Design, synthesis and cytotoxic activity of novel sulfonylurea derivatives of podophyllotoxin

Article abstract of DOI:10.1016/j.bmc.2013.11.035

Three series of novel sulfonylurea podophyllotoxin derivatives were designed, synthesized, and evaluated for in vitro cytotoxicity against four tumor cell lines (A-549, DU-145, KB and KBvin). Compounds 14c (IC₅₀: 1.41-1.76 μM) and 14e (IC₅

Full text of DOI:10.1016/j.bmc.2013.11.035

Bioorganic & Medicinal Chemistry 22 (2014) 204–210
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
Design, synthesis and cytotoxic activity of novel sulfonylurea
derivatives of podophyllotoxin
Zhi-Jun Zhang a, , Jing Tian a, , Li-Ting Wang b, Mei-Juan Wang a, Xiang Nan a, Liu Yang d, Ying-Qian Liu a,
,
⇑
Susan L. Morris-Natschke b, Kuo-Hsiung Lee b,c,
⇑
a School of Pharmacy, Lanzhou University, Lanzhou 730000, PR China
b Natural Products Research Laboratories, UNC Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, NC 27599, United States
c Chinese Medicine Research and Development Center, China Medical University and Hospital, Taichung, Taiwan
d Environmental and Municipal Engineering School, Lanzhou Jiaotong University, Lanzhou 730000, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Three series of novel sulfonylurea podophyllotoxin derivatives were designed, synthesized, and evaluated
Received 1 October 2013
Revised 8 November 2013
Accepted 17 November 2013
Available online 28 November 2013
for in vitro cytotoxicity against four tumor cell lines (A-549, DU-145, KB and KBvin). Compounds 14c
(IC50: 1.41–1.76
l
M) and 14e (IC50: 1.72–2.01
lM) showed superior cytotoxic activity compared with
etoposide (IC50: 2.03 to >20
lM), a clinically available anticancer drug. Significantly, most of the com-
pounds exhibited comparable cytotoxicity against the drug-resistant tumor cell line KBvin, while etopo-
side lost activity completely. Preliminary structure–activity relationship (SAR) correlations indicated that
the 40-O-methyl functionality in podophyllotoxin analogues may be essential to maintain cytotoxic activ-
ity, while an arylsulfonylurea side chain at podophyllotoxin’s 4b position can significantly improve cyto-
toxic activity.
Keywords:
Podophyllotoxin
Sulfonylurea
Synthesis
Ó 2013 Elsevier Ltd. All rights reserved.
Cytotoxic activity
1. Introduction
overcome the drawbacks of 3. Overall, the excellent activity pro-
files of these agents, including improved water solubility, cytotoxic
Podophyllotoxin (1) is a naturally occurring aryltetralin lignan
isolated from various plant species of the Podophyllum family. It ex-
erts cytotoxic activity by inhibiting microtubule assembly.1,2 Enor-
mous progress has been achieved concerning the structural
elements required for activity. These findings led to approval of
etoposide (3) and teniposide (4), two semisynthetic glucoside
derivatives of -O-demethylepipodophyllotoxin (2), as well as eto-
pophos (5), a water-soluble prodrug of 3, as anticancer drugs. Un-
like 1, compounds 3–5 exert cytotoxic activity by inhibiting DNA
topoisomerase II.3–7
Improved understanding of the mechanism(s) of action, along
with extensive structure–activity and pharmacology studies, reen-
ergized interest in further modification studies on the C-4 substitu-
ent of 2 to increase antitumor activity. Accordingly, various C-4
substituents were introduced into the parent molecule leading to
either enhanced or comparable activity. Through C4 modification,
some nonsugar substituted analogues, particularly N-linked cong-
eners, were found to exhibit superior pharmacological properties
to 3, and several clinical trial drug candidates, including NPF (6),8
GL-331 (7),9 and TOP-53 (8),10 emerged as alternatives to
activity, drug resistance profiles, and antitumor spectra, suggested
this compound class could be optimized through rational C-4 mod-
ification. Both a composite pharmacophore model and comparative
molecular field analysis also further demonstrated that the C-4
molecular area could accommodate considerable structural
diversity.11
Based on accumulated SAR studies and critical modeling clues,
we have generated focused libraries of potent aniline, alkylamino,
phenol, thiophenol, and carbohydrate derivatives functionalized
at the C-4 position of 2; among which, some compound have exhib-
ited significant anticancer and DNA topoisomerase II inhibitory
activities.2,12 Especially, 4b-anilino substituted podophyllotoxin
derivatives showed potent cytotoxic activity against some human
parental and drug-resistant cancer cell lines.13–19 From these stud-
ies, 7 proved to be more potent than 3 and underwent phase II clin-
ical trials for the treatment of various cancers. In continuation of
these efforts, we recently found that a series of aroylthiourea deriv-
atives of 4-b-amino-4-desoxypodophyllotoxin displayed potent
antitumor activity with significantly different drug-resistance pro-
files from those of 1.20 Some new compounds exhibited promising
cytotoxicity against the KBvin drug resistant tumor cell line (e.g.,
IC50 0.098 and 0.13 lM), while etoposide lost activity completely.
In addition, some compounds were effective in drug-sensitive and
drug-resistant xenograft models at lower doses than etoposide,
⇑
Corresponding authors. Tel.: +1 (919) 962 0066; fax: +1 (919) 966 3893.
E-mail addresses: yqliu@lzu.edu.cn (Y.-Q. Liu), khlee@email.unc.edu (K.-H. Lee).
These authors contributed equally to this work.
0968-0896/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.bmc.2013.11.035

Z.-J. Zhang et al. / Bioorg. Med. Chem. 22 (2014) 204–210
205
demonstrating potential as drug candidates for anticancer chemo-
therapy. These encouraging results prompted us to further extend
our investigation by synthesizing a novel series of sulfonylurea
podophyllotoxin derivatives. The sulfonylurea group was chosen
based on the facts that this group is commonly found in various
drugs and introduction of a bioactive sulfonylurea group can usu-
ally potentiate the biochemical or pharmacological properties of
the original molecule.21 Therefore, in this paper, we describe our
introduction of sulfonylurea groups into the podophyllotoxin skel-
eton via a coupling reaction and our cytotoxic activity studies on
the resulting compounds (see Fig. 1).
of triphenylphosphine (TPP) and diethyl azodicarboxylate (DEAD),
and subsequently, deprotection with tetrabutylammonium fluo-
ride (Bu4NF).23 Similarly, intermediate 4b-amino-anhydropodo-
phyllotoxin (20) was prepared from 18 through azidation and
catalytic hydrogenation via a similar procedure to that described
above for 11 and 12. Finally, using similar methods to those for
13a–l and 14a–e, target compounds 21a–c were obtained from
20 in yields ranging from 67% to 82%. All newly synthesized com-
pounds were purified by column chromatography and their struc-
tures were confirmed by 1H NMR, 13C NMR, and ESI-MS data.
2.2. Cytotoxicity and SAR
2. Results and discussion
2.1. Chemistry
Target compounds 13a–l, 14a–e and 21a–c were evaluated
for in vitro cytotoxicity against four human tumor cell lines,
A549 (nonsmall cell lung cancer), DU145 (prostate cancer), KB
(nasopharyngeal carcinoma), and KBvin [multi-drug resistant
(MDR) KB subline selected using vincristine], using a sulforhoda-
mine B colorimetric (SRB) assay with triplicate experiments.24
Compound 3 was included as positive control and the results
are summarized in Table 1.
The synthetic routes to target podophyllotoxin derivatives are
outlined in Schemes 1 and 2. Briefly, precursor 4-azidopodo-
phyllotoxins 9 and 10 were prepared from 1 and 2 by employing
the BF3–Et2O/HN3 reagent system. Both 9 and 10 were then re-
duced under hydrogen atmosphere with Pd/C catalyst to yield
the key intermediate 4b-amino congeners 11 and 12, respec-
tively, in excellent yields.22 Next, intermediates 11 and 12 were
coupled with various sulfonylcarbamates in dry toluene to afford
the desired 4b-sulfonylurea podophyllotoxins 13a–l and 14a–e,
respectively, in good yields.
As illustrated in Scheme 2, initially, silyl-protected podophyllo-
toxin 15 was produced in excellent yield following a classical syn-
thetic method with tert-butyldimethylsilyl chloride (TBDMSCl) and
imidazole in DMF. Furthermore, another key precursor anhydrop-
odophyllotoxin (18) was synthesized by the following sequence,
reduction of 15 with lithium aluminum hydride (LiAlH4), followed
by closure of the resulting diol 16 to cyclic ether 17 with a mixture
Notably, compounds 14c and 14e showed superior activity
(IC50 1.41–1.76 and 1.72–2.01
3 (IC50 2.03–3.88 M) against A549, DU-145, and KB tumor cell
lines. Most importantly, these two compounds retained signifi-
cant cytotoxicity (IC50 1.76 and 2.01 M, respectively) against
the drug resistant KBvin tumor cell line, while 3 lost its activity
completely (IC50 >20 M). This result is in agreement with our
lM, respectively) compared with
l
l
l
prior observation that C4-amino substitution of 2 is favorable
for overcoming drug-resistance.19
Although 40-O-methylated derivatives 14c and 14e showed sig-
nificant cytotoxicity, their corresponding 40-hydroxyl analogues
13d and 13i displayed only marginal activity (IC50 8.10–8.76 and
R1
O
O
O
HO
O
HO
O
OH
O
O
OH
O
O
O
O
O
O
O
O
H3CO
OCH3
O
OR2
OCH3
H3CO
R1
R2
H
OH
OCH3
H3CO
3.
4.
Etoposide
Teniposide
CH3
OCH3
1
2. 4'-Demethylepipodophyllotoxin
.Podophyllotoxin
H
O
S
Etopophos
5.
P
OH
OH
CH3
N
H
HN
F
HN
NO2
O
O
O
O
O
O
O
O
O
O
O
O
OCH3
H3CO
H3CO
OCH3
OCH3
H3CO
OH
OH
OH
6
. NPF
8. TOP-53
7
. GL331
Figure 1. Structures of podophyllotoxin derivatives.

206
Z.-J. Zhang et al. / Bioorg. Med. Chem. 22 (2014) 204–210
OH
NH2
N3
O
O
O
O
O
O
/
HN3 C6H6
Pd/H2
EtOAc
O
O
O
O
O
O
BF3-Et2O
OCH3
H3CO
OCH3
OCH3
H3CO
H3CO
OR1
OR1
OR1
1. R1=CH3
9. R1=CH3
11. R1=CH3
2.
R1=H
1
1
10
. R =H
12
. R =H
O
O
S
O
O
O
S
O
HN
N
H
R2
R2
N
H
OC2H5
O
O
R2
O
reflux
13f
13a
13b
CH3
13j
Ο
CH3
14a
14b
14c
C2H5
C4H9
CH3
CH3
C2H5
13g
13c
13d
13k
H3CO
OCH3
OR1
H3CO
OCH 3
13h
13i
CH3
14d
14e
R1=H
13l
13e
13a −l
14a-e
CH3
Cl
F
R1=CH3
OCH 3
Cl
Scheme 1. Synthesis of 4b-sulfonylurea podophyllotoxin congeners 13a–l and 14a–e.
OH
O
Si
O
Si
O
O
O
O
O
O
ΟΗ
OH
Ph3P
DEAD
TBDMSCl
imidazole
LiAlH4
THF
O
O
O
O
OCH3
H3CO
OCH3
H3CO
OCH3
H3CO
OCH3
1
OCH3
16
OCH3
15
O
Si
N3
OH
O
O
O
O
O
O
/
HN3 C6H6
Pd/H2
EtOAc
Bu4NF
THF
O
O
O
BF3¡¤Et2O
OCH3
H3CO
OCH3
OCH3
H3CO
H3CO
OC2H5
OCH3
17
OCH3
19
OCH3
18
O
O
S
O
O
O
NH2
R2 S N
HN
N
H
R2
H
O
R2
O
O
O
O
O
reflux
21a
CH3
O
CH3
CH3
21b
21c
OCH3
H3CO
OCH3
OCH3
21a-c
H3CO
OCH3
20
H3CO
OCH3
Scheme 2. Synthesis of 4b-sulfonylurea anhydropodophyllotoxin congeners 21a–c.
7.95–11.52
l
M, respectively). Similar results were seen in our
These results were unexpected,25 and further investigation is
needed.
previous study,20 and highlight the critical role of the 40-O-methyl
functionality in sulfonylurea-substituted 2-derivatives.
Within the 40-O-demethylated series (13a–l), compounds 13a
and 13b with methyl- and ethyl-sulfonylurea groups, respectively,
4’-O-Methylated derivatives 14a, 14b, and 14c with methyl,
ethyl, and 4-methylphenyl groups on the sulfonylurea side chain
were inactive (IC50 >20
showed marginal to weak cytotoxicity (IC50 7.96–13.95
indicating that the substituent’s size is critical. Except for 13f,
l
M), while 13c with a butyl R2 group
were obviously much less potent (IC50 >20
lM) than 14c and
lM),
14e with phenyl and 4-chlorophenyl groups in the R2 position.

Z.-J. Zhang et al. / Bioorg. Med. Chem. 22 (2014) 204–210
207
Table 1
ker AM-400 spectrometer using TMS as reference (Bruker
Company, USA). Optical rotations were measured on an Autopol
IV polarimeter (Rudolph, USA) in a 10 mm cell at 21 °C. Podophyl-
lotoxin (1) was isolated from the Chinese medicinal herb Juniperus
sabina Linnaeus, and served as the starting material for preparation
of all new derivatives. The starting sulfonylcarbamates were pre-
pared according to the procedure reported previously.26,27 The
key intermediate 4b-amino congeners 11, 12 and 20 were synthe-
sized by our previously reported procedures, and their structures
confirmed by direct comparison with an authentic sample and pre-
viously reported spectroscopic data.21,22
In vitro cytotoxicity of 13a–l, 14a–e and 21a–c against four human tumor cell lines
with etoposide (3) as control
Compd
IC50 (lM)
A549
DU145
KB
KBvin
13a
13b
13c
13d
13e
13f
13g
13h
13i
>20
>20
>20
>20
>20
>20
>20
>20
7.96 0.470
8.25 0.842
7.67 0.489
>20
7.72 1.229
7.82 0.424
9.03 0.142
8.63 0.892
8.00 0.383
8.49 0.291
>20
>20
1.60 0.082
>20
1.89 0.162
>20
11.79 0.22
14.91 0.583
2.58 0.252
11.94 1.042
8.10 0.410
9.66 0.864
>20
10.87 1.280
8.38 0.452
9.49 0.821
>20
13.95 0.740
8.76 0.120
8.79 0.585
>20
8.35 0.681
7.92 0.863
7.95 0.500
13.99 0.653
8.56 0.818
8.62 0.950
>20
>20
1.76 0.263
>20
2.01 0.323
>20
13.17 0.732
>20
9.32 0.337
9.61 0.622
11.52 0.472
11.24 0.824
8.51 0.816
10.53 0.532
>20
9.51 0.414
9.00 0.151
10.56 0.256
11.78 0.291
8.08 0.769
9.70 0.294
>20
4.2. General synthetic procedure for target compounds 13a–l,
14a–e and 21a–c
13j
13k
13l
Key intermediates 11, 12 and 20 (0.2 mmol) were added drop-
wise to a solution of 0.4 mmol of sulfonylcarbamate in dry toluene
(20 mL). The reaction mixture was refluxed for 2–4 h and then con-
centrated. The residue was purified by chromatography on silica
gel using CHCl3/MeOH as eluant to give 13a–l, 14a–e, and 21a–c,
which were stable both at chemical purification stage and under
assay conditions.
14a
14b
14c
14d
14e
21a
21b
21c
Etoposide
>20
>20
1.44 0.080
>20
1.41 0.112
>20
1.75 0.124
>20
1.72 0.181
>20
11.88 0.152
14.29 0.108
2.03 0.121
11.02 0.630
12.02 0.043
3.88 0.199
>20
4.2.1. 4b-N-(Methylsulfonylurea)-4-deoxy-40-demethylepipodo-
phyllotoxin (13a)
40-O-demethylated compounds with phenylsulfonylurea groups
(13c–e and 13g–k) showed similar potency (IC50 7.67–13.99 M)
to 13c against all tested tumor cell lines. Cytotoxic potency was
only slightly affected by the electronegativity or positions of
substituents on the phenyl ring. Moreover, compound 13l with a
2-naphthylsulfonylurea group showed comparable potency to
compounds with a phenyl group.
Subsequently, to investigate whether the lactone moiety can
influence cytotoxic activity, 4b-sulfonylurea anhydropodophyllo-
toxin compounds 21a–c were prepared. As shown in Table 1, com-
pound 21a was inactive, while 21b and 21c were less potent than
the related lactone compounds 13g and 13k, suggesting that the
lactone moiety might be important for antitumor effects. However,
further investigation is warranted including comparison with
40-O-methylated lactone compounds.
Yield: 50%; mp: 180–182 °C; ½a D21
ꢀ
ꢁ 31:4ꢂ (c 0.5, CHCl3); 1H
l
NMR (400 MHz, DMSO-d6) d: 8.29 (s, 1H, –CONHSO2–), 6.87 (s,
1H, 5-H), 6.53 (s, 1H, 8-H), 6.21 (s, 2H, 20,60-H), 6.00 and 5.98
(ABq, 2H, –OCH2O–), 5.01–4.98 (m, 1H, 4-H), 4.49 (d, 1H, 1-H,
J = 5.2 Hz), 4.32 (t, 1H, 11b-H, J = 8 Hz), 3.81 (t, 1H, 11a-H,
J = 9.2 Hz), 3.61 (s, 6H, 30,50-OCH3), 3.25 (s, 3H, 100-H), 3.10 (dd,
1H, 2-H, J = 14.4, 5.2 Hz), 2.98–2.91 (m, 1H, 3-H); 13C NMR
(100 MHz, DMSO-d6) d: 174.7, 152.4, 147.6, 147.3, 146.8, 137.4,
134.8, 132.6, 130.2, 129.8, 128.4, 119.8, 109.5, 108.5, 101.5, 56.2,
42.9, 41.6, 40.8; ESI-MS: m/z 521.0 [M+H]+.
4.2.2. 4b-N-(Ethylsulfonylurea)-4-deoxy-40-demethylepipodo-
phyllotoxin (13b)
Yield: 52%; mp: 160–162 °C; ½a D21
ꢀ
ꢁ 77:6ꢂ (c 0.5, CHCl3); 1H
NMR (400 MHz, DMSO-d6) d: 8.29 (s, 1H, –CONHSO2–), 6.86 (s,
1H, 5-H), 6.53 (s, 1H, 8-H), 6.21 (s, 2H, 20,60-H), 6.00 and 5.98
(ABq, 2H, –OCH2O–), 5.01–4.98 (m, 1H, 4-H), 4.49 (d, 1H, 1-H,
J = 5.2 Hz), 4.32 (t, 1H, 11b-H, J = 8 Hz), 3.78 (t, 2H, 100-H,
J = 10.4 Hz), 3.61 (s, 6H, 30,50-OCH3), 3.15 (dd, 1H, 2-H, J = 14.4,
5.2 Hz), 2.98–2.91 (m, 1H, 3-H), 1.25–1.16(m, 3H, 200-H); 13C NMR
(100 MHz, DMSO-d6) d: 174.6, 152.3, 147.6, 147.3, 146.8, 134.8,
132.6, 130.2, 129.8, 109.7, 109.3, 108.5, 101.5, 56.2, 47.3, 42.9,
40.8, 37.0; ESI-MS: m/z 535.0 [M+H]+.
3. Conclusion
In summary, three series of novel 4b-sulfonylurea podophyllo-
toxin derivatives were designed, synthesized, and evaluated for
cytotoxicity against four tumor cell lines (A-549, DU-145, KB and
KBvin) by using a sulforhodamine B colorimetric assay. Among
them, compounds 14c and 14e were the most promising deriva-
tives with greater potency than 3 and were selected as lead mole-
cules for further development. The cytotoxic results revealed that
the 40-O-methyl functionality was essential in increasing cytotox-
icity in the 1-derived compounds, and aryl substituents on the sul-
fonylurea moiety were advantageous. These findings support our
further optimization of 1 to develop potential anticancer drug can-
didates. Continuing studies to substantiate and improve activity
profiles are underway in our laboratory and will be reported in
due course.
4.2.3. 4b-N-(Butylsulfonylurea)-4-deoxy-40-
demethylepipodophyllotoxin (13c)
Yield: 49%; mp: 161–163 °C; ½a D21
ꢀ
ꢁ 85:4ꢂ (c 0.5, CHCl3); 1H
NMR (400 MHz, DMSO-d6) d: 8.28 (s, 1H, –CONHSO2–), 6.84 (s,
1H, 5-H), 6.47 (s, 1H, 8-H), 6.20 (s, 2H, 20,60-H), 5.98 and 5.96
(ABq, 2H, –OCH2O–), 5.03–5.02 (m, 1H, 4-H), 4.43 (d, 1H, 1-H,
J = 4.8 Hz), 4.29 (t, 1H, 11b-H, J = 8 Hz), 4.03–4.00 (m, 1H, 11a-H),
3.60 (s, 6H, 30,50-OCH3), 3.15-3.07 (m, 1H, 2-H), 2.97 (t, 2H, 100-H,
J = 7.6 Hz), 2.94–2.84 (m, 1H, 3-H), 1.58–1.56 (m, 2H, 200-H),
1.38–1.32 (m, 2H, 300-H), 1.16 (t, 3H, 400-H, J = 6.8 Hz); 13C NMR
(100 MHz, DMSO-d6) d: 147.3, 136.0, 134.8, 108.5, 105.3, 56.1,
43.1, 30.9, 21.3, 13.9; ESI-MS: m/z 585.1 [M+Na]+.
4. Experimental section
4.1. Chemistry
Melting points were taken on a Kofler melting point apparatus
and are uncorrected. Mass spectra were recorded on a Bruker Dal-
tonics APEXII49e spectrometer with ESI source as ionization. 1H
and 13C NMR spectra were recorded at 400 and 100 MHz on a Bru-
4.2.4. 4b-N-(Phenylsulfonylurea)-4-deoxy-40-
demethylepipodophyllotoxin (13d)
Yield: 59%; mp: 195–197 °C; ½a D21
ꢀ
ꢁ 33:8ꢂ (c 0.5, CHCl3); 1H
NMR (400 MHz, DMSO-d6) d: 8.27 (s, 1H, –CONHSO2–), 7.92 (d,

208
Z.-J. Zhang et al. / Bioorg. Med. Chem. 22 (2014) 204–210
2H, 200,600-H, J = 7.6 Hz), 7.69 (t, 1H, 400-H, J = 7.6 Hz), 7.61 (t, 2H,
300,500-H, J = 7.6 Hz), 6.71 (s, 1H, 5-H), 6.51 (s, 1H, 8-H), 6.18 (s,
2H, 20,60-H), 5.99 and 5.97 (ABq, 2H, –OCH2O–), 4.90–4.87 (m,
109.6, 108.6, 101.5, 67.8, 56.2, 50.4, 44.4, 42.8, 40.7, 37.5; ESI-
MS: m/z 601.0 [M+H]+.
1H, 4-H), 4.46 (d, 1H, 1-H, J = 5.2 Hz), 4.13 (t, 1H, 11
a
-H,
4.2.9. 4b-N-(400-Chlorophenylsulfonylurea)-4-deoxy-40-
J = 8 Hz), 3.59 (s, 6H, 30,50-OCH3), 3.10 (dd, 1H, 2-H, J = 14.4,
5.2 Hz), 2.88–2.78 (m, 1H, 3-H); 13C NMR (100 MHz, DMSO-d6) d:
174.4, 167.1, 151.6, 147.4, 147.2, 146.7, 140.3, 134.7, 133.3,
132.5, 130.1, 129.6, 129.1, 127.3, 109.5, 109.1, 108.4, 101.4, 68.1,
56.0, 47.8, 42.8, 40.7, 36.7; ESI-MS: m/z 583.3 [M+H]+.
demethyl-epipodophyllotoxin (13i)
Yield 35%; mp: 162–164 °C; ½a D21
ꢀ
ꢁ 50:8ꢂ (c 0.5, CHCl3); 1H NMR
(400 MHz, DMSO-d6) d: 9.02 (s, 1H, –CONHSO2–), 8.36 (d, 2H,
200,600-H, J = 8.8 Hz), 7.64 (d, 2H, 300,500-H, J = 7.6 Hz), 6.78 (s, 1H,
5-H), 6.62 (s, 1H, 8-H), 6.18 (s, 2H, 20,60-H), 6.00 and 5.98 (ABq,
2H, –OCH2O–), 4.91–4.87 (m, 1H, 4-H), 4.70 (d, 1H, 1-H,
4.2.5. 4b-N-(400-Methoxyphenylsulfonylurea)-4-deoxy-40-
J = 5.2 Hz), 4.17 (t, 1H, 11a
-H, J = 7.6 Hz), 3.60 (s, 6H, 30,50-OCH3),
demethyl-epipodophyllotoxin (13e)
3.17–3.12 (m, 1H, 2-H), 2.88–2.87 (m, 1H, 3-H); 13C NMR
(100 MHz, DMSO-d6) d: 174.5, 147.3, 140.9, 129.4, 129.2, 126.9,
108.5, 106.5, 101.4, 56.1, 55.4, 30.8; ESI-MS: m/z 640.4 [M+Na]+.
Yield: 42%; mp: 166–168 °C; ½a D21
ꢀ
ꢁ 59:4ꢂ (c 0.5, CHCl3); 1H
NMR (400 MHz, DMSO-d6) d: 9.03 (s, 1H, –CONHSO2–), 7.84
(d, 2H, 200,600-H, J = 8.8 Hz), 7.76 (d, 2H, 300,500-H, J = 8.8 Hz), 6.77
(s, 1H, 5-H), 6.51 (s, 1H, 8-H), 6.20 (s, 2H, 20,60-H), 6.02 and
6.01 (ABq, 2H, –OCH2O–), 5.00–4.97 (m, 1H, 4-H), 4.50 (d, 1H,
1-H, J = 4.8 Hz), 4.46-4.41 (m, 2H, 11-H), 3.84 (s, 3H, 400-OCH3),
3.62 (s, 6H, 30,50-OCH3), 3.16 (dd, 1H, 2-H, J = 14, 4.8 Hz),
2.96–2.82 (m, 1H, 3-H); 13C NMR (100 MHz, DMSO-d6) d:
174.0, 162.2, 147.7, 147.3, 146.9, 134.9, 132.3, 129.9, 129.6,
114.3, 109.6, 108.6, 56.1, 42.8, 40.7, 38.0, 30.8; ESI-MS: m/z
630.5 [M+NH4]+.
4.2.10. 4b-N-(Benzylsulfonylurea)-4-deoxy-40-demethyl-
epipodophyllotoxin (13j)
Yield: 50%; mp: 158–160 °C; ½a D21
ꢀ
ꢁ 31:0ꢂ (c 0.5, CHCl3); 1H
NMR (400 MHz, DMSO-d6) d: 8.33 (s, 1H, –CONHSO2–), 7.40 (s,
5H, Ar-H), 6.91 (br s, 1H, 4-NH), 6.85 (s, 1H, 5-H), 6.54 (s, 1H,
8-H), 6.23 (s, 2H, 20,60-H), 6.04 and 6.01 (ABq, 2H, –OCH2O–),
5.09–5.08 (m, 1H, 4-H), 4.49 (d, 1H, 1-H, J = 4.8 Hz), 4.39 (t, 1H,
11b-H, J = 8 Hz), 3.79 (t, 1H, 11a
-H, J = 10 Hz), 3.63 (s, 6H, 30,
50-OCH3), 3.17(s, 2H, –SO2CH2–), 3.10 (dd, 1H, 2-H, J = 14.4,
4.8 Hz), 2.98–2.95 (m, 1H, 3-H); 13C NMR (100 MHz, DMSO-d6) d:
174.5, 152.4, 147.5, 147.3, 146.8, 134.8, 132.5, 130.9, 130.1,
129.9, 129.7, 128.7, 127.3, 109.6, 109.1, 108.5, 101.5, 68.4, 58.1,
56.1, 47.9, 42.9, 40.8, 36.8, 30.8; ESI-MS: m/z 596.5 [M]+.
4.2.6. 4b-N-(400-Methylphenylsulfonylurea)-4-deoxy-40-
demethyl-epipodophyllotoxin (13f)
Yield: 56%; mp: 193–195 °C; ½a D21
ꢀ
ꢁ 50:0ꢂ (c 0.5, CHCl3); 1H
NMR (400 MHz, DMSO-d6) d: 8.29 (br s, 1H, –CONHSO2–),
7.87–7.71 (m, 2H, 200,600-H), 7.23–7.18 (m, 2H, 300,500-H), 6.78 (s,
1H, 5-H), 6.51 (s, 1H, 8-H), 6.20 (s, 2H, 20,60-H), 5.97 and 5.96
(ABq, 2H, –OCH2O–), 4.93–4.92 (m, 1H, 4-H), 4.42 (d, 1H, 1-H,
J = 5.2 Hz), 4.12 (br s, 2H, 11-H, J = 8 Hz), 3.59 (s, 6H, 30,50-OCH3),
3.15 (m, 1H, 2-H), 2.79 (m, 1H, 3-H), 2.336 (s, 3H, 400-CH3); 13C
NMR (100 MHz, DMSO-d6) d: 174.8, 172.5, 147.3, 146.7, 134.8,
132.2, 131.0, 130.4, 129.0, 126.9, 109.5, 109.2, 108.5, 101.4, 68.5,
63.0, 56.2, 48.8, 47.6, 43.0, 40.9, 37.0, 30.9, 21.4; ESI-MS: m/z
597.0 [M+H]+.
4.2.11. 4b-N-(200,400-Dimethoxyphenylsulfonylurea)-4-deoxy-40-
demethyl-epipodophyllotoxin (13k)
Yield: 42%; mp: 166–168 °C; ½a D21
ꢀ
ꢁ 21:0ꢂ (c 0.5, CHCl3); 1H
NMR (400 MHz, DMSO-d6) d: 8.28 (s, 1H, –CONHSO2–), 7.74 (d,
1H, 600-H, J = 8.8 Hz), 6.86 (d, 1H, 4-NH, J = 8 Hz), 6.73 (d, 1H,
300-H, J = 2 Hz), 6.71 (s, 1H, 5-H), 6.65 (dd, 1H, 500-H, J = 8.8, 2 Hz),
6.53 (s, 1H, 8-H), 6.19 (s, 2H, 20,60-H), 6.02 and 6.01 (ABq,
2H, –OCH2O–), 4.89–4.86 (m, 1H, 4-H), 4.51 (d, 1H, 1-H,
J = 5.2 Hz), 4.11 (t, 1H, 11a
-H, J = 8 Hz), 3.85 (s, 6H, 200,400-OCH3),
4.2.7. 4b-N-(400-Isopropylphenylsulfonylurea)-4-deoxy-40-
3.60 (s, 6H, 30,50-OCH3), 2.94 (dd, 1H, 2-H, J = 14.4, 5.2 Hz),
2.88–2.79 (m, 1H, 3-H); 13C NMR (100 MHz, DMSO-d6) d: 174.3,
165.1, 158.0, 151.5, 147.5, 147.2, 146.8, 134.8, 132.5, 130.0,
129.6, 119.0, 109.6, 109.0, 108.5, 105.1, 101.5, 99.3, 68.1, 56.5,
56.1, 47.6, 42.9, 40.8, 36.7, 30.8; ESI-MS: m/z 665.1 [M+Na]+.
demethyl-epipodophyllotoxin (13g)
Yield: 41%; mp: 172–174 °C; ½a D21
ꢀ
ꢁ 53:1ꢂ (c 0.5, CHCl3); 1H
NMR (400 MHz, DMSO-d6) d: 9.04 (s, 1H, –CONHSO2–), 7.84 (d,
2H, 200,600-H, J = 8 Hz), 7.75 (d, 2H, 300,500-H, J = 8 Hz), 6.79 (s, 1H,
5-H), 6.51 (s, 1H, 8-H), 6.21 (s, 2H, 20,60-H), 5.98 and 5.97 (ABq,
2H, –OCH2O–), 5.01–4.98 (m, 1H, 4-H), 4.51 (d, 1H, 1-H,
J = 4.8 Hz), 4.44–4.41 (m, 2H, 11-H), 3.64 (s, 6H, 30,50-OCH3), 3.17
(dd, 1H, 2-H, J = 14.4, 4.8 Hz), 3.01–2.91 (m, 1H, 3-H), 2.88–2.83
(m, 1H, 700-H), 1.22-1.18 (m, 6H, 700-CH3); 13C NMR (100 MHz,
DMSO-d6) d: 174.4, 172.2, 166.7, 164.8, 153.8, 147.7, 147.3,
146.7, 134.8, 132.3, 130.1, 129.9, 129.4, 127.1, 126.9, 109.6,
109.4, 108.6, 101.4, 84.7, 56.2, 50.6, 42.7, 40.7, 37.5, 30.8, 23.6;
ESI-MS: m/z 624.3 [M]+.
4.2.12. 4b-N-(200-Naphthylsulfonylurea)-4-deoxy-40-demethyl-
epipodophyllotoxin (13l)
Yield: 47%; mp: 176–178 °C; ½a D21
ꢀ
ꢁ 16:3ꢂ (c 0.5, CHCl3); 1H
NMR (400 MHz, DMSO-d6) d: 8.43 (s, 1H, –CONHSO2–), 8.31 (s,
1H, 300-H), 8.23 (d, 2H, 100,400-H, J = 8 Hz), 8.08-8.02 (m, 4H,
500,600,700,800-H), 6.83 (s, 1H, 5-H), 6.50 (s, 1H, 8-H), 6.23 (s, 2H,
20,60-H), 6.00 and 5.98 (ABq, 2H, –OCH2O–), 4.99–4.96 (m, 1H,
4-H), 4.46 (d, 1H, 1-H, J = 4.8 Hz), 4.33 (t, 1H, 11b-H, J = 8.4 Hz),
3.80 (t, 1H, 11a
-H, J = 10.8 Hz), 3.62 (s, 6H, 30,50-OCH3), 3.29 (dd,
4.2.8. 4b-N-(400-Fluorophenylsulfonylurea)-4-deoxy-40-
1H, 2-H, J = 14.4, 5.2 Hz), 2.99–2.90 (m, 1H, 3-H); 13C NMR
(100 MHz, DMSO-d6) d: 174.7, 172.2, 170.1, 166.0, 156.4, 147.3,
146.6, 141.3, 140.3, 136.3, 134.8, 132.1, 131.8, 129.6, 129.4,
129.2, 128.5, 127.9, 127.6, 122.6, 109.5, 109.1, 108.5, 101.3, 68.2,
60.2, 56.1, 48.7, 43.0, 40.7, 36.6; ESI-MS: m/z 671.0 [M+K]+.
demethyl-epipodophyllotoxin (13h)
Yield: 38%; mp: 167–169 °C; ½a D21
ꢀ
ꢁ 94:7ꢂ (c 0.5, CHCl3); 1H
NMR (400 MHz, DMSO-d6) d: 9.03 (s, 1H, –CONHSO2–), 7.71
(d, 2H, 200,600-H, J = 8 Hz), 7.28 (d, 2H, 300,500-H, J = 8 Hz), 6.99
(br s, 1H, 4-NH), 6.71 (s, 1H, 5-H), 6.46 (s, 1H, 8-H), 6.18 (s,
2H, 20,60-H), 6.01 and 5.98 (ABq, 2H, –OCH2O–), 5.00–4.97 (m,
1H, 4-H), 4.43 (d, 1H, 1-H, J = 7.2 Hz), 4.03–4.01 (m, 1H,
4.2.13. 4b-N-(Methylsulfonylurea)-4-deoxyepipodophyllotoxin
(14a)
11b-H), 3.89–3.87 (m, 1H, 11
a
-H), 3.62 (s, 6H, 30,50-OCH3),
Yield: 54%; mp: 192–194 °C; ½a D21
ꢀ
ꢁ 33:3ꢂ (c 0.5, CHCl3); 1H
3.15–3.13 (m, 1H, 2-H), 2.93–2.86 (m, 1H, 3-H); 13C NMR
(100 MHz, DMSO-d6) d: 174.5, 151.5, 147.7, 147.3, 146.9,
141.7, 137.3, 134.9, 132.2, 130.8, 129.9, 129.6, 116.5, 114.7,
NMR (400 MHz, DMSO-d6) d: 6.88 (s, 1H, 5-H), 6.53 (s, 1H, 8-H),
6.26 (s, 2H, 20,60-H), 6.00 and 5.99 (ABq, 2H, –OCH2O–), 5.01 (dd,
1H, 4-H, J = 7.6, 4.4 Hz), 4.54 (d, 1H, 1-H, J = 5.2 Hz), 4.34 (t, 1H,

Z.-J. Zhang et al. / Bioorg. Med. Chem. 22 (2014) 204–210
209
11b-H, J = 8 Hz), 3.85–3.80 (m, 1H, 11
a
-H), 3.63 (s, 6H, 30,50-OCH3),
(ABq, 2H, –OCH2O–), 5.00 (dd, 1H, 4-H, J = 8, 3.6 Hz), 4.34 (d, 1H,
1-H, J = 5.2 Hz), 4.04–3.99 (m, 2H, 11-H), 3.92 (t, 1H, 12b-H,
3.60 (s, 3H, 40-OCH3), 3.22 (s, 3H, 100-H), 3.19–3.17 (m, 1H, 2-H),
3.05–2.89 (m, 1H, 3-H); 13C NMR (100 MHz, DMSO-d6) d: 174.6,
152.2, 147.6, 146.9, 136.5, 135.9, 132.2, 130.0, 109.6, 109.4,
108.2, 101.5, 68.6, 60.1, 55.9, 47.9, 43.2, 41.5, 40.7, 37.1, 30.9;
ESI-MS: m/z 535.0 [M+H]+.
J = 7.6 Hz), 3.79 (t, 1H, 12a
-H, J = 7.6 Hz), 3.64 (s, 6H, 30,50-OCH3),
3.61 (s, 3H, 40-OCH3), 2.77–2.73 (m, 1H, 3-H), 2.42–2.40 (m, 1H,
2-H), 1.98 (s, 3H, 100-CH3); 13C NMR (100 MHz, DMSO-d6) d:
170.4, 152.4, 152.0, 147.2, 146.4, 136.7, 136.1, 132.5, 130.6,
109.5, 109.1, 108.9, 107.3, 107.1, 101.2, 69.0, 67.5, 67.4, 60.0,
59.9, 59.8, 55.9, 47.0, 46.9, 44.7, 44.6, 41.4, 41.3, 38.6, 20.8, 14.2;
ESI-MS: m/z 543.0 [M+Na]+.
4.2.14. 4b-N-(Ethylsulfonylurea)-4-deoxyepipodophyllotoxin
(14b)
Yield: 57%; mp: 163–165 °C; ½a D21
ꢀ
ꢁ 85:7ꢂ (c 0.5, CHCl3); 1H
NMR (400 MHz, DMSO-d6) d: 6.87 (s, 1H, 5-H), 6.54 (s, 1H, 8-H),
6.26 (s, 2H, 20,60-H), 6.00 and 5.99 (ABq, 2H, –OCH2O–), 5.01 (dd,
1H, 4-H, J = 8, 4.8 Hz), 4.54 (d, 1H, 1-H, J = 5.2 Hz), 4.34 (t, 1H,
4.2.19. 4b-N-(400-Isopropylphenylsulfonylurea)-4-
deoxyanhydroepipodophyllotoxin (21b)
yield 48.8%; mp: 197–199 °C; ½a D21
ꢀ
ꢁ 76:5ꢂ (c 0.5, CHCl3); 1H
11b-H, J = 8 Hz), 3.79 (t, 1H, 11
a
-H, J = 10.4 Hz), 3.63 (s, 6H, 30,50-
NMR (400 MHz, DMSO-d6) d: 7.81 (d, 2H, 200,600-H, J = 8 Hz), 7.48
(d, 2H, 300,500-H, J = 8 Hz), 6.80 (d, 1H, 4-NH, J = 8.4 Hz), 6.65 (s,
1H, 5-H), 6.43 (s, 1H, 8-H), 6.11 (s, 2H, 20,60-H), 5.97 and 5.96
(ABq, 2H, –OCH2O–), 4.88–4.87 (m, 1H, 4-H), 4.31 (d, 1H, 1-H,
J = 3.6 Hz), 3.88–3.87 (m, 2H, 11-H), 3.62 (s, 6H, 30,50-OCH3), 3.59
(s, 3H, 40-OCH3), 3.00–2.98 (m, 2H, 12-H), 2.72–2.68 (m, 1H, 3-H),
2.34 (m, 2H, 2-H, 700-H), 1.21 (d, 6H, 700-CH3, J = 6.8 Hz); 13C NMR
(100 MHz, DMSO-d6) d: 154.7, 152.8, 151.6, 147.7, 146.8, 137.8,
137.1, 136.6, 132.9, 130.9, 127.8, 127.4, 109.9, 109.2, 107.7,
101.6, 69.3, 67.7, 60.4, 56.3, 47.3, 45.0, 38.9, 33.9, 23.9; ESI-MS:
m/z 624.7 [M]+.
OCH3), 3.60 (s, 3H, 40-OCH3), 3.20 (dd, 1H, 2-H, J = 14.4, 5.2 Hz),
2.99–2.89 (m, 1H, 3-H), 1.23 (t, 3H, 200-H, J = 7.6 Hz); 13C NMR
(100 MHz, DMSO-d6) d: 174.5, 152.3, 147.6, 146.9, 136.4, 135.9,
132.2, 129.8, 116.8, 109.6, 109.3, 108.2, 101.5, 97.5, 68.5, 64.1,
60.1, 55.9, 52.7, 47.2, 43.1, 40.6, 8.1; ESI-MS: m/z 549.0 [M+H]+.
4.2.15. 4b-N-(Phenylsulfonylurea)-4-deoxyepipodophyllotoxin
(14c)
Yield: 54%; mp: 158–160 °C; ½a D21
ꢀ
ꢁ 34:8ꢂ (c 0.5, CHCl3); 1H
NMR (400 MHz, DMSO-d6) d: 7.91 (d, 2H, 200,600-H, J = 7.6 Hz),
7.66–7.54 (m, 3H, 300,400,500-H), 6.93 (br s, 1H, 4-NH), 6.73 (s, 1H,
5-H), 6.51 (s, 1H, 8-H), 6.24 (s, 2H, 20,60-H), 6.01 and 5.99 (ABq,
2H, –OCH2O–), 5.01–4.98 (m, 1H, 4-H), 4.51 (d, 1H, 1-H,
4.2.20. 4b-N-(200,400-Dimethoxyphenylsulfonylurea)-4-
deoxyanhydroepipodophyllotoxin (21c)
J = 5.2 Hz), 4.17-4.13 (m, 1H, 11
a
-H), 3.65–3.60 (s, 9H, 30,40,50-
Yield: 45%; mp: 152–154 °C; ½a D21
ꢀ
ꢁ 40:4ꢂ (c 0.5, CHCl3); 1H
OCH3), 3.21 (dd, 1H, 2-H, J = 14, 5.2 Hz), 2.96–2.87 (m, 1H, 3-H);
13C NMR (100 MHz, DMSO-d6) d: 173.9, 166.7, 152.1, 147.7,
147.0, 140.7, 136.5, 135.8, 133.2, 133.0, 130.8, 129.6, 129.2,
127.5, 109.7, 108.2, 101.5, 60.0, 55.9, 50.6, 42.9, 40.5, 37.7;
ESI-MS: m/z 596.5 [M]+.
NMR (400 MHz, DMSO-d6) d: 7.69 (d, 1H, 600-H, J = 8.8 Hz), 6.74–
6.62 (m, 4H, 4-NH, 5-H, 300-H, 500-H), 6.44 (s, 1H, 8-H), 6.11 (s, 2H,
20,60-H), 5.98 (ABq, 2H, –OCH2O–), 4.84 (dd, 1H, 4-H, J = 8.4,
4 Hz), 4.33 (d, 1H, 1-H, J = 5.6 Hz), 3.91–3.88 (m, 2H, 11-H), 3.84
(s, 3H, 200-OCH3), 3.81 (s, 3H, 400-OCH3), 3.62 (s, 6H, 30,50-OCH3),
3.59 (s, 3H, 40-OCH3), 2.98 (t, 1H, 12b-H, J = 8.4 Hz), 2.71 (t, 1H,
4.2.16. 4b-N-(400-Methylphenylsulfonylurea)-4-
12a
-H, J = 8.8 Hz), 2.37–2.27 (m, 2H, 3, 2-H); 13C NMR (100 MHz,
deoxyepipodophyllotoxin (14d)
DMSO-d6) d: 172.1, 164.8, 157.8, 152.4, 152.3, 151.3, 147.2,
146.5, 136.7, 136.1, 132.3, 130.8, 119.1, 109.5, 109.4, 108.8,
107.3, 107.1, 105.0, 101.2, 101.0, 99.2, 68.9, 67.1, 59.9, 56.3, 46.7,
44.6, 40.0, 38.4, 21.1; ESI-MS: m/z 643.1 [M+H]+.
Yield: 49%; mp: 197–198 °C; ½a D21
ꢀ
ꢁ 57:5ꢂ (c 0.5, CHCl3); 1H
NMR (400 MHz, DMSO-d6) d: 7.81 (d, 2H, 200,600-H, J = 8.4 Hz), 7.41
(d, 2H, 300,500-H, J = 8 Hz), 6.71 (s, 1H, 5-H), 6.52 (s, 1H, 8-H), 6.22
(s, 2H, 20,60-H), 5.99 (ABq, 2H, –OCH2O–), 4.89 (dd, 1H, 4-H, J = 8,
4.8 Hz), 4.51 (d, 1H, 1-H, J = 5.6 Hz), 4.15 (t, 1H, 11b-H, J = 8 Hz),
4.3. Antiproliferative activity assay
4.01–3.95 (m, 1H, 11a
-H), 3.61 (s, 6H, 30,50-OCH3), 3.59 (s, 3H,
40-OCH3), 3.15–3.10 (m, 1H, 2-H), 2.89–2.79 (m, 1H, 3-H), 2.39 (s,
3H, 400-CH3); 13C NMR (100 MHz, DMSO-d6) d: 174.4, 152.1,
147.4, 146.8, 136.4, 135.8, 132.0, 129.3, 127.3, 109.5, 109.2,
108.2, 101.5, 68.3, 60.0, 55.9, 47.7, 43.1, 40.5, 36.9, 30.9, 21.2;
ESI-MS: m/z 649.3 [M+K]+.
Antiproliferative activity was determined by the sulforhoda-
mine B (SRB) colorimetric assay as previously described.26 In brief,
the cells (3–5 ꢃ 103 cells/well) were seeded in 96-well plates filled
with RPMI-1640 medium supplemented with 10% fetal bovine ser-
um (FBS) containing various concentrations of samples, and incu-
bated for 72 h. At the end of the exposure period, the attached
cells were fixed with cold 50% trichloroacetic acid for 30 min fol-
lowed by staining with 0.04% SRB (Sigma Chemical Co.) for
30 min. The bound SRB was solubilized in 10 mM Tris-base and
the absorbance was measured at 515 nm on a Microplate Reader
ELx800 (Bio-Tek Instruments, Winooski, VT) with a Gen5 software.
All results were representative of three or more experiments.
4.2.17. 4b-N-(400-Chlorophenylsulfonylurea)-4-
deoxyepipodophyllotoxin (14e)
Yield: 42%; mp: 160–162 °C; ½a D21
ꢀ
ꢁ 45:1ꢂ (c 0.5, CHCl3); 1H
NMR (400 MHz, DMSO-d6) d: 7.93 (d, 2H, 200,600-H, J = 8.4 Hz), 7.69
(d, 2H, 300,500-H, J = 8.8 Hz), 6.73 (s, 1H, 5-H), 6.52 (s, 1H, 8-H),
6.23 (s, 2H, 20,60-H), 5.99 and 5.98 (ABq, 2H, –OCH2O–), 4.90 (dd,
1H, 4-H, J = 7.6, 4.4 Hz), 4.51 (d, 1H, 1-H, J = 5.2 Hz), 4.18 (t, 1H,
11a
-H, J = 8.4 Hz), 3.61 (s, 6H, 30,50-OCH3), 3.59 (s, 3H, 40-OCH3),
3.17 (dd, 1H, 2-H, J = 14.4, 5.6 Hz), 2.92–2.81 (m, 1H, 3-H); 13C
NMR (100 MHz, DMSO-d6) d: 174.4, 152.1, 147.5, 146.8, 136.5,
135.8, 132.1, 129.8, 129.4, 129.3, 108.2, 101.5, 61.6, 60.1, 55.9,
49.8, 47.8, 43.1, 36.8; ESI-MS: m/z 631.5 [M+H]+.
Acknowledgments
This work was supported financially by the National Natural
Science Foundation of China (30800720, 31371975); the
Fundamental Research Funds for the Central Universities (lzujb-
ky-2013-69); the Young Scholars Science Foundation of Lanzhou
Jiaotong University (2011011), and NIH Grant CA177584 from
the National Cancer Institute awarded to K.H.L. Thanks are also
due to the support of Taiwan Department of Health Cancer Re-
search Center of Excellence (DOH-100-TD-C-111-005).
4.2.18. 4b-N-(Methylsulfonylurea)-4-
deoxyanhydroepipodophyllotoxin (21a)
Yield: 47%; mp: 153–155 °C; ½a D21
ꢀ
ꢁ 51:1ꢂ (c 0.5, CHCl3); 1H
NMR (400 MHz, DMSO-d6) d: 6.88 (d, 1H, 4-NH, J = 8.4 Hz), 6.83
(s, 1H, 5-H), 6.45 (s, 1H, 8-H), 6.14 (s, 2H, 20,60-H), 5.99 and 5.97

210
Z.-J. Zhang et al. / Bioorg. Med. Chem. 22 (2014) 204–210
16. Zhou, X. M.; Wang, Z. Q.; Chen, H. X.; Cheng, Y. C.; Lee, K. H. Pharm. Res. 1993,
References and notes
10, 214.
17. Zhang, Y. L.; Guo, X.; Cheng, Y. C.; Lee, K. H. J. Med. Chem. 1994, 37, 446.
18. Zhu, X. K.; Guan, J.; Tachibana, Y.; Bastow, K. F.; Cho, S. J.; Cheng, H. H.; Cheng,
Y. C.; Gurwith, M.; Lee, K. H. J. Med. Chem. 1999, 42, 2241.
19. Xiao, Z. Y.; Bastow, K. F.; Vance, J. R.; Sidwell, R. S.; Wang, H. K.; Chen, M. S.; Shi,
Q.; Lee, K. H. J. Med. Chem. 2004, 47, 5140.
20. Li, W. Q.; Wang, X. L.; Qian, K. D.; Liu, Y. Q.; Wang, C. Y.; Yang, L.; Tian, J.;
Morris-Natschke, S. L.; Zhou, X. W.; Lee, K. H. Bioorg. Med. Chem. 2013, 21, 2363.
21. Casini, A.; Scozzafava, A.; Mastrolorenzo, A.; Supuran, C. T. Curr. Cancer Drug
Targets 2002, 2, 55.
22. Yu, Y. P.; Chen, S. Y.; Wang, Y. G.; Chen, Y. Z. Tetrahedron Lett. 1999, 40, 1967.
23. Zhou, X. M.; Lee, K. J. H. J.; Cheng, J.; Wu, S. S.; Chen, H. X.; Guo, X.; Cheng, Y. C.;
Lee, K. H. J. Med. Chem. 1994, 37, 287.
24. Skehan, P.; Storeng, R.; Scudiero, D.; Monks, A.; McMahon, J.; Vistica, D.;
Warren, J. T.; Bokesch, H.; Kenney, S.; Boyd, M. R. J. Natl. Cancer Inst. 1990, 82,
1107.
1. Desbène, S.; Giorgi-Renault, S. Curr. Med. Chem. Anti-Cancer Agents 2002, 2, 71.
2. Liu, Y. Q.; Yang, L.; Tian, X. Curr. Bioact. Compd. 2007, 3, 37.
3. Gordaliza, M.; Castro, M. A.; del Corral, J. M.; Feliciano, A. S. Curr. Pharm. Des.
2000, 6, 1811.
4. Xu, H.; Lv, M.; Tian, X. Curr. Med. Chem. 2009, 16, 327.
5. De Jong, R. S.; Slijfer, E. A. M.; Uges, B. R. A.; Mulder, N. H.; de Vries, E. G. E. Br. J.
Cancer 1997, 76, 1480.
6. Lee, K. H.; Beers, S. A.; Mori, M.; Wang, Z.; Kuo, Y. H.; Li, L.; Liu, S. Y.; Chang, J. Y.;
Han, F. S.; Chen, Y. C. J. Med. Chem. 1990, 33, 1364.
7. Youngjae, Y. Curr. Pharm. Des. 2005, 11, 1695.
8. Zhang, Y. L.; Tropscha, A.; McPhail, A. T.; Lee, K. H. J. Med. Chem. 1994, 37, 1460.
9. Huang, T. S.; Lee, C. C.; Chao, Y.; Shu, C.-H.; Chen, L. T.; Chen, L. L.; Chen, M. H.;
Yuan, C. C.; Peng, W. J. Pharm. Res. 1999, 16, 997.
10. Byl, J. A. W.; Cline, S. D.; Utsugi, T.; Kobunai, T.; Yamada, Y.; Osheroff, N.
Biochemistry 2001, 40, 712.
11. Bromberg, K. D.; Burgin, A. B.; Osheroff, N. J. Biol. Chem. 2003, 278, 7406.
12. Lee, K. H. J. Nat. Prod. 2004, 67, 273.
13. Lee, K. H.; Beers, S. A.; Mori, M.; Wang, Z. Q.; Kuo, Y. H.; Li, L.; Liu, S. Y.; Chang, J.
Y.; Han, F. S.; Cheng, Y. C. J. Med. Chem. 1990, 33, 1364.
14. Wang, Z. Q.; Kuo, Y. H.; Schnur, D.; Bowen, J. P.; Liu, S. Y.; Han, F. S.; Chang, J. Y.;
Cheng, Y. C.; Lee, K. H. J. Med. Chem. 1990, 33, 2660.
25. Gutanvarc’h, D.; Duca, M.; Boukarim, C.; Kraus-Berthier, L.; Léonce, S.; Pierré,
A.; Pfeiffer, B.; Renard, P.; Arimondo, P. B.; Monneret, C.; Dauzonne, D. J. Med.
Chem. 2004, 47, 2365.
26. Xi, P. X.; Xu, Z. H.; Liu, X. H. J. Fluoresc. 2009, 19, 63.
27. Xi, P. X.; Xu, Z. H.; Liu, X. H. Chem. Pharm. Bull. (Tokyo) 2008, 56, 541.
15. Zhou, X. M.; Wang, Z. Q.; Chang, J. Y.; Chen, H. X.; Cheng, Y. C.; Lee, K. H. J. Med.
Chem. 1991, 34, 3346.