Synthesis and antimicrobial study of organoiridium amido-sulfadoxine complexes

Article abstract of DOI:10.1016/j.ica.2020.120175

Two new ligands, pyridylamido-sulfadoxine (L1) and quinolylamido-sulfadoxine (L2), were prepared by the reaction of the antimicrobial sulfadrug, sulfadoxine, with either 2-picolinic acid or 2-quinaldic acid. Subsequent reaction with a [Cp^xIrCl₂]₂ dimer (where Cp^x = pentamethylcyclopentadiene, tetramethylphenylcyclopentadiene or tetramethylbiphenylcyclopentadiene) yielded six new amidosulfadoxine-derivatized iridium complexes (C1-C6) in moderate to good yields, where the ligands act as N,N’-bidentate chelators. Proton and carbon NMR spectroscopy, mass spectrometry and HPLC data were used to characterize and confirm the purity of all compounds. Aquation chemistry studies on the complexes revealed slow water substitution of the chlorido ancillary ligand. The inhibitory activities of complexes C1-C6 were determined against Mycobacterium tuberculosis (Mtb) H37Rv and Plasmodium falciparum (Pf) strains, 3D7, Dd2 and HB3, as well as the HEK cell line. The ligands showed no appreciable antimicrobial activity, with most of the complexes exhibiting weak to moderate inhibition of Pf and Mtb. However, one complex (C6) displayed potent activity against Pf 3D7 (IC₅₀ of 0.975 μM) and the multidrug-resistant Pf Dd2 (IC₅₀ of 0.766 μM).

Full text of DOI:10.1016/j.ica.2020.120175

Inorganica Chimica Acta 517 (2021) 120175
Contents lists available at ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Research paper
Synthesis and antimicrobial study of organoiridium
amido-sulfadoxine complexes
a
b
b
c
c,d
Timothy J. Kotz ´e , Sandra Duffy , Vicky M Avery , Audrey Jordaan , Digby F. Warner
,
a
e
a,*
Leigh Loots , Gregory S. Smith , Prinessa Chellan
a
Department of Chemistry and Polymer Science, Stellenbosch University, Matieland, Western Cape, South Africa
Discovery Biology, Griffith Institute for Drug Discovery, Griffith University, Nathan, Queensland 4111, Australia
b
c
SAMRC/NHLS/UCT Molecular Mycobacteriology Research Unit, Department of Pathology and Institute of Infectious Disease and Molecular Medicine (IDM), Faculty of
Health Sciences, University of Cape Town, Cape Town, South Africa
d
Wellcome Centre for Infectious Diseases Research in Africa (CIDRI-Africa), Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
e
Department of Chemistry, University of Cape Town, Cape Town, South Africa
A R T I C L E I N F O
A B S T R A C T
Keywords:
Two new ligands, pyridylamido-sulfadoxine (L1) and quinolylamido-sulfadoxine (L2), were prepared by the
Bioorganometallic
Organoiridium
Sulfadoxine
reaction of the antimicrobial sulfadrug, sulfadoxine, with either 2-picolinic acid or 2-quinaldic acid. Subsequent
x
x
reaction with a [Cp IrCl
2
]
2
dimer (where Cp = pentamethylcyclopentadiene, tetramethylphenylcyclopentadiene
or tetramethylbiphenylcyclopentadiene) yielded six new amidosulfadoxine-derivatized iridium complexes (C1-
C6) in moderate to good yields, where the ligands act as N,N’-bidentate chelators. Proton and carbon NMR
spectroscopy, mass spectrometry and HPLC data were used to characterize and confirm the purity of all com-
pounds. Aquation chemistry studies on the complexes revealed slow water substitution of the chlorido ancillary
ligand. The inhibitory activities of complexes C1-C6 were determined against Mycobacterium tuberculosis (Mtb)
H37Rv and Plasmodium falciparum (Pf) strains, 3D7, Dd2 and HB3, as well as the HEK cell line. The ligands
showed no appreciable antimicrobial activity, with most of the complexes exhibiting weak to moderate inhi-
bition of Pf and Mtb. However, one complex (C6) displayed potent activity against Pf 3D7 (IC50 of 0.975 µM) and
the multidrug-resistant Pf Dd2 (IC50 of 0.766 µM).
Antimalarial
Antitubercular
1
. Introduction
Tuberculosis is caused by Mycobacterium tuberculosis (Mtb) and is
resistance to the two frontline drugs prescribed for standard treatment,
isoniazid and rifampicin, while extensively drug resistant TB (XDR-TB)
is additionally resistant to fluoroquinolones and at least one of the
injectable second-line aminoglycosides [1]. The emergence and spread
of drug-resistant Mtb strains therefore places a premium on the identi-
fication of new antimycobacterial agents that possess novel mechanisms
of action and, preferably, the capacity to shorten treatment durations,
currently set at a minimum six months for drug-susceptible disease.
Plasmodium parasites are the causative agents of malaria, a life-
threatening infectious disease transmitted by female Anopheles
mosquitoes that is both curable and preventable [3]. P. falciparum and
P. vivax are the two species that are the most dangerous, with
P. falciparum causing 99.7% of all malaria cases in the WHO African
Region and most cases in the Eastern Mediterranean, Western Pacific
and South-East Asian regions [3,4]. Although great progress was made
in reducing the number of cases worldwide up till 2015, since then no
spread primarily via aerosols released by infected individuals. Approx-
imately 1.7 billion people are infected with latent Mtb with 5–10% likely
to develop the disease in their lifetime [1]. In 2018, an estimated 10
million new cases were reported worldwide of which South Africa
contributed a major portion [1]. The decline in TB incidence rates per
year is currently close to 2% which is still far too low. If definitive
progress towards the eradication of this epidemic is to be made then this
percentage needs to be increased nearly three-fold [1]. To further
illustrate the importance of research in this field it is to be noted that,
prior to the COVID-19 pandemic, Mtb was the leading cause of death
globally owing to an infectious disease [1]. Drug-resistant TB accounts
for almost a third of all antimicrobial resistant (AMR) deaths annually
[
2]. Multi-drug resistant TB (MDR-TB) is defined by the WHO as
*
Corresponding author.
E-mail address: p.chellan@sun.ac.za (P. Chellan).
https://doi.org/10.1016/j.ica.2020.120175
Received 20 October 2020; Received in revised form 30 November 2020; Accepted 30 November 2020
Available online 2 December 2020
0
020-1693/© 2020 Elsevier B.V. All rights reserved.

T.J. Kotz ´e et al.
Inorganica Chimica Acta 517 (2021) 120175
significant progress has been made [4]. Children under the age of 5 are
the most vulnerable group and account for 61% of the 435 000 deaths in
still used to treat certain cases of malaria and as a preventative treatment
in pregnant women [4]. They were initially employed as antitubercular
drugs, but with the discovery of isoniazid, rifampicin and streptomycin,
were largely made obsolete owing to their lower efficacy [42]. With the
rise of drug resistance and the trend of repurposing, it could prove
beneficial to relook at these pharmacophores for solutions.
2
017 of which 11 countries account for nearly 70%, all but 1 being in
Africa. There are several approaches to targeting the parasite and pre-
venting its transmission including malaria vector control, which consists
of preventing infection by use of insecticidal mosquito nets and indoor
residual spraying of insecticides [3,4].
Several accounts have been published reporting an increase in bio-
logical activity when a clinical drug or organic pharmacophore is
incorporated into a metal complex [7,31,43-46]. This increase in ac-
tivity has also been documented for sulfonamides and a range of
different sulfonamide metal complexes have been developed
[43,47,48]. They have been screened for a multitude of biological ap-
plications, including as anticancer [49,50], antimicrobial or antifungal
agents [51,52] and, as carbonic anhydrase inhibitors (which have
application to a variety of illnesses) [53-56]. Mondelli et al. investigated
cobalt sulfonamide complexes of sulfapyridine, sulfadimethoxine, sul-
famethazine, sulfamerazine, sulfamethoxazole and sulfamethizole as
inhibitors of Mtb [57]. The complexes generally showed comparable
activity to that of their metal free ligands. Studies on ferrocenyl and
cyrhetrenyl sulfonamide complexes revealed moderate activity on Mtb
strains [58].
Cases of resistance against most of the current antimalarials,
including the WHO recommended artemisinin-based combination
therapy, illustrate the dire need for development of new effective
treatments [5,6].
The use of metals in medicine has gained significant attention owing
to the incredible versatility that can be achieved by differences in
oxidation state, coordination number, geometries, electronic properties
and stability. Each of these can be adjusted and modified by selecting the
appropriate ligands and using various synthetic methods, allowing for
an incredible variety of possibilities in design [7-21]. More recently,
there has been a surge of research into metal complexes of drugs that
have already been used in treatments and their direct repurposing or
derivatisation for other therapies [22-30]. In cases where resistance has
appeared to the original therapy, the metal complex may be active and
function via a different mode of action against the disease [7,9,31-33].
Sulfonamide-containing drugs have been in use as antimicrobials
since the early 20th century and were some of the first chemothera-
peutics to be systematically employed [7,34]. They are still prevalent in
the pharmaceutical industry and are used for a wide range of treatments
In a previous study, we showed that the incorporation of organo-
metallic rhodium and iridium half-sandwich moieties into the drug
sulfadoxine effectively ‘switched on’ it’s antimalarial and antitubercular
activity [15]. The sulfadoxine drug on its own was not active while the
complexes showed low micromolar activities. We also found that the
complexes, which underwent slow exchange of the chlorido ligand with
water, were better inhibitors of malarial parasite growth [15]. The
iridium derivatives (Fig. 1, C7 – C12) were the most promising com-
plexes, therefore we have decided to extend our studies on organo-
iridium sulfadoxine complexes. The previously reported complexes C7 –
C12 were cationic complexes where the imino ligands chelated to the
metal in an N,N’-bidentate fashion. To extend our work on organome-
tallic sulfa-drug complexes, we wished to determine if neutral N,N’-
chelated complexes would be more potent than the cationic analogues.
[
35]. Sulfonamides are believed to target the synthesis of tetrahydrofolic
acid, an important cofactor in the synthesis of DNA and methionine,
through competitive inhibition of dihydropteroate synthase, a bacterial
enzyme that produces the precursors for tetrahydrofolic acid from para-
aminobenzoic acid [36]. Their low toxicity and affordability make them
very attractive candidates for drug research and they have been found to
be effective for a wide variety of treatments, having been employed as
antibacterial, antiviral, antitumour and antifungal agents, to name a few
[
34,36-41]. Sulfadoxine (Fig. 1) in combination with pyrimethamine is
Fig. 1. Structures of Sulfadoxine (Sf), the imino ligands (L3 and L4) and iridium(III) imino-sulfadoxine complexes (C7 – C12) previously studied [15].
2

T.J. Kotz ´e et al.
Inorganica Chimica Acta 517 (2021) 120175
Thus, we report the synthesis and study of a small library of new sul-
fadoxine iridium complexes (C1-C6) where the heteroaromatic-imino
group of (C7-C12, Fig. 1) is replaced with an heteroaromatic amido
group. The complexes were tested against Plasmodium falciparum (Pf)
strains Dd2, 3D7 and HB3, the Mtb H37Rv strain and the HEK cell line in
dose–response assays.
2
. Results and discussion
2
.1. Synthesis
The new amido ligands, L1 and L2, were prepared by reaction of the
corresponding acid chloride (generated in situ) and sulfadoxine (Scheme
) and were obtained in moderate yields. Both ligands displayed similar
absorption bands in their infrared spectra. For L1, the amide N
1
–
H
ꢀ 1
stretch is observed at 3339 cm with the sulfonamide N H stretch
–
ꢀ 1
appearing at 3165 cm , a slightly lower frequency compared to sulfa-
Fig. 2. Molecular structure of Amido-Sf-L1 with atom labelling. ORTEP ther-
mal ellipsoids are drawn at 50% probability level. Hydrogen atoms (with the
exception of H5 and H6) have been omitted for clarity.
doxine. A strong, sharp absorption band is observed for the carbonyl of
ꢀ
1
the amide functional group at 1681 cm . Further analyses with proton
NMR spectroscopy show the amide proton for L1 and L2 resonates as
singlets at 10.27 (L1) and 10.49 (L2) ppm. The proton of the carbon
ortho to nitrogen in the pyridyl ring (L1) was observed as a doublet at
cm 1 in the ligand (L1). Additionally, no absorption band was observed
ꢀ
ꢀ 1
for the NH stretch of the amide (observed at 3339 cm for L1). The
8
.62 ppm. Some of the aromatic protons of the quinolyl ring in L2
–
ꢀ 1
ꢀ 1
C
–
N stretch of the pyridyl ring shifts from 1584 cm to 1603 cm ,
overlap, making it difficult to discern if the ortho proton also resonates as
a doublet as expected. 13C NMR spectroscopy revealed that the amide
indicative of coordination through the nitrogen atoms of the pyridyl ring
and the amide.2
8,29
The shift to low frequency of the
ν
(CO) stretch and to
carbon resonates at ca. 162 ppm for both ligands. These shifts agree with
similar pyridyl amide compounds reported [59,60]. The ligands were
also subjected to mass spectral analysis using ESI-MS and the base peak
–
–
high frequency of the pyridyl
ν(C
N) stretch is a consequence of the
back-bonding between the nitrogen and Ir metal center. This results in
–
+
greater donation of electron-density from the C O group into the pyr-
–
observed corresponds to the [M] molecular ion.
–
–
–
N
idyl ring, thus weakening the C
bond despite the Mꢀ N bond formed. The band at 1525 cm seen in the
spectrum for L1 and attributed to the amide N H bend, is not observed
–
O bond and strengthening the C
Crystals of L1 were obtained by layering a dichloromethane solution
of the ligand with hexane and leaving to stand in a sealed vial for several
days at room temperature. The molecular structure for L1 is shown in
Fig. 2. The needle-like crystals were transparent and crystallised in the
triclinic space group, P1 . General crystal data and selected bond lengths
and angles are given in Tables 1 and 2. The bond lengths and angles
determined for L1 were similar for other sulfonamide-containing
structures in the literature [61,62].
ꢀ
1
–
for C1 further confirming deprotonation of the amide nitrogen prior to
complexation. As the electronegativity of the metal centre increases
within the series, there is a slight general shift to higher frequencies for
all the bands observed. In particular, for complexes C4-C6, the quinolyl
–
–
C
–
N stretch combines with the C
–
O stretch to form a broad band
which could not be separately identified.
Complexes C1-C6 were prepared using a microwave synthetic
method. Ligands, L1 or L2, were combined with the appropriate iridium
dimer and sodium bicarbonate in methanol (Scheme 2) and subjected to
Formation of C1 is further confirmed by the absence of the amide NH
peak from the 1H NMR spectrum. Upon complexation, the changes in
chemical shifts compared to L1 are not large, with the proton of the
carbon ortho to the nitrogen of the pyridyl ring shifting from 8.62 ppm to
◦
microwave irradiation for 10 min at 150 C, resulting in isolation of the
complexes as either yellow or orange amorphous solids in moderate to
high yields.
8
1
.58 ppm. The protons for the methyl groups of the Cp* ring resonate at
xph
xbiph
.38 ppm. The complexes containing the Cp or Cp
ligand (C2, C3,
Characterisation data for all complexes were similar, therefore
complex C1 is discussed as a representative example. The IR spectrum of
x
C5 and C6) display separate methyl peaks for the coordinating Cp
moiety. This is the result of the inequivalence introduced by the attached
phenyl or biphenyl ring along with the induced chirality of the metal
ꢀ
1
C1 revealed a large shift in the carbonyl signal to 1621 cm from 1681
Scheme 1. Synthesis of L1 and L2 via an acid chloride. (i) oxalyl chloride / cat. DMF / 2–5 h, 0 ◦C / dichloromethane; (ii) 2–3 h, Pyridine, rt, Acetonitrile.
3

T.J. Kotz ´e et al.
Inorganica Chimica Acta 517 (2021) 120175
+
Table 1
all complexes displayed a base peak that corresponds to the [Mꢀ Cl]
Crystal data and structure refinement for L1.
molecular ion. The purity of all ligands and complexes was determined
by HPLC to be between 95 and > 99%. Together, the mass spectral and
HPLC data obtained confirms only one species was present for each
compound with no impurities.
Empirical formula
18 17 5 5
C H N O S
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
415.42
100(2)
0.71073
Triclinic
P1
2.2. Aquation chemistry for C1-C6
◦
Unit cell dimensions (Å,
)
a = 8.319(2), α = 109.559(4);
Given the aqueous environment that drugs are administered or
screened in, it is important to study the speciation of potential metal-
lodrugs in water. All of the complexes contain a chlorido ligand that
could be displaced by water in aqueous media. In order to study the
aquation of complexes C1-C6, we used two approaches. First, in situ
b = 10.194(3), β = 100.736(4);
c = 12.280(3), γ = 103.451(4)
Volume (Å)
913.9(4)
Z
2
ꢀ
3
Calculated density (g cm
)
ꢀ
1.51
1
Absorption coefficient (mm
)
0.221
reaction of the appropriate complex with an excess of deuterium oxide at
F000
432
◦
3
37 C in the presence of an equimolar amount of AgNO
3
to make sure
Crystal size (mm )
0.118 × 0.073 × 0.048
1.838 to 27.572
that the deuterium oxide complexes (C1-D
2
O – C6-D
2
O) were prepared.
θ range for data collection (θ)
Miller index ranges
ꢀ 10 ≤ h ≤ 10 ꢀ 15 ≤ l ≤ 15 ꢀ 13 ≤ k ≤ 13
24,537
Second, complexes C1-C6 were incubated in deuterium oxide without
Reflections collected
◦
AgNO
3
at 37 C to determine whether complexes would undergo
Independent reflections
Completeness to θmax (%)
Max. and min. transmission
Refinement method
4207 [Rint = 0.0496]
0.998
aquation without the presence of a halide abstraction reagent. After
filtration and addition of TMS as internal standard, solutions were
analysed using proton NMR spectroscopy. It was assumed that any
0.9354 and 1.000
2
Full-matrix least-squares on F
Data / restraints / parameters
4207 / 0 / 272
1.045
2
material soluble in D O was a deuterium oxide species (all chlorido
2
Goodness-of-fit on F
complexes are insoluble in water), where a deuterium molecule co-
Final R indices [I > 2
σ
(I)]
R1 = 0.0402
wR2 = 0.0970
R1 = 0.0512
wR2 = 0.1028
0.508 and ꢀ 0.443
–
ordinates to the metal centre, forming a cationic complex with NO
the counterion. The overlaid spectra of C1-D
without AgNO are shown in Fig. 3. Spectra for the other complexes are
3
as
2
O and C1 after incubation
R indices (all data)
3
ꢀ
3
Largest diff. peak and hole (e Å
)
shown in the supplementary data (Figs. S1-S5).
It is clear from the NMR spectra that complex C1 does not undergo
aquation after 18 h in the absence of AgNO
nitrogen of the pyridyl ring for C1-D O (Fig. 3, Blue spectrum) is seen at
.01 ppm, while that of the incubated C1 resonates at 8.91 ppm. Similar
observations were made for complexes C2 and C4. Complex C3 did not
3
. The proton ortho to the
2
9
Table 2
Selected bond lengths and angles for L1.
undergo aquation in presence of AgNO
3
even at increased temperatures
Bond Length
Length (Å)
◦
of 45 – 50 C, and it is likely that the steric bulk of the biphenyl moiety
bound to the metal centre prevents access to the chlorido ligand. The
lack of aquation of C3 was confirmed with MS. For complex C5, the
species in solution was too dilute and no definitive assignments could be
made from the spectra. C6 was extremely insoluble under the conditions
used and based on the results for aquation of C3, it was assumed that
similar results would be obtained.
N2– C6
1.358(2)
1.230(2)
1.407(3)
1.501(3)
1.761(2)
1.434(1)
1.429(1)
1.649(2)
1.396(2)
1.339(3)
1.372(2)
0.84(2)
O1-C6
C7-N2
C6-C5
C10-S1
S1-O3
S1-O2
S1-N3
The results of the aquation studies show that the chlorido was either
N3-C13
2
not displaced by D O or was extremely slow in being substituted. This
O5-C15
C14-O4
suggests that, during the in vitro inhibitory experiments, the active
species of complexes C1-C6 is most likely either the chlorido derivatives
or that the complexes remain intact long enough to reach their target
before undergoing aquation.
H6-N3
H5-N2
0.84(3)
◦
Bond angles
O3-S1-O2
O3-S1-N3
O3-S1-C10
O2-S1-N3
O2-S1-C10
N3-S1-C10
C7-N2-C6
C7-N2-H5
C6-N2-H5
S1-N3-C13
S1-N3-H6
C13-N3-H6
Torsion Angles
C4-C5-C6-N2
C6-N2-C7-C8
S1-N3-C13-N5
N3-S1-C10-C11
Angle ( )
119.55(9)
103.45(9)
108.58(9)
109.32(9)
109.29(9)
105.71(9)
126.9(2)
117(2)
2.3. In vitro antimycobacterial screening
Complexes C1-C6 were screened for activity against the Mtb H37Rv
strain. For the anti-tubercular studies, the minimum inhibitory con-
centration that inhibits 90% of cell growth (MIC90) of Mtb H37Rv was
determined using two different media (Table 3), one enriched with
casitone, glucose and tyloxapol (7H9 CAS GLU Tx) and the other with
ADC (albumin-dextrose-catalase), glucose and Tween80 (7H9 ADC GLU
Tw).
116(2)
125.5(1)
110(2)
118(2)
◦
( )
ꢀ 166.8(2)
21.6(3)
No activity is observed when the compounds are tested in the media
enriched with ADC, demonstrating that the activities of these com-
pounds are sensitive to the type of media used. The data from experi-
ments using the 7H9 CAS GLU Tx medium shows only C1, C3 and C4
having any detectable activity after 14 days. C3 was the best inhibitor
with a MIC99 of 34.3 µM after 14 days. As antimycobacterial agents,
these compounds are not very effective in vitro.
ꢀ 13.1(3)
105.9(2)
centre. As the length of the Cp moiety is extended with a phenyl (Cpxph)
x
xbiph
and biphenyl (Cp
), the protons of these added phenyl rings resonate
1
3
between 7.30 ppm and 7.70 ppm. In the C spectrum, the quaternary
x
carbons of the Cp ring appear as one singlet for C1 and C4 and as
separate peaks for complexes C2, C3, C5 and C6. The ESI-MS spectra for
4

T.J. Kotz ´e et al.
Inorganica Chimica Acta 517 (2021) 120175
Scheme 2. General synthetic procedure for the complexes C1-C6.
2
Fig. 3. Aqua species of C1-D O (Blue), prepared by incubation with silver nitrate, overlaid with the incubated chlorido species of C1 (Red) with no silver nitrate.
Both spectra are referenced to TMS. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
2
.4. In vitro antiplasmodial evaluation and cytotoxicity
Table 3
MIC90 data for L1, L2, C1-C6, and the control drug, rifampicin (Rfm) against
Mtb H37Rv.
Complexes C1-C6 and their corresponding metal-free ligands were
evaluated for their in vitro antiplasmodial activity against Plasmodium
falciparum malarial parasite strains 3D7 (CQ-sensitive and sulfadoxine-
resistant), Dd2 (multidrug resistant strain) and HB3 (pyrimethamine-
resistant and CQ-sensitive strain). The percentage inhibition at a com-
pound concentration of 80 µM was first determined to ascertain if the
complexes show activity (Fig. 4 and Table S1 in supplementary infor-
mation). Both ligands, L1 and L2, show no appreciable inhibition. For the
complexes, a general increase in percentage inhibition was observed
when moving from the pyridyl (C1-C3) to the quinolyl systems (C4-C6).
When comparing the percentage inhibitions, C4 (92.4% (3D7), 92.7%
Compound
7H9 CAS GLU
7H9 ADC GLU
a
b
Tx
Tw
c
c
Day 7 (µM)
Day 14 (µM)
Day 7
Day 14
c
c
(
µM)
(µM)
d
d
d
d
L1
n.a
n.a
n.a
n.a
n.a
n.a
n.a
n.a
n.a
n.a
n.a
d
d
d
d
d
d
d
d
d
d
L2
n.a
n.a
n.a
d
d
C1
C2
C3
C4
C5
C6
Rfm
n.a
80.4
n.a
d
d
d
n.a
n.a
n.a
d
68.3
d
34.3
75.5
n.a
d
n.a
n.a
d
d
d
n.a
n.a
n.a
(
Dd2), 87.1% (H3B)) and C6 (97.1% (3D7), 96.7% (Dd2), 91.8% (H3B))
d
d
d
n.a
n.a
n.a
show consistently high inhibition across all Pf strains (Table 4). These
complexes were also less cytotoxic on the non-tumorigenic HEK cell line.
Based on our previous study of the imino derivatives [15], where we
observed a distinct increase in activity based on ‘hydrophobicity’, we
hypothesised a similar trend for complexes C1-C6. However, from the
percentage inhibition data, we see no discernible trend in the activities
0.032
0.016
0.004
0.005
a
Middlebrook 7H9 media supplemented with casitone, glucose and tyloxapol
Middlebrook 7H9 media supplemented with ADC (albumin-dextrose-cata-
b
lase), glucose and Tween80.
c
MIC90 values were determined in µg/ml and converted to µM.
Not active up to the highest concentration tested (125 µg/ml).
d
xph
based on structure. The pyridyl Cp complex, C2, was essentially inac-
xph
tive across all three parasite strains while the quinolyl Cp complex, C5,
5

T.J. Kotz ´e et al.
Inorganica Chimica Acta 517 (2021) 120175
Fig. 4. Percent inhibition data for the ligands (L1 and L2) and complexes (C1-C6) on the Pf parasite 3D7 (CQ-sensitive and sulfadoxine-resistant), Dd2 (multidrug
resistant strain) and HB3 (pyrimethamine-resistant and CQ-sensitive) strains and HEK (human embryonic kidney) cell line.
complex. With the exception of C6, all of the complexes displayed very
Table 4
low activities on the Mycobacterium tuberculosis and plasmodium falcip-
IC50 data for C6, C12 [15], sulfadoxine (sf) [15] and control drugs Chloroquine
arum strains studied. No trend in activity could be linked to the aqueous
(
CQ), Puromycin (PMN), Artemisinin (ART), Pyrimethamine (PYM) against Pf
solubility or structures of the amido complexes against malaria. C6 was
revealed to be the most promising antimalarial with IC50′s ≤ 1.0 µM
against the three Pf strains assayed.
parasite 3D7 (CQ-sensitive and sulfadoxine-resistant), Dd2 (multidrug resistant
strain) and HB3 (pyrimethamine-resistant and CQ-sensitive) strains.
a
a
a
Compound
3D7 IC50
Dd2 IC50
H3B IC50
C6
0.78 (0.142)
0.25 (0.04)
1.09 (0.23)
0.83 (0.08)
4
. Experimental Section.
b
c
C12
0.17 (0.07)
n.t
b
c
Sf
> 20 µM
> 20 µM
n.t
4
.1. Chemicals and reagents
CQ
0.036 (0.014) nM
0.057 (0.003) nM
0.005 (7.743 × 10
nM
0.205 (0.004) nM
0.063 (0.002) nM
0.005 (1.414 × 10
nM
0.048 (0.005) nM
0.099 (0.004) nM
0.003 (6.364 × 10
nM
PMN
ART
-
4
-4
-4
)
)
)
Sulfadoxine (95%), 2-picolinic acid, quinaldic acid, salicylaldehyde,
-hydroxynapthaldehyde, oxalyl chloride (2 M in dichloromethane),
2
-
4
d
d
PYM
0.003 (1.48 × 10
)
43% at 4µM
86.5% at 4 µM
pyridine, magnesium sulfate, sodium bicarbonate, 1,2,3,4,5-pentame-
thylcyclopentadiene, 2,3,4,5-tetramethyl-2-cyclopentenone, phenyl
magnesium bromide (1 M in THF), silver nitrate, hydrocortisone,
reserpine, phosphate buffered saline tablets and all reagent solvents and
nM
a
Standard error is given in parentheses.
Data from reference [15].
Not tested.
b
c
d
deuterated solvents (dimethylsulfoxide‑d
obtained from Sigma Aldrich (Merck). IrCl
Heraeus South Africa. All purchased reagents were used as received.
Dichloro(pentamethylcyclopentadienyl)iridium(III) dimer, dichloro
tetramethylphenylcyclopentadienyl)iridium(III) dimer and dichloro
tetramethylbiphenylcyclopentadienyl)iridium(III) dimer were synthe-
6
and chloroform‑d
1
) were
percent inhibition tested at 4 µM.
3
⋅nH O was purchased from
2
was moderately active (44.6% (3D7), 34.6% (Dd2), 42.3% (H3B)).
The two complexes showing the best percentage inhibition (C4 and
C6) were assayed to determine their IC50-values on the Pf strains.
However, at the time of testing, the IC50 for C4 could not be determined
as its sigmoidal dose response curve did not give a plateau and it was
therefore considered inactive. The sub–micromolar IC50-values
observed for complex C6 (IC50 = 0.78 (3D7), 1.09 (Dd2), 0.83 (H3B)
µM) show it to be the most promising complex in the amido-sulfadoxine
complex library. However, it is not as active as its imino derivative (C12)
(
(
sized according to a literature method [63].
4
.2. Instrumentation
IR spectroscopy was performed using a Thermo Nicolet Nexus 470 by
1
13
means of potassium bromide pellets. NMR data ( H, C) were recorded
on either a 300 MHz Varian VNMRS or a 400 MHz Varian Unity Inova
[
15]. It’s clear that the amido-sulfadoxine complexes (C1-C6) reported
here are not as potent as their imino-sulfadoxine counterparts (C7-C12)
1
spectrometer. H NMR chemical shifts are reported in ppm and coupling
previously studied [15].
constants in Hertz and were internally referenced to dime-
6 1
thylsulfoxide‑d (2.50 ppm) or chloroform‑d (7.26 ppm). Data was
3
. Conclusions
processed using MestReNova 11.0.4–18998. Mass spectrometry was
performed on a Waters Synapt G2 with an ESI probe in ESI Positive mode
using a Cone Voltage of 15 V. Microwave syntheses were carried out in a
CEM Discover SP microwave reactor. UV–vis data were recorded with a
Shimadzu UV–vis spectrophotometer.
Two new ligands
–
pyridylamido-sulfadoxine (L1) and
quinolylamido-sulfadoxine (L2) – were successfully synthesized along
with their organoiridium complexes (C1-C6). Spectral characterisation
and the crystal structure for L1 confirmed the structural integrity of
these compounds. The aquation studies showed an increased difficulty
in removal of the chlorido ligand as the bulk of the half-sandwich moiety
increased, especially for the tetramethylbiphenylcyclopentadiene ana-
logues (C3 and C6), suggesting that the active species is the chlorido
4
.3. Synthesis of pyridylamido-sulfadoxine (L1)
2
-Picolinic acid (103 mg, 0.837 mmol) was stirred in dry dichloro-
◦
methane (20.0 mL) under nitrogen and cooled to 0 C. Oxalyl chloride
6

T.J. Kotz ´e et al.
Inorganica Chimica Acta 517 (2021) 120175
(
2 M in dichloromethane, 484 µL, 0.966 mmol) was then added to the
subside before the vial was opened and cooled to room temperature. The
resulting solid was filtered and washed with Methanol/Ether before it
was recrystallised from dichloromethane/hexane to afford the pure
product.
solution followed by a catalytic amount of dimethylformamide (50.0
◦
µL). The reaction solution was stirred for 2 h at 0 C before the solvent
was removed and the crude residue re-dissolved in acetonitrile (10.0
◦
mL) and cooled again to 0 C. Sulfadoxine (200 mg, 0.644 mmol) was
added dropwise (10.0 mL) over 5 min and pyridine (77.8 µL, 0.966
4.5.1. C1
◦
mmol) was added. The reaction solution was stirred at 0 C for 30 min
Dichloro(pentamethylcyclopentadienyl)iridium(III) dimer (50.0 mg,
and for a further 1.5 h at room temperature. The purple precipitate
formed was filtered, washed with acetonitrile and kept aside. The sol-
vent was removed from the filtrate and the crude residue re-dissolved in
dichloromethane (20.0 mL). This was washed with a solution of satu-
rated sodium bicarbonate (3 × 10.0 mL) and the organic portions dried
0.0628 mmol), L1 (52.1 mg, 0.126 mmol), and NaHCO
3
(10.5 mg, 0.126
mmol) was reacted in methanol (1.50 mL) in a 10.0 mL microwave vial
1
to afford complex C1 as a yellow powder in 84% yield (82.8 mg).
H
NMR (400 MHz, CDCl
3
): δ
H
8.58 (d, 1H, 3J = 5.6 Hz, pyridyl-H),
3
8.19–8.07 (m, 4H, pyrimidine-H, pyridyl-H, phenyl-H), 7.94 (t, 1H,
J
3
4
over MgSO . The solvent was evaporated, and the off-white powder
= 7.7 Hz, pyridyl-H), 7.87 (d, 2H, J = 8.8 Hz, phenyl-H), 7.53 (m, 1H,
pyridyl-H), 3.97 (s, 3H, CH ), 3.84 (s, 3H, CH ).
), 1.38 (s, 15H, Cp*–CH
C NMR (101 MHz, DMSO): δ 167.86, 161.52, 153.46, 152.99, 151.40,
150.62, 139.42, 134.79, 128.59, 127.48, 127.12, 126.81, 125.43, 86.39,
obtained was combined with the purple precipitate and recrystallised
3
3
3
1
3
from dichloromethane /hexane and washed with acetonitrile to give L1
C
1
as a pure white powder in 67% yield (979 mg). H NMR (300 MHz,
3
ꢀ 1
–
–
–
–
CDCl
3
): δ
H
10.27 (s, 1H, amide-NH), 8.62 (d, 1H, J = 4.7 Hz, pyridyl-
60.26, 54.04, 7.93. FT-IR (KBr, cm ):
ν
= 1619 (C
O), 1599 (C N),
3
–
–
–
H), 8.29 (d, 1H,
J
=
7.8 Hz, pyridyl-H), 8.20–8.14 (m, 3H,
1577 (C
–
N), 1561 (C
N). (+)-HR-ESI-MS: m/z (%) 742.1687
+
+
pyrimidine-H and phenyl-H), 7.97–7.90 (m, 3H, pyridyl-H and phenyl-
H), 7.82 (s, 1H, sulfonamide-H), 7.55–7.49 (m, 1H, pyridyl-H), 3.97
([Mꢀ Cl] , 100%), 778.1456 ([M+H] , 2%). HPLC purity: 96.7%; tr’
=
10.93 min.
1
3
(
s, 3H, CH
3
), 3.86 (s, 3H, CH
3
). C NMR (75 MHz, CDCl
3 C
): δ 162.3,
1
1
60.8, 149.7, 149.0, 148.1, 142.3, 137.9, 134.0, 130.0, 127.0, 126.5,
4.5.2. C2
ꢀ
1
–
–
22.6, 119.0, 60.6, 54.1. FT-IR (KBr, cm
)
–
υ
= 1681 (C
O), 1584
Dichloro(tetramethylphenylcyclopentadienyl)iridium(III)
dimer
–
–
–
–H), 3165 (N
(
(
C
–
N), 1525 (C
N), 3339 (N
H). (+)-HR-ESI-MS: m/z
(50.0 mg, 0.054 mmol), L1 (45.1 mg, 0.109 mmol) and NaHCO (9.10
3
+
+
%) 416.1023 ([M+H] , 100%), 438.0841 ([M+Na] , 5%); HPLC pu-
mg, 0.109 mmol) were reacted together in methanol (1.50 mL) to afford
1
rity: 97%; tr’ = 15.08 min.
complex C2 as a bright yellow powder in 75% yield (68.7 mg). H NMR
3
(
300 MHz, CDCl
) δ
3 H
8.28 (d, 1H, J = 5.4 Hz, pyridyl-H), 8.19–8.07 (m,
4
.4. Synthesis of quinolylamido-sulfadoxine (L2)
4H, pyridyl-H, pyrimidine-H, phenyl-H), 7.94 – 7.86 (m, 1H, pyridyl-H),
3
x
7
.82 (d, 2H, J = 8.6 Hz, phenyl-H), 7.49–7.38 (m, 5H, Cp -phenyl-H),
Quinaldic acid (109 mg, 0.628 mmol) was stirred in dry dichloro-
7.38–7.34 (m, 1H, pyridyl-H), 3.98 (s, 3H, CH
3
), 3.85 (s, 3H, CH
3
), 1.70
), 1.12 (s,
C
168.69, 160.77, 154.54,
◦
x
x
x
methane (15.0 mL) under nitrogen and cooled to 0 C. Oxalyl chloride
(s, 3H, Cp -CH
3
), 1.48 (s, 3H, Cp -CH
3
), 1.21 (s, 3H, Cp -CH
3
x
). 13C NMR (101 MHz, CDCl
(
2 M in dichloromethane, 362 µL, 0.725 mmol) was then added followed
3H, Cp -CH
3
3
) δ
by a catalytic amount of dimethylformamide (50.0 µL). The solution was
stirred for 5 h at 0 C before the solvent was removed and the crude
153.19, 149.88, 149.78, 138.80, 134.12, 130.16, 130.06, 129.16,
◦
128.80, 128.62, 127.77, 127.21, 126.67, 126.42, 99.00, 92.58, 86.04,
◦
ꢀ 1
residue re-dissolved in acetonitrile (10.0 mL) and cooled again to 0 C.
82.64, 81.65, 60.55, 54.10, 9.71, 9.38, 8.52, 8.09. FT-IR (KBr, cm ):
ν
–
–
–
–
Sulfadoxine (150 mg, 0.483 mmol) was then added dropwise (10.0 mL)
= 1623 (C
–
O), 1600 (C
–
N), 1577 (C
–
N), 1560 (C
–
N). (+)-HR-ESI-
+
+
over 5 min and then pyridine (58.4 µL, 0.725 mmol). The reaction so-
MS: m/z (%) 804.1844 ([Mꢀ Cl] , 100%), 840.1575 ([M+H] , 2%).
◦
lution was stirred at 0 C for 30 min before stirring a further 2.5 h at
HPLC purity: 97%, tr’ = 13.79 min.
room temperature. The solvent was removed from the reaction mixture
and the crude residue re-dissolved in dichloromethane (20.0 mL) and
washed with saturated sodium bicarbonate (3 × 10.0 mL), distilled
water (3 × 10.0 mL) and brine (2 × 10.0 mL). The solvent was removed,
and the residue left to dry overnight on the high vacuum pump before
being re-dissolved in dichloromethane and filtered through celite™ to
remove any residual NaCl. Evaporation of the solvent yielded the crude
product that was recrystallised from dichloromethane /hexane (1:2) to
4.5.3. C3
Dichloro(tetramethylbiphenylcyclopentadienyl)iridium(III) dimer
(50.0 mg, 0.0470 mmol), L1 (38.7 mg, 0.0930 mmol) and NaHCO
3
(7.80 mg, 0.0930 mmol) were reacted together in methanol (1.50 mL) to
1
afford complex C3 as a light-yellow powder in 65% yield (55.9 mg). H
NMR (300 MHz, CDCl
3
): δ
H
8.32 (d, 1H, 3J = 5.5 Hz, pyridyl-H),
8.19–8.09 (m, 4H, pyrimidine-H, phenyl-H, pyridyl-H), 7.94 – 7.87
3
give L2 as a pure off-white microcrystalline solid in 60% yield (134 mg).
(m, 1H, pyridyl-H), 7.84 (d, 2H, J = 8.9 Hz, phenyl-H), 7.67–7.61 (m,
1
x
x
H NMR (400 MHz, CDCl
3
): δ
H
10.49 (s, 1H, amide-NH), 8.42–8.36 (m,
4H, Cp -phenyl-H), 7.58–7.32 (m, 6H, Cp -phenyl-H), 3.98 (s, 3H, CH
3
),
), 1.27 (s,
). 13C NMR (75 MHz, CDCl
): δ
x
x
2
H, quinolyl-H), 8.24–8.16 (m, 4H, quinolyl-H, pyrimidine-H and
3.85 (s, 3H, CH
3
), 1.74 (s, 3H, Cp -CH
3
), 1.49 (s, 3H, Cp -CH
3
3
3
x
x
phenyl-H), 8.02 (d, 2H, J = 8.8 Hz, phenyl-H), 7.94 (d, 1H, J = 8.2 Hz,
3H, Cp -CH
3
), 1.11 (s, 3H, Cp -CH
3
3
C
quinolyl-H), 7.87–7.81 (m, 1H, quinolyl-H), 7.79 (s, 1H, sulfonamide-
168.84, 160.91, 154.62, 153.30, 150.07, 149.94, 141.41, 140.03,
138.97, 134.34, 130.59, 129.22, 129.10, 128.90, 127.98, 127.95,
127.84, 127.34, 127.04, 126.77, 126.59, 99.22, 92.76, 86.10, 82.90,
NH), 7.82–7.65 (m, 1H, quinolyl-H), 3.98 (s, 3H, CH
3
), 3.87 (s, 3H,
1
3
CH
3
). C NMR (101 MHz, CDCl
3
): δ
C
162.67, 160.97, 149.88, 148.95,
ꢀ 1
1
46.39, 142.48, 138.30, 134.19, 130.75, 130.18, 129.79, 129.77,
28.69, 128.03, 126.58, 119.20, 118.83, 60.72, 54.30. FT-IR (KBr,
81.39, 60.67, 54.21, 9.89, 9.57, 8.64, 8.17. FT-IR (KBr, cm ):
υ
1618
–
–
–
–
–
–
–
1
(C
–
O), 1598 (C
N), 1580 (C
N), 1661 (C
N). (+)-HR-ESI-MS: m/z
ꢀ
1
–
–
–
–
–
+
+
cm
)
υ
= 1679 (C
–
O), 1577 (C
N), 1531 (C
N), 3287 (N
–
H), 3177
(%) 880.2172 ([M - Cl] , 100%), 916.1915 ([M+H] , 2%) HPLC purity:
+
(
(
N
–
H). (+)-HR-ESI-MS: m/z (%) 466.1179 ([M+H] , 100%), 488.1001
97.9%; tr’ = 18.07 min.
+
[M+Na] , 2%). HPLC purity: 98%; tr’ = 20.51 min.
4
.5.4. C4
4
.5. General method for synthesis of complexes C1-C6
Dichloro(pentamethylcyclopentadienyl)iridium(III) dimer (50.0 mg,
0
3
.0630 mmol), L2 (58.4 mg, 0.126 mmol) and NaHCO (10.6 mg, 0.126
The appropriate ligand (2 mol equiv.) was added to a stirred sus-
mmol) were reacted in methanol (1.50 mL) to afford complex C4 as an
1
pension of the appropriate iridium metal dimer (1 mol equiv.) and
NaHCO (2 mol equiv.) in dry methanol in a microwave vial. The vial
orange powder in 77% yield (80.5 mg). H NMR (400 MHz, CDCl
3
): δ
H
3
3
8.60 (d, 1H, J = 8.7 Hz, quinolyl-H), 8.34 (d, 1H, J = 8.5 Hz, quinolyl-
H), 8.26–8.21 (m, 3H, phenyl-H, quinolyl-H), 8.17 (s, 1H, pyrimidine-
H), 8.07 (d, 2H, 3J = 8.9 Hz, phenyl-H), 7.93 (d, 1H, J = 8.1 Hz,
3
was then sealed and placed in the microwave reactor and heated to 150
◦
3
C for 10 min at 150 W, after which, any effervescence was allowed to
7

T.J. Kotz ´e et al.
Inorganica Chimica Acta 517 (2021) 120175
quinolyl-H), 7.86 (m, 1H, quinolyl-H), 7.72 (m, 1H, quinolyl-H), 3.96 (s,
interface. Calculated positions were used to place hydrogen atoms and
non-hydrogen atoms were refined anisotropically. Hydrogens on oxygen
and nitrogen atoms were located with electron density maps. Crystal
data, structure refinement parameters and selected bonds and angles are
summarised in Table 1 and Table 2.
1
3
3
H, CH
3
), 3.83 (s, 3H, CH
) δ 168.91, 160.73, 156.61, 153.36, 149.78, 145.14, 139.69,
33.13, 131.10, 130.70, 129.80, 128.93, 128.67, 128.62, 126.83,
3
), 1.28 (s, 15H, Cp*–CH
3
). C NMR (101
MHz, CDCl
3
1
1
ꢀ 1
26.37, 122.41, 87.16, 60.53, 54.09, 8.62. FT-IR (KBr, cm ):
ν = 1615
–
–
–
–
–
–
(
(
C
O), 1580 (C
N), 1663 (C
N). (+)-HR-ESI-MS: m/z (%) 792.1824
+
+
[M - Cl] , 100%), 828.1567 ([M+H] , 7%). HPLC purity: > 99%; tr’
=
4.7. HPLC purity determination
1
3.61 min.
Purity measurements by HPLC were carried out using the Agilent
1220 system with a DAD and 100 µL loop. The column used was a
Kinetex® 5 µm C18 100 Å, 150 × 4.6 mm with a 5 µm pore size. The
4
.5.5. C5
Dichloro(tetramethylphenylcyclopentadienyl)iridium(III)
dimer
(9.10
(
50.0 mg, 0.0540 mmol), L2 (50.5 mg, 0.109 mmol) and NaHCO
3
mobile phase was H O 0.1% TFA (A) / MeCN 0.1% TFA (B). Elution was
2
mg, 0.109 mmol) were reacted in methanol (1.50 mL) to afford complex
carried out using gradient: t = 0 min 10% B, t = 30 min 80% B, t = 40
1
C5 as an orange powder in 75% yield (73.0 mg). H NMR (300 MHz,
min 80% B, t = 41 min 10% B, and t = 55 min 10% B over a 55 min
3
3
ꢀ 1
CDCl
3
): δ
H
8.46 (d, 1H, J = 8.8 Hz, quinolyl-H), 8.34 (d, 1H, J = 8.4
period. The flow rate was 1 mL⋅min , and the detection wavelength
3
Hz, quinolyl-H), 8.27 (d, 1H, J = 8.4 Hz, quinolyl-H), 8.17 (s, 1H,
was set at 254 nm and 400 nm with the reference wavelength at 360 nm.
pyrimidine-H), 8.12 (d, 2H, 3J = 9.0 Hz, phenyl-H), 8.06 (d, 2H, J =
3
Samples were dissolved in 10% MeCN/90% H O at ca. 100 µM. Sample
2
3
9
1
3
.0 Hz, phenyl-H), 7.87 (d, 1H, J = 8.3 Hz, quinolyl-H), 7.63–7.56 (m,
injections were half the loop volume (50 µL) with needle washes of
x
H, quinolyl-H), 7.45–7.30 (m, 6H, Cp -phenyl-H, quinolyl-H), 3.97 (s,
MeCN and H O between injections. It was assumed that all species in a
2
x
x
H, CH
), 1.41 (s, 3H, Cp -CH
CDCl
): δ
3
), 3.84 (s, 3H, CH
3
), 1.50 (s, 3H, Cp -CH
3
), 1.45 (s, 3H, Cp -
). 13C NMR (75 MHz,
sample have the same extinction coefficient at 254 nm and 400 nm. All
x
x
CH
3
3
), 0.90 (s, 3H, Cp -CH
3
peaks were manually integrated.
3
C
169.39, 160.89, 156.48, 153.44, 149.92, 145.11, 140.04,
1
1
8
1
8
9
33.64, 131.16, 131.02, 130.81, 130.07, 129.79, 129.07, 128.87,
4.8. General procedure for generation of aqua species with AgNO3.
The complex was stirred for 18 h with an equimolar quantity of
28.66, 128.47, 127.12, 126.53, 122.66, 95.98, 95.86, 87.49, 83.49,
ꢀ
1
1.57, 60.69, 54.25, 10.27, 9.71, 8.66, 8.37. FT-IR (KBr, cm ):
ν =
–
–
–
–
◦
622 (C
O), 1582 (C
–
N), 1663 (C
–
N). (+)-HR-ESI-MS: m/z (%)
AgNO in deuterium oxide (1.20 mL) at 37 C in an oil bath. The solution
3
+
+
54.2007 ([M - Cl] , 100%), 890.1763 ([M+H] , 22%). HPLC purity:
was subsequently filtered through a plug of Celite™ and collected in an
NMR tube and 1–2 drops of TMS added as internal standard. Solutions
7.2%; tr’ = 16.24 min.
1
were then analysed with H NMR.
4
.5.6. C6
Dichloro(tetramethylbiphenylcyclopentadienyl)iridium(III) dimer
4.8.1. C1-D O
2
-
2
-2
(
(
50.0 mg, 0.0470 mmol), L2 (43.4 mg, 0.0930 mmol) and NaHCO
3
(9.30 mg, 1.20 × 10 mmol) and AgNO3 (2.10 mg, 1.20 × 10
1
7.80 mg, 0.0930 mmol) were reacted in methanol (1.50 mL) to afford
2 2
mmol) were reacted in D O (1.20 mL). H NMR (400 MHz, D O) δ 9.01
3
1
complex C6 as an orange powder in 56% yield (50.0 mg). H NMR (400
(d, 1H, J = 5.4 Hz, pyridyl-H), 8.30–8.24 (m, 1H, pyridyl-H), 8.16–8.06
3
3
MHz, CDCl
3
): δ 8.47 (d, 1H, J = 8.8 Hz, quinolyl-H), 8.34 (d, 1H, J =
H
(m, 4H, pyridyl-H, pyrimidine-H, phenyl-H), 7.91–7.85 (m, 1H, pyridyl-
3
3
8
.4 Hz, quinolyl-H), 8.28 (d, 1H, J = 8.4 Hz, quinolyl-H), 8.17 (s, 1H,
H), 7.46 (d, 2H, J = 8.9 Hz, phenyl-H), 3.99 (s, 3H, CH ), 3.83 (s, 3H,
3
3
3
pyrimidine-H), 8.15 (d, 2H, J = 8.9 Hz, phenyl-H), 8.07 (d, 2H, J =
CH ), 1.27 (s,15H, Cp*–CH ).
3
3
8
.9 Hz, phenyl-H), 7.86 (d, 1H, 3J = 8.2 Hz, quinolyl-H), 7.78 (s, 1H,
x
sulfonamide-NH), 7.65–7.54 (m, 5H, quinolyl-H, Cp -phenyl-H),
4.8.2. C2-D O
2
x
x
-2
-2
7
.51–7.44 (m, 2H, Cp -phenyl-H), 7.44 – 7.35 (m, 4H, quinolyl-H, Cp -
(10.0 mg, 1.20 × 10 mmol) and AgNO3 (2.10 mg, 1.20 × 10
x
1
phenyl-H), 3.97 (s, 3H, CH
3
), 3.84 (s, 3H, CH
3
), 1.52 (s, 3H, Cp -CH
3
),
C
mmol) were reacted in D O (1.20 mL). H NMR (400 MHz, D O): δ 8.94
3 3
2
2
H
x
x
x
).13
1
.50 (s, 3H, Cp -CH
3
), 1.40 (s, 3H, Cp -CH
): δ
45.13, 141.16, 140.13, 140.06, 133.67, 131.02, 130.83, 130.22,
3
), 0.95 (s, 3H, Cp -CH
3
(d, 1H, J = 5.4 Hz, pyridyl-H), 8.31 (m, 1H, pyridyl-H), 8.17 (d, 1H, J
3
NMR (101 MHz, CDCl
3
C
169.40, 160.89, 156.49, 153.44, 149.92,
= 7.6 Hz, pyridyl-H), 8.04 (s, 1H, pyrimidine-H), 7.92 (d, 2H, J = 8.6
3
x
1
1
1
6
Hz, phenyl-H), 7.85 (m, 1H, pyridyl-H), 7.47 (t, 1H, J = 7.7 Hz, Cp -
3 3
30.12, 130.06, 129.13, 129.08, 128.90, 128.66, 127.96, 127.62,
27.13, 127.06, 126.54, 122.68, 95.93, 95.73, 87.82, 83.37, 81.39,
phenyl-H), 7.36 (t, 2H, J = 7.7 Hz, phenyl-H), 7.18(d, 2H, J = 8.6 Hz,
3 x
phenyl-H), 7.12 (d, 2H, J = 7.7 Hz, Cp -phenyl-H), 4.03 (s, 3H, CH ),
3
ꢀ
1
x
x
0.69, 54.25, 10.34, 9.83, 8.64, 8.36. FT-IR (KBr, cm ):
ν
= 1623
3 3 3
3.80 (s, 3H, CH ), 1.58 (s, 6H, Cp -CH ), 1.09 (s, 6H, Cp -CH ).
–
–
–
–
–
–
(
(
C
O), 1579 (C
N), 1661 (C
N). (+)-HR-ESI-MS: m/z (%) 930.2319
+
+
[M - Cl] , 100%), 966.2080 ([M+H] , 18%). HPLC purity: 94%; tr’
=
2
4.8.3. C4-D O
-
2
-2
2
0.23 min.
(9.90 mg, 1.20 × 10 mmol) and AgNO3 (2.00 mg, 1.20 × 10
1
mmol) were reacted in D
2
O (1.20 mL). H NMR (400 MHz, D
2
O): δ
H
8.79
3
3
4
.6. X-ray crystallographic data collection
(d, 1H, J = 8.6 Hz, quinolyl-H), 8.50 (d, 1H, J = 9.0 Hz, quinolyl-H),
8
.23 (d, 1H, 3J = 8.2 Hz, quinolyl-H) 8.14–8.20 (m, 2H, quinolyl-H),
3
Crystals of L1 were grown by layering a dichloromethane solution of
8.03 (d, 2H, J = 8.5 Hz, phenyl-H), 7.90–7.97 (m, 2H, quinolyl-H,
3
L1 with hexane and left to stand in a sealed vial for several days at room
temperature. A crystal of diffraction quality was selected for analysis
and mounted in oil. Low temperature X-ray diffraction data collection
for L1 was performed at 100(2) K on a Bruker APEX II DUO CCD
pyrimidine-H), 7.67 (d, 2H, J = 8.5 Hz, phenyl-H), 3.94 (s, 3H, CH
3.82 (s, 3H, CH ).
), 1.19 (s, 15H, Cp*–CH
3
),
3
3
4.9. General procedure for generation of aqua complexes without AgNO
3
diffractometer using graphite-monochromated MoK
α
radiation
(
0.71073 Å). An Oxford Cryostream plus, 700 series cryostat that was
The complex was dissolved in deuterated acetone (300 µL) and then
mixed with deuterium oxide (900 µL) in a vial for a final solution of 25%
(v/v) deuterated acetone/deuterium oxide (1.20 mL). The resultant
attached to the diffractometer cooled the sample. Data were collected up
to 55.1 2θ. Lp and absorption corrections applied, µ = 0.221 mmꢀ 1
◦
.
◦
Bruker diffraction, SAINT [64] software was used for data reduction and
unit cell determinations, while SADABS [51,65] was used for absorption
corrections. SHELXL-16 [66] and SHELXT-14 [66] was used to refine
and solve crystal structures with the X-seed [67,68] graphical user
mixture was then stirred for 18 h at 37 C in an oil bath. The solution was
subsequently filtered through a plug of Celite™ and collected in an NMR
tube and 1–2 drops of TMS was added as internal standard. Samples
1
were analysed with
H NMR and then submitted for ESI-mass
8

T.J. Kotz ´e et al.
Inorganica Chimica Acta 517 (2021) 120175
spectrometry analysis.
compounds using GraphPad Prism 4.0, and the non-linear regression,
sigmoidal dose response variable slope and the IC50 determined (where
two or more points formed a plateau in the software). The data was
generated from two biological replicates in duplicate of the three strains
used.
4
.10. M. tuberculosis MIC determination assay.
The minimum inhibitory concentration (MIC) was determined using
the standard broth micro dilution method, as described previously.
Briefly, a 10 mL culture of Mycobacterium tuberculosis pMSp12::GFP [69-
4.12. Human embryonic kidney (HEK293) mammalian cell cytotoxicity
7
1] was grown to an optical density (OD600) of 0.6 – 0.7. Cultures were
diluted prior to inoculation of assays, as follows: (i) 1:100 in Gaste-Fe
glycerol–alanine–salts) medium pH 6.6, supplemented with 0.05%
HEK293 cells were cultured in DMEM culture media supplemented
with 10% Foetal Bovine Serum (FBS). The cells were harvested and
dispensed into 384 well sterile black, clear base microtitre plates at 2000
cells/well (45 µL). The plates were left to settle, and the cells attach
(
Tween-80 and 1% Glycerol [72,73]; (ii) 1:500 in 7H9 supplemented
with 10% Albumin Dextrose Catalase supplement (ADC), 0.4% Glucose
and 0.05% Tween-80.[72,73] The compounds to be tested were recon-
stituted in DMSO.
◦
overnight in a standard tissue culture incubator at 5% CO , 37 C and
2
60% humidity. After overnight incubation, 5 µL of diluted compound (as
described in the section, Evaluation of in vitro activity against
P. falciparum asexual blood stages) was added to the cell containing
plates and incubated for a further 72 h. After incubation the supernatant
from the wells was removed and 40ul of 40 µM resazurin in DMEM
media (FBS free) added to all wells. The plates were incubated for 6 h
then measured for fluorescent intensity using the PerkinElmer Envision.
The data were analysed as in the Plasmodium falciparum methods
section.
Two-fold serial dilutions of the test compound were prepared across
a 96-well microtitre plate, after which 50 L of the diluted M. tuberculosis
μ
cultures were added to each well in the serial dilution. The plate layout
was a modification of the method previously described [74]. Assay
controls used were a minimum growth control (Rifampicin at 2xMIC),
and a maximum growth control (5% DMSO).
The microtitre plates were sealed in a secondary container and
◦
incubated at 37 C with 5% CO
2
and humidification. Relative fluores-
cence (excitation 485 nm; emission 520 nm) was measured using a plate
reader (FLUOstar OPTIMA, BMG LABTECH), at day 7 and day 14. The
raw fluorescence data were archived and analysed using the CDD Vault
from Collaborative Drug Discovery, in which, data are normalised to the
minimum and maximum inhibition controls to generate a dose response
curve (% inhibition), using the Levenberg-Marquardt damped least-
squares method, from which the MIC90 is calculated (The Collabora-
tive Drug Discovery database, Burlingame, CA www.collaborativedrug.
com). The lowest concentration of drug that inhibits growth of >90% of
Declaration of Competing Interest
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influence
the work reported in this paper.
Acknowledgements
the bacterial population is considered to be the MIC90
.
We thank the National Research Foundation (NRF) of South Africa
(
Thuthuka grant: 106952). Research reported in this publication was
4
.11. Evaluation of in vitro activity against P. falciparum asexual blood
supported by the Strategic Health Innovation Partnerships (SHIP) Unit
of the South African Medical Research Council with funds received from
the South African Department of Science Innovation (to D.F.W.). This
study was also supported by the Australian Research Council
stages [75]
Stock solutions of the compounds to be tested were prepared in
DMSO (20 mM). The stock solutions were further diluted in 384-well
polypropylene microtitre plates to produce 3 doses per log dose
response with final assay concentrations of the compounds ranging be-
tween 80 µM and 0.8 nM. A 1:25 dilution was then made of the com-
pound plates with sterile water in a 384-well polystyrene plate and 5 µL
of these wells were then transferred into a 384-well imaging plate. 4%
DMSO and 50 µM Puromycin were used as controls under the same
conditions and dilutions as that of the compounds.
(
LP120200557 award to V.M.A.). We thank the Australian Red Cross
Blood Bank for the provision of fresh red blood cells, without which the
Plasmodium falciparum research could not have been performed. This
work was also supported by the National Health and Medical Research
Council Postgraduate Scholarship (NHMRC APP1150359), a Griffith
University Postgraduate Scholarship and Discovery Biology Post-
graduate Scholarship all awarded to Sandra Duffy.
A Plasmodium falciparum standard genomic reference strain (3D7),
multidrug resistant strain (Dd2) and gametocyte forming pyrimeth-
amine resistant and chloroquine sensitive strain (HB3) were cultured
within the medium RPMI-1640 which was supplemented with 10 mM
Appendix A. Supplementary data
Appendix A contains the supplementary data for this paper. CCDC
1
949937 contains the crystallographic data for this article, in CIF
HEPES, 25 µg/mL hypoxanthine, 5% human serum and 2.5 mg/mL
format. These data can be obtained free of charge at www.ccdc.cam.ac.
uk/conts/retrieving.html [or from the Cambridge Crystallographic Data
Centre, 12, Union Road, Cambridge CB2 1EZ, UK; fax: (internat.) +44-
◦
Albumax while being incubated at 37 C under 5% CO
2
, 5% O
2
and 90%
2
N . Sorbitol synchronization was performed twice, consecutively, dur-
ing the intra-erythrocytic lifecycles to provide ring-stage parasites for
the assays [76]. The ring stage parasite culture had its percentage par-
asitaemia and percentage haematocrit adjusted to 2% and 0.3%,
respectively, and thereafter 45 µL of the adjusted parasite culture was
added to compound containing imaging plates prepared as described
earlier. The imaging plates were then incubated for 72 h under the same
conditions as described for the original cultures. The plates were then
1
223/336-033; E-mail: deposit@ccdc.cam.ac.uk]. Supplementary data
to this article can be found online at https://doi.org/10.1016/j.ica.20
0.120175.
2
References
[
1] World Health Organization, Global Tuberculosis Report, 2019.
′
stained with 4 ,6-diamidino-2-phenylindole (DAPI) and incubated
[2] E.A. Hillard, G. Jaouen, Organometallics 30 (1) (2011) 20–27.
[
[
[
3] W. Castro, M. Navarro, C. Biot, Future Med. Chem. 5 (1) (2013) 81–96.
4] A.H. Ngo, S. Bose, L.H. Do, Chem. Eur. J. 24 (42) (2018) 10584–10594.
5] K. Na-Bangchang, J. Karbwang, Fund. Clin. Pharmacol. 23 (4) (2009) 387–409.
overnight at room temperature before being imaged on an Opera
confocal high content imaging system. Accapella scripting software was
used to determine the number of classified parasites which was subse-
quently normalized to obtain the percentage inhibition with regards to
the two plate controls, 0.4% DMSO and 5 µM Puromycin. The normal-
ized inhibition data was then plotted against the log concentration of the
[6] F.P. L’Abbate, R. Müller, R. Openshaw, J.M. Combrinck, K.A. de Villiers, R. Hunter,
T.J. Egan, Eur. J. Med. Chem. 159 (2018) 243–254.
[
7] M. Rizzotto, Metal Complexes as Antimicrobial Agents, in: V. Bobbarala (Ed.), A
Search for Antibacterial Agents, IntechOpen2012.
[8] P.C.A. Bruijnincx, P.J. Sadler, Curr. Opin. Chem. Biol. 12 (2) (2008) 197–206.
9

T.J. Kotz ´e et al.
Inorganica Chimica Acta 517 (2021) 120175
[
9] J.A. Obaleye, A.C. Tella, M.O. Bamigboye, Metal Complexes as Prospective
Antibacterial Agents, in: V. Bobbarala (Ed.), A Search for Antibacterial Agents,
IntechOpen2012.
[45] L.-J. Ming, Med. Res. Rev. 23 (6) (2003) 697–762.
[46] H. Keypour, M. Shayesteh, M. Rezaeivala, F. Chalabian, Y. Elerman,
O. Buyukgungor, J. Mol. Struct. 1032 (2013) 62–68.
[
[
[
[
10] M. Navarro, W. Castro, C. Biot, Organometallics 31 (16) (2012) 5715–5727.
11] N. Chavain, C. Biot, Curr. Med. Chem. 17 (25) (2010) 2729–2745.
12] T.I. Kostelnik, C. Orvig, Chem. Rev. 119 (2) (2019) 902–956.
[47] M. Mondelli, V. Brun ´e , G. Borthagaray, J. Ellena, O.R. Nascimento, C.Q. Leite, A.
A. Batista, M.H. Torre, J. Inorg. Biochem. 102 (2) (2008) 285–292.
[48] R.R. Coombs, M.K. Ringer, J.M. Blacquiere, J.C. Smith, J.S. Neilsen, Y.-S. Uh, J.
B. Gilbert, L.J. Leger, H. Zhang, A.M. Irving, S.L. Wheaton, C.M. Vogels, S.
A. Westcott, A. Decken, F.J. Baerlocher, Transit. Met. Chem. 30 (4) (2005)
411–418.
13] C. Zhen-Feng, C. Orvig, L. Hong, Curr. Top. Med. Chem. 17 (28) (2017)
3
131–3145.
[
[
14] K.D. Mjos, C. Orvig, Chem. Rev. 114 (8) (2014) 4540–4563.
15] P. Chellan, V.M. Avery, S. Duffy, J.A. Triccas, G. Nagalingam, C. Tam, L.W. Cheng,
J. Liu, K.M. Land, G.J. Clarkson, I. Romero-Canel o´ n, P.J. Sadler, Chem. Eur. J. 24
[49] M. Zaki, F. Arjmand, S. Tabassum, Inorg. Chim. Acta 444 (2016) 1–22.
[50] Z.H. Chohan, H.A. Shad, J. Enzyme Inhib. Med. Chem. 27 (3) (2012) 403–412.
[51] Z.H. Chohan, H.A. Shad, M.H. Youssoufi, T. Ben Hadda, Eur. J. Med. Chem. 45 (7)
(2010) 2893–2901.
(
40) (2018) 10078–10090.
16] M. Navarro, C. Gabbiani, L. Messori, D. Gambino, Drug Discov. Today 15 (23)
2010) 1070–1078.
17] A. van Niekerk, P. Chellan, S.F. Mapolie, Eur. J. Inorg. Chem. 2019 (30) (2019)
[
[
[
[
(
[52] Z.H. Chohan, H. Mahmood ul, K.M. Khan, C.T. Supuran, J. Enzyme Inhib. Med.
Chem. 20 (2) (2005) 183–188.
3
432–3455.
[53] N.U. Hassan Khan, S. Zaib, K. Sultana, I. Khan, B. Mougang-Soume, H. Nadeem,
M. Hassan, J. Iqbal, RSC Adv. 5 (38) (2015) 30125–30132.
18] P. Chellan, T. Stringer, A. Shokar, A. Au, C. Tam, L.W. Cheng, G.S. Smith, K.
M. Land, Inorg. Chem. Commun. 102 (2019) 1–4.
[54] A. Nocentini, M. Ferraroni, F. Carta, M. Ceruso, P. Gratteri, C. Lanzi, E. Masini, C.
T. Supuran, J. Med. Chem. 59 (23) (2016) 10692–10704.
19] E. Ekengard, L. Glans, I. Cassells, T. Fogeron, P. Govender, T. Stringer, P. Chellan,
G.C. Lisensky, W.H. Hersh, I. Doverbratt, S. Lidin, C. de Kock, P.J. Smith, G.
S. Smith, E. Nordlander, Dalton Trans. 44 (44) (2015) 19314–19329.
20] P. Chellan, K.M. Land, A. Shokar, A. Au, S.H. An, D. Taylor, P.J. Smith, T. Riedel, P.
J. Dyson, K. Chibale, G.S. Smith, Dalton Trans. 43 (2) (2014) 513–526.
21] P. Chellan, K.M. Land, A. Shokar, A. Au, S.H. An, D. Taylor, P.J. Smith, K. Chibale,
G.S. Smith, Organometallics 32 (17) (2013) 4793–4804.
˙
[55] C. Yenikaya, H. Ilkimen, M.M. Demirel, B. Ceyhan, M. Bülbül, E. Tunca, J. Braz.
Chem. Soc. 27 (2016) 1706–1714.
[
[
[
[
[
[
[
[56] E. Bruno, M.R. Buemi, A. Di Fiore, L. De Luca, S. Ferro, A. Angeli, R. Cirilli,
D. Sadutto, V. Alterio, S.M. Monti, C.T. Supuran, G. De Simone, R. Gitto, J. Med.
Chem. 60 (10) (2017) 4316–4326.
[57] M. Mondelli, F. Pavan, P.C. de Souza, C.Q. Leite, J. Ellena, O.R. Nascimento,
G. Facchin, M.H. Torre, J. Mol. Struct. 1036 (2013) 180–187.
[58] C. Quintana, G. Silva, A.H. Klahn, V. Artigas, M. Fuentealba, C. Biot, I. Halloum,
L. Kremer, N. Novoa, R. Arancibia, Polyhedron 134 (2017) 166–172.
[59] P. Doig, P.A. Boriack-Sjodin, J. Dumas, J. Hu, K. Itoh, K. Johnson, S. Kazmirski,
T. Kinoshita, S. Kuroda, T.-O. Sato, K. Sugimoto, K. Tohyama, H. Aoi,
K. Wakamatsu, H. Wang, Bioorg. Med. Chem. 22 (21) (2014) 6256–6269.
[60] Q. Li, S.-Y. Zhang, G. He, Z. Ai, W.A. Nack, G. Chen, Org. Lett. 16 (6) (2014)
1764–1767.
22] F. Dubar, C. Slomianny, J. Khalife, D. Dive, H. Kalamou, Y. Gu ´e rardel, P. Grellier,
C. Biot, Angew. Chem. Int. Ed. 52 (30) (2013) 7690–7693.
23] J. Hess, G. Panic, M. Patra, L. Mastrobuoni, B. Spingler, S. Roy, J. Keiser, G. Gasser,
A.C.S. Infect, Dis. 3 (9) (2017) 645–652.
24] E.V. Capparelli, R. Bricker-Ford, M.J. Rogers, J.H. McKerrow, S.L. Reed,
Antimicrob Agents Chemother 61 (1) (2016) e01947–16.
25] S. Vale-Costa, N. Vale, J. Matos, A. Tom a´ s, R. Moreira, P. Gomes, M.S. Gomes,
Antimicrob. Agents Chemother. 56 (11) (2012) 5774–5781.
26] J. Lecina, P. Cort ´e s, M. Llagostera, C. Piera, J. Suades, Bioorg. Med. Chem. 22 (13)
[61] Ü.O. Ozdemir, P. Güvenç, E. S¸ ahin, F. Hamurcu, Inorg. Chim. Acta 362 (8) (2009)
2613–2618.
¨ ¨
(
2014) 3262–3269.
[
[
[
27] G. Jaouen, A. Vessi `e res, S. Top, Chem. Soc. Rev. 44 (24) (2015) 8802–8817.
28] B. Reta, B. Erko, Trop. Med. Int. Health 18 (11) (2013) 1338–1343.
29] M. Patra, K. Ingram, A. Leonidova, V. Pierroz, S. Ferrari, M.N. Robertson, M.
H. Todd, J. Keiser, G. Gasser, J. Med. Chem. 56 (22) (2013) 9192–9198.
30] J. Hess, M. Patra, V. Pierroz, B. Spingler, A. Jabbar, S. Ferrari, R.B. Gasser,
G. Gasser, Organometallics 35 (19) (2016) 3369–3377.
[62] S.-N. Li, Q.-G. Zhai, M.-C. Hu, Y.-C. Jiang, Inorg. Chim. Acta 362 (7) (2009)
2217–2221.
[63] J. T o¨ nnemann, J. Risse, Z. Grote, R. Scopelliti, K. Severin, Eur. J. Inorg. Chem.
2013 (26) (2013) 4558–4562.
[
[
[
[
[64] A. Çapcı, M.M. Lorion, H. Wang, N. Simon, M. Leidenberger, M.C. Borges Silva, D.
R.M. Moreira, Y. Zhu, Y. Meng, J.Y. Chen, Y.M. Lee, O. Friedrich, B. Kappes,
J. Wang, L. Ackermann, S.B. Tsogoeva, Angew. Chem. Int. Ed. 58 (37) (2019)
13066–13079.
31] B. Xing, C.-W. Yu, P.-L. Ho, K.-H. Chow, T. Cheung, H. Gu, Z. Cai, B. Xu, J. Med.
Chem. 46 (23) (2003) 4904–4909.
32] L.C. Eiter, N.W. Hall, C.S. Day, G. Saluta, G.L. Kucera, U. Bierbach, J. Med. Chem.
[65] R. Blessing, Acta Cryst. A 51 (1) (1995) 33–38.
5
2 (21) (2009) 6519–6522.
[66] G.M. Sheldrick, Acta Cryst. C 71 (1) (2015) 3–8.
33] E.H.S. Sousa, L.A. Basso, D.S. Santos, I.C.N. Di o´ genes, E. Longhinotti, L.G. de
[67] L.J. Barbour, J. Supramol. Chem. 1 (4) (2001) 189–191.
[68] J.L. Atwood, L.J. Barbour, Crys. Growth Des. 3 (1) (2003) 3–8.
[69] G.L. Abrahams, A. Kumar, S. Savvi, A.W. Hung, S. Wen, C. Abell, C.E. Barry, D.
R. Sherman, H.I.M. Boshoff, V. Mizrahi, Chem. Biol. 19 (7) (2012) 844–854.
[70] L. Collins, S.G. Franzblau, Antimicrob Agents Chemother 41 (5) (1997)
1004–1009.
´
França Lopes, I. de Sousa Moreira, J. Biol. Inorg. Chem. 17 (2) (2012) 275–283.
[
[
[
[
[
[
34] R.J. Henry, Bacteriol. Rev 7 (4) (1943) 175–262.
35] A. Kołaczek, I. Fusiarz, J. Lawecka, D. Branowska, Chemik 68 (7) (2014) 620–628.
36] E.E. Connor, Prim. Care Update Ob. Gyns. 5 (1) (1998) 32–35.
37] T.H. Maren, Annu. Rev. Pharmacol. Toxicol. 16 (1) (1976) 309–327.
38] T. Owa, T. Nagasu, Expert Opin. Ther. Pat. 10 (11) (2000) 1725–1740.
39] A. Kleemann, J. Engel, B. Kutscher, D. Reichert, Pharmaceutical Substances:
Syntheses, Patents, Applications, 1st ed., Thieme, Stuttgart, 1999.
40] W.R. Roush, S.L. Gwaltney, J. Cheng, K.A. Scheidt, J.H. McKerrow, E. Hansell,
J. Am. Chem. Soc. 120 (42) (1998) 10994–10995.
[71] L.A. Collins, M.N. Torrero, S.G. Franzblau, Antimicrob. Agents Chemother. 42 (2)
(1998) 344–347.
[72] J.J. De Voss, K. Rutter, B.G. Schroeder, H. Su, Y. Zhu, C.E. Barry, 3rd, Proc. Natl.
Acad. Sci. U S A 97(3) (2000) 1252-1257.
[
[
[
[
[
[73] S.G. Franzblau, M.A. DeGroote, S.H. Cho, K. Andries, E. Nuermberger, I.M. Orme,
K. Mdluli, I. Angulo-Barturen, T. Dick, V. Dartois, A.J. Lenaerts, Tuberculosis 92 (6)
(2012) 453–488.
41] A. Burger, M. Wolff, Burger’s Medicinal Chemistry and Drug Discovery, 1st ed.,
Wiley, New York, 1995.
42] P. Forgacs, N.L. Wengenack, L. Hall, S.K. Zimmerman, M.L. Silverman, G.
D. Roberts, Antimicrob. Agents Chemother. 53 (11) (2009) 4789.
43] E. Kremer, G. Facchin, E. Est ´e vez, P. Albor ´e s, E.J. Baran, J. Ellena, M.H. Torre,
J. Inorg. Biochem. 100 (7) (2006) 1167–1175.
[74] J. Ollinger, M.A. Bailey, G.C. Moraski, A. Casey, S. Florio, T. Alling, M.J. Miller,
T. Parish, PLOS ONE 8 (4) (2013), e60531.
[75] S. Duffy, V.M. Avery, Am J Trop Med Hyg 86 (1) (2012) 84–92.
[76] C. Lambros, J.P. Vanderberg, J. Parasitol. 65 (3) (1979) 418–420.
44] C.M. Sharaby, M.F. Amine, A.A. Hamed, J. Mol. Struct. 1134 (2017) 208–216.
1
0