Synthesis and biological evaluation of cytotoxic activity of novel anthracene l-rhamnopyranosides

Article abstract of DOI:10.1016/j.bmc.2010.05.064

A series of anthracene l-rhamnopyranosides were designed and synthesized in a practical way and their cytotoxic activity was examined in vitro. Most compounds exhibited both potent cytotoxicity against several tumor cell lines and high DNA binding capacity. The preliminary results showed that subtle modifications of rhamnosyl moiety in anthracene rhamnosides with acetyl group had a selective toxicity for different tumor cells and the displacement of C-10 carbonyl group in emodin by acetylmethylene group was helpful to improve the inhibitory activity. Lipophilicity of the anthracene glycosides was not a crucial factor for cytotoxicity and most molecules with good cytotoxicity could inhibit the catalytic activity of Top2α.

Full text of DOI:10.1016/j.bmc.2010.05.064

Bioorganic & Medicinal Chemistry 18 (2010) 5183–5193
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
Synthesis and biological evaluation of cytotoxic activity of novel anthracene
L-rhamnopyranosides
a,
Gaopeng Song c, , Hongchun Liu b, , Wei Zhang a, Meiyu Geng b, , Yingxia Li
*
*
a School of Pharmacy, Fudan University, Shanghai 201203, China
b Division of Antitumor Pharmacology, Shanghai Institute of Materia Medica Chinese Academy of Sciences, Shanghai 201203, China
c College of Resources and Environment, South China Agricultural University, Guangzhou 510642, China
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of anthracene L-rhamnopyranosides were designed and synthesized in a practical way and their
Received 25 March 2010
Revised 21 May 2010
Accepted 22 May 2010
Available online 31 May 2010
cytotoxic activity was examined in vitro. Most compounds exhibited both potent cytotoxicity against
several tumor cell lines and high DNA binding capacity. The preliminary results showed that subtle mod-
ifications of rhamnosyl moiety in anthracene rhamnosides with acetyl group had a selective toxicity for
different tumor cells and the displacement of C-10 carbonyl group in emodin by acetylmethylene group
was helpful to improve the inhibitory activity. Lipophilicity of the anthracene glycosides was not a crucial
factor for cytotoxicity and most molecules with good cytotoxicity could inhibit the catalytic activity of
Keywords:
Anthracene
Derivatives
Synthesis
L-rhamnopyranosides
Top2a.
Ó 2010 Elsevier Ltd. All rights reserved.
Cytotoxicity
DNA binding
1. Introduction
chains such as polymethyleneamine, sugar or heterocycle to emo-
din, was usually effective to gain higher antitumor activity.7,8 We
are more attracted by two natural emodin glycosides 20,30-di-O-ace-
As is well known, proliferative disorders are expected to be one
of the major causes of death in the 21st century. Although many
strategies can be followed by drug designers in order to identify
new chemical entities for a more effective treatment of cancer,
the crucial decision is always the selection of a suitable starting
point from the vast chemical space.1 It is the chemical modification
of bioactive components from medicinal herbs that is one of the
most common approaches in drug discovery and improvement of
therapeutic properties.2 Many natural and synthetic compounds
based on tricyclic planar chromophore framework, fully or par-
tially consisting of anthraquinone, anthrapyrazole, or acridine,
show interesting cytostatic and antitumor properties.3,4
Emodin, as an important component of a Chinese herb, has re-
ceived considerable attention by many synthetic chemists and bio-
chemists. Structurally it belongs to anthraquinones as do
daunorubicin and mitoxantrone which are some of the most pow-
erful cytostatics. Recently it was reported that emodin could induce
the apoptosis of certain cancer cells.5,6 However, emodin showed
low DNA binding affinity, and low or insignificant cytotoxicity
against various cancer cells.2 It was proved that the addition of side
tylfrangulin A (1) and frangulin B (2) (Fig. 1), which bear L-rhamno-
syl moieties at C3–OH of emodin and showed much more cytotoxic
activity against KB cells than emodin,9,10 indicating that such sugar
appendages lead to conspicuous changes of their antitumor activ-
ity.9 Another two natural products 3 and 4 (Fig. 1), analogs of glyco-
side 1 with two acetyl groups on the different hydroxyls of
rhamnosyl moiety, were isolated by Peter and Abegaz,11 while their
antitumor activity has not been reported up to now.
With the continuous interest in the effect of sugar attach-
ments to a planar aromatic molecule on the biological activity
and in order to search for potential new antitumor agents, we
decided to investigate the effect of subtle modifications of
rhamnosyl moiety of emodin rhamnosides on the tumor cell
growth inhibitory activity. Here, we would like to report the syn-
thesis of three natural emodin glycosides 2, 3 and 4 along with
their analogs 5, 6 and 7 (Fig. 1), which bear the L-rhamnosyl moi-
eties with acyl modification. Another three emodin derivatives 8,
9 and 10 (Fig. 1) were also provided by the installation of
rhamnosyl residue onto 1,8-di-O-methoxy-emodin and 10-acet-
yl-emodin in order to study the influence of subtle modifications
of emodin skeleton on the tumor cell growth inhibitory activity.
Both cytotoxic activity and DNA binding capacity of all natural
and designed compounds were evaluated in vitro. The results
obtained have rendered important clues to the understanding
of the cytotoxic profile for these types of compounds.
* Corresponding authors. Tel.: +86 21 51980127; fax: +86 21 51980127 (Y.X.L.);
tel.: +86 21 50806702; fax: +86 532 50806722 (M.Y.G.).
E-mail addresses: mygeng@mail.shcnc.ac.cn (M. Geng), liyx417@fudan.edu.cn (Y.
Li).
These authors contributed equally to this work.
0968-0896/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2010.05.064

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G. Song et al. / Bioorg. Med. Chem. 18 (2010) 5183–5193
OH
OH
O
O
OR
OR
2
O
2
O
CH
O
3
CH
3
O
R
3
R O
O
3
R O
1
R O
2
AcO
R O
1
AcO
5 R =R =n-PrCO, R =H;
8 R =H, R =Me, R =CO;
1 R =R =Ac, R =H;
1
2
3
1
2
3
1
2
3
6 R =R =H, R =Ac;
9
R =Ac, R =H, R =Ac;
2 R =R =R =H;
1
2
3
1 2 3
1
1
2
3
3
10 R =R =H; R =Ac
3 R =R =Ac, R =H;
1
2
3
2
7 R =R =Ac, R = 2',3'-di-O
1 2 3
4 R =R =Ac, R =H;
2
3
1
acetyl-L-rhamnopyranosyl
Figure 1. Chemical structures of anthracene glycosides 1–10.
provide 29, which was subjected to the Lev cleavage with hydra-
zine acetate to obtain the target compound 7 smoothly.
2. Results and discussion
2.1. Chemistry
Rhamnosides of emodin derivatives 8, 9, 10 were prepared as
outlined in Scheme 4. Treatment of the known compound 3012
with MeI in the presence of K2CO3 afforded intermediate 31, which
was subjected to hydrazine acetate to cleave the Lev group, fur-
nishing the target compound 8. Acetylation of compound 3212
led to the formation of the target compound 9 as a diastereoisomer
mixture along with 1,8-O-diacetate byproduct 33. The ratio of each
diastereoisomer for compounds 9 and 33 was about 3:1 and 4:1,
respectively, which could be determined by NMR. However, Séve-
net and co-workers9 reported only one pure diastereoisomer of 9
was afforded under the similar conditions. The preparation of the
target compound 10 was first tried by the similar route as that
for 9. Therefore, intermediate 34 was first synthesized from com-
pound 35, which was afforded by reducing the known compound
30 with Zn–AcOH. During a trial of the preparation of 10 by treat-
ing 34 with hydrazine acetate, we found that two pairs of the meso
and racemic bianthrones 369 were obtained without the target
compound 10 observed. Then we replaced the Lev group in 34 with
benzyl group. Thus treatment compound 1 with benzyl trichloro-
acetimidate 3714 was performed under the promotion of TfOH to
provide compound 38, which was then reduced by Zn–AcOH and
followed by acetylation to furnish 40. Finally debenzylation was
carried out by hydrogenolysis using Pd/C to provide the target
compound 10 as a diastereoisomer mixture, of which the ratio of
each diastereoisomer was about 100:1, which was determined by
NMR.
We have reported the successful synthesis of compound 1
previously by glycosylation of 1,8-O-di-n-hexanoyl emodin12 with
L-rhamnopyranosyl trichloroacetimidate under the promotion of
BF3ꢀEt2O, followed by deprotection of Hex groups in the presence
of PhSH and DBU.12 In the present study, the synthesis of target
compounds 2–6 was done by the similar route as that for com-
pound 1 described previously by us.12
First four trichloroacetimidate donors 11–14 were prepared as
shown in Scheme 1, respectively. Treatment of the known com-
pound 1513or 1613 with levulinic acid in the presence of EDCꢀHCl
and DMAP afforded compound 17 or 18, respectively. Selective
cleavage of PMB at C3–OH of known compound 1913 was per-
formed smoothly with DDQ, and then the subsequent acylation
gave compound 20. The known compound 2113 was subjected to
removal of the 2,3-O-isopropylidene group and then butyrylation
of the corresponding OH to provide compound 22. Hydrolysis of
17, 18, 20 or 22 with N-bromosuccinimide (NBS) in acetone–H2O,
followed by treatment with CCl3CN and DBU gave trichloroacetim-
idate 11–14, respectively.
The preparation of the target compounds 2–6 was performed as
shown in Scheme 2. With the known acceptor 2312 and required
donors 11–14 in hand, the coupling reactions were performed un-
der the promotion of BF3ꢀEt2O to provide the desired
rhamnosylanthraquinones 24–27. The subsequent deprotection
of the n-hexanoyl group and the Lev group with hydrazine acetate
was carried out simultaneously to afford compounds 3–6. To the
best of our knowledge, this was the first report that phenol ester
was removed successfully with hydrazine acetate, which greatly
facilitated the synthesis of emodin glycosides.12 Cleavage of all
phenol and alkyl esters of the intermediate 24 was performed
smoothly with MeONa to provide 2 in 85.7% yield. Thus, the total
2.2. Cytotoxicity against tumor cells
To examine the potential ability of the natural and artificially
designed anthracene L-rhamnopyranosides 1–10, both their cyto-
toxicity and DNA binding capacity were tested in vitro, respec-
tively. Table 1 shows the IC50 values of compounds 1–10 and 33
against three types of tumor cells in culture. The results indicate
that (a) in the case of the emodin rhamnopyranosides 1–7, most
compounds except 3 and 5 exhibited better cytotoxicity against
the three tumor cells than emodin, which proved that the addition
synthesis of three natural occurring anthraquinone L-rhamnopyr-
anosides 2, 3 and 4 was achieved for the first time.
The synthesis of the target compound 7 was depicted in
Scheme 3. With the acceptor 1 and donor 2812 in hand, their cou-
pling reaction was performed under the promotion of TMSOTf to
of
L-rhamnosyl residue was critical to improve cytotoxicity. (b)
NH
STol
STol
O
CCl3
a
O
O
b
AcO
R2O
AcO
R4O
O
AcO
OR1
OR3
R4O
OR3
11 R3=Ac, R4=Lev;
14 R3=R4=Lev;
15 R1=Ac, R2=H;
16 R1=R2=H;
17 R3=Ac, R4=Lev;
18 R3=R4=Lev;
Scheme 1.1. Reagents and conditions: (a) EDCꢀHCl, DMAP, levulinic acid, CH2Cl2, 83.5% for 17, 97.5% for 18; (b) (i) NBS, acetone–H2O; (ii) DBU, CNCCl3, CH2Cl2.

G. Song et al. / Bioorg. Med. Chem. 18 (2010) 5183–5193
5185
NH
STol
STol
O
CCl3
a
O
O
b
AcO
PMBO
AcO
AcO
O
AcO
OLev
OLev
20
AcO
OLev
12
19
Scheme 1.2. Reagents and conditions: (a) (i) DDQ; (ii) Ac2O, DMAP, pyridine, 90.0% for two steps; (b) (i) NBS, acetone–H2O; (ii) DBU, CNCCl3, CH2Cl2.
NH
STol
STol
O
CCl3
a
O
O
b
LevO
21
LevO
O
LevO
O
n-PrCOO
O
OOCPr-n
n-PrCOO
OOCPr-n
22
13
Scheme 1.3. Reagents and conditions: (a) (i) 80% AcOH; (ii) n-PrCOCl, DMAP, pyridine, 72.4% over two steps; (b) (i) NBS, acetone–H2O; (ii) DBU, CNCCl3, CH2Cl2.
NH
OHex
OHex
OHex
OHex
24-27
O
O
O
CCl
3
a
+
O
R O
3
O
HO
CH
CH
R O
3
3
2
OR
1
O
O
O
R O
23
3
11-14
R O
2
OR
1
11 R =R =Ac, R =Lev;
1
2
1
1
3
3
2
2
2
1
24 R =R =Ac, R =Lev;
1 3 2
12 R =R =Ac, R =Lev;
25 R =R =Ac, R =Lev;
2 3 3
13 R =R =n-PrCO, R =Lev;
4
26 R =R =n-PrCO, R =Lev;
1 2 3
14 R =R =Lev, R =Ac.
c
3
27 R =R =Lev, R =Ac.
1
2
3
OH
OH
O
OH
OH
O
O
3 R =R =Ac, R =H;
1
3
2
4 R =R =Ac, R =H;
2
1
3
2
1
b
5 R =R =n-PrCO, R =H;
3
O
CH
O
CH
3
6 R =R =H, R =Ac.
3
1
2
3
O
2
O
O
HO
R O
3
HO
R O
2
3, 4, 5, 6
OH
OR
1
Scheme 2. Reagents and conditions: (a) BF3ꢀEt2O, CH2Cl2, 98.0% for 24, 98.2% for 25, 96.9% for 26, 93.8% for 27; (b) AcOH–NH2NH2, 77.8% for 3, 78.2% for 4, 75.6% for 5, 75.2%
for 6; (c) MeONa, 85.7%.
OH
O
O
OH
OH
O
O
OH
NH
O
CCl3
b
a
1
+
O
CH3
O
CH3
LevO
AcO
O
OAc
LevO
O
HO
AcO
AcO
O
O
O
O
O
AcO
AcO
AcO
AcO
OAc
OAc
28
29
7
Scheme 3. Reagents and conditions: (a) TMSOTf, CH2Cl2, 94.1%; (b) AcOH–NH2NH2, 76.2%.
Among compounds 1–7, compound 1 showed the strongest cyto-
toxicity against KB and HL-60 cells, while compound 4 exhibited
stronger cytotoxicity against MDA-MB-231 than the other emodin
rhamnopyranosides, indicating subtle modifications of rhamnosyl
moiety with acetyl group had a selective toxicity for different tu-
mor cells. (c) The influence of the length of acyl chain on cytotox-
icity was clear when compared compound 1 and 5. (d) The
decreased inhibition of compound 7 against KB and HL-60 cells
(about eightfold and fourfold) comparing with 1 suggested intro-
ducing more sugar residue did not favor the activity. (e) Blocking
both C1–OH and C8–OH of compound 1 with methyl group (8) re-
sulted in a loss of antitumor activity, which proved that both C1–
OH and C8–OH of emodin were essential for the activity. (f) Much
stronger inhibition of 10 than 1 (about 10-fold increase) suggested
replacing C-10 carbonyl group of emodin with acetylmethylene
group favored the activity.
Compound
9 displayed the good cytotoxicity among the
compounds above. In order to investigate its cell selectivity, cyto-
toxic activity against a normal cell line, human microvascular
endothelial cell (HMEC), was tested. The IC50 value of compound

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G. Song et al. / Bioorg. Med. Chem. 18 (2010) 5183–5193
OH
OH
OAc
OAc
OH
OH
O
O
O
a
+
O
O
O
Ac
Ac
O
O
O
AcO
AcO
HO
AcO
32
AcO
AcO
9
33
d
OAc
OAc
OAc
OH
OH
O
OMe
OMe
OMe
OMe
O
O
O
c
O
O
O
O
1
O
O
O
HO
O
LevO
AcO
HO
8
AcO
31
AcO
OAc
OAc
OAc
c
OH
OH
O
OH
OH
O
O
OH
OH
O
a
O
O
O
Ac
O
LevO
AcO
O
O
LevO
LevO
34
AcO
AcO
OAc
OAc
OAc
35
30
OH
c
OH
O
c
OH
OH
O
O
HO
R=
RO
AcO
O
OAc
H
H
OR
Ac
O
HO
AcO
10
AcO
O
OH
OH
36
OH
OH
OH
OH
O
O
OH
OH
O
O
NH
d
e
O
CCl3
+
O
O
O
O
1
O
O
BnO
AcO
O
HO
BnO
39
37
AcO
38
AcO
OAc
OAc
OAc
O
OH
OH
O
OH
OH
a
f
O
O
Ac
Ac
O
O
BnO
40
10
HO
AcO
AcO
OAc
OAc
Scheme 4. Reagents and conditions: (a) Ac2O, pyridine, 42.6% for 9, 38.7% for 34, 40.6% for 40; (b) K2CO3, MeI, acetone, 95.3%; (c) AcOH–NH2NH2, 91.3%; (d) Zn/AcOH, 79.4%;
(e) 37, TfOH, CH2Cl2, 67.8%; (f) Pd/C, H2, 90.4%.
9 against HMEC was 16.2
as much as against tumor cells. The result suggested that com-
pound 9 had cell selectivity to a certain extent.
l
M, which was reduced almost 20 times
each compound 1–10 and 33. All the compounds 1–10 and 33
showed similar lipophilicity with log P values in the range of
ꢁ1.18 to ꢁ1.68 (Table 2). Lipophilicity did not exert a significant
effect on cytotoxicity for compounds, pointing out that lipophilic-
ity of the molecules was not a crucial factor for cytotoxicity.
2.3. Prediction of lipophilicity
The partition coefficient log P is a parameter which describes
the manner in which a drug partitions between polar and non-po-
lar phases, and it has been demonstrated to be an indispensable
tool in predicting the transport and activity of drugs. Table 2 gath-
ered the values of log P, determined by using ACD lab program for
2.4. DNA binding properties
Competitive displacement (C50) fluorometric assays with DNA-
bound ethidium can be used15 to determine ‘apparent’ equilibrium
constants (Kapp) for drug binding, as the C50 value is approximately

G. Song et al. / Bioorg. Med. Chem. 18 (2010) 5183–5193
5187
Table 1
cell-free system. As shown in Figure 2, in the absence of com-
pounds, kDNA was decatenated to minicircles which disappeared
in the presence of adriamycin and compound 1, 2, 6, 7, 9, 33, indi-
cating that compound 1, 2, 6, 7, 9, 33 could inhibit the catalytic
IC50 cytotoxicity values (lM) of anthracene L-rhamnopyranosides against tumor cells
(data derived from the mean of three independent assays)
Compound
KB
HL-60
MDA-MB-231
activity of Top2a.
1
2
4
6
7
9
10
33
1.1
2.1
>20
>20
8.3
0.7
0.3
1.1
>20
>20
3.6
>20
>20
1.2
7.9
>20
0.8
0.4
1.7
>20
>20
15.7
>20
>20
11.8
1.1
0.8
1.5
>20
>20
3. Conclusions
A series of novel anthracene rhamnopyranosides based on emo-
din and its derivatives were synthesized in a practical way and
their cytotoxic activity was tested in vitro. The preliminary results
3, 5, 8
Emodin
showed that the introduction of some L-rhamnosyl moieties to
emodin or its derivatives could significantly improve cytotoxicity,
notably subtle modifications of rhamnosyl moiety with acetyl
group had a selective toxicity for different tumor cells, both C1–
Table 2
Lipophilicity (log P) of the target compounds 1–10 and 33
OH and C8–OH of emodin L-rhamnopyranosides were essential
for antitumor activity, and displacement of C-10 carbonyl group
of emodin by acetylmethylene group was helpful to improve the
inhibitory activity. All anthracene glycosides had higher DNA bind-
ing constants but there was not quantitative correspondence be-
tween binding with calf thymus DNA and in vitro potency.
Lipophilicity of the molecules was not a crucial factor for cytotox-
icity and most anthracene glycosides with good cytotoxicity could
Compound
log P
1
2
3
4
5
6
7
8
9
ꢁ1.18
ꢁ1.44
ꢁ1.18
ꢁ1.18
0.87
ꢁ1.31
ꢁ1.63
ꢁ1.11
ꢁ1.25
ꢁ1.38
ꢁ1.68
inhibit the catalytic activity of Top2a.
10
33
4. General methods
Solvents were purified in a conventional manner. Thin layer
chromatography (TLC) was performed on precoated E. Merck Silica
Gel 60 F254 plates. Flash column chromatography was performed
on silica gel (200–300 mesh, Qingdao, China). Optical rotations
were determined with a Perkin–Elmer Model 241 MC polarimeter.
1H NMR and 13C NMR spectra were taken on a JEOL JNM-ECP 600
spectrometer with tetramethylsilane as an internal standard, and
chemical shifts are recorded in ppm values. Mass spectra were re-
corded on a Q-TOF Global mass spectrometer.
inversely proportional to the binding constant.16 The Kapp values of
anthracene -rhamnopyranosides 1–10 and 33 calculated for calf
L
thymus DNA, are reported in Table 3. All the glycosides had higher
DNA binding constants than emodin, indicating that the introduc-
tion of rhamnosyl residue dramatically increased the DNA binding
capacity of emodin or its derivatives. The relative binding affinities
as indicated by the binding constants Kapp are in the order of 1 > 8
and 9 > 33, which indicates that blocking the C1–OH and C8–OH in
emodin resulted in the reduction of the DNA binding capacity.
There is not quantitative correspondence between binding with
calf thymus DNA and in vitro potency. It seems that the best results
in cytotoxicity are obtained where high values of Kapp with calf
thymus DNA are combined with good cytotoxicity in vitro.
4.1. p-Tolyl 3-O-levulinyl-2,4-di-O-acetyl-1-thio-a-L-
rhamnopyranoside (17)
To a solution of compound 15 (2.0 g, 5.6 mmol) in dry CH2Cl2
(50 mL), levulinic acid (786.1 mg, 6.8 mmol), EDC (1.4 g,
6.8 mmol), and DMAP (68.9 mg, 0.6 mmol) were added under ar-
gon. The mixture was stirred for 12 h, diluted with CH2Cl2
(150 mL), washed with H2O (100 mL), 1 M HCl (2 ꢂ 100 mL), satu-
rated aqueous NaHCO3 (2 ꢂ 100 mL), and brine (2 ꢂ 100 mL), dried
over Na2SO4, and concentrated under reduced pressure. The resi-
due was purified by silica gel column chromatography (10:1, v/v,
petroleum ether/EtOAc) to give 17 (2.13 g, 83.5%) as a white solid;
2.5. Inhibitions of DNA topoisomerase II
a
DNA topoisomerase II (Top2) is a well-known anticancer target.
Anthracyclines antibiotics, especially adriamycin (ADM), are the
typical representatives of DNA topoisomerase II inhibitors. In order
to investigate whether anthracene
the similar mechanism as adriamycin, inhibition of TopoII
L
-rhamnopyranosides shared
activ-
Rf 0.44 (2:1, petroleum ether/EtOAc); ½a D25
ꢃ
ꢁ90.4 (c 0.10, CHCl3). 1H
a
ity was measured by the ATP-dependent decatenation of kDNA in a
NMR (CDCl3): d 7.35 (d, 2H, J = 8.0 Hz, Ar-H), 7.12 (d, 2H, J = 8.0 Hz,
Ar-H), 5.47 (dd, 1H, J = 3.2, 1.8 Hz, H-2), 5.33 (d, 1H, J = 1.4 Hz, H-1),
5.29 (dd, 1H, J = 10.1, 3.2 Hz, H-3), 5.15 (t, 1H, J = 9.9 Hz, H-4),
4.34–4.39 (m, 1H, H-5), 2.77–2.82, 2.55–2.66, 2.41–2.46 (m, 4H,
COCH2), 2.32 (s, 3H, PhCH3), 2.18, 2.14, 2.13 (each s, each 3H,
3 ꢂ COCH3), 1.24 (d, 3H, J = 6.0 Hz, 6-CH3); 13C NMR (CDCl3): d
206.2, 171.6, 170.2, 170.0, 138.2, 132.4, 129.9, 129.4, 86.0, 71.2,
70.8, 69.6, 67.6, 37.6, 29.7, 27.8, 21.1, 20.9, 20.8, 17.3; ESI MS: calcd
for [M+H]+ m/z 453.2; found, 453.2.
Table 3
DNA binding ability of the target compounds 1–10 and 33
Compound
Compound
Kapp (10ꢁ7 Mꢁ1
)
Kaapp (10ꢁ7 Mꢁ1
)
Emodin
0.0075
1.43
1.19
0.81
1.58
2.86
6
7
8
9
10
33
1.52
1.88
0.28
1.36
1.20
0.33
1
2
3
4
5
4.2. p-Tolyl 2,3-di-O-levulinyl-4-O-acetyl-1-thio-a-L-rhamnopy-
ranoside (18)
Kaapp ¼ ð1:26=C50Þ ꢂ 10ꢁ7 in which 1.26 is the concentration (
lM) of ethidium in
ethidium–DNA complex, C50 is drug concentration (lM) to effect 50% drop in
fluorescence of bound ethidium, and 107 is the value of Kapp assumed for ethidium
in the complex.
To a solution of compound 16 (1.0 g, 3.2 mmol) in dry THF
(50 mL), levulinic acid (0.95 g, 8.01 mmol), EDC (1.84 g,

5188
G. Song et al. / Bioorg. Med. Chem. 18 (2010) 5183–5193
Figure 2. Anthracene
L-rhamnopyranosides or adriamycin inhibited topo II-mediated kDNA decatenation in the cell-free system. The positions of kDNA and minicircles were
indicated.
9.60 mmol) and DMAP (0.16 g, 1.28 mmol) were added under ar-
gon. The mixture was stirred for 12 h and then concentrated. The
residue was dissolved with CH2Cl2 (150 mL), washed with H2O
(100 mL), 1 M HCl (2 ꢂ 100 mL), saturated aqueous NaHCO3
(2 ꢂ 100 mL), and brine (2 ꢂ 100 mL), dried over Na2SO4, and con-
centrated under reduced pressure. The residue was purified by
silica gel column chromatography (3:1, v/v, petroleum ether/
EtOAc) to give 18 (1.58 g, 97.5%) as a white solid; Rf 0.44 (1:1,
4.4. p-Tolyl 2,3-di-O-butyryl-4-O-levulinyl-1-thio-a-L-rhamno-
pyranoside (22)
The solution of compound 21 (1.51 g, 3.80 mmol) in 80%
AcOH (30 mL) was stirred for 1.5 h at 80 °C, then concentrated.
To a solution of the residue in dry pyridine (30 mL) were added
BtCl (1.18 mL, 11.40 mmol) and DMAP (0.26 g, 1.52 mmol) at
0 °C. The reaction mixture was stirred for an additional 8 h
while warming to room temperature. When TLC (petroleum
ether/EtOAc, 3:1) showed complete conversion, MeOH (2 mL)
was carefully added to destroy excess Bt2O, and the mixture
was diluted with CH2Cl2 (200 mL) The organic layer was shaken
with 1 M HCl (3 ꢂ 100 mL), followed by washing with saturated
aqueous NaHCO3 (3 ꢂ 100 mL) and water (3 ꢂ 100 mL). Finally
the organic layer was separated, dried over Na2SO4, and evapo-
rated to syrup. The crude product was purified by silica gel col-
umn chromatography (5:1, v/v, petroleum ether/EtOAc) to give
petroleum ether/EtOAc); ½a D25
ꢃ
ꢁ50.2 (c 0.11, CHCl3); 1H NMR
(CDCl3): d 7.40 (d, 2H, J = 8.0 Hz, Ar-H), 7.17 (d, 2H, J = 8.0 Hz,
Ar-H), 5.55 (dd, 1H, J = 3.6, 1.2 Hz, H-2), 5.36 (d, 1H, J = 1.4 Hz,
H-1), 5.32 (dd, 1H, J = 10.2, 3.6 Hz, H-3), 5.17 (t-like, 1H,
J = 10.2, 9.6 Hz, H-4), 4.40–4.43 (m, 1H, H-5), 2.49–2.87 (m, 8H,
4 ꢂ CH2), 2.38 (s, 3H, PhCH3), 2.25, 2.23, 2.18 (each s, each 3H,
3 ꢂ COCH3), 1.29 (d, 3H, J = 6.0 Hz, 6-CH3); 13C NMR (CDCl3): d
207.4, 206.3, 171.7, 170.8, 170.1, 138.6, 132.6 (two), 130.0
(two), 129.2, 86.0, 71.4, 70.9, 69.6, 67.7, 37.8, 37.7, 29.9, 29.8,
28.0, 27.9, 21.2, 20.9, 17.4; ESIMS: calcd for [M+H]+ m/z 509.2;
found, 509.2.
22 (1.40 g, 72.4%); Rf 0.83 (1:1, petroleum ether/EtOAc); ½a D25
ꢃ
ꢁ93.7 (c 0.11, CHCl3); 1H NMR (CDCl3):
d 7.37 (d, 2H,
J = 8.3 Hz, Ar-H), 7.13 (d, 2H, J = 8.2 Hz, Ar-H), 5.52 (dd, 1H,
J = 3.0, 1.2 Hz, H-2), 5.33 (d, 1H, J = 1.8 Hz, H-1), 5.31 (dd, 1H,
J = 10.1, 3.0 Hz, H-3), 5.16 (t-like, 1H, J = 10.2, 9.6 Hz, H-4),
4.34–4.40 (m, 1H, H-5), 2.74–2.78 (m, 2H, COCH2), 2.52–2.62
(m, 2H, COCH2), 2.37–2.38 (m, 2H, COCH2), 2.33 (s, 3H, PhCH3),
2.23–2.28 (m, 2H, COCH2), 2.20 (s, 3H, CH3CO), 1.60–1.69 (m,
4H, 2 ꢂ CH2), 1.26 (d, 3H, J = 6.6 Hz, CH3), 0.97 (t, 3H,
J = 7.8 Hz, CH3), 0.93 (t, 3H, J = 7.8 Hz, CH3); 13C NMR (CDCl3):
d 206.2, 173.3, 172.7, 171.9, 138.3, 132.6 (two), 130.2 (two),
129.6, 86.2, 71.5, 71.2, 69.1, 67.8, 37.8, 36.1, 35.9, 29.9, 28.0,
21.2, 18.5, 18.2, 17.4, 13.7; ESIMS: calcd for [M+Na]+ m/z
531.2; found, 531.2.
4.3. p-Tolyl 2-O-levulinyl-3,4-di-O-acetyl-thio-1-a-L-rhamnopy-
ranoside (20)
To a solution of compound 19 (1.24 g, 2.31 mmol) in CH2Cl2
(15 mL) and H2O (1 mL), DDQ (0.67 g, 2.96 mmol) was added under
argon. The mixture was stirred for 2 h, diluted with CH2Cl2
(100 mL), washed with saturated aqueous NaHCO3 (2 ꢂ 50 mL),
and brine (2 ꢂ 50 mL), dried over Na2SO4, and concentrated. The
residue was purified by silica gel column chromatography (2:1,
v/v, petroleum ether/EtOAc) to afford
a white solid (0.98 g,
90.7%); to a stirred solution of the white solid (0.68 g, 1.66 mmol)
in dry CH2Cl2 (30 mL) at 0 °C were added Ac2O (0.24 mL,
2.50 mmol), Et3N (0.69 mL, 4.98 mmol) and DMAP (40.5 mg,
0.33 mmol). The mixture was stirred for 12 h, diluted with CH2Cl2
(100 mL), washed with 1 M HCl (2 ꢂ 50 mL), saturated aqueous
NaHCO3 (2 ꢂ 50 mL), and brine (2 ꢂ 50 mL), dried over Na2SO4,
and concentrated to dryness. The residue was purified by silica
gel column chromatography (3:1, v/v, petroleum ether/EtOAc) to
give compound 20 (0.70 g, 99.2%); Rf 0.47 (1:1, petroleum ether/
4.5. General procedure for the preparation of different suitable
protected rhamnopyranosyl trichloroacetimidate (11–14)
To a stirred solution of 17, 18, 20, 22 (1.0 equiv) in acetone and
H2O (v/v = 9:1) at ꢁ20 °C was added NBS (2.0 equiv). After 20 min,
the reaction was quenched with saturated aqueous NaHCO3 and
concentrated. The residue was diluted with CHCl3 and washed
with saturated aqueous NaHCO3, brine, dried over Na2SO4, and
concentrated in vacuo. The residue was purified by silica gel col-
umn chromatography (petroleum ether/EtOAc) to afford each
product. To a stirred solution of above product (1 equiv) and
CCl3CN (6.0 equiv) in dry CH2Cl2 at 0 °C was added DBU (0.5 equiv).
After 2 h, the solution was concentrated. The residue was purified
fast by silica gel column chromatography (3:1, v/v, petroleum
ether/EtOAc) to afford crude 11–14, which could be used directly
in the next step.
EtOAc); ½a 2D5
ꢃ
ꢁ60.4 (c 0.17, CHCl3); 1H NMR (CDCl3): d 7.42 (d,
2H, J = 8.0 Hz, Ar-H), 7.20 (d, 2H, J = 8.0 Hz, Ar-H), 5.57 (dd, 1H,
J = 3.0, 1.2 Hz, H-2), 5.39 (d, 1H, J = 1.4 Hz, H-1), 5.35 (dd, 1H,
J = 10.1, 3.0 Hz, H-3), 5.19 (t, 1H, J = 10.2 Hz, H-4), 4.42–4.47 (m,
1H, H-5), 2.40 (s, 3H, Ar-CH3), 2.20, 2.15, 2.09 (each s, each 3H,
3 ꢂ COCH3), 1.31 (d, 3H, J = 6.0 Hz, 6-CH3); 13C NMR (CDCl3): d
206.1, 171.7, 170.1, 170.0, 138.3, 132.6, 130.1, 129.4, 86.0, 715,
71.3, 69.4, 67.7, 37.9, 29.9, 28.1, 21.2, 20.9, 20.7, 17.4; ESIMS: calcd
for [M+H]+ m/z 453.2; found, 453.2.

G. Song et al. / Bioorg. Med. Chem. 18 (2010) 5183–5193
5189
4.6. General procedure for the preparation of 1,8-di-O-n-hexa-
(two), 22.5, 21.7, 18.5, 18.3, 17.5, 14.3, 13.7; ESIMS: calcd for
noyl-3-(20,30,40-substituted-
27)
a
-L
-rhamnopyranosyl)-emodin (24–
[M+Na]+ m/z 851.4; found, 851.4.
4.6.4. 1,8-Di-O-n-hexanoyl-3-(20,30-di-O-levulinyl-40-O-acetyl-
L-rhamnopyranosyl)-emodin (27)
a-
To a solution of compound 23 (1.0 equiv), appropriate rhamno-
pyranosyl trichloroacetimidate 11–14 (1.2 equiv) and 4 Å molecu-
lar sieves in dry CH2Cl2 (20 mL) was added BF3ꢀEt2O (1 equiv) at
0 °C under argon. The reaction mixture was allowed to stir for
2 h under this condition, while warmed to room temperature until
TLC indicated that the reaction was complete. The reaction was
quenched by Et3N (five drops) and concentrated. The residue was
purified by silica gel column chromatography (5:1?2:1, v/v, petro-
leum ether/EtOAc) to give a appropriate compound 24–27.
A yellow solid, yield 93.8%; Rf 0.10 (2:1, petroleum ether/
EtOAc); ½a 2D5
ꢃ
ꢁ50.7 (c 0.10, CHCl3); 1H NMR (CDCl3): d 7.98 (d,
1H, J = 1.2 Hz, Ar-H), 7.83 (d, 1H, J = 2.6 Hz, Ar-H), 7.16 (d, 1H,
J = 1.3 Hz, Ar-H), 7.03 (d, 1H, J = 2.4 Hz, Ar-H), 5.61 (d, 1H,
J = 1.8 Hz, H-10), 5.41–5.44 (m, 1H, H-20, H-30), 5.14 (t, 1H,
J = 10.3 Hz, H-40), 3.86–3.89 (m, 1H, H-50), 2.24–2.80 (m, 12H,
6 ꢂ CH2CO), 2.46 (s, 3H, Ar-CH3), 2.20 (s, 3H, CH3CO), 2.18 (s,
3H, CH3CO), 2.09 (s, 3H, CH3CO), 1.80–1.82 (m, 4H, 2 ꢂ CH2),
1.40–1.44 (m, 8H, 4 ꢂ CH2), 1.19 (d, 3H, J = 6.0 Hz, CH3), 0.94 (t,
3H, J = 7.1 Hz, CH3), 0.93 (t, 3H, J = 7.1 Hz, CH3); 13C NMR (CDCl3):
d 206.4, 206.1, 182.0, 179.6, 172.3, 172.0, 171.8, 171.1, 170.0,
159.6, 150.4, 146.0, 136.2, 134.2, 131.0, 126.0, 123.4, 121.1,
118.0, 112.0, 95.5, 70.2, 69.2, 68.9, 68.0, 37.9, 37.8, 34.4 (two),
31.6, 29.9, 29.8, 28.0 (two), 24.3 (two), 22.5, 21.7, 20.9, 17.5,
14.1; ESIMS: calcd for [M+Na]+ m/z 873.3; found, m/z 873.3.
4.6.1. 1,8-Di-O-n-hexanoyl-3-(20,40-di-O-acetyl-30-O-levulinyl-
-rhamnopyranosyl)-emodin (24)
a-
L
An orange solid, yield 98.0%; Rf 0.18 (2:1, petroleum ether/
EtOAc); ½a 2D5
ꢃ
ꢁ78.7 (c 0.11, CHCl3); 1H NMR (CDCl3): d 7.97 (s-like,
1H, Ar-H), 7.83 (t, 1H, J = 2.4 Hz, Ar-H), 7.16 (s-like, 1H, Ar-H),
7.02 (t, 1H, J = 2.4 Hz, Ar-H), 5.63 (s-like, 1H, H-10), 5.46 (td, 1H,
J = 10.3, 3.6 Hz, H-30), 5.40 (dd, 1H, J = 3.2, 1.8 Hz, H-20), 5.19
(td, 1H, J = 10.2, 2.4 Hz, H-40), 3.85–3.89 (m, 1H, H-50), 2.54–2.79
(m, 8H, 4 ꢂ CH2CO), 2.46 (s, 3H, Ar-CH3), 2.19 (s, 3H, CH3CO),
2.16 (s, 3H, CH3CO), 2.09 (s, 3H, CH3CO), 1.78–1.82 (m, 4H,
2 ꢂ CH2), 1.38–1.42 (m, 8H, 4 ꢂ CH2), 1.23 (dd, 3H, J = 6.0,
1.8 Hz, CH3), 0.92–0.94 (m, 6H, 2 ꢂ CH3); 13C NMR (CDCl3): d
206.2, 182.0, 179.6, 172.3, 172.0, 171.8, 170.2, 170.1, 159.6,
152.4, 150.4, 146.0, 136.2, 134.2, 131.0, 126.0, 123.4, 121.1,
118.0, 111.9, 95.5, 70.3, 69.2, 68.9, 68.1, 37.8, 34.4 (two), 31.6,
29.8, 27.9, 24.3, 22.5, 21.7, 20.9, 20.7, 17.5, 14.1; ESIMS: calcd
for [M+Na]+ m/z 817.3; found, 817.3.
4.7. General procedure for the preparation of 3-(20,30,40-substi-
tuted-a-L-rhamnopyranosyl)-emodin (3–6)
To a stirred solution of 24–27 (1 equiv) in CH2Cl2 and CH3OH
(v/v, 1:1) was added NH2NH2–HOAc (10 or 20 equiv). After 5 h,
the solution was concentrated. Then the residue was purified by
silica gel column chromatography (petroleum ether/acetone) to af-
ford compound 3–6, respectively.
4.7.1. 3-(20,40-Di-O-acetyl-
a-L-rhamnopyranosyl)-emodin (3)
A red solid, yield 77.8%; Rf 0.41 (2:1, petroleum ether/acetone);
4.6.2. 1,8-Di-O-n-hexanoyl-3-(30,40-di-O-acetyl-20-O-levulinyl-
-rhamnopyranosyl)-emodin (25)
a-
½
a 2D5
ꢃ
ꢁ82.8 (c 0.11, CHCl3); 1H NMR (CDCl3): d 12.20 (s, 1H, OH),
L
11.98 (s, 1H, OH), 7.58 (s-like, 1H, Ar-H), 7.40 (d, 1H, J = 2.4 Hz,
Ar-H), 7.04 (s, 1H, Ar-H), 6.84 (d, 1H, J = 2.4 Hz, Ar-H), 5.65 (s,
1H, H-10), 5.21–5.22 (m, 1H, H-20), 4.91 (t-like, 1H, J = 10.3,
9.6 Hz, H-40), 4.18–4.19 (m, 1H, H-30), 3.78–3.83 (m, 1H, H-50),
2.40 (s, 3H, Ar-CH3), 2.19 (s, 3H, CH3CO), 2.10 (s, 3H, CH3CO),
1.17 (d, 3H, J = 6.6 Hz, CH3); 13C NMR (CDCl3): d 191.1, 181.7,
171.5, 170.6, 165.0, 162.7, 162.4, 148.9, 135.5, 133.2, 124.7,
121.6, 113.7, 111.6, 109.5, 95.1, 74.2, 72.0, 68.3, 67.7, 22.3, 21.1,
17.5; HRESIMS: calcd for C25H23O11 499.1240; found, 499.1237.
A yellow solid, yield 98.2%; Rf 0.18 (2:1, petroleum ether/
EtOAc); ½a 2D5
ꢃ
ꢁ63.4 (c 0.10, CHCl3); 1H NMR (CDCl3): d 8.01 (d,
1H, J = 1.2 Hz, Ar-H), 7.87 (d, 1H, J = 2.6 Hz, Ar-H), 7.19 (d, 1H,
J = 1.2 Hz, Ar-H), 7.08 (d, 1H, J = 2.4 Hz, Ar-H), 5.65 (d, 1H,
J = 1.2 Hz, H-10), 5.45–5.47 (m, 1H, H-20, H-30), 5.17 (t-like, 1H,
J = 10.3, 9.7 Hz, H-40), 3.90–3.92 (m, 1H, H-50), 2.70–2.83 (m, 6H,
3 ꢂ CH2CO), 2.50 (s, 3H, Ar-CH3), 2.27–2.30 (m, 2H, CH2CO), 2.24
(s, 3H, CH3CO), 2.07 (s, 3H, CH3CO), 2.06 (s, 3H, CH3CO), 1.83–
1.86 (m, 4H, 2 ꢂ CH2), 1.42–1.46 (m, 8H, 4 ꢂ CH2), 1.22 (d, 3H,
J = 6.6 Hz, CH3), 0.97 (t, 3H, J = 7.1 Hz, CH3), 0.96 (t, 3H, J = 7.1 Hz,
CH3); 13C NMR (CDCl3): d 206.0, 182.0, 179.6, 172.3, 172.0, 171.7,
170.1, 170.0, 159.6, 152.4, 150.4, 146.0, 136.2, 134.2, 131.0,
126.0, 123.4, 121.1, 118.0, 112.0, 95.5, 70.6, 69.3, 68.6, 68.0, 38.0,
34.4 (two), 31.6, 29.9, 28.0, 24.3 (two), 22.5, 21.7, 20.8, 20.7,
17.5, 14.1; ESIMS: calcd for [M+Na]+ m/z 817.3; found, 817.3.
4.7.2. 3-(30,40-Di-O-acetyl-
a-L-rhamnopyranosyl)-emodin (4)
A red solid, yield 78.2%; Rf 0.40 (2:1, petroleum ether/acetone);
½
a 2D5
ꢃ
ꢁ145.1 (c 0.09, CHCl3); 1H NMR (CDCl3): d 12.27 (s, 1H, OH),
12.05 (s, 1H, OH), 7.64 (d, 1H, J = 1.2 Hz, Ar-H), 7.51 (d, 1H,
J = 2.4 Hz, Ar-H), 7.10 (s-like, 1H, Ar-H), 6.95 (d, 1H, J = 2.4 Hz,
Ar-H), 5.71 (d, 1H, J = 1.8 Hz, H-10), 5.42 (dd, 1H, J = 10.2, 2.4 Hz,
H-30), 4.91 (t-like, 1H, J = 10.3, 9.6 Hz, H-40), 4.31 (br s, 1H, H-20),
3.90–3.93 (m, 1H, H-50), 2.47 (s, 3H, Ar-CH3), 2.16 (s, 3H, CH3CO),
2.07 (s, 3H, CH3CO), 1.22 (d, 3H, J = 6.0 Hz, CH3); 13C NMR (CDCl3):
d 191.1, 181.6, 171.2 170.1 165.0, 162.7, 162.5, 148.9, 135.5, 133.1,
124.6, 121.5, 113.6, 111.5, 109.5 (two), 97.2, 71.3, 70.9, 69.1, 67.9,
4.6.3. 1,8-Di-O-n-hexanoyl-3-(20,30-di-O-butyryl-40-O-levulinyl-
a-
L-rhamnopyranosyl)-emodin (26)
A yellow solid, yield 96.9%; Rf 0.55 (2:1, petroleum ether/
EtOAc); ½a 2D5
ꢃ
ꢁ70.2 (c 0.11, CHCl3); 1H NMR (CDCl3): d 7.93 (s-like,
1H, Ar-H), 7.80 (d, 1H, J = 2.4 Hz, Ar-H), 7.11 (s-like, 1H, Ar-H), 7.00
(d, 1H, J = 2.4 Hz, Ar-H), 5.57 (d, 1H, J = 1.2 Hz, H-10), 5.43 (dd, 1H,
J = 10.2, 3.6 Hz, H-30), 5.40 (dd, 1H, J = 3.6, 1.8 Hz, H-20), 5.12 (t-like,
1H, J = 10.2, 9.6 Hz, H-40), 3.84–3.86 (m, 1H, H-50), 2.62–2.68 (m,
6H, 3 ꢂ CH2CO), 2.45–2.48 (m, 2H, CH2CO), 2.42 (s, 3H, Ar-CH3),
2.35–2.38 (m, 2H, CH2CO), 2.19–2.26 (m, 2H, CH2CO), 2.10 (s, 3H,
CH3CO), 1.74–1.79 (m, 4H, 2 ꢂ CH2), 1.62–1.67 (m, 4H, 2 ꢂ CH2),
1.54–1.58 (m, 2H, CH2), 1.16 (d, 3H, J = 6.0 Hz, CH3), 0.86–0.95
(m, 12H, 4 ꢂ CH3); 13C NMR (CDCl3): d 206.1, 182.0, 179.6, 172.7,
172.6, 172.3, 172.0, 171.8, 163.6, 159.7, 152.3, 150.4, 146.0,
136.2, 134.2, 131.0, 126.1, 123.4, 121.0, 118.0, 112.0, 95.7, 70.8,
69.0, 68.3, 68.1, 37.8, 36.1, 35.9, 34.4 (two), 31.6, 29.8, 28.0, 24.3
29.8, 22,3, 21.0, 20.9, 17.5; HRESIMS: calcd for
499.1240; found, 499.1243.
C25H23O11
4.7.3. 3-(20,30-Di-O-butyryl-
a-L-rhamnopyranosyl)-emodin (5)
A red solid, yield 75.6%; Rf 0.51(2:1, petroleum ether/ace-
tone); ½a 2D5
ꢃ
ꢁ119.8 (c 0.10, CHCl3); 1H NMR (CDCl3): d 12.20
(s, 1H, OH), 12.00 (s, 1H, OH), 7.59 (s-like, 1H, Ar-H), 7.45 (d,
1H, J = 1.8 Hz, Ar-H), 7.04 (s, 1H, Ar-H), 6.88 (d, 1H, J = 2.4 Hz,
Ar-H), 5.57 (d, 1H, J = 1.2 Hz, H-10), 5.42 (dd, 1H, J = 3.6, 1.8 Hz,
H-20), 5.31 (dd, 1H, J = 9.6, 3.6 Hz, H-30), 3.76–3.79 (m, 1H, H-
50), 3.70 (td, 1H, J = 10.2, 4.8 Hz, H-40), 2.42 (s, 3H, Ar-CH3),
2.24–2.32 (m, 4H, 2 ꢂ CH2CO), 1.64–1.70 (m, 4H, 2 ꢂ CH2), 1.32

5190
G. Song et al. / Bioorg. Med. Chem. 18 (2010) 5183–5193
(d, 3H, J = 6.0 Hz, CH3), 0.98 (t, 3H, J = 7.2 Hz, CH3), 0.94 (t, 3H,
J = 7.2 Hz, CH3); 13C NMR (CDCl3): d 191.1, 181.6, 173.9, 172.6,
164.9, 162.7, 162.5, 148.9, 135.5, 133.2, 124.6, 121.5, 113.6,
111.5, 109.6, 109.4, 95.7, 71.6, 71.2, 70.3, 69.3, 36.1, 22.3,
171.8, 170.0, 169.9, 169.8, 164.8, 162.6, 162.3, 148.8, 135.5,
133.1, 124.5, 121.4, 113.6, 111.6, 109.7, 109.1, 99.4, 95.2, 37.6,
29.7, 27.9, 22.2, 20.9, 20.8, 20.7, 18.1, 17.2; ESIMS: calcd for
[M+H]+ m/z 827.2; found: m/z 827.1.
18.6, 18.3, 17.7, 13.7 (two); HRESIMS: calcd for
555.1866; found, 555.1859.
C29H31O11
4.10. 3-(200,300-Di-O-acetyl-
a-L
-rhamnopyranosyl-(1?4)-20,30-di-
O-acetyl- -rhamnopyranosyl)-emodin (7)
a
-L
4.7.4. 3-(40-O-Acetyl-
a-L-rhamnopyranosyl)-emodin (6)
A red solid, yield 75.2%; Rf 0.12 (2:1, petroleum ether/acetone);
Compound 7 was prepared in a similar way as 3 in 76.2% yield;
½
a 2D5
ꢃ
ꢁ146.1 (c 0.10, CHCl3); 1H NMR (CDCl3): d 12.26 (s, 1H, OH),
Rf 0.43 (3:1, petroleum ether/acetone); ½a D25
ꢁ163.1 (c 0.13, CHCl3);
ꢃ
12.04 (s, 1H, OH), 7.62 (d, 1H, J = 1.2 Hz, Ar-H), 7.46 (d, 1H,
J = 2.4 Hz, Ar-H), 7.09 (s-like, 1H, Ar-H), 6.93 (d, 1H, J = 2.4 Hz, Ar-
H), 5.72 (d, 1H, J = 1.2 Hz, H-10), 4.89 (t, 1H, J = 9.6 Hz, H-40), 4.19
(dd, 1H, J = 3.6, 1.2 Hz, H-20), 4.10 (dd, 1H, J = 9.6, 3.6 Hz, H-30),
3.81–3.83 (m, 1H, H-50), 2.45 (s, 3H, Ar-CH3), 2.19 (s, 3H, CH3CO),
2.07 (s, 3H, CH3CO), 1.20 (d, 3H, J = 6.0 Hz, CH3); 13C NMR (CDCl3):
d 191.1, 181.8, 172.3, 165.0, 162.7, 162.6, 148.9, 135.5, 133.2,
124.7. 121.5, 113.7, 111.4, 109.5, 109.4, 97.3, 75.1, 70.4, 70.1,
67.2, 22.3, 21.1, 17.6; HRESIMS: calcd for C23H21O10 457.1135;
found, 457.1135.
1H NMR (CDCl3): d 12.24 (s, 1H, OH), 12.05 (s, 1H, OH), 7.64 (d, 1H,
J = 1.1 Hz, Ar-H), 7.52 (d, 1H, J = 2.6 Hz, Ar-H), 7.09 (d, 1H,
J = 0.8 Hz, Ar-H), 6.93 (d, 1H, J = 2.5 Hz, Ar-H), 5.59 (d, 1H,
J = 1.9 Hz, H-10), 5.47 (dd, 1H, J = 3.3, 1.8 Hz, H-20), 5.43 (dd, 1H,
J = 9.5, 3.3 Hz, H-30), 5.11 (dd, 1H, J = 3.3, 1.8 Hz, H-200), 5.03 (dd,
1H, J = 9.5, 3.3 Hz, H-300), 4.99 (d, 1H, J = 1.8 Hz, H-100), 3.77–3.91
(m, 3H, H-400, H-50, H-500), 3.64 (t, 1 H, J = 9.5 Hz, H-40), 2.46 (s,
3H, Ar-CH3), 2.18, 2.13, 2.11, 2.09 (each s, each 3H, CH3CO), 1.36
(d, 3H, J = 5.9 Hz, CH3), 1.34 (d, 3H, J = 6.2 Hz, CH3); 13C NMR
(CDCl3): d 191.1, 181.5, 171.2, 170.1, 169.8, 164.8, 162.6, 162.3,
148.8, 135.5, 133.1, 124.5, 121.5, 113.6, 111.6, 109.7, 109.2, 99.4,
95.2, 78.4, 71.8, 71.2, 71.1, 70.4, 69.8, 69.3, 68.5, 22.2, 20.9, 20.8,
20.7, 18.1, 17.3; HRESIMS: calcd for C35H37O17 729.2031; found,
729.2018.
4.8. 3-(a-L-Rhamnopyranosyl)-emodin (2)
To a stirred solution of 24 (0.40 g, 0.50 mmol) in CH2Cl2
(5 mL) and CH3OH (5 mL) was added MeONa (20 mg). The reac-
tion mixture was stirred at room temperature for 30 min, after
which the reaction mixture was neutralized with Dowex
50 ꢂ 8(H+) resin until pH 7, filtered and concentrated. The resi-
due was recrystallized from absolute ethanol to give compound
4.11. 1,8-Di-O-methxyl-3-(20,30-di-O-acetyl-40-O-levulinyl-
a-L-
rhamnopyranosyl)-emodin (31)
To a stirred solution of 30 (0.10 g, 0.17 mmol) in dry acetone
(10 mL) were added K2CO3 (1.16 g, 8.36 mmol) and MeI
(0.32 mL, 5.1 mmol). The reaction mixture was refluxed at
60 °C under argon for 24 h, then filtrated and concentrated in
vacuo. The residue was purified by silica gel column chromatog-
raphy (3:1, v/v, petroleum ether/acetone) to give a yellow solid
31 (100.5 mg, 95.3%) with Rf 0.17 (2:1, petroleum ether/ace-
2 (0.18 g, 85.7%); ½a D25
ꢃ
ꢁ104.6 (c 0.12, DMSO); 1H NMR (DMSO-
d6): d 11.98 (s, 1H, OH), 11.86 (s, 1H, OH), 7.41 (br s, 1H, Ar-H),
7.19 (d, 1H, J = 1.8 Hz, Ar-H), 7.11 (br s, 1H, Ar-H), 6.87 (d, 1H,
J = 1.8 Hz, Ar-H), 5.59 (s, 1H, H-10), 5.23 (d, 1H, J = 4.4 Hz, OH),
4.96 (d, 1H, J = 5.8 Hz, OH), 4.88 (d, 1H, J = 5.9 Hz, OH), 3.87–
3.89 (m, 1H, H-30), 3.65–3.3.69 (m, 1H, H-50), 3.41–3.45 (m,
1H, H-20), 3.31–3.34 (m, 1H, H-40), 2.39 (s, 3H, Ar-CH3), 1.14
(d, 3H, J = 6.2 Hz, CH3); 13C NMR (DMSO-d6): d 190.5, 181.4,
164.3, 163.2, 162.0, 149.1, 135.2, 133.2, 124.7, 121.1, 113.8,
111.2, 109.6, 109.0, 99.0, 72.1, 70.8, 70.7, 70.3, 22.1, 18.3; HRE-
SIMS: calcd for C21H19O9 415.1029; found, 415.1042.
tone); ½a 2D5
ꢃ
ꢁ101.3 (c 0.12, CHCl3); 1H NMR (CDCl3): d 7.65 (s-
like, 1H, Ar-H), 7.52 (d, 1H, J = 2.6 Hz, Ar-H), 7.10 (s-like, 1H,
Ar-H), 6.95 (d, 1H, J = 2.6 Hz, Ar-H), 5.66 (d, 1H, J = 1.9 Hz, H-
10), 5.54 (dd, 1H, J = 9.9, 3.3 Hz, H-30), 5.44 (dd, 1H, J = 3.3,
1.8 Hz, H-20), 5.19 (t, 1H, J = 9.9 Hz, H-40), 3.99, 3.98 (each s,
each 3H, each OCH3), 3.93–3.95 (m, 1H, H-50), 2.74–2.77 (m,
2H, CH2CO), 2.52–2.55 (m, 2H, CH2CO), (m, 2H, CH2CO), 2.47
(s, 3H, Ar-CH3), 2.21, 2.18, 2.10 (each s, each 3H, CH3CO), 1.22
4.9. 3-(200,300-Di-O-acetyl-400-O-levulinyl-
(1?4)-20,30-di-O-acetyl-
-rhamnopyranosyl)-emodin (29)
a-L-rhamnopyranosyl-
a-L
(d, 3H, J = 6.2 Hz, CH3); 13C NMR (CDCl3):
d 206.1, 183.9,
To
(260 mg, 0.53 mmol) and 4 Å molecular sieves in dry CH2Cl2
(20 mL) was added TMSOTf (15
L, 0.082 mmol) at ꢁ30 °C under
a
mixture of compound
1
(200 mg, 0.41 mmol), 28
181.7, 171.8, 170.3, 170.1, 161.7, 159.8, 159.5, 144.9, 137.9,
136.5, 134.4, 129.0, 128.2, 125.3, 119.7, 119.5, 118.9, 106.3,
105.0, 95.2, 70.8, 69.4, 68.6, 67.8, 56.7, 56.5, 37.7, 29.7, 29.4,
27.9, 22.7, 22.1, 21.5, 20.9, 20.8, 17.4; ESIMS: calcd for [M+H]+
m/z 627.2; found: m/z 627.2.
l
argon. The reaction mixture was allowed to stir for 1 h under
this condition, while warmed to room temperature until TLC
indicated that the reaction was complete. After the reaction
was quenched by Et3N (five drops), the mixture was concen-
trated. The obtained residue was purified by silica gel column
chromatography (5:1, v/v, petroleum ether/acetone) to give a
yellow solid 29 (0.32 g, 94.1%); Rf 0.40 (2:1, petroleum ether/
4.12. 1,8-Di-O-methxyl-3-(20,30-di-O-acetyl-
a-L-
rhamnopyranosyl)-emodin (8)
8 was prepared in a similar way as 3 in 91.3% yield; Rf 0.15 (2:1,
acetone);
½
a 2D5
ꢃ
ꢁ126.0 (c 0.10, CHCl3); 1H NMR (CDCl3):
d
petroleum ether/acetone); ½a D25
ꢃ
ꢁ117.3 (c 0.10, CHCl3); 1H NMR
12.25 (s, 1H, OH), 12.05 (s, 1H, OH), 7.65 (d, 1H, J = 1.5 Hz, Ar-
H), 7.53 (d, 1H, J = 2.6 Hz, Ar-H), 7.09 (d, 1H, J = 1.5 Hz, Ar-H),
6.93 (d, 1H, J = 2.5 Hz, Ar-H), 5.59 (d, 1H, J = 1.4 Hz, H-10), 5.48
(dd, 1H, J = 3.3, 1.9 Hz, H-20), 5.43 (dd, 1H, J = 9.5, 3.3 Hz, H-
300), 5.24 (dd, 1H, J = 9.5, 3.3 Hz, H-30), 5.13 (dd, 1H, J = 3.3,
1.8 Hz, H-200), 5.09 (t-like, 1H, J = 10.3, 9.9 Hz, H-400), 5.00 (d,
1H, J = 1.8 Hz, H-100), 3.87–3.97 (m, 2H, H-50, H-500), 3.78 (t, 1H,
J = 9.5 Hz, H-40), 2.73 (t, 2H, J = 6.2 Hz, CH2CO), 2.49–2.52 (m,
2H, CH2CO), 2.46 (s, 3H, Ar-CH3), 2.18, 2.17, 2.14, 2.10, 2.03
(each s, each 3H, CH3CO), 1.37 (d, 3H, J = 6.2 Hz, CH3), 1.22 (d,
3H, J = 6.4 Hz, CH3); 13C NMR (CDCl3): d 206.0, 191.1, 181.5,
(CDCl3): d 7.63 (s-like, 1H, Ar-H), 7.52 (d, 1H, J = 2.4 Hz, Ar-H),
7.10 (s-like, 1H, Ar-H), 6.96 (d, 1H, J = 2.4 Hz, Ar-H), 5.66 (d, 1H,
J = 1.8 Hz, H-10), 5.45 (dd, 1H, J = 3.0, 1.8 Hz, H-20), 5.39 (dd, 1H,
J = 9.6, 3.3 Hz, H-30), 3.99, 3.98 (each s, each 3H, each OCH3),
3.85–3.87 (m, 1H, H-50), 3.77 (t, 1H, J = 9.6 Hz, H-40), 2.47 (s, 3H,
Ar-CH3), 2.20, 2.12 (each s, each 3H, CH3CO), 1.35 (d, 3H,
J = 6.6 Hz, CH3); 13C NMR (CDCl3): d 183.9, 181.8, 171.0, 170.1,
167.4, 161.7, 159.8, 153.2, 144.9, 136.4, 134.5, 121.5, 119.7,
119.4, 119.0, 106.4, 105.3, 95.5, 71.6, 70.7, 70.1, 69.7, 56.7, 56.5,
26.0, 22.9, 22.7, 22.1, 21.0, 20.9, 17.7; HRESIMS: calcd for
C27H29O11 529.1710; found, 529.1721.

G. Song et al. / Bioorg. Med. Chem. 18 (2010) 5183–5193
5191
4.13. 3-(20,30,40-Tri-O-acetyl-
a
-
L
-rhamnopyranosyl)-10-acetyl-
½
a 2D5
ꢃ
ꢁ57.3 (c 0.16, CHCl3); 1H NMR (CDCl3): d 12.55 (s, 1H, OH),
emodin (9) and 1,8-di-O-acetyl-3-(20,30,40-tri-O-acetyl-
a-L
-
*12.53 (s, 1H, OH), 12.25 (s, 1H, OH), *12.24 (s, 1H, OH), 7.35 (t-like,
3H, J = 8.0, 6.6 Hz, Ph-H), 7.28–7.31 (m, 2H, Ph-H), 6.80 (s-like, 1H,
rhamnopyranosyl)-10-acetyl-emodin (33)
*
Ar-H), 6.71 (s-like, 1H, Ar-H), 6.69 (d, 1H, J = 1.4 Hz, Ar-H), 6.58
To a stirred solution of 32 (0.10 g, 0.21 mmol) in Ac2O (10 mL)
was added dry pyridine (125 L, 1.55 mmol). The reaction mixture
was stirred at room temperature for 6 h, then concentrated and
purified by silica gel column chromatography (5:1, v/v, petroleum
ether/acetone) to give a yellow solid 9 (50 mg, 42.6%); 1H NMR
(dd, 1H, J = 4.4, 2.2 Hz, Ar-H), 5.52 (d, 1H, J = 1.5 Hz, H-10), *5.49
(d, 1H, J = 1.1 Hz, H-10), 5.58 (dd, 1H, J = 3.7, 1.8 Hz, H-20), 5.47
(dd, 1H, J = 9.9, 3.3 Hz, H-30), *5.46 (dd, 1H, J = 9.9, 3.3 Hz, H-30),
l
*
5.42 (dd, 1H, J = 3.7, 1.8 Hz, H-20), 5.04 (s, 1H, H-10), 5.02 (s, 1H,
*
H-10), 4.72 (d, 1H, J = 11.3 Hz, Ph-CH2-1), 4.71 (d, 1H, J = 11.3 Hz,
*
(CDCl3): d 12.57 (s, 1H, OH), 12.55 (s, 1H, OH), 12.25 (s, 1H, OH),
Ph-CH2-1), 4.66 (d, 1H, J = 11.3 Hz, Ph-CH2-2), *4.65 (d, 1H,
J = 11.3 Hz, Ph-CH2-2), 3.81–3.88 (m, 1H, H-50), 3.59 (t, 1H,
J = 9.5 Hz, H-40), 2.37 (s, 3H, Ar-CH3), 2.20, 2.17, 2.02, (each s, each
3H, CH3CO), 1.33 (d, 3H, J = 6.2 Hz, CH3), *1.29 (d, 3H, J = 6.2 Hz,
CH3); 13C NMR (CDCl3): d 201.9, 201.8, 191.6, 191.5, 169.9, 169.8,
165.6, 165.5, 163.2, 162.1, 162.0, 148.4, 140.0 (two), 137.8, 137.5,
137.4, 128.4, 127.9, 127.6, 120.0, 117.7, 112.4, 110.3, 110.2,
108.1, 107.6, 103.8, 103.5, 103.6, 95.3, 95.2, 78.4, 75.2, 71.0, 69.7,
69.6, 69.1 (two), 59.0, 58.9, 24.7, 24.6, 22.1, 20.9, 17.9 (two);
ESIMS: calcd for [MꢁH]ꢁ m/z 617.2; found, 617.1.
*12.24 (s, 1H, OH), 6.82 (s-like, 1H, Ar-H), 6.71 (d, 2H, J = 1.4 Hz,
*
Ar-H), 6.70 (d, 2H, J = 2.9 Hz, Ar-H), 6.61 (d, 1H, J = 2.2 Hz, Ar-H),
*6.60 (d, 1H, J = 2.5 Hz, Ar-H), 5.56 (d, 1H, J = 1.5 Hz, H-10), *5.53
(d, 1H, J = 1.5 Hz, H-10), *5.46 (dd, 1H, J = 9.9, 3.7 Hz, H-30), 5.45
(dd, 1H, J = 9.9, 3.7 Hz, H-30), 5.42 (dd, 1H, J = 3.7, 1.8 Hz, H-20),
*
*
5.17 (t, 1H, J = 9.9 Hz, H-40), 5.16 (t, 1H, J = 9.9 Hz, H-40), 5.06 (s,
1H, H-10), 5.03 (s, 1H, H-10), 3.87–3.93 (m, 1H, H-50), 2.38 (s, 3H,
Ar-CH3), 2.22, 2.07, 2.06, 2.04 (each s, each 3H, CH3CO), 1.21 (d,
3H, J = 6.2 Hz, CH3), *1.20 (d, 3H, J = 6.2 Hz, CH3); 13C NMR (CDCl3):
d 202.0, 191.6 (two), 170.0 (two), 169.9, 165.7, 165.6, 163.3, 161.9,
161.8, 148.6, 140.1, 137.4, 120.0, 117.8, 112.4, 110.4, 108.0, 107.6,
103.8, 103.7, 95.3, 95.2, 70.6, 69.2, 69.1, 68.7, 68.6, 67.8 (two), 59.0,
58.9, 29.7, 24.7, 24.6, 22.1, 20.9, 20.8, 20.7, 17.5, 17.4; HRESIMS:
calcd for C29H29O12 569.1659; found, 569.1674. The other yellow
solid 33 (55 mg, 40.9%); 1H NMR (CDCl3): d 7.13 (br s, 2H, Ar-H),
4.16. 3-(20,30-Di-O-acetyl-40-O-levulinyl-
a-L-rhamnopyranosyl)-
10-methylene-emodin (35)
To a solution of compound 30 (0.35 g, 0.59 mmol) in AcOH
(20 mL) was added Zn (1.34 g, 20.48 mmol) at 80 °C under argon.
After stirred for 8 h, the mixture was filtrated and concentrated
in vacuo. The residue was purified by silica gel column chromatog-
raphy (3:1, v/v, petroleum ether/acetone) to give a yellow solid 35
*7.04 (d, 1H, J = 2.6 Hz, Ar-H), 7.02 (d, 1H, J = 2.6 Hz, Ar-H), 6.96
*
(br s, 2H, Ar-H), *6.88 (d, 1H, J = 2.2 Hz, Ar-H), *6.87 (d, 1H,
J = 2.6 Hz, Ar-H), 5.55 (s-like, 1H, H-10), *5.53 (s-like, 1H, H-10),
5.44 (dd, 1H, J = 9.9, 3.3 Hz, H-30), 5.41–5.42 (m, 1H, H-20), 5.16
(t, 1H, J = 9.9 Hz, H-40), 5.09 (s, 1H, H-10), *5.07 (s, 1H, H-10),
3.88–3.91 (m, 1H, H-50), 2.42 (s, 3H, Ar-CH3), 2.21, 2.20, 2.06,
(0.27 g, 79.4%) with Rf 0.48 (2:1, petroleum ether/acetone); ½a D25
ꢃ
ꢁ94.4 (c 0.11, CHCl3); 1H NMR (CDCl3): d 12.58 (s, 1H, OH), 12.25
(s, 1H, OH), 6.61 (d, 2H, J = 2.5 Hz, Ar-H), 6.59 (d, 2H, J = 1.1 Hz,
Ar-H), 5.58 (d, 1H, J = 1.4 Hz, H-100), 5.51 (dd, 1H, J = 10.3, 3.7 Hz,
H-30), 5.42 (dd, 1H, J = 3.7, 1.9 Hz, H-20), 5.18 (t, 1H, J = 9.8 Hz,
H-40), 4.24 (s, 2H, Ar-CH2), 3.93–3.94 (m, 1H, H-50), 2.74–2.77 (m,
2H, CH2CO), 2.52–2.55 (m, 2H, CH2CO), 2.36 (s, 3H, Ar-CH3), 2.20,
2.18, 2.09 (each s, each 3H, CH3CO), 1.22 (d, 3H, J = 7.3 Hz, CH3);
13C NMR (CDCl3): d 206.1, 192.1, 171.8, 170.2, 170.0, 165.1,
162.8, 161.4, 147.6, 143.8, 141.1, 119.7, 115.9, 113.4, 111.4,
107.2, 102.2, 95.2, 70.8, 69.4, 68.3, 67.7, 37.7, 32.9, 29.7, 27.8,
22.1, 20.9, 20.7, 17.4; HRESIMS: calcd for C30H31O12 583.1816;
found, 583.1821.
*
2.04 (each s, each 3H, CH3CO), 1.21 (d, 3H, J = 6.2 Hz, CH3), 1.20
(d, 3H, J = 6.2 Hz, CH3); 13C NMR (CDCl3): d 202.7, 202.5, 180.5,
180.3, 169.9, 169.8, 169.4 (two), 159.1, 159.0, 152.7, 150.8, 150.7,
145.3, 140.0, 137.7, 129.6, 129.0, 128.2, 126.3, 124.7, 121.9,
119.7, 115.2, 112.8, 112.4, 112.2, 112.1, 95.5, 70.5, 69.1 (two),
68.5, 67.8 (two), 60.1, 59.9, 53.4, 24.5, 24.4, 21.5, 21.1 (two),
20.8, 20.7 (two), 17.4 (two); HRESIMS: calcd for
655.2027; found, 655.2011.
C33H35O14
4.14. 3-(20,30-Di-O-acetyl-40-O-levulinyl-
a-L-rhamnopyranosyl)-
10-acetyl-emodin (34)
4.17. 3-(20,30-Di-O-acetyl-40-O-benzyl-
a-L-rhamnopyranosyl)-
Inasimilarwayas9with35insteadof32, 34wasaffordedin38.7%
yield. 1H NMR (CDCl3): d 12.79 (s, 1H, OH), *12.76 (s, 1H, OH), 12.06 (s,
1H, OH), *12.05 (s, 1H, OH), 6.97 (s-like, 2H, Ar-H), 6.96 (d, 2H,
J = 0.7 Hz, Ar-H), *6.84 (d, 2H, J = 2.9 Hz, Ar-H), *6.81 (s-like, 1H, Ar-
H), 6.80 (s-like, 1H, Ar-H), 5.63 (d, 1H, J = 1.5 Hz, H-10), *5.60 (d, 1H,
J = 1.5 Hz, H-10), 5.58 (dd, 1H, J = 3.7, 1.8 Hz, H-20), 5.47–5.51 (m,
1H, H-30), 5.18–5.23 (m, 1H, H-40), *5.05 (s, 1H, H-10), 5.03 (s, 1H, H-
10), 3.87–3.96 (m, 1H, H-50), 2.74–2.79 (m, 2H, CH2CO), 2.52–2.56
(m, 2H, CH2CO), 2.40 (s, 3H, Ar-CH3), *2.39 (s, 3H, Ar-CH3), 2.21,
2.20, 2.19, 2.18, 2.17, 2.10, 2.09 (each s, each 3H, CH3CO), 1.25 (d,
3H, J = 6.2 Hz, CH3), *1.23 (d, 3H, J = 6.2 Hz, CH3); 13C NMR (CDCl3): d
206.1, 200.9, 200.8, 191.6, 191.5, 171.8 (two), 170.2, 170.1 (two),
170.0, 164.5, 164.4, 163.1 (two), 157.9, 157.8, 148.8, 148.7, 140.1,
137.0 (two), 120.5, 120.4, 117.8 (two), 104.5, 104.2, 103.6, 103.5,
103.4, 96.1, 95.9, 70.7, 70.5, 69.2, 68.4, 68.3, 67.9, 59.5, 59.3, 37.7,
29.7, 27.9, 27.4, 26.8, 24.7, 22.3, 20.9, 20.7, 17.4, 17.3; HRESIMS: calcd
for C32H33O13 625.1921; found, 625.1949.
10-methylene-emodin (39)
Compound 39 was prepared in a similar way as 35 in 78.4%
yield; Rf 0.27 (3:1, petroleum ether/EtOAc); ½a D25
ꢁ130.2 (c 0.10,
ꢃ
CHCl3); 1H NMR (CDCl3): d 12.57 (s, 1H, OH), 12.26 (s, 1H, OH),
7.26–7.35 (m, 5H, Ph-H), 6.69 (s, 2H, Ar-H), 6.60 (s, 1H, Ar-H),
6.56 (s, 1H, Ar-H), 5.49–5.52 (m, 2H, H-20, H-30), 5.43 (s, 1H,
H-10), 4.72 (d, 1H, J = 11.0 Hz, Ph-CH2-1), 4.67 (d, 1H, J = 11.0 Hz,
Ph-CH2-2), 4.22 (s, 2H, Ar-CH2), 3.87–3.90 (m, 1H, H-50), 3.59 (t,
1H, J = 9.7 Hz, H-40), 2.35 (s, 3H, Ar-CH3), 2.20 (s, 3H, CH3CO),
2.02 (s, 3H, CH3CO), 1.32 (d, 3H, J = 6.4 Hz, CH3); 13C NMR (CDCl3):
d 192.1, 170.0, 169.9, 165.1, 162.7, 161.6, 147.5, 143.7, 141.1,
137.8, 128.5, 127.9, 127.6, 119.7, 115.9, 113.4, 111.2, 107.5,
102.0, 95.1, 78.5, 75.2, 71.2, 69.8, 69.0, 32.8, 22.1, 20.9 (two),
17.9; HRESIMS: calcd for C32H31O10 575.1917; found, 575.1920.
4.18. 3-(20,30-Di-O-acetyl-40-O-benzyl-
a-L-rhamnopyranosyl)-
emodin (38)
4.15. 3-(20,30-Di-O-acetyl-40-O-benzyl-
a-L-rhamnopyranosyl)-
10-acetyl-emodin (40)
To a solution of compound 1 (200 mg, 0.41 mmol), 37 (260 mg,
0.82 mmol) and 4 Å molecular sieves in dry CH2Cl2 (20 mL) was
By use of the same procedure as 9 starting from 39, 40 was syn-
thesized in 40.6% yield; Rf 0.56 (3:1, petroleum ether/acetone);
added TfOH (185
mixture was allowed to stir for 12 h under this condition, while
lL, 0.21 mmol) at 0 °C under argon. The reaction

5192
G. Song et al. / Bioorg. Med. Chem. 18 (2010) 5183–5193
warmed to room temperature until TLC indicated that the reac-
tion was complete. The reaction was quenched by Et3N (five
drops) and concentrated. The residue was purified by silica gel
column chromatography (5:1, v/v, petroleum ether/acetone) to
J = 9.5, 9.2 Hz, H-40), 2.39 (s, 3H, Ar-CH3), 2.20 (s, 3H, CH3CO),
2.19 (s, 3H, CH3CO), 2.18 (s, 3H, CH3CO), 2.17 (s, 3H, CH3CO), 2.12
(s, 3H, CH3CO), *1.36 (d, 3H, J = 6.4 Hz, CH3), 1.34 (d, 3H,
J = 6.4 Hz, CH3); 13C NMR (CDCl3): d 202.1, 201.8, 191.6, 191.5,
171.0, 169.9, 165.6, 165.5, 163.2, 162.1, 161.9, 148.5, 140.0 (two),
137.5, 137.4, 120.0, 117.7, 112.4, 110.3, 110.2, 108.1, 107.6,
103.8, 103.6, 95.5, 95.3, 71.6, 70.8, 70.0, 69.9, 69.4 (two), 59.0,
58.8, 29.7, 29.2, 24.6 (two), 22.1, 20.9, 20.8, 17.6, 17.5; HRESIMS:
calcd for C27H27O11 527.1553; found, 527.1566.
give a yellow solid 38 (0.16 g, 67.8%); ½a D25
ꢁ98.2 (c 0.12, CHCl3);
ꢃ
1H NMR (CDCl3): d 12.25 (s, 1H, OH), 12.06 (s, 1H, OH), 7.64 (d,
1H, J = 1.3 Hz, Ar-H), 7.50 (d, 1H, J = 2.3 Hz, Ar-H), 7.34–7.36 (m,
2H, Ph-H), 7.29–7.31 (m, 3H, Ph-H), 7.09 (br s, 1H, Ar-H), 6.91
(d, 1H, J = 2.7 Hz, Ar-H), 5.60 (d, 1H, J = 1.8 Hz, H-10), 5.49 (dd,
1H, J = 9.2, 3.2 Hz, H-30), 5.46 (dd, 1H, J = 3.2, 1.8 Hz, H-20), 4.73
(d, 1H, J = 11.0 Hz, Ph-CH2-1), 4.67 (d, 1H, J = 11.5 Hz, Ph-CH2-2),
3.84–3.88 (m, 1H, H-50), 3.60 (t-like, 1H, J = 9.6, 9.2 Hz, H-40),
2.45 (s, 3H, Ar-CH3), 2.21 (s, 3H, CH3CO), 2.03 (s, 3H, CH3CO),
1.32 (d, 3H, J = 6.4 Hz, CH3); 13C NMR (CDCl3): d 191.0, 181.5,
170.0, 169.8, 164.8, 162.5, 162.3, 148.7, 137.8, 135.3, 133.1,
129.1, 128.4, 127.9, 127.6, 124.5, 121.4, 113.5, 111.4, 109.5,
109.2, 95.3, 78.3, 75.1, 71.1, 69.6, 69.2, 22.2, 20.9, 17.9; HRESIMS:
calcd for C32H29O11 589.1710; found, 589.1701.
4.21. Cytotoxic assay
The cytotoxicity of compounds was examined using a normal
cell line, human microvascular endothelial cell line(HMEC) and a
panel of human tumor cell lines, including one human promyelo-
cytic leukemia cell line (HL-60), one human oral epidermoid carci-
noma cell line (KB), and one human breast carcinoma cell lines
(MDA-MB-231). Cells were seeded into 96-well plates and treated
in triplicate with gradient concentrations of compounds at 37 °C
for 72 h. Cytotoxicity to leukemia cells was assessed by MTT assay
as previously described.17,18 SRB was applied to adherent tumor
cells.18–20 The cytotoxicity of compounds was expressed as an
IC50, determined by the Logit method from at least three indepen-
dent experiments.
4.19. Dimerization of prinoidin (36)
To a stirred solution of 35 (0.10 g, 0.17 mmol) in CH2Cl2 (10 mL)
and CH3OH (10 mL) was added NH2NH2–HOAc (0.16 g, 1.7 mmol).
After 3 h, the solution was concentrated. Then the residue was
purified by silica gel column chromatography (3:1, v/v, petroleum
ether/acetone) to afford a yellow solid 36 (0.12 g, 73.5%); 1H NMR
(CDCl3): d 12.46 (s, 1H, OH), 12.19 (s, 1H, OH), 12.14 (s, 1H, OH),
12.04 (s, 1H, OH), 11.92 (s, 1H, OH), 11.84 (s, 1H, OH), 11.67 (s,
1H, OH), 6.97, 6.95 (each br s, each 1H, Ar-H), 6.93 (s-like, 1H,
Ar-H), 6.86 (br s, 1H, Ar-H), 6.81 (s-like, 1H, Ar-H), 6.73 (d, 1H,
J = 2.6 Hz, Ar-H), 6.69 (d, 1H, J = 2.2 Hz, Ar-H), 6.64, 6.63 (each br
s, each 1H, Ar-H), 6.50 (d, 1H, J = 2.5 Hz, Ar-H), 6.49 (d, 1H,
J = 2.2 Hz, Ar-H), 5.81 (d, 1H, J = 1.4 Hz, H-10), *5.61 (d, 1H,
4.22. Fluorescence binding studies
The fluorometric assays was described like that reported by
McConnaughie.15 The C50 values for ethidium displacement from
calf thymus DNA was determined using aqueous buffer (10 mM
Na2HPO4, 10 mM NaH2PO4, 1 mM EDTA, pH 7.0) containing
1.26
All measurements were made in 10 mm quartz cuvettes at
25 °C using Perkin–Elmer LS5 instrument (excitation at
lM ethidium bromide and 1 lM calf thymus DNA, respectively.
*
J = 1.8 Hz, H-10), 5.52 (dd, 1H, J = 3.3, 1.4 Hz, H-20), 5.49 (dd, 1H,
a
*
J = 3.7, 1.9 Hz, H-20), 5.44 (dd, 1H, J = 10.2, 3.7 Hz, H-30), 5.39 (dd,
522 nm; emission at 584 nm) following serial addition of aliquots
of a stock drug solution (ꢄ5 mM in DMSO). The C50 values are de-
fined as the drug concentrations which reduce the fluorescence of
the DNA-bound ethidium by 50% and are reported as the mean
from three determinations. Apparent equilibrium binding con-
*
*
1H, J = 3.7, 1.9 Hz, H-20), 5.36 (dd, 1H, J = 9.9, 3.7 Hz, H-30), 5.29
(dd, 1H, J = 3.0, 2.2 Hz, H-20), *5.19 (dd, 1H, J = 9.9, 3.7 Hz, H-30),
5.17 (br s, 1H, Ar-H), 4.53 (s, 1H, H-10), *4.49 (d, 1H, J = 3.7 Hz,
*
H-10), 4.46 (d, 1H, J = 4.0 Hz, H-10), 4.37 (s, 1H, H-10), 3.92–3.97
(m, 1H, H-40), 3.65–3.79 (m, 1H, H-50), 2.52, 2.50 (each s, each
3H, Ar-CH3), 2.24, 2.23, 2.22, 2.19, 2.17, 2.16, 2.15, 2.14, 2.13,
2.05 (each s, each 3H, CH3CO), 1.44 (d, 3H, J = 6.2 Hz, CH3), 1.42
stants were calculated from the C50 values (in
l
M) using the fol-
and with
lowing equation: Kapp = (1.26/C50) ꢂ 10ꢁ7Kethidium
,
a
value of Kethidium = 107 Mꢁ1 for ethidium bromide.21
*
*
(d, 3H, J = 6.2 Hz, CH3), 1.36 (d, 3H, J = 5.9 Hz, CH3), 1.35 (d, 3H,
J = 6.2 Hz, CH3); 13C NMR (CDCl3): d 190.6, 190.2, 171.9, 170.9
(two), 170.0 (two), 164.8, 164.4, 163.3, 162.3, 161.9, 161.2, 161.1,
159.8, 159.5, 129.7, 121.8, 121.1, 120.7, 120.6, 117.5, 117.2,
117.1, 113.3, 113.0, 111.1, 110.6, 11.0, 109.5, 108.6, 104.0, 101.8,
101.6, 95.6, 94.9, 94.5 (two), 72.1, 71.4, 71.3, 71.1, 70.8, 70.1,
70.0, 69.8, 69.7 (two), 69.6, 69.4, 56.6, 56.0, 55.7, 22.7, 22.3, 22.2,
21.9, 21.8, 21.1, 21.0, 20.9 (two), 20.8, 17.7, 17.6, 17.5 (two);
ESIMS: calcd for [MꢁH]ꢁ m/z 969.2; found: m/z 969.2.
Acknowledgment
This project was supported by the national Natural Basic Re-
search Program of China (No. 2003CB716400).
References and notes
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4.20. 3-(20,30-Di-O-acetyl-
a-L-rhamnopyranosyl)-10-acetyl-
emodin (10)
A suspension of 40 (0.11 g, 0.18 mmol) and Pd/C (80 mg, 10%) in
CH2Cl2–EtOH (1:1, 10 mL) was stirred under H2 for 12 h and then
filtered and concentrated. The residue was purified by silica gel
column chromatography (3:1, v/v, petroleum ether/acetone) give
10 (85 mg, 90.4%) with Rf 0.76 (2:1, petroleum ether/acetone);
½
a 2D5
ꢃ
ꢁ94.5 (c 0.11, CHCl3); 1H NMR (CDCl3): d 12.55 (s, 1H, OH),
*12.53 (s, 1H, OH), 12.24 (s, 1H, OH), *12.23 (s, 1H, OH), 6.80 (s,
*
1H, Ar-H), 6.70 (s-like, 2H, Ar-H), 6.59 (s, 1H, Ar-H), 5.55 (d, 1H,
*
J = 1.4 Hz, H-10), 5.51 (d, 1H, J = 1.4 Hz, H-10), 5.40 (dd, 1H, J = 2.9,
1.4 Hz, H-20), 5.30 (dd, 1H, J = 9.9, 3.7 Hz, H-30), 5.04 (s, 1H, H-
*
10), 5.01 (s, 1H, H-10), 3.76–3.82 (m, 1H, H-50), 3.73 (t-like, 1H,

G. Song et al. / Bioorg. Med. Chem. 18 (2010) 5183–5193
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