Synthesis of novel 4,6-diaryl-2-aminopyrimidines as potential antiplasmodial agents

Article abstract of DOI:10.1007/s00044-012-0328-z

A novel series of 4,6-diaryl-2-aminopyrimidines 8a-o has been synthesized and evaluated for in vitro antiplasmodial activity against Plasmodium falciparum. Out of the 15 compounds synthesized and tested, 6 compounds have shown IC₅₀ values in the range of 1.61-9.53 μg/mL. These compounds are several times more potent than chloroquine and quinine, the two standard drugs used for the purpose of comparison.

Full text of DOI:10.1007/s00044-012-0328-z

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res (2013) 22:3309–3315
DOI 10.1007/s00044-012-0328-z
ORIGINAL RESEARCH
Synthesis of novel 4,6-diaryl-2-aminopyrimidines as potential
antiplasmodial agents
•
Rajani Giridhar Riyaj S. Tamboli
•
•
Dhaval G. Prajapati Sanket Soni
•
•
Sarita Gupta M. R. Yadav
Received: 4 July 2012 / Accepted: 6 November 2012 / Published online: 22 November 2012
Ó Springer Science+Business Media New York 2012
Abstract
A
novel series of 4,6-diaryl-2-aminopyr-
Pyrimethamine 1, trimethoprim 2, and other antifolates
(proguanil 3 and chlorproguanil 4) used for the treatment of
P. falciparum infection, targeting dihydrofolate reductase
(DHFR) (Fig. 1) were identified as potent antimalarial
agents several decades ago and are still the mainstay
antifolate drugs used in the treatment and prevention of
malaria. All these drugs have a higher affinity for binding
to P. falciparum DHFR over human DHFR. It is well
accepted that differences in their binding affinity account
for their higher therapeutic index (Rastelli et al., 2000).
The parasite is observed to develop resistance to conven-
tional antimalarial drugs due to mutations in the active site
of their DHFR (Gregson and Plowe, 2005). As a result,
discovery of novel antimalarial agents effective against
resistant strains of the parasite is one of the greatest chal-
lenges facing the control of malaria today (Hyde, 2007;
Tripathi et al., 2005). Discovering new drugs that attack
key targets which are involved in the metabolism of the
malarial pathogen is the need of the hour (Wells, 2010;
Ridley, 2002; Mui et al., 2008).
imidines 8a–o has been synthesized and evaluated for
in vitro antiplasmodial activity against Plasmodium falci-
parum. Out of the 15 compounds synthesized and tested,
6 compounds have shown IC50 values in the range of
1.61–9.53 lg/mL. These compounds are several times
more potent than chloroquine and quinine, the two standard
drugs used for the purpose of comparison.
Keywords 2-Aminopyrimidines ꢀ Chloroquine ꢀ
Plasmodium falciparum ꢀ Antiplasmodial agents
Introduction
Malaria is re-emerging as the biggest infectious killerwith an
estimated 3.3 billion people at risk in 2010 and is currently
the first priority tropical disease of the World Health Orga-
nization (WHO) (World Malaria Report, 2011). The four
identified species of the parasite responsible for inflicting
human malaria are Plasmodium falciparum, Plasmodium
vivax, Plasmodium ovale, and Plasmodium malariae. Of
these, the former two account for more than 95 % of malaria
cases in the world (Snow et al., 2005). Although, the disease
can be treated in just 48 h, it can cause fatal complications, if
the diagnosis and treatment are delayed.
The structural requirements for DHFR inhibitors have
been well documented (Sirichaiwat et al., 2004; Warhurst,
1998; Yuthavong, 2002; Mishra et al., 2006). The inhibi-
tors should have the following basic characteristics: (a) A
heterocyclic ring system which can be accommodated in
the hydrophobic active site pocket of DHFR; (b) A suitable
group at position 2 of the heterocyclic ring for hydrogen
bonding with both the carboxyl oxygens of Asp-54; (c) A
substituent at position 4 which can form hydrogen bonding
with oxygens of amino acid backbone residues i.e., Ile-164
and Ile-14; (d) Substituent at position 5 should be non-
polar as it would be positioned in the hydrophobic core of
the enzyme active site. The DHFR-2,4-diamino-pyrimidine
interactions (Falco et al., 1951; Rollo, 1975) are self
explanatory for the development of such moieties
R. Giridhar (&) ꢀ R. S. Tamboli ꢀ D. G. Prajapati ꢀ M. R. Yadav
Pharmacy Department, Faculty of Technology and Engineering,
Kalabhavan, The M. S. University of Baroda, Vadodara 390 001,
India
e-mail: rajanimsu@rediffmail.com
S. Soni ꢀ S. Gupta
Department of Biochemistry, Faculty of Science, The M.
S. University of Baroda, Vadodara 390 001, India
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Med Chem Res (2013) 22:3309–3315
H3C
esters 5a–o, by base-catalyzed Baker-Venkataraman trans-
formation (Baker, 1933). Condensation of 2-hydroxyace-
tophenones with various substituted benzoic acids in dry
pyridine and POCl3 furnished the esters 5a–o. IR spectra of
1,3-diketones showed absorption bands for C=O in the range
of 1,615–1,625 cm-1. Treatment of the diketones with conc.
H2SO4 led to formation of flavones (7a–o) (Marder et al.,
1998). Formation of the flavones 7a–o was confirmed by the
appearance of C=O absorption bands at 1,640–1,660 cm-1
in their IR spectra. Reaction of the flavones 7a–o with a slight
excess of guanidine hydrochloride in alkaline medium
afforded 4,6-diaryl-2-amino-pyrimidines 8a–o. All the syn-
thesized compounds were characterized by spectral and
elemental analysis.
MeO
MeO
MeO
H2N
N
N
N
N
Cl
NH2
NH2
C
H2
H2N
(1)
(2)
Cl
NH2
HN
CH3
N
NH2
HN
Cl
N
H3C
N
H3C
N
Cl
CH3
NH2
(4)
NH2
(3)
Fig. 1 Clinically used antimalarial agents
(Agarwal et al., 2005a, b, c) as antimalarial/antiplasmodial
agents. Position-6 of the heterocyclic rings (six-membered)
are unexplored. So, it was envisaged to explore the potential
of 4,6-diaryl-2-aminopyrimidines as antiplasmodial agents.
In our ongoing program involving the synthesis of small
bioactive heterocyclic molecules, we have previously repor-
ted antileukemic, antiproliferative and antiplatelet activity of
some diaryldiazepines (Ramajayam et al., 2008) and diaryl-
pyrimidines (Ramajayam et al., 2005; Giridhar et al., 2012).
This communication describes the synthesis, docking studies
and preliminary in vitro evaluation of some novel 4,6-diaryl-
2-aminopyrimidines as potential antiplasmodial leads.
Compounds 8a–o showed a characteristic peak at
around 3,200 cm-1 for O–H stretching and asymmetric and
symmetric N–H stretching bands at 3,500 and 3,350 cm-1
,
1
respectively in their IR spectra. In the H NMR spectra,
NH2 protons appeared at d 5.1–6.0 and the pyrimidinyl
proton (C5–H) appeared as a sharp singlet at d 7.3–7.5. A
downfield value of d 13–14 for the –OH protons is indic-
ative of the existence of a partial six-membered ring as
shown in the structure. In the 13C NMR spectra, the d
values of the carbons are in confirmity with the structures
of the synthesized compounds.
Antiplasmodial activity
Results and discussion
All the synthesized compounds were screened for anti-
plasmodial activity on chloroquine sensitive P. falciparum
MRC 20 strains. Strain of P. falciparum was cultured
continuously according to the candle jar method (Trager
and Jensen, 1976; Soni and Gupta, 2009), in vitro in human
red blood cells (blood type B?) with 5 % hematocrit in
LIQUID RPMI 1640 medium (HIMEDIA) supplemented
Chemistry
The diarylpyrimidine derivatives reported in this paper were
prepared according to Scheme 1. The key intermediate 1,3-
diketones 6a–o required for the work were obtained from the
Y
O
COOH
Y
OH
CH3
OH
O
O
a
b
X
Y
+
X
X
CH3
O
O
O
(6a-o)
(5a-o)
Y
c
Y
X
O
d
A
B
X
O
N
N
O
(7a-o)
H
NH2
(8a-o)
Reagents and conditions: (a) POCl3, dry pyridine, rt, 2 h; (b) fused KOH, dry pyridine, rt, 2 h; (c) AcOH, catalytic
H2SO4, 100 oC, 1 h; (d) Guanidine hydrochloride, KOH, MeOH, reflux, 6-8 h.
Scheme 1 Synthesis of 4,6-diaryl-2-aminopyrimidines
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Med Chem Res (2013) 22:3309–3315
3311
with 25 mM HEPES (Sigma), 0.2 % sodium bicarbonate
(Sigma) and 10 % human B? serum. Slides of culture were
observed after 3, 6, and 24 h for regular development of
parasite stages. The inhibition of parasite growth in the
drug-treated groups was calculated as follows:
Table 1 Structures and antiplasmodial activity of the compounds
8a–o
X
6'
Y
6"
5"
2"
5'
4''
3"
4'
3'
5
4
6
2'
Control ꢁ Treated
O
N
N 1
Percentage inhibition ¼
ꢂ 100
H
3
2
Control
NH2
where; ‘‘control’’ is the parasitemia in the non-treated
group and ‘‘treated’’ is the parasitemia in the drug-treated
group, expressed as percentages. All values are expressed
as percentage growth inhibition. Dose–response curves
were obtained by plotting percentage inhibition against log
concentration. The values of the compounds provided a
mid-point value where parasite growth would be 50 %.
Linear regression analysis was applied to the linear portion
of the sigmoidal curve and IC50 values were derived for
each test compound. The IC50 value of chloroquine and
quinine was determined to be 10 and 29 lg/mL, respec-
tively (Karle et al., 1992). The IC50 values of test com-
pounds are given in Table 1.
8a-o
Comp. no.
X
Y
ICa50 (lg/mL)b
8a
40-OCH3
40-OCH3
40-OCH3
40-OCH3
50-OCH3
50-OCH3
50-OCH3
50-OCH3
40-Benzyloxy
40-Benzyloxy
40-Benzyloxy
40-Benzyloxy
40-Benzyloxy
40-Benzyloxy
40-Benzyloxy
–
400-Cl
400-OCH3
400-F
400-CH3
300-OCH3
200-Cl
300-Cl
400-F
400-OCH3
300-OCH3
300,400-di-OCH3
400-F
200-Cl
400-CH3
300-CH3
–
21.35 3.16c
1.78 0.58d
15.25 2.01e
8.71 1.37c
[25 2.30e
29.35 2.68e
9.53 1.39c
25.52 2.22e
5.01 0.98c
7.61 2.37c
1.61 0.40d
16.67 1.83e
18.87 1.88c
14.87 1.62c
35.56 4.10c
10 2.73c
8b
8c
8d
8e
8f
8g
8h
8i
8j
Docking studies
8k
8l
The molecular docking studies of 4,6-diaryl-2-aminopyr-
imidines with the pfDHFR binding site showed very clear
preference to the inhibitor binding pocket. Most of the
compounds bind in a similar fashion with the 2-aminopy-
rimidine ring occupying the interior of the deep cleft and
its 4-phenyl substitution extending toward the hydrophobic
binding cavity. The 2-aminopyrimidine core of the com-
pounds was fit in the pocket by a combination of both van
Der Waals and hydrophobic interactions with the protein.
The aromatic ring of Phe-58 stabilizes the 4-phenyl ring
with bulky benzyloxy substitution by p–p interactions. The
hydroxyl group of 4-phenyl group further stabilizes the
protein–ligand complex by hydrogen bonding with Ile-164
8m
8n
8o
Chloroquine
Quinine
–
–
29 2.40c
The parasite strain used for the assay is chloroquine sensitive strain of
P. falciparum MRC 20 and the results are represented as a single
reading; average was calculated by counting three different fields of
culture slide
a
The assay is stage specific inhibition assay to check development of
schizonts to trophozoites
b
IC50 values SD
Cell lysis observed after c [25, d [12.5, e [50 (lg/mL)
˚
with distance 2.055 A in case of benzyloxy and an opposite
orientation has been observed in case of 40-methoxyphenyl
of Phe-58 and the 4-phenyl ring. The displacement of this
benzyloxy moiety with methoxy at 40- or 50-position in
compounds 8a–h, led to comparable decrease in the
inhibitory activity whereas replacement with halo-substi-
tuted phenyl ring at position 6 in compounds 8a, 8c, 8f–h,
8l, and 8m cause decrease in the hydrophobic interactions,
thus lowering down the inhibition. In contrast, the com-
pounds 8b and 8i–k bearing 40- or 30-methoxyphenyl ring
show similar activity profiles displaying better antiplas-
modial effect. However, docking studies that were per-
formed could not explain the reduction in activity of
compound 8e with 300-methoxy substituent which may be
due to steric hindrance because of 50-methoxy group at
position 4.
showing hydrogen bonding with Gly-166 with distance
˚
1.966 A.
The substituents at position 4 of the 2-aminopyrimidine
ring have significant effect on the inhibitory activity. As
per our docking studies, bulkier substituents are preferred
at this position due to hydrophobic environment provided
by the side chains of Ile-14, Leu-46, Try-48, Ile-164, and
Leu-119. Compounds bearing 40-methoxy and 40-benzyl-
oxy substituents displayed a binding mode as shown by
representative compounds 8b and 8k in Figs. 2 and 3,
respectively. These compounds showed hydrophobic
interactions with Ile-14, Leu-46, Try-48, Ile-164, and Leu-
119. In addition to these hydrophobic interactions, p
interactions are also found to occur between the p system
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Med Chem Res (2013) 22:3309–3315
Fig. 2 Docked conformation of
compound 8b in the pfDHFR
active site
Fig. 3 Docked conformation of
compound 8k in the pfDHFR
active site
Structure–activity relationships
hydrophobic benzyloxy substitution on hydroxyphenyl ring
showed the highest potency. Compounds with benzyloxy
group and methoxy or methyl groups showed comparable
activities. Compounds 8d, 8g, 8i, and 8j showed IC50
values \10 lg/mL.
The in vitro biological activity of the synthesized pyrimi-
dine derivatives has shown encouraging results against the
chloroquine sensitive strain. Out of the 15 novel com-
pounds; two compounds 8b and 8k have been found to be
more potent than the standard drug chloroquine with IC50
values of 1.78 and 1.61 lg/mL, respectively. Compound
8b bears 4-methoxy substitution on both the phenyl rings
of the pyrimidine ring system. Replacement of 400-methoxy
group of phenyl ring of compound 8b by methyl group
caused a decrease in potency (8d). The weak activity of
halo-substituted compounds might be due to decrease in
electron density in the phenyl ring. Compound 8k with
300,400-dimethoxy group on phenyl ring and highly
Conclusion
Fifteen novel 4,6-diaryl-2-aminopyrimidines 8a–o have
been synthesized as potential antiplasmodial drugs. Of the
synthesized compounds, five compounds showed IC50
values in the range of 1.61–9.53 lg/mL, whereas four
compounds showed IC50 values comparable to quinine,
which was used as a standard drug in the study. These
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Med Chem Res (2013) 22:3309–3315
3313
compounds may serve to be ideal leads for further opti-
mization of their structures to provide newer and safer
antimalarial/antiplasmodial drugs.
potassium hydroxide (1.5 g) was refluxed in methanol
(30 ml) for 6–8 h. After the completion of the reaction, the
mixture was poured into crushed ice-acetic acid mixture
(50 g, 30 %). The yellow solid so obtained was filtered,
washed with water, and recrystallized from methanol.
Experimental
4-(20-Hydroxy-40-methoxyphenyl)-6-(400-chlorophenyl)-
2-aminopyrimidine (8a) Yield 33 %; Yellow crystals
from MeOH; mp 215–217 °C; IR (KBr) mmax: 3494, 3365,
Docking studies
1
Docking studies were performed with crystallographic 3D
structure of pfDHFR receptor (PDB Code: 3QGT) (Van-
2923, 1618 cm-1; H NMR (400 MHz, CDCl3): d 3.89
(s, 3H, OCH3), 5.19 (s, 2H, NH2), 6.59 (s, 1H, ArH),
7.29–7.30 (m, 2H, ArH), 7.32–7.34 (d, J = 7.6, 2H, ArH),
7.40 (1H, Pyri), 7.42–7.44 (d, J = 7.4, 2H, ArH); MS m/z;
328.76 (M?1); Anal. Calcd for C17H14ClN3O2: C, 62.30;
H, 4.31; N, 12.82. Found: C, 62.35; H, 4.22; N, 13.02.
¨
ichtanankul et al., 2011) using Glide (Schrodinger, New
York, USA, 2009). It performs grid-based ligand docking
with energetics and searches for favorable interactions
between one or more small ligand molecules and a larger
receptor molecule, usually a protein. Docking calculations
were first performed in SP mode and then in XP mode. All
the molecules were built within Maestro using the Built
module and an exhaustive conformational search was car-
ried out for all molecules using OPLS_2005 force field,
imposing a cutoff of allowed value of the total conforma-
tional energy compared to the lowest-energy state. A
minimization cycle for conjugate gradient and steepest
4-(20-Hydroxy-40-methoxyphenyl)-6-(400-methoxyphenyl)-
2-aminopyrimidine (8b) Yield 35 %; Yellow crystals
from MeOH; mp 223–225 °C; IR (KBr) mmax: 3410, 3300
(NH2), 3173.9 (OH), 1635 cm-1 1H NMR (400 MHz,
;
CDCl3): d 3.88 (s, 3H, OCH3), 3.91 (s, 3H, OCH3), 5.15
(s, 2H, NH2), 6.54–6.57 (m, 2H, ArH), 6.60 (s, 1H, ArH),
7.35 (s, 1H, pyri), 7.36–7.37 (d, J = 7.8, 2H, ArH),
7.42–7.43 (d, J = 7.84, 2H, ArH); MS m/z; 324.13 (M?1);
Anal. Calcd for C18H17N3O3: C, 66.86; H, 5.30; N, 13.00.
Found: C, 66.78; H, 5.21, N, 13.00.
˚
descent minimizations were used with default value 0.05 A
˚
for the initial step size and 1.00 A for the maximum step
size.
Chemical studies
4-(20-Hydroxy-40-methoxyphenyl)-6-(400-fluorophenyl)-
2-aminopyrimidine (8c) Yield 25 %; Yellow crystals
from MeOH; mp 205–207 °C; IR (KBr) mmax: 3500, 3180,
Melting points were determined in open capillaries using
Toshniwal melting point apparatus and are uncorrected. IR
spectra (in cm-1) were recorded using KBr pellets on a
Shimadzu 8300 instrument; and H NMR and 13C NMR
3120, 1620 cm-1 1H NMR (400 MHz, CDCl3): d 3.8
;
(s, 3H, OCH3), 5.1 (2H, NH2), 7.39 (s, 1H, Pyri), 6.9–7.6
(7H, ArH), 13.19 (br, 1H, OH); 13C NMR (400 MHz,
CDCl3): d 55.44, 100.91, 101.90, 107.47, 110.56, 115.78,
116.00, 128.35, 129.20, 129.28, 133.25, 160.22, 163.08,
163.28, 163.80, 164.47, 165.87; MS m/z; 312.1 (M?1);
Anal. Calcd for C17H14FN3O2: C, 65.59; H, 4.53; N, 13.50.
Found: C, 65.50; H, 4.62; N, 13.39.
1
spectra were recorded in CDCl3 on a Bruker Avance II
spectrometer (400 MHz), using tetramethylsilane as an
internal standard. Chemical shifts are reported in parts per
million (d, in ppm) where s, br, t, and m indicate singlet,
broad, triplet, and multiplet, respectively. Elemental anal-
yses were recorded on a Perkin Elmer PE 2400 CHNS
analyzer. Mass spectra were recorded on APISciEX mass
spectrometer equipped with an electrospray ionization
(ESI) interface. Column chromatography was carried out
using silica gel (100–200 mesh). Thin-layer chromatogra-
phy (TLC) was performed on precoated Silica gel Merck
plates. Compounds were visualized by illuminating with
UV light (254 nm) or exposure to iodine vapors. Solvents
were purified using standard purification techniques.
4-(20-Hydroxy-40-methoxyphenyl)-6-(400-methylphenyl)-
2-aminopyrimidine (8d) Yield 16 %; Yellow crystals
from MeOH; mp 195–197 °C; IR (KBr) mmax: 3500, 3380,
1
3120, 1620 cm-1; H NMR (400 MHz, CDCl3): d 2.44
(s, 3H, CH3), 3.8 (s, 3H, OCH3), 5.1 (2H, NH2), 6.4–8.0
(m, 7H, ArH), 7.34 (s, 1H, Pyri), 13.96 (br, 1H, OH); MS
m/z; 308.2 (M?1); Anal. Calcd for C18H17N3O2: C, 70.34;
H, 5.58; N, 13.67. Found: C, 70.30; H, 5.62; N, 13.60.
General method for the preparation of 4,6-diaryl-2-
aminopyrimidine derivatives (8a–o)
4-(20-Hydroxy-50-methoxyphenyl)-6-(300-methoxyphenyl)-
2-aminopyrimidine (8e) Yield 54 %; Yellow crystals
from MeOH; mp 158–160 °C; IR (KBr) mmax: 3430, 3320,
A mixture of an appropriate flavone 7a–o (0.5 g,
0.002 mol), guanidine hydrochloride (0.7 g, 0.07 mol) and
3220, 1599 cm-1
;
1H NMR (400 MHz, CDCl3): d 3.8
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Med Chem Res (2013) 22:3309–3315
4-(40-Benzyloxyphenyl-20-hydroxy)-6-(300,400-dimethoxyphenyl)-
2-aminopyrimidine (8k) Yield 32 %; Yellow crystals from
MeOH; mp 198–200 °C; IR (KBr) mmax: 3420, 3322,
(s, 3H, OCH3), 4.1 (s, 3H, OCH3) 5.1 (2H, NH2), 7.36
(s, 1H, Pyri), 6.9–7.8 (7H, ArH), 13.19 (br, 1H, OH); MS
m/z; 324.2 (M?1); Anal. Calcd for C18H17N3O3: C, 66.86;
H, 5.30; N, 13.00. Found: C, 66.80; H, 5.36; N, 12.90.
3210, 1647 cm-1 1H NMR (400 MHz, CDCl3): d 3.9
;
(s, 3H, OCH3), 4.0 (s, 3H, OCH3), 5.12 (s, 2H, OCH2Ar),
5.3 (2H, NH2), 6.9–7.9 (m, 12H, ArH), 7.36 (s, 1H, Pyri),
11.03 (br, 1H, OH); MS m/z; 430.2 (M?1); Anal. Calcd for
C25H23N3O4: C, 69.92; H, 5.40; N, 9.78. Found: C, 69.95;
H, 5.37; N, 9.77.
4-(20-Hydroxy-50-methoxyphenyl)-6-(200-chlorophenyl)-
2-aminopyrimidine (8f) Yield 52 %; Yellow crystals
from MeOH; mp 163–165 °C; IR (KBr) mmax: 3480, 3310,
3110, 1655 cm-1 1H NMR (400 MHz, CDCl3): d 3.8
;
(s, 3H, OCH3), 5.2 (2H, NH2), 7.39 (s, 1H, Pyri), 6.9–7.9
(7H, ArH), 13.09 (br, 1H, OH); MS m/z; 328.2 (M?1);
Anal. Calcd for C17H14ClN3O2: C, 62.30; H, 4.31; N,
12.82. Found: C, 62.34; H, 4.27; N, 12.79.
4-(40-Benzyloxyphenyl-20-hydroxy)-6-(400-fluorophenyl)-
2-aminopyrimidine (8l) Yield 45 %; Yellow crystals
from MeOH; mp 195–196 °C; IR (KBr) mmax: 3493, 3318,
1
3220, 1652 cm-1; H NMR (400 MHz, CDCl3): d 5.12
4-(20-Hydroxy-50-methoxyphenyl)-6-(300-chlorophenyl)-
2-aminopyrimidine (8g) Yield 70 %; Yellow crystals
from MeOH; mp 178–179 °C; IR (KBr) mmax: 3456, 3352,
(s, 2H, OCH2Ar), 6.5 (2H, NH2), 6.6–8.1 (m, 12H, ArH),
7.35 (s, 1H, Pyri), 12.01 (br, 1H, OH); MS m/z; 388.2
(M?1); Anal. Calcd for C23H18FN3O2: C, 71.31; H, 4.68;
N, 10.85. Found: C, 71.27; H, 4.70; N, 10.86.
3110, 1640 cm-1 1H NMR (400 MHz, CDCl3): d 3.8
;
(s, 3H, OCH3), 5.2 (2H, NH2), 7.37 (s, 1H, Pyri), 7.0–7.8
(7H, ArH), 13.84 (br, 1H, OH); 13C NMR (400 MHz,
CDCl3): d 56.13, 102.10, 111.48, 117.36, 119.37, 119.84,
125.27, 127.38, 130.08, 130.78, 135.01, 139.14, 152.24,
154.94, 160.79, 165.16, 166.00; MS m/z; 328.2 (M?1);
Anal. Calcd for C17H14ClN3O2: C, 62.30; H, 4.31; N,
12.82. Found: C, 62.36; H, 4.30; N, 12.85.
4-(40-Benzyloxyphenyl-20-hydroxy)-6-(200-chlorophenyl)-
2-aminopyrimidine (8m) Yield 35 %; Yellow crystals
from MeOH; mp 161–162 °C; IR (KBr) mmax: 3450, 3315,
1
3220, 1652 cm-1; H NMR (400 MHz, CDCl3): d 5.10
(s, 2H, OCH2Ar), 5.15 (2H, NH2), 7.34–7.39 (m, 5H, ArH),
6.55–7.71 (m, 7H, ArH), 7.35 (s, 1H, Pyri), 13.88 (br, 1H,
OH); MS m/z; 404.1 (M?1); Anal. Calcd for
C23H18ClN3O2: C, 68.40; H, 4.49; N, 10.40. Found: C,
68.40; H, 4.51; N, 10.40.
4-(20-Hydroxy-50-methoxyphenyl)-6-(400-fluorophenyl)-
2-aminopyrimidine (8h) Yield 56 %; Yellow crystals
from MeOH; mp 202–203 °C; IR (KBr) mmax: 3460, 3310,
3222, 1640 cm-1 1H NMR (400 MHz, CDCl3): d 3.8
;
4-(40-Benzyloxyphenyl-20-hydroxy)-6-(400-methylphenyl)-
2-aminopyrimidine (8n) Yield 56 %; Yellow crystals
from MeOH; mp 215–216 °C; IR (KBr) mmax: 3428, 3323,
(s, 3H, OCH3), 5.1 (2H, NH2), 7.34 (s, 1H, Pyri), 6.9–7.8
(7H, ArH), 13.16 (br, 1H, OH); MS m/z; 312.2 (M?1);
Anal. Calcd for C17H14FN3O2: C, 65.59; H, 4.53; N, 13.50.
Found: C, 65.51; H, 4.57; N, 13.54.
3204, 1647 cm-1 1H NMR (400 MHz, CDCl3): d 2.4
;
(s, 3H, CH3), 5.10 (s, 2H, OCH2Ar), 6.44 (2H, NH2), 7.2–7.4
(m, 5H, ArH), 7.4–7.8 (m, 7H, ArH), 7.35 (s, 1H, Pyri); MS
m/z; 384.1 (M?1); Anal. Calcd for C24H21N3O2: C, 75.18; H,
5.52; N, 10.96. Found: C, 75.30; H, 5.50; N, 10.90.
4-(40-Benzyloxyphenyl-20-hydroxy)-6-(400-methoxyphenyl)-
2-aminopyrimidine (8i) Yield 55 %; Yellow crystals
from MeOH; mp 226–227 °C; IR (KBr) mmax: 3495, 3347,
4-(40-Benzyloxyphenyl-20-hydroxy)-6-(300-methylphenyl)-
2-aminopyrimidine (8o) Yield 29 %; Yellow crystals
from MeOH; mp 165–167 °C; IR (KBr) mmax: 3450, 3330,
3223, 1652 cm-1 1H NMR (400 MHz, CDCl3): d 3.4
;
(s, 3H, OCH3), 5.12 (s, 2H, OCH2Ar), 6.5 (2H, NH2), 6.6–8.1
(m, 12H, ArH), 7.35 (s, 1H, Pyri), 10.07 (br, 1H, OH); MS
m/z; 400.2 (M?1); Anal. Calcd for C24H21N3O3: C, 72.16; H,
5.30; N, 10.52. Found: C, 72.21; H, 5.28; N, 10.52.
3200, 1607 cm-1 1H NMR (400 MHz, CDCl3): d 2.1
;
(s, 3H, CH3), 5.11 (s, 2H, OCH2Ar), 6.2 (2H, NH2), 7.2–7.4
(m, 5H, ArH), 6.9–7.8 (m, 7H, ArH), 7.35 (s, 1H, Pyri); MS
m/z; 384.1 (M?1); Anal. Calcd for C24H21N3O2: C, 75.18;
H, 5.52; N, 10.96. Found: C, 75.28; H, 5.51; N, 10.92.
4-(40-Benzyloxyphenyl-20-hydroxy)-6-(300-methoxyphenyl)-
2-aminopyrimidine (8j) Yield 47 %; Yellow crystals
from MeOH; mp 154–155 °C; IR (KBr) mmax: 3400, 3338,
3223, 1652 cm-1 1H NMR (400 MHz, CDCl3): d 3.9
;
Antiplasmodial activity
(s, 3H, OCH3), 5.12 (s, 2H, OCH2Ar), 5.3 (2H, NH2), 6.6–8.1
(m, 12H, ArH), 7.39 (s, 1H, Pyri), 10.53 (br, 1H, OH); MS
m/z; 400.2 (M?1); Anal. Calcd for C24H21N3O3: C, 72.16; H,
5.30; N, 10.52. Found: C, 72.18; H, 5.29; N, 10.52.
The chloroquine sensitive P. falciparum MRC 20 was
obtained from the National Institute of Malaria Research
(NIMR), New Delhi, India. The culture was synchronized
123

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