Design, synthesis and biological evaluation of 3-aryl-rhodanine benzoic acids as anti-apoptotic protein Bcl-2 inhibitors

Article abstract of DOI:10.1016/j.bmcl.2015.09.051

A new class of 3-aryl-rhodanine benzoic acid derivatives were designed, synthesized, and evaluated for their inhibition activities against anti-apoptotic Bcl-2 proteins. The potent compounds 33 and 41 bound to Bcl-2 with submicromolar K_i values and had selectivities to Bcl-2/Mcl-1 over Bcl-xL. In addition, they exhibited obvious antiproliferative activities in three human tumor cell lines (MDA-MB-231, K562 and PC-3).

Full text of DOI:10.1016/j.bmcl.2015.09.051

Bioorganic & Medicinal Chemistry Letters xxx (2015) xxx–xxx
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Design, synthesis and biological evaluation of 3-aryl-rhodanine
benzoic acids as anti-apoptotic protein Bcl-2 inhibitors
⇑
Huansheng Fu, Xuben Hou, Lei Wang, Yanyan Dun, Xinying Yang, Hao Fang
Department of Medicinal Chemistry, Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmacy, Shandong University, 44 West Wenhua Rd, Ji’nan 250012,
PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
A new class of 3-aryl-rhodanine benzoic acid derivatives were designed, synthesized, and evaluated for
their inhibition activities against anti-apoptotic Bcl-2 proteins. The potent compounds 33 and 41 bound
to Bcl-2 with submicromolar Ki values and had selectivities to Bcl-2/Mcl-1 over Bcl-xL. In addition, they
exhibited obvious antiproliferative activities in three human tumor cell lines (MDA-MB-231, K562 and
PC-3).
Received 11 May 2015
Revised 5 September 2015
Accepted 22 September 2015
Available online xxxx
Ó 2015 Published by Elsevier Ltd.
Keywords:
Apoptosis
Bcl-2
Inhibitor
Rhodanine
Apoptosis is a highly conserved process which is triggered by
cellular stimuli of internal or external. Evasion of apoptosis is a
hallmark of human cancer and contributes to the resistance to con-
ventional therapies.1 As a result, targeting key apoptosis regulators
is promising therapeutic strategy for malignancies treatment.
The Bcl-2 (B-cell lymphocyte/leukemia-2) family proteins are
key regulators of apoptosis and composed of anti-apoptotic pro-
teins, including Bcl-2, Bcl-xL, Mcl-1, Bfl-1/A1, Bcl-B and Bcl-w,
and pro-apoptotic proteins, such as BAK, BAX, BID, BIM and
BAD.2,3 Studies show that the anti-apoptotic Bcl-2 proteins are
over-expressed in multiple types of human cancers such as B-cell
lymphomas,4 prostate cancers5 and breast carcinomas.6 And they
are contributors of cancer initiation, progression, and resistance
to current anti-tumor treatments.7 As
a consequence, anti-
apoptotic Bcl-2 proteins have become attractive targets for the
treatment of various human cancers and different series of small-
molecule inhibitors have been reported.8–13 Navitoclax (ABT-263,
1), a dual inhibitor of Bcl-2 and Bcl-xL,14–17 and Obatoclax
(GX15-070, 2), a pan Bcl-2 family inhibitor,18–21 were currently
in phase I/II clinical trials (Fig. 1).
Rhodanine (2-thioxo-4-thiazolidinone) is a very common active
fragment in antitumor agents,22–24 and some rhodanine-based
derivatives have been developed as potent Bcl-2 family
inhibitors.25–30 The first of them, BH3I-1 (3), bound to the BH3
binding site of Bcl-2 proteins and induce apoptosis.25 After that,
Figure 1. Representative small-molecule inhibitors of anti-apoptotic Bcl-2
proteins.
WL-276 (4) was developed and the preliminary biological activity
assay showed that it could suppress tumor growth.30 And further
SAR studies and optimization of WL-276 has been done by our
group.31 Recently, we found a new rhodanine compound 5 with
⇑
Corresponding author. Tel./fax: +86 531 88382731.
E-mail address: haofangcn@sdu.edu.cn (H. Fang).
http://dx.doi.org/10.1016/j.bmcl.2015.09.051
0960-894X/Ó 2015 Published by Elsevier Ltd.
Please cite this article in press as: Fu, H.; et al. Bioorg. Med. Chem. Lett. (2015), http://dx.doi.org/10.1016/j.bmcl.2015.09.051

2
H. Fu et al. / Bioorg. Med. Chem. Lett. xxx (2015) xxx–xxx
3-aryl-rhodanine benzoic acid structure showed 18% inhibition
against Bcl-2 protein at 100 M, which indicated that the
ities against Bcl-2 proteins and their in vitro antiproliferative
activities.
l
3-aryl-5-ylidene-rhodanine benzoic acid derivatives might possess
potential Bcl-2 inhibition. In our on-going studies, further struc-
tural modifications were focused on the 3-position of rhodanine
with more complicated aryl or benzyl group and another aromatic
ring (–Ar–X–) was introduced to 5-position of rhodanine based on
previous studies (Fig. 2). Herein, we report the synthesis of a series
of 3-aryl-rhodanine benzoic acid derivatives, their inhibition activ-
As shown in Scheme 1, the intermediates substituted 8a–8e
were prepared through substitution32 and/or coupling33 reaction.
And the N-arylsubstituted rhodanines were prepared through
two different methods. While 13a–13c and 13e–13o were follow-
ing the same literature,34 4-nitrophenyl rhodanine (13d) was syn-
thesized from 4-nitroaniline (12d) and bis(carboxymethyl)
trithiocarbonate35 (Scheme 2).
Figure 2. Representative rhodanine-based Bcl-2 inhibitors and design of our 3-aryl-rhodanine benzoic acid derivatives.
Scheme 1. Synthesis of intermediates 8a–8e. Reagents and conditions: (a) K2CO3, acetone, reflux; (b) NaHCO3, THF, 0 °C; (c) oxalyl chloride, NaHCO3, THF, 0 °C.
Scheme 2. Synthesis of target compounds 14–44. Reagents and conditions: (a) (i) CS2, Et3N, ethanol; (ii) ClCH2COONa, H2O; (iii) 6 M HCl, 85 °C; (b) SC(SCH2COOH)2, H2O,
reflux; (c) NH4Ac, HAc, reflux.
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H. Fu et al. / Bioorg. Med. Chem. Lett. xxx (2015) xxx–xxx
3
Table 2
After all the intermediates had been synthesized, the target
The binding affinities of representative target compounds to three Bcl-2 proteins
compounds 14–44 were afforded through the aldol reaction of 13
with 8 in the presence of acetic acid and ammonium acetate.36
Using fluorescence polarization assays (FPAs), affinities of the
target compounds for Bcl-2 were tabulated as Ki values in Table 1.
According to the data in Table 1, many target compounds showed
better affinities for Bcl-2 protein than the previous compound 5.
And some exhibited similar activities compared with WL-276. Also,
both the substituents on aromatic ring A (R) or C (R0, –COOH) and
the linker X between aromatic ring B and C had important effects
on the binding affinity for Bcl-2. For example, when R was hydro-
Compd
Kia
Bcl-2
(lM)
Bcl-xL
Mcl-1
19
21
22
33
41
42
WL-276
Gossypol
>10
>10
>10
3.9 0.9
>10
>10
0.57 0.24
0.64
3.1 0.8
2.0 0.2
1.6 0.2
0.90 0.10
0.61 0.06
4.3 0.7
0.50 0.04
0.44
3.2 0.5
3.9 1.7
3.7 1.2
0.72 0.07
0.70 0.11
1.6 0.4
0.29 0.04
0.31
gen, compounds 14–18 displayed poor affinities (Ki P 9 lM). And
a
Each value was reproduced in three independent assays and expressed with
most of the substitutions on 3- or 4-position of the phenyl A did
not improve the activities except 4-nitro, 4-bromo and 4-iodo
(27, 41 and 42). While 4-nitro and 4-iodo groups minor increased
standard deviations.
the affinities of 27 (Ki = 3.1
stituted 41 showed higher affinities with the Ki value of 0.61
l
M) and 42 (Ki = 4.3
l
M), 4-bromo sub-
M.
phenyl A were benefit for the interaction of inhibitors and the
Bcl-2 protein. Moreover, the activity of 43 also confirmed this
hypothesis. Its poor affinity for Bcl-2 was likely due to the elec-
tron-withdrawing fluorine substituents. Besides, the fact that tar-
get compound 44 displayed poor affinity for Bcl-2 suggested
addition of one methylene between phenyl A and rhodanine did
not improve the compounds’ activities.
l
The results indicated that halogen substitution on 4-position of
phenyl A exhibited significant effect on binding affinities. On the
other hand, the substituents on ortho-position of phenyl A signifi-
cantly impacted the activities as well. For example, o-methyl and
o-methoxy substituted compounds (19, 21, 22, 33, 34) showed
much better activities than unsubstituted 14–18. The results indi-
cated that electron donating groups (EDGs) on ortho-position of
And for the substituents on aromatic ring C, 2-nitro and 5-car-
boxy disubstitution was better than 4-carboxyl monosubstitution,
Table 1
The structure and in vitro Bcl-2 inhibitory activity of 14–44
Compd
R
n
X
R0
Position of –COOH
Kia
(lM)
5
>10
>10
>10
>10
9.0 4.4
>10
3.1 0.8
>10
2.0 0.2
1.6 0.2
10 2.5
>10
>10
>10
3.1 0.9
>10
>10
>10
>10
>10
0.90 0.10
7.6 1.5
>10
9.6 2.2
>10
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
WL-276
H
H
H
H
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
4-OCH2–
3-OCH2–
4-OCH2CONH–
4-OCH2–
4-CONH–
3-OCH2–
4-OCH2CONH–
4-OCH2–
3-OCH2–
4-OCH2CONH–
4-OCH2–
3-OCH2–
4-OCH2CONH–
4-OCH2–
4-CONH–
4-OCH2–
4-OCH2CONH–
4-OCH2–
4-OCH2CONH–
4-OCH2–
4-OCH2CONH–
4-OCH2–
4-OCH2–
4-OCH2–
4-OCH2–
—
—
—
2-NO2
4-OH
—
—
—
—
—
—
—
4
4
4
5
3
4
4
4
4
4
4
4
4
5
3
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
H
2-CH3
2-CH3
2-OCH3
2-OCH3
2-OCH3
4-NO2
4-NO2
4-NO2
4-NO2
4-NO2
3-CH3
3-CH3
4-CH3
4-CH3
2,6-(CH3)2
2,6-(CH3)2
4-OCH3
3-NO2
4-COCH3
3-CF3
4-F
—
2-NO2
4-OH
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
>10
>10
>10
0.61 0.06
4.3 0.7
>10
>10
0.50 0.04
4-OCH2–
4-OCH2–
4-OCH2–
4-OCH2–
4-OCH2–
4-OCH2–
4-Cl
4-Br
4-I
2,6-F2
4-F
—
a
Each value was reproduced in three independent assays and expressed with standard deviations.
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4
H. Fu et al. / Bioorg. Med. Chem. Lett. xxx (2015) xxx–xxx
Figure 3. (A) Docked compound 41 with Bcl-2 (PDB code 2O2F). (B) The docking mode of compound 41 in the active site of Bcl-2 protein.
as both the two target compounds 17 and 27 showed more potent
activities than 4-carboxyl substituted 14 and 24.
better or similar compared with WL-276 against all the tested can-
cer cells. And it appeared that all the target compounds showed
better growth inhibition activities toward solid tumor cell
(MDA-MB-231 and PC-3) than blood cancer (K562). Of them, 41
had slightly higher inhibitory potency than 33 against the tested
tumor cells.
In conclusion, we had designed and synthesized a series of rho-
danine-based benzoic acid derivatives as Bcl-2 inhibitors. The
strong affinities of compounds 19, 21, 22, 33 and 41 suggested that
the ortho-methylphenyl, ortho-methoxyphenyl and para-bro-
mophenyl substituents on 3-position of rhodanine and a suitable
linking group between aromatic rings B and C were benefit for
potency. Also, they had much better activities than the initial com-
pound 5. In addition, all the tested compounds showed Bcl-2/Mcl-1
selectivities over Bcl-xL, and the most potent 33 and 41 displayed
obvious antiproliferative activities. These results indicated that
rhodanine-based benzoic acid derivatives could be used as lead
compounds to develop novel Bcl-2 inhibitors.
In addition, the linker X between aromatic ring B and C also
affected the affinity activities. When R0 was the same substituent,
the compounds 21 and 22 had good appetency with Ki value in
the low micromolar range in the case of the phenoxyl group was
connected with alkylbenzoic acid. Nevertheless, 23 showed poor
affinity activity (Ki = 10 lM) owing to the acetamidobenzoic acid
linked. Also, 19–20 and 33–34 had the same trends. This result
suggested that X was important to binding affinities as well.
We also explored if these rhodanine-based benzoic acid com-
pounds could inhibit other anti-apoptotic Bcl-2 proteins. Six com-
pounds 19, 21, 22, 33, 41 and 42, which showed potent binding
affinities for Bcl-2 with Ki of low micromolar, were chosen to eval-
uate their activities against Mcl-1 and Bcl-xL (Table 2). The results
showed that all the compounds exhibited good affinities for Bcl-2
and Mcl-1. But they had poor inhibitory activity against Bcl-xL. It
suggested that the rhodanine-based benzoic acid derivatives might
have Bcl-2/Mcl-1 selectivities.
To better studying the interactions of these rhodanine-based
benzoic acid derivatives to Bcl-2 protein, the most potent com-
pound 41 were chosen to dock with Bcl-2 protein in the active site
using AutoDock 4.2,37 which was a widely used docking program
with exceptional accuracy (Fig. 3). The results suggested that com-
pound 41 could reasonably bind to the active pocket of Bcl-2 pro-
tein. And the benzoic acid group could form one hydrogen bond
with Phe109.
Acknowledgments
Thanks for the binding assay for Bcl-2 proteins by Prof. Renxiao
Wang from Shanghai Institute of Organic Chemistry in China. This
work was supported by National Natural Science Foundation China
(No. 21172133), Shandong Natural Science Fund for Distinguished
Young Scholars (No. JQ201319) and the Program for New Century
Excellent Talents in University (No. NCET-12-0337).
To further examine the activities of rhodanine-based benzoic
acids at the cellular level, the potent target compounds 33 and
41 were selected to test their antiproliferative activities taking
WL-276 and Gossypol as control. Three cancer cells, MDA-MB-
231 (human breast cancer cell), K562 (human myelogenous leuke-
mia cell) and PC-3 (human prostate cancer cell), were evaluated
using MTT (3-[4,5-dimethyl-2-thiazolyl]-2,5-diphenyl-2H-tetra-
zoliumbromide) assay. According to the data in Table 3, both 33
and 41 displayed obvious antiproliferative activities, which were
References and notes
1. Hanahan, D.; Weinberg, Robert A. Cell 2011, 144, 646.
2. Cory, S.; Adams, J. M. Nat. Rev. Cancer 2002, 2, 647.
3. Bose, P.; Grant, S. Leuk. Res. Rep. 2013, 2, 12.
4. Korsmeyer, S. J. Cancer Res. 1999, 59, 1693s.
5. Rosser, C. J.; Reyes, A. O.; Vakar-Lopez, F.; Levy, L. B.; Kuban, D. A.; Hoover, D. C.;
Lee, A. K.; Pisters, L. L. Int. J. Radiat. Oncol. Biol. Phys. 2003, 56, 1.
6. Jaberipour, M.; Habibagahi, M.; Hosseini, A.; Abbasi, M.; Sobhani-Lari, A.; Talei,
A.; Ghaderi, A. Indian J. Cancer 2010, 47, 412.
7. Kirkin, V.; Joos, S.; Zornig, M. Biochim. Biophys. Acta 2004, 1644, 229.
8. Petros, A. M.; Swann, S. L.; Song, D.; Swinger, K.; Park, C.; Zhang, H.; Wendt, M.
D.; Kunzer, A. R.; Souers, A. J.; Sun, C. Bioorg. Med. Chem. Lett. 2014, 24, 1484.
9. Song, T.; Li, X.; Chang, X.; Liang, X.; Zhao, Y.; Wu, G.; Xie, S.; Su, P.; Wu, Z.; Feng,
Y.; Zhang, Z. Bioorg. Med. Chem. 2013, 21, 11.
Table 3
Antiproliferative activities of representative compounds
10. Zheng, C. H.; Yang, H.; Zhang, M.; Lu, S. H.; Shi, D.; Wang, J.; Chen, X. H.; Ren, X.
H.; Liu, J.; Lv, J. G.; Zhu, J.; Zhou, Y. J. Bioorg. Med. Chem. Lett. 2012, 22, 39.
11. Tang, G.; Ding, K.; Nikolovska-Coleska, Z.; Yang, C. Y.; Qiu, S.; Shangary, S.;
Wang, R.; Guo, J.; Gao, W.; Meagher, J.; Stuckey, J.; Krajewski, K.; Jiang, S.;
Roller, P. P.; Wang, S. J. Med. Chem. 2007, 50, 3163.
12. Wang, G.; Nikolovska-Coleska, Z.; Yang, C. Y.; Wang, R.; Tang, G.; Guo, J.;
Shangary, S.; Qiu, S.; Gao, W.; Yang, D.; Meagher, J.; Stuckey, J.; Krajewski, K.;
Jiang, S.; Roller, P. P.; Abaan, H. O.; Tomita, Y.; Wang, S. J. Med. Chem. 2006, 49,
6139.
a
Compd
IC50
(l
M)
MDA-MB-231
K562
PC-3
33
41
WL-276
Gossypol
25.6 1.8
19.8 1.1
>30
46.6 3.2
43.8 1.5
32.8 + 1.4
7.31 0.34
25.8 3.4
18.9 1.9
>30
4.80 1.00
5.61 0.18
a
13. Kaneko, M.; Nakashima, T.; Uosaki, Y.; Hara, M.; Ikeda, S.; Kanda, Y. Bioorg. Med.
Chem. Lett. 2001, 11, 887.
Inhibitory data are means of no fewer than two independent determinations
and expressed with standard deviations.
Please cite this article in press as: Fu, H.; et al. Bioorg. Med. Chem. Lett. (2015), http://dx.doi.org/10.1016/j.bmcl.2015.09.051

H. Fu et al. / Bioorg. Med. Chem. Lett. xxx (2015) xxx–xxx
5
14. Vlahovic, G.; Karantza, V.; Wang, D.; Cosgrove, D.; Rudersdorf, N.; Yang, J.;
Xiong, H.; Busman, T.; Mabry, M. Invest. New Drugs 2014, 32, 976.
15. Xiong, H.; Pradhan, R. S.; Nada, A.; Krivoshik, A. P.; Holen, K. D.; Rhodes, J. W.;
Gordon, G. B.; Humerickhouse, R.; Awni, W. M. Anticancer Res. 2014, 34, 3739.
16. Cleary, J. M.; Lima, C. M.; Hurwitz, H. I.; Montero, A. J.; Franklin, C.; Yang, J.;
Graham, A.; Busman, T.; Mabry, M.; Holen, K.; Shapiro, G. I.; Uronis, H. Invest.
New Drugs 2014, 32, 937.
17. Park, C. M.; Bruncko, M.; Adickes, J.; Bauch, J.; Ding, H.; Kunzer, A.; Marsh, K. C.;
Nimmer, P.; Shoemaker, A. R.; Song, X.; Tahir, S. K.; Tse, C.; Wang, X.; Wendt, M.
D.; Yang, X.; Zhang, H.; Fesik, S. W.; Rosenberg, S. H.; Elmore, S. W. J. Med. Chem.
2008, 51, 6902.
18. Oh, J. H.; Lee, J. Y.; Park, J. H.; No, J. H.; Lee, N. K. Mol. Cells 2015, 38, 279.
19. Schimmer, A. D.; Raza, A.; Carter, T. H.; Claxton, D.; Erba, H.; DeAngelo, D. J.;
Tallman, M. S.; Goard, C.; Borthakur, G. PLoS One 2014, 9, e108694.
20. Goy, A.; Hernandez-Ilzaliturri, F. J.; Kahl, B.; Ford, P.; Protomastro, E.; Berger, M.
Leuk. Lymphoma 2014, 55, 2761.
28. Bernardo, P. H.; Sivaraman, T.; Wan, K. F.; Xu, J.; Krishnamoorthy, J.; Song, C.
M.; Tian, L.; Chin, J. S.; Lim, D. S.; Mok, H. Y.; Yu, V. C.; Tong, J. C.; Chai, C. L. J.
Med. Chem. 2010, 53, 2314.
29. Li, H. Q.; Yang, J.; Ma, S.; Qiao, C. Bioorg. Med. Chem. 2012, 20, 4194.
30. Wang, L.; Sloper, D. T.; Addo, S. N.; Tian, D.; Slaton, J. W.; Xing, C. Cancer Res.
2008, 68, 4377.
31. Wan, Y.; Wu, S.; Xiao, G.; Liu, T.; Hou, X.; Chen, C.; Guan, P.; Yang, X.; Fang, H.
Bioorg. Med. Chem. 2015, 23, 1994.
32. Krishnamachari, V.; Levine, L. H.; Zhou, C.; Paré, P. W. Chem. Res. Toxicol. 2004,
17, 795.
33. Fu, H.; Han, L.; Hou, X.; Dun, Y.; Wang, L.; Gong, X.; Fang, H. Bioorg. Med. Chem.
2015, 23, 5774.
34. Shahwar, D.; Tahir, M. N.; Yasmeen, A.; Ahmad, N.; Khan, M. A. Acta Crystallogr.
2009, E65, o3014.
35. Brown, F. C.; Bradsher, C. K.; Morgan, E. C.; Tetenbaum, M.; Wilder, P., Jr. J. Am.
Chem. Soc. 1956, 78, 384.
21. Chiappori, A.; Williams, C.; Northfelt, D. W.; Adams, J. W.; Malik, S.; Edelman,
M. J.; Rosen, P.; Van Echo, D. A.; Berger, M. S.; Haura, E. B. J. Thorac. Oncol. 2014,
9, 121.
36. Procedure for the synthesis of representative (Z)-4-((4-((3-(4-bromophenyl)-4-
oxo-2-thioxothiazolidin-5-ylidene)methyl)phenoxy)methyl)benzoic acid (41):
3-(4-bromophenyl)rhodanine
(13m,
0.14 g,
0.5 mmol)
and
4-((4-
22. Azizmohammadi, M.; Khoobi, M.; Ramazani, A.; Emami, S.; Zarrin, A.; Firuzi, O.;
Miri, R.; Shafiee, A. Eur. J. Med. Chem. 2013, 59, 15.
23. Min, G.; Lee, S. K.; Kim, H. N.; Han, Y. M.; Lee, R. H.; Jeong, D. G.; Han, D. C.;
Kwon, B. M. Bioorg. Med. Chem. Lett. 2013, 23, 3769.
24. Ramesh, V.; Ananda Rao, B.; Sharma, P.; Swarna, B.; Thummuri, D.; Srinivas, K.;
Naidu, V. G.; Jayathirtha Rao, V. Eur. J. Med. Chem. 2014, 83, 569.
25. Degterev, A.; Lugovskoy, A.; Cardone, M.; Mulley, B.; Wagner, G.; Mitchison, T.;
Yuan, J. Nat. Cell Biol. 2001, 3, 173.
26. Bernardo, P. H.; Sivaraman, T.; Wan, K.-F.; Xu, J.; Krishnamoorthy, J.; Song, C.
M.; Tian, L.; Chin, J. S. F.; Lim, D. S. W.; Mok, H. Y. K.; Yu, V. C.; Tong, J. C.; Chai, C.
L. L. Pure Appl. Chem. 2011, 83, 723.
formylphenoxy)methyl)benzoic acid (8a, 0.13 g, 0.5 mmol) were dissolved in
acetic acid (3 ml) under reflux condition. Ammonium acetate (0.15 g, 2 mmol)
was then added. The mixture was stirred 0.5 h, and precipitation occurred. The
precipitate was filtered off, washed with acetic acid and absolute ethanol to
afford the product. Yellow solid: mp 263–265 °C; yield 90%. 1H NMR (300 MHz,
DMSO-d6) d 12.99 (s, 1H), 7.98 (d, J = 8.4 Hz, 2H), 7.82 (s, 1H), 7.78 (d, J = 8.7 Hz,
2H), 7.68 (d, J = 8.7 Hz, 2H), 7.59 (d, J = 8.4 Hz, 2H), 7.41 (d, J = 8.7 Hz, 2H), 7.24
(d, J = 8.7 Hz, 2H), 5.32 (s, 2H). 13C NMR (100 MHz, DMSO-d6) d 191.8, 167.0,
165.4, 160.9, 141.3, 135.6, 133.4, 130.4, 129.5, 127.5, 125.5, 118.2, 116.1, 113.0,
112.9, 112.8, 112.7, 69.0. HRMS (AP-ESI) m/z calcd for C24H16BrNO4S2 [M+H]+
525.9777, found 525.9836.
27. Lugovskoy, A. A.; Degterev, A. I.; Fahmy, A. F.; Zhou, P.; Gross, J. D.; Yuan, J.;
Wagner, G. J. Am. Chem. Soc. 2002, 124, 1234.
37. Hou, X.; Du, J.; Zhang, J.; Du, L.; Fang, H.; Li, M. J. Chem. Inf. Model. 2013, 53, 188.
Please cite this article in press as: Fu, H.; et al. Bioorg. Med. Chem. Lett. (2015), http://dx.doi.org/10.1016/j.bmcl.2015.09.051