Pyrazolopyridine antiherpetics: SAR of C2′ and C7 amine substituents

Article abstract of DOI:10.1016/j.bmc.2005.01.044

A novel series of potent pyrazolo[1,5-a]pyridine inhibitors of herpes simplex virus 1 replication have been identified. Several complimentary synthetic methods were developed to allow facile access to a diverse set of analogs from common late stage interm

Full text of DOI:10.1016/j.bmc.2005.01.044

Bioorganic & Medicinal Chemistry 13 (2005) 2397–2411
Pyrazolopyridine antiherpetics: SAR of C20 and C7
amine substituents
Brian A. Johns,a,* Kristjan S. Gudmundsson,a Elizabeth M. Turner,a Scott H. Allen,a
Vicente A. Samano,a John A. Ray,a George A. Freeman,a F. Leslie Boyd, Jr.,a
Connie J. Sexton,b Dean W. Selleseth,b Katrina L. Creechb and Kelly R. Monirib
aDepartment of Medicinal Chemistry, GlaxoSmithKline Research and Development, Five Moore Drive, Research Triangle Park,
NC 27709-3398, USA
bDepartment of Virology, GlaxoSmithKline Research and Development, Five Moore Drive, Research Triangle Park,
NC 27709-3398, USA
Received 13 December 2004; revised 24 January 2005; accepted 25 January 2005
Abstract—A novel series of potent pyrazolo[1,5-a]pyridine inhibitors of herpes simplex virus 1 replication have been identified. Sev-
eral complimentary synthetic methods were developed to allow facile access to a diverse set of analogs from common late stage inter-
mediates. Detailed examination of the amine substituents at the C20 position of the pyrimidine and C7 position of the core
pyrazolopyridine is described. The antiviral data suggests that non-polar amines are preferred for optimal activity. Additionally,
the 20 position has been shown to require an NH group to retain activity levels similar to that of the gold standard acyclovir.
Ó 2005 Elsevier Ltd. All rights reserved.
1. Introduction
F
F
Herpesviruses are a large family of double-stranded
DNA viruses that infect most animal species.1 Within
the herpesvirus family, there are eight members that in-
fect humans. Of particular concern are herpes simplex
viruses 1 and 2 (HSV-1, HSV-2) due to their high preva-
lence and resulting symptoms of oral fever blisters and
genital lesions, respectively. The current gold standard
therapy based on acyclovir (3) and its prodrug valacyclo-
vir is both safe and efficacious, however there is still sig-
nificant interest in finding new therapeutic agents with a
different mode of action.2 Our group recently identified
pyrazolo[1,5-a]pyridine GW3733 (1)3 and its corre-
sponding imidazo[1,2-a]pyridine derivative GW4637
(2)4 as potent and selective inhibitors of herpes simplex
viruses HSV-1 and HSV-2 (Fig. 1).
N
N
N
3
NH
NH
N
N
N
7
N
N
2'
HN
HN
GW3733 (1)
GW4637 (2)
O
N
N
HN
H2N
N
HO
O
Acyclovir (ACV) (3)
Figure 1.
The 7-amino-3-pyrimidyl substituted pyrazolo[1,5-a]-
pyridine 1 was initially identified as a hit from a high
throughput antiviral screen.5 Early screening results sug-
gested that a 7 substituent and in particular a 7-amino
group gave good activity albeit based on a limited data
set around the core heterocyclic scaffold. Pyrazolopyr-
idine 1 was the only analog with the C20/C7 diamine
substitution pattern available for study at the conclusion
Keywords: Pyrazolo[1,5-a]pyridine; Antiherpetic; HSV.
*
Corresponding author. Tel.: +1 9194836006; fax: +1 9194836053;
e-mail: brian.a.johns@gsk.com
0968-0896/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2005.01.044

2398
B. A. Johns et al. / Bioorg. Med. Chem. 13 (2005) 2397–2411
of the screen. The lack of antiviral data in this series and
encouraging potency provided impetus to develop a
chemistry strategy to explore the overall SARof the pyr-
azolopyridine core structure. It was an early goal of our
synthetic effort to explore the SARattributes of the
combination of C20 and C7 amines in particular. The
screening hit GW3733 had originally been isolated as
an undesired by-product during late stage synthetic
manipulations targeting alternative structures for an
unrelated program.6 Because of this, an efficient synthe-
sis of 20,7-diamino substituted 3-pyrimidyl-pyrazolo-
pyridines had not been established. To this end,
several complimentary synthetic strategies were devel-
oped to efficiently derivatize the 20 and 7 position at a
late stage in the synthesis to allow for diversification
of the analogs from a handful of common advanced
intermediates.
NH
NR3R4
F
F
X
H2N
C
b
d
N
N
N
Cl
N
Cl
R
4 R = H
H
7 X = H,OH
8 X = O
a
c
6 R = CHO
F
E R = Cl
e
D R = NR1R2
N
N
R
N
N
R3R4N
Scheme 2. Reagents and conditions: (a) POCl3, DMF, H2O, 95%; (b)
ethynyl-MgBr, THF, ꢀ78 to 0 °C, 88%; (c) MnO2, CHCl3, 77%; (d)
K2CO3 or NaOEt, NMP or EtOH, D; (e) HNR1R2, D or HNR1R2,
Pd(OAc)2, rac-BINAP, Cs2CO3, PhMe, 85–100 °C.
2. Chemistry7
The previously described pyrazolopyridine intermediate
43 served as a key branching point for a number of C20
and C7 analogs. The 3- and 7-position of this unique
heterocycle lend nicely to orthogonal functionalization
due to their nucleophilic and electrophilic character,
respectively. The two synthetic routes described in
Schemes 1 and 2 allow for either an early or late manip-
ulation of the C3 and C7 positions as desired, to maxi-
mize the flexibility of the common intermediate 4.
The first route (Scheme 1) focused on constructing the
pyrimidine with the aim of introducing diversity at the
C20 position as the final step in the synthetic sequence.
This methodology takes advantage of the nucleophilic
nature of the 3 position of pyrazolopyridine intermedi-
ate 4 under Friedel–Crafts acylation conditions, thus
upon treatment with an acylating agent, methyl ketone
5 was obtained. At this point it was necessary to intro-
duce the C7 amine group prior to final elaboration of
the pyrimidine moiety. Direct nucleophilic displacement
of the 7-chloro substituent provided results that were
highly dependent on the choice of amine under thermal
conditions and did not provide the level of reproducibil-
ity that was desired. However, a Buchwald–Hartwig pal-
ladium catalyzed version of this transformation proved
to be quite general resulting in good to excellent yields
of A employing a wide variety of amines.8 Methyl ke-
tone A was treated with neat dimethylformamide di-
methyl acetal under reflux for several days to produce
the corresponding vinylogous amide B. Subsequent
exposure of B to a series of guanidines C gave the fully
elaborated C3 pyrimidine analogs D.
A complementary strategy (Scheme 2) was developed
whereby the 7-amine could be installed at the final stage
of the synthesis to allow for an efficient diversification of
the C7 substituent. This amine-last strategy required
modifications beyond simply re-ordering the steps of
the synthesis outlined in Scheme 1. This was primarily
due to the inability of the 7-chloro substituent to toler-
ate the harsh conditions of the vinylogous amide forma-
tion and its subsequent condensation with various
guanidines used to form the C3 pyrimidine. An alterna-
tive pyrimidine condensation strategy was developed
whereby a more reactive vinylogous amide surrogate
was used, which could also be formed under significantly
milder conditions to retain the integrity of the 7-chloro
group through the synthesis. The alternative strategy
made use of a more reactive alkynyl ketone functionality
in place of the vinylogous amide resulting in milder con-
densation conditions. This strategy removed the need
for the DMF–DMA condensation and the dimethyl-
amine associated with it at elevated temperatures.9
F
F
b
c
N
N
N
N
O
Cl
NR1R2
R
A
4 R = H
a
5 R = C(O)Me
NH
F
F
H2N
NR3R4
C
d
N
N
N
N
O
NR1R2
R3R4N
NR1R2
N
N
Intermediate 4 was subjected to Vilsmeier–Haack
formylation conditions to provide aldehyde 6 in excel-
lent yield. The commercially available ethynyl Grignard
reagent added smoothly to aldehyde 6 at low tempera-
ture to provide the propargyl alcohol 7. This material
could be oxidized using manganese dioxide to the alkyn-
N
D
B
Scheme 1. Reagents and conditions: (a) Ac2O, BF3ÆOEt2, PhMe,
100 °C, 77%; (b) Pd(OAc)2, ( )-BINAP, Cs2CO3, HNR1R2, PhMe,
85–100 °C; (c) DMF–DMA, D; (d) t-BuOK, THF, D.

B. A. Johns et al. / Bioorg. Med. Chem. 13 (2005) 2397–2411
2399
yl ketone 8. At this point the reactive unsaturated ke-
tone 8 was condensed with a series of guanidines C to
provide the cyclized pyrimidines E containing the C7
chloro substituent. These penultimate intermediates
could be subjected to either thermal or Buchwald–Hart-
wig amination conditions to rapidly modify the C7
amino substituent as a final step in the sequence.
20 position at various points in the synthesis. Oxidation
of the C20 S-methyl group to the corresponding sulfox-
ide was readily accomplished by treatment with 1 equiv
of m-CPBA in dichloromethane. The sulfoxides were
routinely isolated and could be stored for extended peri-
ods. Treatment of the sulfoxide 17 with a wide variety of
amines at ambient or slightly elevated temperatures re-
sulted in clean displacement of the sulfoxide to give
the C7 unsubstituted pyrazolopyridine F. Alternatively
C7 protio derivative 14 could be treated with a strong
base to selectively deprotonate the 7 position.12 This
could be further functionalized by trapping the resulting
anion with an electrophile such as CCl4 (R= Cl, 15), or
dimethyl disulfide (R= SMe, 16). The 20-methylthio
pyrimidine derivatives (14, 15, 16) could be further func-
tionalized in an analogous fashion by oxidation to their
corresponding sulfoxides (17, 18, 19) followed by amine
displacement. In the case of bis-S-methyl derivative 16
the oxidation was not regioselective but by treatment
with 2 equiv of m-CPBA the bis-sulfoxide product could
be obtained cleanly. Double displacement of the two
sulfoxides was achieved to yield a version of the target
pyrazolopyridine D where identical amines were substi-
tuted at the 20 and 7 positions. In the case of the
7-chloro derivative 15, the oxidation/displacement proto-
col left the 7-Cl group untouched due to the relatively
low temperatures required to displace the 20 sulfoxide
18 and gave the desired 7-halo derivative E, the penulti-
mate intermediate in Scheme 2 outlined above. At higher
temperatures, the 7-chloro could be displaced to yield
the diamine D in an analogous fashion to that of the
bis-sulfoxide 19. Alternatively, the 7-chloro derivative
E could be isolated and re-subjected to conditions
employing a different amine at elevated temperatures
or under palladium mediated conditions as described
above to yield the versions of D containing differing
amino groups at the 20 and 7 positions.
A third method was developed utilizing a [3 + 2] cyclo-
addition strategy10 (Scheme 3). With this method an
electrophilic a diaryl alkyne is treated with an N-amino-
pyridinium salt to form upon treatment with base in one
pot a diaryl substituted pyrazolopyridine. In prepara-
tion for the cyclization event, alkyne 12 was readily pre-
pared via a Sonogashira coupling of 4-iodopyrimidine
1011 and terminal alkyne 11. Treatment of alkyne 12
with the commercially available N-aminopyridinium io-
dide 13 in the presence of DBU provided pyrazolopyr-
idine core 14. The C20 methylthio functionalized
pyrazolopyridine 14 proved to be a useful intermediate
allowing for either introduction of the C7 or the C20
amine first followed by functionalization of the remain-
ing position based on the conditions employed. This also
allowed the 20 amine to be introduced via nucleophilic
substitution rather than as part of a preformed guani-
dine as in the previous routes. While the 20 thioether
was resistant to amine displacement using thermal con-
ditions the corresponding sulfoxide was easily displaced
and provided a facile method to selectively activate the
X
b
N
F
N
N
4-F-C6H4C≡CH
N
12
MeS
11
SMe
9 X = Cl
10 X = I
a
F
A minor permutation of the above methods outlined in
Scheme 3 involved taking advantage of the unique reac-
tivity of the C7 chloro substituent. Subjecting the
7-chloro-20-methylthio derivative 15 to palladium medi-
ated amination prior to oxidation of the sulfur resulted
in a mild and selective conversion to the 7-amino-
20methylthio derivative G with complete regioselectivity.
Oxidation and displacement of the 20 S-methyl group
proceeded as before to give the fully elaborated pyrazolo-
c
f
N
N
NH2
N+
I-
R
N
N
MeS
13
14 R = H
d or e
15 R = Cl
16 R = SMe
F
pyridine
D
(Scheme 4). This strategy effectively
F
g
F
N
N
N
R
N
N
R
b,c
N
N
N
D
N
N
S+
R3R4N
Me
R
O
N
N
F R = H
17 R = H
d
MeS
E R = Cl
18 R = Cl
g
D
R = NR3R4
19 R = S(O)Me
15 R = Cl
a
G R = NR1R2
Scheme 3. Reagents and conditions: (a) aqueous HI, 99%; (b)
PdCl2(PPh3)2, CuI, THF, 73%; (c) DBU, MeCN, 0 °C to rt, 79%; (d)
n-BuLi, CCl4, THF; (e) n-BuLi, MeSSMe, THF; (f) m-CPBA, CH2Cl2,
0 °C, 99%; (g) HNR3R4; (h) HNR1R2, D or HNR1R2, Pd(OAc)2, rac-
BINAP, Cs2CO3, PhMe, 85–100 °C.
Scheme 4. Reagents and conditions: (a) HNR1R2, Pd(OAc)2, rac-
BINAP, Cs2CO3, PhMe, 85–100 °C; (b) m-CPBA, CH2Cl2, 0 °C; (c)
HNR3R4, D.

2400
B. A. Johns et al. / Bioorg. Med. Chem. 13 (2005) 2397–2411
atively weak nucleophile ammonia or aqueous ammo-
F
F
nium hydroxide, which we thought would require
much harsher conditions. The resultant azide would
then be reduced to its corresponding amine and thereby
gain access to the parent unsubstituted derivative 29.
Interestingly, we observed only the 7-amino derivative
29 upon treating 20 with sodium azide in DMF at
100 °C overnight followed by an aqueous work-up. It
was not immediately clear how this occurred however
we propose a possible mechanism in Scheme 6. The
addition of azide is suspected to proceed as planned
but rather than an addition elimination reaction we pro-
pose an aziridine ring formation across the C6–C7 dou-
ble bond of the pyrazolopyridine ring system as depicted
by structure 23 resulting in the loss of N2. The chloro-
aziridine could then eliminate chloride to form the azi-
rine 24, which could rearrange the presence of water
to reduce the increasing ring strain while forming the
7-amino-pyrazolopyridine derivative 29 (Scheme 6). At
this time we have not examined this process in detail,
but it does appear to be reproducible and give the
7-amino derivative 29 as the sole product.
a
N
N
N
N
O
NR1R2
NR1R2
N
N
S
R
N
H R = H
B
b
G R = CH3
Scheme 5. Reagents: (a) thiourea, KOH, EtOH; (b) NaOH, H2O, MeI.
reversed the substitution order described above simply
based on the orthogonal reactivity of the 20 and 7 posi-
tion functionality present in intermediate 15.
The methylthio-pyrimidine G has also been accessed
using a variation on the chemistry described in Scheme
1 to offer an alternative route into this useful penulti-
mate intermediate. In this case, vinylogous amide B
can be treated with thiourea to produce the correspond-
ing thiol substituted pyrimidine H. Methylation of this
material with methyl iodide using Schotten–Bauman
3. Results and discussion
conditions produced the S-methyl pyrimidine
(Scheme 5).
G
The initial screening hit GW3733 (1) established an ini-
tial lead with similar potency to the ꢀgold standardꢁ acy-
clovir (Table 1, entries 1 and 2) in Vero cell culture. Also
noteworthy is that the pyrazolopyridines described here-
in are not DNA synthesis inhibitors and thus have a dif-
ferent mechanism of action from the currently marketed
nucleoside analogs. We were very excited about our
prospects and decided to look at several close analogs
that might enhance the activity or increase the drug-like
properties of the molecule.13 One of the primary draw-
backs with GW3733 (1) is its inherent lipophilicity and
limited solubility in a biologically relevant medium. As
During our 7-amino SARinvestigations we desired to
access the parent unsubstituted 7-NH2 compound 29.
We were of course interested in the activity of this deriv-
ative but also thought it might offer an opportunity for
additional SARmodifications via reductive amination
methodology. Our first attempt to access the 7-NH2
analog was designed to take advantage of the electro-
philic nature of the 7-chloro derivative 20 via treatment
with sodium azide to produce the 7-azido derivative 21.
The azide strategy was chosen primarily to avoid the rel-
F
F
F
[R]
NaN3
N
N
N
N
N
N3
N
NH2
DMF
Cl
N
N
N
N
N
100oC
N
HN
HN
HN
21
29
20
(not isolated)
F
+H2O
F
-N3
F
-Cl-
-N2
N
N
N
N
N
N
Cl
Cl
N
N
N
N
H2O
N
N
N
N
N
N
N
HN
HN
HN
22
23
24
Scheme 6.

B. A. Johns et al. / Bioorg. Med. Chem. 13 (2005) 2397–2411
2401
Table 1. HSV-1 antiviral activity and cytotoxicity of C20/C7 analogs containing 1° and 2° amine substituents
F
H
N
N
N
N
R1
N
R3
N
H
Entry
Compd
R3–
R1–
—
EC50 (lM)
CC50 (lM)
1
ACV
1
—
0.39
0.26
0.48
0.33
0.41
0.46
0.46
1.07
0.83
1.46
0.6
>100
>160
>40
>160
>40
>40
>40
126
18
2
–c-C5H9
–n-C4H9
–n-C4H9
–c-C5H9
–n-C4H9
–H
–c-C5H9
–Allyl
3
25
26
27
28
29
30
31
32
33
34
35
36
4
–n-C4H9
–n-C4H9
–c-C3H5
–c-C5H9
–n-C4H9
H
5
6
7
8
–c-C3H5
–c-C5H9
–n-C4H9
–c-C5H9
–c-C5H9
–(CH2)3OH
–n-C4H9
9
10
11
12
13
14
–CH3
>40
>40
>40
19
–Pyrrolidine
–Morpholine
–n-C4H9
–(CH2)2OCH3
1.23
4.44
0.25
33
(CH2)2-
N
15
16
37
38
–n-C4H9
4.19
0.41
>5
12
O
(CH2)2-
N
–n-C4H9
O
(CH2)3-
N
17
18
39
40
–c-C5H9
6.07
4.33
15
O
N
N
–n-C4H9
ND
(CH2)3-
2-Py–CH2–
–c-C5H9
–Ph
19
20
21
22
23
24
25
41
42
43
44
45
46
47
–n-C4H9
3.67
1.74
0.46
1.22
0.57
>40
ND
>40
>40
>40
>40
>40
>40
4-MeOC6H4–
–c-C5H9
–c-C5H9
4-MeOC6H4–
4-FC6H4–
4-FC6H4–
–c-C5H9
–c-C5H9
4-FC6H4–
4-FC6H4–
3.25
Vero cells, SC-16 strain. EC50 is the concentration at which 50% efficacy in the antiviral assay is observed. CC50 is the concentration at which 50%
cytotoxicity is observed.
can be seen in Table 1, several analogs with similar lipo-
philicity to that of the cyclopentylamine substituent
were constructed and there was minimal dependence
of activity on the steric bulk of these greasy amines (en-
tries 2–10). At most an approximate five-fold loss in
activity was observed by altering the hydrocarbon char-
acter of the cyclopentyl group. In most cases this re-
sulted from a decrease in the hydrocarbon character
rather than an added functionality. However, when
more polar functionality was introduced, the activity
did decrease in general with basic amines tethered to
the C20 position being the weakest inhibitors (entries
15 and 17–19). Neutral or electron deficient aryl groups
at the 20 position were tolerated nearly as well as ali-
phatic amines (entries 21 and 23) while electron rich sub-
stituents were not as active (entry 22). Similarly anilino
groups at the 7 position resulted in an order of magni-
tude decrease in potency compared to GW3733 (entries
24 and 25).
Additional structural variations were examined consist-
ing of analogs containing tertiary nitrogens at the 20
and/or 7 positions. A clear trend noted from these data
was the requirement that the 20 position contain an NH
moiety to retain interesting levels of activity (Table 2,
entries 1, 4–5, 9–11). The 7 position was less sensitive
to changing to the fully substituted nitrogen with several
analogs delivering compounds with sub-micromolar
activity (entries 3, 7–8). The piperidine containing ana-
log 50 had activity similar to the NH containing deriva-
tive GW3733 (1).
Several analogs were also assayed against HSV-2 in or-
der to assure ourselves that the activity we observed for
the inhibition of HSV-1 in the above Tables 1 and 2 was
not diverging from the ultimate target virus. As can be
seen in Table 3, the activity levels and rank ordering
of compounds is very similar for both HSV-1 and
HSV-2. Again, the C20 NH substituted analogs were

2402
B. A. Johns et al. / Bioorg. Med. Chem. 13 (2005) 2397–2411
Table 2. HSV-1 antiviral activity and cytotoxicity of C20/C7 analogs containing tertiary amine substituents
F
R1
N
N
N
N
R2
N
R4
N
R3
Entry
Compd
R3R4N–
R1R2N–
EC50 (lM)
CC50 (lM)
1
2
3
4
5
6
48
49
50
51
52
53
Pyrrolidine
–NH-c-C5H9
–NH-c-C5H9
–NMe2
–NH-n-C4H9
Pyrrolidine
Piperidine
Pyrrolidine
–NH-c-C5H9
–NMe2
4.9
>160
>40
>40
ND
>40
>40
1.21
0.34
5.47
1.45
1.30
–NMe2
–NH-n-C4H9
N
7
54
–NH-n-C4H9
0.77
5.5
N
CH3
Morpholine
8
9
55
56
–NH-n-C4H9
Morpholine
0.95
14.7
>40
ND
–NH-n-C4H9
N
10
11
57
58
–NH-n-C4H9
6.74
11.1
ND
N
(CH2)2OH
N
–NH-n-C4H9
58
N
(CH2)2OCH3
Vero cells, SC-16 strain. EC50 is the concentration at which 50% efficacy in the antiviral assay is observed. CC50 is the concentration at which 50%
cytotoxicity is observed.
Table 3. HSV-2 antiviral activity
Entry
Compd
R3R4N–
R1R2N–
EC50 (M)
1
ACV
1
—
—
–NH-c-C5H9
–NH–allyl
0.16
0.16
0.74
<0.16
0.27
0.32
4.1
2
–NH-c-C5H9
–NH-n-C4H9
–NH-n-C4H9
–NH-c-C5H9
–NH-n-C4H9
–NH2
3
25
26
27
28
29
30
31
32
33
36
4
–NH-n-C4H9
–NH-n-C4H9
–NH-c-C3H5
–NH-c-C5H9
–NH-n-C4H9
–NH2
5
6
7
8
–NH-c-C3H5
–NH-c-C5H9
–NH-n-C4H9
–NH-c-C5H9
–NH-n-C4H9
0.99
0.79
2.78
0.54
0.60
9
10
11
12
–NH–CH3
–Pyrrolidine
–NH(CH2)2OCH3
(CH2)2-NH-
N
13
37
–n-C4H9
5.0
O
14
15
16
42
52
53
–NH-c-C5H9
–NMe2
–NH-n-C4H9
4-MeOC6H4NH–
–NH-c-C5H9
–NMe2
5.5
4.0
2.36
EC50 is the concentration at which 50% efficacy in the antiviral assay is observed.
superior to the unsubstituted and tertiary substituted
analogs. Also worth noting was the sub-micromolar
activity observed for several of these analogs, which is
comparable or better than that of the gold standard acy-
clovir. The above compounds have not been widely
screened against other herpesviruses. Several representa-
tive examples have been inactive against other viruses
such as hepatitis B and HIV-1.

B. A. Johns et al. / Bioorg. Med. Chem. 13 (2005) 2397–2411
2403
4. Conclusions
5.2.2. 1-[7-(Cyclopentylamino)-2-(4-fluorophenyl)pyraz-
olo[1,5-a]pyridin-3-yl]ethanone (59). To a solution of ke-
tone 5 (2.7 g, 9.5 mmol) in toluene (50 mL) was added
successively racemic-BINAP (378 mg, 0.6 mmol),
Cs2CO3 (4.7 g, 14.3 mmol), cyclopentylamine (4.7 mL,
47.5 mmol), and Pd(OAc)2 (86 mg, 0.4 mmol). The
resultant mixture was heated to 95 °C for 2.5 h at which
time the reaction was judged complete by thin layer
chromatography. The solution was cooled to rt and
ether was added. The organic layer was washed with
water and brine. The aqueous layer was extracted with
ether and the combined organics dried over MgSO4. Fil-
tration and concentration followed by flash chromato-
graphy (4:1 hexanes–EtOAc) provided 7-amino
In summary, a series of novel antiviral compounds have
been identified, which show similar activity against her-
pes simplex virus to that of the gold standard acyclovir.
This new series of inhibitors are not DNA synthesis
inhibitors like the currently marketed nucleoside ana-
logs. The 20,7-diamino substitution pattern about the
3-pyrimidylpyrazolo[1,5-a]pyridine core scaffold has
been shown to affect the antiviral activity based on
numerous examples of combinations of amine groups.
The most potent analogs have been shown to require a
20 NH moiety while the 7 position is slightly more toler-
ant of a number of amino substituents including pri-
mary, secondary, and tertiary nitrogens. This new class
of inhibitor shows potent antiviral activity separated
from cytotoxicity that suggest its potential use as a thera-
peutic intervention in HSV-infected patients.
1
derivative 59 (3.1 g, 95%) as a yellow solid. H NMR
(CDCl3): d 7.62 (d, 1H), 7.55 (dd, 2H), 7.40 (t, 1H),
7.15 (t, 2H), 6.10 (d, 1H), 5.99 (d, 1H), 3.94 (m, 1H),
2.09 (s, 3H), 2.12–2.04 (m, 2H), 1.78–1.58 (m, 6H); 13C
NMR(CDCl 3): d 192.63, 163.28 (d, JCF = 247.3 Hz),
154.89, 142.65, 142.38, 131.66 (d, JCF = 8.3 Hz) 131.09,
130.03 (d, JCF = 3.8 Hz), 115.33 (d, JCF = 22.0 Hz),
111.32, 105.41, 91.97, 53.81, 33.21, 30.10, 23.96; 19F
5. Experimental
5.1. General
NMR(CDCl ): d ꢀ112.70; MS m/z 338 (M+1).
3
1H and 13C NMRspectra were obtained on Varian Unity
Plus NMRspectrometers at 300 or 400 MHz, and 75 or
100 MHz, respectively. 19F NMRspectra were recorded
at 282 MHz. Mass spectra were obtained on Micromass
Platform or ZMD mass spectrometers from Micromass
Ltd, Altrincham, UK, using either atmospheric chemical
ionization (APCI) or electrospray ionization (ESI). Sol-
vents were purchased as anhydrous grade and used with-
out further purification. Unless otherwise stated, column
chromatography for the purification of some compounds,
used Merck silica gel 60 (230–400 mesh), and the stated
solvent system under pressure. All compounds were char-
acterized as their free-base form unless otherwise stated.
On occasion the corresponding hydrochloride salts were
formed to generate solids where noted. Combustion anal-
yses were performed by Atlantic Microlabs, Inc. Nor-
cross, Ga. In liu of elemental analysis, compound purity
was assessed by high field 1H NMRand HPLC. Biologi-
cal results were obtained with compounds of >98% purity
as determined by the above methods.
5.2.3. (2E)-1-[7-(Cyclopentylamino)-2-(4-fluorophenyl)-
pyrazolo[1,5-a]pyridin-3-yl]-3-(dimethylamino)-2-propen-
1-one (60). A solution of 59 (3.1 g, 9.2 mmol) in DMF–
dimethyl acetal (25 mL) was heated at reflux for 6 days.
The mixture was cooled to room temperature, EtOAc
was added followed by water. The organic layer was
washed with brine. The aqueous layer was extracted
with EtOAc and the combined organics were dried over
MgSO4. Filtration and concentration followed by flash
chromatography (EtOAc) provided enamine 60 (3.6 g,
1
99%) as a tinted oil. H NMR(CDCl 3): d 7.73–7.61
(m, 4H), 7.32 (t, 1H), 7.14 (t, 2H), 6.03 (d, 1H), 5.96
(d, 1H), 5.05 (d, 1H), 3.99 (m, 1H), 5.15–2.42 (br, 6H),
2.19–2.08 (m, 2H), 1.86–1.62 (m, 6H); 19F NMR
(CDCl3): d ꢀ113.75; MS m/z 393 (M+1).
5.2.4. N-Cyclopentylguanidine hydrochloride (61).14 To a
solution of 2-methyl-2-thiopseudourea sulfate (13.9 g,
50.0 mmol) in water (40 mL) was added cyclopentyl-
amine (14.8 mL, 150 mmol). The resultant mixture was
heated to 55 °C for 20 min and then to reflux for
2.5 h. The mixture was cooled to room temperature
and concentrated in vacuo and azeotroped with MeOH.
Water was added (ꢁ100 mL) and Amberlite IRA 400
(Clꢀ) resin was added. The mixture was stirred for 1 h
and then the resin was removed by filtration. The solu-
tion was concentrated in vacuo and azeotroped with
MeOH. The residue was recrystallized from MeOH–ace-
tone to yield N-cyclopentylguanidine hydrochloride (61)
(7.0 g, 86%) as a fine white solid. 1H NMR(D 2O): d 3.62
(m, 1H), 1.75 (m, 2H), 1.52–1.32 (m, 6H); 13C NMR
(D2O): d 156.23, 53.11, 32.15, 23.13; MS m/z 128 (M+1).
5.2. Synthesis of GW3733 (1)
5.2.1. 1-[7-Chloro-2-(4-fluorophenyl)pyrazolo[1,5-a]pyr-
idin-3-yl]ethanone (5). To a solution of 43 (10.0 g,
40.5 mmol) in toluene (225 mL) at rt was added Ac2O
(4.6 mL, 48.6 mmol). BF3ÆOEt2 (5.6 mL, 44.6 mmol)
was then added dropwise and the resultant solution
was heated to reflux for 3.5 h. The reaction mixture
was cooled to rt and quenched by the dropwise addition
of aq NaHCO3. Ether was added and the organic layer
was washed with brine. The aqueous layer was extracted
with ether and the combined organics were dried over
MgSO4, filtered, and concentrated. The residue was
purified by recrystallization from EtOAc–hexanes
to give methyl ketone 5 (9.0 g, 77%) as reddish needles.
5.2.5. N-Cyclopentyl-3-[2-(cyclopentylamino)-4-pyrimidi-
nyl]-2-(4-fluorophenyl)pyrazolo[1,5-a]pyridin-7-amine (1).
To a solution of 60 (3.5 g, 8.9 mmol) in THF (36 mL,
0.25 M) was added N-cyclopentylguanidine hydrochlo-
ride (61) (1.9 g, 11.6 mmol), followed by solid t-BuOK
(2.6 g, 23.2 mmol) in two portions. The resultant
1H NMR(CDCl ): d 8.41 (d, 1H), 7.59 (m, 2H), 7.45
3
(dd, 1H), 7.26–7.13 (m, 3H), 2.15 (s, 3H); 19F NMR
(CDCl3): d ꢀ112.06; MS m/z 289 (M+1).

2404
B. A. Johns et al. / Bioorg. Med. Chem. 13 (2005) 2397–2411
solution was heated to reflux for 23 h. Upon cooling to
rt, ether was added followed by water. The organics
were washed with brine, and the aqueous layer was ex-
tracted with ether. The combined organics were dried
over MgSO4, filtered, and concentrated in vacuo. The
residue was purified by flash chromatography on silica
was filtered through a pad of Celite and the filtrate was
concentrated in vacuo to give ketone 8 (4.0 g, 77%) as a
yellow solid. 1H NMR(CDCl 3): d 8.45 (d, 1H), 7.67 (m,
2H), 7.50 (t, 1H), 7.19 (d, 1H), 7.12 (t, 2H), 2.93 (s, 1H);
MS m/z 299 (M+1).
1
to give 1 (3.7 g, 91%) as an off-white solid. H NMR
5.3.4.
N-Butyl-4-[7-chloro-2-(4-fluorophenyl)pyrazolo-
(CDCl3): d 7.97 (d, 1H), 7.68 (d, 1H), 7.59 (dd, 2H),
7.27 (t, 1H), 7.10 (t, 2H), 6.24 (d, 1H), 5.99 (d, 1H),
5.96 (d, 1H), 5.01 (d, 1H), 4.28 (m, 1H), 3.97 (m, 1H),
2.12–1.99 (m, 4H), 1.79–1.44 (m, 12H); 13C NMR
(CDCl3): d 163.12 (d, JCF = 246.6 Hz), 162.09, 161.53,
156.67, 152.15, 142.66, 141.09, 131.46 (d, JCF = 8.0 Hz),
129.92 (d, JCF = 3.1 Hz), 128.39, 115.45 (d,
JCF = 21.3 Hz), 108.68, 107.13, 105.15, 90.13, 53.84,
[1,5-a]pyridin-3-yl]-2-pyrimidinamine (61). To a solution
of ketone 8 (0.5 g, 1.7 mmol) in EtOH (10 mL) was
added N-butylguanidine sulfate15 (0.5 g, 2.2 mmol) and
NaOEt (0.8 mL, 21 wt % in EtOH, 2.2 mmol) at rt.
After 2 h, water was added and the resultant mixture
was extracted with EtOAc. The combined organics were
dried over Na2SO4, filtered, and concentrated. The resi-
due was purified by flash chromatography on silica to
52.87, 33.50, 33.30, 24.05, 23.70; 19F NMR(CDCl ): d
give pyrimidine 61 (0.4 g, 59%) as a fluffy pale yellow
3
1
ꢀ113.49; MS m/z 457 (M+1). Anal. Calcd for
C27H29FN6: C, 71.03; H, 6.40; N, 18.41. Found: C,
71.20; H, 6.37; N, 18.52.
solid. H NMR(CDCl ): d 8.40 (d, 1H), 8.07 (d, 1H),
3
7.65 (m, 2H), 7.29 (m, 1H), 7.15 (t, 2H), 7.06 (d, 1H),
6.32 (d, 1H), 5.16 (br s, 1H), 3.49 (q, 2H), 1.71–1.41
(m, 4H), 0.99 (t, 3H); 19F NMR(CDCl ): d ꢀ112.77;
3
5.3. N-Allyl-3-[2-(butylamino)-4-pyrimidinyl]-2-(4-fluoro-
phenyl)-pyrazolo[1,5-a]pyridin-7-amine (25)
MS m/z 396 (M+1).
5.3.5. N-Allyl-3-[2-(butylamino)-4-pyrimidinyl]-2-(4-fluo-
rophenyl)-pyrazolo[1,5-a]pyridin-7-amine (25). A solution
of 61 (150 mg, 0.4 mmol) in allylamine (5 mL, 67 mmol)
was heated at 85 °C in a sealed tube for 88 h. After cool-
ing and concentrating the reaction mixture, flash chro-
5.3.1.
7-Chloro-2-(4-fluorophenyl)pyrazolo[1,5-a]pyr-
idine-3-carbaldehyde (6). DMF (100 mL) was cooled to
0 °C and treated with phosphorous oxychloride
(5.7 mL, 60.8 mmol). After the addition was complete,
the mixture was warmed to room temperature and stir-
red for 1 h. To this was added pyrazolopyridine 4
(10.0 g, 40.5 mmol) and the resultant solution was stir-
red overnight. Water was added, followed by CH2Cl2.
The aqueous layer was extracted with CH2Cl2. The
combined organics were washed with brine, dried over
MgSO4, filtered, and concentrated. The residue was
recrystallized from ether and hexanes to give aldehyde
6 (10.6 g, 95%) as a fluffy white solid. 1H NMR(CDCl 3):
d 10.07 (s, 1H), 8.37 (d, 1H), 7.78 (m, 2H), 7.48 (t, 1H),
matography (4:1 hexanes–EtOAc) afforded 25 (140 mg,
1
88%) as a pale yellow foam. H NMR(CDCl ): d 7.89
3
(br s, 1H), 7.78 (d, 1H), 7.62 (m, 2H), 7.36 (t, 1H),
7.16 (t, 2H), 6.31–6.26 (m, 2H), 6.09–5.92 (m, 2H),
5.39–5.24 (m, 2H), 4.06 (t, 2H), 3.50 (q, 2H), 1.72–1.41
(m, 4H), 0.98 (t, 3H); 19F NMR(CDCl ): d ꢀ113.16;
3
MS m/z 417 (M+1). Anal. Calcd for C24H25FN6: C,
69.21; H, 6.05; N, 20.18. Found: C, 69.27; H, 6.07; N,
20.03.
7.20 (m, 3H); 19F NMR(CDCl ): d ꢀ111.25; MS m/z
5.4. N-Butyl-3-[2-(butylamino)-4-pyrimidinyl]-2-(4-fluoro-
phenyl)pyrazolo[1,5-a]pyridin-7-amine (26)
3
275 (M+1). Anal. Calcd for C14H8ClFN2O: C, 61.22;
H, 2.94; N, 10.20. Found: C, 61.34; H, 2.90; N, 10.15;
mp 212–213 °C (decomp.).
Compound 26 was made in a similar manner as de-
scribed for compound 1 to give a yellow solid. Rf 0.67
(1:1 hexanes–EtOAc); 1H NMR(CDCl 3): d 7.98 (d,
1H), 7.68 (d, 1H), 7.59 (m, 2H), 7.27 (t, 1H), 7.10 (t,
2H), 6.25 (d, 1H), 6.00–5.96 (m, 2H), 5.05 (m, 1H),
3.41 (m, 2H), 3.33 (m, 2H), 1.71 (m, 2H), 1.60 (m,
2H), 1.50–1.36 (m, 4H), 0.97–0.91 (m, 6H); MS m/z
433 (M+1).
5.3.2. 1-[7-Chloro-2-(4-fluorophenyl)pyrazolo[1,5-a]pyr-
idin-3-yl]-2-propyn-1-ol (7). To a cold (0 °C) solution of
aldehyde 6 (5.5 g, 20.0 mmol) in THF (130 mL) was
added ethynylmagnesium bromide (100 mL, 0.5 M in
THF, 50.0 mmol) dropwise. The resultant mixture was
stirred at that temperature until the reaction judged
complete by TLC (1 h). The resultant solution was
quenched with water and extracted with ether. The
organic layer was washed with water and brine and
the combined organics were dried over Na2SO4. Filtra-
tion and concentration followed by recrystallization
5.5. N-Butyl-3-[2-(cyclopentylamino)-4-pyrimidinyl]-2-(4-
fluorophenyl)pyrazolo[1,5-a]pyridin-7-amine (27)
Compound 27 was made in a similar manner as de-
scribed for compound 1 to give a yellow solid. 1H
from CH2Cl2 provided alcohol 7 (5.3 g, 88%) as a pale
yellow crystalline solid. H NMR(CDCl ): d 8.04 (d,
1
NMR(CDCl ): d 8.01 (d, 1H), 7.73 (d, 1H), 7.62 (m,
3
3
1H), 7.79 (m, 2H), 7.20 (m, 3H), 7.01 (d, 1H), 5.77 (m,
1H), 2.69 (d, 1H), 2.32 (d, 1H); MS m/z 301 (M+1).
2H), 7.29 (t, 1H), 7.12 (t, 2H), 6.28 (d, 1H), 6.05
(m, 1H), 5.98 (d, 1H), 5.27 (br, 1H), 4.32 (m, 1H),
3.34 (m, 2H), 2.10–2.00 (m, 2H), 1.77–1.41 (m, 10H),
5.3.3. 1-[7-Chloro-2-(4-fluorophenyl)pyrazolo[1,5-a]pyr-
idin-3-yl]-2-propyn-1-one (8). To a solution of alcohol 7
(5.3 g, 17.6 mmol) in CH2Cl2 (600 mL) was added
MnO2 (61.3 g, 705 mmol). The reaction mixture was
stirred at room temperature for 20 min. The suspension
0.97 (t, 3H); 13C NMR(CDCl 3):
d 163.03 (d,
JCF = 244.5 Hz), 162.14, 161.41, 156.74, 152.10,
142.99, 141.02, 131.36 (d, JCF = 8.0 Hz) 129.92 (d,
JCF = 3.0 Hz), 128.31, 115.36 (d, JCF = 21.0 Hz),
108.58, 107.9, 105.17, 89.21, 52.79, 42.27, 33.40, 31.06,

B. A. Johns et al. / Bioorg. Med. Chem. 13 (2005) 2397–2411
2405
23.65, 20.13, 13.70; 19F NMR(CDCl ): d ꢀ113.42; MS
0.1 mmol) in DMF (4 mL) was added NaN3 (85 mg,
1.3 mmol). The resultant mixture was heated to 100 °C
for 18 h. The reaction mixture was cooled to room tem-
perature and ether was added. The organic layer was
washed with brine. The aqueous layer was extracted
with ether and the combined organics dried over
MgSO4. Filtration and concentration followed by flash
chromatography (2:1–1:1 hexanes–ethyl acetate) pro-
3
m/z 445 (M+1).
5.6. 3-[2-(Butylamino)-4-pyrimidinyl]-N-cyclopropyl-2-(4-
fluorophenyl)pyrazolo[1,5-a]pyridin-7-amine (28)
Compound 28 was made in a similar manner as de-
scribed for compound 25, to give a fluffy pale yellow
1
1
solid. H NMR(CDCl ): d 8.40 (d, 1H), 8.07 (d, 1H),
vided compound 31 (30 mg, 60%) as an oil. H NMR
3
7.65 (m, 2H), 7.29 (m, 1H), 7.15 (t, 2H), 7.06 (d, 1H),
6.32 (d, 1H), 5.16 (br s, 1H), 3.49 (q, 2H), 1.71–1.41
(CDCl3): d 7.97 (d, 1H), 7.77 (d, 1H), 7.60 (m, 2H),
7.22 (m, 1H), 7.10 (t, 2H), 6.26 (d, 1H), 6.14 (d, 1H),
5.26 (s, 2H), 5.09 (d, 1H), 4.29 (m, 1H), 2.06–1.99 (m,
2H), 1.75–1.45 (m, 6H); MS m/z 389 (M+1). This mate-
rial was taken up in ether and treated with hydrochloric
acid in ether to yield a yellow precipitate, which was iso-
lated by filtration as a hydrochloride salt.
(m, 4H), 0.99 (t, 3H); 19F NMR(CDCl ): d ꢀ112.77;
3
MS m/z 396 (M+1).
5.7. 3-(2-Amino-4-pyrimidinyl)-N-cyclopentyl-2-(4-fluoro-
phenyl)pyrazolo-[1,5-a]pyridin-7-amine (29)
Compound 29 was made in a similar manner as de-
scribed for compound 1 to give a white solid. 1H
5.10. 3-[2-(Butylamino)-4-pyrimidinyl]-2-(4-fluorophen-
yl)-N-methylpyrazolo[1,5-a]pyridin-7-amine (32)
NMR(CDCl ): d 7.98 (d, 1H), 7.66 (d, 1H), 7.59 (m,
3
2H), 7.28 (t, 1H), 7.10 (t, 2H), 6.31 (d, 1H), 6.00 (d,
1H), 5.96 (d, 1H), 4.97 (br s, 2H), 3.96 (m, 1H), 2.14–
In a similar manner as described in for compound 25, 7-
chloro derivative 61 was heated with methylamine (40%
aqueous soln) in a sealed tube to give 7-N-methyl deriv-
ative 32 as a pale yellow solid. 1H NMR(CDCl 3): d 8.01
(d, 1H), 7.75 (d, 1H), 7.62 (m, 2H), 7.34 (t, 1H), 7.13 (t,
2H), 6.30 (d, 1H), 6.03–5.99 (m, 2H), 5.11 (br, 1H), 3.46
(q, 2H), 3.10 (d, 3H), 1.69–1.42 (m, 4H), 0.97 (t, 3H); 19F
2.06 (m, 2H), 1.83–1.63 (m, 6H); 13C NMR(CDCl ): d
3
163.39 (d, JCF = 246.6 Hz), 163.20, 162.25, 157.27,
152.33, 142.88, 141.32, 131.64 (d, JCF = 8.4 Hz), 129.91
(d, JCF = 3.8 Hz), 128.84, 115.75 (d, JCF = 22.0 Hz),
110.31, 106.85, 105.31, 90.53, 54.06, 33.53, 24.27; 19F
NMR(CDCl ): d ꢀ113.20; MS m/z 389 (M+1). Anal.
NMR(CDCl ): d ꢀ113.39; MS m/z 391 (M+1).
3
3
Calcd for C22H21FN6: C, 68.03; H, 5.45; N, 21.63.
Found: C, 67.96; H, 5.50; N, 21.82.
5.11. 3-[2-(Cyclopentylamino)pyrimidin-4-yl]-2-(4-fluoro-
phenyl)-N-pyrrolidin-1-ylpyrazolo[1,5-a]pyridin-7-amine
(33)
5.8. N-Butyl-3-[2-(cyclopropylamino)-4-pyrimidinyl]-2-(4-
fluorophenyl)-pyrazolo[1,5-a]pyridin-7-amine (30)
To
a
solution 4-[7-chloro-2-(4-fluorophenyl)pyraz-
Compound 30 was made in a similar manner as de-
scribed for compound 1 to give a white solid. Rf 0.55
(1:1 hexanes–EtOAc); 1H NMR(CDCl 3): d 8.09 (d,
1H), 7.92 (d, 1H), 7.67 (dd, 2H), 7.34 (t, 1H), 7.18 (t,
2H), 6.37 (d, 1H), 6.09–6.04 (m, 2H), 5.53 (br, 1H),
3.40 (m, 2H), 2.88 (m, 1H), 1.79 (m, 2H), 1.52 (m,
2H), 1.02 (t, 3H), 0.88 (m, 2H), 0.64 (m, 2H); MS m/z
417 (M+1).
olo[1,5-a]pyridin-3-yl]-N-cyclopentyl-2-pyrimidinamine
(62) (120 mg, 0.3 mmol) in anhydrous toluene (5 mL)
was added rac-BINAP (18 mg, 0.03 mmol), Cs2CO3
(380 mg, 1.2 mmol), N-aminopyrrolidine hydrochloride
(180 mg, 1.5 mmol), and Pd(OAc)2 (4.3 mg, 0.02 mmol)
and the mixture was heated to 100 °C under nitrogen
atmosphere for 3 h. Excess BINAP (18 mg, 0.03 mmol)
and Pd(OAc)2 (4.3 mg, 0.03 mmol) and the mixture
was heated to 100 °C for 4 h. The mixture was parti-
tioned between EtOAc and water and the organic layer
was dried (Na2SO4), concentrated, and purified by chro-
matography (silica gel, hexanes–EtOAc, 4:1) to provide
5.9. 3-[2-(Cyclopentylamino)-4-pyrimidinyl]-2-(4-fluoro-
phenyl)pyrazolo[1,5-a]pyridin-7-amine (31)
1
5.9.1. 4-[7-Chloro-2-(4-fluorophenyl)pyrazolo[1,5-a]pyr-
idin-3-yl]-N-cyclopentyl-2-pyrimidinamine (62). In a sim-
ilar manner as described for compound 61 ketone 8
(210 mg, 0.7 mmol), cyclopentylguanidine hydrochlo-
ride (61) (291 mg, 2.1 mmol), and K2CO3 (345 mg,
2.1 mmol) were heated at 120 °C for 1.5 h in NMP
the title compound as a yellow solid foam (25 mg). H
NMR(CDCl 3): d 1.6–1.5 (m, 2H), 1.7–1.6 (m, 2H),
1.8–1.7 (m, 2H), 1.9 (br s, 4H), 2.1–2.0 (m, 2H), 3.0
(br s, 4H), 4.33 (sextuplet, 1H), 5.4 (br s, 1H), 6.28 (d,
1H), 6.56 (s, 1H), 6.64 (d, 1H), 7.14 (t, 2H), 7.38 (t,
1H), 7.62 (dd, 2H), 7.79 (d, 1H), 7.96 (br s, 1H); MS
m/z 458 (M+1).
(8 mL) to form 7-chloro derivative 62 (125 mg, 44%)
1
as a white foam. H NMR(CDCl ): d 8.42 (d, 1H),
3
8.09 (d, 1H), 7.67 (dd, 2H), 7.30 (m, 1H), 7.17 (t, 2H),
7.06 (d, 1H), 6.33 (d, 1H), 5.30 (d, 1H), 4.35 (m, 1H),
2.18–2.05 (m, 2H), 1.84–1.52 (m, 6H); 19F NMR
(CDCl3): d ꢀ112.78; MS m/z 408 (M+1).
5.12. 3-[2-(Cyclopentylamino)pyrimidin-4-yl]-2-(4-fluoro-
phenyl)-N-morpholin-4-ylpyrazolo[1,5-a]pyridin-7-amine
(34)
The title compound was prepared in a similar manner as
compound 33 to give a yellow foam. 1H NMR(CDCl 3):
d 1.6–1.5 (m, 2H), 1.7–1.6 (m, 2H), 1.8–1.7 (m, 2H), 2.1–
2.0 (m, 2H), 2.99 (s, 4H), 3.85 (br s, 4H), 4.35 (m, 1H),
5.25 (br s, 1H), 6.28 (d, 1H), 6.66 (d, 1H), 6.72 (s, 1H),
5.9.2. 3-[2-(Cyclopentylamino)-4-pyrimidinyl]-2-(4-fluoro-
phenyl)pyrazolo[1,5-a]pyridin-7-amine (31). To a solution
of 4-[7-chloro-2-(4-fluorophenyl)pyrazolo[1,5-a]pyridin-
3-yl]-N-cyclopentyl-2-pyrimidinamine
(62)
(53 mg,

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B. A. Johns et al. / Bioorg. Med. Chem. 13 (2005) 2397–2411
7.14 (t, 2H), 7.37 (t, 1H), 7.63 (dd, 2H), 7.83 (d, 1H),
7.98 (br d, 1H); MS m/z 474 (M+1).
1H), 7.16 (t, 2H), 6.34 (d, 1H), 6.04 (m, 2H), 3.67–3.60
(m, 4H), 3.39 (q, 2H), 1.79–1.45 (m, 6H), 1.00 (t, 3H);
19F NMR(CDCl ): d ꢀ113.10; MS m/z 435 (M+1).
3
5.13. 3-({4-[7-(Butylamino)-2-(4-fluorophenyl)pyrazolo-
[1,5-a]pyridin-3-yl]-2-pyrimidinyl}amino)-1-propanol (35)
5.14. 3-[2-(Butylamino)-4-pyrimidinyl]-2-(4-fluorophen-
yl)-N-(2-methoxyethyl)pyrazolo[1,5-a]pyridin-7-amine
(36)
5.13.1. 4-[7-(Butylamino)-2-(4-fluorophenyl)pyrazolo[1,5-
a]pyridin-3-yl]-2-pyrimidinethiolate (64). A solution of
(2E)-1-[7-(butylamino)-2-(4-fluorophenyl)pyrazolo[1,5-
a]pyridin-3-yl]-3-(dimethylamino)-2-propen-1-one (63)
(5.92 g, 15.6 mmol), thiourea (2.40 g, 31.1 mmol), and
KOH (15.6 mL, 1.0 N in ethanol) in 200 mL of EtOH
was heated to reflux until starting material was con-
sumed. The reaction was cooled to room temperature
and the resulting precipitate was isolated by filtration.
After washing with EtOAc, compound 64 (1.68 g,
44%) was isolated as a tan solid as the potassium salt.
1H NMR(DMSO- d6): d 7.68–7.61 (m, 4H), 7.29–7.23
(m, 3H), 6.88 (m, 1H), 6.08 (d, 1H), 6.00 (d, 1H),
3.32–3.22 (m, 2H), 1.59 (m, 2H), 1.34 (m, 2H), 0.87 (t,
3H); MS m/z 392 (M+1).
Compound 36 was made in a similar manner as de-
scribed for compound 25 to give a yellow foam. 1H
NMR(CDCl ): d 8.02 (d, 1H), 7.76 (d, 1H), 7.65 (m,
3
2H), 7.32 (t, 1H), 7.15 (t, 2H), 6.29 (m, 2H), 6.05 (d,
1H), 5.10 (br, 1H), 3.72 (t, 2H), 3.57 (q, 2H), 3.47 (q,
2H), 3.43 (s, 3H), 1.69–1.44 (m, 4H), 0.98 (t, 3H); MS
m/z 435 (M+1).
5.15. N-Butyl-2-(4-fluorophenyl)-3-(2-{[2-(4-morpholin-
yl)ethyl]amino}-4-pyrimidinyl)pyrazolo[1,5-a]pyridin-7-
amine (37)
Compound 37 was made in a similar manner as de-
scribed for compound 35 to give a yellow solid. 1H
5.13.2. N-Butyl-2-(4-fluorophenyl)-3-[2-(methylsulfanyl)-
4-pyrimidinyl]pyrazolo[1,5-a]pyridin-7-amine (65).
NMR(CDCl ): d 8.02 (d, 1H), 7.72 (d, 1H), 7.63 (dd,
3
A
2H), 7.33 (t, 1H), 7.14 (t, 2H), 6.31 (d, 1H), 6.03–6.01
(m, 2H), 5.65 (br, 1H), 3.75 (br, 4H), 3.57 (q, 2H),
3.39 (q, 2H), 2.65 (t, 2H), 2.53 (br, 4H), 1.81–1.46 (m,
mixture of thiol 64 (2.9 g, 6.9 mmol) in 50 mL water
was treated with iodomethane (0.9 mL, 13.8 mmol)
and NaOH (4.1 mL, 5 N aqueous solution) and allowed
to stir at room temperature for 4 h. The mixture was di-
luted with additional water and extracted with CH2Cl2.
The organic layers were washed with brine, dried over
MgSO4, and concentrated. Flash column chromatogra-
phy eluting with 9:1 hexanes–EtOAc afforded methyl-
4H), 0.99 (t, 3H); 19F NMR(CDCl ): d ꢀ113.31; MS
3
m/z 490 (M+1).
5.16. 3-[2-(Butylamino)-4-pyrimidinyl]-2-(4-fluorophen-
yl)-N-[2-(4-morpholinyl)ethyl]pyrazolo[1,5-a]pyridin-7-
amine (38)
1
thio ether 65 (1.6 g, 56%) as a yellow foam. H NMR
(CDCl3): d 8.15 (d, 1H), 7.73 (d, 1H), 7.56 (m, 2H),
7.33 (t, 1H), 7.13 (t, 2H), 6.62 (d, 1H), 6.02 (m, 2H),
3.35 (q, 2H), 2.55 (s, 3H), 1.76–1.41 (m, 4H), 0.95
(t, 3H); 19F NMR(CDCl 3): d ꢀ112.75; MS m/z 408
(M+1).
Compound 38 was made in a similar manner as de-
scribed for compound 25 to give a yellow solid. 1H
NMR(CDCl ): d 7.97 (br, 1H), 7.76 (d, 1H), 7.65 (m,
3
2H), 7.34 (t, 1H), 7.16 (t, 2H), 6.54 (t, 1H), 6.32 (d,
1H), 6.04 (d, 1H), 3.76 (t, 4H), 3.48 (m, 4H), 2.78 (t,
2H), 2.55 (br, 4H), 1.68–1.44 (m, 4H), 0.98 (t, 3H);
MS m/z 490 (M+1).
5.13.3.
3-({4-[7-(Butylamino)-2-(4-fluorophenyl)pyraz-
olo[1,5-a]pyridin-3-yl]-2-pyrimidinyl}amino)-1-propanol (35).
To a cold (0 °C) solution of methylthio ether 65 (1.5 g,
3.7 mmol) in 50 mL chloroform was added m-CPBA
(0.9 g, 70–75%, 3.7 mmol). The reaction was allowed
to warm to rt. After stirring for 5 h, another 0.2 g m-
CPBA acid was added and the reaction was stirred for
15 min. The reaction was diluted with aqueous NaHCO3
and extracted with CH2Cl2. The organic extracts were
washed with brine, dried over MgSO4, and concen-
trated. The crude product was recrystallized from
EtOAc and hexanes to afford the corresponding sulfox-
5.17. N-Cyclopentyl-2-(4-fluorophenyl)-3-(2-{[3-(4-mor-
pholinyl)propyl]-amino}-4-pyrimidinyl)pyrazolo[1,5-a]-
pyridin-7-amine (39)
Compound 39 was made in a similar manner as de-
scribed for compound 1 to give a tan solid. H NMR
1
(CDCl3): d 7.97 (d, 1H), 7.69 (d, 1H), 7.59 (dd, 2H),
7.26 (t, 1H), 7.10 (t, 2H), 6.24 (d, 1H), 6.00 (d, 1H),
5.96 (d, 1H), 5.70 (br, 1H), 3.97 (m, 1H), 3.71 (m,
4H), 3.49 (m, 2H), 2.48–2.45 (m, 6H), 2.10 (m, 2H),
1
ide (66) (950 mg, 60%) as an orange solid. H NMR
1.83–1.59 (m, 8H); 19F NMR(CDCl ): d ꢀ113.46; MS
3
(CDCl3): d 8.40 (br, 1H), 7.99 (d, 1H), 7.58 (m, 2H),
7.45 (t, 1H), 7.20 (t, 2H), 6.94 (d, 1H), 6.13 (d, 1H),
6.10 (br, 1H), 3.38 (m, 2H), 2.98 (s, 3H), 1.79–1.42 (m,
4H), 0.97 (t, 3H); MS m/z 422 (Mꢀ1). The sulfoxide
66 (50 mg, 0.12 mmol) and 3-amino-1-propanol
(0.45 mL, 5.9 mmol) in 2 mL THF were heated to reflux
for 4 h, then the mixture was cooled to rt and concen-
trated. Flash column chromatography eluting with a
gradient of 0–100% EtOAc in hexanes afforded the ana-
log 35 (46.3 mg, 90%) as a yellow foam. 1H NMR
(CDCl3): d 7.97 (d, 1H), 7.67–7.61 (m, 3H), 7.35 (t,
m/z 516 (M+1).
5.18. N-Butyl-2-(4-fluorophenyl)-3-(2-{[3-(1H-imidazol-
1-yl)propyl]amino}-4-pyrimidinyl)pyrazolo[1,5-a]pyridin-
7-amine (40)
Compound 40 was made in a similar manner as de-
scribed for compound 35 to give a yellow oil. 1H
NMR(CDCl ): d 8.01 (d, 1H), 7.65–7.61 (m, 3H), 7.54
3
(s, 1H), 7.34 (t, 1H), 7.15 (t, 2H), 7.08 (s, 1H), 6.97 (s,
1H), 6.37 (d, 1H), 6.07–6.03 (m, 2H), 5.32 (br, 1H),

B. A. Johns et al. / Bioorg. Med. Chem. 13 (2005) 2397–2411
2407
4.08 (t, 2H), 3.48 (q, 2H), 3.39 (q, 2H), 2.14 (m, 2H),
1.77 (m, 2H), 1.51 (m, 2H), 1.00 (t, 3H); MS m/z 485
(M+1). This material was treated with anhydrous
hydrochloride in ether to provide a hydrochloride salt
as a gold solid.
76%) to give a white crystalline solid. 1H NMR(CDCl 3):
d 8.15 (d, 1H), 7.69–7.59 (m, 5H), 7.32–7.27 (m, 3H),
7.18–7.13 (m, 3H), 7.02 (t, 1H), 6.49 (d, 1H), 6.06–6.01
(m, 2H), 4.01 (m, 1H), 2.20–2.10 (m, 2H), 1.86–1.64
(m, 6H); 13C NMR(CDCl 3): d 163.20 (d, JCF
=
246.6 Hz), 161.55, 160.11, 156.76, 152.27, 142.72,
141.15, 139.74, 131.47 (d, JCF = 8.3 Hz), 129.72 (d,
JCF = 3.4 Hz), 128.82, 128.66, 122.28, 119.52, 115.60
(d, JCF = 21.3 Hz), 110.83, 106.91, 105.15, 90.34, 53.86,
33.32, 24.05; MS m/z 465 (M+1).
5.19. N-Butyl-2-(4-fluorophenyl)-3-{2-[(2-pyridinyl-
methyl)amino]-4-pyrimidinyl}pyrazolo[1,5-a]pyridin-7-
amine (41)
Compound 41 was made in a similar manner as de-
scribed for compound 35 to give a solid. 1H NMR
(CDCl3): d 8.62 (d, 1H), 8.05 (d, 1H), 7.65 (m, 3H),
7.38 (d, 1H), 7.27–7.12 (m, 4H), 6.37 (d, 1H), 6.13 (br,
1H), 6.02–6.00 (m, 2H), 4.83 (d, 2H), 3.38 (q, 2H),
1.75 (m, 2H), 1.49 (m, 2H), 0.99 (t, 3H); 19F NMR
(CDCl3): d ꢀ113.22; MS m/z 468 (M+1). This material
was treated with anhydrous hydrochloride in ether to
provide a hydrochloride salt as a brown solid.
5.22. N-Cyclopentyl-2-(4-fluorophenyl)-3-[2-(4-methoxy-
anilino)-4-pyrimidinyl]pyrazolo[1,5-a]pyridin-7-amine
(44)
5.22.1. N-(4-Methoxyphenyl)guanidinium nitrate (68). To
a rt solution of 4-methoxyaniline (10.0 g, 81.2 mmol) in
ethanol (100 mL) was added cyanamide (7.2 mL,
50 wt % in water, 93.37 mmol) followed by the dropwise
addition of concentrated nitric acid (5.7 mL). The mix-
ture was heated at reflux for 3 h and allowed to cool
to room temperature. The resulting crystals were iso-
lated on a filter to yield guanidinium salt 68 (7.1 g,
5.20. 3-[2-(Cyclopentylamino)-4-pyrimidinyl]-2-(4-fluoro-
phenyl)-N-(4-methoxyphenyl)pyrazolo[1,5-a]pyridin-7-
amine (42)
1
38%) as a violet crystals. H NMR(DMSO- d6): d 9.39
Compound 42 was made in a similar manner as de-
scribed for compound 25 to give a white solid. 1H
(s, 1H), 7.22 (s, 3H), 7.17 (d, 2H), 6.99 (d, 2H), 3.76
(s, 3H); 13C NMR(DMSO- d6): d 158.17, 156.26,
127.48, 127.27, 114.90, 55.40; MS m/z 166 (M+1 of free
base).
NMR(CDCl ): d 7.99 (d, 1H), 7.84 (d, 1H), 7.70–7.64
3
(m, 3H), 7.32–7.26 (m, 3H), 7.17 (t, 2H), 9.67 (d, 2H),
6.34–6.31 (m, 2H), 5.43 (br, 1H), 4.35 (m, 1H), 3.85 (s,
3H), 2.11–2.03 (m, 2H), 1.83–1.55 (m, 6H); 19F NMR
(CDCl3): d ꢀ112.97; MS m/z 495 (M+1).
5.22.2. N-Cyclopentyl-2-(4-fluorophenyl)-3-[2-(4-meth-
oxyanilino)-4-pyrimidinyl]pyrazolo[1,5-a]pyridin-7-amine
(44). Compound 44 was made in a similar manner as de-
scribed for compound 43 to give a white solid. 1H NMR
(CDCl3): d 8.15 (d, 1H), 7.70–7.66 (m, 3H), 7.52–7.49 (d,
2H), 7.33–7.30 (m, 2H), 7.19 (t, 2H), 6.92–6.89 (m, 2H),
6.48 (d, 1H), 6.09–6.04 (m, 2H), 4.03 (m, 1H), 3.85 (s,
3H), 2.17 (m, 2H), 1.90–1.65 (m, 6H); 19F NMR
(CDCl3): d ꢀ113.17; MS m/z 495 (M+1).
5.21. 3-(2-Anilino-4-pyrimidinyl)-N-cyclopentyl-2-(4-
fluorophenyl)-pyrazolo[1,5-a]pyridin-7-amine (43)
5.21.1. N-Phenylguanidinium nitrate (67). To a room
temperature solution of aniline (10.0 g, 107 mmol) in
ethanol (100 mL) was added cyanamide (9.6 mL,
50 wt % in water, 123 mmol) followed by the dropwise
addition of concentrated HNO3 (7.6 mL). The mixture
was heated at reflux for 3.5 h and allowed to cool to
room temperature. The mixture was concentrated in
vacuo and the residue was crystallized from MeOH/
EtOAc/CH2Cl2 to yield guanidinium salt 67 (6.7 g,
5.23. N-Cyclopentyl-3-[2-(4-fluoroanilino)-4-pyrimidinyl]-
2-(4-fluorophenyl)pyrazolo[1,5-a]pyridin-7-amine (45)
5.23.1. N-(4-Fluorophenyl)guanidinium nitrate (69). In a
similar manner as described for compound 68 from 4-
fluoroaniline (10 g, 90 mmol) was obtained N-(4-fluoro-
phenyl)guanidine nitrate 69 (7.1 g, 37%) as a powder. 1H
1
32%) as a white crystalline solid. H NMR(DMSO-
d6): d 9.63 (s, 1H), 7.44 (t, 2H), 7.37 (br s, 3H), 7.29
(t, 1H), 7.23 (d, 2H); 13C NMR(DMSO- d6): d 156.36,
135.99, 130.40, 127.19, 125.18; MS m/z 136 (M+1 of free
base).
NMR(D O): d 7.23–7.08 (m, 4H); 19F NMR (D2O): d
2
ꢀ114.38; 13C NMR(D 2O): d 161.99 (d, JCF = 243.5 Hz),
156.83, 130.18 (d, JCF = 3.0 Hz),128.76 (d, JCF =
9.1 Hz), 116.87 (d, JCF = 22.8 Hz); MS m/z 154 (M+1
of free base).
5.21.2. 3-(2-Anilino-4-pyrimidinyl)-N-cyclopentyl-2-(4-
fluorophenyl)pyrazolo[1,5-a]pyridin-7-amine (43). To a
solution of vinylogous amide 60 (100 mg, 0.3 mmol) in
DMF (5 mL) was added N-phenylguanidinium nitrate
67 (252 mg, 1.3 mmol) and K2CO3 (175 mg, 1.3 mmol).
The suspension was heated at 140 °C (bath temperature)
for 21 h. The mixture was cooled to rt, ether was added
followed by water. The organic layer was washed with
brine. The aqueous layer was extracted with ether and
the combined organics were dried over MgSO4. Filtra-
tion and concentration followed by flash chromatogra-
phy (2:1 hexanes–EtOAc) provided pyrimidine 43,
which was recrystallized from ether/hexanes (90 mg,
5.23.2. N-Cyclopentyl-3-[2-(4-fluoroanilino)-4-pyrimidin-
yl]-2-(4-fluorophenyl)pyrazolo-[1,5-a]pyridin-7-amine
(45). Compound 45 was made in a similar manner as de-
scribed for compound 43 to give a white solid. 1H NMR
(CDCl3): d 8.13 (d, 1H), 7.65–7.59 (m, 3H), 7.51 (m,
2H), 7.28 (t, 1H), 7.14 (t, 2H), 6.89 (t, 2H), 6.49 (d,
1H), 6.05–6.01 (m, 2H), 4.00 (m, 1H), 2.18–2.10 (m,
2H), 1.86–1.67 (m, 6H); 13C NMR(CDCl ): d 163.21
3
(d, JCF = 246.6 Hz), 161.56, 160.16, 158.46 (d, JCF
239.7 Hz), 156.84, 152.29, 142.75, 141.13, 135.71 (d,
=
JCF = 3.1 Hz), 131.6 (d, JCF = 8.4 Hz), 129.73 (d,

2408
B. A. Johns et al. / Bioorg. Med. Chem. 13 (2005) 2397–2411
JCF = 3.8 Hz), 128.69, 121.50 (d, JCF = 8.3 Hz), 115.60
(d, JCF = 21.3 Hz), 115.33 (d, JCF = 22.0 Hz), 110.79,
106.84, 104.99, 90.35, 53.88, 33.32, 24.05; 19F NMR
(CDCl3): d ꢀ113.09, ꢀ121.26; MS m/z 483 (M+1).
J = 8.7 Hz, 2H), 6.96 (td, J = 6.9, 1.1 Hz, 1H), 6.70 (d,
J = 5.5 Hz, 1H), 2.61 (s, 3H); MS m/z 337 (M+1). Anal.
Calcd for C18H13FN4S: C, 64.27; H, 3.90; N, 16.66.
Found: C, 64.35; H, 3.87; N, 16.70.
5.24. N,2-Bis(4-fluorophenyl)-3-{2-[(4-fluorophenyl)-
amino]pyrimidin-4-yl}pyrazolo[1,5-a]pyridin-7-amine (8v)
5.24.4.
2-(4-Fluorophenyl)-3-[2-(methylsulfinyl)-4-pyr-
imidinyl]pyrazolo[1,5-a]pyridine (17). To a cold (0 °C)
solution (14) (1.50 g, 4.5 mmol) in CH2Cl2 (150 mL)
was added m-CPBA (1.08 g, 6.2 mmol). The reaction
mixture was warmed to rt and stirred overnight. Satu-
rated aq NaS2O3 was added and stirred for 1 h. The
resulting mixture was partitioned between saturated aq
NaHCO3 and CH2Cl2. The organic layer was washed
with water and brine, then dried over Na2SO4. Filtration
and concentration provided sulfoxide 17 (1.6 g, 99%) as
a beige solid. H NMR(300 MHz, CDCl ): d 8.80 (d,
J = 8.9 Hz, 1H), 8.56 (d, J = 6.9 Hz, 1H), 8.49 (d,
J = 5.5 Hz, 1H), 7.61 (dd, J = 8.6, 5.4 Hz, 2H), 7.51
(m, 1H), 7.23 (t, J = 8.6 Hz, 2H), 7.08–7.03 (m, 2H),
3.02 (s, 3H); MS m/z 353 (M+1).
5.24.1. 4-Iodo-2-(methylthio)pyrimidine (10). To a stir-
ring solution of hydriodic acid (100 mL, 4.46 M in
water, 0.4 mol) was added 4-chloro-(2-methyl-
thio)pyrimidine (9) (18.0 g, 0.12 mol). The reaction mix-
ture was stirred at rt for 6 h, during which a clumpy
precipitate formed. The clumps were broken apart and
the reaction mixture was stirred an additional 2 h. The
solids were collected on a filter, then taken up in water.
Saturated aqueous NaHCO3 solution was added until
the solution was basic, upon which the aqueous mixture
was extracted with CHCl3. The organic layer was
washed with 10% aq. NaHSO3 solution and water, then
dried over MgSO4. Filtration and concentration pro-
1
3
vided 4-iodo-2-(methylthio)pyrimidine (10) (25.0 g,
5.24.5.
N-(4-Fluorophenyl)-4-[2-(4-fluorophenyl)pyraz-
1
99%) as a white solid. H NMR(300 MHz, CDCl ): d
olo[1,5-a]pyridin-3-yl]-2-pyrimidinamine (70). To a sus-
pension of sulfoxide 17 (430 mg, 1.2 mmol) in dioxane
(500 lL) was added 4-fluoroaniline (232 lL, 2.4 mmol).
The reaction mixture was heated at 90 °C in a sealed
tube for 2 days. The reaction mixture was cooled, then
partitioned between EtOAc and saturated aq NaHCO3.
The organic layer was washed with water and brine,
then dried over Na2SO4. Filtration and concentration,
followed by flash chromatography (15–100% EtOAc
in hexanes) provided anilinopyrimidine 70 (200 mg,
41%) as a white solid. Rf 0.05 (4:1 hexanes–EtOAc);
1H NMR(400 MHz, CDCl 3): d 8.52 (d, J = 6.9 Hz,
1H), 8.30 (d, J = 9.0 Hz, 1H), 8.18 (d, J = 5.3 Hz, 1H),
7.63 (dd, J = 8.6, 5.4 Hz, 2H), 7.54 (dd, J = 9.0,
4.8 Hz, 2H), 7.29 (m, 1H), 7.16 (t, J = 8.6 Hz, 2H),
7.09 (s, 1H), 7.02 (t, J = 8.6 Hz, 2H), 6.93 (td, J = 6.9,
1.2 Hz, 1H), 6.54 (d, J = 5.3 Hz, 1H). MS m/z 400
(M+1).
3
7.99 (d, J = 5.1 Hz, 1H), 7.39 (d, J = 5.1 Hz, 1H), 2.53
(s, 3H); MS m/z 253 (M+1).
5.24.2. 4-[(4-Fluorophenyl)ethynyl]-2-(methylthio)pyrim-
idine (12). To a solution of iodide (10) (15.0 g,
67.3 mmol) in THF (90 mL) was added triethylamine
(12.2 mL, 87.5 mmol). PdCl2(PPh3)2 (1.90 g, 2.7 mmol)
and CuI (769 mg, 4.0 mmol) were added simultaneously.
A solution of 1-ethynyl-4-fluorobenzene (11) (8.50 mL,
74.0 mmol) in THF (10 mL) was added dropwise and
the reaction mixture was stirred at room temperature
for 6 h. Water (20 mL) was added and the resulting solu-
tion was concentrated on rotovap to remove the excess
THF. The predominantly aqueous mixture was ex-
tracted with EtOAc and washed with water and brine.
The organic layer was dried over Na2SO4. Filtration
and concentration, followed by flash chromatography
(100% CH2Cl2) provided diaryl alkyne 12 (12.0 g,
73%) as a pale yellow solid. Rf 0.85 (49:1 CH2Cl2–
MeOH). 1H NMR(300 MHz, CDCl 3): d 8.52 (d,
J = 5.1 Hz, 1H), 7.62 (dd, J = 8.5, 5.5 Hz, 2H), 7.13–
7.06 (m, 3H), 2.60 (s, 3H); MS m/z 245 (M+1).
5.24.6. 4-[7-Chloro-2-(4-fluorophenyl)pyrazolo[1,5-a]pyr-
idin-3-yl]-N-(4-fluorophenyl)-2-pyrimidinamine (71). To a
cold (0 °C) solution of diisopropylamine (164 lL,
1.2 mmol) in THF (2 mL) was added butyllithium
(719 lL, 1.6 M in hexanes, 1.1 mmol) dropwise. The
reaction mixture was stirred at 0 °C for 10 min then
cooled to ꢀ78 °C. The reaction mixture was transferred
via syringe to a cold (ꢀ78 °C) solution of pyrazolopyr-
idine 70 (153 mg, 0.383 mmol) in THF (4 mL). The reac-
tion mixture was stirred at ꢀ78 °C for 10 min. CCl4
(222 lL, 2.30 mmol) was added and stirred at ꢀ78 °C
for 30 min. The reaction was quenched with water and
warmed to room temperature. The resultant mixture
was extracted with EtOAc. The organic layer was
washed with water and brine, then dried over Na2SO4.
Filtration and concentration, followed by flash chroma-
tography (5–30% EtOAc in hexanes) provided 7-chloro
derivative 71 (109 mg, 66%) as a pale yellow solid. Rf
0.25 (4:1 hexanes–EtOAc); 1H NMR(300 MHz,
CDCl3): d 8.21 (d, J = 8.9 Hz, 1H), 8.10 (d, J = 5.3 Hz,
1H), 7.55 (dd, J = 8.6, 5.5 Hz, 2H), 7.50–7.44 (m, 3H),
7.16 (m, 1H), 7.05 (t, J = 8.7 Hz, 2H), 6.98 (d,
5.24.3. 2-(4-Fluorophenyl)-3-[2-(methylthio)-4-pyrimidin-
yl]pyrazolo[1,5-a]pyridine (14). To a cold (0 °C) solution
of alkyne 12 (4.00 g, 16.4 mmol) and 1-aminopyridinium
iodide (13) (3.63 g, 16.4 mmol) in acetonitrile (100 mL)
was added DBU (2.45 mL, 16.4 mmol). The reaction
mixture was warmed to rt and stirred 3 days. The reac-
tion mixture was quenched with water and concentrated
in vacuo to remove the excess acetonitrile. The resultant
mixture was partitioned between EtOAc and water. The
organic layer was washed with water and brine, then
dried over Na2SO4. Filtration and concentration, fol-
lowed by flash chromatography (20–25% EtOAc in hex-
anes) provided pyrazolopyridine 14 (4.34 g, 79%) as a
1
pale yellow solid. Rf 0.20 (4:1 hexanes–ethyl acetate); H
NMR(400 MHz, CDCl ): d 8.52 (d, J = 6.8 Hz, 1H),
3
8.47 (d, J = 8.9 Hz, 1H), 8.24 (d, J = 5.5 Hz, 1H), 7.59
(dd, J = 8.6, 5.3 Hz, 2H), 7.39 (m, 1H), 7.17 (t,

B. A. Johns et al. / Bioorg. Med. Chem. 13 (2005) 2397–2411
2409
J = 7.3 Hz, 1H), 6.89 (t, J = 8.7 Hz, 2H), 6.42 (d,
J = 5.3 Hz, 1H); MS m/z 434 (M+1).
to produce the title compound (6.3 g, 51%) as a white
1
crystalline solid. H NMR (D2O): d 3.17 (m, 4H), 1.78
(m, 4H); 13C NMR(D O): d 154.28, 46.97, 24.92; MS
m/z 114 (M+1).
2
5.24.7. N,2-Bis(4-fluorophenyl)-3-{2-[(4-fluorophenyl)amino]-
4-pyrimidinyl}pyrazolo[1,5-a]pyridin-7-amine (46). To a
solution of 71 (102 mg, 0.24 mmol) in 4-fluoroaniline
(6.00 mL, 63.3 mmol) was added rac-BINAP (44 mg,
0.07 mmol), Cs2CO3 (115 mg, 0.4 mmol), and
Pd(OAc)2 (11 mg, 0.05 mmol), respectively. The reac-
tion mixture was heated at 140 °C for 4 h. The reac-
tion mixture was cooled and quenched with water,
then extracted with EtOAc. The organic layer was
washed with water and brine then dried over Na2SO4.
Filtration and concentration provided a crude mass,
which was placed under high vacuum to remove the
excess 4-fluoroaniline. The resulting material was chro-
matographed on silica gel (15–40% EtOAc in hexanes)
to provide bis 4-fluoroaniline derivative 46 (54 mg,
45%) as a beige solid. Rf 0.20 (4:1 hexanes–EtOAc);
1H NMR(400 MHz, CDCl 3): d 8.18 (d, J = 5.3 Hz,
1H), 7.79 (s, 1H), 7.75 (d, J = 8.6 Hz, 1H), 7.67 (dd,
J = 8.6, 5.4 Hz, 2H), 7.52 (dd, J = 9.0, 4.8 Hz, 2H),
7.34 (dd, J = 8.9, 4.8 Hz, 2H), 7.28–7.23 (m, 2H),
7.20–7.11 (m, 4H), 6.99 (t, J = 8.8 Hz, 2H), 6.54 (d,
J = 5.3 Hz, 1H), 6.40 (d, J = 7.6 Hz, 1H); MS m/z
509 (M+H)+.
5.26.2. N-Butyl-2-(4-fluorophenyl)-3-[2-(1-pyrrolidinyl)-
4-pyrimidinyl]pyrazolo[1,5-a]pyridin-7-amine (48). Com-
pound 48 was made in a similar manner as described
for compound 1 using guanidine 72, to give a yellow
1
solid. H NMR(CDCl ): d 8.03 (d, 1H), 7.76 (d, 1H),
3
7.59 (m, 2H), 7.26 (t, 1H), 7.09 (t, 2H), 6.20 (d, 1H),
5.99–5.95 (m, 2H), 3.61 (m, 4H), 3.32 (m, 2H), 1.98
(m, 4H), 1.70 (m, 2H), 1.44 (m, 2H), 0.94 (t, 3H); 13C
NMR(CDCl 3): d 163.07 (d, JCF = 246.5 Hz), 161.04,
160.48, 156.56, 152.19, 143.01, 141.13, 131.45 (d,
JCF = 8.4 Hz), 130.05 (d, JCF = 3.0 Hz), 128.34, 115.38
(d, JCF = 21.2 Hz), 107.46, 107.22, 105.50, 89.19,
46.59, 42.33, 31.11, 25.55, 20.19, 13.75; MS m/z 431
(M+1).
5.27. N-Cyclopentyl-4-[2-(4-fluorophenyl)-7-(1-pyrrolidin-
yl)pyrazolo[1,5-a]pyridin-3-yl]-2-pyrimidinamine (49)
Compound 49 was made in a similar manner as de-
scribed for compound 1 to give a yellow solid. 1H
NMR(CDCl 3): d 7.95 (d, 1H), 7.82 (d, 1H), 7.61
(m, 2H), 7.22 (t, 1H), 7.08 (t, 2H), 6.28 (d, 1H),
6.07 (d, 1H), 5.25 (br s, 1H), 4.31 (m, 1H), 3.72 (m,
4H), 2.02 (m, 6H), 1.75–1.49 (m, 6H); MS m/z 443
(M+1).
5.25. 3-[2-(Cyclopentylamino)pyrimidin-4-yl]-N,2-bis(4-
fluorophenyl)pyrazolo[1,5-a]pyridin-7-amine (47)
To a solution of 62 (143 mg, 0.351 mmol) in 4-fluoro-
aniline (7.00 mL, 73.9 mmol) was added rac-BINAP
(66 mg, 0.11 mmol), Cs2CO3 (172 mg, 0.53 mmol),
and Pd(OAc)2 (16 mg, 0.07 mmol), respectively. The
reaction mixture was heated at 140 °C for 4 h. The
reaction mixture was cooled and quenched with water,
then extracted with EtOAc. The organic layer was
washed with water and brine then dried over Na2SO4.
Filtration and concentration provided a crude mass,
which was placed under high vacuum to remove the ex-
cess 4-fluoroaniline. The resulting material was chro-
matographed on silica gel (10–40% ethyl acetate in
hexanes) to provide 7-anilino derivative 47 (35 mg,
21%) as a light yellow solid. 1H NMR(300 MHz,
5.28. N-Cyclopentyl-4-[2-(4-fluorophenyl)-7-piperidin-1-
ylpyrazolo[1,5-a]pyridin-3-yl]pyrimidin-2-amine (50)
Compound 50 was made in a similar manner as de-
scribed for compound 1 to give a yellow solid. Mp
198–199 °C; 1H NMR(CDCl 3): d 1.9–1.5 (m, 12H),
2.1–2.0 (m, 2H), 3.4 (s, 4H), 4.37 (m, 1H), 5.2 (br s,
1H), 6.38–6.30 (m, 2H), 7.1 (t, 2H), 7.28 (t, 1H), 7.68
(dd, 2H), 8.02 (br d, 2H); MS m/z 457 (M+1). Anal.
Calcd for C27H29FN6: C, 71.03; H, 6.40; N, 18.41.
Found: C, 70.80; H, 6.40; N, 18.18.
5.29. 4-[2-(4-Fluorophenyl)-7-(1-pyrrolidinyl)pyraz-
olo[1,5-a]pyridin-3-yl]-N,N-dimethyl-2-pyrimidinamine
(51)
CDCl3):
d
8.06 (d, J = 5.2 Hz, 1H), 7.89 (d,
J = 8.8 Hz, 1H), 7.81 (s, 1H), 7.68 (dd, J = 8.6,
5.4 Hz, 2H), 7.35 (m, 2H), 7.20–7.10 (m, 3H), 6.86 (t,
J = 8.7 Hz, 1H), 6.62 (m, 1H), 6.41 (d, J = 7.8 Hz,
1H), 6.34 (d, J = 5.3 Hz, 1H), 5.14 (d, J = 7.5 Hz,
1H), 4.35 (m, 1H), 2.08 (m, 2H), 1.80–1.50 (m, 6H);
MS m/z 483 (M+H)+. Anal. Calcd for C28H24F2N6:
C, 69.70; H, 5.01; N, 17.42. Found: C, 69.91; H,
4.99; N, 17.33.
Compound 51 was made in a similar manner as de-
scribed for compound 1 to give a yellow crystalline solid.
1H NMR(CDCl 3): d 8.05 (d, 1H), 7.81 (d, 1H), 7.61 (m,
2H), 7.21 (t, 1H), 7.07 (t, 2H), 6.27 (d, 1H), 6.06 (d, 1H),
3.71 (m, 4H), 3.21 (s, 6H), 2.01 (m, 4H); MS m/z 403
(M+1).
5.26. N-Butyl-2-(4-fluorophenyl)-3-[2-(1-pyrrolidinyl)-4-
pyrimidinyl]pyrazolo[1,5-a]pyridin-7-amine (48)
5.30. N-Cyclopentyl-3-[2-(dimethylamino)-4-pyrimidinyl]-
2-(4-fluorophenyl)pyrazolo[1,5-a]pyridin-7-amine (52)
5.26.1. 1-Pyrrolidinecarboximidamide sulfate (72). O-
Methylisourea hydrogensulfate (10 g, 58.1 mmol) and
pyrrolidine (12.1 mL, 145.2 mmol) were heated at reflux
in 10 mL of water for 2 h. The solvent was removed in
vacuo and the residue was azeotroped with methanol.
The resultant material was recrystallized from EtOH
Compound 52 was made in a similar manner as de-
scribed for compound 1 to give a white solid. 1H
NMR(CDCl ): d 8.13 (d, 1H), 7.75 (d, 1H), 7.67 (dd,
3
2H), 7.33 (t, 1H), 7.16 (t, 2H), 6.30 (d, 1H), 6.06–6.04
(m, 2H), 4.02 (m, 1H), 3.26 (s, 6H), 2.16 (m, 2H),
1.84–1.65 (m, 6H); MS m/z 417 (M+1).

2410
B. A. Johns et al. / Bioorg. Med. Chem. 13 (2005) 2397–2411
5.31. 3-[2-(Butylamino)-4-pyrimidinyl]-2-(4-fluorophen-
yl)-N,N-dimethylpyrazolo[1,5-a]pyridin-7-amine (53)
1H), 6.18 (d, 1H), 3.64 (br, 4H), 3.46 (t, 2H), 3.38–
3.22 (m, 7H), 2.44 (br, 4H), 1.63 (m, 2H), 1.38 (m,
2H), 0.92 (t, 3H); 19F NMR(CDCl ): d ꢀ113.59; MS
3
Compound 53 was made in a similar manner as de-
scribed for compound 1 to give a yellow solid. 1H
m/z 504 (M+1). This material was treated with anhy-
drous hydrochloride in ether to provide a hydrochloride
salt as an orange solid.
NMR(CDCl ): d 8.00 (m, 2H), 7.62 (m, 2H), 7.28 (t,
3
1H), 7.08 (t, 2H), 6.29 (m, 2H), 5.24 (br s, 1H), 3.44
(m, 2H), 3.09 (s, 6H), 1.65–1.38 (m, 4H), 0.94 (t, 3H);
MS m/z 405 (M+1).
5.37. HSV antiviral assay
5.37.1. Cell culture and HSV infection. Vero 76 cells
(American Type Culture Collection, Manassas, VA)
were grown and passed in MEM with Earleꢁs salts, L-
glutamine, penicillin, and streptomycin (Invitrogen Life
Technologies, Carlsbad, CA) supplemented with 8%
fetal bovine serum (FBS) (Hyclone Laboratories, Logan,
UT). The amount of FBS was reduced to 2% for assays.
5.32. N-Butyl-4-[2-(4-fluorophenyl)-7-(4-methyl-1-piper-
azinyl)pyrazolo[1,5-a]pyridin-3-yl]-2-pyrimidinamine (54)
Compound 54 was made in a similar manner as de-
scribed for compound 1 to give an off-white foam. H
1
NMR(DMSO- d6): d 7.98 (m, 2H), 7.58 (t, 2H), 7.35
(t, 1H), 7.26 (t, 2H), 7.04 (br s, 1H), 6.46 (d, 1H), 6.14
(br s, 1H), 3.37 (br s, 4H), 3.20 (d, 2H), 2.49 (s, 4H),
2.20 (s, 3H), 1.46 (m, 2H), 1.28 (m, 2H), 0.84 (t, 3H);
19F NMR(DMSO- d6): d ꢀ113.56; MS m/z 460 (M+1).
Vero cells were infected in suspension with either HSV-1
or HSV-2 for 45 min at 37 °C at a multiplicity of infec-
tion of 0.001. Infected cells were plated at a density of
50,000 cells/well into 96-well tissue culture plates con-
taining antiviral test compounds and incubated at
37 °C for 40–48 h.
5.33. N-Butyl-4-[2-(4-fluorophenyl)-7-(4-morpholin-
yl)pyrazolo[1,5-a]pyridin-3-yl]-2-pyrimidinamine (55)
Compound 55 was made in a similar manner as de-
scribed for compound 1 to give an off-white foam. H
5.37.2. HSV DNA hybridization. The effect of com-
pounds on HSV replication was assessed by conven-
tional DNA hybridization. Cell lysates were prepared
for hybridization by removing growth medium from
HSV-infected Vero cells 2 days post-infection and add-
ing 150 lL lysis buffer (0.2 N NaOH with 1% NP-40)
to each well. The lysates were then incubated at room
temperature for 5 days in a humidified chamber to en-
sure complete DNA hydrolysis. Samples of the lysates
were neutralized in a phosphate-buffered guanidine iso-
thiocyanate (GuSCN) solution and combined with a
digoxigenin-labeled 710 bp DNA fragment of the HSV
UL15 open reading frame. The hybridization solution
was heated to 90 °C for 6 min and incubated at 42 °C
overnight. Immobilized hybrids were detected by incu-
bation with anti-digoxigenin HRP-conjugated antibody
(Boehringer Mannheim, Indianapolis, IN) and subse-
quent addition of SuperSignalÒ substrate (Pierce, Rock-
ford, MD). The resulting chemiluminescent signal from
compound-treated cells was compared to that of com-
pound-free cells to obtain percent inhibitions, which
were used to construct dose response curves to derive
50% inhibitory concentrations (IC50).
1
NMR(CDCl ): d 8.14 (d, 1H), 8.03 (m, 1H), 7.68 (m,
3
2H), 7.37 (t, 1H), 7.17 (t, 2H), 6.39 (m, 2H), 5.52 (br
s, 1H), 4.04 (m, 4H), 3.66 (m, 6H), 1.70 (m, 2H), 1.52
(m, 2H), 1.02 (t, 3H); MS m/z 447 (M+1).
5.34. N-Butyl-2-(4-fluorophenyl)-3-[2-(4-morpholinyl)-4-
pyrimidinyl]pyrazolo[1,5-a]pyridin-7-amine (56)
Compound 56 was made in a similar manner as de-
scribed for compound 35 to give an off-white foam. H
1
NMR(DMSO- d6): d 8.09 (d, 1H), 7.56 (dd, 2H), 7.44
(d, 1H), 7.35 (t, 1H), 7.26 (t, 2H), 7.06 (t, 1H), 6.30 (d,
1H), 6.14 (d, 1H), 3.59 (m, 8H), 3.28 (m, 2H), 1.59 (m,
2H), 1.33 (m, 2H), 0.87 (t, 3H); 19F NMR(DMSO-
d6): d ꢀ113.70; MS m/z 447 (M+1).
5.35. 2-(4-{4-[7-(Butylamino)-2-(4-fluorophenyl)pyraz-
olo[1,5-a]pyridin-3-yl]-2-pyrimidinyl}-1-piperazinyl)etha-
nol (57)
Compound 57 was made in a similar manner as de-
scribed for compound 35 to give a pale yellow solid.
1H NMR(DMSO- d6): d 8.12 (d, 1H), 7.61 (m, 2H),
7.48 (d, 1H), 7.39 (t, 1H), 7.30 (t, 2H), 7.09 (t, 1H),
6.31 (d, 1H), 6.18 (d, 1H), 4.43 (br, 1H), 3.64 (br, 4H),
3.53 (q, 2H), 3.38–3.27 (m, 4H), 2.44 (br, 4H), 1.63
(m, 2H), 1.37 (m, 2H), 0.91 (t, 3H); 19F NMR(CDCl 3):
d ꢀ113.30; MS m/z 490 (M+1).
5.38. Cytotoxicity assay
Compounds were dissolved in DMSO at a stock concen-
tration of 10 mM and serially diluted twofold in DMSO.
Dilutions were carried out in columns 1–9 of a 96-well,
v-bottom polypropylene plate. Columns 10, 11, and 12
are control columns that do not contain compound.
Plates are then seeded at 10,000 cells/well, columns 1–
11, in Minimum Essential medium containing Earleꢁs
salt and L-glutamine and supplemented with 10% heat-
inactivated fetal bovine serum, 1% penicillin–streptomy-
cin, and 1% L-glutamine (200 mM) resulting in a final
250-fold drug dilution. Thus the maximum compound
concentration used in the assay is 40 lM while the final
DMSO concentration is 0.4%. Plates are incubated at
5.36. N-Butyl-2-(4-fluorophenyl)-3-{2-[4-(2-methoxy-
ethyl)-1-piperazinyl]-4-pyrimidinyl}pyrazolo[1,5-a]pyr-
idin-7-amine (58)
Compound 58 was made in a similar manner as de-
scribed for compound 35 to give a pale yellow oil. H
1
NMR(DMSO- d6): d 8.11 (d, 1H), 7.61 (dd, 2H), 7.48
(d, 1H), 7.40 (t, 1H), 7.30 (t, 2H), 7.09 (t, 1H), 6.31 (d,

B. A. Johns et al. / Bioorg. Med. Chem. 13 (2005) 2397–2411
2411
6. Alberti, M. J.; Baldwin, I. R.; Cheung, M.; Cockerill, S.;
Flack, S.; Harris, P. A.; Jung, D. K.; Peckham, G.; Peel,
M. R.; Stanford, J. B.; Stevens, K.; Veal, J. M. WO 02/
16359, 2002; Chem. Abstr. 2002, 136, 200184.
7. The representation of compounds follows the convention
that specific compounds are numbered (1, 2, 3. . .) as they
appear in the manuscript while generic structures contain-
ing variable groups ꢀRꢁ are represented with letters (A, B,
C. . .).
8. (a) Wolfe, J. P.; Wagaw, S.; Buchwald, S. L. J. Am.
Chem. Soc. 1996, 118, 7215; (b) Harris, M. C.; Geis, O.;
Buchwald, S. L. J. Org. Chem. 1999, 64, 6019; (c) Wolfe,
J. P.; Buchwald, S. L. J. Org. Chem. 2000, 65, 1144;
(d) Hartwig, J. F. Angew. Chem., Int. Ed. 1998, 37,
2046.
9. An alternative approach to further functionalize methyl
ketone 5 by treatment with dimethylformamide–dimethyl-
acetal to form the vinylogous amide containing the
7-chloro substituent resulted in variable levels of 7-dimeth-
ylamino derived side products. Presumably this arises via
direct nucleophilic displacement of the 7-chloro substitu-
ent by dimethylamine liberated from the DMF–DMA
during extended reaction times. This could be minimized
by use of dimethylformamide di-tert-butylacetal, which
gave much reduced reaction times.
10. (a) Huisgen, R.; Grashey, R.; Krischke, R. Tetrahedron
Lett. 1962, 3, 387; (b) Anderson, P. L.; Hasak, J. P.;
Kahle, A. D.; Paolella, N. A.; Shapiro, M. J. J. Hetero-
cycl. Chem. 1981, 18, 1149; (c) Akahane, A.; Katayama,
H.; Mitsunaga, T.; Kita, Y.; Kusunoki, T.; Terai, T.;
Yoshida, K.; Shiokawa, Y. Bioorg. Med. Chem. Lett.
1996, 6, 2059; (d) Zanka, A.; Uematsu, R.; Morinaga, Y.;
Yasuda, H.; Yamazaki, H. Org. Process Res. Dev. 1999, 3,
389.
11. Majeed, A. J.; Antonsen, O.; Benneche, T.; Undheim, K.
Tetrahedron 1989, 45, 993.
12. (a) Finkelstein, B. L. J. Org. Chem. 1992, 57, 5538; (b)
Aboul-Fadl, T.; Lober, S.; Gmeiner, P. Synthesis 2000,
1727.
37 °C in a humidified, 5% CO2 atmosphere and growth
inhibition is measured after 3 days.
Cytotoxicity is determined in Vero cells using the Cell-
Titer 96Ò Aqueous Non-Radioactive Cell Proliferation
Assay (Promega Corporation, G1111). Metabolically
active cells will convert methylthiazol tetrazolium inner
salt (MTS), through the actions of cellular dehydrogen-
ases, into a colorized formazan end product. On day 3,
MTS solution is added to the assay plates, incubated for
1.5–2 h at 37 °C in a humidified, 5% CO2 atmosphere,
and absorbance is measured at 490 nm using the Wallac
Victor2 1420 multilabel counter (Perkin–Elmer, Welles-
ley, NA). RoboFit 2000 curve-fitting software is then
used to obtain a CC50 (50% cytotoxicity concentration)
value from the curves generated.
References and notes
1. Roizman, B.; Pellett, P. E. In Fields Virology; Knipe, D.
M., Howley, P. M., Eds.; Lippincott Williams and
Wilkins: Philadelphia, PA, 2001; Vol. 2, p 2381.
2. (a) Corey, L.; Tyring, S.; Sacks, S.; Warren, T.; Beutner,
K.; Patel, R.; Wald, A.; Mertz, G.; Paavonen, J. Abstract
of papers, 42nd Interscience Conference on Antimicrobial
Agents and Chemotherapy, San Diego, CA; American
Society for Microbiology: Washington, DC, 2002;
Abstract LB3; (b) Oien, N. L.; Brideau, R. J.; Hopkins,
T. A., et al. Antimicrob. Agents Chemother. 2002, 46, 724;
(c) Brideau, R. J.; Knechtel, M. L.; Huang, A., et al.
Antiviral Res. 2002, 54, 19; (d) Wathen, M. W. Rev. Med.
Virol. 2002, 12, 167; (e) Jurk, M.; Heil, R.; Vollmer, J.,
et al. Nat. Immunol. 2002, 3, 499; (f) Stanley, M. A. Clin.
Exp. Dermatol. 2002, 27, 571; (g) Crute, J. J.; Grygon, C.
A.; Hargrave, K. D.; Simoneau, B.; Faucher, A.-M.;
Bolger, G.; Kibler, P.; Liuzzi, M.; Cordingley, M. G. Nat.
Med. 2002, 8, 386; (h) Kleymann, G.; Fischer, R.; Betz, U.
A. K.; Hendrix, M.; Bender, W.; Schneider, U.; Handke,
G.; Eckenberg, P., et al. Nat. Med. 2002, 8, 392.
3. Johns, B. A.; Gudmundsson, K. S.; Turner, E. M.; Allen,
S. H.; Jung, D. K.; Sexton, C. J.; Boyd, F. L., Jr.; Peel, M.
R. Tetrahedron 2003, 59, 9001.
13. For GW3733; clog P = 6.7. Solubility in HCl (pH =
1.2) = 6.7 lg/mL. Phosphate-buffered saline (pH = 7.4)
1.2 lg/mL.
14. Cyclopentyl guanidine 61 (NR3R4 = c-C5H9) was made
via a modification of methods described in Bannard, R. A.
B.; Casselman, A. A.; Cockburn, W. F.; Brown, G. M.
Can. J. Chem. 1958, 36, 1541.
4. Gudmundsson, K. S.; Johns, B. A. Org. Lett. 2003, 5,
1369.
5. Sexton, C. J.; Selleseth, D. W.; Jansen, R. W., unpublished
results.
15. For a general procedure for the synthesis of substituted
guanidinium salts, see: Fearing, R. B.; Fox, S. W. J. Am.
Chem. Soc. 1954, 76, 4382.