Glycolipids from the Formosan soft coral Lobophytum crassum

Article abstract of DOI:10.1248/cpb.55.1720

Three glycolipids (1-3), possessing a sugar moiety at C-2 of glycerol ether, have been isolated from the Formosan soft coral Lobophytum crassum. Their structures were elucidated by spectroscopic methods, particularly in 1D- and 2D-NMR experiments. The absolute configurations on the sugar portion and lipid aglycon of 1-3 were determined by methanolysis, chemical transformation and the application of Mosher's method on 1 and 3. Compounds 1-3 exhibited weak cytotoxic activities.

Full text of DOI:10.1248/cpb.55.1720

1720
Chem. Pharm. Bull. 55(12) 1720—1723 (2007)
Vol. 55, No. 12
Glycolipids from the Formosan Soft Coral Lobophytum crassum
Chih-Hua CHAO,a Ho-Cheng HUANG,a,b Yang-Chang WU,c Chung-Kuang LU,d,e Chang-Feng DAI,f and
,a,g
*
Jyh-Horng SHEU
a Department of Marine Biotechnology and Resources, National Sun Yat-sen University; Kaohsiung 804, Taiwan, R.O.C.:
b Department of Chemical and Materials Engineering, Cheng Shiu University; Kaohsiung 833, Taiwan, R.O.C.: c Graduate
Institute of Natural Products, Kaohsiung Medical University; Kaohsiung 807, Taiwan, R.O.C.: d National Museum of
e
Marine Biology and Aquarium; Institute of Marine Biotechnology, National Dong Hwa University; Checheng, Pingtung
944, Taiwan, R.O.C.: and f Institute of Oceanography, National Taiwan University; Taipei 106, Taiwan, R.O.C.: and g Asian
Pacific Ocean Research Center, National Sun Yat-sen University; Kaohsiung 804, Taiwan, R.O.C.
Received August 6, 2007; accepted September 14, 2007
Three glycolipids (1—3), possessing a sugar moiety at C-2 of glycerol ether, have been isolated from the For-
mosan soft coral Lobophytum crassum. Their structures were elucidated by spectroscopic methods, particularly
in 1D- and 2D-NMR experiments. The absolute configurations on the sugar portion and lipid aglycon of 1—3
were determined by methanolysis, chemical transformation and the application of Mosher’s method on 1 and 3.
Compounds 1—3 exhibited weak cytotoxic activities.
Key words Lobophytum crassum; glycolipid; coral; R-batyl alcohol; R-chimyl alcohol; arabinopyranoside
During the course of our investigation on the bioactive bon resonance at d 100.4 (d) in the HMQC spectrum. Except
chemical constituents from marine invertebrates,1—6) we have for the above carbon (C-1ꢃ), the 13C-NMR spectrum of 1 ex-
investigated a soft coral Lobophytum crassum collected from hibited eight oxygenated carbons, including four oxymethyl-
Taiwanese waters. Earlier studies of the genus Lobophytum enes at dC 71.7 (t), 71.1 (t), 64.5 (t), and 63.0 (t), and four
have led to the isolation of terpenoids, of which some have oxymethines at dC 78.5 (d), 71.0 (d), 70.8 (d), and 70.1 (d)
shown cytotoxic,7—10) anti-HIV,11) and antibacterial12) activi- (Table 1). Above data together with the methyl group reso-
ties. In this paper we report the isolation and structural eluci- nanting at dH 0.85 (3H, t, Jꢂ6.6 Hz) and methylenes at dH
dation of three new glycolipids 1—3 (Fig. 1) from this organ- 1.26 (br s) revealed the structure of 1 to be a glycoside with a
ism. The absolute configurations of 1—3 were determined by long aliphatic chain.
the comparison of specific optical rotations of sugar and
The gross structure of metabolite 1 was further establish-
1
aglycon moieties with known compounds, chemical conver- ed by the 2D-NMR studies, particularly in H–1H COSY,
sions, and the application of Mosher’s method. Cytotoxicity HMQC and HMBC experiments. The correlations of H–1H
1
of metabolites 1—3 against the growth of a limited panel of COSY revealed proton–proton sequences, from H-1ꢃ to H-5ꢃ,
cancer cells of HepG2, Hep3B (human liver carcinoma), H2-1 to H2-3, H2-1ꢄ to H2-2ꢄ, and H2-15ꢄ to H3-16ꢄ, as shown
MDA-MB-231 (human breast carcinoma), and Ca9-22 in Fig. 2. The HMBC correlations from H-1ꢃ to C-5ꢃ and C-
(human gingival carcinoma) is also discussed.
2, as well as other correlations illustrated in Fig. 2, estab-
lished a pyranose and a glycerol ether moiety. The pyranose
was identified as b-arabinopyranose by analysis of coupling
Results and Discussion
(2R)-1-Hydroxy-3-hexadecyloxy-propyl-b-D-arabinopyra- constants of the related protons (Table 1). HR-ESI mass
noside (1) was isolated as amorphous white solid. Its HR- spectrum and the above 2D-NMR spectroscopic analysis led
ESI-MS exhibited a pseudomolecular ion peak at m/z to the establishment of the aglycon to be chimyl alcohol.
471.3296 [MꢀNa]ꢀ (Calcd for C24H48O7Na, 471.3298), cor-
The absolute configurations on the sugar portion and lipid
responding to the molecular formula C24H48O7, indicating aglycon were determined on the basis of methanolysis,
one degree of unsaturation. The 1 : 2 ratio of carbon and pro- chemical transformation and the application of the modified
ton atoms and high oxygen content in its molecular formula Mosher’s method. As shown in Chart 1, methanolysis of 1
and strong absorption bands at nmax 3391, 1142, 1075, and with 1 N HCl(aq)–MeOH (1 : 1) yielded the methyl arabinopy-
1007 cmꢁ1 in IR spectrum suggested that 1 might be a gly- ranoside and the chimyl alcohol. The glycerol-based portion
colipid. An anomeric glycoside proton resonance was ob- was found to be 2R-chimyl alcohol, [a]D22 ꢁ2°.13) The sugar-
served at d 5.67 (1H, d, Jꢂ3.3 Hz), corresponding to a car- containing portion was further treated with 1 N HCl(aq) and
the sugar thus obtained was shown to be (ꢁ)-D-arabinose,
Fig. 2. Selective 1H–1H COSY and HMBC Correlations of 1
Fig. 1. Structures of Metabolites 1—3
∗ To whom correspondence should be addressed. e-mail: sheu@mail.nsysu.edu.tw
© 2007 Pharmaceutical Society of Japan

December 2007
1721
Table 1. 1H- and 13C-NMR Spectral Data of Compounds 1—3
1
2
3
C #
1Ha)
4.14 br s
13Cb)
1Ha)
4.14 br s
13Cb)
1Ha)
13Cb)
1
63.0 (t)d)
63.0 (t)
4.55 dd (11.4, 3.9)
4.46 dd (11.4, 6.6)
4.36 m
3.75 dd (10.2, 5.4)
3.67 dd (10.2, 5.4)
5.55 d (3.6)
4.61 dd (9.0. 3.6)
4.47 m
65.1 (t)
2
3
4.37 m
78.5 (d)
71.1 (t)
4.37 m
78.5 (d)
71.1 (t)
74.9 (d)
70.2 (t)
3.89 dd (10.2, 4.2)c)
3.85 dd (10.2, 5.4)
5.67 d (3.3)
4.62 dd (9.0. 3.3)
4.50 dd (9.0, 3.3)
4.36 br s
3.89 dd (10.2, 4.2)
3.85 dd (10.2, 5.4)
5.67 d (3.3)
4.62 dd (9.0. 3.3)
4.50 dd (9.0, 3.3)
4.36 br s
4.47 dd (12.0, 1.5)
4.07 dd (12.0, 2.7)
3.46 t (6.3)
1.54 m
1ꢃ
2ꢃ
3ꢃ
4ꢃ
5ꢃ
100.4 (d)
70.8 (d)
71.0 (d)
70.1 (d)
64.5 (t)
100.4 (d)
70.8 (d)
71.0 (d)
70.1 (d)
64.5 (t)
100.7 (d)
70.5 (d)
70.9 (d)
70.2 (d)
64.5 (t)
4.40 br s
4.47 dd (12.0, 1.5)
4.07 dd (12.0, 2.7)
3.46 t (6.3)
1.54 m
1.26 m
4.36 dd (12.0, 1.8)
4.09 dd (12.0, 2.4)
3.43 t (6.3)
1.55 m
1.26 m
1ꢄ
2ꢄ
3ꢄ
71.7 (t)
30.1 (t)
26.4 (t)
71.7 (t)
30.1 (t)
26.4 (t)
71.7 (t)
30.0 (t)
26.4 (t)
1.26 m
4ꢄ—13ꢄ
14ꢄ
15ꢄ
1.26 br s
1.26 br s
1.26 br s
0.85 t (6.6)
29.6—30.0 (t)
32.1 (t)
22.9 (t)
1.26 br s
1.26 br s
1.26 br s
1.26 br s
29.6—30.0 (t)
29.6—30.0 (t)
29.6—30.0 (t)
32.1 (t)
1.26 br s
1.26 br s
1.26 br s
0.86 t (6.6)
29.6—30.0 (t)
32.1 (t)
22.9 (t)
16ꢄ
14.2 (q)
14.3 (q)
17ꢄ
1.26 br s
22.9 (t)
18ꢄ
0.85 t (6.6)
14.2 (q)
OAc
2.02 s
20.7 (q)
170.7 (s)
a) Spectra recorded at 300 MHz in pyridine-d5. b) Spectra recorded at 75 MHz in pyridine-d5. c) J values (in Hz) in parentheses. d) Multiplicity deduced by DEPT and
indicated by usual symbols.
Chart 1. Chemical Conversions from 1 to 1a—e and Chemical Shift Differences of MTPA Esters 1c and 1d
[a]D22 ꢁ110°,14) by comparison of specific optical rotation (1c) and (R)-MTPA ester (1d) were summarized in Chart 1
and TLC analysis with the authentic sample. The absolute and indicated the S-configuration at C-2ꢃ; hence, the sugar
configuration of chimyl alcohol (1a) was further confirmed moiety of 1 was deduced as D-arabinose.
by the calculation of the chemical shift difference of two di-
(2R)-1-Hydroxy-3-octadecyloxy-propyl-b-D-arabinopyra-
astereotopic protons of H2-1 in bis-(R)-MTPA ester (1b), noside (2) had the molecular formula of C26H52O7, 28 mass
which was prepared from 1a with (S)-MTPA chloride. Previ- units higher than that of 1, as determined by HR-ESI-MS.
ous study has shown that the chemical shift difference of two The H- and 13C-NMR spectral data of 2 were found to be
1
diastereotopic protons of H2-1, resonating as two doublets of very similar with those of 1. Compound 2 is more strongly
doublets, in 2S-glycerol ether was 0.26 ppm, while that in retained by the reverse stationary phase in ODS column than
2R-glycerol ether was 0.31 ppm.15) In the case of 1b, the 1, implying that 2 might possess longer aliphatic chain. In-
above two protons were found to resonate at d 4.73 and 4.42 spection of 2D-NMR spectral data of 2 allowed the establish-
(Dꢂ0.31 ppm), indicating R configuration at C-2, the same ment of the same planar structure as that of 1, with the slight
as that deduced by specific optical rotation. The absolute difference of aliphatic chain length at 3-O position. Hence,
configuration of the sugar moiety was also determined by the the glycerol moiety of 2 was derived from batyl alcohol. The
application of Mosher’s method16,17) on the acetonide deriva- absolute stereochemistry of 2 was suggested to be the same
tive 1e. The chemical shift differences of (S)-MTPA ester as that of 1 due to the biogenetic consideration as well as the

1722
Vol. 55, No. 12
Chart 2. Chemical Conversions from 3 to 1d and Chemical Shift Differences of MTPA Esters 3a and 3b
Table 2. Cytotoxicity Data of Compounds 1—3
tivities toward the above cancer cell lines with IC50’s ranged
from 9.2 to 15.0 mg/ml.
Cell lines IC50 (mg/ml)
Compound
Hep G2
Hep 3B
MDA-MB-231
Ca9-22
Experimental
General Procedure Optical rotations were measured on a Jasco P-1020
polarimeter. IR spectra were recorded on Jasco FT/IR-4100 fourier trans-
form infrared spectrophotometer. The NMR spectra were recorded on Varian
Mercury-Plus 300 FT-NMR instruments at 300 MHz for 1H, and 75 MHz for
13C in pyridine-d5, and chemical shifts are referenced to dC 135.5 ppm and
dH 8.71 ppm. Nuclear Overhauser and exchange spectroscopy (NOESY),
1H–1H correlation spectroscopy (COSY), heteronuclear multiple quantum
1
2
3
10.8
9.2
11.3
0.2
12.7
9.7
9.7
0.2
14.5
11.1
12.4
0.2
12.0
15.0
9.5
Doxorubicin
0.1
1
same sign of specific optical rotations, and similarity of
NMR spectral data.
coherence (HMQC), and H-detected multiple-bond heteronuclear multiple
quantum coherence (HMBC) experiments were performed by using standard
Varian pulse sequences. LR-MS and HR-MS were obtained by ESI on a
Bruker APEX II mass spectrometer. Silica gel 60 (Merck, 230—400 mesh)
was used for column chromatography. Precoated Silica gel plates (Merck
Kieselgel 60 F254 0.2 mm) were used for analytical TLC. High-performance
liquid chromatography (HPLC) was performed on a Shimadzu LC-10AT VP
apparatus equipped with a Shimadzu SPD-10A VP UV detector and with a
Purospher® STAR RP-18e column (250ꢅ10 mm, 5 mm). (ꢁ)-D-Arabinose
was purchased from Aldrich.
(2R)-1-Acetoxy-3-hexadecyloxy-propyl-b-D-arabinopyra-
noside (3) was obtained as a white powder. Its HR-ESI-MS
exhibited a molecular ion peak at m/z 513.3404 [MꢀNa]ꢀ
and established a molecular formula of C26H50O8, corre-
sponding to two degrees of unsaturation. The IR spectrum of
3 revealed the presence of hydroxyl (nmax 3418 cmꢁ1) and
ester (nmax 1741 cmꢁ1) moieties. The ester was identified
Animal Material The soft coral L. crassum was collected by hand
using scuba at the coast of Kenting, in January, 2004, at a depth of 10 m, and
1
as an acetoxyl from the H-NMR data at d 2.02 (3H, s)
and the 13C-NMR data at d 20.7 (q) and 170.7 (s) (Table 1). was stored in a freezer until extraction. A voucher specimen was deposited
in the Department of Marine Biotechnology and Resources, National Sun
The attaching of acetoxy group at C-1 was confirmed
by the HMBC correlation from H2-1 to the acetate carbonyl
carbon. Therefore, 3 was identified as a C-1 acetoxy deriva-
Yat-sen University (specimen no. 200401-9).
Extraction and Isolation The soft coral L. crassum (1.1 kg fresh wt.)
was collected and freeze-dried. The freeze-dried material was minced and
tive of 1.
To establish the absolute configuration on C-2ꢃ of
extracted exhaustively with EtOH (3ꢅ2 l). The organic extract was concen-
trated to an aqueous suspension and was further partitioned between EtOAc
and water. The EtOAc extract (23 g) was fractionated by open column chro-
matography on silica gel using n-hexane–EtOAc and EtOAc–MeOH mix-
tures of increasing polarity. A fraction eluted with EtOAc–MeOH (4 : 1) was
subjected to separation by a Sephadex LH-20 column (2ꢅ90 cm) using ace-
tone and followed by reverse phase HPLC (acetone–H2O, 1 : 4) to afford
compounds 1—3 (24.6, 14.0, 13.2 mg, respectively).
(2R)-1-Hydroxy-3-hexadecyloxy-propyl-b-D-arabinopyranoside (1):
Amorphous white solid; [a]D22 ꢁ26° (cꢂ2.46, MeOH); IR (KBr) nmax 3391,
2919, 2851, 1142, 1075, 1007 cmꢁ1; for 1H- and 13C-NMR data, see Tables 1
and 2; ESI-MS m/z 471 [MꢀNa]ꢀ, HR-ESI-MS m/z 471.3296 [MꢀNa]ꢀ
(Calcd for C24H48O7Na, 471.3298).
the sugar moiety of 3, the modified Mosher’s method
was applied on the acetonide derivative of 3 (Chart 2). As
shown in Chart 2, the chemical conversion from 3 to
1d through methanolysis of 3b at 50 °C followed by the
treatment with 2,2-dimethoxypropane and then (S)-MTPA
chloride in pyridine to obtain 1d demonstrated that both 1
and 3 possess the same absolute configurations at all chiral
centers. The chemical shift differences of (S)-MTPA ester
(3a) and (R)-MTPA ester (3b) were summarized in Chart 2
and also suggested the S-configuration at C-2ꢃ, the same as
that of 1.
(2R)-1-Hydroxy-3-octadecyloxy-propyl-b-D-arabinopyranoside (2):
Amorphous white solid; [a]D22 ꢁ25° (cꢂ1.40, MeOH); IR (KBr) nmax 3391,
2921, 2853, 1142, 1075, 1007 cmꢁ1; for 1H- and 13C-NMR data, see Tables 1
and 2; ESI-MS m/z 499 [MꢀNa]ꢀ, HR-ESI-MS m/z 499.3609 [MꢀNa]ꢀ
(Calcd for C26H52O7Na, 499.3611).
The cytotoxicity of compounds 1—3 against HepG2,
Hep3B, MDA-MB-231, and Ca9-22 cancer cells was shown
in Table 2. It was found that all of 1—3 showed cytotoxic ac-
(2R)-1-Acetoxy-3-hexadecyloxy-propyl-b-D-arabinopyranoside (3):

December 2007
1723
Amorphous white solid; [a]D22 ꢁ20° (cꢂ1.32, MeOH); IR (KBr) nmax 3418, m, Ph), 5.15 (1H, dd, Jꢂ7.5, 2.2 Hz, H-2ꢃ), 5.13 (1H, br s, H-1ꢃ), 4.33 (1H,
1741, 1238, 1142, 1079, 1007 cmꢁ1; for 1H- and 13C-NMR data, see Tables 1 m, H-3ꢃ), 3.85 (1H, m, H-2), 3.59 (3H, s, OCH3), 3.17 (2H, m, H-3), 3.27
and 2; ESI-MS m/z 513 [MꢀNa]ꢀ, HR-ESI-MS m/z 513.3404 [MꢀNa]ꢀ (2H, t, Jꢂ6.6 Hz, H-1ꢄ), 2.03 (3H, s, OAc), 1.55—1.58 (3H, overlapped with
(Calcd for C26H50O8Na, 513.3403).
H2O, CH3), 1.47 (1H, m, H-2ꢄa), 1.37 (3H, s, CH3), 1.26 (1H, br s, H-2ꢄb),
1.26 (26H, br s, H2-3ꢄ—H2-15ꢄ), 0.88 t (3H, t, Jꢂ6.6 Hz, H-16ꢄ).
Conversion of 3b to 1d To a mixture of 3b (1.0 mg) and MeOH
(0.3 ml) was added 0.3 ml of 1 N HCl(aq). The reaction was stirred at 50 °C for
Acid Hydrolysis of 1 To a mixture of 1 (5.0 mg) and MeOH (0.3 ml)
was added 0.3 ml of 1 N HCl(aq). The reaction was carried out under refluxing
for 16 h. The reaction mixture was then cooled to room temperature and ex-
tracted with n-hexane. Hexane layer was concentrated and chromatographed 4 h. Water (1 ml) was added to the mixture and then extracted with n-hexane
over silica gel using n-hexane–CH2Cl2 (1 : 2) as eluent to obtain chimyl alco-
(3ꢅ2 ml). Hexane layer was concentrated and then dried in vacuum. The
hol (2.5 mg, 68%), [a]D22 ꢁ2° (cꢂ0.25, CHCl3). The MeOH–water layer, residue was redissolved in acetone (0.3 ml), and then subsequently added
containing methyl arabinoside (mixture of a- and b-anomers), was evapo- 1,2-dimethoxypropane (0.3 ml) and catalytic amount of CF3COOH. The re-
rated to dryness and followed by treated with 1 N HCl at 190 °C for
action mixture was stirred at room temperature for 16 h and then concen-
1.5 h. Then, the aqueous layer was concentrated under reduce pressure trated to dryness. The residue was redissolved in dry pyridine (0.4 ml) and
and the residue was chromatographied over silica gel using CHCl3–ace- added (S)-MTPA chloride (20 ml). The reaction was stirred for another 16 h.
tone–MeOH–H2O (8 : 2 : 3 : 1) as eluent to yield (ꢁ)-D-arabinose (0.4 mg,
The reaction mixture was concentrated and chromatographed over silica gel
23%), [a]D22 ꢁ110° (cꢂ0.040, H2O), which was confirmed by using n-hexane–EtOAc (8 : 1) as eluent to obtain a diester (0.9 mg, 73%), of
co-TLC analysis with authentic sample (CHCl3–acetone–MeOH–H2O, which the 1H-NMR data was consistent with that of 1d.
6 : 2 : 4 : 1, Rf 0.47).
Cytotoxicity Testing Cell lines were purchased from the American
Preparation of Bis-(R)-MTPA Ester (1b) To a solution of chimyl alco- Type Culture Collection (ATCC). Cytotoxicity assays were performed using
hol (1.0 mg) in dry pyridine (0.4 ml) was added (S)-MTPA chloride (20 ml),
the MTT [3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyl-tetrazolium bromide]
and the solution was allowed to stand overnight at room temperature for colorimetric method.18,19)
16 h. The reaction was quenched by the addition of 1.0 ml of water, followed
by extraction with CH2Cl2 (3ꢅ1 ml). The CH2Cl2-soluble layers were com-
Acknowledgments Financial support was provided by Ministry of Edu-
bined, dried over anhydrous MgSO4 and evaporated. The residue was sub- cation (C030313) and National Science Council of Taiwan (NSC 95-2323-
jected to short silica-gel column using n-hexane–CH2Cl2 (1 : 1) to yield bis-
(R)-MTPA ester (1b) (0.2 mg, 8%) in trace amount and the C-1 substituted
B-110-002) awarded to J.-H. S.
mono-(R)-MTPA ester was the major product (1.5 mg, 89%). 1H-NMR References
(CDCl3) of 1b: dH 7.33—7.49 (10H, m, 2ꢅPh), 5.43 (1H, m, H-2), 4.73
(1H, dd, Jꢂ12.3, 2.8 Hz, H-1a), 4.42 (1H, dd, Jꢂ12.3, 6.3 Hz, H-1b), 3.49
(2H, m, H-3), 3.48 (3H, s, OCH3), 3.40 (3H, s, OCH3), 3.30 (2H, t,
Jꢂ6.6 Hz, H2-1ꢄ), 1.26 (28H, br s, H2-2ꢄ—H2-15ꢄ), 0.88 t (3H, t, Jꢂ6.6 Hz,
H-16ꢄ); 1H-NMR (CDCl3) of mono-(R)-MTPA ester: dH 7.40—7.55 (5 H,
m, Ph), 4.38 (2H, d, Jꢂ5.0 Hz, H2-1), 4.03 (1H, m, H-2), 3.57 (3H, s,
OCH3), 3.36—3.49 (4H, m, H2-3, H2-1ꢄ), 1.26 (28H, br s, H2-2ꢄ—H2-15ꢄ),
0.88 t (3H, t, Jꢂ6.6 Hz, H-16ꢄ).
Preparation of MTPA Esters 1c, 1d, 3a and 3b To a solution of 1
(2 mg) in dry acetone (0.3 ml) was added 1,2-dimethoxypropane (0.3 ml) and
catalytic amount of CF3COOH, and the reaction mixture was stirred at room
temperature for 16 h. The mixture was concentrated and divided into two
equal portions. One portion was converted to (S)-MTPA ester (1c) (1.5 mg,
73%) with (R)-MTPA chloride (20 ml) and the other was converted to (R)-
MTPA ester (1d) (2.0 mg, 97%) with (S)-MTPA chloride (20 ml) according
to the procedure of the preparation of bis-(R)-MTPA ester (1b). 1H-NMR
(CDCl3) of 1c: dH 7.36—7.56 (10H, m, 2ꢅPh), 5.24 (1H, d, Jꢂ3.3 Hz, H-
1ꢃ), 5.09 (1H, dd, Jꢂ7.9, 3.3 Hz, H-2ꢃ), 4.59 (1H, dd, Jꢂ12.0, 3.3 Hz, H-1a),
4.25 (1H, dd, Jꢂ12.0, 6.3 Hz, H-1b), 4.07 (1H, m, H-2), 3.99 (1H, dd,
Jꢂ7.9, 5.4 Hz, H-3ꢃ), 3.91 (1H, dd, Jꢂ13.7, 2.5 Hz, H-5ꢃa), 3.82 (1H, d,
1) Wu S.-L., Sung P.-J., Su J.-H., Sheu J.-H., J. Nat. Prod., 66, 1252—
1256 (2003).
2) Sheu J.-H., Huang L.-F., Chen S.-P., Yang Y.-L., Sung P.-J., Wang G.-
H., Su J.-H., Chao C.-H., Hu W.-P., Wang J.-J., J. Nat. Prod., 66, 917—
921 (2003).
3) Sheu J.-H., Wang G.-H., Duh C.-Y., Soong K., J. Nat. Prod., 66, 662—
666 (2003).
4) Ahmed A. F., Su J.-H., Shiue R.-T., Pan X.-J., Dai C.-F., Kuo Y.-H.,
Sheu J.-H., J. Nat. Prod., 67, 592—597 (2004).
5) Ahmed A. F., Su J.-H., Kuo Y.-H., Sheu J.-H., J. Nat. Prod., 67,
2079—2082 (2004).
6) Chao C.-H., Huang L.-F., Yang Y.-L., Su J.-H., Wang G.-H., Chiang
M. Y., Wu Y.-C., Dai C.-F., Sheu J.-H., J. Nat. Prod., 68, 880—885
(2005).
7) Wang S. K., Duh C. Y., Wang Y., Cheng M. C., Soong K., Fang L. S.,
J. Nat. Prod., 55, 1430—1435 (1992).
8) Morris L, A., Christie E. M., Jaspars M., van Ofwegen L. P., J. Nat.
Prod., 61, 538—541 (1998).
9) Duh C. Y., Wang S. K., Huang B. T., Dai C. F., J. Nat. Prod., 63,
884—885 (2000).
Jꢂ13.7 Hz, H-5ꢃb), 3.81 (1H, m, H-4ꢃ), 3.55 (3H, s, OCH3), 3.51 (3H, s, 10) Wang L. T., Wang S. K., Soong K., Duh C. Y., Chem. Pharm. Bull.,
OCH3), 3.38 (2H, m H-3), 3.30 (2H, t, Jꢂ6.6 Hz, H-1ꢄ), 1.52 (3H, s, CH3), 55, 766—770 (2007).
1.47 (1H, m, H-2ꢄa) 1.30 (3H, s, CH3), 1.26 (1H, br s, H-2ꢄb), 1.26 (26H, br 11) Rashid M. A., Gustafson K. R., Boyd M. R., J. Nat. Prod., 63, 531—
s, H2-3ꢄ—H2-15ꢄ), 0.88 t (3H, t, Jꢂ6.6 Hz, H-16ꢄ); 1H-NMR (CDCl3) of 1d:
533 (2000).
dH 7.39—7.58 (10H, m, 2ꢅPh), 5.09 (1H, dd, Jꢂ7.9, 3.3 Hz, H-2ꢃ), 5.07 12) Vanisree M., Subbaraju G. V., Asian J. Chem., 14, 957—960 (2002).
(1H, br s, H-1ꢃ), 4.54 (1H, dd, Jꢂ11.7, 2.9 Hz, H-1a), 4.22 (1H, dd, Jꢂ11.7, 13) Myers B. L., Crews P., J. Org. Chem., 48, 3583—3585 (1983).
5.9 Hz, H-1b), 4.19 (1H, dd, Jꢂ7.9, 5.4 Hz, H-3ꢃ), 4.01 (1H, dd, Jꢂ5.4, 14) Koren-Goldshlager G., Klein P., Rudi A., Benayahu Y., Schleyer M.,
2.5 Hz, H-4ꢃ), 3.89 (1H, dd, Jꢂ13.4, 2.5 Hz, H-5ꢃa), 3.85 (1H, m, H-2), 3.75
Kashman Y., J. Nat. Prod., 59, 262—266 (1996).
(1H, d, Jꢂ13.4 Hz, H-5ꢃb), 3.58 (3H, s, OCH3), 3.47 (3H, s, OCH3), 3.25 15) Do M. N., Erickson K. L., Tetrahedron Lett., 24, 5699—5702 (1983).
(2H, br t, Jꢂ6.3 Hz, H-1ꢄ), 3.13 (2H, br d, Jꢂ6.0 Hz, H-3), 1.54 (3H, s,
CH3), 1.47 (1H, m, H-2ꢄa) 1.34 (3H, s, CH3), 1.26 (1H, br s, H-2ꢄb), 1.26
16) Ohtani I., Kusumi T., Kashman Y., Kakisawa H., J. Am. Chem. Soc.,
113, 4092—4096 (1991).
(26H, br s, H2-3ꢄ—H2-15ꢄ), 0.88 t (3H, t, Jꢂ6.6 Hz, H-16ꢄ). The same pro- 17) Randazzo A., Bifulco G., Giannini C., Bucci M., Debitus C., Cirino
cedure was treated with 3 (2.5 mg) to obtain the (S)-MTPA ester (3a) G., Gomez-Paloma L., J. Am. Chem. Soc., 123, 10870—10876 (2001).
(1.6 mg, 84%) and (R)-MTPA ester (3b) (1.9 mg, 100%). Selective 1H-NMR 18) Alley M. C., Scudiero D. A., Monks A., Hursey M. L., Czerwinski M.
(CDCl3) of 3a: dH 7.40—7.59 (5H, m, Ph), 5.28 (1H, d, Jꢂ3.4 Hz, H-1ꢃ),
5.18 (1H, dd, Jꢂ7.5, 3.4 Hz, H-2ꢃ), 4.30 (1H, m, H-3ꢃ), 4.00 (1H, m, H-2),
J., Fine D. L., Abbott B. J., Mayo J. G., Shoemaker R. H., Boyd M. R.,
Cancer Res., 48, 589—601 (1988).
3.55 (3H, s, OCH3), 3.42 (2H, m, H-3), 3.34 (2H, t, Jꢂ6.6 Hz, H-1ꢄ), 1.55— 19) Scudiero D. A., Shoemaker R. H., Paull K. D., Monks A., Tierney S.,
1.58 (3H, overlapped with H2O, CH3), 1.47 (1H, m, H-2ꢄa), 1.34 (3H, s,
CH3), 1.26 (1H, br s, H-2ꢄb), 1.26 (26H, br s, H2-3ꢄ—H2-15ꢄ), 0.88 t (3H, t,
Jꢂ6.6 Hz, H-16ꢄ); Selective 1H-NMR (CDCl3) of 3b: dH 7.39—7.60 (5H,
Nofziger T. H., Currens M. J., Seniff D., Boyd M. R., Cancer Res., 48,
4827—4833 (1988).