Bromophenol derivatives from the red alga Rhodomela confervoides

Article abstract of DOI:10.1021/np030546+

Eight new bromophenol derivatives, 2,3-dibromo-4,5-dihydroxybenzyl methyl sulfoxide (1), 4-(2,3-dibromo-4,5-dihydroxyphenyl)-3-butene-2-one (2), 2-(3-bromo-5-hydroxy-4-methoxyphenyl)-3-(2,3-dibromo-4,5-dihydroxyphenyl) propionic acid (3), 2-(3-bromo-5-hydroxy-4-methoxyphenyl)-3-(2,3-dibromo-4,5- dihydroxyphenyl)propionic acid methyl ester (4), 2-phenyl-3-(2,3-dibromo-4,5- dihydroxyphenyl)propionic acid (5), 4′-methoxy-2″,3′,3″- tribromo-4″,5′,5″-trihydroxydiphenylacetic acid (6), and 3-bromo-5-hydroxy-4-methoxyphenylacetic acid (7) and its methyl ester (8), together with a known bromophenol, 3-bromo-5-hydroxy-4-methoxybenzoic acid (9), were isolated from the red alga Rhodomela confervoides. Their structures were elucidated by spectroscopic methods including IR, EIMS, FABMS, ESIMS, HRFABMS, HRESIMS, 1D and 2D NMR, and single-crystal X-ray structure analysis. Compounds 1-4, 8, and 9 were found inactive against several human cancer cell lines and microorganisms.

Full text of DOI:10.1021/np030546+

1
032
J . Nat. Prod. 2004, 67, 1032-1035
Br om op h en ol Der iva tives fr om th e Red Alga Rh od om ela con fer void es
†
‡
†
†
†
†
‡
†
J ielu Zhao, Xiao Fan, Sujuan Wang, Shuai Li, Suqin Shang, Yongchun Yang, Nianjun Xu, Yang L u¨ , and
J iangong Shi*,
†
Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Bejing 100050, and
Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071
Received December 31, 2003
Eight new bromophenol derivatives, 2,3-dibromo-4,5-dihydroxybenzyl methyl sulfoxide (1), 4-(2,3-dibromo-
4
,5-dihydroxyphenyl)-3-butene-2-one (2), 2-(3-bromo-5-hydroxy-4-methoxyphenyl)-3-(2,3-dibromo-4,5-di-
hydroxyphenyl)propionic acid (3), 2-(3-bromo-5-hydroxy-4-methoxyphenyl)-3-(2,3-dibromo-4,5-dihydroxy-
phenyl)propionic acid methyl ester (4), 2-phenyl-3-(2,3-dibromo-4,5-dihydroxyphenyl)propionic acid (5),
4
′-methoxy-2′′,3′,3′′-tribromo-4′′,5′,5′′-trihydroxydiphenylacetic acid (6), and 3-bromo-5-hydroxy-4-meth-
oxyphenylacetic acid (7) and its methyl ester (8), together with a known bromophenol, 3-bromo-5-hydroxy-
-methoxybenzoic acid (9), were isolated from the red alga Rhodomela confervoides. Their structures
were elucidated by spectroscopic methods including IR, EIMS, FABMS, ESIMS, HRFABMS, HRESIMS,
4
1
D and 2D NMR, and single-crystal X-ray structure analysis. Compounds 1-4, 8, and 9 were found inactive
against several human cancer cell lines and microorganisms.
The red marine algae of the Rhodomelaceae family are
rich sources of bromophenols. Previous chemical studies
on some species of this family have resulted in the
characterization of more than 30 monoaryl and diaryl
1
-12
8
bromophenols.
Some of them showed feeding deterrent,
R-glucosidase inhibitory,11 and growth stimulatory activi-
ties. As part of our recently initiated program to assess
systematically the chemical and biological diversity of
seaweeds distributed in the gulf of the Yellow Sea, China,
13
1
4 bromophenols including monoaryl, diaryl, and triaryl
structural types have been previously reported from a
sample of Rhodomela confervoides collected at the coast of
Qingdao, China.1
4,15
Continuing our investigation on the
same material, we report here the isolation and structure
elucidation of nine bromophenol derivatives (1-9). Among
them, compound 1 possesses a unique sulfoxide structural
feature. Compound 7 was previously synthesized as an
inhibitor of protein kinase C,16,17 and compound 9 was
synthesized and evaluated as an inhibitor of liver catechol
1
8
O-methyltransferase and human renal thiopurinemeth-
yltransferase.19 Compounds 1-4, 8, and 9 were evaluated,
but found inactive, against several human cancer cell lines
hydroxyl groups at 3438 cm- as well as the characteristic
1
(IC50 >10 µg/mL) including lung adenocarcinoma (A549),
-1
absorption bands for aromatic rings at 1599 and 1504 cm
The FABMS exhibited a characteristic quasi-molecular ion
peak cluster at m/z 343/345/347 (1:2:1) [M + H] suggesting
the presence of two bromine atoms, and the molecular
.
stomach cancer (BGC-823), breast cancer (MCF-7), hepato-
ma (Bel7402), and human colon cancer (HCT-8) cell lines,
as well as three microorganisms (MIC50 > 100 µg/mL)
including Staphylococcus aureus, Escherichia coli, and
Candida albicans.
+
formula C
8
H
8
O
3
Br
H NMR spectrum of 1 showed an aromatic singlet at δ
6.89 (1H, s, H-6), a methyl singlet at δ 2.55 (3H, s, SOCH ),
2
S was determined by HRFABMS. The
1
Resu lts a n d Discu ssion
3
and a typical AB spin coupling system attributed to an
isolated methylene at δ 4.19 (1H, d, J ) 13.5 Hz, H-7a)
and 4.02 (1H, d, J ) 13.5 Hz, H-7b), as well as two
exchangeable broad singlets of phenolic hydroxyl protons
The air-dried and ground red alga Rhodomela confer-
voides was extracted with 95% EtOH, and the concentrated
extract was suspended in water and then partitioned with
EtOAc. The EtOAc extract was chromatographed over
silica gel eluting with a gradient of increasing MeOH
1
3
at δ 9.72 (1H, s, OH-4) and 10.10 (1H, s, OH-5). The
C
NMR and DEPT spectra of 1 displayed eight carbon signals
for a penta-substituted benzene ring, a methyl, and a
methylene. A strong fragment cluster at m/z 279/281/283
3
(0-100%) in CHCl . Further purification of the resulting
fractions by a variety of chromatographic techniques
yielded bromophenols 1-9.
(1:2:1) in the FABMS of 1 and the similarity between the
Compound 1 was obtained as colorless crystals, mp 168-
70 °C. The IR spectrum showed an absorption band for
NMR data of 1 and 2,3-dibromo-4,5-dihydroxybenzyl alco-
hol11 suggested the presence of a 2,3-dibromo-4,5-dihy-
droxybenzyl moiety in 1. This was unambiguously con-
firmed by long-range correlations from H-6 to C-1, C-2, C-4,
1
*
To whom correspondence should be addressed. Tel: 86-10-83154789.
Fax: 86-10-63017757. E-mail: shijg@imm.ac.cn.
†
Institute of Materia Medica.
Institute of Oceanology.
‡
2
C-5, and C-7, from H -7 to C-1, C-2, and C-6, and from the
1
0.1021/np030546+ CCC: $27.50
© 2004 American Chemical Society and American Society of Pharmacognosy
Published on Web 06/25/2004

Bromophenol Derivatives from Rhodomela Confervoides
J ournal of Natural Products, 2004, Vol. 67, No. 6 1033
propionic acid unit in 3. In addition, the NMR spectra
showed that there is one methoxyl group at δ
H
3.79 (3H, s,
OCH ) and δ 60.7 (q). The unambiguous assignments of
3
C
the proton and carbon signals and the establishment of the
structure were based on the HMQC and HMBC experi-
ments. In combination with the chemical shift values of
the two benzene rings, long-range correlations of C-1′, C-3′,
C-4′, and C-5′ with both H-2′ and H-6′, and C-4′ with the
methoxyl protons in the HMBC spectrum, revealed that
the 1,3,4,5-tetra-substituted benzene ring is a 3-bromo-5-
hydroxy-4-methoxyphenyl, while correlations from H-6′′ to
C-1′′, C-2′′, C-4′′, and C-5′′ established that the 1,2,3,4,5-
penta-substituted benzene ring is a 2,3-dibromo-4,5-dihy-
droxyphenyl. In addition, correlations of the carboxyl
carbon (C-1) with H-2, H-3a, and H-3b confirmed the
presence of the 2,3-disubstituted propionic acid unit, while
correlations from H-2 to C-1′, C-2′, and C-6′ and from both
H-3a and H-3b to C-1′′, C-2′′, and C-6′′ unambiguously
located the 3-bromo-5-hydroxy-4-methoxyphenyl and 2,3-
dibromo-4,5-dihydroxyphenyl at C-2 and C-3 of the propi-
onic acid unit, respectively. Therefore, the structure of 3
was determined as 2-(3-bromo-5-hydroxy-4-methoxyphe-
nyl)-3-(2,3-dibromo-4,5-dihydroxyphenyl)propionic acid.
F igu r e 1. Key HMBC correlations of compound 1 and 3.
exchangeable phenolic protons to C-4 and C-5 in the HMBC
spectrum of 1. In combination with the chemical shift
values of the methyl group (δ
molecular composition of 1 (C
H
2.55 and δ
C
43.0) and the
8
H
8
O
3
Br S), the strong HMBC
2
correlation from the methyl protons to the methylene
carbon (C-7) unequivocally revealed that the 2,3-dibromo-
4
,5-dihydroxybenzyl moiety was connected with the methyl
through a sulfoxide group. Therefore, the structure of 1 was
determined as 2,3-dibromo-4,5-dihydroxybenzyl methyl
sulfoxide. It is considered to be a racemate since no optical
rotation was observed for 1. The X-ray structure analysis
confirmed the above structural assignment of 1. The
PLUTO drawing, with the atom-numbering scheme indi-
cated, is shown in the Supporting Information. The second
Compound 4 was obtained as a brown gum. Its negative
mode ESIMS gave a tribrominated quasi-molecular ion
1
space group P2 /c of the crystal indicated that 1 is optically
inactive in the crystal state.
-
peak cluster at m/z 551/553/555/557 (1:3:3:1) [M - H] ,
which is 14 mass units more than that of 3. The IR and
NMR spectra of 4 (see Experimental Section) showed
resemblance to those of 3 except the appearance of an
Compound 2 was obtained as brown needles, mp 165-
1
66 °C. The IR spectrum (KBr) showed absorption bands
-
1
for hydroxyl (3431 cm ) and conjugated carbonyl (1712
cm-1) groups and aromatic rings (1595, 1464 cm-1). Its
negative mode ESIMS exhibited dibrominated molecular
H C
additional methoxyl signal at δ 3.58 (3H, s) and δ 52.2
(
q, OCH ) in the NMR spectra of 4, suggesting that 4 is a
3
methyl ester of 3. This was confirmed by the HMBC
experiment of 4 and the acidic hydrolysis of 4 yielding 3.
Consequently, 4 was unequivocally assigned as 2-(3-bromo-
-
ion peaks at m/z 333/335/337 (1: 2: 1) [M - H] . In
combination with the NMR data, the molecular formula of
1
2
was established as C10
H
8
O
3
Br
2
. The H NMR spectrum
5
-hydroxy-4-methoxyphenyl)-3-(2,3-dibromo-4,5-dihydrox-
of 2 showed an aromatic singlet at δ 7.32 (1H, s, H-6′), two
trans coupled olefinic proton doublets (J ) 16.0 Hz) at δ
yphenyl)propionic acid methyl ester.
Compound 5 was obtained as a brown gum, and the IR
spectrum (KBr) showed absorption bands for hydroxyl
6
.53 (H-3) and 7.86 (H-4), and an acetyl singlet at δ 2.31
(
3H). Besides the acetyl carbons (δ 197.4 and 26.3) and the
-
1
-1
1
3
(3330 cm ) and conjugated carbonyl (1712 cm ) groups
two olefinic carbons (δ 142.6 and 113.7), the C NMR
spectra of 2 displayed six carbon signals attributed to a
-1
and aromatic rings (1601, 1468 cm ). The negative FABMS
spectrum showed a dibrominated quasi-molecular ion peak
cluster at 413/415/417 (1:2:1) [M - H] . In combination
with the NMR data, the molecular formula of 5 was
2
,3-dibromo-4,5-dihydroxyphenyl moiety. Therefore, the
-
structure of 2 was elucidated as 4-(2,3-dibromo-4,5-dihy-
droxyphenyl)-3-butene-2-one, which was further confirmed
by single-crystal X-ray structure analysis. The PLUTO
drawing, with the atom-numbering scheme indicated, is
shown in Supporting Information.
established as C15
at δ 7.26 (1H, t, J ) 7.5 Hz, H-4′), 7.32 (2H, t, J ) 7.5 Hz,
H-3′, 5′), and 7.38 (2H, d, J ) 7.5 Hz, H-2′, 6′) and δ 128.1
C-4′), 129.5 (C-3′ and C-5′), 128.8 (C-2′ and C-6′), and 140.1
(C-1′) revealed the presence of a phenyl unit in the
structure of 5. Meanwhile, signals at δ 6.78 (1H, s, H-6′′)
12 4 2
H O Br . In the NMR spectra, signals
H
C
(
Compound 3 was obtained as a brown gum and showed
-1
IR absorptions for hydroxyl (3400 cm ) and carbonyl (1705
-1
-1
cm ) groups and aromatic rings (1568 and 1485 cm ). The
negative mode ESIMS of 3 gave a characteristic tribro-
monated quasi-molecular ion peak cluster at 537/539/541/
H
C
and δ 132.1 (s, C-1′′), 116.7 (s, C-2′′), 113.8 (s, C-3′′), 144.0
(s, C-4′′), 145.3 (s C-5′′), and 117.8 (d, C-6′′) demonstrated
the presence of a 2,3-dibromo-4,5-dihydroxyphenyl moiety
in 5. In addition, a 2,3-disubstituted propionic acid unit
-
5
43 (1:3:3:1) [M - H] , and the molecular formula C16
13 6
H O -
Br was determined by HRESIMS at m/z 560.8152 [M +
3
+
79
Na] (calcd for C16
H
13
O
6
Br
3
Na 560.8160). Three aromatic
H
was indicated by an ABX coupling system at δ 3.97 (1H,
signals at δ 7.05 (1H, d, J ) 1.5 Hz, H-2′), 6.93 (1H, d, J )
dd, J ) 6.0, 9.0 Hz, H-2), 3.43 (1H, dd, J ) 9.0, 14.0 Hz,
1
1
1
.5 Hz, H-6′), and 6.79 (1H, s, H-6′′) in the H NMR
H-3a), and 3.05 (1H, dd, J ) 6.0, 14.0 Hz, H-3b) in the H
2
spectrum and 12 sp carbon signals including three me-
C
NMR spectrum and carbon signals at δ 174.3 (s, C-1), 52.1
(d, C-2), and 41.9 (t, C-3) in the 13C NMR spectrum. The
existence of the above three moieties was confirmed by the
HMQC and HMBC experiments of 5. In the HMBC
spectrum, correlations from H-2 to C-2′ and C-6′ and from
H-3 to C-2′′ and C-6′′ unequivocally established that the
phenyl and 2,3-dibromo-4,5-dihydroxyphenyl were located
at C-2 and C-3, respectively, of the 2,3-disubstituted
propionic acid unit. Accordingly, the structure of 5 was
determined as 2-phenyl-3-(2,3-dibromo-4,5-dihydroxyphe-
nyl)propionic acid.
thines and nine quaternary carbons (four oxygenated, δ >
43 ppm) in the 1 C NMR and DEPT spectra (see Experi-
3
1
mental Section) indicated the presence of two benzene rings
with 1,2,3,4,5-penta and 1,3,4,5-tetra substitution patterns.
Meanwhile, an ABX spin coupling system at δ 3.85 (1H,
dd, J ) 9.5, 6.0 Hz, H-2), 3.34 (1H, dd, J ) 14.0, 9.5 Hz,
1
H-3a), and 3.02 (1H, dd, J ) 14.0, 6.0 Hz, H-3b) in the H
NMR spectrum and three carbon signals at δ 173.8 (s, C-1),
1
3
5
1.0 (d, C-2), and 41.6 (t, C-3) in the C NMR and DEPT
spectra demonstrated the presence of a 2,3-disubstituted

1
034 J ournal of Natural Products, 2004, Vol. 67, No. 6
Zhao et al.
Compound 6 was obtained as a brown gum, and its
GF254 plates. Spots were visualized under UV light or by
negative mode ESIMS exhibited tribrominated molecular
ion peaks at m/z 523/525/527/529 (1: 3:3: 1) [M - H] . In
combination with NMR data, the molecular formula of 6
3
spraying with 3% FeCl in EtOH. HPLC was performed using
-
an Alltima C18 10 µm preparative column (22 × 250 mm).
X-ray diffraction intensity data of 1 and 2 were collected
on a Rigaku R-AXIS RAPID diffractometer with graphite-
monochromated Mo KR radiation (λ ) 0.71067 Å) by the ω
scan technique (scan width 0-220°, 2θ e 55° for 1 and 0-180°,
was established as C15
11 6 3
H O Br . The NMR spectra of 6
were in close agreement with those of 3, except for the
absence of signals for the methylene, suggesting that the
2
θ e 50° for 2) and were corrected by Lorentz and polarization.
2
,3-disubstituted propionic acid unit of 3 was replaced by
A total of 2276 and 1582 reflections were collected, of which
1
respectively. The structures of 1 and 2 were solved by direct
a disubstituted acetic acid unit of 6. The NMR signal
assignments and the structure of 6 were confirmed by
HMQC and HMBC experiments of 6. In the HMBC
spectrum of 6, long-range correlations from H-2 to C-1, C-2′,
C-6′, C-2′′, and C-6′′ confirmed the diarylacetic acid struc-
ture of 6. Thus, the structure of 6 was determined as 4′-
methoxy-2′′,3′,3′′-tribromo-4′′,5′,5′′-trihydroxydiphenylace-
tic acid. Compounds 3-6 did not show any optical rotation,
suggesting these to be racemic mixtures.
2
2
913 and 1396 with |F| G 3σ|F| were observed for 1 and 2,
methods and refined by block-matrix least-squares procedures
2
to Rw ) 0.079 [w ) 1/σ|F| ], R ) 0.060 of 1 and R ) 0.089 [w
w
2
) 1/σ|F| ], R ) 0.087 of 2, respectively. Hydrogen positions
were found from difference Fourier maps and geometric
calculations. All calculations were carried out on a PC com-
puter by using the NOMCSDP program system.
Ma ter ia l. The red alga Rhodomela confervoides were col-
lected at the coast of Qingdao, China, in May 2001 and
identified by Professor B.-M Xia. A voucher specimen (No.
The IR, MS, and NMR spectra of 7 and 9 were in good
agreement with those reported for 3-bromo-5-hydroxy-4-
methoxyphenylacetic acid and 3-bromo-5-hydroxy-4-meth-
2
00102) was deposited at the Department of Marine Algae
Chemistry, Institute of Oceanology, Chinese Academy of
Sciences, Qingdao 266071.
oxybenzoic acid, respectively. 7 has been synthesized as a
protein kinase C inhibitor,1
6,17
and 9 was synthesized as
Extr a ction a n d Isola tion . Air-dried R. confervoides (14.4
kg) was extracted with EtOH at room temperature for 3 × 48
h. After the solvent was removed under reduced pressure at
<40 °C, a dark residue was obtained. The residue was
suspended in water and then partitioned with EtOAc. The
EtOAc fraction (594.6 g) was chromatographed over silica gel
an inhibitor of catechol O-methyltransferase (COMT) and
human renal thiopurinemethyltransferase.1
8,19
However, 7
and 9 were obtained as natural products for the first time,
and their 13C NMR data assigned by HMQC and HMBC
experiments were included (see Experimental Section)
since these data did not appear in the previous literature.
(
1200 g) eluting with a gradient of increasing MeOH (0-100%)
in CHCl and separated into 24 fractions (I-XXIV) on the basis
of TLC analyses. Fraction XI (13 g) was chromatographed over
Sephadex LH-20 eluting with petroleum ether-CHCl -MeOH
5: 5: 1), decolored by column chromatography over Bio-Beads
3
The EIMS of 8 gave a molecular ion peak cluster with
1
1
4 mass units more than that of 7, and the IR and H NMR
3
spectra of 8 were very similar to those of 7 except for the
(
appearance of signals for an additional methoxyl at δ 3.63
SX3 using CHCl -EtOAc (1: 1), and then separated by flash
3
1
(3H, s, COOCH
3
) in the H NMR spectrum of 8, suggesting
chromatography to yield compound 1 (15 mg) and reverse-
that 8 is 3-bromo-5-hydroxy-4-methoxyphenylacetic acid
phase preparative HPLC using MeOH-H
as mobile phase to yield 2 (6 mg) and 5 (4 mg). Fraction XII
21 g) was chromatographed over reverse-phase MPLC eluting
with a gradient of increasing MeOH in H O and separated into
three subfractions. Each subfraction was decolored by Sepha-
dex LH-20 eluting with CHCl
2
O-AcOH (60:40:0.1)
methyl ester, which was further confirmed by 13C NMR,
(
HMQC, and HMBC experiments and the acidic hydrolysis
of 8 producing 7. Compounds 4 and 8 were considered not
to be artifacts from methylation of 3 and 7, respectively,
since the methylation did not occur in the simulated
isolation conditions by heating the methanol solutions of
2
3
-MeOH (1:1) to give corre-
sponding decolored subfractions. The first fraction was then
separated by reverse-phase preparative HPLC using MeOH-
3
and 7 either with or without silica gel at 45 °C for 48 h.
H O-AcOH (60:40:0.1) as mobile phase to yield 7 (15 mg) and
2
Compounds 1, 3, 8, and 9 were tested for their antimi-
crobial activity against Staphylococcus aureus, Escherichia
coli, and Candida albicans and showed no growth inhibi-
9 (10 mg). The second subfraction was purified by normal-
phase preparative HPLC using hexane-2-propanol (50:50) as
mobile phase to yield 6 (14 mg) and 8 (153 mg). The last
subfraction was separated by reverse-phase preparative HPLC
tion at 100 µg/mL. Cytotoxicities of compounds 1, 2, 3, 4,
using MeOH-H
(213 mg) and 4 (27 mg).
,3-Dib r om o-4,5-d ih yd r oxyb en zyl m et h yl su lfoxid e
1): colorless crystals (water-methanol, 1:1), mp 168-170 °C;
IR (KBr) νmax 3438, 3005, 2700, 1599, 1504, 1410, 1346, 1281,
2
O-AcOH (70:30:0.1) as mobile phase to yield
and 8 were evaluated using the MTT method2
0,21
against
3
several human cancer cell lines including lung adenocar-
cinoma (A549), stomach cancer (BGC-823), breast cancer
MCF-7), hepatoma (Bel7402), and human colon cancer
HCT-8) cell lines, but were found to be inactive at 10 µg/
mL.
2
(
(
(
-1 1
1
182, 1005, 966, 887, 856, 727, 648 cm ; H NMR (DMSO-d
500 MHz) δ 10.10 (1H, br, s, OH-5), 9.72 (1H, br, s, OH-4),
.89 (1H, s, H-6), 4.19 (1H, d, J ) 13.5 MHz, H-7a), 4.02 (1H,
6
,
6
1
3
Exp er im en ta l Section
d, J ) 13.5 MHz, H-7b), 2.55 (3H, s, H-8); C NMR (DMSO-
, 125 MHz) δ 128.0 (s, C-1), 120.9 (s, C-2), 118.5 (s, C-3),
49.9 (s, C-4), 150.2 (s, C-5), 122.9 (d, C-6), 65.8 (t, C-7), 43.0
q, C-8); FABMS m/z 343, 345, 347 [M + H] (13, 26, 14), 283
21), 281 (42), 279 (22), 185 (58), 133 (33), 93 (100), 75 (50),
d
1
(
(
5
3
6
Gen er a l Exp er im en ta l P r oced u r es. Melting points were
determined on an XT-4 micro melting point apparatus and are
uncorrected. IR spectra were recorded as KBr disks on a
Nicolet Impact 400 FT-IR spectrophotometer. 1D- and 2D-
+
79
8 9 3 2
7 (40); HRFABMS m/z 342.8641 (calcd for C H O Br S
1
NMR spectra were obtained at 500 and 125 MHz for H and
42.8639).
1
3
C, respectively, on an Inova 500 MHz spectrometer in DMSO
and acetone-d with solvent peaks as references. EIMS,
Cr ysta l d a ta of 1: C
8 8 3 2 r
H O Br S, M 344.02, monoclinic,
6
space group P2 /c, a ) 12.506(1) Å, b ) 4.473(1) Å, c ) 19.156
1
FABMS, and HRFABMS data were measured with a Micro-
mass Autospec-Ultima ETOF spectrometer; ESIMS and
HRESIMS data were measured with an Applied Biosystems
Qtrap spectrometer and a Bruker AOEXIII 7.0 TESLA FTMS,
respectively. Column chromatography was performed with
silica gel (200-300 mesh), Bio-Beads SX3 (200-400 mesh),
RP-18 reverse-phase silica gel (43-60 µm), and Sephadex
LH-20. TLC was carried out with glass precoated silica gel
3
(
2) Å, â ) 91.89(1)°; V ) 1071.0(2) Å , Z ) 4, D ) 2.134 g
c
-3
cm ; crystal dimensions 0.14 × 0.12 × 0.20 mm; see Support-
ing Information for more details.
4
-(2,3-Dib r om o-4,5-d ih yd r oxyp h en yl)-3-b u t en e-2-on e
(2): brown crystals (MeOH-H O), mp 165-166 °C; IR (KBr)
2
ν
max
3431, 2962, 2918, 2850, 1712, 1595, 1464, 1398, 1261,
-1
1097, 1026, 968, 802, 698 cm ; H NMR (acetone-d
6
, 500 MHz)
δ 7.86 (1H, d, J ) 16.0 Hz, H-4), 6.53 (1H, d, J ) 16.0 Hz,

Bromophenol Derivatives from Rhodomela Confervoides
J ournal of Natural Products, 2004, Vol. 67, No. 6 1035
H-3), 2.31 (3H, s, H-1), 7.32 (1H, s, H-6′); 13C NMR (acetone-
113.9 (s, C-3′′), 144.7 (s, C-4′′), 145.1 (s, C-5′′), 116.4 (d, C-6′′),
-
d
6
, 125 MHz) δ 26.3 (q, C-1), 197.4 (s, C-2), 113.7 (d, C-3), 142.6
d, C-4), 130.7 (s, C-1′), 118.8 (s, C-2′), 114.4 (s, C-3′), 146.0 (s,
C-4′), 147.7 (s, C-5′), 128.0 (d, C-6′); ESIMS m/z 333, 335, 337
60.7 (q, OCH
3
); ESIMS m/z 523, 525, 527, 529 [M - H] .
(
3-Br om o-5-h yd r oxy-4-m et h oxyp h en yla cet ic a cid (7):
1
3
C NMR (acetone-d
133.8 (s, C-1), 125. 1 (d, C-2), 117.0 (s, C-3), 144.6 (s, C-4),
151.6 (s, C-5), 118.0 (d, C-6), 60.6 (q, OCH ); HREIMS m/z
6
, 125 MHz) δ 173.1 (s, C-8), 40.7 (t, C-7),
-
[
M - H] .
Cr ysta l d a ta of 2: C10
H
8
O
3
Br
2
, M
r
335.98, orthorhombic,
3
7
9
space group P2
1
/a, a ) 7.371(1) Å, b ) 12.271(1) Å, c )
9 9 4
259.9679 (calcd for C H O Br 259.9684).
3
1
2
2.234(1) Å, â ) 83.12(1)°; V ) 1098.58(19) Å , Z ) 4, D
c
)
3-Br om o-5-h ydr oxy-4-m eth oxyph en ylacetic acid m eth -
-
3
.019 g cm ; crystal dimensions 0.05 × 0.05 × 0.20 mm; see
yl ester (8): brown gum; IR (KBr) νmax 3402, 2951, 2835, 1732,
-
1
1
Supporting Information for more details.
-(3-Br om o-5-h yd r oxy-4-m eth oxyp h en yl)-3-(2,3-d ibr o-
1570, 1489, 1429, 1290, 1234, 1165, 991, 837, 607 cm ; H
2
NMR (acetone-d
6.85 (1H, d, J ) 2.0 Hz, H-6), 3.54 (2H, s, H-7), 3.79 (3H, s,
3 3 6
OCH ), 3.63 (3H, s, COOCH ); C NMR (acetone-d , 125 MHz)
6
, 500 MHz) δ 6.98 (1H, d, J ) 2.0 Hz, H-2),
m o-4,5-d ih yd r oxyp h en yl)p r op ion ic a cid (3): brown gum;
IR (KBr) νmax 3400, 2937, 1705, 1568, 1485, 1427, 1406, 1275,
1
3
-
1
1
1
232, 1182, 989, 926, 860, 820, 754, 652 cm
;
H NMR
δ 171.9 (s, C-8), 40.2 (t, C-7), 133.1 (s, C-1), 125.2 (d, C-2), 117.2
(
acetone-d
6
, 500 MHz) δ 3.85 (1H, dd, J ) 9.5, 6.0 Hz, H-2),
(s, C-3), 145.0 (s, C-4), 151.9 (s, C-5), 118.1 (d, C-6), 60.7 (q,
+
3
6
6
.34 (1H, dd, J ) 14.0, 9.5 Hz, H-3a), 3.02 (1H, dd, J ) 14.0,
.0 Hz, H-3b), 6.79 (1H, s, H-6′′), 7.05 (1H, d, J ) 1.5 Hz, H-2′),
.93 (1H, d, J ) 1.5 Hz, H-6′), 3.79 (3H, s, OCH
OCH
3
), 52.1 (q, COOCH
3
); EIMS m/z 274, 276 [M] (68, 70),
217 (99), 215 (100), 202 (8), 200 (8), 174 (5), 172 (5), 121 (13);
1
3
79
3
); C NMR
11 4
HREIMS m/z 273.9824 (calcd for C10H O Br 273.9841).
(acetone-d
6
, 125 MHz) δ 173.8 (s, C-1), 51.0 (d, C-2), 41.6 (t,
Acid ic Hyd r olysis of 8. A solution of 8 (4 mg) in 2 N HCl
(2 mL) was stirred at 50 °C for 4 h and then evaporated to
dryness under reduced pressure. The residue was dissolved
with acetone (0.5 mL) and analyzed by TLC and reversed-
phase HPLC together with 7, indicating that the hydrolysis
product of 8 is identical to 7. The developing solvent system
C-3), 131.5 (s, C-1′′), 116.6 (s, C-2′′), 113.7 (s, C-3′′), 145.3 (s,
C-4′′), 144.1 (s, C-5′′), 117.7 (d, C-6′′), 137.4 (s, C-1′), 123.5 (d,
C-2′), 117.4 (s, C-3′), 145.3 (s, C-4′), 152.0 (s, C-5′), 116.6 (d,
-
C-6′), 60.7 (q, OCH
HRESIMS m/z 560.8152 [M + Na] (calcd for C16
Na 560.8160).
3
); ESIMS m/z 537, 539, 541, 543 [M - H] ;
+
79
13 6 3
H O Br -
3
was CHCl -MeOH-AcOH (6:1:0.1) for TLC. The HPLC
2
-(3-Br om o-5-h yd r oxy-4-m eth oxyp h en yl)-3-(2,3-d ibr o-
analysis was carried out with a YMC-Pack ODS-AM column
(3 µm, 100 × 4.6 mm) and a DAD detector (254 nm) using
methanol-water (7:3) as mobile phase (0.5 mL/min).
3-Br om o-5-h ydr oxy-4-m eth oxyben zoic acid (9): 13C NMR
m o-4,5-d ih yd r oxyp h en yl)p r op ion ic a cid m eth yl ester (4):
brown gum; IR (KBr) νmax 3406, 2927, 2852, 1724, 1568, 1485,
-
1 1
1
429, 1275, 1169, 1128, 991, 926, 860, 802, 762, 652 cm ; H
NMR (acetone-d
H-6′), 6.75 (1H, s, H-6′′), 3.86 (1H, dd, J ) 9.0, 6.5 Hz, H-2),
6
, 500 MHz) δ 7.01 (1H, s, H-2′), 6.91(1H, s,
(acetone-d
6
, 125 MHz) δ 129.0 (s, C-1), 125. 9 (s, C-2), 117.3
(s, C-3), 149.5 (s, C-4), 151.7 (s, C-5), 118.1 (d, C-6), 60.7 (q,
OCH ), 164.1 (s, C-7); FABMS m/z 245, 247 [M - H] (100,
3
98), 173 (29), 171 (31), 167 (14), 81 (10), 79 (10).
-
3
6
.34 (1H, dd, J ) 14.0, 9.0 Hz, H-3a), 3.04 (1H, dd, J ) 14.0,
1
3
.5 Hz, H-3b), 3.58 (3H, s, COOCH
, 125 MHz) δ 173.4 (s, C-1), 51.2 (d, C-2), 41.7
t, C-3), 130.9 (s, C-1′′), 116.3 (s, C-2′′), 113.7 (s, C-3′′), 145.2
3
), 3.79 (3H, s, OCH
3
);
C
NMR (acetone-d
6
Ack n ow led gm en t. The authors are grateful to A. Zeper
for mass spectra measurements. Financial support is from the
NSF (Grant No.99-929-01-26) and National “863” program
(
(
(
(
s, C-4′′), 144.5 (s, C-5′′), 117.5 (d, C-6′′), 137.0 (s, C-1′), 123.4
d, C-2′), 117.4 (s, C-3′), 145.5 (s, C-4′), 152.0 (s, C-5′), 116.4
d, C-6′), 60.6 (q, OCH ), 52.2 (q, COOCH ); ESIMS m/z 551,
3 3
(Grant No. 2001AA620403 and No. 2001AA234021).
-
5
53, 555, 557 [M - H] .
Acid ic Hyd r olysis of 4. A solution of 4 (2 mg) in 2 N HCl
2 mL) was stirred at 50 °C for 4 h and then evaporated to
Su p p or tin g In for m a tion Ava ila ble: Details of X-ray diffraction
of compounds 1 and 2 and MS and 1D and 2D NMR spectra of
compound 3. This material is available free of charge via the Internet
at http://pubs.acs.org.
(
dryness under reduced pressure. The residue was dissolved
with acetone (0.5 mL) and analyzed by TLC and reversed-
phase HPLC together with 3, indicating that the hydrolysis
product of 4 is identical to 3. The developing solvent system
Refer en ces a n d Notes
(
1) Katsui, N.; Suzuki, Y.; Kitamura, S.; Irie, T. Tetrahedron 1967, 23,
185-1188.
(2) Saenger, P.; Pedersen, M.; Rowan, K. S. Phytochemistry 1976, 15,
1
was CHCl
analysis was carried out with a YMC-Pack ODS-AM column
3 µm, 100 × 4.6 mm) and a DAD detector (254 nm) using
methanol-water (7:3) as mobile phase (0.5 mL/min).
-P h en yl-3-(2,3-d ib r om o-4,5-d ih yd r oxyp h en yl)p r op i-
on ic a cid (5): brown gum; IR (KBr) νmax3330, 2918, 2850,
712, 1660, 1601, 1468, 1401, 1385, 1275, 1180, 860, 783, 698
3
-MeOH-AcOH (6:1:0.1) for TLC. The HPLC
1
957-1958.
(
(
(
3) Kurata, K.; Amiya, T.; Nakano, N. Chem. Lett. 1976, 821-822.
4) Kurata, K.; Amiya, T. Chem. Lett. 1977, 1435-1438.
5) Pedersen, M. Phytochemistry 1978, 17, 291-293.
(
2
(6) Kurata, K.; Amiya, T. Bull. Chem. Soc. J pn. 1980, 53, 2020-2022.
(
(
7) Aknin, M.; Samb, A.; Mirailles, J .; Costantino, V.; Fattorusso, E.;
Mangoni, A. Tetrahedron Lett. 1992, 33, 555-558.
1
8) Kurata, K.; Taniguchii, K.; Takashima, K.; Hayashi, I.; Suzuki, M.
Phytochemistry 1997, 45, 485-487.
-
1 1
cm ; H NMR (acetone-d
6
, 500 MHz) δ 3.97 (1H, dd, J ) 6.0,
9
.0 Hz, H-2), 3.43 (1H, dd, J ) 9.0, 13.5 Hz, H-3a), 3.05 (1H,
(9) Lundgren, L.; Olsson, K.; Theander, O. Acta Chem. Scand. B 1979,
3
3, 105-108.
dd, J ) 6.0, 13.5 Hz, H-3b), 7.38 (2H, d, J ) 7.5 Hz, H-2′, 6′),
7
6
(
(
10) Pederson, M.; Saenger, P.; Fries, L. Phytochemistry 1974, 13, 2273.
11) Kurihara, H.; Mitani, T.; Kawabata, J .; Takahashi, K. J . Nat. Prod.
1999, 62, 882-884.
.32 (2H, t, J ) 7.5 Hz, H-3′, 5′), 7.26 (1H, t, J ) 7.5 Hz, H-4′);
.78 (1H, s, H-6′′); 13C NMR (acetone-d
, 125 MHz) δ 174.3 (s,
6
C-1), 52.1 (d, C-2), 41.9 (t, C-3), 140.1 (s, C-1′), 128.8 (d, C-2′,
′), 129.5 (d, C-3′, 5′), 128.1 (d, C-4′), 132.1 (s, C-1′′), 116.7 (s,
(12) Craigie, J . S.; Gruenig, D. E. Science 1967, 157, 1058-1059.
(
13) Kamikawa, T.; Yamagiwa, Y.; Arizuka, M. J . Nat. Prod. 1990, 53,
0-56.
14) Fan, X.; Xu, N.-J .; Shi, J .-G. J . Nat. Prod. 2003, 66, 455-458.
6
5
C-2′′), 113.8 (s, C-3′′), 144.0 (s, C-4′′), 145.3 (s, C-5′′), 117.8 (d,
(
-
C-6′′); FABMS m/z 413, 415, 417 [M - H] (15, 27, 17), 339
(15) Fan, X.; Xu, N.-J .; Yang, Y.-C.; Shi, J .-G. Chin. Chem. Lett. 2003, 14,
8
07-809.
(79), 325 (61), 311 (28), 293 (14), 291 (21), 289 (14), 265 (29),
(
(
(
(
16) Patil, A. D.; Westley, J . W.; Mattern, M. R.; Hofmann, G. A. Int. Appl.
2
(
63 (20), 183 (84), 173 (53), 171 (60), 151 (22), 91 (100), 71
51).
′-Meth oxy-2′′,3′,3′′-tr ibr om o-4′′,5′,5′′-tr ih yd r oxyd ip h e-
n yla cetic a cid (6): brown gum; IR (KBr) νmax3386, 2935,
WO 9525712 A1, 1995.
17) Weller, D. D.; Stirchack, E. P.; Yokoyama, A. J . Org. Chem. 1984,
49, 2061-2063.
18) Borchardt, R. T.; Huber, J . A.; Houston, M. J . Med. Chem. 1982, 25,
4
2
58-263.
699, 1570, 1483, 1404, 1275, 1167, 1124, 991, 860 cm-1; H
NMR (acetone-d , 500 MHz) δ 7.00 (1H, s, H-2′), 6.85 (1H, s,
H-6′), 6.89 (1H, s, H-6′′), 5.32 (1H, s, H-2), 3.80 (3H, s, OCH );
, 125 MHz) δ 172.9 (s, C-1), 57.2 (d, C-2),
1
1
19) Ames, M. M.; Selassie, C. D.; Woodson, L. C.; Loon, J . A. V. Hansch,
6
C.; Weinshilboum, R. M. J . Med. Chem. 1986, 29, 354-358.
(20) Mosumann, T. J . Immunol. Methods 1983, 65, 55-63.
(21) Carmichael, J .; DeGraff, W. G.; Gazdar, A. F.; Minna, J . D.; Mitchell,
J . B. Cancer Res. 1987, 47, 936-942
3
1
3
C NMR (acetone-d
6
1
1
36.6 (s, C-1′), 124.7 (s, C-2′), 117.5 (s, C-3′), 145.3 (s, C-4′),
51.9 (s, C-5′), 117.7 (d, C-6′), 131.8 (s, C-1′′), 117.4 (s, C-2′′),
NP030546+