Pellynols M?O, cytotoxic polyacetylenic alcohols from a Niphates sp. marine sponge

Article abstract of DOI:10.1016/j.tet.2018.05.041

Three new polyacetylenic alcohols, pellynols M?O (1–3), along with two known ones, melyne A (4) and melyne B (5), were isolated from a Niphates sp. marine sponge collected off the South China Sea. The structures of new compounds were determined based on a combination of 1D and 2D NMR analysis, ESI-MSⁿ fragmentation, and chemical (ozonolysis) method. Their absolute configurations were assigned by modified Mosher's method. All the isolates showed potent cytotoxic activity against PC9 and HepG2 human cancer cell lines with IC₅₀ values of 2.9–7.6 μM.

Full text of DOI:10.1016/j.tet.2018.05.041

Accepted Manuscript
Pellynols M−O, cytotoxic polyacetylenic alcohols from a Niphates sp. marine sponge
Jie Wang, Li-Yun Liu, Lei Liu, Kai-Xuan Zhan, Wei-Hua Jiao, Hou-Wen Lin
PII:
S0040-4020(18)30576-3
10.1016/j.tet.2018.05.041
TET 29548
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 7 April 2018
Revised Date: 14 May 2018
Accepted Date: 15 May 2018
Please cite this article as: Wang J, Liu L-Y, Liu L, Zhan K-X, Jiao W-H, Lin H-W, Pellynols M−O,
cytotoxic polyacetylenic alcohols from a Niphates sp. marine sponge, Tetrahedron (2018), doi: 10.1016/
j.tet.2018.05.041.
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ACCEPTED MANUSCRIPT
TOC
Niphates sp.

ACCEPTED MANUSCRIPT
Pellynols M−O, Cytotoxic Polyacetylenic Alcohols from
a Niphates sp. Marine Sponge
Jie Wang1, 2, Li-Yun Liu 2, Lei Liu2, Kai-Xuan Zhan1, Wei-Hua Jiao2,*, and Hou-Wen
Lin1, 2,
*
1 School of Traditional Chinese Materia Medica, Shenyang Pharmaceutical University,
Shenyang 110016, People’s Republic of China
2 Research Center for Marine Drugs, State Key Laboratory of Oncogenes and Related
Genes, Department of Pharmacy, Ren Ji Hospital, School of Medicine, Shanghai
Jiao Tong University, Shanghai 200127, People’s Republic of China
ABSTRACT: Three new polyacetylenic alcohols, pellynols M−O (1−3), along with
two known ones, melyne A (4) and melyne B (5), were isolated from a Niphates sp.
marine sponge collected off the South China Sea. The structures of new compounds
were determined based on a combination of 1D and 2D NMR analysis, ESI-MSn
fragmentation, and chemical (ozonolysis) method. Their absolute configurations were
assigned by modified Mosher’s method. All the isolates showed potent cytotoxic
activity against PC9 and HepG2 human cancer cell lines with IC50 values of 2.9−7.6
ꢀM.
Keywords: marine sponge; Niphates sp.; polyacetylenic alcohols; pellynols M−O;
cytotoxic activity
* Corresponding author.
E-mail address: weihuajiao@hotmail.com (W.-H. J.), franklin67@126.com (H.-W. L.).
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1. Introduction
Polyacetylenes are an intriguing class of metabolites, which are specially referred
to as the metabolites with several enyne moieties.1 They are widespread in the marine
organisms, such as algae,2 corals,3 and sponges.4,5 Most of these compounds exhibited
a remarkable range of biological activities, including antimicrobial,6 HIV reverse
transcriptase inhibitory,7 and cytotoxic activities.8-11 Furthermore, the long-chain
polyacetylenes with more than 15 carbons, which displayed potent cytotoxicity, have
been mainly found from the marine sponges belonging to the order Haplosclerida.12-14
In the course of our ongoing search for cytotoxic compounds from marine
sponges,15-18 we found that the CH2Cl2 extract of a sponge of Niphates sp. showed
potent cytotoxicity against human hepatoma HepG2 cancer cell line, and was selected
for further chemical investigation. Bioassay-guided fractionation of the active extract
resulted in the isolation of three new polyacetylenic alcohols, pellynols M−O (1−3),
along with two known ones, melyne A (4) and melyne B (5). The details of isolation,
structure elucidation, and bioactivity of these polyacetylenic alcohols are reported
herein.
2

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1
33
35
OH
OH
18
6
6
29
OH
OH
4
15
OH
1
2
6
31
20
6
17
OH
OH
31
6
6
6
4
6
5
15
27
OH
OH
OH
OH
3
OH
OH
OH
OH
4
5
Chart 1. Polyacetylenic alcohols isolated from Niphates sp.
2. Results and discussion
The molecular formula of pellynol M (1), C33H48O3, was established by the
1
HRESIMS ion peak at m/z 537.3582 [M + HCOO]−. The H NMR spectrum of 1
(Table 1) displayed two oxygenated methines at δH 4.41 (t, J = 6.0 Hz) and 4.83 (br d,
J = 6.0 Hz), one oxygenated methylene at δH 4.33 (s), one acetylenic proton at δH 2.56
(d, J = 1.8 Hz), and four olefinic protons at δH 5.42 (br d, J = 10.8 Hz), 5.60 (dd, J =
13
15.0, 6.0 Hz), 5.80 (dt, J = 10.8, 7.2 Hz), and 5.90 (dt, J = 15.0, 6.0 Hz). The C
NMR and DEPT spectra of 1 revealed the presence of four olefinic methines (δC 109.3,
128.3, 134.5, and 142.5), two oxygenated methines (δC 62.7 × 2), one oxygenated
3

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methylene (δC 51.3), and eight alkynyl carbons (δC 68.8, 69.7, 74.0, 77.4, 77.6, 80.5,
83.3, and 94.5), together with a series of methylene groups resonanced at δC
28.8−29.5. Interpretation of 2D NMR data allowed for the establishment of three
partial
structures
A–C
(Fig.
1).
The
COSY
correlations
of
H-27/H-28/H-29/H-30/H-31 indicated the existence of the spin system
C27-C28-C29-C30-C31. The HMBC correlations of H-33/C-31, H-31/C-29, C-30, C-32,
and C-33, H2-28/C-30, and H-29/C-27 established the partial structure A. The COSY
correlations of H-13/H-14/H-15/H-16 and H-19/H-20 coupled with the HMBC
correlations of H2-19/C-16, C-17, C-18, and C-20, and H2-14/C-13, C-15, and C-16
constituted the partial structure B. In addition, the partial structure C was elucidated
by the COSY correlations of H-6/H-7/H-8 and the HMBC correlations of H-6/C-3,
C-4, C-5, C-7, and C-8, as well as H2-1/C-2, C-3, and C-4. The coupling constants
15, 16
between H-15 and H-16 (J = 10.8 Hz) suggested the Z-configuration of
∆
double
bond, while the larger coupling constants between H-29 and H-30 (J = 15.0 Hz)
indicated the E-configuration of
29, 30. The location of unit C in the alkyl chain was
∆
determined by analysis of the ESI-MS4 fragmentation (Fig. 1). Furthermore, the
chemical method was applied to assign the position of moiety B. Oxidation of 1 with
O3 followed by NaBH4 reduction afforded a mixture of alcoholic carboxylic acids
(Scheme 1). Subsequent LC-MS analysis of the mixture gave two negative ion peaks
at m/z 215 [M − H]− and 217 [M − H]−, consistent with 12-hydroxy-dodecanoic acid
and 2,11-dihydroxy-undecanoic acid, respectively. Thus, the plane structure of 1 was
determined as depicted. The absolute configuration was determined to be 6R,31R by
4

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the modified Mosher’s method (Fig. 4).
Fig. 1 Key HMBC (→), 1H-1H COSY (ꢀ)correlations and diagnostic ESI-MS4 fragments of 1
Scheme 1. Ozonolysis of compounds 1−3
Pellynol N (2) had the molecular formula C35H52O3, with one more C2H4 (28) than
1
1, as assigned by HRESIMS ion at m/z 565.3891 [M + HCOO]−. The H and 13C
NMR spectra of 2 were almost identical with those of 1 (Table 1), except for the
length of aliphatic chains. Extensive analysis of 2D NMR of 2 resulted in the three
moieties (A−C), consistant with those in 1 (Fig. 2). The placement of unit C in 2 was
verified by ESI-MS4 fragmentation (Fig. 2). Further ozonolysis of 2 followed by
5

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NaBH4 treatment gave
a
mixture of 12-hydroxy-dodecanoic acid and
2,13-dihydroxy-tridecanoic acid, respectively, supported by two ESIMS ions at m/z
215 [M − H]− and 245 [M − H]− (Scheme 1). Thus, the planar structure of 2 was
elucidated as depicted. The absolute configurations of two chiral centers at C-6 and
C-33 were both determined as R by the modified Mosher’s method (Fig. 4
)
.
OH
OH
OH
C
B
A
Fig. 2 Key HMBC (→), 1H-1H COSY (ꢀ)correlations and diagnostic ESI-MS4 fragments of 2
6

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Table 1. 1H (600 MHz) and 13C (150 MHz) NMR Spectroscopic Data of 1−3 in CDCl3
1
2
3
pos
1
δC, mult.
51.3, CH2
77.6, C
δH (J in Hz)
pos
1
δC, mult.
51.4, CH2
77.5, C
δH (J in Hz)
pos
1
δC, mult.
51.3, CH2
77.6, C
δH (J in Hz)
4.33, s
4.34, s
4.33, s
2
2
2
3
69.7, C
3
69.8, C
3
69.7, C
4
68.8, C
4
68.8, C
4
68.8, C
5
80.5, C
5
80.6, C
5
80.5, C
6
62.7, CH
37.4, CH2
25.0, CH2
4.41, t (6.0)
6
62.8, CH
37.5, CH2
25.0, CH2
4.42, t (6.0)
6
62.8, CH
37.5, CH2
25.0, CH2
4.42, t (6.0)
1.71, m
7
1.70, m (7.2)
1.52, m (7.2)
1.26-1.32, m
2.27, q (7.2)
7
1.71, m
7
8
8
1.53, m (7.2)
1.26-1.30, m
2.27, q (7.2)
5.80, dt (10.8, 7.2)
5.43, br d (10.8)
8
1.43, m
9-13
14
15
16
17
18
19
28.8-29.5, CH2
30.0, CH2
142.5, CH
109.3, CH
77.4, C
9-15 28.8-29.6, CH2
9-13 28.8-29.7, CH2
1.25-1.34, m
2.01, q (7.2)
5.34, t (4.8)
5.34, t (4.8)
2.01, q (7.2)
1.25-1.34, m
1.39, m
16
17
18
19
20
21
30.0, CH2
142.5, CH
109.3, CH
77.4, C
14
15
16
17
27.2, CH2
129.9, CH
129.9, CH
27.2, CH2
5.80, dt (10.8, 7.2)
5.42, br d (10.8)
94.5, C
94.5, C
18-24 28.8-29.7, CH2
19.5, CH2
2.32, td (7.2, 1.8)
1.26-1.32, m
19.5, CH2
2.33, td (7.2, 1.8)
1.26-1.30, m
25
26
27
28
29
30
31
28.8, CH2
31.9, CH2
134.6, CH
128.3, CH
62.8, CH
83.4, C
20-27 28.8-29.5, CH2
22-29 28.8-29.6, CH2
2.06, q (7.2)
5.91, dt (15.0, 6.0)
5.60, dd (15.0, 6.0)
4.83, br d (6.0)
28
29
30
31
32
33
31.9, CH2
134.5, CH
128.3, CH
62.7, CH
83.3, C
2.06, q (7.2)
30
31
32
33
34
35
31.9, CH2
134.5, CH
128.3, CH
62.8, CH
83.3, C
2.06, q (7.2)
5.90, dt (15.0, 6.0)
5.60, dd (15.0, 6.0)
4.83, br d (6.0)
5.91, dt (15.0, 6.6)
5.60, dd (15.0, 6.6)
4.83, br d (6.0)
73.9, CH
2.56, d (1.8)
74.0, CH
2.56, d (1.8)
74.0, CH
2.56, d (1.8)
7

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The molecular formula of pellynol O (3) was determined as C31H48O3 by
HRESIMS ion at m/z 513.3585 [M + HCOO]−. Analysis of the 1H and 13C NMR data
revealed that 3 shared the same terminal units A and C with those of 1 and 2 (Fig. 3).
The signals at δH 5.34 (2H, t, J = 4.8 Hz, H-15 and 16) and δC 129.9 (C-15 and 16)
indicated the presence of a double bond. Furthermore, the COSY correlations of
H-13/H-14/H-15 and H-16/H-17/H-18 established moiety B which also supported by
the HMBC correlations of H-15, 16/C-13, C-14, C-17 and C-18. Detailed ESI-MS3
analysis determined the placement of the double bond (Fig. 3). Moreover, chemical
reactions (Scheme 1) followed by LC-MS analysis (m/z 201 [M − H]− and 217 [M −
H]−) afforded the corresponding 1,12-dodecanediol and 2,11-dihydroxy-undecanoic
acid, respectively. Upon the planar structure was determined, the modified Mosher’s
method was applied to assign the absolute configurations of C-6 and C-29 both as R
(Fig. 4).
Fig. 3 Key HMBC (→), 1H-1H COSY (ꢀ)correlations and diagnostic ESI-MS3 fragments of 3
8

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-0.002
-0.049
+0.117
OH
+0.046
+0.030
6
OR+0.053
4
OR
1a R = (S)-MTPA ester
1b R = (R)-MTPA ester
-0.001
-0.038
+0.101
OH
+0.040
+0.031
6
OR+0.051
6
OR
2a R = (S)-MTPA ester
2b R = (R)-MTPA ester
-0.004
OH
-0.053
+0.103 +0.045
+0.033
6
4
+0.052
OR
OR
3a R = (S)-MTPA ester
3b R = (R)-MTPA ester
Fig. 4 ∆δ = δS - δR values in ppm obtained from the MTPA esters of compounds 1−3
The cytotoxicity of 1, 2, 4, and 5 was evaluated against three human cancer cell
lines, PC9 (human lung cancer), HepG2 (human liver carcinoma), and MCF-7 (human
breast cancer) cells, using gefitinib, sorafenib, and 4-hydroxytamoxifen as positive
controls, respectively (Table 2). All the four compounds showed potent cytotoxicity
against human PC9 and HepG2 cancer cell lines with IC50 values of 2.9−7.6 ꢀM.
Especially, 1, 2 and 5 showed potent cytotoxicity against HepG2, which were similar
with that of sorafenib. Above all, the three compounds may be identified as candidate
agents for the treatment of hepatocellular carcinoma. Moreover, their underlying
mechanisms and characteristics of cell growth inhibition will be investigated.
Table 2. Cytotoxic Activity of 1, 2, 4, and 5 against Three Human Cancer Cells
Lines
9

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IC50 (ꢀM)
compound
PC9
3.9 ± 0.1
4.8 ± 0.3
7.6 ± 0.3
4.2 ± 0.2
0.6 ± 0.02
−
HepG2
4.8 ± 0.3
2.9 ± 0.3
5.9 ± 0.4
3.3 ± 0.3
−
MCF-7
12.6 ± 0.4
10.3 ± 0.9
23.7 ± 1.3
8.2 ± 0.4
−
1
2
4
5
gefitinib
sorafenib
4-hydroxytamoxifen
3.7 ± 0.2
−
−
−
5.8 ± 0.4
3. Experimental section
3.1. General Experimental Procedures.
Optical rotation measurements were recorded with an Autopol I polarimeter (no.
30575, Rudolph Research Analytical) and an Autopol VI polarimeter (no. 91003,
Rudolph Research Analytical). The NMR experiments were conducted on Bruker
Avance DRX-600 MHz NMR spectrometers in CDCl3 (δH 7.26/δC 77.16).
High-resolution ESIMS spectra were acquired with a Waters Q-Tof micro YA019
mass spectrometer. Column chromatographic separations were carried out using
Sephadex LH-20 (18−110 ꢀm, Pharmacia Co.) and C18 (15 ꢀm, Santai Technologies,
Inc.). TLC was performed on silica gel HSGF254 plates (Yantai) and visualized by
spraying with anisaldehyde reagent. RP HPLC was performed on a YMC-Pack Pro
C18 column (250 × 10 mm, 5 ꢀm) using a Waters 1525 binary HPLC pump with a
Waters 2998 photodiode array detector.
3.2. Sponge Material.
The marine sponge was collected off the Yongxing Island in the South China Sea
in May 2015 and was identified by Prof. Jin-He Li (Institute of Oceanology, Chinese
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Academy of Sciences, People’s Republic of China) as a Niphates sp. A voucher
specimen (no. 1506) is deposited at Research Center for Marine Drugs, State Key
Laboratory of Oncogenes and Related Genes, Department of Pharmacy, Ren Ji
Hospital, School of Medicine, Shanghai Jiao Tong University.
3.3. Extraction and Isolation.
The frozen Niphates sp. sponge (1.0 kg, wet weight) was extracted with MeOH
for three times. The residue obtained was partitioned between petroleum ether and
MeOH-H2O (9:1). The 90% aqueous MeOH layer was diluted into 60% aqueous
MeOH with H2O and partitioned with CH2Cl2 to yield a CH2Cl2 extract (4.6 g). The
CH2Cl2-soluble fraction was subjected to column chromatography on Sephadex
LH-20 eluted with MeOH to yield three fractions (1−3). Fraction 2 was separated by
RP MPLC with the stepwise elution (10-100% MeCN/H2O) to give eight subfractions
(A−H). Subfraction C were purified by RP HPLC (78% MeCN/H2O) to give 1 (20.0
mg, tR = 54 min). Subfraction D was further purified by RP HPLC (78% MeCN/H2O)
to yield 3 (2.8 mg, tR = 71 min), 2 (13.0 mg, tR = 76 min) and 5 (29.5 mg, tR = 82 min).
Subfraction E afforded 4 (53.0 mg, tR = 96 min), which was isolated by RP HPLC
(78% MeCN/H2O).
1
25
D
3.3.1. Pellynol M (1): white powders; [
α
]
−12.7 (c 0.50, MeOH); H NMR (600
MHz, CDCl3) and 13C NMR (150 MHz, CDCl3) data, Table 1; HRESIMS m/z
537.3582 [M + HCOO]− (calcd for C34H49O5, 537.3580).
1
25
D
3.3.2. Pellynol N (2): white powders; [
α
]
−8.7 (c 1.00, MeOH); H NMR (600
MHz, CDCl3) and 13C NMR (150 MHz, CDCl3) data, Table 1; HRESIMS m/z
11

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565.3891 [M - H]− (calcd for C36H53O5, 565.3893).
3.3.3. Pellynol O (3): white powders; 1H NMR (600 MHz, CDCl3) and 13C NMR (150
MHz, CDCl3) data, Table 1; HRESIMS m/z 513.3585 [M + HCOO]− (calcd for
C32H49O5, 513.3580).
25
D
3.3.4. Melyne A (4): white powders; [
α
]
−11.5 (c 1.38, MeOH); lit.
[α
]
−8.0 (c
D
5.0, CHCl3).19 1H NMR (600 MHz, CDCl3) δH 1.26-1.32 (28H, m), 1.38 (2H, m,
H-27), 1.42 (2H, m, H-8), 1.70 (2H, m, H-7), 2.00 (4H, q, J = 6.0 Hz, H-16, 19), 2.06
(2H, q, J = 7.2 Hz, H-28), 2.56 (1H, d, J = 1.8 Hz, H-33), 4.33 (2H, s, H-1), 4.41 (1H,
t, J = 6.0 Hz, H-6), 4.83 (1H, d, J = 6.0 Hz, H-31), 5.34 (2H, t, J = 4.8 Hz, H-17, 18),
5.60 (1H, dd, J = 15.0, 6.0 Hz, H-30), 5.90 (1H, dt, J = 15.0, 6.0 Hz, H-29); 13C NMR
(150 MHz, CDCl3) δC 25.0 (C-8), 27.2 (C-16, 19), 28.8 (C-27), 29.7 (C-15, 20), 31.9
(C-28), 37.4 (C-7), 51.2 (C-1), 62.7 (C-6, 31), 68.8 (C-4), 69.7 (C-3), 74.0 (C-33),
77.6 (C-2), 80.5 (C-5), 83.3 (C-32), 128.3 (C-30), 129.9 (C-17, 18), 134.6 (C-29).
25
D
3.3.5. Melyne B (5): white powders; [
α
]
−13.0 (c 0.23, MeOH); lit.
[α
]
−7.2 (c
D
4.0, CHCl3).19 1H NMR (600 MHz, CDCl3) δH 1.28-1.32 (26H, m), 1.39 (2H, m,
H-26), 1.43 (2H, m, H-8), 1.70 (2H, m, H-7), 2.00 (4H, q, J = 6.0 Hz, H-15, 18), 2.06
(2H, q, J = 6.6 Hz, H-27), 2.56 (1H, d, J = 2.4 Hz, H-32), 4.33 (2H, s, H-1), 4.41 (1H,
t, J = 6.0 Hz, H-6), 4.83 (1H, d, J = 6.0 Hz, H-30), 5.34 (2H, t, J = 4.2 Hz, H-16, 17),
5.60 (1H, dd, J = 15.0, 6.0 Hz, H-29), 5.91 (1H, dt, J = 15.0, 6.0 Hz, H-28); 13C NMR
(150 MHz, CDCl3) δC 25.0 (C-8), 27.2 (C-15, 18), 28.8 (C-26), 29.7 (C-14, 19), 31.9
(C-27), 37.4 (C-7), 51.3 (C-1), 62.7 (C-6, 30), 68.8 (C-4), 69.7 (C-3), 74.0 (C-32),
77.6 (C-2), 80.5 (C-5), 83.3 (C-31), 128.3 (C-29), 129.9 (C-16, 17), 134.6 (C-28).
12

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3.4. Ozonolysis of 1
−3. Solutions of 1−3 (0.5 mg each) in CH2Cl2 (1 mL) were treated
with O3 for 1 min at −78 °C, respectively. After added NaBH4 (0.5 mg), the reaction
mixtures were stirred for 1 h at room temperature (25 °C).20 The crude products were
concentrated and subjected to LC-MS analysis without further separation.
3.5. Preparation of the (R)- and (S)-MTPA Ester Derivatives. Compounds 1−3 (each 1.0
mg) were transferred into clean NMR tubes, respectively. Under N2 gas stream,
Pyridine-d5 (0.5 mL) and (R)-MTPA chloride (2 µL) or (S)-MTPA chloride (2 µL)
were added into the NMR tubes immediately, and then the NMR tubes were shaken
and conserved in a water bath at 40 °C for 12 h. The 1H NMR spectra were obtained
directly from the NMR reaction tubes.21
3.6. Cytotoxicity Assay. The cytotoxicity of compounds 1, 2, 4, and 5 against PC9,
HepG2, and MCF-7 human cancer cell lines was determined using the MTT
method.22 Compounds were solubilized in DMSO at six different concentrations. 100
ꢀL of cells were inoculated into 96-well plates for 24 h at 37 °C. Each cancer cell line
was treated with the test compounds at various concentrations, in triplicate, for 72 h at
37 °C. Gefitinib, sorafenib, and 4-hydroxytamoxifen were used as positive controls,
respectively. Then the CCK8 solution (10 ꢀL) was added for additional 1 h incubation
at 37 °C. The absorbance at 450 nm was measured in a microplate reader (spectra
MAX190, Molecular Devices, USA), and the IC50 values were derived by nonlinear
regression analysis.
Acknowledgments: This research was supported by National Science Foundation of
China (No. U1605221, 41476121, 41576130, 81741149, and 21502113).
13

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Supplementary Materials: The followings are available online, HRESIMS, ESI-MSn,
1D and 2D NMR data of compounds l–3.
References
1.
2.
3.
4.
Zhou, Z. F.; Menna, M.; Cai, Y. S.; Guo, Y. W. Chem. Rev. 2015, 115, 1543-1596.
Mao, S. C.; Liu, D. Q.; Yu, X. Q.; Lai, X. P. Biochem. Syst. Ecol. 2011, 39, 253-257.
Zhao, M.; He, T.; Shi, S. K.; Song, L. X.; Lu, Y. Nat. Prod. Res. 2018, 32, 1104-1108.
Horikawa, K.; Yagyu, T.; Yoshioka, Y.; Fujiwara, T.; Kanamoto, A.; Okamoto, T.; Ojika,
M. Tetrahedron 2013, 69, 101-106.
5.
6.
7.
8.
Takanashi, E.; Takada, K.; Hashimoto, M.; Itoh, Y.; Ise, Y.; Ohtsuka, S.; Okada, S.;
Matsunaga, S. Tetrahedron 2015, 71, 9564-9570.
Nuzzo, G.; Ciavatta, M. L.; Villani, G.; Manzo, E.; Zanfardino, A.; Varcamonti, M.;
Gavagnin, M. Tetrahedron 2012, 68, 754-760.
Patil, A.; Kokke, W.; Cochran, S.; Francis, T.; Tomszek, T.; Westley, J. J. Nat. Prod. 1992,
55, 1170-1177.
Hitora, Y.; Takada, K.; Okada, S.; Ise, Y.; Matsunaga, S. J. Nat. Prod. 2011, 74,
1262-1267.
9.
Hitora, Y.; Takada, K.; Okada, S.; Matsunaga, S. Tetrahedron 2011, 67, 4530-4534.
Mejia, E. J.; Magranet, L. B.; De Voogd, N. J.; TenDyke, K.; Qiu, D.; Shen, Y. Y.; Zhou,
Z.; Crews, P. J. Nat. Prod. 2013, 76, 425-432.
10.
11.
12.
Mori, K.; Akasaka, K.; Matsunaga, S. Tetrahedron 2014, 70, 392-401.
van Soest, R. W. M.; Fusetani, N.; Andersen, R. J. In Sponge sciences : multidisciplinary
perspectives (Proceedings of the International conference on sponge science, held at the
Lake Biwa Research Institute, Mar. 1996); Watanabe, Y.; Fusetani, N. Eds.; Springer,
1997; pp. 1 - 33.
13.
Lee, Y. J.; Yoo, S. J.; Kang, J. S.; Yun, J.; Shin, H. J.; Lee, J. S.; Lee, H.-S. Lipids 2013,
48, 87-91.
14.
15.
Takada, K.; Okada, S.; Matsunaga, S. Fish. Sci. 2014, 80, 1057-1064.
Zhan, K. X.; Jiao, W. H.; Yang, F.; Li, J.; Wang, S. P.; Li, Y. S.; Han, B. N.; Lin, H. W. J.
14

ACCEPTED MANUSCRIPT
Nat. Prod. 2014, 77, 2678-2684.
16.
17.
18.
Jiao, W. H.; Shi, G. H.; Xu, T. T.; Chen, G. D.; Gu, B. B.; Wang, Z.; Peng, S.; Wang, S. P.;
Li, J.; Han, B. N.; Zhang, W.; Lin, H.-W. J. Nat. Prod. 2016, 79, 406-411.
Jiao, W. H.; Xu, T. T.; Yu, H. B.; Chen, G. D.; Huang, X. J.; Yang, F.; Li, Y. S.; Han, B. N.;
Liu, X. Y.; Lin, H. W. J. Nat. Prod. 2014, 77, 346-350.
Yu, H. B.; Yang, F.; Sun, F.; Ma, G. Y.; Gan, J. H.; Hu, W. Z.; Han, B. N.; Jiao, W. H.; Lin,
H. W. J. Nat. Prod. 2014, 77, 2124-2129.
19.
20.
Quiñoà, E.; Crews, P. Tetrahedron Lett. 1988, 29, 2037-2040.
Aoki, S.; Matsui, K.; Tanaka, K.; Satari, R.; Kobayashi, M. Tetrahedron 2000, 56,
9945-9948.
21.
22.
Zhang, C. L.; Liu, Y. F.; Wang, Y.; Liang, D.; Jiang, Z. B.; Li, L.; Hao, Z. Y.; Luo, H.; Shi,
G. R.; Chen, R. Y.; Cao, Z. Y.; Yu, D. Q. Org. Lett. 2015, 17, 5686-5689.
Hong, L. L.; Sun, J. B.; Yang, F.; Liu, M.; Tang, J.; Sun, F.; Jiao, W. H.; Wang, S. P.;
Zhang, W.; Lin, H. W. RSC Adv. 2017, 7, 23970-23976.
15