Bazzanane sesquiterpenoids from the New Zealand liverwort Frullania falciloba

Article abstract of DOI:10.1248/cpb.54.1347

Two new bazzanane-type sesquiterpenoids have been isolated from the New Zealand liverwort Frullania falciloba. Their structures were confirmed by NMR and CD spectroscopy and chemical reactivity.

Full text of DOI:10.1248/cpb.54.1347

September 2006
Notes
Chem. Pharm. Bull. 54(9) 1347—1349 (2006)
1347
Bazzanane Sesquiterpenoids from the New Zealand Liverwort
Frullania falciloba
Fumihiro NAGASHIMA,* Masao TOYOTA, and Yoshinori ASAKAWA
Faculty of Pharmaceutical Sciences, Tokushima Bunri University; Yamashiro-cho, Tokushima 770–8514, Japan.
Received June 14, 2006; accepted June 28, 2006; published online July 3, 2006
Two new bazzanane-type sesquiterpenoids have been isolated from the New Zealand liverwort Frullania fal-
ciloba. Their structures were confirmed by NMR and CD spectroscopy and chemical reactivity.
Key words liverwort; Frullania falciloba; bazzanane-type; sesquiterpenoid
Liverworts, which contain many different kinds of ter- structure of 1, named 2-oxobazzanene, was established as
penoids and aromatic compounds, are distributed widely shown in Fig. 1.
throughout the world.1,2) The southern hemisphere, especially
The IR spectrum of 2 showed the presence of a carbonyl
New Zealand, has many more endemic liverworts than the group (1703 cmꢀ1) and its molecular formula was deter-
northern hemisphere.3) We have previously reported several mined to be C15H22O2 (Calcd for 234.1620) by high-resolu-
peculiar terpenoids and aromatic compounds from some liv- tion electron impact mass spectrometry (HR-EI-MS). The
erworts endemic to New Zealand.4—8) These terpenoids and 1H- and 13C-NMR spectra (Tables 1, 2) showed the presence
aromatic compounds are chemosystematically specific to liv- of an exo-methylene (dH 4.95, 5.05; dC 109.0 CH2, 156.7 C),
erworts and are used as genetic markers for the species.
two methines associated with an oxygen atom (dH 3.50, 4.18;
Approximately 30 species of Frullania species have been dC 75.3, 79.9), and a ketone carbonyl carbon (dC 211.9), as
recorded in New Zealand.3,9) In general, Frullania species well as a secondary methyl, two tertiary methyls, a methine,
contain elaborate sesquiterpene lactones, such as eudesman- four methylene, and two quaternary carbons. The above
olides and eremophilanolides, that cause potent allergenic spectral data suggested that compound 2 was a tricyclic
contact dermatitis and/or contain bibenzyl derivatives.1,2,10) sesquiterpene ketone. The presence of an ether linkage in the
We have now chemically analyzed Frullania falciloba TAYL. molecule was supported by the results of the IR spectrum
ex LEHM. The fractionation of the ether extract of F. falciloba that lacked the characteristic absorption of a hydroxy group
resulted in the isolation of two new bazzanane-type and the 13C-NMR spectrum that showed two oxygenated
1
sesquiterpenoids 1 and 2. Their structures were determined methines (dC 75.3, 79.9). The H–1H COSY spectrum of
by spectroscopic and chemical means.
2 exhibited the presence of three partial segments: i)
The IR spectrum of 1 established the presence of a conju-
gated carbonyl group (1685 cmꢀ1) and chemical-ionization
mass spectrometry (CI-MS) confirmed a quasimolecular ion
1
at m/z 219 [MꢁH]ꢁ. Its H-NMR spectrum (Table 1) con-
tained three methyls (d 0.99, 1.07, 1.78), an exo-methylene
(d 4.81, 5.04) and an olefinic proton (d 6.59). The 13C-NMR
spectrum (Table 2) exhibited 15 carbons. In combination
with the distortionless enhancement by polarization transfer
(DEPT) spectrum, we detected the presence of an exo-meth-
ylene (d 158.6 C, 108.0 CH2), trisubstituted olefinic carbons
(d 143.7 CH, 134.2 C) and a ketone carbonyl carbon (d
200.7), as well as three methyls, five methylenes and two
quaternary carbons. Based on the above spectral evidence, a
molecular formula of C15H22O was suggested which indi-
cated a bicyclic sesquiterpenoid structure for compound 1.
1
Analysis of the H–1H correlation (1H–1H COSY) and the
heteronuclear multiple bond correlation (HMBC) spectra as
shown in Fig. 1 supported the structure of 1 to be a baz-
zanane-type sesquiterpene ketone. The stereochemistry of 1
was determined to be the same as bazzanenol (3)11—13) by nu-
clear Overhauser and exchange spectroscopy (NOESY). To
confirm the stereochemistry of 1, bazzanenol (3), already
isolated from Bazzania pompeana, was oxidized with
tetrapropylammonium perruthenate (TPAP). The stereo-
chemistry at C-2 of 3 was reconfirmed to be S by the circular
dichroism (CD) spectrum of its p-bromobenzoate derivative
(4). The spectral and optical data of the oxidized product
from 3 was completely identical to that of 1. Accordingly, the
∗ To whom correspondence should be addressed. e-mail: fnaga@ph.bunri-u.ac.jp
© 2006 Pharmaceutical Society of Japan

1348
Vol. 54, No. 9
Table 1. 1H-NMR of 1, 2, 5, and 6 (600 MHz, CDCl3)
H
1
2
5
6
1
2.40 dd (15.7, 1.9)a)
2.46 dd (15.7, 1.1) b
a
2.85 dd (15.7, 3.8) a
2.06 dd (15.7, 1.9) b
2.23 br d (16.2) a
1.47 dd (16.2, 6.0) b
5.13 t (6.0)
1.80 ddddd (7.1, 3.3, 3.3, 3.3, 3.3) 1.69 m
3.78 br s
1.74 ddd (13.2, 4.1, 3.0) a
1.12 dd (13.2, 1.9) b
2.28 br d (13.2)
2.80 m
2.27 m a
1.39 dd (15.7, 5.8) b
2
3
4
5
3.94 t (5.8)
2.33 m
6.59 d sext. (6.0, 1.4)
2.68 br d (18.7) a
2.07 ddd (18.7, 6.3, 1.6) b
2.20 m a
4.18 ddd (3.8, 3.8, 1.9)
1.61 dd (13.5, 1.9) a
2.08 dt (13.5, 3.8) b
2.77 m a
3.79 br s
1.75 ddd (13.2, 4.4, 3.0) a
1.09 dd (13.2, 1.9) b
2.79 m
2.28 m
1.62 m
9
10
11
2.34 br dd (14.6, 6.0) b
1.70 m a
2.35 m b
1.58 dd (12.9, 7.7) a
1.68 dddd (12.9, 12.9, 7.7, 3.6) b
3.50 d (3.6)
1.63—1.68 2H, m
1.45 m b
1.66 m
4.56 d (3.8)
1.42 m a
4.46 br s
1.87 m b
12
13
14
15
1.78 quint. (1.4)
0.99 s
1.22 d (6.9)
1.27 s
0.96 s
4.95 d (2.5)
5.05 s
1.02 d (7.4)
1.09 s
0.96 s
4.79 d (2.7)
5.10 br s
2.09 s
1.12 d (7.1)
1.08 s
1.09 s
4.79 d (3.0)
5.06 s
1.07 s
4.81 d (2.7)
5.04 d (1.9)
OCOCH3
a) Coupling constants (J in Hz) are given in parentheses.
Table 2. 13C-NMR of 1, 2, 5 and 6 (100 MHz, CDCl3)
C
1
2
5
6
1
2
3
4
5
6
7
8
9
10
11
12
13
45.7
200.7
134.2
143.7
33.7
42.2
50.0
158.6
38.7
23.3
53.4
211.9
48.2
75.3
38.5
39.1
50.7
156.7
33.8
30.0
79.9
10.9
26.4
21.9
109.0
40.4
69.0
37.1
71.2
38.9
31.3
49.5
158.9
35.8
31.7
80.4
13.4
28.7
23.2
109.7
170.5
21.4
42.8
67.4
38.6
71.5
39.1
31.4
49.7
159.2
35.5
31.0
80.8
13.4
28.6
23.2
109.0
Fig. 2. Long-Range 1H–13C Correlations of 2
37.0
15.4
19.0
23.7
14
15
108.0
–COCH3
–COCH3
Fig. 3. NOE Correlations of 2
monoacetate 5 and unreacted monoalcohol 6.
1
The IR, H- and 13C-NMR spectra (Tables 1, 2) of 5
(C17H26O3 Calcd for 278.1882) showed the presence of an
acetoxy group (1740, 1240 cmꢀ1; dH 2.09; dC 21.4 CH3,
170.5 C) and a newly observed oxygenated methine (dH
5.13; dC 69.0). Furthermore, the structure of 5 was deter-
Fig. 1. 1H–1H COSY (Bold Lines) and Long-Range 1H–13C (Arrows) Cor-
relations of 1
1
mined to be a monoacetate by the H–1H COSY, HMBC
CH3–CH–CH(O–)–CH2–, ii) –CH2–, and iii) –CH2–CH2– and NOESY spectra. Compound 6 (C15H24O2 Calcd for
CH(O–)–. The correlations of each partial segment were con- 236.1776) was found to be a monoalcohol by spectral analy-
firmed by the HMBC spectrum (Fig. 2). The NOESY spec- sis (Tables 1, 2). Accordingly, the structure of 2 was deter-
trum clarified the stereochemistry of 2 as shown in Fig. 3. To mined to be a bazzanane-type sesquiterpene with a ketone at
obtain further confirmation of the structure, compound 2 was C-2 and an ether linkage between C-4 and C-11. Thus the
reduced with lithium aluminium hydride (LiAlH4), followed structure of 2, named bazzanenoxide, was established as
by acetylation with pyridine and acetic anhydride to give a shown in Fig. 3. Although the absolute configuration of 2,

September 2006
1349
shown in Fig. 3, was assumed by the analysis of its CD spec-
trum (De295 ꢁ0.57),14) further experiment is needed.
Monoacetate (5): Oil, [a]D21 ꢁ267.1° (cꢃ1.74). FT-IR cmꢀ1: 1740, 1240,
1100. 1H- and 13C-NMR: see Tables 1 and 2. HR-EI-MS m/z: 278.1888
(Calcd for C17H26O3: 278.1882). EI-MS m/z (int.): 278 [M]ꢁ (6), 236 (3),
218 (19), 203 (6), 185 (9), 163 (71), 145 (20), 135 (15), 125 (31), 119 (32),
107 (66), 94 (100), 79 (71), 67 (17), 55 (34), 43 (79).
The isolation of sesquiterpenoids and aromatic compounds
from F. falciloba, e.g., ent-cyclocolorenone (7), b-bazzanene
(8), 3-hydroxy-4,3ꢂ-dimethoxybibenzyl (9), and 3-(4ꢂ-
methoxybenzyl)-5,7-dimethoxyphthalide (10), has previously
been reported by our group15,16) and Mali et al.17) Bazzanane-
type sesquiterpenoids are very rare in the plant kingdom.
This type of compound is mainly distributed in the liverwort
Bazzania genus, making bazzananes important chemical
markers of the Bazzania species. In the present study, we re-
port the first isolation of two new bazzanenes 1 and 2 from F.
falciloba. The presence of bibenzyl or phthalide derivatives
could not be detected.
Monoalcohol (6): Oil, [a]2D1 ꢁ263.8° (cꢃ0.94). FT-IR cmꢀ1: 3422. 1H-
and 13C-NMR: see Tables 1 and 2. HR-EI-MS m/z: 236.1765 (Calcd for
C15H24O2: 236.1776). EI-MS m/z (int.): 236 [M]ꢁ (17), 218 (5), 208 (4), 200
(6), 163 (34), 145 (12), 135 (13), 125 (14), 119 (22), 110 (44), 108 (33), 94
(100), 79 (49), 67 (14), 55 (21), 43 (21).
Esterification of 3 To a suspension of 3 (10 mg) in pyridine (2 ml) and
CH2Cl2 (1 ml) was added p-bromobenzoylchloride (42 mg) and 4-dimethyl-
aminopyridine (10 mg) and the mixture was stirred overnight at room tem-
perature. The reaction mixture was filtered and purified on silica gel CC to
yield the benzoate derivative 4 (6.2 mg): UV lmax (EtOH) nm (log e): 245
(3.73) (cꢃ6.82ꢄ10ꢀ5). CD (EtOH): De245 ꢀ6.77° (cꢃ6.82ꢄ10ꢀ5). 1H-
NMR (600 MHz, CDCl3): d 1.00 (3H, s, H-13), 1.04 (3H, s, H-12), 1.38
(1H, m, H-11b), 1.42 (1H, m, H-10), 1.58 (1H, t, Jꢃ12.1 Hz, H-1a), 1.66
(1H, m, H-10), 1.68 (3H, br s, H-12), 1.71 (1H, br d, H-5b), 1.87 (1H, m, H-
11a), 2.11 (1H, ddd, Jꢃ12.1, 6.0, 2.2 Hz, H-1b), 2.20 (1H, m, H-9), 2.30
(1H, m, H-9), 2.33 (1H, br d, Jꢃ18.4 Hz, H-5a), 4.81 (1H, d, Jꢃ2.7 Hz, H-
15), 4.98 (1H, s, H-15), 5.57 (1H, m, H-4), 5.60 (1H, br s, H-2), 7.58 (2H, d,
Jꢃ8.8 Hz, BrC6H4COO–), 7.93 (2H, d, Jꢃ8.8 Hz, BrC6H4COO–). FAB-MS
(m-NBA) m/z: 425, 427 [MꢁNa]ꢁ; (m-NBAꢁKCl) m/z 441, 443 [MꢁK]ꢁ.
EI-MS m/z (int.): 307 [MꢀC7H12]ꢁ (8), 202 (16), 183 (58), 155 (12), 149
(7), 107 (100), 106 (89), 96 (34), 91 (29), 81 (14), 67 (9), 55 (11), 41 (7).
Experimental
General Methods Optical rotations were measured on a Jasco DIP-
1000 polarimeter. IR spectra were recorded on a Shimadzu FTIR 8400S in-
frared spectrophotometer. UV spectra were recorded on a Shimadzu UV-
1650PC UV-visible spectrophotometer. CD spectra were recorded on a Jasco
1
J-725 spectropolarimeter. H- and 13C-NMR spectra were measured on Var-
ian Unity-600 (1H, 600 MHz; 13C, 150 MHz) and Jeol Eclipse-400 (1H,
400 MHz; 13C, 100 MHz) NMR spectrometers. Chemical shift values are ex-
pressed in d (ppm) downfield from tetramethylsilane as an internal standard
(1H-NMR), and relative to the solvent CDCl3 (d: 77.03) as a standard (13C-
NMR). Mass spectra were obtained on a JEOL Mstation JMS 700 instru-
ment. TLC was performed on silica gel 60F254 plates (Merck). Column chro-
matography was performed on silica gel 60 (Merck, 230—400, 35—70
mesh) and Sephadex LH-20 (Amersham Pharmacia Biotech, 1 : 1
CH2Cl2–MeOH as solvent). TLC spots were visualized under UV (254 nm)
light and by spraying with Godin reagent18) and 30% H2SO4, followed by
heating.
Acknowledgments We thank Dr. M. Tanaka and Miss Y. Okamoto
(Tokushima Bunri University) for 600 MHz NMR and mass spectral meas-
urements. Thanks are also due to Prof. J. E. Braggins (Auckland University,
New Zealand) for the collection and identification of the species. We are
grateful to Miss Y. Onishi for experimental assistance. This work was sup-
ported by a Grant-in-Aid for Scientific Research (A) (No. 11309012) from
the Ministry of Education, Culture, Sports, Science and Technology.
Plant Material Frullania falciloba TAYL. ex LEHM. (NZ-267) was col-
lected in Tree Trunk Gorge, New Zealand, in December 2000 and identified
by Dr. J. E. Braggins (University of Auckland, New Zealand), and a voucher
specimen was deposited in the Faculty of Pharmaceutical Sciences,
Tokushima Bunri University.
References and Notes
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1982, pp. 1—285.
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Steglich W., Tamm Ch., Springer, Vienna, 1995, pp. 1—562.
3) Allison K. W., Child J., “The Liverworts of New Zealand,” University
of Otago Press, Dunedin, 1975, pp. 1—300.
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org/nh/tx/Plantae/Bryophyta/ꢁ.
Extraction and Isolation The ether extract (205 mg) of F. falciloba was
divided into seven fractions by column chromatography (CC) on silica gel
using an n-hexane–EtOAc gradient. Fraction 2 was chromatographed on
Sephadex LH-20, silica gel, and preparative HPLC (Chemcosorb 5Si-U,
17 : 3 n-hexane–EtOAc) to give 2-oxobazzanene (1, 9.0 mg). Bazzanenoxide
(2, 10.4 mg) was isolated from Fr. 4 by CC on Sephadex LH-20 and prepara-
tive HPLC (Chemcosorb 5Si-U, 7 : 3 n-hexane–Et2O).
2-Oxobazzanene (1): Oil, [a]D18 ꢁ8.4° (cꢃ0.69). FT-IR cmꢀ1: 1685. UV
1
lmax (EtOH) nm (log e): 238 (3.12) (cꢃ6.12ꢄ10ꢀ4). H- and 13C-NMR: see
Tables 1 and 2. HR-CI-MS (iso-butane) m/z: 219.1738 (Calcd for C15H23O:
219.1749). CI-MS (iso-butane) m/z: 219 [MꢁH]ꢁ, EI-MS m/z (int.): 218
[M]ꢁ (2), 205 (2), 163 (4), 149 (9), 123 (100), 109 (14), 95 (91), 81 (29), 67
(18), 55 (19), 41 (11).
Bazzanenoxide (2): Amorphous, [a]1D8 ꢁ76.2° (cꢃ0.81). FT-IR cmꢀ1
:
1703. CD (EtOH): De295 ꢁ0.57° (cꢃ5.77ꢄ10ꢀ4). 1H- and 13C-NMR: see
Tables 1 and 2. HR-EI-MS m/z: 234.1623 (Calcd for C15H22O2: 234.1620).
EI-MS m/z (int.): 234 [M]ꢁ (13), 207 (3), 175 (2), 163 (100), 145 (18), 135
(10), 119 (9), 107 (11), 94 (36), 79 (21), 63 (14), 55 (15), 43 (58).
10) Asakawa Y., Toyota M., Nagashima F., Hashimoto T., El Hassane L.,
Heterocycles, 54, 1057—1093 (2001).
Oxidation of 3 Tetrapropylammonium perruthenate (14 mg) was added
to a stirred mixture of bazzanenol 3 (42 mg), 4-methylmorpholine-N-oxide
(64.8 mg) and 4 Å molecular sieves (180.2 mg) in dry CH2Cl2 (3 ml) at room
temperature for 1.5 h. The reaction mixture was chromatographed on silica
11) Hayashi S., Matsuo A., Experientia, 26, 347—348 (1970).
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(1987).
1
gel to yield 1 (12.6 mg). The H- and 13C-NMR spectra and optical rotation
([a]1D8 ꢁ7.4°, cꢃ0.95) of the reaction derivative were identical with those of
natural 1.
Reduction and Acetylation of 2 To a suspension of LiAlH4 (10 mg) in
dry Et2O (3 ml) was added the compound 2 (4.9 mg) in dry Et2O (2 ml). The
solution was stirred for 20 min at room temperature, providing a mixture
after the usual work-up. Pyridine (1 ml) and Ac2O (1 ml) were added to the
unpurified mixture and the solution was kept at room temperature overnight.
After work-up, the resulting mixture was chromatographed on Sephadex
LH-20 to yield the monoacetate 5 (2.9 mg) and the unreacted monoalcohol 6
(1.6 mg).
17) Mali R. S., Babu K. N., Jagtap P. G., J. Chem. Soc., Perkin Trans. 1,
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