2-Phenylimidazopyridines, a new series of golgi compounds with potent antiviral activity

Article abstract of DOI:10.1021/jm0704907

Drugs targeted to viral proteins are highly vulnerable to the development of resistant strains. We previously characterized a group of 2-phenylbenzimidazole compounds for their activity against allergy and asthma and more recently established the Golgi as

Full text of DOI:10.1021/jm0704907

5984
J. Med. Chem. 2007, 50, 5984-5993
2-Phenylimidazopyridines, a New Series of Golgi Compounds with Potent Antiviral Activity
Homayon Banie,† Anjana Sinha, Richard J. Thomas, Jagadish C. Sircar, and Mark L. Richards*
AVanir Pharmaceuticals, 101 Enterprise, Aliso Viejo, California 92656
ReceiVed April 26, 2007
Drugs targeted to viral proteins are highly vulnerable to the development of resistant strains. We previously
characterized a group of 2-phenylbenzimidazole compounds for their activity against allergy and asthma
and more recently established the Golgi as their probable site of action. Herein we describe their activity
against the propagation of several virus types through an action on the host cell. The most potent derivatives
are the novel 2-phenylimidazopyridines, the lead compound of which is highly effective for blocking the
spread of topical herpes infection in an animal model. These agents may provide an alternative antiviral
approach, particularly for treating resistant strains.
Introduction
potent imidazopyridine derivative, N-(4-(6-adamantanecarboxa-
mido)-3H-imidazo[4,5-c]pyridin-2-yl)phenyl)adamantanecar-
boxamide (4a) is shown to be highly effective at aborting the
development of vesicles in a guinea pig model of herpes
infection.
The development of small molecule antiviral drugs has
expanded in recent years primarily because of the success of
HIVa (human immunodeficiency virus) drugs such as the
protease and nucleosides reverse transcription inhibitors. How-
ever, viruses are innately efficient at developing resistance to
these agents, thus requiring the use of drug combinations that
target different viral proteins.1 One largely unexplored approach
to the treatment of viral diseases is the development of agents
that target the host cell. Advantages of this strategy include a
vastly expanded list of potential targets, a broader spectrum of
activity, and less (theoretical) susceptibility to the development
of resistance. Brefeldin A (BFA) is one such compound,
disrupting Golgi function through inhibitory action on host cell
ARF-1 GTPase.2 A prominent disadvantage of targeting host
cell proteins is a higher potential for toxicity, which for BFA
is certainly the case. Nonetheless, the absolute dependence of
virus on normal cellular functions and the wealth of unexplored
host cell targets for treating viral diseases warrant further
investigation of this approach.
Chemistry
Synthesis of the 2-phenylbenzimidazole compounds (Series
1, 2) have been described.3,4 Series 3 and 4 compounds are
depicted in Schemes 1 and 2, respectively.
In one method (Scheme 1), 4-aminopicolinic acid was
prepared by catalytic hydrogenation of commercially available
picloram methyl ester (Sigma-Aldrich, St Louis, MO) and used
as the starting material. Simultaneous nitration and rearrange-
ment of 4-aminopicolinic acid by concd H2SO4 and potassium
nitrate followed with esterification of the carboxylic acid group
gave ethyl 4-amino-5-nitropyridine-1-carboxylate. Catalytic
hydrogenation of the latter over palladium on carbon in
2-propanol resulted in ethyl 4,5-diaminopyridine-2-carboxylate
(5). The diamine 5 was coupled to 4-nitrobenzaldehyde (6) in
nitrobenzene at 200 °C to give ethyl 2-(4-nitrophenyl)-3H-
imidazo[4,5-c]pyridine-6-carboxylate (7) as a brown solid.
Hydrolysis of the ethyl ester of 7 with 10% ethanolic NaOH at
reflux gave 2-(4-nitrophenyl)-3H-imidazo[4,5-c]pyridine-6-
carboxylic acid (8). Coupling of the free acid 8 to the appro-
priate alkyl or aliphatic amines with CDI in DMF afforded the
nitro amide 9. The nitro group in 9 was reduced to the
corresponding amine of 10 and finally coupled with an appro-
priate acid chloride to yield the final compounds of this series
3a to 3e.
We previously described a new class of 2-(substituted
phenyl)benzimidazole (2-PB) drugs (1 and 2) that are effective
in animal models of asthma, cancer, and inflammation.3-6
Recent work has shown that these compounds act on the Golgi
apparatus, resulting in a disruption of cisternae, displacement
of resident Golgi proteins, and perturbation of oligosaccharide
processing.7 Because many viruses are known to utilize the
Golgi of host cells during their life cycle, these compounds were
tested for their ability to inhibit virus. We report that these agents
inhibit the infectivity of viruses from several families that share
a common need for host cell Golgi to envelop or move through
the cell. In addition, a novel group of imidazopyridine deriva-
tives (3 and 4) of the 2-PB backbone are described that share
many characteristics with the corresponding 2-PB compounds
but with a higher relative potency for inhibiting virus. The most
* To whom correspondence should be addressed. Phone: (858) 414-
1821. Fax: (949) 643-6815. E-mail: marklrichards@yahoo.com.
† Current address: Department of Immunology, Johnson and Johnson
Pharmaceutical Research and Development, 3210 Merryfield Row, San
Diego, CA 92121.
a Abbreviations: 2-PB, 2-(substituted phenyl)benzimidazole; 2-PIP,
2-(substituted phenyl)imidazopyridine; HIV, human immunodeficiency
virus; ERGIC, endoplasmic reticulum-Golgi intermediate compartment;
BFA, brefeldin A; MOI, multiplicity of infection; PFU, plaque-forming
units; HSV, herpes simplex virus; VSV, vesicular stomatitis virus; MHV,
mouse hepatitis virus; VZV, varicella zoster virus; SV40, simian virus 40.
In another method (Scheme 2), the diamino backbone (13)
was prepared from 2-(4-nitrophenyl)-3H-imidazo[4,5-c]pyridine-
6-carboxylic acid (8). Curtius reaction of the acid 8 with DPPA,
Et3N, and t-BuOH using NMP as a solvent afforded the
nitrocarbamate 11. This carbamate was subjected to nitro group
10.1021/jm0704907 CCC: $37.00 © 2007 American Chemical Society
Published on Web 10/31/2007

AntiViral 2-Phenylimidazopyridines
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 24 5985
Scheme 1a
a Key: (a) Nitrobenzene, 200 °C, 18h; (b) 10% NaOH, EtOH, 90 °C, 1 h, 3 N HCl; (c) RNH2, CDI or PyBop, DMF, RT or 100 °C, 16 h; (d) Raney
nickel, MeOH-THF-DMF, H2, 85 °C, 2 h; (e) (i) R′COCl, Py, RT, 4 h; (ii) 10% NaOH, EtOH, RT, 1 h.
Scheme 2a
a Key: (a) NMP, DPPA, Et3N, tert-BuOH, 85 °C, 6 h; (b) 10% Pd/C, NMP, 45 °C, 12 h; (c) HCl, dioxane, 90 °C, 1 h; (d) (i) RCOCl or R′COCl, Py,
120 °C, 3 h; (ii) 10% NaOH, EtOH, RT, 1 h; (e) NaBH4, EtOH, 90 °C, 1 h.
reduction with palladium on carbon in a Parr shaker to afford
amine 12. The amine carbamate 12 was hydrolyzed with acid
to afford the diamine salt 13 which was coupled with the
appropriate acid chlorides at 120 °C to afford the bisamides
4a-c. For the nonsymmetrical bisamides 4d-g, the amine 12
was coupled with appropriate acid chlorides to afford the amide
carbamates 14d,e. The carbamate group in 14 was hydrolyzed
to the corresponding amine and subsequently coupled with
appropriate acid chlorides in pyridine at 120 °C to afford the
unsymmetrical diamides 4d-g.
General Methods. All reactions were carried out under an
inert argon atmosphere with dry solvents under anhydrous
conditions unless otherwise stated. All dried solvents (THF,
DMF, DCM, NMP, MeOH, pyridine, Et3N) and reagents were
purchased at the highest commercial quality from Aldrich and
used without further purification. Reactions were monitored by
thin layer chromatography (TLC) carried out on 0.25 mm E.
Merck silica gel plates (60F-254) using UV light (λmax ) 254)
for visualization and an acidic mixture of p-anisaldehyde and
phosphomolybdic acid and heat as the developing agents. E.
Merck silica gel (60, particle size 0.043-0.063 mm) was used
for flash column chromatography. NMR spectra were recorded
on Bruker DRX-400 instruments and calibrated using residual
undeuterated solvent as an internal reference. The following
abbreviations (or combinations thereof) were used to explain
the multiplicities: s ) singlet, d ) doublet, t ) triplet, q )
quartet, m ) multiplet, br ) broad. Low-resolution mass spectra
were recorded on an Agilent LC/MS system.
propagation of nine viruses representing eight distinct viral
families. Antiviral potency was compared to their potency for
inhibiting IgE in vitro. New derivatives of these 2-PB com-
pounds were also synthesized and tested, resulting in the
identification of 2-phenylimidazopyridines (2-PIP) as the most
potent antiviral analogues. One of the latter agents 4a was tested
for its ability to prevent vesicular eruption in a guinea pig model
of topical herpes infection.
Reagents. All cell lines and viruses were obtained from
ATCC. Vero, HeLa, and HeLa-H1 cells were cultured in MEM
media (Gibco); NCTC clone 1469 was cultured in high glucose
DMEM media (Gibco). Media formulations contained 10% FBS
(Omega Scientific, Tarzana, CA), 2 mM L-glutamine and 1%
penicillin-streptomycin solution (final 50 units/mL and 50 µg/
mL, respectively) (Gibco), and maintained at 37 °C in a 10%
CO2 (DMEM and MEM) or 5% CO2 (RPMI) atmosphere.
Female hairless IAF/HA-HO guinea pigs were purchased
from Charles River (Wilmington, MA). Murine recombinant
IL-4 was obtained from PeproTech, Inc. (Rocky Hill, NJ). Anti-
mouse CD40 antibody was obtained from BD-Pharmingen (San
Jose, CA). Polyclonal goat antibodies against mouse IgE were
prepared in-house as described.8 Horseradish peroxidase-labeled
anti-goat antibody was obtained from Santa Cruz Biotechnology,
Inc.
IgE Response. This assay is described in detail in a previous
report.3 Briefly, spleen cells were isolated from na¨ıve female
BALB/c mice and cultured for 4 days in the presence or absence
of IL-4 (10 ng/mL) and anti-CD40 antibody (100 ng/mL).
ELISA plates were prepared by coating with 1 µg/mL goat anti-
mouse IgE overnight followed by an overnight incubation with
the 4-day culture supernatants at 4 °C. IgE was quantified
following successive 90 min incubations with biotinylated goat
Biological Methods
General Approach. To determine the specificity of their
antiviral effect, 2-PB compounds were tested against the

5986 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 24
Table 1. Structure and Antiviral Activity of 2-Phenylbenzimidazolesa
Banie et al.
a Antiproliferative supersedes antiviral effect.
anti-mouse IgE, alkaline phosphatase-streptavidin (Zymed,
Carlsbad, CA), and 100 µL of phenolphthalein monophosphate,
DCHA salt (40 mg/mL). Absorption was measured at 540λ.
to estimate virus spread. MHV infectivity was visually estimated
from the prevalence of clumped or lysed cells. SV40 infectivity
was assessed by syncytia formation.
In Vivo HSV-2 Model. Female hairless IAF/HA-HO guinea
pigs were anesthetized with isoflurane (Abbott Laboratories,
North Chicago, IL) and inoculated with 1 million plaque forming
units (PFU) of HSV-2 (MS strain) with a tattoo marker
(Spaulding and Rogers Inc., Voorheesville, NY). Each guinea
pig was inoculated with virus at three sites on the back, and
the treatment modality was rotated between each of the sites.
Drug treatment was initiated 24 h after inoculation by applying
50 µL of vehicle/drug and continued four times per day at about
2.5 h intervals. Results were assessed on day 4 following
inoculation. Delivery of 4a was accomplished in a vehicle
consisting of 38% Gelucire 44/14, (Gattefosse´, Cedex, France),
38% polyethylene glycol 400, 10% tween 80, and 10%
1-methyl-2-pyrrolidinone (Sigma-Aldrich).
Viral Propagation. Cells were seeded at approximately
50 000/well in 24-well polystyrene plates. After 24 h fresh media
was added without or with virus at a multiplicity of infection
(MOI) of 0.1 or less, along with drug. Vero cells were infected
with herpes simplex virus (HSV), vaccinia, vesicular stomatitis
virus (VSV), California encephalitis, San Angelo, or Simian
virus 40 (SV40). Mouse hepatitis virus (MHV) was grown in
NCTC clone-1469 cells, and Modoc and Rhino viruses were
grown in HeLa-H1 cells. When viral infectivity became evident,
cells were washed and stained (1 g of methylene blue, 0.5 g of
carbol fushin, 400 mL of methanol) for 10 min at room
temperature. For plaque-forming viruses (HSV, vaccinia, Mo-
doc, California Encephalitis, San Angelo, VSV, and Rhino),
visual enumeration of clear zones on the culture plates was used

AntiViral 2-Phenylimidazopyridines
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 24 5987
Results and Discussion
Using a proteomic approach, we previously localized the
molecular activity of 2-PB compounds to a group of proteins
that function within the Golgi, whereas proteins of other
organelles involved in synthesis, processing, and transport are
apparently left unperturbed.7 The affected proteins normally
move in an anterograde fashion co-incident with the natural
process of Golgi maturation and recycled back to proximal Golgi
membranes by coatomer-coated vesicles known as COPI.9 In
cells exposed to 2-PB compounds, there is a defect in the
recycling of these proteins from the distal membranes (trans-
Golgi or trans-Golgi network) to the proximal membranes of
the Golgi apparatus, resulting in the displacement of these
proteins from the juxtanuclear region. This is normally followed
by their degradation in the proteosome or lysosome,7 although
in resistant cancer cells these proteins are not degraded.5
Moreover, co-incident with the displacement of these proteins
is a change in the morphology of Golgi cisternae and a protein
glycosylation defect that gives rise to EndoH sensitivity thus
further implicating enzymes localized to the Golgi.7 Finally,
these actions are observed following exposure to the same drug
concentrations that give rise to suppression of cytokine and IgE
responses.
The impact of these agents on the Golgi of eukaryotic cells
would suggest that they may affect the propagation of certain
viruses that employ the Golgi for their intracellular maturation.
Viruses exhibit multiple structure types, encode a diverse array
of proteins, and employ a variety of mechanisms to reproduce
and spread from cell to cell. To aid its packaging, lipid
envelopment, and transportation through the host cell, viruses
utilize many cellular proteins and organelles. Many viruses
appear to rely on the Golgi apparatus, for example, to contribute
membrane for lipid envelopment or to participate in the
processing of critical viral proteins. Because 2-PB compounds
cause dysfunctions in protein and presumably lipid processing
events,7 the activity of these agents was tested against virus.
Selected 2-PB compounds were tested for their effect on nine
viruses representing eight different families (Table 1). Four
different cell lines were used to grow virus in vitro. Compounds
chosen for testing represent a cross-section of the agents
previously tested for their activity against IgE3,4 including
compounds previously shown to be effective in models of
allergy (1d) and cancer (2a, 1c). Of the 11 viruses tested, 9
(HSV-1, HSV-2, VZV, vaccinia, MHV, California Encephalitis,
San Angelo, Modoc, and Rhino) were highly susceptible to the
action of 2-PB drugs while 2 (VSV and SV40) showed
substantial resistance. Not shown are the results with HSV-1
or VZV of the HerpesViridae, which paralleled the results with
HSV-2 (data not shown).
Figure 1. The IC50 of a series of paired 2-PB and 2-PIP compounds
against IgE response in vitro are plotted. Each data point plots the IC50
of a benzimidazole (2-PB) and aza-derivative (2-PIP), which differ only
in the “Z” position (C or N, respectively). A. IC50s for analogues having
the OC-N - N-CO amide linkage are plotted. The mean IC50 values
for 2-PB and aza-derivative (2-PIP) compounds are 19 nM and 18 nM,
respectively. B. IC50s for analogues having the N-CO-N-CO amide
linkage are plotted. Mean values for 2-PB and 2-PIP compounds are
29 nM and 180 nM, respectively. Two-tailed comparison showed a
significant correlation between the IC50s for the paired 2-PB and 2-PIP
compounds (P < 0.0002).
vaccinia, Small Pox) and PicornaViridae (e.g., Rhinovirus,
Polio). Moreover, because they act on the Golgi, these com-
pounds may inhibit viruses from other families known to rely
on this organelle, including viruses from ArenaViridae (e.g.,
Lassa), CalciViridae (e.g., Norwalk), FiloViridae (e.g., Ebola),
HepadnaViridae (e.g., Hepatitis B), RetroViridae (e.g., HIV),
and TogaViridae (e.g., rubella).
Viruses that are not affected by these drugs include SV40
(PapoVaViridae) and VSV (RhabdoViridae). While the G protein
of the lipid enveloped VSV is glycosylated within the Golgi,12
its processing has not been reported to be critical for function.
SV40 is nonenveloped, and there have been no reports linking
any critical Golgi processing events for this virus.13 Interestingly,
another compound known to inhibit Golgi function, BFA, has
been reported to block SV40 infectivity.14 However this action
of BFA is mediated by perturbation of the caveosome, a non-
Golgi organelle important for the life cycle of SV40. These
results differentiate the action of BFA from 2-PB compounds,
confirm the putative site of activity of these agents, and further
underline the importance of the Golgi for the infectivity of many
important viral pathogens.
While testing new analogues of the 2-PB compounds, a group
of 2-phenylimidazopyridine derivatives (2-PIP) with a high
potency for suppressing IgE response were identified. A number
of analogues of the 2-PIP compounds were then synthesized
and tested for IgE suppression, revealing a close parallel with
the potency of 2-PB compounds. Because of their greater
potential as therapeutic agents, only two of the four series of
benzimidazole compounds4 are compared. When orienting the
amide linkages flanking the imidazole core as mirror images
With the exception of Rhinovirus of the PicornaViridae
family, viruses susceptible to the action of these compounds
have been reported to use membranes of the Golgi, a pre-Golgi
compartment known as the ERGIC (endoplasmic reticulum-
Golgi intermediate compartment), or the trans-Golgi network
for their envelopment.10 Rhinovirus on the other hand, are
nonenveloped and thus do not require lipid. They do however
pass through the ERGIC during their life cycle and have been
reported to perturb Golgi function.11 Thus, all of the susceptible
viruses are linked by their requirement for a functioning Golgi.
These viruses are members of virus families that include
important human pathogens such as BunyaViridae (e.g., Cali-
fornia Encephalitis, San Angelo, Hanta), CoronaViridae (e.g.,
SARS), FlaViViridae (e.g., Modoc, Hepatitis C, West Nile),
HerpesViridae (e.g., HSV-1, HSV-2, VZV), PoxViridae (e.g.,

5988 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 24
Table 2. Structure and Antiviral Activity of 2-Phenylimidazopyridinesa
Banie et al.
a Antiproliferative supersedes antiviral effect.
(OC-N - N-CO; series 2 and 4), a comparable inhibition of
IgE results for the corresponding 2-PB and 2-PIP analogues
(Figure 1A). A similar comparison wherein the amides are in
tandem (N-CO-N-CO; series 1 and 3), however, results in a
steeper curve indicating that the comparable 2-PIP compounds
are of lower potency than the 2-PB analogues (Figure 1B). This
loss of activity probably results from an interaction between
the aza nitrogen with the amide. Thus with the caveat that the
series 3 2-PIP agents have lower relative potency than the
corresponding series 1 2-PB compounds, the SAR previously
developed for IgE suppression by the 2-PB compounds4 applies
to the new 2-PIP agents.
Table 2 shows the antiviral activity of selected 2-PIP
compounds, which for the most part also follows the pattern
observed with the 2-PB compounds in Table 1. Indeed, a
comparison of the activity of the 24 compounds listed in Tables
1 and 2 against HSV-2 (HerpesViridae) versus vaccinia virus
(PoxViridae) in Vero cells forms a linear relationship (Figure
2). This linearity was maintained when comparing IC50s for
inhibition of HSV-2 with other susceptible viruses, including
MHV, Modoc, and Rhino viruses (see Supporting Information).
The relationships did not achieve significance when comparing
activity against HSV-2 with members of the BunyaViridae
(California Encephalitis and San Angelo viruses), although a
tendency for a positive relationship is evident. These results
suggest that in general 2-PB and 2-PIP compounds inhibit IgE
and virus through a common mechanism.
Nonetheless, there is a decided potency advantage for IgE
inhibition (Tables 1 and 2), although the difference appears to
be less obvious for the 2-PIP compounds than the 2-PB
derivatives. This is illustrated by directly comparing the relative
potencies of matching 2-PB and 2-PIP compounds against IgE
and virus; i.e., 2d versus 4a, 2a versus 4b, and 1d versus 3c.
Expression of this relationship by averaging the IC50s of the

AntiViral 2-Phenylimidazopyridines
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 24 5989
Figure 2. The IC50s of all 24 compounds listed in Tables 1 and 2
against the propagation of HSV-2 and vaccinia virus are compared.
Two-tailed comparison reveals a highly significant correlation between
the inhibitory effects on the two viruses (P < 0.0001).
Figure 4. The effect of hydroxyl substitution on the terminal ring
adamantyl. The anti-IgE and antiviral activity of compounds with
terminal adamantyl groups, with and without hydroxyl substitutions,
are compared. For each, a ratio of the IC50 for virus (HSV-2 or vaccinia
virus) divided by the IC50 for IgE is plotted. The 2-PB compound 1d
is paired with its 4-OH-1-adamantyl analogue 1e, and the 2-PIP com-
pound 4a is paired with its (phenyl side) 4-OH-1-adamantyl analogue
4f and the (imidazopyridine side) 4-OH-1-adamantyl analogue 4g.
potency for inhibition of IgE and virus is directly compared
for compounds that differ only by the presence of oxygen
moieties in the terminal adamantyl (Figure 4). For example,
the IC50 ratio for IgE/virus for 1d is 25 while for 1e the value
rises to 150. Similar results were noted for 2-PIP compounds
wherein the discrepancy between IgE and virus climbed from
an average ratio of 8 for the unoxidized bisadamantyl compound
(4a) to 90 with a 4-substituted OH on the right adamantyl (4f)
and 1700 for the 4-substituted OH on the left adamantyl (4g).
While the reason for the lower relative potency of these oxidized
analogues is unknown, these more hydrophilic analogues have
been shown to accumulate in lower relative intracellular
concentrations than their nonoxidized forms (data not shown).
Although this would suggest that reduced cellular penetration
or retention of the oxidized analogues may translate to a reduced
effect on virus, why the same effect is not observed for IgE
responses is not known.
Figure 3. The IC50s in Tables 1 and 2 for the suppression of IgE and
HSV-2 are compared. Compounds with oxygen-substituted adamantyl
groups are shown separately as triangles. Low potency compounds (IC50
> 2000 nM) were omitted from the graph. 2-Tailed comparisons of
IgE versus HSV-2 for all compounds in Tables 1 and 2 show a
significant correlation (P ) 0.0373). When the same statistics are
applied to the triangles and circles separately, each comparison resulted
in P values of less than 0.0001. Similar comparisons between the IC50s
of all compounds versus IgE and susceptible viruses showed positive
trends: vaccinia, P ) 0.019; MHV, 0.0087; California Encephalitis, P
) 0.565; San Angelo, P ) 0.404; Modoc, P ) 0.0319; and Rhino, P
) 0.0065. In contrast, similar comparisons for SV40 and VSV growth
did not yield significant correlations (P > 0.05).
To demonstrate that the antiviral activity can translate to an
in vivo model, selected compounds were tested in a topical
model of HSV infection, including the compound currently in
clinical trials for asthma and allergy (1d) and the highly potent
2-PIP compound 4a. A topical approach obviates other potential
in vivo effects of these agents such as on cytokines, thus
simplifying interpretation of the results. This is all the more
important because of the lower potency and thus higher
anticipated dosing required for suppression of virus than IgE
or cytokines. Guinea pigs were infected with HSV-2 and
treatment initiated the following day with drug (2%) or vehicle
four times a day for 3 days. The efficacy of 1d was no better
than vehicle (data not shown); representative results for 4a are
illustrated in Figure 5. While a modest effect was noted for
vehicle, an ointment containing 2% 4a completely suppressed
the appearance of vesicles. We are unaware of previous reports
illustrating this level of response. The difference in response
between 1d and 4a can be explained by lipid solubility and
potency, both of which favor 4a. Lipid solubility would translate
to improved skin penetration. Moreover, based on a 300-fold
potency advantage for 4a and an ED50 of 0.5% (data not shown),
a concentration of 30% of 1d would be minimally required to
achieve efficacy. These results underscore the potential utility
of 4a for treating viral infections, at least in topical applications.
six compounds against all viruses (except VSV and SV40) in
Tables 1 and 2 and dividing this hybrid figure by their IC50
against IgE yields a ratio of 23 for 2-PB compounds (2d, 2a,
1d) versus 4 for the corresponding 2-PIP derivatives (4a, 4b,
3c). While this comparison is based on only three pairs of
compounds, it does suggest that the 2-PIP derivatives have
stronger activity against virus than the 2-PB compounds.
Although the relationship between IgE and virus inhibition
generally follows a linear pattern for all compounds, a few
notable outliers are noted in Figure 3. This was first observed
in the Table 1 compounds 1b and 1e, which have oxidized
terminal adamantyl groups. Both compounds are over 100-fold
more potent against IgE than HSV or vaccinia, whereas the
parent compound (1d) shows only a 25-fold preference against
IgE. Thus in selecting 2-PIP analogues for testing against virus,
several with oxidized adamantyl groups were chosen (Table 2).
As shown for the 2-PB derivatives, 2-PIP compounds containing
oxygen on the terminal cyclic moieties (4f, 4d, 4g, 3b) were
considerably less potent for inhibiting virus relative to IgE, thus
confirming the negative impact of oxygen substitution. The

5990 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 24
Banie et al.
carefully. The mixture was shaken in Parr shaker 4 h at 40 °C and
then overnight at 70 °C. The catalyst was removed by filtration,
and the solution was adjusted to pH 3 with concd HCl (ap-
proximately 20 mL). The product immediately precipitated, and
the reaction mixture was left at 4 °C for 3 h. Filtration, washing
with minimal volume of ice-water, and drying over vacuum gave
22.4 g (77%) of 4-aminopyridine-2-carboxylic acid as a fine off-
white solid.
Ethyl 4-Amino-5-nitropyridine-2-carboxylate. Potassium ni-
trate (6.2 g, 61.3 mmol) was added to a cooled solution of 4
aminopyridine-2-carboxylic acid (8.46 g, 61.3 mmol) in concd H2-
SO4 (60 mL). After being stirred 20 min at room temperature, the
reaction mixture was heated at 75 °C for 2 h. The reaction mixture
was again cooled to 0 °C in an ice bath, and 180 mL of ice cold
ethanol was added with stirring. The resulting mixture was stirred
at 60 °C overnight and then cooled to room temperature. The
reaction mixture was slowly added to an ice cold potassium acetate
solution (240 g in 0.450 L of water) resulting in the precipitation
of product mixed with potassium sulfate. The product was filtered
and washed several times with ice cold water yielding 8.74 g (68%)
of ethyl 4-amino-5-nitropyridine-2-carboxylate as an off-white
1
colored solid. H NMR (400 MHz, DMSO-d6): δ 14.0 (1H, br s,
NH2), 9.0 (1H, s, Ar-H), 8.20 (1H, br s, NH), 6.66 (1H, s, Ar-H),
4.36 (1H, q, J ) 6.0 Hz, CH2-CH3), 1.30 (3H, t, J ) 6.0 Hz, CH2-
CH3).
Ethyl 4,5-Diaminopyridine-2-carboxylate (5). Ethyl 4-amino-
5-nitropyridine-2-carboxylate (13.3 g, 63.0 mmol) was reduced with
10% Pd/C (2.60 g) in a cyclohexene/2-propanol mixture (15 mL/
100 mL) under reflux conditions for 12 h. The reaction mixture
was freed from catalyst, and solvent was evaporated to afford ethyl
4,5-diaminopyridine-2-carboxylate (5, 11.3 g, 99%). 1H NMR (400
MHz, DMSO-d6): δ 7.70 (1H, s, Ar-H), 7.21 (1H, s, Ar-H), 5.51
(2H, br s, NH2), 5.25 (2H, br s, NH2), 4.20 (2H, q, J ) 6.0 Hz,
CH2-CH3), 1.26 (3H, t, J ) 6.0 Hz, CH2-CH3); MS m/z: 182.1 (M
+ H+).
Ethyl 2-(4-Nitrophenyl)-3H-imidazo[4,5-c]pyridine-6-carbox-
ylate (7): Ethyl 4,5 diaminopyridine-2-carboxylate (5, 10.86 g, 60.0
mmol) and 4-nitrobenzaldehyde (6, 11.0 g, 1.2 equiv) were refluxed
in nitrobenzene (100 mL) at 200 °C for 18 h. The reaction mixture
was cooled and diluted with diethyl ether (1 L), and the solid was
filtered. The solid was washed with additional volumes of ether
and dried in vacuum (7, 15.9 g, 83%). 1H NMR (400 MHz, DMSO-
d6): δ 13.65 (1H, br s, NH), 9.09 (1H, s, Ar-H), 8.47 (1H, 4H,
m, Ar-H), 8.33 (1H, br s, Ar-H), 4.35 (1H, q, J ) 6.0 Hz, CH2-
CH3), 1.35 (3H, t, J ) 6.0 Hz, CH2-CH3); MS m/z: 285 (M +
H+).
Figure 5. Prevention of HSV-2 vesicle formation in a guinea pig model
of topical herpes. HSV-2 (MS strain) was inoculated on the back of
six hairless guinea pigs in three distinct sites such that each guinea pig
served as its own control. Treatment sites were rotated. Topical
treatment was initiated on day 2 with 100 µL of vehicle, 100 µL of
2% 4a, or nothing, and repeated four times a day for 3 days. The guinea
pigs were photographed each day until maximum viral response could
be assessed, which occurred on day 4. Shown are representative
responses from each treatment group.
2-(4-Nitrophenyl)-3H-imidazo[4,5-c]pyridine-6-carboxylic Acid
(8). The ester 7 (9.75 g, 31.25 mmol) was dissolved in 10% NaOH
(80 mL) and EtOH (200 mL) and refluxed at 90 °C for 1 h. The
reaction mixture was filtered and acidified with 3 N HCl (100 mL),
and a reddish brown solid was filtered, washed with H2O and
methanol, and dried under high vacuum yielding 8 (8.24 g, 93%).
1H NMR (400 MHz, DMSO-d6): δ 14.00 (1H, br s, CO2H), 8.91
(1H, br s, Ar-H), 8.56 (2H, br m, Ar-H), 8.41 (2H, br m, Ar-
H), 8.25 (1H, br s, Ar-H).
N-Adamantyl-2-(4-nitrophenyl)-3H-imidazo[4,5-c]pyridine-
6-carboxamide (9a). CDI (0.255 g, 1.5 equiv) was added to a
solution of acid 8 (0.300 g, 1.05 mmol) in dry DMF (10 mL) and
heated at 80 °C for 3 h. Two batches of adamantinamine (0.226 g,
1.5 mmol) were added at 2 h interval, and the reaction mixture
was heated at 100 °C for 16 h. The mixture was poured into water,
and a yellow solid 9a was filtered (0.210 g, 50%). MS m/z: 418
(M + H+). The solid was used for the next step without further
purification.
Conclusion
This report describes the antiviral activity of a group of
2-(substituted phenyl)benzimidazole compounds (series 1 and
2), as well as the synthesis and antiviral activity of a novel group
of imidazopyridine (series 3 and 4) derivatives. Viruses inhibited
by these compounds comprise several families that are important
causes of human disease and which rely on the Golgi for their
envelopment and processing. While the antiviral activity of most
of the compounds parallels their anti-IgE activity, those with
oxidized terminal adamantyl groups substantially lose antiviral
potency without affecting their inhibition of IgE. The imida-
zopyridine derivatives are more potent than the benzimidazoles
against virus, and one of the former agents 4a is highly effective
in a guinea pig model of herpes infection. These results support
further investigation of these compounds for the treatment of
many viral pathogens.
N-(4-Oxoadamantyl)-2-(4-nitrophenyl)-3H-imidazo[4,5-c]py-
ridine-6-carboxamide (9b). The nitro acid 8 (0.215 g, 0.76 mmol)
was stirred with PyBop (0.600 g, 1.5 equiv) in DMF (5 mL) at
room temperature for 16 h. 4-Oxoadamantamine hydrochloride salt
(0.230 g, 1.15 mmol), DMAP (0.080 g, 0.76 mmol), and pyridine
(20 mL) were added and stirred overnight. The reaction mixture
Experimental Section
Compounds 3a-e. 4-Aminopyridine-2-carboxylic Acid. The
picloram methyl ester (55.0 g, 0.215 mmol) was dissolved in 10%
LiOH (0.3 L), and then 8.0 g 10% palladium carbon (wet) was added

AntiViral 2-Phenylimidazopyridines
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 24 5991
was poured into water and the solid was filtered (9b, 0.300 g, 90%)
and used for the next step.
13.64 (1H, br s, NH), 9.57 (1H, s, NH), 9.38 (1H, s, NH), 9.02
(1H, s, Ar-H), 8.99 (1H, s, Ar-H), 8.18 (4H, m, Ar-H), 2.2-
1.60 (30H, series of m, adamantyl); MS m/z: 550.6 (M+); Anal.
(C34H39N5O2·H2O) C, H, N, S.
2-(4-Nitrophenyl)-N-(pyridin-2-yl)-3H-imidazo-[4,5-c]pyridine-
6-carboxamide (9c). This compound was prepared by using a
similar method as described for 9a using 8 (1.0 g, 3.5 mmol) and
2-aminopyridine (0.5 g, 5.3 mmol). Following filtration, a yellow
solid was obtained (9c, 0.850 g, 66%) and used for the next step
without further purification.
2-(4-Aminophenyl)-N-(adamantyl)-3H-imidazo[4,5-c]pyridine-
6-carboxamide (10a). A solution of 9a (0.210 g, 0.50 mmol) was
reduced with Raney nickel (0.300 mL) in a mixture of MeOH/
THF (15 mL/5 mL) at 85 °C for 2 h under H2 atmosphere. The
product was freed from catalyst and evaporated to dryness (10a,
0.190 g, 98%). The amine 10a was used for the next step without
further purification.
2-(4-Aminophenyl)-N-(4-oxoadamantyl)-3H-imidazo[4,5-c]py-
ridine-6-carboxamide (10b). The nitroamide 9b (0.200 g, 0.46
mmol) was stirred with 10% palladium on carbon (0.050 g) in
EtOH-THF (3:1) mixture at room temperature for 16 h. The amine
was freed from catalyst, and the solvent was evaporated to yield
10b (0.100 g, 97%), which was used for the next step without
further purification.
2-(4-Aminophenyl)-N-(pyridin-2-yl)-3H-imidazo[4,5-c]pyridine-
6-carboxamide (10c). The nitropyridine amide 9c (0.458 g, 1.27
mmol) was reduced over 10% palladium carbon (0.100 g) in
MeOH-THF-DMF mixture (10 mL-10 mL-2.5 mL) at 80 °C
for 7 h. The amine amide was freed from catalyst and solvent was
removed. Water was added, and yellow solid was filtered (10c,
0.178 g, 40%) and used for the next step.
Compounds 4a-g. tert-Butyl 2-(4-Nitrophenyl)-3H-imidazo-
[4,5-c]pyridin-6-ylcarbamate (11). To a stirring solution of nitro
acid 8 (10.7 g, 37.7 mmol) and triethylamine (5.8 mL, 1.1 equiv)
in NMP (100 mL) was added diphenylphosphoryl azide (9.0 mL,
1.1 equiv) dropwise, and the reaction mixture was further stirred
at room temperature overnight. Tertiary butanol (100 mL) was
added, and the reaction mixture was heated at 85 °C for 6 h. After
being cooled to room temperature, the reaction mixture was treated
slowly with 100 mL of saturated NaHCO3 followed by 200 mL
water, heated to 85 °C for 10 min, and filtered hot. The filter cake
was rinsed with additional water and dried in vacuum to get the
yellow solid 11 (10.2 g, 76%). 1H NMR (400 MHz, DMSO-d6): δ
13.86 (1H, br s, NH), 9.70 (1H, br s, NH), 8.72 (1H, br s, Ar-H),
8.47 (4H, br m, Ar-H), 7.99 (1H, br s, Ar-H), 1.51 (9H, s, Boc);
MS m/z: 356.4 (M + H+).
tert-Butyl 2-(4-aminophenyl)-3H-imidazo[4,5-c]pyridin-6-yl-
carbamate (12). The nitro carbamate 11 (10.2 g, 29.0 mmol) was
dissolved in NMP (120 mL) and reduced over 10% Pd/C (2.0 g)
in Parr shaker at 45 °C for 12 h. The amine carbamate 12 was
freed from catalyst, and NMP was evaporated. To the residue was
added THF, and solid was filtered. The THF layer was evaporated,
affording the amine 12 (7.0 g, 70%). 1H NMR (400 MHz, DMSO-
d6): δ 12.74 (1H, br s, NH), 9.62 (1H, s, NH), 8.46 (1H, s, Ar-
H), 7.95 (3H, m, Ar-H), 6.69 (2H, s, Ar-H), 5.70 (2H, s, NH2),
1.50 (9H, s, Boc); MS m/z: 326.4 (M + H+).
2-(4-(Adamantanecarboxamido)phenyl)-N-(pyridin-2-yl)-3H-
imidazo[4,5-c]pyridine-6-carboxamide (3c). Adamantine carbonyl
chloride (0.208 g, 1.04 mmol) was added to a solution of amine
10c (0.230 g, 0.69 mmol) in pyridine (5 mL), and the reaction
mixture was further stirred at room temperature for 16 h. The
reaction was quenched with water and solid was filtered. The solid
was dissolved in MeOH-EtOAc and reprecipitated with ether
yielding 3c (0.148 g, 43%). Mp 356 °C; 1H NMR (400 MHz,
DMSO-d6): δ 13.64 (1H, br s, NH), 10.54 (1H, s, NH), 9.38 (1H,
s, NH), 8.95 (1H, m, Ar-H), 8.45 (2H, d, J ) 7.6 Hz, Ar-H),
8.28 (2H, d, J ) 8.4 Hz, Ar-H), 7.88 (3H, m, Ar-H), 7.15 (1H,
m, Ar-H), 2.70 (3H, br s, adamantyl), 1.73 (6H, br s, adamantyl),
1.39 (6H, br s, adamantyl); MS m/z: 493.6 (M+); Anal. (C29H28N6O8·
H2O) C, H, N, S.
2-(4-Aminophenyl)-3H-imidazo[4,5-c]pyridin-6-amine Dihy-
drochloride (13). To a solution of amine carbamate 12 (1.0 g, 3.07
mmol) in dioxane (5 mL) was added 4 M HCl solution in dioxane
(7 mL), and reaction mixture was heated at 90 °C for 1 h. The
solid was filtered and washed with THF, affording the diamine salt
1
13 (0.83 g, 91%). H NMR (400 MHz, DMSO-d6): δ 12.15 (1H,
br s, NH), 8.20 (2H, s, Ar-H), 7.77 (2H, m, Ar-H), 6.78 (2H, s,
Ar-H) 5.65 (4H, br s, NH2); MS m/z: 226 (M + H+).
tert-Butyl 2-(4-(4-Oxoadamantanecarboxamido)phenyl)-3H-
imidazo[4,5-c]pyridin-6-ylcarbamate (14d). To a solution of 12
(0.305 g, 0.94 mmol) in dry pyridine (5 mL) was added 4-oxoad-
mantane carbonyl chloride (0.330 g, 1.55 mmol), and the reaction
mixture was stirred at room temperature for 16 h. The crude 14d
was hydrolyzed with 4 M HCl (4 mL) in dioxane at 90 °C for 1 h,
and amine salt was filtered (14d, 0.340 g, 84% in two steps).
tert-Butyl-2-(4-(adamantanecarboxamido)phenyl)-3H-imidazo-
[4,5-c]-pyridin-6-ylcarbamate (14e). A solution of aminecarbamate
12 (0.325 g, 1.0 mmol), adamantane carbonyl chloride (0.300 g,
1.5 mmol) in pyridine (5 mL) was stirred at room temperature for
overnight yielding crude 14e (0.460 g). The crude 14e (0.465 g,
0.94 mmol) was dissolved in 4.0 M HCl in dioxane (5 mL) and
stirred at 90 °C for 1 h. The amine salt was filtered (14e, 0.270 g,
64% in two steps).
Compounds 3a, 3b, and 3d were prepared by applying a method
similar to that described for 3c.
2-(4-(4-Chlorophenylamido)phenyl)-N-adamantyl-3H-imidazo-
1
[4,5-c]pyridine-6-carboxamide (3a). Mp 364 °C; H NMR (400
MHz, DMSO-d6): δ 13.45 (1H, br s, NH), 10.48 (1H, s, NH), 9.43
(1H, s, NH), 8.96 (1H, m, Ar-H), 8.24 (7H, m, Ar-H), 7.61 (2H,
m, Ar-H), 2.12 (9H, m, adamantyl), 1.62 (6H, m, adamantyl); MS
m/z: 526.4 (M+); Anal. (C30H28ClN5O2·H2O) C, H, N, S.
N-(4-Chlorophenyl)-2-(4-(4-oxoadamantanecarboxamido)-
phenyl)-3H-imidazo[4,5-c]pyridine-6-caboxamide (3b). Mp 343 °C;
1H NMR (400 MHz, DMSO-d6): δ 13.55 (1H, br s, NH), 10.59
(1H, s, NH), 9.43 (1H, s, NH), 8.97 (1H, m, Ar-H), 8.14 (7H, m,
Ar-H), 7.63 (2H, m, Ar-H), 2.65-1.80 (13H, m, adamantyl); MS
m/z: 540.5 (M+); Anal. (C30H26ClN5O3·H2O) C, H, N, S.
N-(4-(6-(Adamantanecarboxamido)-3H-imidazo[4,5-c]pyridin-
2-yl)phenyl)adamantanecarboxamide (4a). To a solution of
diamine hydrochloride 13 (0.200 g, 0.50 mmol) in dry pyridine
(10 mL) was added adamantane carbonyl chloride (0.250 g, 0.150
mmol), and the reaction mixture was heated at 120 °C for 3 h. The
reaction mixture was added to water, and solid was filtered. The
solid was stirred with 10% NaOH (3 mL) in EtOH (10 mL) at
room temperature for 1 h. The EtOH was evaporated, water was
added, and the solid was filtered. The off white solid was passed
through a short bed of SiO2 gel using THF as a solvent. The solvent
was evaporated, and solid was crystallized from MeOH to yield
2-(4-(3-Hydroxyadamantanecarboxamido)phenyl)-N-(4-oxoad-
amantane)-3H-imidazo[4,5-c]pyridine-6-carboxamide (3d). Mp
367 °C; 1H NMR (400 MHz, DMSO-d6): δ 13.59 (1H, br s, NH),
9.43 (1H, s, NH), 8.89 (1H, s, NH), 8.18 (4H, m, Ar-H), 7.93
(2H, m, Ar-H), 4.70 (1H, s, OH), 3.73-3.60 (1H, br s, 4Heq and
4Hax, 4-hydroxyadamantyl), 2.3-1.20 (26H, series of m, adaman-
tyl); MS m/z: 580.5(M+); Anal. (C34H37N5O4·2H2O) C, H, N, S.
2-(4-(Adamantanecarboxamido)phenyl)-N-adamantyl-3H-
imidazo[4,5-c]pyridine-6-carboxamide (3e). The amine 10a (0.190
g, 0.49 mmol) and adamantanecarbonyl chloride (0.195 g, 2.0
mmol) were dissolved in pyridine (5 mL) and stirred at room
temperature for overnight. The reaction mixture was poured into
water, and solid 3e was filtered and recrystallized with ethyl acetate
1
4a (0.150 g, 50%). Mp 265 °C; H NMR (400 MHz, DMSO-d6):
δ 13.02 (1H, br s, NH), 9.48 (1H, br s, NH), 9.37 (1H, br s, NH),
8.64 (1H, s, Ar-H), 8.24 (1H, s, Ar-H), 8.08 (2H, d, J ) 5.0 Hz,
Ar-H), 7.88 (2H, d, J ) 5.0 Hz, Ar-H), 2.03-1.60 (30 H, series
of m, adamantyl); MS m/z: 449.6 (M + H+); Anal. (C34H39N5O2
× 0.85H2O) C, H, N.
N-(4-(6-(Cyclohexanecarboxamido)-3H-imidazo[4,5-c]pyridin-
2-yl)phenyl)cyclohexanecarboxamide (4b). A solution of 13
1
(0.210 g, 80%). Mp 396 °C; H NMR (400 MHz, DMSO-d6): δ

5992 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 24
Banie et al.
(0.080 g, 0.24 mmol) in dry pyridine (10 mL) and cyclohexan-
ecarbonyl chloride (0.120 mL, 0.76 mmol) was heated at 100 °C
for 3 h. The reaction mixture was quenched with water, gummy
solid was filtered, and the filtrate was stirred with 10% NaOH (2
mL) in EtOH (10 mL) at room temperature for 1 h. The solvent
was evaporated, water was added, and solid was filtered. The solid
was passed through a bed of SiO2 gel. Elution with ethyl acetate
d6): δ 9.35 (2H, m, NH2), 8.50 (1H, s, Ar-H), 8.20 (1H, s, Ar-
H), 8.10 (2H, m, Ar-H), 7.85 (2H, m, Ar-H), 4.70 (1H, br s,
OH), 3.72-3.60 (1H, br s, 4Heq and 4Hax of 4-hydroxyadamantyl),
2.30-1.30 (28H, series of m, adamantyl); MS m/z: 601.5 (M+);
Anal. (C34H39N5O3 × 3H2O) C, H, N, S.
Acknowledgment. The authors thank Dr. Sunil Kumar KC
for critical review of the manuscript.
1
afforded 4b as light yellow solid (0.055 g, 51%). Mp 235 °C; H
NMR (400 MHz, DMSO-d6): δ 12.99 (1H, br s, NH), 10.27 (1H,
br s, NH), 10.07 (1H, br s, NH), 8.61 (1H, br s, Ar-H), 8.27 (1H,
br s, Ar-H), 8.07 (2H, d, J ) 8.0 Hz, Ar-H), 7.79 (2H, d, J )
9.0 Hz, Ar-H), 2.52 (1H, m, cyclohexyl), 2.36 (1H, m, cyclohexyl),
1.83-1.17 (20 H, series of m, cyclohexyl); MS m/z: 446.5 (M +
H+), 444.6 (M - H+); Anal. (C26H31N5O2 × 0.91H2O) C, H, N.
N-(4-(6-(4-Oxoadamantanecarboxamido)-3H-imidazo[4,5-c]-
pyridin-2-yl)phenyl)-4-oxoadamantanecarboxamide (4c). To a
solution of 13 (0.212 g. 0.71 mmol) in dry pyridine (10 mL) was
added 4-ketoadamantanecarbonyl chloride (0.600 g, 4 equiv), and
the reaction mixture was heated at 120 °C for 3 h. This afforded
4c as an off-white solid (0.136 g, 30%). Mp 258-268 °C; 1H NMR
(400 MHz, DMSO-d6): δ 13.01 (1H, s, NH), 9.88 (1H, s, NH),
9.57 (1H, s, NH), 8.65 (1H, s, Ar-H), 8.22 (1H, s, Ar-H), 8.10
(2H, br d, J ) 10.0 Hz Ar-H), 7.86 (2H, br d, J ) 10.0 Hz, Ar-
H), 2.47 (2H, br m, adamantyl), 2.32 (2H, br m, adamantyl), 2.24-
2.15 (14H, m, adamantyl), 2.06 (4H, br m, adamantyl), 1.89 (4H,
br m, adamantyl); MS m/z: 578.8 (M+); Anal. (C34H35N5O4 × 1
H2O) C, H, N, S.
Supporting Information Available: Experimental procedures
and spectral data. This material is available via the Internet at http://
pubs.acs.org.
References
(1) (a) Grant, R. M.; Hecht, F. M.; Warmerdam, M.; Liu, L.; Liegler,
T.; Petropoulos, C J.; Hellman, N. S.; Chesney, M.; Busch, M. P.;
Kahn, J. O. Time trends in primary HIV-1 drug resistance among
recently infected persons. JAMA 2002, 288, 181-188. (b) Iannello,
A.; Debbeche, O.; Martin, E.; Attalah, L. H.; Samarani, S.; Ahmad,
A. Viral strategies for evading antiviral cellular immune responses
of the host. J. Leukoc. Biol. 2006, 79, 16-35.
(2) Lippincott-Schwartz, J.; Yuan, L. C.; Bonifacino, J. S.; Klausner, R.
D. Rapid redistribution of Golgi proteins into the ER in cells treated
with brefeldin A: evidence for membrane cycling from Golgi to ER.
Cell 1989, 56, 801-813.
(3) Richards, M. L.; Lio, S. C.; Sinha, A.; Tieu, K. K.; Sircar, J. C.
Novel 2-(substituted phenyl)benzimidazole derivatives with potent
activity against IgE, cytokines, and CD23 for the treatment of allergy
and asthma. J. Med. Chem. 2004, 47, 6451-6454.
N-(2-(4-(4-Oxoadamantanecarboxamido)phenyl)-3H-imidazo-
[4,5-c]pyridin-6-yl)adamantanecarboxamide (4d). To a solution
of amine 14 (0.160 g, 0.40 mmol) in dry pyridine (10 mL) was
added adamantanecarbonyl chloride (0.120 g, 0.42 mmol), and the
reaction mixture was stirred at 120 °C for 4 h. After the usual
workup, this afforded the desired product 4d (0.080 g, 35%). Mp
250 °C; 1H NMR (400 MHz, DMSO-d6): δ 13.05 (1H, br s, NH),
9.56 (1H, br s, NH), 9.46 (1H, br s, NH), 8.26 (1H, br s, Ar-H),
8.24 (1H, br s, Ar-H), 8.11 (2H, d, J ) 10.0 Hz, Ar-H), 7.87
(2H, d, J ) 10.0 Hz, Ar-H), 2.47 (1H, br m, adamantyl), 2.32
(1H, br m, adamantyl), 2.20-1.80 (26H, br m and br s, adamantyl);
MS m/z: 564 (M + H+); Anal. (C34H37N5O3 × 1.36H2O).
N-(2-(4-(Adamantanecarboxamido)phenyl)-3H-imidazo[4,5-
c]pyridin-6-yl)pyridine-2-carboxamide (4e). A solution of amine
14 (0.065 g, 0.197 mmol) and adamantanecarbonyl chloride (0.060
g, 0.30 mmol) in dry pyridine (5 mL) was stirred at 80 °C for 2 h.
The resulting solid was treated with 10% NaOH for 1 h. The solid
was filtered and passed through SiO2 gel. Elution with EtOAc
(4) Richards, M. L.; Lio, S. C.; Sinha, A.; Banie, H.; Thomas, R. J.;
Major, M.; Tanji, M.; Sircar, J. Substituted 2-phenyl-benzimidazole
derivatives: novel compounds that suppress key markers of allergy.
Eur. J. Med. Chem. 2006, 41, 950-969.
(5) Lio, S. C.; Johnson, J.; Chatterjee, A.; Ludwig, J. W.; Millis, D.;
Banie, H.; Sircar, J. C.; Sinha, A.; Richards, M. L. Disruption of
Golgi processing by 2-(substituted phenyl) benzimidazole derivatives
blocks cell proliferation and slows tumor growth. Cancer Chemother.
Pharmacol. 2007, in press, Epub ahead of print.
(6) Ludwig, J. W.; Richards, M. L. Targeting the secretory pathway for
anti-inflammatory drug development. Curr. Top. Med. Chem. 2006,
6, 165-178.
(7) (a) Ludwig, J. W.; Soneff, R-M.; Banie, H.; Marcantonio, D.; Scholz,
W.; Galang, C.; Johnson, J.; Sircar, J. C.; Chatterjee, A.; Richards,
M. L. Novel 2-phenyl-benzimidazole inhibitors of cytokines and
cellular proliferation foster Golgi enzyme depletion through acceler-
ated degradation. Eur. J. Pharmacol. 2007 (submitted for publication).
(b) Ludwig, J. W.; Banie, H.; Galang, C.; Lio, S. C.; Sircar, J. C.
Richards, M. L. Golgi processing defect induced by AVP-13358
results in a loss of processing and expression of CD23. 2007
(Manuscript in preparation).
1
afforded diamide 4e (0.039 g, 40%). Mp 305 °C; H NMR (400
(8) Marcelletti, J. F.; Katz, D. H. Elicitation of antigen-induced primary
and secondary murine IgE antibody responses in vitro. Cell. Immunol.
1991, 135, 471-489.
MHz, DMSO-d6,): δ 13.19 (1H, br s, NH), 10.47 (1H, br s, NH),
9.39 (1H, br s, NH), 8.76 (1H, d, J ) 4.5 Hz, Ar-H), 8.73 (1H, br
s, Ar-H), 8.45 (1H, br s, Ar-H), 8.24 (1H, d, J ) 8.0 Hz, Ar-
H), 8.11 (3H, m, Ar-H), 7.89 (2H, d, J ) 8.5 Hz, Ar-H), 7.72
(1H, dt, J ) 5.0 and 7.5 Hz, Ar-H), 2.0 (3H, br s, adamantyl),
1.92 (6H, br s, adamantyl), 1.72 (6H, br s, adamantyl); MS m/z:
493.5 (M + H+); Anal. (C29H28N6O2 × 1.23H2O) C, H, N.
N-(4-(6-(Adamantanecarboxamido)-3H-imidazo[4,5-c]pyridin-
2-yl)phenyl)-4-hydroxyadamantanecarboxamide (4f). To a solu-
tion of 4d (0.080 g, 0.142 mmol) in EtOH (10 mL) was added
NaBH4 (0.038 g, 1.0 mmol), and the reaction mixture was stirred
at 90 °C for 1 h. Ethanol was removed, and the residue was washed
with water. The product was dissolved in MeOH and THF and
filtered to remove inorganic residue. The product 4f was precipitated
with MeOH-EtOAc as a white solid and filtered (0.035 g, 43%).
1H NMR (400 MHz, DMSO-d6): δ 13.05 (1H, br s, NH), 9.36
(2H, br s, NH), 8.59 (1H, br s, Ar-H), 8.29 (1H, br s, Ar-H),
8.10 (2H, d, J ) 8.3 Hz, Ar-H), 7.85 (2H, br d, J ) 8.3 Hz, Ar-
H), 4.70 (1H, br s, OH), 3.72-3.60 (1H, br s, 4Heq and 4Hax of
4-hydroxyadamantyl), 2.20-1.40 (28H, series of m, adamantyl);
MS m/z: 566.6 (M + H+), 601.5 (M + Cl-); Anal. (C34H39N5O3
× 3.5H2O) C, H, N.
(9) (a) Beznoussenko, G. V.; Mironov, A. A. Models of intracellular
transport and evolution of the Golgi complex. Anat. Rec. 2002, 268,
226-238. (b) Pelham, H. R.; Rothman, J. E. The debate about
transport in the Golgi-two sides of the same coin? Cell 2000, 102,
713-719. (c) Marsh, B. J.; Howell, K. E. The mammalian Golgi-
complex debates. Nat. ReV. Mol. Cell Biol. 2002, 3, 789-795. (d)
Storrie, B.; Pepperkok, R.; Nilsson, T. Breaking the COPI monopoly
on Golgi recycling. Trends Cell Biol. 2000, 10, 385-391.
(10) (a) Granzow, H.; Klupp, B. G.; Fuchs, W.; Veits, J.; Osterrieder, N.;
Mettenleiter, T. C. Egress of alpha herpes viruses: comparative
ultrastructural study. J. Virol. 2001, 75, 3675-3684. (b) Husain, M.;
Moss, B. Vaccinia virus F13L protein with a conserved phospholipase
catalytic motif induces colocalization of the B5R envelope glyco-
protein in post-Golgi vesicles. J. Virol. 2001, 75, 7528-7542. (c)
Pettersson, R. F.; Melin, L. Synthesis, assembly and intracellular
transport of BunyaViridae membrane proteins. In The BunyaViridae;
Elliott, R. M., Ed.; Springer-Verlag: Berlin, Germany, 1996; pp 159-
188. (d) Gerrard, S. R.; Nichol, S. T. Characterization of the Golgi
retention motif of Rift Valley fever virus G(N) glycoprotein. J. Virol.
2002, 76, 12200-12210. (e) Klumperman, J.; Locker, J. K.; Meijer,
A.; Horzinek, M. C.; Geuze, H. J.; Rottier, P. J. Coronavirus M
proteins accumulate in the Golgi complex beyond the site of virion
budding. J. Virol. 1994, 68, 6523-6534. (f) Mackenzie, J. M.; Jones,
M. K.; Westaway, E. G. Markers for trans-Golgi membranes and
the intermediate compartment localize to induced membranes with
distinct replication functions in flavivirus-infected cells. J. Virol. 1999,
73, 9555-9567.
N-(2-(4-(Adamantanecarboxamido)phenyl)-3H-imidazo[4,5-
c]pyridin-6-yl)-4-hydroxyadamantaneamide (4g). This compound
was made similar to 4f. Mp 356 °C; 1H NMR (400 MHz, DMSO-

AntiViral 2-Phenylimidazopyridines
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 24 5993
(11) de Jong, A. S.; Visch, H. J.; de Mattia, F.; van Dommelen, M. M.;
Swarts, H. G.; Luyten, T.; Callewaert, G.; Melchers, W. J.; Willems,
P. H.; van Kuppeveld, F. J. The coxsackievirus 2B protein increases
efflux of ions from the endoplasmic reticulum and Golgi, thereby
inhibiting protein trafficking through the Golgi. J. Biol. Chem. 2006,
281, 14144-14150.
(12) Whitt, M. A.; Zagouras, P.; Crise, B.; Rose, J. K. A fusion-defective
mutant of the vesicular stomatitis virus glycoprotein. J. Virol. 1990,
64, 4907-4913.
(13) Pelkmans, L.; Puntener, D.; Helenius, A. Local actin polymerization
and dynamin recruitment in SV40-induced internalization of caveolae.
Science 2002, 296, 535-539.
(14) Norkin, L. C.; Anderson, H. A.; Wolfrom, S. A.; Oppenheim, A.
Caveolar endocytosis of simian virus 40 is followed by brefeldin
A-sensitive transport to the endoplasmic reticulum, where the virus
disassembles. J. Virol. 2002, 76, 5156-5166.
JM0704907