SAR studies on trisubstituted benzimidazoles as inhibitors of Mtb FtsZ for the development of novel antitubercular agents

Article abstract of DOI:10.1021/jm401468w

FtsZ, an essential protein for bacterial cell division, is a highly promising therapeutic target, especially for the discovery and development of new-generation anti-TB agents. Following up the identification of two lead 2,5,6-trisubstituted benzimidazole

Full text of DOI:10.1021/jm401468w

Article
pubs.acs.org/jmc
SAR Studies on Trisubstituted Benzimidazoles as Inhibitors of Mtb
FtsZ for the Development of Novel Antitubercular Agents
Divya Awasthi,† Kunal Kumar,† Susan E. Knudson,‡ Richard A. Slayden,‡ and Iwao Ojima†,*
†Department of Chemistry and Institute of Chemical Biology and Drug Discovery, Stony Brook University, Stony Brook, New York
11794-3400, United States
‡Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado 80523-1682, United
States
S
* Supporting Information
ABSTRACT: FtsZ, an essential protein for bacterial cell
division, is a highly promising therapeutic target, especially for
the discovery and development of new-generation anti-TB
agents. Following up the identification of two lead 2,5,6-
trisubstituted benzimidazoles, 1 and 2, targeting Mtb-FtsZ in
our previous study, an extensive SAR study for optimization of
these lead compounds was performed through systematic
modification of the 5 and 6 positions. This study has
successfully led to the discovery of a highly potent advanced
lead 5f (MIC = 0.06 μg/mL) and several other compounds with comparable potencies. These advanced lead compounds possess
a dimethylamino group at the 6 position. The functional groups at the 5 position exhibit substantial effects on the antibacterial
activity as well. In vitro experiments such as the FtsZ polymerization inhibitory assay and TEM analysis of Mtb-FtsZ treated with
5f and others indicate that Mtb-FtsZ is the molecular target for their antibacterial activity.
structure known as the “Z-ring”.10−14 The recruitment of
INTRODUCTION
■
several other cell division proteins leads to Z-ring contraction,
Tuberculosis (TB) was responsible for 1.4 million deaths in
resulting in septum formation and eventually cell division.10−14
2011, which was second only to HIV/AIDS related fatalities
Accordingly, the inhibition of proper FtsZ assembly would
among all infectious diseases.1,2 TB is caused by Mycobacterium
block the septum formation and then cell division, which
tuberculosis (Mtb) and is highly contagious when airborne.3 It
should lead to bacterial growth inhibition and cell
has been estimated that 90% of humans who are exposed to or
infected with the pathogen have latent TB, which has a 10%
death.6,8,9,15−17
Recently, FtsZ inhibitors have been actively investigated for
chance of progressing to an active-TB diseased state during
their lifetime.4,5 Recent statistics from the World Health
pathogen specific as well as broad-spectrum antibacterial drug
discovery against a variety of pathogens.6,18 Several classes of
Organization (WHO) indicate an estimated 8.7 million new TB
cases globally in 2011.1,2 Among these cases, 13% were HIV-
compounds have been identified as promising leads for
antibacterial drug development, including OTBA,19 2-alkox-
positive individuals with 430 000 deaths, which demonstrates
ycarbonylaminopyridines,20 2-carbamoylpteridine,21 taxanes,15
the ability of the bacteria to target immunocompromised
benzimidazoles,22 GTP analogues,23,24 benzo[c]-
patients.1,2 It has been reported that MDR-TB is the causative
phenathridines,25,26 isoquinolines,27−29 PC190723,30,31 Zan-
agent of 3.7% of the new cases and 20% of the previously
trins,7 and chrysophaentins.32 However, against Mtb FtsZ,
only taxanes15 and benzimidazoles22 have emerged as
promising leads in the past several years after the pioneering
work by the Southern Research Institute group.20,21,27,33
We have previously reported the design and synthesis of
libraries of 2,5,6- and 2,5,7-trisubstituted benzimidazoles, which
gave a good number of hit compounds through screening
against Mtb H37Rv strain at 5 μg/mL.22 Moreover, selected
lead compounds from these hits were found to exhibit excellent
MIC values in the range of 0.39−6.1 μg/mL against drug
sensitive (H37Rv) as well as drug resistant strains (Figure 1).22
reported cases worldwide.1,2 MDR-TB resistant to at least one
of the three injectable “second-line” antibiotics and fluoroqui-
nolones is classified as extensively drug-resistant TB (XDR-
TB). About 9% of MDR-TB cases have been classified as XDR-
TB by WHO, and 84 countries have reported at least one case
of XDR-TB.1,2
The widespread resistance to existing therapeutics has
become a key hurdle for effective treatment of the disease.
Therefore, in order to counterattack the drug resistance, there
is a dire need for the identification of novel therapeutic targets.
In this context, FtsZ, an essential bacterial cytokinesis protein,
is a highly promising therapeutic target.6−9 In the presence of
GTP, FtsZ polymerizes bidirectionally at the center of the cell
on the inner membrane to form a highly dynamic helical
Received: September 22, 2013
© XXXX American Chemical Society
A
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Figure 1. Early lead compounds from hit benzimidazoles.22
These lead compounds inhibited Mtb FtsZ assembly in a dose
dependent manner while enhancing the GTPase activity.22
Subsequently, benzimidazoles 1 and 2 were found to be
bactericidal and also active against nonreplicating Mtb grown
under low oxygen conditions.34 The latter result is particularly
exciting, since it indicates that these compounds have potential
to be effective against latent TB infection. Furthermore, 1
exhibited good efficacy in vivo in the standard acute infection
model using immune incompetent GKO mice.35 These
promising results will be published elsewhere shortly.
Since these two lead compounds have shown very promising
antibacterial activities in vitro and in vivo, we set out for the
SAR study and optimization of these leads through systematic
structural modifications at the 5 and 6 positions, keeping the
cyclohexyl group at the 2 position intact as shown in Figure 2.
5-fluoroaniline with various amines afforded 5-dialkylaminodi-
nitroanilines 2a−g in 94−98% yields. The acylation of 2a−g
with cyclohexanecarbonyl chloride gave the corresponding N-
acylanilines 3a−g in 75−95% yields. One-pot reduction and the
subsequent cyclization in the presence of stannous chloride
dihydrate and 4 M hydrochloric acid gave 5-aminobenzimida-
zoles 4a−g in 65−79% yields. The derivatization of 4a−g was
carried out using five different methods depending on the
functional group to be introduced, and analytically pure
compounds 5, 6, and 7 were obtained in 42−97% yields after
chromatographic purification. Compounds 5, 6, and 7 bear a
carbamate, urea, and amide group, respectively, at the 5
position.
EVALUATION OF ANTIBACTERIAL ACTIVITIES AND
■
SAR STUDY
The 2,5,6-trisubstituted benzimidazoles 5, 6, and 7 (63
compounds) were evaluated for their activity against Mtb
H37Rv using the “microplate Alamar Blue sssay (MABA)”.36
The antibacterial activities of the compounds are indicated by
MIC values.
Since the early lead compounds 1 (MIC = 0.63 μg/mL) and
2 (MIC = 0.39 μg/mL) possess a carbamate group at the 5
position, we examined the effect of different carbamate groups
at the 5 position as well as different dialkylamino groups at the
6 position on the potency against Mtb (H37Rv). Results are
summarized in Table 1.
As Table 1 shows, the substituents at both 5 and 6 positions
have substantial effects on antibacterial activity, but it is very
clear that bulky dialkylamino groups at the 6 position are
detrimental to the potency of compounds (5b, 5c, 5d, 5e). On
the contrary, a smaller dialkyl group, i.e., dimethylamino group,
at the 6 position exerts a remarkable enhancement in potency
(5f, 5h, 5l, 5p), leading to the discovery of a highly active lead
compound 5f (MIC = 0.06 μg/mL), which is 11 times more
potent than 1. The nature of carbamate groups at the 5 position
exhibits moderate effects on the potency. An analogue of 1, 5g
bearing a branched alkyl carbamate group at the 5-position
showed substantially lower potency with MIC > 50 μg/mL, but
another analogue 5h with a benzyl carbamate group showed
Figure 2. Optimization of 2,5,6-trisubstituted benzimidazoles.
We describe here our SAR study and successful optimization of
the early lead compounds, which has led to the identification of
a highly potent lead compound 5f (MIC = 0.06 μg/mL) and
others with comparable potencies.
CHEMICAL SYNTHESIS
■
Synthesis of compounds for the optimization library of 2,5,6-
trisubstituted benzimidazoles (63 compounds in total) is
outlined in Scheme 1, which in most part follows the protocol
previously published by our laboratory.22 The aromatic
nucleophilic substitution of commercially available 2,4-dinitro-
B
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a
22
,
Scheme 1. Synthesis of 2,5,6-Trisubstituted Benzimidazoles
a
Reagents and conditions: (a) R1R2NH, DIPEA, THF, 2 h, room temperature (rt)/12 h, 50 °C; (b) cyclohexanecarbonyl chloride, pyridine, reflux,
overnight; (c) SnCl2·2H2O, 4 M HCl, EtOH, reflux, 4 h; (d) R3COCl, Et3N, 0 °C to rt, overnight; (e) R3COOH, EDC.HCl, DMAP, CH2Cl2, reflux,
overnight; (f) R3NCO, Et3N, reflux, overnight; (g) (i) 1,1′-carbonyldiimidazole, CH2Cl2, reflux, 4 h; (ii) R3OH, CH2Cl2, reflux, overnight; (h)
R3OSu ester, CH2Cl2, 0 °C to rt, overnight.
enhanced potency. The introduction of an ethylene glycol
moiety into the carbamate group should increase solubility in
aqueous media. 2-(Methoxy)ethyl and 2-(ethoxy)ethyl carba-
mate groups are well tolerated, and 5l bearing a 5-
dimethylamino moiety possesses high potency. However, the
use of the MeO(CH2CH2O)2-carbamate group resulted in a
substantial decrease in potency (5m). A polar and lipophilic
2,2,2-trifluoroethyl carbamate group is well tolerated (5n, 5o,
5p).
Next, we examined the effect of urea moieties at the 5
position on the antibacterial activity. As Table 2 shows, the
introduction of a urea group to the 5 position in place of a
carbamate group is detrimental to the potency (6a−f).
Nevertheless, compound 6g with a 5-dimethylamino group
retains good potency.
As exemplified in Figure 1, we identified several lead
compounds showing good antibacterial activities (MIC = 3.1
μg/mL), which bear a benzamide group at the 5 position. In a
manner similar to compounds 1 and 2, 2-cyclohexyl-6-N,N-
diethylamino-5-(4-methoxybenzamido)-1H-benzo[d]imidazole
(4) is equally active against drug-sensitive (H37Rv) and drug-
resistant clinical isolates of Mtb.22 Since the amide linkage may
have better metabolic stability in vivo, we synthesized 40
compounds for the SAR study and evaluated their activity
against Mtb H37Rv. Results are summarized in Table 3.
Compounds 7a-1−15 bear a 6-diethylamino group, 7b-1−7
bear a 6-pyrrolidino group, 7c-1−17 bear a 6-dimethylamino
group, and 7d bears a 6-dipropylamino group.
is by far the best substituent in this library of 2,5,6-trisubstituted
benzimidazoles. As anticipated, 5-benzamido-6-dipropylamino-
benzimidazole (7d) does not show appreciable activity.
In the 6-diethylamino series of compounds (7a-1−15), the
potency is very sensitive to the substitution pattern of the 5-
benzamide moiety. Thus, the compounds with 4-difluorome-
thoxy-, 4-trifluoromethoxy-, 4-ethoxy-, 4-propyl-, 4-bromo-, 4-
fluoro-, 2,4-difluoro-, and 3-bromobenzamide moieties at the 5
position do not show appreciable antibacterial activity (MIC >
100 μg/mL). 4-Methyl-, 4-ethyl-, 4-dimethylaminobenzamide
moieties as well as pyrazin-2-ylcarbonylamino and pentanamide
moieties are tolerated. 4-Ethylbenzamide analogue of com-
pound 4, 7a-5, shows better potency than the parent
compound (MIC = 1.56 μg/mL). 4-Dimethylamino- and 3-
vinylbenzamide moieties as well as ethoxyacetamide moiety
show only modest activities.
In the 6-pyrrolidinylamino series of compounds (7b-1−7),
the potency of the compounds is much less sensitive to the
substitution pattern of the 5-amido moiety. Nevertheless, 3-
phenylpropanamide and ethoxyacetamide moieties decrease
potency. Two compounds bearing 4-methylbenzamide and 4-
bromobenzamide moieties, 7b-3 (MIC = 3.13 μg/mL) and 7b-
4 (MIC = 1.56 μg/mL) possess better activity than compound
4.
In the 6-dimethylamino series of compounds (7c-1−17), all
compounds examined possess good to excellent antibacterial
activities, wherein nine compounds have MIC less than 1.0 μg/
mL. The results clearly indicate that the introduction of the
dimethylamino group to the 6 position is a breakthrough in this
SAR study. Also, the 4-substituents on the 5-benzamide moiety
are found to be beneficial to increase the potency. The most
As Table 3 shows, the bulkiness of the 6-dialkylamino group
exerts a dramatic influence on the antibacterial activity of these
compounds, and it is very clear that the 6-dimethylamino group
C
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Table 1. Antibacterial Activity of Benzimidazoles 5 against
Mtb H37Rv Strain (MIC, μg/mL) and Their Cytotoxicity
(IC50, μg/mL)
Table 2. Antibacterial Activity of Benzimidazoles 6 against
Mtb H37Rv Strain (MIC, μg/mL) and Their Cytotoxicity
(IC50, μg/mL)
The unbiased ability of these compounds to kill drug-resistant
strains of Mtb demonstrates the significance of FtsZ as the drug
target to develop new generation anti-TB drugs.
Mtb-FtsZ POLYMERIZATION INHIBITORY ASSAY
■
To confirm that this series of compounds actually target Mtb
FtsZ, the most potent compound 5f was selected for the light
scattering assay.22,38 In addition, compounds 5p and 7c-6 with
MIC of 0.63 and 0.16 μg/mL, respectively, were also tested. As
Figure 3 shows, 5f, 5p, and 7c-6 inhibit the assembly of Mtb
FtsZ in a dose dependent manner. Since the extent of light
scattering correlates to the extent of FtsZ polymerization/
aggregation, reduction in light scattering in the presence of the
compounds demonstrates their inhibitory effect on Mtb FtsZ
assembly.
TRANSMISSION ELECTRON MICROSCOPY (TEM)
ANALYSIS
■
TEM imaging of Mtb FtsZ is also useful to validate the
molecular target of lead compounds.22 Mtb FtsZ (5 μM) was
incubated with 40 or 80 μM of 5f followed by addition of GTP
(25 μM) to initiate polymerization. The TEM images of Mtb
FtsZ treated with 40 μM 5f clearly show reduction in the
density and population of FtsZ polymers, protofilaments, and
aggregates when compared to the untreated protein polymers
(Figure 4A,B). The effect is more apparent at 80 μM treatment
(Figure 4C). In addition to inhibiting the assembly of Mtb FtsZ
in the presence of GTP, 5f was also capable of disrupting the
formed FtsZ polymers and aggregates as shown by images D
and E. Mtb FtsZ (5 μM) was polymerized by adding GTP (25
μM) and then treated with 40 or 80 μM 5f. The polymerized
protein was depolymerized/disassembled after the addition of
5f. These results clearly indicate that 5f interacts with Mtb FtsZ
and deters its normal GTP initiated polymerization.
potent compounds in this series, at present, are 7c-4 and 7c-6
(MIC = 0.16 μg/mL). Thus, 7c-4 and 7c-6 have emerged as
advanced lead compounds together with 5f for further
preclinical drug development. Table 4 lists nine most potent
compounds found based on this SAR study.
These advanced lead compounds are also highly active
against clinical isolates of Mtb, possessing different resistance
profiles. Table 5 shows the antibacterial activity of two
representative advanced lead compounds, 5f and 7c-6, against
four Mtb strains: laboratory strain H37Rv (drug sensitive),
clinical strain NHN382 (isoniazide-resistant, Kat G S315t
mutation),37 clinical strain TN587 (isoniazide-resistant, Kat G
3315T mutation),37 and clinical strain W210 (drug-sensitive).37
Both 5f and 7c-6 possess substantially higher potency than
compound 1 for all strains, and more importantly there is no
difference in their potencies against drug-resistant Mtb strains.
D
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Table 3. Antibacterial Activity of Benzimidazoles 7 against Mtb H37Rv Strain (MIC, μg/mL) and Their Cytotoxicity (IC50, μg/
a
mL)
a
n.d.* = not determined.
compounds through systematic modifications. It has been
found that the nature of the 6-amino group exerts remarkable
effects on the antibacterial activity. For example, long or bulky
6-alkylamino groups are detrimental to the activity. On the
contrary, a small dimethylamino group at this position
dramatically increases the potency. This breakthrough finding
in this SAR study has led to the discovery of 5f with exceptional
CONCLUSIONS
■
The extensive SAR study on 2-cyclohexyl-5,6-disubstituted
benzimidazoles for their antibacterial activities against Mtb
H37Rv strain was performed, building upon the identification
of promising early lead compounds 1 and 2 in our previous
study. The purpose of this SAR study was to optimize the
nitrogen substituents at the 5 and 6 positions of these two lead
E
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Table 4. Nine Most Potent 6-Dimethylaminobenzimidazoles
(Mtb H37Rv, μg/mL)
Figure 3. Dose dependent inhibition of Mtb FtsZ polymerization by 5f
(A), 5p (B), and 7c-6 (C).
Table 5. Antibacterial Activity (MIC μg/mL) of 5f and 7c-6
against Clinical Isolates of Mtb
Furthermore, the TEM analysis has revealed that the preformed
FtsZ polymers and their aggregates are effectively disassembled
by 5f. These observations strongly suggest that the advanced
lead benzimidazoles have a novel mechanism of action on the
inhibition of Mtb FtsZ assembly and Z-ring formation.
Extensive preclinical evaluations for the pharmacological
properties of these advanced lead compounds as well as in
vivo efficacy evaluations are actively underway, and the results
will be reported in due course.
Mtb strain
compd
INH
H37Rv
NHN382
TN587
W210
0.013
0.63
0.06
0.16
0.25
1.25
0.06
0.16
0.25
1.25
0.13
0.16
0.01
1.25
0.06
0.16
SB-P3G2
5f
7c-6
EXPERIMENTAL SECTION
potency (MIC = 0.06 μg/mL), which bears a butoxycarbony-
lamino group at the 5 position and a dimethylamino group at
the 6 position. Also, 12 other compounds were found to
possess comparable potencies (MIC < 0.63 μg/mL), including
7c-6 (MIC = 0.16 μg/mL), bearing a 4-ethylbenzamido group
at the 5 position and a dimethylamino group at the 6 position.
These advanced lead compounds do not show appreciable
cytotoxicity against Vero cells (IC50 > 100 μg/mL). The
advanced leads 5f and 7c-6 exhibit the same potencies against
drug-resistant Mtb clinical isolates, as anticipated. Other
important findings in this SAR study include the fact that
urea groups at the 5 position are detrimental to the antibacterial
activity of this series of benzimidazoles, while carbamate and
amide groups are well tolerated, although alkylamides and
heteroaromatic amides are not favorable. The light scattering
assays for FtsZ polymerization inhibition by selected advanced
lead compounds, 5f, 5p, and 7c-6, show effective dose-
dependent inhibition, which validates that Mtb FtsZ is the
molecular target of these compounds. The TEM analysis also
supports the mechanism of action for these compounds.
■
Methods. 1H and 13C NMR spectra were measured on a Bruker or
Varian 300, 400, or 500 MHz NMR spectrometer. Melting points were
measured on a Thomas-Hoover capillary melting point apparatus and
are uncorrected. TLC was performed on silica coated aluminum sheets
(thickness 200 μm) or alumina coated (thickness 200 μm) aluminum
sheets supplied by Sorbent Technologies, and column chromatog-
raphy was carried out on Siliaflash P60 silica gel, 40−63 μm (230−400
mesh), supplied by Silicycle. Aluminum oxide, activated, neutral,
Brockmann grade I, 58 Å, was supplied by Alfa Aesar. High-resolution
mass spectra were obtained from the Mass Spectrometry Laboratory,
University of Illinois at UrbanaChampaign, Urbana, IL. Purity of
synthesized compounds was determined by a Shimadzu LC-2010A
HT series HPLC assembly or Agilent 1100 series HPLC assembly.
Four analytical conditions were used and noted as a part of the
characterization data for synthesized compounds. HPLC (1):
Adsorbosphere silica 5 μm, 250 mm × 4.6 mm column, isopropanol
and hexanes, flow rate of 1 mL/min, t = 0−40 min, gradient of 5−50%
isopropanol. HPLC (2): Adsorbosphere silica 5 μm, 250 mm × 4.6
mm column, isopropanol and hexanes, flow rate of 1.0 mL/min, t = 0−
20 min, gradient of 5−50% isopropanol. HPLC (3): Kinetex PFP, 2.6
μm, 4.6 mm × 100 mm column, methanol and water, flow rate of 0.3
F
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Figure 4. TEM Images of FtsZ. FtsZ (5 μM) was polymerized by GTP (25 μM) in the absence (A) and presence of 5f at 40 μM (B) and 80 μM
(C). Images D and E display the effect of the compound on preformed polymers, wherein FtsZ polymers formed after addition of GTP were treated
with 40 μM (D) or 80 μM (E) 5f. Images are at 49000× magnification (scale bar 500 nm).
mL/min, t = 0−30 min, gradient of 40−95% MeOH. HPLC (4):
Kinetex PFP, 2.6 μm, 4.6 mm × 100 mm column, solvent A of water/
acetonitrile, 95:5 (25 mM ammonium acetate, pH 6.5), solvent B of
water/acetonitrile, 5:95 (25 mM ammonium acetate, pH 6.5),
temperature of 25 °C, flow rate of 1.0 mL/min, t = 0−15 min,
gradient of 20−95% solvent B. Measurements were made at 254 and
303 nm.
Light scattering assays were performed using a PTI-QM4
spectrofluorimeter. FEI Tecnai12 BioTwinG transmission electron
microscope with an AMT XR-60 CCD digital camera system was used
to acquire transmission electron microscopy images.
Materials. BL21(DE3) cells, His-Bind protein purification resin,
and the buffers were purchased from Novagen. Bradford kit for protein
concentration determination was purchased from Sigma. Buffer salts
(reagent grade or better), solvents (HPLC grade or better), and all the
other chemicals were purchased from Fisher Scientific Co. (Pittsburgh,
PA). The chemicals were purchased from Aldrich Co., Synquest Inc.,
and Sigma and purified before use by standard methods.
Tetrahydrofuran (THF) was freshly distilled from sodium metal and
benzophenone. Dichloromethane was also distilled immediately prior
to use under nitrogen from calcium hydride. Compounds, 2a, 2b, 2e−
g, 3a, 3b, 3e−g, 4a, 4b, and 4e−g were prepared using the procedures
previously published by us.22
(br s, 6 H), 6.01 (br s, 1 H), 6.41 (br s, 2H), 8.8 (br s, 1 H); 13C NMR
(101 MHz, CDCl3) δ 42.5 100.7, 123.6, 128.8, 130.5, 147.9, 150.7.
HRMS (ESI) m/z calcd for C8H10N4O4 H+: 227.0775. Found:
227.0778 (Δ = 1.4 ppm).
1-Cyclohexylamido-2,4-dinitro-5-N,N-di-n-propylaminoben-
zene (3d). A solution of 2d (1.25 g, 4.40 mmol) and cyclo-
hexanecarbonyl chloride (0.721 mL, 5.34 mmol) in pyridine (10 mL)
was refluxed overnight. After completion of the reaction, pyridine was
removed in vacuo to give a brown solid. This crude mixture was
washed with methanol and collected by filteration to afford 3d as a
yellow solid which was used directly in the following step. MS (ESI)
m/z 393.2 (M + 1)+.
The same procedure was used for the synthesis of 3c.
1-Cyclohexylamido-5-N,N-dimethylamino-2,4-dinitroben-
zene (3c). Yellow solid (90% yield); mp 148−149 °C; 1H NMR (300
MHz, CDCl3) δ 1.21−1.43 (m, 3 H), 1.67−1.79 (m, 1 H), 1.80−1.94
(m, 2 H), 1.97−2.09 (m, 2 H), 2.32−2.45 (m, 1 H), 3.06 (s, 6 H), 8.60
(s, 1 H), 8.85 (s, 1 H), 11.00 (s, 1 H); 13C NMR (101 MHz, CDCl3) δ
25.5, 25.6, 29.4, 42.5, 47.3, 106.1, 125.0, 127.4, 131.3, 138.7, 150.1,
175.9. HRMS (ESI) m/z calcd for C15H20N4O5H+: 337.1507. Found:
337.1511 (Δ = 1.3 ppm).
5-Amino-2-cyclohexyl-6-N,N-di-n-propylamino-1H-benzo-
[d]imidazole (4d). To a solution of 3d from a previous step (1.75 g,
4.45 mmol) in ethanol (50 mL) was added solid stannous chloride
dihydrate (7.03 g, 31.1 mmol). Concentrated hydrochloric acid (15
mL) was added to the reaction mixture such that the final
concentration of HCl is 4 M in the reaction flask. The reaction
mixture was refluxed for 4 h. Upon completion, the reaction mixture
was basified with 30% sodium hydroxide solution. Excess stannous
chloride formed a soluble salt in excess base. The desired product was
extracted with dichloromethane and purified by flash chromatography
on silica gel using ethyl acetate as eluent to afford 4d as a pale green
solid (721 mg, 55% yield in two steps): mp 76−78 °C; 1H NMR (400
MHz, CDCl3) δ 0.78 (t, 6 H, J = 7.4 Hz), 1.20−1.23 (m, 3 H), 1.35−
1.40 (m, 4 H), 1.59−1.63 (m, 5 H), 2.01 (d, 2 H, J = 7.28 Hz), 2.77
(m, 5 H), 6.80 (s, 1 H), 7.25 (s, 1 H); 13C NMR (100 MHz, CDCl3) δ
11.60, 20.45, 25.64, 25.91, 31.84, 38.43, 57.04, 98.19, 110.0, 132.9,
134.3, 135.0, 140.0, 158.0. HRMS (ESI) m/z calcd for C19H30N4H+:
315.2543. Found: 315.2549 (Δ = 1.9 ppm).
2,4-Dinitro-5-N,N-di-n-propylaminoaniline (2d). To a solution
of 5-fluoro-2,4-dinitroaniline (1.01 g, 4.97 mmol) and diisopropyle-
thylamine (DIPEA) (1.04 mL, 5.96 mmol) in THF (50 mL) was
added di-n-propylamine (818 μL, 5.96 mmol). The reaction mixture
was stirred at 50 °C overnight. After completion of the reaction,
solvent was evaporated and water was added to give a yellow
precipitate. The solution was extracted with dichloromethane (30 mL
× 3). The organic layer was collected, dried over anhydrous
magnesium sulfate, and evaporated to give 2d as a yellow solid
1
(1.25 g, 89% yield): mp 68−70 °C; H NMR (400 MHz, CDCl3) δ
0.86 (t, 6 H, J = 7.4 Hz), 1.60 (m, 4 H), 3.12 (t, 4 H, J = 7.28 Hz),
6.09 (s, 1 H), 6.40 (br s, NH), 8.75 (s, 1 H); 13C NMR (100 MHz,
CDCl3) δ 11.28, 20.45, 53.51, 102.9, 123.4, 128.3, 131.7, 147.6, 150.1;
MS (ESI) m/z 283.1 (M + 1)+.
The same procedure was used for the synthesis of 2c.
5-N,N-Dimethylamino-2,4-dinitroaniline (2c). Yellow solid
1
(98% yield); mp 164−165 °C; H NMR (300 MHz, CDCl3) δ 2.94
The same procedure was used for the synthesis of 4c.
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dx.doi.org/10.1021/jm401468w | J. Med. Chem. XXXX, XXX, XXX−XXX

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5-Amino-2-cyclohexyl-6-N,N-dimethylamino-1H-benzo[d]-
imidazole (4c). Light brown solid (69% yield); mp 135−137 °C; 1H
NMR (300 MHz, CDCl3) δ 1.14−1.46 (m, 4 H), 1.54−1.86 (m, 5 H),
1.99−2.17 (m, 2 H), 2.64 (s, 6 H), 2.73−2.87 (m, 1 H), 6.81 (s, 5 H),
7.26 (s, 1 H); 13C NMR (101 MHz, CDCl3) δ 26.0, 26.2, 32.2, 38.8,
44.8, 98.9, 106.7, 133.1, 134.5, 138.0, 138.3, 158.2. HRMS (ESI) m/z
calcd for C15H22N4H+: 259.1917. Found: 259.1914 (Δ = −1.2 ppm).
2-Cyclohexyl-5-(3-propylurea)-6-pyrrolidinyl-1H-benzo[d]-
imidazole (6f). To a solution of 4b (100 mg, 0.35 mmol) in
dichloromethane (DCM) (3 mL) was added n-propyl isocyanate (32.9
mg, 0.39 mmol) and triethylamine (0.39 mmol). The mixture was
refluxed for 14 h and then diluted with ethyl acetate, transferred to a
separatory funnel, and washed with water, saturated sodium
bicarbonate solution, and brine. The organic layer was dried over
magnesium sulfate and concentrated using rotary evaporator. The
crude product was purified by flash chromatography (column was
packed with DCM, 2% methanol was used steadily increasing to 5%
methanol) to obtain the product as a white solid (80% yield); mp
231−232 °C; 1H NMR (400 MHz, methanol-d4) δ 0.95 (t, J = 7.2 Hz,
3 H), 1.26−1.69 (m, 8 H), 1.75−1.78 (m, 1 H), 1.84−1.88 (m, 2 H),
1.92−2.11 (m, 6 H), 2.83 (m, 1 H), 3.04 (s, 4 H), 3.16 (t, J = 7.03 Hz,
2 H), 7.24 (s, 1 H), 7.92 (s, 1 H); 13C NMR (126 MHz, methanol-d4)
δ 11.9, 24.6, 25.5, 27.1, 27.4, 33.0, 40.0, 42.9, 53.9, 106.3, 107.1, 130.9,
134.5, 136.5, 139.2, 159.2, 160.5. HRMS (FAB) m/z calcd for
C21H31N5OH+: 370.2601. Found: 370.2611 (Δ = 2.6 ppm). HPLC
(1): t =17.7 min, purity > 99%.
5-(4-Benzylurea)-2-cyclohexyl-6-pyrrolidinyl-1H-benzo[d]-
imidazole (6e). White solid (91% yield); mp 225−226 °C; 1H NMR
(500 MHz, methanol-d4) δ 1.26−1.49 (m, 3 H), 1.56−1.68 (m, 2 H),
1.71−1.79 (m, 1 H), 1.80−1.89 (m, 2 H), 1.92 (br s, 4 H), 1.98−2.10
(m, 2 H), 2.80−2.85 (m, 1 H), 3.01 (br s, 4 H), 4.39 (s, 2 H), 7.18−
7.26 (m, 2 H), 7.26−7.37 (m, 4 H), 7.96 (s, 1 H); 13C NMR (126
MHz, methanol-d4) δ 25.5, 27.1, 27.3, 33.0, 39.9, 44.8, 53.8, 106.2,
107.4, 128.2, 128.4, 129.7, 130.7, 134.4, 136.5, 139.4, 141.3, 159.1,
160.5. HRMS (FAB) m/z calcd for C25H31N5OH+: 418.2601. Found:
418.2604 (Δ = 0.6 ppm). HPLC (1): t = 14.5 min, purity > 99%.
5-(4-Butylurea)-2-cyclohexyl-6-N,N-dimethylamino-1H-
benzo[d]imidazole (6g). White solid (74% yield); mp 185−186 °C;
1H NMR (400 MHz, methanol-d4) δ 1.71 (t, J = 7.28 Hz, 3 H), 1.98−
2.27 (m, 7 H), 2.30−2.44 (m, 2 H), 2.49 (d, J = 12.30 Hz, 1 H), 2.54−
2.65 (m, 2 H), 2.73−2.85 (m, 2 H), 3.38 (s, 6 H), 3.57 (m, 1 H), 3.89
(q, J = 6.53 Hz, 2 H), 4.15 (br s, 1 H), 7.80 (br s, 1 H), 8.05 (br s, 1
H), 8.83 (br s, 1 H), 8.97 (s, 1 H), 12.54 (br s, 1 H); 13C NMR (126
MHz, methanol-d4) δ 14.3, 21.2, 27.0, 27.3, 32.9, 33.5, 39.7, 40.7, 45.8,
104.3, 107.7, 132.3, 134.3, 135.0, 141.4, 158.8, 160.1. HRMS (FAB)
m/z calcd for C20H31N5OH+: 358.2601. Found: 358.2609 (Δ = 2.1
ppm). HPLC (1): t = 15.3 min, purity > 99%.
5-Butoxycarbonylamino-2-cyclohexyl-6-N,N-dipropylami-
no-1H-benzo[d]imidazole (5a). To a solution of 4d (124 mg, 0.39
mmol) in dichloromethane (5 mL) was added a solution of N-
butoxycarbonyloxysuccinimide (80 mg, 0.39 mmol) in dichloro-
methane (10 mL) dropwise at room temperature. The reaction
mixture was stirred at room temperature overnight and after
completion of the reaction, the reaction mixture was concentrated.
The crude was purified via flash chromatography on silica gel (gradient
20−40% EtOAc/hexanes) to give 5a as a white solid (72 mg, 33%
yield): mp 128−130 °C; 1H NMR (400 MHz, CDCl3) δ 0.83 (t, 6 H, J
= 7.2 Hz), 0.94 (t, 3 H, J = 7.5 Hz), 1.33 (m, 9 H), 1.65−1.69 (m, 5
H), 1.80−1.82 (m, 2 H, J = 10 Hz), 2.05−2.07 (m, 2 H, J = 10 Hz),
2.79−2.81 (m, 5 H), 4.17 (t, 2 H, J = 6.8 Hz), 7.47 (s, 1 H), 8.22 (s, 1
H), 8.54 (s, 1 H); 13C NMR (100 MHz, CDCl3) δ 11.70, 13.74, 19.09,
20.61, 25.78, 26.00, 31.04, 31.76, 38.42, 58.59, 64.82, 99.39, 112.6,
131.9, 135.4, 154.1, 158.8, 173.3. HRMS (ESI) m/z calcd for
C24H38N4O2 H+: 415.3068. Found: 415.3073 (Δ = 1.3 ppm). HPLC
(1): t = 6.1 min, purity > 97%.
The same procedure was followed for the synthesis of 6a−g.
5-(4-Butylurea)-2-cyclohexyl-6-N,N-diethylamino-1H-benzo-
1
[d]imidazole (6a). White solid (70% yield); mp 197−198 °C; H
NMR (500 MHz, methanol-d4) δ 0.95−1.10 (m, 9 H), 1.36−1.66 (m,
7 H), 1.67−1.79 (m, 2 H), 1.80−1.90 (m, 1 H), 1.90−2.01 (m, 2 H),
2.14 (d, J = 13.73 Hz, 2 H), 2.93 (m, 1 H), 3.06 (quin, J = 7.20 Hz, 4
H), 3.29 (q, J = 7.20 Hz, 2 H), 7.42 (d, J = 7.02 Hz, 1 H), 8.27 (d, J =
7.63 Hz, 2 H); 13C NMR (126 MHz, methanol-d4) δ 13.0, 13.01 14.3,
21.3, 27.1, 27.4, 33.0, 33.5, 40.0, 40.7, 51.7, 103.2, 111.3, 135.3, 135.9,
136.2, 158.7, 160.7. HRMS (FAB) m/z calcd for C22H35N5OH+:
386.2914. Found: 386.2911 (Δ = −0.9 ppm). HPLC (1): t = 12.7 min,
purity > 99%.
5-(Benzylurea)-2-cyclohexyl-6-N,N-diethylamino-1H-benzo-
The same procedure was used for the synthesis of 5b.
1
[d]imidazole (6b). White solid (94% yield); mp 198−199 °C; H
5-Benzyloxycarbonylamino-2-cyclohexyl-6-N,N-dipropyla-
mino-1H-benzo[d]imidazole (5b). White solid (51% yield); mp
138−140 °C; 1H NMR (400 MHz, CDCl3) δ 0.80 (t, 6 H, J = 7.2 Hz),
1.32−1.34 (m, 7 H), 1.59−1.62 (m, 3 H), 1.77−1.79 (m, 2 H, J = 10
Hz), 2.04−2.06 (m, 2 H, J = 10 Hz), 2.77−2.80 (m, 5 H), 5.23 (s, 2
H), 7.37 (m, 5 H), 7.49 (s, 1 H), 8.24 (s, 1 H), 8.67 (s, 1 H), 9.84 (s, 1
H); 13C NMR (100 MHz, CDCl3) δ 11.70, 20.57, 25.77, 25.96, 31.76,
38.42, 58.66, 66.57, 98.87, 113.3, 127.9, 128.1, 128.5, 131.7, 135.3,
136.4, 153.6, 158.9. HRMS (ESI) m/z calcd for C27H36N4O2H+:
449.2911. Found: 449.2909 (Δ = −0.4 ppm). HPLC (1): t = 6.5 min,
purity > 99%.
NMR (400 MHz, methanol-d4) δ 0.90 (t, J = 7.15 Hz, 6 H), 1.23−1.52
(m, 4 H), 1.57−1.70 (m, 2 H), 1.77 (d, J = 14.31 Hz, 1 H), 1.86 (d, J =
13.05 Hz, 2 H), 1.98−2.12 (m, 2 H), 2.84−2.87 (m, 1 H), 2.95 (q, J =
7.00 Hz, 4 H), 4.34−4.45 (m, 2 H), 7.19−7.26 (m, 1 H), 7.28−7.39
(m, 5 H), 8.22 (s, 1 H); 13C NMR (101 MHz, methanol-d4) δ 13.0,
27.1, 27.3, 33.0, 40.0, 44.8, 51.6, 103.4, 111.3, 128.2, 128.4, 129.7,
135.1, 136.0, 136.3, 141.3, 158.5, 160.8. HRMS (FAB) m/z calcd for
C25H33N5OH+: 420.2758. Found: 420.2761 (Δ = 0.7 ppm). HPLC
(1): t = 13.4 min, purity > 99%.
2-Cyclohexyl-6-N,N-diethylamino-5-(3-propylurea)-1H-
benzo[d]imidazole (6c). White solid (87% yield); mp 216−217 °C;
1H NMR (400 MHz, methanol-d4) δ 0.87−1.01 (m, 9 H), 1.23−1.50
5-Butyloxycarbonylamino-2-cyclohexyl-6-N,N-dimethylami-
no-1H-benzo[d]imidazole (5f). A solution of 4c (100 mg, 0.39
mmol) and 1,1′-carbonyldiimidazole (69 mg, 0.43 mmol) in
dichloromethane (2 mL) was stirred under reflux conditions for 4 h.
After all the starting material had disappeared, n-butanol (71 μL, 0.77
mmol) was added and the mixture was refluxed for an additional 12 h.
After the completion of the reaction, the reaction mixture was
concentrated. The crude was purified by flash chromatography on
silica gel (gradient, 30−70% ethyl acetate/hexanes) to give 5f as a
(m, 4 H), 1.51−1.70 (m, 4 H), 1.71−1.79 (m, 1 H), 1.85 (dt, J =
13.18, 3.33 Hz, 2 H), 2.05 (d, J = 13.40 Hz, 2 H), 2.84−2.88 (m, 1 H),
2.96 (q, J = 7.2 Hz, 4 H), 3.16 (t, J = 7.20 Hz, 2 H), 7.33 (s, 1 H), 8.20
(s, 1 H); 13C NMR (101 MHz, methanol-d4) δ 11.9, 13.0, 24.5, 27.1,
27.4, 33.0, 40.0, 42.8, 51.6, 103.2, 111.3, 135.3, 136.0,136.2, 158.7,
160.7. HRMS (FAB) m/z calcd for C21H33N5OH+: 372.2758. Found:
372.2754 (Δ = −1.0 ppm). HPLC (1): t = 12.6 min, purity > 99%.
5-(4-Butylurea)-2-cyclohexyl-6-pyrrolidinyl-1H-benzo[d]-
imidazole (6d). White solid (96% yield); mp 206−207 °C; 1H NMR
(400 MHz, methanol-d4) δ 0.95 (t, J = 7.2 Hz, 3 H), 1.26−1.55 (m, 7
H), 1.56−1.70 (m, 2 H), 1.71−1.82 (m, 1 H), 1.82−1.91 (m, 2 H),
1.91−2.11 (m, 6 H), 2.79−2.87 (m, 1 H), 3.03 (br s, 4 H), 3.20 (t, J =
7.2 Hz, 2 H), 7.24 (s, 1 H), 7.94 (s, 1 H); 13C NMR (101 MHz,
methanol-d4) δ 14.3, 21.2, 27.12, 25.5, 27.3, 33.0, 33.5, 39.9, 40.8, 53.9,
106.3, 107.1, 131.0, 134.4, 136.4, 139.3, 159.2, 160.4. HRMS (FAB)
m/z calcd for C22H33N5OH+: 384.2758. Found: 384.2755 (Δ = −0.8
ppm). HPLC (1): t = 14.2 min, purity > 99%.
1
white solid (111 mg, 79% yield): mp 182−183 °C; H NMR (300
MHz, CDCl3) δ 0.97 (t, J = 7.28 Hz, 3 H), 1.23−1.51 (m, 6 H), 1.55−
1.78 (m, 5 H), 1.79−1.91 (m, 2 H), 2.10 (d, J = 12.91 Hz, 2 H), 2.64
(s, 6 H), 2.76−2.92 (m, 1 H), 4.20 (t, J = 6.73 Hz, 2 H), 7.55 (br s, 1
H), 8.20 (br s, 2 H), 9.20 (br s, 1 H); 13C NMR (101 MHz, CDCl3) δ
14.0, 19.3, 26.0, 26.2, 31.3, 32.0, 38.6, 45.8, 65.2, 100.9, 109.5, 129.8,
132.1, 136.6, 139.1, 154.4, 159.0. HRMS (FAB) m/z calcd for
C20H30N4O2H+: 359.2442. Found: 359.2443 (Δ = 0.4 ppm). HPLC
(1): t = 8.9 min, purity > 99%.
The same procedure was used for the synthesis of 5c−p.
H
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Journal of Medicinal Chemistry
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5-Butyloxycarbonylamino-2-cyclohexyl-6-N,N-dimethyl-N-
ethylethylenediamino-1H-benzo[d]imidazole (5c). White solid
(44% yield); mp 141−143 °C; 1H NMR (400 MHz, CDCl3) δ 0.86 (t,
3 H, J = 7.2 Hz), 0.94 (t, 3 H, J = 7.2 Hz), 1.23−1.27 (m, 3 H), 1.41−
1.43 (m, 2 H), 1.67−1.75 (m, 6 H), 2.00 (m, 2 H, J = 10 Hz), 2.19 (s,
6 H), 2.74−2.75 (m, 1 H), 2.92−2.93 (m, 4 H), 4.16 (t, 2 H, J = 7.2
Hz), 7.47 (s, 1 H), 8.24 (s, 1 H), 9.88 (s, 1 H); 13C NMR (100 MHz,
CDCl3) δ 13.08, 13.73, 19.12, 25.77, 26.01, 31.12, 31.70, 38.48, 45.03,
50.99, 55.03, 57.04, 64.51, 100.2, 113.8, 131.8, 132.9, 135.0, 138.8,
154.9, 159.2. HRMS (ESI) m/z calcd for C24H39N5O2H+: 430.3176.
Found: 430.3179 (Δ = 0.7 ppm). HPLC (3): t = 23.8 min, purity >
98%.
5-Butyloxycarbonylamino-2-cyclohexyl-6-N,N,N-trimethyle-
thylenediamino-1H-benzo[d]imidazole (5d). White solid (45%
yield); mp 116−118 °C; 1H NMR (400 MHz, CDCl3) δ 0.95 (t, 3 H, J
= 7.2 Hz), 1.24−1.45 (m, 6 H), 1.60−1.68 (m, 5 H), 1.79−1.80 (m, 2
H), 2.03−2.04 (m, 2 H), 2.24 (s, 6 H), 2.31 (t, 2 H, J = 7.2 Hz), 2.68
(s, 3 H), 2.84−2.85 (m, 3 H), 4.17 (t, 2 H, J = 6.8 Hz), 7.49 (s, 1 h),
8.26 (s, 1 H), 9.80 (s, 1 H); 13C NMR (100 MHz, CDCl3) δ 13.77,
19.15, 25.81, 26.01, 31.16, 31.77, 38.45, 43.65, 45.41, 57.02, 57.23,
64.55, 100.0, 112.3, 131.2, 137.8, 154.8, 158.8. HRMS (ESI) m/z calcd
for C23H37N5O2H+: 416.3020. Found: 416.3031 (Δ = 2.6 ppm).
HPLC (1): t = 6.5, purity > 98%.
2.05 (m, 2 H, J = 10 Hz), 2.78−2.88 (m, 5 H), 3.52−3.57 (m, 2 H, J =
7 Hz), 3.68−3.69 (m, 2 H), 4.33 (t, 2 H, J = 6.5 Hz), 7.40 (s, 1 H),
8.23 (br s, 1 H), 8.58 (s, 1 H); 13C NMR (100 MHz, CDCl3) δ 12.49,
15.03, 25.72, 25.94, 31.74, 38.44, 50.34, 64.10, 66.61, 68.73, 99.27,
112.9, 131.9, 134.2, 138.0, 153.7, 159.1. HRMS (ESI) m/z calcd for
C22H34N4O3H+: 403.2703. Found: 403.2711 (Δ = 1.9 ppm). HPLC
(1): t = 9.1 min, purity > 97%.
2-Cyclohexyl-5-ethoxyethoxycarbonylamino-6-pyrrolidinyl-
1H-benzo[d]imidazole (5k). White solid (56% yield); mp 72−73
1
°C; H NMR (400 MHz, CDCl3) δ 1.19−1.22 (m, 6 H), 1.54−1.57
(m, 3 H), 1.72−1.75 (m, 2 H), 1.89 (br s, 4 H), 1.99−2.02 (m, 2 H, J
= 10 Hz), 2.76−2.78 (m, 1 H), 2.90 (br s, 4 H), 3.51−3.56 (m, 2 H, J
= 7.2 Hz), 3.68 (t, 2 H, J = 6.5 Hz), 4.32 (t, 2 H, J = 6.5 Hz), 7.38 (s, 1
H), 8.08 (bs, 1 H), 8.16 (bs, 1 H); 13C NMR (100 MHz, CDCl3) δ
15.01, 24.25, 25.69, 25.91, 31.72, 38.38, 53.57, 64.14, 66.59, 68.73,
101.5, 108.8, 129.5, 132.1, 135.7, 136.8, 153.8, 159.0. HRMS (ESI) m/
z calcd for C22H32N4O3H+: 401.2547. Found: 401.2550 (Δ = 0.7
ppm). HPLC (1): t = 11.8 min, purity > 99%.
2-Cyclohexyl-5-ethoxyethoxycarbonylamino-6-N,N-dime-
thylamino-1H-benzo[d]imidazole (5l). White solid (86% yield);
mp 158−159 °C; 1H NMR (500 MHz, CDCl3) δ 1.20−1.44 (m, 7 H),
1.62 (qd, J = 12.31, 3.05 Hz, 2 H), 1.72 (d, J = 12.82 Hz, 1 H), 1.83 (d,
J = 13.12 Hz, 2 H), 2.09 (d, J = 12.51 Hz, 2 H), 2.61 (s, 6 H), 2.77−
2.93 (m, 1 H), 3.58 (q, J = 5.00 Hz, 2 H), 3.71 (t, J = 5.00 Hz, 2 H),
4.36 (t, J = 5.00 Hz, 2 H), 7.51 (br s, 1 H), 8.07−8.48 (m, 2 H), 9.40
(br s, 1 H); 13C NMR (126 MHz, CDCl3) δ 15.3, 26.0, 26.2, 29.9,
32.0, 38.6, 45.9, 64.4, 66.9, 69.0, 99.5, 111.1, 129.7, 139.0, 154.0, 159.0.
HRMS (FAB) m/z calcd for C20H30N4O3H+: 375.2391. Found:
375.2410 (Δ = 5.1 ppm). HPLC (1): t = 12.7 min, purity > 99%.
2-Cyclohexyl-6-N,N-diethylamino-5-(2-methoxyethoxye-
thoxycarbonylamino)-1H-benzo[d]imidazole (5m). White solid
(52% yield); mp 109−110 °C; 1HNMR (400 MHz, CDCl3) δ 0.87 (t,
6 H, J = 7.2 Hz), 1.25−1.32 (m, 3 H), 1.58−1.63 (m, 3 H), 1.70−1.78
(m, 2 H), 2.05−2.08 (m, 2 H, J = 10 Hz), 2.87−2.88 (m, 5 H), 3.37 (s,
3 H), 3.57 (bs, 2 H), 3.67 (t, 2 H, J = 7 Hz), 3.76 (t, 2 H, J = 7 Hz),
4.34 (t, 2 H, J = 6.5 Hz), 7.42 (s, 1 H), 8.22 (bs, 1 H), 8.56 (s, 1 H);
13C NMR (100 MHz, CDCl3) δ 12.53, 25.75, 25.95, 31.74, 38.42,
5-Butyloxycarbonylamino-2-cyclohexyl-6-N,N,N-triethyle-
thylenediamino-1H-benzo[d]imidazole (5e). White solid (60%
yield); mp 150−151 °C; 1H NMR (400 MHz, CDCl3) δ 0.95 (t, 3 H, J
= 7.2 Hz), 0.97−1.00 (m, 9 H), 1.24−1.48 (m, 6 H), 1.57−1.70 (m, 6
H), 1.78−1.79 (m, 2 H), 2.02−2.05 (m, 2 H), 2.37 (t, 2 H, J = 7.2
Hz), 2.50−2.55 (m, 4 H, J = 7.2 Hz), 2.76−2.79 (m, 1 H), 2.93−2.95
(m, 4 H), 4.17 (t, 2 H, J = 6.9 Hz), 7.52 (s, 1 H), 8.23 (s, 1 H), 9.84 (s,
1 H), 10.5 (s, 1 H); 13C NMR (100 MHz, CDCl3) δ 11.10, 12.96,
13.73, 19.12, 25.79, 26.03, 31.30, 31.70, 38.48, 46.81, 50.41, 50.67,
55.34, 64.56, 100.5, 113.6, 131.6, 132.7, 135.4, 138.9, 154.9, 159.1.
HRMS (ESI) m/z calcd for C26H43N5O2H+: 458.3489. Found:
458.3489 (Δ = 0.0 ppm). HPLC (1): t = 25.5 min, purity > 99%.
2-Cyclohexyl-6-N,N-diethylamino-5-(1-methylbutoxycarbo-
nylamino)-1H-benzo[d]imidazole (5g). White solid (50% yield;
1
mp 88−90 °C; H NMR (400 MHz, CDCl3) δ 0.88−0.92 (m, 9 H),
50.34, 58.98, 63.92, 69.58, 70.43, 71.84, 99.81, 112.5, 132.0, 134.2,
153.6, 159.0. HRMS (ESI) m/z calcd for C23H36N4O4H+: 433.2809.
Found: 433.2815 (Δ = 1.4 ppm). HPLC (1): t = 16.9 min, purity >
97%.
1.37−1.63 (m, 16 H), 1.79−1.81 (m, 2 H, J = 10 Hz), 2.07−2.10 (m, 2
H, J = 10 Hz), 2.83−2.93 (m, 5 H), 4.90−4.93 (m, 1 H), 7.45 (s, 1 H),
8.22 (s, 1 H), 8.41 (s, 1 H); 13C NMR (100 MHz, CDCl3) δ 12.68,
13.96, 18.72, 20.34, 25.76, 25.97, 29.67, 31.74, 38.35, 50.41, 71.46,
99.98, 112.2, 132.6, 134.5, 153.9, 158.6. HRMS (ESI) m/z calcd for
C23H36N4O2H+: 401.2911. Found: 401.2917 (Δ = 1.5 ppm). HPLC
(1): t = 6.8 min, purity > 97%.
2-Cyclohexyl-6-N,N-diethylamino-5-trifluoroethoxycarbony-
lamino-1H-benzo[d]imidazole (5n). White solid (42% yield); mp
203−204 °C; 1H NMR (400 MHz, CDCl3) δ 0.90 (t, 6 H, J = 6.9 Hz),
1.25−1.37 (m, 4 H), 1.61−1.65 (m, 4 H), 1.81−1.84 (m, 2 H), 2.09−
2.10 (m, 2 H), 2.85−2.94 (m, 5H), 4.53−4.57 (m, 2 H, J = 8.5 Hz),
7.51 (s, 1 H), 8.13 (s, 1 H), 8.78 (s, 1 H), 9.76 (s, 1 H); 13C NMR
(100 MHz, CDCl3) δ 12.69, 25.81, 25.99, 31.83, 38.49, 50.59, 98.99,
113.5, 119.0, 121.7, 124.5, 127.3, 131.1, 131.4, 139.0, 151.5, 159.2.
HRMS (ESI) m/z calcd for C20H27F3N4O2H+: 413.2159. Found:
413.2175 (Δ = 3.8 ppm). HPLC (1): t = 7.3 min, purity > 99%.
2-Cyclohexyl-5-trifluoroethoxycarbonylamino-6-prrolidinyl-
1H-benzo[d]imidazole (5o). White solid (69% yield); mp 123−125
5-Benzyloxycarbonylamino-2-cyclohexyl-6-N,N-dimethyla-
mino-1H-benzo[d]imidazole (5h). White solid (82% yield); mp
1
145−146 °C; H NMR (300 MHz, CDCl3) δ 1.15−1.40 (m, 3 H),
1.45−1.87 (m, 5 H), 2.03 (d, J = 11.73 Hz, 2 H), 2.60 (s, 6 H), 2.74−
2.92 (m, 1 H), 5.23 (s, 2 H), 7.28−7.60 (m, 6 H), 8.14−8.42 (m, 2 H),
10.23 (br s, 1 H); 13C NMR (126 MHz, CDCl3) δ 21.8, 25.9, 26.1,
31.80, 31.84, 38.3, 38.3, 45.8, 67.1, 100.9, 109.5, 128.5, 128.8, 129.9,
131.6, 136.0 136.4, 139.4, 153.9, 158.9, 175.9. HRMS (FAB) m/z calcd
for C23H28N4O2H+: 393.2285. Found: 393.2290 (Δ = 1.3 ppm).
HPLC (1): t = 9.0 min, purity > 99%.
1
°C; H NMR (400 MHz, CDCl3) δ 1.16−1.31 (m, 3 H), 1.59−1.62
(m, 3 H), 1.75−1.78 (m, 2 H), 1.92 (bs, 4 H), 2.03−2.07 (m, 2H),
2.79−2.82 (m, 1 H), 2.92−2.93 (m, 4 H), 4.52−4.59 (q, 2 H, J = 7.4
Hz), 7.41 (s, 1 H), 8.12 (s, 1 H), 8.21 (s, 1 H); 13C NMR (100 MHz,
CDCl3) δ 24.30, 25.70, 25.92, 31.82, 38.48, 53.65, 102.0, 108.8, 118.9,
121.7, 124.4, 127.2, 128.7, 135.9, 151.7, 159.4. HRMS (ESI) m/z calcd
for C20H25F3N4O2H+: 411.2002. Found: 411.2007 (Δ = 1.2 ppm).
HPLC (1): t = 7.1 min, purity > 97%.
2-Cyclohexyl-5-methoxyethoxycarbonylamino-6-pyrrolidin-
yl-1H-benzo[d]imidazole (5i). White solid (55% yield): mp 75−77
1
°C; H NMR (400 MHz, CDCl3) δ 1.25−1.43 (m, 3 H), 1.57−1.93
(m, 6 H), 1.88 (br s, 4 H), 2.00−2.02 (m, 2 H, J = 10 Hz), 2.76−2.77
(m, 1 H), 2.89 (br s, 4 H), 3.39 (s, 3 H), 3.64 (t, 2 H, J = 6.5 Hz), 4.32
(t, 2 H, J = 6.5 Hz), 7.37 (s, 1 H), 8.09 (br s, 1 H), 8.16 (br s, 1 H);
13C NMR (100 MHz, CDCl3) δ 24.22, 25.66, 25.88, 31.70, 38.37,
2-Cyclohexyl-5-trifluoroethoxycarbonylamino-6-N,N-dime-
thylamino-1H-benzo[d]imidazole (5p). White solid (70% yield);
mp 190−191 °C;1H NMR (400 MHz, CDCl3) δ 1.05−1.43 (m, 4 H),
1.50−1.91 (m, 5 H), 1.96−2.21 (m, 2 H), 2.61 (s, 6 H), 2.83−2.89
(m, 1 H), 4.56 (q, J = 8.53 Hz, 2 H), 7.45 (s, 1 H), 8.19 (s, 1 H), 8.41
(s, 1 H); 13C NMR (101 MHz, CDCl3) δ 14.3, 22.8, 25.9, 26.2, 32.1,
38.8, 45.8, 60.4, 60.7, 61.1, 61.5, 101.8, 109.7, 119.2, 121.9, 124.7,
127.5, 128.6, 139.1, 151.8, 159.8. HRMS (FAB) m/z calcd for
53.55, 58.87, 63.89, 70.81, 101.6, 108.7,129.4, 132.3, 135.7, 136.9,
153.8, 159.1. HRMS (ESI) m/z calcd for C21H30N4O3H+: 387.2390.
Found: 387.2400 (Δ = 2.6 ppm). HPLC (1): t = 14.2 min, purity >
97%.
2-Cyclohexyl-5-ethoxyethoxycarbonylamino-6-N,N-diethy-
lamino-1H-benzo[d]imidazole (5j). White solid (42% yield); mp
158−160 °C; 1H NMR (400 MHz, CDCl3) δ 0.84 (t, 6 H, J = 7.2 Hz),
1.19−1.22 (m, 5 H), 1.57−1.60 (m, 3 H), 1.74−1.77 (m, 2 H), 2.02−
I
dx.doi.org/10.1021/jm401468w | J. Med. Chem. XXXX, XXX, XXX−XXX

Journal of Medicinal Chemistry
Article
C18H23F3N4O2H+: 385.1846. Found: 385.1851 (Δ = 1.3 ppm). HPLC
(1): t = 9.1 min, purity > 99%.
161.8, 164.7. HRMS (ESI) m/z calcd for C26H34N4O2H+: 435.2754.
Found: 435.2754 (Δ = 0.0 ppm). HPLC (1): t = 8.6 min, purity >
99%.
5-Benzamido-2-cyclohexyl-6-N,N-dimethylamino-1H-benzo-
[d]imidazole (7c-1). To a solution of 4c (70 mg, 0.27 mmol) in 2 mL
of dichloromethane was added 1-ethyl-3-(3-dimethylaminopropyl)-
carbodiimide (57.5 mg, 0.3 mmol) (EDC) and benzoic acid (36.4 mg,
0.30 mmol). 4-Dimethylaminopyridine (DMAP) (36.4 mg, 0.30
mmol) was added to the above reaction mixture, and the mixture
was refluxed overnight. After completion of the reaction as indicated
by TLC, the reaction mixture was diluted with dichloromethane,
transferred to a separatory funnel and the organic layer was washed
with water, sodium bicarbonate, and finally brine. The organic layer
was dried over magnesium sulfate and concentrated using rotary
evaporator. The crude product was purified by flash chromatography
(column was packed with hexane, 30% ethyl acetate was used with
gradual increase to 50% ethyl acetate) to obtain the product as a white
2-Cyclohexyl-6-N,N-diethylamino-5-(4-ethylbenzamido)-1H-
benzo[d]imidazole (7a-5). White solid (75% yield); mp 175−177
°C; 1H NMR (400 MHz, CDCl3) δ 0.94−1.03 (m, 9 H), 1.26 (t, 3 H,
J = 7.6 Hz), 1.46−1.56 (m, 5 H), 1.91−1.94 (m, 2 H, J = 10 Hz),
2.68−2.75 (m, 3 H), 2.99 (q, 4 H, J = 7.2 Hz), 7.36 (d, 2 H, J = 8.5
Hz), 7.56 (s, 1 H), 7.93 (d, 2 H, J = 8.6 Hz), 9.03 (s, 1 H), 10.41 (s, 1
H); 13C NMR (100 MHz, CDCl3) δ 13.02, 15.26, 25.50, 25.82, 28.76,
31.68, 38.37, 50.73, 100.9, 113.1, 126.9, 128.4, 131.6, 131.9, 132.8,
134.8, 139.6, 148.3, 160.0, 165.1. HRMS (ESI) m/z calcd for
C26H34N4OH+: 419.2805. Found: 419.2809 (Δ = 0.9 ppm). HPLC
(1): t = 7.2 min, purity > 99%.
2-Cyclohexyl-6-N,N-diethylamino-5-(4-N,N-dimethylbenza-
mido)-1H-benzo[d]imidazole (7a-7). White solid (65% yield); mp
189−191 °C; 1H NMR (400 MHz, CDCl3) δ 0.96 (t, 6 H, J = 7.6 Hz),
1.08−1.11 (m, 3 H), 1.53−1.64 (m, 5 H), 1.90−1.94 (m, 2 H, J = 10
Hz), 2.69 (m, 1 H), 2.99 (q, 4 H, J = 7.2 Hz), 3.06 (s, 6 H), 6.79 (d, 2
H, J = 8.5 Hz), 7.54 (s, 1 H), 7.92 (d, 2 H, J = 8.6 Hz), 8.98 (s, 1 H),
10.26 (s, 1 H); 13C NMR (100 MHz, CDCl3) δ 13.08, 25.58, 25.91,
31.70, 38.37, 40.09, 50.71, 100.6, 111.35, 113.0, 122.0, 128.5, 132.0,
133.0, 134.7, 139.2, 152.5, 159.7, 165.2. HRMS (ESI) m/z calcd for
C26H35N5OH+: 434.2914. Found: 434.2914 (Δ = 0.0 ppm). HPLC
(1): t = 4.6 min, purity > 99%.
2-Cyclohexyl-6-N,N-diethylamino-5-(2-pyrazinamido)-1H-
benzo[d]imidazole (7a-8). White solid (64% yield); mp > 230 °C;
1H NMR (400 MHz, CDCl3) δ 0.96 (t, 6 H, J = 7.6 Hz), 1.14−1.16
(m, 3 H), 1.53−1.64 (m, 5 H), 2.01−2.02 (m, 2 H), 2.76−2.8 (m, 1
H), 2.99 (q, 4 H, J = 7.2 Hz), 7.55 (s, 1 H), 8.65 (d, 2 H, J = 8.6 Hz),
8.77 (d, 2 H, J = 8.6 Hz), 8.92 (s, 1 H), 9.53 (s, 1 H), 10.91 (s, 1 H);
13C NMR (100 MHz, CDCl3) δ 13.05, 25.66, 25.94, 31.82, 38.64,
50.54, 101.1, 113.6, 131.1, 136.3, 139.9, 142.9, 144.4, 145.6, 147.0,
160.1, 160.6. HRMS (ESI) m/z calcd for C22H28N6OH+: 393.2397.
Found: 393.2412 (Δ = 3.8 ppm). HPLC (1): t = 10.9 min, purity >
99%.
1
solid (83 mg, 85% yield): mp 158−159 °C; H NMR (300 MHz,
CDCl3) δ 1.07−1.19 (m, 3 H), 1.54−1.71 (m, 5 H), 1.97−2.03 (m, 2
H, J = 12.9 Hz), 2.74 (s, 6 H), 2.85 (m, 1 H), 7.58 (m, 3 H), 7.67 (s, 1
H), 7.95 (d, 1H, J = 6.6 Hz), 8.91 (s, 1 H), 9.88 (s, 1 H); 13C NMR
(126 MHz, CDCl3) δ 25.9, 26.1, 29.9, 32.0, 38.6, 46.2, 101.8, 110.9,
127.2, 129.0, 129.2, 131.4, 132.0, 135.8, 139.4, 139.9, 160.1, 165.7.
HRMS (FAB) m/z calcd for C22H26N4OH+: 363.2179. Found:
363.2190 (Δ = 2.9 ppm). HPLC (1): t = 11.0 min, purity > 99%.
The same procedure was followed for the synthesis of 7d, 7a-1−3,
7a-5, 7a-7−10, 7a-15, 7b-1, 7b-4, 7b-7, 7c-3−6, 7c-11, 7c-12, and 7c-
16.
5-Benzamido-2-cyclohexyl-6-N,N-di-n-propylamino-1H-
benzo[d]imidazole (7d). White solid (52% yield): mp 212−213 °C;
1H NMR (400 MHz, CDCl3) δ 0.78 (t, 6 H, J = 7.2 Hz), 1.05−1.08
(m, 3 H), 1.36−1.39 (m, 4 H), 1.54−1.63 (m, 5 H), 1.90−1.95 (m, 2
H, J = 10 Hz), 2.65−2.67 (m, 1 H), 2.88−2.89 (m, 4 H, J = 7.5 Hz),
7.56−7.60 (m, 3 H), 7.99 (d, 2 H, J = 6.9 Hz), 9.00 (s, 1 H), 10.40 (s,
1 H); 13C NMR (100 MHz, CDCl3) δ 11.72, 20.69, 20.81, 25.57,
25.87, 31.71, 38.40, 59.10, 100.8, 113.3, 126.8, 128.9, 131.2, 131.6,
131.7, 135.4, 135.8, 139.7, 160.1, 165.2. HRMS (ESI) m/z calcd for
C26H34N4OH+: 419.2805. Found: 419.2813 (Δ = 1.9 ppm). HPLC
(1): t = 6.3 min, purity > 99%.
2-Cyclohexyl-6-N,N-diethylamino-5-(4-difluoromethoxyben-
zamido)-1H-benzo[d]imidazole (7a-1). White solid (66% yield);
mp 194−196 °C; 1H NMR (400 MHz, CDCl3) δ 0.95 (t, 6 H, J = 7.2
Hz), 1.07−1.10 (m, 3 H), 1.54−1.64 (m, 5 H), 1.96−1.98 (m, 2 H, J =
10 Hz), 2.69−2.70 (m, 1 H), 2.99 (q, 4 H, J = 7.2 Hz), 6.61 (t, 1 H
(CHF2), J = 73 Hz), 7.28 (d, 2 H, J = 8.5 Hz), 7.57 (s, 1 H), 8.00 (d, 2
H, J = 8.6 Hz), 8.92 (s, 1 H), 10.40 (s, 1 H); 13C NMR (100 MHz,
CDCl3) δ 13.07, 25.55, 25.88, 31.70, 38.48, 50.79, 100.8, 112.7, 113.2,
115.3, 117.9, 119.5, 128.7, 131.5, 131.8, 132.3, 139.7, 153.5, 160.0,
163.8. HRMS (ESI) m/z calcd for C25H30F2N4O2H+: 457.2409.
Found: 457.2411 (Δ = 0.4 ppm). HPLC (1): t = 8.9 min, purity >
99%.
5-(4-Bromobenzamido)-2-cyclohexyl-6-N,N-diethylamino-
1H-benzo[d]imidazole (7a-9). White solid (61% yield); mp >230
°C; mixture of rotamers, 1H NMR (400 MHz, CDCl3) δ 0.89 (t, 6 H, J
= 7.2 Hz), 1.27−1.40 (m, 3 H), 1.57−1.67 (m, 3 H), 1.76−1.78 (m, 2
H), 1.96−1.98 (m, 2 H, J = 10 Hz), 2.80−2.81 (m, 1 H), 2.95−3.01
(m, 4 H, J = 7 Hz), 7.52 (m, 1 H), 7.81−7.82 (m, 4 H), 8.51 (s, 1 H),
10.1 (m, 2 H), 12.0 (m, 1 H); 13C NMR (100 MHz, CDCl3) δ 12.82,
25.47, 25.54, 31.22, 37.68, 49.92, 100.1, 112.9, 125.4, 128.6, 130.9,
131.5, 132.0, 133.9, 134.4, 139.4, 159.2, 162.4. HRMS (ESI) m/z calcd
for C24H29BrN4OH+: 469.1597. Found: 469.1604 (Δ = 1.5 ppm).
HPLC (1): t = 7.6 min, purity > 99%.
5-(3-Bromobenzamido)-2-cyclohexyl-6-N,N-diethylamino-
1H-benzo[d]imidazole (7a-10). White solid (71% yield); mp 218−
1
220 °C; H NMR (400 MHz, CDCl3) δ 0.95 (t, 6 H, J = 7.2 Hz),
1.09−1.10 (m, 3 H), 1.57−1.66 (m, 5 H), 1.94−1.96 (m, 2 H, J = 10
Hz), 2.69−2.70 (m, 1 H), 2.99−3.00 (m, 4 H), 7.41 (t, 1 H, J = 7.8
Hz), 7.58 (s, 1 H), 7.69 (d, 1 H, J = 7.7 Hz), 7.84 (d, 1 H, J = 7.7 Hz),
8.14 (s, 1 H), 8.93 (s, 1 H), 10.42 (s, 1 H), 11.39 (s, 1 H); 13C NMR
(100 MHz, CDCl3) δ 13.07, 25.57, 25.84, 31.69, 38.43, 50.69, 100.8,
113.3, 123.2, 124.9, 130.4, 130.5, 131.2, 131.8, 134.6, 135.0, 137.4,
139.8, 160.1, 163.4. HRMS (ESI) m/z calcd for C24H29N4OH+:
469.1597. Found: 469.1604 (Δ = 1.5 ppm). HPLC (1): t = 8.0 min,
purity > 99%.
2-Cyclohexyl-6-N,N-diethylamino-5-(2-propoxyacetamido)-
1H-benzo[d]imidazole (7a-15). White solid (64% yield); mp 148−
150 °C; 1H NMR (400 MHz, CDCl3) δ 0.94 (t, 6 H, J = 7.2 Hz), 1.01
(t, 3 H, J = 7.5 Hz), 1.23−1.46 (m, 3 H), 1.57−1.72 (m, 5 H), 1.85−
1.88 (m, 2 H, J = 10 Hz), 2.12−2.15 (m, 2 H, J = 10 Hz), 2.83−2.85
(m, 1 H), 2.94 (q, 4 H, J = 7.2 Hz), 3.59 (t, 2 H, J = 6.5 Hz), 4.15 (s, 2
H), 7.55 (s, 1 H), 8.77 (s, 1 H), 10.44 (s, 1 H); 13C NMR (100 MHz,
CDCl3) δ 10.40, 12.75, 22.98, 25.87, 26.11, 31.74, 38.66, 50.42, 70.98,
73.46, 100.7, 113.4, 131.0, 131.6, 135.2, 139.6, 159.6, 167.7. HRMS
(ESI) m/z calcd for C22H34N4O2H+: 387.2754. Found: 387.2769 (Δ =
3.9 ppm). HPLC (1): t = 8.4 min, purity > 99%.
2-Cyclohexyl-6-N,N-diethylamino-5-(4-trifluoromethoxy-
benzamido)-1H-benzo[d]imidazole (7a-2). White solid (71%
1
yield); mp 207−208 °C; H NMR (400 MHz, CDCl3) δ 0.96 (t, 6
H, J = 7.2 Hz), 1.09−1.11 (m, 3 H), 1.55−1.66 (m, 5 H), 1.96−1.98
(m, 2 H, J = 10 Hz), 2.68−2.70 (m, 1 H), 3.00 (q, 4 H, J = 7.2 Hz),
7.25 (d, 2 H, J = 8.5 Hz), 7.58 (s, 1 H), 8.02 (d, 2 H, J = 8.6 Hz), 8.92
(s, 1 H), 10.43 (s, 1 H); 13C NMR (100 MHz, CDCl3) δ 13.10, 25.59,
25.88, 31.72, 38.49, 50.84, 100.8, 113.5, 119.0, 121.0, 121.6, 128.7,
131.5, 133.8, 135.0, 151.6, 159.9, 163.5. HRMS (ESI) m/z calcd for
C25H29F3N4O2H+: 475.2315. Found: 475.2323 (Δ = 1.7 ppm). HPLC
(1): t = 7.5 min, purity > 99%.
2-Cyclohexyl-5-(4-ethoxybenzamido)-6-N,N-diethylamino-
1H-benzo[d]imidazole (7a-3). White solid (41% yield); mp 191−
1
193 °C; H NMR (400 MHz, CDCl3) δ 0.96 (t, 6 H, J = 7.2 Hz),
1.07−1.10 (m, 3 H), 1.45 (t, 6 H, J = 7.2 Hz), 1.55−1.66 (m, 5 H),
1.94−1.97 (m, 2 H, J = 10 Hz), 2.68−2.70 (m, 1 H), 3.00 (q, 4 H, J =
7.2 Hz), 4.13 (q, 2 H, J = 7 Hz) 7.03 (d, 2 H, J = 8.8 Hz), 7.55 (s, 1
H), 7.94 (d, 2 H, J = 8.8 Hz), 8.95 (s, 1 H), 10.32 (s, 1 H); 13C NMR
(100 MHz, CDCl3) δ 13.10, 14.68, 25.60, 25.93, 31.71, 38.43, 50.77,
63.74, 100.7, 113.2, 114.6, 127.4, 128.7, 131.8, 134.9, 139.3, 159.8,
J
dx.doi.org/10.1021/jm401468w | J. Med. Chem. XXXX, XXX, XXX−XXX

Journal of Medicinal Chemistry
Article
5-Benzamido-2-cyclohexyl-6-pyrrolinyl-1H-benzo[d]-
32.0, 38.6, 46.1, 101.8, 110.8, 127.3, 128.7, 129.1, 129.2, 131.5, 133.3,
139.3, 139.8, 148.7, 160.0, 160.1, 165.8. HRMS (FAB) m/z calcd for
C24H30N4OH+: 391.2492. Found: 391.2500 (Δ = 1.9 ppm). HPLC
(1): t = 9.9 min, purity > 99%.
1
imidazole (7b-1). White solid (76% yield); mp 197−198 °C; H
NMR (500 MHz, CDCl3) δ 1.04−1.35 (m, 4 H), 1.51−1.68 (m, 3 H),
1.74 (dt, J = 13.20, 3.32 Hz, 2 H), 1.92−2.11 (m, 6 H), 2.75 (m, 1 H),
3.07 (br s, 4 H), 7.46−7.71 (m, 4 H), 7.95 (d, J = 8.80 Hz, 2 H), 8.86
(s, 1 H), 9.91 (br s, 1 H), 10.45 (br s, 1 H); 13C NMR (126 MHz,
CDCl3) δ 24.6, 25.9, 26.2, 32.0, 38.7, 54.2, 101.8, 111.1, 127.1, 129.2,
129.9, 131.9, 135.7, 136.0, 159.8, 165.3. HRMS (FAB) m/z calcd for
C24H28N4OH+: 389.2336. Found: 389.2349 (Δ = 3.4 ppm). HPLC
(1): t = 8.1 min, purity > 99%.
5-(4-Bromobenzamido)-2-cyclohexyl-6-pyrrolidinyl-1H-
benzo[d]imidazole (7b-4). White solid (76% yield); mp 215−216
°C; 1H NMR (500 MHz, DMSO-d6) δ 1.19−1.45 (m, 3 H), 1.58 (qd,
J = 12.21, 3.05 Hz, 2 H), 1.64−1.74 (m, 1 H), 1.79 (dt, J = 12.89, 3.17
Hz, 2 H), 1.88 (br s, 4 H), 2.00 (d, J = 10.68 Hz, 2 H), 2.72−2.86 (m,
1 H), 3.06 (br s, 4 H), 7.16 (br s, 1 H), 7.68−7.86 (m, 3 H), 7.91 (d, J
= 8.24 Hz, 2 H), 9.82 (s, 4 H), 11.90 (br s, 1 H); 13C NMR (101
MHz, DMSO-d6 at 55 °C) δ 24.1, 25.2, 25.4, 31.0, 37.5, 51.9, 124.9,
125.8, 128.9, 131.4, 134.0, 138.3, 158.6, 163.4. HRMS (FAB) m/z
calcd for C24H27BrN4OH+: 467.1441. Found: 467.1443 (Δ = 0.4
ppm). HPLC (2): t = 9.6 min, purity > 98%.
5-(4-Bromobenzamido)-2-cyclohexyl-6-N,N-dimethylamino-
1H-benzo[d]imidazole (7c-11). Yellow solid (78% yield); mp 207−
1
208 °C; H NMR (500 MHz, methanol-d4) δ 0.80−1.02 (m, 1 H),
1.16−2.21 (m, 13 H), 2.54−3.00 (m, 7 H), 7.44 (s, 1 H), 7.60−7.98
(m, 4 H), 8.46 (s, 1 H); 13C NMR (126 MHz, methanol-d4) δ 27.1,
27.3, 31.9, 33.0, 40.0, 46.1, 65.6, 106.9, 108.2, 127.6, 129.9, 130.0,
133.4, 135.5, 142.3, 161.6, 166.2. HRMS (FAB) m/z calcd for
C22H25BrN4OH+: 441.1285. Found: 441.1287 (Δ = 0.6 ppm). HPLC
(1): t = 9.9 min, purity > 99%.
5-(3-Bromobenzamido)-2-cyclohexyl-6-N,N-dimethylamino-
1H-benzo[d]imidazole (7c-12). Yellow solid (59% yield); mp 148−
1
149 °C; H NMR (500 MHz, methanol-d4) δ 1.28−1.38 (m, 1 H),
1.40−1.52 (m, 2 H), 1.57−1.93 (m, 5 H), 2.06 (d, J = 11.60 Hz, 2 H),
2.65−2.80 (m, 6 H), 2.80−2.93 (m, 1 H), 7.38−7.49 (m, 2 H), 7.66−
7.76 (m, 1 H), 7.80−7.91 (m, 1 H), 8.02−8.13 (m, 1 H), 8.43 (s, 1
H); 13C NMR (126 MHz, methanol-d4) δ 27.10, 27.31, 32.9, 39.95,
46.06, 106.96, 108.03, 124.08, 126.62, 129.75, 131.56, 131.91, 135.21,
135.95, 137.36, 138.51, 138.53, 142.33, 142.36, 161.53, 161.55, 165.48,
165.54. HRMS (FAB) m/z calcd for C22H25BrN4OH+: 441.1285.
Found: 441.1288 (Δ = 0.8 ppm). HPLC (1): t = 10.5 min, purity >
99%.
2-Cyclohexyl-5-(2-propoxyacetamido)-6-(pyrrolidin-1-yl)-
1H-benzo[d]imidazole (7b-7). White solid (78% yield); mp 179−
1
181 °C; H NMR (300 MHz, CDCl3) δ 1.01 (t, 3 H, J = 7.5 Hz),
1.35−1.38 (m, 3 H), 1.70−1.72 (m, 5 H), 1.80−1.82 (m, 2 H), 1.94
(br s, 4 H), 2.09−2.12 (m, 2 H), 2.81−2.87 (m, 1 H), 2.99 (br s, 4 H),
3.56 (t, 2 H, J = 6.5 Hz), 4.12 (s, 2 H), 7.54 (s, 1 H), 8.69 (s, 1 H),
9.93 (s, 1 H); 13C NMR (100 MHz, CDCl3) δ 10.48, 22.96, 24.27,
25.84, 26.07, 31.76, 38.63, 53.46, 70.90, 73.46, 101.5, 110.2, 128.6,
130.8, 135.8, 139.7, 159.5, 167.6. HRMS (ESI) m/z calcd for
C22H32N4O2H+: 385.2598. Found: 385.2594 (Δ = −1.0 ppm). HPLC
(1): t = 9.7 min, purity > 99%.
2-Cyclohexyl-5-(4-difluoromethoxybenzamido)-6-N,N-dime-
thylamino-1H-benzo[d]imidazole (7c-3). White solid (65% yield);
mp 183−185 °C; 1H NMR (400 MHz, CDCl3) δ 1.02−1.33 (m, 5 H),
1.51−1.79 (m, 6 H), 2.00 (d, J = 13.55 Hz, 2 H), 2.72 (s, 7 H), 6.61
(d, J = 73.53 Hz, 1 H), 7.25−7.31 (m, 2 H), 7.59 (s, 1 H), 7.97 (d, J =
9.03 Hz, 2 H), 8.82 (s, 1 H), 9.87 (s, 1 H); 13C NMR (126 MHz,
CDCl3) δ 14.3, 25.9, 26.1, 31.8, 32.0, 34.9, 38.7, 46.1, 101.8, 110.9,
113.5, 115.6, 117.7, 119.7, 128.9, 129.1, 132.7, 139.5, 153.8, 160.1,
164.4. HRMS (FAB) m/z calcd for C23H26F2N4O2H+: 429.2097.
Found: 429.2100 (Δ = 0.8 ppm). HPLC (1): t = 12.8 min, purity >
99%.
2-Cyclohexyl-6-N,N-dimethylamino-5-(2-propoxyacetami-
do)-1H-benzo[d]imidazole (7c-16). White solid (61% yield); mp
146−148 °C; 1H NMR (400 MHz, CDCl3) δ 1.03 (t, 3 H, J = 7.2 Hz),
1.23−1.33 (m, 3 H), 1.60−1.72 (m, 5 H), 1.81−1.84 (m, 2 H, J = 10
Hz), 2.09−2.12 (m, 2 H, J = 10 Hz), 2.82 (s, 6 H), 2.83−2.85 (m, 1
H), 3.58 (t, 2 H, J = 6.5 Hz), 4.14 (s, 2 H), 7.53 (s, 1 H), 8.71 (s, 1 H),
10.07 (s, 1 H); 13C NMR (100 MHz, CDCl3) δ 10.42, 23.01, 25.89,
26.13, 31.83, 38.71, 45.68, 70.95, 73.53, 100.7, 113.4, 128.1, 131.6,
135.2, 139.2, 159.8, 167.9. HRMS (ESI) m/z calcd for C20H30N4O2H+:
359.2441. Found: 359.2450 (Δ = 2.5 ppm). HPLC (1): t = 10.2 min,
purity > 99%.
2-Cyclohexyl-5-(4-methoxybenzamido)-6-N,N-dimethylami-
no-1H-benzo[d]imidazole (7c-2). To a solution of 4c (100 mg, 0.39
mmol) in dichloromethane (2 mL) was added triethylamine (60 μL,
0.43 mmol). To this, 4-methoxybenzoyl chloride (53.3 μL, 0.39
mmol) was added dropwise at 0 °C and reacted at room temperature.
After completion of the reaction, the reaction mixture was diluted with
ethyl acetate and transferred to a separatory funnel. The organic layer
was washed with saturated sodium bicarbonate solution, followed by
water and finally brine. The organic layer was dried over magnesium
sulfate. The crude product was purified by flash chromatography on
silica gel (gradient, 30−70% ethyl acetate/hexanes) to obtain the
product which was then treated with activated charcoal to yield the
2-Cyclohexyl-5-(4-trifluoromethoxybenzamido)-6-N,N-di-
methylamino-1H-benzo[d]imidazole (7c-4). White solid (70%
1
yield); mp 210−211 °C; H NMR (400 MHz, CDCl3) δ 1.08−1.31
(m, 3 H), 1.53−1.70 (m, 3 H), 1.70−1.81 (m, 2 H), 1.99−2.09 (m, 2
H), 2.69−2.83 (m, 7 H), 7.35−7.42 (m, 2 H), 7.60 (s, 1 H), 7.97−8.04
(m, 2 H), 8.81 (s, 1 H), 9.90 (s, 1 H); 13C NMR (101 MHz, CDCl3) δ
25.68, 25.93, 31.78, 38.47, 45.95, 119.08, 121.00, 121.01, 128.85,
128.91, 133.95, 139.43, 151.64, 159.68, 163.91. HRMS (FAB) m/z
calcd for C23H25F3N4O2H+: 447.2002. Found: 447.2007 (Δ = 1.0
ppm). HPLC (1): t = 10.3 min, purity > 99%.
1
product as a white solid (130 mg, 86%): mp 201−202 °C; H NMR
(300 MHz, CDCl3) δ 1.06−1.15 (m, 3 H), 1.54−1.68 (m, 5 H), 1.94−
1.98 (m, 2 H, J = 12.9 Hz), 2.67−2.71 (m, 7 H), 3.90 (s, 3 H), 7.04 (d,
1 H, J = 9 Hz), 7.60 (s, 1H), 7.93 (d, 2 H, J = 9 Hz), 8.86 (s, 1 H),
9.82 (s, 1 H); 13C NMR (101 MHz, CDCl3) δ 25.8, 26.1, 32.0, 38.7,
46.1, 55.7, 101.9, 110.6, 114.3, 127.9, 129.0, 129.0, 131.6, 139.3, 160.1,
162.6, 165.2. HRMS (FAB) m/z calcd for C23H28N4O2H+: 393.2285.
Found: 393.2285 (Δ = 0.0 ppm). HPLC (1): t = 13.2 min, purity >
99%.
2-Cyclohexyl-6-N,N-dimethylamino-5-(4-methylbenzami-
do)-1H-benzo[d]imidazole (7c-5). White solid (76% yield); mp
1
179−180 °C; H NMR (500 MHz, CDCl3) δ 1.05−1.27 (m, 3 H),
1.50−1.77 (m, 5 H), 1.99 (d, J = 12.51 Hz, 2 H), 2.46 (s, 3 H), 2.66−
2.78 (m, 7 H), 7.35 (d, J = 8.24 Hz, 2 H), 7.61 (s, 1 H), 7.87 (d, J =
8.24 Hz, 2 H), 8.89 (s, 1 H), 9.90 (s, 1 H), 10.65 (br s, 1 H); 13C
NMR (126 MHz, CDCl3) δ 21.7, 25.9, 26.2, 32.0, 38.6, 46.1, 101.7,
110.9, 127.2, 129.2, 129.8, 131.3, 133.0, 139.4, 139.8, 142.5, 159.9,
165.7. HRMS (FAB) m/z calcd for C23H28N4OH+: 377.2336. Found:
377.2349 (Δ = 3.5 ppm). HPLC (1): t = 10.6 min, purity > 99%.
2-Cyclohexyl-5-(4-ethylbenzamido)-6-N,N-dimethylamino-
1H-benzo[d]imidazole (7c-6). White solid (72% yield); mp 177−
178 °C; 1H NMR (400 MHz, CDCl3) δ 1.03−1.23 (m, 3 H), 1.30 (t, J
= 7.65 Hz, 3 H), 1.50−1.63 (m, 3 H), 1.68 (d, J = 7.28 Hz, 2 H), 1.97
(d, J = 11.80 Hz, 2 H), 2.60−2.87 (m, 9 H), 7.38 (d, J = 8.03 Hz, 2 H),
7.61 (br s, 1 H), 7.90 (d, J = 8.03 Hz, 2 H), 8.93 (d, J = 5.02 Hz, 1 H),
9.93 (br s, 3 H); 13C NMR (101 MHz, CDCl3) δ 15.6, 25.9, 26.1, 29.1,
The same procedure was used for the synthesis of 7a-4, 7a-6, 7a-
11−14, 7b-2, 7b-3, 7b-5, 7b-6, 7c-2, 7c-7−10, 7c-13−15, and 7c-17.
2-Cyclohexyl-6-N,N-diethylamino-5-(4-methylbenzamido)-
1H-benzo[d]imidazole (7a-4). White solid (65% yield); mp 183−
184 °C; 1H NMR (300 MHz, CDCl3) δ 0.97 (t, 6 H, J = 6 Hz), 1.20−
1.30 (m, 3 H), 1.58−1.78 (m, 5 H), 2.06−2.08 (m, 2 H), 2.45 (s, 3 H),
2.76−2.77 (m, 1 H), 3.03 (q, 4 H, J = 7.2 Hz), 7.34 (d, 2 H, J = 8.4
Hz) 7.59 (s, 1 H), 7.87 (d, 2 H, J = 8.1 Hz), 8.91 (s, 1 H), 10.31 (s, 1
H); 13C NMR (100 MHz, CDCl3) δ 13.09, 21.48, 25.63, 25.92, 31.72,
38.40, 50.75, 100.9, 113.1, 126.8, 129.6, 131.8, 132.7, 135.0, 139.4,
142.1, 159.8, 165.1. HRMS (FAB) m/z calcd for C25H32N4OH+:
405.2649. Found: 405.2654 (Δ = 1.2 ppm). HPLC (4): t = 10.1 min,
purity > 99%.
K
dx.doi.org/10.1021/jm401468w | J. Med. Chem. XXXX, XXX, XXX−XXX

Journal of Medicinal Chemistry
Article
2-Cyclohexyl-6-N,N-diethylamino-5-(4-propylbenzamido)-
1H-benzo[d]imidazole (7a-6). White solid (56% yield); mp 169−
171 °C; 1H NMR (400 MHz, CDCl3) δ 0.98−1.10 (m, 12 H), 1.56−
1.69 (m, 7 H), 1.93−1.95 (m, 2 H, J = 10 Hz), 2.67−2.71 (m, 3 H),
3.01 (q, 4 H, J = 7.2 Hz), 7.36 (d, 2 H, J = 8.5 Hz), 7.57 (s, 1 H), 7.92
(d, 2 H, J = 8.6 Hz), 9.00 (s, 1 H), 10.40 (s, 1 H); 13C NMR (100
MHz, CDCl3) δ 13.08, 13.73, 24.29, 25.59, 25.89, 31.72, 37.90, 38.40,
50.78, 100.8, 113.2, 126.9, 129.0, 131.8, 132.8, 134.9, 146.9, 159.9,
165.1. HRMS (ESI) m/z calcd for C27H36N4OH+: 433.2962. Found:
433.2961 (Δ = −0.2 ppm). HPLC (1): t = 7.5 min, purity > 99%..
2-Cyclohexyl-6-N,N-dimethylamino-5-(4-propylbenzamido)-
1H-benzo[d]imidazole (7c-7). White solid (75% yield); mp 190−
H), 7.91 (d, J = 8.8 Hz, 2 H), 8.80 (s, 1 H), 9.77 (br s, 1 H); 13C NMR
(101 MHz, CDCl3) δ 24.6, 25.9, 26.2, 32.0, 38.7, 54.1, 55.7, 100.2,
114.4, 128.0, 128.9, 130.1, 136.0, 159.7, 162.6, 164.9. HRMS (FAB)
m/z calcd for C25H30N4O2H+: 419.2442. Found: 419.2450 (Δ = 2.0
ppm). HPLC (2): t = 12.8 min, purity > 98%.
2-Cyclohexyl-5-(4-methylbenzamido)-6-pyrrolodinyl-1H-
benzo[d]imidazole (7b-3). White solid (40% yield); mp 179−180
1
°C; H NMR (500 MHz, CDCl3) δ 1.00−1.37 (m, 4 H), 1.49−1.65
(m, 3 H), 1.71 (dt, J = 13.05, 3.40 Hz, 2 H), 1.92−2.09 (m, 6 H), 2.45
(s, 3 H), 2.73 (m, 1 H), 3.05 (br s, 4 H), 7.34 (d, J = 8.24 Hz, 2 H),
7.58 (br s, 1 H), 7.85 (d, J = 8.20 Hz, 2 H), 8.86 (s, 1 H), 9.85 (br s, 1
H), 10.70 (br s, 1 H); 13C NMR (126 MHz, CDCl3) δ 21.7, 24.6, 25.9,
26.2, 32.0, 38.7, 54.1, 101.9, 110.9, 127.1, 129.8, 129.9, 130.1, 131.3,
132.9, 136.0, 139.9, 142.4, 159.9, 165.4. HRMS (FAB) m/z calcd for
C25H30N4OH+: 403.2492. Found: 403.2496 (Δ = 0.9 ppm). HPLC
(2): t = 9.1 min, purity > 98%.
1
191 °C; H NMR (400 MHz, CDCl3) δ 0.98 (t, J = 7.40 Hz, 3 H),
1.03−1.36 (m, 4 H), 1.48−1.77 (m, 8 H), 1.94 (d, J = 13.30 Hz, 2 H),
2.62−2.80 (m, 9 H), 7.36 (d, J = 8.28 Hz, 2 H), 7.61 (s, 1 H), 7.91 (d,
J = 8.03 Hz, 2 H), 8.94 (s, 1 H), 9.95 (s, 1 H), 11.15 (br s, 1 H); 13C
NMR (101 MHz, CDCl3) δ 14.0, 24.5, 25.8, 26.1, 32.0, 38.1, 38.6,
46.1, 101.8, 110.8, 127.2, 129.0, 129.3, 131.5, 133.2, 139.3, 139.8,
147.2, 160.2, 165.8. HRMS (FAB) m/z calcd for C25H32N4OH+:
405.2649. Found: 405.2651 (Δ = 0.5 ppm). HPLC (1): t = 8.0 min,
purity > 99%.
2-Cyclohexyl-6-N,N-diethylamino-5-(4-fluorobenzamido)-
1H-benzo[d]imidazole (7a-11). White solid (71% yield); mp 213−
214 °C; 1H NMR (400 MHz, methanol-d4) δ 0.98 (t, 6 H, J = 7.2 Hz),
1.09−1.46 (m, 3 H), 1.66−170 (m, 3 H), 1.86−1.89 (m, 2 H), 2.08−
2.12 (m, 2 H, J = 10 Hz), 2.89−2.92 (m, 1 H), 3.04−3.10 (m, 4 H, J =
7.16 Hz), 7.31 (t, 1 H, J = 7.8 Hz), 7.49 (s, 1 H), 7.97−7.99 (m, 1 H),
8.66 (s, 1 H); 13C NMR (100 MHz, methanol-d4) δ13.55, 27.11,
27.33, 32.98, 40.03, 51.89, 117.0, 117.2, 130.5, 130.6, 132.8, 133.3,
137.3, 161.7, 165.2, 165.4, 167.7. HRMS (ESI) m/z calcd for
C24H29FN4OH+: 409.2398. Found: 409.2401 (Δ = 0.7 ppm). HPLC
(1): t = 8.3 min, purity > 99%.
2-Cyclohexyl-6-N,N-diethylamino-5-(2,4-difluorobenzami-
do)-1H-benzo[d]imidazole (7a-12). White solid (79% yield); mp
204−206 °C; 1H NMR (400 MHz, methanol-d4) δ 0.94 (t, 6 H, J = 7.2
Hz), 1.32−1.47 (m, 3 H), 1.64−1.78 (m, 5 H), 1.84−1.86 (m, 2 H, J =
10 Hz), 2.05−2.09 (m, 2 H, J = 10 Hz), 2.77−2.79 (m, 1 H), 2.84−
2.89 (m, 4 H), 7.16−7.18 (m, 2 H), 7.46 (s, 1 H), 8.13−8.19 (m, 1 H),
8.72 (s, 1 H); 13C NMR (100 MHz, methanol-d4) δ 13.15, 27.11,
27.33, 32.97, 40.02, 51.70, 105.0, 105.7, 111.5, 113.7, 119.8, 134.7,
135.7, 137.3, 160.9, 161.4, 161.7, 163.5, 165.4, 167.9. HRMS (ESI) m/
z calcd for C24H28F2N4OH+: 427.2304. Found: 427.2309 (Δ = 1.1
ppm). HPLC (1): t = 7.1 min, purity > 99%.
2-Cyclohexyl-5-(3-phenylpropanamido)-6-pyrrolidinyl-1H-
benzo[d]imidazole (7b-5). White solid (97% yield); mp 146−147
1
°C; H NMR (500 MHz, CDCl3) δ 1.16−1.40 (m, 4 H), 1.57−1.73
(m, 3 H), 1.80 (dt, J = 13.05, 3.40 Hz, 2 H), 1.84−1.94 (m, 4 H), 2.09
(d, J = 12.90 Hz, 2 H), 2.76 (t, J = 7.40 Hz, 2 H), 2.80−2.92 (m, 5 H),
3.11 (t, J = 7.40 Hz, 2 H), 7.15−7.34 (m, 5 H), 7.47 (s, 1 H), 8.58 (s, 1
H), 8.75 (br s, 1 H); 13C NMR (126 MHz, CDCl3) δ 24.5, 26.0, 26.2,
29.9, 32.0, 32.2, 38.7, 40.5, 53.7, 103.2, 109.3, 126.6, 128.5, 128.8,
129.4, 131.6, 136.0, 138.5, 140.6, 159.6, 170.4. HRMS (FAB) m/z
calcd for C26H32N4OH+: 417.2649. Found: 417.2654 (Δ = 1.2 ppm).
HPLC (2): t = 11.3 min, purity > 98%.
2-Cyclohexyl-5-hexanamido-6-pyrrolidinyl-1H-benzo[d]-
imidazole (7b-6). White solid; 61% yield; mp 127−129 °C; 1H NMR
(400 MHz, CDCl3) δ 0.91 (t, 3 H, J = 7.2 Hz), 1.20−1.43 (m, 7 H),
1.63−1.85 (m, 7 H), 1.97 (br s, 4 H), 2.05−2.07 (m, 2 H), 2.47 (t, 2
H, J = 7.2 Hz), 2.83−2.85 (m, 1 H), 2.99 (br s, 4 H), 7.52 (s, 1 H),
8.59 (s, 1 H), 8.91 (s, 1 H); 13C NMR (100 MHz, CDCl3) δ 13.86,
22.43, 24.33, 25.84, 26.09, 31.43, 31.78, 38.57, 53.72, 102.3, 109.7,
129.4, 131.4, 135.5, 138.5, 159.4, 171.2. HRMS (ESI) m/z calcd for
C23H34N4O: 383.2805. Found: 383.2811 (Δ = 1.5 ppm). HPLC (2): t
= 8.8 min, purity > 98%.
5-(4-tert-Butylbenzamido)-2-cyclohexyl-6-N,N-dimethylami-
no-1H-benzo[d]imidazole (7c-8). White solid (74% yield); mp
1
222−223 °C; H NMR (500 MHz, CDCl3) δ 0.96−1.20 (m, 4 H),
1.39 (s, 9 H), 1.49−1.72 (m, 5 H), 1.96 (d, J = 12.21 Hz, 2 H), 2.74 (s,
7 H), 7.58 (d, J = 8.24 Hz, 3 H), 7.93 (d, J = 8.54 Hz, 2 H), 8.97 (s, 1
H), 9.98 (s, 1 H), 11.00 (s, 1 H); 13C NMR (126 MHz, CDCl3) δ
25.8, 26.1, 31.4, 32.0, 35.2, 38.6, 46.2, 101.7, 110.9, 126.2, 127.1, 129.2,
133.0, 139.3, 139.8, 155.5, 160.1, 165.8. HRMS (FAB) m/z calcd for
C26H34N4OH+: 419.2805. Found: 419.2809 (Δ = 0.9 ppm). HPLC
(1): t = 9.0 min, purity > 99%.
5-(3-Allylbenzamido)-2-cyclohexyl-6-N,N-diethylamino-1H-
benzo[d]imidazole (7a-13). White solid (69% yield); mp 89−90
1
°C; H NMR (400 MHz, CDCl3) δ 0.96 (t, 6 H, J = 7.2 Hz), 1.09−
1.10 (m, 3 H), 1.55−1.58 (m, 5 H), 1.91−1.95 (m, 2 H, J = 10 Hz),
2.67 (m, 1 H), 3.00 (q, 4 H, J = 7.2 Hz), 5.36 (d, 1 H, J = 11.1 Hz),
5.85 (d, 1 H, J = 17.5 Hz), 6.75−6.80 (m, 1 H), 7.50 (t, 1 H, J = 7.7
Hz), 7.55 (s, 1 H), 7.61 (d, 1 H, J = 7.7 Hz), 8.82 (d, 1 H, J = 7.8 Hz),
8.04 (s, 1 H); 13C NMR (100 MHz, CDCl3) δ 13.06, 25.49, 25.78,
31.64, 38.39, 50.66, 101.2, 112.9, 115.3, 124.9, 125.7, 129.0, 129.3,
131.4, 135.0, 135.7, 138.3, 160.0, 164.9. HRMS (ESI) m/z calcd for
C26H32N4OH+: 417.2649. Found: 417.2648 (Δ = −0.2 ppm). HPLC
(1): t = 7.3 min, purity > 99%.
2-Cyclohexyl-6-N,N-dimethylamino-5-(thiophene-2-carbox-
amido)-1H-benzo[d]imidazole (7c-9). White solid (75% yield); mp
1
139−140 °C; H NMR (500 MHz, CDCl3) δ 1.00−1.08 (m, 1 H),
1.11−1.24 (m, 2 H), 1.51−1.61 (m, 3 H), 1.63−1.69 (m, 2 H), 1.97
(d, J = 11.90 Hz, 2 H), 2.12 (s, 1 H), 2.69 (s, 6 H), 2.77−2.84 (m, 1
H), 7.16 (dd, J = 4.88, 3.66 Hz, 1 H), 7.56 (d, J = 1.00 Hz, 2 H), 7.67
(dd, J = 3.66, 0.61 Hz, 1 H), 8.72 (s, 1 H), 9.75 (s, 1 H), 10.20 (br s, 1
H); 13C NMR (126 MHz, CDCl3) δ 22.2, 25.7, 26.1, 31.8, 38.5, 45.9,
102.6, 109.7, 128.2, 128.4, 128.7, 130.8, 131.7, 137.9, 139.5, 140.1,
160.1, 160.1, 175.3. HRMS (FAB) m/z calcd for C20H23N4OSH+:
369.1744. Found: 369.1742 (Δ = −0.4 ppm). HPLC (1): t = 11.8 min,
purity > 98%.
2-Cyclohexyl-6-N,N-diethylamino-5-(hexanamido)-1H-
benzo[d]imidazole (7a-14). White solid; 56% yield; mp 183−184
1
°C; H NMR (400 MHz, CDCl3) δ 0.91−1.01 (m, 9 H), 1.23−1.39
(m, 7 H), 1.63−1.83 (m, 7 H), 2.10−2.13 (m, 2 H), 2.47 (t, 2 H, J =
7.2 Hz), 2.86−2.88 (m, 1 H), 2.94 (q, 4 H, J = 7.2 Hz), 7.50 (s, 1 H),
8.74 (s, 1 H), 9.46 (s, 1 H); 13C NMR (100 MHz, CDCl3) δ 12.89,
13.81, 22.39, 25.88, 26.11, 31.43, 31.55, 38.59, 38.72, 50.60, 101.0,
112.6, 131.6, 132.0, 134.4, 139.0, 159.7, 171.1. HRMS (ESI) m/z calcd
for C23H36N4O: 385.2962. Found:385.2967 (Δ = 1.3 ppm). HPLC
(2): t = 6.6 min, purity > 98%.
2-Cyclohexyl-5-(furan-2-carboxamido)-6-N,N-dimethylami-
no-1H-benzo[d]imidazole (7c-10). White solid (71% yield); mp
1
214−215 °C; H NMR (400 MHz, CDCl3) δ 1.10−1.37 (m, 3 H),
1.55−1.84 (m, 5 H), 2.06 (d, J = 14.81 Hz, 2 H), 2.67−2.88 (m, 7 H),
6.56−6.66 (m, J = 3.60, 1.90 Hz, 1 H), 7.22−7.32 (m, 1 H), 7.52−7.68
(m, 2 H), 8.79 (s, 1 H), 9.98 (s, 1 H), 10.59 (s, 1 H); 13C NMR (101
MHz, CDCl3) δ 25.9, 26.2, 32.0, 38.7, 46.0, 101.8, 110.8, 112.6, 114.9,
128.6, 131.2, 139.6, 139.9, 144.7, 148.8, 156.4, 159.9. HRMS (FAB)
m/z calcd for C20H24N4O2H+: 353.1972. Found: 353.1982 (Δ = 2.8
ppm). HPLC (1): t = 11.6 min, purity > 99%.
2-Cyclohexyl-5-(4-methoxybenzamido)-6-pyrrolydinyl-1H-
benzo[d]imidazole (7b-2). White solid (56% yield); mp 195−196
1
°C; H NMR (400 MHz, CDCl3) δ 1.08−1.35 (m, 5 H), 1.52−1.69
(m, 3 H), 1.70−1.80 (m, 2 H), 1.96−2.10 (m, 6 H), 2.76 (m, 1 H),
3.06 (br s, 4 H), 3.90 (s, 3 H), 7.03 (d, J = 8.8 Hz, 2 H), 7.57 (br s, 1
L
dx.doi.org/10.1021/jm401468w | J. Med. Chem. XXXX, XXX, XXX−XXX

Journal of Medicinal Chemistry
Article
2-Cyclohexyl-5-(4-fluorobenzamido)-6-N,N-dimethylamino-
1H-benzo[d]imidazole (7c-13). White solid (70% yield); mp 196−
containing 2× Alamar Blue, were added to the wells to a final
concentration of 1.3 × 104 cells per well. The plates were incubated for
3 days at 37 °C. The IC50 was calculated according to manufacturer
directions.
1
197 °C; H NMR (500 MHz, methanol-d4) δ 2.00−2.26 (m, 3 H),
2.34−2.45 (m, 2 H), 2.46−2.55 (m, 1 H), 2.60 (dt, J = 12.97, 3.28 Hz,
2 H), 2.81 (d, J = 13.12 Hz, 2 H), 3.48 (s, 6 H), 3.58−3.67 (m, 1 H),
8.20 (t, J = 8.85 Hz, 2 H), 8.82 (dd, J = 8.85, 5.49 Hz, 2 H), 9.07 (br s,
1 H), 10.50 (br s, 1 H), 12.80 (s, 1 H); 13C NMR (126 MHz,
methanol-d4) δ 35.1, 35.2, 40.9, 47.3, 54.9, 111.6, 112.1, 119.5, 121.1,
125.3, 125.5, 136.7, 137.5, 139.2, 139.3, 140.3, 141.1, 141.1, 149.3,
150.7, 168.8, 172.7, 174.7. HRMS (FAB) m/z calcd for
C22H25FN4OH+: 381.2085. Found: 381.2088 (Δ = 0.7 ppm). HPLC
(1): t = 11.4 min, purity > 99%.
Mtb FtsZ Protein Preparation.22 E. coli expression plasmid
encoding the ftsz gene (pET 15b vector) was transformed into 100 μL
of BL21(DE3) cells. The transformed cells were plated onto LB plates
containing 100 μg/mL ampicilin. The antibiotic concentration was
kept the same for the following steps. The plates were incubated
overnight at 37 °C. The colonies were picked and grown in 10 mL of
LB medium at 37 °C at 250 rpm shake rate. The inoculum was
transferred to 1 L of LB medium in a 4 L flask and grown to an OD of
0.6 at A600. Then 1 mM IPTG was added to induce protein
expression overnight at 25 °C at 250 rpm shake rate. Next day the cells
were harvested at 4225g for 15 min and resuspended in approximately
20−30 mL of binding buffer (500 mM NaCl, 20 mM sodium
phosphate, pH 7.8). The resuspended cells were lysed using cell
disruptor. The lysate was centrifuged in an ultracentrifuge at 126 603g,
4 °C for 90 min. The supernatant was filtered and loaded onto Ni2+-
NTA column washed with 50 mL of binding buffer and eluted using a
gradient of binding buffer with 30−500 mM imidazole. The eluted
protein was first dialyzed against the polymerization buffer (50 mM
MES, 5 mM MgCl2, 50 mM KCl, pH 6.5) and then polymerization
buffer containing 10% v/v glycerol. Alternatively, the eluted protein
was dialyzed against buffer containing 50 mM Tris, 5 mM MgCl2, 50
mM KCl, pH 7.2, followed by buffer containing 10% v/v glycerol. The
protein after dialysis was concentrated and stored at −80 °C for
further use. Since the number of aromatic residues in Mtb FtsZ protein
are low (Tyr, 1; Trp, 0), it is not reliable to follow concentration of
protein by scanning at A280. The concentration of protein was
therefore ascertained using the Bradford kit from Sigma.
2-Cyclohexyl-5-(2,4-difluorobenzamido)-6-N,N-dimethyla-
mino-1H-benzo[d]imidazole (7c-14). White solid (70% yield); mp
1
212−213 °C; H NMR (400 MHz, methanol-d4) δ 1.29−1.55 (m, 3
H), 1.58−1.94 (m, 5 H), 2.07 (d, J = 12.05 Hz, 2 H), 2.72 (s, 6 H),
2.81−2.95 (m, 1 H), 7.10−7.24 (m, 2 H), 7.45 (s, 1 H), 8.06−8.21
(m, 1 H), 8.63 (s, 1 H); 13C NMR (101 MHz, methanol-d4) δ 27.12,
27.34, 30.81, 32.98, 40.00 46.16, 105.42, 105.69, 105.71, 105.97,
106.17, 108.39, 113.54, 113.57, 113.76, 113.78, 119.94, 119.97, 120.05,
120.09, 130.57, 134.62, 134.65, 134.72, 134.76, 141.75, 161.04, 161.16,
161.54, 161.90, 161.94, 163.53, 163.65, 165.26, 165.39, 167.79. HRMS
(FAB) m/z calcd for C22H24F2N4OH+: 399.1991. Found: 399.1988 (Δ
= −0.7 ppm). HPLC (1): t = 8.9 min, purity > 99%.
2-Cyclohexyl-5-(hexanamido)-6-N,N-dimethylamino-1H-
benzo[d]imidazole (7c-15). White solid (63% yield); mp 114−117
1
°C; H NMR (400 MHz, CDCl3) δ 0.90 (t, 3 H, J = 7.2 Hz), 1.30−
1.39 (m, 7 H), 1.63−1.83 (m, 7 H), 2.06−2.10 (m, 2 H), 2.46 (t, 2 H,
J = 7.2 Hz), 2.65 (s, 6 H), 2.82−2.84 (m, 1 H), 7.51 (s, 1 H), 8.62 (s, 1
H), 8.97 (s, 1 H); 13C NMR (100 MHz, CDCl3) δ 13.89, 22.41, 25.80,
26.07, 31.43, 31.77, 38.56, 45.69, 101.8, 110.1, 128.6, 138.7, 159.6,
171.4. HRMS (ESI) m/z calcd for C21H32N4OH+: 357.2649. Found:
357.2650 (Δ = 0.2 ppm). HPLC (2): t = 8.9 min, purity > 99%.
2-Cyclohexyl-5-[2-(4-methoxyphenyl)acetamido]-6-N,N-di-
methylamino-1H-benzo[d]imidazole (7c-17). White solid (88%
Polymerization Assay.22,38 FtsZ (15 μM) was equilibrated in
polymerization buffer (50 mM MES, 100 mM KCl, 5 mM MgCl2, pH
6.5) at 25 °C. Polymerization was measured by light scattering using a
PTI-QM4 spectrofluorimeter set at 400 nm excitation/emission, 2 nm
slit width, 860 V. Polymerization was initiated with 50 μM GTP and
monitored for up to 30 min. Compound stock solutions were prepared
in DMSO and incubated with Mtb FtsZ prior to initiation of
polymerization with GTP. The percentage of DMSO was maintained
at 2% for all experiments.
1
yield); mp 167−168 °C; H NMR (400 MHz, CDCl3) δ 1.17−1.42
(m, 3 H), 1.55−1.77 (m, 3 H), 1.83 (d, J = 12.80 Hz, 2 H), 2.12 (d, J =
12.05 Hz, 2 H), 2.34 (s, 6 H), 2.79−3.00 (m, 1 H), 3.78 (s, 2 H), 3.83
(s, 3 H), 6.95 (d, J = 8.28 Hz, 6 H), 7.28 (s, 2 H), 7.44 (s, 1 H), 8.63
(s, 1 H), 9.00 (s, 1 H); 13C NMR (101 MHz, CDCl3) δ 26.0, 26.2,
31.9, 38.7, 44.8, 45.5, 55.6, 101.8, 109.9, 114.0, 114.7, 126.7, 129.3,
130.5, 131.0, 139.5, 159.4, 159.5, 169.9. HRMS (FAB) m/z calcd for
C24H30N4O2H+: 407.2442. Found: 407.2246 (Δ = 1.1 ppm). HPLC
(1): t = 13.4 min, purity > 99%.
Transmission Electron Microscopy (TEM) Analysis.22 Stock
solution of compound 5f was prepared in ethanol. Mtb FtsZ (5 μM)
was incubated with 40 or 80 μM compound 5f in the polymerization
buffer (50 mM MES, 5 mM MgCl2, 100 mM KCl, pH 6.5) for 15 min
on ice. To each solution was added GTP to the final concentration of
25 μM. The resulting solution was incubated at 37 °C for 30 min. The
incubated solution was diluted 2 times with the polymerization buffer
and immediately transferred to carbon coated 300 mesh formvar
copper grid and negatively stained with 1% uranyl acetate. To visualize
the effect of compound 5f on preformed polymers, Mtb FtsZ (5 μM)
was allowed to polymerize at 37 °C in the presence of GTP (25 μM)
for 30 min. Compound 5f (40 or 80 μM) was added to the
polymerized protein and incubated for additional 5 min. The resulting
solution was diluted 2 times with the polymerization buffer and
immediately transferred to carbon coated 300 mesh formvar copper
grid and negatively stained with 1% uranyl acetate. The samples were
viewed with a FEI Tecnai12 BioTwinG transmission electron
microscope at 80 kV. Digital images were acquired with an AMT
XR-60 CCD digital camera system.
Bacterial Strains and Growth.22,37 H37Rv, the drug sensitive
laboratory strain of Mtb, and clinical Mtb strains W210, NHN382, and
TN587 exhibiting different resistant profiles to isoniazid were used.
For evaluation of drug sensitivity all strains were grown in Difco 7H9
Middlebrook liquid medium (BD Biosciences, 271310) supplemented
with 10% Middlebrook OADC enrichment (VWR, 9000-614), 0.05%
Tween (G-Biosciences, 786-519), and 0.2% glycerol at 37 °C.
Antibacterial Activity.22,36 M. tuberculosis H37Rv strain and
clinical isolates were used in the antibacterial studies, which were
grown at 37 °C in Difco 7H9 Middlebrook liquid medium
supplemented with 10% Middlebrook OADC enrichment, 0.05%
Tween, and 0.2% glycerol. The minimum inhibitory concentration
(MIC) of the compounds was determined by the microplate Alamar
Blue assay (MABA) in triplicate. The compounds were prepared in
DMSO and were serially diluted 2-fold in 96-well microtiter plates.
Bacteria were added to the appropriate wells in the plate, and the
plates were incubated for 6 days at 37 °C. Alamar Blue was added to
the plates, and the plates were incubated for an additional 24 h at 37
°C. The MIC was the lowest concentration (μg/mL) of compound
that inhibited bacterial growth and prevented a color change.
ASSOCIATED CONTENT
Cytotoxicity Assay. The cytotoxicity of the compounds was tested
against a cell line that originated from the epithelial cells from the
kidneys of Cercopithecus aethiops (Vero). Vero cells were grown
without CO2 in L15 medium supplemented with antibiotics and heat
inactivated calf serum. Serial 2-fold dilutions of the drugs were
prepared in the 96-well microplates. The Vero cells, in medium
■
S
* Supporting Information
NMR spectral of new benzimidazole intermediates. This
material is available free of charge via the Internet at http://
pubs.acs.org.
M
dx.doi.org/10.1021/jm401468w | J. Med. Chem. XXXX, XXX, XXX−XXX

Journal of Medicinal Chemistry
Article
(17) Slayden, R. A.; Knudson, D. L.; Belisle, J. T. Identification of cell
cycle regulators in Mycobacterium tuberculosis by inhibition of septum
formation and global transcriptional analysis. Microbiology 2006, 152,
1789−1797.
(18) Awasthi, D.; Kumar, K.; Ojima, I. Therapeutic potential of FtsZ
inhibition: a patent perspective. Expert Opin. Ther. Pat. 2011, 21, 657−
679.
AUTHOR INFORMATION
Corresponding Author
*To whom correspondences should be addressed. Phone: 631-
632-1339. Fax: 631-632-7942. E-mail: iwao.ojima@stonybrook.
edu.
■
Notes
(19) Beuria, T. K.; Singh, P.; Surolia, A.; Panda, D. Promoting
assembly and bundling of FtsZ as a strategy to inhibit bacterial cell
division: a new approach for developing novel antibacterial drugs.
Biochem. J. 2009, 423, 61−69.
(20) White, E. L.; Suling, W. J.; Ross, L. J.; Seitz, L. E.; Reynolds, R.
C. 2-Alkoxycarbonylaminopyridines: inhibitors of Mycobacterium
tuberculosis FtsZ. J. Antimicrob. Chemother. 2002, 50, 111−114.
(21) Reynolds, R. C.; Srivastava, S.; Ross, L. J.; Suling, W. J.; White,
E. L. A new 2-carbamoyl pteridine that inhibits mycobacterial FtsZ.
Bioorg. Med. Chem. Lett. 2004, 14, 3161−3164.
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This research is supported by grants from the National
Institutes of Health (Grant AI078251 to I.O. and Grant
AI082164 to R.A.S.). The authors gratefully acknowledge the
technical support of Susan Van Horn for TEM operation at the
Microscopy Imaging Center at Stony Brook University, NY.
(22) Kumar, K.; Awasthi, D.; Lee, S.-Y.; Zanardi, I.; Ruzsicska, B.;
Knudson, S.; Tonge, P. J.; Slayden, R. A.; Ojima, I. Novel trisubstituted
benzimidazoles, targeting Mtb FtsZ, as a new class of antitubercular
agents. J. Med. Chem. 2011, 54, 374−381.
(23) Laeppchen, T.; Hartog, A. F.; Pinas, V. A.; Koomen, G.-J.; Den
Blaauwen, T. GTP analogue inhibits polymerization and GTPase
activity of the bacterial protein FtsZ without affecting its eukaryotic
homologue tubulin. Biochemistry 2005, 44, 7879−7884.
(24) Paradis-Bleau, C.; Beaumont, M.; Sanschagrin, F.; Voyer, N.;
Levesque, R. C. Parallel solid synthesis of inhibitors of the essential cell
division FtsZ enzyme as a new potential class of antibacterials. Bioorg.
Med. Chem. 2007, 15, 1330−1340.
(25) Parhi, A.; Kelley, C.; Kaul, M.; Pilch, D. S.; LaVoie, E. J.
Antibacterial activity of substituted 5-methylbenzo[c]-
phenanthridinium derivatives. Bioorg. Med. Chem. Lett. 2012, 22,
7080−7083.
(26) Beuria, T. K.; Santra, M. K.; Panda, D. Sanguinarine blocks
cytokinesis in bacteria by inhibiting FtsZ assembly and bundling.
Biochemistry 2005, 44, 16584−16593.
(27) Mathew, B.; Ross, L.; Reynolds, R. C. A novel quinoline
derivative that inhibits mycobacterial FtsZ. Tuberculosis (Oxford, U. K.)
2013, 93, 398−400.
REFERENCES
■
(1) Executive Summary of Global Tuberculosis Report 2012 by
World Health Organization: http://www.who.int/tb/publications/
global_report/gtbr12_executivesummary.pdf.
(2) Gandhi, N. R.; Moll, A.; Sturm, A. W.; Pawinski, R.; Govender,
T.; Lalloo, U.; Zeller, K.; Andrews, J.; Friedland, G. Extensively drug-
resistant tuberculosis as a cause of death in patients co-infected with
tuberculosis and HIV in a rural area of South Africa. Lancet 2006, 368,
1575−1580.
(3) Bloom, B. R.; Murray, C. J. Tuberculosis: commentary on a
reemergent killer. Science 1992, 257, 1055−1064.
(4) Centers for Disease Control and Prevention. Tuberculosis: Basic
TB Facts. http://www.cdc.gov/tb/topic/basics/default.html.
(5) Raviglione, M. C. Issues facing TB control (7). Multiple drug-
resistant tuberculosis. Scott. Med. J. 2000, 45, 52−55 (discussion 56).
(6) Kumar, K.; Awasthi, D.; Berger, W. T.; Tonge, P. J.; Slayden, R.
A.; Ojima, I. Discovery of anti-TB agents that target the cell-division
protein FtsZ. Future Med. Chem. 2010, 2, 1305−1323.
(7) Margalit, D. N.; Romberg, L.; Mets, R. B.; Hebert, A. M.;
Mitchison, T. J.; Kirschner, M. W.; RayChaudhuri, D. Targeting cell
division: small-molecule inhibitors of FtsZ GTPase perturb cytokinetic
ring assembly and induce bacterial lethality. [Erratum to document
cited in CA141:271048]. Proc. Natl. Acad. Sci. U.S.A. 2004, 101, 13969.
(8) Vollmer, W. The prokaryotic cytoskeleton: a putative target for
inhibitors and antibiotics? Appl. Microbiol. Biotechnol. 2006, 73, 37−47.
(9) Huang, Q.; Tonge Peter, J.; Slayden Richard, A.; Kirikae, T.;
Ojima, I. FtsZ: a novel target for tuberculosis drug discovery. Curr.
Top. Med. Chem. 2007, 7, 527−543.
(10) Ben-Yehuda, S.; Losick, R. Asymmetric cell division in B. subtilis
involves a spiral-like intermediate of the cytokinetic protein FtsZ. Cell
(Cambridge, MA, U. S.) 2002, 109, 257−266.
(11) Goehring, N. W.; Beckwith, J. Diverse paths to midcell:
assembly of the bacterial cell division machinery. Curr. Biol. 2005, 15,
R514−R526.
(12) Leung, A. K.; White, L. E.; Ross, L. J.; Reynolds, R. C.; DeVito,
J. A.; Borhani, D. W. Structure of Mycobacterium tuberculosis FtsZ
reveals unexpected, G protein-like conformational switches. J. Mol.
Biol. 2004, 342, 953−970.
(13) Moller-Jensen, J.; Loewe, J. Increasing complexity of the
bacterial cytoskeleton. Curr. Opin. Cell Biol. 2005, 17, 75−81.
(14) Thanedar, S.; Margolin, W. FtsZ exhibits rapid movement and
oscillation waves in helix-like patterns in Escherichia coli. Curr. Biol.
2004, 14, 1167−1173.
(15) Huang, Q.; Kirikae, F.; Kirikae, T.; Pepe, A.; Amin, A.; Respicio,
L.; Slayden, R. A.; Tonge, P. J.; Ojima, I. Targeting FtsZ for
antituberculosis drug discovery: noncytotoxic taxanes as novel
antituberculosis agents. J. Med. Chem. 2006, 49, 463−466.
(16) Respicio, L.; Nair, P. A.; Huang, Q.; Burcu, A. B.; Tracz, S.;
Truglio, J. J.; Kisker, C.; Raleigh, D. P.; Ojima, I.; Knudson, D. L.;
Tonge, P. J.; Slayden, R. A. Characterizing septum inhibition in
Mycobacterium tuberculosis for novel drug discovery. Tuberculosis 2008,
88, 420−429.
(28) Kelley, C.; Zhang, Y.; Parhi, A.; Kaul, M.; Pilch, D. S.; LaVoie, E.
J. 3-Phenyl substituted 6,7-dimethoxyisoquinoline derivatives as FtsZ-
targeting antibacterial agents. Bioorg. Med. Chem. 2012, 20, 7012−
7029.
(29) Parhi, A.; Lu, S.; Kelley, C.; Kaul, M.; Pilch, D. S.; LaVoie, E. J.
Antibacterial activity of substituted dibenzo[a,g]quinolizin-7-ium
derivatives. Bioorg. Med. Chem. Lett. 2012, 22, 6962−6966.
(30) Haydon, D. J.; Stokes, N. R.; Ure, R.; Galbraith, G.; Bennett, J.
M.; Brown, D. R.; Baker, P. J.; Barynin, V. V.; Rice, D. W.;
Sedelnikova, S. E.; Heal, J. R.; Sheridan, J. M.; Aiwale, S. T.; Chauhan,
P. K.; Srivastava, A.; Taneja, A.; Collins, I.; Errington, J.; Czaplewski, L.
G. An inhibitor of FtsZ with potent and selective anti-staphylococcal
activity. Science (Washington, DC, U. S.) 2008, 321, 1673−1675.
(31) Haydon, D. J.; Bennett, J. M.; Brown, D.; Collins, I.; Galbraith,
G.; Lancett, P.; Macdonald, R.; Stokes, N. R.; Chauhan, P. K.; Sutariya,
J. K.; Nayal, N.; Srivastava, A.; Beanland, J.; Hall, R.; Henstock, V.;
Noula, C.; Rockley, C.; Czaplewski, L. Creating an antibacterial with in
vivo efficacy: synthesis and characterization of potent inhibitors of the
bacterial cell division protein FtsZ with improved pharmaceutical
properties. J. Med. Chem. 2010, 53, 3927−3936.
(32) Plaza, A.; Keffer, J. L.; Bifulco, G.; Lloyd, J. R.; Bewley, C. A.
Chrysophaentins A−H, antibacterial bisdiarylbutene macrocycles that
inhibit the bacterial cell division protein FtsZ. J. Am. Chem. Soc. 2010,
132, 9069−9077.
(33) Mathew, B.; Srivastava, S.; Ross, L. J.; Suling, W. J.; White, E. L.;
Woolhiser, L. K.; Lenaerts, A. J.; Reynolds, R. C. Novel pyridopyrazine
and pyrimidothiazine derivatives as FtsZ inhibitors. Bioorg. Med. Chem.
2011, 19, 7120−7128.
(34) Awasthi, D.; Park, B.; Kumar, K.; Melief, E.; Knudson, S.;
Slayden, R. A.; Ojima, I. Synthesis and Biological Evaluation of Novel
N
dx.doi.org/10.1021/jm401468w | J. Med. Chem. XXXX, XXX, XXX−XXX

Journal of Medicinal Chemistry
Article
Antitubercular Trisubstituted Benzimidazoles and C-seco Taxoids
Targeting FtsZ. Presented at the 243rd National Meeting and
Exposition of the American Chemical Society, San Diego, CA,
March 25−29, 2012; MEDI 388.
(35) Kumar, K.; Awasthi, D.; Park, B.; Melief, E.; Cummings, J.;
Knudson, S.; Slayden, R. A.; Ojima, I. Synthesis, Optimization and
Biological Evaluation of Novel Benzimidazoles as Efficacious
Antitubercular and Broad-Spectrum Antimicrobial Agents, Targeting
FtsZ. Presented at the 244th National Meeting and Exposition of the
American Chemical Society, Philadelphia, PA, August 19−23,2012;
MEDI 18447.
(36) Collins, L.; Franzblau, S. G. Microplate Alamar blue assay versus
BACTEC 460 system for high-throughput screening of compounds
against Mycobacterium tuberculosis and Mycobacterium avium. Anti-
microb. Agents Chemother. 1997, 41, 1004−1009.
(37) Boyne, M. E.; Sullivan, T. J.; amEnde, C. W.; Lu, H.; Gruppo,
V.; Heaslip, D.; Amin, A. G.; Chatterjee, D.; Lenaerts, A.; Tonge, P. J.;
Slayden, R. A. Targeting fatty acid biosynthesis for the development of
novel chemotherapeutics against Mycobacterium tuberculosis: evaluation
of A-ring-modified diphenyl ethers as high-affinity InhA inhibitors.
Antimicrob. Agents Chemother. 2007, 51, 3562−3567.
(38) White, E. L.; Ross, L. J.; Reynolds, R. C.; Seitz, L. E.; Moore, G.
D.; Borhani, D. W. Slow polymerization of Mycobacterium tuberculosis
FtsZ. J. Bacteriol. 2000, 182, 4028−4034.
O
dx.doi.org/10.1021/jm401468w | J. Med. Chem. XXXX, XXX, XXX−XXX