4-Aminoquinoline-pyrimidine-aminoalkanols: Synthesis, in vitro antimalarial activity, docking studies and ADME predictions

Article abstract of DOI:10.1039/c5nj00094g

Twenty-four new 4-aminoquinoline-pyrimidine hybrids containing a terminal aliphatic amino-alcohol chain were synthesized and assessed for their antimalarial activity against chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of Plasmodium falciparum. All of the compounds displayed potent antiplasmodial activities (IC₅₀ values in the range of 0.05-10.47 μM) with no appreciable cytotoxicity towards mammalian cells, up to the highest tested concentration of 12 μM. Molecular docking studies of the most active compounds (8b-8f, 8u and 8v) with both wild type and quadruple mutant Pf-DHFR-TS were performed, which exhibited interactions comparable to conventional folate inhibitors. ADME predictions also revealed favourable pharmacokinetic parameters for the synthesized hybrids, which warrants their suitability for development as potent antimalarials.

Full text of DOI:10.1039/c5nj00094g

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4-Aminoquinoline-pyrimidine-aminoalkanols:
synthesis, in vitro antimalarial activity, docking
studies and ADME predictions†‡
Cite this: New J. Chem., 2015,
39, 3474
Mohit Tripathi,a Shabana I. Khan,b Anuj Thakur,a Prija Ponnana and
Diwan S. Rawat*a
Twenty-four new 4-aminoquinoline-pyrimidine hybrids containing a terminal aliphatic amino-alcohol
chain were synthesized and assessed for their antimalarial activity against chloroquine-sensitive (D6) and
chloroquine-resistant (W2) strains of Plasmodium falciparum. All of the compounds displayed potent
antiplasmodial activities (IC50 values in the range of 0.05–10.47 mM) with no appreciable cytotoxicity
towards mammalian cells, up to the highest tested concentration of 12 mM. Molecular docking studies of
the most active compounds (8b–8f, 8u and 8v) with both wild type and quadruple mutant Pf-DHFR-TS
were performed, which exhibited interactions comparable to conventional folate inhibitors. ADME predictions
also revealed favourable pharmacokinetic parameters for the synthesized hybrids, which warrants their
suitability for development as potent antimalarials.
Received (in Montpellier, France)
13th January 2015,
Accepted 17th February 2015
DOI: 10.1039/c5nj00094g
www.rsc.org/njc
Introduction
Drug-resistance is not only a major public health concern but also
rattles the scientific community involved in drug research. This
problem is rising in epic proportions and mounting an enormous
pressure on governments and researchers worldwide. A rational
strategy to counter drug-resistant diseases is to combine two or
more active compounds with independent modes of action
(combination therapy) to prevent the advent of resistance. This
strategy was first formulated for anti-tuberculosis chemother-
apy,1,2 followed by cancer chemotherapy,3 and lately for the
treatment of malaria4 and AIDS.5 Malaria, transmitted to humans
through the bite of a female Anopheles mosquito, is caused by
infection with any of the five species of Plasmodium, of which
P. falciparum is the most lethal. According to the WHO World
Malaria Report 2013, 97 countries had ongoing malaria trans-
mission in 2013 with an estimated 3.4 billion people at risk of
malaria, of which 1.2 billion are at a high risk.6
Fig. 1 Conventional antimalarial drugs.
(pyrimethamine, cycloguanil etc.) and artemisinins remained
The development and use of anti-malarial medications such a mainstay towards the control and treatment of malaria
as chloroquine (CQ, a 4-aminoquinoline), folate inhibitors (Fig. 1). However, with a spate of reports on drug-resistant
parasite strains, including the recent findings of artemisinin-
resistance in four south-east Asian countries of the Greater
Mekong sub-region,6,7–9 there is a dire need to develop cost-
effective anti-malarials. Currently, WHO recommends artemisinin-
based combination therapy (ACT) with a conventional anti-
malarial agent, particularly for infections caused by P. falciparum.6
Several strategies have been explored towards the develop-
ment of new antimalarial agents to address the problem of
drug-resistance. The concept of molecular hybrids has shown
a Department of Chemistry, University of Delhi, Delhi 110007, India.
E-mail: dsrawat@chemistry.du.ac.in; Fax: +91-11-27667501;
Tel: +91-11-27667465
b National Centre for Natural Products Research, University of Mississippi,
MS-38677, USA
† Dedicated to Dr D. S. Bhakuni on the occasion of his 85th birthday.
‡ Electronic supplementary information (ESI) available: Experimental protocol
for the computational studies and 1H NMR/13C NMR spectra of representative
compounds. See DOI: 10.1039/c5nj00094g
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promising results and may hold a key role en route to solving
this menacing problem. In hybrid antimalarials, two (or more)
discrete antimalarial scaffolds are linked covalently, through a
spacer, in anticipation that these compounds may act by
concurrently inhibiting two or more traditional targets.10 These
multi-targeted hybrids not only counter the threat of drug-
resistance against the parent pharmacophore(s), but also over-
come most of the problems associated with the combination
therapies by ensuring more predictable pharmacokinetic profiles,
a reduced risk of drug–drug interactions and most significantly,
patient-compliance. Lately, numerous hybrids for the treatment
of malaria have been reported11,12 and 4-aminoquinoline based
hybrids have exhibited the most encouraging results.12–17 Some of
them are currently undergoing pre-clinical studies.13 4-Amino-
quinolines disrupt the parasite’s detoxification pathway for
conversion of the toxic-heme to non-toxic hemozoin18 within
its digestive vacuole. This target is ideal as it is host-derived and
inherently not under the control of the parasite.19 Thus, long-
acting 4-aminoquinolines, with the added advantages of an easy
and cheap synthesis and excellent clinical efficacy, remain
crucial for the development of antimalarial molecular hybrids.
Towards this end, we had previously reported 4-aminoquinoline
based hybrids with folate inhibitor triazine20–22 and pyrimidine23–26
pharmacophores.
Fig. 2 Design of the 4-aminoquinoline-pyrimidine hybrids.
K2CO3 and with DMF (N,N-dimethylformamide) as a solvent, lead-
ing to the desired 4-aminoquinoline-pyrimidine-aminoalkanols
(8a–x) in good yields. During the course of the synthesis, it was
observed that the solubility of the 6-methyl pyrimidine hybrids was
better than their non-methyl counterparts in organic solvents.
Additionally, a steady increase in the lipophilicity of the hybrids
was observed with an increasing chain length of the amino-alcohols.
It was envisaged that the hybridization of such DHFR-
inhibitors with 4-aminoquinolines may result in more potent
molecules that may act by simultaneously disrupting the heme-
detoxification pathway and halting the tetrahydrofolate synthesis
of the malarial parasite. In order to study the effects of structural
modifications at the pyrimidine core of the 4-aminoquinoline-
Biological activities
pyrimidine conjugates on their antimalarial potency and pharma- The antimalarial potentials of all the synthesized hybrids
cokinetic behaviour, and in the larger interest of deducing the against both CQ-sensitive (D6) and CQ-resistant (W2) strains
structure–activity relationships, we decided to substitute the cyclic of P. falciparum were assessed via a previously reported proce-
secondary amines attached to the pyrimidine nucleus with various dure based on calculation of the plasmodial LDH activity.27,28
open chain aliphatic amino-alcohols (Fig. 2). Also, analogous All of the 24 compounds showed potent antimalarial activity,
conjugates without a methyl group at the 6th position of the with seven compounds (8b–8e and 8t–8v) displaying sub-
pyrimidine ring were prepared. In addition, molecular docking micromolar IC50 values against both of the P. falciparum strains
with Pf-DHFR-TS and prediction of the ADME properties of the (Table 1). Compound 8e exhibited comparable activity (IC50
=
active compounds were performed to perceive the compounds’ 0.05 mM) to CQ against the CQ-sensitive (D6) strain, whereas
possible mode of action and their aptness towards further devel- hybrids 8b (0.47 mM), 8c (0.34 mM) and 8d (0.41 mM) displayed
opment into a drug, respectively.
antimalarial activities akin to the reference drug against the
CQ-resistant strain.
As mentioned earlier, the lipophilicities of the 6-methyl
pyrimidine analogues were found to be better in comparison
to the non-methyl analogues, and a gradual rise in their lipo-
philicity was observed on increasing the chain length of the
Results and discussion
Chemistry
Scheme 1 depicts the synthetic route to the present hybrids. amino-alcohols attached to the pyrimidine nucleus. The cumu-
Commercially available 4,7-dichloroquinoline (1) was selected lative effects of both these structural features on the lipophilicity
as the starting material to which various diaminoalkanes (2a–c) of the hybrids were also correspondingly observed for their
were appended via SNAr reactions, by heating under neat antimalarial activities, and this can be noticed in Table 1,
conditions, to give intermediates 3a–c. These intermediates especially on comparing the series 8o–s (having no methyl group
were then reacted with either 2,4-dichloropyrimidine (4a) or on pyrimidine) with the 8t–x series of compounds (having a
2,4-dichloro-6-methylpyrimidine (4b) to yield, respectively, methyl group at the 6th position of pyrimidine). These results
intermediates 5a–c or 6a–c. The intermediates (5 or 6) were are in concordance with the earlier reported observations on the
then reacted with various aliphatic linear chain amino-alcohols relation of higher antiplasmodial activity to better lipophilicity of
(7a–e) at an elevated temperature (120 1C) in the presence of the quinoline antimalarials.29,30 The resistance index (RI) values
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Scheme 1 (i) Neat, 120–130 1C, 6 h, 70–90%; (ii) N,N-diisopropylethylamine, THF, 0 1C–RT, 14 h, 80–85%; (iii) K2CO3, DMF, 120 1C, 10 h, 70–90%.
Table 1 The in vitro antimalarial activity and cytotoxicity of the 4-aminoquinoline-pyrimidine-aminoalkanolsa
P. falciparum (D6 clone)
P. falciparum (W2 clone)
Resistance
index (RI)
Cytotoxicity (VERO cells),
IC50 (mM)
SI
IC50 (mM)
SI
Compound
R
n1
n2
IC50 (mM)
8a
8b
8c
8d
8e
8f
8g
8h
8i
8j
8k
8l
8m
8n
8o
8p
8q
8r
8s
8t
8u
8v
8w
8x
CQ
Me
Me
Me
Me
Me
H
H
H
H
H
Me
Me
Me
Me
H
H
H
1
1
1
1
1
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
—
—
1
2
3
4
5
1
2
3
4
5
1
2
3
4
1
2
3
4
5
1
2
3
4
5
—
—
3.37
0.13
0.12
0.12
0.05
3.95
1.87
10.47
3.87
3.35
3.72
3.23
3.08
2.64
1.66
2.57
2.74
3.05
3.17
0.15
0.13
0.13
1.54
1.43
0.04
0.01
43.8
494
2.22
0.47
0.34
0.41
0.63
4.15
2.6
6.01
4.02
2.62
2.71
3.46
1.9
2.07
1.92
2.13
2.14
2.62
2.53
0.91
0.89
0.63
1.54
1.19
0.43
NA
45.7
426.2
434.8
427.9
417.5
43.1
44.7
42
42.9
44.2
44.5
43.4
46
45.4
46.4
45.6
45.4
44.2
44.2
413
412.9
417.6
47
0.65
3.61
2.83
3.42
12.6
1.05
1.39
0.57
1.04
0.78
0.73
1.07
0.62
0.78
1.15
0.83
0.78
0.86
0.80
6.07
6.85
4.85
1.0
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NT
499.3
492.5
4216.4
43.2
46.6
41.1
43
43.3
43.3
43.7
43.7
44.2
47.4
44.6
44.2
43.6
43.4
476.7
485.2
482
H
H
Me
Me
Me
Me
Me
—
47
47.3
4372
—
48.7
434.6
—
0.83
10.75
—
Pyrimethamine
—
a
SI, selectivity index = (IC50 for cytotoxicity to VERO cells)/(IC50 for antimalarial activity); RI, resistance index = IC50 (W2 strain)/IC50 (D6 strain);
NC: no cytotoxicity up to 12 mM; VERO: monkey kidney fibroblasts; NA: not active up to 19 mM; NT: not tested.
of these molecules, which represent the ratio of the IC50 value 12 mM, which in turn signifies their safety towards mammalian cells
against the CQ-resistant strain to the IC50 value against the and is correspondingly indicative of a higher therapeutic index.
CQ-sensitive strain, were significantly lower (up to 0.57) than Accordingly, the selectivity index (SI) values for these hybrids
for CQ (RI = 10.75), indicating that the synthesized hybrids were (defined as the ratio of the IC50 value for cytotoxicity to VERO cells
potent against both the sensitive and resistant P. falciparum and the IC50 value for antimalarial activity) were high.
strains. A lower RI is suggestive of a promising lead antimalarial
On comparing the presently synthesized molecules with the
as this exemplifies its equipotent nature irrespective of the previously reported lead compounds,23–26 it was found that
vulnerability of the strain, which further signifies its utility in substituting the carbocyclic/aromatic amines attached to the
solving the drug resistance nuisance.
pyrimidine nucleus with open chain amino-alcohols brings
All of the synthesized hybrids were also assessed for mammalian about a slight decrease in their antimalarial activities. However,
cytotoxicity by testing them against VERO cells. None of the hybrids the present analogues have a significantly lower resistance index
exhibited any cytotoxicity up to the highest tested concentration of implying that these hybrids are more compliant for solving
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the plasmodial drug resistance issue. Moreover, this structural quadruple mutant Pf-DHFR-TS (PDB ID: 3QGT and 3QG2,
modification wiped out any inherent mammalian cytotoxicity respectively) structures using Glide v5.831, and the results are
associated with previously reported molecules.23–26 Overall, the summarized in Table 2. The docked conformations of the best
derivatives containing 6-methyl pyrimidine (8a–e, 8k–n and 8t–x) scoring ligands (8b and 8c) in the binding pocket of wild type
were more active than the corresponding non-methyl pyrimidine and quadruple mutant Pf-DHFR-TS are illustrated in Fig. 3.
derivatives and analogues having an ethylene diamine linker
The most active compounds in the study displayed excellent
(n1 = 1, 8a–e) or a butane-diamine linker (n1 = 3, 8t–x) were found binding affinities towards both the quadruple mutant
to be the most potent against both of the plasmodial strains.
(À62.49 kcal molÀ1 to À42.01 kcal molÀ1) and wild type
(À55.27 kcal molÀ1 to À37.77 kcal molÀ1) Pf-DHFR-TS struc-
tures, which are comparable to those of the native substrate
dihydrofolate and standard Pf-DHFR inhibitors (pyrimethamine,
WR99210 and cycloguanil; Table 2). It was observed that com-
pounds 8b–f (with an ethylene diamine linker between the
4-aminoquinoline and pyrimidine rings) had better Glide energy
scores than the corresponding analogues having a butane-1,4-
diamine linker (8u and 8v).
Computational studies
To gain a better understanding of the molecular basis through
which these aminoquinoline-pyrimidines work, molecular
docking studies of the most active compounds (8b–8f, 8u and
8v) were performed in the active sites of both the wild type and
Fig. 3 represents the docking conformations of the highest
scoring compounds 8b and 8c for both the wild type and
mutant Pf-DHFR-TS structures, respectively, and elucidates
the hydrogen-bonding pattern, together with any p–p inter-
actions and van der Waals interactions, for the predicted
binding poses and the binding pocket residues. Compound
8b, with the lowest binding energy (À62.49 kcal molÀ1) and a
significantly good XP score (À6.88 kcal molÀ1) for the quadruple
mutant Pf-DHFR, shows the formation of a H-bond between its
terminal –OH group and the carboxyl side chain of Asp54 in both
types of Pf-DHFR protein. Another hydrogen bonding interaction
is observed between the pyrimidine’s terminal –NH group and
the Ile164 main chain oxygen atom within the wild type
Pf-DHFR. Furthermore, the pyrimidine ring of compound 8b
shows a p–p interaction with the aromatic ring of Phe58 in the
mutant protein’s active site.
Table 2 Glide docking energies and docking scores for aminoquinoline-
pyrimidine hybrids 8b–8f, 8u and 8v, along with the reference com-
pounds, in wild type and quadruple mutant Pf-DHFR-TS
Docking results with
quadruple mutant
Pf-DHFR-TS
Docking results with
wild type Pf-DHFR-TS
Glide energy XP GScore Glide energy XP GScore
Compounds
8b
8c
8d
8e
8f
8u
8v
À55.27
À52.55
À41.48
À47.33
À48.96
À37.77
À39.04
À65.11
À8.60
À8.55
À7.70
À6.95
À7.20
À6.68
À6.95
À9.34
À9.08
À5.61
À8.83
À62.49
À49.94
À47.08
À47.24
À46.45
À42.01
À44.56
À63.69
À46.48
À40.07
À59.48
À6.88
À6.81
À6.51
À6.41
À5.76
À5.37
À5.53
À10.59
À9.39
À5.93
À8.68
Dihydrofolate
Pyrimethamine À44.55
WR99210
À38.04
À37.97
Cycloguanil
Fig. 3 3D and 2D docking poses showing the interactions of compounds 8b and 8c in the binding sites of (A) wild type Pf-DHFR-TS (PDB ID: 3QGT) and
(B) quadruple mutant Pf-DHFR-TS (PDB ID: 3QG2).
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Compound 8c is another molecule that was estimated to structural changes in the protein’s binding site, the I164L
display a low binding energy (À49.94 kcal molÀ1) and a mutation leads to a spatial shifting of the residues 164–167
correspondingly high Glide score (À6.81) against the quadruple and influences the cavity of the binding site in such a way that
mutant Pf-DHFR-TS protein and it exhibits a similar hydrogen- it leads to steric clashing of Phe58 with rigid inhibitors such
bonding pattern between the terminal –OH group of the as pyrimethamine and cycloguanil.32 In the present docking
molecule and the carboxyl side chain of Asp54. Compound 8c study, we have observed H–bond interactions between the test
also forms H-bond interactions between the pyrimidine’s compounds and Asp54 (Fig. 3), which is noteworthy, as this
terminal –NH group and the Ile164 main chain oxygen atom active site residue is crucial for ligand binding in DHFR and
in the wild type Pf-DHFR’s active site, or with Leu164 in the this interaction is also observed for the DHFR native substrate
mutant Pf-DHFR, akin to that observed for compound 8b.
viz. dihydrofolate. Moreover, the highest scoring ligand 8b is at
Resistance against conventional Pf-DHFR inhibitors is attri- a convenient distance from Phe58, thus evading steric inter-
buted to a quadruple mutation (N51I, C59R, S108N and I164L) action with Phe58’s aromatic side chain, while at the same time
in the binding site of Pf-DHFR which, in turn, impedes efficient forming a p–p interaction with it.
binding of the folate inhibitors with the enzyme. While the
The S108N mutation modifies the active site of Pf-DHFR and
N51I and C59R mutations do not stimulate any major induces a steric confrontation between the side chain of Asn108
and the rigid p-chlorophenyl moiety in pyrimethamine and
cycloguanil in the binding domain of the protein.32 However,
if the inhibitor molecule is so designed as to dwell within the
surface volume of the native substrate, there is less likelihood
of it being prone to resistance occurring due to steric inter-
actions in the mutant protein’s binding site.33,34 To address
this possibility, the docking poses of the most active com-
pounds in the present study, along with those of the reference
molecules, were superimposed on the dihydrofolate surface
envelope (Fig. 4), which clearly demonstrated that the test
compounds possessing flexible aliphatic linker chains occupy
a similar volume to that of the native substrate while, at the
same time, evade any steric confrontation(s) with Asn108.
To further check the drugability of the synthesized
aminoquinoline-pyrimidine hybrids, ADMET predictions for
the most active compounds (8b–8f, 8u and 8v), using Qikprop
v3.535, were performed and the results are presented in Table 3.
Parameters of Lipinski’s rule of 5, which describes a primary
Fig. 4 Molecular overlay of the docking poses of the most active test
criterion for the drug-likeness of a molecule,36 were calculated
compounds (grey sticks), cycloguanil (blue sticks), pyrimethamine (red
for the test compounds and the Qikprop results for the various
sticks) and the Pf-DHFR substrate dihydrofolate (yellow balls and sticks)
parameters are shown in Table 3.
at the binding site of the quadruple mutant Pf-DHFR-TS (PDB ID: 3QG2).
Table 3 Prediction of Lipinski’s ‘rule of 5’ for the most active aminoquinoline-pyrimidine hybrids (8b–8f, 8u and 8v) and other ADMET properties
Compound
8b
8c
8d
8e
8f
8u
8v
Pyr
Cyg
Lipinski’s ‘rule of 5’a
mol_MW
donor HB
386.88
4
400.91
4
414.94
4
428.96
4
400.91
4
414.94
4
428.96
4
248.71
4
253.73
5
accpt HB
QPlogPo/w
Rule of Five
7
2.77
0
7
3.16
0
7
3.51
0
7
3.87
0
7
3.56
0
7
3.93
0
7
4.4
0
3
1.81
0
3
0.89
0
ADMET properties
Percent Human Oral Absorptiona
(480% high, o25% poor)
QPPCaco (nms) (o25 poor, 4500 great)a
QplogBB (À3.0 to 1.2)a
87.91
89.90
91.96
94.07
92.32
94.56
100
84.35
68.81
315.57
À1.36
322.82
À0.03
À4.95
95.33
10
305.31
À1.532
306.63
0.07
À5.40
95.31
11
304.6
À1.64
305.78
0.16
À5.61
95.32
12
304.96
À1.75
306.20
0.26
À5.79
95.32
13
307.37
À1.73
341.05
0.17
À6.39
95.12
11
310.69
À1.83
345.04
0.27
À6.55
95.18
12
311.19
À1.99
345.64
0.41
À6.91
95.18
13
412.29
À0.78
468.85
À0.24
À4.32
73.73
4
111.85
À0.17
126.60
À0.31
À4.58
76.26
2
QPPMDCK (o25 poor, 4500 great)a
QplogKhsa (À1.5 to 1.5)a
QPlogHERG (below À5 causes concern)a
PSA (7.0–200.0)a
#rotor (0–15)a
a
Calculated using QikProp v 3.5. The ranges/recommended values, shown in parentheses, were calculated from 95% of known drugs;
Pyr = pyrimethamine; Cyg = cycloguanil.
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The test compounds displayed zero violation of Lipinski’s properties suggestive of their further refinement into orally-
rule of 5, signifying that these compounds are anticipated to active anti-malarial drug molecules.
possess drug-like properties. Furthermore, this prediction also
implies that the test compounds can be used as prospective
orally-active antimalarials. This notion was further supported
Experimental
All of the reagents and starting materials were purchased from
Sigma Aldrich and were used as supplied. Progress of the
reaction was monitored by TLC (E. Merck Kieselgel 60 F254)
and visualization was accomplished using UV light and iodine.
All of the intermediates and final compounds were purified
using silica gel column chromatography (100–200 mesh silica;
elution with 0–15% methanol–chloroform). 1H NMR and 13C
NMR spectra were recorded on a Jeol Spectrospin spectrometer
at 400 MHz and 100 MHz, respectively, and the chemical shift
values are given in parts per million (ppm) on the delta scale (d)
and are referenced to tetramethylsilane (TMS) which was used
as an internal standard. IR spectra were recorded on a Perkin-
Elmer FT-IR spectrophotometer either using KBr pellets or as a
film in chloroform, and the values are expressed in cmÀ1. Mass
spectra were recorded on an Agilent Accurate Mass Q-TOF MS
system or a micromass LCT Mass Spectrometer/Data system.
Melting points were recorded on EZ-Melt automated melting
point apparatus, Stanford Research Systems and are uncor-
rected. The procedures used for the biological evaluation of
the synthesized compounds for antimalarial and mammalian
cytotoxic activities have been previously described.27,28 Detailed
methodology for the computational studies of the active com-
pounds has been elucidated in an earlier report.37
by prediction of the oral drug absorption (Percent Human Oral
Absorption), which was highly encouraging for all of the test
compounds. QPPCaco, i.e. Caco-2 cell permeability estima-
tions, for all of the test compounds exhibited favourable values,
comparable to those of standard Pf-DHFR-inhibitors and sugges-
tive of their good intestinal absorption/permeation. Moreover, the
polar surface areas of the active test compounds fall adequately in
the permissible range and the rotatable bonds are o15 (Table 3).
The latter descriptors are again important for prediction of the oral
bioavailability of a compound as studies have revealed that oral
bioavailability is affected by molecular flexibility, which in turn can
be predicted by the polar surface area (7 Å2–200 Å2) and number of
rotatable bonds (o15).
Furthermore, all the inhibitors were predicted to lie within
the acceptable range for QPlogKhsa (human serum albumin
binding prediction; acceptable range: À1.5 to 1.5). Likewise,
QPlogBB (blood/brain partition coefficient) and QPPMDCK
(estimation of MDCK cell permeability; a model for the
blood/brain barrier) show satisfactory values for all of the test
compounds. Additionally, the QPlogHERG descriptor (prediction
of hERG potassium channel blocking potency) for compound 8b
was predicted to have a value in the permissible range and as good
as for the reference compounds. Thus, in totality, the most active
compounds were shown to possess excellent predicted absorption,
distribution, metabolism and excretion parameters, suggestive of
their development as orally-active lead molecules.
Typical procedure for the synthesis of intermediate 3a and
related compounds (3b–3c)
A mixture of 4,7-dichloroquinoline (1, 10.0 g, 50.49 mmol) and
ethane-1,2-diamine (2a, 16.9 mL, 252.45 mmol) was stirred at
120 1C for 6 h (Scheme 1). The reaction mixture was then cooled
to room temperature and ice-cold water was added to it. The
solid thus obtained was filtered off and washed with excess
water. Similarly, intermediates 3b and 3c were obtained by
reacting 1 with propane-1,3-diamine (2b) or butane-1,4-diamine
(2c), respectively. The crude-products were crystallized using
ethanol, and the characterization data obtained corresponds to
that reported in the literature.38
Conclusions
The present investigation describes the synthesis of twenty-four
4-aminoquinoline-pyrimidine-alkanols and the evaluation of
their antimalarial potentials against chloroquine-sensitive
(D6) and chloroquine-resistant (W2) strains of Plasmodium
falciparum. Seven hybrids 8b–8e and 8t–8v were found to
possess sub-micromolar IC50 values against both of the plasmo-
dial strains. The current hybrids were slightly less active than
previously described lead aminoquinoline-pyrimidine conju-
gates but were found to possess better resistance indices without
Typical procedure for the synthesis of intermediate 5a and
related compounds (5b–c) and (6a–c)
any cytotoxicity against mammalian cells (VERO). Docking To a solution of 2,4-dichloropyrimidine (4a, 5.0 g, 33.56 mmol)
studies of the most active compounds 8b–8e, 8u and 8v with in THF at 0 1C, intermediate 3a (7.4 g, 33.56 mol) was added,
both wild type and mutant Pf-DHFR-TS were performed, which followed by the drop-wise addition of N,N-diisopropylethyl-
displayed strong interactions between the ligand and binding- amine (11.7 mL, 67.12 mmol). The reaction mixture was then
site residues, analogous to known DHFR-inhibitors and the stirred overnight (14 h) at ambient temperature. After comple-
native substrate. The presence of a terminal amino-alcohol chain tion of the reaction, as observed by TLC, the excess THF was
at the pyrimidine core was found to be imperative for binding evaporated and the residue was diluted with water and
within the DHFR active site. Furthermore, the flexibility of the extracted using ethyl acetate (3 Â 100 mL). The combined
synthesized hybrids was shown to facilitate the evasion of any organic layer was washed with brine, dried over Na2SO4, and
steric confrontation(s) resulting from the amino acid mutations evaporated to dryness under reduced pressure. The crude product
in the mutant Pf-DHFR protein. The most active compounds was purified by column chromatography using 5% MeOH–CHCl3
were predicted to be endowed with favourable pharmacokinetic as the eluent to afford pure compound 5a. In a similar manner,
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intermediates 5b and 5c were obtained by the reaction of 4a with anal. calcd for C20H25ClN6O: C, 59.92; H, 6.29; N, 20.96; found: C,
intermediates 3b and 3c, respectively. The corresponding inter- 59.99; H, 6.35; N, 21.01; ESI-MS (m/z): 401.20 (M + H)+, 403.19
mediates 6a–c were obtained by reacting 2,4-dichloro-6-methyl- (MH + 2)+.
pyrimidine (4b), instead of 2,4-dichloro pyrimidine (4a), with the
5-((4-((2-((7-Chloroquinolin-4-yl)amino)ethyl)amino)-6-methyl
intermediates 3a–c, respectively. The characterization data pyrimidin-2-yl)amino)pentan-1-ol (8d). Off-white solid; yield:
obtained for all of the synthesized intermediates corresponds to 83%; mp 144–146 1C; IR (nmax/cmÀ1, KBr): 3293, 2928, 2861,
that reported previously in literature.23–26
1586, 1507, 1341, 1203, 1137, 802; 1H NMR (400 MHz, DMSO-d6):
d
H 1.29–1.33 (m, 2H), 1.38–1.43 (m, 2H), 1.45–1.52 (m, 2H), 2.00
General procedure for the synthesis of 4-aminoquinoline-pyri-
midine hybrids (8a–x)
(s, 3H), 3.20–3.25 (m, 2H), 3.34–3.52 (m, 6H), 4.34 (br s, 1H), 5.57
(s, 1H), 6.34 (br s, 1H), 6.55 (d, 1H, J = 5.13 Hz), 6.95 (br s, 1H),
To a solution of 5 or 6 (2 mmol) in DMF (10 mL), the respective 7.41–7.43 (m, 2H), 7.78 (d, 1H, J = 2.20 Hz), 8.18 (d, 1H, J = 9.52
amino-alcohol (7a–e, 3 eq.) was added and the reaction mixture Hz), 8.39 (d, 1H, J = 5.13 Hz); 13C NMR (100 MHz, DMSO-d6): dC
was allowed to stir at 120 1C for 10 h. Upon completion of the 23.08, 23.41, 29.29, 32.38, 38.16, 40.63, 42.56, 60.69, 98.65,
reaction (as inferred through TLC), the reaction mixture was 117.40, 124.04, 127.46, 133.42, 149.02, 150.12, 151.87, 161.98,
allowed to cool to an ambient temperature and was then 163.35; anal. calcd for C21H27ClN6O: C, 60.79; H, 6.56; N, 20.25;
diluted with ice-cold water (15 mL). The mixture was then found: C, 60.88; H, 6.59; N, 20.29; ESI-MS (m/z): 415.20 (M + H)+,
extracted with 10% isopropanol in chloroform (3 Â 50 mL) 417.21 (MH + 2)+.
and the combined organic extract was dried over Na2SO4 and
6-((4-((2-((7-Chloroquinolin-4-yl)amino)ethyl)amino)-6-methyl
concentrated in vacuo. The crude residue thus obtained was pyrimidin-2-yl)amino)hexan-1-ol (8e). Yellow solid; yield: 75%;
purified by column chromatography using 0–15% MeOH– mp 134–136 1C; IR (nmax/cmÀ1, film): 3296, 2929, 2585, 1578,
1
CHCl3 as the eluent, to afford the respective compounds 8a–x 1330, 1213, 1138, 1079, 802; H NMR (400 MHz, DMSO-d6): dH
in good yields. The characterization data for all of the final 1.22–1.27 (m, 4H), 1.35–1.38 (m, 2H), 1.46–1.48 (m, 2H), 2.00
compounds is detailed as follows:
(s, 3H), 3.20–3.25 (m, 2H), 3.34–3.52 (m, 6H), 4.34 (br s, 1H), 5.58
2-((4-((2-((7-Chloroquinolin-4-yl)amino)ethyl)amino)-6-methyl (s, 1H), 6.34 (br s, 1H), 6.55 (d, 1H, J = 5.13 Hz), 7.06 (br s, 1H),
pyrimidin-2-yl)amino)ethanol (8a). White solid; yield: 86%; mp 7.41–7.46 (m, 2H), 7.78 (d, 1H, J = 1.46 Hz), 8.20 (d, 1H, J =
160–162 1C; IR (nmax/cmÀ1, KBr): 3317, 2926, 1583, 1430, 1380, 8.79 Hz), 8.39 (d, 1H, J = 5.86 Hz); ESI-HRMS (m/z) calcd for
1
1233, 1139, 1066, 801; H NMR (400 MHz, DMSO-d6): dH 2.01 C22H29ClN6O: 428.2091 (M+), found: 429.2165 (M + H)+, 431.2147
(m, 3H), 3.33–3.35 (m, 2H), 3.41–3.42 (m, 2H), 3.49–3.52 (m, 4H), (MH + 2)+.
3.83 (br s, 1H), 5.61 (s, 1H), 6.30 (br s, 1H), 6.57 (d, 1H, J =
2-((4-((3-((7-Chloroquinolin-4-yl)amino)propyl)amino)pyrimidin-
5.86 Hz), 7.05 (br s, 1H), 7.43 (dd, 2H, J = 2.20 Hz, 8.79 Hz), 7.78 2-yl)amino)ethanol (8f). Pale-yellow solid; yield: 86%; mp 172–
(d, 1H, J = 2.20 Hz), 8.19 (d, 1H, J = 8.79 Hz), 8.41 (d, 1H, J = 174 1C; IR (nmax/cmÀ1, KBr): 3240, 2926, 2850, 1582, 1079, 795;
5.86 Hz); 13C NMR (100 MHz, DMSO-d6): dC 23.34, 38.06, 42.51, 1H NMR (400 MHz, DMSO-d6): dH 1.87–1.94 (m, 2H), 3.23–3.27
43.53, 60.61, 98.68, 117.38, 124.03, 124.09, 127.46, 133.42, (m, 2H), 3.31–3.34 (m, 4H), 3.44–3.47 (m, 2H), 4.68 (br s, 1H), 5.73
149.01, 150.09, 151.95, 162.01, 163.36; ESI-HRMS (m/z) calcd (d, 1H, J = 5.49 Hz), 6.21 (br s, 1H), 6.47 (d, 1H, J = 5.49 Hz), 6.99
for C18H21ClN6O: 372.1465 (M+), found: 373.1535 (M + H)+, (br s, 1H), 7.30–7.33 (m, 1H), 7.44 (dd, 1H, J = 2.44 Hz, 9.16 Hz), 7.62
375.1521 (MH + 2)+.
(br s, 1H), 7.78 (d, 1H, J = 1.83 Hz), 8.26 (d, 1H, J = 9.16 Hz), 8.38
3-((4-((2-((7-Chloroquinolin-4-yl)amino)ethyl)amino)-6-methyl (d, 1H, J = 5.49 Hz); 13C NMR (100 MHz, DMSO-d6): dC 23.72, 33.74,
pyrimidin-2-yl)amino)propan-1-ol (8b). Off-white solid; yield: 36.34, 39.50, 56.50, 94.75, 113.53, 120.10, 120.16, 123.47, 129.47,
81%; mp 144–146 1C; IR (nmax/cmÀ1, KBr): 3312, 2928, 2852, 145.04, 146.16, 147.87, 158.05, 158.71; ESI-HRMS (m/z) calcd for
1582, 1425, 1230, 1141, 1076, 807; 1H NMR (400 MHz, DMSO-d6): C18H21ClN6O: 372.1465 (M+), found: 373.1542 (M + H)+, 375.1528
dH 1.61–1.67 (m, 2H), 2.02 (s, 3H), 3.28–3.33 (m, 2H), 3.43–3.46 (MH + 2)+.
(m, 4H), 3.54 (br s, 3H), 5.63 (s, 1H), 6.58 (d, 2H, J = 5.13 Hz), 7.44
3-((4-((3-((7-Chloroquinolin-4-yl)amino)propyl)amino)pyrimidin-
(d, 2H, J = 8.79 Hz), 7.54 (br s, 1H), 7.79 (d, 1H, J = 2.20 Hz), 8.21 2-yl)amino)propan-1-ol (8g). Yellow solid; yield: 82%; mp 118–
(d, 1H, J = 8.79 Hz), 8.41 (d, 1H, J = 5.13 Hz); 13C NMR (100 MHz, 120 1C; IR (nmax/cmÀ1, KBr): 3256, 2926, 2854, 1584, 1329, 1234,
DMSO-d6): dC 21.19, 32.53, 37.83, 41.14, 42.35, 58.61, 98.67, 1135, 1078, 794; 1H NMR (400 MHz, DMSO-d6): dH 1.56–1.62
103.45, 114.20, 117.32, 124.10, 124.17, 127.13, 133.59, 148.60, (m, 2H), 1.86–1.93 (m, 2H), 3.17–3.24 (m, 2H), 3.35–3.42 (m, 6H),
150.29, 151.55, 163.27; ESI-HRMS (m/z) calcd for C19H23ClN6O: 4.11 (br s, 1H), 5.70 (d, 1H, J = 5.86 Hz), 6.28 (br s, 1H), 6.47 (d, 1H,
386.1622 (M+), found: 387.1688 (M + H)+, 389.1676 (MH + 2)+.
J = 5.13 Hz), 6.95 (br s, 1H), 7.31 (m, 1H), 7.44 (dd, 1H, J = 2.20 Hz,
4-((4-((2-((7-Chloroquinolin-4-yl)amino)ethyl)amino)-6-methyl 8.79 Hz), 7.61 (br s, 1H), 7.77 (d, 1H, J = 2.20 Hz), 8.26 (d, 1H,
pyrimidin-2-yl)amino)butan-1-ol (8c). White solid; yield: 78%; J = 8.79 Hz), 8.38 (d, 1H, J = 5.13 Hz); 13C NMR (100 MHz, DMSO-
mp 174–176 1C; IR (nmax/cmÀ1, KBr): 3265, 2925, 2856, 1588, d6): dC 29.41, 34.31, 39.50, 42.00, 60.43, 100.38, 119.18, 125.74,
1356, 1138, 796; 1H NMR (400 MHz, DMSO-d6): dH 1.42–1.53 125.79, 129.12, 135.11, 150.71, 151.81, 153.54, 163.73, 164.36; ESI-
(m, 4H), 2.00 (s, 3H), 3.22–3.26 (m, 2H), 3.34–3.42 (m, 4H), 3.52 HRMS (m/z) calcd for C19H23ClN6O: 386.1622 (M+), found: 387.1696
(br s, 2H), 4.38 (br s, 1H), 5.57 (s, 1H), 6.36 (br s, 1H), 6.56 (d, 1H, (M + H)+, 389.1681 (MH + 2)+.
J = 5.13 Hz), 6.92 (br s, 1H), 7.41–7.44 (m, 2H), 7.78 (d, 1H, J =
4-((4-((3-((7-Chloroquinolin-4-yl)amino)propyl)amino)pyrimidin-
2.20 Hz), 8.17 (d, 1H, J = 9.52 Hz), 8.39 (d, 1H, J = 5.13 Hz); 2-yl)amino)butan-1-ol (8h). Pale-yellow solid; yield: 83%; mp
3480 | New J. Chem., 2015, 39, 3474--3483
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122–124 1C; IR (nmax/cmÀ1, KBr): 3276, 2926, 2856, 2345, 1581, 5.55 (s, 1H), 6.23 (br s, 1H), 6.46 (d, 1H, J = 5.13 Hz), 6.82 (br s, 1H),
1364, 1235, 1136, 1079, 974, 851, 794; 1H NMR (400 MHz, 7.30–7.32 (m, 1H), 7.44 (dd, 1H, J = 2.20 Hz, 8.79 Hz), 7.77 (d, 1H,
DMSO-d6): dH 1.36–1.41 (m, 4H), 1.87–1.90 (m, 2H), 3.90–3.12 J = 2.20 Hz), 8.26 (d, 1H, J = 8.79 Hz), 8.37 (d, 1H, J = 5.86 Hz); 13
C
(m, 2H), 3.33–3.38 (m, 6H), 4.22 (br s, 1H), 5.72 (d, 1H, J = NMR (100 MHz, DMSO-d6): dC 20.39, 25.14, 29.59, 34.50, 39.50,
6.59 Hz), 6.31 (br s, 1H), 6.47 (d, 1H, J = 5.86 Hz), 7.01 (br s, 1H), 42.10, 50.45, 57.89, 60.45, 100.54, 119.30, 125.90, 125.94, 129.25,
7.44 (m, 2H), 7.57 (br s, 1H), 7.77 (d, 1H, J = 2.20 Hz), 8.23 135.26, 150.84, 151.95, 153.69, 163.82, 165.82; ESI-HRMS (m/z)
(d, 1H, J = 8.79 Hz), 8.35 (d, 1H, J = 5.13 Hz); 13C NMR (100 MHz, calcd for C20H25ClN6O: 400.1778 (M+), found: 401.1855 (M + H)+,
DMSO-d6): dC 25.92, 27.61, 30.05, 40.24, 40.40, 60.62, 98.67, 403.1827 (MH + 2)+.
117.42, 124.11, 124.16, 127.21, 133.51, 148.75, 150.23, 151.62,
162.60; ESI-HRMS (m/z) calcd for C20H25ClN6O: 400.1778 (M+), pyrimidin-2-yl)amino)butan-1-ol (8m). Pale-yellow solid; yield:
found: 401.1858 (M + H)+, 403.1832 (MH + 2)+. 85%; mp 100–102 1C; IR (nmax/cmÀ1, KBr): 3313, 2926, 2850,
4-((4-((3-((7-Chloroquinolin-4-yl)amino)propyl)amino)-6-methyl
5-((4-((3-((7-Chloroquinolin-4-yl)amino)propyl)amino)pyrimidin- 1586, 1247, 1135, 1051, 799; 1H NMR (400 MHz, DMSO-d6):
2-yl)amino)pentan-1-ol (8i). Off-white solid; yield: 78%; mp dH 1.33–1.45 (m, 4H), 1.87–1.93 (m, 2H), 2.01 (s, 3H), 3.14–3.18
124–126 1C; IR (nmax/cmÀ1, KBr): 3416, 3254, 2915, 2870, (m, 2H), 3.30–3.39 (m, 6H), 3.81(br s, 1H), 5.62 (s, 1H), 6.47 (d, 1H,
1587, 1534, 1408, 1358, 1227, 1138, 1066, 974, 852, 800, 714; J = 5.50 Hz), 6.54 (br s, 1H), 7.21 (br s, 1H), 7.42–7.45 (m, 2H), 7.78
1H NMR (400 MHz, DMSO-d6): dH 1.22–1.25 (m, 2H), 1.35–1.43 (d, 1H, J = 2.29 Hz), 8.30 (d, 1H, J = 9.16 Hz), 8.37 (d, 1H,
(m, 4H), 1.87–1.93 (m, 2H), 3.11–3.13 (m, 2H), 3.30–3.39 J = 5.50 Hz); 13C NMR (100 MHz, DMSO-d6): dC 26.49, 28.22,
(m, 6H), 4.39 (br s, 1H), 5.71 (d, 1H, J = 5.34 Hz), 6.38 (br s, 30.59, 38.39, 40.95, 61.20, 99.24, 118.00, 124.69, 124.79, 127.72,
1H), 6.47 (d, 1H, J = 5.34 Hz), 7.04 (br s, 1H), 7.35–7.37 (m, 1H), 134.13, 149.25, 150.85, 152.10, 163.75; ESI-HRMS (m/z) calcd for
7.44 (dd, 1H, J = 2.29 Hz, 9.16 Hz), 7.60 (br s, 1H), 7.77 (d, 1H, C21H27ClN6O: 414.1935 (M+), found: 415.2010 (M + H)+, 417.1989
J = 1.53 Hz), 8.27 (d, 1H, J = 9.16 Hz), 8.38 (d, 1H, J = 5.39 Hz); (MH + 2)+.
ESI-HRMS (m/z) calcd for C21H27ClN6O: 414.1935 (M+), found:
5-((4-((3-((7-Chloroquinolin-4-yl)amino)propyl)amino)-6-methyl
pyrimidin-2-yl)amino)pentan-1-ol (8n). Orange solid; yield: 82%;
415.2012 (M + H)+, 417.1991 (MH + 2)+.
6-((4-((3-((7-Chloroquinolin-4-yl)amino)propyl)amino)pyrimidin- mp 144–146 1C; IR (nmax/cmÀ1, KBr): 3422, 3245, 2933, 2852,
2-yl)amino)hexan-1-ol (8j). Off-white solid; yield: 86%; mp 118– 1578, 1354, 1139, 1071, 802; 1H NMR (400 MHz, DMSO-d6):
120 1C; IR (nmax/cmÀ1, KBr): 3422, 2927, 2855, 1591, 1406, 1237, dH 1.21–1.28 (m, 2H), 1.33–1.45 (m, 4H), 1.86–1.93 (m, 2H),
1136, 1078, 899, 851, 794; 1H NMR (400 MHz, DMSO-d6): dH 2.01 (m, 3H), 3.11–3.17 (m, 2H), 3.30–3.36 (m, 6H), 4.07
1.20–1.24 (m, 4H), 1.35–1.40 (m, 4H), 1.90–1.96 (m, 2H), 3.10– (br s, 1H), 5.60 (s, 1H), 6.46 (d, 2H, J = 5.50 Hz), 7.08 (br s,
3.15 (m, 2H), 3.33–3.39 (m, 6H), 4.30 (br s, 1H), 5.77 (d, 1H, 1H), 7.37–7.40 (m, 1H), 7.44 (dd, 1H, J = 2.29 Hz, 9.16 Hz),
J = 6.10 Hz), 6.47 (d, 1H, J = 5.19 Hz), 6.61 (br s, 1H), 7.25 (br s, 7.78 (d, 1H, J = 2.29 Hz), 8.29 (d, 1H, J = 9.16 Hz), 8.37 (d, 1H,
1H), 7.43–7.47 (m, 2H), 7.61 (d, 1H, J = 5.49 Hz), 7.78 (d, 1H, J = J = 5.50 Hz); 13C NMR (100 MHz, DMSO-d6): dC 22.97, 27.64,
1.83 Hz), 8.31 (d, 1H, J = 9.16 Hz), 8.37 (d, 1H, J = 4.88 Hz); 13
C
29.07, 32.29, 37.78, 40.44, 60.64, 62.77, 98.61, 117.40, 124.02,
NMR (100 MHz, DMSO-d6): dC 21.11, 25.29, 26.37, 27.50, 29.18, 124.12, 127.18, 133.45, 148.74, 150.17, 151.55, 160.89, 163.17;
32.49, 37.65, 40.40, 60.62, 98.59, 117.34, 124.10, 124.21, 126.93, anal. calcd for C22H29ClN6O: C, 61.60; H, 6.81; N, 19.59; found: C,
133.59, 148.43, 150.33, 151.28, 162.52; ESI-HRMS (m/z) calcd 61.71; H, 6.88; N, 19.65; ESI-MS (m/z): 429.24 (M + H)+, 431.25
for C22H29ClN6O: 428.2091 (M+), found: 429.2168 (M + H)+, (MH + 2)+.
431.2149 (MH + 2)+.
2-((4-((4-((7-Chloroquinolin-4-yl)amino)butyl)amino)pyrimidin-
2-((4-((3-((7-Chloroquinolin-4-yl)amino)propyl)amino)-6-methyl 2-yl)amino)ethanol (8o). Pale yellow solid; yield: 85%; mp 178–
pyrimidin-2-yl)amino)ethanol (8k). Yellow solid; yield: 88%; mp 180 1C; IR (nmax/cmÀ1, KBr): 3318, 3246, 2918, 2854, 1586, 1331,
206–208 1C; IR (nmax/cmÀ1, KBr): 3299, 2925, 2871, 1583, 1534, 1135, 1069, 796; 1H NMR (400 MHz, DMSO-d6): dH 1.59–1.73
1450, 1367, 1282, 1200, 1140, 1073, 849, 802, 764; 1H NMR (m, 4H), 3.23–3.30 (m, 6H), 3.45–3.48 (m, 2H), 4.66 (br s, 1H), 5.70
(400 MHz, DMSO-d6): dH 1.87–1.90 (m, 2H), 2.01 (s, 3H), 3.16– (d, 1H, J = 5.86 Hz), 6.21 (br s, 1H), 6.46 (d, 1H, J = 5.13 Hz), 6.91
3.26 (m, 8H), 4.43 (br s, 1H), 5.62 (s, 1H), 6.33 (br s, 1H), 6.48 (br s, 1H), 7.30–7.33 (m, 1H), 7.43 (dd, 1H, J = 2.20 Hz, 8.79 Hz),
(d, 1H, J = 5.86 Hz), 7.07 (br s, 1H), 7.38 (br s, 1H), 7.45 (dd, 1H, J = 7.60 (br s, 1H), 7.77 (d, 1H, J = 2.20 Hz), 8.26 (d, 1H, J = 8.79 Hz),
2.20 Hz, 9.52 Hz), 7.78 (d, 1H, J = 2.20 Hz), 8.27 (d, 1H, J = 8.79 Hz), 8.37 (d, 1H, J = 5.86 Hz); 13C NMR (100 MHz, DMSO-d6): dC 25.37,
8.37 (d, 1H, J = 5.13 Hz); 13C NMR (100 MHz, DMSO-d6): dC 21.26, 26.65, 35.78, 42.19, 43.50, 60.56, 79.20, 98.65, 117.46, 124.01,
27.57, 40.17, 43.36, 60.40, 62.80, 98.68, 117.40, 124.15, 124.25, 124.13, 127.40, 133.44, 149.01, 150.15, 154.29, 162.06, 162.66;
127.07, 133.59, 148.59, 150.30, 151.49, 163.17, 165.17, 165.18, anal. calcd for C19H23ClN6O: C, 58.99; H, 5.99; N, 21.72; found:
172.35; ESI-HRMS (m/z) calcd for C19H23ClN6O: 386.1622 (M+), C, 59.06; H, 6.08; N, 21.81; ESI-MS (m/z): 387.18 (M + H)+, 389.19
found: 387.1699 (M + H)+, 389.1671 (MH + 2)+.
(MH + 2)+.
3-((4-((4-((7-Chloroquinolin-4-yl)amino)butyl)amino)pyrimidin-
3-((4-((3-((7-Chloroquinolin-4-yl)amino)propyl)amino)-6-methyl
pyrimidin-2-yl)amino)propan-1-ol (8l). Off-white solid; yield: 90%; 2-yl)amino)propan-1-ol (8p). Off-white solid; yield: 86%; mp 102–
mp 108–110 1C; IR (nmax/cmÀ1, KBr): 3356, 3244, 2904, 2849, 1582, 104 1C; IR (nmax/cmÀ1, KBr): 3313, 2929, 2851, 1602, 1331,
1
1429, 1382, 1330, 1238, 1139, 1077, 977, 847, 805, 760; H NMR 1252, 1045, 796; 1H NMR (400 MHz, DMSO-d6): dH 1.59–1.62
(400 MHz, DMSO-d6): dH 1.55–1.61 (m, 2H), 1.85–1.92 (m, 2H), (m, 4H), 1.66–1.70 (m, 2H), 3.21–3.29 (m, 6H), 3.39–3.43
1.98 (s, 3H), 3.16–3.24 (m, 4H), 3.40–3.44 (m, 4H), 4.35 (br s, 1H), (m, 2H), 3.72 (br s, 1H), 5.70 (d, 1H, J = 5.49 Hz), 6.38 (br s, 1H),
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6.46 (d, 1H, J = 5.49 Hz), 6.95 (br s, 1H), 7.34 (br s, 1H), 7.43 (dd,
3-((4-((4-((7-Chloroquinolin-4-yl)amino)butyl)amino)-6-methyl
1H, J = 1.83 Hz, 8.54 Hz), 7.59 (br s, 1H), 7.77 (d, 1H, J = 1.83 Hz), pyrimidin-2-yl)amino)propan-1-ol (8u). Off-white solid; yield:
8.27 (d, 1H, J = 8.54 Hz), 8.37 (d, 1H, J = 5.49 Hz); 13C NMR (100 84%; mp 110 1C; IR (nmax/cmÀ1, film): 3297, 2929, 2859, 1580,
1
MHz, DMSO-d6): dC 25.32, 26.57, 30.63, 32.54, 37.73, 42.13, 58.66, 1332, 1247, 1136, 1078, 799; H NMR (400 MHz, DMSO-d6): dH
98.60, 117.39, 123.95, 124.11, 127.27, 133.38, 148.88, 150.14, 1.58–1.67 (m, 6H), 1.99 (s, 3H), 3.23–3.29 (m, 6H), 3.39–3.43
151.70, 161.61, 161.65, 162.58; anal. calcd for C20H25ClN6O: C, (m, 2H), 3.71 (br s, 1H), 5.55 (s, 1H), 6.45 (d, 2H, J = 5.49 Hz), 6.75
59.92; H, 6.29; N, 20.96; found: C, 59.97; H, 6.36; N, 21.03; ESI-MS (br s, 1H), 7.30–7.32 (m, 1H), 7.43 (d, 1H, J = 8.54 Hz), 7.75–7.77
(m/z): 401.19 (M + H)+, 403.18 (MH + 2)+.
(m, 1H), 8.27 (d, 1H, J = 8.54 Hz), 8.37 (d, 1H, J = 5.49 Hz); 13C
4-((4-((4-((7-Chloroquinolin-4-yl)amino)butyl)amino)pyrimidin- NMR (100 MHz, DMSO-d6): dC 25.33, 26.71, 32.69, 37.62, 42.14,
2-yl)amino)butan-1-ol (8q). Off-white solid; yield: 90%; mp 124– 58.58, 98.63, 117.44, 123.94, 124.11, 127.43, 133.33, 149.07,
126 1C; IR (nmax/cmÀ1, film): 3295, 2925, 2856, 1582, 1455, 1369, 150.07, 151.88, 161.98, 163.26; anal. calcd for C21H27ClN6O: C,
1136, 1082, 759; 1H NMR (400 MHz, DMSO-d6): dH 1.41–1.48 60.79; H, 6.56; N, 20.25; found: C, 60.83; H, 6.61; N, 20.27; ESI-MS
(m, 4H), 1.62–1.70 (m, 4H), 3.15–3.18 (m, 2H), 3.28–3.30 (m, 4H), (m/z): 415.22 (M + H)+, 417.21 (MH + 2)+.
3.36–3.39 (m, 2H), 3.72 (br s, 1H), 5.70 (d, 1H, J = 5.49 Hz), 6.46
4-((4-((4-((7-Chloroquinolin-4-yl)amino)butyl)amino)-6-methyl
(d, 2H, J = 4.88 Hz), 6.99 (br s, 1H), 7.34 (br s, 1H), 7.43 (d, 1H, pyrimidin-2-yl)amino)butan-1-ol (8v). Pale-yellow solid; yield:
J = 9.16 Hz), 7.59 (br s, 1H), 7.77 (br s, 1H), 8.27 (d, 1H, J = 9.16 Hz), 81%; mp 116–118 1C; IR (nmax/cmÀ1, film): 3303, 2925, 2856,
1
8.37 (d, 1H, J = 4.88 Hz); 13C NMR (100 MHz, DMSO-d6): dC 25.35, 1580, 1366, 1136, 1079, 802; H NMR (400 MHz, DMSO-d6): dH
25.98, 26.61, 30.07, 40.44, 42.16, 60.64, 98.64, 117.40, 124.04, 1.39–1.49 (m, 4H), 1.59–1.71 (m, 4H), 1.99 (s, 3H), 3.15–3.20
124.14, 127.27, 133.46, 148.87, 150.19, 151.71, 162.59; anal. calcd (m, 2H), 3.25–3.28 (m, 4H), 3.36–3.39 (m, 2H), 3.81 (br s, 1H),
for C21H27ClN6O: C, 60.79; H, 6.56; N, 20.25; found: C, 60.87; 5.55 (s, 1H), 6.44 (d, 2H, J = 5.50 Hz), 6.77 (br s, 1H), 7.29–7.32
H, 6.61; N, 20.35; ESI-MS (m/z): 415.21 (M + H)+, 417.22 (MH + 2)+. (m, 1H), 7.41 (dd, 1H, J = 2.29 Hz, 9.16 Hz), 7.77 (d, 1H, J =
5-((4-((4-((7-Chloroquinolin-4-yl)amino)butyl)amino)pyrimidin- 2.29 Hz), 8.26 (d, 1H, J = 9.16 Hz), 8.36 (d, 1H, J = 5.50 Hz); 13C
2-yl)amino)pentan-1-ol (8r). Orange semi-solid; yield: 78%; IR NMR (100 MHz, DMSO-d6): dC 25.34, 26.01, 30.07, 40.39, 42.15,
(nmax/cmÀ1, film): 3250, 2925, 2854, 1579, 1456, 1363, 1214, 756; 60.66, 98.62, 117.44, 123.94, 124.10, 127.41, 133.34, 149.06,
1H NMR (400 MHz, DMSO-d6): dH 1.20–1.30 (m, 2H), 1.35–1.49 150.09, 151.85, 161.63, 163.26; anal. calcd for C22H29ClN6O: C,
(m, 4H), 1.64–1.71 (m, 4H), 3.19–3.21 (m, 2H), 3.33–3.36 (m, 6H), 61.60; H, 6.81; N, 19.59; found: C, 61.68; H, 6.85; N, 19.67; ESI-MS
4.52 (br s, 2H), 5.90 (br s, 1H), 6.51 (d, 1H, J = 5.50 Hz), 7.26 (br s, (m/z): 429.22 (M + H)+, 431.23 (MH + 2)+.
1H), 7.45 (d, 1H, J = 9.16 Hz), 7.60–7.62 (m, 1H), 7.83 (d, 1H, J =
5-((4-((4-((7-Chloroquinolin-4-yl)amino)butyl)amino)-6-methyl
2.29 Hz), 7.90 (br s, 1H), 8.38 (d, 1H, J = 5.50 Hz), 8.42–8.44 pyrimidin-2-yl)amino)pentan-1-ol (8w). Off-white solid; yield:
(m, 1H); 13C NMR (100 MHz, DMSO-d6): dC 21.21, 22.91, 25.20, 75%; mp 128–130 1C; IR (nmax/cmÀ1, film): 3284, 2924, 2854,
1
26.20, 28.78, 32.18, 40.44, 42.18, 60.59, 98.54, 117.06, 124.43, 1576, 1366, 1136, 1079, 802; H NMR (400 MHz, DMSO-d6): dH
124.68, 125.64, 134.23, 146.92, 149.92, 151.15, 162.31, 162.39; 1.21–1.46 (m, 6H), 1.62–1.69 (m, 4H), 2.01 (s, 3H), 3.15–3.19
anal. calcd for C22H29ClN6O: C, 61.60; H, 6.81; N, 19.59; found: (m, 2H), 3.26–3.31 (m, 4H), 3.33–3.36 (m, 2H), 4.12 (br s, 1H),
C, 61.67; H, 6.83; N, 19.64; ESI-MS (m/z): 429.22 (M + H)+, 431.21 5.59 (s, 1H), 6.45 (d, 1H, J = 5.49 Hz), 7.35–7.38 (m, 2H), 7.42
(MH + 2)+.
(dd, 2H, J = 1.83 Hz, 9.16 Hz), 7.76–7.78 (m, 1H), 8.28 (d, 1H, J =
6-((4-((4-((7-Chloroquinolin-4-yl)amino)butyl)amino)pyrimidin- 9.16 Hz), 8.36 (d, 1H, J = 5.49 Hz); ESI-HRMS (m/z) calcd for
2-yl)amino)hexan-1-ol (8s). Yellow semi-solid; yield: 82%; IR (nmax
C23H31ClN6O: 442.2248 (M+), found: 443.2322 (M + H)+, 445.2305
/
cmÀ1, film): 3252, 2928, 2857, 1578, 1451, 1212, 1053, 803, 747; (MH + 2)+.
1H NMR (400 MHz, DMSO-d6): dH 1.21–1.26 (m, 4H), 1.35–1.46
6-((4-((4-((7-Chloroquinolin-4-yl)amino)butyl)amino)-6-methyl
(m, 4H), 1.65–1.70 (m, 4H), 3.16–3.21 (m, 2H), 3.32–3.36 (m, 7H), pyrimidin-2-yl)amino)hexan-1-ol (8x). Off-white solid; yield: 72%;
5.93–5.94 (m, 1H), 6.56 (d, 1H, J = 5.95 Hz), 7.50 (dd, 2H, J = mp 136–138 1C; IR (nmax/cmÀ1, film): 3284, 2925, 2857, 1577,
1
2.29 Hz, 9.16 Hz), 7.61–7.62 (m, 1H), 7.85 (d, 2H, J = 2.29 Hz), 8.05 1365, 1280, 1136, 804; H NMR (400 MHz, DMSO-d6): dH 1.21–
(br s, 1H), 8.39–8.44 (m, 2H); anal. calcd for C23H31ClN6O: C, 1.25 (m, 4H), 1.35–1.44 (m, 4H), 1.60–1.68 (m, 4H), 1.99 (s, 3H),
62.36; H, 7.05; N, 18.97; found: C, 62.41; H, 7.12; N, 19.04; ESI-MS 3.12–3.17 (m, 2H), 3.25–3.28 (m, 4H), 3.32–3.36 (m, 2H), 3.79
(m/z): 443.24 (M + H)+, 445.24 (MH + 2)+.
(br s, 1H), 5.54 (s, 1H), 6.44 (d, 2H, J = 5.34 Hz), 6.82 (br s, 1H),
2-((4-((4-((7-Chloroquinolin-4-yl)amino)butyl)amino)-6-methyl 7.31–7.33 (m, 1H), 7.42 (dd, 1H, J = 2.29 Hz, 9.16 Hz), 7.76–7.77
pyrimidin-2-yl)amino)ethanol (8t). White solid; yield: 86%; mp (m, 1H), 8.26 (d, 1H, J = 9.16 Hz), 8.35–8.36 (m, 1H); ESI-HRMS
182–184 1C; IR (nmax/cmÀ1, film): 3295, 2919, 854, 1576, 1362, (m/z) calcd for C24H33ClN6O: 456.2404 (M+), found: 457.2468
1136, 1075, 813; 1H NMR (400 MHz, DMSO-d6): dH 1.58–1.63 (M + H)+, 459.2459 (MH + 2)+.
(m, 2H), 1.65–1.71 (m, 2H), 1.99 (s, 3H), 3.23–3.30 (m, 4H), 3.44–
3.47 (m, 5H), 5.56 (s, 1H), 6.17 (br s, 1H), 6.46 (d, 1H, J = 5.13 Hz),
6.75 (br s, 1H), 7.30–7.32 (m, 1H), 7.42 (dd, 1H, J = 2.20 Hz, 8.79
Hz), 7.76 (d, 1H, J = 2.20 Hz), 8.26 (d, 1H, J = 8.79 Hz), 8.36 (d, 1H,
Acknowledgements
J = 5.13 Hz); anal. calcd for C20H25ClN6O: C, 59.92; H, 6.29; DSR thanks the Council of Scientific and Industrial Research
N, 20.96; found: C, 59.97; H, 6.36; N, 21.03; ESI-MS (m/z) calcd: [No. 02(0049)/12/EMR-II] New Delhi, India for financial sup-
401.21 (M + H)+, 403.22 (MH + 2)+.
port. MT is thankful to DST for the award of INSPIRE senior
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17 K. Singh, H. Kaur, P. Smith, C. D. Kock, K. Chibale and
J. Balzarini, J. Med. Chem., 2014, 57, 435–448.
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20 S. Manohar, S. I. Khan and D. S. Rawat, Bioorg. Med. Chem.
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research fellowship. AT and PP are thankful to CSIR for the
awards of senior research fellowship and research associateship,
respectively. SIK is thankful to the United States Department
of Agriculture (USDA), Agricultural Research Service Specific
Cooperative Agreement No. 58-6408-2-0009 for partial support
of this work. The authors thank CIF-USIC, University of Delhi,
Delhi for analytical data and DU-DST mass spectrometer facility
for mass data. Mr John Trott is acknowledged for excellent
technical support in the testing of biological activity at NCNPR.
21 S. Manohar, S. I. Khan and D. S. Rawat, Chem. Biol. Drug
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22 S. Manohar, S. I. Khan and D. S. Rawat, Chem. Biol. Drug
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