Antirhino/enteroviral vinylacetylene benzimidazoles: A study of their activity and oral plasma levels in mice

Article abstract of DOI:10.1021/jm970423k

In an effort to find an orally bioavailable antiviral for the treatment of rhino/enteroviral infections, a series of vinylacetylene benzimidazoles (11a-o, 12, and 18a) was made. Initial studies of this class of antivirals showed that fluorine substitution on the left-hand phenyl ring in combination with the vinylacetylene moiety gave the requisite mix of physical properties to achieve good in vitro antiviral activity as well as respectable oral bioavailability in rhesus monkeys. To ascertain the generality of this finding and to broaden the scope of the structure-activity relationship (SAR), the present study concentrated on fluoro substitution of this class of molecules. The initial antiviral activity for each analogue was measured using human rhinovirus 14 (HRV-14). This served as an indicator of general antiviral activity for SAR purposes. Subsequently, the spectrum of antirhino/enteroviral activity of the more interesting analogues was evaluated through testing against a panel of seven additional rhino/enteroviruses. Broad-spectrum activity was present and consistent for all analogues tested, and it tracked closely with the antiviral activity observed against HRV-14. A simple screening protocol for oral bioavailability was established whereby compounds were administered orally to mice and plasma levels were measured. This procedure facilitated the evaluation of numerous analogues in a rapid manner. The C(max) was used as a measure of oral bioavailability to allow relative ranking of compounds. In general, fluorine substitution directly on the left-hand aromatic ring does give good oral blood levels. However, fluorine incorporation at other positions in the molecule was not as effective at maintaining either the activity or the oral plasma levels. The constructive combination of activity and oral plasma levels was maximized in three derivatives: 11a,e,g.

Full text of DOI:10.1021/jm970423k

J . Med. Chem. 1997, 40, 3937-3946
3937
An tir h in o/En ter ovir a l Vin yla cetylen e Ben zim id a zoles: A Stu d y of Th eir Activity
a n d Or a l P la sm a Levels in Mice
Mark J . Tebbe,* Wayne A. Spitzer, Frantz Victor, Shawn C. Miller, Chris C. Lee, Thomas R. Sattelberg, Sr.,
Emma McKinney, and J oseph C. Tang
Infectious Diseases Research, Lilly Research Laboratories, Lilly Corporate Center, Indianapolis, Indiana 46285
Received J une 26, 1997X
In an effort to find an orally bioavailable antiviral for the treatment of rhino/enteroviral
infections, a series of vinylacetylene benzimidazoles (11a -o, 12, and 18a ) was made. Initial
studies of this class of antivirals showed that fluorine substitution on the left-hand phenyl
ring in combination with the vinylacetylene moiety gave the requisite mix of physical properties
to achieve good in vitro antiviral activity as well as respectable oral bioavailability in rhesus
monkeys. To ascertain the generality of this finding and to broaden the scope of the structure-
activity relationship (SAR), the present study concentrated on fluoro substitution of this class
of molecules. The initial antiviral activity for each analogue was measured using human
rhinovirus 14 (HRV-14). This served as an indicator of general antiviral activity for SAR
purposes. Subsequently, the spectrum of antirhino/enteroviral activity of the more interesting
analogues was evaluated through testing against a panel of seven additional rhino/enterovi-
ruses. Broad-spectrum activity was present and consistent for all analogues tested, and it
tracked closely with the antiviral activity observed against HRV-14. A simple screening protocol
for oral bioavailability was established whereby compounds were administered orally to mice
and plasma levels were measured. This procedure facilitated the evaluation of numerous
analogues in a rapid manner. The Cmax was used as a measure of oral bioavailability to allow
relative ranking of compounds. In general, fluorine substitution directly on the left-hand
aromatic ring does give good oral blood levels. However, fluorine incorporation at other positions
in the molecule was not as effective at maintaining either the activity or the oral plasma levels.
The constructive combination of activity and oral plasma levels was maximized in three
derivatives: 11a ,e,g.
Ch a r t 1
In tr od u ction
The benzimidazoles1-4 are a unique, potent, and
broad-spectrum class of antirhino/enteroviral agents
discovered over 25 years ago through routine screening
of Lilly’s research file compounds against rhino- and
polioviruses.5-9 In the early 1980s, two candidates from
this series, Enviroxime and Enviradene (Chart 1), were
evaluated in the clinic. Enviroxime (1) possesses sig-
nificant antiviral activity against human rhinovirus 14
(HRV-14) (IC50 ) 0.05 µg/mL) as well as a broad
spectrum of activity against both rhino- and entero-
viruses.10-13 However, when Enviroxime was dosed
orally in humans, it showed very low blood levels and
caused an emetic response similar to that observed
earlier in toxicology studies in dogs. An intranasal route
of delivery was then explored, but confounding results
obtained in these studies led to the decision to return
to the discovery process to look for a compound that
would exhibit the desired oral bioavailability but lack
the emetic side effect.14,15 Enviradene (2) seemed to
meet these criteria in animal models. It possesses
improved pharmacokinetics in dogs and caused no
emesis.16 Additionally, when Enviradene was dosed
orally to humans, there was no emesis. Unfortunately,
the peak plasma levels did not surpass the antiviral IC50
value, and development was discontinued before chal-
lenge studies were initiated.17 In light of the nature of
the failure of these compounds in the clinic, it should
be noted that the key test of efficacy (i.e., administration
of an orally bioavailable agent for the treatment of
rhino/enteroviral infections) was never accomplished.
Notwithstanding these prior disappointments, this se-
ries has the potential to provide a compound active
against the causative agent and not merely the symp-
toms of the common cold.
Although the exact mechanism of action of these
compounds remains unclear, it is known that they
inhibit replication and, specifically, that they selectively
inhibit (+)-strand RNA synthesis.18
Efforts to identify
the true target of the benzimidazoles through experi-
ments designed to produce resistant mutants have
failed. However, “drug tolerant” viruses that exhibit no
increase in their IC50 value when tested in standard
plaque reduction assays can be isolated. These viruses
contain mutations in the RNA genome that code for
amino acid changes in the viral protein 3A.18 This
X Abstract published in Advance ACS Abstracts, November 1, 1997.
S0022-2623(97)00423-8 CCC: $14.00 © 1997 American Chemical Society

3938 J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 24
Tebbe et al.
Sch em e 1a
protein has no known catalytic function, but it is
intimately involved in the replication complex. This
potentially implies that these compounds interfere in
some way with the replication complex.19 In the ab-
sence of knowledge of the actual molecular target, tissue
culture assays served as a guide for the structure-
activity relationship (SAR).
Recognition of the unique nature of these compounds
and the fact that the key test of efficacy remained
unanswered led to the initiation of an intense study of
the benzimidazoles to find an analogue capable of
overcoming the lack of oral plasma levels seen with the
previous two clinical candidates. These efforts have,
therefore, focused on optimization of the oral bioavail-
ability of these compounds along with the antiviral
activity since these two parameters are directly related
and largely determine the deliverable activity for an
orally administered compound. Our initial communica-
tion in this area detailed the information on the first
members of the vinylacetylene family,20 and now we
wish to report on the expansion of the SAR, synthetic
improvements in this series, and oral plasma concentra-
tions in mice.
Ch em istr y
The intriguing combination of activity and oral bio-
availability seen in rhesus monkeys for the p-fluoro
acetylene derivative 11c provided the impetus for
further studies of this class of molecules. The original
route used to synthesize this compound was cumber-
some and inefficient and did not allow for rapid syn-
thesis of additional analogues in sufficient quantities
to be useful; therefore, a new synthetic route was
required.
a
(a) i. KOtBu (2.0 equiv), 0 °C, DMF, ii. H2O2 (3.25 equiv), 0
i
°C; (b) H2, Ra-Ni, THF; (c) PrSO2Cl (1.4 equiv), pyridine (5.0
equiv), CH2Cl2; (d) CNBr (1.0 equiv), NaOH (1.0 equiv), PrOH;
(e) HCCCH2Br (3.5 equiv), Mg (4.2 equiv), HgCl2 (0.088 equiv),
THF:Et2O, 1:1; (f) i. TBDMSOTf (1.1 equiv), 2,6-lutidine (1.2
equiv), CH2Cl2, ii. Et3N (4.5 equiv), DMAP (2.5 equiv), MsCl (3.8
equiv).
i
The first of the changes to the synthetic scheme came
in the initial step. Previously, joining of the left-hand
phenyl with the benzimidazole portion had been ac-
complished with Friedel-Crafts chemistry. This lim-
ited both the type and pattern of substitution available
on the left-hand side of the molecule. In the new route
(Scheme 1), it was found that 5-chloro-2-nitroanilines
5 served very nicely as activated acceptors in nucleo-
philic substitution reactions with the anion of variously
substituted phenylacetonitriles 4.21 Additionally, the
nitrile intermediate (not shown) could be oxidatively
decyanated in situ to provide the desired 3-amino-4-
nitrobenzophenone 6. This modification in the reaction
sequence offers a number of advantages. First, the
procedure is simple, and it affords the desired inter-
mediate 6 in high yield (79%). Second, the reaction is
quite general, accommodating a variety of substitutions
in both the phenylacetonitrile (4) and the nitroaniline
(5) portions of the benzophenone without significant
modification of the reaction conditions. Furthermore,
a wide variety of substituted phenylacetonitriles are
commercially available, and additional substitution
patterns can be accessed readily through synthesis. The
oxidation step was initially performed by bubbling
oxygen through the reaction mixture; however, it was
subsequently found that 30% aqueous hydrogen perox-
ide was easier to manipulate and resulted in better
yields. Finally, it was found that 2 equiv of base was
necessary to drive the first step (nucleophilic aromatic
substitution) of the reaction to completion due to the
increased acidity of the R hydrogen of the nitrile
Ch a r t 2
intermediate. By adding the hydrogen peroxide to the
reaction mixture following completion of the first step,
the overall reaction to give ketone 6 can be conveniently
accomplished in a simple one-pot procedure.
The next three steps were carried out unchanged from
the former route. Thus, reduction of the nitro group of
6 gave diamine 7 (94% yield), selective sulfonylation of
the more nucleophilic aniline nitrogen of 7 furnished
the desired sulfonylated product 8 in 88% yield, and
reaction of compound 8 with cyanogen bromide provided
the desired 2-aminobenzimidazole 9 (54% yield), a
versatile intermediate for analogue preparation. Sub-
stitution of the isopropylsulfonyl group with other
groups was also desired and was easily attained. For
example, by use of dimethylsulfamoyl chloride in place
of the 2-propanesulfonyl chloride in the synthesis, 12
was readily produced (Chart 2).
The next task was installation of the vinylacetylene
moiety. In the original scheme, this had been achieved
through a multistep sequence involving addition of
propargylmagnesium bromide to ketone 9, protection of

Antirhino/ Enteroviral Vinylacetylene Benzimidazoles
J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 24 3939
Sch em e 2a
Sch em e 3a
a
(a) i. LiHMDS (6.0 equiv), 13 (5.0 equiv), -78 °C, THF, ii.
separate isomers; (b) 14a , CsF, CH3CN:CH2Cl2, 5:1.
the alkyne of the resultant propargyl alcohol 10 with
Co2(CO)8, elimination of the tertiary alcohol under acidic
conditions, and finally deprotection of the alkyne to
reveal the vinylacetylene (11). This sequence was
employed due to problems with the vinylacetylene’s
stability when the unprotected propargyl alcohol (10)
was subjected to the acidic elimination reaction condi-
tions. This route for conversion of the ketone to the
vinylacetylene was unattractive for several reasons, and
this reaction sequence was ultimately the major impedi-
ment to analogue preparation in the overall synthetic
scheme. The yield for this particular transformation
was only ∼10%, and the purification was complicated
by the cobalt byproducts liberated in the last step.
Two alternatives were investigated for the installation
of the acetylene moiety. The first utilized the same
propargyl Grignard addition as in the initial synthesis
to generate 10, but the elimination was executed under
basic conditions. In situ protection of the 2-amino of
benzimidazole 10 as the silylamine followed by reaction
of the hindered tertiary alcohol with mesyl chloride,
Et3N, and DMAP produced a mixture of the cis and
trans olefin isomers from which the desired trans
vinylacetylene 11 could be isolated in moderate yields
(19%). The use of the in situ protection of the silylamine
was not necessary for the reaction to proceed, but it did
eliminate the 10-20% of the undesired 2-aminosulfo-
nylated material observed in its absence. This set of
conditions offered several advantages to the cobalt
protection route. The yield of isolated trans material
was doubled to 19%, and the separation was now easier.
As well, the three-step sequence previously required for
the transformation of the propargyl alcohol to the
vinylacetylene had been reduced to one step. A second
approach was examined which involved use of Horner-
Wadsworth-Emmons (H-W-E) reagent 1322 to pro-
duce vinylacetylene 14 in one step from ketone 9c
(Scheme 2). Subsequent deprotection of the silylacety-
lene furnished the desired final compound 11c. This
reaction was first performed using 3 equiv of the
H-W-E reagent, but this led to incomplete consump-
tion of starting material. The use of 5 equiv of reagent
did drive the reaction to completion; however, the excess
reagents required complicated the separation, and a low
yield (3.5%) of the desired trans isomer 14a was
obtained. Furthermore, the deprotection of the silyl-
acetylene to give the final product 11c was not a high-
yielding process (45%). Although these reactions were
not optimized, it seemed that the first of the two routes
examined was superior, and it was routinely used.
Examination of the olefin geometry produced under
the mesyl chloride elimination reaction conditions yields
an observation worthy of further mention. The ratio of
trans to cis obtained under these conditions is domi-
nated by the electronic nature of the left-hand phenyl
a
(a) CH3MgBr (5.0 equiv), 0 °C, THF:Et2O; (b) p-TSA (2.25
equiv), CHCl3; (c) NBS (1.5 equiv), THF, reflux; (d) (Ph3)2PdCl2
(0.033 equiv), iPr2NH (10.0 equiv), CuI (0.10 equiv), CH3CCH,
THF.
unit.23 For example, p-methoxy- and p-dimethylamino-
substituted rings give predominantly the undesired cis
isomer (trans:cis ) ∼1:3), while p-fluoro substitution
gives mostly the trans isomer (trans:cis ) 2:1). One
possible explanation of these ratios is afforded upon
analysis of the transition state of the elimination.
Although the reaction conditions certainly favor an E2-
like process, it is known that R-aryl substitution can
shift the mechanism toward the E1 end of the mecha-
nistic continuum. In this case, the developing positive
charge on the carbon attached to the two aromatic
systems could be conjugatively stabilized through the
π-framework of one of the two aromatic systems more
than by the other due to the steric limitations of the
system. If the left-hand phenyl ring has electron-
donating substituents, it can better serve to stabilize
the partial positive charge than can the pendent ben-
zimidazole moiety. As such, due to the eclipsing effect,
the elimination will favor the isomer which places the
acetylene group opposite to the left-hand phenyl. When
the left-hand phenyl contains electron-withdrawing
substituents, the benzimidazole is now better suited to
stabilize the transient positive charge. As a result, the
elimination places the acetylene away from the benz-
imidazole portion of the molecule favoring the trans
product.
In addition to our examination of substituent effects
on the aromatic rings, the consequence of substitution
of the acetylene was also briefly studied. Since the
routine synthetic scheme was not amenable to the
preparation of this type of compound (e.g., methyl-
substituted acetylene derivative 18a ), the route shown
in Scheme 3 was developed. This process delivered 18a
in four steps from ketone 9a . Reaction of 9a with
methylmagnesium bromide followed by elimination of
water with p-TSA easily afforded olefin 16. The bro-
mination of 16 was not selective and gave a mixture of
trans and cis bromides 17a ,b as a 1:1 mixture as well
as the dibromide product 17c.24 The monobromo de-
rivatives were crystallized out of the reaction mixture
and used without further purification in a palladium-
catalyzed coupling reaction25 with propyne to yield the

3940 J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 24
Tebbe et al.
Ta ble 1. Antiviral Activity and Cellular Toxicity against
HRV-14
Ta ble 2. Antiviral Activity and Cellular Toxicity against
HRV-14
compd
9a
12
18a
IC50 (µg/mL)a,b
TC50 (µg/mL)b,c
2.1(1)
15.9
>100
3.1
0.061(2)
0.26(2)
a
b
HRV-14 plaque reduction assay. The superscript number is
the number of replicates. c HRV-14 CPE/XTT assay.
dazole with a nitrogen (to make an imidazopyridine)
resulted in complete abrogation of activity.26 This
indicates that the electronics of the benzimidazole core
are very important for activity. Apparently, only cer-
tain, if any, substitutions on the benzimidazole core will
be tolerated.
In an effort to begin to probe the effect of changes at
the N-1 position, dimethylsulfamoyl derivative 12 was
evaluated (Table 2). This change delivered essentially
an equipotent analogue of its isopropylsulfonyl coun-
terpart 11a but offered a compound with substantially
different chemical, and potentially different pharma-
ceutical, properties: a result that could be of paramount
importance in further studies. One example of the
differences imparted by this isosteric replacement is the
ability of 12 to readily form salts.
IC50
TC50
compd
X
Y
(µg/mL)a,b
(µg/mL)c
3
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
5-F
7-F
0.094(3)
0.060(6)
0.092(5)
0.13(4)
0.11(3)
0.17(2)
0.19(3)
0.061(3)
0.059(1)
0.075(1)
0.117(3)
0.40(3)
0.55(3)
0.21(3)
1.5(1) d
2.8(1)
11
5.3
66
5.8
63
11a
11b
11c
11d
11e
11f
11g
11h
11i
11j
11k
11l
11m
11n
11o
3-F
2-F
4-F
2,5-diF
3,5-diF
3,4-diF
3-F, 4-OMe
4-OMe
4-Me
4-NMe2
3-CF3
4-OCF3
3-Cl
32
19
5.5
5.2
5.7
5.3
>100
18
20
13
57
H
H
a
b
Although it was known that the sp2 substituent
should be trans and sterically small, the effect of
substitution of the terminal acetylene hydrogen for a
methyl group was unknown. Synthesis and testing of
analogue 18a confirmed the stringent spatial require-
ment in this region of the molecule and show that the
addition of a methyl group reduces activity substantially
(Table 2). Furthermore, ketone 9a was also tested to
confirm that the trans functionality is important and
that an sp2 center is not sufficient for good activity.
Although this ketone certainly exhibits an antiviral
effect, the approximate 50-fold drop in activity under-
scores the importance of the trans substituent.
Br oa d -Sp ectr u m Testin g. To ensure that the typi-
cal broad-spectrum nature of the benzimidazole class
was present and consistent among the vinylacetylene
subclass, a panel of seven additional viruses was chosen
as representative of the large number of human rhi-
noviruses (at least 110 serotypes) and human enterovi-
ruses (at least 68 serotypes). The constituents of this
panel include two viruses from the minor rhinovirus
receptor subgroup, human rhinovirus 1A (HRV-1A) and
human rhinovirus 2 (HRV-2); one additional virus from
the major rhinovirus receptor subgroup,27 human rhi-
novirus 16 (HRV-16); a prototypical enterovirus, polio-
virus 1 (PV-1); and three non-polio enteroviruses,
coxsackievirus A21 (CA21), coxsackievirus A21 mouse
muscle-adapted (CA21M), and coxsackievirus B3 (CB3).
By carefully selecting these viruses to span the major
classes of rhino/enteroviruses, it was felt that any
divergence of the SAR would become apparent. As can
be seen in Table 3, the broad-spectrum activity was
found to be intact in all of the analogues tested. Indeed,
it is also gratifying to note that the magnitude as well
as the absolute number for the antiviral activity against
HRV-14 is predictive of the activity across the spectrum
of viruses tested (compare IC50 data in Table 1 to
averaged, av, data in Table 3).
HRV-14 plaque reduction assay except where noted. The
superscript number is the number of replicates. c HRV-14 CPE/
XTT assay. PV-1 plaque reduction assay, tested as a 1:1 mixture
d
of cis and trans isomers.
desired methyl-substituted analogues 18a ,b. Subse-
quent separation of this isomeric mixture furnished
pure isomer 18a for antiviral evaluation.
Resu lts a n d Discu ssion
An tivir al P oten cy Evalu ation . HRV-14 was picked
as the routine and initial virus for testing due to the
amount of information known about this serotype. To
establish the antiviral activity of the compounds versus
a general cellular toxicity, compounds were first tested
in a cytopathic effect assay. As can be seen in Table 1,
the therapeutic index for these compounds (ratio of TC50
over IC50) is generally quite high (∼100-700), and no
associations between cellular toxicity and antiviral
activity are apparent. Analysis of the antiviral IC50
values from the plaque reduction assay (Table 1) does
yield several general trends. Although the mono- and
disubstituted fluoro analogues that were examined do
exhibit similar IC50 values, the m-fluoro compound 11a
does appear to be slightly more active than the other
substitution patterns examined. There is a suggestion
of the influence of electronic effects on the activity as
evidenced by comparison of derivatives with electron-
donating substituents at the para position (11g-i)
versus electron-withdrawing substituents at this site
(11c,l) with electron-donating groups being favored.
Steric interactions at the meta position appear to be
important since replacement of the fluorine with a
chlorine (11a vs 11m ) led to a considerable loss in
activity. This was further substantiated by trifluorom-
ethyl analogue 11k . In an effort to examine substitution
of the benzimidazole core, derivatives 11n ,o which
placed a fluorine in the 5 and 7 positions, respectively,
were prepared. These compounds suffer a significant
drop in activity. This result was not altogether unex-
pected due to the work reported by Kelley et al. who
demonstrated that replacement of C-4 of the benzimi-
Or a l P la sm a Level Scr een in g. On the basis of the
limited number of analogues made in the previous
study,20 the combination of fluorine and acetylene

Antirhino/ Enteroviral Vinylacetylene Benzimidazoles
J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 24 3941
Ta ble 4. Oral Plasma Concentrations in Mice
Ta ble 3. Broad-Spectrum Antiviral Activity Evaluationa
HRV- HRV- HRV- PV-
compd
Cmax (µg/mL)a
compd
Cmax (µg/mL)a
compd 1A
2
16
1
CA21 CA21M CB3
av
1
2
0.89
5.1
12
9.2
9.2
11i
11j
11k
11l
11m
11n
11o
12
0.61
0.21
4.9b
2.0
3
0.033 0.065 0.039 0.037 0.037 0.089 0.10 0.057
0.027 0.069 0.057 0.037 0.085 0.046 0.032 0.050
11a
11b
11c
11d
11e
11f
11g
11h
11j
11l
11a
11b
11c
11d
11e
11f
11g
0.035 0.050 0.070 0.045b 0.079 0.10
0.050 0.061
0.062 0.095 0.085
0.078 0.091 0.098 0.067 0.10
0.096 0.079 0.099 0.032 0.069 0.10
0.12 0.18 0.26 0.12 0.19 0.23
0.12 0.23 0.55 0.082b 0.247 0.22
18
0.10 0.083
0.14 0.18
0.10 0.22
9.3
16c
18b
2.9
0.52
8.4
0.64
0.049 0.054 0.060 0.016 0.032 0.029 0.035 0.039
0.030 0.041 0.029 0.040 0.047 0.051 0.055 0.042
9.2d
18a
a
Compounds were dosed at 100 mg/kg. Blood from three mice
0.048 0.060 0.080 0.059b 0.14
0.13
0.50
0.18
0.060 0.082
0.70 0.36
0.17 0.17
was pooled. The Cmax was within a 4-h time frame unless noted.
0.26 0.35 0.22 0.27
0.22
0.23
The Cmax was at 6 h. c Dosed as a 1:1 mixture of cis:trans isomers
b
11m 0.13 0.12 0.19 0.15
d
which were indistinguishable by HPLC. Cmax estimated at 9.2
12
18a
0.053 0.050 0.040 0.047b 0.10
0.14 0.28 0.090 0.12b 0.33
0.090 0.070 0.064
0.36 0.19 0.22
µg/mL for a 100 mg/kg dose of pure 11g (actually dosed at 100
mg/kg as a 1:1 mixture of cis:trans isomers which were distin-
guishable by HPLC: Cmax(11g) ) 4.6 µg/mL, Cmax(11g′) ) 5.5 µg/
mL).
a
Values are IC50’s in µg/mL, are single determinations, and
b
were run with Enviroxime as
a standard. Enviroxime was
unusually high in this assay (0.48 µg/mL), so values were corrected
back to 0.05 µg/mL.
respectively. These data add further support to the
applicability of this crude screening model.
appeared promising in terms of attaining adequate oral
plasma levels. This led to a focus on fluoro-containing
derivatives to try and understand the scope of the initial
trend that was observed. With the clinical experience
of Enviroxime and Enviradene and the followup studies
done with the vinylacetylenes both in rodents and in
monkeys, a diverse set of data existed for consideration
of how best to approach the issue of optimizing oral
plasma levels. Since a relatively large number of
compounds needed to be evaluated, it was not practical
to use monkeys as a screening animal. Evaluation of
the metabolism data generated earlier for 11c indicated
that the mouse would be a good small-animal model for
testing of oral absorption of the vinylacetylenes.20
Therefore, a screening protocol was developed in which
mice were dosed by oral gavage with the test compound
as a 1:5 mixture with poly(vinylpyrrolidone) (PVP-30).
Since this was being run as a screening tool, Cmax’s were
chosen as the criteria for comparison of compounds. As
such, blood was drawn more frequently early in the
experiment (0.25, 0.5, 1, 2, and 4 h) to ensure that the
Cmax was represented. In the rare cases where the Cmax
was not found in the 4-h time frame, the experiment
was repeated with extended time points. Plasma
samples were then analyzed by HPLC to determine the
Cmax. These data along with the antiviral activity were
then employed to rank compounds for further pharma-
cokinetic and toxicological evaluation.
On the basis of the results from the oral dosing, the
compounds could be roughly subdivided into three main
groups (Table 4). Those derivatives in the lowest group
(Cmax’s e 5 µg/mL) were considered to be poor candidates
for oral delivery no matter what antiviral activity they
possessed. This eliminated 7 of the 16 compounds
evaluated in the present study. For comparative pur-
poses Enviroxime (1) and Enviradene (2) were both
analyzed in this model. These two compounds which
suffered from poor oral bioavailability in man would
have been eliminated from consideration based on the
results obtained serving to help validate this model. The
next group was one with intermediate plasma levels
(Cmax’s ) 9-12 µg/mL). Six compounds (11a -d ,g and
12) fell into this class. The next level was the highest
(Cmax’s ∼ 18 µg/mL), and only three compounds (11e,m ,n )
achieved this level in the plasma. It is of interest to
note that 11c,n were both previously dosed in monkeys
and found to have 23% and 46% oral bioavailability,
With the blood level data in hand, the antiviral
activity was next taken into consideration. Deliverable
activity was the criterion by which compounds were
ranked, and the oral plasma level and antiviral activity
of the compounds were weighted equally. Using these
criteria, analysis of the compounds which produced the
highest Cmax’s shows that one compound rises above the
other two: the 3,5-difluoro analogue 11e is plainly
superior to 11m or 11n . Evaluation of the middle group
of compounds was approached in a similar manner,
although the differences in this set are definitely more
subtle. The 3-fluoro compound 11a seemed to stand out
given its higher Cmax value and its slightly better
activity. Likewise, the 3-fluoro-4-methoxy derivative
11g was also considered to be of interest due to its
equivalent blood level to the others in this group but
its apparently superior activity. The remaining com-
pounds in this group (11b-d and 12) were all viewed
as being slightly below this first tier of three compounds
picked for advancement into more detailed studies.
Con clu sion
The discovery and development of a drug to treat the
common cold requires a compound which meets a very
stringent set of conditions. First, a successful compound
must possess activity against a subset of a virus family
that minimally encompasses one genus (rhinovirus)
with at least 110 serotypes as well as a second genus
(enterovirus) which adds at least 68 additional serotypes
as far as human pathogenicity is concerned. If this
requirement can be met with sufficient potency across
this vast number of viruses, the target chosen must be
one such that resistance does not rapidly become a
problem. Once these criteria are fulfilled, the challenges
turn toward development issues. For a drug to be of
use for this indication, it will have to be available to
the patient quickly and easily, and it will almost
certainly have to be delivered either orally or intrana-
sally. The other and most important development issue
is safety. A compound for a self-limiting illness with
the potential for multiple courses of therapy per year
and certain use in pediatrics demands a compound with
little or no side effects. Last, the compound will have
to be efficacious in humans, if not providing relief for
those who are already infected at least being useful as
a prophylactic.

3942 J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 24
Tebbe et al.
reaction mixture was again cooled to 0 °C with an ice bath,
and hydrogen peroxide (30 mL of a 30% solution, 326 mmol)
was added. The ice bath was left in place, and the reaction
mixture was stirred overnight, slowly allowing the reaction
mixture to come to room temperature. At this time the color
had changed from an intense blue to dark brown, and the
reaction mixture was poured into approximately 1 L of 1 N
HCl giving a bright orange precipitate. The HCl suspension
was stirred vigorously for about 30 min, and then the orange
solid was collected by filtration and dried in a vacuum oven
at 30 °C for 12 h furnishing 6a (20.5 g, 78.8 mmol, 79% yield)
as an orange solid: 1H NMR (DMSO-d6) δ 6.86 (dd, J ) 8.9,
1.6 Hz, 1H), 7.37 (d, J ) 1.5 Hz, 1H), 7.43-7.72 (m, 6H), 8.08
(d, J ) 8.9 Hz, 1H); IR (CHCl3) 3401, 1671, 1623, 1588, 1501,
1331, 1252 cm-1; UV λmax 234 (ꢀ ) 20 905), 281 (ꢀ ) 11 673),
395 (ꢀ ) 4091), 423 nm (ꢀ ) 5473); FDMS (MeOH) m/z 260
(M+). Anal. (C13H9FN2O3) C, H, N.
B. 3,4-Dia m in o-3′-flu or ob en zop h en on e (7a ). Com-
pound 6a (20.5 g, 78.8 mmol) was placed in a Parr-type
hydrogenation vessel along with THF (500 mL). To this was
added Raney nickel (2.05 g, 10 wt %) which was purchased
from the Davidson Specialty Chemical Co. and then washed
with ethanol and stored under ethanol. The reaction mixture
was shaken for 12 h under hydrogen pressure (60 psi, 4 atm).
After this time, the reaction mixture was filtered to remove
the catalyst. The solvent was then removed in vacuo to give
7a (17.1 g, 74.1 mmol, 94% yield), the desired diamino
compound, as a yellow solid which can be used in the next
step without further purification: 1H NMR (DMSO-d6) δ 4.76
(s, 2H), 5.58 (s, 2H), 6.91 (d, J ) 8 Hz, 1H), 7.07 (s, 1H), 7.32-
7.47 (m, 3H), 7.49-7.61 (m, 1H); IR (CHCl3) 3438, 3377, 3010,
1648, 1618, 1585, 1516, 1446, 1311, 1271, 1249 cm-1; FDMS
(MeOH) m/z 230 (M+). Anal. (C13H11FN2O1) C, H, N.
C. 4-Am in o-3-(1-m et h ylet h a n esu lfon a m id o)-3′-flu o-
r oben zop h en on e (8a ). Compound 7a (17.1 g, 74.1 mmol)
was dissolved in methylene chloride (150 mL) and pyridine
(30 mL, 371 mmol). 2-Propanesulfonyl chloride (12 mL, 105
mmol) was added, and the reaction mixture was stirred at
room temperature for 5 h. At this point, the reaction mixture
was poured into a separatory funnel, 1 N HCl (500 mL) was
added, and the mixture was extracted with ethyl acetate (500
mL). The organic phase was then dried (MgSO4) and the
solvent removed in vacuo. The crude product was then
purified by HPLC (Waters Prep 500, gradient eluent 30-60%
ethyl acetate/hexane) to give the desired product 8a (21.9 g,
65 mmol, 88% yield) as a yellow gum which can be used in
the next step without further purification: 1H NMR (DMSO-
d6) δ 1.26 (d, J ) 7.4 Hz, 6H), 3.24 (septet, J ) 7.1 Hz, 1H),
6.17 (s, 2H), 6.81 (d, J ) 8.9 Hz, 1H), 7.38-7.73 (m, 6H), 8.90
(s, 1H); IR (CHCl3) 3405, 2995, 1649, 1619, 1585, 1441, 1314,
1291, 1142 cm-1; UV λmax 246 (ꢀ ) 13 961), 336 nm (ꢀ ) 15 859);
FDMS (MeOH) m/z 336 (M+). Anal. (C16H17FN2O3S) C, H,
N, S.
We have shown that the vinylacetylene benzimida-
zoles certainly possess the potency and broad spectrum
of activity necessitated as a first step toward a treat-
ment of the common cold. By incorporating concomitant
evaluation of oral plasma levels along with antiviral
activity, we were able to optimize both of these param-
eters to identify not only the most active analogues but
also those that have the highest potential for oral
bioavailability. The generality of the link between
fluorine substitution of the vinylacetylenes and oral
plasma levels was found to be present but not absolute.
Although it is true that each of the derivatives picked
for further evaluation do incorporate a fluorine, a
compound which showed one of the highest plasma
levels was a chlorine-containing molecule. Perhaps then
the discernible trend is that there is an association
between halogen-containing left-hand phenyl units and
oral plasma levels within this series.
Having aptly demonstrated both antiviral activity and
oral plasma levels, this class has cleared the first two
hurdles outlined above. Additionally, one of the mem-
bers of this group (11c) has already been shown to have
good oral bioavailability in monkey (23%) and in rat
(51%) as well as activity in the coxsackievirus A21
mouse model. Further evaluation of the lead com-
pounds identified in this study including more extensive
ADME and toxicological studies is clearly warranted,
and progress toward these goals will be reported in due
course.
Exp er im en ta l Section
Reactions were carried out with continuous stirring under
a positive pressure of nitrogen except where noted. Reagents
and solvents were purchased and used without further puri-
fication. TLC was performed with 0.25-mm silica gel 60 plates
with a 254-nm fluorescent indicator from E. Merck. Plates
were developed in a covered chamber and visualized by
ultraviolet light or by treatment with 5% phosphomolybdic acid
in ethanol followed by heating. Flash chromatography was
carried out with silica gel 60, 230-400 mesh (0.040-0.063-
mm particle size), purchased from EM Science. Reverse-phase
chromatography was carried out with
a Waters PrepLC
System 500A instrument using PrepPAK 500 cartridges for
preparative liquid chromatography. Analytical data for com-
pounds 3 and 11c,h were reported previously.20 Melting points
were determined with a Thomas-Hoover melting point ap-
paratus and are uncorrected. Proton NMR spectra are re-
ported as chemical shifts in parts-per-million (ppm) downfield
from a tetramethylsilane internal standard (0 ppm). 1H NMR
spectra were recorded in the solvent indicated on a GE QE-
300 spectrometer at 300.15 MHz. IR spectra were recorded
on a Nicolet 510P FT-IR spectrometer, UV spectra were
recorded on a Shimadzu UV-2101 PC spectrometer, and field
desorption (FD) mass spectra were recorded on either a VG
ZAB-3F or VG 70-SE instrument. IR spectra, UV spectra,
FDMS spectra, elemental analyses, and some 1H NMR spectra
were provided by the Physical Chemistry Department at Lilly
Research Laboratories.
Gen er a l P r oced u r e for Vin yla cetylen es 11a -o: A.
3-Am in o-4-n it r o-3′-flu or ob en zop h en on e (6a ). 3-Fluoro-
phenylacetonitrile (4a ) (13.5 g, 100 mmol) and 5-chloro-2-
nitroaniline (5a ) (17.25 g, 100 mmol) were placed in a 500-
mL round-bottom flask and dissolved in anhydrous DMF (200
mL). The reaction was cooled to 0 °C with an ice bath, and
potassium tert-butoxide (22.44 g, 200 mmol) was added in one
portion causing the reaction mixture to turn an intense dark
blue. The ice bath was then removed and the reaction mixture
allowed to stir at room temperature for approximately 4 h at
which time the initial reaction was complete by TLC (20%
ethyl acetate/hexanesfast running yellow spot is converted to
a slower running yellow-orange spot). At this point the
D. 6-(3-F lu or ob en zoyl)-1-[(1-m et h ylet h yl)su lfon yl]-
1H-ben zim id a zol-2-a m in e (9a ). Compound 8a (21.9 g, 65
mmol) was dissolved in 2-propanol (120 mL), and 2 N NaOH
(32.5 mL, 65 mmol) was added. The reaction mixture was
cooled to 0 °C with an ice bath, and cyanogen bromide (13 mL,
5 N solution in acetonitrile, 65 mmol) was added. After the
mixture stirred for approximately 1 h at room temperature, a
precipitate began to form. Stirring was continued overnight,
and in the morning the precipitate was collected by filtration
and washed with ether to give 9a (12.7 g, 35.2 mmol, 54%
yield) as an off-white solid: 1H NMR (DMSO-d6) δ 1.30 (d, J
) 6.8 Hz, 6H), 3.95 (septet, J ) 6.8 Hz, 1H), 7.35 (d, J ) 8.3
Hz, 1H), 7.46-7.65 (m, 7H), 7.96 (d, J ) 0.9 Hz, 1H); IR
(CHCl3) 3397, 3016, 1639, 1603, 1586, 1541, 1443, 1283, 1271
cm-1; UV λmax 246 (ꢀ ) 15 589), 320 nm (ꢀ ) 17 567); FDMS
(MeOH) m/z 361 (M+). Anal. (C17H16FN3O3S) C, H, N, S.
E .
DL-r-(3-F lu or op h en yl)-r-[1-[(1-m et h ylet h yl)su l-
fon yl]-2-a m in o-1H-ben zim id a zol-6-yl]-r-p r op a r gylm eth -
a n ol (10a ). To a dry 500-mL three-necked round-bottom flask
equipped with an addition funnel, reflux condenser, and
nitrogen inlet were added magnesium turnings (3.6 g, 148
mmol) and mercuric chloride (0.84 g, 3.10 mmol). Anhydrous
Et2O (150 mL) was added to the flask, and the whole assembly

Antirhino/ Enteroviral Vinylacetylene Benzimidazoles
J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 24 3943
was placed in a water-filled sonicator at room temperature.
Next, the propargyl bromide (13.7 mL, 123 mmol, 80% in
toluene) was added to the addition funnel. This was diluted
with Et2O (100 mL) and then slowly dripped into the flask.
An ice bath was also prepared and kept on hand to control
the reaction. Once initiated, the reaction started refluxing,
and the addition of propargyl bromide was metered to main-
tain a controlled reaction. Sonication was begun at this point
to facilitate complete reaction. This gave a clear, greenish-
colored solution with only a small amount of Mg metal in the
bottom of the flask. At this point, ketone 9a (12.7 g, 35.2
mmol) was placed in a 1000-mL round-bottom flask, and THF
(200 mL) was added (9a was not totally in solution). The
Grignard reagent was then cannulated into the flask contain-
ing 9a . After 2 h, the reaction was quenched by the addition
of ice and 1 N HCl (200 mL). The mixture was then extracted
with ethyl acetate (2 × 100 mL). The organic layers were
combined and washed with saturated aqueous NH4Cl (1 × 80
mL) and brine (1 × 80 mL). The organic layer was dried
(MgSO4), filtered, and concentrated in vacuo to give product
10a (13.6 g, 33.8 mmol, 96% yield) as an orange solid which
was taken on to the next step without further purification:
1H NMR (DMSO-d6) δ 1.23 (dd, J ) 8.4, 6.9 Hz, 6H), 2.69 (t,
J ) 2.3 Hz, 1H), 3.15 (m, 2H), 3.80 (septet, J ) 6.7 Hz, 1H),
6.06 (s, 1H), 6.91 (s, 2H), 6.94-7.37 (m, 5H), 7.68 (s, 1H); IR
(CHCl3) 3506, 3398, 3307, 1639, 1588, 1551, 1441, 1359, 1152,
1043 cm-1; UV λmax 257 (ꢀ ) 15 350), 213 nm (ꢀ ) 36 480);
FDMS (MeOH) m/z 401 (M+). Anal. (C20H20FN3O3S) C, H,
N.
and purified substantially in accordance with procedures (A-
F) listed above for 11a ; 1H NMR (CDCl3) δ 1.38 (d, J ) 6.8
Hz, 6H), 3.05 (d, J ) 2.5 Hz, 1H), 3.61 (septet, J ) 6.8 Hz,
1H), 5.93 (s, 2H), 6.21 (d, J ) 2.5 Hz, 1H), 7.04-7.15 (m, 4H),
7.28 (s, 1H), 7.58 (s, 1H); IR (CHCl3) 3506, 3398, 3307, 2986,
1639, 1493, 1362 cm-1; UV λmax 319.5 (ꢀ ) 24 117), 242.5 (ꢀ )
15 234), 211 nm (ꢀ ) 27 698); FDMS (MeOH) m/z 401 (M+).
Anal. (C20H17F2N3O2S) C, H, N, S.
(Z)-1-[(1-Meth yleth yl)su lfon yl]-6-[1-(3,5-diflu or oph en yl)-
1-bu ten -3-yn yl]-1H-ben zim id a zol-2-a m in e (11e): prepared
and purified substantially in accordance with procedures (A-
F) listed above for 11a ; 1H NMR (CDCl3) δ 1.40 (d, J ) 6.8
Hz, 6H), 3.10 (d, J ) 2.5 Hz, 1H), 3.61 (septet, J ) 6.8 Hz,
1H), 6.03 (d, J ) 2.6 Hz, 1H), 6.04 (s, 2H), 6.82 (dt, J ) 8.8,
2.1 Hz, 1H), 7.00 (d, J ) 6.4 Hz, 2H), 7.08 (d, J ) 8.2 Hz, 1H),
7.28 (d, J ) 8.3 Hz, 1H), 7.53 (d, J ) 0.9 Hz, 1H); IR (CHCl3)
3306, 1694, 1640, 1620, 1547, 1482, 1361, 1155, 1121, 1046
cm-1; UV λmax 318 (ꢀ ) 15 655), 263 (ꢀ ) 17 393), 213 nm (ꢀ )
32 410); FDMS (MeOH) m/z 401 (M+). Anal. (C20H17F2N3O2S)
C, H, N.
(Z)-1-[(1-Meth yleth yl)su lfon yl]-6-[1-(3,4-diflu or oph en yl)-
1-bu ten -3-yn yl]-1H-ben zim id a zol-2-a m in e (11f): prepared
and purified substantially in accordance with procedures (A-
F) listed above for 11a ; 1H NMR (DMSO-d6) δ 1.24 (d, J ) 6.6
Hz, 6H), 3.90 (septet, J ) 6.6 Hz, 1H), 4.10 (d, J ) 2.6 Hz,
1H), 6.22 (d, J ) 2.6 Hz, 1H), 7.07-7.12 (m, 3H), 7.18-7.23
(m, 2H), 7.37 (s, 1H), 7.41-7.58 (m, 2H); IR (CHCl3) 3398,
3306, 2981, 1639, 1517, 1274, 1043 cm-1; UV λmax 319 (ꢀ )
22 343); 261 (ꢀ ) 15 525), 213 nm (ꢀ ) 31 019); FDMS (MeOH)
m/z 401 (M+). Anal. (C20H17F2N3O2S) C, H, N.
F. (E)-1-[(1-Meth yleth yl)su lfon yl]-6-[1-(3-flu or oph en yl)-
1-bu ten -3-yn yl]-1H-ben zim id a zol-2-a m in e (11a ). To a
solution of 10a (13.6 g, 33.8 mmol) in methylene chloride (500
mL) were added 2,6-lutidine (4.71 mL, 40.6 mmol) and tert-
butyldimethylsilyl trifluoromethanesulfonate (8.53 mL, 37.2
mmol). After this mixture stirred for approximately 1 h,
4-(dimethylamino)pyridine (10.3 g, 84.5 mmol), triethylamine
(21.1 mL, 152 mmol), and methanesulfonyl chloride (9.95 mL,
128 mmol) were added. The reaction mixture was allowed to
stir for 2 h. After this time, the reaction mixture was diluted
with methylene chloride (300 mL) and extracted with 1 N HCl
(1 × 100 mL), saturated aqueous NaHCO3 (1 × 100 mL), and
brine (1 × 100 mL). The organic layer was dried (MgSO4),
filtered, and concentrated in vacuo to provide a reddish solid.
This solid was dissolved in acetonitrile (100 mL), and water
(∼50 mL) was added until a brownish solid started to come
out of solution. The mixture was then cooled to 4 °C overnight.
This typically resulted in the formation of a tan precipitate
(mostly cis material) that was subsequently removed by
filtration. The filtrate was ∼3:1 trans:cis. The isomers were
separated using reverse-phase chromatography (gradient elu-
ent of 45-50% acetonitrile in water). Two grams of material
(filtrate) was loaded per run in acetonitrile (∼14 mL) to give
almost baseline separation of the trans and cis isomers. This
gave 11a 28 (2.46 g, 6.42 mmol, 19% yield) with only traces of
the cis material. In cases where the isomeric ratio was only
∼90:10, the ratio could be furthered improved by slurrying the
compound after reverse-phase chromatography with acetoni-
trile (∼5 mL/g). Filtration of this slurry then yielded a solid
with an improved ratio of trans:cis: 1H NMR (CDCl3) δ 1.39
(d, J ) 6.8 Hz, 6H), 3.05 (d, J ) 2.4 Hz, 1H), 3.61 (septet, J
)6.8 Hz, 1H), 6.02 (d, J ) 2.4 Hz, 1H), 6.05 (s, 2H), 7.04-7.10
(m, 2H), 7.14-7.39 (m, 4H), 7.55 (s, 1H); IR (CHCl3) 3506,
3398, 3306, 2999, 1639, 1547, 1442, 1381 cm-1; UV λmax 317 (ꢀ
) 21 897), 263 (ꢀ ) 15 248), 212 nm (ꢀ ) 31 161); mp 150-
(Z)-1-[(1-Met h ylet h yl)su lfon yl]-6-[1-(3-flu or o-4-m et h -
oxyp h en yl)-1-b u t en -3-yn yl]-1H -b en zim id a zol-2-a m in e
11g: prepared and purified substantially in accordance with
procedures (A-F) listed above for 11a ; 1H NMR (CDCl3) δ 1.39
(d, J ) 6.7 Hz, 6H), 3.06 (s, 1H), 3.62 (septet, J ) 6.8 Hz, 1H),
3.93 (s, 3H), 5.91 (d, J ) 0.9 Hz, 1H), 6.45 (s, 2H), 6.95 (t, J )
8.4 Hz, 1H), 7.09 (d, J ) 8.2 Hz, 1H), 7.24 (m, 3H), 7.54 (s,
1H); IR (CHCl3) 3398, 3306, 2960, 2815, 1638, 1271 cm-1; UV
λmax 317 (ꢀ ) 22 342), 273 (ꢀ ) 17 661), 213 nm (ꢀ ) 33 257);
mp 160-165 °C dec; FDMS (MeOH) m/z 413 (M+). Anal.
(C21H20FN3O3S) C, H, N.
(E)-1-[(1-Meth yleth yl)su lfon yl]-6-[1-(4-m eth ylp h en yl)-
1-bu ten -3-yn yl]-1H-ben zim id a zol-2-a m in e (11i): prepared
and purified substantially in accordance with procedures (A-
F) listed above for 11a ; 1H NMR (CDCl3) δ 1.44 (d, J ) 6.8
Hz, 6H), 2.44 (s, 3H), 3.06 (d, J ) 3.0 Hz, 1H), 3.67 (septet, J
) 6.8 Hz, 1H), 6.00 (d, J ) 2.2 Hz, 1H), 7.12 (d, J ) 8.1 Hz,
1H), 7.23 (d, J ) 7.9 Hz, 2H), 7.29 (d, J ) 8.5 Hz, 1H), 7.41 (d,
J ) 7.9 Hz, 2H), 7.64 (s, 1H); IR (CHCl3) 2970, 1638, 1609,
1547, 1310, 1268, 1156, 1044 cm-1; UV λmax 315 (ꢀ ) 20 514),
267 (ꢀ ) 17 276), 212 nm (ꢀ ) 32 191); FDMS (MeOH) m/z 379
(M+). Anal. (C21H21N3O2S) N; C: calcd, 66.47; found, 65.79.
(E )-1-[(1-Me t h y le t h y l)s u lfo n y l]-6-[1-[4-(d im e t h y l-
a m in o )p h e n y l]-1-b u t e n -3-y n y l]-1H -b e n zim id a zo l-2-
a m in e (11j): prepared and purified substantially in ac-
cordance with procedures (A-F) listed above for 11a ; 1H NMR
(CDCl3) δ 1.45 (d, J ) 6.8 Hz, 6H), 3.05 (s, 6H), 3.09 (d, J )
2.4 Hz, 1H), 3.68 (septet, J ) 6.8 Hz, 1H), 5.82 (d, J ) 2.5 Hz,
1H), 6.23 (s, 2H), 6.73 (d, J ) 8.8 Hz, 2H), 7.17 (m, 1H), 7.30
(m, 1H), 7.46 (d, J ) 8.8 Hz, 2H), 7.66 (s, 1H); IR (CHCl3) 3507,
3398, 3306, 1638, 1608, 1584, 1547, 1523, 1439, 1359, 1267,
1155, 1044, 822 cm-1; UV λmax 304 (ꢀ ) 21 040), 211 nm (ꢀ )
26 310); FDMS (MeOH) m/z 408 (M+). Anal. (C22H24N4O2S)
C, H, N.
155 °C dec; FDMS (MeOH) m/z 383 (M+). Anal. (C20H18
-
FN3O2S) C, H, N.
(E)-1-[(1-Meth yleth yl)su lfon yl]-6-[1-[3-(tr iflu or om eth -
yl)ph en yl]-1-bu ten -3-yn yl]-1H-ben zim idazol-2-am in e (11k):
prepared and purified substantially in accordance with pro-
(Z)-1-[(1-Meth yleth yl)su lfon yl]-6-[1-(2-flu or op h en yl)-1-
bu ten -3-yn yl]-1H-ben zim id a zol-2-a m in e (11b): prepared
and purified substantially in accordance with procedures (A-
F) listed above for 11a ; 1H NMR (CDCl3) δ 1.38 (d, J ) 6.9
Hz, 6H), 3.00 (d, J ) 2.4 Hz, 1H), 3.60 (septet, J ) 6.8 Hz,
1H), 6.18 (s, 2H), 6.21 (d, J ) 2.5 Hz, 1H), 7.07-7.27 (m, 4H),
7.35-7.42 (m, 2H), 7.59 (d, J ) 1.4 Hz, 1H); FDMS (MeOH)
m/z 383 (M+). Anal. (C20H18FN3O2S) C, H, N.
1
cedures (A-F) listed above for 11a ; H NMR (CDCl3) δ 1.39
(d, J ) 6.8 Hz, 6H), 3.04 (d, J ) 2.5 Hz, 1H), 3.59 (septet, J )
6.8 Hz, 1H), 5.74 (s, 2H), 6.07 (d, J ) 2.2 Hz, 1H), 7.09-7.14
(m, 1H), 7.23-7.33 (m, 1H), 7.50-7.56 (m, 2H), 7.63 (m, 1H),
7.71 (s, 1H), 7.73 (m, 1H); IR (CHCl3) 3398, 3306, 2960, 1639,
1547, 1360, 1328, 1170, 1132, 1045 cm-1; UV λmax 319 (ꢀ )
19 672), 265 (ꢀ ) 14 485), 214 nm (ꢀ ) 29 852); FDMS (MeOH)
m/z 433 (M+). Anal. (C21H18F3N3O2S) C, H, N, F, S.
(Z)-1-[(1-Meth yleth yl)su lfon yl]-6-[1-(2,5-diflu or oph en yl)-
1-bu ten -3-yn yl]-1H-ben zim id a zol-2-a m in e (11d ): prepared

3944 J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 24
Tebbe et al.
(E )-1-[(1-Me t h y le t h y l)s u lfo n y l]-6-[1-[4-(t r iflu o r o -
m e t h oxy)p h e n yl]-1-b u t e n -3-yn yl]-1H -b e n zim id a zol-2-
a m in e (11l): prepared and purified substantially in ac-
cordance with procedures (A-F) listed above for 11a ; 1H NMR
(CDCl3) δ 1.44 (d, J ) 6.8 Hz, 6H), 3.09 (d, J ) 2.1 Hz, 1H),
3.66 (septet, J ) 6.8 Hz, 1H), 6.02 (s, 2H), 6.05 (d, J ) 2.7 Hz,
1H), 7.11 (m, 1H), 7.25-7.35 (m, 3H), 7.53-7.63 (m, 3H); IR
(CHCl3) 3398, 3306, 1638, 1547, 1387, 1360, 1262, 1227, 1174,
1044 cm-1; UV λmax 319 (ꢀ ) 21 800), 265 (ꢀ ) 16 340), 213 nm
general preparation A-D) in THF (20 mL). After approxi-
mately 15 min, the reaction mixture was warmed to room
temperature, reacted overnight, and then partitioned between
ethyl acetate (500 mL) and saturated aqueous ammonium
chloride (60 mL). The resultant layers were separated, and
the organic layer was washed with brine (1 × 50 mL), dried
(MgSO4), filtered, and concentrated in vacuo to provide 6.16 g
of an oil. This oil was purified using flash chromatography
(silica gel, gradient eluent of 2-5% methanol in methylene
chloride). The fractions containing the desired compound were
combined and dried in vacuo to provide 14a (400 mg, 0.879
mmol, 3.5% yield) and 14b (207 mg, 0.455 mmol, 1.8% yield)
as impure solids. Data for 14a : 1H NMR (CDCl3) δ 0.12 (s,
9H), 1.37 (d, J ) 6.8 Hz, 6H), 3.58 (septet, J ) 6.8 Hz, 1H),
5.96 (s, 1H), 6.66 (brs, 2H), 7.00 (d, J ) 8.6 Hz, 1H), 7.06 (d,
J ) 8.6 Hz, 1H), 7.47 (d, J ) 10.6 Hz, 2H), 7.48 (dd, J ) 23.0,
8.7 Hz, 2H), 7.53 (d, J ) 1.2 Hz, 1H). Data for 14b: 1H NMR
(CDCl3) δ 0.14 (s, 9H), 1.35 (d, J ) 7.0 Hz, 6H), 3.58 (septet,
J ) 7.0 Hz, 1H), 5.93 (s, 1H), 6.14 (brs, 2H), 6.96 (d, J ) 8.6
Hz, 1H), 6.99 (d, J ) 8.6 Hz, 1H), 7.22 (dd, J ) 8.7, 5.6 Hz,
2H), 7.35 (dd, J ) 22.7, 8.7 Hz, 2H), 7.64 (s, 1H).
(E)-1-[(1-Meth yleth yl)su lfon yl]-6-[1-(4-flu or op h en yl)-1-
bu ten -3-yn yl]-1H-ben zim id a zol-2-a m in e (11c). To a solu-
tion of 14a (280 mg, 0.614 mmol) in methylene chloride and
acetonitrile (1:5) was added cesium fluoride (93.3 mg, 0.614
mmol). After approximately 2 h at room temperature, the
reaction mixture was partitioned between brine (30 mL) and
methylene chloride (30 mL). The resultant layers were
separated, and the organic layer was dried (Na2SO4), filtered,
and then concentrated in vacuo to provide an oil. This oil was
purified using reverse-phase column chromatography (eluent
of 0-5% acetonitrile in water) followed by reverse-phase HPLC
(eluent of 60% acetonitrile in water) to provide 11c (106 mg,
0.277 mmol, 45% yield; data previously reported).20
(ꢀ
)
30 850); FDMS (MeOH) m/z 449 (M+). Anal.
(C21H18F3N3O3S) C, H, N.
(Z)-1-[(1-Meth yleth yl)su lfon yl]-6-[1-(3-ch lor op h en yl)-
1-b u t en -3-yn yl]-1H -b en zim id a zol-2-a m in e (11m ): pre-
pared and purified substantially in accordance with procedures
1
(A-F) listed above for 11a ; H NMR (CDCl3) δ 1.44 (d, J )
6.8 Hz, 6H), 3.10 (d, J ) 2.1 Hz, 1H), 3.66 (septet, J ) 6.8 Hz,
1H), 6.07 (d, J ) 2.6 Hz, 1H), 6.15 (s, 2H), 7.13 (m, 1H), 7.30-
7.47 (m, 5H), 7.57 (s, 1H); IR (CHCl3) 3506, 3398, 3306, 2983,
1639, 1547, 1361, 1269, 1155, 1044, 823 cm-1; UV λmax 318 (ꢀ
) 21 950), 265 (ꢀ ) 16 040), 215 nm (ꢀ ) 37 200); FDMS
(MeOH) m/z 399 (M+). Anal. (C20H18ClN3O2S) C, H, N.
(E)-5-F lu or o-1-[(1-m eth yleth yl)su lfon yl]-6-(1-p h en yl-1-
bu ten -3-yn yl)-1H-ben zim id a zol-2-a m in e (11n ) a n d (Z)-5-
F lu or o-1-[(1-m eth yleth yl)su lfon yl]-6-(1-p h en yl-1-bu ten -
3-yn yl)-1H -b en zim id a zol-2-a m in e (11n ′): prepared and
purified substantially in accordance with procedures (A-F)
listed above for 11a except these isomers could not be
separated and as such were tested as a 1:1 mixture; isomer 1
1H NMR (CDCl3) δ 1.44 (d, J ) 6.4 Hz, 6H), 2.99 (s, 1H), 3.62
(m, 1H), 6.20 (s, 1H), 6.79 (s, 2H), 7.00-7.50 (m, 6H), 7.75 (s,
1H); isomer 2 1H NMR (CDCl3) δ 1.46 (d, J ) 6.5 Hz, 6H),
3.16 (s, 1H), 3.62 (m, 1H), 5.95 (s, 1H), 6.70 (s, 2H), 7.00-7.80
(m, 7H); FDMS (MeOH) m/z 383 (M+). Anal. (C20H18FN3O2S)
C, H, N, F, S.
DL-r-(3-F lu or op h en yl)-r-m eth yl-r-[1-[(1-m eth yleth yl)-
su lfon yl]-2-a m in o-1H-ben zim id a zol-6-yl]m eth a n ol (15).
To a 0 °C solution of 9a (25.4 g, 70 mmol) in THF (600 mL)
was slowly added methylmagnesium bromide (117 mL, 350
mmol, 3 M solution in diethyl ether). The reaction was
monitored to ensure that the temperature stayed below room
temperature. After approximately 1 h, the reaction was
quenched by the slow addition of a saturated ammonium
chloride solution. The resulting layers were separated, and
the desired compound was extracted from the aqueous layer
with an additional ethyl acetate (500 mL) wash. The resultant
organic portions were combined, washed with brine (1 × 100
mL), dried (MgSO4), filtered, and concentrated in vacuo to
provide 15 (26.4 g, 70 mmol, 100% yield). The compound was
taken to the next step without further purification.
(E)-7-F lu or o-1-[(1-m eth yleth yl)su lfon yl]-6-(1-p h en yl-1-
bu ten -3-yn yl)-1H-ben zim id a zol-2-a m in e (11o): prepared
and purified substantially in accordance with procedures (A-
F) listed above for 11a except that these isomers could only
be separated by crystallization; trans isomer was crystallized
from acetonitrile:water, ∼4:1, at 4 °C, and structure of this
isomer was determined by heteronuclear NOE experiments
between the fluorine and the olefinic hydrogen; 1H NMR
(CDCl3) δ 1.42 (d, J ) 6.8 Hz, 6H), 3.11 (d, J ) 2.6 Hz, 1H),
3.65 (septet, J ) 6.8 Hz, 1H), 6.01 (d, J ) 2.6 Hz, 1H), 6.27 (s,
2H), 6.86 (dd, J ) 6.8, 8.2 Hz, 1H), 7.30-7.39 (m, 4H), 7.50-
7.53 (m, 2H); IR (CHCl3) 3506, 3398, 3306, 1646, 1384, 1087
cm-1; UV λmax 287 (ꢀ ) 16 790), 240 (ꢀ ) 37 382), 204 nm (ꢀ )
25 933); FDMS (MeOH) m/z 383 (M+). Anal. (C20H18FN3O2S)
H, N; C: calcd, 62.65; found, 62.22.
(Z)-1-[(Dim eth yla m in o)su lfon yl]-6-[1-(4-flu or op h en yl)-
1-bu ten -3-yn yl]-1H-ben zim id a zol-2-a m in e (12). This was
prepared and purified substantially in accordance with pro-
cedures (A-F) listed above for 11a except that dimethylsul-
famoyl chloride was used in place of 2-propanesulfonyl chloride
in procedure C. Subsequent compounds were capable of
forming salts. Therefore, isolation of materials had to be
somewhat altered based on typical procedures for salt-forming
compounds (i.e., after acid washes the water layer was
collected, adjusted to a basic pH, and then extracted with an
organic): 1H NMR (CDCl3) δ 2.94 (s, 6H), 3.09 (d, J ) 2.3 Hz,
1H), 6.07 (d, J ) 2.5 Hz, 1H), 6.21 (brs, 2H), 7.07-7.46 (m,
6H), 7.50 (s, 1H); IR (CHCl3) 3398, 3306, 3019, 2976, 1636,
1610, 1544, 1476, 1442, 1391, 1275, 1170, 1052, 969, 884, 823
cm-1; UV λmax 318 (ꢀ ) 22 150), 259 (ꢀ ) 14 930), 222 nm (ꢀ )
27 680); FDMS (MeOH) m/z 384 (M+). Anal. (C19H17FN4O2S)
C, H, N, F, S.
(E)-1-[(1-Meth yleth yl)su lfon yl]-6-[1-(4-flu or op h en yl)-4-
(t r im e t h ylsilyl)-1-b u t e n -3-yn yl]-1H -b e n zim id a zol-2-
a m in e (14a ) a n d (Z)-1-[(1-Meth yleth yl)su lfon yl]-6-[1-(4-
flu or op h e n yl)-4-(t r im e t h ylsilyl)-1-b u t e n -3-yn yl]-1H -
ben zim id a zol-2-a m in e (14b). To a -78 °C solution of
diethoxy 3-(trimethylsilyl)prop-2-ynylphosphonate (13) (6.21
g, 25 mmol) in anhydrous THF (5 mL) was added lithium bis-
(trimethylsilyl)amide (30 mL, 1 M solution in THF, 30 mmol).
The resultant mixture was stirred for approximately 30 min
and was then added to a -78 °C solution of 9c (1.81 g, 5 mmol,
1-[(1-Meth yleth yl)su lfon yl]-6-[1-(3-flu or op h en yl)eth yl-
en e]-1H-b en zim id a zol-2-a m in e (16). To a solution of 15
(26.4 g, 70 mmol) in chloroform (300 mL) was added p-
toluenesulfonic acid (27 g, 157 mmol). The resultant reaction
mixture was refluxed for approximately 2 h. The reaction was
cooled to room temperature and washed sequentially with
water (1 × 50 mL), saturated sodium bicarbonate (1 × 50 mL),
and brine (1 × 50 mL). It was then dried (MgSO4), filtered,
and concentrated in vacuo to provide a brown foam. This foam
was triturated in diethyl ether and then filtered to provide 16
(22.7 g, 63 mmol, 90% yield) as a tan solid. This compound
can be used without further purification: 1H NMR (CDCl3) δ
1.45 (d, J ) 6.8 Hz, 6H), 3.68 (septet, J ) 6.8 Hz, 1H), 5.52 (s,
2H), 6.35 (s, 2H), 7.04-7.10 (m, 2H), 7.17-7.25 (m, 2H), 7.29-
7.38 (m, 2H), 7.64 (s, 1H); IR (CHCl3) 3420, 1639, 1610, 1579,
1550, 1438, 1359, 1155, 1043 cm-1; UV λmax 280 (ꢀ ) 15 482),
256 nm (ꢀ ) 14 929); FDMS (MeOH) m/z 359 (M+). Anal.
(C18H18FN3O2S) C, H, N.
(E/Z)-1-[(1-Meth yleth yl)su lfon yl]-6-[1-(3-flu or op h en yl)-
2-br om oeth ylen e]-1H-ben zim id a zol-2-a m in e (17a ,b) a n d
1-[(1-Meth yleth yl)su lfon yl]-6-[1-(3-flu or op h en yl)-2,2-d i-
br om oeth ylen e]-1H-ben zim id a zol-2-a m in e (17c). To a
solution of 16 (22.6 g, 63 mmol) in THF (500 mL) was added
N-bromosuccinimide (16.7 g, 93.8 mmol). The resultant reac-
tion mixture was refluxed for approximately 3 h. The reaction
mixture was then cooled to room temperature and stirred
overnight. The reaction mixture was concentrated in vacuo

Antirhino/ Enteroviral Vinylacetylene Benzimidazoles
J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 24 3945
to provide a residue which was dissolved in ethyl acetate (600
mL), washed with water (1 × 60 mL), dried (MgSO4), filtered,
and concentrated in vacuo to provide a red foam. This foam
was dissolved in diethyl ether and then dried in vacuo to
provide 32 g of a red solid. The desired monobromination
products 17a ,b were separated from the dibromide 17c by
precipitation from acetonitrile (∼100 mL) at 4 °C to provide
17a ,b (5.66 g, 12.9 mmol, 20% yield) as a solid. This mixture
of compounds was used without further purification. Isomer
17a was assigned as trans through NMR experiments which
showed an NOE between the olefinic hydrogen and the C-7
and C-5 hydrogens of the benzimidazole core. Data for 17a :
1H NMR (CDCl3) δ 1.44 (d, J ) 6.7 Hz, 6H), 3.66 (septet, J )
6.7 Hz, 1H), 6.19 (s, 2H), 6.81 (s, 1H), 7.05-7.17 (m, 4H), 7.28-
7.31 (m, 1H), 7.41-7.46 (m, 1H), 7.55 (s, 1H). Data for 17b:
1H NMR (CDCl3) δ 1.46 (d, J ) 6.5 Hz, 6H), 3.68 (septet, J )
6.5 Hz, 1H), 6.19 (s, 2H), 6.85 (s, 1H), 6.97 (m, 1H), 7.05-7.17
(m, 3H), 7.28-7.31 (m, 1H), 7.41-7.46 (m, 1H), 7.69 (s, 1H).
Data for 17a ,b: IR (CHCl3) 3430, 1638, 1610, 1548, 1438, 1359,
1155, 1043 cm-1; UV λmax 289 (ꢀ ) 17 127), 262 nm (ꢀ ) 16 964);
FDMS (MeOH) m/z 439 (M+). Anal. (C18H17BrFN3O2S) C, H,
N. Data for 17c: 1H NMR (CDCl3) δ 1.44 (d, J ) 6.8 Hz, 6H),
3.66 (septet, J ) 6.8 Hz, 1H), 6.37 (s, 2H), 7.02-7.17 (m, 4H),
7.30-7.42 (m, 2H), 7.67 (s, 1H); IR (CHCl3) 3430, 1638, 1610,
1549, 1439, 1360, 1155, 1044 cm-1; UV λmax 282 (ꢀ ) 17 107),
257 nm (ꢀ ) 17 821); FDMS (MeOH) m/z 517 (M+). Anal.
(C18H16Br2FN3O2S) H, N; C: calcd, 41.80; found, 43.79.
(Z)-1-[(1-Meth yleth yl)su lfon yl]-6-[1-(3-flu or op h en yl)-1-
p en ten -3-yn yl]-1H-ben zim id a zol-2-a m in e (18a ). To a so-
lution of 17a ,b (4.00 g, 9.1 mmol) in THF (25 mL) was added
bis(triphenylphosphine)palladium(II) chloride (210 mg, 0.3
mmol) followed by diisopropylamine (12.7 mL, 91 mmol). After
the resultant mixture stirred for approximately 10 min, copper-
(I) iodide (170 mg, 0.91 mmol) was added. The resultant
mixture was stirred for another 10 min, and then propyne(g)
was bubbled through the mixture for approximately 1.75 h.
The reaction mixture was diluted with diethyl ether (300 mL),
washed sequentially with a saturated ammonium chloride
solution (1 × 40 mL), a 1 N HCl solution (1 × 40 mL), and a
saturated sodium bicarbonate solution (1 × 40 mL). The
organic layer was dried (MgSO4), filtered, and concentrated
in vacuo to provide a residue. This residue was purified using
flash chromatography (silica gel, gradient eluent of 60-80%
ethyl acetate in hexanes) to give 18a ,b (2.0 g, 5.0 mmol, 55%
yield) as a solid. The trans isomer 18a was then separated
from the cis isomer using reverse-phase chromatography: 1H
NMR (CDCl3) δ 1.44 (d, J ) 6.8 Hz, 6H), 1.99 (s, 3H), 3.66
(septet, J ) 6.8 Hz, 1H), 6.04 (d, J ) 2.0 Hz, 1H), 6.26 (s, 2H),
7.08-7.13 (m, 2H), 7.27-7.41 (m, 4H), 7.58 (s, 1H); IR (CHCl3)
3398, 2984, 1639, 1639, 1610, 1548, 1441, 1360, 1269, 1174,
1155, 1043 cm-1; UV λmax 315 (ꢀ ) 22 318), 267 (ꢀ ) 16 135),
212 nm (ꢀ ) 32 383); FDMS (MeOH) m/z 397 (M+). Anal.
(C21H20FN3O2S) C, H, N.
at 37 °C for the enteroviruses until the DMSO control wells
demonstrated plaques of optimal size. At this time, a solution
containing 10% formalin and 2% sodium acetate was added
to each well to inactivate the virus and fix the cell sheet to
the plastic surface. The fixed cell sheets were stained with
0.5% crystal violet, and the plaques were counted. Results
from duplicate wells at each concentration were averaged and
compared with DMSO control wells. The inhibition of plaque
formation by 50% (IC50) was calculated from the linear region
of the inhibition concentration curve using the method of Reed
and Muench.31
P r ot ocol for Mou se Or a l P la sm a Level Scr een in g
Stu d ies. One equivalent of the compound to be studied was
dissolved in absolute ethanol along with 5 equiv of PVP-30
(Aldrich; poly(vinylpyrrolidone), av MW) 40 000). The solvent
was removed by rotary evaporation to give a glassy foam. The
foam was removed from the flask and ground to a fine powder
using a mortar and pestle. The compound was suspended in
2% Emulphor (98% water). The resulting suspension was then
subjected to extensive sonication to give a fine suspension. The
mice (ICR Swiss white, female mice weighing 15-20 g) were
then dosed (usually 3/group) by both gavage and ip at 100 mg/
kg (dose volume of 0.25 mL).
At selected time intervals (usually 15, 30, 60, 120, and 240
min), the mice were lightly anesthetized over dry ice and bled
from the orbital sinus to obtain blood (0.050 mL/mouse). The
blood from each group was pooled, and an equal volume of
acetonitrile (0.150 mL) was added. After vortexing (10-20 s),
the liquid fraction was separated from the coagulated blood
cell debris by microcentrifugation in the cold for approximately
5 min. The liquid supernatant was then collected and ana-
lyzed by analytical HPLC utilizing C18 reverse-phase columns
with UV detection.
Ack n ow led gm en t. We express our appreciation to
the Physical Chemistry Department of Lilly Research
Laboratories for providing analytical data. Specifically,
we would like to thank Ross J ohnson, Larry Spangle,
and J on Paschal for the NMR structural information
and J ack Campbell for carrying out the hydrogenation
reactions.
Refer en ces
(1) For a nonrelated series of antirhinoviral benzimidazoles, see refs
2-4.
(2) Shipkowitz, N. L.; Bower, R. R.; Schleicher, J . B.; Aquino, F.;
Appell, R. N.; Roderick, W. R. Antiviral Activity of a bis-
Benzimidazole Against Experimental Rhinovirus Infections in
Chimpanzees. Appl. Microbiol. 1972, 23, 117-122.
(3) O’Sullivan, D. G.; Ludlow, C. M. Antiviral Properties of 1-Allyl
and 1-Crotyl Derivatives of 2-(R-Hydroxybenzyl)benzimidazole.
Experientia 1972, 28, 889-890.
Cytop a th ic Effect Assa y. The cytopathic effect (CPE)
assay was performed as described previously29 with a modi-
fication to the method of the quantification of the cytopathic
effect of virus on the cells. Instead of using crystal violet
staining, XTT (2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-
tetrazolium-5-carboxanilide) was used as substrate to quantify
the surviving host cells.30
Gen er a l P la qu e Red u ction Assa y. Susceptible HeLa
cells were grown in 6-well tissue culture cluster plates at 37
°C in minimum essential medium (MEM) with 5% fetal bovine
serum, 10 mM MgSO4, penicillin (100 U/mL), and streptomycin
(100 µg/mL). When confluent monolayers were formed, growth
medium was removed and 0.2 mL/well of an appropriate
dilution of virus was added. After adsorption for 1-2 h at
room temperature, the infected cell sheet was overlaid with
equal parts of 1.5% sterile agarose solution and a 2-fold
concentration of MEM (2% fetal bovine serum, 10 mM MgSO4,
penicillin (100 U/mL), and streptomycin (100 µg/mL)) contain-
ing varying concentrations of the compounds to be tested.
The compounds were dissolved in DMSO at a concentration
of 20 mg/mL, and an aliquot was diluted to the desired
concentration in DMSO before addition to the agar medium
mixture. Plates were incubated at 34 °C for rhinoviruses and
(4) Gwaltney, J . M., J r. The Spectrum of Rhinovirus Inhibition by
2-(R-Hydroxybenzyl)benzimidazole and D-(-)-2-(R-Hydroxyben-
zyl)benzimidazole HCl. Proc. Soc. Exp. Biol. Med. 1968, 129,
665-673.
(5) For reviews or lead articles on chemotherapy for rhinovirus
infections, see refs 6-9.
(6) Fromtling, R. A.; Castaner, J . Vp-63843. Drugs Future 1997, 22,
40-44.
(7) Arruda, E.; Hayden, F. G. Update on Therapy of Influenza and
Rhinovirus Infections. Adv. Exp. Med. Biol. 1996, 394, 175-187.
(8) Carrasco, L. Picornavirus Inhibitors. Pharmacol. Ther. 1994, 64,
215-290.
(9) Sperber, S. J .; Hayden, F. G. Chemotherapy of Rhinovirus Colds.
Antimicrob. Agents Chemother. 1988, 32, 409-419.
(10) Wikel, J . H.; Paget, C. J .; DeLong, D. C.; Nelson, J . D.; Wu, C.
Y. E.; Paschal, J . W.; Dinner, A.; Templeton, R. J .; Chaney, M.
O.; J ones, N. D.; Chamberlin, J . W. Synthesis of Syn and Anti
Isomers of 6-[[(Hydroxyimino)phenyl]methyl]-1-[(1-methylethyl)-
sulfonyl]-1H-benzimidazol-2-amine. Inhibitors of Rhinovirus
Multiplication. J . Med. Chem. 1980, 23, 368-372.
(11) Herrmann, E. C., J r.; Herrmann, J . A.; DeLong, D. C. Compari-
son of the Antiviral Effects of Substituted Benzimidazoles and
Guanidine in Vitro and in Vivo. Antiviral Res. 1981, 1, 301-
314.
(12) DeLong, D. C.; Reed, S. E. Inhibition of Rhinovirus Replication
in Organ Culture by a Potential Antiviral Drug. J . Infect. Dis.
1980, 141, 87-91.

3946 J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 24
Tebbe et al.
(13) DeLong, D. C.; Nelson, J . D.; Wu, C. Y. E.; Warren, B. R.; Wikel,
J . H.; Chamberlin, J .; Montgomery, D.; Paget, C. J . Virus
Inhibition Studies with AR-336 I. Tissue Culture Activity.
Abstracts of the Annual Meeting of the American Society for
Microbiology; American Society for Microbiology: Washington,
DC, 1978; S128, p 234.
(14) DeLong, D. C. Effect of Enviroxime on Rhinovirus Infections in
Humans. In Microbiology; Leive, L., Schlessinger, D., Eds.;
American Society for Microbiology: Washington, DC, 1984; pp
431-434.
(15) Miller, F. D.; Monto, A. S.; DeLong, D. C.; Exelby, A.; Bryan, E.
R.; Srivastava, S. Controlled Trial of Enviroxime Against
Natural Rhinovirus Infections in a Community. Antimicrob.
Agents Chemother. 1985, 27, 102-106.
(16) Enviradene (IND 20204). Virology Section, Summary, p 58,
unpublished results.
(24) In this reaction 1.5 equiv of NBS was used. The correct
stoichiometry is 1.0 equiv of NBS, and in similar systems this
gave a good yield of the monobromide products with no dibro-
mide.
(25) Sonogashira, K.; Tohda, Y.; Hagihara, N. A Convenient Synthesis
of Acetylenes: Catalytic Substitutions of Acetylenic Hydrogen
with Bromoalkenes, Iodoarenes, and Bromopyridines. Tetrahe-
dron Lett. 1975, 16, 4467-4470.
(26) Kelley, J . L.; McLean, E. W.; Davis, R. G.; Crouch, R. Synthesis
of 6-[[(Hydroxyimino)phenyl]methyl]-1-[(1-methylethyl)sulfonyl]-
1-imidazo[4,5-b]pyridin-2-amine. An Aza Analogue of En-
viroxime. J . Heterocycl. Chem. 1990, 27, 1821-1824.
(27) HRV-14 is also a member of the major receptor subgroup.
(28) The trans stereochemistry was assigned in some analogues
definitively by NOE experiments between the olefinic hydrogen
and the C-7 and C-5 hydrogens of the benzimidazole core. In
general, the isomers were assigned by several distinct charac-
teristics. The trans isomer invariably eluted before the cis isomer
on C18 reverse-phase HPLC (ACN:water), the trans isomer has
UV absorbencies at significantly longer wavelengths than the
cis isomer, and the C-7 hydrogen of the trans is further upfield
(17) Enviradene (IND 20204). IND Protocol No. 3, pp 1457-1461,
unpublished results.
(18) Heinz, B. A.; Vance, L. M. The Antiviral Compound Enviroxime
Targets the 3A Coding Region of Rhinovirus and Poliovirus. J .
Virol. 1995, 69, 4189-4197.
(19) Heinz, B. A.; Vance, L. M. Sequence Determinants of 3A-
Mediated Resistance to Enviroxime in Rhinoviruses and En-
teroviruses. J . Virol. 1996, 70, 4854-4857.
(20) Victor, F.; Brown, T. J .; Campanale, K.; Heinz, B. A.; Shipley,
L. A.; Su, K. S.; Tang, J .; Vance, L. M.; Spitzer, W. A. Synthesis,
Antiviral Activity, and Biological Properties of Vinylacetylene
Analogues of Enviroxime. J . Med. Chem. 1997, 40, 1511-1518.
(21) Miller, S. C.; Spitzer, W. A.; Victor, F.; Sattelberg, T. R., Sr.;
Tebbe, M. J . Antiviral Compounds. U.S. Patent 5,545,653.
(22) Gibson, A. W.; Humphrey, G. R.; Kennedy, D. J .; Wright, S. H.
B. Diethyl (3-Trimethylsilyl-2-propynyl)phosphonate, a New
Reagent for the Preparation of Terminal Conjugated Enynes.
Synthesis 1991, 414-416.
1H NMR than the C-7 hydrogen of the cis isomer.
in the
(29) Tang, J .; Colacino, J . M.; Larsen, S. H.; Spitzer, W. Virucidal
Activity of Hypericin Against Enveloped and Nonenveloped DNA
and RNA Viruses. Antiviral Res. 1990, 13, 313-326.
(30) Scudiero, D. A.; Shoemaker, R. H.; Paull, K. D.; Monk, A.;
Tierney, S.; Notziger, T. H.; Currens, M. J .; Seniff, D.; Boyd, M.
R. Evaluation of a Soluble Tetrazolium/Formazan Assay for Cell
Growth and Drug Sensitivity in Culture Using Human and
Other Tumor Cell Lines. Cancer Res. 1988, 48, 4827-4833.
(31) Reed, L. J .; Muench, H. A. A Simple Method of Estimating Fifty
Percent Endpoints. J . Am. Hyg. 1938, 27, 493-497.
(23) For ease of discussion of this point and throughout the paper,
trans is being defined as the acetylene moiety being trans to
the benzimidazole core no matter what the priority rules would
technically dictate.
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