Structure-Activity relationships for a series of quinoline-based compounds active against replicating and nonreplicating mycobacterium tuberculosis

Article abstract of DOI:10.1021/jm900003c

Tuberculosis (TB) remains as a global pandemic that is aggravated by a lack of health care, the spread of HIV, and the emergence of multidrug-resistant TB (MDR-TB) and extensively drug-resistant TB (XDRTB) strains. New anti-TB drugs are urgently required to shorten the long 6-12 month treatment regimen and to battle drug-resistant Mtb strains. We have identified several potent quinoline-based anti-TB compounds, bearing an isoxazole containing side-chain. The most potent compounds, 7g and 13, exhibited submicromolar activity against the replicating bacteria (R-TB), with minimum inhibitory concentrations (MICs) of 0.77 and 0.95 μM, respectively. In general, these compounds also had micromolar activity against the nonreplicating persistent bacteria (NRP-TB) and did not show toxicity on Vero cells up to 128 μM concentration. Compounds 7g and 13 were shown to retain their anti-TB activity against rifampin, isoniazid, and streptomycin resistant Mtb strains. The results suggest that quinoline-isoxazole-based anti-TB compounds are promising leads for new TB drug development.

Full text of DOI:10.1021/jm900003c

J. Med. Chem. 2009, 52, 2109–2118
2109
Structure-Activity Relationships for a Series of Quinoline-Based Compounds Active against
Replicating and Nonreplicating Mycobacterium tuberculosis
Annamaria Lilienkampf,† Jialin Mao,†,‡ Baojie Wan,‡ Yuehong Wang,‡ Scott G. Franzblau,*,‡ and Alan P. Kozikowski*,†
Drug DiscoVery Program, Department of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, UniVersity of Illinois at Chicago,
833 South Wood Street, Chicago, Illinois 60612, Institute for Tuberculosis Research, College of Pharmacy, UniVersity of Illinois at Chicago,
833 South Wood Street, Chicago, Illinois 60612
ReceiVed January 3, 2009
Tuberculosis (TB) remains as a global pandemic that is aggravated by a lack of health care, the spread of
HIV, and the emergence of multidrug-resistant TB (MDR-TB) and extensively drug-resistant TB (XDR-
TB) strains. New anti-TB drugs are urgently required to shorten the long 6-12 month treatment regimen
and to battle drug-resistant Mtb strains. We have identified several potent quinoline-based anti-TB compounds,
bearing an isoxazole containing side-chain. The most potent compounds, 7g and 13, exhibited submicromolar
activity against the replicating bacteria (R-TB), with minimum inhibitory concentrations (MICs) of 0.77
and 0.95 µM, respectively. In general, these compounds also had micromolar activity against the nonreplicating
persistent bacteria (NRP-TB) and did not show toxicity on Vero cells up to 128 µM concentration. Compounds
7g and 13 were shown to retain their anti-TB activity against rifampin, isoniazid, and streptomycin resistant
Mtb strains. The results suggest that quinoline-isoxazole-based anti-TB compounds are promising leads
for new TB drug development.
Introduction
Tuberculosis (TBa), which is caused predominantly by
Mycobacterium tuberculosis (Mtb), is a life-threatening chronic
infection primarily affecting the lungs. The World Health
Organization (WHO) has estimated that one-third of the world’s
population is infected with Mtb, resulting in an estimated 1.7
million deaths from TB in 2006.1 Mtb has the remarkable ability
to lie dormant for years as a latent infection, and approximately
5-10% of the latently infected individuals will eventually
develop an active disease. In addition, TB is a frequent HIV
coinfection and a major cause of death among people living
with HIV/AIDS. Despite the severe global impact of TB, it has
been a neglected disease and no new anti-TB drugs have been
introduced for the last four decades.2
Current TB treatment takes 6-12 months and requires
patients to take a combination of three or four drugs (isoniazid
Figure 1. Examples of quinoline-based anti-TB agents and the outline
of structural modifications on the lead compound.
(INH), rifampin (RMP), pyrazinamide, and ethambutol or
streptomycin (SM)), often leading to poor patient compliance.
The long treatment is necessary due to the presence of a
nonreplicating persistent Mtb phenotype (NRP-TB), which is
the putative cause of disease relapse. All the current drugs target
the replicating form of Mtb (R-TB), however, only RMP and
pyrazinamide have shown activity against NRP-TB.3 Further-
more, recent years have seen an alarming emergence of
multidrug-resistant (MDR-TB) and extensively drug-resistant
(XDR-TB) tuberculosis strains. There is an urgent demand for
new anti-TB drugs possessing novel modes of action, not only
to shorten the long treatment regimen by targeting NRP-TB but
also to battle resistant Mtb strains. In addition, the retrovirals
commonly used in AIDS/HIV treatment are usually not compat-
ible with the current TB treatment, particularly due to the
CYP3A induction by RMP.4
Quinoline-based compounds are known to exhibit anti-TB
properties.5 Fluoroquinolones,6 such as gatifloxcin and moxi-
floxacin, target DNA topoisomerase IV and DNA gyrase and
can be used as anti-TB agents,7 however, they often suffer from
resistance.8 Quinoline-based anti-TB compound 1 (TMC207),9
bearing a bulky biaryl side chain at position C3, is a highly
potent anti-TB agent and is currently in phase II clinical trials
(Figure 1). We have previously reported the quinoline-based
antimalarial drug mefloquine 2 (with a minimum inhibitory
concentration (MIC) of 13 µM),10 and its derivatives,11 to show
moderate activity against Mtb. The activity was significantly
improved with compound 3,12 in which the quinoline core of
* To whom correspondence should be addressed. For A.P.K.: phone,
+1-312-996-7577; fax, +1-312-996-7107; E-mail: kozikowa@uic.edu. For
S.G.F.: phone, +1-312-355-1715; fax, +1-312-355-2693. E-mail: sgf@
uic.edu.
†
Drug Discovery Program, Department of Medicinal Chemistry and
Pharmacognosy, College of Pharmacy, University of Illinois at Chicago.
‡
Institute for Tuberculosis Research, College of Pharmacy, University
of Illinois at Chicago.
a Abbreviations: INH, isoniazid; LORA, low oxygen recovery assay;
MABA, microplate Alamar Blue assay; MIC, minimum inhibitory concen-
tration; MDR-TB, multidrug-resistant tuberculosis; Mtb, Mycobacterium
tuberculosis; NRP-TB, nonreplicating persistent tuberculosis; PPA, poly-
phosphoric acid; R-TB, replicating tuberculosis; RMP, rifampin; SDR-TB,
single drug resistant tuberculosis; SM, streptomycin; TB, tuberculosis; XDR-
TB, extensively drug-resistant tuberculosis.
10.1021/jm900003c CCC: $40.75
2009 American Chemical Society
Published on Web 03/09/2009

2110 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 7
Lilienkampf et al.
Scheme 1a b
,
a Reagents and conditions: (a) PPA, ethyl 4,4,4-trifluoroacetoacetate, 150 °C, 12-48 h; (b) CHtCCH2Br, K2CO3, KI, acetone, reflux; (c) ethyl 2-chloro-
2-(hydroxyimino)acetate, Et3N, ether or THF; (d) 5-(bromomethyl)isoxazole-3-carboxylic acid ethyl ester,14 K2CO3, acetone, reflux; (e) 3-butyn-1-ol, PPh3,
DEAD, THF. b For complete structures see Table 1. The substitution pattern in each intermediate corresponds to the substitution pattern in the final compound
with the same letter.
mefloquine was linked to an isoxazole moiety via an oxymeth-
ylene linker (Figure 1). Compound 3 was shown to have activity
against both R-TB and NRP-TB with an MIC of 0.9 and 12.2
µM, respectively. The ethyl ester moiety in 3 proved to be
important for activity as the corresponding carboxylic acid was
found to be inactive and various amides showed significantly
reduced activity. However, it is possible that the ethyl ester acts
as a prodrug for the corresponding carboxylic acid, which itself
may be unable to penetrate through the thick Mycobacterium
cell wall in the in vitro assay. No CYP3A4 inhibition was
observed with 3, which is a valuable feature in a possible
coadministration regimen with HIV drugs.
In this paper, we describe the synthesis and biological activity
of a series of anti-TB agents based on a quinoline core.
Compound 3 was used as the lead compound, and for this study
three modification sites were chosen: the quinoline core, the
oxymethylene linker, and the isoxazole ring (Figure 1). Various
substituents were introduced around the quinoline core in order
to find the optimal substitution pattern as well as to study
substituent effects. The side chain was kept at C4 position in
all modifications, and the effect of the isoxazole moiety on the
anti-TB activity was investigated by replacement with other
heterocycles. All the synthesized compounds were first evaluated
for their activity against R-TB. Selected compounds were also
tested for their activity against NRP-TB and against single drug
resistant Mtb strains (SDR-TB) as described herein.
alkylating the 4-hydroxyquinolines with 5-(bromomethyl)isox-
azole-3-carboxylic acid ethyl ester,14 as was done for compounds
7a, 7b, 7o, and 7q.
A similar synthetic route was used for compound 10, bearing
an oxyethylene linker, except the acteylenic intermediate 9 was
synthesized via Mitsunobu coupling of 2,8-bis(trifluoromethyl)-
4-quinolinol (4s) and 3-butyn-1-ol (Scheme 1). Compound 13,
with an aryl ether linker, was synthesized starting from 4-chloro-
2-(trifluoromethyl)quinoline (11) (Scheme 2). The addition of
3-hydroxyphenylacetylene yielded the intermediate 12, which
in turn gave the final compound 13 in the cycloaddition reaction
with the nitrile oxide generated from ethyl 2-chloro-2-(hydroxy-
imino)acetate.
Finally, the effect of the isoxazole moiety was studied. The
oxymethylene linker moiety, as well as the original quinoline
core 2,8-bis(trifluoromethyl) substitution, were kept constant,
allowing detailed derivation of structure–activity relationships
(SARs) based on the variations in the anti-TB activity. The
corresponding isoxazoline derivative 15 was synthesized from
4s by employing the same methodology as for the isoxazole
derivatives (Scheme 3). The reverse 3,5-substituted isoxazole
regioisomer 19 was synthesized by alkylating 4s with 3-(chlo-
romethyl)isoxazole-5-carboxylic acid ethyl ester (18), which in
turn was synthesized in two steps starting from chloroacetal-
dehyde (16) (Scheme 4).
The thiazole-2-carboxylic acid ethyl ester derivative 22 was
synthesized via 4-(chloromethyl)-2-thiazolecarboxylic acid ethyl
ester15 (21), which was obtained from ethyl thiooxamate (20)
in a cyclization reaction with 1,3-dichloroacetone (Scheme 5).
Diethyl 2,6-pyridinedicarboxylate (23) was reduced with NaBH4
to 6-(hydroxymethyl)-2-pyridinecarboxylic acid ethyl ester
(24),16 which was coupled with 4s to give the pyridine derivative
25 (Scheme 6). The remaining isoxazole modified compounds
(26-35) were synthesized in good yields by the above
established Williamson ether synthesis protocol with 4s and
commercially available alkylhalides (Scheme 7, Table 2)
followed by standard functional group interconversions.
Chemistry
First, the effect of the quinoline core substitution on the
antibacterial activity was explored (Table 1). The target
compounds 7a-7r, bearing various substituents on the core,
were synthesized in two steps starting from suitably substituted
4-hydroxyquinolines (Scheme 1). The 4-hydroxyquinolines
4a-4s, if not commercially available, were synthesized from
the corresponding anilines in the PPA catalyzed condensation
with ethyl 4,4,4-trifluoroacetoacetate.13 Alkylation of 4c-4n and
4p with propargyl bromide, employing K2CO3 as a base,
produced the acetylenic intermediates 5c-5n and 5p in good
yields. With 7-(trifluoromethyl)-4-quinolinol (4r), the above
Williamson reaction yielded both the N-alkylated and O-
alkylated products 5r and 6. In the final step, the isoxazole
moiety in compounds 7c-7n, 7p, 7r, and 8 was introduced via
dipolar cycloaddition of the nitrile oxide derived from ethyl
2-chloro-2-(hydroxyimino)acetate with the acetylene intermedi-
ates. Alternatively, the final compounds can be synthesized by
Results and Discussion
All the final compounds were first evaluated for their activity
against the Mtb strain H37Rv in a microplate Alamar Blue assay
(MABA).17 The compounds showing good anti-TB activity in
MABA were further evaluated for their potency against NRP-
TB in a low oxygen recovery assay (LORA).18

SAR for Quinoline Compounds ActiVe against M. tuberculosis
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 7 2111
Table 1. Effect of Quinoline Core Substitution and the Linker Moiety on the Anti-TB Activity
compd
R1
R2
R3
-H
R4
R5
-H
MABAa MIC (µM)
LORAa MIC (µM)
Vero cells IC50 (µM)
7a
7b
7c
7d
7e
7f
7g
7h
7i
-H
-H
-H
-H
-H
-H
-H
-CF3
-CF3
-H
-H
-H
-H
-Cl
-F
-H
-H
-H
-H
-H
-H
-H
-H
-H
-H
25.1
10.6
3.2
3.7
1.3
3.8
0.77
1.8
13.2
56.6
25.1
7.6
>128
>128
>128
>128
>128
>128
>128
>128
>128
nd
-H
-H
-CF3
-H
-H
-H
-H
-H
-H
-H
-H
-H
-F
-OCH3
-H
-H
-H
-H
-H
-H
-H
-H
-CF3
-H
-CF3
-CF3
-CF3
-CF3
-CF3
-CF3
-CF3
-CF3
-CF3
-CF3
-CF3
-CF3
-CF3
-CO2Et
-H
-H
-H
-H
-CF3
-H
-H
ndb
nd
-H
-CF3
-H
-H
10.0
10.4
7.0
49.3
39.0
3.7
52.8
nd
nd
15.7
99.7
81.9
nd
9.9
3.7
-CH3
-OCF3
-Cl
-F
-H
2.6
7j
7k
7l
-H
62.9
11.3
1.9
41.2
14.6
66.1
7.9
-H
>128
>128
nd
-Cl
-H
-H
7m
7n
7o
7p
7q
7r
8
10
13
3
-F
-H
-F
nd
-H
-CF3
-H
>128
>128
>128
nd
-H
-Cl
-CF3
-CF3
-H
-H
3.8
3.3
-H
-H
-CF3
-CF3
-CF3
-H
-H
>128
3.4
0.95
0.9-1.9
0.1
nd
-CF3
-H
>128
>128
>128
127
-H
-H
-CF3
12.2
1.9
>128
RMP
INH
0.5
>128
a Mtb H37Rv. b nd: not determined.
Scheme 2a
Scheme 3a
a Reagents and conditions: (a) 3-hydroxyphenylacetylene, t-BuOK, THF,
reflux; (b) ethyl 2-chloro-2-(hydroxyimino)acetate, Et3N, THF.
a Reagents and conditions: (a) CH2dCHCH2Br, K2CO3, KI, acetone,
reflux; (b) ethyl 2-chloro-2-(hydroxyimino)acetate, Et3N, ether.
Several compounds were found to effectively inhibit the
growth of replicating Mtb in MABA with low µM MICs (Table
1). The substitution pattern of the quinoline core was shown to
significantly affect the potency and plausible SARs could be
derived. In the first round of structural modifications, the
trifluoromethyl groups were moved around the quinoline ring
in order to obtain the optimal substitution pattern (7b-7f). The
methylene ether linker was kept at the C4 position in all
modifications. Removal of the trifluoromethyl substituents
(compound 7a) reduced the activity by 20-fold as compared to
the lead 3. The C2-CF3 substituent seemed to contribute more
to the anti-TB activity than the C8-CF3 group (7c vs 7b),
although C7 monosubstituted compounds 7q (MIC 3.8 µM) and
7r (MIC 3.3 µM) also exhibited good activity. Comparable
activity to that of 3 was obtained with C2, C7-disubstitution,
7e having an MIC of 1.3 µM. C2,C5-disubstitution (7f, MIC
3.8 µM) also yielded good anti-TB activity. Introduction of
different substituents at C8 was tolerated (7h-7k), trifluoro-
methyl and methyl groups yielding the best activity (-CF3 g
-CH3 > -OCF3 > -F . -Cl). The C2-CF3 substituent could
also be replaced with an ethyl ester, 7p (MIC 7.9 µM) being
slightly less active than 7c (MIC 3.2 µM). Next, various
trisubstitution patterns were explored and quinoline core
C2,C5,C7-trisubstitution, as with compounds 7g and 7l, seemed
to be preferred. In particular, 5-[[[2,5,7-tris(trifluoromethyl)-4-
quinolinyl]oxy]methyl]-3-isoxazolecarboxylic acid ethyl ester
(7g) was the most potent anti-TB agent in the series, with an

2112 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 7
Lilienkampf et al.
Scheme 4a
Scheme 7a b
,
a Reagents and conditions: (a) NH2OH·HCl, NaOAc, H2O, 1 h; (b)
10-15% NaOCl (aq), CHtCCO2Et, THF, overnight; (c) 4s, K2CO3, KI,
acetone, reflux.
Scheme 5a
a Reagents and conditions: (a) BrCH2R or ClCH2R, K2CO3, KI, acetone,
reflux, 1-12 h; (b) LiOH, THF-MeOH-H2O (8:1:1), 0 °C to rt; (c) NaN3,
NH4Cl, DMF, 100 °C, 2 h; (d) KOH, abs. EtOH, reflux, overnight; (e)
EtMgBr, ether, 0 °C to rt, 15 min. b For structures, see Table 2.
ketone reduced the activity over 20-fold as compared to the
lead compound.
The compounds showing good anti-TB activity in MABA
were also tested for potency against NRP-TB in LORA, which
is a new luminescence-based high-throughput assay developed
for evaluation of activity against the nonreplicating persistent
phenotype in low oxygen conditions.18 Significantly, although
being somewhat weaker, these compounds seemed to retain their
activity in LORA relatively well (Table 1). Compounds 7g and
13 were active also against NRP-TB, with a LORA MIC of
10.0 and 3.7 µM, respectively, and also four other compounds
(7d, 7i, 7l, and 10) exhibited MICs of <10 µM. The SARs
against NRP-TB seemed to be, to some extent, different
compared to the SARs obtained against R-TB. In LORA, the
dichloro derivative 7l (LORA MIC 3.7 µM) exhibited better
activity than 7g. Trifluoromethyl substitution at C6 was favored,
and compound 7d (LORA MIC 7.6 µM) was only 2-fold less
active in LORA. Surprisingly, monosubstitution at C7, which
yielded good activity in MABA, was not tolerated and 7q and
7r were 25-fold less potent in LORA.
a Reagents and conditions: (a) 1,3-dichloroacetone, toluene, reflux; (b)
4s, K2CO3, KI, acetone, reflux.
Scheme 6a
a Reagents and conditions: (a) NaBH4, EtOH, 50 °C; (b) 4s, DEAD,
PPh3, THF.
Vero cells were used for an in vitro cytotoxicity evaluation
for the compounds exhibiting anti-TB activity. In general, these
compounds did not show cytotoxicity (IC50 > 128 µM),
confirming that the anti-TB activity does not arise from general
toxicity of the compound class. The only compounds showing
toxic effects were 35 and the furan derivatives 31 and 32;
however, these compounds did not show good potency and
diverged structurally from the most active compounds. As for
32 (MIC 6.3 µM), 2-nitrofurans have been previously reported
to have anti-TB activity,19 but on the other hand, certain
2-nitrofurans are also known to demonstrate cytotoxicity.20
Finally, the two most active compounds in the series, 13 and
7g, were evaluated against three selected SDR-TB strains (Table
3). The compounds retained their activity against RMP, INH,
and SM resistant strains, suggesting a different mode of action
and indicating that this compound class also holds promise as
lead compounds for treatment of drug resistant TB.
excellent MIC of 0.77 µM. Other trisubstitution patterns, namely
C2, C5, and C8 (7m) or C2, C6, and C8 (7n and 7o), were not
as well tolerated and led to decreased activity.
Elongation of the linker moiety at C4 by one methylene group
decreased activity (10, MIC 3.4 µM) compared to 3, whereas a
more rigid arylether linker yielded excellent activity against the
bacteria (13, MIC 0.95 µM). Introduction of the isoxazole side
chain to the ring nitrogen, to give the quinol-4-one derivative
8, led to a loss of the anti-TB activity. The isoxazole moiety
proved to be essential for good anti-TB activity. All the attempts
to modify this ring structure (15, 19, 22, 25-34) led to reduced
or a complete loss of potency (Table 2). Even subtle changes,
i.e., other nitrogen and oxygen containing heterocycles, were
not well tolerated, for example, regioisomer 19 being 3-fold
and isoxazoline 15 being 20-fold less active. Comparison of
the lead 3 with 19 (MIC 3.6 µM), with the thiazole 22 (MIC
16.5 µM), and the oxazole 34 (MIC > 128 µM) derivatives,
suggests that the correct positioning of the nitrogen in the side
chain ring may play a role in the activity. Compounds 26-28,
which lack a heterocycle on the side chain, as well as the methyl
ester 33 did not show notable activity against Mtb. The
importance of the ester moiety was again proven with compound
35, in which the replacement of the ethyl ester with an ethyl
The SARs obtained from the series suggests a specific
molecular target for these quinoline-isoxazole hybrid com-
pounds. The quinoline-based anti-TB agent 1 has been shown
to target the c subunit of ATP synthase,21 and similarly it has
been suggested that the target of mefloquine (2) in Streptococcus
pneumoniae is an F0F1 bifunctional ATP synthase/ATPase.22

SAR for Quinoline Compounds ActiVe against M. tuberculosis
Table 2. Effect of the Side Chain Heterocycle on Anti-TB Activityd
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 7 2113
a Mtb H37Rv. b Contains 6-8% of the corresponding 3,4-regioisomer (3-[[[2,8-bis(trifluoromethyl)-4-quinolinyl]oxy]methyl]-4-isoxazolecarboxylic acid
ethyl ester), which could not be separated by preparative HPLC. c Not determined. d * indicates the point of attachment.
Table 3. In Vitro Anti-TB Activity against Selected SDR Strains of
Mtb
However, since it was shown that the activity in this series
depends heavily on the isoxazole moiety, it is debatable if these
MIC (µM)
compounds could share the same target in Mtb. 3-Isoxazole-
carboxylic acids are known to inhibit virulence factor Mtb
protein tyrosine phosphatase (MptpB),23 which is suggested to
dephosphorylate human proteins involved in the interferon-γ
signaling pathway24 and thus preventing the initiation of defense
mechanisms in host macrophages. Assuming that the 3-isox-
azolecarboxylic acid ethyl ester is a prodrug for the correspond-
ing acid, our compounds could be potential ligands for MptpB.
On the other hand, it has been shown that MptpB is not essential
for the survival and growth of the mycobacteria in vitro, ruling
out MptpB as the primary target of our compounds.24
H37Rv
r-RMPa
r-INHb
r-SMc
7g
13
RMP
INH
SM
0.77
0.95
0.1
0.5
0.3
0.99
1.27
>32
0.43
0.20
0.98
1.63
0.06
>128
0.38
1.55
1.40
0.05
0.45
>32
a RMP resistant strain. b INH resistant strain. c SM resistant strain.
linker at the C4 position of the lead 3, with a more rigid aryl
ether linker, was successful and as such opens the possibility
for more structural variations in this compound class. Notably,
the two most potent compounds, 7g and 13, had similar activity
against the RMP, INH, and SM resistant Mtb strains. In general,
these compounds did not show toxicity on Vero cells at 128
µM concentration and therefore have excellent selectivity toward
the bacteria. These results suggest quinoline-isoxazole based
compounds to be promising lead structures for TB drug
development, especially due to the notable activity against the
NRP-TB phenotype, as well as against drug resistant Mtb strains.
Clarifications of the metabolic pathways, in vivo efficacy studies,
and target identification are currently under way in our
laboratories.
Conclusions
We have identified a class of quinoline-isoxazole hybrid
compounds with good anti-TB activity against both the replicat-
ing and nonreplicating persistent forms of Mtb. Several com-
pounds showed low micromolar MICs against R-TB in MABA.
The most potent compounds in the series, 7g and 13, exhibited
submicromolar activity, with MABA MICs of 0.77 and 0.95
µM, respectively. Compounds 7d, 7g,-7i, 7l, 10, and 13 also
had good activity against NRP-TB (MICs e 10 µM). Plausible
SARs could be derived from the substitution pattern of the
quinoline core, suggesting that C2,C8- or C2,C7-disubstitution
and C2,C5,C7-trisubstition are preferred. Trifluomethyl substit-
uents yielded the best activity against the bacteria, but also other
groups were tolerated. The isoxazole moiety played a significant
role in the activity, indicating that these compounds are likely
to have a specific Mtb target. Replacement of the oxymethylene
Experimental Section
Biology. The MICs were determined using Mtb H37Rv ATCC
27294 in MABA17 and LORA18 assays according to published
procedures.

2114 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 7
Lilienkampf et al.
MABA. Briefly, the test compound MICs against R-TB were
assessed by the MABA using RMP, INH, and 3 as positive controls.
Compound stock solutions were prepared in DMSO at a concentra-
tion of 12.8 mM, and the final test concentrations ranged from 128
to 0.5 µM. Two-fold dilutions of compounds were prepared in
Middlebrook 7H12 medium (7H9 broth containing 0.1% w/v
casitone, 5.6 µg/mL palmitic acid, 5 mg/mL bovine serum albumin,
4 mg/mL catalase, filter-sterilized) in a volume of 100 µL in 96-
well microplates (black viewplates). Mtb H37RV (100 µL inoculum
of 2 × 105 cfu/mL) was added, yielding a final testing volume of
200 µL. The plates were incubated at 37 °C. On the 7th day of
incubation 12.5 µL of 20% Tween 80 and 20 µL of Alamar Blue
(Trek Diagnostic, Westlake, OH) were added to the test plate. After
incubation at 37 °C for 16-24 h, fluorescence of the wells was
measured (ex 530, em 590 nm). The MICs ware defined as the
lowest concentration effecting a reduction in fluorescence of g90%
relative to the mean of replicate bacteria-only controls. Reported
MICs are an average of two individual measurements.
LORA. Briefly, a low-oxygen adapted culture of recombinant
H37Rv (pFCA-luxAB), expressing a Vibrio harVeyii luciferase gene
with an acetamidase promoter, was grown in a BiostatQ fermentor.
Cells were collected, washed in PBS, and stored at -80 °C. Then
ca. 105 cfu/mL of thawed NRP cells were exposed to 2-fold serial
dilutions of test compound in 7H12 medium in white 96-well plates,
which were incubated 10 days anaerobically at 37 °C. Luminescence
readings were obtained following a 28 h recovery in an aerobic
environment (5% CO2). The data were analyzed graphically, and
the lowest concentration of test compound preventing metabolic
recovery (90% reduction relative to untreated cultures) was
determined as described previously.
Method B. 2,8-Bis(trifluoromethyl)-6-methoxy-4-quinolinol 4o
(0.03 g, 0.1 mmol) and anhydrous K2CO3 (1 g, 7.4 mmol) in
anhydrous acetone (15 mL) were refluxed for 0.5 h. Ethyl
5-(bromomethyl)-3-isoxazolecarboxylate14 (0.045 g, 0.2 mmol) was
added slowly and the reaction mixture was refluxed overnight. After
cooling to room temperature, the mixture was filtered and the filtrate
was evaporated and dried in vacuo. The crude product was purified
by column chromatography (EtOAc-hexane 1:4) to obtain 7o as a
white solid in 95% yield.
5-[[(4-Quinolinyl)oxy]methyl]isoxazole-3-carboxylic Acid Eth-
yl Ester (7a). Synthesized by method B using 4-hydroxyquinoline
1
as a starting material. Yield 54% (white solid). H NMR (CDCl3)
δ 1.43 (3H, t, J ) 7.2 Hz), 4.48 (2H, q, J ) 7.2 Hz), 5.49 (2H, s),
6.88 (1H, d, J ) 8.0 Hz), 6.91 (1H, s), 7.54 (1H, t, J ) 7.2 Hz),
7.73 (1H, t, J ) 8.0 Hz), 8.06 (1H, d, J ) 7.2 Hz), 8.24 (1H, d, J
) 7.2 Hz), 8.79 (1H, d, J ) 8.0 Hz). HRMS (ESI) calculated for
C16H14N2O4 [M + H]+ 299.1032, found 299.1020.
5-[[[8-(Trifluoromethyl)-4-quinolinyl]oxy]methyl]-3-isoxazole-
carboxylic Acid Ethyl Ester (7b). Synthesized by method B using
8-(trifluoromethyl)-4-quinolinol as a starting material. Yield 56%
(white powder). 1H NMR (CDCl3) δ 1.29 (3H, t, J ) 7.2 Hz), 4.46
(2H, q, J ) 7.2 Hz), 5.52 (2H, s), 6.92 (1H, d, J ) 6.0 Hz), 7.59
(1H, t, J ) 9.0 Hz), 8.15 (1H, d, J ) 9.0 Hz), 8.47 (1H, d, J ) 9.0
Hz), 8.90 (1H, d, J ) 6.0 Hz,). HRMS (ESI) calculated for
C17H13F3N2O4 [M + H]+ 367.0906, found 367.0889.
5-[[[2-(Trifluoromethyl)-4-quinolinyl]oxy]methyl]-3-isoxazole-
carboxylic Acid Ethyl Ester (7c). Synthesized by method A by
using 5c as a starting material. Yield 63% (white powder). 1H NMR
(CDCl3) δ 1.44 (3H, t, J ) 7.1 Hz), 4.48 (2H, q, J ) 7.1 Hz), 5.51
(2H, s), 6.92 (1H, s), 7.13 (1H, s), 7.66 (1H, apparent t, J ) 7.8
Hz), 7.84 (1H, apparent t, J ) 7.6 Hz), 8.19 (1H, d, J ) 8.5), 8.25
(1H, d, J ) 8.3). HRMS (ESI) calculated for C17H13F3N2O4 [M +
H]+ 367.0900, found 367.0904.
5-[[[2,6-Bis(trifluoromethyl)-4-quinolinyl]oxy]methyl]-3-isox-
azolecarboxylic Acid Ethyl Ester (7d). Synthesized by method
A by using 5d as a starting material. Yield 70% (white powder).
1H NMR (CDCl3) δ 1.44 (3H, t, J ) 7.1 Hz), 4.48 (2H, q, J ) 7.1
Hz), 5.56 (1H, s), 6.94 (1H, s), 7.24 (1H, s), 8.01 (1H, dd, J ) 1.3
Hz J ) 8.8 Hz), 8.30 (1H, d, J ) 8.8 Hz), 8.54 (1H, s). HRMS
(ESI) calculated for C18H12F6N2O4 [M + H]+ 435.0774, found
435.0782.
Cytotoxicity Assay. Cytotoxicity was determined by exposing
different concentrations of samples to Vero cells. Samples were
dissolved at 12.8 mM in DMSO. Geometric 3-fold dilutions were
performed in growth medium MEM (Gibco, Grand Island, NY)
containing 10% fetal bovine serum (HyClone, Logan, UT), 25 mM
N-(2-hydroxyethyl)-piperazine-N′-2-ethanesulfonic acid (HEPES,
Gibco), 0.2% NaHCO3 (Gibco), and 2 mM glutamine (Irvine
Scientific, Santa Ana, CA). Final DMSO concentrations did not
exceed 1% v/v. Drug dilutions were distributed in duplicate in 96-
well tissue culture plates (Becton Dickinson Labware, Lincoln Park,
NJ) at a volume of 50 µL per well. An equal volume containing
either 5 × 105 log phase Vero cells (CCL-81; American Type
Culture Collection, Rockville, MD) was added to each well and
the cultures were incubated at 37 °C in an atmosphere containing
5% of CO2. After 72 h, cell viability was measured using the
CellTiter 96 aqueous nonradioactive cell proliferation assay (Prome-
ga Corp., Madison, WI) according to the manufacturer’s instruc-
tions. Absorbance at 490 nm was read in a Victor2 multilabel reader
(PerkinElmer). The IC50s were determined using a curve-fitting
program.
5-[[[2,7-Bis(trifluoromethyl)-4-quinolinyl]oxy]methyl]-3-isox-
azolecarboxylic Acid Ethyl Ester (7e). Synthesized by method A
from compound 5e/5f (mixture of regioisomers). The crude product
was first purified by column chromatography to give 7e/7f as an
approximately 1:2 mixture of C5-CF3 and C7-CF3 regioisomers
(yield 67%). The isomers were separated by preparative HPLC to
give 7e and 7f as white powders. For 7e: 1H NMR (CDCl3) δ 1.44
(3H, t, J ) 7.1 Hz), 4.49 (2H, q, J ) 7.1 Hz), 5.55 (1H, s), 6.94
(1H, s), 7.25 (1H, s), 7.83 (1H, d, J ) 8.7 Hz), 8.38 (1H, d, J )
8.7 Hz), 8.5 (1H, s). HRMS (ESI) calculated for C18H12F6N2O4 [M
+ H]+ 435.0774, found 435.0771.
1
Chemistry. H NMR and 13C NMR spectra were recorded on
Bruker spectrometer at 400 and 100 MHz or 300 and 75 MHz,
respectively, with TMS as an internal standard. 19F NMR spectra
were recorded on Bruker spectrometer at 376 MHz with TFA as
an external standard. HRMS experiments were performed on
Q-TOF-2TM (Micromass). TLC was performed with Merck 60 F254
silica gel plates. Column chromatography was performed using
CombiFlash Rf system with RediSep columns or alternatively using
Merck silica gel (40-60 mesh). The purity of the target compounds
was determined to be >95% by analytical HPLC.
General Procedures for the Synthesis of Compounds 7a-7r,
8, 10, and 13-14. Method A. Ethyl 2-chloro-2-(hydroxyimino)ac-
etate (0.27 g, 1.8 mmol) and the acetylene intermediate 5c (0.15 g,
0.6 mmol) were dissolved into anhydrous Et2O (20 mL). Et3N (0.25
mL, 1.8 mmol) in anhydrous Et2O (10 mL) was added to the
solution of 5c via syringe pump over 6 h period and stirred overnight
at room temperature. The reaction mixture was filtered, washed
with Et2O (2 × 15 mL), and the filtrate was evaporated in vacuo.
The crude product was purified by flash chromatography using
gradient elution from hexane to 50% EtOAc-hexane to give
compound 7c as a white powder in 73% yield.
5-[[[2,5-Bis(trifluoromethyl)-4-quinolinyl]oxy]methyl]-3-isox-
1
azolecarboxylic Acid Ethyl Ester (7f). H NMR (CDCl3) δ 1.44
(3H, t, J ) 7.1 Hz), 4.48 (2H, q, J ) 7.1 Hz), 5.54 (1H, s), 6.93
(1H, s), 7.30 (1H, s), 7.86 (1H, apparent t, J ) 8.0 Hz), 8.14 (1H,
d, J ) 7.4 Hz), 8.39 (1H, d, J ) 8.5 Hz). HRMS (ESI) calculated
for C18H12F6N2O4 [M + H]+ 435.0774, found 435.0787.
5-[[[2,5,7-Tris(trifluoromethyl)-4-quinolinyl]oxy]methyl]-3-
isoxazolecarboxylic Acid Ethyl Ester (7g). Synthesized by method
A by using 5g as a starting material. Yield 42% (white powder).
1H NMR (CDCl3) δ 1.45 (3H, t, J ) 7.1 Hz), 4.48 (2H, q, J ) 7.1
Hz), 5.57 (2H, s), 6.94 (1H, s), 7.41 (1H, s), 7.66 (1H, d, J ) 2.1
Hz), 8.28 (1H, d, J ) 2.1 Hz), 8.71 (1H, d, J ) 2.1 Hz). HRMS
(ESI) calculated for C19H11F9N2O4 [M + H]+ 503.0648, found
503.0662.
5-[[[8-Methyl-2-(trifluoromethyl)-4-quinolinyl]oxy]methyl]-
3-isoxazolecarboxylic Acid Ethyl Ester (7h). Synthesized by
method A by using 5h as a starting material. Yield 61% (white
1
powder). H NMR (CDCl3) δ 1.44 (3H, t, J ) 7.1 Hz), 2.81 (3H,
s) 4.47 (2H, q, J ) 7.1 Hz), 5.48 (1H, s), 6.90 (1H, s), 7.11 (1H,

SAR for Quinoline Compounds ActiVe against M. tuberculosis
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 7 2115
s), 7.53 (1H, apparent t, J ) 8.0 Hz), 7.66 (1H, d, J ) 7.0 Hz),
8.08 (1H, d, J ) 8.3 Hz). HRMS (ESI) calculated for C18H15F3N2O4
[M + H]+ 381.1057, found 381.1061.
5-[[[7-(Trifluoromethyl)-4-quinolinyl]oxy]methyl]-3-isoxazole-
carboxylic Acid Ethyl Ester (7r). Synthesized by method A by
using 5r as a starting material. Yield 56% (white powder). 1H NMR
(CDCl3) δ 1.44 (3H, t, J ) 7.1 Hz), 4.47 (2H, q, J ) 7.1 Hz), 5.48
(2H, s), 6.89 (1H, s), 6.92 (1H, d, J ) 5.2 Hz), 7.72 (1H, dd, J )
1.2 Hz, J ) 8.7 Hz), 8.33 (1H, d, J ) 8.7 Hz), 8.37 (1H, s), 8.88
(1H, d, J ) 5.2 Hz). HRMS (ESI) calculated for C17H13F3N2O4 [M
+ H]+ 367.0900, found 367.0900.
5-[[[8-(Trifluoromethoxy)-2-(trifluoromethyl)-4-quinoliny-
l]oxy]methyl]-3-isoxazolecarboxylic Acid Ethyl Ester (7i). Syn-
thesized by method A by using 5i as a starting material. Yield 67%
(white powder). 1H NMR (CDCl3) δ 1.44 (3H, t, J ) 7.1 Hz), 4.48
(2H, q, J ) 7.1 Hz), 5.53 (1H, s), 6.93 (1H, s), 7.21 (1H, s), 7.34
(1H, m), 7.73 (1H, m), 8.19 (1H, dd, J ) 1.0 Hz, J ) 1.0 Hz).
HRMS (ESI) calculated for C18H12F6N2O5 [M + H]+ 451.0723,
found 451.0728.
5-[[[8-Chloro-2-(trifluoromethyl)-4-quinolinyl]oxy]methyl]-3-
isoxazolecarboxylic Acid Ethyl Ester (7j). Synthesized by method
A by using 5j as a starting material. Yield 39% (white powder).
1H NMR (CDCl3) δ 1.44 (3H, t, J ) 7.1 Hz), 4.48 (2H, q, J ) 7.1
Hz), 5.52 (1H, s), 6.92 (1H, s), 7.19 (1H, s), 7.56 (1H, apparent t,
J ) 8.0 Hz), 7.94 (1H, dd, J ) 1.0 Hz, J ) 7.5 Hz), 8.17 (1H, dd,
J ) 1.0 Hz, J ) 8.5 Hz). HRMS (ESI) calculated for
C17H12ClF3N2O4 [M + H]+ 401.0511, found 401.0513.
5-[[[8-Fluoro-2-(trifluoromethyl)-4-quinolinyl]oxy]methyl]-3-
isoxazolecarboxylic Acid Ethyl Ester (7k). Synthesized by method
A by using 5k as a starting material. Yield 65% (white powder).
1H NMR (CDCl3) δ 1.44 (3H, t, J ) 7.1 Hz), 4.48 (2H, q, J ) 7.1
Hz), 5.53 (1H, s), 6.93 (1H, s), 7.20 (1H, s), 7.56 (2H, m), 8.03
(1H, m). HRMS (ESI) calculated for C17H12F4N2O4 [M + H]+
385.0806, found 385.0792.
5-[[4-oxo-7-(Trifluoromethyl)-1(4H)-quinolinyl]methyl]-3-
isoxazolecarboxylic Acid Ethyl Ester (8). Synthesized by fol-
lowing the method A by using 6 as a starting material. The product
was purified by preparative HPLC to give 8a as a white powder in
1
55% yield. H NMR (DMSO-d6) δ 1.27 (3H, t, J ) 7.1 Hz), 4.33
(2H, q, J ) 7.1 Hz), 5.93 (2H, s), 6.27 (1H, d, J ) 7.9 Hz), 6.94
(1H, s), 7.71 (1H, d, J ) 8.3 Hz), 8.16 (1H, s), 8.26 (1H, d, J )
7.9 Hz), 8.37 (1H, d, J ) 8.4 Hz). HRMS (ESI) calculated for
C17H13F3N2O4 [M + H]+ 367.0900, found 367.0897.
5-[[[2,8-Bis(trifluoromethyl)-4-quinolinyl]oxy]ethyl]-3-isox-
azolecarboxylic Acid Ethyl Ester (10). Synthesized by method
A by using 9 as a starting material. Yield 49% (white powder). 1H
NMR (CDCl3) δ 1.41 (3H, t, J ) 7.1 Hz), 3.54 (3H, t, J ) 6.0
Hz), 4.44 (2H, q, J ) 7.1 Hz), 4.62 (2H, t, J ) 6.0 Hz), 6.65 (1H,
s), 7.13 (1H, s), 7.67 (1H, apparent t, J ) 7.9 Hz), 8.15 (1H, d, J
) 7.1 Hz), 8.37 (1H, d, J ) 8.3 Hz). HRMS (ESI) calculated for
C19H14F6N2O4 [M + H]+ 449.0931, found 449.0944.
5-[3-[[2-(Trifluoromethyl)-4-quinolinyl]oxy]phenyl]-3-isox-
azolecarboxylic Acid Ethyl Ester (13). Synthesized by method
A by using 12 as a starting material. Yield 45% (white powder).
1H NMR (CDCl3) δ 1.44 (3H, t, J ) 7.1 Hz), 4.48 (2H, q, J ) 7.1
Hz), 6.88 (1H, s), 7.00 (1H, s), 7.34 (1H, dd, J ) 1.5 Hz, J ) 8.2
Hz), 7.64-7.75 (3H, m), 7.81 (1H, d, J ) 7.8 Hz), 7.89 (1H, m),
8.24 (1H, d, J ) 8.5 Hz), 8.43 (1H, d, J ) 8.4 Hz). HRMS (ESI)
calculated for C22H15F3N2O4 [M + H]+ 429.1057, found 429.1046.
5-[3-[[2,8-Bis(trifluoromethyl)-4-quinolinyl]oxy]phenyl]-4,5-
dihydro-3-isoxazolecarboxylic Acid Ethyl Ester (15). Synthesized
by method A by using 14 as a starting material. Yield 52% (white
solid). 1H NMR (CDCl3) δ 8.35 (1H, d, J ) 8.0 Hz), 8.15 (1H, d,
J ) 7.2 Hz), 7.67 (1H, t, J ) 7.6 Hz), 7.14 (1H, s), 5.36 (1H, s),
4.42 (4H, m), 3.52 (1H, dd, J ) 11.0, J ) 17.6 Hz), 3.37 (1H, dd,
J ) 7.7, J ) 17.6 Hz,), 1.42 (3H, t, J ) 7.2 Hz). 13C NMR (CDCl3)
δ 13.9, 29.3, 46.8, 69.4, 80.3, 97.7 (q, J ) 2 Hz), 122.3 (q, J )
274 Hz), 125.1, 126.5 (q, J ) 274 Hz), 127.6, 128.2 (q, J ) 35
Hz), 129.5 (q, J ) 6 Hz), 132.4, 144.6, 151.5 (q, J ) 35 Hz),
158.8, 160.3, 162.2. HRMS (ESI) calculated for C18H14F6N2O4 [M
+ H]+ 437.0936, found 437.0903.
5-[[[5,7-Dichloro-2-(trifluoromethyl)-4-quinolinyl]oxy]methyl]-
3-isoxazolecarboxylic Acid Ethyl Ester (7l). Synthesized by
method A by using 5l as a starting material. Yield 48% (white
1
powder). H NMR (CDCl3) δ 1.44 (3H, t, J ) 7.1 Hz), 4.48 (2H,
q, J ) 7.1 Hz), 5.48 (2H, s), 6.95 (1H, s), 7.15 (1H, s), 7.66 (1H,
d, J ) 2.1 Hz), 7.66 (1H, d, J ) 2.1 Hz), 8.10 (1H, d, J ) 2.1 Hz).
HRMS (ESI) calculated for C17H11Cl2F3N2O4 [M + H]+ 435.0121,
found 435.0128.
5-[[[5,8-Difluoro-2-(trifluoromethyl)-4-quinolinyl]oxy]methyl]-
3-isoxazolecarboxylic Acid Ethyl Ester (7m). Synthesized by
method A by using 5m as a starting material. Yield 50% (white
1
powder). H NMR (CDCl3) δ 1.44 (3H, t, J ) 7.1 Hz), 4.48 (2H,
q, J ) 7.1 Hz), 5.51 (2H, s), 6.95 (1H, s), 7.22 (1H, s), 7.26 (1H,
m) 7.47 (1H, dt, J ) 9.0 Hz, J ) 4.0 Hz). HRMS (ESI) calculated
for C17H11Cl2F5N2O4 [M + H]+ 403.0712, found 403.0695.
5-[[[6,8-Difluoro-2-(trifluoromethyl)-4-quinolinyl]oxy]methyl]-
3-isoxazolecarboxylic Acid Ethyl Ester (7n). Synthesized by
method A by using 5n as a starting material. Yield 51% (white
1
powder). H NMR (CDCl3) δ 1.44 (3H, t, J ) 7.1 Hz), 4.49 (2H,
2,5-Bis(trifluoromethyl)-4-(3-butyn-1-yloxy)quinoline (9). A
solution of 2,8-bis(trifluoromethyl)-4-quinolinol 4s (0.4 g, 1.4
mmol), butyn-1-ol (0.22 mL, 0.2 g, 2.8 mmol), and PPh3 (0.7 g,
2.8 mmol) in anhydrous THF (15 mL) was cooled to 0 °C. DEAD
(0.45 mL, 0.5 g, 2.8 mmol) was added dropwise and the solution
was stirred for 30 min at room temperature. The solvent was
evaporated and the resulting crude material was purified by flash
chromatography using gradient elution from hexane to 50% hexane-
EtOAc to give compound 9. Yield 97% (pale-yellow powder). 1H
NMR (CDCl3) δ 2.10 (1H, t, J ) 2.6 Hz), 2.90 (2H, m), 4.41 (2H,
t, J ) 6.6 Hz), 7.12 (1H, s), 7.66 (1H, apparent t, J ) 7.6 Hz),
8.14 (1H, d, J ) 7.1 Hz), 8.49 (1H, d, J ) 8.4 Hz). 13C NMR
(CDCl3) δ 19.5, 67.2, 71.0, 79.4, 97.8 (q, J ) 2 Hz), 121.3 (q, J )
276 Hz), 122.4, 123.8 (q, J ) 274 Hz), 126.4, 126.6, 128.5 (q, J )
30 Hz), 129.6 (q, J ) 5 Hz), 144.8, 149.8 (q, J ) 35 Hz), 162.8.
MS-ESI [M + H]+ 334.
4-(3-Ethynylphenoxy)-2-(trifluoromethyl)quinoline (12). To a
solution of 3-hydroxyphenylacetylene (0.32 g, 2.7 mmol) in
anhydrous THF (4 mL), 2.7 mL of 1 M t-BuOK (0.31 g, 2.7 mmol)
in THF and 4-chloro-2-(trifluoromethyl)quinoline (0.6 g, 2.6 mmol)
in anhydrous THF (5 mL) were added dropwise, respectively. The
reaction mixture was heated to reflux for 48 h. After cooling to
room temperature, cold H2O (50 mL) was added and the solution
was made acidic (pH ∼ 4) with 5% HCl, followed by extraction
with EtOAc (3 × 25 mL). The combined organic phases were
washed with brine (20 mL) and dried with Na2SO4. After filtration,
q, J ) 7.1 Hz), 5.52 (2H, s), 6.92 (1H, s), 7.22 (1H, s), 7.36 (1H,
m) 7.65 (1H, m). HRMS (ESI) calculated for C17H11Cl2F5N2O4 [M
+ H]+ 403.0712, found 403.0712.
5-[[[2,8-Bis(trifluoromethyl)-6-methoxy-4-quinolinyl]oxy]m-
ethyl]isoxazole-3-carboxylic Acid Ethyl Ester (7o). Synthesized
by method B by using 4o as a starting material. Yield 95% (white
solid). 1H NMR (CDCl3) δ 1.40 (3H, t, J ) 7.2 Hz), 4.00 (3H, s),
4.48 (2H, q, J ) 7.2 Hz), 7.84 (s, 1H), 7.60 (s, 1H), 7.20 (s, 1H),
6.92 (s, 1H), 5.53 (s, 2H). HRMS (ESI) calculated for C19H14F6N2O5
[M + H]+ 465.0885, found 465.0864.
4-[[5-(Ethoxycarbonyl)-2-isoxazole]methoxy]-2-quinolinecar-
boxylic Acid Ethyl Ester (7p). Synthesized by method A by using
1
5p as a starting material. Yield 52% (white powder). H NMR
(CDCl3) δ 1.44 (3H, t, J ) 7.1 Hz), 1.52 (3H, t, J ) 7.2 Hz), 4.48
(2H, q, J ) 7.1 Hz), 4.57 (2H, q, J ) 7.2 Hz), 5.53 (2H, s), 6.91
(1H, s), 7.63 (2H, m), 7.80 (1H, m), 8.25 (2H, m). HRMS (ESI)
calculated for C19H18N2O6 [M + H]+ 371.1238, found 371.1225.
5-[[(7-Chloro-4-quinolinyl)oxy]methyl]isoxazole-3-carboxyl-
ic Acid Ethyl Ester (7q). Synthesized by method B using 7-chloro-
1
4-quinolol as a starting material. Yield: 54% (white powder). H
NMR (CDCl3) δ 1.43 (3H, t, J ) 7.2 Hz), 4.48 (2H, q, J ) 7.2
Hz), 5.46 (2H, s), 6.82 (1H, d, J ) 4.8 Hz), 6.89 (s, 1H), 7.51 (1H,
d, J ) 6.4 Hz), 8.08 (1H, s), 8.16 (1H, d, J ) 6.4 Hz,), 8.80 (1H,
d, J ) 4.8 Hz). HRMS (ESI) calculated for C16H13ClN2O4 [M +
H]+ 333.0642; found 333.0626.

2116 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 7
Lilienkampf et al.
the solvent was evaporated and the crude product was purified by
flash chromatography using gradient elution from hexane to 8%
EtOAc-hexane. Yield 37% (white powder). H NMR (CDCl3) δ
ethyl)-2-furancarboxylate as the alkyhalide. Yield 75% (white
powder). 1H NMR (CD3OD) δ 1.36 (3H, t, J ) 7.1 Hz), 4.35 (2H,
q, J ) 7.1 Hz), 5.55 (2H, s), 6.86 (1H, d, J ) 3.4 Hz), 7.27 (1H,
d, J ) 3.4 Hz), 7.60 (1H, s), 7.76 (1H, apparent t, J ) 7.7 Hz),
8.22 (1H, d, J ) 7.3 Hz), 8.51 (1H, d, J ) 8.5 Hz). 13C NMR
(CDCl3) δ 14.3, 61.4, 62.9, 97.8 (q, J ) 2 Hz), 113.1, 118.4, 121.1
(q, J ) 276 Hz), 122.2, 123.6 (q, J ) 273 Hz), 126.3, 126.5, 128.4
(q, J ) 30 Hz), 129.5 (q, J ) 5 Hz), 144.7, 145.9, 149.6 (q, J )
35 Hz), 151.5, 158.4, 162.1. HRMS (ESI) calculated for
C19H13F6NO4 [M + H]+ 434.0822, found 434.0829.
4-[(5-Nitro)-2-furanylmethoxy]-2,8-bis(trifluoromethyl)quino-
line (32). Was synthesized by the typical procedure described above
using 2-(bromomethyl)-5-nitrofuran as the alkyhalide. Yield 71%
(pale-yellow solid). 1 H NMR (CDCl3) δ 5.40 (2H, s), 6.84 (1H, d,
J ) 3.7 Hz), 7.23 (1H, s), 7.37 (1H, d, J ) 3.7 Hz), 7.68 (1H,
apparent t, J ) 7.9 Hz), 8.16 (1H, d, J ) 7.3 Hz), 8.43 (1H, d, J
) 8.4 Hz). 13C NMR (CDCl3) δ 62.6, 97.7 (q, J ) 2 Hz), 111.9,
114.0, 121.0 (q, J ) 276 Hz), 121.9, 123.5 (q, J ) 273 Hz), 126.2,
126.7, 128.5 (q, J ) 30 Hz), 129.7 (q, J ) 5 Hz), 144.7, 149.5 (q,
J ) 35 Hz), 150.6, 152.5 (broad s), 161.7. HRMS (ESI) calculated
for C16H8F6N2O4 [M + H]+ 407.0467, found 407.0469.
1
3.17 (1H, s), 6.84 (1H, s), 7.22 (1H, m), 7.35 (1H, m), 7.48 (2H,
m), 7.71 (1H, m), 7.87 (1H, m), 8.22 (1H, d, J ) 8.4 Hz), 8.40
(1H, d, J ) 8.5 Hz). 13C NMR (CDCl3) δ 78.9, 82.2, 100.2 (q, J
) 2 Hz), 121.3 (q, J ) 276 Hz), 121.70, 121.75, 121.8, 124.6,
124.8, 128.2, 129.9, 129.9, 130.1, 130.6, 131.5, 148.8, 148.9 (q, J
) 35 Hz), 153.6, 163.0.
Typical Procedure for the Synthesis of Compounds 19, 22,
26, 28, 30-33. 2,8-Bis(trifluoromethyl)-4-quinolinol 4s (0.2 g, 0.7
mmol) and anhydrous K2CO3 (0.6 g, 4 mmol) were refluxed in
anhydrous acetone (20 mL) for 15 min. Subsequently, KI (60 mg,
0.36 mmol) and methyl 2-(chloromethyl)-1,3-oxazole-4-carboxylate
(0.15 g, 0.85 mmol) were added. The reaction mixture was refluxed
for 2 h until disappearance of the starting material on TLC (EtOAc-
hexane 1:4 as an eluent). The reaction mixture was cooled, filtered,
and the filtrate was evaporated in vacuo. The residue was purified
by flash chromatography using gradient elution from 5% EtOAc-
hexane to 60% EtOAc-hexane to give 33 as a white powder in
97% yield.
3-[[[2,8-Bis(trifluoromethyl)-4-quinolinyl]oxy]methyl]-5-isox-
azolecarboxylic Acid Ethyl Ester (19). Compound 19 was
synthesized by the typical procedure described above using 4s and
4-[[[2,8-Bis(trifluoromethyl)-4-quinolinyl]oxy]methyl]benzo-
ic Acid Ethyl Ester (30). Compound 30 was synthesized by the
typical procedure described above using ethyl 4-(bromomethyl)-
1
1
18 as starting materials. According to H NMR, the product 19 is
benzoate as the alkyhalide. Yield 86% (white powder). H NMR
an inseparable 15:1 mixture of 3,5 and 3,4 regioisomers. Yield 64%
(white solid). For the major isomer 19: H NMR (DMSO-d6) δ
(CDCl3) δ 1.42 (3H, t, J ) 7.1 Hz), 4.41 (2H, q, J ) 7.1 Hz), 5.43
(2H, s), 7.21 (1H, s), 7.59 (2H, d, J ) 8.0 Hz), 7.68 (1H, apparent
t, J ) 7.8 Hz), 8.15 (3H, m), 8.51 (1H, d, J ) 8.4 Hz). 13C NMR
(CDCl3) δ 14.3, 61.2, 70.5, 98.1 (q, J ) 2 Hz), 121.1 (q, J ) 276
Hz), 122.3, 123.6 (q, J ) 274 Hz), 126.33, 126.35, 127.3, 128.4
(q, J ) 30 Hz), 129.5 (q, J ) 5 Hz), 130.2, 131.0, 139.4, 144.7,
149.7 (q, J ) 35 Hz), 162.6, 166.1. HRMS (ESI) calculated for
C21H15F6NO3 [M + H]+ 444.1029, found 444.1036.
1
1.33 (3H, t, J ) 7.1 Hz), 4.39 (2H, q, J ) 7.1 Hz), 5.79 (2H, s),
7.58 (1H, s), 7.80 (1H, s), 7.88 (1H, apparent t, J ) 7.9 Hz), 8.35
(1H, d, J ) 7.2 Hz), 8.58 (1H, d, J ) 8.4 Hz). 13C NMR (DMSO-
d6) δ 13.9, 62.2, 62.7, 99.6 (q, J ) 2 Hz), 109.4, 121.0 (q, J ) 275
Hz), 121.7, 123.7 (q, J ) 273 Hz), 126.3 (q, J ) 30 Hz), 127.1,
127.4, 130.2 (q, J ) 5 Hz), 143.5, 148.5 (q, J ) 35 Hz), 156.0,
160.5 (two overlapping resonances), 162.4. HRMS (ESI) calculated
for C18H12F6N2O4 [M + H]+ 435.0774, found 435.0781.
5-[[[2,8-Bis(trifluoromethyl)-4-quinolinyl]oxy]methyl]-2-thia-
zolecarboxylic Acid Ethyl Ester (22). Compound 22 was synthe-
sized by the typical procedure described above using 21 as the
alkyhalide. Yield 58% (pale-yellow powder). 1H NMR (CDCl3) δ
1.47 (3H, t, J ) 7.1 Hz), 4.53 (2H, q, J ) 7.1 Hz), 5.60 (2H, s),
7.26 (1H, s), 7.66 (1H, apparent t, J ) 8.0 Hz), 7.75 (1H, s), 8.15
(1H, d, J ) 7.2 Hz), 8.49 (1H, d, J ) 8.4 Hz). 13C NMR (CDCl3)
δ 14.3, 63.0, 66.7, 98.1 (q, J ) 2 Hz), 121.1 (q, J ) 276 Hz),
122.2, 123.6 (q, J ) 274 Hz), 123.7, 126.29, 126.33, 128.5 (q, J )
30 Hz), 129.5 (q, J ) 5 Hz), 144.8, 145.3, 149.7 (q, J ) 35 Hz),
152.3, 159.4, 159.6, 162.3. HRMS (ESI) calculated for
C18H12F6N2O3S [M + H]+ 451.0546, found 451.0568.
2-[[[2,8-Bis(trifluoromethyl)-4-quinolinyl]oxy]methyl]-4-ox-
azolecarboxylic Acid Methyl Ester (33). Compound 33 was
synthesized by the typical procedure described above using 2-(chlo-
romethyl)-4-oxazolecarboxylic acid methyl ester as the alkyhalide.
1
Yield 97% (white solid). H NMR (CDCl3) δ 3.96 (3H, s), 5.52
(2H, s), 7.30 (1H, s), 7.13 (1H, s), 7.68 (1H, apparent t, J ) 7.9
Hz), 8.16 (1H, d, J ) 7.3 Hz), 8.34 (1H, s), 8.47 (1H, d, J ) 8.4
Hz). 13C NMR (CDCl3) δ 52.5, 62.4, 97.9 (q, J ) 2 Hz), 121.0 (q,
J ) 276 Hz), 122.0, 123.5 (q, J ) 274 Hz), 124.9, 125.1, 128.5 (q,
J ) 30 Hz), 129.7 (q, J ) 5 Hz), 134.1, 144.7, 145.3, 149.6 (q, J
) 35 Hz), 158.3, 161.0, 161.7. HRMS (ESI) calculated for
C17H10F6N2O4 [M + H]+ 421.0618, found 421.0618.
2-[[[2,8-Bis(trifluoromethyl)-4-quinolinyl]oxy]methyl]-4-ox-
azolecarboxylic Acid Ethyl Ester (34). Compound 33 (80 mg,
0.19 mmol) and KOH (8 mg, 0.14 mmol) were refluxed overnight
in abs EtOH (20 mL). The solvent was evaporated in vacuo and
the residue was dissolved into EtOAc (30 mL), washed with 1 M
HCl (15 mL) and brine (15 mL), and dried with Na2SO4. After
filtration the solvent was evaporated and the crude product was
purified by flash chromatography using gradient eluation from 5%
EtOAc-hexane to 90% EtOAc-hexane. Yield 81% (white solid).
1H NMR (CDCl3) δ 1.41 (3H, t, J ) 7.1 Hz), 4.43 (2H, q, J ) 7.1
Hz), 5.51 (2H, s), 7.31 (1H, s), 7.68 (1H, apparent t, J ) 7.9 Hz),
8.16 (1H, d, J ) 7.3 Hz), 8.34 (1H, s), 8.47 (1H, d, J ) 8.4 Hz).
13C NMR (CDCl3) δ 14.3, 61.7, 62.4, 97.9 (q, J ) 2 Hz), 121.0 (q,
J ) 276 Hz), 122.0, 123.5 (q, J ) 274 Hz), 126.3, 126.6, 128.5 (q,
J ) 30 Hz), 129.7 (q, J ) 5 Hz), 134.4, 144.8, 145.2, 149.6 (q, J
) 35 Hz), 158.2, 160.6, 161.8. HRMS (ESI) calculated for
C18H12F6N2O4 [M + H]+ 435.0774, found 435.0783.
6-[[[2,8-Bis(trifluoromethyl)-4-quinolinyl]oxy]methyl]-2-py-
ridinecarboxylic Acid Ethyl Ester (25). A solution of 6-(hy-
droxymethyl)-2-pyridinecarboxylic acid ethyl ester (24)14 (0.3 g,
1 mmol), 2,8-bis(trifluoromethyl)quinolin-4-ol (4s) (0.2 g, 0.7
mmol), and PPh3 (0.4 g, 1 mmol) in anhydrous THF (15 mL) was
cooled to 0 °C. DEAD (0.25 g, 1.4 mmol, 0.22 mL) was added
dropwise, and the reaction mixture was stirred for 45 min at room
temperature. The solvent was evaporated in vacuo, and the residue
was purified by column chromatography using CH2Cl2 as an eluent
2-[[2,8-Bis(trifluoromethyl)-4-quinolinyl]oxy]acetic Acid Eth-
yl Ester (26). Compound 26 was synthesized by the typical
procedure described above using ethyl bromoacetate as the alky-
1
halide. Yield 90% (white powder). H NMR (CDCl3) δ 1.33 (3H,
t, J ) 7.1 Hz), 4.34 (2H, q, J ) 7.1 Hz), 4.94 (2H, s), 7.00 (1H,
s), 7.69 (1H, apparent t, J ) 7.8 Hz), 8.16 (1H, d, J ) 7.1 Hz),
8.55 (1H, d, J ) 8.4 Hz). 13C NMR (DMSO-d6) δ 14.0, 61.1, 65.9,
99.6 (q, J ) 2 Hz), 121.1 (q, J ) 276 Hz), 121.7, 123.7 (q, J )
273 Hz), 126.4 (q, J ) 30 Hz), 126.8, 127.4, 130.3 (q, J ) 5 Hz),
143.6, 148.5 (q, J ) 34 Hz), 162.5, 167.5. HRMS (ESI) calculated
for C15H11F6NO3 [M + H]+ 368.0716, found 368.0712.
2-[[2,8-Bis(trifluoromethyl)-4-quinolinyl]oxy]acetonitrile (28).
Was synthesized by the typical procedure described above using
bromoacetonitrile as the alkyhalide. Yield 90% (pale-yellow
powder). 1H NMR (CDCl3) δ 5.13 (2H, s), 7.31 (1H, s), 7.20 (1H,
s), 7.75 (1H, apparent t, J ) 7.6 Hz), 8.21 (1H, d, J ) 7.2 Hz),
8.45 (1H, d, J ) 8.4 Hz). 13C NMR (CDCl3) δ 53.9, 97.9 (q, J )
2 Hz), 113.2, 121.0 (q, J ) 276 Hz), 121.8, 123.6 (q, J ) 273 Hz),
126.0, 127.7, 128.9 (q, J ) 31 Hz), 130.2 (q, J ) 5 Hz), 145.0,
149.6 (q, J ) 34 Hz), 160.7. HRMS (ESI) calculated for
C13H6F6N2O [M + H]+ 321.0457, found 321.0442.
5-[[[2,6-Bis(trifluoromethyl)-4-quinolinyl]oxy]methyl]-2-furan-
carboxylic Acid Ethyl Ester (31). Compound 31 was synthesized
by the typical procedure described above using ethyl 5-(chlorom-

SAR for Quinoline Compounds ActiVe against M. tuberculosis
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 7 2117
1
to give compound 25 as a white powder in 81% yield. H NMR
8, 10, and 13, synthesis of the noncommercial 4-hydroxyquinolines
and intermediates 5c-5f, 5h-5n, 5p-5r, 6, 14, and 18, HPLC
chromatograms for key target compounds. This material is available
free of charge via the Internet at http://pubs.acs.org.
(CDCl3) δ 1.47 (3H, t, J ) 7.1 Hz), 4.53 (2H, q, J ) 7.1 Hz), 5.63
(2H, s), 7.28 (1H, s), 7.70 (1H, apparent t, J ) 7.9 Hz), 7.78 (1H,
d, J ) 7.8 Hz), 7.96 (1H, apparent t, J ) 7.8 Hz), 8.16 (2H, m),
8.55 (1H, d, J ) 8.3 Hz). 13C NMR (CDCl3) δ 14.3, 61.3, 71.5,
98.5 (q, J ) 2 Hz), 121.1 (q, J ) 276 Hz), 122.2, 123.6 (q, J )
274 Hz), 124.5, 124.8, 126.2, 126.4, 128.5 (q, J ) 31 Hz), 129.5
(q, J ) 5 Hz), 144.7, 148.3, 149.8 (q, J ) 35 Hz), 155.3, 162.3,
164.8. HRMS (ESI) calculated for C20H14F6N2O3 [M + H]+
445.0981, found 445.0997.
2-[[2,8-Bis(trifluoromethyl)-4-quinolinyl]oxy]acetic Acid (27).
The ester 26 (200 mg, 0.54 mmol) was dissolved into THF-MeOH-
H2O (3:1:1, 6 mL) and cooled to 0 °C. LiOH (50 mg, 2.0 mmol)
was added, and the reaction mixture was stirred at room temperature
for 30 min. After completion, the reaction was quenched with H2O
(50 mL), acidified with 6 M HCl (pH ∼ 3), extracted with EtOAc
(2 × 30 mL), washed with brine (20 mL), and dried with Na2SO4.
After filtration, the solvent was evaporated to give 27 in 98% yield
References
(1) World Health Organization. Global Tuberculosis Control: SurVeillance,
Planning, and Financing; WHO Report 008; WHO Press: Geneva,
Switzerland, 2008.
(2) (a) Spigelman, M. K. New tuberculosis therapeutics: a growing
pipeline. J. Infect. Dis. 2007, 196, S28-S34. (b) Janin, Y. L.
Antituberculosis drugs: ten years of research. Bioorg. Med. Chem.
2007, 15, 2479–2513.
(3) (a) Boshoff, H. I. M.; Barry, C. E., III. Tuberculosissmetabolism and
respiration in the absence of growth. Nat. ReV. Microbiol. 2005, 3,
70–80. (b) Wayne, L. G.; Sohaskey, C. D. Nonreplicating persistence
of Mycobacterium tuberculosis. Annu. ReV. Microbiol. 2001, 55, 139–
163.
(4) Rae, J. M.; Johnson, M. D.; Lippman, M. E.; Flockhart, D. A. Rifampin
is a selective, pleiotropic inducer of drug metabolism genes in human
hepatocytes: studies with cDNA and oligonucleotide expression arrays.
J. Pharmacol. Exp. Ther. 2001, 299, 849–857.
(5) (a) Nayyar, A.; Malde, A.; Jain, R.; Coutinho, E. 3D-QSAR study of
ring-substituted quinoline class of anti-tuberculosis agents. Bioorg.
Med. Chem. 2006, 14, 847–856. (b) Jain, R.; Vaitilingam, B.; Nayyar,
A.; Palde, P. B. Substituted 4-methylquinolines as a new class of anti-
tuberculosis agents. Bioorg. Med. Chem. Lett. 2003, 13, 1051–1054.
(c) Monga, V.; Nayyar, A.; Vaitilingam, B.; Palde, P. B.; Jhamb, S.;
Kaur, S.; Singh, P.; Jain, R. Ring-substituted quinolines. Part 2:
Synthesis and antimycobacterial activities of ring-substituted quino-
linecarbohydrazide and ring-substituted quinolinecarboxamide ana-
logues. Bioorg. Med. Chem. 2004, 12, 6465–6472.
(6) Moadebi, S.; Harder, C. K.; Fitzgerald, M. J.; Elwood, K. R.; Marra,
F. Fluoroquinolones for the treatment of pulmonary tuberculosis. Drugs
2007, 67, 2077–2099.
(7) Drlica, K. Mechanism of fluoroquinolone action. Curr. Opin. Micro-
biol. 1999, 2, 504–508.
(8) (a) Wang, J.-Y.; Lee, L.-N.; Lai, H.-C.; Wang, S.-K.; Jan, I.-S.; Yu,
C.-J.; Hsueh, P.-R.; Yang, P.-C. Fluoroquinolone resistance in My-
cobacterium tuberculosis isolates: associated genetic mutations and
relationship to antimicrobial exposure. J. Antimicrob. Chemother. 2007,
59, 860–865. (b) Escribano, I.; Rodriguez, J. C.; Llorca, B.; Garcia-
Pachon, E.; Ruiz, M.; Royo, G. Importance of the Efflux Pump
Systems in the Resistance of Mycobacterium tuberculosis to Fluoro-
quinolones and Linezolid. Chemotherapy 2007, 53, 397–401.
(9) Andries, K.; Verhasselt, P.; Guillemont, J.; Goehlmann, H. W. H.;
Neefs, J.-M.; Winkler, H.; Van Gestel, J.; Timmerman, P.; Zhu, M.;
Lee, E.; Williams, P.; de Chaffoy, D.; Huitric, E.; Hoffner, S.; Cambau,
E.; Truffot-Pernot, C.; Lounis, N.; Jarlier, V. A diarylquinoline drug
active on the ATP synthase of Mycobacterium tuberculosis. Science
2005, 307, 223–227.
1
as a white powder (HPLC purity 99.5%). H NMR (CD3OD) δ
5.14 (2H, s), 7.33 (1H, s), 7.78 (1H, apparent t, J ) 7.9 Hz), 8.23
(1H, d, J ) 7.2 Hz), 8.64 (1H, d, J ) 8.4 Hz), -OH exchanged.
13C NMR (DMSO-d6) δ 65.8, 99.4 (q, J ) 2 Hz), 121.1 (q, J )
276 Hz), 121.8, 123.7 (q, J ) 273 Hz), 126.4 (q, J ) 30 Hz),
126.9, 127.2, 130.2 (q, J ) 5 Hz), 143.7, 148.5 (q, J ) 34 Hz),
162.7, 168.9. HRMS (ESI) for C13H7F6NO3 [M + H]+ 340.0403,
found 340.0387.
2,8-Bis(trifluoromethyl)-4-(2H-tetrazol-5-ylmethoxy)-quino-
line (29). A mixture of nitrile 28 (100 mg, 0.31 mmol), NaN3 (71
mg, 1.1 mmol), and NH4Cl (58 mg, 1.1 mmol) in anhydrous DMF
(6 mL) was heated to 80 °C for 3 h. The cooled reaction mixture
was quenched with H2O (10 mL) and made acidic (pH ∼ 3) with
5% HCl, resulting in a formation of a white precipitate. EtOAc
(20 mL) was added, and the mixture was stirred until the precipitate
was dissolved. Organic layer was separated, and the aqueous phase
was extracted with EtOAc (20 mL). The combined organic phases
were washed with brine (20 mL) and dried with Na2SO4. After
filtration, the solvent was evaporated and the crude product was
purified by preparative HPLC to give compound 29 in 50% yield
as a white solid. 1H NMR (DMSO-d6) δ 6.02 (2H, s), 7.86 (1H, s),
7.90 (1H, apparent t, J ) 8.0 Hz), 8.35 (1H, d, J ) 7.2 Hz), 8.66
(1H, d, J ) 8.4 Hz). 13C NMR (DMSO-d6) δ 61.4, 99.8 (q, J ) 2
Hz), 121.1 (q, J ) 276 Hz), 121.6, 123.7 (q, J ) 273 Hz), 126.3
(q, J ) 30 Hz), 127.2, 127.3, 130.3 (q, J ) 5 Hz), 143.6, 148.6 (q,
J ) 34 Hz), 153.0 (broad s), 162.3. HRMS (ESI) calculated for
C13H7F6N5O [M + H]+ 364.0628, found 364.0629.
[5-[[[2,6-Bis(trifluoromethyl)-4-quinolinyl]oxy]methyl]-3-isox-
azolyl]-1-propanone (35). Compound 3 (100 mg, 0.23 mmol) in
anhydrous Et2O (15 mL) was cooled to 0 °C followed by dropwise
addition of 3 M EtMgBr in Et2O (0.09 mL, 0.28 mmol, 37 mg).
The reaction mixture was allowed to reach room temperature and
stirred for 15 min. The reaction was quenched with sat. NH4Cl (20
mL), and Et2O (20 mL) was added. The organic phase was
separated, washed with brine (20 mL) and water (20 mL), and dried
with Na2SO4. After filtration, the solvent was evaporated. Purifica-
tion by flash chromatography, using gradient eluation from hexane
to 80% EtOAc-hexane, afforded compound 35 as a white powder
(10) Jayaprakash, S.; Iso, Y.; Wan, B.; Franzblau, S. G.; Kozikowski, A. P.
Design, Synthesis, and SAR Studies of Mefloquine-Based Ligands as
Potential Antituberculosis Agents. ChemMedChem 2006, 1, 593–597.
(11) Mao, J.; Wang, Y.; Wan, B.; Kozikowski, A. P.; Franzblau, S. G.
Design, Synthesis, and Pharmacological Evaluation of Mefloquine-
Based Ligands as Novel Antituberculosis Agents. ChemMedChem
2007, 2, 1624–1630.
(12) Mao, J.; Wan, B.; Wang, Y.; Franzblau, S. G.; Kozikowski, A. P.
HTS chemical hybridization, and drug design identify a chemically
unique antituberculosis agentscoupling serendipity and rational ap-
proaches to drug discovery. ChemMedChem 2007, 2, 811–813.
(13) Liu, W.; Dragan, V.; Strong, H. L.; Wu, Y.; Wen, Z.; Liang, J. K.;
Durutlic, H.; Sutherland, Karen W.; Pilcher, A. S. Process for
preparation of 8-piperazinyl-quinoline derivatives PCT Int. Appl.
WO2007146072A2, 2007.
(14) Micetich, R. G.; Shaw, C. C.; Hall, T. W.; Spevak, P.; Fortier, R. A.;
Wolfert, P.; Foster, B. C.; Bains, B. K. The 5-alkoxymethyl-,
5-alkylthiomethyl-, and 5-dialkylaminomethylisoxazoles. Heterocycles
1985, 23, 571–583.
(15) Lee, C. B.; Wu, Z.; Zhang, F.; Chappell, M. D.; Stachel, S. J.; Chou,
T.-C.; Guan, Y.; Danishefsky, S. J. Insights into Long-Range Structural
Effects on the Stereochemistry of Aldol Condensations: A Practical
Total Synthesis of Desoxyepothilone F. J. Am. Chem. Soc. 2001, 123,
5249–5259.
1
in 75% yield. H NMR (CDCl3) δ 1.25 (3H, t, J ) 7.3 Hz), 3.13
(2H, q, J ) 7.3 Hz), 5.52 (2H, s), 7.88 (1H, s), 7.23 (1H, s), 7.70
(1H, apparent t, J ) 7.8 Hz), 8.18 (1H, d, J ) 7.1 Hz), 8.46 (1H,
d, J ) 8.4 Hz). 13C NMR (CDCl3) δ 7.4, 33.4, 61.4, 97.7 (q, J )
2 Hz), 103.2, 121.0 (q, J ) 276 Hz), 121.9, 123.5 (q, J ) 274 Hz),
126.1, 126.8, 128.7 (q, J ) 30 Hz), 129.7 (q, J ) 5 Hz), 144.8,
149.6 (q, J ) 35 Hz), 161.7, 161.8, 166.7, 194.5. HRMS (ESI)
calculated for C18H12F6N2O3 [M + H]+ 419.0830, found 419.0832.
Acknowledgment. A.L. thanks The Academy of Finland for
a fellowship (grant 120441). TB Alliance is acknowledged for
financial support.
(16) (a) Charbonniere, L.; Weibel, N.; Retailleau, P.; Ziessel, R. Relation-
ship between the ligand structure and the luminescent properties of
water-soluble lanthanide complexes containing bis(bipyridine) anionic
arms. Chem.sEur. J. 2006, 13, 346–358. (b) Dan, A.; Shiyama, T.;
Yamazaki, K.; Kusunose, N.; Fujita, K.; Sato, H.; Matsui, K.; Kitano,
M. Discovery of hydroxamic acid analogs as dual inhibitors of
Supporting Information Available: HPLC purity determina-
tions, 13C NMR or 19F NMR data for the target compounds 7a-7r,

2118 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 7
Lilienkampf et al.
phosphodiesterase-1 and -5. Bioorg. Med. Chem. Lett. 2005, 15, 4085–
4090.
and modes of toxicity in different cell lines. Xenobiotica 1999, 29,
1157–1169. (b) Moreno, S. N. J.; Docampo, R. Mechanism of
toxicity of nitro compounds used in the chemotherapy of trichomo-
niasis. EnViron. Health Perspect. 1985, 64, 199–208.
(17) Franzblau, S. G.; Witzig, R. S.; Mclaughlin, J. C.; Torres, P.; Madico,
G.; Hernandez, A.; Degnan, M. T.; Cook, M. B.; Quenzer, V. K.;
Ferguson, R. M.; Gilman, R. H. Rapid, low-technology MIC deter-
mination with clinical Mycobacterium tuberculosis isolates by using
the microplate Alamar Blue assay. J. Clin. Microbiol. 1998, 36, 362–
366.
(21) Koul, A.; Dendouga, N.; Vergauwen, K.; Molenberghs, B.; Vranckx,
L.; Willebrords, R.; Ristic, Z.; Lill, H.; Dorange, I.; Guillemont, J.;
Bald, D.; Andries, K. Diarylquinolines target subunit c of mycobac-
terial ATP synthase. Nat. Chem. Biol. 2007, 3, 323–324.
(18) Cho, S. H.; Warit, S.; Wan, B.; Hwang, C. H.; Pauli, G. F.; Franzblau,
S. G. Low-Oxygen-Recovery Assay for High-Throughput Screening
of Compounds against Nonreplicating Mycobacterium tuberculosis.
Antimicrob. Agents Chemother. 2007, 51, 1380–1385.
(22) Martin-Galiano, A. J.; Gorgojo, B.; Kunin, C. M.; de la Campa, A. G.
Mefloquine and new related compounds target the F0 complex of the
F0F1 H+-ATPase of Streptococcus pneumonia. Antimicrob. Agents
Chemother. 2002, 46, 1680–1687.
(19) (a) Tangallapally, R. P.; Yendapally, R.; Daniels, A. J.; Lee,
R. E. B.; Lee, R. E. Nitrofurans as novel anti-tuberculosis agents:
identification, development and evaluation. Curr. Top. Med. Chem.
2007, 7, 509–526. (b) Tangallapally, R. P.; Yendapally, R.; Lee,
R. E.; Lenaerts, A. J. M.; Lee, R. E. Synthesis and Evaluation of
Cyclic Secondary Amine Substituted Phenyl and Benzyl Nitro-
furanyl Amides as Novel Antituberculosis Agents. J. Med. Chem.
2005, 48, 8261–8269.
(23) Soellner, M. B.; Rawls, K. A.; Grundner, C.; Alber, T.; Ellman, J. A.
Fragment-Based Substrate Activity Screening Method for the Identi-
fication of Potent Inhibitors of the Mycobacterium tuberculosis
Phosphatase PtpB. J. Am. Chem. Soc. 2007, 129, 9613–9615.
(24) Singh, R.; Rao, V.; Shakila, H.; Gupta, R.; Khera, A.; Dhar, N.; Singh,
A.; Koul, A.; Singh, Y.; Naseema, M.; Narayanan, P. R.; Paramasivan,
C. N.; Ramanathan, V. D.; Tyagi, A. K. Disruption of mptpB impairs
the ability of Mycobacterium tuberculosis to survive in guinea pigs.
Mol. Microbiol. 2003, 50, 751–762.
(20) (a) De Angelis, I.; Rossi, L.; Pedersen, J. Z.; Vignoli, A. L.;
Vincentini, O.; Hoogenboom, L. A. P.; Polman, T. H. G.; Stammati,
A.; Zucco, F. Metabolism of furazolidone: alternative pathways
JM900003C