Synthesis and Anti-proliferative Activity of N,N′-bis-substituted 1,2,4-Triazolium Salts against Breast Cancer and Prostate Cancer Cell Lines

Article abstract of DOI:10.1002/jhet.3428

A series of 1,4-N,N′-bis-substituted 1,2,4-triazolium bromide salts were synthesized and tested for anti-proliferative activity. 1,4-Bis(naphthalen-2-ylmethyl)-1,2,4-triazolium bromide (2) showed activity against MDA-MB-468 breast cancer and PC-3 prostate

Full text of DOI:10.1002/jhet.3428

0
Month 2018
Synthesis and Anti-proliferative Activity of N,N -bis-substituted 1,2,4-
Triazolium Salts against Breast Cancer and Prostate Cancer Cell Lines
a
a
b
c
a
d
Zi Jie Lin, Jared Bies, Shanina S. Johnson, John D. Gorden, Jacqueline F. Strickland, Monica Frazier,
a
a
Jonathan M. Meyers,
and Kerri L. Shelton *
a
Department of Chemistry, Columbus State University, Columbus, GA 31907, USA
b
Department of Chemistry, Spelman College, Atlanta, GA 30314, USA
Department of Chemistry, Auburn University, Auburn, AL 36849, USA
c
d
Department of Biology, Columbus State University, Columbus, GA 31907, USA
*
E-mail: taylor_kerri1@columbusstate.edu
Received August 7, 2018
DOI 10.1002/jhet.3428
Published online 00 Month 2018 in Wiley Online Library (wileyonlinelibrary.com).
0
A series of 1,4-N,N -bis-substituted 1,2,4-triazolium bromide salts were synthesized and tested for anti-
proliferative activity. 1,4-Bis(naphthalen-2-ylmethyl)-1,2,4-triazolium bromide (2) showed activity against
MDA-MB-468 breast cancer and PC-3 prostate cancer cell lines.
J. Heterocyclic Chem., 00, 00 (2018).
INTRODUCTION
compounds [6]. One of these compounds, 1,4-dibenzyl-
,2,4-triazolium bromide (1, Fig. 1), has been shown to
1
The continued challenge of combating cancer,
America’s second leading cause of death, has driven
wide-ranging exploration into novel anticancer therapies
be an antimalarial agent; however, its anti-proliferative
effect on cancer cells has not been reported [7,8].
Two of the most common cancers found in men
(prostate) and women (breast) generally start as hormone-
dependent tumors [9,10]. However, some breast and
prostate cancers are hormone independent [11]. The goal
of this study is to investigate substituent properties,
particularly hydrophilicity, on the therapeutic potential of
1,2,4-triazole derivatives in hormone-independent
breast and prostate cancers. Additionally, the effect of
the heterocycle parent was explored for three
bis(naphthylmethyl)-substituted heterocyclic bromide salts.
Salt 1 was synthesized and tested for anticancer activity
against hormone-independent breast and prostate cancer
cell lines (MDA-MB-468 and PC-3, respectively). Two
[1]. Imidazolium and benzimidazolium salts have recently
been shown to have anticancer activity in non-small cell
lung cancer cell lines [2–4]. Recent advances in the
design of these nitrogen-containing heterocyclic
compounds, such as imidazolium and benzimidazolium
salts, have highlighted the importance of substituent
properties, particularly hydrophilicity, on therapeutic
potential [2,3]. Hydrophilicity is critical to drug
absorption and distribution in aqueous biological solutions
(e.g., blood). There is a constant effort to balance drug
activity and bioavailability. This holds true for
imidazolium and benzimidazolium salts, which despite
potent anticancer activity, exhibit poor aqueous solubility.
Considering these challenges, triazolium salts are
attractive targets for optimization as effective antitumor
agents because of their increased dipole moment.
Triazole derivatives have been used extensively for
medicinal purposes ranging from analgesic to anti-
inflammatory properties [5,6]. Additionally, progress has
been made in the design of triazole-derived antimicrobial
0
additional N,N -bis-substituted 1,2,4-triazolium bromide
salts (2 and 3, Fig. 1) were synthesized and tested to
determine the effect of the solubilizing group on aqueous
solubility and anticancer activity against these cell lines.
The role of the parent heterocycle was also explored by
comparing new compounds with literature imidazolium
salts 4 and 5 (Fig. 1). All treatments were compared with
the chemotherapeutic agent tamoxifen [11].
©
2018 Wiley Periodicals, Inc.

Z. J. Lin, J. Bies, S. S. Johnson, J. D. Gorden, J. F. Strickland, M. Frazier,
J. M. Meyers, and K. L. Shelton
Vol 000
0
Figure 1. Schematic representation of N,N -bis-substituted 1,2,4-triazolium bromide salts (1–3) and literature imidazolium bromide salts (4 and 5).
0
Scheme 1. Synthesis of the N,N -bis-substituted-1,2,4-triazolium bromide salts (1–3).
1
4
RESULTS AND DISCUSSION
alkylation of N and N nitrogen atoms in the triazole
0
ring and transformation into the N,N -bis-substituted
1,2,4-triazolium salts were corroborated by the C NMR
spectra. Electrospray ionization (ESI)-MS in the positive
0
13
Scheme 1 outlines the synthetic procedure of the N,N -
bis-substituted 1,2,4-triazolium salts 1–3 from
commercially available 1,2,4-triazole with yields ranging
from 26 to 62%. The salts were prepared by stirring the
mode was conducted for 1–3, and the corresponding
[M-Br] signal further confirmed identification of the
+
1
,2,4-triazole with a minimum of 1.1 equivalents of a
salts. The structure of 2 was further confirmed by X-ray
crystallography (Fig. 2). Single crystals were grown from
the slow evaporation of a concentrated solution of
ethanol. The carbonyl frequencies of 3 were observed at
hydroxide base (NaOH or KOH) in acetonitrile and
alcohol solvent mixture (9:1, v : v) and one molar
equivalent of the alkyl bromide to yield the mono-
substituted intermediate. Following the removal of the
white precipitate, presumed to be a bromide salt (NaBr or
KBr), a second equivalent of the alkyl halide was added.
The mixture was heated at reflux overnight to yield 1–3.
Salt 3 was isolated in a low yield. The electron-
withdrawing nature of the acyl group is likely to decrease
the nucleophilicity of the mono-substituted 1,2,4-triazole
intermediate and lowering the yield. Inclusion of the
carbonyl group on the alkyl halide reagent may have also
contributed to undesired side reactions. Salts 4 and 5
were synthesized according to literature procedures [2].
ꢀ
1
ꢀ1
1685 cm
infrared spectroscopy.
(C¼O) and 1702 cm
(C¼O) in the
The antimicrobial activity and planar benzyl substituents
of 1 made it an attractive candidate for potential anticancer
activity. Compound 1 had favorable water solubility (log
P = ꢀ1.88 ± 0.06, Table 1) but exhibited poor anti-
proliferative activity against the breast cancer cell line
(IC50 = 86.4 ± 0.2 μM, Table 1) with more than 70%
0
All N,N -bis-substituted 1,2,4-triazolium bromide
1
13
salts 1–3 were characterized by H and C NMR
spectroscopy, high-resolution mass spectrometry (MS),
1
elemental analysis, and melting point determination. H
0
NMR spectroscopy confirmed the formation of the N,N -
bis-substituted 1,2,4-triazolium bromide salts 1–3 with
1
5
the downfield shift in the H NMR of the C -H
Figure 2. Ball and stick structure of 2 based on X-ray crystallography
data. [Color figure can be viewed at wileyonlinelibrary.com]
triazolium proton between 10 and 11 ppm. Similarly,
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

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Month 2018
N,N -bis-substituted 1,2,4-Triazolium Salts
Table 1
Previous work indicated that a bis(naphthylmethyl)-
substituted imidazolium salt was more effective against
tested cancer cells than the dibenzyl analogue [2].
Therefore, the bis(naphthylmethyl) triazolium salt 2 was
synthesized and tested. Salt 2 displayed a substantial
increase in potency (IC50 = 15.79 ± 0.37 μM) and anti-
proliferative activity with less than 15% proliferation at
30 μM against the breast cancer cell line compared with
IC50 values of compounds 1–5 and tamoxifen dissolved in aqueous
growth media against breast cancer (MDA-MB-468) and prostate cancer
(
PC-3) cell lines.
Compound
Breast (μM)
Prostate (μM)
Log P
1
2
3
4
86.4 ± 0.2
15.79 ± 0.37
100 ± 0.15
5.0 ± 0.4
9.7 ± 0.4
22.5 ± 0.4
20.14 ± 0.04
–
ꢀ1.88 ± 0.06
0.17 ± 0.01
0.6 ± 0.1
0.73 ± 0.08
1.3 ± 0.3
–
3.4 ± 0.3
35.07 ± 0.36
9.58 ± 0.23
1. Salt 2 was also more potent than tamoxifen
5
(IC50 = 22.5 ± 0.4 μM) against the breast cancer cell
Tamoxifen
line. However, the increased activity came at the
expense of solubility (log P = 0.17 ± 0.01). Salt 2 was
much less effective against the prostate cancer cell line
The octanol/water partition coefficient is reported as the log P for com-
pounds 1–5. IC50 was not determined for 2 and 3 because of very low
activity.
(75 ± 4% proliferation remaining at 30 μM, Fig. 4).
breast cell proliferation remaining at 30 μM (Fig. 3).
Compound 1 was fivefold more potent against the
prostate cancer cell line (IC50 = 20.14 ± 0.04 μM).
This apparent differential activity suggests that
modification of the parent heterocycle may provide a
route to cell selectivity.
Figure 3. Proliferation of MDA-MB-468 breast cancer cells treated with 1–5. Compounds 1 and 3 had very little anti-proliferative effects even at 30 μM.
Compounds 2, 4, and 5 showed similar anti-proliferative effects at 30 μM. [Color figure can be viewed at wileyonlinelibrary.com]
Figure 4. Proliferation of PC-3 prostate cancer cells treated with 2, 4, and 5. Compounds 4 and 5 showed similar anti-proliferative effects against both
cancer types. In contrast to activity against the breast cancer cell line, salt 2 exhibited very low activity against the prostate cell line. [Color figure can be
viewed at wileyonlinelibrary.com]
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Z. J. Lin, J. Bies, S. S. Johnson, J. D. Gorden, J. F. Strickland, M. Frazier,
J. M. Meyers, and K. L. Shelton
Vol 000
The rigid ring structure of the naphthyl substituent was
necessary for the activity of a bis(naphthylmethyl)
solvents were purchased from Fisher Scientific and Acros
Organics. All reagents and solvents were used as received
without further purification. Melting points were obtained
on a MeltTemp apparatus. Deuterated solvents were
imidazolium salt
4
and
a
bis(naphthylmethyl)
benzimidazolium salt 5 against several non-small cell
lung cancer cell lines [2]. However, the introduction of
an unsubstituted heteroatom and hydrogen bond acceptor
in the parent compound was not explored. The favorable
solubility and activity of 2 warranted comparisons with
reported salts 4 and 5.
1
purchased from Acros Organics and used as received. H
1
3
and C NMR spectra were recorded in DMSO-d (2.50
6
1
and 39.51 ppm, respectively) on a Varian MR-400 ( H
NMR at 400 MHz and
13
C NMR at 100 MHz)
spectrometer equipped with a OneNMR PZT probe.
Spectra were analyzed and processed using MestReNova
version 10.0.1. All NMR spectra were recorded at 25°C.
Data was reported as follow: chemical shift, multiplicity
(s = singlet, d = doublet, q = quartet, m = multiplet, and
br = broad), and integration. MS was performed by the
University of Akron Mass Spectrometry Laboratory
(Akron, OH). Elemental analysis was performed by the
Microanalysis Laboratory in the Department of Geology
at the University of Akron (Akron, OH).
Introduction of the additional unsubstituted nitrogen
increased water solubility of
2 by fourfold (log
P = 0.17 ± 0.01) compared with 4 (log P = 0.73 ± 0.08,
Table 1). Salt 5 was significantly less soluble (log
P = 1.3 ± 0.3, Table 1). Interestingly, while 2 exhibited
increased aqueous solubility, potency was slightly
decreased against the breast cancer line when compared
with 4 and 5 (Table 1). However, the anti-proliferative
activity of 2 was essentially unchanged at 30 μM versus
4
and 5 (Fig. 1).
X-ray structure determination details. X-ray diffraction
In an attempt to further increase the solubility of the N,
data were collected on a “Bruker APEX CCD”
0
N -bis-substituted 1,2,4-triazolium salts, salt 3, containing
the naphthylacyl substituent, was synthesized and tested.
Aqueous solubility of 3 was slightly decreased (log
P = 0.6 ± 0.1, Table 1) compared with 2, and the
biological activity was all but eliminated in both cell
lines. The decrease in activity, caused by the introduction
of the carbonyls near the parent heterocycle, warrants
further investigation.
diffractometer using Mo Kα radiation (λ = 0.71073 Å).
The crystal was kept at 180 K under nitrogen during unit
cell and data collection. SMART (v. 5.624) was used for
preliminary determination of cell constants and data
collection control. Determination of integrated intensities
and global cell refinement was performed with the Bruker
SAINT software package, and empirical absorption
correction (SADABS) was applied. The structures were
solved with the ShelXS structure solution program using
Direct Methods and refined with the olex2.refine
refinement package using Gauss–Newton minimization
CONCLUSION
[
12–15]. Projections were created on Olex2.1 [14].
0
A set of N,N -bis-substituted 1,2,4-triazolium salts with
Cell viability protocol. Cell culture.
MDA-MB-468
1
4
solubilizing groups at the N and N were synthesized.
Results showed that salt 1 did not possess substantial
anticancer activity, regardless of displaying antimalarial
properties. Furthermore, the naphthylmethyl substituent
was required for anticancer activity in both breast and
prostate cell lines. However, the comparison of salts 2, 4,
and 5 indicated that the 1,2,4-triazole heterocycle offered
breast cancer cells, ATCC-HTB-132 (ATCC, Manassas,
VA), and PC-3 prostate cancer cells, ATCC-CRL-1435
(ATCC), were grown according to manufacturer’s
instructions [16,17]. Briefly, MDA-MB-468 and PC-3
cells were grown in L-15 and DMEM/F12K media,
respectively, supplemented with 10% fetal bovine serum
and 1% antibiotic/antimycotic. PC-3 cells were grown in
an
increased
aqueous
solubility
and
overall
5
% CO incubator at 37°C. MDA-MB-468 cells were
2
hydrophilicity. Future work on azolium salts would
include the investigation of other parent heterocycles, in
addition to the exploration of other solubilizing groups on
grown in the absence of CO2 at 37°C. Media was
replaced every 3 days and split once 80% confluency was
reached.
2
3
5
the atoms (N , C , and C ) in the triazole ring.
Compound solutions. All compounds were resuspended
in growth media to a concentration of 1 mM. Solutions
were then diluted 100-fold to make 100 mM stock
solutions that were diluted for further use in the MTT
EXPERIMENTAL
assay.
General
considerations.
1,2,4-Triazole
and
MTT assays. Cell proliferation was assessed by MTT
Cell Proliferation Assay, ATCC 30-1010K (ATCC),
2-(bromoacetyl) naphthalene were purchased from Alfa
Aesar. 2-(Bromomethyl) naphthalene was purchased from
Tokyo Chemical Industry Co., Ltd (TCI). Benzyl
bromide was purchased from CMD Millipore. All
according to the manufacturer’s instructions.[18] Briefly,
cells were plated in triplicate at 1 × 10 cells/mL with
0.1 mL per well in 96-well plates and allowed to adhere
6
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

0
Month 2018
N,N -bis-substituted 1,2,4-Triazolium Salts
overnight. After 24 h incubation, media was removed, and
cells were treated with 0, 1, 5, 15, and 30 μM of
compounds 1–5 and 50, 40, 25, 10, and 0 μM of
tamoxifen solubilized in fresh complete growth media for
diethyl ether and air dried to provide a white powder.
The product was subsequently recrystallized in ethanol to
yield a white crystalline solid 2; yield 0.98 g (62%); mp:
1
232–236°C; H NMR (400 MHz, DMSO-d ) δ = 10.42
6
7
2 h at 37°C. After incubation, MTT reagent (ATCC)
was added to each well and returned to the incubator for
h at 37°C to produce formazan crystals in the dark.
(s, 1H), 9.41 (s, 1H), 8.07–7.55 (m, 14H), 5.80 (s, 2H),
13
1
5.72 (s, 2H); C{ H} NMR (100 MHz, DMSO-d )
6
4
δ = 145.1, 143.0, 132.9, 132.8, 132.7, 132.6, 130.9,
130.6, 128.9, 128.6, 128.4, 128.3, 128.0, 127.9, 127.7,
127.7, 126.9, 126.9, 126.8, 126.7, 126.2, 126.0, 55.1,
50.9. Anal. Calcd. for C H N Br : C, 66.98; H, 4.68;
Next, MTT detergent was added to solubilize crystals and
incubated for another 2 h in the dark. Absorbance was
read at 570 nm with a reference wavelength of 655 nm.
IC50 values were calculated using the AAT Bioquest IC50
calculator (AAT Bioquest, Inc., Sunnyvale, CA).
Standard deviations were calculated using Microsoft Excel.
24
20
3
1
N, 9.76. Found: C, 66.15; H, 4.61; N, 9.70. HR-MS (ESI
+
+). Calcd for C H N [M-Br] : m/z 350.1652. Found
2
4 20 3
m/z 350.1666.
Crystal data for 1,4-bis(naphthalen-3-ylmethyl)-1,2,4-
Partition coefficient determination.
The partition
coefficient was determined using a shake flask method as
triazolium bromide (2): C H BrN , M = 430.35,
24
20
3
described previously [19].
monoclinic, a = 30.947(7) Å, b = 4.5974 (11) Å,
c = 13.909 (3) Å, β = 94.568 (4), V = 1972.6 (8) Å ,
T = 180 K, space group Cc, Z = 4, 17612 reflections
measured, 3486 independent reflections (Rint = 0.0970).
3
Synthetic
,4-dibenzyl-1,2,4-triazolium
procedures. Synthesis
bromide (1).
of
1
Sodium
hydroxide (0.58 g, 14.50 mmol) was added to a solution
of 1,2,4-triazole (0.51 g, 7.38 mmol) in acetonitrile and
methanol (9:1, v/v, 20 mL). The mixture was stirred and
heated at reflux (0.5 h). Benzyl bromide (1.0 mL,
The final R values were 0.0546 (I > 2σ(I)). The final
1
2
wR(F ) values were 0.1077 (I > 2σ(I)). The final R
values were 0.0901 (all data). The final wR(F ) values
1
2
7.96 mmol) was added, and the solution was heated at
were 0.1201 (all data).
Synthesis of 1,4-bis(2-(naphthalen-2-yl)-2-oxoethyl))-1,2,4-
reflux overnight. The reaction mixture was filtered hot via
vacuum to remove a white precipitate, presumed to be
sodium bromide. Benzyl bromide (1.0 mL, 7.96 mmol)
was added to the filtrate, and the mixture was heated at
reflux overnight. The solution mixture was evaporated
under reduced pressure to generate a yellow colored oil,
and the oil was washed with cold acetone to generate a
white precipitate. The precipitate was filtered via vacuum,
and the solids were recrystallized in hot ethanol to yield a
triazolium bromide (3).
Potassium hydroxide (0.25 g,
4.46 mmol) was added to a solution of 1,2,4-triazole
(0.25 g, 3.65 mmol) in acetonitrile and methanol (9:1,
v/v, 10 mL). The mixture was stirred and heated at reflux
(0.5 h). 2-(Bromoacetyl) naphthalene (0.91 g, 3.65 mmol)
was added, and solution was heated at reflux overnight.
The reaction mixture was filtered hot via vacuum to
remove the precipitate presumed to be sodium bromide.
2-(Bromoacetyl) naphthalene (0.92 g, 3.70 mmol) was
added to the filtrate, and the solution was heated at reflux
overnight. The reaction mixture was filtered via vacuum
filtration to generate a light brown solid. The solvent
residues were removed under reduced pressure to yield a
light brown powder 3; yield 0.46 g (26%); mp: 230–
white spindle crystalline solid 1; yield 0.74 g (30%); mp:
1
1
68–170°C; H NMR (400 MHz, DMSO-d ) δ = 10.47
6
(
5
s, 1H), 9.41 (s, 1H), 7.55–7.37 (m, 10H), 5.65 (s, 2H),
.57 (s, 2H); C{ H} NMR (100 MHz, DMSO-d )
13
1
6
δ = 145.0, 142.7, 133.6, 133.2, 129.1, 128.9, 128.9,
28.9, 128.8, 54.8, 50.6. Anal. Calcd. for C H N Br :
1
1
6
16
3
1
ꢀ
1
1
C, 58.19; H, 4.89; N, 12.73. Found: C, 58.19; H, 4.88;
N, 12.72. HR-MS (ESI+). Calcd for C H N [M-Br] :
233°C; FT-IR (cm ): 1685 (C¼O), 1702 (C¼O); H
+
NMR (400 MHz, DMSO-d ) δ = 10.23 (s, 1H), 9.37 (s,
1
6 16 3
6
m/z 250.1339. Found m/z 250.1351.
1H), 8.91–7.69 (m, 16H), 6.61 (s, 2H), 6.42 (s, 2H);
13
1
Synthesis of 1,4-bis(naphthalen-2-ylmethyl)-1,2,4-triazolium
bromide (2).
C{ H} NMR (100 MHz, DMSO-d ) δ = 190.3, 190.3,
6
Sodium hydroxide (0.29 g, 7.25 mmol)
was added to a solution of 1,2,4-triazole (0.25 g,
145.9, 145.4, 135.6, 135.6, 132.0, 130.9, 130.8, 130.7,
1
1
30.6, 199.7, 129.5, 128.9, 128.8, 127.9, 127.5, 127.4,
23.2, 123.2, 58.5, 54.3. Anal. Calcd. for
3
1
.66 mmol) in acetonitrile and methanol (9:1, v/v,
0 mL). The mixture was stirred and heated at reflux
C H N O Br : C, 64.21; H, 4.15; N, 8.64. Found: C,
26 20 3 2 1
(
3
0.5 h). 2-(Bromomethyl) naphthalene (0.84 g,
.80 mmol) was added, and the solution was heated at
6
4.21; H, 4.14; N, 8.64. HR-MS (ESI+). Calcd for
+
C H N O [M-Br] : m/z 406.1550. Found m/z
26 20 3 2
reflux overnight. The reaction mixture was filtered hot to
remove the white precipitate, presumed to be sodium
bromide. 2-(Bromomethyl) naphthalene (0.82 g,
406.1550.
Synthesis of 1,3-bis(naphthalen-3-ylmethyl)-imidazolium
bromide (4). Compound 4 was synthesized according to
3
.71 mmol) was added to the filtrate, and the solution
literature procedure and used without further purification
[2]. H NMR and other characterization matched
previously reported data [2].
1
was heated at reflux overnight. The resulting precipitate
was collected via vacuum filtration and was washed with
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Z. J. Lin, J. Bies, S. S. Johnson, J. D. Gorden, J. F. Strickland, M. Frazier,
J. M. Meyers, and K. L. Shelton
Vol 000
Synthesis
benzimidazolium bromide (5).
synthesized according to literature procedure and used
without further purification [2]. H NMR and other
of
1,3-bis(naphthalen-3-ylmethyl)-
[5] Hafez, H.; Abbas, H.; El-Gazzar, A. Acta Pharm 2008, 58,
3
1
59.
Compound
5
was
[
6] Vanu, K.; Dinaker, A.; Ananthnarayan, C. Indian J Pharm Sci
999, 61, 202.
[7] Vlahakis, J.; Lazar, C.; Crandall, I.; Szarek, W. Bioorg Med
Chem 2010, 18, 6184.
1
characterization matched previously reported data [2].
[8] Capper, C. P.; Rae, J. M.; Auchus, R. J. Horm Cancer 2016, 7,
149.
[
9] American Cancer Society Cancer Facts & Figures 2018;
Acknowledgments. The project has been funded by the College
of Letters and Sciences, Department of Chemistry and Student
Research and Creative Endeavors (SR ACE) grants at
Columbus State University. 1,2,4-Triazole was donated from
Dr. Floyd Jackson. All MS analysis was completed by Chrys
Wesdimiotis and Selim Gerislioglu (Department of Chemistry,
The University of Akron, Akron, OH). Elemental Analysis was
completed by Thomas Quick (Department of Geology, The
University of Akron, Akron, OH).
American Cancer Society: Atlanta, 2018.
[10] Rau, K. M.; Kang, H. Y.; Cha, T. L.; Miller, S. A.; Hung, M.
C. Endocr Relat Cancer 2005, 12, 511.
11] Crandall, I.; Szarek, W.; Vlahakis, J. Triazolium and
imidazolium salts and uses thereof. US Patent 8632914 B2, January 21,
[
2
2
014.
[
[
12] Bruker, Bruker AXS Inc., Madison, Wisconsin, USA, 2001.
13] Sheldrick, G. M. Acta Crystallogr, Sect A: Found Crystallogr
008, A64, 112.
[14] Dolomanov, O. V.; Bourhis, L. J.; Gildea, R. J.; Howard, J. A.
K.; Puschmann, H. J Appl Cryst 2009, 42, 339.
15] Bourhis, L. J.; Dolomanov, O. V.; Gildea, R. J.; Howard, J. A.
K.; Puschmann, H. Acta Crystallogr, Sect A: Found Crystallogr 2015, 71,
[
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DOI 10.1002/jhet