Synthesis of 2,4,6-trisubstituted pyrimidines as antimalarial agents

Article abstract of DOI:10.1016/j.bmc.2005.04.061

A series of 2,4,6-trisubstituted-pyrimidines were synthesized and evaluated for their in vitro antimalarial activity against Plasmodium falciparum. Of the 18 compounds synthesized, 14 compounds have shown MIC in the range of 0.25-2 μg/mL. These compounds

Full text of DOI:10.1016/j.bmc.2005.04.061

Bioorganic & Medicinal Chemistry 13 (2005) 4645–4650
Synthesis of 2,4,6-trisubstituted pyrimidines as antimalarial agents
Anu Agarwal,a Kumkum Srivastava,b S. K. Purib and Prem M. S. Chauhana,*
aDivision of Medicinal & Process Chemistry, Central Drug Research Institute, Lucknow 226001, India
bDivision of Parasitology, Central Drug Research Institute, Lucknow 226001, India
Received 28 March 2005; revised 21 April 2005; accepted 22 April 2005
Available online 17 May 2005
Abstract—A series of 2,4,6-trisubstituted-pyrimidines were synthesized and evaluated for their in vitro antimalarial activity against
Plasmodium falciparum. Of the 18 compounds synthesized, 14 compounds have shown MIC in the range of 0.25–2 lg/mL. These
compounds are in vitro severalfold more active than pyrimethamine.
Ó 2005 Elsevier Ltd. All rights reserved.
1. Introduction
Malaria is the most serious and widespread parasitic
disease because of its prevalence, virulence and drug
resistance, having an overwhelming impact on public
Fatty acid biosynthesis (FAS) is another important target
site in the discovery of new antimalarials. Pyridine-4-car-
boxylic acid hydrazide (Isoniazid), which is a frontline
drug in the treatment of tuberculosis, is an inhibitor of
an important enzyme (enoyl-ACP reductase) in the fatty
acid biosynthesis pathway. Thus pyridine analogues inhi-
bit the biosynthesis of fatty acids, which are fundamental
for the survival of P. falciparum in the host.7
health in developing regions of the world. Plasmodium
falciparum is the main cause of severe clinical malaria
and death. Endemic mapping indicates that P. falcipa-
rum and P. vivax account for 95% of the malaria
infections.1–3 Each year, more than 500 million people
are infected and close to 2 million die because of ma-
laria. A major thrust in this initiative is the identifica-
tion of new targets that are critical to the disease
process or essential for the survival of the parasite.
The dihydrofolate reductase (DHFR) domain of P.
falciparum is one of the few well-defined targets in
malarial chemotherapy. The enzyme catalyzes the nic-
otinamide adenine dinucleotide phosphate (NADPH)
dependent reduction of dihydrofolate to tetrahydrofo-
late. DHFR has received considerable attention, as it
is the target of pyrimethamine (I) and other antifo-
lates used for the prophylaxis and treatment of P. fal-
ciparum infection.4,5 Because the parasites are
developing resistance to conventional antimalarial
drugs, the development of drugs attacking crucial tar-
gets in the metabolism of the malarial pathogen is
imperative.6
Compounds that act on more than one target sites are
more liable to be active. Based on these observations,
we have synthesized hybrid derivatives having pyrimi-
dine (DHFR inhibitor) along with pyridine moiety
(fatty acid inhibitor).
Antimalarial drugs such as quinine and mefloquine have
a piperidine nucleus, while amopyroquine and cycloqu-
ine have a pyrrolidine moiety. A large number of com-
pounds having piperidine and pyrrolidine moieties
have shown potent antimalarial activity.8 These results
prompted us to synthesize compounds having pyridine
moieties along with pyrimidine and these cyclic amines
at the 2nd position in the pyrimidine ring.
As part of our ongoing program devoted to the synthesis
of diverse heterocycles as anti-infective agents,9 we had
previously reported antimalarial activity in substituted
triazines, pyrimidines and quinolines.10 This communica-
tion describes the in vitro antimalarial activity of pyrim-
Keywords: Dihydrofolate reductase; Antimalarial; Pyrimidine.
*
Corresponding author. Tel.: +91 522 2212411x4332; fax: +91 522
2623405; e-mail addresses: prem_chauhan_2000@yahoo.com;
premsc58@hotmail.com
0968-0896/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2005.04.061

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A. Agarwal et al. / Bioorg. Med. Chem. 13 (2005) 4645–4650
idine derivatives substituted with cyclic amines at the 2nd
position and pyridine nucleus at the 4th position.
parasites into trophozoites and schizonts in the presence
of different concentrations of compounds. The test con-
centration that inhibits the complete maturation into
schizonts was recorded as the minimum inhibitory con-
centration (MIC). Pyrimethamine was used as the stan-
dard reference drug. Activities of all the tested
compounds are shown in Table 1.
2. Chemistry
To synthesize the 2,4,6-trisubstituted-pyrimidine com-
pounds (3a–i and 4a–i), 4-acetylpyridine was reacted
with different aldehydes (a–i) in 10% aq NaOH and
methanol to yield the corresponding chalcones 2a–i.11
Piperidine-1-carboxamidine hydrochloride and pyrroli-
dine-1-carboxamidine hydrochloride were synthesized
by refluxing piperidine and pyrrolidine, respectively,
with S-methyl isothiourea sulfate in water according to
a reported procedure.12 The chalcones 2a–i were further
cyclized with imidine hydrochlorides in the presence of
sodium isopropoxide (synthesized in situ by adding so-
dium metal in isopropanol) to afford the 2,4,6-trisubsti-
tuted pyrimidines 3a–i and 4a–i as shown in Scheme 1.
All the synthesized compounds were well characterized
by spectroscopic methods such as IR, mass, NMR and
elemental analysis.
4. Results and discussion
Among all the 18 compounds tested, 1 compound
showed MIC of 0.25 lg/mL, 3 compounds showed
MIC of 1 lg/mL, and 10 compounds showed MIC of
2 lg/mL.
When the R group was a phenyl ring the pyrrolidine
substituted compound (3a) showed a MIC of 2 lg/mL.
Substitution of the phenyl ring with methoxy group
(3b), methyl group (3f), thiomethyl group (3g) and
chloro group (3i) did not affect the activity. Di- (3c)
and trisubstitution (3d) of the phenyl ring with methoxy
group increased the activity. An almost similar trend
was also observed for piperidine substituted com-
pounds. The phenyl ring substituted compound showed
a MIC of 2 lg/mL. Substitution of methoxy (4b), dime-
thoxy (4c) and thiomethyl group (4g) on the phenyl ring
had no effect on the activity. On substitution of methyl
3. Biological activity
The in vitro antimalarial assay was carried out in 96-well
microtitre plates according to the microassay of Rieck-
mann et al.13 The culture of P. falciparum NF-54 strain
is routinely being maintained in medium RPMI-1640
supplemented with 25 mM HEPES, 1% D-glucose,
0.23% sodium bicarbonate and 10% heat inactivated hu-
man serum.14 The asynchronous parasite of P. falcipa-
rum was synchronized after 5% D-sorbitol treatment to
obtain parasitized cells harbouring only the ring stage.15
For carrying out the assay, an initial ring stage parasita-
emia of ꢀ1% at 3% haematocrit in a total volume of
200 lL of medium RPMI-1640 was uniformly main-
tained. The test compound in 20 lL volume at required
concentration (ranging between 0.25 lg and 50 lg/mL)
in duplicate wells was incubated with parasitized cell
preparation at 37 °C in a candle jar. After 36–40 h incu-
bation, the blood smears from each well were prepared
and stained with giemsa stain. The slides were micro-
scopically observed to record maturation of ring stage
Table 1. Antimalarial in vitro activity against P. falciparum
S. no.
R
MIC (lg/mL)
3(a–j) n = 0 4(a–j) n = 1
a
b
c
d
e
f
C6H5
4OMe
2
2
2
2
2,5-diOMe
2,4,5-triOMe
3,4,5-triOMe
4-Me
1
2
1
1
50
50
2
0.25
g
h
i
4-SMe
3,4-DiMe
4Cl
2
2
10
10
2
2
MIC = Minimum inhibiting concentration for the development of ring
stage parasite into the schizont stage during 40 h incubation.
I: standard drug and pyrimethamine have shown a MIC of 10 lg/mL.
Scheme 1. (a) Different aldehydes (a–j), 10% aq NaOH, methanol, 0 °C–rt, 30 min. (b) (i) Piperidine or pyrrolidine, S-methylisothiourea sulfate,
water, reflux, 15 min. (ii) Barium chloride, reflux, 15 min. (c) Pyrrolidine-1-carboxamidine.HCl (for 3a–j) or piperidine-1-carboxamidineÆHCl (for 4a–
j) sodiumisopropoxide, isopropanol, reflux, 8 h.

A. Agarwal et al. / Bioorg. Med. Chem. 13 (2005) 4645–4650
4647
group at para position the compound (4f) exhibited an
exceptionally drastic increase in activity, having a MIC
of 0.25 lg/mL. Trisubstitution of the phenyl ring with
methoxy group at 2-, 4- and 5-positions increased the
activity, whereas substitution at 3-, 4- and 5-positions
decreased the activity of compounds. In general the
activity profiles in both the pyrrolidine and piperidine
substituted compounds are almost similar.
and then recrystallized from methanol or ethanol to give
crystals of the chalcone.
6.1.1. 3-Phenyl-1-pyridin-4-yl-propenone (2a). The com-
pound was synthesized using method A. Yield: 75%;
mp 172–174 °C; MS: 210 (M+1); IR (KBr) 3521, 1956,
1673, 1595, 1411, 1225 cmÀ1
;
1H NMR (CDCl3,
200 MHz) d (ppm) 8.84 (d, 2H, J = 6.0 Hz), 8.01 (d,
2H, J = 7.8 Hz), 7.86 (d, 1H, J = 15.1 Hz), 7.76 (d, 2H,
J = 6.0 Hz), 7.44–7.40 (m, 3H), 7.36 (d, 1H,
J = 15.1 Hz). Anal. Calcd for C14H11NO: calculated C:
80.36, H: 5.30, N: 6.69. Found: C: 80.56, H: 5.53, N:
6.78.
5. Conclusion
The eighteen 2,4,6-trisubstituted pyrimidines (3a–i and
4a–i) were synthesized as pyrimethamine analogues. In
conclusion one compound has shown MIC of 0.25
lg/mL, three compounds showed MIC of 1 lg/mL,
whereas ten compounds showed MIC of 2 lg/mL. These
compounds are 5–40 times more potent than pyrimeth-
amine. These identified pyrimidines are new leads in
antimalarial chemotherapy. These molecules can be very
useful for further optimization work in malarial
chemotherapy.
6.1.2.
3-(4-Methoxy-phenyl)-1-pyridin-4-yl-propenone
(2b). The compound was synthesized using method A.
Yield: 72%; mp 104–106 °C; MS: 240 (M+1); IR (KBr)
3420, 1946, 1683, 1598, 1489, 1411, 1257 cmÀ1 1H
;
NMR (CDCl3, 200 MHz) d (ppm) 8.83 (d, 2H,
J = 6.1 Hz), 7.89 (d, 2H, J = 8.6 Hz), 7.82 (d, 1H,
J = 15.4 Hz), 7.75 (d, 2H, J = 6.1 Hz), 7.37 (d, 1H,
J = 15.4 Hz), 6.92 (d, 2H, J = 8.6 Hz), 3.88 (s, 3H,
OMe). Anal. Calcd for C15H13NO2: calculated C:
75.30, H: 5.48, N: 5.85. Found: C: 75.54, H: 5.59, N:
5.71.
6. Experimental details
IR spectra were recorded on Beckman Aculab-10, Per-
kin Elmer 881 and FTIR 8210 PC, Scimadzu spectro-
photometers either on KBr discs or in neat. Nuclear
magnetic resonance (NMR) spectra were recorded on
either Bruker Avance DRX-300 MHz or Bruker DPX
200 FT spectrometers using TMS as an internal refer-
ence. FAB mass spectra were recorded on JEOL SX
102/DA 6000 mass spectrometer using argon/xenon
(6 kV, 10 mA) as the FAB gas. Chemical analyses were
carried out on Carlo-Erba-1108 instrument. The melting
points were recorded on an electrically heated melting
point apparatus and are uncorrected.
6.1.3. 3-(2,5-Dimethoxy-phenyl)-1-pyridin-4-yl-propenone
(2c). The compound was synthesized using method B.
Yield: 58%; mp 128–130 °C; MS: 270 (M+1); IR (KBr)
3299, 1956, 1685, 1597, 1456, 1411, 1259 cmÀ1 1H
;
NMR (CDCl3, 200 MHz) d (ppm) 8.85 (d, 2H,
J = 6.0 Hz), 7.82 (d, 1H, J = 15.4 Hz), 7.77 (d, 2H,
J = 6.0 Hz), 7.39 (d, 1H, J = 15.4 Hz), 7.36 (s, 1H),
7.24 (d, 1H, J = 7.2 Hz), 6.76 (d, 1H, J = 7.2 Hz), 3.88
(s, 3H, OMe), 3.85 (s, 3H, OMe). Anal. Calcd for
C16H15NO3: calculated C: 71.36, H: 5.61, N: 5.20.
Found: C: 71.58, H: 5.86, N: 4.97.
6.1.4. 1-Pyridin-4-yl-3-(2,4,5-trimethoxy-phenyl)-prope-
none (2d). The compound was synthesized using method
B. Yield: 64%; mp 160–162 °C; MS: 300 (M+1); IR
6.1. General procedure for the synthesis of compounds
2a–i
(KBr) 3282, 1939, 1689, 1598, 1468, 1420, 1232 cmÀ1
;
Method A: To a cooled solution of 10% NaOH,
1.0 equiv of liquid aldehydes was added. To this solution
1.0 equiv of 4-acetyl pyridine was added dropwise in
about a period of 30 min. The solution was maintained
at 0 °C for an hour and then was allowed to stir at rt.
After some time a solid started separating out. The solu-
tion was further stirred for about 1 h. The solid was fil-
tered out and then recrystallized from methanol or
ethanol to give crystals of the chalcone.
1H NMR (CDCl3, 200 MHz) d (ppm) 8.82 (d, 2H,
J = 5.9 Hz), 7.84 (d, 1H, J = 15.6 Hz), 7.72 (d, 2H,
J = 5.9 Hz), 7.64 (s, 1H), 7.37 (d, 1H, J = 15.6 Hz),
6.72 (s, 1H), 3.96 (s, 3H, OMe), 3.92 (s, 3H, 2OMe).
Anal. Calcd for C17H17NO4: calculated C: 68.21, H:
5.72, N: 4.68. Found: C: 67.98, H: 5.94, N: 4.91.
6.1.5. 1-Pyridin-4-yl-3-(3,4,5-trimethoxy-phenyl)-prope-
none (2e). The compound was synthesized using method
B. Yield: 66%; mp 194–196 °C; MS: 300 (M+1); IR
Method B: In the case of aldehydes, which were solid,
the aldehyde (1 equiv) was first dissolved in minimum
quantity of ethanol or methanol (approx 25 mL) and
then 10% NaOH solution (approx 100 mL) was added
to it to give a clear solution. The solution was cooled
up to 0 °C by applying ice bath below it. Then 1 equiv
of 4-acetyl pyridine was dropwise added to it, in around
a period of 30 min. The solution was maintained at 0 °C
for 1 h and then was allowed to stir at room tempera-
ture. After some time a solid started separating out. This
was stirred for about an hour. The solid was filtered out
(KBr) 3278, 1943, 1687, 1596, 1457, 1445, 1245 cmÀ1
;
1H NMR (CDCl3, 200 MHz) d (ppm) 8.79 (d, 2H,
J = 6.0 Hz), 7.82 (d, 1H, J = 15.2 Hz), 7.70 (d, 2H,
J = 6.0 Hz), 7.37 (d, 1H, J = 15.2 Hz), 7.30 (s, 2H),
3.98 (s, 3H, 2OMe), 3.95 (s, 3H, OMe). Anal. Calcd
for C17H17NO4: calculated C: 68.21, H: 5.72, N: 4.68.
Found: C: 68.47, H: 5.98, N: 4.31.
6.1.6. 1-Pyridin-4-yl-3-p-tolyl-propenone (2f). The com-
pound was synthesized using method A. Yield: 76%;
mp 138–140 °C; MS: 224 (M+1); IR (KBr) 3290, 1967,

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A. Agarwal et al. / Bioorg. Med. Chem. 13 (2005) 4645–4650
1
1689, 1598, 1492, 1412, 1238 cmÀ1; H NMR (CDCl3,
200 MHz) d (ppm) 8.84 (d, 2H, J = 6.0 Hz), 7.84 (d,
1H, J = 15.6 Hz), 7.74 (d, 2H, J = 6.0 Hz), 7.54 (d, 2H,
J = 8.2 Hz), 7.37 (d, 1H, J = 15.6 Hz), 7.24 (d, 2H,
J = 8.2 Hz), 2.39 (s, 3H). Anal. Calcd for C15H13NO:
calculated C: 80.69, H: 5.87, N: 6.27. Found: C: 80.82,
H: 5.62, N: 6.42.
NMR (CDCl3, 200 MHz) d (ppm) 8.76 (d, 2H,
J = 6.1 Hz), 8.13 (d, 2H, J = 4.8 Hz), 7.98 (d, 2H,
J = 6.1 Hz), 7.50–7.47 (m, 3H), 7.37 (s, 1H), 3.76 (t,
4H, J = 6.4 Hz), 2.04 (t, 4H, J = 6.4 Hz); 13C (CDCl3,
50 MHz): 165.2, 162.1, 161.7, 150.3, 145.4, 137.2,
127.8, 129.6, 128.9, 120.8, 103.4, 43.7, 25.4. Anal. Calcd
for C20H19N3: calculated C: 79.70, H: 6.35, N: 13.94.
Found: C: 79.88, H: 6.58, N: 13.64.
6.1.7. 3-(4-Methylsulfanyl-phenyl)-1-pyridin-4-yl-prope-
none (2g). The compound was synthesized using method
A. Yield: 70%; mp 94–96 °C; MS: 256 (M+1); IR (KBr)
6.2.2. 4-(4-Methoxy-phenyl)-6-pyridin-4-yl-2-pyrrolidin-
1-yl-pyrimidine (3b). Yield: 68%; mp 164–166 °C; MS:
332 (M+1); IR (KBr) 2924, 1648, 1576, 1486, 1328,
3412, 1956, 1682, 1595, 1415, 1225 cmÀ1 1H NMR
;
1
1284 cmÀ1; H NMR (CDCl3, 200 MHz) d (ppm) 8.73
(CDCl3, 200 MHz) d (ppm) 8.83 (d, 2H, J = 6.1 Hz),
7.82 (d, 1H, J = 14.9 Hz), 7.76 (d, 2H, J = 6.1 Hz),
7.55 (d, 2H, J = 8.6 Hz), 7.38 (d, 1H, J = 14.9 Hz),
7.26 (d, 2H, J = 8.6 Hz), 2.52 (s, 3H). Anal. Calcd for
C15H13NOS: calculated C: 70.56, H: 5.13, N: 5.49.
Found: C: 70.74, H: 5.34, N: 5.34.
(d, 2H, J = 5.8 Hz), 8.11 (d, 2H, J = 8.8 Hz), 7.96 (d,
2H, J = 5.8 Hz), 7.31 (s, 1H), 7.02 (d, 2H, J = 8.8 Hz),
3.87 (s, 3H, OMe), 3.75 (t, 4H, J = 6.4 Hz), 2.06 (t,
4H, J = 6.4 Hz); 13C (CDCl3, 50 MHz): 165.4, 162.4,
162.2, 161.9, 150.4, 145.5, 129.9, 128.6, 121.0, 114.0,
101.6, 55.4, 43.9, 25.3. Anal. Calcd for C21H21N3O: cal-
culated C: 76.11, H: 6.39, N: 12.68. Found: C: 76.45, H:
6.66, N: 12.41.
6.1.8. 3-(3,4-Dimethyl-phenyl)-1-pyridin-4-yl-propenone
(2h). The compound was synthesized using method A.
Yield: 67%; mp 168–170 °C; MS: 238 (M+1); IR (KBr)
3392, 1952, 1687, 1597, 1424, 1249 cmÀ1 1H NMR
;
6.2.3. 4-(2,5-Dimethoxy-phenyl)-6-pyridin-4-yl-2-pyrroli-
din-1-yl-pyrimidine (3c). Yield: 54%; mp 164–166 °C;
MS: 362 (M+1); IR (KBr) 2926, 1638, 1580, 1480,
(CDCl3, 200 MHz) d (ppm) 8.84 (d, 2H, J = 6.0 Hz),
7.89 (d, 2H, J = 7.8 Hz), 7.83 (d, 1H, J = 15.2 Hz),
7.74 (d, 2H, J = 6.0 Hz), 7.51 (s, 1H), 7.40 (d, 1H,
J = 15.2 Hz), 7.29 (d, 2H, J = 7.8 Hz), 2.37 (s, 3H),
2.34 (s, 3H). Anal. Calcd for C16H15NO: calculated C:
80.98, H: 6.37, N: 5.90. Found: C: 81.24, H: 6.09, N:
5.68.
1325, 1272 cmÀ1
;
1H NMR (CDCl3, 200 MHz) d
(ppm) 8.74 (d, 2H, J = 6.1 Hz), 7.97 (d, 2H,
J = 6.1 Hz), 7.60 (d, 2H, J = 6.2 Hz), 7.29 (s, 1H), 6.97
(s, 1H), 3.75 (t, 4H, J = 6.2 Hz), 2.05 (t, 4H,
J = 6.2 Hz) 3.86 (s, 3H, OMe), 3.84 (s, 3H, OMe); 13C
(CDCl3, 50 MHz): 164.8, 162.6, 162.3, 154.4, 152.9,
150.8, 146.1, 128.4, 121.6, 116.8, 116.6, 113.7, 107.8,
43.9, 56.8, 56.2, 25.5. Anal. Calcd for C22H23N3O2: cal-
culated C: 73.11, H: 6.41, N: 11.63. Found: C: 73.56, H:
6.58, N: 11.41.
6.1.9. 3-(4-Chloro-phenyl)-1-pyridin-4-yl-propenone (2i).
The compound was synthesized using method B. Yield:
68%; mp 205–207 °C; MS: 244 (M+1); IR (KBr) 3297,
1
1948, 1684, 1598, 1489, 1257 cmÀ1; H NMR (CDCl3,
200 MHz) d (ppm) 8.85 (d, 2H, J = 6.1 Hz), 7.86 (d,
1H, J = 15.6 Hz), 7.75 (d, 2H, J = 6.1 Hz), 8.09 (d, 2H,
J = 8.6 Hz), 7.38 (d, 1H, J = 15.6 Hz), 7.52 (d, 2H,
J = 8.6 Hz). Anal. Calcd for C14H10ClNO: calculated
C: 69.00, H: 4.14, N: 5.75. Found: C: 68.74, H: 4.32,
N: 5.44.
6.2.4. 4-Pyridin-4-yl-2-pyrrolidin-1-yl-6-(2,4,5-trimeth-
oxy-phenyl)-pyrimidine (3d). Yield: 68%; mp 164–
166 °C; MS: 392 (M+1); IR (KBr) 2948, 1636, 1584,
1
1486, 1325, 1265 cmÀ1; H NMR (CDCl3, 200 MHz) d
(ppm) 8.73 (d, 2H, J = 5.7 Hz), 7.97 (d, 2H,
J = 5.7 Hz), 7.82 (s, 1H), 7.73 (s, 1H), 6.61 (s, 1H),
3.96 (s, 3H, OMe), 3.93 (s, 3H, OMe), 3.91 (s, 3H,
OMe), 3.74 (t, 4H, J = 6.5 Hz), 2.03 (t, 4H,
J = 6.5 Hz); 13C (CDCl3, 50 MHz): 164.5, 162.5, 162.0,
154.1, 152.3, 150.7, 146.4, 143.9, 121.7, 118.9, 114.3,
107.6, 98.4, 57.2, 57.0, 56.6, 43.8, 25.3. Anal. Calcd for
C23H25N3O3: calculated C: 70.57, H: 6.44, N: 10.73.
Found: C: 70.82, H: 6.59, N: 10.48.
6.2. General procedure for the synthesis of compounds
3a–i
To a solution of 1.0 equiv of pyrrolidin-1-carboxami-
dine hydrochloride in 50 mL of isopropanol, 1.1 equiv
of sodium metal was added. The reaction mixture was
refluxed for 2 h and then different chalcones (2a–i,
1.0 equiv) were added to it and refluxed for 8 h. The sol-
vent was removed from the reaction mixture under re-
duced pressure. Water was added and the aqueous
phase was extracted with chloroform and washed with
brine solution. The organic phase was dried over anhy-
drous Na2SO4, filtered and concentrated. The crude
product was purified by crystallization from methanol
or ethanol or sometimes by column chromatography
on silica gel (2% methanol in chloroform) to afford the
pure compounds.
6.2.5. 4-Pyridin-4-yl-2-pyrrolidin-1-yl-6-(3,4,5-trimeth-
oxy-phenyl)-pyrimidine (3e). Yield: 70%; mp 158–
160 °C; MS: 392 (M+1); IR (KBr) 2932, 1645, 1574,
1
1484, 1319, 1280 cmÀ1; H NMR (CDCl3, 200 MHz) d
(ppm) 8.76 (d, 2H, J = 6.2 Hz), 7.98 (d, 2H,
J = 6.2 Hz), 7.32 (s, 1H), 7.28 (s, 2H), 3.75 (t, 4H,
J = 6.1 Hz), 3.96 (s, 6H, OMe), 3.91 (s, 3H, OMe),
2.04 (t, 4H, J = 6.1 Hz); 13C (CDCl3, 50 MHz): 167.2,
162.8, 163.2, 154.1, 150.8, 145.4, 140.8, 134.7, 121.6,
105.2, 102.7, 61.5, 56.9, 43.9, 25.4. Anal. Calcd for
C23H25N3O3: calculated C: 70.57, H: 6.44, N: 10.73.
Found: C: 70.79, H: 6.65, N: 10.44.
6.2.1. (4-Phenyl)-6-pyridin-4-yl-2-pyrrolidin-1-yl-pyrimi-
dine (3a). Yield: 60%; mp 170–172 °C; MS: 302 (M+1);
1
IR (KBr) 2932, 1645, 1574, 1484, 1319, 1280 cmÀ1; H

A. Agarwal et al. / Bioorg. Med. Chem. 13 (2005) 4645–4650
4649
6.2.6. 4-Pyridin-4-yl-2-pyrrolidin-1-yl-6-p-tolyl-pyrimi-
dine (3f). Yield: 64%; mp 132–134 °C; MS: 316 (M+1);
brine solution. The organic phase was dried over anhy-
drous Na2SO4, filtered and concentrated. The crude
product was purified by crystallization from methanol
or ethanol or sometimes by column chromatography
on silica gel (2% methanol in chloroform) to afford the
pure compounds.
1
IR (KBr) 2926, 1638, 1580, 1480, 1325, 1272 cmÀ1; H
NMR (CDCl3, 200 MHz) d (ppm) 8.74 (d, 2H,
J = 5.6 Hz), 8.04 (d, 2H, J = 7.9 Hz), 7.98 (d, 2H,
J = 5.6 Hz), 7.35 (s, 1H), 7.29 (d, 2H, J = 7.9 Hz), 3.79
(t, 4H, J = 6.6 Hz), 2.43 (s, 3H, Me), 2.04 (t, 4H,
J = 6.6 Hz); 13C (CDCl3, 50 MHz): 165.5, 162.5, 162.0,
150.2, 145.4, 138.1, 133.6, 130.1, 127.2, 121.2, 101.5,
43.8, 25.4, 18.9. Anal. Calcd for C21H21N3: calculated
C: 79.97, H: 6.71, N: 13.32. Found: C: 79.82, H: 6.57,
N: 13.41.
6.3.1. 4-Phenyl-2-piperidin-1-yl-6-pyridin-4-yl-pyrimidine
(4a). Yield: 60%; mp 180–182 °C; MS: 316 (M+1); IR
(KBr) 2926, 1638, 1580, 1480, 1325, 1272 cmÀ1 1H
;
NMR (CDCl3, 200 MHz) d (ppm) 8.76 (d, 2H,
J = 6.1 Hz), 8.12 (d, 2H, J = 7.9 Hz), 7.96 (d, 2H,
J = 6.1 Hz), 7.51–7.47 (m, 3H), 7.35 (s, 1H), 4.02 (t,
4H, J = 4.6 Hz), 1.68 (t, 4H, J = 4.6 Hz); 13C (CDCl3,
50 MHz): 165.4, 162.1, 161.6, 150.2, 145.4, 137.3,
127.8, 129.5, 128.9, 120.8, 103.2, 45.5, 26.3, 25.5. Anal.
Calcd for C21H21N3: calculated C: 79.97, H: 6.71, N:
13.32. Found: C: 79.82, H: 6.57, N: 13.41.
6.2.7. 4-(4-Methylsulfanyl-phenyl)-6-pyridin-4-yl-2-pyrr-
olidin-1-yl-pyrimidine (3g). Yield: 65%; mp 148–150 °C;
MS: 348 (M+1); IR (KBr) 2948, 1636, 1584, 1486,
1325, 1265 cmÀ1
;
1H NMR (CDCl3, 200 MHz) d
(ppm) 8.74 (d, 2H, J = 6.1 Hz), 8.07 (d, 2H,
J = 8.7 Hz), 7.98 (d, 2H, J = 6.1 Hz), 7.36 (s, 1H), 7.33
(d, 2H, J = 8.7 Hz), 3.79 (t, 4H, J = 6.5 Hz), 2.04 (t,
4H, J = 6.5 Hz), 2.54 (s, 3H, SMe); 13C (CDCl3,
50 MHz): 165.6, 163.0, 162.6, 150.7, 145.7, 142.7,
134.4, 127.8, 126.4, 121.4, 102.4, 43.7, 25.3, 16.9. Anal.
Calcd for C21H21N3S: calculated C: 72.59, H: 6.09, N:
12.09. Found: C: 72.82, H: 6.42, N: 12.36.
6.3.2. 4-(4-Methoxy-phenyl)-2-piperidin-1-yl-6-pyridin-4-
yl-pyrimidine (4b). Yield: 62%; mp 160–162 °C; MS: 346
(M+1); IR (KBr) 2948, 1636, 1584, 1486, 1325,
1
1265 cmÀ1; H NMR (CDCl3, 200 MHz) d (ppm) 8.73
(d, 2H, J = 6.0 Hz), 8.09 (d, 2H, J = 8.7 Hz), 7.96 (d,
2H, J = 6.0 Hz), 7.32 (s, 1H), 7.01 (d, 2H, J = 8.7 Hz),
3.94 (t, 4H, J = 4.2 Hz), 3.88 (s, 3H, OMe), 1.69 (t,
4H, J = 4.2 Hz); 13C (CDCl3, 50 MHz): 165.7, 162.7,
162.2, 161.9, 150.7, 146.4, 130.8, 128.9, 121.5, 114.4,
100.9, 55.8, 45.3, 26.3, 25.4. Anal. Calcd for
C22H23N3O: calculated C: 76.49, H: 6.71, N: 12.16.
Found: C: 76.62, H: 6.54, N: 12.41.
6.2.8. 4-(3,4-Dimethyl-phenyl)-6-pyridin-4-yl-2-pyrroli-
din-1-yl-pyrimidine (3h). Yield: 60%; mp 140–142 °C;
MS: 330 (M+1); IR (KBr) 1636, 1584, 1486, 1325,
1
1265 cmÀ1; H NMR (CDCl3, 200 MHz) d (ppm) 8.74
(d, 2H, J = 5.9 Hz), 7.98 (d, 2H, J = 5.9 Hz), 7.89 (s,
1H), 7.85 (d, 1H, J = 7.1 Hz), 7.35 (s, 1H), 7.23 (d,
1H, J = 7.1 Hz), 3.76 (t, 4H, J = 6.4 Hz), 2.04 (t, 4H,
J = 6.4 Hz), 2.36 (s, 3H), 2.33 (s, 3H); 13C (CDCl3,
50 MHz): 166.5, 162.8, 162.7, 150.9, 145.9, 140.2,
137.3, 135.6, 130.5, 128.6, 125.0, 121.6, 102.7, 43.7,
25.4, 20.4, 20.2. Anal. Calcd for C22H23N3: calculated
C: 80.21, H: 7.04, N: 12.76. Found: C: 80.43, H: 7.35,
N: 12.48.
6.3.3. 4-(2,5-Dimethoxy-phenyl)-2-piperidin-1-yl-6-pyri-
din-4-yl-pyrimidine (4c). Yield: 58%; mp 160–162 °C;
MS: 376 (M+1); IR (KBr) 2932, 1645, 1574, 1484,
1319, 1280 cmÀ1
;
1H NMR (CDCl3, 200 MHz) d
(ppm) 8.72 (d, 2H, J = 5.9 Hz), 7.95 (d, 2H,
J = 5.9 Hz), 7.35 (s, 1H), 7.30 (s, 1H), 7.11 (d, 1H,
J = 6.6 Hz), 6.98 (d, 1H, J = 6.6 Hz), 3.98 (t, 4H,
J = 4.4 Hz), 3.87 (s, 3H, OMe), 3.82 (s, 3H, OMe),
1.70 (t, 4H, J = 4.4 Hz); 13C (CDCl3, 50 MHz): 164.9,
162.8, 162.4, 154.4, 152.8, 150.6, 146.1, 128.3, 121.6,
116.9, 116.3, 113.7, 107.6, 57.2, 56.3, 45.5, 26.3, 25.5.
Anal. Calcd for C23H25N3O2: calculated C: 73.57, H:
6.71, N: 11.19. Found: C: 73.76, H: 6.48, N: 11.41.
6.2.9. 4-(4-Chloro-phenyl)-6-pyridin-4-yl-2-pyrrolidin-1-
yl-pyrimidine (3i). Yield: 67%; mp 174–176 °C; MS:
336 (M+1); IR (KBr) 2948, 1636, 1584, 1486, 1325,
1
1265 cmÀ1; H NMR (CDCl3, 200 MHz) d (ppm) 8.76
(d, 2H, J = 6.1 Hz), 8.09 (d, 2H, J = 8.9 Hz), 7.98 (d,
2H, J = 6.1 Hz), 7.49 (d, 2H, J = 8.9 Hz), 7.33 (s, 1H),
3.79 (t, 4H, J = 6.6 Hz), 2.06 (t, 4H, J = 6.6 Hz); 13C
(CDCl3, 50 MHz): 165.4, 162.3, 161.9, 158.8, 145.6,
135.3, 134.4, 130.1, 128.9, 121.3, 103.6, 43.8, 25.4. Anal.
Calcd for C20H18ClN3: calculated C: 71.53, H: 5.40, N:
10.56. Found: C: 71.81, H: 5.57, N: 10.41.
6.3.4. 2-Piperidin-1-yl-4-pyridin-4-yl-6-(2,4,5-trimethoxy-
phenyl)-pyrimidine (4d). Yield: 65%; mp 182–184 °C;
MS: 406 (M+1); IR (KBr) 2924, 1648, 1576, 1486,
1328, 1284 cmÀ1
;
1H NMR (CDCl3, 200 MHz) d
(ppm) 8.76 (d, 2H, J = 6.0 Hz), 7.94 (d, 2H,
J = 6.0 Hz), 7.74 (s, 1H), 7.68 (s, 1H), 6.60 (s, 1H),
3.96 (s, 3H, OMe), 3.98 (t, 4H, J = 4.4 Hz), 3.94 (s,
6H, 2OMe), 1.68 (t, 4H, J = 4.4 Hz); 13C (CDCl3,
50 MHz): 164.8, 162.8, 162.3, 154.4, 152.4, 150.8,
146.5, 143.8, 121.6, 118.8, 114.1, 106.8, 98.3, 57.2,
57.0, 56.6, 45.6, 26.4, 25.4. Anal. Calcd for
C24H27N3O3: calculated C: 71.09, H: 6.71, N: 10.36.
Found: C: 71.45, H: 6.43, N: 10.48.
6.3. General procedure for the synthesis of compounds
4a–i
To a solution of 1.0 equiv of piperidin-1-carboxamidine
hydrochloride in 50 mL of isopropanol, 1.1 equiv of so-
dium metal was added. The reaction mixture was re-
fluxed for 2 h and then different chalcones (1–9,
1.0 equiv) were added to it and refluxed for 8 h. The sol-
vent was removed from the reaction mixture under re-
duced pressure. Water was added and the aqueous
phase was extracted with chloroform and washed with
6.3.5. 2-Piperidin-1-yl-4-pyridin-4-yl-6-(3,4,5-trimethoxy-
phenyl)-pyrimidine (4e). Yield: 67%; mp 172–174 °C;
MS: 406 (M+1); IR (KBr) 2926, 1638, 1580, 1480,

4650
A. Agarwal et al. / Bioorg. Med. Chem. 13 (2005) 4645–4650
1
1325, 1272 cmÀ1; H NMR (CDCl3, 200 MHz) d (ppm)
8.76 (d, 2H, J = 6.1 Hz), 7.95 (d, 2H, J = 6.1 Hz), 7.34
(s, 1H), 7.26 (s, 2H), 4.01 (t, 4H, J = 4.6 Hz), 3.97 (s,
6H, OMe), 3.94 (s, 3H, OMe), 1.68 (t, 4H, J = 4.8 Hz);
13C (CDCl3, 50 MHz): 167.2, 162.8, 163.2, 154.1,
150.8, 145.4, 140.8, 134.6, 121.6, 105.1, 102.7, 60.8,
56.9, 45.6, 26.5, 25.4. Anal. Calcd for C24H27N3O3: cal-
culated C: 71.09, H: 6.71, N: 10.36. Found: C: 71.32, H:
6.38, N: 10.52.
Acknowledgments
A.A. thanks the Council of Scientific and Industrial Re-
search (India) for the award of Senior Research Fellow-
ship. We are also thankful to S.A.I.F. Division, CDRI,
Lucknow for providing spectroscopic data. CDRI com-
munication No. 6726.
References and notes
6.3.6. 2-Piperidin-1-yl-4-pyridin-4-yl-6-p-tolyl-pyrimidine
(4f). Yield: 72%; mp 144–146 °C; MS: 330 (M+1); IR
1. (a) National Institute of Allergy and Infectious Diseases
(NIAID). Global Health Research Plan for HIV/AIDS,
Malaria and Tuberculosis. World Health Organization:
Geneva, 2001; p 18(b) Kumar, A.; Katiyar, S. B.; Agarwal,
A.; Chauhan, P. M. S. Curr. Med. Chem. 2003, 10, 1137–
1150; (c) Shrivastava, S. K.; Chauhan, P. M. S. Curr. Med.
Chem. 2001, 8, 1535; (d) Kumar, A.; Katiyar, S. B.;
Agarwal, A.; Chauhan, P. M. S. Drugs Future 2003, 28, 243.
2. Butcher, G. A.; Sinden, R. E.; Curtis, C. Parasitol. Today
2000, 16, 43.
(KBr) 2936, 1642, 1578, 1488, 1324, 1284 cmÀ1 1H
;
NMR (CDCl3, 200 MHz) d (ppm) 8.73 (d, 2H,
J = 6.1 Hz), 8.01 (d, 2H, J = 7.9 Hz), 7.96 (d, 2H,
J = 6.1 Hz), 7.32 (s, 1H), 7.25 (d, 2H, J = 7.9 Hz), 3.99
(t, 4H, J = 4.2 Hz), 2.42 (s, 3H, Me), 1.70 (t, 4H,
J = 4.2 Hz); 13C (CDCl3, 50 MHz): 166.2, 162.9, 162.6,
150.8, 145.3, 141.2, 135.6, 129.8, 127.4, 121.5, 101.4,
45.3, 26.3, 25.4, 21.8. Anal. Calcd for C22H23N3: calcu-
lated C: 80.21, H: 7.04, N: 12.76. Found: C: 80.62, H:
7.34, N: 12.51.
3. Adams, J. H.; Wu, Y.; Fairfield, A. Parasitol. Today 2000,
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6.3.7.
4-(4-Methylsulfanyl-phenyl)-2-piperidin-1-yl-6-
5. Vilaivan, V.; Saesaengseerung, N.; Jarprung, D.; Kam-
chonwongpaisan, S.; Sirawarapornc, W.; Yuthavong, Y.
Bioorg. Med. Chem. 2003, 11, 217.
6. Rastelli, G.; Sirawaraporm, W.; Sompornpisut, P., et al.
Bioorg. Med. Chem. 2000, 8, 1117.
pyridin-4-yl-pyrimidine (4g). Yield: 71%; mp 166-
168 °C; MS: 362 (M+1); IR (KBr) 2948, 1636, 1584,
1486, 1325, 1265 cmÀ1 1H NMR (CDCl3, 200 MHz)
;
d (ppm) 8.74 (d, 2H, J = 6.0 Hz), 8.04 (d, 2H,
J = 8.4 Hz), 7.95 (d, 2H, J = 6.0 Hz), 7.36 (s, 1H),
7.32 (d, 2H, J = 8.4 Hz), 3.99 (t, 4H, J = 4.4 Hz),
1.69 (t, 4H, J = 4.4 Hz), 2.54 (s, 3H, SMe); 13C
(CDCl3, 50 MHz): 166.2, 163.4, 162.8, 150.8, 145.8,
142.6, 134.5, 127.7, 126.4, 121.4, 101.9, 45.6, 26.5,
25.4, 16.8. Anal. Calcd for C22H23N3S: calculated C:
73.09, H: 6.41, N: 11.62. Found: C: 73.84, H: 6.67,
N: 11.41.
7. Surolia, A.; Ramya, T. N. C.; Ramya, V.; Surolia, N.
Biochem. J. 2004, 383, 401.
8. (a) Batra, S.; Srivastava, P. J. Med. Chem. 2000, 43, 3428;
(b) Brinner, K. M.; Powles, M. A.; Schmatz, D. M.;
Ellman, J. A. Bioorg. Med. Chem. Lett. 2005, 15, 345; (c)
Stocks, P. A.; Raynes, K. J.; Bray, P. G.; Park, B. K.;
Neill, P. M.; Ward, S. A. J. Med. Chem. 2002, 45, 4975; (d)
Delarue, S.; Girault, S.; Maes, L., et al. J. Med. Chem.
2001, 44, 2827.
9. (a) Srivastava, S. K.; Chauhan, P. M. S.; Agarwal, S. K.;
Bhaduri, A. P.; Singh, S. N.; Fatima, N.; Chatterjee, R.
K.; Bose, C. Bioorg. Med. Chem. Lett. 1996, 6, 2623; (b)
Srivastava, S. K.; Agarwal, A.; Chauhan, P. M. S.;
Agarwal, S. K.; Bhaduri, A. P.; Singh, S. N.; Fatima, N.;
Chatterjee, R. K. J. Med. Chem. 1999, 42, 1667; (c)
Srivastava, S. K.; Agarwal, A.; Chauhan, P. M. S.;
Agarwal, S. K.; Bhaduri, A. P.; Singh, S. N.; Fatima, N.;
Chatterjee, R. K. Bioorg. Med. Chem. 1999, 7, 1223; (d)
Srivastava, S. K.; Chauhan, P. M. S.; Bhaduri, A. P.;
Fatima, N.; Chatterjee, R. K. J. Med. Chem. 2000, 43,
2275; (e) Tiwari, S.; Chauhan, P. M. S.; Bhaduri, A. P.;
Fatima, N.; Chatterjee, R. K. Bioorg. Med. Chem. Lett.
2000, 10, 1409.
10. (a) Agarwal, A.; Srivastava, K.; Puri, S. K.; Chauhan, P.
M. S. Bioorg. Med. Chem. Lett. 2005, 15, 531; (b)
Shrivastava, S.; Tiwari, S.; Chauhan, P. M. S.; Puri, S.
K.; Bhaduri, A. P.; Pandey, V. C. Bioorg. Med. Chem.
Lett. 1999, 9, 653; (c) Shrivastava, S.; Tiwari, S.; Shriv-
astava, S. K.; Chauhan, P. M. S.; Bhaduri, A. P.; Pandey,
V. C. Bioorg. Med. Chem. Lett. 1997, 7, 2741.
6.3.8. 4-(3,4-Dimethyl-phenyl)-2-piperidin-1-yl-6-pyridin-
4-yl-pyrimidine (4h). Yield: 66%; mp 160–162 °C; MS:
344 (M+1); IR (KBr) 2926, 1638, 1580, 1480, 1325,
1
1272 cmÀ1; H NMR (CDCl3, 200 MHz) d (ppm) 8.79
(d, 2H, J = 6.1 Hz), 7.97 (d, 2H, J = 6.1 Hz), 7.87 (s,
1H), 7.82 (d, 1H, J = 6.9 Hz), 7.42 (s, 1H), 7.23 (d,
1H, J = 6.9 Hz), 4.04 (t, 4H, J = 4.6 Hz), 2.36 (s, 3H),
2.33 (s, 3H), 1.71 (t, 4H, J = 4.6 Hz); 13C (CDCl3,
50 MHz): 166.2, 163.2, 162.8, 150.8, 145.9, 140.2,
137.4, 135.6, 130.5, 128.7, 125.0, 121.6, 102.8, 45.6,
26.5, 25.4, 20.4, 20.2. Anal. Calcd for C23H25N3: calcu-
lated C: 80.43, H: 7.34, N: 12.23. Found: C: 80.62, H:
7.49, N: 12.45.
6.3.9. 4-(4-Chloro-phenyl)-2-piperidin-1-yl-6-pyridin-4-
yl-pyrimidine (4i). Yield: 68%; mp 196-198 °C; MS:
351 (M+1); IR (KBr) 2948, 1636, 1584, 1486, 1325,
1265 cmÀ1
;
1H NMR (CDCl3, 200 MHz) d (ppm)
8.76 (d, 2H, J = 6.1 Hz), 8.04 (d, 2H, J = 8.1 Hz),
7.95 (d, 2H, J = 6.1 Hz), 7.47 (d, 2H, J = 8.1 Hz),
7.36 (s, 1H), 3.99 (t, 4H, J = 4.5 Hz), 1.70 (t, 4H,
J = 4.5 Hz). 13C (CDCl3, 50 MHz): 166.1, 162.8,
161.9, 159.1, 145.8, 135.2, 134.5, 130.4, 128.8, 121.4,
102.1, 45.5, 26.4, 25.4. Anal. Calcd for C21H20ClN3:
calculated C: 72.09, H: 5.76, N: 10.13. Found: C: 71.
82, H: 5.52, N: 10.42.
11. Marvel, C. S.; Coleman, L. E.; Scott, G. P., Jr. J. Org.
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