Sesquiterpene dimers esterified with diverse small organic acids from the seeds of Sarcandra glabra

Article abstract of DOI:10.1016/j.tet.2015.05.112

11 new sesquiterpene dimers, sarglabolides A-K (1-11), and five known ones were isolated from the seeds of Sarcandra glabra. Their structures were elucidated by spectroscopic data analysis and chemical evidence. Sarglabolide A (1) was verified to exclusively possess a seventeen-membered macrocyclic ester ring formed by the scaffold of the sesquiterpene dimer and small organic acids, different from the eighteen-membered rings of the other reported analogues. The chiral small organic acid moieties were assigned to l-malic acid, d-malic acid, and d-tartaric acid based on the combination of spectroscopy, chemical derivatization and HPLC analysis. Dimers 1, 12 and 13 can significantly inhibit NO production in LPS-induced macrophages with IC₅₀ values at 3.04, 4.65 and 2.33 μmol/L, respectively.

Full text of DOI:10.1016/j.tet.2015.05.112

Tetrahedron 71 (2015) 5362e5370
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Sesquiterpene dimers esterified with diverse small organic acids
from the seeds of Sarcandra glabra
,
,
Peng Wang a b, Jun Luo a, Yang-Mei Zhang a, Ling-Yi Kong a
*
a State Key Laboratory of Natural Medicines, Department of Natural Medicinal Chemistry, China Pharmaceutical University, 24 Tong Jia Xiang, Nanjing
210009, People0s Republic of China
b School of Pharmacy, Yancheng Teachers University, Xiwang Road, Yancheng 224051, People0s Republic of China
a r t i c l e i n f o
a b s t r a c t
Article history:
11 new sesquiterpene dimers, sarglabolides AeK (1e11), and five known ones were isolated from the
seeds of Sarcandra glabra. Their structures were elucidated by spectroscopic data analysis and chemical
evidence. Sarglabolide A (1) was verified to exclusively possess a seventeen-membered macrocyclic ester
ring formed by the scaffold of the sesquiterpene dimer and small organic acids, different from the
eighteen-membered rings of the other reported analogues. The chiral small organic acid moieties were
Received 19 March 2015
Received in revised form 28 May 2015
Accepted 30 May 2015
Available online 16 June 2015
assigned to
chemical derivatization and HPLC analysis. Dimers 1, 12 and 13 can significantly inhibit NO production in
LPS-induced macrophages with IC50 values at 3.04, 4.65 and 2.33 mol/L, respectively.
Ó 2015 Elsevier Ltd. All rights reserved.
L-malic acid, D-malic acid, and D-tartaric acid based on the combination of spectroscopy,
Keywords:
Sarcandra glabra
Sesquiterpene dimer
Small organic acid
Absolute configuration
Nitric oxide
m
1. Introduction
lindenane dimers with novel structures and promising bioactivities
were isolated from S. glabra2g,2h and Sarcandra hainanensis,7 which
inspired us to have a deep investigation of the dimers in this plant.
As a result, 11 new sesquiterpene dimers, sarglabolides AeK (1e11),
and five known ones (12e16) were isolated from the seeds of S.
glabra. Sarglabolide A (1) was verified to exclusively possess a sev-
enteen-membered macrocyclic ester ring formed by the scaffold of
the sesquiterpene dimer and small organic acids, which was dif-
ferent from the eighteen-membered rings of the other reported
analogues. In addition, these dimers contained a variety of small
organic acid moieties, including chiral malic acid and tartaric acid,
which resulted in a challenge in characterization of their absolute
configurations due to the independence of the chiral carbons in
organic acid moieties. A combination of spectroscopy, chemical
derivatization and HPLC analysis was applied to resolve this prob-
lem. The inhibitory effects on NO production in LPS-induced mac-
rophages were evaluated and 1, 12 and 13 showed excellent results.
Herein, we describe the isolation and structural elucidation of the
new compounds as well as the assessment of their bioactivities.
Lindenane-type sesquiterpene dimers, sometimes featured with
an eighteen-membered macrocyclic ester ring under the scaffold,
were considered as the characteristic constituents of the plants of
Chloranthaceae.1 Due to the complex structures and potent bio-
activities, e.g., endothelial activation, Kþ current inhibition, anti-
inflammatory, anti-HIV, and cytotoxic activities,2 these sesquiter-
pene dimers attracted much attention in the past decades. More
than 60 sesquiterpene dimers have been isolated from Chlor-
anthaceae, and most of them comprised the same scaffold con-
structed by two lindenane moieties via a [4þ2] cycloaddition
0
0
between D15(4),5(6) and D8 (9 ) 3
In our previous research work,
.
several medicinal plants of Chloranthaceae had been investigated
for bioactive ingredients, leading to the isolation of some new
lindenane dimers.2c,4
Sarcandra glabra (Thunb.) Nakai (Chloranthaceae), a subshrub
widely growing in China and other East and Southeast Asian
countries, was recorded in China Pharmacopeia as a traditional
herbal medicine for the treatment of inflammation and traumatic
injuries.5 The early studies revealed the abundance of sesquiter-
penes and lindenane dimers in this plant.6 Recently, some
2. Results and discussion
Sarglabolide A (1) was obtained as a white, amorphous powder.
Its molecular formula was established as C40H44O14 by HRESIMS,
which showed the quasimolecular ion peak of 1 [MþNa]þ at m/z
771.2619 (calcd for C40H44O14Na 771.2623). The 1H NMR and HSQC
* Corresponding author. Tel./fax: þ86 25 83271405; e-mail address: cpu_lykong@
126.com (L.-Y. Kong).
http://dx.doi.org/10.1016/j.tet.2015.05.112
0040-4020/Ó 2015 Elsevier Ltd. All rights reserved.

P. Wang et al. / Tetrahedron 71 (2015) 5362e5370
5363
spectra of 1 displayed two pairs of characteristic upfield protons at
dH 0.35 (H-2, dd, J¼7.4, 4.2 Hz), 1.02 (H-2, m), 0.62 (H-20, m) and
0.85 (H-20, m), diagnostic of two cyclopropane rings in the linde-
nane dimers.3 Disregarding 30 carbons belonging to the core
framework of the dimer, 10 carbons were still left, which might
account for the existence of a macrocyclic ester ring under the
scaffold of 1. A tiglyl moiety could be recognized at dH 6.73 (H-300, t,
J¼4.1 Hz), 4.80 (H-400, ddd, J¼15.9, 5.0, 1.1 Hz), 5.22 (H-400, ddd,
J¼15.9, 4.2, 1.5 Hz), and 1.81 (H3-500, d, J¼0.9 Hz), which was
a common substituent at 150-OH in the dimers.
framework of 1 was characterized to be the same as that of 12,
based on the key HMBC correlations from H-15 (dH 2.57 and 2.83) to
C-80 (dC 93.8), C-90 (dC 55.1) and C-100 (dC 44.9), and from H-6 (dH
3.92) to C-80 (dC 93.8). Therefore, the whole planar structure of 1
was obtained as shown in Fig. 1.
Analysis of the ROESY spectrum of 1 revealed its relative con-
figuration (Fig. 2). The correlations of H-1/H-3, H-1/H-9, H-9/H-50,
H-10/H-50, H-30/H-50, H-10/H-150, H-30/H-150 and H-50/H-150 in-
dicated their co-facial orientation that was arbitrarily assigned as
a.
As a result, H3-14, H-6, H-90 and H3-140 were assigned as
b
due to
Besides H2-400, another two oxygenated methylene doublets at
dH 4.35 (H-130, d, J¼12.0 Hz), 5.37 (H-130, d, J¼12.0 Hz), 3.73 (H-150,
d, J¼12.0 Hz) and 4.07 (H-150, d, J¼12.0 Hz) were observed, which
were ascribed to C-130 and C-150 based on the hypothesis of the
macrocylic ester ring. Likewise, an oxygenated methine at dH 4.41
(H-2000, dd, J¼4.1, 2.9 Hz) and a correlated methylene at dH 2.91 (H-
3000, dd, J¼17.0, 2.9 Hz) and 2.96 (H-3000, dd, J¼17.0, 4.1 Hz) suggested
a malic acid moiety probably located at 150-OH in view of its pop-
ularity in these dimers. The 13C NMR spectrum of 1, in accord with
its molecular formula, showed 40 carbon resonances and was
similar to that of shizukaol G (12) except for the greatly upfield
shifted C-150 (dC 66.3 in 1, 72.2 in 12) and greatly downfield shifted
C-40 (dC 90.0 in 1, 77.2 in 12),8 indicating the possible esterification
of 40-OH, instead of 150-OH, with 100-carboxyl. This unprecedented
linkage, forming a 17-membered ring, was confirmed by the ab-
sence of the correlation from H-150 to C-100 in the HMBC spectrum
of 1, which was commonly visible in the analogues. Thus, sargla-
bolide A (1) was found to be the first case that constructed a pen-
dent macrocyclic ester ring by esterification of 40-OH with 4-
hydroxytiglic acid. The complete linkage of the macrocyclic ring
was resolved by the key HMBC correlations from H-400 to C-1000 and
from H-130 to C-4000 (Fig. 2). In addition, the orientation of the malic
residue was determined according to its 13C NMR data, which
showed the head carbonyl C-1000 with larger 13C shift at dC 172.9 and
the terminal carbonyl C-4000 at dC 171.2. The dimerized lindenanes
the ROESY correlations of H3-14/H-6, H-6/H-90, and H-90/H3-140.
Also, the correlation of H-400 and H-500 suggested an E-form of the
double bond in the 4-hydroxytiglic residue. The CD spectrum of 1
was recorded and presented similar data to those of the known
analogues. An exciton chirality CD method was applied to resolve
the absolute configuration of its scaffold.2g,2h Two coupling chro-
mophores in the molecule, i.e. the
p,p,p-conjugated system (C-
7ꢀC-8 and C-11ꢀC-12) and the
a
,
b
-unsaturated
g
-lactone (C-70ꢀC-
110ꢀC-120), generated the split Cotton effects in the CD spectrum of
1, showing a positive first Cotton effect at 255 nm (
D
ε þ4.15) and
a negative second Cotton effect at 221 nm (
D
ε ꢀ26.9). Thus, a right-
handed helicity of two coupling chromophores could be derived
from this positive exciton chirality (Fig. 3). The orientation of 2000-
OH, however, could not be assigned due to its independence away
from the scaffold.
We developed a method involving chemical derivatization and
HPLC analysis to determine the absolute configuration of the malic
residue. Alkaline hydrolysis of 1 and subsequent acidification
afforded a mixture of malic acid and 4-hydroxytiglic acid. In view of
the non-optical activity of 4-hydroxytiglic acid, the specific OR ([a]
23 D) of the organic acids mixture in water was measured and
basically ascribed to malic acid, showing a value of þ2.7ꢁ that was
close to that of the standard
tion in methanol catalyzed by SOCl2, the methyl esters of the or-
D
-malic acid (þ4.2ꢁ). After esterifica-
ganic acids reacted with (S)-MTPA chloride to produce (R)-MTPA
Fig. 1. Structures of sarglabolides AꢀK (1e11) and the known dimers (12e16).

5364
P. Wang et al. / Tetrahedron 71 (2015) 5362e5370
Fig. 2. Key HMBC and ROESY correlations of sarglabolide A (1).
Fig. 3. CD spectrum of 1 recorded in MeOH, and the stereoview of the scaffold of 1. Bold blue lines denote the electronic transition of two dipoles.
esters of dimethyl malate and methyl 4-hydroxytiglate, which were
directly analyzed in HPLC. By comparing the retention time of the
above (R)-MTPA ester of dimethyl malate (tR¼6.62 min) with those
Sarglabolides B (2) and C (3) were considered two isomers of 1
on the basis of their HRESIMS experiments, which afforded the
same molecular formula of C40H44O14 for them. Analysis of the 1H
and 13C NMR spectra of 2 and 3 suggested the close resemblance of
their planar structures. In detail, their 1H NMR spectra exhibited
similar resonance signals and differed only in chemical shifts
(Table 1). The characteristic cyclopropane signals at dH 0.32 (H-2 of
2, dd, J¼7.4, 4.2 Hz), 0.71 (H-20 of 2, td, J¼8.7, 5.8 Hz), 0.36 (H-2 of 3,
of the authentic (R)-MTPA esters prepared from standard D-malic
acid and
L
-malic acid (tR¼6.52 min and 7.72 min, respectively, Fig. 4)
in the same manner, the configuration of the malic residue in 1 was
established as D-form. It was the first case that the sesquiterpene
dimer was esterified with a D-malic acid so far.
Fig. 4. HPLC chromatograms of (R)-MTPA esters of dimethyl malates, eluted with an isocratic methanol/water system (65:35, v/v) at 1 mL/min and monitored at 220 nm. A, B and C
present the products prepared from standard D-malic acid, standard L-malic acid, and the hydrolyzate of 1, respectively.

P. Wang et al. / Tetrahedron 71 (2015) 5362e5370
5365
dd, J¼7.4, 4.2 Hz) and 0.73 (H-20 of 3, td, J¼8.7, 5.8 Hz) suggested
their core frameworks of lindenane dimers. A 4-hydroxytiglic acid
moiety and a malic acid moiety could be recognized in their 1H
NMR spectra, respectively, suggestive of macrocyclic ester rings
possibly formed in their molecules. The 13C NMR spectra of 2 and 3
were almost identical except the relatively large distinctions at C-
130 and the carbons corresponding to the malic residues (Table 4).
Detailed analysis of the HMBC spectra of 2 and 3 confirmed their
planar structures and revealed their close resemblance with 12.
Specifically, 2 possessed the same planar structure as that of 12, and
3 had a reversed orientation of the malic residue relative to 2 and
12, which was confirmed by the HMBC correlations from H-130 (dH
4.76 and 4.85) to C-4000 (the head carboxyl of malic acid, dC 174.2),
(around dC 20) compared with 12.5 The 1H NMR of 4, correspond-
ingly, showed one more oxygenated methylene at dH 4.28 (d, H-13,
J¼15.2 Hz) and 4.35 (d, H-13, J¼15.2 Hz) and one less methyl lo-
cated on a double bond, with an overall similarity with 12. Con-
sequently, 4 was deduced to be a 13- or 500-oxygenated derivative of
12. Further analysis of the NMR data of 4, particularly the key HMBC
correlations from H-13 to C-7, C11 and C-12, confirmed this de-
duction and elucidated its basic structure (Fig. 1), i.e., 13-hydroxyl
shizukaol G. A ROESY and a CD experiments revealed the same
configuration of the scaffold of 4 as that of 12. The malic residue
proved to be L-form by the aforementioned method ([a]23
D¼ꢀ4.1ꢁ, tR¼7.60 min). Thus, sarglabolide D (4) was identified to be
13-hydroxyl shizukaol G.
and from H-400
(
dH 4.53 and 5.04) to C-1000 (the terminal carboxyl of
Sarglabolide E (5) was obtained as a white, amorphous powder.
The HRESIMS spectrum of 5 afforded its molecular formula
malic acid, dC 170.9). On the basis of ROESYand CD experiments, the
relative and absolute configurations of the scaffolds of 2 and 3 were
established and presented the same results as 1. Therefore, malic
residues were deduced to be the only difference between 2, 3 and
12. A series of derivatizations of 2 and 3 and subsequent HPLC
C
40H44O15, suggestive of another oxygenated derivative of 12. The
13C NMR spectrum of 5 also showed one more oxygenated carbon
(
dC 73.1, C-3000) and one less upfield carbon (around dC 37) compared
with 12, and the 1H NMR of 5 displayed one more oxygenated
methine doublet at dH 4.79 (d, H-3000, J¼1.5 Hz). Further in-
terpretation of the NMR data, particularly the key HMBC correla-
tions from the additional oxygenated methine proton (H-3000) to C-
analyses, as same as 1, were conducted and demonstrated that a
D-
malic residue and an -malic residue existed in 2 and 3, respectively,
L
based on the specific OR values of the malic acids hydrolyzed from 2
and 3 (þ4.3ꢁ for 2 and ꢀ6.8ꢁ for 3) and the retention times of their
(R)-MTPA esters in HPLC (6.62 min for 2 and 7.55 min for 3). In other
words, 2 was an epimer of 12 at C-2000, and 3 had a reversed linkage
of malic residue relative to 12.
1000
(
dC 171.3), C-2000
(
dC 72.9) and C-4000
dC 72.9) compared with 12, defined the
(dC 171.3) and the significantly
increased shift of C-2000
(
overall structure of 5 and determined a hydroxyl was located at C-
3000, namely a tartaric residue replacing the malic residue in 12,
Table 1
1H NMR data of compounds 1e4 (500 MHz in CDCl3, J in Hz)
Position
1
2
3
4
1
2
2.09, m
0.35, dd (7.4, 4.2)
1.02, m
2.05, m
0.32, dd (7.4, 4.2)
1.00, m
2.07, m
0.36, dd (7.4, 4.2)
1.02, m
2.08, m
0.39, dd (7.4, 4.2)
1.04, td (8.3, 4.6)
1.86, m
3
1.87, m
1.84, m
1.85, m
6
9
3.92, d (3.3)
4.10, s
3.93, d (3.1)
3.86, s
3.96, d (3.3)
3.86, s
3.90, d (3.3)
3.82, s
13
1.85, s
1.87, s
1.92, s
4.28, d (15.2)
4.35, d (15.2)
1.08, s
2.55, ddd (16.3, 6.0, 3.8)
2.85, br. d (16.3)
1.63, m
0.73, td (8.8, 5.9)
1.32, m
1.41, m
14
15
1.00, s
1.02, s
1.03, s
2.57, ddd (16.3, 6.2, 4.0)
2.83, br.d (16.3)
1.70, m
0.62, m
0.85, m
2.57, ddd (16.3, 5.8, 4.1)
2.79, br.d (16.3)
1.60, m
0.71, td (8.7, 5.8)
1.34, m
2.58, ddd (16.3, 5.9, 4.0)
2.81, br.d (16.3)
1.62, m
0.73, td (8.7, 5.8)
1.33, m
10
20
30
50
60
1.85, m
1.38, m
1.86, m
1.40, m
1.92, m
2.17, dd (13.6, 6.4)
2.46, dd (18.8, 6.4)
3.29, dd (18.8, 13.6)
1.99, dd (6.5, 1.5)
4.35, d (12.0)
5.37, d (12.0)
0.66, s
3.73, d (12.0)
4.07, d (12.0)
6.73, t (4.1)
1.94, m
2.30, dd (19.0, 6.0)
2.87, dd (19.0, 13.8)
1.84, m
4.39, d (12.0)
5.43, d (12.0)
0.80, s
3.67, d (11.9)
4.53, d (11.9)
6.53, t (5.5)
4.59, dd (14.2, 6.6)
5.47, dd (14.2, 5.5)
1.96, br. s
2.32, dd (18.7, 6.0)
2.68, dd (18.7, 13.6)
1.89, m
4.76, d (11.7)
4.85, d (11.7)
0.80, s
3.64, d (12.0)
4.57, d (12.0)
6.65, t (5.7)
4.53, dd (13.9, 7.3)
5.04, dd (13.9, 5.2)
1.92, br. s
2.25, dd (18.8, 6.2)
2.69, dd (18.8, 13.6)
1.95, m
4.76, d (11.7)
4.84, d (11.7)
0.79, s
3.68, d (11.9)
4.56, d (11.9)
6.64, t (5.7)
4.54, dd (14.0, 7.5)
5.04, dd (14.0, 5.2)
1.93, br. s
90
130
140
150
300
400
4.80, ddd (15.9, 5.0, 1.1)
5.22, ddd (15.9, 4.2, 1.5)
1.81, d (0.9)
500
2000
4.41, dd (4.1, 2.9)
4.40, m
2.91, dd (17.8, 4.1)
3.16, dd (17.8, 3.1)
4.35, t (3.4)
4.41, t (3.6)
3000
2.91, dd (17.0, 2.9)
2.96, dd (17.0, 4.1)
3.79, s
2.87, dd (17.1, 4.8)
3.32, dd (17.1, 2.6)
3.70, s
2.91, dd (17.9, 4.3)
3.29, dd (17.9, 3.2)
3.76, s
OCH3
3.74, s
Sarglabolide D (4) was also obtained as a white, amorphous
powder. The HRESIMS experiment allowed an accurate molecular
formula of C40H44O15 to be assigned to 4, suggestive of an oxy-
genated derivative of 12. The 13C NMR spectrum of 4 showed one
more oxygenated carbon (dC 61.1, C-13) and one less upfield carbon
which presented the first case in dimers to date. The relative and
absolute configurations of the scaffold of 5 were established on the
basis of ROESY and CD experiments, respectively. As for the tartaric
residue, the same methodology as the above was applied and
demonstrated the tartaric residue in 5 was D-form according to its

5366
P. Wang et al. / Tetrahedron 71 (2015) 5362e5370
Table 2
1H NMR data of compounds 5e8 (500 MHz in CDCl3 or CD3OD, J in Hz)
Position
5a
6b
7a
8a
1
2
2.07, m
0.39, dd (7.3, 4.1)
1.03, m
1.99, m
2.06, m
2.08, m
0.33, dd (7.3, 4.2)
1.01, m
0.35, dd (7.1, 4.1)
0.99, td (7.8, 4.3)
1.94, m
0.35, dd (7.3, 4.0)
1.02, td (7.7, 4.5)
1.84, m
3
1.86, m
1.85, m
6
9
3.95, d (3.1)
3.83, s
3.89, d (3.4)
3.80, s
3.90, d (3.3)
3.82, s
3.92, d (5.7)
3.93, s
13
1.92, s
4.01, d (14.7)
4.19, d (14.7)
1.15, s
2.53, ddd (16.3, 5.6, 4.1)
2.85, br.d (16.3)
1.67, td (8.3, 4.3)
0.74, td (8.7, 5.5)
1.33, m
4.31, d (15.5)
4.32, d (15.5)
1.07, s
2.56, m
2.81, br. d (16.3)
1.61, m
0.73, td (8.8, 6.0)
1.32, m
1.41, m
1.87, m
2.40, dd (18.8, 6.1)
2.73, m
1.92, s
14
15
1.01, s
1.01, s
2.56, ddd (16.2, 5.9, 3.9)
2.84, br.d (16.2)
1.65, m
0.73, td (8.7, 5.8)
1.32, m
1.42, m
1.98, m
2.35, dd (19.0, 6.2)
2.81, m
1.96, m
4.66, d (11.8)
5.15, d (11.8)
0.80, s
3.71, d (11.9)
4.59, d (11.9)
6.62, t (5.6)
4.93, dd (14.1, 6.7)
5.07, dd (14.1, 5.3)
1.93, br. s
2.58, ddd (16.4, 6.0, 4.0)
2.80, br. d (16.3)
1.61, td (8.3, 4.2)
0.73, td (8.8, 5.9)
1.28, m
1.50, td (8.9, 3.5)
1.88, m
2.32, dd (18.3, 6.0)
2.73, dd (18.3, 13.8)
1.94, m
4.34, d (13.7)
4.40, d (13.7)
0.88, s
3.87, d (11.6)
4.25, d (11.6)
6.78, td (6.2, 1.3)
4.93, br. d (4.3)
10
20
30
50
60
1.38, m
1.78, m
2.45, dd (18.9, 6.2)
2.90, dd (18.9, 13.8)
1.82, m
4.63, d (12.0)
5.09, d (12.0)
0.85, s
3.67, d (11.6)
4.45, d (11.6)
6.74, td (5.4, 1.2)
4.97, dd (14.2, 5.0)
5.04, dd (14.2, 7.3)
1.94, br. s
90
130
1.91, m
4.53, d (12.0)
5.03, d (12.0)
0.80, s
3.68, d (11.9)
4.52, d (11.9)
6.60, t (5.5)
4.64, dd (14.7, 6.8)
5.05, dd (14.7, 5.0)
1.92, br. s
140
150
300
400
500
2000
1.94, br. s
6.89, d (16.3)
4.68, d (1.5)
4.72, d (2.4)
2.52, m
2.95, m
2.74, m
3.72, s
3000
OCH3
OC2H5
4.79, d (1.5)
3.70, s
4.80, d (2.4)
3.66, s
6.88, d (16.3)
3.76, s
4.27, q (7.1)
1.32, t (7.1)
a
Measured in CDCl3.
Measured in CD3OD.
b
specific OR (ꢀ6.3ꢁ for tartaric acid hydrolyzed from 5, and ꢀ14.2ꢁ
established by ROESY and CD, respectively. As a result, sarglabolide
G (7) was determined to be 2000-deoxysarglabolide D.
for standard D
-tartaric acid)9 and tR (5.89 min for tartaric derivative
prepared from 5, 5.89 min for authentic
6.07 min for authentic -tartaric derivative, see supplementary data
-OH at C-2000 and C-3000. Therefore, the
D
-tartaric derivative and
Sarglabolide H (8) was obtained as a white, amorphous powder.
Its molecular formula was assigned as C42H48O14 by HRESIMS. The
1H NMR spectrum of 8 displayed much complicated resonance
signals and had great differences with those of the other dimers.
L
S39ꢀ41), namely, both
a
whole structure of 5 was established as shown in Fig. 1.
Sarglabolide F (6), a white, amorphous powder, was assigned
a molecular formula of C40H44O16 based on the HRESIMS experi-
ment, suggesting a further oxygenated derivative of 4 or 5. A
structural hybrid of 4 and 5 for the structure of 6 could be easily
concluded due to the inclusion of both oxygenated methylene in 4
and oxygenated methine in 5, recognizable at dH 4.01 (d, H-13,
J¼14.7 Hz), 4.19 (d, H-13, J¼14.7 Hz) and 4.80 (d, H-3000, J¼2.4 Hz),
and at dC 61.2 (C-13) and 74.2 (C-3000). A thorough investigation of
the NMR data and CD spectrum of 6 confirmed the conclusion and
elucidated the exact structure except for the configuration of tar-
The resonance signals belonging to an ethoxyl and a 4-
hydroxytiglyl groups could be easily observed. The 1H NMR spec-
trum also showed two olefinic doublets at dH 6.89 (H-2000, d,
J¼16.3 Hz) and 6.88 (H-3000, d, J¼16.3 Hz), reminiscent of an AB spin
system at an E-form double bond. The rest of proton signals could
be easily assigned to the core framework of a sesquiterpene dimer.
Excluding the ethoxyl carbons, the 13C NMR spectrum of 8 dis-
played 40 carbon signals, suggestive of the presence of a malic acid-
related moiety. Detailed analysis of the 13C and HMBC spectra, es-
pecially the HMBC correlations from H-2000
( (dH
dH 6.89) and H-3000
taric residue, which was assigned as D-form, i.e., both
a-oriented
6.88) to C-1000 dC 165.0) and C-4000
(
(
dC 165.0), disclosed that two
hydroxyl, by the same method described as the above ([
a
]23
olefinic carbons replaced the middle two carbons of the malic
residue in the corresponding dimers. Apparently, sarglabolide G (8)
contained a first fumaric residue in its molecule. After the de-
termination of the location of ethoxyl on the basis of a key HMBC
D¼ꢀ5.1ꢁ, tR¼5.89 min). As a result, 6 was characterized as a poly-
hydric dimer as shown in Fig. 1.
Sarglabolide G (7) was isolated as a white, amorphous powder,
and was assigned a molecular formula of C40H44O14 on the basis of
HRESIMS. Appearently, 7 was another isomer of 12. Its 1H NMR
spectrum, however, suggested much resemblance with 4. The ab-
sence of an oxygenated methine signal, corresponding to H-2000 in 4,
suggested that 7 might be a 2000-deoxy derivative of 4. The 13C NMR
spectrum of 7 showed, likewise, a less oxygenated carbon and
a more upfield one compared with 4. Analysis of the HMBC spec-
trum confirmed the above deduction based on the correlations
correlation from ethoxyl to C-4000
(dC 165.0), the planar structure of 8
was established as shown in Fig. 1. The ROESY experiment of 8
afforded the same correlations in the scaffold as those of 1, and
suggested an identical relative configuration. Likewise, its absolute
configuration was determined to be the same as that of 1 by the
similar CD data at 200e260 nm, showing a negative Cotton effect at
217 nm (
D
ε ꢀ5.69) and a positive Cotton effect at 251 ( ε þ1.82).
D
Sarglabolide I (9), a white, amorphous powder, was assigned
a molecular formula of C31H36O9 on the basis of HRESIMS, which,
appearently, suggested no pendent macrocyclic ester ring. The
from H-2000
( ( (dC 29.3) and
dH 2.52 and 2.95) to C-1000 dC 171.9), C-3000
C-4000
(dC 172.1). The relative and absolute configurations of 7 were

P. Wang et al. / Tetrahedron 71 (2015) 5362e5370
5367
H-400 dH 4.34 and 4.40 for 10; dH 4.35 and 4.42 for 11) to C-1000
( (dC
Table 3
1H NMR data of compounds 9e11 (500 MHz in CDCl3 or CD3OD, J in Hz)
173.6 for 10; 173.2 for 11). Instead, the additional oxygenated
methyl and the oxygenated ethyl were found to be esterified with C-
1000 of 10 and 11, respectively, which were supported by their HMBC
correlations. The configurations of both 10 and 11, including their
scaffolds and the malic residues, were established by the afore-
Position
9a
10b
11b
1
2
2.00, m
2.07, m
2.07, m
0.32, dd (7.3, 4.1)
0.98, td (7.8, 4.3)
1.93, m
0.32, dd (7.3, 4.2)
1.01, m
1.84, m
0.32, dd (7.3, 4.0)
1.01, m
1.85, m
3
6
9
13
14
15
mentioned methodology, showing an -malic residue for 10 ([a]23
L
3.94, d (3.3)
4.04, s
3.93, br. s
3.93, s
3.93, br. s
3.93, s
D¼ꢀ2.2ꢁ, tR¼7.72 min), a
D
-malic residue for 11 ([
a
]23 D¼þ2.7ꢁ,
tR¼6.62 min) and the common scaffold for both of them.
1.85, s
1.87, s
1.87, s
Five known sesquiterpene dimers, shizukaol G (12),8 shizukaol B
(13),8 sarcandrolide B (14),2h shizukaol C (15),10 and shizukaol N
(16)11 were isolated and identified by comparison of their 1H and
13C NMR data with those of the reported. All the isolates in this
research possessed the same scaffold, a DielseAlder cycloadded
product of two lindenanes, and differed in the pendent substituents
at C-130 and C-150 (C-40 for 1), suggesting a common biosynthetic
pathway for them. Typically, diverse small organic acids, other than
dominant citric acid in the known dimers, were esterified with 130-
OH. The problem in determination of the configurations of those
chiral small organic acids (malic acid and tartaric acid) could be
thoroughly resolved according to the method developed by us.
Additionally, sarglabolide A (1) presented a first example to be
esterified at OH-40 and construct a 17-membered ring, other than
the eighteen-membered rings in all known analogues. The isolates
in this paper also showed great distinction in composition and
structural features with the reported dimers from the whole plants
of Sarcandra glabra, suggestive of significant distributional differ-
ence of sesquiterpene dimers in this plant.
1.03, s
1.01, s
1.02, s
2.53, ddd
2.57, ddd
2.58, ddd
(16.4, 6.0, 4.2)
2.83, br. d (16.4)
1.61, td (8.2, 4.1)
0.68, td (8.8, 5.5)
1.22, m
(16.3, 5.8, 4.2)
2.77, m
1.60, m
0.72, td (8.8, 5.9)
1.31, m
(16.3, 5.8, 4.2)
2.78, m
1.60, m
0.72, td (8.8, 5.9)
1.32, m
10
20
30
50
60
1.53, td (8.8, 3.6)
1.71, dd (13.8, 6.0)
2.24, dd (18.3, 6.0)
2.78, dd (18.3, 13.9)
1.82, dd (6.1, 1.2)
4.24, d (13.2)
4.26, d (13.2)
0.91, s
1.42, m
1.87, m
1.42, m
1.88, m
2.41, dd (18.6, 6.1)
2.76, dd (18.6, 13.7)
1.87, m
4.78, d (12.9)
4.90, d (12.9)
0.84, s
2.41, dd (18.6, 6.1)
2.77, dd (18.6, 13.7)
1.89, m
4.78, d (12.9)
4.90, d (12.9)
0.84, s
90
130
140
150
3.31, d (10.9)
3.35, d (10.9)
3.75, d (11.8)
4.42, d (11.8)
6.79, t (5.5)
4.34, dd (15.0, 5.5)
4.40, m
3.75, d (11.8)
4.44, d (11.8)
6.80, t (5.5)
4.35, dd (15.0, 5.5)
4.42, m
300
400
500
2000
3000
1.87, br. s
1.87, br. s
4.54, dd (6.8, 4.3)
2.81, dd (16.4, 6.9)
2.93, dd (16.4, 4.2)
3.73, s
4.52, dd (6.8, 4.3)
2.80, dd (16.4, 6.9)
2.92, dd (16.4, 4.2)
3.73, s
As a continuous research on the anti-inflammatory activities of
the sesquiterpene dimers in Chloranthaceae,2c,2d we conducted the
NO release inhibition tests of selective isolates 1, 2, 3, 5, 10, 12 and
13. As a result, compounds 1, 12 and 13 exhibited significant bio-
12-OCH3
1000-OCH3
OC2H5
3.77, s
3.79, s
4.25, q (7.1)
1.30, t (7.1)
a
activities with IC50 values at 3.04, 4.65 and 2.33
respectively.
mmol/L,
Measured in CD3OD.
Measured in CDCl3.
b
3. Experimental section
NMR data of 9 displayed diagnostic features of the scaffolds of the
above dimers. Two pairs of oxygenated methylene doublets at dH
4.26 (1H, d, J¼13.2 Hz), 4.24 (1H, d, J¼13.2 Hz), 3.35 (1H, d,
J¼10.9 Hz), and 3.31 (1H, d, J¼10.9 Hz) were assigned to H2-130 and
H2-150, respectively. Four methyl singlets at dH 3.77 (3H, s), 1.85 (3H,
s), 1.03 (3H, s), and 0.91 (3H, s) corresponded to eOCH3, CH3-13,
CH3-14 and CH3-140, respectively. The characteristic cyclopropane
signals, likewise, could be observed at dH 0.32 (H-2, dd, J¼7.3,
4.1 Hz) and 0.68 (H-20, td, J¼8.8, 5.5 Hz). Besides, the easily rec-
ognizable H-9 and H-6, similar to the above dimers, were also
found at dH 4.04 (H-9, s) and 3.94 (H-6, d, J¼3.3 Hz). Thus, sargla-
bolide I (9) was deduced to have the structure identical to the
scaffolds of the above dimers. Detailed analysis of 1D and 2D NMR
data (Tables 3 and 4) confirmed this deduction. A ROESY and a CD
experiments were conducted to determine the relative and abso-
lute configurations of 9, and gave the same results as the above
dimers.
3.1. General experimental procedures
Optical rotations and CD spectra were obtained on a JASCO P-
1020 polarimeter and a JASCO 810 polarimeter, respectively. UV and
IR spectra were recorded on a Shimadzu UV-2450 spectrometer and
a Bruker Tensor 27 spectrometer, respectively. HRESIMS experi-
ments were performed on an Agilent UPLC-Q-TOF (6520B). NMR
spectra were recorded in CDCl3 or CD3OD on a Bruker AV-500 NMR
instrument at 500 MHz (1H) and 125 MHz (13C). Silica gel (Qingdao
Marine Chemical Co., Ltd., China), MCI gel (Mitsubishi Chemical,
Japan), ODS (FuJi, Japan), and Sephadex LH-20 (Pharmacia, Sweden)
were used for column chromatography. Preparative HPLC was car-
ried out on a Shimadzu LC-6A instrument with an SPD-10A detector
and a shim-pack RP-C18 column (20ꢂ200 mm, 10
mm). RP-MPLC
was carried out on a Quiksep system (H&E Co., Ltd., China). Ana-
lytical HPLC was performed on an Agilent 1200 series instrument
Sarglabolide J (10) and K (11) were also obtained as white,
amorphous powders. Their molecular formulae were established to
be C41H48O15 and C42H50O15, respectively, according to their HRE-
SIMS spectra. The 1H and 13C NMR spectra of 10 and 11 exhibited
close similarity (Tables 3 and 4). Both of them contained the di-
agnostic signals of the 4-hydroxytiglic and malic residues. The
scaffolds of 10 and 11 could be deduced to be the same as the above
dimers from their NMR spectra. An additional oxygenated methyl
for 10 at dH 3.79 (3H, s) and an oxygenated ethyl for 11 at dH 4.25 (2H,
q, J¼7.1 Hz) and 1.30 (3H, t, J¼7.1 Hz) could be recognized in their 1H
NMR spectra, indicating the main distinction between them. Both
10 and 11 were believed to have opened macrocyclic ester rings due
to their molecular formulae and the absent HMBC crosspeaks from
using
(150ꢂ4.6 mm, 5
acid and
a
DAD detector and
a
shim-pack VPeODS column
-(ꢀ)-malic acid, -(þ)-malic
mm). The standard
L
D
D
-(ꢀ)-tartaric acid were purchased from J&K Chemical Ltd.
All solvents and reagents were of analytical grade.
3.2. Plant material
The fresh seeds of S. glabra were collected in Ganzhou, Jiangxi
province, P. R. China in November 2013. The plant material was
authenticated by Prof. Mian Zhang, Department of Medicinal
Plants, China Pharmaceutical University. A voucher specimen (No.
CSH201311) was deposited in the Department of Natural Medicinal
Chemistry, China Pharmaceutical University.

5368
P. Wang et al. / Tetrahedron 71 (2015) 5362e5370
Table 4
13C NMR data of compounds 1e11 (125 MHz)
Position
1a
2a
3a
26.5
4a
26.7
5a
26.8
6b
26.9
7a
26.5
8a
26.3
9b
26.3
10a
26.1
11a
26.1
1
26.5
26.3
2
3
16.2
25.1
16.1
24.9
16.2
25.0
16.3
25.1
16.3
25.1
16.1
25.3
16.2
25.0
16.1
25.0
16.1
25.4
16.1
24.9
16.1
24.9
4
5
6
142.8
132.7
41.7
142.6
132.5
41.4
142.9
132.7
41.6
143.4
131.5
42.5
143.1
131.5
42.0
143.4
133.8
43.0
143.0
132.4
42.2
142.7
132.4
41.3
143.2
133.8
42.0
142.6
132.0
41.2
142.6
132.0
41.2
7
8
9
131.0
201.1
80.1
131.8
201.0
80.0
131.6
201.2
80.0
132.7
202.1
80.0
133.1
201.3
79.7
135.3
203.6
80.8
131.7
201.7
80.1
131.1
200.4
80.3
134.4
202.2
81.2
132.2
200.8
80.2
132.2
200.8
80.2
10
11
12
13
14
15
10
51.2
51.0
51.1
50.9
50.9
52.2
50.9
51.3
52.5
51.1
51.1
147.6
170.8
20.5
15.8
25.4
27.7
14.4
26.5
90.0
60.8
23.2
173.5
93.8
55.1
147.0
170.3
20.1
15.5
25.5
25.7
11.6
28.1
77.4
61.3
24.3
174.6
93.5
55.8
147.2
170.4
20.0
15.6
25.6
26.0
11.7
28.0
77.5
61.2
23.3
175.3
93.7
55.7
148.9
168.3
61.1
15.9
25.5
26.0
11.6
28.1
77.4
60.8
23.4
175.3
93.5
55.1
146.9
170.6
19.7
15.8
25.5
26.2
11.6
28.1
77.4
60.7
24.3
175.0
93.8
55.2
148.9
169.8
61.2
16.1
26.1
26.7
12.4
28.6
77.5
63.0
25.3
177.2
94.5
57.2
148.9
168.2
61.2
15.8
25.5
26.0
11.7
28.1
77.3
61.0
23.7
174.6
93.2
55.1
147.7
168.2
20.5
15.5
25.5
25.7
12.0
28.4
77.6
60.4
22.5
172.3
93.5
55.1
147.1
173.1
20.4
15.8
26.0
26.6
12.7
29.1
79.5
60.5
23.1
174.2
94.7
57.3
146.9
171.2
20.1
15.5
25.4
25.7
11.8
28.2
77.6
61.0
23.3
172.4
93.5
55.6
147.0
171.2
20.1
15.5
25.4
25.7
11.8
28.2
77.6
61.0
23.3
172.4
93.5
55.6
20
30
40
50
60
70
80
90
100
110
120
130
140
150
100
44.9
45.2
45.3
45.4
45.3
46.1
45.3
45.0
45.8
45.2
45.1
123.9
171.7
54.4
26.2
66.3
165.3
129.0
138.0
62.8
123.9
171.9
53.4
26.2
72.7
167.3
129.7
135.3
62.0
123.0
171.4
56.5
25.9
72.0
167.2
130.1
135.6
61.6
123.3
174.2
56.2
25.9
72.2
167.3
130.2
135.5
61.6
123.4
171.3
55.6
25.8
72.7
167.1
130.2
135.1
62.3
124.1
173.2
56.0
26.6
73.7
168.9
130.7
137.0
62.4
123.9
171.6
54.5
26.0
72.5
167.3
129.5
135.8
61.6
127.7
171.0
55.2
26.2
71.8
167.4
130.9
135.3
61.9
128.6
171.5
54.4
27.1
69.3
123.3
171.4
55.8
26.3
72.2
168.0
127.6
142.1
59.9
123.3
171.4
55.8
26.3
72.2
168.0
127.6
142.1
59.9
200
300
400
500
12.8
13.2
12.9
12.9
13.1
12.9
13.1
13.1
12.8
12.8
1000
2000
3000
4000
12-OCH3
1000-OCH3
OC2H5
172.9
67.6
38.4
171.2
52.8
173.7
67.0
37.4
170.6
52.5
170.9
37.5
66.5
174.2
52.7
171.3
66.6
37.6
171.1
52.8
171.3
72.9
73.1
171.3
52.9
172.4
74.1
74.2
172.5
52.8
171.9
28.9
29.3
172.1
52.5
165.0
134.6
133.0
165.0
52.8
173.6
67.4
38.7
170.4
52.9
53.1
173.2
67.4
38.8
170.4
53.1
53.0
61.6
14.2
62.1
14.3
a
Measured in CDCl3.
Measured in CD3OD.
b
3.3. Extraction and isolation
(30.0 mg), 4 (10.5 mg), 5 (13.8 mg), 10 (70.0 mg) and 11 (8.1 mg). Fr.
3 (12 g) was chromatographed on an MCI gel column and eluted
with 40%, 60%, 80% and 100% methanol to obtain four subfractions
Fr. 3.1e4. Fr. 3.2 (1.8 g) was run on an ODS column eluted with 50%
methanol and further purified by preparative HPLC to yield 6
(8.1 mg), 9 (5.6 mg) and 14 (21.2 mg).
The fresh seeds of S. glabra (10 kg) were roughly dried by air and
ground. After extraction with 95% EtOH (3 L) under reflux (4ꢂ2 h)
and successive removal of the solvent under reduced pressure,
a brown and odorous crude extract (460 g) was obtained. Then the
crude extract was suspended in 2.0 L water and successively
extracted by petroleum ether (4ꢂ2 L) and ethyl acetate (3ꢂ2 L).
The ethyl acetate extract (70 g) was subjected to a silica gel
column and eluted with CH2Cl2/MeOH (50:1, 25:1, 10:1, 0:1, v/v) to
afford four fractions (Fr. 1e4). Fr. 2 (27 g) was further applied to
a silica gel column using a continuous gradient of petroleum ether/
acetone (3:1 to 1:1, v/v) to afford 30 subfractions (Fr. 2.1e30). Frs.
2.16e18 were combined and subjected to an ODS column using
a gradient elution of MeOH/H2O (45e60%), yielding a large amount
of 13 (1.0 g). Part of the other eluates were further purified by
preparative HPLC to yield 8 (9.0 mg), 15 (17.6 mg) and 16 (4.3 mg).
Frs. 2.19e26 were combined and chromatographed on an MCI gel
column eluted with 60%, 80% and 100% methanol. The 80% meth-
anol eluate was further run on an LH-20 gel column, and purified by
preparative HPLC to afford 2 (17.8 mg), 3 (34.2 mg), 7 (7.0 mg), and
12 (1.0 g). Frs. 2.27e29 were combined and subjected to an ODS
column, eluted with 30% and 50% methanol. The eluates were pu-
rified by LH-20 gel column and preparative HPLC to yield 1
3.3.1. Sarglabolide A (1). White, amorphous powder; [
(c0.44, MeOH);UV(MeOH)lmax (logε)215(4.36)nm;CD(MeOH,
a
]23 D ꢀ70.3
D
ε)
lmax 383 (þ1.92), 363 (ꢀ1.29), 321 (ꢀ2.36), 255 (þ4.15), 221 (ꢀ26.9)
nm; IR (KBr) nmax 3448, 2939, 2857,1739,1654,1438,1377,1275,1113,
993 cmꢀ1;1Hand13C NMRspectraldata:see Tables1and4;HRESIMS
m/z 771.2619 [MþNa]þ (calcd for C40H44O14Na 771.2623).
3.3.2. Sarglabolide B (2). White, amorphous powder; [
ꢀ106.6 (c 0.29, MeOH); UV (MeOH) lmax (log ε) 217 (4.36) nm; CD
(MeOH,
a]23 D
D
ε) lmax 348 (þ1.06), 306 (ꢀ1.79), 250 (þ7.95), 209 (ꢀ15.5)
nm; IR (KBr) nmax 3446, 2938, 2857, 1738, 1652, 1437, 1378, 1277,
1112, 991 cmꢀ1; 1H and 13C NMR spectral data: see Tables 1 and 4;
HRESIMS m/z 771.2619 [MþNa]þ (calcd for C40H44O14Na 771.2623).
3.3.3. Sarglabolide C (3). White, amorphous powder; [
(c 0.34, MeOH); UV (MeOH) lmax (log ε) 217 (4.36) nm; CD (MeOH,
ε) lmax 384 (þ2.65), 364 (ꢀ0.55), 347 (þ0.83), 250 (þ13.7), 211
a]23 D ꢀ90.9
D

P. Wang et al. / Tetrahedron 71 (2015) 5362e5370
5369
(ꢀ15.2) nm; IR (KBr) nmax 3446, 2938, 2858, 1738, 1652, 1438, 1378,
Tables 3 and 4; HRESIMS m/z 817.3036 [MþNa]þ (calcd for
1276, 1113, 991 cmꢀ1
;
1H and 13C NMR spectral data: see Tables 1
C42H50O15Na 817.3042).
and 4; HRESIMS m/z 771.2620 [MþNa]þ (calcd for C40H44O14Na
771.2623).
3.4. Determination of the absolute configurations of the
malic and tartaric residues in 1e6 and 10e11
3.3.4. Sarglabolide D (4). White, amorphous powder; [
ꢀ18.5 (c 0.35, MeOH); UV (MeOH) lmax (log ε) 211 (4.30) nm; CD
(MeOH,
ε) lmax 384 (þ2.36), 365 (ꢀ1.10), 350 (þ0.60), 322 (ꢀ1.06),
255 (þ4.28), 212 (ꢀ3.60) nm; IR (KBr) nmax 3442, 2939, 2857, 1737,
a]23 D
D
3.4.1. Preparation of (R)-MTPA esters of dimethyl malate and di-
methyl tartarate. Compounds 1e6 and 10e11 (3.0 mg each) were,
1653, 1436, 1379, 1274, 1112, 992 cmꢀ1
;
1H and 13C NMR spectral
respectively, dissolved in 100 mL methanol and added to 100 mL 10%
data: see Tables 1 and 4; HRESIMS m/z 787.2569 [MþNa]þ (calcd for
K2CO3 (methanol/water 2: 1, v/v). After hydrolysis at 60 ꢁC for 2 h,
C
40H44O15Na 787.2572).
the reaction mixtures were blow-dried, then acidified by 0.1 M HCl
(500
m
L) and extracted with EtOAc (500
m
Lꢂ3). The aqueous layers
3.3.5. Sarglabolide E (5). White, amorphous powder; [
(c 0.32, MeOH); UV (MeOH) lmax (log ε) 216 (4.23) nm; CD (MeOH,
ε) lmax 390 (þ1.47), 327 (ꢀ2.10), 254 (þ7.80), 211 (ꢀ12.7) nm; IR
(KBr) nmax 3439, 2939, 2855, 1740, 1654, 1433, 1379, 1276, 1119,
a
]23 D ꢀ51.8
were blow-dried and dissolved in methanol (200 m
L). A drop of
SOCl2 was added to the solution to catalyze the esterification (room
temperature, 12 h). After evaporation, the mixed methyl esters of 4-
hydroxytiglic acid and malic acid (or tartaric acid) were dissolved in
D
993 cmꢀ1
;
1H and 13C NMR spectral data: see Tables 2 and 4;
dry pyridine (100
overnight to obtain the final products. The corresponding authentic
(R)-MTPA esters were also prepared from the commercial -malic
acid, -malic acid, -tartaric acid and
-tartaric acid. The 1H NMR
mL) and reacted with (S)-MTPA chloride (2 mL)
HRESIMS m/z 787.2569 [MþNa]þ (calcd for C40H44O15Na 787.2572).
D
3.3.6. Sarglabolide F (6). White, amorphous powder; [
(c 0.32, MeOH); UV (MeOH) lmax (log ε) 212 (4.29) nm; CD (MeOH,
ε) lmax 391 (þ3.56), 348 (þ1.79), 320 (ꢀ1.23), 257 (þ4.54), 212
(ꢀ9.00) nm; IR (KBr) nmax 3440, 2937, 2855, 1739, 1654, 1434, 1379,
a
]23 D ꢀ45.6
L
D
L
data of the authentic (R)-MTPA esters of dimethyl malates were in
D
accord with the reported.8
(R)-MTPA ester of dimethyl D
-malate: 1H NMR (500 M, CDCl3) dH
1275, 1117, 995 cmꢀ1
;
1H and 13C NMR spectral data: see Tables 2
7.62 (2H, m), 7.40e7.42 (3H, m), 5.72 (1H, dd, J¼8.8, 4.0 Hz), 3.82
(3H, s), 3.64 (3H, s), 3.60 (3H, s), 2.95 (1H, dd, J¼16.7, 4.0 Hz), 2.88
(1H, dd, J¼16.7, 8.8 Hz); HRESIMS m/z 401.0821 [MþNa]þ (calcd for
and 4; HRESIMS m/z 803.2515 [MþNa]þ (calcd for C40H44O16Na
803.2522).
C
16H17F3O7Na 401.0819).
3.3.7. Sarglabolide G (7). White, amorphous powder; [
ꢀ58.3 (c 0.53, MeOH); UV (MeOH) lmax (log ε) 215 (4.29) nm; CD
(MeOH,
ε) lmax 346 (þ0.78), 320 (ꢀ1.67), 251 (þ10.9), 205
(ꢀ16.3) nm; IR (KBr) nmax 3445, 2939, 2858, 1737, 1654, 1436, 1377,
a
]23 D
(R)-MTPA ester of dimethyl L
-malate: 1H NMR (500 M, CDCl3) dH
7.58 (2H, m), 7.41e7.43 (3H, m), 5.71 (1H, dd, J¼9.1, 3.7 Hz), 3.77
(3H, s), 3.70 (3H, s), 3.55 (3H, s), 3.01 (1H, dd, J¼16.9, 3.7 Hz), 2.93
(1H, dd, J¼16.9, 9.1 Hz); HRESIMS m/z 401.0818 [MþNa]þ (calcd for
D
1272, 1109, 995 cmꢀ1
;
1H and 13C NMR spectral data: see Tables 2
C
16H17F3O7Na 401.0819).
and 4; HRESIMS m/z 771.2622 [MþNa]þ (calcd for C40H44O14Na
(R)-MTPA ester of dimethyl D
-tartarate: 1H NMR (500 M, CD2Cl2)
771.2623).
dH 7.50e7.53 (4H, m), 7.39e7.47 (6H, m), 6.00 (2H, s), 3.75 (6H, s),
3.38 (6H, s); HRESIMS m/z 633.1162 [MþNa]þ (calcd for
3.3.8. Sarglabolide H (8). White, amorphous powder; [
ꢀ39.0 (c 0.28, MeOH); UV (MeOH) lmax (log ε) 213 (4.40) nm;
CD (MeOH,
a
]23 D
C
26H24F6O10Na 633.1166).
(R)-MTPA ester of dimethyl L
-tartarate: 1H NMR (500 M, CDCl3)
D
ε) lmax 384 (þ2.93), 364 (ꢀ0.65), 337 (ꢀ1.63),
dH 7.61e7.63 (4H, m), 7.35e7.40 (6H, m), 5.86 (2H, s), 3.57 (6H, s),
324 (ꢀ1.66), 296 (ꢀ1.20), 251 (þ1.82), 217 (ꢀ5.69) nm; IR (KBr)
nmax 3448, 2938, 2855, 1736, 1658, 1436, 1381, 1275, 1116,
3.55 (6H, s); HRESIMS m/z 633.1168 [MþNa]þ (calcd for
C26H24F6O10Na 633.1166).
997 cmꢀ1 1H and 13C NMR spectral data: see Tables 2 and 4;
;
HRESIMS m/z 799.2939 [MþNa]þ (calcd for C42H48O14Na
3.4.2. HPLC analysis of (R)-MTPA esters of dimethyl malate and di-
methyl tartarate. The authentic (R)-MTPA ester of dimethyl
malate and the authentic (R)-MTPA ester of dimethyl -malate were
analyzed on an Agilent 1200 series instrument using a DAD de-
m). The
799.2936).
D-
L
3.3.9. Sarglabolide I (9). White, amorphous powder; [
(c 0.29, MeOH); UV (MeOH) lmax (log ε) 214 (4.48) nm; CD (MeOH,
ε) lmax 378 (þ3.89), 355 (þ2.52), 319 (ꢀ2.24), 254 (þ3.41), 220
(ꢀ11.3) nm; IR (KBr) nmax 3442, 2936, 2857, 1737, 1652, 1438, 1380,
a
]23 D ꢀ68.3
tector and a shim-pack VPeODS column (150ꢂ4.6 mm, 5
m
D
running conditions still included a flow rate of 1 mL/min, a column
temperature of 25 ꢁC, and a detection wavelength at 220 nm. Their
retention times (tR) were 6.52 and 7.72 min, respectively, with
isocratic elution of MeOH/H2O (65:35, v/v). The retention times of
1270, 1120, 982 cmꢀ1 1H and 13C NMR spectral data: see Tables 3
;
and 4; HRESIMS m/z 575.2254 [MþNa]þ (calcd for C31H36O9Na
575.2252).
the authentic (R)-MTPA esters of dimethyl
D-tartarate and dimethyl
L-tartarate were 5.89 and 6.07 min, respectively, with isocratic
3.3.10. Sarglabolide J (10). White, amorphous powder; [
ꢀ71.0 (c 0.28, MeOH); UV (MeOH) lmax (log ε) 217 (4.20) nm; CD
(MeOH,
ε) lmax 366 (ꢀ0.51), 351 (þ1.03), 296 (ꢀ1.22), 253 (þ3.13),
213 (ꢀ9.83) nm; IR (KBr) nmax 3439, 2938, 2860, 1734, 1658, 1436,
a
]23 D
elution of MeOH/H2O (80:20, v/v). The final (R)-MTPA esters pre-
pared from 1e6 and 10e11 were also analyzed under the above
conditions.
D
1377, 1276, 1118, 989 cmꢀ1 1H and 13C NMR spectral data: see
;
Tables 3 and 4; HRESIMS m/z 803.2886 [MþNa]þ (calcd for
3.5. Inhibitory activity assay on NO production
C
41H48O15Na 803.2885).
Raw264.7 cells were seeded into a 96-well plate (105 cells per
well) and pretreated with a range of concentrations of sesquiter-
pene dimers for 1 h, followed by incubation with or without LPS
(100 ng/mL) for 24 h. The supernatant (50 mL) was mixed with an
equal volume of Griess reagent in a 96-well plate for 15 min at room
temperature before measuring the optical density at 570 nm using
3.3.11. Sarglabolide K (11). White, amorphous powder; [
ꢀ79.3 (c 0.39, MeOH); UV (MeOH) lmax (log ε) 219 (4.31) nm; CD
(MeOH,
a]23 D
D
ε) lmax 392 (þ2.09), 365 (ꢀ2.41), 337 (ꢀ2.41), 253
(þ4.07), 215 (ꢀ11.7) nm; IR (KBr) nmax 3438, 2938, 2859, 1734, 1658,
1436, 1376, 1276, 1116, 991 cmꢀ1; 1H and 13C NMR spectral data: see

5370
P. Wang et al. / Tetrahedron 71 (2015) 5362e5370
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Acknowledgements
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708e712; (e) Fang, P. L.; Cao, Y. L.; Yan, H.; Pan, L. L.; Liu, S. C.; Gong, N. B.; Lu, Y.;
This research work was financially supported by the National
Natural Sciences Foundation of China (81430092, 31470416), the
Program for New Century Excellent Talents in University, Ministry of
Education of China (NCET-2013-1035), the Project Funded by the
Priority Academic Program Development of Jiangsu Higher Educa-
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Supplementary data
Supplementary data associated with this article (HRMS, NMR
and CD spectra of new compounds, and HPLC chromatograms of
prepared compounds) can be found in the online version at http://
dx.doi.org/10.1016/j.tet.2015.05.112.
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References and notes
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