinokiol (6)6 permitted the assignment of 1 as a hinokiol
derivative with an extra acetyl group at C-3. The proton
presence of a conjugated diene. The IR spectrum showed
hydroxyl (3433 cm-1) and carbonyl (1716 cm-1) absorp-
tion bands. Its H NMR spectrum contained a singlet
resonating at δ 4.51 (dd, J ) 11.1, 4.9 Hz) was attribut-
able to H-3 with an R-axial orientation and was geminal
to the acetoxyl group. Compound 1 was hydrolyzed with
0.5 N sodium hydroxide to afford a product that was
identical to 6 by comparison with an authentic sample.
On the basis of additional confirmation by DEPT and
2D NMR, the structure of 1 was elucidated as 3â-
acetoxyabieta-8,11,13-trien-12-ol.
1
at δ 9.72 (1H, formyl group situated at a quaternary
carbon) as well as an A2B2X system [δ 6.33 (1H, dd, J
) 17.6, 10.8 Hz, H-14), 5.27 (1H, d, J ) 17.6 Hz, Ha-
15), 5.03 (1H, d, J ) 10.8 Hz, Hb-15), and 4.99 (2H, brs,
H-16)], which was similar to that shown by 6-deoxyan-
dalusal (7).7 Comparison of the chemical shift of the
three methyl singlets of 2 and 7 [δ 1.16 (H3-17), 1.01
(H3-18), 0.65 (H3-20) for 2; δ 1.08 (H3-17), 0.97 (H3-19),
0.83 (H3-20) for 7] showed H3-20 in 2 to be shielded, an
effect attributable to the presence of an axial formyl
group at C-19. The relative stereochemistry was eluci-
dated by the NOESY method; the formyl group exhib-
ited a NOE correlation with H3-20, and H3-20 showed
The new labdadiene-type derivative, compound 2, was
found to have a molecular formula of C20H32O2, and its
UV spectrum showed a maximum at 224 nm due to the
* To whom correspondence should be addressed. Tel.: 886-2-
23690152-119. Fax: 886-2-23636359.
† Department of Chemistry, National Taiwan University.
‡ National Research Institute of Chinese Medicine.
S0163-3864(98)00074-3 CCC: $15.00
© 1998 American Chemical Society and American Society of Pharmacognosy
Published on Web 07/18/1998

998 J ournal of Natural Products, 1998, Vol. 61, No. 8
Li and Kuo
Ta ble 1. 13C NMR Spectral Data of Compounds 1-5 (75 MHz,
spectral data. Analysis of all of the evidence above
confirmed the structure of 3 as 16-hydroxy-19-oxoman-
oyl oxide.
in CDCl3)
position
1
2
3
4
5
1
2
3
4
5
6
7
8
36.5
18.9
80.7
37.2
49.8
24.4
29.9
126.8
147.4
37.9
110.9
150.9
131.8
126.6
26.8
39.1
18.3
34.3
48.3
56.5
20.2
44.5
73.8
60.4
39.4
24.6
34.9
147.2
138.7
113.5
115.8
24.0
24.2
205.4
14.2
38.3
18.3
34.3
48.3
56.7
19.8
43.5
75.0
51.5
37.6
14.7
26.8
76.7
143.8
114.2
68.6
25.7
24.1
205.4
13.9
38.8
18.6
35.3
38.0
48.3
23.9
37.6
148.0
56.5
39.4
40.3
18.3
35.4
39.1
47.3
22.9
36.3
148.3
60.7
38.0
High-resolution EIMS of 4 demonstrated a molecular
formula C19H30O2, and the IR spectrum showed a
conjugated carbonyl group (νmax 1692 cm-1). The exist-
ence of 19 carbons with 29 directly attached protons was
confirmed from 13C/DEPT NMR experiments and indi-
cated an exocyclic double bond [δ 107.8 (t), 148.0 (s)] in
addition to a conjugated aldehyde [δ 195.2 (d), 138.9 (s),
156.3 (d)]. The chemical shifts (C-1 to C-10, C-19 and
C-20) in the 13C NMR spectrum of 4 showed similarities
to those of 13-epitorreferol (9).9 Therefore, the labdane
skeleton and the relative stereochemistry around the
9
10
11
12
13
14
15
16
17
18
19
20
OAc
24.4
146.4
133.6
198.1
27.3
156.3
138.9
195.2
1
rigid decalin ring system could be established. The H
22.7a
22.5a
28.2
16.5
24.9
9.4
107.8
71.9
17.6
14.9
NMR spectrum of 4 indicated the appearance of three
methyl groups (δ 0.76, 0.78, and 1.77), a hydroxymeth-
ylene group [δ 3.10 and 3.14 (1H each, d)], three olefin
protons [δ 4.37, 4.83 (1H each, brs), and 6.41 (1H, br
t)], and one formyl proton (δ 9.32, s). All of these data
were similar to those of the model compound 15-nor-
14-oxo-8(17),12-labdadien-18-oate (10)10 except for the
occurrence of a hydroxymethylene group instead of a
carboxylate group. The formyl proton (H-14) and H-12
were shown to be syn on the basis of an NOE correlation
between them, and the hydroxymethylene group was
assigned in the equatorial position because of the lack
of any NOE correlation between the hydroxymethylene
protons and H3-20. Therefore, the structure of 4 was
proposed as 15-nor-14-oxo-8(17),12-labdadien-18-ol.
108.7
71.8
17.8
15.6
21.3
171.1
a
Interchangeable.
an NOE correlation with H3-17. This evidence indicated
that the formyl group and the two methyl groups at δ
0.65 (H3-17) and 1.16 (H3-20) were all in the axial
orientation. The additional proof for this structure 2 was
obtained by using HMBC and HMQC techniques. Hence,
compound 2 was assigned as 8R-hydroxy-13(16),14-
labdadien-19-al.
Compound 5, [R]27D +8.5°, was analyzed as C18H28O2
by HRMS. Its 13C NMR spectrum showed signals for
18 carbons. The UV absorption at 225 nm and the IR
absorption bands at 3420 (OH), 1667 (CdO), and 887
(>CdCH2) cm-1 suggested the presence of a hydroxyl
group, an enone system, and exocyclic double-bond
functionalities in the molecule. The presence of the
second functionality was further indicated by its 1H
NMR signals at δ 2.25 (3H, s), 6.05 (1H, d, J ) 16.0
Hz), and 6.84 (1H, dd, J ) 16.0, 10.3 Hz), being assigned
to a trans-R,â-unsaturated methyl ketone group. The
third functionality was indicated by its 13C NMR signals
at δ 148.3 (s) and 108.7 (t), which were attributable to
a 1,1-disubstituted olefin. In addition, the 1H NMR
spectrum of 5 also showed signals for two tertiary
methyl groups at δ 0.77 and 0.91 (3H each, s) and two
terminal methylene protons at δ 4.40 and 4.78 (1H each,
brs), and an AB system [δ 3.10 and 3.41 (1H each, d)]
was derived from a hydroxymethylene group. The 1H
and 13C NMR signals of 5 and 15,16-dinor-8(17),11-
labdadien-13-one (11) were compared,11 and the struc-
ture of compound 5 could be deduced as the 18-hydroxy
derivative of 11. The olefinic proton δ 6.84 (H-11) gave
an NOE correlation with an acetyl methyl at δ 2.25 (H3-
14) indicating a cis relationship between H-11 and H3-
14. The methyl group at δ 0.91 (H3-20) correlated to a
signal at δ 0.77 (H3-19) but not to the hydroxymethylene
group. This result also confirmed that the hydroxyl
group has located at C-18. The H2-18 and H-5 signals
as well as the H-5 and H-9 showed NOE correlations
consistent with the structure proposed. Therefore, the
structure of 5 was assigned as 15,16-bisnor-13-oxo-
8(7),11-labdadien-18-ol.
The most polar compound, 3, obtained in this study
exhibited a molecular formula of C20H32O3 on the basis
of HRMS. Its IR spectrum indicated hydroxyl (3432
cm-1), carbonyl (1718 cm-1), and monosubstituted double
bond (3071, 1634, 992, and 908 cm-1) functional groups.
1
The H and 13C NMR spectra showed that 3 contained
an aldehyde (δ 9.72), three singlet methyl groups, a
hydroxymethylene group [δH 3.28 (2H, s), δC 68.6], and
a vinylic ABX system [δ 5.79 (dd, J ) 17.2, 10.8 Hz),
5.24 (dd, J ) 17.2, 1.6 Hz), and 5.11 (dd, J ) 10.8, 1.6
Hz)], similar to jabugodiol (8),8 except that one of the
two hydroxymethylene groups in 8 was replaced by a
formyl group in 3. The presence of the C-9 signal at δ
51.5 (the corresponding signal occurred at 52.8 for 8)
also indicated that 3 is a manoyl oxide derivative.8
Comparison of the two methyl singlets of 3 (δ 1.00, 0.66)
and 2 (δ 1.01, 0.65) indicated that the hydroxymethylene
group [δH 3.28 (2H, s)] in 3 was not situated at C-4â or
C-10, and its most probable location should be either
C-8 or C-13. The similar chemical shifts of C-8 and C-13
of 3 and 8 [δ 75.0 and 76.7 for 3; δ 75.5 and 76.3 for 8]
indicated that the hydroxymethylene group [δH 3.28
(2H, s, H2-16)] was situated at C-13 (H2-16 of 8 is also
equivalent at δ 3.30). Thus, the formyl group of 3 was
placed at C-4â because of the observation of the H3-20
methyl signal resonating at a higher field (δ 0.66).
Regarding the stereochemistry of 3, pronounced NOESY
correlations between the formyl proton (H-19) and H3-
20, H3-20 and H3-17, and H3-17 and H2-16 illustrated
that the protons of H-19, H3-20, H3-17, and H2-16 were
all in the axial orientation. Reduction of 3 with sodium
borohydride in methanol afforded a product that was
identical to (+)-8 by comparing 1H and 13C NMR

Diterpenoids from the Wood of Cunninghamia
J ournal of Natural Products, 1998, Vol. 61, No. 8 999
Exp er im en ta l Section
(CDCl3, 400 MHz) δ 9.72 (1H, s, H-19), 6.33 (1H, dd, J
) 17.6, 10.8 Hz, H-14), 5.27 (1H, d, J ) 17.6 Hz, Ha-
15), 5.03 (1H, d, J ) 10.8 Hz, Hb-15), 4.99 (2H, brs,
H-16), 1.27 (1H, dd, J ) 10.4, 3.2 Hz, H-5), 1.16 (3H, s,
H-17), 1.01 (3H, s, H-18), 0.65 (3H, s, H-20); 13C NMR,
see Table 1; EIMS (70 eV) m/z 304 [M+] (11), 289 (27),
275 (89), 257 (100), 243 (16), 236 (8), 227 (13); HREIMS
m/z 304.2386 (calcd for C20H32O2, 304.2404).
Gen er a l Exp er im en ta l P r oced u r es. Melting points
were determined with a Yanagimoto micromelting point
apparatus and are uncorrected. IR spectra were re-
1
corded on a Perkin-Elmer 781 spectrophotometer. H
and 13C NMR spectra were obtained on a Bruker AM-
300 spectrometer. 2D NMR spectra were run on a
Varian Unity 400 spectrometer. EIMS, FABMS, UV,
and specific rotations were taken on a J EOL J MS-
HX110 mass spectrometer, a Hitachi S-3200 spectrom-
eter, and a J ASCO DIP-180 digital polarimeter, respec-
tively. Extracts were chromatographed on silica gel
(Merck 3374, 70-230 mesh) and purified with a semi-
preparative normal-phase HPLC column (250 × 10 mm,
7 µm, LiChrosorb Si 60).
16-Hyd r oxy-19-oxom a n oyl oxid e (3): pale yellow
oil; [R]27 +19.5° (c 0.19, CHCl3); UV (MeOH) λmax (log
D
ꢀ) 284 (1.26) nm; IR (dry film) νmax 3432 (OH), 3071 (C-
H, vinyl), 1718 (CdO, aldehyde), 1634 (CdC), 1453,
1376, 1073, 992, 908 cm-1; 1H NMR (CDCl3, 400 MHz)
δ 9.72 (1H, s, H-19), 5.79 (1H, dd, J ) 17.2, 10.8 Hz,
H-14), 5.24 (1H, dd, J ) 17.2, 1.6 Hz, Ha-15), 5.11 (1H,
dd, J ) 10.8, 1.6 Hz, Hb-15), 3.28 (2H, s, H-16), 1.27
P la n t Ma ter ia l. The wood of C. konishii Hayata was
collected at Luantashan, Nantau Hsien, Taiwan, in
December 1996 and was identified by Prof. Shao-Shun
Ying, Department of Forestry, National Taiwan Uni-
versity. A voucher specimen (013492) has been depos-
ited at the Herbarium of the Department of Botany,
National Taiwan University, Taipei, Taiwan.
(3H, s, H-17), 1.00 (3H, s, H-18), 0.66 (3H, s, H-20); 13
C
NMR, see Table 1; EIMS (70 eV) m/z 320 [M+] (1), 305
[M+-CH3] (73), 287 (100), 277 (8), 275 (5), 269 (6), 265
(8), 259 (22), 154 (90), 136 (92); HREIMS m/z 320.2344
(calcd for C20H32O3, 320.2353).
15-Nor -14-oxo-8(17),12-la bd a d ien -18-ol (4): amor-
phous; [R]27 +23.8° (c 0.25, CHCl3); UV (MeOH) λmax
D
Extr a ction a n d Isola tion . The wood of C. konishii
was crushed into pieces to give 6.5 kg (air-dried) of raw
material, which was extracted with MeOH (60 L) three
times (7 days each time) at room temperature. The
combined extracts were evaporated in vacuo to give a
black residue (60.2 g) that was suspended in water (500
mL) and partitioned into n-hexane (500 mL × 3), EtOAc
(500 mL × 4), and n-BuOH (500 mL × 3), successively.
The EtOAc fraction (15.6 g) was chromatographed by
silica gel column chromatography (using hexane-EtOAc
and EtOAc-MeOH mixtures as solvent systems). Elu-
tion with hexane-EtOAc (7:3) gave 4, and hexane-
EtOAc (3:2) gave 1, while compounds 2, 3, and 5 were
eluted with hexane-EtOAc (1:1). Further purification
by HPLC gave 1 (2.3 mg), 2 (2.5 mg), 3 (2.5 mg), 4 (2.7
mg), and 5 (3.6 mg) using hexane-EtOAc-CH2Cl2-i-
PrOH (10:1:5:0.2), hexane-EtOAc-CH2Cl2-i-PrOH (6:
1:4:0.2), hexane-EtOAc-CH2Cl2-i-PrOH (3:1:3:0.2),
hexane-EtOAc-CH2Cl2-i-PrOH (10:1:2:0.2), and ac-
etone-CH2Cl2-i-PrOH (1:6:0.2), respectively.
(log ꢀ) 232 (4.08) nm; IR (dry film) νmax 3439 (OH), 3072
(C-H, vinyl), 1692 (CdO, conjugated), 1641 (CdC),
1
1441, 1383, 1034, 990, 893 cm-1; H NMR (CDCl3, 400
MHz) δ 9.32 (1H, s, H-14), 6.41 (1H, t, J ) 7.6 Hz, H-12),
4.83 (1H, brs, Ha-17), 4.37 (1H, brs, Hb-17), 3.41 (1H, d,
J ) 10.9 Hz, Ha-18), 3.10 (1H, d, J ) 10.9 Hz, Hb-18),
1.77 (3H, s, H-16), 1.50 (1H, dd, J ) 10.8, 4.0 Hz, H-5),
0.78 (1H, s, H-20), 0.76 (3H, s, H-19); 13C NMR, see
Table 1; EIMS (70 eV) m/z 290 [M+] (83), 279 (24), 276
(22), 259 (100), 232 (85), 217 (14); HREIMS m/z 290.2242
(calcd for C19H30O2, 290.2247).
15,16-Bisn or -13-oxo-8(17),11(E)-la b d a d ien -18-ol
(5): pale yellow oil; [R]27 +8.5° (c 0.33, CHCl3); UV
D
(MeOH) λmax (log ꢀ) 225 (4.10), 279 (3.31) nm; IR (dry
film) νmax 3420 (OH), 3078 (C-H, vinyl), 1667 (CdO,
conjugated), 1641 (CdC), 1383, 1254, 1041, 887 cm-1
;
1H NMR (CDCl3, 400 MHz) δ 6.84 (1H, dd, J ) 16.0,
10.3 Hz, H-11), 6.05 (1H, d, J ) 16.0 Hz, H-12), 4.78
(1H, brs, Ha-17), 4.40 (1H, brs, Hb-17), 3.41 (1H, d, J )
10.9 Hz, Ha-18), 3.10 (1H, d, J ) 10.9 Hz, Hb-18), 2.51
(1H, d, J ) 10.3 Hz, H-9), 2.25 (3H, s, H-14), 1.47 (1H,
dd, J ) 10.1, 3.8 Hz, H-5), 0.91 (3H, s, H-20), 0.77 (3H,
s, H-19); 13C NMR, see Table 1; EIMS (70 eV) m/z 276
[M+] (100), 245 (67), 207 (15), 154 (80), 136 (76), 107
(37), 91 (29); HREIMS m/z 276.2101 (calcd for C18H28O2,
276.2089).
3â-Acetoxya bieta -8,11,13-tr ien -12-ol (1): pale yel-
low oil; [R]25 +62.9° (c 0.21, CHCl3); UV (MeOH) λmax
D
(log ꢀ) 205 (4.36), 225 (sh, 3.88), 282 (3.42) nm; IR (dry
film) νmax 3413 (OH), 1737 (CdO, ester), 1615, 1495
(benzene ring), 1363, 1234, 1028 cm-1; 1H NMR (CDCl3,
400 MHz) δ 6.81 (1H, s, H-14), 6.58 (1H, s, H-11), 5.03
(1H, brs, OH), 4.51 (1H, dd, J ) 11.1, 4.9 Hz, H-3), 3.09
(1H, sept, J ) 6.8 Hz, H-15), 2.83 (1H, ddd, J ) 12.6,
4.0, 1.5 Hz, Hâ-7), 2.75 (1H, ddd, J ) 12.6, 11.3, 3.5 Hz,
HR-7), 2.17 (1H, ddd, J ) 13.2, 3.3, 3.3 Hz, Hâ-1), 2.05
(3H, s, OAc), 1.60 (1H, ddd, J ) 13.2, 11.0, 3.0 Hz, HR-
1), 1.36 (1H, dd, J ) 12.0, 2.1 Hz, H-5), 1.21, 1.20 (3H
each, d, J ) 6.8 Hz, H-16 and H-17), 1.18 (3H, s, H-20),
0.94 (3H, s, H-19), 0.92 (3H, s, H-18); 13C NMR, see
Table 1; EIMS (70 eV) m/z 344 [M+] (100), 329 (12), 285
(39), 283 (27), 269 (22), 213 (20); HREIMS m/z 344.2354
(calcd for C22H32O3, 344.2353).
Sa p on ifica tion of 1 w ith Na OH in MeOH. Com-
pound 1 (2 mg) in MeOH (1 mL) was stirred at room
temperature with 0.5 N NaOH/MeOH (0.5 mL) under
Ar for 5 h. The reaction mixture was poured into water
(10 mL) and then acidified with 3 N HCl to pH 3. The
solution was extracted with ether (20 mL × 3). The
organic layer was concentrated under reduced pressure
to give a residue. The residue was purified by silica gel
chromatography to afford hinokiol (6) [1 mg, EtOAc-
hexane (4:6)].
8r-Hydr oxy-13(16),14-labdadien -19-al (2): pale yel-
Red u ction of 3 w ith Na BH4. Excess NaBH4 (10 mg)
was added in small portions into a solution of 3 (2.2 mg)
in MeOH (2.5 mL), and the reaction mixture was
allowed to stand for 30 min. The mixture solvent (15
mL each of EtOAc and n-hexane) was added to the
low oil; [R]27 +9.5° (c 0.23, CHCl3); UV (MeOH) λmax
D
(log ꢀ) 224 (4.35) nm; IR (dry film) νmax 3433 (OH), 3085
(C-H, vinyl), 1716 (CdO, aldehyde), 1643, 1593 (CdC-
1
CdC), 1462, 1386, 1081, 990, 903, 893 cm-1; H NMR

1000 J ournal of Natural Products, 1998, Vol. 61, No. 8
Li and Kuo
(4) Kuo, Y. H.; Yu, M. T. J . Nat. Prod. 1997, 60, 648-650.
(5) Kuo, Y. H.; Yu, M. T. Chem. Pharm. Bull. 1996, 44, 1431-1435.
(6) Kuo, Y. H.; Yang, I. C.; Chen, C. S.; Lin, Y. T. J . Chin. Chem.
Soc. 1987, 4, 125-134.
reaction mixture and washed with H2O (10 mL × 3).
Evaporation of the organic layer under reduced pressure
gave a residue that was chromatographed on silica gel
to produce jabugodiol (8) [1.5 mg, EtOAc-hexane (4:
6)].
(7) Algarra, J .; Garcia-Granados, A.; Sa´enz de Buruaga, A.; Sa´enz
de Buruaga, J . M. Phytochemistry 1983, 22, 1779-1782.
(8) Garcia-Granados, A.; Martinez, A.; Onorato, M. E. Phytochem-
istry 1985, 24, 517-521.
Ack n ow led gm en t. This research was supported by
the National Science Council of the Republic of China.
(9) Shiojima, K.; Suzuki, M.; Aoki, H.; Ageta, H. Chem. Pharm. Bull.
1995, 43, 5-8.
(10) Bohlmann, F.; Adler, A.; King, R. M.; Robinson, H. Phytochem-
istry 1982, 21, 173-176.
Refer en ces a n d Notes
(11) Itokawa, H.; Morita, M.; Mihashi, S. Chem. Pharm. Bull. 1980,
28, 3452-3454.
(1) Ikeda, T.; Fujita, Y. J . Chem. Soc. J pn. 1929, 50, 32-45.
(2) Cheng, Y. S.; Lin, C. S. J . Chin. Chem. Soc. 1979, 26, 169-172.
(3) Cheng, Y. S.; Tsai, M. D. Phytochemistry 1972, 11, 2108-2109.
NP980074C