Synthesis and antitumor activity of novel podophyllotoxin derivatives against multidrug-resistant cancer cells

Article abstract of DOI:10.1080/10286020.2011.568941

Seven novel 4-N-substituted podophyllotoxin derivatives with indole rings were prepared and evaluated for cytotoxicity against human cancer cell lines HeLa, KB, KBV, K562, and K562/AO2. Most of them demonstrated improved antitumor activity and weak multidrug resistance compared to the drugs currently available.

Full text of DOI:10.1080/10286020.2011.568941

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Synthesis and antitumor activity of
novel podophyllotoxin derivatives
against multidrug-resistant cancer cells
Yong-En Guo a , Hong Chen b c , Song Zuo b c , Dai-Lin Liu b , Yan-
Ling Lu b c , Jing-Jing Lv b , Shao-Peng Wen d & Tong-Cun Zhang d
a Key Laboratory of Industrial Microbiology, Ministry of Education,
College of Biotechnology, Tianjin University of Science &
Technology , Tianjin, 300457, China
b Pharmacognosy Division, Medical College of Chinese People's
Armed Police Force , Tianjin, 300162, China
c Graduate School of Tianjin Medical University , Tianjin, 300070,
China
d Tianjin Key Laboratory of Industrial Microbiology, College of
Biotechnology, Tianjin University of Science & Technology ,
Tianjin, 300457, China
Published online: 29 Apr 2011.
To cite this article: Yong-En Guo , Hong Chen , Song Zuo , Dai-Lin Liu , Yan-Ling Lu , Jing-Jing Lv ,
Shao-Peng Wen & Tong-Cun Zhang (2011) Synthesis and antitumor activity of novel podophyllotoxin
derivatives against multidrug-resistant cancer cells, Journal of Asian Natural Products Research,
13:05, 417-424, DOI: 10.1080/10286020.2011.568941
To link to this article: http://dx.doi.org/10.1080/10286020.2011.568941
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Journal of Asian Natural Products Research
Vol. 13, No. 5, May 2011, 417–424
Synthesis and antitumor activity of novel podophyllotoxin derivatives
against multidrug-resistant cancer cells
Yong-En Guoa*, Hong Chenbc1, Song Zuobc, Dai-Lin Liub, Yan-Ling Lubc,
Jing-Jing Lvb, Shao-Peng Wend and Tong-Cun Zhangd2
aKey Laboratory of Industrial Microbiology, Ministry of Education, College of Biotechnology,
Tianjin University of Science & Technology, Tianjin 300457, China; Pharmacognosy Division,
b
c
Medical College of Chinese People’s Armed Police Force, Tianjin 300162, China; Graduate
School of Tianjin Medical University, Tianjin 300070, China; dTianjin Key Laboratory of Industrial
Microbiology, College of Biotechnology, Tianjin University of Science & Technology, Tianjin
300457, China
(Received 19 December 2010; final version received 2 March 2011)
Seven novel 4b-N-substituted podophyllotoxin derivatives with indole rings were
prepared and evaluated for cytotoxicity against human cancer cell lines HeLa, KB,
KBV, K562, and K562/AO2. Most of them demonstrated improved antitumor activity
and weak multidrug resistance compared to the drugs currently available.
Keywords: antitumor; podophyllotoxin; indole; prepare; cytotoxicity
1. Introduction
acquired drug resistance, and severe gastro-
intestinal disturbances promoted research-
ers to search after new podophyllotoxin
derivatives [9]. NK611, GL331, and TOP53
are under the clinical trials [10].
Prolonged treatment of carcinoma patients
with certain anticancer medicines can result
in the acquired multiple drug resistance
(MDR) [1], a case associated with the
overproduction of specific tubulin isotypes
and the decreased expression of topoisome-
rases, etc. [2,3]. Increasingly, severe MDR
of tumor is one of the main factors to cause
abortive chemotherapy. Seeking novel syn-
thetic antitumor agents to overcome MDR
has currently been the focus of oncology.
Podophyllotoxin 1 has important anti-
neoplastic and antiviral properties [4,5].
Since the 1950s, extensive structure modi-
fications have been performed to reduce its
toxic side effects. Its derivatives such as
etoposide (VP-16, 2) and teniposide (VM-
26) have been widely used as anticancer
drugs clinically to treat small cell lung
cancer, testicular carcinoma, and lymphoma
[6–8]. However, their low water solubility,
Previous studies showed that replace-
ment of the C-4 sugar moiety in VP-16 with
a non-sugar substituent through O-, S-, or N-
linkage was significant in overcoming
MDR. Generally, 4b-N-substituted podo-
phyllotoxin derivatives exhibit superior
anticancer activity compared to VP-16
against some of human cancer cell lines,
buttheO-andS-linkedderivativesarenotso
active as their N-linked congeners [11–14].
Indibulin 3 also shows significant
antitumor activity against a variety of
tumors in vitro and in vivo. It destabilizes
microtubules in the tumor cells and in a cell-
free system [15]. Further research revealed
that it was neither a substrate of p-gp170 nor
of multidrug resistance-associated protein
*Corresponding author. Email: guoye@tust.edu.cn
ISSN 1028-6020 print/ISSN 1477-2213 online
q 2011 Taylor & Francis
DOI: 10.1080/10286020.2011.568941
http://www.informaworld.com

418
Y.-E. Guo et al.
O
H3C
O
O
HO
OH
O
O
O
Cl
N
O
NH
O
N
O
H3CO
OCH3
OH
Indibulin 3
Etoposide 2
a. microtubulin inhibitor different from
traditional agents;
blocking cell cycle transition
b. lack of neurotoxicity;
small drug molecule;
a. topoisomerase II inhibitor
b. relatively severe toxicity;
low water solubility;
acquired multidrug-resistance;
gastrointestinal disturbances, etc.
efficacy against multidrug resistance.
R
N
O
O
O
O
HN
Cl
OCH3
OCH3
O
O
OCH3
Target compounds
Chart 1. Design of the novel podophyllotoxin derivatives.
(MRP), and retained its antitumor efficacy
in cell lines with MDR or MRP phenotypes.
Additionally, the administration of indibu-
lin to rats revealed no deficiency in motor
function and no change in nerve conduction
velocity (NCV). It suggested that indibulin
is free of neurotoxicity [16].
indibulin with the structure of 4b-amino
podophyllotoxin, as illustrated in Chart 1.
Recently, in our group many podo-
phyllotoxin derivatives were synthesized
and evaluated, including 4-O-substituents
and 4-N-substituents of podophyllotoxin
parent nucleus with electron-rich or
electron-poor substituents in indole rings
[17]. It comes out that combination of
indoles (with N-electron-rich or aromatic
ring electron-rich substituents) and 4-N-
substituted podophyllotoxin derivatives
can get potential candidates. In this
paper, seven unreported 4b-N-indol-3-
ylglyoxyl-substituted podophyllotoxin
The microtubulin-binding sites of
podophyllotoxin and indibulin are differ-
ent. To overcome MDR by inhibiting
human DNA topoisomerase II and lower
podophyllotoxin’s toxicity, some podo-
phyllotoxin derivatives based on indol-3-
yl-glyoxyl substituents were designed by
replacing the pyridin-4-ylamino moiety of

Journal of Asian Natural Products Research
419
6''
R2
4''
1''N
R3
O
O
2''
HN
5
8
11
3
O
O
O
12
1
O
3'
H3CO5'
OCH3
R1
Compound
R1
R2
R3
OCH3
4''-carbomethoxy
4''-carbomethoxy
4''-carbomethoxy
5''-fluoro
H
9a
OCH3
OH
2'''-fluorobenzyl
4'''-methylbenzyl
2'''-chlorobenzyl
2'''-chlorobenzyl
benzoyl
9b
9c
9d
9e
9f
OH
OCH3
OCH3
OCH3
5''-fluoro
4''-carbomethoxy
4''-carbomethoxy
acetyl
9g
Figure 1. Structures of synthesized podophyllotoxin derivatives.
derivatives as shown in Figure 1 were
synthesized and evaluated against human
cancer cell lines.
chlorides [18]. N-acylation of compound
9a, a very weak secondary amine, afforded
corresponding compounds 9f–g, as shown
in Scheme 2. Most probably more side
reactions, i.e. acetylation at the methox-
yphenyl groups, occurred when stronger
acylation agent acetyl chloride was used in
comparison with benzoyl chloride. How-
ever, when milder acetic anhydride was
applied under the same reaction condition
with 5-methylindole as the substrate
instead, 80% yield of product was obtained
[19]. Acetic anhydride will be tried in our
future experiment.
2. Results and discussion
The podophyllotoxin compounds 9a–e as
shown in Figure 1 were prepared according
to Scheme 1. N-substituted indoles 5,
readily available from indole 4 and aralkyl
chlorides with NaH as catalyst, reacted with
oxalyl chloride to afford 2-(N-aralkylindol-
3-yl)glyoxyloyl chlorides 6, as important
intermediates to get compounds 9a–e. In
our research, Friedel–Crafts acylation of
indoles with oxalyl chloride gave 3-
substituted products (via the more stable
carbocation intermediates with two com-
plete phenyl rings as the resonants) in higher
yields. Ether was the most effective solvent,
allowing precipitation of the glyoxyloyl
Using compound 9a as the example of
1
target compounds, its H NMR spectrum
revealed proton signals of three methoxy
groups, respectively, at d 3.76 (s, 6H, 30, 50-
OCH3) and 3.82 (s, 3H, 40-OCH3), eight
aromatic protons at d 6.31 (s, 2H, H-20, 60),

420
Y.-E. Guo et al.
Cl
O
R2
O
b
R2
a
R2
R2
N
N
N
N
R3
H
O
R3
R3
HN
O
4
5
6
e
O
O
OH
N3
O
NH2
O
O
O
O
O
O
O
O
O
d
O
O
O
O
O
H3CO
C
R1
H3
OCH3
H3CO
OCH3
H3CO
OCH3
H3CO
R
1
9a-e
R
1
R1
8
1
Scheme 1. Synthetic route to compounds 9a–e: (a) aralkyl chloride, NaH, DMF, 08C; (b) oxalyl
chloride, Et2O, 08C; (c) CF3CO2H, NaN3, CH2Cl2, rt; (d) 10% Pd/C, HCO2NH4, CH2Cl2, rt; and
(e) DMAP, TEA, CH2Cl2, rt.
6.48 (s, 1H, H-8), 6.79 (s, 1H, H-5), and
7.35–7.77 (m, 4H, H-200, 500, 600, 700),
successively. The signals of methylene
group at d 5.98 (d, 1H, J ¼ 1.0 Hz,
OCH2O) and 5.99 (d, 1H, J ¼ 1.0 Hz,
OCH2O), and the other aliphatic proton
signals at d 3.97 (s, 3H, CO2CH3), 4.10 (m,
1H, H-11b), 4.42 (m, 1H, H-11a), 2.99–
3.02 (m, 2H, H-2, 3), 4.52 (d, 1H,
J ¼ 3.4 Hz, H-1), and 5.21 (dd, 1H,
J ¼ 3.8, 8.1 Hz, H-4) were also detected in
the 1H NMR spectrum. The reported signals
of H-4, H-3, H-2, and H-1 of podophyllo-
toxin are located atd 4.59 (m, 1H, H-4), 2.85
(m, 2H, H-2, 3), and 4.75 (d, 1H,
J ¼ 8.8 Hz, H-1) [20]. Stronger van der
Waals effects, due to H-11a’s more
closeness to H-2, H-4 and other groups in
space than H-11b, explain why its 1H NMR
signal appears downfield and it is coupled
with H-11b. Two protons at dioxymethy-
lene group come into resonance at different
frequencies, and are coupled to each other.
Each of their signals is split into doublet.
The assignment of the configurations at C-4
for our target compounds 9a–g was based
on the coupling constants of H-3/H-4. The
4a-substituted podophyllotoxins have a
J3,4 $ 10.0Hz as H-3 is trans to H-4.
However, 7.8 Hz # J3,4 # 8.1 Hz in 1H
NMR of the target compounds 9a–g
suggests that they have 4b-configurations,
because of a cis relationship between H-3
and H-4 [21].
As shown in Table 1, compounds 9a,
9d, and 9e exhibit strong biological activity
against HeLa cells, obviously better than
that of reference compounds, while deriva-
tives 9b, 9c, 9d, 9f, and 9 g are more
effective against K562 and K562/AO2
cells in vitro than VP-16.
In conclusion, compounds 9b–g
showed promising anticancer activity,
especially an important advantage in anti-
multidrug resistance activity. In the prelimi-
nary structure–activity relationship (SAR)
study, we predicted that the N-substituted
CO2CH3
O
CO2CH3
O
R3
N
HN
O
NH
HN
O
O
O
O
O
O
O
O
f
O
OCH3
H3CO
OCH3
OCH3
H3CO
OCH3
9f-g
9a
Scheme 2. Synthetic route to compounds
9f–g: (f) acyl chlorides, TEA, CH2Cl2, rt.

Journal of Asian Natural Products Research
421
Table 1. IC50 values of the novel podophyllotoxin derivatives.
IC50 (mmol/L)
Compound
HeLa
K562
K562/AO2
KB
KBV
9a
9b
9c
9d
9e
9f
9 g
VP-16
VCR
ADM
1.05
5.237
3.805
0.15
0.99 ^ 0.60
0.29 ^ 0.19
0.23 ^ 0.16
0.40 ^ 0.14
1.22 ^ 0.35
0.31 ^ 0.18
0.46 ^ 0.37
0.9 ^ 0.08
–
4.04 ^ 0.97
0.12 ^ 0.06
0.70 ^ 0.02
0.29 ^ 0.26
0.62 ^ 0.28
0.22 ^ 0.20
0.10 ^ 0.01
7.05 ^ 5.08
–
3.99 ^ 1.28
2.49 ^ 0.94
0.88 ^ 0.23
1.00 ^ 0.78
4.99 ^ 1.36
1.03 ^ 0.38
1.62 ^ 1.25
3.36 ^ 1.05
0.93 ^ 0.26
–
6.28 ^ 2.05
3.49 ^ 1.05
3.62 ^ 2.17
3.16 ^ 1.46
5.46 ^ 3.65
2.59 ^ 0.28
2.30 ^ 2.17
55.47 ^ 4.36
50.30 ^ 3.84
–
0.73
10.67
11.11
2.11 ^ 1.17
–
–
1.77 ^ 0.1
.167.6
Notes: (a) Cytotoxicity against HeLa, KB, and KBV cell lines and against K562 and K562/AO2 cell lines was
measured, respectively, by the standard MTT and SRB assay method. (b) Each value represents the mean ^ SD
of three independent experiments.
electron-rich substituents in indole were the
key groups contributing much to antitumor
activity, while R1 substituents in podophyl-
lotoxinparentnucleusshowednosignificant
influence on their bioactivity.
mixture of 70% NaH (51 mg, 1.5 mmol) in
anhydrous DMF (1 ml) at 08C. After the
mixture was stirred at room temperature
(rt) for 1 h and cooled to 08C, 2-
fluorobenzyl chloride (0.15 g, 1.05 mmol)
was added, and the solution was stirred at
rt for an additional 3.5 h. The reaction
solution was poured into icy water (50 ml),
and stirring continued until precipitation
appeared. The solid was filtered and
washed with water. N-substituted indole
was obtained, dried, and used for the next
step without further purification.
3. Experimental
3.1 General experimental procedures
Melting points were determined on an X-4
digital melting point apparatus and are
uncorrected. The 1H NMR spectra were
recorded on a Bruker ARX-300 spectropho-
tometer, with tetramethylsilane (TMS) as
the internal standard. Mass spectral data
wereobtainedonAgilent 6210TOFMS. All
materials and reagents were used without
further purification unless stated. Ninety-
eight percent of podophyllotoxin was
purchased from the Nanjing Qingze Cor-
poration, Nanjing, China. CH2Cl2 was
refluxed over P2O5 and distilled. Et2O was
distilled over sodium with benzophenone as
monitor.
Oxalyl chloride (0.14 g, 1.1 mmol)
was added dropwise to a solution of N-
(2-fluorobenzyl)-4-carbomethoxyindole
(0.27 g, 0.90 mmol) in anhydrous ether
(10 ml) at 08C, and stirring continued at rt
for 6 h. The solid was filtered and washed
with dry petroleum ether. The mixture of
above crude 2-[N-(2-fluorobenzyl)-4-
carbo-methoxyindol-3-yl]glyoxyloyl chlo-
ride (0.35 g, 0.90 mmol), compound 8
(0.41 g, 1.0 mmol), two drops of triethyl
amine, and DMAP (4-dimethylaminopyr-
idine, 3.0 mg) in dry dichloromethane
(10 ml) was stirred for 12 h. The reaction
mixture was washed with water, dried over
anhydrous MgSO4, and concentrated in
vacuo. The residue was dissolved in
acetone and chromatographed on silica-
gel plate using petroleum ether and ethyl
3.2 General synthetic methods
3.2.1 4b-2-[N-(2000-Fluorobenzyl)-400-
carbomethoxyindol-300-yl]glyoxylamido 4-
deoxypodophyllotoxin (9b)
4-Carbomethoxy indole (0.19 g, 1.0 mmol)
in anhydrous DMF (N,N-dimethylform-
amide; 2 ml) was added dropwise to a

422
Y.-E. Guo et al.
acetate (1:1) as eluent to give compound
9b (0.51 g, overall yield 67% in three steps
Compound 9a: White solid, overall
yield 75% in two steps of reactions, mp
273.9–274.88C. 1H NMR spectral data
(CDCl3) (see Table 2). HR-ESI-MS m/z:
643.1906 [M þ H]þ (calculated for C34H31
N2O11, 643.1928).
1
of reactions) as light yellow solid. For H
NMR spectral data (CDCl3) (see Table 2).
HR-ESI-MS m/z: 751.2305 [M þ H]þ
(calculated for C41H36FN2O11, 751.2303).
Compounds 9a and 9c–e were pre-
pared as described above.
Compound 9c: White solid, overall
yield 70% in three steps of reactions, mp
Table 2. 1H NMR spectral data for the target compounds 9a–g.
Compound
1H NMR (d/ppm)
9a
2.99–3.02 (m, 2H, H-2, 3), 3.76 (s, 6H, 30, 50-OCH3), 3.82 (s, 3H, 40-OCH3), 3.97
(s, 3H, CO2CH3), 4.10 (m, 1H, H-11b), 4.42 (m, 1H, H-11a), 4.52 (d, 1H, J ¼ 3.4 Hz,
H-1), 5.21 (dd, 1H, J ¼ 3.8, 8.1 Hz, H-4), 5.98 (d, 1H, J ¼ 1.0 Hz, OCH2O), 5.99
(d, 1H, J ¼ 1.0 Hz, OCH2O), 6.31 (s, 2H, H-20, 60), 6.48 (s, 1H, H-8), 6.79 (s, 1H, H-
5), 7.35–7.77 (m, 4H, H-200, 500, 600, 700), 8.87 (d, 1H, J ¼ 3.8 Hz, CONH), 10.21
(s, 1H, NH in indolyl ring).
9b
9c
9d
9e
9f
2.99–3.02 (m, 2H, H-2, 3), 3.76 (s, 6H, 30, 50-OCH3), 3.82 (s, 3H, 40-OCH3), 3.97
(s, 3H, CO2CH3), 4.11 (m, 1H, H-11b), 4.44 (m, 1H, H-11a), 4.63 (d, 1H, J ¼ 4.7 Hz,
H-1), 5.21 (dd, 1H, J ¼ 3.8, 8.1 Hz, H-4), 5.48 (s, 2H, CH2 in benzyl group), 5.98
(d, 1H, J ¼ 1.0 Hz, OCH2O), 5.99 (d, 1H, J ¼ 1.0 Hz, OCH2O), 6.31 (s, 2H, H-20, 60),
6.53 (s, 1H, H-8), 6.79 (s, 1H, H-5), 7.04–7.33 (m, 4H, H-3000, 4000, 5000, 6000 in benzyl
group), 7.35–7.62 (m, 4H, H-200, 500, 600, 700), 8.94 (d, 1H, J ¼ 3.8 Hz, CONH).
2.33 (s, 3H, CH3), 2.99–3.02 (m, 2H, H-2, 3), 3.76 (s, 6H, 30, 50-OCH3), 3.97 (s, 3H,
CO2CH3), 4.12 (m, 1H, H-11b), 4.42 (m, 1H, H-11a), 4.49 (s, 1H, H-1), 5.21 (dd, 1H,
J ¼ 4.0, 7.9 Hz, H-4), 5.39 (s, 2H, CH2 in benzyl group), 5.98 (d, 1H, J ¼ 1.3 Hz,
OCH2O), 5.99 (d, 1H, J ¼ 1.3 Hz, OCH2O), 6.28 (s, 2H, H-20, 60), 6.43 (s, 1H, H-8),
6.78 (s, 1H, H-5), 7.07–7.17 (m, 4H, H-2000, 3000, 5000, 6000 in benzyl group), 7.34–7.70
(m, 4H, H-200, 500, 600, 700), 8.91 (d, 1H, J ¼ 4.0 Hz, CONH).
3.00–3.10 (m, 2H, H-2, 3), 3.79 (s, 6H, 30, 50-OCH3), 4.08 (m, 1H, H-11b), 4.44
(m, 1H, H-11a), 4.65 (d, 1H, J ¼ 4.0 Hz, H-1), 5.25 (dd, 1H, J ¼ 4.3, 8.1 Hz, H-4),
5.56 (s, 2H, CH2 in benzyl group), 5.98 (d, 1H, J ¼ 1.2 Hz, OCH2O), 6.01 (d, 1H,
J ¼ 1.2 Hz, OCH2O), 6.32 (s, 2H, H-20, 60), 6.55 (s, 1H, H-8), 6.75 (s, 1H, H-5), 7.02–
7.33 (m, 4H, H-3000, 4000, 5000, 6000 in benzyl group), 7.34–8.07 (m, 4H, H-200, 400, 600, 700),
9.06 (d, 1H, J ¼ 4.3 Hz, CONH).
3.00–3.05 (m, 2H, H-2, 3), 3.75 (s, 6H, 30, 50-OCH3), 3.81 (s, 3H, 40-OCH3), 4.12
(m, 1H, H-11b), 4.42 (m, 1H, H-11a), 4.60 (d, 1H, J ¼ 3.2 Hz, H-1), 5.25 (dd, 1H,
J ¼ 3.6, 7.8 Hz, H-4), 5.51 (s, 2H, CH2 in benzyl group), 5.98 (d, 1H, J ¼ 1.0 Hz,
OCH2O), 5.99 (d, 1H, J ¼ 1.0 Hz, OCH2O), 6.30 (s, 2H, H-20, 60), 6.46 (s, 1H, H-8),
6.77 (s, 1H, H-5), 7.02–7.33 (m, 4H, H-3000, 4000, 5000, 6000 in benzyl group), 7.34–8.08
(m, 4H, H-200, 400, 600, 700), 9.05 (d, 1H, J ¼ 3.6 Hz, CONH).
2.99–3.05 (m, 2H, H-2, 3), 3.75 (s, 6H, 30, 50-OCH3), 3.81 (s, 3H, 40-OCH3), 3.97
(s, 3H, CO2CH3), 4.12 (m, 1H, H-11b), 4.42 (m, 1H, H-11a), 4.49 (d, 1H, J ¼ 4.5 Hz,
H-1), 5.22 (dd, 1H, J ¼ 4.4, 7.9 Hz, H-4), 5.98 (d, 1H, J ¼ 1.8 Hz, OCH2O), 5.99
(d, 1H, J ¼ 1.8 Hz, OCH2O), 6.32 (s, 2H, H-20, 60), 6.56 (s, 1H, H-8), 6.85(s, 1H, H-
5), 7.31–7.62 (m, 5H, H-2000, 3000, 4000, 5000, 6000 in benzoyl group), 7.67–8.08 (m, 4H, H-
200, 500, 600, 700), 8.91 (d, 1H, J ¼ 4.4 Hz, CONH).
9 g
2.20 (s, 3H, COCH3), 2.99–3.05 (m, 2H, H-2, 3), 3.76 (s, 6H, 30, 50-OCH3), 3.81
(s, 3H, 40-OCH3), 3.96 (s, 3H, CO2CH3), 4.10 (m, 1H, H-11b), 4.36–4.54 (m, 1H,
H-1), 4.42 (m, 1H, H-11a), 5.20 (m, 1H, H-4), 5.98 (s, 1H, OCH2O), 5.99 (s, 1H,
OCH2O), 6.29 (s, 2H, H-20, 60), 6.47 (s, 1H, H-8), 6.87(s, 1H, H-5), 7.44–7.90 (m, 4H,
H-200, 500, 600, 700), 8.96 (d, 1H, J ¼ 3.8 Hz, CONH).

Journal of Asian Natural Products Research
423
146.0–147.08C. 1H NMR spectral data
(CDCl3) (see Table 2). HR-ESI-MS m/z:
733.2448 [M þ H]þ (calculated for
C41H37N2O11, 733.2397).
K562 (human erythroleukemia cells),
K562/AO2 (multidrug-resistant human
erythroleukemia cells induced by doxor-
ubicin), KB (human oral squamous carci-
noma cells), and KBV (MDR human oral
squamous carcinoma cells) using vincris-
tine sulfate, VP-16 2, and adriamycin as
reference compounds. The screening pro-
cedure was based on the standard 3-(4,5-
dimethyl-2-thiazyl)-2,5-diphenyl-2H-tet-
razolium bromide (MTT) or sulforhoda-
mine B (SRB) method [22]. IC50 values of
compounds 9a–g (see Table 1).
Compound 9d: Light yellow solid,
overall yield 48% in three steps of reactions,
mp 154.0–154.28C, 1H NMR spectral data
(CDCl3) (see Table 2). HR-ESI-MS m/z:
713.1717 [M þ H]þ (calculated for C38H31-
ClFN2O9, 713.1702).
Compound 9e: White solid, overall
yield 52% in three steps of reactions, mp
167.0–168.08C, 1H NMR spectral data
(CDCl3) (see Table 2). HR-ESI-MS m/z:
727.1835 [M þ H]þ (calculated for C39-
H33ClFN2O9, 727.1859).
4. Conclusion
The promising results obtained from these
new derivatives make them become poten-
tial candidates. It is valuable for us to further
prepare and evaluate their new derivatives.
3.2.2 Preparation of 4b-2-(N-benzoyl-400-
carbomethoxyindol-300-yl)glyoxylamido 4-
deoxypodophyllotoxin (9f)
Acknowledgements
After the solution of compound 9a (0.64 g,
0.97 mmol), benzoyl chloride (0.14 g,
1 mmol), two drops of triethyl amine, and
DMAP (3.0 mg) in anhydrous CH2Cl2
(10 ml) are stirred at rt for 6 h, the reaction
mixture was washed with water, dried over
anhydrous MgSO4, and concentrated in
vacuo. The residue was dissolved in acetone
and chromatographed on silica-gel plate
using petroleum ether and ethyl acetate
(1:1) as eluent to afford 0.67g of compound
This work was financially supported by the
National Natural Science Foundation of China
(No. 30873363), the Key Project of Science
Foundation of Tianjin (09ZCKFNC01200), and
the Program of Science Foundation of Tianjin
(08JCYBJC070000).
Notes
1. Email: chenhongtian06@yahoo.com.cn
2. Email: tony@tust.edu.cn
1
9f as white powder, yield 90%. H NMR
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