Benzimidazoquinazolines as new potent anti-TB chemotypes: Design, synthesis, and biological evaluation

Article abstract of DOI:10.1016/j.bioorg.2020.103774

In search for new molecular entities as anti-TB agents, the benzimidazoquinazoline polyheterocyclic scaffold has been designed adopting the scaffold hopping strategy. Thirty-two compounds have been synthesized through an improved tandem decarboxylative nucleophilic addition cyclocondensation reaction of o-phenylenediamine with isatoic anhydride followed by further cyclocondensation of the intermediately formed 2-(o-aminoaryl)benzimidazole with trialkyl orthoformate/acetate. The resultant benzimidazoquinazolines were evaluated in vitro for anti-TB activity against M. tuberculosis H₃₇Rv (ATCC27294 strain). Fourteen compounds exhibiting MIC values in the range of 0.4–6.25 μg/mL were subjected to cell viability test against RAW 264.7 cell lines and were found to be non-toxic (<30% inhibition at 50 μg/mL). The active compounds were further evaluated against INH resistant Mtb strains. The most active compound 6x [MIC (H37Rv) of 0.4 μg/mL] and the compound 6d [MIC (H37Rv) of 0.78 μg/mL] were also found to be active against INH resistant Mtb strain with MIC values of 12.5 and 0.78 μg/mL, respectively.

Full text of DOI:10.1016/j.bioorg.2020.103774

BioorganicChemistry99(2020)103774
Contents lists available at ScienceDirect
Bioorganic Chemistry
journal homepage: www.elsevier.com/locate/bioorg
Benzimidazoquinazolines as new potent anti-TB chemotypes: Design,
synthesis, and biological evaluation
Pradeep S. Jadhavara, Kshitij I. Patela, Tejas M. Dhameliyaa, Nirjhar Sahaa,
⁎
Maulikkumar D. Vajaa, Vagolu Siva Krishnab, Dharmarajan Sriramb, Asit K. Chakrabortia,
a Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research (NIPER), Sector 67, S.A.S. Nagar, Punjab 160062, India
b Department of Pharmacy, Birla Institute of Technology & Science – Pilani, Hyderabad Campus, Jawahar Nagar, Hyderabad 500 078, India
A R T I C L E I N F O
A B S T R A C T
Keywords:
In search for new molecular entities as anti-TB agents, the benzimidazoquinazoline polyheterocyclic scaffold has
been designed adopting the scaffold hopping strategy. Thirty-two compounds have been synthesized through an
improved tandem decarboxylative nucleophilic addition cyclocondensation reaction of o-phenylenediamine
with isatoic anhydride followed by further cyclocondensation of the intermediately formed 2-(o-aminoaryl)
benzimidazole with trialkyl orthoformate/acetate. The resultant benzimidazoquinazolines were evaluated in
vitro for anti-TB activity against M. tuberculosis H37Rv (ATCC27294 strain). Fourteen compounds exhibiting MIC
values in the range of 0.4–6.25 µg/mL were subjected to cell viability test against RAW 264.7 cell lines and were
found to be non-toxic (< 30% inhibition at 50 µg/mL). The active compounds were further evaluated against
INH resistant Mtb strains. The most active compound 6x [MIC (H37Rv) of 0.4 µg/mL] and the compound 6d
[MIC (H37Rv) of 0.78 µg/mL] were also found to be active against INH resistant Mtb strain with MIC values of
12.5 and 0.78 µg/mL, respectively.
Polyheterocycle
Benzimidazoquinolines
New anti-TB chemotypes
Anti-TB (H37Rv) activity
INH resistant-Mtb
1. Introduction
TB drugs is being realized to be inadequate to combat with TB [4–9].
Therefore, there is pressing need for development of new anti-TB agents
Tuberculosis (TB), a highly contagious and chronic infectious dis-
ease, responsible for the estimated death of 1.3 million TB infected and
300 000 TB-HIV co-infected patients in 2017 [1] has plagued the
human being since ancient times. The path finding discovery by Robert
Koch [2] on identification of Mycobacterium tuberculosis (Mtb) as the
causative agent for this deadly infection has provided impetus to sci-
entists to develop therapeutic agents to combat with TB. However,
despite of the advances in our understanding of the disease pathogen-
esis of Mtb, it has been difficult to treat TB which continues to be the
reason of high death toll of human lives. Recently bedaquiline and
delamanid have been approved for treatment of multi-drug resistant
tuberculosis (MDR-TB) independently. The clinical trials attempted in
India, South Africa and Armenia to use both of these drugs in combi-
nation on TB patients resulted in a safe combination with low risk of
cardiotoxicity and a few adverse side effects [3]. The emergence of
resistance strains of Mtb such as the extensively drug resistant tu-
berculosis (XDR-TB), and total drug resistant tuberculosis (TDR-TB), the
treatment and control of TB infection adopting the directly observed
treatment short therapy (DOTS) using the first line and second line anti-
effective against drug sensitive and drug resistant strains of Mtb.
1.1. Design
Towards our endeavour in finding new anti-TB chemotypes [10–14]
we realized that designing polyheterocyclic scaffold would offer new
and more effective therapeutic agents to treat TB. We were attracted by
the anti-TB potential of the 2-substituted benzimidazole core [15–20]
and the quinazoline motif [21–24]. This, inspired us to adopt the
scaffold hopping strategy [11,13,14,25–28] to design the benzimida-
zoquinazoline polyheterocyclic motif (Fig. 1) as new anti-TB scaffold.
We observed that though there are limited reports on the biological
activities of benzimidazoquinazolines such as anti-convulsant [29],
anti-cancer [30–32], anti-inflammatory [33], anti-fungal [34], and
anti-microbial [35,36] activities that are indicative of the pharmaco-
phoric potential of the benzimidazoquinazoline scaffold, however,
there has been no report on the anti-TB activity of this motif. Hence, we
planned to synthesize alkylimidazoquinoline derivatives and evaluate
their anti-TB activity.
⁎ Corresponding author at: Department of Chemistry, Indian Institute of Technology- Ropar (IIT-Ropar), Rupnagar, Punjab 140001, India.
E-mail addresses: akchakraborti@niper.ac.in, chakrabortiak@iitrpr.ac.in (A.K. Chakraborti).
https://doi.org/10.1016/j.bioorg.2020.103774
Received 11 February 2020; Accepted 16 March 2020
Availableonline19March2020
0045-2068/©2020ElsevierInc.Allrightsreserved.

P.S. Jadhavar, et al.
BioorganicChemistry99(2020)103774
Fig. 1. Design of benzimidazoquinazoline motif as
new anti-TB scaffold.
Scheme 1. Synthetic route for the preparation of 2-alkylbenzimidazoquinazolines.
2. Results and discussion
isolation from the reaction mixture followed by chromatographic pur-
ification to obtain the final product due to the use of large amount of
HOAc which acts as the solvent as well as a protic acid catalyst. We
reasoned that as 2 represents activated electrophilic species, the reac-
tion of 2 with 3 may not require any catalytic assistance. However, it
has been reported [53] that the reaction of 2 with 3 in aprotic polar
solvents in the absence of any protic acid catalyst leads to the formation
of the 2-(2′-aminophenyl)-1H-benzimidazole (4) and 6,7-dihy-
drobenzimidazo[1,2-c]quinazolin-6-ones (10) (Scheme 3).
2.1. Chemistry
The target benzimidazoquinazoline derivatives (6) were synthesized
following the route depicted in Scheme 1 that involved the tandem
nucleophilic attack of the o-phenylenediamines (3) on the isatoic an-
hydrides (2), prepared from the corresponding isatins (1), and dec-
arboxylative cyclocondensation to form the intermediate 2-(2′-amino-
phenyl)benzimidazoles (4) followed by cyclocondensation reaction
with trialkyl orthoformate/acetate (5) derivatives.
We realized that as the isatoic anhydride 2 is a bis-electrophile the
formation of the desired product 4 and the side product 10 is due to the
initial competitive nucleophilic attack of one the NH2 groups of 3 on the
aroyl and imide carbonyl groups of 2, respectively. Such type of dif-
ferential product formation during the reaction of bis-electrophilic
substrates with bis-nucleophilic agents has been reported [54]. We
reasoned that solvent may play an important role in controlling the
selectivity of the initial nucleophilic attack on the aroyl and imidic
carbonyl group of 2 as the various physio-chemical properties (e.g.,
polarity, polarizing ability, hydrogen bond donor and acceptor ability
etc.) are known to influence on nucleophilic substitution reaction
[55–57]. Thus, the decarboxylative cyclocondensation of the un-
substituted isatoic anhydride 2a with the unsubstituted o-phenylene-
diamine 3a was performed in various aprotic, protic, ethereal, halo-
genated hydrocarbon, and hydrocarbon solvents (Table 1) at different
temperature. Complete consumption of the starting material was ob-
served in the case of PhMe. Performing the reaction in PhMe at 70 °C for
12 h afforded the unsubstituted 2-(2′-aminophenyl)-1H-benzimidazole
4a in 77% yield without the necessity of any special/elaborative iso-
lation and purification procedure. The product got precipitated when
the reaction mixture was cooled to room temperature. Filtration and
washing with PhMe gave the desired product 4a. The use of DMSO
under reflux for 20 min afforded 4a in 68% yield along with the side
product 10 in 17% yield [53].
During our initial attempt towards the execution of the synthetic
plan we realized that the literature reports for the preparation of the
key intermediates 2-(2′-aminophenyl)-1H-benzimidazoles (4) involve
either (i) direct condensation of 2-aminobenzoic acids (7) with o-phe-
nylenediamines (3) in polyphosphoric acid (PPA) at 160–250 °C for
3–4 h [37–39] or (ii) a multi-step sequence involving the oxidative
cyclocondensation
of
o-phenylenediamines
(3)
with
o-ni-
trobenzaldehydes (8) to form the corresponding 2-(2′-nitrophenyl)-1H-
benzimidazoles (9) followed by reduction of the nitro group [40–46]
(Scheme 2).
The direct condensation approach is desirable compared to the two
step oxidative cyclocondensation reduction process as it would avoid
the use of large amount of transition metal-based reagents required as
oxidizing and reducing agents. However, due to the poor electro-
philicity of the carboxyl group in 7 it becomes necessary to perform the
reaction in PPA at high temperature. Though the requirement to use
such harsh reaction condition for benzazole ring formation can be
avoided in performing the direct cyclocondensation under microwave
heating [47,48] the electrophilic activation of the carboxylic acid to the
aryl ester or acid chloride [49–51] would enable benzazole formation
under milder conditions. Towards this, the isatoic anhydrides (2) are
recognised as the synthetic equivalents of electrophilically activated
masked 2-aminobenzoic acids (7).
The commercially available substituted isatin derivatives (1) were
subjected to the Bayer-Villiger oxidation using m-chloroperoxybenzoic
acid (mCPBA) in HOAc for 4 h at rt [58,59] to obtain the corresponding
isatoic anhydride derivatives (2) (Table 2). The final products were
The decarboxylative cyclocondensation of 2 with 3 to from 4 has
been reported in performing the reaction in HOAc at 90 °C for 1–3 h.
[52] However, it requires elaborative workup procedure for product
Scheme 2. Literature reported synthetic routes for the preparation of 2-(2′-aminophenyl)-1H-benzimidazoles.
2

P.S. Jadhavar, et al.
BioorganicChemistry99(2020)103774
Scheme 3. The reaction of isatoic anhydrides (2)
with o-phenylenediamines (3) leading to 2-(2′-
aminophenyl)-1H-benzimidazoles (4) and 6,7-di-
hydrobenzimidazo[1,2-c]quinazolin-6-ones (10).
Table 1
Table 2
Reaction of isatoic anhydride 2a with o-phenylenediamines (3a) in different
solvents under various conditions to form 4a.a
Synthesis of the isatoic anhydride derivatives (2) from substituted isatins (1).a
Entry
R1
Product
Yield (%)b
Entry
Solvent
Temp (°C)
Yield (%)b
1
2
3
4
5
Br
2a
2b
2c
2d
2e
87
75
80
71
70
Cl
1
DMF
70
0
F
2
DMF
reflux
MW
reflux
70
0
Me
OMe
3
DMF
0
4
NMP
0
5
NMP
0
a
The solution of isatin (1) (1 mmol) and mCPBA (1.5 mmol, 1.5 equiv) in
6
DMA
reflux
70
0
HOAc (2 mL) was stirred magnetically at rt for 4 h.
7
DMA
0
b
Isolated yield of 2.
8
Formamide
Formamide
MeCN
reflux
70
0
9
0
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
reflux
reflux
70
0
Table 3
DMSO
52
23
30
0
Synthesis of the 2-(2′-aminophenyl)benzimidazole derivatives (4) from sub-
stituted isatoic anhydrides (2) and o-phenylenediamines (3).a
DMSO
MeOH
reflux
rtc
MeOH
EtOH
reflux
rtc
32
0
EtOH
TFE
reflux
reflux
reflux
reflux
70
42
0
H2O
H2Od
0
Toluene
Toluene
Toluene
Chlorobenzene
Chlorobenzene
Chlorobenzene
Neat
76
77
0
rtc
Entry
R1
R2
R3
Product
Yield (%)b
reflux
70
70
54
trace
51
0
1
2
3
4
5
6
7
8
H
H
H
H
H
H
H
H
H
H
H
H
H
4a
4b
4c
4d
4e
4f
81
66
68
75
55
48
62
58
rtc
F
130
Cl
Neat
70
Br
CH3
OMe
H
Dioxane
Dioxane
THF
reflux
70
38
31
25
R2 = R3 = (CH)4
4g
4h
reflux
H
Cl
Cl
a
The magnetically stirred mixture of 2a (1 mmol) and 3a (1 mmol, 1 equiv)
in the specified solvent (1.5 mL) was treated at the indicated tempareture for
12 h.
a
The mixture of isatoic anhydride (2) (1 mmol) and o-phenylene diamine (3)
(1 mmol, 1 equiv) in PhMe (2 mL) was heated under reflux for 12 h.
b
b
Isolated yield of 4a.
Isolated yield of 4.
c
rt = 25–30 °C.
d
The reaction was performed in the presence of 10 mol% SDOSS.
2.2. Biological evaluation
isolated by filtration in 70–87% yields and did not require further
purification.
2.2.1. Determination of MIC against M. tuberculosis H37Rv
The synthesized alkylbenzimidazoquinazolines (6) were subjected
to in vitro anti-TB activity against M. tuberculosis H37Rv (ATCC 27294
strain) (Table 5, Fig. 2) [61]. The minimum inhibitory concentration
(MIC), minimum concentration in µg/mL of the compound required for
99% inhibition of bacterial growth, of 6 and those of the standard drugs
such as isoniazid (INH), rifampicin (R), ethambutol (E), pyrazinamide
(Z) and ciprofloxacin (Cfx) were determined in triplicate at pH 7.4. All
of these synthesized compounds showed MIC values in the micromolar
range (0.40– > 25 µg/mL). Out of these, eleven compounds exhibited
MIC in the range of 1.56–6.25 µg/mL, two compounds 6d and 6v were
active at 0.78 µg/mL and compound 6x was the most active (MIC
0.40 µg/mL or 1.45 µM) from this series of compounds.
To bring about the variations in the final molecule it was thought to
prepare the derivatives of the key intermediate. The substituted isatoic
anhydrides 2 were treated with the various substituted o-phenylene-
diamines 3 in PhMe at 70 °C for 12 h to generate the various substituted
2-(2′-aminophenyl)-1H-benzimidazole derivatives (4a-h, Table 3). In
each case the desired product 4 was obtained by cooling the reaction
mixture to rt wherein the products precipitated out as solid that were
filtered out and washed with PhMe to obtain the pure products.
Thirty two benzimidazoquinazoline derivatives (6) were synthe-
sized in 30–96% yields (Table 4) by treating the 2-(2′-aminophenyl)-
1H-benzimidazoles (4a-h) with ethyl ortho esters (5) in DMF at 100 ˚C.
[60]
Further, we screened the total nine active compounds with
3

P.S. Jadhavar, et al.
BioorganicChemistry99(2020)103774
Table 4
Table 5
The cyclocondensation of the 2-(2′-aminophenyl)-1H-benzimidazoles (4a-h)
with the ortho esters (5) to forme the benzimidazoquinazoline derivatives 6.a
The anti-TB activity and in vitro cell viability of alkylbenzimidazoquinazolines
6 and a few standard anti-TB drugs against M. tuberculosis H37Rv (ATCC
27294).
Entry Compd. No. MICa
MICa
Cytotoxicity (%)c MIC (µg/
Against
Against
drug
mL)d
drug
Against
INH
sensitive
Mtb
sensitive
Mtb
resistant
Mtb
(µg/mL)
(µM)a,b
1
6a
6b
6c
1.56
1.56
25
7.12
6.69
101.10
2.98
ND
14.67
14.56
ND
3.125
1.56
ND
2
Entry
4
R1
R2
R3
R4
Product
Yield 6 (%)b
3
4
6d
6e
6f
0.78
> 25
6.25
25
21.70
ND
0.78
ND
1
4a
4a
4a
4a
4a
4b
4b
4b
4b
4b
4c
4c
4c
4c
4c
4d
4d
4d
4d
4d
4e
4e
4e
4e
4e
4f
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
6a
6b
6c
96
92
89
87
90
86
84
82
76
81
79
81
84
80
81
79
81
87
71
80
83
78
77
72
79
65
81
87
80
76
79
30
5
2
H
Me
Et
6
26.35
99.50
ND
19.70
ND
ND
3
H
7
6g
6h
6i
ND
4
H
n-Pr
n-Bu
H
6d
6e
8
> 25
25
ND
ND
5
H
9
89.51
42.61
ND
ND
ND
6
F
6f
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
6j
12.5
> 25
> 25
6.25
> 25
25
ND
ND
7
F
Me
Et
6g
6h
6i
6k
6l
ND
ND
8
F
ND
ND
ND
9
F
n-Pr
n-Bu
H
6m
6n
6o
6p
6q
6r
22.18
ND
32.12
ND
ND
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
F
6j
ND
Cl
Cl
Cl
Cl
Cl
Br
Br
Br
Br
Br
CH3
CH3
CH3
CH3
CH3
OMe
H
6k
6l
80.70
10.48
40.04
38.32
4.59
8.82
ND
ND
ND
Me
Et
3.125
12.5
12.5
1.56
3.125
> 25
0.78
25
10.16
ND
12.5
ND
6m
6n
6o
6p
6q
6r
n-Pr
n-Bu
H
ND
ND
6s
22.13
30.12
ND
> 25
6.25
ND
6t
Me
Et
6u
6v
6w
6x
6y
6z
3.15
95.67
1.45
86.39
47.48
ND
21.82
ND
1.56
ND
n-Pr
n-Bu
H
6s
6t
0.40
25
12.65
ND
12.5
ND
6u
6v
6w
6x
6y
6z
Me
Et
12.5
> 25
6.25
25
ND
ND
6aa
6ab
6ac
6ad
6ae
6af
INH
R
ND
ND
n-Pr
n-Bu
Me
H
22.06
84.08
20.07
4.79
20.68
ND
23.42
ND
ND
ND
6.25
1.56
6.25
0.098
0.197
1.56
6.25
1.56
18.88
18.46
23.00
ND
ND
4g
4g
4g
4g
4g
4h
R2 = R3 = (CH)4
R2 = R3 = (CH)4
R2 = R3 = (CH)4
R2 = R3 = (CH)4
R2 = R3 = (CH)4
6aa
6ab
6ac
6ad
6ae
6af
12.5
ND
H
Me
Et
H
0.72
0.24
7.64
50.77
4.71
H
n-Pr
n-Bu
Me
ND
ND
H
E
ND
ND
H
Cl
Cl
Z
ND
ND
a
Cfx
ND
ND
To the magnetically stirred solution of 4 (1 mmol) in DMF (2 mL) was
added the triethyl ortho ester (5) (1 mmol, 1.5 equiv) and the mixture was
heated at 100 °C for 12 h. bIsolated yield of 6.
a
For 99% inhibition of M. tuberculosis H37Rv ATCC 27294 strain.
bConversion of the MIC value of µg/mL determined as under foot note ‘a’ into
µM. c% inhibition at 50 µg/mL concentration determined against RAW 264.7
cell lines. dFor 99% inhibition of M. tuberculosis H37Rv ATCC 27294 strain re-
sistant to INH. ND: Not determined.
MIC ≤ 3.125 µg/mL (6a, 6b, 6d, 6p, 6s, 6t, 6v, 6x, and 6ae) against
INH resistant Mtb strain, and found 6d as the potent compound with
MIC of 0.78 µg/mL (Table 5). Two compounds (6b and 6v) displayed
good activity with MIC of 1.56 µg/mL and compounds 6a and 6t were
also found potent against INH resistant strain with MIC of 1.56 and
3.125 µg/mL.
compounds can be written as shown in Fig. 4.
2.2.3.1. Effect of C ring substitution. In our first attempt we tried to
introduce sp3 hybridization on the flat benzimidazoquinazoline core by
substitution of the alkyl group at the C6 position. The introduction of
sp3 hybridization increases the drug likeness of the molecule by
affecting its physicochemical properties and binding to the target
protein [62,63]. The effect of alkyl group substitution on C-ring of
benzimidazoquinazoline is seen on the MIC values.
2.2.2. In vitro cell viability test
The in vitro cell viability of a few selected benzimidazoquinazolines
(6a, 6b, 6d, 6f, 6m, 6p, 6s, 6t, 6v, 6x, 6ab, 6ad, 6ae and 6af) with
MIC ≤ 6.25 µg/mL was determined against RAW 264.7 cell lines using
MTT assay at 50 μg/mL (Table 5, Fig. 3) that revealed the non-cytotoxic
nature of these compounds. The most active compounds 6d, 6v (MIC of
0.78 µg/mL) and 6x (MIC of 0.40 µg/mL) exhibited selectivity index of
64, 64 and 125 respectively and emerged as the most promising anti-TB
leads.
Compound 6a having no alkyl group was active at 1.56 µg/mL.
When the methyl group is placed at the C-6 position the anti-TB activity
was found to be retained in resultant compound 6b which was equi-
potent to 6a. However, the introduction of the ethyl (6c) or butyl (6e)
group at this position (C-6) led to decrease in anti-TB activity. The
propyl group substitution at C-6 led to the compound 6d with much
superior anti-TB activity with MIC of 0.78 µg/mL (Table 6).
2.2.3. Structure activity relationship (SAR)
The structure activity relationship (SAR) of the benzimidazoquina-
zolines could be drawn by correlating the MIC (µg/mL) values of the
compounds with the specific changes in the structure made by various
substitution on the core moieties. General structure for this class of
2.2.3.2. Effect of D ring substitution. The substitution on D ring has also
shown influence on the anti-TB activity of these compounds. Halogen
4

P.S. Jadhavar, et al.
BioorganicChemistry99(2020)103774
Fig. 2. The anti-TB activity data profile of the synthesized compounds in comparison with that of the standard anti-TB drugs.
substitution has a varied effect on the anti-TB activity. When the
fluorine group is substituted at C-2 position of ring D, the resultant
compound 6f showed a decrease in the anti-TB activity compared to
that of 6a. A similar trend is observed in the corresponding compounds
bearing alkyl substituent at the C-6 position in ring C (e.g., 6g-6j as
compared to 6b-e). The incorporation of chloro or bromine at the C-2
position in the D ring also in general showed an overall decrease in the
anti-TB activity except for the bromo derivative 6s which though was
equipotent to 6a with MIC of 1.56 µg/mL but exhibits inferior activity
compared to the parent compound 6d bearing a nPr substituent at the C-
6 position in ring C (Table 7).
Fig. 4. General structure of 2-alkylbenzimidazoquinazolines.
membered aromatic ring in general appears to be detrimental to the
anti-TB potential as except for the compound 6ae that retains the anti-
TB activity (with MIC value of 1.56 µg/mL comparable to that of 6a)
(Table 9).
The methyl group substitution at C-2 position on the D ring leads to
the most potent anti-TB compound 6x with the MIC of 0.40 µg/mL. This
compound also has C-6 nPr substitution in ring C which further confirms
the earlier observation of the importance of the nPr group at this po-
sition for anti-Mtb activity (Table 8).
2.3. Evaluation of drug-like properties of the active compounds
These active compounds with MIC ≤ 6.25 µg/mL were also tested
for amenability to the Lipinski rule of five. According to this rule, the
2.2.3.3. Effect of fusion on ring A. The fusion of A ring with the six
Fig. 3. In vitro cytotoxicity profile of active compounds with MIC ≤ 6.25 µg/mL.
5

P.S. Jadhavar, et al.
BioorganicChemistry99(2020)103774
Table 6
Table 9
Effect of substitutions at Ring C on the anti-TB activity.
Effect of substitutions at Ring C on the anti-TB activity of 6ab.
Compd. No.
R1
MIC (µg/mL)
6ab
6ac
6ad
6ae
6af
H
> 25
6.25
25
Compd. No.
R1
MIC (µg/mL)a
Me
Et
6a
6b
6c
6d
6e
H
1.56
1.56
25
n-Pr
n-Bu
6.25
1.56
Me
Et
n-Pr
n-Bu
0.78
> 25
a99% inhibition of growth of M. tuberculosis H37Rv (ATCC 27294 strain).
a
For 99% inhibition of growth of M. tuberculosis H37Rv (ATCC 27294
possess more than 10 HB acceptors, molecular weight (MW) should not
be greater than 500 Da, and the octanol–water partition coefficient
(cLogP) should not be greater than 5 [64]. These properties have been
computed by using the Molinspiration Online Software v2016.10 [65]
(Table 10) that reveal that these compounds 6a, 6b, 6d, 6f, 6p, 6v and
6ab followed the Lipinski rule and showed no violation of the above
criteria. Therefore, these active ligands are likely to have the potential
to be an active drug candidate.
strain).
Table 7
Effect of halogen substitutions at Ring D on the anti-TB activity.
3. Conclusions
In this study alkylbenzimidazoquinazolines have been revealed as
new anti-TB chemotypes. Thirty two compounds have been synthesized
and tested for anti-TB activity. Fourteen compounds displayed good in
vitro anti-mycobacterial activity, with MIC in low micromolar range
against replicating TB. The most potent compound 6x exhibited MIC of
0.40 µg/mL more than that of the standard drugs E, Z and Cfx against
drug sensitive Mtb strain and compound 6d was found as the potent
compound with MIC of 0.78 µg/mL against INH resistant Mtb strain.
The early SAR for this class of compounds has been established. The in
vitro cell viability of a few benzimidazoquinazolines with MIC of
≤6.25 µg/mL against RAW 264.7 cell lines revealed the non-cytotoxic
nature of these compounds. The major improvements in activity were
observed when the C-6 substitution is propyl group and the D ring
substitution has methyl group. Compounds 6a, 6b, 6d, 6f, 6p, 6v and
6ab followed the Lipinski rule and showed no violation of the above
criteria. In conclusion, this study has provided a novel scaffold for the
anti-TB drug discovery process.
Compd. No.
R1
MIC (µg/mL)
Compd. No.
R1
MIC (µg/mL)a
6f (X = F)
6g (X = F)
6h (X = F)
6i (X = F)
6j (X = F)
6k (X = Cl)
6l (X = Cl)
6m(X = Cl)
H
6.25
25
6n (X = Cl)
6o (X = Cl)
6p (X = Br)
6q (X = Br)
6r (X = Br)
6s (X = Br)
6t (X = Br)
n-Pr
n-Bu
H
> 25
25
Me
Et
> 25
25
3.125
12.5
12.5
1.56
3.125
n-Pr
n-Bu
H
Me
12.5
> 25
> 25
6.25
Et
n-Pr
n-Bu
Me
Et
a
For 99% inhibition of growth of M. tuberculosis H37Rv (ATCC 27294
strain).
Table 8
Effect of substitutions on Ring C on the anti-TB activity of 6u.
4. Experimental section
4.1. General chemistry
The glass wares were thoroughly washed and dried in an oven.
Chemicals and all solvents were commercially available (Aldrich
Chemical, Merck AG, Fluka and S-D Fine Chemicals) and used without
further purification. The 1H/13C NMR spectra were recorded on a
Bruker Advance 400/100 MHz NMR spectrometer in CDCl3 with re-
sidual undeuterated solvent (CDCl3: 7.26/77.0) using TMS as an in-
ternal standard. Chemical shifts (δ) are given in ppm and J values are
given in Hz. 13C NMR spectra were fully decoupled and were referenced
to the middle peak of the solvent CDCl3 at 77.0 ppm. Splitting pattern
were designated as s, singlet; br s, broad singlet; d, doublet; dd, doublet
of doublet; t, triplet; q, quartet; qnt, quintet; sxt, sixtet; m, multiplet.
Mass spectra were recorded on mass spectrometer (ESI). Infra-red (IR)
spectra were recorded on Perkin Elmer FT-IR spectrometer in the range
4000–600 cm−1 either as neat samples for liquids or using KBr for
preparing pellets for solid samples. Compounds were routinely checked
Compd. No.
R1
MIC (µg/mL)a
6u
6v
6x
6y
6z
H
> 25
0.78
25
Me
Et
n-Pr
n-Bu
0.40
25
a
For 99% inhibition of growth of M. tuberculosis H37Rv (ATCC 27294
strain).
drug likeliness of a molecule to be an orally active drug is characterized
by the non-violation of more than one of the following four criteria:
should not have more than five hydrogen bond (HB) donors, should not
6

P.S. Jadhavar, et al.
BioorganicChemistry99(2020)103774
Table 10
Calculated Lipinski properties of compounds with anti-TB activity (MIC ≤ 6.25 µg/mL).
Entry
Compd No.
MIC (µg/mL)a
nViolb
cLogPc,d
Mol. Wt.c,e
No. of HBAf,g
No. of HBDf,h
No. of RBf,i
Acceptable Range
≤5
≤500
≤10
3
≤5
0
≤5
0
1
6a
1.56
1.56
0.78
6.25
6.25
3.125
1.56
3.125
0.78
0.40
6.25
6.25
1.56
6.25
0
0
0
0
1
0
1
1
0
1
0
1
1
1
3.27
3.77
4.83
3.42
5.02
4.14
5.70
6.23
4.27
5.33
4.95
6.00
6.53
5.08
219.24
233.27
261.32
237.23
281.74
298.14
340.22
354.24
247.29
275.35
283.33
311.38
325.41
302.16
2
6b
6d
6f
3
0
0
3
3
0
2
4
3
0
0
5
6m
6p
6s
3
0
1
6
3
0
0
7
3
0
2
8
6t
3
0
3
9
6v
3
0
0
10
11
12
13
14
6x
3
0
2
6ab
6ad
6ae
6af
3
0
0
3
0
2
3
0
3
3
0
0
a
b
c
d
e
f
g
h
i
For 99% Inhibition of the growth of M. tuberculosis H37Rv (ATCC 27294 strain).
nViol, no. of violations.
Calculated using ChembioDraw Ultra 12.0.
cLog P, octanol-water partition co-efficient.
MW, molecular weight.
Calculated using Molinspiration property engine v 2016.10.
HBA, no. of hydrogen bond acceptors.
HBD, no. of hydrogen bond donors.
RB, no. of rotatable bonds.
for their purity on the silica gel GF-254 and visualized under UV at
wavelength 254 nm. Melting points were measured with Gupta scien-
tific melting point apparatus and were uncorrected. Evaporation of
solvents was performed at reduced pressure, using a rotary evaporator.
HPLC (model SCL-10AVP, Shimadzu, Japan) of all the target com-
pounds has been performed using Qualisil Gold C18 column
(4.6 × 250 mm, 5 µm, LCGC Chromatography Solution Pvt. Ltd) and
acetonitrile:water (70:30) as the mobile phase at 30 °C utilizing 20 µL of
the sample with flow rate of 1 mL min−1 using binary pump. Photo
diode array detector was used for variable wavelength ranging from
200 to 800 nM. For interpretation of the results of HPLC, Class VP
software was used. Elemental analyses were performed on organic
element analyzer (Thermo SCIENTIFIC FLASH 2000) and, indicated by
the symbols of the elements or functions were within 0.4% of the
theoretical values. For interpretation of the results of elemental ana-
lysis, Eager Xperience software was used.
triethyl orthoformate (0.3 g, 5 mmol, 2 equiv) in DMF (2.5 mL) was
treated at 100 °C (oil bath) for 12 h. The crude reaction mixture was
poured into crushed ice (10 g) and the precipitated solid was filtered to
obtain 6a as white solid (210.5 mg, 96%); mp > 220 °C; 1H NMR
(400 MHz, CDCl3) δ (ppm) 9.15 (s, 1H), 8.69 (d, J = 7.9 Hz, 1H),
8.04–7.97 (m, 3H), 7.83–7.47 (m, 4H); 13C NMR (100 MHz, CDCl3) δ
(ppm) 146.36, 144.03, 142.57, 136.13, 131.79, 128.67, 128.52,
128.15, 126.17, 124.22, 123.29, 120.32, 119.32, 110.08; MS (ESI) m/z:
219.98 (M+H)+. HPLC analysis: retention time = 3.267 min; peak
area, 100%.
4.1.4. 6-Methylbenzo[4,5]imidazo[1,2-c]quinazoline (6b): [66]
White solid (214.6 mg, 92%); mp
>
220 °C; 1H NMR (CDCl3,
400 MHz) δ (ppm) 8.69–8.67 (m, 1H), 8.06–8.03 (m, 2H), 7.90–7.89
(m, 1H), 7.79–7.75 (m, 1H), 7.67–7.63 (m, 1H), 7.60–7.56 (m, 1H),
7.48–7.44 (m, 1H), 3.21 (s, 3H); 13C NMR (100 MHz, CDCl3) δ (ppm)
147.67, 144.37, 142.26, 131.74, 129.45, 127.70, 127.35, 125.60,
124.11, 123.07, 120.23, 118.09, 114.02, 24.13; HPLC analysis: reten-
tion time = 4.133 min; peak area, 100%.
4.1.1. Typical procedure for the preparation of isatoic anhydride.
Preparation of 2a [58,59]
To the magnetically stirred solution of the 5-bromoisatin (1)
(0.22 g, 1 mmol) in HOAc (2 mL) was added of mCPBA (2.5 g,
1.5 mmol, 1.5 equiv) and the resultant mixture was stirred magnetically
for another 4 h (TLC). The crude reaction mixture was filtered and
washed with aq NaHCO3 to afford 2a as light red solid (0.21 g, 87%).
4.1.5. 6-Ethylbenzo[4,5]imidazo[1,2-c]quinazoline (6c): [67]
White solid (220.1 mg, 89%); mp
>
220 °C; 1H NMR (CDCl3,
400 MHz) δ (ppm) 8.71 (d, J = 7.9 Hz, 1H), 8.06 (d, J = 8.4 Hz, 2H),
7.95–7.93 (m, 1H), 7.80–7.76 (m, 1H), 7.67–7.63 (m, 1H), 7.61–7.57
(m, 1H), 7.51–7.46 (m, 1H), 3.52 (q, J = 7.3 Hz, 2H), 1.66 (t,
J = 7.3 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ (ppm) 151.58, 148.02,
144.45, 142.26, 131.65, 129.01, 127.62, 125.47, 124.12, 123.07,
120.24, 118.17, 114.44, 29.38, 10.30; HPLC analysis: retention
time = 4.417 min; peak area, 92.37%.
4.1.2. Typical procedure for the preparation of 2-(2′-aminophenyl)
benzimidazole. Synthesis of 4a
The mixture of 2a (0.16 g, 1 mmol) and 3a (0.11 g, 1 mmol) in
PhMe (2 mL) was heated under reflux for 12 h. The reaction mixture
was cooled to rt, filtered, and the solid residue washed with hexane to
afford 4a as white solid (0.17 g, 81%); mp 213–216 °C; IR (KBr, cm−1
)
4.1.6. 6-Propylbenzo[4,5]imidazo[1,2-c]quinazoline (6d): [68]
3442, 1676, 1545, 1472, 1258, 1132; 1H NMR (CDCl3, 400 MHz) δ
(ppm) 8.30 (d, J = 7.9 Hz, 1H), 7.97 (d, J = 15.5 Hz, 1H), 7.79 (d,
J = 3.4 Hz, 2H) 7.53–7.61 (m, 3H), 7.47–7.50 (m, 1H), 7.28–7.34 (m,
White solid (227.3 mg, 87%); mp
>
220 °C; 1H NMR (CDCl3,
400 MHz) δ (ppm) 8.70 (d, J = 7.8 Hz, 1H), 8.06–7.91 (m, 3H), 7.78 (t,
J = 7.6 Hz, 1H), 7.67–7.57 (m, 2H), 7.50–7.47 (m, 1H), 3.44 (t,
J = 7.6 Hz, 2H), 2.18–2.08 (m, 2H), 1.26 (t, J = 7.3 Hz, 3H); 13C NMR
(100 MHz, CDCl3) δ (ppm) 150.64, 148.06, 144.46, 142.21, 131.66,
129.02, 127.61, 127.58, 125.47, 124.11, 123.08, 120.27, 118.17,
7H), 6.39 (d, J = 15.5 Hz, 1H); MS (APCI) m/z: 325.21 (M+H)+
.
4.1.3. Typical
benzimidazoquinazoline. Synthesis of 6a [60]
The magnetically stirred mixture of 4a (0.41 g, 2.5 mmol) and
experimental
procedure
for
the
synthesis
of
114.30,
37.87,
19.35,
13.87;
HPLC
analysis:
retention
time = 4.850 min; peak area, 100%.
7

P.S. Jadhavar, et al.
BioorganicChemistry99(2020)103774
4.1.7. 6-Butylbenzo[4,5]imidazo[1,2-c]quinazoline (6e): [60]
Light grey solid (247.8 mg, 90%); mp > 220 °C; 1H NMR (CDCl3,
400 MHz) δ (ppm) 8.72 (d, J = 7.8 Hz, 1H), 8.05 (q, J = 9.2 Hz, 2H),
7.94 (d, J = 8.0 Hz, 1H), 7.79 (t, J = 7.6 Hz, 1H), 7.69–7.59 (m, 2H),
7.53–7.49 (m, 1H), 3.49 (t, J = 13.9 Hz, 2H), 2.13–2.05 (m, 2H),
1.74–1.63 (m, 2H), 1.10 (t, J = 7.4 Hz, 3H); 13C NMR (100 MHz,
CDCl3) δ (ppm) 150.90, 144.51, 142.25, 131.67, 129.06, 127.61,
127.58, 125.49, 124.13, 123.10, 120.31, 118.19, 114.33, 35.82, 27.94,
22.54, 13.97; HPLC analysis: retention time = 5.600 min; peak area,
96.77%.
2H), 8.69 (d, J = 2.4 Hz, 1H), 7.8 (dd, J = 8.7, 2.4 Hz, 1H), 7.66–7.61
(m, 1H), 7.57–7.53 (m, 1H); 13C NMR (100 MHz, CDCl3) δ (ppm)
145.22, 143.97, 140.93, 136.27, 134.58, 132.19, 130.03, 128.11,
126.47, 123.76, 123.72, 120.55, 120.42, 110.21; HPLC analysis: re-
tention time = 4.158 min; peak area, 100%.
4.1.14. 2-Chloro-6-methylbenzo[4,5]imidazo[1,2-c]quinazoline (6l): [70]
White solid (216.8 mg, 81%); mp
>
220 °C; 1H NMR (CDCl3,
400 MHz) δ (ppm) 8.67 (d, J = 2.3 Hz, 1H), 8.09–8.04 (m, 2H),
7.84–7.82 (m, 1H), 7.71–7.69 (m, 1H), 7.63–7.59 (m, 1H), 7.53–7.49
(m, 1H), 3.22 (s, 3H); 13C NMR (100 MHz, CDCl3) δ (ppm) 147.92,
146.58, 144.32, 140.64, 133.45, 132.12, 129.41, 128.93, 125.89,
123.54, 123.52, 120.46, 119.18, 114.10, 24.15; MS (ESI) m/z: 268.18
(M+H)+; HPLC analysis: retention time = 4.608 min; peak area,
100%.
4.1.8. 2-Fluorobenzo[4,5]imidazo[1,2-c]quinazoline (6f): [66]
Yellow solid (204.0 mg, 86%); mp 190–193 °C; 1H NMR (CDCl3,
400 MHz) δ (ppm) 9.12 (s, 1H), 8.32 (dd, J = 8.4, 2.8 Hz, 1H),
8.04–7.98 (m, 3H), 7.62–7.58 (m, 1H), 7.54–7.48 (m, 2H); 13C NMR
(100 MHz, CDCl3) δ (ppm) 160.68, 143.93, 139.21, 135.48, 131.01,
130.92, 126.39, 123.69, 120.51, 120.32, 120.08, 115.76, 112.55,
110.22, 109.69, 109.45; HPLC analysis: retention time = 3.225 min;
peak area, 100%.
4.1.15. 2-Chloro-6-ethylbenzo[4,5]imidazo[1,2-c]quinazoline (6m)
Yellow solid (236.7 mg, 84%); mp > 220 °C; 1H NMR (CDCl3,
400 MHz) δ (ppm) 8.84 (d, J = 2.08 Hz, 1H), 8.06–8.03 (m, 2H),
7.85–7.77 (m, 2H), 7.61–7.58 (m, 1H), 7.52–7.47 (m, 1H), 3.49 (q,
J = 6.7 Hz, 2H), 1.63 (t, J = 8.00 Hz, 3H); 13C NMR (100 MHz, CDCl3)
δ (ppm) 151.98, 146.65, 144.39, 140.95, 134.76, 129.34, 128.99,
126.66, 125.74, 123.51, 121.18, 120.46, 119.62, 114.51, 29.40, 10.25;
HRMS (ESI) m/z calcd for C16H13ClN3 [M+H+], 282.0798; Found
282.0797. HPLC analysis: retention time = 4.292 min; peak area,
100%.
4.1.9. 2-Fluoro-6-methylbenzo[4,5]imidazo[1,2-c]quinazoline (6g):
White solid (211.1 mg, 84%); mp 196–197 °C; 1H NMR (CDCl3,
400 MHz) δ (ppm) 8.35 (dd, J = 8.35, 2.4 Hz, 1H), 8.09 (q, J = 7.7 Hz,
2H), 7.92 (q, J = 4.6, Hz, 1H), 7.63–7.61 (m, 1H), 7.55–7.50 (m, 2H),
3.24 (s, 3H); 13C NMR (100 MHz, CDCl3) δ (ppm) 154.30, 141.00,
138.80, 137.70, 136.00, 134.00, 129.73, 125.82, 123.4, 120.48,
120.05, 114.13, 109.21, 24.02; HRMS (ESI) m/z calcd for C15H11FN3
[M+H], 252.0937; Found 252.0937. HPLC analysis: retention
time = 4.225 min; peak area, 100%.
4.1.16. 2-Chloro-6-propylbenzo[4,5]imidazo[1,2-c]quinazoline
[70]
(6n):
Yellow solid (236.6 mg, 80%); mp 196–197 °C; 1H NMR (CDCl3,
400 MHz) δ (ppm) 8.66 (s, 1H), 8.0 (dd, J = 8.1, 8.0 Hz, 2H), 7.85–7.83
(m, 1H), 7.70–7.68 (m, 1H), 7.61–7.58 (m, 1H), 7.52–7.48 (m, 1H),
3.42 (t, J = 7.2 Hz, 2H), 2.12 (m, 2H), 1.25 (t, J = 7.0 Hz, 3H); 13C
NMR (100 MHz, CDCl3) δ (ppm) 150.85, 146.84, 144.36, 140.55,
133.30, 131.97, 129.12, 128.97, 125.71, 123.50, 120.45, 119.22,
114.37, 37.79, 19.21, 13.85; MS (ESI) m/z: 296.51 (M+H)+; HPLC
analysis: retention time = 5.500 min; peak area, 100%.
4.1.10. 6-Ethyl-2-fluorobenzo[4,5]imidazo[1,2-c]quinazoline (6h)
White solid (217.5 mg, 82%); mp
>
220 °C; 1H NMR (CDCl3,
400 MHz) δ (ppm) 8.32 (dd, J = 8.6, 2.8 Hz, 1H), 8.06–8.03 (m, 2H),
7.94–7.91 (m, 1H), 7.61–7.57 (m, 1H), 7.51–7.45 (m, 2H), 3.50 (q,
J = 7.3 Hz, 2H), 1.63 (t, J = 7.3 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ
(ppm) 151.10, 148.58, 144.36, 140.93, 138.95, 130.05, 129.96,
129.01, 125.67, 123.44, 120.44, 119.94, 119.41, 114.54, 109.41,
109.16, 29.28, 10.23; HRMS (ESI) m/z calcd for C16H13FN3 [M+H],
266.1094;
Found
266.1100.
HPLC
analysis:
retention
4.1.17. 6-Butyl-2-chlorobenzo[4,5]imidazo[1,2-c]quinazoline (6o)
White solid (250.9 mg, 81%); mp 186–189 °C; IR (KBr, cm−1) 3408,
1602, 1535, 1466, 1276, 1181, 743; 1H NMR (CDCl3, 400 MHz) δ
(ppm) 8.69 (d, J = 2.3 Hz, 1H), 8.07–7.96 (m, 2H), 7.86 (d, J = 8.7 Hz,
1H), 7.72–7.69 (m, 1H), 7.65–7.57 (m, 1H), 7.55–7.50 (m, 1H), 3.47 (t,
J = 7.8 Hz, 2H), 2.08 (qnt, J = 7.7 Hz, 2H), 1.69 (sxt, J = 7.5 Hz, 2H),
1.09 (t, J = 7.32 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ (ppm) 151.13,
146.87, 144.43, 140.60, 133.32, 132.01, 129.13, 125.74, 123.54,
123.50, 120.50, 119.26, 114.40, 35.75, 27.81, 22.51, 13.96; HRMS
(ESI) m/z calcd for C18H17ClN3 310.1111 [M+H+], Found 310.1105.
HPLC analysis: retention time = 6.675 min; peak area, 100%.
time = 4.467 min; peak area, 100%.
4.1.11. 2-Fluoro-6-propylbenzo[4,5]imidazo[1,2-c]quinazoline (6i)
White solid (212.3 mg, 76%); mp 202–205 °C; 1H NMR (CDCl3,
400 MHz) δ (ppm) 8.81 (s, 1H), 7.99 (dd, J = 8.0, 2H), 7.82–7.80 (m,
1H), 7.76–7.73 (m, 1H), 7.60–7.56 (m, 1H), 7.50–7.46 (m, 1H), 3.39 (t,
J = 7.6 Hz, 2H), 2.10 (sxt, J = 7.5 Hz, 2H), 1.23 (t, J = 7.4 Hz, 3H);
13C NMR (100 MHz, CDCl3) δ (ppm) 151.03, 146.7, 144.39, 140.9,
134.76, 129.3, 128.99, 126.7, 125.74, 123.51, 120.48, 114.37, 37.84,
19.20, 13.84; HRMS (ESI) m/z calcd for C17H15FN3 280.1250 [M+H+],
Found 280.1247. HPLC analysis: retention time = 5.375 min; peak
area, 100%.
4.1.18. 2-Bromobenzo[4,5]imidazo[1,2-c]quinazoline (6p)
White solid (235.5 mg, 79%); mp
>
220 °C; 1H NMR (CDCl3,
4.1.12. 6-Butyl-2-fluorobenzo[4,5]imidazo[1,2-c]quinazoline (6j)
400 MHz) δ (ppm) 9.13 (s, 1H), 8.81 (s, 1H), 8.01–7.95 (m, 2H),
7.87–7.83 (m, 2H), 7.62–7.59 (m, 1H), 7.53–7.49 (m, 1H); 13C NMR
(100 MHz, CDCl3) δ (ppm) 145.02, 143.99, 141.26, 136.38, 134.95,
130.15, 128.12, 126.84, 126.47, 123.75, 122.48, 120.73, 120.54,
110.18; HRMS (ESI) m/z calcd for C14H9BrN3 [M+H+], 297.9980;
Found 297.9990. HPLC analysis: retention time = 4.292 min; peak
area, 100%.
White solid (237.6 mg, 81%); mp
>
220 °C; 1H NMR (CDCl3,
400 MHz) δ (ppm) 8.34–8.32 (m, 1H), 8.07–8.01 (m, 2H), 7.93–7.89
(m, 1H), 7.61–7.59 (m, 1H), 7.54–7.48 (m, 2H), 3.47 (t, J = 7.7 Hz,
2H), 2.08–2.05 (m, 2H), 1.71–1.66 (m, 2H), 1.10 (t, J = 7.3 Hz, 3H);
13C NMR (100 MHz, CDCl3) δ (ppm) 162.53, 150.15, 144.35, 138.85,
129.98, 129.89, 129.00, 125.66, 123.44, 120.45, 120.18, 119.94,
119.48, 114.41, 109.40, 109.16, 35.66, 29.71, 27.85, 13.96; HRMS
(ESI) m/z calcd for C18H17FN3 [M+H+], 294.1407; Found 294.1400.
HPLC analysis: retention time = 5.758 min; peak area, 100%.
4.1.19. 2-Bromo-6-methylbenzo[4,5]imidazo[1,2-c]quinazoline
[71]
(6q):
White solid (252.8 mg, 81%); mp > 220 °C; IR (KBr, cm−1) 3408,
1626, 1536, 308, 1380, 742; 1H NMR (CDCl3, 400 MHz) δ (ppm) 8.85
(s, 1H), 8.10–8.04 (m, 2H), 7.84–7.51 (m, 4H), 3.22 (s, 3H); 13C NMR
(100 MHz, CDCl3) 134.08, 129.08, 126.69, 125.53, 121.31, 120.49,
4.1.13. 2-Chlorobenzo[4,5]imidazo[1,2-c]quinazoline (6k): [69]
White solid (200.4 mg, 79%); mp
>
220 °C; 1H NMR (CDCl3,
400 MHz) δ (ppm) 9.17 (s, 1H), 8.69 (d, J = 2.4 Hz, 1H), 8.06–8.00 (m,
8

P.S. Jadhavar, et al.
BioorganicChemistry99(2020)103774
114.10, 29.70, 24.14; HPLC analysis: retention time = 4.472 min; peak
area, 100%.
2.57 (s, 3H), 2.05 (sxt, J = 5.7 Hz, 2H), 1.23 (t, J = 7.4 Hz, 3H); 13C
NMR (100 MHz, CDCl3) δ (ppm) 149.80, 148.10, 144.46, 140.26,
137.88, 133.15, 129.08, 127.33, 125.38, 123.68, 122.94, 120.20,
117.86, 114.28, 37.82, 21.50, 19.39, 13.87; HPLC analysis: retention
time = 5.675 min; peak area, 100%.
4.1.20. 2-Bromo-6-ethylbenzo[4,5]imidazo[1,2-c]quinazoline (6r): [71]
White solid (283.8 mg, 87%); mp
>
220 °C; 1H NMR (CDCl3,
400 MHz): δ (ppm) 8.01 (d, J = 8.0 Hz, 1H), 7.77–7.75 (m, 1H),
7.60–7.52 (m, 3H), 7.28–7.23 (m, 2H), 3.36 (q, J = 2.7 Hz, 2H), 1.30
(t, J = 10.0 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ (ppm) 151.96,
146.65, 144.40, 140.95, 134.75, 129.34, 128.99, 126.66, 125.74,
123.49, 121.17, 120.46, 119.62, 114.50, 29.39, 10.14; MS (ESI) m/z:
326.03 (M)+; HPLC analysis: retention time = 5.675 min; peak area,
100%.
4.1.27. 6-Butyl-2-methylbenzo[4,5]imidazo[1,2-c]quinazoline (6y)
Yellow solid (228.6 mg, 79%); mp > 220 °C; 1H NMR (CDCl3,
400 MHz) δ (ppm) 8.49 (s, 1H), 8.03 (d, J = 8.0 Hz, 1H), 7.98 (d,
J = 8.3 Hz, 1H), 7.80 (d, J = 8.2 Hz, 1H), 7.59–7.55 (m, 2H),
7.49–7.45 (m, 1H), 3.44 (t, J = 7.8 Hz, 2H), 2.58 (s, 3H), 2.05 (qnt,
J = 7.7 Hz, 2H), 1.72–1.61 (m, 2H), 1.08 (t, J = 7.4 Hz, 3H); 13C NMR
(100 MHz, CDCl3) δ (ppm) 150.05, 144.14, 144.48, 140.29, 137.88,
133.17, 129.10, 127.32, 125.40, 123.69, 122.95, 120.22, 117.87,
114.31, 35.77, 27.98, 22.55, 21.50, 13.98; HRMS (ESI) m/z calcd for
4.1.21. 2-Bromo-6-propylbenzo[4,5]imidazo[1,2-c]quinazoline (6s): [71]
White solid (241.6 mg, 71%); mp
>
220 °C; 1H NMR (CDCl3,
400 MHz) δ (ppm) 8.86 (s, 1H), 8.03–7.56 (m, 6H), 3.43 (s, 2H), 2.14
(s, 2H), 1.26 (s, 3H); 13C NMR (100 MHz, CDCl3) δ (ppm) 151.05,
146.51, 144.39, 140.90, 134.77, 129.29, 129.00, 126.66, 125.76,
123.52 121.18, 120.49, 119.61, 114.38, 37.85, 19.22, 13.85; HPLC
analysis: retention time = 5.592 min; peak area, 97.32%.
C
19H20N3[M+H+], 290.1657; Found 290.1666. HPLC analysis: reten-
tion time = 5.715 min; peak area, 100%.
4.1.28. 2-Methoxy-6-methylbenzo[4,5]imidazo[1,2-c]quinazoline (6z)
White solid (171.1 mg, 65%); mp
>
220 °C; 1H NMR (CDCl3,
400 MHz) δ (ppm) 8.09–8.03 (m, 3H), 7.82 (d, J = 8.9 Hz, 1H), 7.59 (t,
J = 7.6 Hz, 1H), 7.50–7.48 (m, 1H), 7.4 (dd, J = 8.9, 2.8 Hz, 1H), 4.02
(s, 3H), 3.20 (s, 3H); 13C NMR (100 MHz, CDCl3) δ (ppm) 158.94,
147.69, 145.39, 144.24, 136.89, 129.51, 128.92, 125.59, 123.00,
122.18, 120.09, 118.85, 114.14, 103.78, 56.01, 23.94; HRMS (ESI) m/z
calcd for C16H14N3O [M+H+], 264.1137; Found 264.1143. HPLC
analysis: retention time = 4.333 min; peak area, 100%.
4.1.22. 2-Bromo-6-butylbenzo[4,5]imidazo[1,2-c]quinazoline (6t)
White solid (283.4 mg, 80%); mp
>
220 °C; 1H NMR (CDCl3,
400 MHz) δ (ppm) 8.86 (s, 1H), 8.04–7.80 (m, 3H), 7.61–7.53 (m, 3H),
3.47 (s, 2H), 2.07 (s, 2H), 1.66 (s, 2H), 1.10 (s, 3H); 13C NMR
(100 MHz, CDCl3) δ (ppm) 150.0, 147.12, 144.32, 140.92, 134.90,
134.78, 129.27, 129.06, 125.77, 123.53, 121.17, 120.47, 114.39,
35.78, 27.78, 22.51, 13.96; HRMS (ESI) m/z calcd for C18H17BrN3 [M
+Na+], 354.0606; Found 354.0614. HPLC analysis: retention
time = 7.083 min; peak area, 100%.
4.1.29. Naphtho[2′,3′:4,5]imidazo[1,2-c]quinazoline (6aa)
Yellow solid (171.1 mg, 65%); mp > 220 °C; 1H NMR (CDCl3,
400 MHz) δ (ppm) 9.20 (s, 1H), 8.71 (d, J = 8.9 Hz, 1H), 8.43 (s, 1H),
8.38 (s, 1H), 8.12–8.06 (m, 2H), 7.99–7.97 (m, 1H), 7.85–7.81 (m, 1H),
7.72 (t, J = 7.6 Hz, 1H), 7.57–7.52 (m, 2H); 13C NMR (100 MHz,
CDCl3) δ (ppm) 149.26, 136.69, 132.63, 132.35, 130.07, 128.90,
128.66, 128.54, 127.84, 125.20, 125.14, 124.80, 117.07, 106.86;
HRMS (ESI) m/z calcd for C18H12N3 [M+H+], 270.1031; Found
270.1034. HPLC analysis: retention time = 4.483 min; peak area,
100%.
4.1.23. 2-Methylbenzo[4,5]imidazo[1,2-c]quinazoline (6u)
White solid (193.6 mg, 83%); mp
>
220 °C; 1H NMR (CDCl3,
400 MHz) δ (ppm) 9.10 (s, 1H), 8.48 (s, 1H), 8.01–7.96 (m, 2H), 7.88
(d, J = 8.3 Hz, 1H), 7.62–7.56 (m, 2H), 7.51–7.46 (m, 1H), 2.59 (s,
3H); 13C NMR (100 MHz, CDCl3) δ (ppm) 146.41, 143.97, 140.60,
139.18, 135.41, 133.30, 128.25, 128.20, 126.11, 123.86, 123.19,
120.22, 118.99, 110.10, 21.61; HRMS (ESI) m/z calcd for C15H12N3 [M
+H+], 234.1031; Found 234.1040. HPLC analysis: retention
time = 4.158 min; peak area, 100%.
4.1.30. 6-Methylnaphtho[2′,3′:4,5]imidazo[1,2-c]quinazoline (6ab)
White solid (246.5 mg, 87%); mp
>
220 °C; 1H NMR (CDCl3,
4.1.24. 2,6-Dimethylbenzo[4,5]imidazo[1,2-c]quinazoline (6v): [70]
400 MHz): 1H NMR (400 MHz, CDCl3) δ (ppm) 8.70 (d, J = 7.9 Hz,
1H), 8.42 (d, J = 9.4 Hz, 2H), 8.09–8.04 (m, 2H), 7.89–7.81 (m, 1H),
7.81–7.77 (m, 1H), 7.67–7.62 (m, 1H), 7.55–7.51 (m, 2H), 3.29 (s, 3H);
13C NMR (100 MHz, CDCl3) δ (ppm) 148.34, 143.58, 143.30, 143.07,
132.55, 131.65, 130.22, 129.97, 128.23, 128.03, 127.65, 127.31,
125.29, 124.85, 124.65, 117.86, 116.62, 111.38, 24.28; HRMS (ESI) m/
z calcd for C19H14N3 [M+H+], 284.1188; Found 284.1192. HPLC
analysis: retention time = 5.492 min; peak area, 97.32%.
White solid (192.9 mg, 78%); mp
>
220 °C; 1H NMR (CDCl3,
400 MHz) δ (ppm) 8.41 (bs, 1H), 7.97–7.94 (m, 2H), 7.71–7.69 (m,
1H), 7.51–7.47 (m, 2H), 7.39–7.37 (m, 1H), 3.11 (s, 3H), 2.50 (s, 3H);
13C NMR (100 MHz, CDCl3) δ (ppm) 147.80, 146.85, 144.35, 140.33,
138.05, 133.29, 129.52, 127.10, 125.56, 123.72, 122.98, 120.17,
117.78, 114.04, 24.06, 21.51; MS (ESI) m/z: 248.39 (M+H)+; HPLC
analysis: retention time = 4.225 min; peak area, 100%.
4.1.25. 6-Ethyl-2-methylbenzo[4,5]imidazo[1,2-c]quinazoline (6w)
4.1.31. 6-Ethylnaphtho[2′,3′:4,5]imidazo[1,2-c]quinazoline (6ac)
White solid (237.9 mg, 80%); mp 207–209 °C; 1H NMR (CDCl3,
400 MHz) δ (ppm) 8.72 (d, J = 8.0 Hz, 1H), 8.44 (d, J = 4.0 Hz, 2H),
8.10–8.09 (m, 2H), 7.94–7.92 (m, 1H), 7.83–7.78 (m, 1H), 7.67–7.63
(m, 1H), 7.57–7.53 (m, 2H), 3.62 (q, J = 6.7 Hz, 2H), 1.72 (t,
J = 8.0 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ (ppm) 152.21, 143.70,
143.05, 132.47, 131.58, 130.04, 129.84, 128.30, 127.60, 127.58,
125.26, 124.79, 124.65, 117.94, 116.58, 111.82, 29.48, 10.25; HRMS
(ESI) m/z calcd for C20H16N3 [M+H+], 298.1344; Found 298.1343.
HPLC analysis: retention time = 5.683 min; peak area, 95.53%.
White solid (201.2 mg, 77%); mp
>
220 °C; 1H NMR (CDCl3,
400 MHz) δ (ppm) 8.48 (s, 1H), 8.04–8.01 (m, 2H), 7.82–7.80 (m, 1H),
7.63–7.54 (m, 2H), 7.47–7.43 (m, 1H), 3.48 (q, J = 6.7 Hz, 2H), 2.58
(s, 3H), 1.63 (t, J = 6.0 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ (ppm)
150.73, 148.02, 144.40, 140.29, 137.87, 133.14, 129.03, 127.34,
125.36, 123.67, 122.91, 120.13, 117.82, 114.41, 29.29, 21.49, 10.31;
HRMS (ESI) m/z calcd for C17H16N3 [M+Na+], 262.1344; Found
262.1353. HPLC analysis: retention time = 4.933 min; peak area,
100%.
4.1.26. 2-Methyl-6-propylbenzo[4,5]imidazo[1,2-c]quinazoline
[70]
(6x):
4.1.32. 6-Propylnaphtho[2′,3′:4,5]imidazo[1,2-c]quinazoline (6ad)
Yellow solid (236.6 mg, 76%); mp > 220 °C; 1H NMR (CDCl3,
400 MHz): δ (ppm) 8.72–8.70 (m, 1H), 8.07–8.05 (m, 2H), 8.02–7.93
(m, 1H), 7.89–7.87 (m, 1H), 7.81–7.76 (m, 1H), 7.68–7.28 (m, 4H),
3.46 (t, J = 8.0 Hz, 2H), 2.19–2.09 (m, 2H), 1.27 (t, J = 6.0 Hz, 3H);
Yellow solid (198.3 mg, 72%); mp > 220 °C; 1H NMR (CDCl3,
400 MHz) δ (ppm) 8.48 (s, 1H), 8.02–7.95 (m, 2H), 7.79 (d, J = 8.3 Hz,
1H), 7.58–7.54 (m, 2H), 7.47–7.43 (m, 1H), 3.40 (t, J = 7.7 Hz, 2H),
9

P.S. Jadhavar, et al.
BioorganicChemistry99(2020)103774
13C NMR (100 MHz, CDCl3) δ (ppm) 150.64, 148.06, 144.46, 142.20,
131.66, 129.70, 129.42, 129.02, 127.61, 127.58, 126.65, 125.48,
124.11, 123.09, 120.27, 118.17, 114.30, 109.14, 37.87, 19.36, 13.87;
Anal. Calcd for C21H17N3 Elemental Analysis: C, 81.00; H, 5.50; N,
13.49. Found: C, 81.02; H, 5.52; N, 13.47. HPLC analysis: retention
time = 6.258 min; peak area, 100%.
Delhi for financial assistance. M.D.V. also thanks University Grants
Commission (UGC), New Delhi for research fellowship.
Appendix A. Supplementary material
Supplementary data to this article can be found online at https://
doi.org/10.1016/j.bioorg.2020.103774.
4.1.33. 6-Butylnaphtho[2′,3′:4,5]imidazo[1,2-c]quinazoline (6ae)
220 °C; 1H NMR (CDCl3,
References
White solid (257.1 mg, 79%); mp
>
400 MHz) δ (ppm) 8.74–8.71 (m, 1H), 8.46–8.41 (m, 2H), 8.13–8.08
(m, 2H), 7.93–7.92 (m, 1H), 7.83–7.81 (m, 1H), 7.68–7.66 (m, 1H),
7.58–7.55 (m, 2H), 3.59 (t, J = 7.8 Hz, 2H), 2.17–2.13 (m, 2H), 1.77
(q, J = 8.0 Hz, 2H), 1.15 (t, J = 7.4 Hz, 3H); 13C NMR (100 MHz,
CDCl3) δ (ppm) 151.54, 151.01, 143.76, 143.03, 132.50, 131.61,
130.03, 128.34, 128.04, 127.58, 127.55, 125.29, 124.81, 124.67,
117.96, 116.65, 111.73, 108.49, 35.86, 27.89, 22.60, 14.03; HRMS
(ESI) m/z calcd for C22H20N3 [M+H+], 326.1657; Found 326.1662.
HPLC analysis: retention time = 7.133 min; peak area, 97.55%.
[1] World Health Organization (WHO), Global Tuberculosis Report, 2018. https://
www.who.int/tb/publications/global_report/en/.
[2] Nobel Foundation. The Nobel Prize in Physiology or Medicine 1905, http://www.
nobelprize.org/nobel_prizes/medicine/laureates/1905/%253E.
[3] E. Mohr, G. Ferlazzo, C. Hewison, V. De Azevedo, P. Isaakidis, Bedaquiline and
delamanid in combination for treatment of drug-resistant tuberculosis, Lancet
Infect. Dis. 19 (2019) 470.
[4] B.F. de Lima, M. Tavares, Risk factors for extensively drug-resistant tuberculosis: a
review, Clin. Respir. J. 8 (2014) 11–23.
[5] P.S. Jadhavar, M.D. Vaja, T.M. Dhameliya, A.K. Chakraborti, Oxazolidinones as
anti-tubercular agents: discovery, development and future perspectives, Curr. Med.
Chem. 22 (2015) 4379–4397.
[6] K. Dheda, C.E. Barry 3rd, G. Maartens, Tuberculosis, Lancet 387 (2015) 1211–1226.
[7] M.M. Islam, H.M.A. Hameed, J. Mugweru, C. Chhotaray, C. Wang, Y. Tan, J. Liu,
X. Li, S. Tan, I. Ojima, W.W. Yew, E. Nuermberger, G. Lamichhane, T. Zhang, Drug
resistance mechanisms and novel drug targets for tuberculosis therapy, J. Gene.
Genom. 44 (2017) 21–37.
4.1.34. 9,10-Dichloro-6-methylbenzo[4,5]imidazo[1,2-c]quinazoline
(6af): [70]
White solid (90.6 mg, 30%); mp
>
220 °C; 1H NMR (CDCl3,
400 MHz) δ (ppm) 8.62 (d, J = 7.2 Hz, 1H), 8.13 (s, 1H), 8.09 (s, 1H),
7.90–7.89 (m, 1H), 7.83–7.79 (m, 1H), 7.69–7.66 (m, 1H), 3.18 (s, 3H);
13C NMR (100 MHz, CDCl3) δ (ppm) 149.32, 146.83, 143.71, 142.42,
132.42, 129.96, 128.40, 128.12, 127.60, 126.88, 124.24, 121.10,
117.69, 115.30, 23.90; MS (ESI) m/z: 301.93 (M)+; HPLC analysis:
retention time = 5.500 min; peak area, 100%.
[8] H.M.A. Hameed, Md.M. Islam, C. Chhotaray, C. Wang, Y. Liu, Y. Tan, X. Li, S. Tan,
V. Delorme, W.W. Yew, J. Liu, T. Zhang, Molecular targets related drug resistance
mechanisms in MDR-, XDR-, and TDR-mycobacterium tuberculosis strains, Front.
Cell. Infect. Microbiol. 9 (2018) 114.
[9] T.M Walker, M. Merker, A.M Knoblauch, P. Helbling, O.D. Schoch, M.J van der
Werf, K. Kranzer, L. Fiebig, S. Kröger, W. Haas, H. Hoffmann, A. Indra, A. Egli, D.M
Cirillo, J. Robert, T.R. Rogers, R. Groenheit, A.T. Mengshoel, V. Mathys, M.
Haanperä, D. van Soolingen, S. Niemann, E.C Böttger, P.M. Keller, and the MDR-TB
Cluster Consortium, A cluster of multidrug-resistant Mycobacterium tuberculosis
among patients arriving in Europe from the Horn of Africa: a molecular epide-
miological study, Lancet Infect Dis. 18 (2018) 431–440.
4.2. Biological evaluation
[10] P. Shah, T.M. Dhameliya, R. Bansal, M. Nautiyal, D.N. Kommi, P.S. Jadhavar,
J.P. Sridevi, P. Yogeeswari, D. Sriram, A.K. Chakraborti, N-arylalkylbenzo[d]thia-
zole-2-carboxamides as anti-mycobacterial agents: design, new methods of synth-
esis and biological evaluation, Med. Chem. Commun. 5 (2014) 1489–1495.
[11] S. Pancholia, T.M. Dhameliya, P. Shah, P.S. Jadhavar, J.P. Sridevi, P. Yogeshwari,
D. Sriram, A.K. Chakraborti, Benzo[d]thiazol-2-yl(piperazin-1-yl)methanones as
new anti-mycobacterial chemotypes: design, synthesis, biological evaluation and
3D-QSAR studies, Eur. J. Med. Chem. 116 (2016) 187–199.
4.2.1. Determination of minimum inhibitory concentration
Two-fold serial dilutions of each test compound/drug were prepared
and incorporated into agar medium with oleic acid, albumin, dextrose,
and catalase growth supplement to get final concentrations of 50, 25,
12.5, 6.25, 3.125, 1.56, and 0.78 μg/mL. Inoculum of M. tuberculosis
ATCC 27294 was prepared from fresh agar slants with growth supple-
ment adjusted to 1 mg/ mL (wet weight) in Tween 80 (0.05%) saline
diluted to 10−2 to give a concentration of ~107 colony forming unit
(cfu)/mL. Five microliters of this bacterial suspension was spotted onto
agar tubes containing different concentrations of the drug as discussed
above. The tubes were incubated at 37 °C, and final readings (as MIC in
μg/mL) were determined after 28 days. The MIC is defined as the
minimum concentration of compound required to give complete in-
hibition of bacterial growth. This method is similar to that re-
commended by the National Committee for Clinical Laboratory
Standards for the determination of MIC in triplicate. Isoniazid (INH),
Rifampin (R), Ethambutol (E), Pyrazinamide (Z) and Ciprofloxacin
(Cfx) was procured from commercial sources.
[12] T.M. Dhameliya, R. Tiwari, A. Banerjee, S. Pancholia, D. Sriram, D. Panda,
A.K. Chakraborti, Benzo[d]thiazole-2-carbanilides as new anti-TB chemotypes: de-
sign, synthesis, biological evaluation, and structure-activity relationship, Eur. J.
Med. Chem. 155 (2018) 364–380.
[13] P.S. Jadhavar, T.M. Dhameliya, M.D. Vaja, D. Kumar, J.P. Sridevi, P. Yogeeswari,
D. Sriram, A.K. Chakraborti, Synthesis, biological evaluation and structure-activity
relationship of 2-styrylquinazolones as anti-tubercular agents, Bioorg. Med. Chem.
Lett. 26 (2016) 2663–2669.
[14] B. Tanwar, A. Kumar, P. Yogeeswari, D. Sriram, A.K. Chakraborti, Design, devel-
opment of new synthetic methodology, and biological evaluation of substituted
quinolines as new anti-tubercular leads, Bioorg. Med. Chem. Lett. 26 (2016)
5960–5966.
[15] D. Awasthi, K. Kumar, S.E. Knudson, R.A. Slayden, I. Ojima, SAR Studies on tri-
substituted benzimidazoles as inhibitors of Mtb FtsZ for the development of novel
antitubercular agents, J. Med. Chem. 56 (2013) 9756–9770.
[16] K. Kumar, D. Awasthi, S.-Y. Lee, I. Zanardi, B. Ruzsicska, S.E. Knudson, P.J. Tonge,
R.A. Slayden, I. Ojima, Novel trisubstituted benzimidazoles, targeting Mtb FtsZ, as a
new class of antitubercular agents, J. Med. Chem. 54 (2011) 374–381.
[17] S.E. Knudson, K. Kumar, D. Awasthi, I. Ojima, R.A. Slayden, In vitro-in vivo activity
relationship of substituted benzimidazole cell division inhibitors with activity
against mycobacterium tuberculosis, Tuberculosis 94 (2014) 271–276.
[18] S.E. Knudson, D. Awasthi, K. Kumar, A. Carreau, L. Goullieux, S. Lagrange,
H. Vermet, I. Ojima, R.A. Slayden, Cell division inhibitors with efficacy equivalent
to isoniazid in the acute murine Mycobacterium tuberculosis infection model, J.
Antimicrob. Chemother. 17 (2015) 3070–3073.
4.2.2. In vitro cell viability assay
In-vitro cell viability of the anti-TB compounds with
MIC ≤ 6.25 µg/mL was determined against RAW 264.7 cell lines at
50 µg/mL concentration. After 72 h of exposure, viability was assessed
on the basis of cellular conversion of MTT [(3-(4,5-dimethylthiazol-2-
yl)-2,5-diphenyl tetrazolium bromide)] assay into a formazan product
using the non-radioactive cell proliferation assay.
[19] N.S. Chandrasekera, T. Alling, M.A. Bailey, M. Files, J.V. Early, J. Ollinger,
Y. Ovechkina, T. Masquelin, P.V. Desai, J.W. Cramer, P.A. Hipskind, J.O. Odingo,
T. Parish, Identification of phenoxyalkylbenzimidazoles with anti-tubercular ac-
tivity, J. Med. Chem. 58 (2015) 7273–7285.
Declaration of Competing Interest
[20] R.S. Keri, C.K. Rajappa, S.A. Patil, B.M. Nagaraja, Benzimidazole-core as an anti-
mycobacterial agent, Pharmacol. Rep. 68 (2016) 1254–1265.
The authors declare no competing financial interest.
[21] O.A. Olayinka, Y.A. Oluwatosin, V.A. Damilola, E.O. Fisayo, O.O. Ayodele,
Undeniable pharmacological potentials of quinazoline motifs in therapeutic medi-
cine, Am. J. Drug Disc. Dev. 7 (2017) 1–24.
Acknowledgements
[22] T. Gupta, A. Rohila, A. Pathak, M.J. Akhtar, M.R. Haider, M.S. Yar, Current per-
spectives on quinazolines with potent biological activities: a review, Synth.
Commun. 48 (2018) 1099–1127.
The authors thank the Department of Pharmaceuticals (DoP), New
10

P.S. Jadhavar, et al.
BioorganicChemistry99(2020)103774
[23] T. Wang, G. Bemis, B. Hanzelka, H. Zuccola, M. Wynn, C.S. Moody, J. Green,
C. Locher, A. Liu, H. Gao, Y. Xu, S. Wang, J. Wang, Y.L. Bennani, J.A. Thomson,
U. Müh, Mtb PKNA/PKNB dual inhibition provides selectivity advantages for in-
hibitor design to minimize host kinase interactions, ACS Med. Chem. Lett. 8 (2017)
1224–1229.
F. Sorana, E. Marcantoni, Efficient one-pot two catalyst system in the construction
of 2-substituted benzimidazoles: synthesis of benzimidazo[1,2-c]quinazolines, Org.
Biomol. Chem. 13 (2015) 11687–11695.
[45] M.M. Zhang, Y. Wang, J.Q. Liu, X.S. Wang, An efficient green synthesis of 5H-spiro
[benzo[4,5]imidazo[1,2-c]quinazoline-6,3′-indolin]-2′-ones catalyzed by iodine in
ionic liquids, Heterocycl. Commun. 23 (2017) 385–388.
[24] M.V. Papadopoulou, W.D. Bloomer, H.S. Rosenzweig, M. Kaiser, The anti-
trypanosomal and antitubercular activity of some nitro(triazole/imidazole)-based
aromatic amines, Eur. J. Med. Chem. 138 (2017) 1106–1113.
[46] W.J. Si, X. Wang, M. Chen, M.Q. Wang, A.M. Lua, C.L. Yang, Design, synthesis,
antifungal activity and 3D-QSAR study of novel pyrazole carboxamide and niaci-
namide derivatives containing benzimidazole moiety, New J. Chem. 43 (2019)
3000–3010.
[25] S. Bhagat, M. Supriya, S. Pathak, D. Sriram, A.K. Chakraborti, α-
Sulfonamidophosphonates as new anti-mycobacterial chemotypes: design, devel-
opment of synthetic methodology, and biological evaluation, Bioorg. Chem. 82
(2019) 246–252.
[47] R. Kumar, C. Selvam, G. Kaur, A.K. Chakraborti, Synlett 9 (2005) 1401–1404.
[48] A.K. Chakraborti, C. Selvam, G. Kaur, S. Bhagat, Synlett 5 (2004) 851–855.
[49] A.K. Chakraborti, S. Rudrawar, L. Sharma, G. Kaur, Synlett 9 (2004) 1533–1536.
[50] S. Rudrawar, A. Kondaskar, A.K. Chakraborti, Synthesis 15 (2005) 2521–2526.
[51] D. Kumar, S. Rudrawar, A.K. Chakraborti, Aust. J. Chem. 61 (2008) 881–887.
[52] A.H. Shinde, S. Arepally, M.D. Baravkar, D.S. Sharada, Nickel-catalyzed aerobic
oxidative isocyanide insertion: access to benzimidazoquinazoline derivatives via
sequential double annulation cascade (SDAC) strategy, J. Org. Chem. 82 (2016)
331–342.
[26] S. Bhagat, P. Shah, S.K. Garg, S. Mishra, P.K. Kaur, S. Singh, A.K. Chakraborti, α-
Aminophosphonates as novel anti-leishmanial chemotypes: synthesis, biological
evaluation, and CoMFA studies, MedChemComm. 5 (2014) 665–670.
[27] K. Seth, S.K. Garg, R. Kumar, P. Purohit, V.S. Meena, R. Goyal, U.C. Banerjee,
A.K. Chakraborti, 2-(2-Arylphenyl)benzoxazole as a novel anti-inflammatory scaf-
fold: synthesis and biological evaluation, ACS Med. Chem. Lett. 5 (2014) 512–516.
[28] H. Sun, G. Tawa, A. Wallqvist, Classification of scaffold hopping approaches, Drug
Disc. Today 17 (2012) 310–324.
[53] E.C. Taylor, F. Yoneda, Condensed imidazoles from α-diamines and isatoic anhy-
drides, Angew. Chem. Int. Ed. 6 (1967) 878–879.
[29] L.N. Vostrova, T.A. Voronina, T.L. Karaseva, S.A. Gernega, É.I. Ivanov,
A.M. Kirichenko, M.Y. Totrova, L.N. Vostrova, T.A. Voronina, T.L. Karaseva,
S.A. Gernega, É.I. Ivanov, A.M. Kirichenko, M.Y. Totrova, Synthesis and antic-
onvulsant activity of benzimidazo[1,2-c]quinazolines, Pharm. Chem. J. 20 (1986)
404–406.
[54] T.M. Dhameliya, S.S. Chourasiya, E. Mishra, P.S. Jadhavar, P.V. Bharatam,
A.K. Chakraborti, Rationalisation of benzazole-2-carboxylate vs benzazine-3-one/
benzazine-2,3-dione selectivity switch during cyclocondensation of 2-amino thio-
phenols/phenols/anilines with 1,2-biselectrophiles in aqueous medium, J. Org.
Chem. 82 (2017) 10077–10091.
[30] M.F. Braña, M.J. Pérez de Vega, D. Perron, D. Conlon, P.F. Bousquet, S.P. Robinson,
Benzimidazo[1,2-c]quinazoline dimers as potential antitumor agents, J. Heterocycl
Chem. 34 (1997) 807–812.
[55] A.K. Chakraborti, M.K. Nayak, L. Sharma, Selective deprotection of aryl acetates,
benzoates, pivalates and tosylates under non-hydrolytic and virtually neutral con-
dition, J. Org. Chem. 64 (1999) 8027–8030.
[31] C. Lamazzi, S. Léonce, B. Pfeiffer, P. Renard, G. Guillaumet, C.W. Reese, T. Bessona,
Expeditious synthesis and cytotoxic activity of new cyanoindolo[3,2-c]quinolines
and benzimidazo[1,2-c]quinazolines, Bioorg. Med. Chem. Lett. 10 (2000)
2183–2185.
[56] A.K. Chakraborti, L. Sharma, M.K. Nayak, The influence of hydrogen bonding in
activation of nucleophile: PhSH – (Catalytic) KF in NMP as an efficient protocol for
selective cleavage of alkyl/aryl esters and aryl alkyl ethers under nonhydrolytic and
neutral conditions, J. Org. Chem. 67 (2002) 2541–2547.
[32] L.D. Via, O. Gia, S.M. Magno, A.D. Settimo, A.M. Marini, G. Primofiore,
F.D. Settimo, S. Salerno, Synthesis, in vitro antiproliferative activity and DNA-in-
teraction of benzimidazoquinazoline derivatives as potential anti-tumor agents, Il
Farmaco 56 (2001) 159–167.
[57] A.K. Chakraborti, L. Sharma, M.K. Nayak, Demand-based thiolate anion generation
under virtually neutral conditions: the influence of steric and electronic factors on
chemo- and regio-selective cleavage of aryl alkyl ethers, J. Org. Chem. 67 (2002)
6406–6414.
[33] G.D. Galarce, R.E. Foncea, A.M. Edwards, H. Pessoamahana, C.D. Pessoamahana,
R.A. Ebensperger, Biological evaluation of novel 6-Arylbenzimidazo [1,2-c]quina-
zoline derivatives as inhibitors of LPS-induced TNF-alpha secretion, Biol. Res. 41
(2008) 43–50.
[58] B.R. Baker, R.E. Schaub, J.P. Joseph, F.J. McEvoy, J.H. Williams, An antimalarial
alakaloid from hydrangea. XVII. Some 5-substituted derivatives, J. Org. Chem. 17
(1952) 164–176.
[34] B.A. Insuasty, H. Torres, J. Quiroga, R. Abonía, R. Rodríquez, M. Nogeras,
A. Sánchez, C. Saitz, S.L. Alvarez, S.A. Zacchino, Synthesis, characterization and in
vitro antifungal evaluation of novel benzimidazol[1,2-c]quinazolines, J. Chil.
Chem. Soc. 51 (2006) 927–932.
[59] G. Reissenweber, D. Mangold, Oxidation of isatins to isatoic anhydrides and 2,3-
dioxo-1,4-benzoxazines, Angew. Chem. Int. Ed. 4 (1980) 222–223.
[60] M.S. Khajavi, K. Rad-Moghadam, H. Hazarkhani, A facile synthesis of 6-substituted
benzimidazo[1,2-c]quinazolines under microwave irradiation, Synth. Commun. 29
(1999) 2617–2624.
[35] R. Rohini, K. Shanker, P.M. Reddy, Y.-P. Ho, V. Ravinder, Mono and bis-6-ar-
ylbenzimidazo [1,2-c]quinazolines: a new class of antimicrobial agents, Eur. J. Med.
Chem. 44 (2009) 3330–3339.
[61] P. Wayne, National Committee for Clinical Laboratory Standards. Anti-myco-
bacterial susceptibility testing for Mycobacterium tuberculosis, tentative standard
M24-T, 1995.
[36] R. Rohini, K. Shanker, P.M. Reddy, V. Ravinder, Synthesis and antimicrobial ac-
tivities of a new class of 6-arylbenzimidazo[1,2-c]quinazolines, J. Braz. Chem. Soc.
21 (2010) 49–57.
[62] F. Lovering, J. Bikker, C. Humblet, Escape from flatland: increasing saturation as an
approach to improving clinical success, J. Med. Chem. 52 (2009) 6752–6756.
[63] P.D. Leeson, B. Springthorpe, The influence of drug-like concepts on decision-
making in medicinal chemistry, Nat. Rev. Drug Dis. 6 (2007) 881–890.
[64] C.A. Lipinski, F. Lombardo, B.W. Dominy, P.J. Feeney, Experimental and compu-
tational approaches to estimate solubility and permeability in drug discovery and
development settings, Adv. Drug Deliv. Rev. 46 (2001) 3–26.
[37] D.W. Hein, R.J. Alheim, J.J. Leavitt, The use of polyphosphoric acid in the synthesis
of 2-aryl- and 2-alkyl-substituted benzimidazoles, benzoxazoles and benzothiazo-
lesl, J. Am. Chem. Soc. 79 (1957) 427–429.
[38] N.C. Desai, N. Bhatt, M. Kumar, A. Makwana, Synthesis, characterization and an-
timicrobial activity of some 3-(2-(1H-benzo[d]imidazole-2-yl)phenyl)-2-ar-
ylthiazolidin-4-ones, Ind. J. Chem. 50B (2011) 941–945.
[65] Molinspiration Online Software, http://www.molinspiration.com/services/ (ac-
cessed August 2, 2018).
[39] S.S. Chhajed, C.D. Upasani, Synthesis, biological screening and molecular modeling
studies of novel 3-chloro-4-substituted-1-(2-(1H-benzimidazol-2-yl)phenyl))-aze-
tidin-2-ones, J. Enzyme Inhib. Med. Chem. 27 (2011) 504–508.
[40] M.M. Henary, Y. Wu, J. Cody, S. Sumalekshmy, J. Li, S. Mandal, C.J. Fahrni,
Excited-state intramolecular proton transfer in 2-(2'-arylsulfonamidophenyl)benzi-
midazole derivatives: the effect of donor and acceptor substituents, J. Org. Chem.
72 (2007) 4784–4797.
[66] P.D.Q. Dao, S.L. Ho, C.S. Cho, Synthesis of N-fused benzimidazole-4,7-diones via
sequential copper-catalyzed C-N coupling/cyclization and oxidation, ACS Omega 3
(2018) 5643–5653.
[67] A. Davoodnia, Microwave assisted synthesis of fused benzimidazoles, Asian J.
Chem. 22 (2010) 1591–1594.
[68] Q. Liu, H. Yang, Y. Jiang, Y. Zhao, H. Fu, General and efficient copper-catalyzed
aerobic oxidative synthesis of N-fused heterocycles using amino acids as the ni-
trogen source, RSC Adv. 3 (2013) 15636–15644.
[41] B. Saha, S. Sharma, B. Kundu, Efficient method for the synthesis of benzimidazo-
quinazoline derivatives with three-point diversity, Synth. Commun. 37 (2007)
3455–3470.
[69] A. Kumar, N.K. Nandwana, S. Dhiman, H.K. Saini, I. Kumar, Synthesis of quina-
zolinones, imidazo[1,2-c] quinazolines and imidazo[4,5-c]quinolines through
tandem reductive amination of aryl halides and oxidative amination of C(sp3)-H
bond, Eur. J. Org. Chem. 2017 (2017) 514–522.
[42] D.P. Mahana, C.E. Bustos, J.M. Raipán, J.C. Pacheco, H.P. Mahana, Microwave-
assisted synthesis and regioisomeric structural elucidation of novel benzimidazo
[1,2d][1,4]benzodiazepinone derivatives, Arkivoc xii (2009) 131–140.
[43] Y.X. Liao, K. Li, M.Y. Wu, T. Wu, X.Q. Yu, A selenium-contained aggregation-in-
duced “turnon” fluorescent probe for hydrogen peroxide, Org. Biomol. Chem. 12
(2014) 3004–3008.
[70] S. Xu, J. Lu, H. Fu, Copper-catalyzed cascade synthesis of benzimidazoquinazoline
derivatives under mild condition, Chem. Commun. 47 (2011) 5596–5598.
[71] R.H. Bahekar, A.R.R. Rao, New Bronchodilators-2: synthesis of 6-alkylbenzimidazo
[1,2-c]quinazolines, Ind. J. Pharm. Sci. 62 (2000) 41–45.
[44] C. Cimarelli, M.D. Nicola, S. Diomedi, R. Giovannini, D. Hamprecht, R. Properzi,
11