Synthesis, antiprotozoal, antimicrobial, β-hematin inhibition, cytotoxicity and methemoglobin (MetHb) formation activities of bis(8-aminoquinolines)

Article abstract of DOI:10.1016/j.bmc.2010.11.036

In continuing our search of potent antimalarials based on 8-aminoquinoline structural framework, three series of novel bis(8-aminoquinolines) using convenient one to four steps synthetic procedures were synthesized. The bisquinolines were evaluated for in vitro antimalarial (Plasmodium falciparum), antileishmanial (Leishmania donovani), antimicrobial (a panel of pathogenic bacteria and fungi), cytotoxicity, β-hematin inhibitory and methemoglobin (MetHb) formation activities. Several compounds exhibited superior antimalarial activities compared to parent drug primaquine. Selected compounds (44, 61 and 79) when tested for in vivo blood-schizontocidal antimalarial activity (Plasmodium berghei) displayed potent blood-schizontocial activities. The bisquinolines showed negligible MetHb formation (0.2-1.2%) underlining their potential in the treatment of glucose-6-phosphate dehydrogenase deficient patients. The bisquinoline analogues (36, 73 and 79) also exhibited promising in vitro antileishmanial activity, and antimicrobial activities (43, 44 and 76) against a panel of pathogenic bacteria and fungi. The results of this study provide evidence that bis(8-aminoquinolines), like their bis(4-aminoquinolines) and artemisinin dimers counterparts, are a promising class of antimalarial agents.

Full text of DOI:10.1016/j.bmc.2010.11.036

Bioorganic & Medicinal Chemistry 19 (2011) 197–210
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
Synthesis, antiprotozoal, antimicrobial, b-hematin inhibition, cytotoxicity
and methemoglobin (MetHb) formation activities of bis(8-aminoquinolines)
Kirandeep Kaur a, Meenakshi Jain a, Shabana I. Khan c,d, Melissa R. Jacob c, Babu L. Tekwani c,e, Savita Singh b,
Prati Pal Singh b, Rahul Jain a,
⇑
a Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research, Sector 67, S. A. S. Nagar, Punjab 160 062, India
b Department of Pharmacology and Toxicology, National Institute of Pharmaceutical Education and Research, Sector 67, S. A. S. Nagar, Punjab 160 062, India
c National Center for Natural Products Research, School of Pharmacy, University of Mississippi, MS 38677, USA
d Department of Pharmacognosy, School of Pharmacy, University of Mississippi, MS 38677, USA
e Department of Pharmacology, School of Pharmacy, University of Mississippi, MS 38677, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
In continuing our search of potent antimalarials based on 8-aminoquinoline structural framework, three
series of novel bis(8-aminoquinolines) using convenient one to four steps synthetic procedures were
synthesized. The bisquinolines were evaluated for in vitro antimalarial (Plasmodium falciparum), antile-
ishmanial (Leishmania donovani), antimicrobial (a panel of pathogenic bacteria and fungi), cytotoxicity,
b-hematin inhibitory and methemoglobin (MetHb) formation activities. Several compounds exhibited
superior antimalarial activities compared to parent drug primaquine. Selected compounds (44, 61 and
79) when tested for in vivo blood-schizontocidal antimalarial activity (Plasmodium berghei) displayed
potent blood-schizontocial activities. The bisquinolines showed negligible MetHb formation (0.2–1.2%)
underlining their potential in the treatment of glucose-6-phosphate dehydrogenase deficient patients.
The bisquinoline analogues (36, 73 and 79) also exhibited promising in vitro antileishmanial activity,
and antimicrobial activities (43, 44 and 76) against a panel of pathogenic bacteria and fungi. The results
of this study provide evidence that bis(8-aminoquinolines), like their bis(4-aminoquinolines) and arte-
misinin dimers counterparts, are a promising class of antimalarial agents.
Received 22 September 2010
Revised 16 November 2010
Accepted 16 November 2010
Available online 25 November 2010
Keywords:
Malaria
8-Aminoquinolines
Bisquinolines
Primaquine
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
cose-6-phosphate dehydrogenase (G6PD) deficiency.7 PQ is also
known to have poor pharmacokinetic properties with a short half
Malaria is a serious parasitic disease, which ranks third among
the major infectious diseases in causing deaths after pneumococcal
acute respiratory infections, and tuberculosis. Approximately 1.5–
2.5 million people die of malaria every year, accounting for about
5% of all fatalities in the world.1 The uncontrolled and irrational
use of existing blood-schizontocidal (for example, chloroquine)
and limited use of newer blood-schizontocidal antimalarials (for
example, artemisinin and its derivatives) has limited the clinical
options to treat malaria.2 The 8-aminoquinolines exemplified by
primaquine (PQ, 1, Fig. 1) display activity against all four species
of Plasmodium that infect human. PQ, a tissue schizontocidal anti-
malarial, is the only clinical drug available for the treatment of
relapsing cases of malaria. Although PQ is effective against all life
cycle stages of human malaria parasite, its use is often associated
with serious adverse effects as a consequence of its toxic metabo-
lites.3–6 Its clinical use as a tissue-schizontocide is limited by side
effects such as severe hematotoxicities in patients with the glu-
life of 4–6 h.8 It has been shown that in rodents, the PQ is rapidly
metabolized, and two major metabolites start appearing in the
blood in about 30 min, one of which has been identified as 4-(6-
methoxyquinolin-8-ylamino)pentanoic acid (carboxyprimaquine,
2, Fig. 1), a product also reported by the microbiological degrada-
tion of PQ.9 The modulation of PQ structure has resulted in less
toxic and promising blood-schizontocides.3,9,10 We have recently
shown that appropriate substitution on the quinoline ring and on
the side-chain results in the PQ analogues exhibiting promising
antimicrobial and antileishmanial activities, in addition to potent
antimalarial activities.11–17
The dimers of known antimalarial agents has been an area of ac-
tive interest. For example, a number of bis(4-aminoquinolines)18–21
and bis-artemisinins22–24 are known to display activities superior
to their monomeric counterparts. Superior activity of the artemis-
inin dimers is attributed to their dual functionality and increased
number of peroxide linkage, which is essential for expression of
activity. The higher efficacy of the bis(4-aminoquinolines) against
chloroquine resistant parasites is explained by the greater number
of protonation sites compared with the chloroquine resulting in
⇑
Corresponding author. Tel.: +91 172 229 2024; fax: +91 172 221 4692.
E-mail address: rahuljain@niper.ac.in (R. Jain).
0968-0896/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2010.11.036

198
K. Kaur et al. / Bioorg. Med. Chem. 19 (2011) 197–210
O
O
O
O
O
N
N
N
C(CH3)3
NH2
N
NH
NH
NH
NH
NH2
NH2
CO2H
1
2
3
4
Figure 1. 8-Aminoquinolines.
their accumulation to a higher degree in the face of a decreased
pH gradient in the chloroquine resistant parasites. Although,
dimers of 4-aminquinolines and artemisinin are extensively inves-
tigated, the potential of bis(8-aminoquinolines) in antimalarial
drug discovery is not fully explored. Blanton et al. reported the
synthesis of varied chain length amino group containing dimeric
8-aminoquinolines; however, all analogues were inactive as
blood-schizontocides.25,26
2. Results and discussion
2.1. Chemistry
We have earlier observed that the cationic amino acid conju-
gates of 8-aminoquinolines exhibit promising biological activi-
ties.14 The 8-aminoquinolines conjugated to Lys, Arg, and Orn
provide two free amino groups (a- and side-chain NH2 or guani-
The importance of dimers in 4-aminoquinoline and artemisinin
classes prompted us to examine the unexplored potential of bis(8-
aminoquinolines) in antimalarial chemotherapy. The synthesis of
bis(8-aminoquinolines) can be justified due to following facts: (i)
It is known that rapid metabolism of 8-aminoquinolines results
in the removal of side-chain amino group to yield inactive metab-
olites, including 2. We believe that the side-chain primary amino
group present as an amide or secondary amine in the synthesized
bis(8-aminoquinolines) could prevent metabolic degradation
resulting in increased activity; (ii) due to increase in steric bulk,
the bis(8-aminoquinolines) are expected to penetrate less into
the red blood cell that may not allow destabilization of red cell
membrane inducing hemolysis, the main cause of toxicity. Thus,
synthesis of bis(8-aminoquinolines) appears to be an attractive
strategy to develop analogues with improved blood-schizontocidal
activity and reduced MetHb toxicity. We report herein, synthesis,
detailed antiprotozoal, and antimicrobial activities of bis(8-amino-
quinolines) linked through their side-chain using a set of linkers,
including amino acids.
dino group), which can be manipulated to synthesize a series of
bis(8-aminoquinolines). In order to maintain the structural simi-
larity with earlier reported monomers,14 conjugates of 8-amino-
quinolines were coupled through their free
a-NH2 group with PQ
(1), and 2-tert-butylprimaquine (3, Fig. 1) to obtain bis(8-amino-
quinolines) linked through cationic amino acids (35–44, Scheme 1).
The starting material, PQ (1) was obtained commercially, while its
analogues, 3 and (4-ethyl-5-pentyloxy)primaquine (4, Fig. 1) were
synthesized following previously published procedure.12,13 The
reaction of 1 or 3 with suitably orthogonally protected
acids in the presence of 1,3-diisopropylcarbodiimide (DIC) readily
provided - and side-chain NH2 protected amino acid conjugates
5–14. Depending upon its nature, -NH2 protecting group in 5–
D/L-amino
a
a
14 was removed under acidic or basic conditions to afford 15–24.
The compounds 15–24 upon coupling reaction with 1 or 3 in the
presence of 1,10-carbonyldiimidazole (CDI) afforded protected
bis(8-quinolinmaines) 25–34. The side-chain amino protecting
groups in the compounds 25–34 were removed by either acidolysis
or hydrogenolysis to afford desired bis(8-aminoquinolines) 35–44.
O
O
O
N
R
N
R
i
N
R
ii
NH
NH
R1
R1
NH
81-92%
74-79%
H
N
H
N
NH2
NHFmoc/Boc
NH2
O
O
1.
3.
R = H
R = C(CH3)3
5-14
15-17, 21, 22.
18, 20, 23, 24.
R1 = L-Lys(Z)/Arg(Z)2/Orn(Z)
D
= -Lys(Boc)/Orn(Boc)
R1
R1 = L-Lys(Z)/Orn(Z)/Arg(Z)2
R1 = D-Lys(Boc)/Orn(Boc)/Arg(Pmc)
19. R1 = D-Arg(Pmc)
64-85% iii
O
O
O
O
N
R
N
R
NH
R1
O
N
R
NH
R2
O
N
R
H
N
3
H
N
3
NH
NH
iv
N
H
N
H
N
H
N
H
3
3
78-97%
O
O
25-34
35-44
R = H/C(CH3)3
2 = Lys/Arg/Orn
R1 = Lys(Boc)/Lys(Z)/Arg(Z)2/Arg(Pmc)/
R
Orn(Z)/Orn(Boc)
Scheme 1. Reagents and conditions: (i) DIC, Fmoc/Boc-NH–CH(R1)–CO2H, DCM, 0 °C–rt, 4 h; (ii) 4 N HCl in MeOH, rt, 45 min, 20% NH4OH or 20% piperidine in DCM, 20 min,
rt; (iii) CDI, 1 or 3, DCM, rt, 5 h; (iv) Pd–C/H2, MeOH, rt, 4 h or 4 N HCl in MeOH, rt, 45 min or 8 N HCl in MeOH, rt, 8 h.

K. Kaur et al. / Bioorg. Med. Chem. 19 (2011) 197–210
199
The anionic amino acids, Asp and Glu contain three groups, which
provide suitable functionalities for the synthesis of bis(8-amino-
quinolines). We have earlier observed that the presence of free
NH2 group in the side-chain is essential for the activity of 8-amino-
quinolines.14 Therefore, in this series we decided to synthesize
bis(8-aminoquinolines) (60–64, Scheme 2) by first coupling
tivities of the electrophile, temperature range varying from 0 °C to
70 °C and reaction time of 3 h to 24 h was used. The coupling
reactions with 1,10-carbonyldiimidazole (CDI), 1,10-thiocarbonyldi-
imidazole (TCDI), bis(2-chloroethyl)amine and 2,6/3,4/3,5-pyridin-
edicarbonyl chloride were carried out at ambient temperature. The
electrophiles like N-(chlorocarbonyl)isocyanate, chloromethyl
chloroformate, oxalyl chloride and chlorocarbonylsulfenyl chloride
gave products at 0 °C; while, condensation reaction using chloro-
acetic acid was achieved in THF at 70 °C.
8-aminoquinolines with Asp or Glu residues through their
group followed by linking another molecule of 8-aminoquinolines
to the side-chain b/ -CO2H group. The coupling reaction of 1 or 3
with suitable orthogonally protected -amino acids using DIC
a-CO2H
c
D/L
afforded 45–49. The benzyl ester or tert-butyl ester group in com-
pounds 45–49 was cleaved using Pd–C/H2 or acidolysis to provide
analogues 50–54. The latter compounds, 50–54 upon coupling reac-
tion with 1 or 3 using DIC provided side-chain protected analogues
55–59. The t-Boc group in compounds 55–58 was removed by acid-
olysis to provide 60–63, while Fmoc group in the compound 59 was
cleaved with a 20% solution of piperidine to give analogue 64.
We also report one-pot synthesis of bis(8-aminoquinolines) 66–
85 attached via both aliphatic and aromatic linkers to examine
their effect on the antimalarial activity (Scheme 3). The bisquino-
lines 66–85 were obtained by covalent attachment of 1, 3 and 4
through the linker at the side-chain primary amino group. The
8-aminoquinolines 1, 3 and 4 upon reaction with various electro-
philes 65 either under neat conditions in the presence of excess tri-
ethylamine (Et3N), or in anhydrous tetrahydrofuran (THF), or
dichloromethane (DCM) in the presence of catalytic Et3N afforded
analogues 66–85 in good yields. Depending upon the relative reac-
2.2. Antimalarial activity, cytotoxicity, inhibition of b-hematin
(BH) and MetHb formation
Determination of in vitro antimalarial activity was based on the
assay of plasmodial LDH activity.27 The antimalarial activities of all
synthesized analogues are reported as IC50 values against chloro-
quine-sensitive (D6) and chloroquine-resistant (W2) strains of
Plasmodium falciparum in Tables 1–3.
The bis(8-aminoquinolines) 35–44 linked through amino acids
(Series 1) were active against both strains of plasmodium, except
41. Among the series, 44 [R = C(CH3)3, R1 = D-Orn] was the most ac-
tive and exhibited IC50 values of 0.34 and 0.30
and W2 strains, respectively. While, analogue 43 showed IC50 of
1.6 and 1.3 g/mL against D6 and W2 strains, respectively. The
IC50 values of remaining analogues were in the range of 2.4–
4.2 g/mL for D6 strain and 1.5–3.2 g/mL for W2 strain. The
lg/mL against D6
l
l
l
bis(8-aminoquinolines) 60–64 (Series 2) were less active with
O
O
O
N
R
N
R
N
R
i
CO2Bn
COOH
n
NH
ii
NH
NH
H
N
H
N
n
NH2
70-90%
87-95%
NHR1
NHR1
O
O
1. R = H
45-48.
50-53.
R
R1 = Boc
1 = Boc
PQ-D-COCH2CH(CO2H)NHFmoc
3.
R = C(CH3)3
49. PQ-D-COCH2CH(CO2tBu)NHFmoc
54.
81-88%
iii
O
O
O
O
N
R
N
R
HN
HN
N
R
O
O
N
R
NHR1
NH2
H
N
H
N
iv
NH
NH
N
H
N
H
3
3
n
3
3
n
74-92%
O
O
55-59
R1 =Boc/Fmoc
60-64
R = H/C(CH3)3, n = 1 or 2
Scheme 2. Reagents and conditions: (i) DIC, R1NH–CHCOOH(CH2)n–CO2Bn, DCM, 0 °C–rt, 4 h; (ii) Pd–C/H2, MeOH, rt, 4 h or 6 N HCl, rt, 5 h, 20% NH4OH; (iii) DIC, 1 or 3, DCM,
0 °C–rt, 4 h; (iv) 4 N HCl in MeOH, rt, 45 min or 20% piperidine in DCM, rt, 20 min.
R
R1
N
R
R1
N
R
R1
N
O
O
O
R2
R2
R2
i
NH
NH
+
NH
Y
Y
H
N
H
N
X
NH2
7-70%
X
65
66-85
1.
R = R1 = R2 = H
3. R = R1 = H, R2 = C(CH3)3
4. R = OC5H11, R1 = C2H9, R2 = H
X = Linker
Y = Cl / CO2H / NCO or N
N
Scheme 3. Reagents and conditions: (i) Et3N, 0–70 °C, 4–24 h or Et3N, 0–70 °C, THF/CH2Cl2, 4–24 h or CH2Cl2, rt, 24 h.

200
K. Kaur et al. / Bioorg. Med. Chem. 19 (2011) 197–210
Table 1
In vitro antimalarial activity (P. falciparum), cytotoxicity, b-hematin (BH) inhibition, methemoglobin (MetHb) formation and in vitro antileishmanial activity (L. donovani) of bis(8-
aminoquinolines) (35–44) (Series 1)
O
O
N
R
N
R
NH
R1
O
H
N
3
NH
N
H
N
H
3
O
Cytotoxicity
(Vero)
MetHb toxicity
(% MetHb formation
at 20 lg/mL)
L. donovani
P. falciparum (D6)
IC50 g/mL)
2.7
3.2
2.8
3.6
2.4
4.2
NA
4.0
1.6
0.34
2.0
P. falciparum (W2)
IC50 g/mL)
2.7
1.8
2.0
2.8
1.5
2.8
BH inhibition
Compd No.
R
R1
(
l
(l
IC50
(
lg/mL)
IC50
(
lM)
IC50
(l
g/mL)
IC90
>40
(lg/mL)
35
36
37
38
39
40
41
42
43
44
PQ
H
H
H
H
H
H
Lys
Arg
Orn
Lys
Arg
Orn
Lys
Orn
Lys
Orn
(
(
(
(
(
(
(
(
(
(
L
L
L
)
)
)
)
)
)
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
80
90
88
162
88
154
>1000
152
45
10.8
>1000
3.75
3.1
7.9
2.8
5.5
6.10
1.1
0.2
18
3.1
14
18.5
19
18
19
18
21
20
7.2
40
D
D
D
36
36
39
38
33
36
34
C(CH3)3
C(CH3)3
C(CH3)3
C(CH3)3
L)
NA
L)
3.2
1.3
0.3
2.8
D
)
)
2.25
2.3
10
D
19.9
NA
IC50 and IC90 are the sample concentration that kills 50% and 90% cells compared to vehicle control. NC, not cytotoxic up to 10
IC50 = 0.014 g/mL (D6 clone); IC50 = 0.1 g/mL, (W2 clone). Artemisinin: IC50 = 0.015 g/mL (D6 clone); IC50 = 0.009 g/mL (W2 clone). BH inhibition activity: Chloroquine:
IC50 = 80 M, BPQ: IC50 = 2.9 M, PQ: IC50 >1000 M. Antileishmanial activity: Pentamidine: IC50 = 1 g/mL, IC90 = 3.8 g/mL. Amphotericin B: IC50 = 0.19 g/mL,
g/mL.
lg/mL. NA, not active. Chloroquine:
l
l
l
l
l
l
l
l
l
l
IC90 = 0.35
l
Table 2
In vitro antimalarial activity (P. falciparum), cytotoxicity, b-hematin (BH) inhibition, methemoglobin (MetHb) formation and in vitro antileishmanial activity (L. donovani) of bis(8-
aminoquinolines) (60–64) (Series 2)
O
O
N
R
NH
N
R
O
NH2
H
N
3
NH
N
H
3
n
O
MetHb toxicity
(% MetHb formation
at 20 lg/mL)
L. donovani
P. falciparum (D6) P. falciparum (W2) Cytotoxicity (Vero) BH inhibition
Compd No.
R
n
IC50
(l
g/mL)
IC50
(
lg/mL)
IC50
(
lg/mL)
IC50
(lM)
IC50
(l
g/mL) IC90 (lg/mL)
60
61
62
63
64
PQ
H
H
1
2
1
2
1
(
(
(
(
(
L
L
L
L
)
)
)
)
4.76
2.7
NA
4.7
3.3
2.0
3.8
2.2
3.2
2.3
3.6
2.8
NC
NC
NC
NC
NC
NC
185
85
140
>1000
120
>1000
5.4
13.35
1.55
3.3
7.25
10
6.2
16
15
3.9
11.5
19.9
30
35
33
10.7
31
C(CH3)3
C(CH3)3
H
D
)
NA
IC50 and IC90 are the sample concentration that kills 50% and 90% cells compared to vehicle control. NC, not cytotoxic up to 10
IC50 = 0.014 g/mL (D6 clone); IC50 = 0.1 g/mL (W2 clone). Artemisinin: IC50 = 0.015 g/mL (D6 clone); IC50 = 0.009 g/mL (W2 clone). BH inhibition activity: Chloroquine:
IC50 = 80 M, BPQ: IC50 = 2.9 M, PQ: IC50 >1000 M. Antileishmanial activity: Pentamidine: IC50 = 1 g/mL, IC90 = 3.8 g/mL. Amphotericin B: IC50 = 0.19 g/mL,
IC90 = 0.35 g/mL.
lg/mL. NA, not active. Chloroquine:
l
l
l
l
l
l
l
l
l
l
l
IC50 values in the range of 2.7–4.76
3.8 g/mL (W2 strain).
In Series 3, the most promising analogue 84, a bisquinoline
derivative linked through pyridine-3,4-dicarbonyl linker displayed
IC50 of 1.5 g/mL for D6 clone and 0.87 g/mL for W2 clone. Ana-
logues 70 and 73 showed IC50 of 1.7 and 1.5 g/mL for D6 clone,
respectively, and 1.3 g/mL for W2 clone. While, analogue 79, dis-
played IC50 of 2.6 g/mL, and 1.5 g/mL for D6 and W2 strains,
respectively. Remaining analogues were also active (IC50 values
in the range of 1.7–4.76 lg/mL) with the exception of 41, 62, 71–
72, 75, 77–78, and 83.
In vitro cytotoxicity of all the analogues was determined against
mammalian kidney cell line (Vero) up to a highest concentration of
l
g/mL (D6 strain) and 2.2–
10 l
g/mL by neutral red assay.28,29 None of the compounds were
l
found cytotoxic indicating a selectivity of antimalarial action.
Blocking heme detoxification is one of the main mechanism of
antimalarial action of quinolines, and we have recently reported
that potent blood-schizontocidal antimalarial activity of 3 is possi-
bly due to its inhibition of heme crystallization.30 In another re-
port, effects of amino acids on the formation of b-hematin (BH)
was investigated, and results showed that BH formation was signif-
icantly inhibited by basic amino acids due to their abilities to com-
plex with heme.31 Therefore, synthesized bisquinolines were
assayed for inhibition of BH formation according to a procedure re-
ported earlier.32 Analogue 44 (Series 1) inhibited BH formation
l
l
l
l
l
l
with a lower IC50 value (10.8 lM) in comparison to several other

Table 3
In vitro antimalarial activity (P. falciparum), cytotoxicity, b-hematin (BH) inhibition, methemoglobin (MetHb) formation and in vitro antileishmanial activity (L. donovani) of bis(8-aminoquinolines) (66–85) (Series 3)
R
R
R
R1
1
O
O
N
R2
N
R2
NH
NH
H
N
H
N
X
Compd No.
R
R1
R2
X
P. falciparum (D6)
P. falciparum (W2)
Cytotoxicity (Vero)
BH Inhibition
IC50 M)
MetHb toxicity (% MetHb
formation at 20 lg/mL)
L. donovani
g/mL) IC90 (lg/mL)
IC50
(l
g/mL)
IC50
(l
g/mL)
IC50
(lg/mL)
(
l
IC50
(l
66
67
68
69
70
71
72
73
74
75
76
77
78
79
H
H
H
H
H
H
H
H
C2H5
C2H5
H
H
H
H
H
H
H
H
H
CO
CS
CO
CS
CO
CS
COCH2
COCH2
CONHCO
CONHCO
COOCH2
COS
4.76
2.3
3.0
3.0
1.7
NA
NA
1.5
4.76
NA
2.6
NA
NA
2.6
4.76
2.4
3.7
2.3
1.3
4.76
NA
1.3
3.4
NA
2.7
4.76
NA
1.5
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
>1000
>1000
>1000
>1000
80
>1000
>1000
75
155
>1000
101
153
>1000
180
9.8
3.7
1.0
0.75
4.7
1.7
20.3
1.1
2.25
8.8
NA
4
NA
9
NA
20
NA
31
C(CH3)3
C(CH3)3
H
H
OC5H11
OC5H11
3.5
40
20
2.9
NA
25
20
20
15
2.99
7
NA
NA
7.8
NA
>40
38
38
>40
27
H
H
H
H
H
H
H
H
H
C(CH3)3
H
C(CH3)3
H
H
H
H
5.3
10.9
6.45
8.4
COCO
CH2CH2NHCH2CH2
H
80
81
H
H
H
H
H
H
2.2
3.0
2.3
1.7
NC
NC
123
108
5.7
6.5
NA
NA
NA
N
O
O
N
3.55
O
O
N
82
83
84
H
H
H
H
H
H
H
3.3
NA
1.5
3.0
NC
NC
NC
110
5.5
18
NA
16
NA
NA
31
O
O
O
O
C(CH3)3
C(CH3)3
4.5
>1000
0.25
1.2
N
N
0.87
70
O
O
N
85
H
H
C(CH3)3
2.7
2.0
1.8
2.8
NC
NC
120
0.55
10
19
NA
NA
O
O
PQ
>1000
19.9
IC50 and IC90 are the sample concentration that kills 50% and 90% cells compared to vehicle control. NC, not cytotoxic up to 10
IC50 = 0.009 g/mL (W2 clone). BH inhibition activity: Chloroquine: IC50 = 80 M, BPQ: IC50 = 2.9 M, PQ: IC50 >1000
l
g/mL. NA, not active. Chloroquine: IC50 = 0.014
l
g/mL (D6 clone); IC50 = 0.1
l
g/mL (W2 clone). Artemisinin: IC50 = 0.015
lg/mL (D6 clone);
l
l
l
l
M. Antileishmanial activity: Pentamidine: IC50 = 1
l
g/mL, IC90 = 3.8
lg/mL. Amphotericin B: IC50 = 0.19
l
g/mL, IC90 = 0.35 g/mL.
l

202
K. Kaur et al. / Bioorg. Med. Chem. 19 (2011) 197–210
Table 4
In vivo (P. berghei) antimalarial activity of selected bis(8-aminoquinolines)
Compd No.
P. berghei
(10 mg/kg/day ꢀ 4, oral)
(25 mg/kg/day ꢀ 4, oral)
(50 mg/kg/day ꢀ 4, oral)
(100 mg/kg/day ꢀ 4, oral)
36
37
43
44
61
62
63
66
68
74
76
79
PQ
–
ꢁ
(0/6) Inactive
(6/6) Curative
(0/6) Inactive
(5/6) Suppressive
(6/6) Curative
(6/6) Curative
(0/6) Inactive
(0/6) Inactive
(0/6) Inactive
(0/6) Inactive
(0/6) Inactive
(5/6) Suppressive
(6/6) Curative
(0/6) Inactive
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
(5/6) Suppressive
(6/6) Curative
(6/6) Curative
(4/6) Suppressive
(6/6) Curative
(6/6) Curative
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
(3/6) Suppressive
(6/6) Curative
(6/6) Curative
ꢁ
ꢁ
ꢁ
The term ‘curative’ indicates complete elimination of malaria parasites from the body and animals survive up to day D+60. The term ‘suppressive’ indicates that all of the
treated animals show negative parasitemia up to D+7. However, by D+60, some mice die, and some survive with complete elimination of parasitemia as indicated by numbers
given in parentheses. The term ‘inactive’ indicates that the treated animals show positive parasitemia either on D+4 or D+7 and usually die by D+14. ‘‘ꢁ’’, not tested.
analogues of the series (IC50 values ranging between 45 and
162 M). The compounds 60–64 of the Series 2 inhibited BH for-
mation with IC50 values in the range of 85–185 M. Among bis-
quinolines 66–85 of Series 3, analogues 70, 73 and 84 displayed
IC50 values of 80, 75 and 70 M, respectively compared to IC50 of
80 M for standard drug chloroquine (Tables 1–3). It has been pro-
posed that pKa of the side chain amino function contributes sub-
stantially to antimalarial activity of chloroquine. Therefore, it is
possible that reduced basicity of these bisquinolines due to de-
creased pKa values is responsible for moderate b-hematin
inhibition.
Several bisquinolines of Series 3 also exhibited antileishmanial
activities to a considerable extent (Table 3). Of these analogues,
70, 73 and 79 were most potent with IC50 values of 3.5, 2.9, and
l
l
2.99
pared to the IC50 of 1
drug, pentamidine. The analogues 67, and 69 were also promising
(IC50 = 4–9 g/mL and IC90 = 20–31 g/mL).
l
g/mL and IC90 of 7.0, 7.8, and 27
l
g/mL, respectively, com-
l
lg/mL and IC90 of 3.8
lg/mL for standard
l
l
l
2.4. Antimicrobial activities
The bisquinolines were also tested for their antibacterial prop-
erties against Staphylococcus aureus, methicillin-resistant S. aureus
ATCC 43300 (MRSA), Mycobacterium intracellulare ATCC 23068,
Escherichia coli ATCC 35218, and Pseudomonas aeruginosa ATCC
27853. Susceptibility testing is performed using a modified version
of the CLSI (formerly NCCLS) methods.36–40 M. intracellulare is
tested using a modified method of Franzblau et al.41 None of the
analogues were active against E. coli and P. aeruginosa (data not
shown). Analogues 43 and 44 were active against S. aureus. Their
Hematotoxicity by 8-aminoquinolines is caused due to their
metabolism to the toxic metabolites, which are unstable and diffi-
cult to isolate. The synthesized analogues were also tested for
metabolism-linked methemoglobin (MetHb) toxicity in vitro and
% MetHb formation was calculated at 20 lg/mL of the test com-
pound, in comparison to vehicle control.33 A number of analogues
showed lower MetHb formation (Series 1: 0.2–7.9%, Series 2: 1.55–
13.35%, and Series 3: 0.25–20.3%) compared to PQ (10%) as shown
in Tables 1–3. Analogues 42 (Series 1), 62 (Series 2), 68, 69, 83, and
85 (Series 3) induced substantially lower MetHb formation (0.2–
1.2%) than others, including standard drug, PQ.
IC50 values were 1.78–2.73
activity at 5 g/mL, for both strains of S. aureus. Analogues 36–42
also possessed moderate activity against MRSA with IC50 values
in the range of 6.5–15 g/mL and MIC of 20 g/mL. All were bacte-
ricidal at 20 g/mL, except analogues 38 and 40. The activities
were also observed against M. intracellulare with 36, 42, 43, and
44 (IC50 ranged between 7.12 and 15 g/mL, MIC = 20 g/mL, and
MBC = 20 g/mL, for analogue 36). The bis(8-aminoquinolines) of
Series 2 were also active against MRSA; 62 and 63 being most ac-
tive with IC50 values of 6.5 and 8.5 g/mL, MIC of 10 and 20 g/mL,
respectively, and bactericidal at 20 g/mL. The analogues of Series
lg/mL and they showed a bactericidal
l
Selected analogues were evaluated in vivo for the blood-schiz-
ontocidal antimalarial activity against Plasmodium berghei (sensi-
tive strain) in a rodent malaria model using procedure described
earlier (Table 4).12 The analogues 44, 61 and 79 exhibited signifi-
cantly high activity and cured 100% mice at a dose of 25 mg/kg,
and were suppressive at the lowest tested dose of 10 mg/kg. The
l
l
l
l
l
l
PQ dimer, 36, linked through
L-Arg was curative at 100 mg/kg,
l
l
while analogues 43 and 76 were suppressive at the same concen-
tration with 5/6 mice surviving on day 60. Remaining of the tested
analogues 37, 62, 63, 66, 68, and 74 were inactive at the highest
test dose of 100 mg/kg.
l
3 also exhibited antibacterial activity against MRSA with the
exception of 79. Of these, 67, 71 and 84 were bactericidal
(IC50 = 3–15
lg/mL, MIC = 5–20 lg/mL, and MBC = 10–20 lg/mL).
Analogue 67 also exhibited promising activity against M. intracellu-
2.3. Antileishmanial activities
lare (IC50, MIC and MBC of 4.5, 10 and 20 lg/mL, respectively)
(Table 5).
The antileishmanial activities of the bisquinolines were evalu-
ated in vitro against Leishmania donovani promastigotes by Alamar
The antifungal activities of the bis(8-aminoquinolines) against
the opportunistic fungi Candida albicans ATCC 90028, Cryptococcus
neoformans ATCC 90113, and Aspergillus fumigatus ATCC 90906,
along with the positive control amphotericin B are reported in
Blue assay.34,35 From Series 1, 36 (R = H, R1 =
L
-Arg) exhibited better
g/mL, and IC90 = 7.2 g/mL)
compared to other compounds of the series (IC50 in the range of
14–21 g/mL, and IC90 in the range of 33–40 g/mL) as shown in
Table 1. Among the analogues of Series 2, 60 (R = H, n = 1) and 63
[R = C(CH3)3, n = 2] were more active (IC50 = 6.2 and 3.9 g/mL
and IC90 = 30 and 10.7 g/mL, respectively) than others (Table 2).
antileishmanial activity (IC50 = 3.1
l
l
Table 6. All compounds were inactive at 20 lg/mL against Candida
l
l
glabrata, Candida krusei, and A. fumigatus (data not shown). The
bis(8-aminoquinolines) of all three series showed activities against
C. neoformans to a variable extent and were found to be fungicidal
except 67 (Table 6). The bis(8-aminoquinolines) 60, 61, and 62
l
l

K. Kaur et al. / Bioorg. Med. Chem. 19 (2011) 197–210
203
Table 5
In vitro antibacterial activities of bis(8-aminoquinolines)
Compd No.
S. aureus
MIC ( g/mL)
MRSA
M. intracellulare
IC50
(l
g/mL)
l
MBC (
l
g/mL)
IC50
(lg/mL)
MIC (lg/mL)
MBC (lg/mL)
IC50
(l
g/mL)
MIC (
lg/mL)
MBC (lg/mL)
36
38
39
40
41
42
43
44
60
61
62
63
64
67
70
71
73
79
84
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
5
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
5
15
10
15
10
20
20
20
20
20
20
5
20
NA
20
NA
20
20
5
15
20
20
ꢁ
NA
NA
NA
NA
15
7.12
10.05
20
NA
NA
NA
NA
20
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
20
ꢁ
ꢁ
ꢁ
8
ꢁ
6.5
1.97
1.78
15
2.58
2.73
ꢁ
20
20
5
5
5
5
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
20
20
10
20
NA
5.0
20
5.0
20
NA
20
NA
NA
20
20
NA
10
NA
10
NA
NA
20
NA
20
NA
NA
20
10
NA
20
ꢁ
15
15
ꢁ
6.5
8.5
15
3.0
8.5
3.5
15
NA
NA
15
4.5
NA
15
15
10
NA
ꢁ
ꢁ
ꢁ
ꢁ
NA
NA
NA
20
ꢁ
ꢁ
NA
20
NA
ꢁ
NA
15
ꢁ
NA
IC50 = the concentration (
growth). MBC, minimum bactericidal concentration (the lowest concentration in
l
g/mL) that affords 50% growth inhibition. MIC, minimum inhibitory concentration (the lowest concentration in
l
g/mL that allows no detectable
g/mL that kills the organism). ‘‘ꢁ’’ not tested. NA, no activity at the highest test con-
g/mL, MBC = 50 g/mL (Sa); IC50 = 0.09 g/mL, MIC = 0.31 g/mL, MBC = 2.5 g/mL (MRSA);
l
centration of 20
lg/mL. Ciprofloxacin: IC50 = 0.12
l
g/mL, MIC = 0.50
l
l
l
l
l
IC50 = 0.3
l
g/mL, MIC = 0.63 g/mL, MBC = 2.5 g/mL (Mi).
l
l
Table 6
lines) produced promising antimalarial activity in vitro against
drug-sensitive and drug-resistant strains of P. falciparum, and po-
tent activity in the rodent malaria model in vivo. The inhibition
of b-hematin formation by bisquinolines, although moderate, indi-
cated it as a plausible pathway of their antimalarial activity. The
metHb formation was observed for a considerably lower extent
by several analogues compared to PQ, thereby offering new ave-
nues for the treatment of patients suffering from severe hemato-
toxicities due to the deficiency of cytosolic enzyme G6PD. The
most promising analogue 44 not only produced promising
in vitro and in vivo antimalarial activity but also exhibited promis-
ing in vitro antimicrobial activities. Analogues 36, 70 and 73 exhib-
ited best antileishmanial activities, while analogue 76 exhibited
highest antifungal activity (against C. neoformans). The combina-
tion of broad spectrum of activities without any cytotoxic effects
to the mammalian cells added to substantially reduced MetHb for-
mation capabilities makes bis(8-aminoquinolines) as a promising
new structural class of compounds.
In vitro antifungal activities of bis(8-aminoquinolines)
Compd No.
C. albicans
C. neoformans
IC50
g/mL)
MIC
MFC
g/mL)
IC50
g/mL)
MIC
MFC
(lg/mL)
(
l
(
lg/mL)
(
l
(
l
(
lg/mL)
36
37
38
39
40
42
43
44
60
61
62
67
71
76
79
NA
NA
NA
NA
NA
15
17.86
>20
NA
NA
NA
10
NA
NA
NA
NA
NA
NA
20
NA
NA
NA
NA
20
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
6.5
15
10
15
7
15
6.45
9.97
7.5
15
10
10
20
20
20
10
20
10
20
10
20
20
NA
20
5
10
20
20
20
10
20
10
20
10
20
20
NA
20
5
15
10
4.5
15
10
NA
NA
20
NA
NA
20
20
IC50 = the concentration (
inhibitory concentration (the lowest concentration in
detectable growth). MFC, minimum fungicidal concentration (the lowest concen-
tration in g/mL that kills the organism). NA, no activity at the highest test con-
centration of 20 g/mL. Amphotericin B: IC50 = 0.25 g/mL, MIC = 0.63 g/mL,
MFC = 1.25 g/mL (Ca); IC50 = 0.75 g/mL, MIC = 1.25 g/mL, MFC = 1.5 g/mL (Cn).
l
g/mL) that affords 50% growth inhibition. MIC, minimum
l
g/mL that allows no
3. Experimental
l
3.1. Material and methods
l
l
l
l
l
l
l
The synthesized bisquinolines were checked for their purity on
pre-coated silica gel G254 TLC plates (Merck) and the spots were
visualized under UV light and by exposing them to iodine vapors.
Column chromatographic purification was carried out on Merck
silica gel (100–200 mesh). Melting points were recorded on a cap-
illary melting point apparatus and are uncorrected. All solvents
used for synthesis were of analytical grade and used without any
further purification unless otherwise stated. 1H and 13C NMR spec-
tra were recorded on a 300 MHz Bruker FT-NMR (Avance DPX 300)
spectrometer using tetramethylsilane as internal standard and the
chemical shifts are reported in d units. Mass spectra were recorded
on a Finnigan Mat LCQ spectrometer (APCI/ESI). Elemental analyses
were recorded on Elementar Vario EL spectrometer. The elemental
analyses of all final compounds were within 0.4% of the expected
values, unless otherwise stated. All reagents were purchased from
Aldrich Chemicals Ltd.
(Series 2) showed moderate activity against C. neoformans. The
analogue 60 produced IC50 value of 7.5 g/mL, and MIC and MFC
values of 10 g/mL; while, analogues 61 and 62 exhibited the
IC50 values of 15 and 10 g/mL, respectively, and were fungicidal
at 20 g/mL. Among the bis(8-aminoquinolines) of Series 3, ana-
logues 67, 71, 76 and 79 were active against C. neoformans with
IC50 values ranging between 4.5 and 15 g/mL. The promising ana-
logue 76 exhibited IC50 of 4.5 g/mL, MIC of 5 g/mL, and was also
fungicidal at 5 g/mL.
l
l
l
l
l
l
l
l
2.5. Conclusions
We have synthesized three series of bisquinolines based upon
8-aminoquinolines structural framework. The bis(8-aminoquino-

204
K. Kaur et al. / Bioorg. Med. Chem. 19 (2011) 197–210
3.2. General method for the synthesis of protected bis(8-
quinolinamines) (25–34)
6H), 3.70 (m, 2H), 3.36 (m, 6H), 1.91 (m, 14H), 1.57 (s, 9H), 1.41
(m, 6H); 13C NMR (CDCl3): d 173.7, 158.8, 156.8, 145.4, 144.8,
135.8, 135.4, 122.4, 97.3, 92.1, 81.2, 55.7, 54.2, 48.3, 48.2, 40.7,
39.7, 34.5, 34.3, 32.7, 32.4, 30.1, 28.9, 27.4, 26.6, 23.2, 21.0; MS
(APCI): m/z 773 (M+1); Anal. Calcd for C42H60N8O6 (772.4): C,
65.26; H, 7.82; N, 14.50. Found: C, 65.34; H, 7.74; N, 14.63.
A mixture of 15–24 (0.58 mmol) and CDI (0.64 mmol) in anhy-
drous CH2Cl2 (5 mL) was stirred at ambient temperature for
30 min. At that time, TLC showed the absence of starting material.
8-aminoquinoline (1 or 3, 0.58 mmol) was added and the reaction
mixture was stirred for another 5 h. The reaction mixture was di-
luted with CH2Cl2 (20 mL) and washed with water (3 ꢀ 10 mL) fol-
lowed by brine solution (5 mL). The organic layer was dried
(Na2SO4) and concentrated to afford crude product. Purified by col-
umn chromatography on silica gel (100–200 mesh) using 1.5%
CH3OH in CH2Cl2 to give 25–34 as viscous oil.
3.2.5. N-{4-[(6-methoxyquinolin-8-yl)amino]pentyl}-N2-({4-[(6-
methoxyquinolin-8-yl)amino]pentyl}carbamoyl)-N5-{N-[(2,2,5,
7,8-pentamethyl-3,4-dihydro-2H-chromen-6-yl)sulfonyl]
carbamimidoyl}-
L-ornithinamide (29)
Yield: 64%; oil; IR (CH2Cl2): 3031, 1665, 1386 cmꢁ1
;
1H NMR
(CDCl3): d 8.72 (br s, 2H), 8.42 (d, 2H, J = 2.8 Hz), 7.84 (d, 2H,
J = 7.8 Hz), 7.22 (dd, 2H, J = 2.8 and 7.8 Hz), 6.25 (d, 2H,
J = 2.1 Hz), 6.18 (d, 2H, J = 2.1 Hz), 5.62 (br s, 2H), 4.25 (t, 1H,
J = 6.4 Hz), 3.91 (s, 6H), 3.50 (m, 2H), 3.21 (m, 6H), 2.49 (m, 11H),
1.72 (m, 12H), 1.21 (m, 12H); 13C NMR (CDCl3): d 172.1, 158.3,
156.6, 155.4, 152.6, 143.8, 134.4, 134.1, 133.8, 128.9, 123.1,
120.8, 117.0, 95.8, 90.7, 54.1, 46.7, 43.9, 39.6, 38.5, 32.9, 31.7,
25.7, 25.0, 24.5, 24.1, 23.2, 20.3, 19.3, 17.5, 16.4; MS (ESI): m/z
989.1 (M+23); Anal. Calcd for C51H70N10O7S (966.5): C, 63.33; H,
7.29; N, 14.48. Found: C, 63.24; H, 7.35; N, 14.65.
3.2.1. Benzyl{(5R)-6-({4-[(6-methoxyquinolin-8-yl)amino]
pentyl}amino)-5-[({4-[(6-methoxy-quinolin-8-yl)amino]
pentyl}carbamoyl)amino]-6-oxohexyl}carbamate (25)
Yield: 85%; oil; IR (CH2Cl2): 3338, 1696 cmꢁ1 1H NMR (CDCl3):
;
d 8.51 (d, 2H, J = 4.4 Hz), 7.89 (d, 2H, J = 8.1 Hz), 7.30 (m, 7H), 6.87
(br s, 2H), 6.32 (m, 2H), 6.25 (m, 2H), 6.02 (br s, 2H), 5.05 (s, 2H),
4.96 (br s, 2H), 4.17 (t, 1H, J = 5.1 Hz), 3.87 (s, 6H), 3.55 (m, 2H),
3.26 (m, 6H), 1.61 (m, 14H), 1.25 (d, 6H, J = 6.0 Hz); 13C NMR
(CDCl3): d 174.8, 159.4, 156.4, 144.9, 144.3, 136.6, 135.3, 129.8,
128.4, 128.0, 121.8, 96.7, 91.6, 66.5, 55.2, 54.9, 51.9, 47.8, 42.1,
40.6, 34.6, 29.6, 23.4, 22.7, 20.5; MS (ESI): m/z 807 (M+1); Anal.
Calcd for C45H58N8O6 (806.5): C, 66.97; H, 7.24; N, 13.89. Found:
C, 67.07; H, 7.15; N, 13.73.
3.2.6. tert-Butyl{(4S)-5-({4-[(6-methoxyquinolin-8-yl)amino]
pentyl}amino)-4-[({4-[(6-methoxyquinolin-8-yl)amino]
pentyl}carbamoyl)amino]-5-oxopentyl}carbamate (30)
Yield: 71%; oil; IR (CH2Cl2): 3436, 1681 cmꢁ1 1H NMR (CDCl3):
;
d 8.51 (m, 2H), 7.91 (m, 2H), 7.30 (m, 2H), 6.32 (m, 2H), 6.24 (m,
2H), 4.31 (t, 1H, J = 6.1 Hz), 3.86 (s, 6H), 3.51 (m, 2H), 3.16 (m,
6H), 1.75 (m, 12H), 1.38 (s, 9H), 1.28 (m, 6H); 13C NMR (CDCl3): d
172.3, 159.2, 157.8, 145.6, 143.8, 135.3, 135.0, 122.7, 97.2, 92.1,
80.8, 55.7, 54.2, 48.8, 48.2, 40.6, 38.8, 34.7, 32.8, 32.4, 30.1, 28.9,
27.4, 23.6, 23.2, 21.0; MS (APCI): m/z 759 (M+1); Anal. Calcd for
3.2.2. Benzyl(N0-[(benzyloxy)carbonyl]-N-{(4R)-5-({4-[(6-
methoxyquinolin-8-yl)amino]pentyl}amino)-4-[({4-[(6-
methoxyquinolin-8-yl)amino]pentyl}carbamoyl)amino]-5-
oxopentyl}carbamimidoyl)carbamate (26)
Yield: 77%; oil; IR (CH2Cl2): 3436, 1693 cmꢁ1 1H NMR (CDCl3):
;
d 9.32 (br s, 2H), 8.49 (d, 2H, J = 4.1 Hz), 7.87 (d, 2H, J = 8.5 Hz), 7.31
(m, 12H), 6.83 (br s, 2H), 6.35 (m, 2H), 6.28 (m, 2H), 5.98 (br s, 2H),
5.11 (s, 2H), 5.09 (s, 2H), 5.02 (br s, 2H), 4.27 (t, 1H, J = 5.8 Hz), 3.86
(s, 6H), 3.62 (m, 2H), 3.22 (m, 6H), 1.69 (m, 12H), 1.30 (d, 6H,
J = 6.5 Hz); 13C NMR (CDCl3): d 171.2, 160.1, 159.6, 156.8, 144.9,
143.9, 135.6, 134.8, 129.9, 128.8, 128.5, 127.9, 122.2, 120.5, 96.8,
92.1, 65.7, 55.1, 47.9, 45.8, 41.3, 39.7, 39.2, 33.7, 32.8, 28.3, 25.2,
21.7; MS (APCI): m/z 969 (M+1); Anal. Calcd for C53H64N10O8
(968.4): C, 65.68; H, 6.66; N, 14.45. Found: C, 65.75; H, 6.72; N,
14.32.
C41H58N8O6 (758.4): C, 64.88; H, 7.70; N, 14.76. Found: C, 64.75;
H, 7.64; N, 14.81.
3.2.7. Benzyl{(5R)-6-({4-[(2-tert-butyl-6-methoxyquinolin-8-
yl)amino]pentyl}amino)-5-[({4-[(2-tert-butyl-6-methoxyquino-
lin-8-yl)amino]pentyl}carbamoyl)amino]-6-oxohexyl}carba-
mate (31)
Yield: 80%; oil; IR (CH2Cl2): 3436, 1691 cmꢁ1 1H NMR (CDCl3):
;
d 7.85 (d, 2H, J = 8.5 Hz), 7.42 (d, 2H, J = 8.5 Hz), 7.37 (m, 5H), 6.29
(d, 2H, J = 1.5 Hz), 6.24 (d, 2H, J = 1.5 Hz), 5.07 (s, 2H), 4.11 (t, 1H,
J = 6.0 Hz), 3.85 (s, 6H), 3.51 (m, 2H), 3.22 (m, 6H), 1.84 (m, 14H),
1.41 (s, 18H), 1.28 (d, 6H, J = 6.2 Hz); 13C NMR (CDCl3): d 173.8,
163.8, 159.3, 158.8, 158.4, 157.2, 145.4, 137.1, 135.5, 134.1,
129.0, 128.6, 128.5, 128.0, 119.3, 97.1, 91.9, 67.0, 57.4, 55.6, 54.2,
48.4, 48.3, 41.0, 40.8, 39.9, 38.2, 34.6, 32.8, 30.8, 29.9, 29.7, 27.4,
26.4, 23.1, 21.1; MS (APCI): m/z 919 (M+1); Anal. Calcd for
3.2.3. Benzyl{(4R)-5-({4-[(6-methoxyquinolin-8-yl)amino]
pentyl}amino)-4-[({4-[(6-methoxyquinolin-8-yl)amino]
pentyl}carbamoyl)amino]-5-oxopentyl}carbamate (27)
Yield: 79%; oil; IR (CH2Cl2): 3338, 1695 cmꢁ1 1H NMR (CDCl3):
;
d 8.52 (d, 2H, J = 4.2 Hz), 7.92 (d, 2H, J = 8.6 Hz), 7.34 (m, 7H), 6.70
(br s, 2H), 6.31 (m, 2H), 6.25 (m, 2H), 5.95 (br s, 2H), 5.11 (s, 2H),
4.78 (br s, 1H), 4.68 (br s, 1H), 4.30 (t, 1H, J = 5.3 Hz), 3.88 (s,
6H), 3.53 (m, 2H), 3.21 (m, 4H), 3.14 (t, 2H, J = 5.9 Hz), 1.78–1.53
(m, 12H), 1.32 (d, 6H, J = 6.3 Hz); 13C NMR (CDCl3): d 173.0,
159.4, 159.3, 156.5, 144.9, 144.4, 135.8, 135.3, 134.8, 129.9,
122.0, 121.8, 96.7, 92.1, 91.6, 65.2, 55.1, 47.9, 40.8, 40.3, 33.8,
33.7, 31.2, 30.9, 28.3, 26.0, 20.7; MS (APCI): m/z 793 (M+1); Anal.
Calcd for C44H56N8O6 (792.3): C, 66.64; H, 7.12; N, 14.13. Found:
C, 66.58; H, 7.24; N, 14.27.
C53H74N8O6 (918.5): C, 69.25; H, 8.11; N, 12.19. Found: C, 69.33;
H, 8.20; N, 12.05.
3.2.8. Benzyl{(4R)-5-({4-[(2-tert-butyl-6-methoxyquinolin-8-
yl)amino]pentyl}amino)-4-[({4-[(2-tert-butyl-6-methoxyquin-
olin-8-yl)amino]pentyl}carbamoyl)amino]-5-
oxopentyl}carbamate (32)
Yield: 77%; oil; IR (CH2Cl2): 3385, 1663 cmꢁ1 1H NMR (CDCl3):
;
d 7.85 (d, 2H, J = 8.5 Hz), 7.41 (d, 2H, J = 8.5 Hz), 7.29 (m, 5H), 6.54
(br s, 2H), 6.29 (d, 2H, J = 2.7 Hz), 6.23 (d, 2H, J = 2.7 Hz), 6.09 (br s,
2H), 5.85 (br s, 1H), 5.04 (s, 2H), 4.87 (br s, 1H), 3.85 (s, 6H), 3.54
(m, 2H), 3.20 (m, 7H), 1.61 (m, 12H), 1.40 (s, 18H), 1.28 (m, 6H);
13C NMR (CDCl3): d 172.8, 163.4, 163.3, 158.8, 158.7, 144.8,
139.2, 134.9, 133.5, 128.4, 128.0, 127.4, 118.7, 114.0, 96.6, 91.4,
66.6, 55.1, 53.1, 47.9, 47.6, 40.0, 39.3, 37.6, 34.0, 33.7, 31.6, 30.2,
29.6, 29.3, 29.1, 28.9, 26.7, 25.9, 22.6, 20.6; MS (MALDI): m/z 905
3.2.4. tert-Butyl{(5S)-6-({4-[(6-methoxyquinolin-8-yl)amino]
pentyl}amino)-5-[({4-[(6-methoxyquinolin-8-yl)amino]
pentyl}carbamoyl)amino]-6-oxohexyl}carbamate (28)
Yield: 75%; oil; IR (CH2Cl2): 3334, 1705, 1665 cmꢁ1 1H NMR
;
(CDCl3): d 8.69 (m, 2H), 8.08 (m, 2H), 7.47 (m, 2H), 7.00 (br s,
1H), 6.49 (m, 2H), 6.42 (m, 2H), 5.87 (br s, 1H), 5.78 (br s, 1H),
5.33 (br s, 1H), 5.23 (br s, 1H), 4.39 (t, 1H, J = 5.7 Hz), 4.04 (s,

K. Kaur et al. / Bioorg. Med. Chem. 19 (2011) 197–210
205
(M+1); Anal. Calcd for C52H72N8O6 (904.5): C, 69.00; H, 8.02; N,
12.38. Found: C, 69.07; H, 8.17; N, 12.51.
and 8.2 Hz), 6.98 (br s, 1H), 6.28 (m, 2H), 6.21 (m, 2H), 5.89 (br s,
2H), 4.13 (t, 1H, J = 6.0 Hz), 3.82 (s, 6H), 3.46 (m, 2H), 3.05 (m,
6H), 1.51 (m, 12H), 1.25 (d, 6H, J = 6.0 Hz); 13C NMR (free base,
CDCl3): d 173.5, 159.3, 158.9, 157.3, 144.8, 144.3, 135.2, 134.9,
129.9, 121.9, 96.9, 91.7, 55.2, 53.4, 47.4, 40.8, 40.2, 39.4, 33.9,
29.7, 26.8, 25.9, 25.0, 20.3; MS (APCI): m/z 701 (M+1).
3.2.9. tert-Butyl{(5S)-6-({4-[(2-tert-butyl-6-methoxyquinolin-8-
yl)amino]pentyl}amino)-5-[({4-[(2-tert-butyl-6-methoxyquin-
olin-8-yl)amino]pentyl}carbamoyl)amino]-6-oxohexyl}-
carbamate (33)
Yield: 84%; oil; IR (CH2Cl2): 3360, 1673 cmꢁ1
;
1H NMR (CDCl3):
3.3.3. N-{4-[(6-Methoxyquinolin-8-yl)amino]pentyl}-N2-({4-[(6-
d 7.85 (d, 2H, J = 8.5 Hz), 7.42 (d, 2H, J = 8.5 Hz), 6.48 (br s, 1H), 6.30
(m, 2H), 6.22 (m, 2H), 6.11 (br s, 2H), 5.06 (br s, 2H), 4.21 (t, 1H,
J = 5.8 Hz), 3.87 (s, 6H), 3.56 (m, 2H), 3.19 (m, 6H), 1.65 (m, 14H),
1.41 (m, 27H), 1.28 (d, 6H, J = 6.2 Hz); 13C NMR (CDCl3): d 174.3,
169.0, 163.4, 157.5, 145.4, 135.5, 134.1, 128.0, 119.3, 97.1, 91.9,
71.2, 55.7, 48.4, 38.2, 34.2, 30.8, 30.1, 28.9, 21.2, 21.1; MS (APCI):
m/z 885 (M+1); Anal. Calcd for C50H76N8O6 (884.5): C, 67.84; H,
8.65; N, 12.66. Found: C, 67.79; H, 8.74; N, 12.54.
methoxyquinolin-8-yl)amino]pentyl}carbamoyl)-
D
-ornithin-
amideꢂ3HCl (37)
Yield: 83%; hygroscopic solid; IR (KBr): 3383 cmꢁ1
;
1H NMR
(CD3OD): d 8.86 (m, 2H), 8.80 (m, 2H), 7.92 (m, 2H), 7.04 (m,
2H), 6.91 (m, 2H), 4.10 (t, 1H, J = 5.7 Hz), 3.98 (m, 6H), 3.81 (m,
2H), 2.99 (m, 6H), 1.98–1.74 (m, 12H), 1.36 (m, 6H); 13C NMR
(CD3OD): d 173.8, 170.1, 158.6, 145.9, 141.3, 134.0, 123.5, 98.1,
92.7, 56.7, 54.9, 50.2, 40.8, 40.4, 34.6, 30.4, 29.9, 27.2, 25.4, 24.2,
20.1; MS (APCI): m/z 659 (M+1).
3.2.10. tert-Butyl{(4S)-5-({4-[(2-tert-butyl-6-methoxyquinolin-
8-yl)amino]pentyl}amino)-4-[({4-[(2-tert-butyl-6-methoxy-
quinolin-8-yl)amino]pentyl}carbamoyl)amino]-5-oxopen-
tyl}carbamate (34)
3.3.4. N-{4-[(6-Methoxyquinolin-8-yl)amino]pentyl}-N2-({4-[(6-
methoxyquinolin-8-yl)amino]pentyl}carbamoyl)-L-lysina-
mideꢂ3HCl (38)
Yield: 97%; hygroscopic solid; IR (KBr): 3404, 1648 cmꢁ1 1H
;
Yield: 80%; oil; IR (CH2Cl2): 3378, 1686 cmꢁ1 1H NMR (CDCl3):
;
NMR (CD3OD): d 8.96 (m, 6H), 7.89 (m, 2H), 7.61 (m, 2H), 4.19 (t,
1H, J = 5.2 Hz), 3.96 (s, 6H), 3.73 (m, 2H), 3.35 (m, 4H), 3.01 (t,
2H, J = 6.0 Hz), 1.71 (m, 14H), 1.32 (m, 6H); 13C NMR (CD3OD): d
176.0, 162.8, 161.1, 145.9, 141.3, 140.3, 135.7, 133.9, 120.9,
107.1, 97.4, 57.0, 54.2, 41.4, 40.9, 34.3, 28.4, 28.2, 27.3, 24.2,
20.1; MS (APCI): m/z 673 (M+1).
d 7.86 (d, 2H, J = 8.5 Hz), 7.42 (d, 2H, J = 8.5 Hz), 6.66 (br s, 1H), 6.30
(m, 4H), 6.11 (br s, 2H), 5.20 (br s, 1H), 4.73 (br s, 1H), 3.86 (s, 6H),
3.56 (m, 3H), 3.18 (m, 6H), 1.64 (m, 12H), 1.41 (m, 27H), 1.28 (m,
6H); 13C NMR (CDCl3): d 172.9, 163.4, 163.3, 158.8, 158.7, 144.9,
139.3, 134.9, 133.5, 118.7, 114.0, 96.6, 91.4, 80.6, 66.6, 55.1, 53.1,
47.9, 40.0, 39.3, 37.6, 33.7, 31.6, 29.3, 22.6, 21.2; MS (APCI): m/z
871 (M+1); Anal. Calcd for C49H74N8O6 (870.5): C, 67.56; H, 8.56;
N, 12.86. Found: C, 67.46; H, 8.51; N, 12.94.
3.3.5. N-{4-[(6-Methoxyquinolin-8-yl)amino]pentyl}-N2-({4-[(6-
methoxyquinolin-8-yl)amino]pentyl}carbamoyl)-
L-arginina-
mideꢂ3HCl (39)
3.3. General method for the synthesis of N-{4-[(6-methoxy-2-
substituted-quinolin-8-yl)amino]-pentyl}-N2-({4-[(6-methoxy-
Yield: 86%; hygroscopic solid; IR (KBr): 3433 cmꢁ1
;
1H NMR
(CD3OD): d 8.88 (m, 2H), 8.73 (m, 2H), 7.81 (m, 2H), 7.52 (m,
4H), 4.15 (t, 1H, J = 5.7 Hz), 3.87 (s, 6H), 3.64 (m, 2H), 3.15 (m,
6H), 2.02–1.75 (m, 12H), 1.24 (d, 6H, J = 5.3 Hz); 13C NMR (CD3OD):
d 175.6, 162.9, 161.9, 161.5, 159.0, 146.7, 146.2, 141.2, 140.4,
139.2, 138.8, 135.7, 134.0, 120.9, 97.4, 92.1, 57.1, 42.4, 41.6, 34.4,
34.1, 33.9, 31.1, 28.1, 27.5, 26.8, 22.7, 20.3; MS (APCI): m/z 701
(M+1).
2-substituted-quinolin-8-yl)amino]pentyl}-carbamoyl)-
D/
L
-lysinamide/argininamide/ornithinamide (35–44)
(a) Removal of Z group: To a mixture of 25–27, 31 and 32
(0.12 mmol) and 10% Pd–C (0.04 g) in glacial acetic acid (1 mL)
and CH3OH (20 mL) was bubbled H2 gas for 4 h. The catalyst was
removed and solvent evaporated to obtain the product as oily
syrup, which upon treatment with ethereal HCl (2 N solution) pro-
vided 35–37, 41 and 42 as hydrochloride salts.(b) Removal of t-Boc
and Pmc groups: A solution of 28–30, 31 and 32 (0.43 mmol) in 6 N
methanolic HCl (10 mL) was stirred at ambient temperature for
45 min (for t-Boc group) or 8 N HCl in MeOH (10 mL) for 8 h (for
Pmc group). The solvent was removed to afford 38–40, 41 and 42
as hygroscopic salts.
3.3.6. N-{4-[(6-Methoxyquinolin-8-yl)amino]pentyl}-N2-({4-[(6-
methoxyquinolin-8-yl)amino]pentyl}carbamoyl)-L-ornithin-
amideꢂ3HCl (40)
Yield: 91%; hygroscopic solid; IR (KBr): 3400, 1631 cmꢁ1 1H
;
NMR (CD3OD): d 8.86 (m, 2H), 8.74 (m, 2H), 7.81 (m, 2H), 6.90
(m, 2H), 6.85 (m, 2H), 4.13 (t, 1H, J = 6.0 Hz), 3.87 (s, 6H), 3.65
(m, 2H), 3.22 (m, 4H), 2.90 (t, 2H, J = 6.4 Hz), 1.62 (m, 12H), 1.29
(m, 6H); 13C NMR (CD3OD): d 171.4, 160.9, 144.6, 143.8, 139.7,
138.5, 133.9, 132.1, 121.7, 121.6, 119.1, 97.6, 93.1, 55.2, 53.4,
39.5, 38.7, 32.5, 29.5, 29.1, 28.7, 26.5, 25.6, 23.9, 23.6, 21.5; MS
(APCI): m/z 659 (M+1).
3.3.1. N-{4-[(6-Methoxyquinolin-8-yl)amino]pentyl}-N2-({4-[(6-
methoxyquinolin-8-yl)amino]pentyl}carbamoyl)-D-lysina-
mideꢂ3HCl (35)
Yield: 81%; hygroscopic solid; IR (KBr): 3338, 1664 cmꢁ1 1H
;
NMR (CD3OD): d 8.84 (m, 4H), 7.90 (m, 2H), 6.81 (m, 4H), 4.25 (t,
1H, J = 5.1 Hz), 3.97 (s, 6H), 3.76 (m, 2H), 3.35 (m, 4H), 2.96 (t,
2H, J = 5.6 Hz), 1.74 (m, 14H), 1.25 (d, 6H, J = 6.5 Hz); 13C NMR
(CD3OD): d 172.1, 161.9, 158.9, 145.3, 140.2, 139.3, 133.0, 122.6,
106.7, 97.4, 56.1, 50.9, 41.0, 39.9, 33.3, 32.1, 27.4, 26.8, 26.1,
23.3, 19.8; MS (APCI): m/z 673 (M+1).
3.3.7. N-{4-[(2-tert-Butyl-6-methoxyquinolin-8-yl)amino]
pentyl}-N2-({4-[(2-tert-butyl-6-methoxyquinlin-8-yl)amino]
pentyl}carbamoyl)-
D
-lysinamideꢂ3HCl (41)
Yield: 84%; hygroscopic solid; IR (KBr): 3391, 1643 cmꢁ1
;
1H
NMR (free base, CDCl3): d 7.85 (d, 2H, J = 7.8 Hz), 7.42 (d, 2H,
J = 7.8 Hz), 6.76 (br s, 1H), 6.29 (m, 2H), 6.22 (m, 2H), 6.10 (br s,
2H), 4.67 (br s, 2H), 4.23 (t, 1H, J = 6.4 Hz), 3.85 (s, 6H), 3.53 (m,
2H), 3.21 (m, 4H), 2.67 (t, 2H, J = 5.3 Hz), 2.22 (br s, 2H), 1.60 (m,
14H), 1.40 (s, 18H), 1.27 (d, 6H, J = 5.7 Hz); 13C NMR (free base,
CDCl3): d 174.3, 169.0, 163.2, 157.7, 145.4, 144.0, 135.5, 134.1,
128.0, 119.3, 97.1, 91.9, 55.7, 53.0, 48.4, 38.2, 34.6, 30.8, 30.2,
21.1; MS (APCI): m/z 785 (M+1).
3.3.2. N-{4-[(6-Methoxyquinolin-8-yl)amino]pentyl}-N2-({4-[(6-
methoxyquinolin-8-yl)amino]pentyl}carbamoyl)-
D
-arginina-
mideꢂ3HCl (36)
Yield: 78%; hygroscopic solid; IR (KBr): 3435 cmꢁ1
;
1H NMR
(free base, CDCl3):
d
8.48 (d, 2H, J = 4.0 Hz), 7.87 (d, 2H,
J = 8.2 Hz), 7.71 (br s, 1H), 7.42 (br s, 1H), 7.24 (dd, 2H, J = 4.0

206
K. Kaur et al. / Bioorg. Med. Chem. 19 (2011) 197–210
3.3.8. N-{4-[(2-tert-Butyl-6-methoxyquinolin-8-yl)amino]
pentyl}-N2-({4-[(2-tert-butyl-6-methoxyquinolin-8-yl)amino]
(m, 4H), 2.65 (m, 2H), 1.58 (m, 8H), 1.42 (s, 9H), 1.27 (d, 6H,
J = 6.1 Hz); 13C NMR (CDCl3): d 171.7, 170.5, 159.4, 155.5, 144.9,
144.3, 135.3, 134.7, 121.8, 114.0, 96.7, 91.6, 79.3, 55.2, 50.6, 47.7,
42.2, 39.5, 39.4, 36.1, 33.7, 31.9, 29.7, 28.2, 26.1, 22.6; MS (APCI):
m/z 716 (M+1).
pentyl}carbamoyl)-
D
-ornithinamideꢂ3HCl (42)
Yield: 79%; hygroscopic solid; IR (KBr): 3403, 1678 cmꢁ1
;
1H
NMR (CD3OD): d 8.37 (d, 2H, J = 8.1 Hz), 7.81 (d, 2H, J = 8.1 Hz),
7.20 (m, 2H), 7.18 (m, 2H), 4.10 (t, 1H, J = 5.1 Hz), 3.98 (s, 6H),
3.86 (m, 2H), 3.25 (m, 6H), 1.77 (m, 12H), 1.49 (s, 18H), 1.28 (d,
6H, J = 6.1 Hz); 13C NMR (CD3OD): d 175.1, 169.3, 158.2, 145.0,
144.8, 137.9, 132.4, 121.9, 119.3, 97.1, 91.9, 60.1, 56.8, 54.9, 40.7,
39.3, 32.1, 30.8, 30.4, 27.5, 26.6, 25.0, 21.1; MS (APCI): m/z 771
(M+1).
3.4.2. tert-Butyl[(2S)-1,5-bis({4-[(6-methoxyquinolin-8-
yl)amino]pentyl}amino)-1,5-dioxopentan-2-yl]carbamate (56)
Yield: 83%; oil; IR (CH2Cl2): 3323, 1735, 1657 cmꢁ1 1H NMR
;
(CDCl3): d 8.51 (d, 2H, J = 3.9 Hz), 7.92 (d, 2H, J = 8.2 Hz), 7.29
(dd, 2H, J = 3.9 and 8.2 Hz), 6.32 (m, 3H), 6.27 (m, 2H), 5.81 (br s,
2H), 5.74 (br s, 2H), 4.07 (t, 1H, J = 5.9 Hz), 3.87 (s, 6H), 3.59
(m, 2H), 3.23 (m, 4H), 2.88 (t, 2H, J = 6.3 Hz), 2.17 (m, 2H), 1.89
(m, 8H), 1.39 (s, 9H), 1.27 (d, 6H, J = 6.0 Hz); 13C NMR (CDCl3): d
173.4, 172.1, 163.1, 159.9, 145.4, 144.8, 135.8, 135.4, 130.4,
122.4, 97.4, 92.4, 80.4, 55.7, 54.1, 48.3, 40.1, 37.0, 34.5, 33.2,
31.9, 30.2, 28.8, 26.6, 21.0; MS (APCI): m/z 730 (M+1).
3.3.9. N-{4-[(2-tert-Butyl-6-methoxyquinolin-8-yl)amino]
pentyl}-N2-({4-[(2-tert-butyl-6-methoxyquinolin-8-yl)amino]
pentyl}carbamoyl)-
L
-lysinamideꢂ3HCl (43)
Yield: 92%; hygroscopic solid; IR (KBr): 3360, 1686 cmꢁ1
;
1H
NMR (CD3OD): d 8.34 (d, 2H, J = 8.8 Hz), 7.81 (d, 2H, J = 8.8 Hz),
7.71 (m, 2H), 7.59 (m, 2H), 4.12 (t, 1H, J = 7.2 Hz), 3.99 (s, 6H),
3.23 (m, 2H), 3.14 (m, 4H), 2.96 (t, 2H, J = 7.2 Hz), 1.81–1.69 (m,
14H), 1.49 (s, 18H), 1.37 (d, 6H, J = 6.4 Hz); 13C NMR (CD3OD): d
176.0, 169.4, 160.9, 158.5, 144.7, 137.9, 136.6, 130.2, 122.2, 97.3,
91.6, 57.0, 41.0, 40.9, 39.6, 32.4, 30.8, 30.5, 28.5, 27.9, 24.2, 21.3;
MS (APCI): m/z 785 (M+1).
3.4.3. tert-Butyl[(2S)-1,4-bis({4-[(2-tert-butyl-6-methoxy-
quinolin-8-yl)amino]pentyl}amino)-1,4-dioxobutan-2-yl]
carbamate (57)
Yield: 88%; oil; IR (CH2Cl2): 3308, 1645 cmꢁ1 1H NMR (CDCl3):
;
d 7.85 (d, 2H, J = 7.8 Hz), 7.42 (d, 2H, J = 7.8 Hz), 6.99 (br s, 2H), 6.30
(m, 2H), 6.23 (m, 2H), 6.11 (br s, 1H), 5.87 (br s, 2H), 4.39 (m, 1H),
3.86 (s, 6H), 3.56 (m, 2H), 3.24 (m, 4H, J = 5.9 Hz), 2.63 (m, 2H), 1.58
(m, 8H), 1.41 (m, 27H), 1.28 (d, 6H, J = 5.7 Hz); 13C NMR (CDCl3): d
170.9, 163.2, 158.7, 144.8, 134.9, 133.5, 127.4, 118.8, 96.6, 91.4,
80.6, 55.1, 47.8, 39.5, 37.6, 33.8, 30.2, 28.3, 26.1, 23.5, 20.5; MS
(APCI): m/z 828 (M+1).
3.3.10. N-{4-[(6-Methoxyquinolin-8-yl)amino]pentyl}-N2-({4-
[(6-methoxyquinolin-8-yl)amino]pentyl}carbamoyl)-
L
-lysina-
mideꢂ3HCl (44)
Yield: 94%; hygroscopic solid; IR (KBr): 3398, 1678 cmꢁ1
;
1H
NMR (CD3OD): d 8.34 (d, 2H, J = 8.7 Hz), 7.81 (d, 2H, J = 8.7 Hz),
7.56 (m, 2H), 7.46 (m, 2H), 4.08 (t, 1H, J = 5.7 Hz), 3.98 (s, 6H),
3.22 (m, 2H), 3.00 (m, 4H), 2.70 (t, 2H, J = 7.0 Hz), 1.79 (m, 12H),
1.48 (s, 18H), 1.36 (m, 6H); 13C NMR (CD3OD): d 172.3, 162.3,
161.8, 154.3, 145.6, 135.2, 134.7, 128.3, 120.5, 98.2, 91.6, 55.5,
39.2, 38.9, 37.9, 30.5, 29.0, 26.1, 25.2, 23.6, 21.6; MS (APCI): m/z
771 (M+1).
3.4.4. tert-Butyl[(2S)-1,5-bis({4-[(2-tert-butyl-6-methoxyquin-
olin-8-yl)amino]pentyl}amino)-1,5-dioxopentan-2-yl]
carbamate (58)
Yield: 85%; oil; IR (CH2Cl2): 3383, 1700, 1657 cmꢁ1 1H NMR
;
(CDCl3): d 7.86 (d, 2H, J = 8.6 Hz), 7.43 (d, 2H, J = 8.6 Hz), 6.80 (br
s, 1H), 6.66 (br s, 1H), 6.31 (d, 2H, J = 2.1 Hz), 6.25 (d, 2H,
J = 2.1 Hz), 6.12 (br s, 1H), 5.99 (br s, 1H), 5.68 (br s, 1H), 4.01
(t, 1H, J = 6.0 Hz), 3.87 (s, 6H), 3.56 (m, 2H), 3.29 (m, 4H), 2.02
(t, 2H, J = 6.5 Hz), 1.78–1.62 (m, 10H), 1.42 (m, 27H), 1.31 (d, 6H,
J = 6.1 Hz); 13C NMR (CDCl3): d 171.4, 163.3, 158.8, 153.6, 144.8,
134.9, 133.5, 127.4, 118.7, 96.7, 91.4, 79.7, 55.1, 53.1, 47.8, 47.1,
43.1, 39.7, 37.6, 34.0, 31.6, 30.2, 28.9, 28.2, 26.1, 22.3, 20.7; MS
(ESI): m/z 842 (M+1).
3.4. General method for the synthesis of protected bis(8-
quinolinamines) (55–59)
(a) Removal of benzyl ester group: To a mixture of 45–48
(0.1 mmol), 10% Pd–C (0.04 g) in glacial acetic acid (1 mL) and
CH3OH (20 mL), H2 gas was bubbled for 4 h. The catalyst was fil-
tered and solvent removed to afford 50–53 as oily syrup.(b) Re-
moval of tert-butyl ester group: A solution of 49 in 6 N HCl (5 mL)
was stirred for 5 h at ambient temperature. The solvent was re-
moved to afford HCl salt, which was dissolved in water (5 mL)
and neutralized by drop wise addition of 25% NH4OH solution.
The mixture was extracted with CH2Cl2 (3 ꢀ 20 mL). The organic
layer washed with brine (5 mL) and dried (Na2SO4). The solvent
was removed to afford 54 as oil. The formation of intermediate
products 50–54 was confirmed by TLC and mass spectral analysis,
which were used for the next step without any purification.
To an ice cooled stirred solution of 8-aminoquinoline (1 or 3,
0.24 mmol) and 50–54 (0.24 mmol) in anhydrous CH2Cl2 (5 mL),
DIC (0.26 mmol) was added. The reaction mixture was allowed to
attain room temperature and stirring was continued for another
4 h. The solvent was removed yielding the crude product, which
was purified by column chromatography on silica gel (100–200
mesh) using 1.2–2% CH3OH in CH2Cl2 to afford 55–59 as oil.
3.4.5. 9H-Fluoren-9-ylmethyl[(2R)-1,4-bis({4-[(6-methoxy-
quinolin-8-yl)amino]pentyl}amino)-1,4-dioxobutan-2-yl]
carbamate (59)
Yield: 87%; oil; IR (CH2Cl2): 3356, 1709, 1675 cmꢁ1 1H NMR
;
(CDCl3): d 8.51 (d, 2H, J = 3.9 Hz), 7.91 (d, 2H, J = 7.5 Hz), 7.74 (d,
2H, J = 7.4 Hz), 7.57 (d, 2H, J = 6.6 Hz), 7.39 (m, 6H), 6.93 (br s,
2H), 6.38 (br s, 2H), 6.32 (m, 2H), 6.25 (m, 2H), 5.97 (br s, 1H),
4.39 (d, 2H, J = 6.5 Hz), 4.18 (m, 2H), 3.86 (s, 6H), 3.57 (m, 2H),
3.21 (m, 4H), 2.73 (m, 2H), 1.59 (m, 8H), 1.26 (d, 6H, J = 6.1 Hz);
13C NMR (CDCl3): d 172.1, 169.9, 169.6, 158.4, 153.1, 143.9,
142.7, 140.2, 134.3, 133.8, 128.9, 126.7, 124.0, 118.9, 95.8, 95.7,
90.7, 90.6, 66.1, 54.1, 50.7, 46.7, 46.1, 38.5, 37.0, 32.7, 29.8, 28.6,
25.1, 25.0, 24.9, 21.0; MS (APCI): m/z 838 (M+1).
3.5. General method for the synthesis of
N1,N4-bis{4-[(6-methoxy-2-substituted-quinolin-8-yl)amino]
3.4.1. tert-Butyl[(2S)-1,4-bis({4-[(6-methoxyquinolin-8-
pentyl}-D/L-aspartamide/glutamamide (60–64)
yl)amino]pentyl}amino)-1,4-dioxobutan-2-yl]carbamate (55)
Yield: 81%; oil; IR (CH2Cl2): 3338, 1656 cmꢁ1
d 8.52 (d, 2H, J = 3.9 Hz), 7.92 (d, 2H, J = 8.0 Hz), 7.31 (dd, 2H, J = 3.9
and 8.0 Hz), 6.86 (br s, 2H), 6.54 (br s, 2H), 6.32 (m, 2H), 6.25 (m,
2H), 5.98 (br s, 1H), 4.38 (m, 1H), 3.87 (s, 6H), 3.57 (m, 2H), 3.22
;
1H NMR (CDCl3):
A solution of t-Boc group protected bis(8-aminoquinolines)
(55–58, 0.30 mmol) was stirred at ambient temperature in HCl
(5 mL, 6 N solution) for 45 min. The removal of solvent pro-
vides salts of 60–63 in good yields. In case of Fmoc group, to

K. Kaur et al. / Bioorg. Med. Chem. 19 (2011) 197–210
207
8-aminoquinoline (59, 0.54 mmol) a solution of 20% piperidine in
CH2Cl2 (10 mL) was added and reaction mixture was stirred for
20 min. The solvent was removed and the crude product was puri-
fied by silica gel (100–200 mesh) column chromatography eluting
with 3% CH3OH in CH2Cl2 to afford 64, which upon treatment with
HCl (2 N in ether) provided its hydrochloride salt.
temperature for 24 h. The solvent was distilled off. The reaction
mixture was dissolved in CH2Cl2 (20 mL) and washed with water
(3 ꢀ 5 mL) followed by brine solution (5 mL). The organic layer
was dried (Na2SO4) and concentrated to afford crude product,
which was purified by column chromatography on silica gel
(100–200 mesh) using 1.5% CH3OH in CH2Cl2 to provide product
as viscous oil. Treatment with HCl solution (2 N in ether) provided
their HCl salts.
3.5.1. N1,N4-Bis{4-[(6-methoxyquinolin-8-yl)amino]pentyl}-
L
-aspartamideꢂ3HCl (60)
Yield: 88%; hygroscopic solid; IR (KBr): 3435, 1638 cmꢁ1 1H
;
3.6.1. 1,3-Bis{4-[(6-methoxyquinolin-8-yl)amino]pentyl}
ureaꢂ2HCl (66)
NMR (CD3OD): d 8.83 (m, 4H), 7.88 (m, 2H), 7.00 (m, 2H), 6.86
(m, 2H), 4.24 (m, 1H), 3.97 (m, 6H), 3.76 (m, 2H), 3.33 (m, 4H),
2.43 (m, 2H), 1.87 (m, 8H), 1.32 (m, 6H); 13C NMR (CD3OD): d
172.3, 171.3, 161.9, 145.3, 140.3, 139.4, 133.0, 122.6, 96.4, 91.8,
66.3, 56.2, 39.9, 39.7, 36.3, 33.5, 26.4, 21.2; MS (APCI): m/z 616
(M+1).
Yield: 55%; hygroscopic solid; IR (free base, CH2Cl2): 3378,
1680 cmꢁ1 1H NMR (free base, CDCl3): d 8.52 (dd, 2H, J = 1.3 and
;
4.1 Hz), 7.92 (d, 2H, J = 8.0 Hz), 7.30 (dd, 2H, J = 4.1 and 8.0 Hz),
6.31 (d, 2H, J = 2.3 Hz), 6.27 (d, 2H, J = 2.3 Hz), 5.98 (br s, 2H),
3.86 (s, 6H), 3.52 (m, 4H), 3.14 (m, 2H), 1.67–1.59 (m, 8H), 1.27
(d, 6H, J = 6.3 Hz); 13C NMR (free base, CDCl3): d 172.2, 159.9,
145.4, 144.8, 135.8, 130.4, 128.2, 120.5, 97.3, 92.2, 55.7, 48.3,
42.7, 34.5, 26.7, 21.8; MS (APCI): m/z 545 (M+1).
3.5.2. N1,N5-Bis{4-[(6-methoxyquinolin-8-yl)amino]pentyl}-
L
-glutamamideꢂ3HCl (61)
Yield: 86%; hygroscopic solid; IR (KBr): 3391, 1673 cmꢁ1 1H
;
NMR (CD3OD): d 8.87 (m, 4H), 7.91 (m, 2H), 7.02 (m, 2H), 6.85
(m, 2H), 3.97 (m, 6H), 3.78 (t, 3H), 3.04 (m, 4H), 2.56 (t, 2H,
J = 5.6 Hz), 2.19 (m, 2H), 1.89 (m, 8H), 1.26 (m, 6H); 13C NMR
(CD3OD): d 174.2, 169.0, 161.9, 145.3, 140.1, 139.1, 133.0, 122.6,
96.5, 92.4, 66.2, 56.2, 53.5, 51.0, 49.3, 49.0, 40.3, 39.9, 34.9, 33.4,
31.6, 27.9, 26.3, 26.1, 19.1; MS (APCI): m/z 630 (M+1).
3.6.2. 1,3-Bis{4-[(6-methoxyquinolin-8-yl)amino]pentyl}
thioureaꢂ2HCl (67)
Yield: 52%; hygroscopic solid; IR (free base, CH2Cl2): 3374,
1615 cmꢁ1 1H NMR (free base, CDCl3): d 8.50 (d, 2H, J = 3.9 Hz),
;
7.89 (d, 2H, J = 7.8 Hz), 7.30 (dd, 2H, J = 3.9 and 7.8 Hz), 6.51 (d,
2H, J = 2.1 Hz), 6.45 (d, 2H, J = 2.1 Hz), 6.00 (br s, 2H), 3.87 (s,
6H), 3.55 (m, 4H), 3.14 (m, 2H), 1.65 (m, 8H), 1.25 (d, 6H,
J = 6.1 Hz); 13C NMR (free base, CDCl3): d 183.6, 158.4, 145.8,
144.7, 134.8, 131.4, 128.6, 121.8, 97.8, 92.3, 55.1, 48.9, 41.2, 34.1,
26.8, 21.6; MS (ESI): m/z 583.1 (M+23).
3.5.3. N1,N4-Bis{4-[(2-tert-butyl-6-methoxyquinolin-8-
yl)amino]pentyl}-
L
-aspartamideꢂ3HCl (62)
Yield: 90%; hygroscopic solid; IR (KBr): 3401, 1646 cmꢁ1
;
1H
NMR (CD3OD): d 8.40 (d, 2H, J = 7.8 Hz), 7.83 (d, 2H, J = 7.8 Hz),
7.71 (m, 2H), 7.50 (m, 2H), 4.12 (m, 1H), 3.97 (m, 6H), 3.51 (m,
2H), 3.36 (m, 4H), 2.05 (m, 2H), 1.76 (m, 8H), 1.51 (m, 18H), 1.32
(m, 6H); 13C NMR (CD3OD): d 170.4, 168.7, 161.3, 157.4, 145.6,
144.3, 137.6, 135.3, 121.3, 118.4, 107.4, 94.5, 66.3, 59.6, 56.3,
51.1, 39.5, 38.7, 36.2, 31.3, 29.9, 26.0, 25.9, 22.0; MS (ESI): m/z
728 (M+1).
3.6.3. 1,3-Bis{4-[(2-tert-butyl-6-methoxyquinolin-8-
yl)amino]pentyl}ureaꢂ2HCl (68)
Yield: 62%; hygroscopic solid; IR (free base, CH2Cl2): 3316,
1660 cmꢁ1 1H NMR (free base, CDCl3): d 7.84 (d, 2H, J = 8.6 Hz),
;
7.41 (d, 2H, J = 8.6 Hz), 6.30 (d, 2H, J = 1.9 Hz), 6.25 (d, 2H,
J = 1.9 Hz), 6.12 (br s, 2H), 3.85 (s, 6H), 3.58 (m, 2H), 3.12 (m,
4H), 1.59 (m, 8H), 1.41 (s, 18H), 1.28 (d, 6H, J = 6.3 Hz); 13C NMR
(free base, CDCl3): d 171.7, 162.5, 157.9, 143.8, 135.5, 129.0,
128.4, 119.3, 97.1, 92.0, 55.7, 48.4, 40.0, 34.4, 30.8, 28.9, 26.7,
21.1; MS (APCI): m/z 657 (M+1).
3.5.4. N1,N5-Bis{4-[(2-tert-butyl-6-methoxyquinolin-8-
yl)amino]pentyl}-
L
-glutamamideꢂ3HCl (63)
Yield: 92%; hygroscopic solid; IR (KBr): 3438, 1658 cmꢁ1
;
1H
NMR (CD3OD): d 8.34 (d, 2H, J = 8.6 Hz), 7.80 (d, 2H, J = 8.6 Hz),
7.59 (m, 2H), 7.42 (m, 2H), 4.10 (m, 1H), 3.97 (m, 6H), 3.78 (m,
2H), 3.31 (m, 4H), 2.00 (t, 2H, J = 5.6 Hz), 1.74 (m, 2H), 1.65 (m,
8H), 1.49 (s, 18H), 1.37 (m, 6H); 13C NMR (CD3OD): d 170.9,
169.8, 161.5, 157.5, 145.7, 138.0, 131.4, 129.4, 121.4, 118.3,
107.5, 93.1, 66.2, 59.5, 56.4, 53.4, 44.1, 38.7, 31.3, 29.9, 21.7,
20.4; MS (ESI): m/z 742 (M+1).
3.6.4. 1,3-Bis{4-[(2-tert-butyl-6-methoxyquinolin-8-
yl)amino]pentyl}thioureaꢂ2HCl (69)
Yield: 60%; hygroscopic solid; IR (free base, CH2Cl2): 3363,
1651 cmꢁ1 1H NMR (free base, CDCl3): d 7.83 (d, 2H, J = 8.5 Hz),
;
7.41 (d, 2H, J = 8.5 Hz), 6.30–6.25 (m, 4H), 6.08 (br s, 1H), 5.64
(br s, 1H), 3.85 (m, 6H), 3.55 (m, 2H), 3.25 (m, 4H), 1.59 (m, 8H),
1.41 (s, 18H), 1.26 (d, 6H, J = 6.3 Hz); 13C NMR (free base, CDCl3):
d 181.4, 163.5, 158.8, 144.7, 135.0, 133.5, 127.5, 118.9, 97.0, 91.8,
55.2, 47.9, 44.3, 37.7, 33.8, 30.2, 25.4, 20.7; MS (APCI): m/z 673
(M+1).
3.5.5. N1,N4-Bis{4-[(6-methoxyquinolin-8-yl)amino]pentyl}-
D
-aspartamideꢂ3HCl (64)
Yield:74%;hygroscopicsolid;IR(KBr):3405, 1687 cmꢁ1; 1HNMR
(free base, CDCl3): d 8.53 (dd, 2H, J = 1.4 and 4.1 Hz), 7.92 (dd, 2H,
J = 1.4 and 8.2 Hz), 7.30 (dd, 2H, J = 4.1 and 8.2 Hz), 6.82 (br s, 2H),
6.32 (d, 2H, J = 2.3 Hz), 6.26 (d, 2H, J = 2.3 Hz), 5.99 (br s, 2H), 3.88
(s, 6H), 3.59 (m, 3H), 3.25 (m, 4H), 2.59 (m, 2H), 2.09 (br s, 2H),
1.69 (m, 8H), 1.28 (d, 6H, J = 6.3 Hz); 13C NMR (free base, CDCl3): d
170.9, 169.2, 162.6, 140.9, 135.7, 123.0, 118.9, 97.1, 92.3, 56.5,
40.5, 40.3, 36.8, 34.2, 26.9, 23.7, 19.8; MS (APCI): m/z 616 (M+1).
3.6.5. 1,3-Bis{4-[4-ethyl-6-methoxy-5-(pentyloxy)quinolin-8-
ylamino]pentyl}ureaꢂ2HCl (70)
Yield: 39%; hygroscopic solid; IR (free base, CH2Cl2): 3376,
1669 cmꢁ1 1H NMR (free base, CDCl3): d 8.32 (d, 2H, J = 4.2 Hz),
;
7.55 (d, 2H, J = 4.2 Hz), 6.85 (br s, 2H), 6.37 (s, 2H), 3.89 (s, 6H),
3.83 (t, 4H, J = 6.9 Hz), 3.57 (m, 2H), 3.43 (m, 4H), 3.21 (q, 4H,
J = 7.2 Hz), 1.98 (m, 20H), 1.55 (m, 18H); 13C NMR (free base,
CDCl3): d 169.3, 151.1, 141.8, 134.6, 134.5, 134.0, 128.5, 128.1,
122.4, 94.5, 56.9, 53.3, 50.8, 48.1, 38.1, 34.2, 29.6, 26.4, 26.2,
22.5, 20.7, 14.0; MS (APCI): m/z 773 (M+1).
3.6. General method for the synthesis of 1,3-bis{4-[(6-methoxy-
2/4,5-substituted-quinolin-8-yl)amino]pentyl}urea/
thioureaꢂ2HCl (66–71)
A solution of CDI or TCDI (0.19 mmol) and 8-aminoquinoline (1,
3, or 4, 0.39 mmol) in dry CH2Cl2 (5 mL) was stirred at ambient

208
K. Kaur et al. / Bioorg. Med. Chem. 19 (2011) 197–210
3.6.6. 1,3-Bis{4-[4-ethyl-6-methoxy-5-(pentyloxy)quinolin-8-
ylamino]pentyl}thioureaꢂ2HCl (71)
3.8.1. N,N0-Bis{4-[(6-methoxyquinolin-8-yl)
amino]pentyl}dicarbonimidic diamideꢂ2HCl (74)
Yield: 42%; hygroscopic solid; IR (free base, CH2Cl2): 3365,
Yield: 70%; hygroscopic solid; IR (free base, CH2Cl2): 3382, 1689,
1668 cmꢁ1; 1H NMR (free base, CDCl3): d 8.77 (br s, 1H), 8.52 (br s,
1H), 8.06 (d, 2H, J = 4.2 Hz), 7.91 (d, 2H, J = 8.5 Hz), 7.22 (dd, 2H,
J = 4.2 and 8.5 Hz), 6.32–6.27 (m, 4H), 3.87 (s, 6H), 3.62 (m, 2H),
3.24 (t, 4H, J = 6.1 Hz), 1.64 (m, 8H), 1.28 (d, 6H, J = 5.7 Hz); 13C
NMR (free base, CDCl3): d 160.0, 157.6, 149.4, 145.5, 135.9, 135.2,
130.4, 122.3, 107.6, 97.3, 92.2, 55.7, 53.2, 48.4, 34.6, 27.1, 21.0;
MS (APCI): m/z 588 (M+1).
1606 cmꢁ1 1H NMR (free base, CDCl3): d 8.36 (d, 2H, J = 4.2 Hz),
;
7.09 (d, 2H, J = 4.2 Hz), 6.44 (s, 2H), 5.88 (br s, 2H), 3.94 (s, 6H),
3.89 (t, 4H, J = 6.8 Hz), 3.61 (m, 2H), 3.33 (m, 4H), 3.25 (q, 4H,
J = 7.2 Hz), 1.83 (t, 6H, J = 7.2 Hz), 1.64–1.55 (m, 20H), 1.43 (m,
12H); 13C NMR (free base, CDCl3): d 182.3, 151.1, 144.3, 134.5,
134.1, 128.5, 128.1, 122.4, 94.6, 56.9, 50.8, 48.1, 39.3, 32.1, 28.5,
26.2, 20.7, 19.2, 13.9; MS (APCI): m/z 789 (M+1).
3.7. General method for the synthesis of
3.8.2. N,N0-Bis{4-[(2-tert-butyl-6-methoxyquinolin-8-yl)
amino]pentyl}dicarbonimidic diamideꢂ2HCl (75)
N,N2-bis{4-[(6-methoxy-2-substituted-quinolin-8-
yl)amino]pentyl}glycinamideꢂ2HCl (72 and 73)
Yield: 38%; hygroscopic solid; IR (free base, CH2Cl2): 3374,
1682, 1665 cmꢁ1 1H NMR (free base, CDCl3): d 7.98 (d, 2H,
;
A mixture of 8-aminoquinoline (1 or 3, 1.08 mmol), chloroacetic
acid (4.32 mmol) and Et3N (4.32 mmol) in anhydrous THF (15 mL)
was refluxed for 24 h. The solvent was removed under reduced
pressure. The residue was dissolved in CH2Cl2 (50 mL) and washed
with water (3 ꢀ 10 mL) followed by brine solution (5 mL). The or-
ganic layer was dried (Na2SO4) and solvent was removed under re-
duced pressure. Column chromatographic purification of crude
product on silica gel (100–200 mesh) using 2% CH3OH in CH2Cl2
gave product as viscous oil, which upon treatment with HCl solu-
tion (2 N in ether) provided 72 and 73 as HCl salts.
J = 8.6 Hz), 7.85 (d, 2H, J = 8.6 Hz), 6.30 (s, 2H), 6.25 (s, 2H), 6.15
(br s, 2H), 3.86 (s, 6H), 3.59 (m, 2H), 3.27 (t, 4H, J = 6.2 Hz), 1.64
(m, 8H), 1.42 (s, 18H), 1.31 (d, 6H, J = 6.1 Hz); 13C NMR (free base,
CDCl3): d 168.2, 159.4, 157.0, 145.5, 135.8, 135.4, 128.9, 123.7,
107.0, 96.9, 55.7, 48.5, 40.3, 34.7, 32.8, 30.5, 27.0, 21.1; MS (APCI):
m/z 700 (M+1).
3.9. General method for the synthesis of bisquinolines 76–78
To an ice cooled stirred solution of 1 (0.772 mmol) and Et3N
(0.772 mmol) in anhydrous CH2Cl2 (5 mL), chloromethyl chlorofor-
mate or chlorocarbonylsulfenyl chloride or oxalyl chloride
(0.386 mmol) was added drop wise. The reaction mixture was al-
lowed to warm to ambient temperature and stirring continued
for another 6 h. The reaction mixture was concentrated, and resi-
due was dissolved in CH2Cl2 (20 mL). The organic layer was washed
with water (3 ꢀ 10 mL) followed by brine solution (5 mL). Organic
layer was dried over Na2SO4 and concentrated to obtain crude
product. Pure product was isolated as viscous oil by column chro-
matography on silica gel (100–200 mesh) using 1.5% CH3OH in
CH2Cl2. Treatment with HCl solution (2 N in ether) provided 76–
78 as HCl salts.
3.7.1. N,N2-Bis{4-[(6-methoxyquinolin-8-yl)amino]pentyl}
glycinamideꢂ2HCl (72)
Yield: 21%; hygroscopic solid; IR (free base, CH2Cl2): 3436,
1637 cmꢁ1 1H NMR (free base, CDCl3): d 8.53 (dd, 2H, J = 1.5 and
;
4.2 Hz), 7.94 (dd, 2H, J = 1.5 and 8.2 Hz), 7.33 (dd, 2H, J = 4.2 and
8.2 Hz), 6.34 (d, 2H, J = 2.3 Hz), 6.28 (d, 2H, J = 2.3 Hz), 5.96 (br s,
2H), 3.88 (s, 6H), 3.68 (m, 4H), 3.27 (t, 2H, J = 5.6 Hz), 2.30 (t, 2H,
J = 6.4 Hz), 1.87–1.63 (m, 8H), 1.30 (d, 6H, J = 6.3 Hz); 13C NMR (free
base, CDCl3): d 173.4, 159.4, 144.9, 144.3, 135.3, 134.9, 129.9,
121.9, 96.9, 91.8, 62.3, 55.2, 47.8, 39.5, 34.0, 26.1, 20.6; MS (APCI):
m/z 559 (M+1).
3.7.2. N,N2-Bis{4-[(2-tert-butyl-6-methoxyquinolin-8-yl)-
amino]pentyl}-glycinamideꢂ2HCl (73)
3.9.1. ({4-[(6-Methoxyquinolin-8-yl)amino]pentyl}amino)
methyl{4-[(6-methoxy-quinolin-8-yl)amino]pentyl}
carbamateꢂ2HCl (76)
Yield: 18%; hygroscopic solid; IR (free base, CH2Cl2): 3391,
1648 cmꢁ1
;
1H NMR (free base, CDCl3): d 7.87 (d, 2H, J = 8.5 Hz),
Yield: 63%; hygroscopic solid; IR (free base, CH2Cl2): 3375,
7.43 (d, 2H, J = 8.5 Hz), 6.50 (br s, 2H), 6.32 (s, 2H), 6.34 (s, 2H),
4.02 (s, 2H), 3.87 (s, 6H), 3.60 (m, 2H), 3.36 (m, 2H), 2.58 (t, 2H,
J = 5.9 Hz), 1.79–1.60 (m, 8H), 1.42 (s, 18H), 1.30 (d, 6H,
J = 6.1 Hz); 13C NMR (free base, CDCl3): d 170.4, 162.5, 157.6,
143.8, 134.0, 132.6, 126.4, 117.0, 95.6, 90.5, 61.1, 54.2, 46.8, 37.8,
36.6, 32.5, 29.2, 24.9, 20.9; MS (APCI): m/z 671 (M+1).
1742 cmꢁ1 1H NMR (free base, CDCl3): d 8.53 (dd, 2H, J = 1.4 and
;
4.2 Hz), 7.93 (dd, 2H, J = 1.4 and 8.2 Hz), 7.32 (dd, 2H, J = 4.2 and
8.2 Hz), 6.34 (d, 2H, J = 2.3 Hz), 6.28 (d, 2H, J = 2.3 Hz), 6.00 (br s,
1H), 5.74 (s, 2H), 4.90 (br s, 1H), 3.88 (s, 6H), 3.64 (m, 2H), 3.26
(m, 4H), 1.72–1.62 (m, 8H), 1.31 (d, 6H, J = 6.3 Hz); 13C NMR (free
base, CDCl3): d 159.9, 154.1, 145.4, 144.9, 135.8, 135.3, 130.4,
122.4, 97.3, 92.3, 71.0, 55.7, 48.3, 41.7, 34.3, 26.9, 21.1; MS (APCI):
m/z 574.8 (M+1).
3.8. General method for the synthesis
of N,N0-Bis{4-[(6-methoxy-2-substituted-quinolin-8-yl)amino]-
pentyl}dicarbonimidic diamideꢂ2HCl (74 and 75)
3.9.2. ({4-[(6-Methoxyquinolin-8-yl)amino]pentyl}amino)[({4-
[(6-methoxyquinolin-8-yl)amino]pentyl}amino)sulfanyl]
methanoneꢂ2HCl (77)
To an ice cooled stirred solution of 1 or 3 (1.31 mmol) and
Et3N (0.65 mmol) in anhydrous CH2Cl2 (10 mL), N-(chlorocar-
bonyl)isocyanate (0.65 mmol) was added drop wise. The reaction
mixture was allowed to attain room temperature and stirring
continued for another 3 h. The solvent was then removed under
reduced pressure. The residue was dissolved in CH2Cl2 (20 mL),
and organic layer was washed with water (3 ꢀ 10 mL) followed
by brine solution (5 mL). The organic layer was dried over
Na2SO4 and concentrated to obtain crude product, which was
purified by column chromatography on silica gel (100–200
mesh) using 2.5% CH3OH in CH2Cl2 to afford products, which
were converted to their hydrogen chloride salts upon treatment
with HCl solution (2 N in ether).
Yield: 66%; hygroscopic solid; IR (free base, CH2Cl2): 3370,
1659 cmꢁ1 1H NMR (free base, CDCl3): d 8.51 (m, 4H), 7.91 (m,
;
2H), 6.33 (m, 4H), 5.98 (br s, 1H), 5.49 (br s, 1H), 3.89 (s, 6H),
3.57 (m, 2H), 3.34 (m, 4H), 1.61 (m, 8H), 1.25 (d, 6H, J = 6.1 Hz);
13C NMR (free base, CDCl3): d 162.1, 160.0, 148.4, 145.1, 135.4,
133.8, 130.5, 123.3, 97.4, 92.3, 55.7, 48.3, 41.6, 34.3, 26.9, 21.0;
MS (APCI): m/z 577 (M+1).
3.9.3. N,N0-Bis{4-[(6-methoxyquinolin-8-yl)amino]pentyl}
ethanediamideꢂ2HCl (78)
Yield: 7%; hygroscopic solid; IR (free base, CH2Cl2): 3381,
1659 cmꢁ1 1H NMR (free base, CDCl3): d 8.52 (d, 2H, J = 3.2 Hz),
;

K. Kaur et al. / Bioorg. Med. Chem. 19 (2011) 197–210
209
7.91 (d, 2H, J = 8.0 Hz), 7.30 (dd, 2H, J = 3.2 and 8.0 Hz), 6.32 (s, 2H),
6.27 (s, 2H), 3.87 (s, 6H), 3.63 (m, 2H), 3.33 (t, 4H, J = 5.5 Hz), 1.71
(m, 8H), 1.29 (d, 6H, J = 6.2 Hz); 13C NMR (free base, CDCl3): d
160.4, 159.9, 145.4, 144.8, 135.9, 135.2, 130.4, 122.3, 97.3, 92.3,
55.7, 48.3, 40.2, 34.5, 26.6, 21.1; MS (APCI): m/z 573 (M+1).
J = 4.0 Hz), 8.35 (s, 1H), 7.90 (d, 2H, J = 8.2 Hz), 7.29 (dd, 2H,
J = 4.0 and 8.2 Hz), 6.30 (s, 2H), 6.25 (s, 2H), 5.94 (br s, 2H), 3.84
(s, 6H), 3.60–3.42 (m, 6H), 1.70 (m, 8H), 1.27 (d, 6H, J = 6.1 Hz);
13C NMR (free base, CDCl3): d 165.5, 159.9, 151.0, 145.3, 144.8,
135.8, 135.4, 133.7, 130.4, 130.3, 122.4, 97.5, 92.4, 55.7, 48.3,
40.7, 34.5, 26.6, 21.1; MS (APCI): m/z 650 (M+1).
1
1
0
4
3.10. Synthesis of N ,N -(iminodiethane-2,1-diyl)bis[N -
(6-methoxyquinolin-8-yl)pentane-1,4-diamine]ꢂ2HCl (79)
3.11.4. N,N0-Bis{4-[(2-tert-butyl-6-methoxyquinolin-8-
yl)amino]pentyl}pyridine-2,6-dicarboxamide.3HCl (83)
Yield: 55%; hygroscopic solid; IR (free base, CH2Cl2): 3391,
A mixture of 1 (0.965 mmol), Et3N (0.965 mmol) and bis(2-chlo-
roethyl)amine (0.482 mmol) was stirred at room temperature for
14 h. At this stage, EtOAc (20 mL) was added and the separated
Et3NꢂHCl salt was filtered. The filtrate was concentrated and resi-
due was purified by column chromatography on silica gel (100–
200 mesh) using 7% CH3OH in CH2Cl2 to afford pure product, which
was converted to HCl salt upon treating with 2 N solution of HCl in
ether. Yield: 82%; hygroscopic solid; IR (free base, CH2Cl2):
1661 cmꢁ1 1H NMR (free base, CDCl3): d 8.32 (d, 2H, J = 7.7 Hz),
;
8.01 (d, 1H, J = 7.7 Hz), 7.84 (d, 2H, J = 8.6 Hz), 7.41 (d, 2H, J = 8.6
Hz), 6.28 (d, 2H, J = 2.4 Hz), 6.22 (d, 2H, J = 2.3 Hz), 3.82 (s, 6H),
3.48 (m, 6H), 1.76 (m, 8H), 1.39 (s, 18H), 1.27 (d, 6H, J = 6.6 Hz);
13C NMR (free base, CDCl3): d 162.8, 162.3, 157.7, 147.8, 143.8,
137.7, 133.9, 133.5, 126.4, 125.5, 117.7, 95.5, 90.4, 55.9, 54.0,
46.8, 36.6, 33.2, 25.8, 21.6; MS (APCI): m/z 762 (M+1).
3428 cmꢁ1 1H NMR (free base, CDCl3): d 8.52 (d, 2H, J = 3.2 Hz),
;
7.91 (d, 2H, J = 8.0 Hz), 7.32 (dd, 2H, J = 3.2 and 8.0 Hz), 6.32 (s,
2H), 6.26 (s, 2H), 5.97 (br s, 1H), 4.04 (br s, 1H), 3.87 (s, 6H), 3.63
(m, 2H), 3.33 (m, 12H), 1.71 (m, 8H), 1.29 (d, 6H, J = 6.2 Hz); 13C
NMR (free base, CDCl3): d 159.9, 145.3, 145.8, 135.8, 135.3, 130.4,
122.4, 97.5, 92.4, 55.7, 51.7, 48.2, 41.0, 34.1, 26.6, 20.8; MS (APCI):
m/z 588 (M+1).
3.11.5. N,N0-Bis{4-[(2-tert-butyl-6-methoxyquinolin-8-yl)
amino]pentyl}pyridine-3,4-dicarboxamideꢂ3HCl (84)
Yield: 22%; hygroscopic solid; IR (free base, CH2Cl2): 3435,
1655 cmꢁ1 1H NMR (free base, CDCl3): d 8.72 (s, 1H), 8.57 (d,
;
1H, J = 2.8 Hz), 7.83 (d, 2H, J = 8.5 Hz), 7.41 (d, 2H, J = 8.5 Hz),
7.33 (d, 1H, J = 2.8 Hz), 6.28 (s, 2H), 6.22 (s, 2H), 6.11 (br s, 2H),
3.86 (s, 6H), 3.67 (m, 6H), 1.70 (m, 8H), 1.40 (s, 18H), 1.29 (d, 6H,
J = 6.2 Hz); 13C NMR (free base, CDCl3): d 169.0, 167.9, 157.7,
152.9, 144.1, 143.4, 134.4, 134.0, 128.3, 124.1, 118.0, 96.0, 90.4,
56.0, 43.6, 35.8, 34.2, 30.9, 26.6, 21.5; MS (MALDI): m/z 762 (M+1).
3.11. General method for the synthesis of N,N0-bis{4-[(6-
methoxy-2-substituted-quinolin-8-yl)amino]pentyl}pyridine-
2,6/3,4/3,5-dicarboxamideꢂ2HCl (80–85)
A mixture of 8-aminoquinoline (1 or 3, 0.980 mmol), Et3N
(0.980 mmol) and pyridine-2,6/3,4/3,5-dicarbonyl chloride (0.490
mmol) was stirred in anhydrous THF (15 mL) at room temperature
for 12 h and filtered. The filtrate was concentrated and residue was
purified by column chromatography on silica gel (100–200 mesh)
using 1% CH3OH in CH2Cl2 to afford 80–85 as viscous oil, which
were converted to HCl salts upon treatment with a 2 N solution
of ethereal HCl.
3.11.6. N,N0-Bis{4-[(2-tert-butyl-6-methoxyquinolin-8-yl)
amino]pentyl}pyridine-3,5-dicarboxamideꢂ3HCl (85)
Yield: 45%; hygroscopic solid; IR (free base, CH2Cl2): 3391,
1660 cmꢁ1 1H NMR (free base, CDCl3): d 9.12 (d, 2H, J = 1.9 Hz),
;
8.43 (d, 1H, J = 1.9 Hz), 8.02 (d, 2H, J = 8.5 Hz), 7.60 (d, 2H,
J = 8.5 Hz), 6.47 (d, 2H, J = 2.1 Hz), 6.42 (d, 2H, J = 2.1 Hz), 6.31 (br
s, 2H), 4.02 (s, 6H), 3.69 (m, 6H), 1.95 (m, 8H), 1.59 (s, 18H), 1.50
(d, 6H, J = 6.6 Hz); 13C NMR (free base, CDCl3): d 163.8, 162.4,
157.7, 149.2, 143.7, 134.0, 133.5, 132.0, 128.8, 117.8, 95.8, 90.7,
56.0, 54.1, 46.8, 36.6, 33.1, 30.5, 25.0, 21.6; MS (APCI): m/z 762
(M+1).
3.11.1. N,N0-Bis{4-[(6-methoxyquinolin-8-yl)amino]pentyl}
pyridine-2,6-dicarboxamideꢂ3HCl (80)
Yield: 63%; hygroscopic solid; IR (free base, CH2Cl2): 3391,
1659 cmꢁ1
;
1H NMR (free base, CDCl3): d 8.48 (d, 2H, J = 4.0 Hz),
Acknowledgements
8.32 (d, 2H, J = 7.7 Hz), 7.97 (m, 3H), 7.28 (dd, 2H, J = 4.0 and
7.8 Hz), 6.30 (d, 2H, J = 2.1 Hz), 6.20 (d, 2H, J = 2.1 Hz), 5.93 (br s,
2H), 3.84 (s, 6H), 3.53 (m, 2H), 3.42 (t, 4H, J = 6.8 Hz), 1.60 (m,
8H), 1.26 (d, 6H, J = 6.2 Hz); 13C NMR (free base, CDCl3): d 164.0,
159.9, 149.4, 145.3, 144.7, 139.3, 135.8, 135.4, 130.4, 125.4,
122.3, 97.4, 92.2, 55.7, 48.2, 40.0, 34.5, 26.8, 21.0; MS (APCI): m/z
650 (M+1).
Dr. Kirandeep Kaur thanks the Council of Scientific and Indus-
trial Research (CSIR), New Delhi for the award of Senior Research
Fellowship. Mr. John Trott, Ms. Marsha Wright and Mr. Rajnish
Sahu are acknowledged for their excellent technical help in the
in vitro screening of biological activity. Antimicrobial screening
was supported by the NIH, NIAID, Division of AIDS, Grant No. AI
27094, and the USDA Agricultural Research Service Specific Coop-
erative Agreement No. 58-6408-2-0009.
3.11.2. N,N0-Bis{4-[(6-methoxyquinolin-8-yl)amino]pentyl}
pyridine-3,4-dicarboxamideꢂ3HCl (81)
Yield: 35%; hygroscopic solid; IR (free base, CH2Cl2): 3392,
Supplementary data
1634 cmꢁ1 1H NMR (free base, CDCl3): d 8.76 (s, 1H), 8.63 (d,
;
1H, J = 5.0 Hz), 8.48 (d, 2H, J = 3.9 Hz), 7.91 (d, 2H, J = 7.4 Hz),
7.40 (d, 1H, J = 5.0 Hz), 7.29 (dd, 2H, J = 3.9 and 7.4 Hz), 6.31 (d,
2H, J = 1.8 Hz), 6.26 (d, 2H, J = 1.8 Hz), 5.98 (br s, 2H), 3.85 (s,
6H), 3.59 (m, 2H), 3.37 (t, 4H, J = 6.1 Hz), 1.70 (m, 8H), 1.28 (d,
6H, J = 6.3 Hz); 13C NMR (free base, CDCl3): d 167.5, 159.9, 152.0,
149.9, 144.8, 142.0, 135.8, 135.3, 129.4, 122.6, 122.4, 97.4, 55.7,
48.3, 40.7, 34.3, 26.5, 21.1; MS (APCI): m/z 650 (M+1).
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.bmc.2010.11.036.
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;

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