Synthesis and evaluation of naphthyridine compounds as antimalarial agents

Article abstract of DOI:10.1016/j.bmcl.2007.09.044

Primaquine is the drug of choice for the radical cure of Plasmodium vivax malaria, but possesses serious side effects. In this study novel primaquine analogues were designed and synthesized. Lower toxicity was achieved by reducing or eliminating the tendency of forming chemically reactive and toxic intermediates and metabolites. In vitro and in vivo studies found that synthesized compounds were less toxic than the parent compound primaquine, while preserving the desired antimalarial activity. Some of these compounds possess a therapeutic index over 10 times superior to that of the commonly used antimalarial drug chloroquine. These compounds, as well as the underlying design rationale, may find usefulness in the discovery and development of new antimalarial drugs.

Full text of DOI:10.1016/j.bmcl.2007.09.044

Available online at www.sciencedirect.com
Bioorganic & Medicinal Chemistry Letters 17 (2007) 6101–6106
Synthesis and evaluation of naphthyridine compounds
as antimalarial agents
Shuren Zhu,a,* Quan Zhang,a Chandrashekar Gudise,b Li Meng,a Lai Wei,a
Erika Smitha and Yuliang Kongc
aRadix Pharmaceuticals Inc., 880 College Pkwy, Rockville, MD 20850, USA
bIndian Institute of Chemical Technology, Tarnaka, Hyderabad 500 007, India
cInstitute of Materia Medica, Chinese Academy of Sciences, 555 Zu Chong Zhi Road, Shanghai 201203, China
Received 10 August 2007; revised 9 September 2007; accepted 12 September 2007
Available online 15 September 2007
Abstract—Primaquine is the drug of choice for the radical cure of Plasmodium vivax malaria, but possesses serious side effects. In
this study novel primaquine analogues were designed and synthesized. Lower toxicity was achieved by reducing or eliminating the
tendency of forming chemically reactive and toxic intermediates and metabolites. In vitro and in vivo studies found that synthesized
compounds were less toxic than the parent compound primaquine, while preserving the desired antimalarial activity. Some of these
compounds possess a therapeutic index over 10 times superior to that of the commonly used antimalarial drug chloroquine. These
compounds, as well as the underlying design rationale, may find usefulness in the discovery and development of new antimalarial
drugs.
ꢀ 2007 Elsevier Ltd. All rights reserved.
Malaria is the best known protozoal disease, caused by
one of four species of the sporazoa type—Plasmodium
falciparum, Plasmodium vivax, Plasmodium ovale, and
Plasmodium malariae. The malaria parasite has now be-
come resistant to the best antimalarial drugs, and can
now be found in at least 100 tropical and subtropical
countries. Worldwide, malaria infects 300–600 million
people and kills about three million in a year.1
modification of its chemical structure. Introduction of
4-methyl and 5-phenoxy5,6 or alkoxy groups7 have pro-
duced analogues with much superior tissue and blood
schizonticidal activity. However, toxicity studies have
shown that these analogues also have a greater potential
of producing methemoglobin.8 Tafenoquine (also
known as WR 238605) is a primaquine analogue and
is underdevelopment for the treatment of relapsing ma-
laria.9 However, tafenoquine would also cause hemoly-
sis in persons with G6PD deficiency, and must not be
used during pregnancy because of its potential effect
on the fetus.10 Therefore, further research in the discov-
ery and development of novel molecule entities as safe,
effective, and low cost replacement for primaquine is ur-
gently needed.
Primaquine (Fig. 1) is the drug of choice for the radical
cure of P. vivax malaria for over 40 years.2 Primaquine
mode of action could be based in the capacity of pri-
maquine to bind to the parasite’s DNA and modify its
properties.3 Primaquine, however, like all its predeces-
sors, is by no means non-oxic. Among the serious side
effects it could produce are acute hemolysis in patients
with certain types of glucose 6-phosphate dehydroge-
nase deficiency, methemoglobinemia, and severe gastro-
intestinal disturbances.4
Over the years, several attempts have been made to im-
prove the therapeutic index of primaquine through
Keywords: Primaquine; Antimalarial.
*
Corresponding author. Tel.: +1 301 675 3714; fax: +1 301 424
1927; e-mail: shuren.zhu@gmail.com
Figure 1.
0960-894X/$ - see front matter ꢀ 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2007.09.044

6102
S. Zhu et al. / Bioorg. Med. Chem. Lett. 17 (2007) 6101–6106
Early mechanistic studies of primaquine have estab-
lished that primaquine hemotoxicity was due to
metabolites of the drug, rather than the parent com-
pound. Phenolic metabolites of primaquine have been
identified in the biological fluids of experimental ani-
mals and have long been suggested as candidate
hemotoxic species.11–13 These compounds were shown
to induce a variety of oxidative effects in both normal
and G6PD-deficient red cells, including stimulation of
hexose monophosphate shunt activity, hemoglobin
oxidation, and glutathione depletion.14–16 Both
5-hydroxyprimaquine and 5-hydroxy-6-desmethylpri-
maquine are direct-acting hemolytic agents. These
mechanistic studies have suggested that 5-hydroxypri-
maquine forms a redox pair with its p-quinoneimine
analogue and that the 5,6-diphenolic metabolite forms
a redox pair with either an o-quinone or a p-quinonei-
mine. It has also been suggested that the hemotoxicity
of primaquine is associated with arylhydroxylamine
metabolites.17 Primaquine is known to undergo
N-dealkylation (oxidative deamination) in humans to
yield 6-methoxy-8-aminoquinoline (MAQ). It has been
concluded that MAQ could be converted to the corre-
sponding 8-hydroxylamino metabolite (i.e., MAQ–
NOH) and that this metabolite could be capable of
inducing methemoglobinemia and hemolytic damage
by forming a redox pair with its nitroso analogue.17
tion.18,19 Toxic phenolic metabolites arise when C-5
position of the quinoline ring becomes oxidized and
this process can be made unfavorable by blocking
the C-5 position of the quinoline ring. Naphthyridine
closely resembles quinoline, yet possesses higher oxida-
tion potential due to the introduction of the second
nitrogen on the aromatic system. Although a naph-
thyridine analogue of primaquine has previously been
synthesized,18,19 there was no systemic evaluation of
naphthyridine analogues of primaquine to date. (II)
Introducing a second substitution at the a position
of the aliphatic side chain so that oxidative deamina-
tion will be disfavored. These compounds (1–12) now
bear a dimethyl group at the a position, or the a po-
sition is part of a new cyclopropane unit. (III) Com-
pounds 7–12 also bear a substitution at position 2
of the aromatic ring. It has been reported that intro-
ducing an alkyl or alkoxy group at position 2 of the
aromatic ring reduces the toxicity of a compound
(induction of methemoglobin).20,21
Scheme 1 describes the synthesis of compound 1. Com-
pounds 2–6 were synthesized in similar routes. The syn-
thesis began with 6-methoxy-pyridin-3-ylamine (13).
Condensation of 13 with propane-1,2,3-triol under
strong acidic condition22 furnished 2-methoxy-[1,5]-
naphthyridine (14), which underwent oxidation with 3-
chloroperbenzoic acid to give 2-methoxy-[1,5]-naph-
thyridine 1-oxide (15). Compound 15 then reacted with
phosphorus(III) oxychloride,23 to furnish 4-chloro-2-
methoxy-[1,5]naphthyridine (16). After deprotonation
with sodium hydride, 2-(4-amino-4-methyl-pentyl)-iso-
indole-1,3-dione (17) reacted with compound 16 in a
SN2 type mode, which is followed by removal of the
protective group on the terminal amine, to furnish
N4-(2-methoxy-[1,5]naphthyridin-4-yl)-4-methyl-pentane-
1,4-diamine (1).24,25
As continued efforts in antimalarial drug discovery at
our laboratory, novel primaquine analogues were de-
signed and synthesized. These compounds (1–12) are
shown in Figure 2. Lower toxicity will be achieved
by reducing the tendency to form chemically reactive
and toxic intermediates and metabolites. To achieve
this goal, the following strategies are employed: (I)
Replacing the quinoline moiety with a [1,5]naphthyri-
dine core to prevent hydroxylation at C-5 posi-
Figure 2.

S. Zhu et al. / Bioorg. Med. Chem. Lett. 17 (2007) 6101–6106
6103
Scheme 1.
The synthesis of compounds 7–12 follows a different
route. Scheme 2 describes the synthesis of compound
7. Compounds 8–12 were synthesized in similar proce-
dures. Condensation of 3-amino-pyridine-2-carboxylic
acid ethyl ester (18) with diethyl malonate followed by
cyclization and decarboxylation afforded [1,5]-naph-
thyridine-2,4-diol (19), which then reacted with
phosphorus oxychloride to furnish 2,4-dichloro-[1,5]-
naphthyridine (20). Acid methanolysis of 20 gave
4-chloro-2-methoxy-[1,5]-naphthyridine (21) as the ma-
jor isomer and 2-chloro-4-methoxy-[1,5]naphthyridine
(22) as the minor one. The synthesis of 21 is a modified
method of McCaustland and Cheng19 Compound 7 was
then synthesized from intermediate 21, using the method
described above.26
ity (IC50 <= 0.11 lM), superior to that of chloroquine
(IC50 = 0.31 lM).
The target compounds were also evaluated for the
blood-schizontocidal antimalarial activity against
P. berghei (sensitive strain) and P. yoelii nigeriensis (mul-
tidrug-resistant strain) in a rodent model (Table 1),
using previously reported protocols.29
The objective of this investigation was to prepare less
toxic analogue of primaquine. As mentioned earlier, pri-
maquine and related metabolites are capable of inducing
methemoglobinemia and hemolytic damage. Therefore,
in vivo MetHb-inducing properties estimation of
compounds 1–12 was carried out in Mastomys coucha
(Table 2), a rodent animal model using previously
reported protocols.30 Primaquine was used as the stan-
dard drug for the test.
In vitro antimalarial activities of compounds 1–12 as
IC50 values for the inhibition of chloroquine-resistant
P. falciparum strain W2 were determined (Table 1),
using previously reported protocols.27,28 Most com-
pounds in this class exhibited potent antimalarial activ-
Replacing the quinoline moiety in primaquine with
1,5-naphthyridine clearly offers advantages. Primaquine
Scheme 2.

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S. Zhu et al. / Bioorg. Med. Chem. Lett. 17 (2007) 6101–6106
Table 1. In vitro (P. falciparum) and in vivo (P. berghei and P. yoelii nigeriensis) antimalarial studiesa
TIe
b
LD50 (mg/kg)
c
ED50 (mg/kg)
d
ED50 (mg/kg)
Compound
IC50 for P. falciparum W2 (lM)
1
0.065
0.077
0.11
130
155
1.8
2.1
72
163
2
0.95
0.33
1.6
0.89
0.28
1.4
3
167
145
506
91
4
0.057
0.072
0.10
5
161
175
0.88
0.29
1.6
1.0
183
603
6
0.38
2.0
7
0.033
0.021
0.045
0.058
0.047
0.055
>10
>200
>200
>200
>200
>200
>200
55
>125
>133
>278
>267
>645
>769
ND
35
8
1.5
1.7
9
0.72
0.75
0.31
0.26
ND
2.0
0.65
0.68
0.41
0.23
ND
ND
10
11
12
PQ
CQ
0.31
70
a Antimalarial activities were determined after ip administration of the compounds once daily for 4 days to infected mice. The first drug adminis-
tration began 1 h after ip inoculation with malarial strain. PQ, primaquine. CQ, chloroquine. ND, not determined.
b Acute toxicity was determined after one single drug injection into four non-infected random-bred Swiss mice and expressed as the 50% lethal dose
(LD50), which corresponds to the dose leading to deaths of 50% of the subjects 10 days after the drug injection.
c The 50% efficient dose (ED50), which is the dose leading to 50% parasite (P. berghei) growth inhibition compared to the control (treated with an
equal volume of vehicle), was evaluated from a plot of activity (expressed as a percentage of the control) versus the log dose.
d The parasite is P. yoelii nigeriensis.
e TI (therapeutic index) was calculated on the basis of the acute LD50/ED50 (P. berghei) ratios.
P. berghei (sensitive strain) and P. yoelii nigeriensis (mul-
tidrug-resistant strain). They were over three times less
toxic than the parent compound primaquine, as measured
by the in vivo LD50. These compounds did not show any
increase in MetHb, whereas primaquine induced 3.4% in-
crease in MetHb. Replacing the a,a-dimethyl group in
compounds 1–3 with a bioisosteric cyclopropyl group
gives compounds 4–6. This modification did not signifi-
cantly alter the efficacy and toxicity of a compound. How-
ever, introducing a substitution at position 2 of the
naphthyridine ring further reduces the toxicity, while pre-
serving the desired antimalarial activity.
Table 2. In vivo methemoglobin (MetHb) toxicity estimation in
Mastomys couchaa
Compound
% of MetHb
1
0.10
À0.12
À0.15
0.10
2
3
4
5
À0.12
À0.10
0.13
6
7
8
À0.11
À0.10
0.095
À0.12
0.14
9
10
11
12
Variation of the side chain substitution at the position 6
of the naphthyridine ring did not have profound effect
on their toxicity. However, an increase in the lipophilic-
ity of a compound has consequently improved the effi-
cacy. For example, when the methyl group in
compound 1 is replaced by the more lipophilic isopropyl
group as in compound 3, efficacy is increased by sixfold,
while toxicity is more or less flat.
PQ
Vehicle
3.4
À0.14
a Compound was administered at a dose of 15 mg/kg per day for 3
days. Data are means SEM for each group of animals (set of three
experiments). PQ, primaquine.
itself is not active against P. falciparum strains in vitro.
However, all new compounds (1–12) exhibited potent
in vitro antimalarial activity against chloroquine-resis-
tant P. falciparum strain W2. It is not clear why this ser-
ies of compounds are effective against P. falciparum
while primaquine, the compound on which the work is
based, is ineffective. It is believed that changing the
structure of the aromatic core of primaquine will change
the mode of action, hence rendering the compound ac-
tive in vitro against P. falciparum. Previous studies have
also found that analogues with an alkyl substitution at
position 2 of the aromatic ring possess in vitro antima-
larial activity against P. falciparum.21
In conclusion, new primaquine analogues were designed
and synthesized. Some of these compounds (3, 6, 11, 12)
possess a therapeutic index over ten times superior to
that of the commonly used antimalarial drug chloro-
quine. These compounds, as well as the underlying de-
sign rationale, may find usefulness in the discovery
and development of new antimalarial drugs.
Acknowledgments
This research was partially supported by a grant from
the National Institutes of Health (R44 AI063734 to
S.Z.). The content is solely the responsibility of the
authors and does not necessarily represent the official
views of the funding agency.
Compounds 1–12 have also shown excellent in vivo
blood-schizontocidal antimalarial activity against both

S. Zhu et al. / Bioorg. Med. Chem. Lett. 17 (2007) 6101–6106
6105
[1,5]naphthyridine (16). Compound 15 (600 mg) was
dissolved in 5 mL of phosphorus(III) oxychloride. The
resulting solution was heated at reflux for 2 h. It was
cooled, slowly poured into 6 N aqueous NaOH (200 mL)
with ice-water cooling, and extracted with ethyl acetate
(4· 60 mL). The combined organic extracts were concen-
trated and purified by silica gel flash chromatography (5%
methanol/chloroform, with 0.5% ammonia) to give 16. N4-
(2-Methoxy-[1,5]naphthyridin-4-yl)-4-methyl-pentane-1,4-
diamine (1). One hundred and sixty-five milligrams of
sodium hydride was suspended in 10 mL of anhydrous
N,N-dimethyl-formamide. It was cooled in an ice-water
bath. Six hunderd and sixty-five milligrams of 2-(4-amino-
4-methyl-pentyl)-isoindole-1,3-dione (17) was added in.
This solution was maintained at 0 ꢁC for 30 min. 1.2 g of
4-chloro-2-methoxy-[1,5]naphthyridine (16) was then
added in. The resulting solution was heated at 80 ꢁC for
2 h. At this time, condensation between 16 and 17 was
completed. The reaction mixture was quenched with the
addition of saturated aqueous sodium bicarbonate
(15 mL), and extracted with chloroform (3· 25 mL). The
combined chloroform extracts were concentrated, the
resulting oil was re-dissolved in 5 mL of methanol, and
1 mL of hydrazine is added in 2 h later, the reaction
mixture was partitioned between water (25 mL) and
chloroform (25 mL), aqueous layer was then further
extracted with chloroform (4· 20 mL). The combined
organic extracts were concentrated and purified by silica
gel flash chromatography (20% methanol/chloroform,
with 0.5% ammonia) to furnish 1.
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25. Newly synthesized compounds possess satisfactory spec-
troscopic and analytical data. Compound 1 (hydrochlo-
ride salt): mp 277–278 ꢁC. 1H NMR (D2O): 9.05 (d,
J = 7.2 Hz, 1H), 8.48 (d, J = 7.2 Hz, 1H), 7.63 (t,
J = 7.2 Hz, 1H), 6.67 (s, 1H), 4.11 (s, 3H), 2.85 (m, 2H),
1.84 (m, 2H), 1.64 (t, J = 5.8 Hz, 2H), 1.19 (s, 6H). 13C
NMR: 168.4, 160.2, 150.3, 148.9, 137.2, 127.6, 110.3,
105.7, 58.8, 52.1, 45.5, 43.6, 28.9, 27.1. Anal. Calcd for
C15H22N4OÆHCl: C, 57.96; H, 7.46; Cl, 11.41; N, 18.03.
Found: C, 57.88; H, 7.51; Cl, 11.37; N, 18.11. Compound
1
2 (hydrochloride salt): mp 285–286 ꢁC. H NMR (D2O):
9.08 (d, J = 7.1 Hz, 1H), 8.51 (d, J = 7.1 Hz, 1H), 7.59 (t,
J = 7.1 Hz, 1H), 6.72 (s, 1H), 4.33 (q, J = 7.5 Hz, 2H), 2.86
(m, 2H), 1.82 (m, 2H), 1.66 (t, J = 7.5 Hz, 3H), 1.62 (t,
J = 5.9 Hz, 2H), 1.20 (s, 6H). 13C NMR: 166.1, 161.8,
151.4, 147.4, 138.1, 127.9, 111.2, 107.5, 68.1, 53.2, 44.7,
43.1, 28.8, 26.2, 18.9. Anal. Calcd for C16H24N4OÆHCl: C,
59.16; H, 7.76; Cl, 10.91; N, 17.25. Found: C, 59.22; H,
7.71; Cl, 10.97; N, 17.31. Compound 3 (hydrochloride
salt): mp 291–292 ꢁC. 1H NMR (D2O): 9.11 (d, J = 7.3 Hz,
1H), 8.44 (d, J = 7.3 Hz, 1H), 7.67 (t, J = 7.3 Hz, 1H), 6.63
(s, 1H), 4.48 (m, 1H), 2.83 (m, 2H), 1.85 (m, 2H), 1.75 (d,
J = 7.7 Hz, 6H), 1.65 (t, J = 5.8 Hz, 2H), 1.11 (s, 6H). 13C
NMR: 169.1, 160.7, 149.8, 147.7, 138.0, 128.5, 109.4,
106.3, 73.5, 53.4, 44.9, 43.2, 29.0, 27.4, 23.9. Anal. Calcd
for C17H26N4OÆHCl: C, 60.25; H, 8.03; Cl, 10.46; N, 16.53.
Found: C, 60.33; H, 7.99; Cl, 10.50; N, 16.48. Compound
20. LaMontagne, M. P.; Blumbergs, P.; Smith, D. C. J. Med.
Chem. 1989, 32, 1728.
21. Jain, M.; Vangapandu, S.; Sachdeva, S.; Singh, S.; Singh,
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Jain, R. J. Med. Chem. 2004, 47, 285.
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Tetrahedron Lett. 2002, 43, 3747.
23. Paudler, W. W.; Pokorny, D. J.; Cornrich, S. J. J.
Heterocycl. Chem. 1970, 70, 291.
24. Synthesis procedure: 2-Methoxy-[1,5]naphthyridine (14).
12.4 g of 6-methoxy-pyridin-3-ylamine (13) and 18.4 g of
propane-1,2,3-triol were dissolved in 180 mL of methanol.
Sodium 3-nitrobenzenesulfonate (4.5 g) and sulfuric acid
(98%, 0.98 g) were added in. The resulting solution was
heated at 140 ꢁC in a sealed tube for 12 h. It was allowed
to cool down, and methanol was evaporated in a rotary
evaporator under reduced pressure to give a slurry, which
was re-dissolved in 100 mL of 6 N aqueous NaOH. The
resulting solution was continuously extracted with
chloroform. Concentration of the chloroform extracts
furnished 14 as essentially pure compound. 2-Methoxy-
[1,5]naphthyridine 1-oxide (15). Compound 14 (6.4 g) and
3-chloroperbenzoic acid (10.4 g) were dissolved in 150 mL
of chloroform. The resulting solution was heated at reflux
for 3 h. It was cooled, washed with 6 N aqueous NaOH
(50 mL), and dried over anhydrous sodium sulfate. Silica
gel flash chromatography (10% methanol/chloroform,
with 0.5% ammonia) furnished 15. 4-Chloro-2-methoxy-
1
4 (hydrochloride salt): mp 269–270 ꢁC. H NMR (D2O):
9.01 (d, J = 7.0 Hz, 1H), 8.43 (d, J = 7.0 Hz, 1H), 7.71 (t,
J = 7.0 Hz, 1H), 6.72 (s, 1H), 4.09 (s, 3H), 2.83 (m, 2H),
1.86 (m, 2H), 1.61 (t, J = 5.9 Hz, 2H), 0.41 (d, J = 5.1 Hz,
2H), 0.33 (d, J = 5.1 Hz, 2H). 13C NMR: 169.9, 162.1,
151.8, 148.1, 138.7, 127.1, 111.6, 104.9, 59.2, 46.8, 43.1,
39.8, 27.9, 12.1. Anal. Calcd for C15H20N4OÆHCl: C,
58.34; H, 6.85; Cl, 11.48; N, 18.14. Found: C, 58.41; H,
6.82; Cl, 11.43; N, 18.21. Compound 5 (hydrochloride
salt): mp 274–275 ꢁC. 1H NMR (D2O): 9.06 (d, J = 7.2 Hz,
1H), 8.49 (d, J = 7.2 Hz, 1H), 7.66 (t, J = 7.2 Hz, 1H), 6.78
(s, 1H), 4.35 (q, J = 7.4 Hz, 2H), 2.81 (m, 2H), 1.82 (m,

6106
S. Zhu et al. / Bioorg. Med. Chem. Lett. 17 (2007) 6101–6106
2H), 1.68 (t, J = 7.4 Hz, 3H), 1.62 (t, J = 5.9 Hz,2H), 0.40
C17H24N4O2ÆHCl: C, 57.87; H, 7.14; Cl, 10.05; N, 15.88.
Found: C, 57.91; H, 7.11; Cl, 10.11; N, 15.94. Compound
10 (hydrochloride salt): mp 276–277 ꢁC. H NMR (D2O):
(d, J = 5.2 Hz, 2H), 0.34 (d, J = 5.2 Hz, 2H). 13C NMR:
168.3, 161.7, 152.4, 147.3, 139.1, 128.4, 113.1, 106.1, 69.2,
47.3, 42.7, 38.5, 28.1, 19.5, 12.4. Anal. Calcd for
C16H22N4OÆHCl: C, 59.53; H, 7.18; Cl, 10.98; N, 17.35.
Found: C, 59.60; H, 7.14; Cl, 10.89; N, 17.41. Compound
1
8.58 (d, J = 6.8 Hz, 1H), 7.38 (d, J = 6.8 Hz, 1H), 6.25 (s,
1H), 4.39 (q, J = 7.2 Hz, 2H), 2.84 (m, 2H), 1.91 (m, 2H),
1.71 (t, J = 7.2 Hz, 3H), 1.69 (t, J = 5.6 Hz, 2H), 0.42 (d,
J = 5.3 Hz, 2H), 0.32 (d, J = 5.3 Hz, 2H). 13C NMR:
169.1, 161.1, 158.8, 150.9, 148.1, 138.3, 126.7, 119.7, 108.2,
68.4, 44.3, 40.9, 38.1, 27.6, 19.1, 12.9. Anal. Calcd for
C17H21F3N4OÆHCl: C, 52.24; H, 5.67; Cl, 9.07; F, 14.58;
N, 14.34. Found: C, 52.27; H, 5.63; Cl, 9.12; F, 14.51; N,
14.41. Compound 11 (hydrochloride salt): mp 290–291 ꢁC.
1H NMR (D2O): 8.51 (d, J = 6.9 Hz, 1H), 7.29 (d,
J = 6.9 Hz, 1H), 6.25 (s, 1H), 4.52 (m, 1H), 4.29 (s, 3H),
2.81 (m, 2H), 1.91 (m, 2H), 1.78 (d, J = 7.4 Hz, 6H), 1.69
(t,J = 5.8 Hz, 2H), 0.38 (d, J = 5.4 Hz, 2H), 0.30 (d,
J = 5.4 Hz, 2H). 13C NMR: 170.2, 164.8, 159.1, 151.2,
148.7, 138.9, 117.8, 106.2, 72.7, 61.9, 45.4, 40.5, 38.1, 27.8,
22.8, 12.2. Anal. Calcd for C18H26N4O2ÆHCl: C, 58.93; H,
7.42; Cl, 9.66; N, 15.27. Found: C, 58.88; H, 7.45; Cl, 9.63;
N, 15.33. Compound 12 (hydrochloride salt): mp 283–
284 ꢁC. 1H NMR (D2O): 8.69 (d, J = 7.1 Hz, 1H), 7.31 (d,
J = 7.1 Hz, 1H), 6.29 (s, 1H), 4.59 (m, 1H), 2.80 (m, 2H),
1.87 (m, 2H), 1.72 (d, J = 7.3 Hz, 6H), 1.63 (t, J = 5.8 Hz,
1
6 (hydrochloride salt): mp 279–280 ꢁC. H NMR (D2O):
9.11 (d, J = 7.3 Hz, 1H), 8.40 (d, J = 7.3 Hz, 1H), 7.67 (t,
J = 7.3 Hz, 1H), 6.62 (s, 1H), 4.43 (m, 1H), 2.91 (m, 2H),
1.89 (m, 2H), 1.71 (d, J = 7.5 Hz, 6H), 1.67 (t, J = 5.7 Hz,
2H), 0.38 (d, J = 5.2 Hz, 2H), 0.31 (d, J = 5.2 Hz, 2H). 13
C
NMR: 168.3, 162.6, 150.9, 148.7, 137.8, 127.5, 111.9,
105.6, 72.6, 48.1, 44.2, 38.3, 28.2, 22.7, 13.2. Anal. Calcd
for C17H24N4OÆHCl: C, 60.61; H, 7.48; Cl, 10.52; N, 16.63.
Found: C, 60.54; H, 7.52; Cl, 10.48; N, 16.71.
26. Newly synthesized compounds possess satisfactory spec-
troscopic and analytical data. Compound 7 (hydrochlo-
ride salt): mp 286–287 ꢁC. 1H NMR (D2O): 8.63 (d,
J = 6.9 Hz, 1H), 7.18 (d, J = 6.9 Hz, 1H), 6.37 (s, 1H), 4.34
(s, 3H), 4.15 (s, 3H), 2.81 (m, 2H), 1.91 (m, 2H), 1.67 (t,
J = 5.9 Hz, 2H), 1.22 (s, 6H). 13C NMR: 170.3, 167.3,
159.1, 150.9, 148.6, 138.4, 119.7, 107.3, 60.4, 58.5, 52.9,
44.3, 42.5, 28.6, 26.9. Anal. Calcd for C16H24N4O2ÆHCl: C,
56.38; H, 7.39; Cl, 10.40; N, 16.44. Found: C, 56.32; H,
7.41; Cl, 10.42; N, 16.39. Compound 8 (hydrochloride
salt): mp 278–279 ꢁC. 1H NMR (D2O): 8.54 (d, J = 7.1 Hz,
1H), 7.42 (d, J = 7.1 Hz, 1H), 6.29 (s, 1H), 4.17 (s, 3H),
2.87 (m, 2H), 1.84 (m, 2H), 1.64 (t, J = 5.7 Hz, 2H), 1.20
(s, 6H). 13C NMR: 168.5, 160.4, 158.3, 151.2, 147.2, 139.1,
124.3, 118.7, 106.9, 59.2, 52.4, 43.9, 41.8, 29.1, 26.7. Anal.
Calcd for C16H21F3N4OÆHCl: C, 50.73; H, 5.85; Cl, 9.36;
F, 15.05; N, 14.79. Found: C, 50.81; H, 5.82; Cl, 9.29; F,
15.14; N, 14.82. Compound 9 (hydrochloride salt): mp
284–285 ꢁC. 1H NMR (D2O): 8.58 (d, J = 7.1 Hz, 1H),
7.22 (d, J = 7.1 Hz, 1H), 6.31 (s, 1H), 4.38 (q, J = 7.3 Hz,
2H), 4.27 (s, 3H), 2.86 (m, 2H), 1.86 (m, 2H), 1.72 (t,
J = 7.3 Hz, 3H), 1.65 (t, J = 5.9 Hz, 2H), 0.41 (d,
J = 5.3 Hz, 2H), 0.32 (d, J = 5.3 Hz, 2H). 13C NMR:
169.8, 166.5, 159.4, 150.7, 149.3, 138.6, 118.4, 106.8, 69.9,
61.3, 44.9, 41.9, 37.7, 26.5, 19.2, 11.7. Anal. Calcd for
2H), 0.35 (d, J = 5.4 Hz, 2H), 0.29 (d, J = 5.4 Hz, 2H). 13
C
NMR: 169.9, 162.4, 157.9, 152.1, 149.4, 137.1, 128.3,
118.5, 107.1, 71.9, 45.0, 40.3, 39.2, 27.1, 22.2, 12.3. Anal.
Calcd for C18H23F3N4OÆHCl: C, 53.40; H, 5.98; Cl, 8.76;
F, 14.08; N, 13.84. Found: C, 53.44; H, 5.95; Cl, 8.82; F,
14.02; N, 13.90.
27. Desjardins, R. E.; Canfield, C. J.; Haynes, D. E.;
Chulay, J. D. Antimicrob. Agents Chemother. 1979, 16,
710.
28. Chulay, J. D.; Haynes, J. D.; Diggs, C. L. Exp. Parasitol.
1983, 55, 138.
29. Vangapandu, S.; Sachdeva, S.; Jain, M.; Singh, S.; Singh,
P. P.; Kaul, C. L.; Jain, R. Bioorg. Med. Chem. 2003, 11,
4557.
30. Srivastava, P.; Singh, S.; Jain, G. K.; Puri, S. K.; Pandey,
V. C. Ecotoxicol. Environ. Saf. 2000, 45, 236.