Three new indole alkaloid derivatives from the roots of Murraya paniculata

Article abstract of DOI:10.1080/10286020.2017.1327950

Three new indole alkaloid derivatives, named paniculidines D?F (1?3), and six known analogs (4?9) were isolated from the roots of Murraya paniculata. The structures were elucidated on the basis of comprehensive HRESIMS, UV, IR, and NMR spectroscopic data

Full text of DOI:10.1080/10286020.2017.1327950

Journal of Asian Natural Products Research
ISSN: 1028-6020 (Print) 1477-2213 (Online) Journal homepage: http://www.tandfonline.com/loi/ganp20
Three new indole alkaloid derivatives from the
roots of Murraya paniculata
Xiao-Ting Wang, Ke-Wu Zeng, Ming-Bo Zhao, Peng-Fei Tu, Jun Li & Yong Jiang
To cite this article: Xiao-Ting Wang, Ke-Wu Zeng, Ming-Bo Zhao, Peng-Fei Tu, Jun Li & Yong
Jiang (2017): Three new indole alkaloid derivatives from the roots of Murraya paniculata, Journal of
Asian Natural Products Research, DOI: 10.1080/10286020.2017.1327950
To link to this article: http://dx.doi.org/10.1080/10286020.2017.1327950
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Date: 22 May 2017, At: 08:46

Journal of asian natural Products research, 2017
https://doi.org/10.1080/10286020.2017.1327950
Three new indole alkaloid derivatives from the roots of
Murraya paniculata
Xiao-Ting Wang, Ke-Wu Zeng, Ming-Bo Zhao, Peng-Fei Tu, Jun Li and Yong Jiang
state Key laboratory of natural and Biomimetic drugs, school of Pharmaceutical sciences, Peking university,
Beijing 100191, china
ABSTRACT
ARTICLE HISTORY
received 17 March 2017
accepted 5 May 2017
Three new indole alkaloid derivatives, named paniculidines D‒F
(1‒3), and six known analogs (4‒9) were isolated from the roots
of Murraya paniculata. The structures were elucidated on the basis
of comprehensive HRESIMS, UV, IR, and NMR spectroscopic data
analysis and comparison with the data reported in literature. The
absolute configurations of new compounds were assigned via the
determination of specific optical rotation, Mosher′s method, and ECD
spectra. Compound 3 is the first heterodimer of C-N linked indole and
coumarin derivatives.
KEYWORDS
rutaceae; Murraya
paniculata; indole alkaloids;
heterodimer
OH
H3CO
HO
O
O
H
OH
N
N
H
H3CO
OCH3
3
1
Murraya paniculata
1. Introduction
e Murraya genus belongs to the Rutaceae family, including 14 species and 2 varieties all
over the world. Murraya paniculata (L.) Jack, is a shrub distributed widely in India, Southeast
Asia, and South China. e roots of M. paniculata have been used as a folk medicine for
the treatment of gout, contusion, and bone ache [1]. Previous phytochemical investigations
revealed that many bioactive compounds, such as indole alkaloids [1,2], coumarins [3–5],
and flavonoids [6–8], were isolated from M. paniculata, with the activities of anti-inflam-
matory, anti-implantation, antidiarrhoeal, anti-diabetic, antioxidant, antinociceptive, anti-
microbial, and anticancer effects [9–11].
Indole alkaloid derivatives are a type of very important heterocyclic compounds for the
drug discovery and cell biology study. ere has been an increasing interest in using the
indole alkaloid derivatives as bioactive molecules against inflammation, microbes, cancer,
CONTACT Jun li
lijun@bjmu.edu.cn; Yong Jiang
yongjiang@bjmu.edu.cn
supplemental data for this article can be accessed here https://doi.org/10.1080/10286020.2017.1327950.
© 2017 informa uK limited, trading as taylor & francis Group

2
X.-T. WANG ET AL.
4'
5'
10'
6'
6'
7'
3'
2'
O
R2
OH
14
O
14
13
12
4'
10'
9'
H
H3CO
HO
O
11
10
8'
8'
NH
12
12'
14'
O
11'
12'
OH
12
4
2
3
10
2
9
4
3'
5
6
2'
13'
N
8
N
R1
2
14'
H3CO
10
14
15'
N
6
8
7
N
H
8
H
4
OCH3
4 R1= H
R2= COOCH3
6
5 R1= OCH3 R2= CH2OH
1
6 R1= H
R2= CH2OH
3
2
Figure 1. the structures of compounds 1–6.
and various kinds of disorders in the human body [12]. As a continuation of a search for
indole analogs from Murraya species, we report here the isolation and structural eluci-
dation of three new indole alkaloids (1‒3) and six known analogs (4‒9) from the roots of
M. paniculata (Figure 1).
2. Results and discussion
e 95% aqueous EtOH extract of the roots of M. paniculata was suspended in H2O and
partitioned successively with petroleum ether and CHCl3. e CHCl3-soluble portion was
subjected repeatedly to silica gel and Sephadex LH-20 column chromatography (CC) fol-
lowed by semipreparative RP-HPLC to afford three new indole alkaloid derivatives, named
paniculidines D‒F (1‒3), and six known analogs, including paniculidines A‒C (4‒6) [1],
tanakine (7) [13], indol-3-carbaldehyde (8) [14], and yuehchukene (9) [15].
Paniculidine D (1) was obtained as a light brown oil, with [ꢀ]2D3 + 36.0 (c 0.10, MeOH).
Its molecular formula was determined as C14H19NO2 on the basis of a protonated ion at
m/z 234.1495 [M + H]+ in the positive HRESIMS and the 13C NMR data. e UV spectrum
showed a maximal absorption at 271 nm and the IR spectrum showed absorption bands
for aromatic ring (1601, 1499, and 1452 cm−1) functionality. e 1H NMR data (Table 1)
revealed the presence of a 3,7-disubstituted indole unit [δH 6.95 (1H, brs), 7.22 (1H, d,
J = 7.8 Hz), 7.03 (1H, t, J = 7.8 Hz), 6.65 (1H, d, J = 7.8 Hz)], three methylene signals [δH
2.71‒2.77, 2.81‒2.87 (each 1H, m); 1.50‒1.58, 1.82‒1.89 (each 1H, m); 3.49 (1H, dd, J = 10.5,
6.5 Hz), 3.57 (1H, dd, J = 10.5, 5.7 Hz)], one methine signal [δH 1.70‒1.77 (1H, m)], and one
methyl signal [δH 1.02 (3H, d, J = 6.7 Hz)]. e NMR spectroscopic data of 1 were similar
to those of paniculidine B (5) [1]. e main difference between these two compounds is
the methoxy group in 5 shifs from the nitrogen atom to the C-7 position of the indole unit
in 1, deduced from the HMBC correlations between H-5 and C-7/C-9, H-6 and C-4/C-5/
C-7/C-8, and OCH3-7 and C-7 (Figure 2). e sign of the specific optical rotation of 1 is
the same as that of 5, whose configuration is 12R. erefore, the structure of paniculidine
D (1) was established as (2R)-methyl-4-(7′-methoxy-indole-3′-yl)-1-butanol.
Paniculidine E (2) was obtained as a light brown oil, with[ꢀ]2D3 + 22.5 (c 0.08, MeOH). Its
positive mode HRESIMS showed a pseudomolecular ion at m/z 403.2377 [M + H]+, which,
in conjunction with the 13C NMR data, established a molecular formula of C26H30N2O2. e
1H NMR data (Table 1) revealed the presence of two 3-substituted indole units [δH 7.81 (1H,
brs), 6.91 (1H, brs), 7.59 (1H, d, J = 7.8 Hz), 7.10 (1H, overlapped), 7.19 (1H, overlapped),
7.33 (1H, d, J = 8.1 Hz); 7.83 (1H, brs), 6.92 (1H, brs), 7.60 (1H, d, J = 7.8 Hz), 7.10 (1H,
overlapped), 7.19 (1H, overlapped), 7.34 (1H, d, J = 8.1 Hz)], and two isopentenyl derivative

JOURNAL OF ASIAN NATURAL PRODUCTS RESEARCH
3
Table 1. 1h and 13c nMr spectral data of 1–3 (1h: 500 Mhz and 13c: 125 Mhz, in cdcl3).
1
2
3
Position
δH (J, Hz)
δC
δH (J, Hz)
δC
δH (J, Hz)
δC
2
3
4
5
6
7
8
9
10
11
12
13
6.95, brs
120.7
117.3
111.8
119.6
101.9
146.3
126.9
128.9
22.8
6.91, brs
121.2
116.0
119.0
119.3
122.1
111.2
136.5
127.6
7.50, brs
124.4
117.2
111.8
119.5
103.6
147.7
127.8
129.9
22.8
7.22, d (7.8)
7.03, t (7.8)
6.65, d (7.8)
7.59, d (7.8)
7.10, overlapped
7.19, overlapped
7.33, d (8.1)
7.13, d (7.9)
6.98, t (7.9)
6.69, d (7.9)
2.81‒2.87, m; 2.71‒2.77, m
1.82‒1.89, m; 1.50‒1.58, m
1.70‒1.77, m
2.76‒2.79, m
22.6 2.73‒2.81, m; 2.63‒2.71, m
33.7 2.08‒2.15, m; 1.79‒1.88, m
35.7
68.4
34.3 1.76‒1.85, m; 1.47‒1.54, m
33.4
35.8
68.4
2.52‒2.59, m
39.5
1.67‒1.74, m
3.57, dd (10.5,5.7);
3.49, dd (10.5,6.5)
177.0 3.51‒3.55, m; 3.43‒3.49, m
14
2′
3′
4′
5′
6′
7′
8′
9′
1.02, d (6.7)
16.7
1.22, d (6.9)
6.92, brs
17.4
121.5
116.7
119.1
119.3
122.1
111.2
136.5
127.6
23.0
0.98, d (6.7)
16.8
160.3
113.4
143.8
129.1
108.3
161.0
115.8
153.7
113.4
6.22, d (9.5)
7.57, d (9.5)
7.34, d (8.7)
6.82, d (8.7)
7.60, d (7.8)
7.10, overlapped
7.19, overlapped
7.34, d (8.1)
10′
2.81‒2.88, m; 2.76‒2.79,
m
1.79‒1.88, m; 1.58‒1.64,
m
11′
32.6
7.41, d (10.0)
5.47, d (10.0)
55.6
12′
13′
14′
15′
1.88‒1.95, m
3.97‒4.04, m
1.04, d (6.5)
33.9
69.2
17.0
77.1
144.3
114.5
16.8
4.93, s; 4.71, s
1.78, s
och3-7
och3-7′
nh-1
nh-1′
4.07, s
3.94, s
55.9
56.2
8.18, brs
7.81, brs
7.83, brs
Figure 2. the key hMBc correlations of compounds 1–3.
groups [δH 2.76‒2.79 (2H, m), 1.79‒1.88, 2.08‒2.15 (each 1H, m), 2.52‒2.59 (1H, m), 1.22
(3H, d, J = 6.9 Hz); 2.76‒2.79, 2.81‒2.88 (each 1H, m), 1.58‒1.64, 1.79‒1.88 (each 1H, m),
1.88‒1.95 (1H, m), 3.97‒4.04 (2H, m), 1.04 (3H, d, J = 6.5 Hz)]. ese data, along with 26
carbon resonances in the 13C NMR spectrum, suggested 2 to be a dimeric indole alkaloid
composed of one 2-methyl-4-(3-indolyl)-butyric acid and one paniculidine C (6) units [1].

4
X.-T. WANG ET AL.
ese two units were linked by an ester bond on the basis of the HMBC correlations of
H-13′ and C-13/C-11′/C-12′/C-14′. e absolute configuration of 2 was deduced as (12R,
12′R) via alkaline hydrolysis and comparison of the specific optical rotation with those in
literature [1]. us, the structure of paniculidine E (2) was elucidated as shown.
Paniculidine F (3) was obtained as a light yellow oil. Its molecular formula was assigned
13
as C29H33NO6 based on the C NMR spectroscopic data and a pseudomolecular ion at
m/z 492.2379 [M + H]+ was observed in the positive mode HRESIMS. e 1H NMR data
(Table 1) indicated the presence of a 7-methoxy-8-isopentenyl coumarin moiety similar to
auraptenol [16] [δH 6.22 (1H, d, J = 9.5 Hz), 7.57 (1H, d, J = 9.5 Hz), 6.82 (1H, d, J = 8.7 Hz),
7.34 (1H, d, J = 8.7 Hz), 3.94 (3H, s)], and an indole unit similar to compound 1 [δH 6.69
(1H, d, J = 7.9 Hz), 6.98 (1H, t, J = 7.9 Hz), 7.13 (1H, d, J = 7.9 Hz), 7.50 (1H, brs)]. ese
two units were linked through N-C-11′ deduced from the HMBC correlations of H-11′ and
C-2/C-8/C-7′/C-8′/C-9′/C-12′.
e coupling constant between H-11ʹ and H-12ʹ (J = 10.0 Hz) indicated that 3 is a threo
isomer. e absolute configuration of C-12′ was determined as S by the Mosher’s method
(Figure 3), and the absolute configuration of C-11′ was deduced as S. Moreover, the ECD
spectrum of 3 was calculated using the TDDFT method at the B3LYP/6-31G(d) level,
which is a powerful tool and widely used for the determination of absolute configuration
of natural products [17]. e calculated ECD spectrum of (11′S,12′S)-3 agreed well with
the experimental one (Figure 4). erefore, the absolute configuration of 3 was assigned as
(11ʹS,12ʹS), and the structure of paniculidine F (3) was elucidated as shown.
e roots of M. paniculata have been used as a folk medicine for the treatment of inflam-
mation-related diseases. us, in our study, all the isolates were tested for their inhibition
activities on NO production stimulated by lipopolysaccharide in BV-2 microglial cells.
However, these compounds showed no inhibitory effect at the concentration of 100 μM.
3. Experimental
3.1. General experimental procedures
Specific optical rotation data were acquired on a Rudolph Autopol III automatic polar-
imeter (Rudolph Research, Fairfield, New jersey, U.S.A.). UV spectra were recorded on a
Shimadzu UV-2450 spectrophotometer (Shimadzu Corporation, Kyoto, Japan). IR spectra
Figure 3. Δδ = δr − δs values obtained from the 1h nMr spectra of the MPa esters of 3.

JOURNAL OF ASIAN NATURAL PRODUCTS RESEARCH
5
Figure 4. calculated and experimental ecd spectra of 3.
were recorded on a ermo Nicolet Nexus 470 FT-IR spectrometer (ermo Nicolet, Vernon
Hills, Illinois, U.S.A.). ECD data were acquired on a JASCO 810 CD spectrophotometer
(Jasco Corporation, Tokyo, Japan). NMR spectra were recorded on a Varian INOVA-500
NMR spectrometer (Agilent Technologies, Santa Clara, California, U.S.A.), using CDCl3
as solvent and the chemical shifs were referenced to the solvent residual peak. HRESIMS
experiments were measured on a Waters Xevo G2 Q-TOF mass spectrometer (Waters MS
Technologies, Manchester, UK). Silica gel (100–200 mesh or 200–300 mesh, Qingdao Marine
Chemical Co. Ltd., China) and Sephadex LH-20 (Amersham Biosciences, Sweden) were
used for open CC. Preparative HPLC were carried out using a Agilent Zorbax Eclipse
XDB-C18 column (9.4 × 250 mm, 5 μm) on an Agilent 1260 system (Agilent Technologies
Inc., Santa Clara, California, U.S.A.) with a DAD detector. Fractions and compounds were
monitored at 210 nm and 330 nm. TLC analyses were carried out on the pre-coated silica
gel GF254 plates (Qingdao Marine Chemical Co. Ltd., China). Spots were visualized under
the UV lights (254 and 365 nm). All the solvents used for isolation were of analytical grade
and the solvents used for HPLC were of HPLC grade.
3.2. Plant material
e roots of Murraya paniculata were collected from Lihu Township, Guangxi Province,
China, in June 2015, and were identified by Prof. Peng-Fei Tu. A voucher specimen (No.
MP201506) has been deposited at the Herbarium of the Peking University Modern Research
Center for Traditional Chinese Medicine.
3.3. Extraction and isolation
e roots of M. paniculata (9.3 kg) were extracted three times with 95% aqueous EtOH at
room temperature. e extract was evaporated under reduced pressure, and the residue
(500 g) was suspended in H2O and partitioned successively with petroleum ether and CHCl3.
e CHCl3 extract (150 g) was subjected to silica gel CC and eluted with a stepwise gradient
of petroleum ether–EtOAc (7:3, 3:2, 2:3, 1:4, and 0:1, v/v) to afford nine fractions (A–I).

6
X.-T. WANG ET AL.
Fraction A (10 g) was separated on silica gel CC eluting with petroleum ether–acetone (10:1,
4:1, v/v) to afford six subfractions (A1–A6). Subfractions A4 (2 g) and A5 (2 g) were further
chromatographed over Sephadex LH-20 eluting with CH2Cl2–MeOH (1:1, v/v) to afford Frs.
A4-5 (0.3 g) and A5-4 (0.5 g), respectively, which were further purified by semipreparative
RP-HPLC using a mobile phase of MeCN–H2O (70:30, v/v, 2 ml/min) to give 9 (7 mg, tR
35.6 min) and 2 (5 mg, tR 17.9 min), respectively. Fraction B (15 g) was separated on silica
gel CC eluting with petroleum ether–acetone (4:1, v/v) to afford six fractions (B1–B6).
Subfraction B1 (3 g) was further chromatographed over Sephadex LH-20 (CH2Cl2–MeOH,
1:1, v/v) and ODS (MeOH–H2O, 7:3, v/v) to afford Fr. B1-5-31 (0.6 g), which was further
purified by semipreparative RP-HPLC using a mobile phase of MeCN–H2O (70:30, v/v,
2 ml/min) to give 4 (28 mg, tR 31.3 min) and 5 (21 mg, tR 24.4 min). Fraction C (18 g)
was separated on silica gel CC (CH2Cl2–acetone, 1:0–100:1, v/v) to afford four fractions
(C1–C4). Subfraction C3 (5 g) was chromatographed successively on silica gel (petroleum
ether–acetone, 3:1, v/v) and Sephadex LH-20 (CH2Cl2–MeOH, 1:1, v/v) CC to afford Fr.
C3-2-5 (2 g), which was further purified by semipreparative RP-HPLC using a mobile
phase of MeCN–H2O (35:65, v/v, 2 ml/min) to give 1 (11 mg, tR 39.0 min) and 6 (13 mg, tR
34.5 min). Fraction D (30 g) was separated on silica gel (petroleum ether–acetone, 7:3, v/v)
and Sephadex LH-20 (CH2Cl2–MeOH, 1:1, v/v) CC to afford Fr. D3-4-1 (1 g), which was
further separated by preparative TLC (petroleum ether–acetone, 3:2, v/v) to give 7 (3 mg)
and 8 (3 mg). Fraction E (30 g) was separated on silica gel (petroleum ether–acetone, 3:2,
v/v) and Sephadex LH-20 (CH2Cl2–MeOH, 1:1, v/v) CC to afford Fr. E4-3-3 (2 g), which
was further purified by semipreparative RP-HPLC using a mobile phase of MeCN–H2O
(40:60, v/v, 3 ml/min) to give 3 (3 mg, tR 60.5 min).
3.3.1. Paniculidine D (1)
Light brown oil,[ꢀ]2D3 + 36.0 (c 0.10, MeOH); UV (MeOH) λmax (log ε) 222 (4.40), 271 (3.55)
nm; IR (KBr) νmax 3399, 2918, 2851, 1713, 1601, 1578, 1499, 1452, 1374, 1259, 1034 cm−1;
1H and 13C NMR spectral data, see Table 1; HRESIMS: m/z 234.1495 [M + H]+ (calcd for
C14H20NO2, 234.1494).
3.3.2. Paniculidine E (2)
Light brown oil, [ꢀ]2D3 + 22.5 (c 0.08, MeOH); UV (MeOH) λ (log ε) 203 (4.52), 223
max
(4.69), 282 (3.96) nm; IR (KBr) νmax 3400, 2918, 2851, 1713, 1604, 1456, 1361, 1222, 1026,
530 cm−1; 1H and 13C NMR spectral data, see Table 1; HRESIMS: m/z 403.2377 [M + H]+
(calcd for C26H30N2O2, 403.2386).
3.3.3. Paniculidine F (3)
Light yellow oil,[ꢀ]23 + 17.5 (c 0.08, MeOH); UV (MeOH) λmax (log ε) 204 (4.68), 299 (4.03),
326 (3.98) nm; IR D(KBr) νmax 3445, 2918, 2850, 1735, 1713, 1604, 1363, 1029, 905, 836,
578 cm−1; 1H and 13C NMR spectral data, see Table 1; HRESIMS: m/z 492.2379 [M + H]+
(calcd for C29H34NO6, 492.2386).
3.4. Determination of absolute configuration of compound 2
Compound 2 (1.3 mg) and K2CO3 (2.2 mg) were dissolved in MeOH (2 ml) for 4 h at 80 °C.
e reaction product was acidized with 0.1 M HCl and then extracted with CH2Cl2 for three

JOURNAL OF ASIAN NATURAL PRODUCTS RESEARCH
7
times. Afer being concentrated to dryness, the organic residue was separated by semipre-
parative HPLC [1.0 ml/min, MeCN/0.1%HCOOH–H2O (45:55)] to yield 2-methyl-4-(3-
indolyl)-butyric acid (a), and paniculidine C (b) (each 0.3 mg) at 11.3 min and 12.7 min,
respectively. e structures of compounds a and b were identified by LC-MS (Figure S25,
Supporting Information) under the following conditions: an Agilent 1260 chromatograph
equipped with an Agilent Zorbax SB-Aq RP C18 column (4.6 × 250 mm, 5 μm); column
temperature: 35 °C; mobile phase: 0–30 min MeCN/0.1%HCOOH–H2O (10:90–100:0); flow
rate: 1.0 ml/min; UV detection wavelength: 210 nm. e molecular weights of a and b were
m/z 217 and 203, respectively. e signs of the specific optical rotation of a [[ꢀ]2D5 + 46.7
(c 0.03, MeOH)] and b [[ꢀ]25 + 53.3 (c 0.03, MeOH)] were the same as that of 6. Hence, the
absolute configuration of 2Dwas deduced as (12R, 12′R).
3.5. Preparation of the (R)- and (S)-MPA esters of 3
Compound 3 (1.0 mg) was dissolved in 350 μl of CH2Cl2, and DCC (0.8 mg), DMAP
(0.5 mg), and (R)-MPA (0.6 mg) were then added sequentially. e reaction mixture was
stirred for 16 h at room temperature. e crude products were separated by semiprepara-
tive HPLC [1.0 ml/min, MeCN/H2O (80:20)] to yield the (R)-MPA ester 3r at 6.5 min. In
a similar manner, (S)-MPA ester 3s was prepared by semipreparative HPLC [1.0 ml/min,
MeCN/H2O (80:20)] at 6.7 min, from the reaction of 3 (1.0 mg) with (S)-MPA.
(R)-MPA ester (3r): 1H NMR (CDCl3, 500 MHz): δH 7.55 (1H, d, J = 9.3 Hz, H-4′), 7.46
(1H, d, J = 10.2 Hz, H-11′), 7.43 (1H, s, H-2), 7.37 (1H, d, J = 8.7 Hz, H-5′), 7.04 (1H, d,
J = 7.8 Hz, H-4), 6.99 (1H, t, J = 7.8 Hz, H-5), 6.86 (1H, d, J = 8.7 Hz, H-6′), 6.73 (1H, d,
J = 7.8 Hz, H-6), 6.22 (1H, d, J = 9.3 Hz, H-3′), 4.89 (1H, s, H-14′), 4.64 (1H, s, H-14′), 4.12
(3H, s, OCH3-7), 4.07 (1H, m, H-13), 3.99 (3H, s, OCH3-7′), 3.93 (1H, m, H-13), 2.61 (1H,
m, H-10), 2.53 (1H, m, H-10), 1.80 (1H, m, H-11), 1.73 (1H, m, H-12), 1.67 (3H, s, H-15′),
1.62 (1H, m, H-11), 0.88 (3H, d, J = 6.6 Hz, H-14). (S)-MPA ester (3s): 1H NMR (CDCl3,
500 MHz): δH 7.53 (1H, d, J = 9.6 Hz, H-4′), 7.45 (1H, d, J = 10.2 Hz, H-11′), 7.42 (1H, s,
H-2), 7.32 (1H, d, J = 8.7 Hz, H-5′), 6.98 (1H, d, J = 7.7 Hz, H-4), 6.94 (1H, t, J = 7.7 Hz,
H-5), 6.79 (1H, d, J = 8.7 Hz, H-6′), 6.65 (1H, d, J = 7.7 Hz, H-6), 6.21 (1H, d, J = 9.6 Hz,
H-3′), 5.07 (1H, s, H-14′), 4.46 (1H, s, H-14′), 4.08 (3H, s, OCH3-7), 4.03 (1H, m, H-13),
3.92 (3H, s, OCH3-7′), 3.99 (1H, m, H-13), 2.60 (1H, m, H-10), 2.34 (1H, m, H-10), 1.80
(1H, m, H-11), 1.73 (1H, m, H-12), 1.62 (1H, m, H-11), 1.45 (3H, s, H-15′), 0.84 (3H, d,
J = 6.7 Hz, H-14).
Disclosure statement
No potential conflict of interest was reported by the authors.
Funding
is work was financially supported by National Natural Sciences Foundation of China [NSFC; grant
numbers 81473106, 81222051]; and National Key Technology R&D Program “New Drug Innovation”
of China [grant number 2012ZX09301002-002-002].

8
X.-T. WANG ET AL.
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