Halichoblelides B and C, potent cytotoxic macrolides from a Streptomyces species separated from a marine fish

Article abstract of DOI:10.1016/j.tetlet.2012.03.114

Halichoblelide B (1) and C (2), novel macrolides with potent cytotoxicity against tumor cells in culture, have been isolated from a strain of Streptomyces hygroscopicus originally derived from the marine fish Halichoeres bleekeri, and their absolute stereostructures have been elucidated on the basis of spectroscopic analyses using 1D and 2D NMR techniques and chemical transformations. These compounds exhibited significant cytotoxicity against human cancer cell lines.

Full text of DOI:10.1016/j.tetlet.2012.03.114

Tetrahedron Letters 53 (2012) 2842–2846
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Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Halichoblelides B and C, potent cytotoxic macrolides from a Streptomyces
species separated from a marine fish
⇑
Takeshi Yamada , Takashi Kikuchi, Reiko Tanaka, Atsushi Numata
Osaka University of Pharmaceutical Sciences, 4-20-1, Nasahara, Takatsuki, Osaka 569-1094, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
Halichoblelide B (1) and C (2), novel macrolides with potent cytotoxicity against tumor cells in culture,
have been isolated from a strain of Streptomyces hygroscopicus originally derived from the marine fish
Halichoeres bleekeri, and their absolute stereostructures have been elucidated on the basis of spectro-
scopic analyses using 1D and 2D NMR techniques and chemical transformations. These compounds
exhibited significant cytotoxicity against human cancer cell lines.
Received 19 January 2012
Revised 21 March 2012
Accepted 28 March 2012
Available online 1 April 2012
Ó 2012 Elsevier Ltd. All rights reserved.
Keywords:
Streptomyces hygroscopicus
Marine fish
Halichoblelide
16-Membered ring macrolide
Cytotoxic activity
Based on the fact that some of the bioactive materials isolated
from marine animals have been produced by bacteria, we have fo-
cused on new antitumor materials from microorganisms isolated
from marine species.1–3 We previously reported that a cytotoxic
compound, halichoblelide A (3), member of elaiophylin,4,5 was pro-
duced by a strain of Streptomyces hygroscopicus OUPS-N92 isolated
from the marine fish Halichoeres bleekeri.6 Our continuing search
for cytotoxic metabolites from this strain led to the isolation of
two new 16-membered ring macrolides designated halichoblelides
B (1)7 and C (2).8 Both metabolites exhibited significant cytotoxic
activity against the murine P388 lymphocytic leukemia cell line,
and in addition, appreciable cytotoxicity against a disease-oriented
panel of 39 human cancer cell lines. We describe herein the abso-
lute stereostructure and biological activities of 1 and 2.
The microorganism from Halichoeres bleekeri was cultured at
27 °C for 6 weeks in a medium (120 L) containing 0.1% cone steep
liquor and 1% dextrin in artificial seawater adjusted to pH 7.5. This
culture had more volume and longer incubation than that reported
previously.6 After incubation, the AcOEt extract of the culture fil-
trate was purified by bioassay-directed fractionation (cytotoxicity
against P388 cells) employing stepwise a combination of Sephadex
LH-20, silica gel column chromatography, and reverse phased HPLC
to afford halichoblelide B (1, 10.2 mg) and C (2, 8.5 mg) as colorless
powders, respectively.
ion mass spectrometry (HRSIMS). The UV spectrum of 1 exhibited
absorption bands characteristic of a conjugated carbonyl group. In
addition, the IR spectrum exhibited absorption bands at 3425,
1708, 1643, and 1638 cm–1, characteristic of hydroxy groups, con-
jugated lactone carbonyls, and double bonds. A close inspection of
the 1H and 13C NMR spectra of 1 (Table 1) using DEPT and 1H–13
C
correlation spectroscopy (COSY) revealed the presence of two pri-
mary methyls (C-21 and C-210), nine secondary methyls (C-16–C-
19, C-27, and C-160–C-190), three oxymethyls (11-OCH3, 110-
OCH3, and 130-OCH3), five sp3-hybridized methylenes (C-12, C-20,
C-23, C-120, and C-200), twenty sp3-methines (C-6–C-10, C-13–C-
15, C-22, C-24–C-26, C-60–C-100, and C-130–C-150) including eleven
oxymethines (C-7, C-9, C-13, C-15, C-24–C-26, C-70, C-90, C-130, and
C-150), and one anomeric methine (C-22), two anomeric quater-
nary sp3-carbons (C-11 and C-110), two 1,3-diene moieties (C-2–
C-5 and C-20–C-50), two ester carbonyls (C-1 and C-10), and four hy-
droxyl groups. The 1H–1H COSY analysis of 1 led to five partial
structures as shown by bold-faced lines in Figure 1. The geometri-
cal configuration of both the conjugated diene moieties (C-2–C-5
and C-20–C-50) was deduced as trans-s-trans from the coupling
0
0
0
0
constants of the olefinic protons (J2,3 = J2 ,3 = 15.6 Hz, J3,4 = J3 ,4
=
11.6 Hz, and J4,5 = J4 ,5 = 15.3 Hz) and NOEs (H-3/H-5 and H-30/H-
50). The connection of these five units and the remaining functional
groups was determined on the basis of the key HMBC correlations
summarized in Figure 1, and the planar structure of 1 was eluci-
dated as 11,110-dimethylelaiophylin eliminated one sugar unit.
In NOESY experiment, the observed NOEs for unit A closely
looked like those for the same unit in halichoblelide A (3)
0
0
Halichoblelide B (1) had the molecular formula C51H84O15 as
established from the [M+Na]+ peak in high-resolution secondary
(Fig. 2). The vicinal coupling constants from C-6 to C-10 (J 6,7
10.2, J7,8 = 1.2, J8,9 = 9.8, and J9,10 = 1.8 Hz) also corresponded to
=
⇑
Corresponding author.
E-mail address: yamada@gly.oups.ac.jp (T. Yamada).
0040-4039/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tetlet.2012.03.114

T. Yamada et al. / Tetrahedron Letters 53 (2012) 2842–2846
2843
Figure 1. Typical 2D NMR correlations in halichoblelide B (1).
Table 1
NMR spectral data for halichoblelide B (1) and C (2) in CDC13
1
2
a
a
Position
dH
J (Hz)
dC
Position
dH
J (Hz)
dC
1
2
3
4
5
6
7
8
9
10
11
12
b
13
14
15
16
17
18
19
20A
B
21
22
169.5 (q)b
121.3 (t)
145.1 (t)
131.7 (t)
144.5 (t)
41.3 (t)
77.9 (t)
36.6 (t)
69.7 (t)
38.0 (t)
1
2
3
4
5
6
7
8
9
10
11
12
b
13
14
15
16
17
18
19
20
21
22
23
b
169.5 (q)b
121.3 (t)
145.1 (t)
131.8 (t)
144.5 (t)
41.3 (t)
77.9 (t)
36.6 (t)
69.7 (t)
38.0 (t)
5.67
6.98
6.10
5.65
2.52
4.93
1.88
3.48
2.04
d
15.6 (3)
5.67
6.98
6.10
5.65
2.52
4.93
1.88
3.48
2.04
d
15.6 (3)
dd
dd
dd
tq
dd
dqd
br d
qd
15.6 (2), 11.6 (4)
15.3 (5), 11.6 (3)
15.3 (4), 10.2 (6)
10.2 (5, 7), 6.8 (17)
10.2 (6), 1.2 (8)
9.8 (9), 7.0 (18), 1.2 (7)
9.8 (8)
dd
dd
dd
tq
dd
dqd
ddd
qd
15.6 (2), 11.6 (4)
15.1 (5), 11.6 (3)
15.1 (4), 10.1 (6)
10.1 (5, 7), 6.8 (17)
10.1 (6), 2.2 (8)
10.3 (9), 7.0 (18), 2.2 (7)
10.3 (8), 3.8 (9-OH), 1.0 (10)
7.1 (19), 1.0 (9)
7.1 (19), 1.8 (9)
103.2 (q)
34.2 (s)
103.2 (q)
34.0 (s)
a
2.32
1.39
3.84
1.21
3.50
1.19
1.03
0.89
0.96
1.44
1.62
0.85
5.04
1.79
1.82
3.96
3.61
3.99
1.24
3.32
3.05
2.15
2.04
dd
dd
td
tt
dq
d
d
d
d
dqd
dqd
t
t
dt
ddd
br d
br s
qd
d
br s
s
br s
br s
13.6 (12b), 4.5 (13)
13.6 (12
10.6 (12b, 14), 4.5 (12
10.6 (13, 15), 3.8 (20A, 20B)
10.6 (14), 6.3 (16)
6.3 (15)
6.8 (6)
7.0 (8)
a
2.30
1.40
3.54
1.25
3.32
1.19
1.03
0.87
0.97
0.91
dd
dd
td
tq
dq
d
d
d
d
d
13.6 (12b), 4.5 (13)
13.6 (12a), 10.4 (13)
10.4 (12b, 14), 4.5 (12
10.4 (13, 15), 7.0 (20)
10.4 (14), 6.2 (16)
6.2 (15)
6.8 (6)
7.0 (8)
7.1 (10)
7.0 (14)
a
), 10.6 (13)
a)
70.1 (t)
47.4 (t)
67.8 (t)
19.0 (p)
15.1 (p)
9.5 (p)
a
)
73.3 (t)
42.6 (t)
70.6 (t)
19.2 (p)
15.1 (p)
9.5 (p)
7.1 (10)
7.2 (p)
19.4 (s)
7.2 (p)
13.4 (p)
13.2 (20B), 7.6 (21), 3.8 (14)
13.2 (20A), 7.6 (21), 3.8 (14)
7.6 (20A, 20B)
9.2 (p)
93.2 (t)
33.4 (s)
5.03
1.82
1.80
3.96
3.62
3.99
1.24
3.34
3.05
2.17
1.94
br s
dt
ddd
br d
br s
qd
d
br s
s
93.0 (t)
33.4 (s)
2.3 (23
12.3 (23b), 2.3 (22, 24)
12.3 (23 ), 10.8 (24), 2.3 (22)
a
, 23b)
a
12.3 (23b), 2.7 (22, 24)
12.3 (23 ), 9.8 (24), 2.7 (22)
9.8 (22b)
23
b
24
25
26
27
a
a
a
24
25
26
27
66.1 (t)
71.5 (t)
65.7 (t)
16.8 (p)
10.8 (23b)
66.1 (t)
71.4 (t)
65.8 (t)
16.8 (p)
6.8 (27), 1.8 (25)
6.8 (26)
6.9 (27), 1.8 (25)
6.9 (26)
9-OH
9-OH
11-OCH3
24-OH
25-OH
10
11-OCH3
23-OH
24-OH
46.6 (p)
46.6
br s
br s
169.5 (q)
121.3 (t)
145.1 (t)
131.7 (t)
144.5 (t)
41.3 (t)
77.9 (t)
36.6 (t)
69.7 (t)
38.0 (t)
103.3 (q)
34.2 (s)
10
169.5 (q)
121.3 (t)
145.1 (t)
131.8 (t)
144.5 (t)
41.3 (t)
77.9 (t)
36.6 (t)
69.7 (t)
38.0 (t)
103.3 (q)
34.2 (s)
20
5.67
6.98
6.10
5.65
2.52
4.95
1.91
3.48
2.03
d
15.6 (30)
20
5.67
6.98
6.10
5.65
2.52
4.95
1.91
3.50
2.04
d
15.6 (30)
30
dd
dd
dd
tq
dd
dqd
br d
qd
15.6 (20), 11.6 (40)
15.3 (50), 11.6 (30)
15.3 (40), 10.2 (60)
10.2 (50, 70), 6.8 (170)
10.2 (60), 1.2 (80)
9.5 (9), 7.0 (180), 1.2 (70)
9.5 (80)
30
dd
dd
dd
tq
dd
dqd
ddd
qd
15.6 (20), 11.6 (40)
15.1 (50), 11.6 (30)
15.1 (40), 10.1 (60)
10.1 (50, 70), 6.8 (170)
10.1 (60), 2.2 (80)
40
40
50
50
60
60
70
70
80
80
10.3 (90), 7.0 (180), 2.2 (70)
10.3 (80), 3.8 (90-OH), 1.0 (100)
7.1 (190), 1.0 (90)
90
90
100
110
120a
b
7.1 (190), 1.8 (90)
100
110
120
2.38
1.40
3.34
1.13
3.45
1.19
1.04
0.90
dd
dd
td
tt
dq
d
13.6 (120b), 4.5 (130)
2.38
1.40
3.34
1.13
3.45
1.19
1.04
0.89
dd
dd
td
tt
dq
d
13.6 (120b), 4.5 (130)
13.6 (120a), 10.4 (130)
13.6 (120a), 10.6 (130)
10.6 (120b, 140), 4.5 (120a
130
140
150
160
170
180
)
75.8 (t)
47.6 (t)
68.4 (t)
19.1 (p)
15.1 (p)
9.5 (p)
130
140
150
160
170
180
10.4 (120b, 140), 4.5 (120a
)
75.9 (t)
48.1 (t)
68.4 (t)
19.1 (p)
15.1 (p)
9.5 (p)
10.6 (130, 150), 3.8 (200A, 200B)
10.6 (140), 6.3 (160)
6.3 (150)
10.4 (130, 150), 3.8 (200A, 200B)
10.4 (140), 6.2 (160)
6.2 (150)
d
d
6.8 (60)
7.0 (80)
d
d
6.8 (60)
7.0 (80)
(continued on next page)

2844
T. Yamada et al. / Tetrahedron Letters 53 (2012) 2842–2846
Table 1 (continued)
1
2
a
a
Position
dH
J (Hz)
dC
Position
dH
J (Hz)
dC
190
0.97
d
7.1 (100)
7.2 (p)
19.4 (s)
190
0.97
1.46
1.59
0.87
3.36
3.07
3.33
d
7.1 (100)
7.2 (p)
19.4 (s)
200A
1.46
1.58
0.87
3.39
3.07
3.33
dqd
dqd
t
br s
s
13.2 (200B) 7.6 (210), 3.8 (140)
13.2 (200A) 7.6 (210), 3.8 (140)
7.6 (200A, 200B)
200A
dqd
dqd
t
br s
s
13.2 (200B), 7.6 (210), 3.8 (140)
13.2 (200A), 7.6 (210), 3.8 (140)
7.6 (200A, 200B)
B
210
90-OH
110-OCH3
130-OCH3
B
210
90-OH
110-OCH3
130-OCH3
10.0 (p)
10.1 (p)
46.6 (p)
56.3 (p)
46.6 (p)
56.3 (p)
s
s
a
1H chemical shift values (d ppm from SiMe4) followed by multiplicity and then the coupling constants (J/Hz). Figures in parentheses indicate the proton coupling with that
position.
b
Letters, p, s, t, and q, in parentheses indicate respectively primary, secondary, tertiary, and quaternary carbons, assigned by DEPT.
Figure 2. Observed NOEs for unit A in 1.
those of 36 (Table 1). In addition, the measured coupling constants
cific rotation (Scheme 1). This evidence demonstrated that units A
and B in 1 were the same absolute configuration as unit A in 3.6 On
the other hand, the derivative 5 from unit C in 1 was also identical
with that from 3.6 The negative Cotton effect observed in the CD
spectrum of the bis-p-bromobezoate 5 supported the absolute con-
figuration of 4 as shown in Scheme 1. The absolute configuration of
4 and 5 led us to determine the absolute stereostructures of the
three units (A, B, and C), respectively, and consequently the abso-
lute stereostructure for halichoblelide B (1).
(Table 1) and NOEs of unit B closely resembled those of unit A.
Therefore we deduced that units A and B have the same stereo-
chemistry and conformation as unit A in 3. We had established
the absolute stereostructure of 3 by degradation.6,9 In the examina-
tion, the absolute stereostructure for the degradated product 4
from unit A in 3 had been elucidated by application of the modified
Mosher’s method.10 The degradation of 1 gave the product 4, which
was identical with that from 3 for NMR spectral data and the spe-

T. Yamada et al. / Tetrahedron Letters 53 (2012) 2842–2846
2845
Scheme 1. Reagents and conditions: (a) Pd-C/H2, rt; (b) p-TsOH/MeOH, rt; (c) c-H2SO4/MeOH, rt; (d) p-BrBzCl/pyridine, rt.
Table 2
the signal for one of the ethyl group in 1 was replaced by that
for a methyl group [dH 0.91, dC 13.44] in 2. The 1H–1H and HMBC
correlations implied that the ethyl group at C-14 in 1 was replaced
by a methyl group in 2 (vide info). Degradation of 2 also gave the
bis-p-bromobenzoate 5. The analysis of coupling constants and
NOE signals for 2 suggested that the relative stereochemistry of
units A and B in 2 was the same as those in 1. In addition, the Cot-
Cytotoxicity of halichoblelide B (1), C (2), and A (3) against a panel of 39 human
cancer cell lines
Origin of cancer
Breast
Cell line
LogGI50 (M)a
2
1
3
HBC-4
BSY-1
HBC-5
MCF-7
MDA-MB-231
U-251
SF-268
SF-295
SF-539
SNB-75
SNB-78
HCC2998
KM-12
ꢀ5.72
ꢀ5.71
ꢀ5.71
ꢀ5.69
ꢀ5.71
ꢀ5.75
ꢀ5.76
ꢀ5.74
ꢀ5.59
ꢀ5.73
ꢀ5.63
ꢀ5.71
ꢀ5.71
ꢀ5.72
ꢀ5.71
ꢀ5.73
ꢀ5.71
ꢀ5.74
ꢀ5.78
ꢀ5.75
ꢀ5.75
ꢀ5.76
ꢀ5.75
ꢀ5.69
ꢀ5.71
ꢀ5.65
ꢀ5.72
ꢀ5.70
ꢀ5.70
ꢀ5.76
ꢀ5.74
ꢀ5.78
ꢀ5.76
ꢀ5.80
ꢀ5.72
ꢀ5.71
ꢀ5.75
ꢀ5.71
ꢀ5.72
ꢀ5.70
ꢀ6.20
ꢀ6.03
ꢀ5.73
ꢀ5.89
ꢀ5.84
ꢀ5.65
ꢀ5.78
ꢀ5.79
ꢀ6.01
ꢀ5.56
ꢀ5.95
ꢀ5.82
ꢀ5.80
ꢀ5.75
ꢀ5.81
ꢀ5.90
ꢀ6.18
ꢀ6.32
ꢀ5.96
ꢀ6.12
ꢀ6.23
ꢀ6.56
ꢀ5.74
ꢀ6.43
ꢀ5.73
ꢀ5.77
ꢀ5.80
ꢀ5.61
ꢀ6.52
ꢀ5.73
ꢀ5.85
ꢀ5.81
ꢀ5.88
ꢀ5.69
ꢀ6.26
ꢀ6.31
ꢀ5.78
ꢀ5.98
ꢀ5.72
ꢀ5.78
ꢀ5.81
ꢀ5.70
ꢀ5.63
ꢀ5.73
ꢀ5.74
ꢀ5.75
ꢀ5.96
ꢀ5.95
ꢀ5.85
ꢀ5.75
ꢀ5.74
ꢀ7.73
ꢀ5.75
ꢀ5.78
ꢀ5.68
ꢀ5.79
ꢀ5.73
ꢀ5.71
ꢀ5.72
ꢀ5.68
ꢀ5.81
ꢀ5.69
ꢀ5.73
ꢀ5.73
ꢀ5.74
ꢀ5.70
ꢀ5.74
ꢀ5.74
ꢀ5.77
ꢀ5.71
ꢀ5.75
ꢀ5.77
ꢀ5.70
ꢀ5.73
ꢀ5.76
ꢀ5.75
ꢀ5.72
ton effect in the CD spectra and the [a]D value for 2 closely resem-
bled those of 1.7,8 The above evidence led us to deduce the absolute
stereostructure of halichoblelide C (2).
Central nervous system
The cancer cell growth inhibitory properties of halichoblelide B
(1) and C (2) were examined using a disease-oriented panel of 39
human cancer cell lines (HCC panel) from the Japanese Foundation
for Cancer Research.11,12 The results of them together with halicho-
blelide A (3) are shown in Table 2. All of these metabolites exhib-
ited significant cytotoxic activity against the 39 human cancer cell
lines (Table 2). Halichoblelide C (2) also showed appreciable cyto-
toxic activity against the cell lines (Table 2). As shown in Table 2,
the delta and range values of 2 were 0.63, and 1.00, respectively
(effective value: delta P 0.5 as well as range P 1.0), disclosing that
this compound showed selective cytotoxic activity. Furthermore,
evaluation of the pattern of differential cytotoxicity using the
COMPARE program12 suggested the mode of action for 2 to be dif-
ferent from that shown by any other anticancer drug developed to
date.
Colon
Lung
HT-29
HCT-15
HCT-116
NCI-H23
NCI-H226
NCI-H522
NCI-H460
A549
DMS273
DMS114
LOX-IMVI
OVCAR-3
OVCAR-4
OVCAR-5
OVCAR-8
SK-OV-3
RXF-631L
ACHN
St-4
MKN1
MKN7
MKN28
MKN45
MKN74
DU-145
PC-3
Melanoma
Ovary
Acknowledgements
We thank Dr. T. Ito (National Institute of Technology and Eval-
uation, Biological Resource Center) and Dr. T. Yamori (Screening
Committee of Anticancer Drugs supported by a Grant-in-Aid for
Scientific Research on the Priority Area ‘‘Cancer’’ from the Ministry
of Education, Culture, Sports, Science and Technology, Japan) for
identification of the fungal strain, and for performing the assay
for cytotoxicity using the panel of 39 human cell lines, respectively.
We are grateful to Ms. M. Fujitake and Dr. K. Minoura of this uni-
versity for MS and NMR measurements, respectively. This study
was supported by a Grant-in-aid for Scientific Research from the
Japan Society for the Promotion of Science.
Kidney
Stomach
Prostate
MG-MIDb
Deltac
ꢀ5.72
ꢀ5.93
ꢀ5.75
0.08
0.21
0.63
0.22
0.33
Ranged
1.00
Supplementary data
a
Log concentration of compounds for inhibition of cell growth at 50% compared
to control.
b
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.tetlet.2012.03.114.
Mean value of logGI50 over all cell lines tested.
The difference in logGI50 value of the most sensitive cell and MG-MID value.
The difference in logGI50 value of the most sensitive cell and the least sensitive
c
d
cell.
References and notes
1. Yamada, T.; Iritani, M.; Doi, M.; Minoura, K.; Ito, T.; Numata, A. J. Chem. Soc.,
Perkin Trans. 1 2001, 3046–3053.
2. Yamada, T.; Iritani, M.; Minoura, K.; Kawai, K.; Numata, A. Org. Biomol. Chem.
2004, 2, 2131–2135.
Halichoblelide C (2) had the molecular formula C50H82O15 as
established by HRSIMS. The general features of its 1H and 13C
NMR spectra (Table 1) closely resembled those of 1 except that

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T. Yamada et al. / Tetrahedron Letters 53 (2012) 2842–2846
3. Yamada, T.; Iritani, M.; Ohishi, H.; Tanaka, K.; Minoura, K.; Doi, M.; Numata, A.
Org. Biomol. Chem. 2007, 5, 3979–3986. and references cited therein.
4. Arai, M. J. Antibiot. 1960, Ser. A 13, 46–50.
5. Fiedler, H.-P.; Worner, W.; Zahner, H. J. Antibiot. 1981, 34, 1107–1118.
6. Yamada, T.; Minoura, K.; Numata, A. Tetrahedron Lett. 2002, 43, 1721–1724.
1645, and 1635; HRSIMS m/z 945.5532 [M+Na]+ (calcd for C50H82O15Na:
945.5532); CD k (c 1.38 ꢁ 10ꢀ4 M in EtOH)/nm 316 (
De 0), 280 (+19.22), 262
(0), and 251 (ꢀ20.36). 1H and 13C NMR data are listed in Tables 1 and S2
(Supplementary data).
9. Hammann, P.; Kretzschmar, G.; Seibert, G. J. Antibiot. 1990, 43, 1431–1440.
10. Ohtani, I.; Kusumi, T.; Kashman, Y.; Kakisawa, H. J. Am. Chem. Soc. 1991, 113,
4092–4096.
11. Yamori, T.; Matsunaga, A.; Sato, S.; Yamazaki, K.; Komi, A.; Ishizu, K.; Mita, I.;
Edatsugi, H.; Matsuba, Y.; Takezawa, K.; Nakanishi, O.; Kohno, H.; Nakajima, Y.;
Komatsu, H.; Andoh, T.; Tsuruo, T. Cancer Res. 1999, 59, 4042–4049.
12. Yamori, T. Cancer Chemother. Pharmacol. 2003, 52, S74–S79.
7. Halichoblelide B (1): colorless powder, mp 143–145 °C, [
a
]
ꢀ32.2 (c 0.19 in
D
EtOH); kmax (EtOH)/nm 253 (log 4.46);
e
m
max (KBr)/cmꢀ1 3425, 1708, 1643, and
1638 (C@C); HRSIMS m/z 959.5691 [M+Na]+ (calcd for C51H84O15Na:
959.5697); CD k (c 2.21 ꢁ 10ꢀ4 M in EtOH)/nm 315 (
De 0), 280 (+16.54), 263
(0), and 249 (ꢀ23.36). 1H and 13C NMR data are listed in Tables 1 and S1
(Supplementary data).
8. Halichoblelide C (3): colorless powder, mp 148–150 °C, [
a
]
D
ꢀ36.8 (c 0.09 in
EtOH); kmax (EtOH)/nm 255 (log
e
4.37); mmax (KBr)/cmꢀ1 3432, 1711, 1701,