Synthesis, antimalarial, antileishmanial, antimicrobial, cytotoxicity, and methemoglobin (MetHB) formation activities of new 8-quinolinamines

Article abstract of DOI:10.1016/j.bmc.2006.10.036

We report the synthesis, in vitro antiprotozoal (against Plasmodium and Leishmania), antimicrobial, cytotoxicity (Vero and MetHb-producing properties), and in vivo antimalarial activities of two series of 8-quinolinamines. N1-{4-[2-(tert-Butyl)-6-methoxy-8-quinolylamino]pentyl}-(2S/2R)-2-aminosubstitutedamides (21-33) and N1-[4-(4-ethyl-6-methoxy-5-pentyloxy-8-quinolylamino)pentyl]-(2S/2R)-2-aminosubstitutedamides (51-63) were synthesized in six steps from 6-methoxy-8-nitroquinoline and 4-methoxy-2-nitro-5-pentyloxyaniline, respectively. Several analogs displayed promising antimalarial activity in vitro against Plasmodium falciparum D6 (chloroquine-sensitive) and W2 (chloroquine-resistant) clones with high selectivity indices versus mammalian cells. The most promising analogs (21-24) also displayed potent antimalarial activity in vivo in a Plasmodium berghei-infected mouse model. Most interestingly, many analogs exhibited promising in vitro antileishmanial activity against Leishmania donovani promastigotes, and antimicrobial activities against a panel of pathogenic bacteria and fungi. Several analogs, notably 21-24, 26-32, and 60, showed less MetHb formation compared to primaquine indicating the potential of these compounds in 8-quinolinamine-based antimalarial drug development.

Full text of DOI:10.1016/j.bmc.2006.10.036

Bioorganic & Medicinal Chemistry 15 (2007) 915–930
Synthesis, antimalarial, antileishmanial, antimicrobial,
cytotoxicity, and methemoglobin (MetHB) formation activities
of new 8-quinolinamines
Kirandeep Kaur,a Sanjay R. Patel,a,ꢀ Premanand Patil,a,ꢀ Meenakshi Jain,a
Shabana I. Khan,b Melissa R. Jacob,b Shobana Ganesan,c
Babu L. Tekwanib,c and Rahul Jaina,*
aDepartment of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research,
Sector 67, S.A.S. Nagar, Punjab 160 062, India
bNational Center for Natural Products Research, School of Pharmacy, University of Mississippi, MS 38677, USA
cDepartment of Pharmacology, School of Pharmacy, University of Mississippi, MS 38677, USA
Received 3 October 2006; accepted 18 October 2006
Available online 20 October 2006
Abstract—We report the synthesis, in vitro antiprotozoal (against Plasmodium and Leishmania), antimicrobial, cytotoxicity (Vero and
MetHb-producing properties), and in vivo antimalarial activities of two series of 8-quinolinamines. N1-{4-[2-(tert-Butyl)-6-methoxy-8-
quinolylamino]pentyl}-(2S/2R)-2-aminosubstitutedamides (21–33) and N1-[4-(4-ethyl-6-methoxy-5-pentyloxy-8-quinolylamino)pen-
tyl]-(2S/2R)-2-aminosubstitutedamides (51–63) were synthesized in six steps from 6-methoxy-8-nitroquinoline and 4-methoxy-2-nitro-
5-pentyloxyaniline, respectively. Several analogs displayed promising antimalarial activity in vitro against Plasmodium falciparum D6
(chloroquine-sensitive) and W2 (chloroquine-resistant) clones with high selectivity indices versus mammalian cells. The most promising
analogs (21–24) also displayed potent antimalarial activity in vivo in a Plasmodium berghei-infected mouse model. Most interestingly,
many analogs exhibited promising in vitro antileishmanial activity against Leishmania donovani promastigotes, and antimicrobial activ-
ities against a panel of pathogenic bacteria and fungi. Several analogs, notably 21–24, 26–32, and 60, showed less MetHb formation
compared to primaquine indicating the potential of these compounds in 8-quinolinamine-based antimalarial drug development.
ꢀ 2006 Elsevier Ltd. All rights reserved.
1. Introduction
the genus Leishmania with different clinical forms rang-
ing from cutaneous leishmaniasis (CL) with skin lesions
to visceral leishmaniasis (VL) with enlargement of liver,
spleen, and bone marrow dysfunctions.2 The disease is
endemic worldwide with estimated 12 million cases,
which are mostly centered in Asia, Mediterranean re-
gions of Europe, Africa, Central America, and South
America. VL caused due to infection with Leishmania
donovani is fatal if left untreated.
Protozoan infections remain a major threat to public
health especially in the tropical parts of the world. More
than a third of world’s population is at risk of contract-
ing malaria. It is estimated that approximately 7000 peo-
ple, mainly children under the age of 5 years and
pregnant women in Africa and other parts of world,
die of malaria every day.1 Malaria is one of the main
obstacles to socio-economic development in sub-Saha-
ran Africa and other tropical regions of the world.
In the early 1970s, it was believed that virtually any
microbial infection could be treated, as a wide range
of antimicrobial agents (antibiotics) were available.
The belief proved short-lived, when pathogens resistant
to the conventional antibiotics routinely used to treat
microbial infections emerged. The widespread use of
antibiotics allowed many microbial strains to evolve
ways to adapt or become resistant to the currently avail-
able treatment regimens, resulting in an urgent need for
new antimicrobial drugs.3,4
Leishmaniasis is a group of diseases caused by infection
with intracellular species of the parasitic protozoan of
Keywords: 8-Quinolinamines; Synthesis; Malaria; Leishmania; Antimi-
crobial; Cytotoxicity; Methemoglobin toxicity.
*
Corresponding author. Tel.: +91 0172 221 4682; fax: +91 0172 221
4692; e-mail: rahuljain@niper.ac.in
These authors contributed equally to this work.
ꢀ
0968-0896/$ - see front matter ꢀ 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2006.10.036

916
K. Kaur et al. / Bioorg. Med. Chem. 15 (2007) 915–930
The emergence of Plasmodium falciparum strains resis-
tant to almost all the antimalarials currently in use has
prompted researchers around the world to search for
its effective replacement. This occurrence revitalized
research efforts to discover an entirely new structural
class of compounds or revisit the existing antimalarials
which were earlier considered inactive against P. falcipa-
rum.5 8-Quinolinamines, including primaquine (1, PQ,
Fig. 1), constitute an interesting and versatile class of
drugs,5 which in addition to antimalarial activity against
Plasmodium vivax and Plasmodium ovale also exhibit
antileishmanial6,7 and anticoccidial activities.8 PQ has
a limited role in current malaria chemotherapy due to
its limited activity against asexual blood stages of the
malaria parasite, severe hematotoxicities in patients with
the glucose-6-phosphate dehydrogenase (G-6-PD) defi-
ciency,9 and a short half-life due to its rapid metabolism
to inactive and toxic metabolites.10–13 Despite these neg-
ative attributes, PQ is deemed a worthy candidate for
additional structural optimization because it is the only
antimalarial drug which exhibits a certain degree of
activity against almost all the stages in the life cycle of
the human malaria parasite.5 We have already reported
two new 8-quinolinamines (2 and 3, Fig. 1) with
promising blood schizontocidal antimalarial activities.
2-tert-Butylprimaquine 2 (suppressive at 10 mg/kg, in
vivo against Plasmodium berghei) was synthesized to
eliminate a putative oxidative metabolic pathway known
for several quinoline ring-containing antimalarial drugs
including quinine by the placement of a bulky metabol-
ically stable tert-butyl group at C-2 of the heterocycle.14
While, 4-ethyl-5-pentyloxyprimaquine 3 (suppressive at
5 mg/kg, in vivo against P. berghei) was synthesized to
optimize substitution at the C-4 and C-5 position of
PQ, known sites of transformation to inactive/toxic
metabolites.15 It is known that approximately 35–83%
of PQ is metabolized to the inactive 4-(6-methoxy-quin-
olin-8-ylamino)pentanoic acid in a primate model.11 We
have reported antimalarial activities of several L-amino
acid conjugates of PQ in which the amino acid residue
possibly protects the side-chain amino group of PQ
from oxidation to the above-mentioned carboxylic
acid.16–18 In continuation of our efforts on the develop-
ment of 8-quinolinamines as a versatile bioactive class of
compounds, we report herein synthesis of two series of
the amino acid-conjugated 8-quinolinamines 21–33 and
51–63 (Fig. 2), in which side-chain amino group of the
most promising 8-quinolinamines 2 and 3 was deriva-
tized,19 and their in vitro and in vivo antimalarial activ-
ity, Vero cell cytotoxicity, in vitro MetHb-inducing
properties, and in vitro antileishmanial and antimicrobi-
al activity.
2. Chemistry
Commercially available 6-methoxy-8-nitroquinoline 4
upon direct ring-alkylation via a silver-catalyzed radical
oxidative decarboxylation of trimethylacetic acid by
ammonium persulfate in CH3CN and 10% H2SO4 at
70–80 ꢁC for 15 min produced 2-tert-butyl-6-methoxy-
8-nitroquinoline 5 (Scheme 1).14 The reaction is highly
regiospecific and provides an efficient method for direct
ring-alkylation of electron deficient quinoline ring under
acidic reaction conditions. Catalytic hydrogenation of
the latter compound 5 in 95% ethyl alcohol with wet ra-
ney-nickel catalyst (T1 grade) at 45 psi in a Parr hydrog-
enator for 45 min gave the highly hygroscopic and light-
sensitive 2-tert-butyl-6-methoxy-8-quinolinamine
6
which was subjected to the next step without purifica-
tion. Condensation of 6 with 2-(4-bromopentyl)-1,3-iso-
indolinedione20 in the presence of Et3N at 120 ꢁC for
24 h provided the 2-[4-(2-tert-butyl-6-methoxy-8-quin-
olylamino)pentyl]-1,3-isoindolinedione 7, which upon
hydrazinolysis with hydrazine hydrate in 95% ethyl alco-
hol at 80 ꢁC for 8 h afforded the N8-(4-amino-1-meth-
ylbutyl)-2-(tert-butyl)-6-methoxy-8-quinolinamine
(Scheme 1).14
2
H11C5O
H3CO
C2H5
H3CO
H3CO
N
N
C(CH3)3
NH2
N
NH
NH
NH
NH2
NH2
H3C
1. Primaquine (PQ)
Figure 1. Structures of primaquine (1) and promising 8-quinolinamines 2–3.
H3C
H3C
2. 2-tert-Butylprimaquine
3. 4-Ethyl-5-pentyloxyprimaquine
H11C5O
H3CO
C2H5
N
H3CO
N
C(CH3)3
NH
R3
NH
R
H
H
N
N
O
H3C
NH2
H3C
NH2
O
51-63
R = L/D- amino acid side chain
Figure 2. General structure of the newly synthesized 8-quinolinamines.
21-33

K. Kaur et al. / Bioorg. Med. Chem. 15 (2007) 915–930
H3CO H3CO
917
H3CO
ii
i
N
N
C(CH3)3
N
C(CH3)3
NO2
NO2
NH2
4
5
6
iii
H3CO
H3CO
H3CO
iv
v
N
C(CH3)3
NPhth
N
C(CH3)3
N
C(CH3)3
NH2
NH
NH
R
NH
H
N
O
NH-Cbz/Boc
2
8-20
7
vi
H3CO
N
C(CH3)3
NH
R
H
N
O
H3C
NH2
21-33
Scheme 1. Reagents and conditions: (i) (CH3)3CCO2H, AgNO3, (NH4)2S2O8, 10% H2SO4, CH3CN, 70 ꢁC; (ii) raney Ni, EtOH, H2, 45 psi, 45 min;
(iii) 2-(4-bromopentyl)-1,3-isoindolinedione, Et3N, 120 ꢁC, 24 h; (iv) NH2NH2ÆH2O, EtOH, reflux, 8 h; (v) suitably N- and side-chain protected L/D-
amino acid, DCC, DCM, rt, 6 h; (vi) H2/Pd/C, MeOH, 1 h, rt or 4 N HCl/MeOH, 1 h, rt or 30% HBr/AcOH, 45 min, rt.
Reaction of 1-chloro-3-pentanone by its addition in
two equal portions to the well-stirred homogeneous mix-
ture of 4-methoxy-2-nitro-5-pentyloxyaniline 34 and
o-phosphoric acid at 80 ꢁC followed by the addition of
As2O5 produced the 4-ethyl-6-methoxy-8-nitro-5-pentyl-
oxyquinoline 35. The latter compound 35 was convert-
ed to N8-(4-amino-1-methylbutyl)-4-ethyl-6-methoxy-5-
pentyloxy-8-quinolinamine 3 in three steps following
aforementioned procedure (Scheme 2).17
oxy-8-quinolylamino)pentylcarbamoyl]alkyl}carbamic
acid benzyl/tert-butyl esters 38–50 were deprotected
using the procedure(s) described in Section 5.3 to pro-
vide N1-{4-[2-(tert-butyl)-6-methoxy-8-quinolylamino]
pentyl}-(2S/2R)-2-aminosubstitutedamides 21–33 and
N1-[4-(4-ethyl-6-methoxy-5-pentyloxy-8-quinolylamino)
pentyl]-(2S/2R)-2-aminosubstitutedamides 51–63, respec-
tively (Schemes 1 and 2).
Compounds 2 and 3 upon reaction with suitably side-
chain protected Cbz/Boc-L/D-amino acid in the presence
of DCC in DCM for 6 h at ambient temperature gave the
(S/R)-{alkoxycarbonylamino-1-[4-(2-tert-butyl-6-meth-
oxy-8-quinolylamino)pentylcarbamoyl]alkyl}carbamic
acid benzyl/tert-butyl esters 8–20 and (S/R)-{alkoxycar-
bonylamino-1-[4-(4-ethyl-6-methoxy-5-pentyloxy-8-quin-
olylamino)pentylcarbamoyl]alkyl}carbamic acid benzyl/
tert-butyl esters 38–50, respectively (Schemes 1 and 2).
3. Biological activities
3.1. Antimalarial, cytotoxicity, and MetHb activities
Determination of in vitro antimalarial activity was
based on the plasmodial LDH activity.21 As shown in
Tables 1 and 2, antimalarial activities of analogs 21–33
and 51–63 are reported as IC50 values versus chloro-
quine-sensitive (D6) and chloroquine-resistant (W2)
strains of P. falciparum. Analogs 21–24 (series 1) were
most potent with IC50 values in the range of 180–
300 ng/mL for D6 and 300–450 ng/mL for W2 com-
pared to IC50 of 2000 and 2800 ng/mL for standard drug
primaquine (Table 1). While, remaining analogs 25–32
Finally, (S/R)-{alkoxycarbonylamino-1-[4-(2-tert-butyl-
6-methoxy-8-quinolylamino)pentylcarbamoyl]alkyl}car-
bamic acid benzyl/tert-butyl esters 8–20 and (S/R)-{alk-
oxycarbonylamino-1-[4-(4-ethyl-6-methoxy-5-pentyl-

918
K. Kaur et al. / Bioorg. Med. Chem. 15 (2007) 915–930
H11C5O
H3CO
H11C5O
H3CO
C2H5
N
H11C5O
H3CO
C2H5
N
ii
i
NH2
NO2
34
NO2
NH2
36
35
iii
H11C5O
C2H5
H11C5O
H3CO
C2H5
H11C5O
H3CO
C2H5
H3CO
v
iv
N
N
N
NH
NH
NH
R
H
N
NH2
NPhth
Cbz/Boc
H3C
H3C
H3C
N
H
O
38-50
3
37
vi
H11C5O
H3CO
C2H5
N
NH
R
H
N
H3C
NH2
O
51-63
Scheme 2. Reagents and conditions: (i) 1-chloro-3-pentanone, 85% o-H3PO4, As2O5, 80 ꢁC, 3 h; (ii) raney nickel, EtOH, H2, 45 psi, 45 min; (iii) 2-(4-
bromopentyl)-1,3-isoindolinedione, Et3N, 120 ꢁC, 24 h; (iv) NH2NH2ÆH2O, EtOH, reflux, 8 h; (v) suitably N- and side-chain protected L/D-amino
acid, DCC, DCM, rt, 6 h; (vi) H2/Pd/C, MeOH, 1 h, rt or 4 N HCl/MeOH, 1 h, rt or 30% HBr/AcOH, 45 min, rt.
produced modest IC50 in the range between 770 and
2800 ng/mL for D6 strain and between 600 and
2300 ng/mL for drug-resistant W2 strain of P. falcipa-
rum. Analog 33 was found to be inactive. In contrast,
analogs 51–63 were less active (Table 2). The most active
compound 51 of this series exhibited IC50 of 580 ng/mL
for D6 strain and 730 ng/mL for W2 strain of P. falcipa-
rum. The remaining analogs produced modest IC50 in
the range between 700 and 4760 ng/mL for D6 clone
and between 950 and 3600 ng/mL for W2 clone
(Table 2).
>79 to 53 for W2 clone) compared to 11.9 (D6 clone)
and 8.5 (W2 clone) for PQ indicating their better safety
profile.
Hematotoxicity by 8-quinolinamines is caused due to
their metabolism to the toxic metabolites, which are
unstable and difficult to isolate.24 The analogs of both
series were also tested for metabolism-linked methemo-
globin toxicity in vitro and % MetHb formation was cal-
culated at 20 lg/mL in comparison to vehicle control.25
All the analogs of series 1 (21–33) induced substantially
less % MetHb formation (26.8–40.6%) compared to PQ
(47.9%) as shown in Table 1. All the tested analogs of
series 2 produced almost similar MetHb formation as
that of PQ except analog 60 which showed significantly
lower 34.2% MetHb formation (Table 2).
The in vitro cytotoxicity of analogs (series 1–2) was
determined against mammalian kidney fibroblast (Vero)
cell line (obtained from ATCC) up to a highest concen-
tration of 23.8 lg/mL by neutral red assay.22,23 None of
the compounds were cytotoxic up to the highest test
concentration. The selectivity index (ratio of IC50 in
Vero cells to IC50 in P. falciparum strain) for all
compounds was calculated (Tables 1 and 2). Analogs
21–24 (series 1) with highest antimalarial activity
were found to exhibit a very high selectivity index to
plasmodial strains (>132 to >79.33 for D6 clone and
The most active analogs 21–24 (series 1) were selected
for in vivo evaluation of the blood-schizontocidal anti-
malarial activity against P. berghei (sensitive strain) in
a rodent malaria model as described (Table 3).14 Briefly;
mice (6 mice per group) were dosed orally at 100, 50, 25,
and 10 mg/kg/day · 4 (oral). Chloroquine was used as a

K. Kaur et al. / Bioorg. Med. Chem. 15 (2007) 915–930
919
Table 1. In vitro antimalarial activity (Plasmodium falciparum), cytotoxicity, and MetHb formation activities of the N1-{4-[2-(tert-butyl)-6-methoxy-
8-quinolylamino]pentyl}-(2S/2R)-2-aminosubstitutedamides 21–33 (series 1)
H3CO
N
C(CH3)3
H
NH
N
R
H3C
O
Compound
R
Plasmodium falciparum
(D6 clone)
Plasmodium falciparum
(W2 clone)
Vero cell
cytotoxicity
MetHb
Toxicity
IC50 (ng/mL) Sel. indexa IC50 (ng/mL) Sel. Indexa IC50 (ng/mL) % MetHb formation (20 lg/mL)
21
22
23
24
25
26
27
28
29
30
31
32
33
(R)-Lys
(R)-Orn
(S)-Arg
(R)-Arg
(S)-His
180
190
>132.2
>125.3
>79.3
>85.0
>19.8
>10.8
>8.5
300
370
>79.3
>64.3
>52.9
>59.5
>19.8
>10.8
>10.3
>25.9
>36.6
>39.7
>35.5
>31.3
—
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
40.1
34.6
34.2
39.2
26.8
40.6
28.2
35.7
34.3
34.5
36.5
35.0
NT
300
280
450
400
1200
2200
2800
770
1200
2200
2300
920
(R)-His
(S)-Trp
(S)-Phe
(S)-Tyr
(S)-Met
(S)-Ser
>30.9
>27.4
>27.4
>23.8
>27.0
—
870
870
650
600
1000
880
670
760
(R)-(Bzl)-Cys
(R)-Cys
NA
2000
NA
2800
Primaquine (PQ)
>11.9
>8.5
47.9
NC, not cytotoxic upto 23,800 ng/mL (23.8 lg/mL). NT, not tested. NA, Not active. Chloroquine: IC50 = 14 ng/mL, Sel. index = 1700 (D6 clone);
IC50 = 100 ng/mL, Sel. index = 238 (W6 clone). Artemisinin: IC50 = 15.2 ng/mL, Sel. index = 1565 (D6 clone); IC50 = 9 ng/mL, Sel. index = 2644 (W6
clone).
a Selectivity index is the ratio of IC50 in Vero cells to IC50 in Plasmodium falciparum (D6 or W2).
Table 2. In vitro antimalarial activity (Plasmodium falciparum), cytotoxicity, and MetHb formation activity of the N1-[4-(4-ethyl-6-methoxy-5-
pentyloxy-8-quinolylamino)pentyl]-(2S/2R)-2-aminosubstitutedamides 51–63 (series 2)
H11C5O
H3CO
C2H5
N
NH
H
N
R
H3C
O
Compound
R
Plasmodium falciparum
Plasmodium falciparum
Vero cell
cytotoxicity
MetHb
toxicity
(D6 clone)
(W2 clone)
IC50 (ng/mL) Sel. indexa IC50 (ng/mL) Sel. indexa IC50 (ng/mL) % MetHb formation (20 lg/mL)
51
52
53
54
55
56
57
58
59
60
61
62
63
(R)-Lys
(R)-Orn
(S)-Arg
(R)-Arg
(S)-His
(R)-His
(S)-Trp
(S)-Phe
(S)-Tyr
(S)-Met
(S)-Ser
580
700
>41.0
>34.0
>18.3
>17.0
—
730
>32.6
>18.3
>3.4
>2.8
—
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
48.7
43.6
39.2
46.1
NT
1300
1400
1700
NA
1300
1400
NA
NA
860
—
NA
950
—
NT
>20.9
>6.4
>6.3
>12.5
>5.0
>11.9
—
>18.9
>10.8
>7.2
>13.2
>6.6
>19.8
—
39.1
NT
3700
3800
1900
4760
2200
3300
1800
3600
1200
NA
NT
34.2
NT
(R)-(Bzl)-Cys 2000
(R)-Cys
NT
NA
2000
47.5
47.9
Primaquine (PQ)
>11.9
2800
>8.5
NC, not cytotoxic upto 23,800 ng/mL (23.8 lg/mL). NT, not tested. NA, not active. Selectivity index is the ratio of IC50 in Vero cells to IC50 in
Plasmodium falciparum (D6 or W2). Chloroquine: IC50 = 14 ng/mL, Sel. index = 1700 (D6 clone); IC50 = 100 ng/mL, Sel. index = 238 (W6 clone).
Artemisinin: IC50 = 15.2 ng/mL, Sel. index = 1565 (D6 clone); IC50 = 9 ng/mL, Sel. index = 2644 (W6 clone).
a Selectivity index is the ratio of IC50 in Vero cells to IC50 in P. falciparum (D6 or W2).

920
K. Kaur et al. / Bioorg. Med. Chem. 15 (2007) 915–930
Table 3. In vivo (Plasmodium berghei) antimalarial activity of the 8-quinolinamine analogs 21–24
Compound
Plasmodium berghei (mg/kg/day · 4, oral)
10
25
50
100
21
22
(2/6) active
(6/6) curative
(0/6) inactive
—
(6/6) curative
(6/6) curative
(3/6) active
(6/6) curative
—
(6/6) curative
(6/6) curative
(6/6) curative
(6/6) curative
(0/6) inactive
—
—
23
24
(0/6) inactive
—
Primaquine (PQ)
—
The term ‘curative’ indicates complete elimination of malaria parasites from the body, and animals survive up to day D + 60. The term ‘active’ or
‘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.
positive control at a suppressive dose of 10 mg/kg/
day · 4 (oral). The negative consisted of untreated (vehi-
cle only) mice in which 100% mortality was observed
within 6–8 days, with a mean survival time of 6.2 days.
The compounds/vehicle were administered on days 0–3
postinfection. All compounds produced 100% cure at
the primary test dose of 100 mg/kg. Analogs 21–22
and 24 were also curative at the lower test dose of
50 mg/kg, while 23 was found to show suppressive activ-
ity. The most potent compound 21 also produced a
100% cure rate at the lower test dose of 25 mg/kg and
was suppressive at the lowest test dose of 10 mg/kg
(2/6 cures) (Table 3). These results are in agreement with
our earlier observation that attachment of a cationic
side-chain amino acid led to a considerable increase in
antimalarial activity of 8-quinolinamines.15 It can be
presumed that these side-chain modified ring-substituted
PQ analogs have substantially improved therapeutic in-
dex (higher blood-schizontocidal antimalarial activity
and reduced MetHb toxicity) possibly due to their re-
duced penetration into the red cells because of steric hin-
drance that does not allow destabilization of the red cell
membrane, inducing hemolysis, which is the source of
main toxicity. At the same time, attachment of an amino
acid residue may serve to protect the PQ’s primary side-
chain amino function against metabolic processes dis-
cussed earlier.
Table 4. In vitro antileishmenial (Leishmania donovani) activity of the
8-quinolinamine analogs 21–33 and 51–63
Compound
Leishmania donovani
IC50 (lg/mL) IC90 (lg/mL)
12
4.6
7.5
16
21
22
37
26
30
38
18
30
23
24
25
26
4
6.5
2.9
2.7
3
27
28
6.5
6.6
6.6
29
30
9.5
4.5
4
32
31
32
24
18
33
51
15
33
39
17
17
52
53
37
18
19
>40
>40
NA
NA
54
55
NA
NA
56
57
3.3
6.7
58
59
4.2
4.4
26
26
60
61
19
19
4.6
37
38
62
63
23
29
6
19.9
3.2. Antileishmanial activities
Primaquine (PQ)
NA
IC50 and IC90 are the sample conc that kill 50% and 90% cells com-
pared to vehicle control. NA, no activity. Pentamidine: IC50 = 1 lg/
mL, IC90 = 3.8 lg/mL. Amphotericin B: IC50 = 0.19 lg/mL,
IC90 = 0.35 lg/mL.
Antileishmanial activity of the compounds was tested
in vitro against a culture of L. donovani promastigotes
by Alamar Blue assay.26,27 It was interesting to note that
8-quinolinamine analogs 25, 27–29, 32, 57–59, and 62
exhibited stronger antileishmanial activities with IC50
values ranging between 2.7 and 4.6 lg/mL (Table 4) in
comparison to the activity of PQ (IC50 = 19.9 lg/mL).
The activity was comparable to the standard drug pent-
amidine (IC50 = 1 lg/mL) used as positive control. Their
IC90 values ranged from 6.5 to 18 lg/mL as compared to
IC90 of 3.8 lg/mL for pentamidine. However, they were
much less potent than amphotericin B (IC50 = 0.19 and
IC90 = 0.35 lg/mL).
reported in Table 5 including the positive control Cipro-
floxacin. Most of the analogs (e.g., 21–32, 57–59) exhibit-
ed promising antibacterial activity against MRS
(IC50 = 3–15 lg/mL and MIC = 5–20 lg/mL). Com-
pounds 57 and 27 were bactericidal at 5 and 10 lg/mL,
respectively (Table 5). Analogs 22–24, 27–29, and 32 also
showed activity against M. intracellulare (IC50 = 4.5–
15 lg/mL and MIC = 10–20 lg/mL). Analogs 27 and 29
were the most potent against both MRS (IC50 = 3 lg/
mL, MIC = 5 lg/mL, MBC = 10 lg/mL) and M. intracel-
lulare (IC50 = 7 lg/mL, MIC = 10 lg/mL, MBC = 20 lg/
mL) and were bactericidal to both organisms. Analog 57
was the most bactericidal against MRS with an IC50 of
3.3. Antimicrobial activities
The antibacterial activities of the 8-quinolinamines 21–33
and 51–63 against methicillin-resistant Staphylococcus
aureus (MRS) and Mycobacterium intracellulare are

K. Kaur et al. / Bioorg. Med. Chem. 15 (2007) 915–930
921
Table 5. In vitro antibacterial activities of the 8-quinolinamine analogs 21–33 and 51–63
Compound
Methicillin-resistant Staphylococcus aureus (MRS)
Mycobacterium intracellulare
IC50 (lg/mL)
MIC (lg/mL)
MBC (lg/mL)
IC50 (lg/mL)
MIC (lg/mL)
MBC (lg/mL)
21
22
23
24
25
26
27
28
29
30
31
32
33
51
52
53
54
55
56
57
58
59
60
61
62
63
15
8
20
20
NA
NA
20
NA
9
NA
20
NA
NA
NA
NA
NA
NA
20
7
20
20
15
7
20
10
9
20
20
7
10
10
NA
NA
7
NA
NA
10
6
20
10
3
5
10
7
NA
20
10
20
10
NA
20
3
5
20
4.5
NA
NA
10
10
6.5
4
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
5
NA
NA
20
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
10
10
15
15
15
15
NA
NA
NA
3
NA
NA
20
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
5
6.5
6
10
10
NA
NA
NA
NA
NA
NA
NA
NA
6.5
NA
NA
NA
NA
NA
IC50 = the concentration (lg/mL) that affords 50% growth inhibition. MIC, minimum inhibitory concentration (the lowest concentration in lg/mL
that allows no detectable growth). MBC, minimum bactericidal concentration (the lowest concentration in lg/mL that kills the organism). NA, no
activity at the highest test concentration of 20 lg/mL. Ciprofloxacin: IC50 = 0.09 lg/mL, MIC = 0.31 lg/mL, MBC = 2.5 lg/mL (MRS);
IC50 = 0.3 lg/mL, MIC = 0.63 lg/mL, MBC = 2.5 lg/mL (Mi).
3.0 lg/mL, MIC and MBC of 5 lg/mL but was inactive
against M. intracellulare at the highest test concentration
of 20 lg/mL (Table 5).
reported analogs have exhibited potent in vitro activity
against drug-sensitive and drug-resistant malaria para-
sites. Analogs 21–24 have also displayed promising anti-
malarial activity in vivo in a P. berghei-mouse malaria
model. The most potent compound 21 was found cura-
tive at 25 mg/kg and suppressive at 10 mg/kg. The po-
tent 8-quinolinamines were also found to exhibit high
selectivity index and a significantly reduced methemo-
globin toxicity, indicating their better safety profiles
than primaquine. Several analogs also displayed high
antileishmanial activities comparable to standard drug
pentamidine and superior to that of primaquine. The
compounds were also evaluated against a panel of path-
ogenic bacteria and fungi, and displayed promising
activities. In conclusion, the results of this study confirm
that 8-quinolinamines are a versatile class of compounds
that exhibit broad-spectrum activities against parasitic
and infectious diseases. The careful structural optimiza-
tion of this class of compounds could lead to promising
agents with utility in treatment of malaria, leishmania-
sis, and opportunistic infections.
The antifungal activities of the 8-quinolinamines 21–33
and 51–63 against the opportunistic yeast Candida
albicans, Candida glabrata, Candida krusei, and Crypto-
coccus neoformans, along with the positive control
Amphotericin B, are summarized in Table 6. All com-
pounds were inactive at 20 lg/mL against the filamen-
tous fungus Aspergillus fumigatus (data not shown).
Analog 57 was the most potent of all 8-quinolinamines
tested and produced fungicidal activities against C. albi-
cans (IC50 = 10 lg/mL, MIC = 20 lg/mL, MFC = 20 lg/
mL), C. glabrata (IC50 = 4 lg/mL, MIC = 10 lg/mL,
MFC = 10 lg/mL),
C.
krusei
(IC50 = 7 lg/mL,
MIC = 10 lg/mL, MFC = 10 lg/mL), and C. neofor-
mans (IC50 = 3.5 lg/mL, MIC = 5 lg/mL, MFC = 5 lg/
mL). All analogs (excluding 60, 61 and 63) exhibited
promising activity against C. neoformans with MFCs
as low as 5 lg/mL (analogs 21–23, 25, 27, 57–58, 62)
(Table 6).
5. Experimental
5.1. Synthesis
4. Conclusions
We have reported synthesis and biological activities of
two new series of 8-quinolinamines. Several of the
Melting points were recorded on Mettler DSC 851 or
capillary melting point apparatus and are uncorrected.

922
K. Kaur et al. / Bioorg. Med. Chem. 15 (2007) 915–930
Table 6. In vitro antifungal activities of the 8-quinolinamine analogs 21–33 and 51–63
Compound
Candida albicans
MIC MFC
(lg/mL) (lg/mL) (lg/mL) (lg/mL) (lg/mL) (lg/mL) (lg/mL) (lg/mL) (lg/mL) (lg/mL) (lg/mL) (lg/mL)
Candida glabrata
Candida krusei
Cryptococcus neoformans
IC50
IC50
MIC MFC
IC50
MIC MFC
IC50 MIC MFC
21
22
23
24
25
26
27
28
29
30
31
32
33
51
52
53
54
55
56
57
58
59
60
61
62
63
NA
NA
NA
NA
NA
15
NA
NA
NA
NA
NA
20
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
20
NA
15
NA
NA
20
NA
NA
NA
NA
NA
NA
NA
NA
20
15
8
20
20
20
20
3.5
3.5
3.5
3.5
3
5
5
5
5
15
8.5
15
20
20
20
20
5
5
NA
NA
15
NA
NA
NA
20
10
5
10
5
9.5
7.5
10
20
10
20
20
3.5
3.5
3.5
3
5
10
5
15
20
15
20
20
5
NA
15
NA
20
NA
7
NA
20
15
NA
10
NA
20
10
5
10
10
20
10
10
10
20
20
10
20
20
20
5
7.5
NA
15
NA
15
NA
20
NA
15
NA
NA
20
NA
NA
20
NA
20
NA
20
10
20
10
10
10
10
20
10
20
20
20
5
6.5
3.5
6.5
6
NA
NA
NA
NA
NA
NA
NA
NA
10
NA
NA
NA
NA
NA
NA
NA
NA
20
7.5
NA
NA
NA
NA
NA
NA
NA
4
20
NA
NA
NA
NA
NA
NA
NA
NA
10
NA
NA
NA
NA
NA
NA
NA
NA
10
NA
NA
NA
NA
NA
NA
NA
10
NA
NA
NA
NA
NA
NA
NA
10
NA
NA
15
4.5
6
NA
NA
NA
NA
7
15
10
10
3.5
3.5
3.5
NA
NA
3.5
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
15
10
NA
20
NA
20
15
8
20
20
20
20
5
5
5
10
NA
NA
5
NA
NA
15
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
5
NA
NA
NA
IC50 = the concentration (lg/mL) that affords 50% growth inhibition. MIC, minimum inhibitory concentration (the lowest concentration in lg/mL
that allows no detectable growth). MFC, minimum fungicidal concentration (the lowest concentration in lg/mL that kills the organism). NA, no
activity at the highest test concentration of 20 lg/mL. Amphotericin B: IC50 = 0.25 lg/mL, MIC = 0.63 lg/mL, MFC = 1.25 lg/mL (Ca);
IC50 = 0.07 lg/mL, MIC = 0.31 lg/mL, MFC = 0.625 lg/mL (Cg); IC50 = 0.6 lg/mL, MIC = 1.25 lg/mL, MFC = 1.25 lg/mL (Ck); IC50 = 0.75 lg/
mL, MIC = 1.25 lg/mL, MFC = 1.5 lg/mL (Cn).
1H spectra were recorded on 300 MHz Bruker FT-NMR
(Avance DPX300) spectrometer using tetramethylsilane
as internal standard and the chemical shifts are reported
in d units. Mass spectra were recorded on HRMS (Finn-
igan Mat LCQ spectrometer) (APCI/ESI). Elemental
analyses were recorded on Elementar Vario EL spec-
trometer. All chromatographic purification was per-
formed with silica gel 60 (230–400 mesh), whereas all
TLC (silica gel) development was performed on silica
gel-coated (Merck Kiesel 60 F254, 0.2 mm thickness)
sheets. All chemicals were purchased from Aldrich
Chemical Ltd (Milwaukee, WI, USA). Solvents used
for the chemical synthesis acquired from commercial
sources were of analytical grade, and were used without
further purification unless otherwise stated.
and suitably side-chain protected Cbz/Boc-L/D-amino
acid (1.1 mmol) in CH2Cl2 (15 mL), DCC (1.1 mmol)
was added. Reaction mixture was allowed to attain
ambient temperature and stirring was continued for
another 6 h. The solvent was removed under reduced
pressure and ethyl acetate (20 mL) was added to the res-
idue. The reaction mixture was kept in refrigerator over-
night and the separated 1,3-dicyclohexylurea (DCU)
was filtered. Filtrate was washed with saturated sodium
bicarbonate solution (3· 5 mL) followed by water (2·
5 mL) and dried over Na2SO4. The solvent was removed
under reduced pressure to afford the crude product,
which was purified by flash column chromatography
on silica gel using EtOAc/hexanes (30:70) to afford the
(S/R)-{alkoxycarbonylamino-1-[4-(2-tert-butyl-6-meth-
oxy-8-quinolylamino)pentylcarbamoyl]alkyl}carbamic
acid benzyl/tert-butyl esters (8–20) and (S/R)-{alkoxy-
carbonylamino-1-[4-(4-ethyl-6-methoxy-5-pentyloxy-8-
quinolylamino)pentylcarbamoyl]alkyl}carbamic acid
benzyl/tert-butyl esters (38–50).
5.2. General method for the synthesis of (S/R)-{alkoxy-
carbonylamino-1-[4-(2-tert-butyl-6-methoxy-8-quinolyla-
mino)pentylcarbamoyl]alkyl}carbamic acid benzyl/tert-
butyl esters (8–20) and (S/R)-{alkoxycarbonylamino-1-[4-
(4-ethyl-6-methoxy-5-pentyloxy-8- quinolylamino)pentyl-
carbamoyl]alkyl}carbamic acid benzyl/tert-butyl esters
(38–50)
5.2.1. (R)-{5-Benzyloxycarbonylamino-1-[4-(2-tert-butyl-
6-methoxy-8-quinolylamino)pentylcarbamoyl]pentyl}car-
bamic acid benzyl ester (8). Yield: 85%; oil. IR (neat):
1
To an ice cooled stirred solution of N8-(4-amino-1-
methylbutyl)-2-(tert-butyl)-6-methoxy-8-quinolinamine14
(2, 1 mmol) or N8-(4-amino-1-methylbutyl)-4-ethyl-6-
methoxy-5-pentyloxy-8-quinolinamine17 (3, 1 mmol)
3431, 3019, 2855, 1713, 1675 cmꢀ1. H NMR (CDCl3):
d 7.86 (d, 1H, J = 8.60 Hz), 7.40 (d, 1H, J = 8.55 Hz),
7.31 (m, 10H), 6.30 (d, 1H, J = 2.40 Hz), 6.24 (d, 1H,
J = 2.40 Hz), 5.04 (m, 4H), 4.10 (m, 1H), 3.84 (s, 3H),

K. Kaur et al. / Bioorg. Med. Chem. 15 (2007) 915–930
923
3.58 (m, 2H), 3.27 (m, 2H), 3.12 (m, 2H), 1.41 (m, 10H),
1.40 (s, 9H), 0.89 (d, 3H, J = 6.50 Hz); APCIMS: m/z
712 (M+1); Anal. Calcd for C41H53N5O6 (711.9): C,
69.17; H, 7.50; N, 9.84. Found: C, 69.34; H, 7.34; N,
9.99.
5.2.6. (R)-{2-(3-Benzyloxymethyl-1H-imidazol-4-yl)-1-[4-
(2-tert-butyl-6-methoxy-8-quinolylamino)pentylcarba-
moyl]ethyl}carbamic acid tert-butyl ester (13). Yield:
1
90%; oil. IR (neat): 3426, 2965, 2870, 1726 cmꢀ1. H
NMR (CDCl3): d 7.90 (d, 1H, J = 8.60 Hz), 7.50 (s,
1H), 7.44 (d, 1H, J = 8.60 Hz), 7.30 (m, 5H), 6.90 (s,
1H), 6.32 (s, 1H), 6.24 (s, 1H), 6.12 (br s, 1H), 5.95
(m, 2H), 5.34 (br s, 1H), 5.22 (m, 2H), 4.50 (m, 1H),
3.84 (s, 3H), 3.17 (m, 2H), 3.08 (m, 3H), 1.67 (m, 4H),
1.40 (s, 9H), 1.40 (s, 9H), 1.30 (d, 3H, J = 6.30 Hz);
APCIMS: m/z 673 (M+1); Anal. Calcd for C38H52-
N6O5 (672.9): C, 67.83; H, 7.79; N, 12.49. Found: C,
67.53; H, 7.88; N, 12.20.
5.2.2. (R)-{4-tert-Butoxycarbonylamino-1-[4-(2-tert-bu-
tyl-6-methoxy-8-quinolylamino)pentylcarbamoyl]butyl}
carbamic acid tert-butyl ester (9). Yield: 75%; oil. IR
(neat): 3362, 2965, 2863, 1715, 1694 cmꢀ1 1H NMR
.
(CDCl3): d 7.86 (d, 1H, J = 8.60 Hz), 7.40 (d, 1H,
J = 8.58 Hz), 6.30 (d, 1H, J = 2.30 Hz), 6.24 (s, 1H,
J = 2.30 Hz), 5.14 (br s, 1H), 4.64 (br s, 1H), 4.10 (m,
1H), 3.87 (s, 3H), 3.32 (t, 2H, J = 6.60 Hz), 3.05 (m,
1H), 1.65 (m, 4H), 1.59 (m, 6H), 1.42 (m, 18H), 1.40
(s, 9H), 1.29 (d, 3H, J = 6.40 Hz); APCIMS: m/z 630
(M+1); Anal. Calcd for C34H55N5O6 (629.8): C, 64.84;
H, 8.80; N, 11.12. Found: C, 64.54; H, 8.99; N, 10.99.
5.2.7. (S)-[1-[4-(2-tert-Butyl-6-methoxy-8-quinolylami-
no)pentylcarbamoyl]-2-(1H-indol-3-yl)ethyl]carbamic
acid tert-butyl ester (14). Yield: 96%; oil. IR (neat): 3384,
1
2927, 2854, 1694 cmꢀ1. H NMR (CDCl3): d 7.91 (d,
1H, J = 8.60 Hz), 7.47 (d, 1H, J = 8.60 Hz), 7.10 (m,
5H), 6.89 (d, 1H, J = 5.70 Hz), 6.35 (s, 1H), 6.22 (s,
1H), 6.05 (br s, 1H), 5.39 (br s, 1H), 4.36 (m, 1H),
3.90 (s, 3H), 3.46 (m, 2H), 3.28 (m, 2H), 3.03 (m, 1H),
1.55 (m, 4H), 1.42 (s, 9H), 1.25 (s, 9H), 0.88 (d, 3H,
J = 6.50 Hz); APCIMS: m/z 602 (M+1); Anal. Calcd
for C35H47N5O4 (601.8): C, 69.86; H, 7.87; N, 11.64.
Found: C, 69.55; H, 7.63; N, 12.03.
5.2.3. (S)-{4-(N,N0-Bisbenzyloxycarbonylguanidino)-1-[4-
(2-tert-butyl-6-methoxy-8-quinolylamino)pentylcarba-
moyl]butyl}carbamic acid tert-butyl ester (10). Yield:
67%; mp 113–115 ꢁC. IR (KBr): 3384, 2965, 2843,
1
1718 cmꢀ1. H NMR (CDCl3): d 9.40 (br s, 2H), 7.86
(d, 1H, J = 8.60 Hz), 7.40 (d, 1H, J = 8.60 Hz), 7.35
(m, 10H), 6.55 (br s, 1H), 6.30 (s, 1H), 6.21 (s, 1H),
6.08 (br s, 1H), 5.21 (m, 2H), 5.09 (m, 2H), 4.96 (m,
1H), 4.29 (m, 2H), 3.86 (s, 3H), 3.65 (m, 2H), 3.47 (t,
2H, J = 6.70 Hz), 2.97 (m, 1H), 1.71 (m, 6H), 1.42 (s,
9H), 1.38 (s, 9H), 1.26 (d, 3H, J = 6.0 Hz); APCIMS:
m/z 841 (M+1); Anal. Calcd for C46H61N7O8 (840.0):
C, 65.77; H, 7.32; N, 11.67. Found: C, 66.03; H, 6.99;
N, 11.57.
5.2.8. (S)-{1-[4-(2-tert-Butyl-6-methoxy-8-quinolylami-
no)pentylcarbamoyl]-3-methylsulfanylpropyl}carbamic
acid tert-butyl ester (15). Yield: 90%; oil. IR (neat): 3345,
1
2965, 2870, 1694 cmꢀ1. H NMR (CDCl3): d 7.86 (d,
1H, J = 8.60 Hz), 7.40 (d, 1H, J = 8.60 Hz), 6.30 (d,
1H, J = 2.40 Hz), 6.24 (d, 1H, J = 2.40 Hz), 6.14 (br s,
1H), 5.18 (br s, 1H), 4.17 (m, 1H), 3.86 (s, 3H), 3.60
(m, 1H), 3.29 (m, 2H), 2.55 (m, 2H), 2.06 (m, 2H),
1.65 (m, 7H), 1.42 (s, 9H), 1.40 (s, 9H), 1.22 (d, 3H,
J = 6.40 Hz); APCIMS: m/z 547 (M+1); Anal. Calcd
for C29H46N4O4S (546.8): C, 63.70; H, 8.48; N, 10.25.
Found: C, 63.31; H, 8.78; N, 10.12.
5.2.4. (R)-{4-(N,N0-Bisbenzyloxycarbonylguanidino)-1-
[4-(2-tert-butyl-6-methoxy-8-quinolylamino)pentylcarba-
moyl]butyl}carbamic acid tert-butyl ester (11). Yield:
70%; mp 114–116 ꢁC. IR (KBr): 3390, 2970, 2840,
1688, 1727 cmꢀ1 1H NMR (CDCl3): d 9.43 (br s,
.
1H), 9.40 (br s, 1H), 7.84 (d, 1H, J = 8.70 Hz), 7.42
(d, 1H, J = 8.70 Hz), 7.33 (m, 10H), 6.51 (br s,
1H), 6.32 (s, 1H), 6.25 (s, 1H), 6.10 (br s, 1H),
5.20 (m, 2H), 5.14 (m, 2H), 4.93 (m, 1H), 4.23 (m,
2H), 3.80 (s, 3H), 3.67 (m, 2H), 3.44 (t, 2H,
J = 6.70 Hz), 2.99 (m, 1H), 1.73 (m, 6H), 1.42 (s,
9H), 1.40 (s, 9H), 1.25 (d, 3H, J = 6.0 Hz); APCIMS:
m/z 841 (M+1); Anal. Calcd for C46H61N7O8 (840.0):
C, 65.77; H, 7.32; N, 11.67. Found: C, 65.70; H,
7.55; N, 11.41.
5.2.9. (S)-{1-[4-(2-tert-Butyl-6-methoxy-8-quinolylami-
no)pentylcarbamoyl]-2-phenylethyl}carbamic acid tert-
butyl ester (16). Yield: 92%; oil. IR (neat): 3383, 2965,
1
2875, 1724, 1678 cmꢀ1. H NMR (CDCl3): d 7.86 (d,
1H, J = 8.60 Hz), 7.40 (d, 1H, J = 8.60 Hz), 7.22 (m,
5H), 6.30 (s, 1H), 6.22 (s, 1H), 6.09 (br s, 1H), 5.68
(br s, 1H,), 4.23 (m, 1H), 3.86 (s, 3H), 3.53 (m, 1H),
3.20 (m, 2H), 2.98 (m, 2H), 1.64 (m, 4H), 1.42 (s, 9H),
1.37 (s, 9H), 1.25 (d, 3H, J = 6.50 Hz); APCIMS: m/z
563 (M+1); Anal. Calcd for C33H46N4O4 (562.7): C,
70.43; H, 8.24; N, 9.96. Found: C, 70.79; H, 8.18; N,
10.24.
5.2.5. (S)-{2-(3-Benzyloxymethyl-1H-imidazol-4-yl)-1-[4-
(2-tert-butyl-6-methoxy-8-quinolylamino)pentylcarba-
moyl]ethyl}carbamic acid tert-butyl ester (12). Yield:
85%; oil. IR (neat): 3476, 2965, 2863, 1698, 1091 cmꢀ1
.
5.2.10. (S)-{2-(4-Benzyloxyphenyl)1-[4-(2-tert-butyl-6-
methoxy-8-quinolylamino)-pentylcarbamoyl]ethyl}car-
bamic acid tert-butyl ester (17). Yield: 97%; oil. IR
1H NMR (CDCl3): d 7.86 (d, 1H, J = 8.60 Hz), 7.48 (s,
1H), 7.44 (d, 1H, J = 8.60 Hz), 7.29 (m, 5H), 6.88 (s,
1H), 6.30 (s, 1H), 6.23 (s, 1H), 6.10 (br s, 1H), 5.98
(m, 2H), 5.33 (br s, 1H), 5.21 (m, 2H), 4.47 (m, 1H),
3.85 (s, 3H), 3.13 (m, 2H), 3.05 (m, 3H), 1.65 (m, 4H),
1.42 (s, 9H), 1.38 (s, 9H), 1.28 (d, 3H, J = 6.50 Hz);
APCIMS: m/z 673 (M+1); Anal. Calcd for C38H52-
N6O5 (672.9): C, 67.83; H, 7.79; N, 12.49. Found: C,
67.96; H, 7.51; N, 12.31.
(neat): 3324, 2929, 2854, 1690, 1124 cmꢀ1 1H NMR
.
(CDCl3): d 7.86 (d, 1H, J = 8.60 Hz), 7.40 (d, 1H,
J = 8.60 Hz), 7.24 (m, 5H), 7.10 (d, 2H, J = 7.50 Hz),
6.86 (d, 2H, J = 7.50 Hz), 6.30 (d, 1H, J = 2.30 Hz),
6.22 (d, 1H, J = 2.30 Hz), 6.09 (br s, 1H), 5.73 (br s,
1H), 5.03 (m, 1H), 4.93 (m, 2H), 3.86 (s, 3H), 3.55 (m,
2H), 3.20 (m, 2H), 2.98 (m, 1H), 1.64 (m, 4H), 1.42 (s,

924
K. Kaur et al. / Bioorg. Med. Chem. 15 (2007) 915–930
9H), 1.37 (s, 9H), 1.26 (d, 3H, J = 6.48 Hz); APCIMS:
m/z 669 (M+1); Anal. Calcd for C40H52N4O5 (668.9):
C, 71.83; H, 7.84; N, 8.38. Found: C, 71.66; H, 7.98;
N, 8.14.
J = 6.9 Hz), 3.63 (m, 1H), 3.27–3.20 (m, 6H), 1.70 (m,
14H), 1.39 (s, 18H), 1.28 (m, 6H), 0.94 (t, 3H,
J = 7.0 Hz); APCIMS: m/z 688 (M+1); Anal. Calcd for
C37H61N5O7 (687.9): C, 64.60; H, 8.94; N, 10.18. Found:
C, 64.31; H, 8.55; N, 10.37.
5.2.11. (S)-{2-Benzyloxy-1-[4-(2-tert-butyl-6-methoxy-8-
quinolylamino)pentylcarbamoyl]ethyl}carbamic acid tert-
butyl ester (18). Yield: 80%; oil. IR (neat): 3372, 2966,
5.2.16. (S)-{4-(N,N0-Bisbenzyloxycarbonylguanidino)-1-
[4-(4-ethyl-6-methoxy-5-pentyloxy-8-quinolylamino)pen-
tylcarbamoyl]butyl}carbamic acid benzyl ester (40).
Yield: 77%; mp 120–122 ꢁC. IR (KBr): 3384, 3292,
2848, 1707 cmꢀ1 1H NMR (CDCl3): d 7.86 (d, 1H,
.
J = 8.58 Hz), 7.40 (d, 1H, J = 8.56 Hz), 7.33 (m, 5H),
6.44 (br s, 1H), 6.30 (d, 1H, J = 2.20 Hz), 6.24 (s, 1H),
6.12 (br s, 1H), 5.40 (br s, 1H), 4.52 (m, 2H), 4.21 (m,
1H), 3.86 (s, 3H), 3.52 (m, 2H), 3.33 (m, 1H), 3.29 (d,
2H, J = 6.36 Hz), 1.64 (m, 4H), 1.42 (s, 9H), 1.39 (s,
9H), 1.26 (d, 3H, J = 6.48 Hz); APCIMS: m/z 593
(M+1); Anal. Calcd for C34H48N4O5 (592.8): C, 68.89;
H, 8.16; N, 9.45. Found: C, 69.12; H, 7.99; N, 9.17.
1
1704, 1642 cmꢀ1. H NMR (CDCl3): d 9.42 (br s, 1H),
9.29 (br s, 1H), 8.38 (d, 1H, J = 4.0 Hz), 7.34 (m,
15H), 7.11 (d, 1H, J = 3.60 Hz), 6.57 (br s, 1H), 6.38
(s, 1H), 6.27 (br s, 1H), 6.01 (br s, 1H), 5.20 (s, 2H),
5.11 (m, 4H), 4.31 (m, 1H), 3.95 (s, 3H), 3.86 (t, 2H,
J = 6.70 Hz), 3.51 (m, 1H), 3.37 (m, 2H), 2.92 (m, 2H),
1.74 (m, 6H), 1.38 (m, 8H), 1.30 (m, 6H), 1.19 (d, 2H,
J = 6.0 Hz), 0.92 (t, 3H, J = 6.80 Hz); APCIMS: m/z
933 (M+1); Anal. Calcd for C52H65N7O9 (932.1): C,
67.00; H, 7.03; N, 10.50. Found: C, 67.19; H, 7.30; N,
10.32.
5.2.12. (R)-{2-Benzylsulfanyl-1-[4-(2-tert-butyl-6-meth-
oxy-8-quinolylamino)pentylcarbamoyl]ethyl}carbamic
acid tert-butyl ester (19). Yield: 95%; oil. IR (neat): 3324,
1
2959, 2856, 1659 cmꢀ1. H NMR (CDCl3): d 7.86 (d,
1H, J = 8.58 Hz), 7.43 (d, 1H, J = 8.58 Hz), 7.30 (m,
5H), 6.30 (d, 1H, J = 2.28 Hz), 6.25 (d, 1H,
J = 2.21 Hz), 6.14 (m, 2H), 5.26 (br s, 1H), 4.15 (m,
1H), 3.86 (s, 3H), 3.59 (m, 2H), 3.30 (m, 2H), 2.78 (m,
1H), 1.64 (m, 4H), 1.41 (s, 9H), 1.37 (s, 9H), 1.25 (d,
3H, J = 6.48 Hz); APCIMS: m/z 609 (M+1); Anal.
Calcd for C34H48N4O4S (608.9): C, 67.07; H, 7.95; N,
9.20. Found: C, 69.12; H, 7.99; N, 9.17.
5.2.17. (R)-{4-(N,N0-Bisbenzyloxycarbonylguanidino)-1-
[4-(4-ethyl-6-methoxy-5-pentyloxy-8-quinolylamino)pen-
tylcarbamoyl]butyl}carbamic acid benzyl ester (41).
Yield: 75%; mp 120–122 ꢁC. IR (KBr): 3385, 3292,
1
1716, 1623 cmꢀ1. H NMR (CDCl3): d 9.41 (br s, 1H),
9.29 (br s, 1H), 8.39 (d, 1H, J = 4.30 Hz), 7.35 (m,
15H), 7.11 (d, 1H, J = 4.20 Hz), 6.58 (br s, 1H), 6.39
(s, 1H), 6.27 (br s, 1H), 6.02 (br s, 1H), 5.20 (s, 2H),
5.11 (m, 4H), 4.31 (m, 1H), 3.95 (s, 3H), 3.86 (t, 2H,
J = 7.10 Hz), 3.52 (m, 1H), 3.25 (m, 2H), 2.92 (m, 2H),
1.77 (m, 6H), 1.44–1.36 (m, 8H), 1.31 (m, 6H), 1.19 (d,
2H, J = 6.20 Hz), 0.94 (t, 3H, J = 7.0 Hz); APCIMS:
m/z 933 (M+1); Anal. Calcd for C52H65N7O9 (932.1):
C, 67.00; H, 7.03; N, 10.50. Found: C, 66.77; H, 6.88;
N, 10.89.
5.2.13. (R)-{1-[4-(2-tert-Butyl-6-methoxy-8-quinolylami-
no)pentylcarbamoyl]-2-trityl-sulfanylethyl}carbamic acid
tert-butyl ester (20). Yield: 90%; oil. IR (neat): 3324,
1
2929, 2856, 1662 cmꢀ1. H NMR (CDCl3): d 7.86 (d,
1H, J = 8.37 Hz), 7.34 (m, 15H), 7.21 (d, 1H,
J = 8.41 Hz), 6.30 (s, 1H), 6.22 (s, 1H), 6.09 (br s, 1H),
5.98 (br s, 1H), 4.81 (m, 1H), 3.86 (s, 3H), 3.52 (m,
2H), 3.22 (m, 2H), 2.50 (m, 1H), 1.61 (m, 4H), 1.41 (s,
9H), 1.37 (s, 9H), 1.25 (d, 3H, J = 5.13 Hz); APCIMS:
m/z 762 (M+1); Anal. Calcd for C46H56N4O4S (761.0):
C, 72.60; H, 7.42; N, 7.36. Found: C, 72.51; H, 7.64;
N, 7.57.
5.2.18. (S)-{2-(1-Benzyloxymethyl-1H-imidazol-4-yl)-1-
[4-(4-ethyl-6-methoxy-5-pentyloxy-8-quinolylamino)-pen-
tylcarbamoyl]ethyl}carbmic acid tert-butyl ester (42).
1
Yield: 73%; oil. IR (neat): 3332, 1662 cmꢀ1. H NMR
(CDCl3): d 8.39 (d, 1H, J = 4.0 Hz), 7.50 (d, 1H,
J = 5.0 Hz), 7.30 (m, 5H), 7.12 (d, 1H, J = 4.4 Hz),
6.89 (s, 1H), 6.42 (s, 1H), 6.04 (br s, 1H), 5.31 (m,
3H), 4.49 (s, 2H), 4.34 (m, 1H), 3.97 (s, 3H), 3.87 (t,
2H, J = 7.0 Hz), 3.57 (m, 1H), 3.22 (m, 2H), 3.14 (m,
2H), 3.06 (d, 2H, J = 7.0 Hz), 1.83 (m, 2H), 1.45 (m,
17H), 1.28 (m, 6H), 0.94 (t, 3H, J = 7.0 Hz); APCIMS:
m/z 731 (M+1); Anal. Calcd for C41H58N6O6 (730.9):
C, 67.37; H, 8.00; N, 11.50. Found: C, 67.76; H, 7.77;
N, 11.21.
5.2.14. (R)-{5-Benzyloxycarbonylamino-1-[4-(4-ethyl-6-
methoxy-5-pentyloxy-8-quinolylamino)pentylcarbamoyl]
pentyl}carbamic acid benzyl ester (38). Yield: 84%; oil.
1
IR (neat): 3303, 1684 cmꢀ1. H NMR (CDCl3): d 8.38
(m, 1H), 7.31 (m, 10H), 7.13 (m, 1H), 6.48 (s, 1H),
5.07 (m, 4H), 4.13 (m, 1H), 3.97 (s, 3H), 3.86 (t, 2H,
J = 7.0 Hz), 3.64 (m, 1H), 3.20 (m, 6H), 1.56 (m, 15H),
1.27 (m, 6H), 0.92 (t, 3H, J = 7.2 Hz); APCIMS: m/z
770.4 (M+1); Anal. Calcd for C44H59N5O7 (769.7): C,
68.64; H, 7.72; N, 9.10. Found: C, 68.95; H, 7.39; N,
9.47.
5.2.19. (R)-{2-(1-Benzyloxymethyl-1H-imidazol-4-yl)-1-
[4-(4-ethyl-6-methoxy-5-pentyloxy-8-quinolylamino)pen-
tylcarbamoyl]ethyl}carbamic acid tert-butyl ester (43).
1
5.2.15. (R)-{4-tert-Butoxycarbonylamino-1-[4-(4-ethyl-6-
methoxy-5-pentyloxy-8-quinolylamino)pentylcarbamoyl]
butyl}carbamic acid tert-butyl ester (39). Yield: 67%; oil.
Yield: 67%; oil. IR (neat): 3316, 1675 cmꢀ1. H NMR
(CDCl3): d 8.38 (d, 1H, J = 4.0 Hz), 7.48 (d, 1H,
J = 5.3 Hz), 7.29 (m, 5H), 7.10 (d, 1H, J = 4.2 Hz),
6.89 (s, 1H), 6.42 (s, 1H), 6.06 (br s, 1H), 5.29 (m,
3H), 4.48 (s, 2H), 4.32 (m, 1H), 3.96 (s, 3H), 3.87 (t,
2H, J = 7.0 Hz), 3.57 (m, 1H), 3.23 (m, 2H), 3.13 (m,
2H), 3.05 (d, 2H, J = 7.1 Hz), 1.83 (t, 2H), 1.46 (m,
1
IR (neat): 3333, 1694 cmꢀ1. H NMR (CDCl3): d 8.38
(d, 1H, J = 4.4 Hz), 7.12 (d, 1H, J = 4.3 Hz), 6.51 (br
s, 1H), 6.43 (s, 1H), 6.06 (br s, 1H), 5.15 (br s, 1H),
4.67 (br s, 1H), 4.12 (m, 1H), 3.96 (s, 3H), 3.87 (t, 2H,

K. Kaur et al. / Bioorg. Med. Chem. 15 (2007) 915–930
925
17H), 1.27 (m, 6H), 0.94 (t, 3H, J = 6.9 Hz); APCIMS:
m/z 731 (M+1); Anal. Calcd for C41H58N6O6 (730.9):
C, 67.37; H, 8.00; N, 11.50. Found: C, 68.00; H, 8.34;
N, 11.75.
J = 4.0 Hz), 7.27 (m, 5H), 7.11 (d, 1H, J = 4.2 Hz),
6.47 (br s, 1H), 6.42 (s, 1H), 6.07 (br s, 1H), 5.39 (br
s, 1H), 4.50 (m, 2H), 4.25 (m, 1H), 3.96 (s, 3H), 3.87
(t, 2H, J = 7.18 Hz), 3.60 (m, 1H), 3.55 (m, 2H), 3.26
(m, 4H), 1.80 (m, 2H), 1.65 (m, 8H), 1.39 (s, 9H), 1.27
(m, 6H), 0.94 (t, 3H, J = 6.9 Hz); APCIMS: m/z 651
(M+1); Anal. Calcd for C37H54N4O6 (650.8): C, 68.28;
H, 8.36; N, 8.61. Found: C, 68.56; H, 8.09; N, 8.21.
5.2.20. (S)-[1-[4-(4-Ethyl-6-methoxy-5-pentyloxy-8-quin-
olylamino)pentylcarbamoyl]-2-(1H-indol-3-yl)ethyl]car-
bamic acid tert-butyl ester (44). Yield: 76%; mp 46–
48 ꢁC. IR (KBr): 3320, 1701, 1659 cmꢀ1
.
1H NMR
(CDCl3): d 9.53 (br s, 1H), 9.05 (br s, 1H), 8.48 (d,
1H, J = 4.5 Hz), 7.70 (m, 2H), 7.30–6.98 (m, 5H), 6.42
(s, 1H), 5.85 (s, 1H), 5.53 (br s, 1H), 4.44 (m, 1H),
3.97 (s, 3H), 3.91 (t, 2H, J = 6.9 Hz), 3.51 (m, 1H),
3.30 (m, 4H), 3.06 (m, 2H), 1.85 (m, 7H), 1.65 (m,
6H), 1.40 (s, 9H), 1.32 (m, 6H), 0.95 (t, 3H,
J = 7.0 Hz); APCIMS: m/z 660 (M+1); Anal. Calcd for
C38H53N5O5 (659.9): C, 69.17; H, 8.10; N, 10.61. Found:
C, 69.45; H, 8.02; N, 10.31.
5.2.25. (R)-{2-Benzylsulfanyl-1-[4-(4-ethyl-6-methoxy-5-
pentyloxy-8-quinolylamino)pentylcarbamoyl]ethyl}car-
bamic acid tert-butyl ester (49). Yield 97%; oil. IR (neat):
3324, 1652 cmꢀ1 1H NMR (CDCl3): d 8.39 (d, 1H,
.
J = 4.5 Hz), 7.32–7.21 (m, 5H), 7.12 (d, 1H,
J = 4.3 Hz), 6.43 (s, 1H), 6.24 (br s, 1H), 6.06 (br s,
1H), 5.25 (br s, 1H), 4.15 (m, 1H), 4.05 (s, 3H), 3.87
(t, 2H, J = 6.9 Hz), 3.71 (d, 2H, J = 2.9 Hz), 3.63 (m,
1H), 3.25 (m, 4H), 2.82 (m, 2H), 1.80 (m, 2H), 1.64
(m, 8H), 1.37 (s, 9H), 1.29–1.25 (m, 6H), 0.94 (t, 3H,
J = 7.0 Hz); APCIMS: m/z 667 (M+1); Anal. Calcd for
C37H54N4O5S (666.9): C, 66.63; H, 8.16; N, 8.40.
Found: C, 66.33; H, 8.44; N, 8.21.
5.2.21. (S)-1-[4-(4-Ethyl-6-methoxy-5-pentyloxy-8-quin-
olylamino)pentylcarbamoyl]-2-phenylethyl}carbamic acid
tert-butyl ester (45). Yield 73%; oil. IR (neat): 3392,
1718, 1668 cmꢀ1 1H NMR (CDCl3): d 8.39 (d, 1H,
.
J = 3.4 Hz), 7.18 (m, 6H), 6.41 (s, 1H), 6.03 (br s, 1H),
5.87 (br s, 1H), 5.11 (br s, 1H), 4.25 (m, 1H), 3.96 (s,
3H), 3.87 (t, 2H, J = 6.7 Hz), 3.58 (m, 1H), 3.23 (m,
4H), 3.02 (m, 2H), 1.83 (m, 2H), 1.53 (m, 8H), 1.38 (s,
9H), 1.30 (m, 6H), 0.94 (t, 3H, J = 6.7 Hz); APCIMS:
m/z 621 (M+1); Anal. Calcd for C36H52N4O5 (620.8):
C, 69.65; H, 8.44; N, 9.02. Found: C, 69.78; H, 8.23;
N, 9.34.
5.2.26. (R)-{{1-[4-(4-Ethyl-6-methoxy-5-pentyloxy-8-quin-
olylamino)pentylcarbamoyl]-2-tritylsulfanylethyl}carbam-
ic acid tert-butyl ester (50). Yield 98%; oil. IR (neat):
1
3322, 1666 cmꢀ1. H NMR (CDCl3): d 8.37 (m, 1H),
7.40 (m, 5H), 7.24 (m, 10H), 7.11 (m, 1H), 6.41 (s,
1H), 6.04 (br s, 2H), 4.80 (br s, 1H), 4.12 (m, 1H),
3.95 (s, 3H), 3.89 (t, 2H, J = 6.7 Hz), 3.60 (m, 1H),
3.22 (m, 4H), 2.04 (m, 2H), 1.82 (m, 2H), 1.63 (m,
8H), 1.38 (s, 9H), 1.27 (m, 6H), 0.94 (t, 3H,
J = 6.70 Hz); APCIMS: m/z 820 (M+1); Anal. Calcd
for C49H62N4O5S (819.1): C, 71.85; H, 7.63; N, 6.84.
Found: C, 72.11; H, 7.39; N, 7.02.
5.2.22. (S)-{2-(4-Benzyloxyphenyl)-1-[4-(4-ethyl-6-meth-
oxy-5-pentyloxy-8-quinolylamino)pentylcarbamoyl]ethyl}car-
bamic acid tert-butyl ester (46). Yield 97%; mp 60–62 ꢁC.
1
IR (KBr): 3335, 1684, 1654 cmꢀ1. H NMR (CDCl3): d
8.38 (d, 1H, J = 4.2 Hz), 7.35 (m, 5H), 7.09 (m, 3H), 6.87
(m, 2H), 6.42 (s, 1H), 6.02 (br s, 1H), 5.74 (br s, 1H),
5.03 (br s, 1H), 4.96 (m, 2H), 4.19 (m, 1H), 3.95 (s,
3H), 3.86 (t, 2H, J = 6.8 Hz), 3.59 (m, 1H), 3.22 (m,
4H), 2.99 (m, 2H), 1.77 (m, 2H), 1.60 (m, 8H), 1.39 (s,
9H), 1.27 (m, 6H), 0.94 (t, 3H, J = 7.0 Hz); APCIMS:
m/z 727 (M+1); Anal. Calcd for C43H58N4O6 (726.9):
C, 71.05; H, 8.04; N, 7.71. Found: C, 71.41; H, 8.21;
N, 7.48.
5.3. General method for the synthesis of N1-{4-[2-(tert-
butyl)-6-methoxy-8-quinolylamino]pentyl}-(2S/2R)-2-ami-
nosubstitutedamides (21–33) and N1-[4-(4-ethyl-6-meth-
oxy-5-pentyloxy-8-quinolylamino)pentyl]-(2S/2R)-2-ami-
nosubstitutedamides (51–63)
In cases where a-amino group was protected with N-a-
tert-butoxycarbonyl (tert-Boc) group, following proto-
col was used.
5.2.23. (S)-{1-[4-(4-Ethyl-6-methoxy-5-pentyloxy-8-quin-
olylamino)pentylcarbamoyl]-3-methylsulfanylpropyl}car-
bamic acid tert-butyl ester (47). Yield 85%; mp 46–48 ꢁC.
To a solution of tert-Boc-protected quinoline derivatives
(0.5 mmol) was added 4 N methanolic HCl solution
(5 mL). Reaction mixture was allowed to stir at ambient
temperature for 1 h. Solvent was removed under re-
duced pressure to afford oil, which upon crystallization
with anhydrous diethyl ether gave product.
1
IR (KBr): 3320, 1693, 1660 cmꢀ1. H NMR (CDCl3): d
8.40 (d, 1H, J = 4.3 Hz), 7.13 (m, 1H), 6.44 (s, 1H), 6.28
(br s, 1H), 5.17 (br s, 1H), 4.20 (m, 2H), 3.96 (s, 3H),
3.88 (t, 2H, J = 7.0 Hz), 3.64 (m, 1H), 3.26 (m, 4H),
2.53 (m, 2H), 2.07 (m, 5H), 1.85 (m, 4H), 1.68 (m,
6H), 1.41 (s, 9H), 1.26 (m, 6H), 0.94 (t, 3H,
J = 7.0 Hz); APCIMS: m/z 605 (M+1); Anal. Calcd for
C32H52N4O5S (604.8): C, 63.54; H, 8.67; N, 9.26.
Found: C, 63.24; H, 8.44; N, 8.91.
In cases where a-amino group was protected with N-a-
benzyloxycarbonyl (Cbz) group, following protocol
was used.
To a mixture of Cbz-protected quinoline derivatives
(0.5 mmol), glacial acetic acid (1 mL), and 10% Pd/C
(0.1 g) in methanol (20 mL) was bubbled a slow stream
of hydrogen gas for 1 h. The catalyst was removed by
filtration, and filtrate was concentrated under reduced
pressure to afford oil, which upon treatment with a
5.2.24. (S)-{2-Benzyloxy-1-[4-(4-ethyl-6-methoxy-5-pen-
tyloxy-8-quinolylamino)pentylcarbamoyl]ethyl}carbamic
acid tert-butyl ester (48). Yield 77%; oil. IR (neat): 3401,
1742, 1664 cmꢀ1 1H NMR (CDCl3): d 8.38 (d, 1H,
.

926
K. Kaur et al. / Bioorg. Med. Chem. 15 (2007) 915–930
solution of ethereal hydrogen chloride produced prod-
uct. Recrystallized from diethyl ether.
2H, J = 6.28 Hz), 3.23 (m, 1H), 3.04 (m, 2H) 1.50 (m,
4H), 1.24 (s, 9H), 1.12 (d, 3H, J = 5.20 Hz); APCIMS:
m/z 453 (M+1); Anal. Calcd for C25H39Cl3N6O2
(562.0): C, 53.43; H, 6.99; N, 14.95. Found: C, 53.72;
H, 7.21; N, 14.68.
Alternatively, in cases where amino acid was protected
with benzyl (Bzl) and tert-Boc groups, following proto-
col was used.
5.3.6. N1-{4-[2-(tert-Butyl)-6-methoxy-8-quinolylamino]pen-
tyl}-(2R)-2-amino-3-(1H-imidazol-4-yl)propanamideÆ3HCl
(26). Yield: 79%; mp (salt) 120–122 ꢁC. IR (KBr): 3402,
A mixture of fully protected amino acid conjugates of 8-
quinolinamine (0.5 mmol) and 30% HBr in acetic acid
(5 mL) was stirred at ambient temperature for 30 min.
Solvent was removed under reduced pressure to afford
oil, which upon recrystallization with diethyl ether gave
desired product.
1
2931, 2856, 1682 cmꢀ1. H NMR (CD3OD): d 8.82 (s,
1H), 8.73 (d, 1H, J = 8.76 Hz), 8.49 (br s, 1H), 7.79 (d,
1H, J = 8.80 Hz), 7.75 (s, 1H), 7.52 (s, 1H), 7.28 (s,
1H), 4.29 (m, 1H), 4.06 (br s, 1H), 3.88 (s, 3H), 3.48
(m, 2H), 3.34 (m, 2H), 3.24 (m, 1H), 1.45 (m, 4H),
1.31 (s, 9H), 1.14 (d, 3H, J = 6.48 Hz); APCI: m/z 453
(M+1); Anal. Calcd for C25H39Cl3N6O2 (562.0): C,
53.43; H, 6.99; N, 14.95. Found: C, 53.21; H, 6.88; N,
14.88.
5.3.1. N1-{4-[2-(tert-Butyl)-6-methoxy-8-quinolylamino]
pentyl}-(2R)-2,6-diaminohexanamideÆ3HCl (21). Yield:
95%; mp (salt) 108–110 ꢁC. IR (KBr): 3392, 3019,
1
2856, 1690 cmꢀ1. H NMR (CD3OD): d 7.72 (m, 2H),
7.60 (m, 2H), 4.22 (br s, 2H), 4.10 (m, 1H), 4.06 (m,
4H), 3.85 (s, 3H), 3.81 (m, 1H), 1.68 (m, 4H), 1.35 (m,
6H), 0.97 (m, 12H); APCIMS: m/z 444 (M+1); Anal.
Calcd for C25H44Cl3N5O2 (553.0): C, 54.30; H, 8.02;
N, 12.66. Found: C, 53.94; H, 7.77; N, 12.95.
5.3.7. N1-{4-[2-(tert-Butyl)-6-methoxy-8-quinolylamino]pen-
tyl}-(2S)-2-amino-3-(1H-indol-3-yl)propanamideÆ2HCl
(27). Yield: 85%; mp (salt) 117–119 ꢁC. IR (KBr): 3387,
1
2926, 1675 cmꢀ1. H NMR (DMSO-d6): d 8.26 (br s,
1H), 8.18 (d, 1H, J = 8.40 Hz), 7.69 (m, 2H), 7.40 (d,
1H, J = 8.0 Hz), 7.25 (s, 1H), 7.11 (m, 1H), 7.00 (m,
1H), 6.86 (m, 2H), 4.27 (m, 1H), 3.94 (s, 3H), 3.22 (m,
2H), 3.04 (m, 2H), 2.54 (m, 1H), 1.64 (m, 4H), 1.43 (s,
9H), 1.26 (d, 3H, J = 6.52 Hz); APCIMS: m/z 502
(M+1); Anal. Calcd for C30H41Cl2N5O2 (574.6): C,
62.71; H, 7.19; N, 12.19. Found: C, 62.98; H, 7.43; N,
12.99.
5.3.2. N1-{4-[2-(tert-Butyl)-6-methoxy-8-quinolylamino]
pentyl}-(2R)-2,6-diaminopentanamideꢁ3HCl (22). Yield:
96%; mp (salt) 100–102 ꢁC. IR (KBr): 3390, 2962,
1673 cmꢀ1
.
1H NMR (D2O):
d
8.22 (d, 1H,
J = 8.81 Hz), 7.72 (m, 2H), 7.26 (s, 1H), 4.71 (m, 1H),
3.90 (s, 3H), 3.18 (t, 2H, J = 6.28 Hz), 2.97 (m, 3H),
1.85 (m, 4H), 1.80 (m, 4H), 1.38 (s, 9H), 1.27 (d, 3H,
J = 6.48 Hz); APCIMS: m/z 430 (M+1); Anal. Calcd
for C24H42Cl3N5O2 (539.0): C, 53.48; H, 7.85; N,
12.99. Found: C, 53.23; H, 7.47; N, 12.76.
5.3.8. N1-{4-[2-(tert-Butyl)-6-methoxy-8-quinolylamino]pen-
tyl}-(2S)-2-amino-3-phenylpropanamideÆ2HCl (28). Yield:
84%; mp (salt) 105–107 ꢁC. IR (KBr): 3413, 2948,
5.3.3. N1-{4-[2-(tert-Butyl)-6-methoxy-8-quinolylamino]
pentyl}-(2S)-2-amino-5-amino(imino)methylaminopen-
tanamideÆ3HCl (23). Yield: 67%; mp (salt) 112–114 ꢁC.
1674 cmꢀ1
.
1H NMR (D2O):
d
8.47 (d, 1H,
J = 8.70 Hz), 7.93 (d, 1H, J = 8.70 Hz), 7.36 (m, 7H),
4.25 (m, 1H), 4.10 (s, 3H), 3.55 (t, 2H, J = 7.02 Hz),
3.33 (m, 1H), 3.18 (m, 2H), 1.81 (m, 4H), 1.61 (s, 9H),
1.27 (d, 3H, J = 6.52 Hz); APCIMS: m/z 463 (M+1);
Anal. Calcd for C28H40Cl2N4O2 (535.6): C, 62.80; H,
7.53; N, 10.46. Found: C, 62.60; H, 7.26; N, 10.19.
1
IR (KBr): 3407, 2963, 1666 cmꢀ1. H NMR (D2O): d
8.01 (d, 1H, J = 8.80 Hz), 7.49 (d, 1H, J = 8.80 Hz),
7.21 (s, 1H), 7.04 (s, 1H), 4.55 (m, 1H), 3.63 (s, 3H),
3.30 (m, 2H), 2.79 (m, 5H), 1.50 (m, 6H), 1.31 (s, 9H),
1.04 (d, 3H, J = 6.52 Hz); APCIMS: m/z 472 (M+1);
Anal. Calcd for C25H44Cl3N7O2 (581.0): C, 51.68; H,
7.63; N, 16.87. Found: C, 51.21; H, 7.44; N, 17.09.
5.3.9. N1-{4-[2-(tert-Butyl)-6-methoxy-8-quinolylamino]pen-
tyl}-(2S)-2-amino-3-(4-hydroxyphenyl)propanamideÆ2HCl
(29). Yield: 79%; mp (salt) 85–87 ꢁC. IR (KBr): 3247,
1
5.3.4. N1-{4-[2-(tert-Butyl)-6-methoxy-8-quinolylamino]
pentyl}-(2R)-2-amino-5-amino(imino)methylaminopen-
tanamide.3HCl (24). Yield: 83%; mp (salt) 111–112 ꢁC.
2922, 2856, 1671 cmꢀ1. H NMR (CD3OD): d 8.30 (d,
1H, J = 8.90 Hz), 7.80 (d, 1H, J = 8.90 Hz), 7.10 (m,
3H), 6.78 (m, 3H), 6.09 (br s, 1H), 4.01 (m, 1H), 3.95
(s, 3H), 3.49 (t, 2H, J = 6.62 Hz), 3.31 (m, 2H), 2.98
(m, 1H), 1.52 (m, 4H), 1.42 (s, 9H), 1.20 (m, 3H); APC-
IMS: m/z 479 (M+1); Anal. Calcd for C28H40Cl2N4O3
(551.6): C, 60.97; H, 7.31; N, 10.16. Found: C, 61.28;
H, 7.44; N, 10.34.
1
IR (KBr): 3355, 2929, 1667 cmꢀ1. H NMR (D2O): d
8.10 (d, 1H, J = 8.70 Hz), 7.53 (d, 1H, J = 8.70 Hz),
7.20 (s, 1H), 7.02 (s, 1H), 4.51 (m, 1H), 3.65 (s, 3H),
3.32 (m, 2H), 2.81 (m, 5H), 1.55 (m, 6H), 1.30 (s, 9H),
1.04 (d, 3H, J = 6.52 Hz); APCIMS: m/z 472 (M+1);
Anal. Calcd for C25H44Cl3N7O2 (581.0): C, 51.68; H,
7.63; N, 16.87. Found: C, 51.89; H, 7.96; N, 16.68.
5.3.10. N1-{4-[2-(tert-Butyl)-6-methoxy-8-quinolylamino]
pentyl}-(2S)-2-amino-4-methylsulfanylbutanamideÆ2HCl
(30). Yield: 62%; mp (salt) 70–72 ꢁC. IR (KBr): 3402,
5.3.5. N1-{4-[2-(tert-Butyl)-6-methoxy-8-quinolylamino]pen-
tyl}-(2S)-2-amino-3-(1H-imidazol-4-yl)propanamideÆ3HCl
(25). Yield: 70%; mp (salt) 121–123 ꢁC. IR (KBr): 3418,
1
2929, 2856, 1679 cmꢀ1. H NMR (DMSO-d6): d 8.69
(br s, 1H), 8.36 (br s, 1H), 8.16 (d, 1H, J = 8.60 Hz),
7.63 (d, 1H, J = 8.60 Hz), 7.66 (m, 2H), 3.84 (s, 3H),
3.78 (m, 1H), 3.15 (m, 2H), 2.99 (m, 1H), 2.50 (m,
2H), 2.04 (s, 2H), 1.55 (m, 7H), 1.39 (s, 9H), 1.22 (d,
1
2929, 2870, 1679 cmꢀ1. H NMR (D2O): d 8.62 (s, 1H),
8.39 (d, 1H, J = 8.52 Hz), 7.56 (d, 1H, J = 8.52 Hz), 7.45
(s, 1H), 7.32 (m, 2H), 4.13 (m, 1H), 3.47 (s, 3H), 3.40 (t,

K. Kaur et al. / Bioorg. Med. Chem. 15 (2007) 915–930
927
3H, J = 6.52 Hz); APCIMS: m/z 447 (M+1); Anal.
Calcd for C24H40Cl2N4O2S (519.6): C, 55.48; H, 7.76;
N, 10.78. Found: C, 55.24; H, 7.97; N, 10.67.
5.3.16. N1[4-(4-Ethyl-6-methoxy-5-pentyloxy-8-quinolyl-
amino)pentyl]-(2S)-2-amino-5-amino(imino)methylamin-
opentanamideÆ3HCl (53). Yield: 67%; mp (salt) 101–
1
104 ꢁC (dec). IR (neat, free base): 3374, 1680 cmꢀ1. H
5.3.11. N1-{4-[2-(tert-Butyl)-6-methoxy-8-quinolylamino]
pentyl}-(2S)-2-amino-3-hydroxypropanamideÆ2HBr (31).
Yield: 65%; mp (salt) 78–80 ꢁC. IR (KBr): 3400, 2890,
NMR (free base, CD3OD):
d
8.36 (d, 1H,
J = 4.30 Hz), 7.19 (d, 1H, J = 4.40 Hz), 6.58 (s, 1H),
3.96 (s, 3H), 3.89 (t, 2H, J = 6.80 Hz), 3.65 (m, 2H),
3.27 (m, 4H), 3.15 (m, 2H), 1.60 (m, 16H), 1.31–1.26
(m, 6H), 0.96 (t, 3H, J = 7.0 Hz); APCIMS: m/z 530
(M+1); Anal. Calcd for C28H50Cl3N7O3 (639.1): C,
52.62; H, 7.89; N, 15.34. Found: C, 52.86; H, 8.07; N,
15.63.
1685 cmꢀ1 1H NMR (DMSO-d6): d 8.64 (br s, 1H),
.
8.27 (d, 1H, J = 8.20 Hz), 8.19 (br s, 1H), 7.68 (d, 1H,
J = 8.60 Hz), 6.83 (s, 1H), 6.71 (s, 1H), 4.01 (m, 1H),
3.86 (s, 3H), 3.84 (m, 2H), 3.70 (m, 1H), 3.20 (m, 2H),
1.75 (br s, 1H), 1.63 (m, 4H), 1.45 (s, 9H), 1.27 (d, 3H,
J = 5.30 Hz); APCIMS: m/z 403 (M+1); Anal. Calcd
for C22H36Br2N4O3 (564.4): C, 46.82; H, 6.43; N, 9.93.
Found: C, 47.09; H, 6.33; N, 9.78.
5.3.17. N1[4-(4-Ethyl-6-methoxy-5-pentyloxy-8-quinolyl-
amino)pentyl]-(2R)-2-amino-5-amino(imino)methylamin-
opentanamideÆ3HCl (54). Yield: 84%; mp (salt) 100–
5.3.12. N1-{4-[2-(tert-Butyl)-6-methoxy-8-quinolylamino]
pentyl}-(2R)-2-amino-3-benzylsulfanylpropanamideÆ2HCl
(32). Yield: 61%; mp (salt) 94–96 ꢁC. IR (KBr): 3402,
103 ꢁC (dec). IR (neat, free base): 3369, 1716.1 cmꢀ1
.
1H NMR (free base, CDCl3):
d 8.38 (d, 1H,
J = 4.30 Hz), 7.11 (d, 1H, J = 4.30 Hz), 6.44 (s, 1H),
3.96 (s, 3H), 3.87 (t, 2H, J = 6.90 Hz), 3.63 (m, 2H),
3.24 (m, 2H), 2.78 (m, 2H), 2.03 (br s, 1H), 1.83 (m,
2H), 1.47 (m, 16H), 1.26 (m, 6H), 0.94 (t, 3H,
J = 6.9 Hz); APCIMS: m/z 530 (M+1); Anal. Calcd for
C28H50Cl3N7O3 (639.1): C, 52.62; H, 7.89; N, 15.34.
Found: C, 52.34; H, 7.65; N, 15.12.
2930, 2870, 1674 cmꢀ1 1H NMR (D2O): d 8.11 (d,
.
1H, J = 8.90 Hz), 7.56 (d, 1H, J = 8.90 Hz), 7.01 (m,
7H), 3.86 (m, 1H), 3.74 (s, 3H), 3.51 (m, 2H), 3.12 (m,
2H), 2.97 (m, 1H), 2.67 (d, 2H, J = 6.30 Hz), 1.54 (m,
4H), 1.24 (s, 9H), 1.16 (d, 3H, J = 6.48 Hz); APCIMS:
m/z 509 (M+1); Anal. Calcd for C29H42Cl2N4O2S
(581.7): C, 59.88; H, 7.28; N, 9.63. Found: C, 60.15;
H, 7.33; N, 9.88.
5.3.18. N1-[4-(4-Ethyl-6-methoxy-5-pentyloxy-8-quinolyl-
amino)pentyl]-(2S)-2-amino-3-(1H-imidazol-4-yl)propan-
amideÆ3HCl (55). Yield: 96%; mp (salt) 122–124 ꢁC
5.3.13. N1-{4-[2-(tert-Butyl)-6-methoxy-8-quinolylamino]
pentyl}-(2R)-2-amino-3-sulfanylpropanamideÆ2HBr (33).
Yield: 76%; mp (salt) 77–79 ꢁC. IR (KBr): 3402, 2930,
1
(dec). IR (KBr): 3402, 1679 cmꢀ1. H NMR (CD3OD):
d 9.25 (s, 1H), 8.71 (d, 1H, J = 4.90 Hz), 7.60 (m, 3H),
4.53 (m, 1H), 4.08 (m, 5H), 3.97 (m, 1H), 3.42 (m,
6H), 1.85 (m, 2H), 1.63 (m, 10H), 1.36 (m, 6H), 0.97
(t, 3H, J = 6.90 Hz); APCIMS: m/z 511 (M+1); Anal.
Calcd for C28H45Cl3N6O3 (620.1): C, 54.24; H, 7.32;
N, 13.55. Found: C, 53.90; H, 7.03; N, 13.47.
1668 cmꢀ1 1H NMR (DMSO-d6): d 8.57 (br s, 1H),
.
8.31 (br s, 1H), 8.03 (d, 1H, J = 8.80 Hz), 7.56 (d, 1H,
J = 8.80 Hz), 6.50 (s, 1H), 6.50 (s, 1H), 3.99 (m, 1H),
3.78 (s, 3H), 3.68 (m, 2H), 3.20 (m, 2H), 3.02 (m, 1H),
1.55 (m, 4H), 1.34 (s, 9H), 1.16 (d, 3H, J = 6.48 Hz) ;
APCIMS: m/z 419 (M+1); Anal. Calcd for
C22H36Br2N4O2S (580.4): C, 45.52; H, 6.25; N, 9.65.
Found: C, 45.33; H, 6.33; N, 9.47.
5.3.19. N1-[4-(4-Ethyl-6-methoxy-5-pentyloxy-8-quinolyl-
amino)pentyl]-(2R)-2-amino-3-(1H-imidazol-4-yl)propan-
amideÆ3HCl (56). Yield: 87%; mp (salt) 124–126 ꢁC
1
5.3.14. N1-[4-(4-Ethyl-6-methoxy-pentyloxy-8-quinoly-
lamino)pentyl]-(2R)-2,6-diaminohexanamideÆ3HCl (51).
Yield: 86%; mp (salt) 119–122 ꢁC (dec). IR (neat, free
(dec). IR (KBr): 3387, 1679 cmꢀ1. H NMR (CD3OD):
d 9.15 (s, 1H), 8.61 (d, 1H, J = 5.0 Hz), 7.50 (m, 3H),
4.35 (m, 1H), 3.99 (m, 5H), 3.85 (m, 1H), 3.38 (m,
6H), 1.77 (m, 8H), 1.43 (m, 4H), 1.30 (m, 6H), 0.88 (t,
3H, J = 6.90 Hz); APCIMS: m/z 511 (M+1); Anal.
Calcd for C28H45Cl3N6O3 (620.1): C, 54.24; H, 7.32;
N, 13.55. Found: C, 54.55; H, 7.09; N, 13.33.
1
base): 3382, 1576 cmꢀ1. H NMR (free base, CD3OD):
d 8.36 (d, 1H, J = 4.40), 7.19 (d, 1H, J = 4.40), 6.58 (s,
1H), 3.96 (s, 3H), 3.89 (t, 2H, J = 6.80 Hz), 3.71 (m,
2H), 3.30 (m, 4H), 2.87 (m, 2H), 1.50 (m, 18H), 1.30
(m, 6H), 0.96 (t, 3H, J = 7.10 Hz); APCIMS: m/z 502
(M+1); Anal. Calcd for C28H50Cl3N5O3 (611.1): C,
55.03; H, 8.25; N, 11.46. Found: C, 54.77; H, 8.48; N,
11.83.
5.3.20. N1-[4-(4-Ethyl-6-methoxy-5-pentyloxy-8-quinolyl-
amino)pentyl]-(2S)-2-amino-3-(1H-indol-3-yl)propana-
mideÆ2HCl (57). Yield: 63%; mp (salt) 114–116 ꢁC (dec).
1
IR (KBr): 3370, 1668 cmꢀ1. H NMR (CD3OD): d 8.66
5.3.15. N1[4-(4-Ethyl-6-methoxy-5-pentyloxy-8-quinolyl-
amino)pentyl]-(2R)-2,5-diaminopentanamideÆ3HCl (52).
Yield: 79%; mp (salt) 117–120 ꢁC (dec). IR (KBr):
(d, 1H, J = 4.60 Hz), 7.59 (m, 2H), 7.51 (s, 1H), 7.33 (m,
1H), 7.20 (s, 1H), 7.03 (m, 2H), 4.06 (m, 5H), 3.82 (m,
2H), 3.35 (d, 2H, J = 6.30 Hz), 3.19 (m, 4H), 1.81 (m,
4H), 1.45 (m, 8H), 1.30 (m, 6H), 0.96 (t, 3H,
J = 6.80 Hz); APCIMS: m/z 560 (M+1); Anal. Calcd
for C33H47Cl2N5O3 (632.7): C, 62.65; H, 7.49; N,
11.07. Found: C, 62.88; H, 7.75; N, 13.33.
1
3402, 1668 cmꢀ1. H NMR (CD3OD): d 8.70 (d, 1H,
J = 5.0 Hz), 7.59 (s, 1H), 7.58 (d, 1H, J = 5.0 Hz), 4.13
(t, 2H, J = 6.60 Hz), 4.08 (s, 3H) 3.96 (m, 2H), 3.48
(m, 2H), 3.36 (m, 2H), 3.02 (m, 2H), 1.90 (m, 12H),
1.50 (m, 4H), 1.40 (m, 6H), 0.99 (t, 3H, J = 7.0 Hz);
APCIMS: m/z 488 (M+1); Anal. Calcd for C27H48-
Cl3N5O3 (597.1): C, 54.31; H, 8.10; N, 11.73. Found:
C, 54.77; H, 8.48; N, 11.83.
5.3.21. N1-[4-(4-Ethyl-6-methoxy-5-pentyloxy-8-quinolyl-
amino)pentyl]-(2S)-2-amino-3-phenylpropanamideÆ2HCl
(58). Yield: 76%; mp (salt) 104–106 ꢁC (dec). IR (KBr):

928
K. Kaur et al. / Bioorg. Med. Chem. 15 (2007) 915–930
1
1
3414, 1664 cmꢀ1. H NMR (CD3OD): d 8.75 (m, 1H),
7.64 (m, 1H), 7.53 (d, 1H, J = 6.10 Hz), 7.23 (m, 3H),
7.13 (d, 2H, J = 8.10 Hz), 4.11 (s, 3H), 3.93 (m, 2H),
3.87 (m, 2H), 3.37 (m, 2H), 3.00 (m, 4H), 1.85 (m,
2H), 1.52 (m, 10H), 1.30 (m, 6H), 0.97 (t, 3H,
J = 6.20 Hz); APCIMS: m/z 521 (M+1); Anal. Calcd
for C31H46Cl2N4O3 (593.6): C, 62.72; H, 7.81; N, 9.44.
Found: C, 62.97; H, 7.58; N, 9.68.
IR (KBr): 3402, 1672 cmꢀ1. H NMR (CD3OD): d 8.59
(d, 1H, J = 4.90 Hz), 7.52 (s, 1H), 7.43 (d, 1H
J = 4.80 Hz), 4.00 (m, 5H), 3.83 (m, 1H), 3.58 (m, 1H),
3.31 (m, 4H), 3.03 (m, 2H), 1.68 (m, 9H), 1.38 (m,
4H), 1.23 (m, 6H), 0.88 (t, 3H, J = 7.0 Hz); APCIMS:
m/z 477 (M+1); Anal. Calcd for C25H42Br2N4O3S
(638.5): C, 47.03; H, 6.63; N, 8.77. Found: C, 47.36;
H, 6.47; N, 8.52.
5.3.22. N1-[4-(4-Ethyl-6-methoxy-5-pentyloxy-8-quinolyl-
amino)pentyl]-(2S)-2-amino-3-(4-hydroxyphenyl)propan-
amideÆ2HBr (59). Yield: 80%; mp (salt) 130–132 ꢁC
5.4. Assay for methemoglobin (MetHb) toxicity
An in vitro biotransformation-linked assay was used to
evaluate methemoglobin toxicity of the analogs at 20 lg/
mL. The method involves simultaneous incubation of
the test compounds with the mouse liver microsomes
and human erythrocytes followed by determination of
methemoglobin formation.25 This allows the unstable
metabolites generated in situ to react with the human
erythrocytes. The assay mixture (500 lL) contained
100 lL erythrocyte suspension (50% hematocrit),
100 lL NADPH regenerating co-factors and enzyme
mix (0.8 lM NADP, 5 lM glucose-6-phosphate, 3 lM
MgCl2, and 0.2 U glucose-6-phosphate dehydrogenase),
100 lL KCl (31 lM), 25 lL microsomes (equivalent to
500 lg protein), 5 lL test compound, and 170 lL potas-
sium phosphate buffer (100 mM, pH 7.4). The reaction
tubes were loosely covered with aluminum foil and
maintained at 37 ꢁC in a metabolic water bath with con-
stant shaking at 80 rpm for 1 h. The tubes were chilled
on ice and centrifuged at 1000 rpm for 10 min. The
supernatants were discarded and the erythrocyte pellets
were hemolyzed with 2 mL of the lysis buffer (0.277%
potassium dihydrogen phosphate, 0.289% disodium
hydrogen phosphate, and 0.05% Triton X-100; pH
7.8). The methemoglobin levels relative to total hemo-
globin in the lysates were measured by the spectrophoto-
metric technique of Evelyn and Malloy adapted to
96-well plates.28
1
(dec). IR (KBr): 3408, 1667 cmꢀ1. H NMR (CD3OD):
d 8.69 (d, 1H, J = 4.30 Hz), 7.60 (s, 1H), 7.55 (m, 1H),
7.34 (s, 1H), 7.11 (m, 2H), 6.86 (m, 1H), 4.27 (m, 1H),
4.15 (m, 5H), 3.45 (m, 2H), 3.13 (m, 2H), 2.97 (m,
2H), 1.83 (m, 2H), 1.54 (m, 10H), 1.32 (m, 6H), 0.97
(t, 3H, J = 7.0 Hz); APCIMS: m/z 537 (M+1); Anal.
Calcd for C31H46Cl2N4O4 (609.7): C, 61.08; H, 7.61;
N, 9.19. Found: C, 61.37; H, 7.88; N, 9.23.
5.3.23. N1-[4-(4-Ethyl-6-methoxy-5-pentyloxy-8-quin-
olylamino)pentyl]-(2S)-2-amino-4-methylsulfanylbu-
tanamideÆ2HCl (60). Yield: 91%; mp (salt) 72–74 ꢁC
1
(dec). IR (KBr): 3355, 1668 cmꢀ1. H NMR (CD3OD):
d 8.68 (d, 1H, J = 4.90 Hz), 7.56 (s, 1H), 7.55 (d, 1H,
J = 4.30 Hz), 4.11 (t, 2H, J = 6.50 Hz), 4.06 (s, 3H),
3.98 (m, 2H), 3.47 (m, 2H), 3.27 (m, 2H), 2.54 (t, 2H,
J = 7.40 Hz), 2.06 (m, 5H), 1.87 (m, 2H), 1.77 (m,
2H), 1.50 (m, 8H), 1.36 (m, 6H), 0.97 (t, 3H,
J = 7.10 Hz); APCIMS: m/z 505 (M+1); Anal. Calcd
for C27H46Cl2N4O3S (577.8): C, 56.14; H, 8.03; N,
9.70. Found: C, 56.45; H, 7.87; N, 10.06.
5.3.24. N1-[4-(4-Ethyl-6-methoxy-5-pentyloxy-8-qui-
nolylamino)pentyl]-(2S)-2-amino-3-hydroxypropiona-
mideÆ2HBr(61). Yield: 96%; mp (salt) 88–90 ꢁC (dec).
IR (KBr): 3402, 1672 cmꢀ1 1H NMR (CD3OD): d
.
8.61 (d, 1H, J = 4.80 Hz), 7.54 (s, 1H), 7.46 (d, 1H,
J = 4.80 Hz), 4.15 (m, 1H), 4.02 (t, 2H, J = 6.10 Hz),
3.98 (s, 3H), 3.84 (m, 2H), 3.37 (m, 2H), 3.21 (m,
2H), 1.97 (m, 2H), 1.78 (m, 4H), 1.65 (m, 4H), 1.44
(m, 4H), 1.28 (m, 6H), 0.88 (t, 3H, J = 7.20 Hz); APC-
IMS: m/z 461 (M+1); Anal. Calcd for C25H42Br2N4O4
(622.4): C, 48.24; H, 6.80; N, 9.00. Found: C, 48.44;
H, 6.75; N, 8.68.
5.5. Assay for antimicrobial activity
All organisms are obtained from the American Type
Culture Collection (Manassas, VA). They include the
fungi C. albicans ATCC 90028, C. glabrata ATCC
90030, C. krusei ATCC 6258, C. neoformans ATCC
90113, and A. fumigatus ATCC 90906, and the bacteria
methicillin-resistant S. aureus ATCC 43300 (MRS) and
M. intracellulare ATCC 23068. Susceptibility testing is
performed using a modified version of the CLSI (for-
merly NCCLS) methods.29–32 M. intracellulare is tested
using a modified method of Franzblau et al.33 Samples
are serially diluted in 20% DMSO/saline and transferred
in duplicate to 96-well flat-bottomed microplates. Inoc-
ula are prepared by correcting the OD630 of microbe sus-
pensions in incubation broth [RPMI 1640/2% dextrose/
0.03% glutamine/Mops at pH 6.0 (Cellgro) for C. albi-
cans, Sabouraud Dextrose for C. neoformans, cation-
adjusted Mueller–Hinton (Difco) at pH 7.3 for
MRS, 5% Alamar BlueTM (BioSource International,
Camarillo, CA) in Middlebrook 7H9 broth with OADC
enrichment, pH 7.3, for M. intracellulare, and 5%
Alamar BlueTM/RPMI 1640 broth (2% dextrose, 0.03%
glutamine, buffered with 0.165 M Mops at pH 7.3) for
5.3.25. N1-[4-(4-Ethyl-6-methoxy-5-pentyloxy-8-quin-
olylamino)pentyl]-(2R)-2-amino-3-benzylsulfanylpropana-
mideÆ2HCl (62). Yield 79%; mp (salt) 94–96 ꢁC (dec). IR
1
(KBr): 3321, 1682 cmꢀ1. H NMR (CD3OD): d 8.57 (d,
1H, J = 4.10 Hz), 7.44 (d, 1H, J = 4.70 Hz), 7.43 (s, 1H),
7.18 (m, 5H), 4.00 (t, 2H, J = 6.40 Hz), 3.96 (s, 3H), 3.84
(m, 1H), 3.82 (m, 1H), 3.70 (d, 2H, J = 4.70 Hz), 3.34
(m, 2H), 3.21 (m, 2H), 2.78 (m, 2H), 1.75 (m, 4H), 1.65
(m, 4H), 1.44 (m, 4H), 1.27 (m, 6H), 0.88 (t, 3H,
J = 7.0 Hz); APCIMS: m/z 567 (M+1); Anal. Calcd for
C32H48Cl2N4O3S (639.7): C, 60.08; H, 7.56; N, 8.76.
Found: C, 60.35; H, 7.84; N, 8.95.
5.3.26. N1-[4-(4-Ethyl-6-methoxy-5-pentyloxy-8-qui-
nolylamino)pentyl]-(2R)-2-amino-3-sulfanylpropana-
mideÆ2HBr (63). Yield 83%; mp (salt) 102–104 ꢁC (dec).

K. Kaur et al. / Bioorg. Med. Chem. 15 (2007) 915–930
929
A. fumigatus to afford final target inocula of: C. albicans:
1.0 · 104, C. neoformans: 1.0 · 105, M. intracellulare:
2.0 · 106, MRS, C. glabrata, C. krusei: 5.0 · 105 CFU/
mL, and A. fumigatus: 3.0 · 104 CFU/mL. Drug con-
trols [Ciprofloxacin (ICN Biomedicals, Ohio) for bacte-
ria and Amphotericin B (ICN Biomedicals, Ohio) for
fungi] are included in each assay. All organisms are read
at either 630 nm using the EL-340 Biokinetics Reader
(Bio-Tek Instruments, Vermont) or 544ex/590em (M.
intracellulare, A. fumigatus) using the Polarstar Galaxy
Plate Reader (BMG LabTechnologies, Germany) prior
to and after incubation: C. albicans, MRS, C. glabrata,
and C. krusei at 37 ꢁC for 18–24 h, C. neoformans and
A. fumigatus at 30 ꢁC for 68–72 h, and M. intracellulare
at 37 ꢁC and 10% CO2 for 68–72 h. The MIC is defined
as the lowest test concentration that allows no
detectable growth (for M. intracellulare and A. fumiga-
tus, no color change from blue to pink). Minimum fun-
gicidal or bactericidal concentrations are determined by
removing 5 lL from each clear (or blue) well,
transferring to agar and incubating as previously
mentioned. The MFC/MBC is defined as the lowest test
concentration that kills the organism (allows no growth
on agar).
for conducting antimalarial testing. The biological test-
ing was supported by the NIH, NIAID, Division of
AIDS, Grant No. AI 27094, and the USDA Agricultur-
al Research Service Specific Cooperative Agreement No.
58-6408-2-0009.
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Acknowledgments
This research project was supported by the Council of
Scientific and Industrial Research, New Delhi, India
(Grant No. 01(1555)/98/EMR-II). Kirandeep Kaur
thanks the Council of Scientific and Industrial Research
(CSIR), India, for the award of Junior Research Fellow-
ship. The authors thank Marsha Wright for conducting
the antifungal and antibacterial testing and John Trott
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