Design, synthesis and evaluation of acridine and fused-quinoline derivatives as potential anti-tuberculosis agents

Article abstract of DOI:10.1016/j.ejmech.2013.12.013

The synthesis of twelve acridine and polycyclic acridine derivatives prepared via the Friedl?nder reaction is described. The one-pot reactions of 2-amino-5-chloro or 5-nitro-benzophenones and a variety of cyclanones and indanones were carried out in a MW

Full text of DOI:10.1016/j.ejmech.2013.12.013

European Journal of Medicinal Chemistry 73 (2014) 243e249
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Design, synthesis and evaluation of acridine and fused-quinoline
derivatives as potential anti-tuberculosis agents
*
Gisela C. Muscia, Graciela Y. Buldain, Silvia E. Asís
Departamento de Química Orgánica, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junín 956, C1113AAB Ciudad Autónoma de Buenos
Aires, Argentina
a r t i c l e i n f o
a b s t r a c t
Article history:
The synthesis of twelve acridine and polycyclic acridine derivatives prepared via the Friedländer reaction
is described. The one-pot reactions of 2-amino-5-chloro or 5-nitro-benzophenones and a variety of
cyclanones and indanones were carried out in a MW oven under TFA catalysis in good yields. The
products were designed according natural antituberculosis products and were evaluated for growth
inhibitory activity towards Mycobacterium tuberculosis H37Rv (Mtb) through the National Institute of
Allergy and Infectious Diseases (NIAID, USA). Three of them underwent additional testings. The cyclo-
penta[b]quinoline derivative 9 and the acridine derivative 13 showed remarkable MIC values against the
rifampin resistant strain. The former exhibited bactericidal activity at 50 mg/mL, its intracellular activity is
similar to rifampin and it was not cytotoxic at low concentrations so it can be considered a new lead
compound.
Received 10 September 2013
Received in revised form
22 November 2013
Accepted 14 December 2013
Available online 25 December 2013
Keywords:
Mycobacterium tuberculosis
Acridine derivatives
Friedländer synthesis
Inhibitor
Ó 2013 Elsevier Masson SAS. All rights reserved.
1. Introduction
cell toxicity from anti-TB activity. The two most interesting com-
pounds were found to inhibit the growth of M. tuberculosis H37Rv
Currently, one third of the world’s population is infected with
Mycobacterium tuberculosis and 8.9e9.9 million new and relapse
cases of tuberculosis (TB) are reported every year. The emergence of
new cases, the increased incidence of multi-drug resistant strains of
M. tuberculosis, the adverse effects of first- and second-line anti-
tuberculosis drugs, and the incidence of TB associated with viral
infections (Human Immunodeficiency Virus, HIV) have led to
renewed research interest in natural products in the hope of
discovering new antitubercular leads.
Natural products and some of their derivatives have been re-
ported to exhibit remarkable growth inhibitory activity towards
M. tuberculosis and some of them have been selected as prototype
molecules for the development of new antitubercular agents. A
large group of alkaloids with complex structures and potent
inhibitory activity was described [1].
but negligible cytotoxicity towards Vero and P388 cells [2].
Acridine derivatives, atebrin and quinacrine, have been widely
used in malaria chemotherapy during World War II in the absence
of quinine and this skeleton is still being explored for betters an-
timalarials. In 2006, a series of 9-substituted tetrahydroacridines
was synthesized and evaluated against M. tuberculosis H37Rv and
H37Ra strains and exhibited potent activities comparable to the
standard drugs [3]. In 2004, Jain et al. [4] reported a series of
substituted quinolones with high anti-TB activity. The most effec-
tive compound, 2,8-dicyclopentyl-4-methylquinoline exhibited
activity against both drug-sensitive and drug-resistant
M. tuberculosis. It is worthwhile to mention that many of these
analogs were initially synthesized as the precursors for targeted
antimalarials.
More recently, three quinoline alkaloids (2e4) isolated from the
leaves of Lunasia amara Blanco (Rutaceae) revealed interesting ac-
tivity against M. tuberculosis H37Rv, Fig. 2 [5].
Investigations of extracts from the ascidian Lissoclinum notti and
Diplosoma sp. led to the isolation of reported pyridoacridone al-
kaloids. Among them, ascididemin (1) exhibited potent antituber-
cular activity but it also showed high toxicity against Vero cells (SI
values >1), Fig. 1. For this reason, a series of simplified tetracyclic-
core analogous were prepared in an effort to decouple mammalian
For the above exposed, the chemotherapeutic properties of
acridone and quinoline alkaloids and their synthetic analogs
continue to attract interest.
In this regard, we have prepared the acridindione derivative 5
employing
a
MW-assisted three-component Hantzsch-type
condensation of aniline, benzaldehyde and dimedone [6] but
it showed no inhibition against M. tuberculosis (National Institute
of Allergy and Infectious Diseases, NIAID, USA). 1,2,3,4-
* Corresponding author. Tel.: þ54 11 4964 8251; fax: þ54 11 4964 8252.
E-mail addresses: elizabet@ffyb.uba.ar, silviaeasis@yahoo.com.ar (S.E. Asís).
0223-5234/$ e see front matter Ó 2013 Elsevier Masson SAS. All rights reserved.
http://dx.doi.org/10.1016/j.ejmech.2013.12.013

244
G.C. Muscia et al. / European Journal of Medicinal Chemistry 73 (2014) 243e249
R1
R1
N
N
O
R4
R3
R2
R2
R4
R3
N
O
+
O
NH2
N
Scheme 1. Synthesis of quinolines via the Friedländer reaction.
1
and cyclopentanone were used as starting materials to obtain
compounds 6e9 and 13e15, meanwhile 2-indanone produced 10,
1-indanone 11 and 16, and 1,3-indanodione yielded 12 and 17.
Certain substituted 1-indanones were employed in 2007 for
achieving indenoquinolines also via Friedländer synthesis but in
the presence of sodium ethoxide as catalyst at refluxing tempera-
ture of ethanol [10].
Although the features of the Friedländer reaction are generally
well understood, its mechanism has not unambiguously estab-
lished. Experimental reports support two different mechanistic
proposals. One pathway involves the initial formation of the Schiff
base from the 2-amino-substituted aromatic compound and the
carbonyl partner followed by an intramolecular aldol reaction to
give the hydroxyl imine adduct with subsequent loss of water to
produce the quinoline. Alternatively, it has been proposed that the
initial rate-limiting step is an intermolecular aldol reaction which
in turns gives the quinoline [11]. However it is well established that
MW-reactants interactions are increased with the polarity of the
material. We could assume the formation of the Schiff base fol-
lowed by cyclodehydration considering the possible MW activation
effects by dipoleedipole interactions according to the literature
[12].
Fig. 1. Structure of ascididemin.
Tetrahydroacridin-9-one and three fused 4-quinolone analogs were
also synthesized under MW irradiation with shorter reaction time
and from easily starting materials compared to the known methods
in order to design potential anti-tuberculosis agents [7]. On the
other hand, a series of novel acridine derivatives was reported as
potent DNA-binding and apoptosis-inducing antitumor agents [8].
We have previously prepared a series of polysubstituted quin-
olines synthesized via the microwave-assisted Friedländer reaction
and a catalytic amount of concentrated hydrochloric acid (Scheme
1). These products were obtained in good yields at short times and
were tested against the parasites causing malaria, leishmaniasis
and trypanosomiasis, other types of neglected diseases. Among
them the tetrahydroacridine derivative 6 was also described [9],
Scheme 2.
The aim of the present study was to prepare a number of analogs
of 6 in order to explore preliminary aspects of the structureeantiTB
activity relationship. The synthetic procedure involves the Fried-
länder reaction under MW irradiation and trifluoroacetic acid (TFA)
catalysis and the targeted products resemble both quinoline and
acridine nuclei from natural antitubercular compounds.
2.2. Biological evaluation
2. Results and discussion
2.2.1. In vitro activity against M. tuberculosis
2.1. Chemistry
The synthesized products 6e17 were evaluated for growth
inhibitory activity towards M. tuberculosis H37Rv (Mtb) through the
National Institute of Allergy and Infectious Diseases (NIAID, USA).
The structure of the named compounds and their IC50 and IC90
values are shown in Table 1. Amikacin, cycloserine, ethambutol,
isoniazid, pyrimethamin, primethamine and rifampim were used as
reference drugs.
Herein, the synthesis of twelve acridine and polyclyclic acridine
derivatives (6e17) prepared via the Friedländer reaction is
described (Table 1). The one-pot reactions of 2-amino-5-chloro or
5-nitro-benzophenones and a variety of cyclanones and indanones
were carried out in a MW oven at constant power (400 W), Scheme
2. The reactions proceed to completion between 2 and 7 min in
good to excellent yields, meanwhile when they were performed
under conventional heating the reaction times extended to 2e3 h
and the yields were lower or similar, as it was shown earlier [9]. The
use of TFA as catalyst proved to be more efficient and milder than
the hydrochloric acid catalysis in both experimental conditions.
Cyclic ketones such as cyclohexanone, cycloheptanone, dimedone
Compounds 9, 13 and 14 exhibited IC50 values of 73.41, 44.35
and 61.93 mM, respectively and underwent additional testing. This
subset was determined by an algorithm that considered primarily
activity and analytical quality of the samples but also considered
other aspects such as chemotype series and solubility.
This testing includes in vitro testing of H37Rv under both
anaerobic and aerobic conditions as well as minimal bactericidal
concentration (MBC). Single drug resistant strain testing (isoniazid,
rifampin and moxifloxacin resistant Mtb strains) and intracellular
inhibition of Mtb H37Rv growth using murine macrophage cell line
and cytotoxicity in this cell-line were also determined.
OCH3
OCH3
OCH3
O
O
O
N
N
N
O
O
2.2.2. Minimal inhibitory concentration (MIC)
The MIC for each compound was determined by testing ten,
two-fold dilutions in concentration ranges. The MIC is reported as
2
3
4
O
Ph
O
the lowest concentration (mg/mL) of drug that visually inhibited
growth of the organism. In addition, the percentage of inhibition at
the MIC is provided (Table 2). Rifampin and isoniazid were used as
positive controls. Although MIC values of compounds 9, 13 and 14
were higher than the MIC values for the reference drugs, the tested
compounds showed good percent inhibition values (83, 69 and 72%
respectively) against the rifampin resistant strain (RMP-R). Com-
pounds 9 and 13 exhibited the best results.
N
H
5
Fig. 2. Quinoline alkaloids isolated from L. amara B (2e4) and a synthetic acridindione
derivative 5.

G.C. Muscia et al. / European Journal of Medicinal Chemistry 73 (2014) 243e249
245
Ph
Ph
O
R
R
O
TFA
MW
+
n
N
n
NH2
R= Cl, NO2
6 R = Cl, n = 2
7 R = Cl, n = 3
9 R = Cl, n = 1
13 R = NO2, n = 2
14 R = NO2, n = 3
n = 1,2,3
or
Ph
N
Ph
O
R
R
R
O
or
or
N
10 R = Cl
11 R = Cl
16 R = NO2
Ph
O
Ph
N
O
O
O
R
N
O
O
12 R = Cl
17 R = NO2
8 R = Cl
15 R = NO2
Scheme 2. Synthetic pathway for the preparation of compounds 6e17.
2.2.3. Minimal bactericidal concentration (MBC)
The established rejection value of >40 colonies for the MBC
assay was based on the calculated concentration of Mtb in the MIC
fold above the mid. Drug cytotoxicity is reported as cell prolifera-
tion, macrophage toxicity (MTT) or percentage of viability (Table 4).
Compound 9 showed a similar tendency as rifampin, so at higher
drug concentrations lower UFC are obtained and the log reduction
is higher. Meanwhile, compounds 13 and 14 did not follow this
pattern. Concerning citotoxicity, compounds 9 and 14 exhibited
percentages of viability comparable to rifampin at low and mid
concentrations, so they are not toxic to macrophages; however at
high concentrations the three tested compounds are citotoxic.
plates. Results, reported as mg/mL concentration, are determined
based on Colony Forming Units (CFUs) enumerated from agar
plates. Only agar plates with countable colonies have reportable
counts. If a compound lacks bactericidal activity, many times the
CFUs are too numerous to count (TNTC) and are thus reported as
such. Results are provided in Table 3. According to them, only
compound 9 proved bactericidal activity (50
mg/mL) without
observing any CFU at that concentration.
3. Conclusions
2.2.4. Low-oxygen recovery assay (LORA)
We herein show the syntheses of 12 new acridine derivatives
inspired in natural occurring antitubercular and three of them
exhibited inhibition activity against M. tuberculosis (Mtb) H37Rv.
This series could be obtained in good yields and short times in a
one-pot MW-assisted Friedländer reaction with affordable starting
materials and under TFA catalysis. The cyclopenta[b]quinoline de-
rivative 9 and the acridine derivative 13 had remarkable MIC values
against the rifampin resistant strain but only compound 9 exhibited
Traditional screening of drugs against M. tuberculosis only ad-
dresses or targets the organism in an active replicating state. It is
well documented that Mtb can reside in a state of non-replicating
persistence (NRP) which has not been adequately assessed in the
development of new antimicrobials. Results for the LORA assay are
reported as the lowest concentration (mg/mL) of drug that visually
inhibited growth of the organism. This NRP state is considered an
antimicrobial tolerance factor, so LORA may identify drugs that
could reduce anti-tubercular treatment period. Compounds 9 and
13 exhibited higher MIC values under anaerobic than under aerobic
conditions. Only compound 14 showed the same MIC value for both
experimental conditions.
bactericidal activity at 50 mg/mL Furthermore, its intracellular ac-
tivity is similar to rifampin and it was not citotoxic at low con-
centrations. Summarizing, this derivative can be considered a new
lead structure for designing new tricyclic analogs with lower
toxicity towards macrophages and improved anti-tuberculosis
activity.
2.2.5. Intracellular drug activity
Intracellular drug activity is reported as log reduction values
calculated as reduction in Mtb concentration from zero hour to 7
days post-infection. The three concentrations chosen were based
on the MIC data generated in the HTS primary screen. The mid
concentration bracketed the reported MIC with the lower concen-
tration ten-fold below the mid and the higher concentration ten-
4. Material and methods
The structures of the synthesized compounds were established
through their 1H and 13C NMR, MS and IR spectra. Melting points
were determined in a capillary Electrothermal 9100 SERIES-Digital
apparatus and are uncorrected. 1H and 13C NMR spectra were

246
G.C. Muscia et al. / European Journal of Medicinal Chemistry 73 (2014) 243e249
Table 1
60 F254 Merck. Microwave-assisted reactions were carried out in a
CEM Discover oven.
Acridine and polycyclic derivatives 6e17 and their in vitro activity against
M. tuberculosis H37Rv.
Compound
IC50
(m
M)
IC90 (mM)
4.1. Synthesis
4.1.1. General procedure for the synthesis of compounds 6e17
>100.00
>100.00
>100.00
>100.00
A
neat mixture of 1.00 mmol of 2-amino-5-chlorobenzo
phenone or 2-amino-5-nitrobenzophenone and 1.50 mmol of the
corresponding cyclanone with 0.15 mL TFA was subjected to MW
irradiation, at 400 W and 250 ꢁC. The completion of the reaction
was determined by TLC.
4.1.1.1. 7-chloro-9-phenyl-1,2,3,4-tetrahydroacridine
6. Reaction
time 6 min, it was triturated at rt with cyclohexane, white solid, mp
>100.00
>100.00
>100.00
(225e227)ꢁC, yield 80%. Pf lit. 225e227 ꢁC, yield 52% [9]. 1H NMR
(DCCl3):
2.69 (2H, m, CH2), 3.64e3.72 (2H, m, CH2), 7.21e8.98 (8H, m, PheH
and HeteH). 13C NMR (DCCl3):
22.6, 25.7, 31.4, 122.6, 123.7, 124.3,
126.2, 127.8, 129.3, 129.4, 129.8, 134.7, 138.8, 139.7, 151.5, 162.4. IR
(cmꢂ1):
3019, 2942, 1630, 1580, 1478, 1178, 717. Calcd analysis for
19H16ClN, %: C, 77.68; H, 5.49; N, 4.77. Found, %: C, 77.74; H, 5.85; N,
4.99.
d 1.82e1.85 (2H, m, CH2), 1.98e2.03 (2H, m, CH2), 2.65e
d
73.41
y
C
>100.00
>100.00
>100.00
>100.00
4.1.1.2. 2-Chloro-11-phenyl-7,8,9,10-tetrahydro-6H-cyclohepta[b]
quinoline 7. Reaction time 7 min, it was crystallized from EtOH,
white solid, mp (193e195)ꢁC. Pf lit. 175 ꢁC [13], yield 44%. 1H NMR
(DCCl3):
d 1.5e1.7 (2H, m, CH2), 1.75e1.95 (4H, m, CH2), 2.65e2.75
(2H, m, CH2), 3.2e3.4 (2H, m, CH2), 7.19e7.25 (3H, m, PheH), 7.51e
7.56 (2H, m, PheH), 7.58 (1H, s), 7.84 (1H, d, J ¼ 9.0 Hz), 7.99 (1H, d,
>100.00
>100.00
J ¼ 9.0 Hz). 13C NMR (DCCl3):
d 23.8, 27.5, 31.0, 35.2, 39.1, 122.6,
123.6, 124.2, 126.2, 127.8, 129.4, 129.6, 129.9, 136.5, 138.4, 141.4,
151.4, 161.0. IR (cmꢂ1):
y 2955, 2889, 1489, 831, 707. Calcd analysis
for C20H18ClN, %: C, 78.04; H, 5.89; N, 4.55. Found, %: C, 78.20; H,
6.06; N, 4.83.
44.35
61.93
>100.00
4.1.1.3. 7-Chloro-3,3-dimethyl-9-phenyl-3,4-dihydroacridin-1(2H)-
95.41
one 8. Reaction time 3 min, it was crystallized from EtOH, yellow
solid, mp (207e208)ꢁC, yield: 85%. 1H NMR (CDCl3):
d 1.24 (6H, s,
2 ꢃ CH3), 2.57 (2H, s, CH2), 3.28 (2H, s, CH2), 7.14e7.17 (2H, m, Phe
H), 7.49 (1H, d, J ¼ 9.2 Hz, HeteH), 7.54e7.69 (3H, m, PheH), 7.72
(1H, dd, J ¼ 2.2 and 9.2 Hz, HeteH), 8.06 (1H, d, J ¼ 2.2 Hz, HeteH).
>100.00
>100.00
>100.00
>100.00
13C NMR (CDCl3):
d 27.3, 29.3, 30.4, 46.2, 53.2, 122.6, 127.7, 127.8,
128.2, 128.9, 130.4, 132.1, 133.7, 147.0, 152.5, 161.3, 198.6. IR (cmꢂ1):
y
3; 074; 1,757, 1,645, 1,277, 837, 754. Calcd analysis for C21H18ClNO,
%: C, 75.11; H, 5.40; N, 4.17. Found, %: C, 75.20; H, 5.32; N, 4.10.
4.1.1.4. 7-Chloro-9-phenyl-2,3-dihydro-1H-cyclopenta[b]quinoline 9.
>100.00
>100.00
Reaction time 3.5 min, it was triturated at rt with cyclohexane, yellow
solid, mp (129e131)ꢁC, yield 60%. 1H NMR (DMSO-d6):
d 2.19e2.21
(2H, m, N]CH2eCH2eCH2), 2.89 (2H, t, J ¼ 7.5 Hz, N]CH2eCH2e
CH2), 3.20 (2H, t, J ¼ 7.5 Hz, N]CH2eCH2eCH2), 7.47 (2H, d, J ¼ 7.1 Hz,
PheH), 7.51 (1H, d, J ¼ 2.3 Hz, HeteH), 7.57 (1H, t, J ¼ 7.3 Hz, PheH),
7.62 (2H, t, J ¼ 7.3 Hz, PheH), 7.76 (1H, dd, J ¼ 2.3 and 8.9 Hz, HeteH),
Amikacin
0.07
12.47
<1.56
0.18
37.35
>5.00
0.02
0.08
13.49
32.79
0.29
74.96
>5.00
0.02
Cycloserine
Ethambutol
Isoniazid
Pyrimethamin
Primethamine
Rifampin
8.06 (1H, d, J ¼ 8.9 Hz, HeteH).13C NMR (DMSO-d6):
d 23.4, 30.3, 34.5,
124.4,127.0, 129.2, 129.4, 129.5, 129.9, 131.2, 135.3,135.9,142.9, 144.6,
168.0. MS (m/z): 279 (Mþ, 100.0), 244 ([Mþ ꢂ Cl], 94.6), 202
([Mþ ꢂ C6H5], 8.5), 167 ([Mþ ꢂ C6H5Cl], 7.2). Calcd analysis for
recorded at room temperature using a Bruker 300 MHz spec-
trometer. The operating frequencies for protons and carbons were
C18H14ClN: C, 77.40; H, 5.15; N, 5.02. Found, %: C, 77.16; H, 5.07; N, 5.10.
300.13 and 75.46 MHz, respectively. The chemical shifts (
d
) were
4.1.1.5. 2-Chloro-11-phenyl-6H-indeno[2,1-b]quinoline
Reaction time 6 min, it was triturated at rt with EtOH, orange solid,
mp (254e255)ꢁC, yield 81%. 1H NMR (DCCl3):
3.86 (2H, s, CH2),
10.
given in ppm. IR spectra were recorded on an FT Perkin Elmer
Spectrum One from KBr discs. Mass spectra were measured on MS/
DSQ II. Elemental analysis (C, H and N) were performed on an
Exeter CE 440 and the results were within ꢀ0.4% of the calculated
values. Analytical TLCs were performed on DC-Alufolien Kieselgel
d
7.32e7.51 (5H, m, PheH), 7.53e7.58 (4H, m, PheH), 7.62 (1H, d,
J ¼ 9.0 Hz, HeteH), 8.05 (1H, d, J ¼ 9.0 Hz, HeteH), 8.89 (1H, s, Hete
H). 13C NMR (DCCl3):
d 40.9, 119.6, 122.6, 124.1, 126.9, 127.6, 127.8,

G.C. Muscia et al. / European Journal of Medicinal Chemistry 73 (2014) 243e249
247
Table 2
MIC values of compounds 9, 13 and 14.
Compound
MIC H37Rv (
m
g/mL)
% Inhib.a
MIC INH-Rb
(
m
g/mL)
% Inhib.
MIC RMP-Rc
(
m
g/mL)
% Inhib.
MIC OFX-Rd
(
m
g/mL)
% Inhib.
9
13
14
12.5
12.5
75
0.049
NA
88
52
76
65
NA
6.25
6.25
37.5
0.02
NA
69
41
52
74
NA
6.25
3.125
37.5
NAe
83
69
72
NA
85
12.5
3.125
37.5
1.56
NA
81
50
70
71
NA
Rifampin (pos control)
Isoniazid (pos control)
0.02
a
Percent inhibition at the MIC concentration.
INH-R ¼ isoniazid resistance.
b
c
RMP-R ¼ rifampin resistance.
d
e
OFX-R ¼ ofloxacin resistance.
NA ¼ not applicable: compound not used in assay.
128.7,129.0,130.6,130.7,134.3,137.2,139.2,139.8,140.1,142.6,146.1,
159.3. Calcd analysis for C22H14ClN, %: C, 80.61; H, 4.30; N, 4.27.
Found, %: C, 80.58; H, 4.38; N, 4.33.
white solid, mp (179e181)ꢁC, yield 44%. 1H NMR (DCCl3):
d 1.05e
1.08 (2H, m, CH2), 1.52e1.56 (2H, m, CH2), 1.58e1.67 (2H, m, CH2),
2.87e2.97 (2H, m, CH2), 3.01e3.08 (2H, m, CH2), 7.33e7.54 (5H, m,
PheH), 8.13 (1H, d, J ¼ 9.0 Hz, HeteH), 8.25 (1H, d, J ¼ 2.1 Hz, Hete
H), 8.42 (1H, dd, J ¼ 2.1 and 9.0 Hz, HeteH). 13C NMR (DCCl3):
d 21.3,
4.1.1.6. 8-Chloro-10-phenyl-11H-indeno[1,2-b]quinoline
Reaction time 2 min, it was triturated at rt with EtOH, white solid,
mp (250e251)ꢁC, yield 92%. 1H NMR (DCCl3):
4.09 (2H, s, CH2),
11.
22.1, 24.7, 28.8, 36.3, 120.9, 121.4, 125.2, 127.5, 128.4, 129.3, 130.1,
130.6, 136.7, 143.2, 148.4, 165.7. MS (m/z): 322 (Mþ, 70.0), 272
([Mþ ꢂ NO2], 37.0), 245 ([Mþ ꢂ C6H5], 19.0), 198 ([Mþ ꢂ C5H10],
100.0). Calcd analysis for C20H18N2O2: C, 75.45; H, 5.70; N, 8.80.
Found, %: C, 75.63; H, 5.90; N, 8.73.
d
7.51e7.84 (5H, m, PheH), 7.67e7.70 (3H, m, PheH), 7.76 (1H, d,
J ¼ 2.0 Hz, HeteH), 7.82 (1H, dd, J ¼ 2.0 and 9.0 Hz, HeteH), 9.16
(1H, d, J ¼ 9.0 Hz, HeteH), 9.34 (1H, d, J ¼ 7.7 Hz, PheH). 13C NMR
(DCCl3):
d 35.6, 124.3, 126.1, 127.7, 128.6, 129.5, 129.8, 130.2, 131.0,
133.4, 133.8,134.2, 135.0,135.6,136.4, 137.4, 147.9, 151.7, 156.4. Calcd
analysis for C22H14ClN, %: C, 80.61; H, 4.30; N, 4.27. Found, %: C,
80.63; H, 4.36; N, 4.30.
4.1.1.10. 3,3-Dimethyl-7-nitro-9-phenyl-3,4-dihydroacridin-1(2H)-
one 15. Reaction time 4 min, it was crystallized from acetone,
yellow solid, mp (167e169)ꢁC, yield 76%. 1H NMR (DMSO-d6):
d 1.12
(2H, s, CH2), 2.51 (6H, s, CH3), 3.35 (2H, s, CH2), 7.28e7.29 (2H, m,
PheH), 7.55e7.56 (3H, m, PheH), 8.21 (1H, d, J ¼ 2.5 Hz, HeteH),
8.25 (1H, d, J ¼ 9.2 Hz, HeteH), 8.54 (1H, dd, J ¼ 2.5 and 9.2 Hz, Hete
4.1.1.7. 8-Chloro-10-phenyl-11H-indeno[1,2-b]quinolin-11-one
Reaction time 4.5 min, it was crystallized from EtOH, yellow solid,
mp (239e241)ꢁC, yield 93%. 1H NMR (DMSO-d6):
7.40-7.43 (3H, m,
12.
d
H). 13C NMR (DMSO-d6):
d 28.3, 32.3, 48.0, 53.7, 124.5, 124.6, 125.3,
PheH), 7.46e7.51 (6H, m, PheH), 8.45 (1H, d, J ¼ 9.1 Hz, HeteH),
126.4, 128.5, 128.7, 128.8, 130.9, 136.5, 145.5, 150.6, 151.9, 165.9,
197.4. Calcd analysis for C21H18N2O3: C, 72.82; H, 5.24; N, 8.09.
Found, %: C, 72.90; H, 5.30; N, 8.12.
8.67 (1H, d, J ¼ 9.1 Hz, HeteH), 8.82 (1H, s, HeteH). 13C NMR
(DMSO-d6):
d 118.4, 121.0, 121.4, 123.4, 124.1, 125.8, 127.1, 128.4,
129.6, 130.1, 130.6, 131.1, 133.6, 136.2, 137.0, 142.3, 145.2, 148.1, 150.4,
194.4. Calcd analysis for C22H12ClNO, %: C, 77.31; H, 3.54; N, 4.10.
Found, %: C, 77.38; H, 3.50; N, 4.15.
4.1.1.11. 8-Nitro-10-phenyl-11H-indeno[1,2-b]quinoline
Reaction time 2.50 min, it was triturated at rt with EtOH, yellow
solid, mp > 300 ꢁC, yield 70% 1H NMR (CDCl3):
3.96 (2H, s, CH2),
16.
d
4.1.1.8. 7-Nitro-9-phenyl-1,2,3,4-tetrahydroacridine
Reaction time 6 min, it was crystallized from water, yellow solid,
mp (156e158)ꢁC, yield 52%. 1H NMR (DCCl3):
1.77e1.85 (2H, m,
13.
7.52 (2H, d, J ¼ 6.5 Hz, PheH), 7.57e7.68 (6H, m, PheH), 8.37 (1H, d,
J ¼ 9.0 Hz, HeteH), 8.39 (1H, d, J ¼ 2.7 Hz, PheH), 8.49e8.51 (1H,
dd, J ¼ 2.5 and 9.3 Hz, HeteH), 8.69 (1H, d, J ¼ 2.5 Hz, PheH). 13
C
d
CH2), 1.95e2.04 (2H, m, CH2), 2.64 (2H, t, J ¼ 6.4 Hz, CH2), 3.23 (2H,
t, J ¼ 6.7 Hz, CH2), 7.22e7.26 (2H, m, PheH), 7.53e7.58 (3H, m, Phe
H), 8.10 (1H, d, J ¼ 9.2 Hz, HeteH), 8.29 (1H, d, J ¼ 2.6 Hz, HeteH),
NMR (CDCl3):
d 34.1, 122.4, 122.8, 122.9, 125.4, 125.5, 127.9, 129.1,
129.2, 130.7, 131.3, 134.8, 134.9,144.9, 145.4, 145.8. Calcd analysis for
22H14N2O2: C, 78.09; H, 4.17; N, 8.28. Found, %: C, 78.13; H, 4.22; N,
C
8.31.
8.36 (1H, dd, J ¼ 2.6 Hz and 9.2 Hz). 13C NMR (DCCl3):
d 22.5, 22.6,
28.1, 34.5, 121.9, 122.9, 125.7, 128.6, 128.9, 129.0, 130.1, 130.8, 135.3,
144.9, 148.3, 148.4, 163.5. MS (m/z): 304 (Mþ, 100.0), 257
([Mþ ꢂ NO2], 33.3), 227 ([Mþ ꢂ C6H5], 5.4). Calcd analysis for
4.1.1.12. 8-Nitro-10-phenyl-11H-indeno[1,2-b]quinolin-11-one
17.
Reaction time 2.5 min, it was crystallized from acetone-water,
C
19H16N2O2: C, 74.98; H, 5.30; N, 9.20. Found, %: C, 72.63; H, 5.10; N,
yellow solid, mp (297e299)ꢁC, yield 65%. 1H NMR (DMSO-d6):
9.41.
d
7.37e7.42 (4H, m, PheH), 7.44e7.57 (5H, m, PheH), 8.51 (1H, d,
J ¼ 9.2 Hz, HeteH), 8.58 (1H, d, J ¼ 9.2 Hz, HeteH), 8.62 (1H, s, Hete
H). 13C NMR (DMSO-d6):
118.1, 121.3, 121.4, 123.6, 124.2, 125.7,
4.1.1.9. 2-Nitro-11-phenyl-7,8,9,10-tetrahydro-6H-cyclohepta[b]
quinoline 14. Reaction time 3 min, it was triturated at rt with EtOH,
d
127.4, 128.5, 129.7, 130.4, 130.7, 131.3, 133.7, 136.3, 137.1, 142.4, 145.5,
148.3, 150.7, 193.8. Calcd analysis for C22H12N2O3: C, 74.99; H, 3.43;
N, 7.95. Found, %: C, 75.12; H, 3.50; N, 8.00.
Table 3
MBC results for compounds 9, 13 and 14.
4.2. Antituberculosis tests
Compound
CBM (
m
g/mL)
Colony count (CFU)
9
13
14
Rifampin
50
ea
e
0
4.2.1. In vitro activity against M. tuberculosis (Mtb)
All manipulations of Mtb H37Rv were conducted in accordance
with the Biosafety in Microbiological and Biomedical Laboratories
(BMBL) 5th Edition in Biosafety Level 3 containment laboratories
[14].
TNTCb
TNTC
39
1.56
a
MBC above the established rejection value of ꢄ40 colonies.
TNTC ¼ too numerous to count.
b

248
G.C. Muscia et al. / European Journal of Medicinal Chemistry 73 (2014) 243e249
Table 4
Macrophage and MTT results.
Compd.
Macrophage log
reduction (low conc.)
Macrophage log
reduction (mid conc.)
Macrophage log
reduction (high conc.)
MTT % viability
(low conc.)
MTT % viability
(mid conc.)
MTT % viability
(high conc.)
9
13
14
1.00
1.80
1.24
0.46
1.82
1.25
1.19
1.83
3.12
1.72
1.41
1.85
86
67
82
82
79
63
79
86
<10
25
<10
78
Rifampin (pos control)
The assay uses Mtb H37Rv in a 384-well plate format with in-
plate DMSO carrier controls, 3.198 M amikacin, 0.17 M amika-
cin controls and 320 compounds. The Mtb H37Rv þ DMSO carrier
control provides a 100% growth control for each plate. The 3.198
amikacin completely inhibits growth of the bacteria and is used in
place of uninoculated media as the background control; whereas,
colonies were enumerated. The MBC is defined as the lowest con-
centration ( g/mL) of compound exhibiting 99.9% kill over the
same time period used to determine the MIC (18e24 h). MBC values
greater than 16 times the MIC typically indicate antimicrobial
tolerance.
m
m
m
mM
the 0.17 mM amikacin control approximates the MIC of amikacin
4.2.4. Low-oxygen recovery assay (LORA)
ranging from 30 to 80% inhibition indicative of positive growth
inhibition and proper assay performance. The media used for both
compound preparation and Mtb H37Rv plating was assessed for
contamination by plating two 384-well plates with media alone.
The plates were checked for contamination by visual inspection
and end-point detection. The compounds were evaluated in 10-
point stacked plate dose response method. Compounds were seri-
Briefly, microplates were prepared in the same manner as the
MIC testing format. Instead of incubating aerobically, the plates are
placed under anaerobic conditions using a MACS MIC automated jar
gassing system and incubated for 7 days at 37 ꢁC. The plates were
subsequently transferred to an ambient gaseous condition (5% CO2)
for 7 days after which the plates are read visually and individual
wells scored for turbidity, partial clearing or complete clearing.
Testing was conducted in duplicate and the following controls were
included in each test plate: i) medium only (sterility control); ii)
organism in medium (negative control); and iii) rifampin or
isoniazid (positive control). Results are reported as the lowest
ally diluted 1:2 from 100 mM thru 0.195 mM. For end-point detection
the Promega reagent BacTiter-GloÔ Microbial Cell Viability (BTG)
was used. The BTG reagent lyses the bacteria for the ATP quantifi-
cation using luciferase production as an end-point detection point.
After seven days of incubation, the assay plates were removed from
the incubator and allowed to equilibrate to room temperature.
Twenty-five microliters of BTG reagent, one third of the final vol-
ume of the well, was added using a Matrix WellMate. The BTG
plates were briefly incubated for 20 min at room temperature,
sealed with Perkin Elmer clear TopSeal A and read from the top
using luminescence on a Perkin Elmer Envision.
concentration (mg/mL) of drug that visually inhibits growth of the
organism.
4.2.5. Intracellular drug activity
Briefly, the murine J774 cell line was propagated in RPMI 1640
supplemented with L-glutamine and fetal bovine serum (FBS). Cells
were maintained in tissue culture flasks at 37 ꢁC in the presence of
5% CO2. For infection studies, J774 cells were transferred to 12-well
tissue culture chambers in 1 mL volumes at a density of 2.0 ꢃ 105 in
the presence of 10% FBS. After overnight incubation, the medium
was replaced with fresh medium containing 1% FBS to stop
macrophage division while maintaining cell viability. Twenty-four
hours later, the macrophage monolayer was enumerated with an
ocular micrometer for total number of cells per well to determine
the infection ratio. The medium was removed and replaced with
1 mL of fresh medium with 1% FBS containing Mtb at a multiplicity
of infection (MOI) of 5 Mycobacteria/macrophage. The cells are
infected for 4 h after which time non phagocytosed Mycobacteria
were washed from the monolayers and fresh medium added. Drugs
were then added, using 3 concentrations, and infection allowed
proceeding for 7 days. At 0 and 7 days, the macrophages were lysed
with sodium dodecyl sulfate, treated with DNAase, diluted and
plated onto 7H10 agar to determine the cell number or colony
forming units (CFU). Each drug concentration was tested in dupli-
cate and rifampin was used as the positive control drug. A drug
cytotoxicity control plate assay (MTT proliferation) was also con-
ducted in parallel using uninfected macrophages to confirm that
concentrations utilized for testing were not toxic to the
macrophages.
4.2.2. Minimal inhibitory concentration (MIC)
The broth microdilution assay format following guidelines
established by the Clinical and Laboratory Standards Institute (CLSI)
is routinely utilized for MIC testing. Briefly, testing was conducted
using 96-well, U-bottom microplates with an assay volume of
0.2 mL/well. First, the test media, Middlebrook 7H9 broth supple-
mented with OADC Enrichment (BD BioSciences; Sparks, MD), was
added (0.1 mL/well) to each well. The test compounds, solubilized
in appropriate solvent and subsequently diluted in test media, were
subsequently added (0.1 mL/well) to appropriate wells at twice the
intended starting concentration and serially diluted two-fold across
the plate. The plates were then inoculated (0.1 mL/well) with a
targeted concentration of 1.0 ꢃ 106 CFU/mL M. tuberculosis and
incubated at 37 ꢁC for 7 days in approximately 90% humidity.
Following incubation, the plates were read visually and individual
wells scored for turbidity, partial clearing or complete clearing.
Testing was conducted in duplicate and the following controls were
included in each test plate: i) medium only (sterility control); ii)
organism in medium (negative control); and iii) rifampin or
isoniazid (positive control). The MIC is reported as the lowest
concentration (
organism.
mg/mL) of drug that visually inhibits growth of the
4.2.3. Minimal bactericidal concentration (MBC)
4.2.6. Bacteria
The MBC is determined subsequent to MIC testing by sub-
culturing diluted aliquots from wells that fail to exhibit macro-
scopic growth. The sample aliquots were inoculated onto Mid-
dlebrook 7H10 agar plates and subsequently incubated for 16e21
days at 37 ꢁC. Once growth was readily apparent, the bacterial
MIC screening was conducted for Mtb H37Rv (SRI 1345), isoni-
azid (INH)-resistant Mtb (SRI 1369), rifampin (RMP)-resistant Mtb
(SRI 1367), and ofloxacin (OFX)-resistant Mtb (SRI 4000). MBC,
LORA and intracellular drug screening assays were conducted using
only Mtb H37Rv (SRI 1345).

G.C. Muscia et al. / European Journal of Medicinal Chemistry 73 (2014) 243e249
249
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Acknowledgments
This work was supported by National Institutes of Health and
the National Institute of Allergy and Infectious Diseases, Contract
Nꢁ HHSN272201100012I. Financial help was received from Consejo
Nacional de Investigaciones Científicas y Técnicas (CONICET) to G. Y.
Buldain (PIP 441) and from Universidad de Buenos Aires (UBACyT
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Appendix A. Supplementary data
Supplementary data related to this article can be found at http://
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