Synthesis and selective cyclooxygenase-2 (COX-2) inhibitory activity of a series of novel bicyclic pyrazoles

Article abstract of DOI:10.1016/j.bmc.2004.01.012

Novel series of pyrazolo[5,1-b]1,3-oxazolidines, pyrazolo[5,1-b]1,3- oxazines and imidazolidino[1,2-d]pyrazoles were synthesized. These compounds were evaluated in vitro for their ability to inhibit cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) in human whole blood (HWB). Several of the compounds were found to be novel and selective COX-2 inhibitors, the most potent and selective being 1-(5-cyclohexyl (2H,3H-pyrazolo[5,1-b]-1,3- oxazolidin-6-yl)-4-(methylsulfonyl)benzene, 7a (IC_5o for COX-1>100 μM; for COX-2=1.3 μM).

Full text of DOI:10.1016/j.bmc.2004.01.012

Bioorganic & Medicinal Chemistry 12 (2004) 1357–1366
Synthesis and selective cyclooxygenase-2 (COX-2) inhibitory
activity of a series of novel bicyclic pyrazoles§
Ramani R. Ranatunge,*,{ David S. Garvey, David R. Janero, L. Gordon Letts,
Allison M. Martino, Madhavi G. Murty, Stewart K. Richardson,
Delano V. Young and Irina S. Zemetseva
NitroMed Inc., 12 Oak Park Drive, Bedford, MA 01730, USA
Received 20 November 2003; revised 13 January 2004; accepted 14 January 2004
Abstract—Novel series of pyrazolo[5,1-b]1,3-oxazolidines, pyrazolo[5,1-b]1,3-oxazines and imidazolidino[1,2-d]pyrazoles were syn-
thesized. These compounds were evaluated in vitro for their ability to inhibit cyclooxygenase-1 (COX-1) and cyclooxygenase-2
(COX-2) in human whole blood (HWB). Several of the compounds were found to be novel and selective COX-2 inhibitors, the most
potent and selective being 1-(5-cyclohexyl (2H,3H-pyrazolo[5,1-b]-1,3-oxazolidin-6-yl)-4-(methylsulfonyl)benzene, 7a (IC5o for
COX-1>100 mM; for COX-2=1.3 mM).
# 2004 Elsevier Ltd. All rights reserved.
1. Introduction
Nonsteroidal anti-inflammatory drugs (NSAIDs) are
widely used to treat acute or chronic inflammation and
offer symptomatic pain relief.1,2 Conventional NSAIDs
act by non selective inhibition of cyclooxygenase (COX)
enzymes, which catalyze the formation of pros-
taglandins (PGs) from arachidonic acid.3À5 There are at
least two main mammalian COX isoforms, COX-1 and
COX-2.6,7 Constitutive COX-1 has housekeeping func-
tions, including low-level production of gastroprotective
PGs, whereas COX-2 is induced in inflammatory cells
and generates PGs that help mediate the inflammatory
response. Adverse gastrointestinal (GI) side-effects of
conventional NSAIDs largely reflect inhibition of COX-1
and the associated reduction in gastroprotection.8À11 In
contrast, selective COX-2 inhibitors such as Cel-
ecoxib,12 Rofecoxib13 and Valdecoxib14 exert anti-
inflammatory and analgesic activity in the clinic with
markedly less GI toxicity than traditional NSAIDs.
The improved GI tolerance of COX-2 selective inhibi-
tors notwithstanding, there is evidence to suggest that
COX-2 selective inhibitors may inhibit COX-1 and
induce GI irritation or ulceration with long-term use or
at higher doses.15À18 Preclinical cardiovascular and
renal liabilities of at least some COX-2 selective inhibi-
tors have also been reported.19 Thus there is still a need
for new, selective COX-2 inhibitors with an improved
safety profile.
§A portion of this work was presented in a poster at the 225th ACS
National Meeting, Medicinal Chemistry (abstr. #245), New Orleans,
LA, USA, 23–27 March 2003.
* Corresponding author. Tel.: +1-781-685-9739; fax: +1-781-275-
1127; e-mail: rbandarage@nitromed.com
Following the senior author, contributors appear in alphabetical
order.
{
A search of the literature revealed very few reports of
COX-2 selective inhibitors containing a bicyclic core.
0968-0896/$ - see front matter # 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2004.01.012

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R. R. Ranatunge et al. / Bioorg. Med. Chem. 12 (2004) 1357–1366
Two examples are the imidazo[1,2-a]-pyridines20 and
the pyrazolo[1,5-b]pyridazines21 which contain a planar
central unit. A slightly less rigid system can be found in
the 2,3-dihydro-1H-pyrrolines as exemplified by ML
3000.22À27 We now wish to report the synthesis and
COX-2 selective inhibition of a series of novel bicyclic-
pyrazole inhibitors. While this manuscript was in pre-
paration, a patent28 appeared covering this structural
core, but the compounds reported herein have not been
fully described or characterized.
In fact, minor quantities of 9 or 11 were formed during
the bromination of 4 or 10, indicating that cyclization
was spontaneous but slow in the absence of base.
Methyl sulfides 9 and 11 were oxidized to the sulfones
(7a–c, 12a) with Oxone1 in high yield. Alternatively,
7a–c could be synthesized from 4 by reversing the order
of oxidation and cyclization (4 to 5 to 6 to 7). In this
route however, the oxidation of 4 gave a low isolated
yield due to the high polarity and insolubility of 5.
Imidazolidino[1,2-d]pyrazoles (21, 22, 24, 25) were pre-
pared as illustrated in Scheme 2. The ketonitrile inter-
mediate 16 was prepared in three steps from
commercially available 4-methylthiobenzyl alcohol 13.
Reaction of 13 with SOCl2 gave 14 in 97% yield. Sub-
stitution of the chloride with NaCN gave the nitrile 15
which, upon acylation with cyclohexanecarbonyl chlo-
ride in the presence of LiHMDS, afforded ketonitrile 16.
This was condensed with 2-hydroxyethyl hydrazine in
glacial acetic acid at 100 ꢀC to give 5-amino-1(2-hydro-
xyethyl)pyrazole 17. Mesylation of 17 afforded 18,
which was cyclized in the presence of K2CO3 at 60 ꢀC
for 3 days to give imidazolidino[1,2-d]pyrazole 19. Oxi-
dation of the sulfide group of 19 with Oxone1 at room
temperature gave a significant amount of N-oxide as a
by-product together with the desired product 20. When
the reaction was repeated at 0 ꢀC, N-oxide formation
was greatly reduced. Acylation of 20 with acetic anhy-
dride gave 4-acetylimidazolidino[1,2-d]pyrazole 21. On
the other hand, alkylation of 20 with methyl iodide and
K2CO3 in DMF at room temperature gave N-methyl-
imidazolidino [1,2-d]pyrazole 22.
2. Chemistry
The general routes outlined in Schemes 1–3 were used to
synthesize all compounds described herein. The key
synthetic step for construction of the bicyclic-pyrazole
core involves either basic or acidic cyclization of 2-
hydroxyalkyl pyrazole intermediates (4, 10, 18, 26).
As shown in Scheme 1, pyrazolo[5,1-b]1,3-oxazolidines
7a–c and pyrazolo[5,1-b]1,3-oxazine 12 were obtained
from commercially available 2-(4-methylthiophenyl)-
acetic acid, 1. This was converted into the corresponding
methyl ester 2, whose enolate, prepared using LiHMDS,
reacted with acid chlorides to give the ketoesters 3 in
high yield. This was condensed with hydrazinoalkanols29
in glacial acetic acid at 100 ꢀC to obtain 2-hydroxyalkyl
substituted pyrazoles 4 and 10 in high yield. In most cases,
1,3,4-substituted pyrazoles (4, 10) were formed exclusively.
In those few cases where the 1,2,3-regioisomer was also
formed as a minor by-product, it was readily removed
by column chromatography followed by recrystalliza-
tion. Bicyclic-pyrazoles 9 and 11 were obtained by bro-
mination of 4 or 10 with CBr4 and PPh3 (or polymer
supported PPh3) followed by cyclization using K2CO3.
Incorporating an acid group into the molecule could be
useful either to improve its solubility or to allow for further
chemical modification. Therefore, imdazolidino[1,2-d]-
Scheme 1. (a) MeOH, c. H2SO4, rfx, 16 h; (b) LiHMDS, RCOCl, THF; (c) gl. acetic acid, NH2NH(CH2)2OH, 100 ꢀC, 1 h; (d) gl. acetic acid,
NH2NH(CH2)3OH, 100 ꢀC, 1 h; (e) polymer supported-PPh3, CBr4, DMF, rt, 3 days or CBr4, PPh3, CH2Cl2, rt, 3 days; (f) K2CO3/DMF, rt, 1 h; (g)
Oxone, MeOH/H2O, rt.

R. R. Ranatunge et al. / Bioorg. Med. Chem. 12 (2004) 1357–1366
1359
pyrazolyl-2-acetic acid 25 (Scheme 2) was targeted.
Compound 19 was alkylated with tert-butylbromoacetate
in the presence of K2CO3 to give 23, which was oxidized
with Oxone1 at 0 ꢀC to give the sulfone 24. Cleavage of
the tert-butyl ester group in 24 afforded imidazoli-
dino[1,2-d]pyrazolyl-2-acetic acid 25.
were assayed against COX-1 at 100 mM and COX-2 at
10 mM and 1 mM (Table 1). For the most potent and
selective COX-2 inhibitors, full IC50’s were then deter-
mined (Table 2).
The results reported in Table 1 show that the sub-
stituent at the position 5 of the pyrazolo[5,1-b]oxazoli-
dine is critically important. Having a cyclohexyl group,
7a showed selective COX-2 inhibition (COX-2 inhibi-
tion: 90% at 10 mM and 25% at 1 mM; COX-1 inhibi-
tion: 25% at 100 mM). Replacement of the cyclohexyl
group at position 5 of 7a by a phenyl group enhanced
COX-1 inhibitory activity slightly (COX-1 inhibition by
7b: 40% at 100 mM) while leaving COX-2 activity
unaffected. Surprisingly, substitution of a benzyl group
at position 5, as in 7c, resulted in complete loss of COX-1
and COX-2 activity. The COX inhibitory IC50’s for 7a
(COX-1>100 mM; COX-2 1.3mM) confirmed the con-
clusion that 7a is a highly potent and selective COX-2
inhibitor (Table 2).
In order to incoporate a gem dimethyl group, as found
in ML 3000, compound 28 was targeted and prepared as
shown in Scheme 3. Ketoester 3a was condensed with 1-
hydrazino-2-methyl-2-propanol30 in glacial acetic acid
at 100 ꢀC for 1 h to give the pyrazolediol 26. This was
subjected to cyclization under acidic conditions to pro-
vide the methyl sufide 27 along with unreacted 26. Oxi-
dation of methyl sulfide 27 with Oxone1 gave the
pyrazolo[5,1-b]1,3-oxazolidine 28.
3. Results and discussion
The compounds were tested for their ability to inhibit
COX-1 and COX-2 isozymes in human whole blood
(HWB).31À32 For this initial in vitro screen, compounds
On the basis of the COX-2 potency and selectivity
demonstrated by pyrazolo[5,1-b]oxazolidine 7a, this was
Scheme 2. (a) SOCl2, toluene, rt, 30 min, 97%; (b) NaCN, DMSO, rt, 2 h, 89%; (c) cyclohexanecarbonyl chloride, LiHMDS, THF, À78 ꢀC to rt,
67%; (d) gl. acetic acid, NH2NH(CH2)2OH, 100 ꢀC, 1 h, 64%; (e) MsCl, Et3N, CH2Cl2, 0 ꢀC, 10 min, 64%; (f) K2CO3, DMF, 60 ꢀC, 3 days, 44%;
(g) Oxone, MeOH, H2O, 0 ꢀC, 2 h; (h) MeI, K2CO3, rt, 7 days, 39%; (i) Ac2O, DMAP, CH2Cl2, rt, 16 h, 36%; (j) tert-Butylbromoacetate, K2CO3,
DMF, rt, 5d, 80%; (k) TFA, CH2Cl2, rt, 3 h, 69%.
Scheme 3. (a) gl. acetic acid, NH2NHCH2C(CH3)2OH, 100 ꢀC, 1 h; (b) neat phosphoric acd, 70 ꢀC, 6 h; (c) Oxone, MeOH/H2O, rt, 2 h.

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R. R. Ranatunge et al. / Bioorg. Med. Chem. 12 (2004) 1357–1366
Table 1. In vitro human whole blood COX-1 and COX-2 inhibition by bicyclic-pyrazole derivatives
% Inhibition HWBa
COX -2
COX-1
Compd
R
R1
100 mM
10 mM
1 mM
7a
7b
7c
Cyclohexyl
Phenyl
Benzyl
25
40
0
90
90
0
25
20
0
12a
Cyclohexyl
35
25
10
20
21
22
24
25
–H
–COCH3
–CH3
–CH2COOtBu
–CH2COOH
65
20
0
50
48
80
10
38
55
34
5
0
0
55
0
28
0
12.5
0
Celecoxib
Rofecoxib
65b
75
100
100
50
75
a Percent inhibition of COX-1 (100 mM) or COX-2 (10 and 1 mM) in human whole blood. Assays were performed in duplicate. Average % inhibition
using blood from two donors (see Experimental).
b COX-inhibition at 30 mM Celecoxib.
selected for further modification (Table 1). Changing
the bicyclic ring from five- to six-membered (to give
pyrazolo[5,1-b]oxazine 12) significantly compromised
COX-2 potency (COX-2 inhibition: 25% at 10 mM and
10% at 1 mM). This loss of COX-2 inhibitory potency
suggests that, in this series, a fused six-membered
bicyclic ring is detrimental to COX-2 activity.
and 5% at 1 mM; COX-1 inhibition: 65% at 100 mM).
Additional substitution at the available nitrogen of 20,
specifically N-acylation (to give 21) and N-methylation
(to give 22), reduced all COX inhibitory activity. Com-
pound 24, containing a bulky and hydrophobic tert-
butyl ester, showed good, but seemingly concentration
independent, COX-2 activity (COX-2 inhibition: 55% at
both 10 mM and 1 mM) and moderate selectivity versus
COX-1 (COX-1 inhibition: 50% at 100 mM) in com-
parison to 7a. The acid 25 was found to be a less potent
COX-2 inhibitor than 24. In view of the greater activity
of 24 over 25, other ester and amide derivatives could be
envisioned as rational attempts to enhance COX-2
inhibitor potency and selectivity. Finally, we explored
the effect of substitution on the saturated ring of 7a,
since the potent and selective COX-2 inhibitor ML 3000
has a bicyclic ring system substituted with two methyl
groups. Compound 28, which appeared to mimic this
feature, had however, almost zero activity indicating
that other features of ML 3000 are important con-
tributors to enzyme binding.
We next investigated substituting the oxygen in com-
pound 7a with a nitrogen atom. To this end, a series of
imidazolidino[1,2-d]pyrazoles was synthesized (Scheme
2) and evaluated for COX inhibition (Table 1). Com-
pound 20 showed good potency toward COX-2 at 10
mM, although with reduced COX-2 selectivity in com-
parison to 7a (COX-2 inhibition by 20: 80% at 10 mM
Table 2. IC50 Values of bicyclic-pyrazole, 7a and some standard
COX-2 inhibitors in human blood
IC50 (mM)
Compd
COX-1
COX-2
Celecoxib
Rofecoxib
ML300021
7a
14
40
1.2
0.3
0.21a
1.3
4. Conclusion
Activation of a hydroxyalkyl group attached to the
pyrazole nucleus followed by cyclization produced three
new series of bicyclic-pyrazoles. Several compounds
>100
a IC50 value for inhibition of cyclooxygenases.23

R. R. Ranatunge et al. / Bioorg. Med. Chem. 12 (2004) 1357–1366
1361
were found to be selective COX-2 inhibitors, the most
potent and selective being the pyrazolo[5,1-b]1,3-oxazo-
lidine 7a (IC50’s for COX-1>100 mM; COX-2 1.3 mM).
Although marginally less potent than celecoxib and
rofecoxib (Table 1), identification of 7a as a lead com-
pound from such a small series of compounds is
encouraging. Modification of 7a may generate still more
potent and selective inhibitors.
5.3. 1-(5-Cyclohexyl(2H,3H-pyrazolo[5,1-b]1,3-oxazolidin-
6-yl)-4-(methylsulfonyl) benzene (7a)
5.3.1. Methyl 2-(4-methylthiophenyl)acetate (2). Con-
centrated sulfuric acid (1 mL) was added dropwise to a
solution of 2-(4-methylthiophenyl)acetic acid 1 (5.0 g,
27.4 mmol) in MeOH (40 mL) at room temperature.
The resultant mixture was heated at 50 ꢀC for 16 h,
cooled to room temperature and the solvent was eva-
porated. The residue was dissolved in EtOAc, washed
with saturated NaHCO3, dried over Na2SO4 and fil-
tered. The filtrate was evaporated to give 2 (5.4 g,
ꢁ100%) as a viscous oil. 1H NMR d 7.18–7.26 (m, 4H),
3.69 (s, 3H), 3.58 (s, 2H), 2.47 (s, 3H). 13C NMR d
172.0, 137.4, 130.9, 129.8, 127.0, 52.1, 40.7, 16.0. MS
m/z 197 (MH+), 214 (MNH+4 ), 219 (MNa+), 137 (M-
COOCH3). Anal. calcd (C10H12O2S): C, 61.20; H, 6.16.
Found: C, 60.79; H, 5.80.
5. Experimental
5.1. COX-Inhibition—HWB assay
Fresh human blood, obtained by informed consent
from non-fasted donors of either sex who had not taken
asprin or any NSAID during the prior 14 days, was
collected in sodium heparin (20 units/mL) and dis-
tributed in 1 mL aliquots per well of 24-well tissue cul-
ture plate. The plates were placed on a gently rotating
platform shaker in a 5% CO2 incubator at 37 ꢀC for 15
min. Test compounds were dissolved and diluted in
DMSO, and 1 mL of each dilution of the test compound
was added per well in duplicate wells. To induce COX-
2, lipopolysaccharide from E. coli (Sigma Chemical Co.,
St. Louis, MO) was added at 10 mg/mL to appropriate
wells 15 min after the addition of the test compounds.
To activate COX-1, the calcium ionophore A23187
(Sigma Chemical Co., St Louis, MO) was added to a
final concentration of 25 mM to separate wells 4.75 h
after the addition of the test compounds. At 30 min
after A23187 addition or 5 h after LPS addition, all
incubations were terminated. The blood samples were
processed for thromboxane B2 determination and
assayed in duplicate by EIA (Cayman Chemical Co.,
Ann Arbor, MI).31 COX inhibition data in the text and
tables are derived from averages of two EIA determin-
ations on each of duplicate blood sample from two
donors.
5.3.2. Methyl 3-cyclohexyl-2-(4-methylthiophenyl)-3-oxo-
propanoate (3a). To a stirred solution of 2 (4.9 g, 25.0
mmol) in THF (50 mL) was added dropwise a solution
of lithium bis(trimethylsilyl)amide (1 M solution in
THF, 62.4 mL, 62.4 mmol) at À78 ꢀC under nitrogen.
The resulting solution was stirred at À78 ꢀC for 10 min
and then at room temperature for 1 h. The reaction
mixture was cooled to À78 ꢀC and cyclohexanecarbonyl
chloride (5.49 g, 37.4 mmol) was added dropwise. The
mixture was allowed to warm to 0 ꢀC over 1 h and then
stirred at 0 ꢀC for 1 h. Saturated NH4Cl was added and
the organic layer was separated. The aqueous phase was
extracted with EtOAc and the combined organic phases
were washed with brine and dried over Na2SO4. The
residue after filtration and evaporation of the solvent
was chromatographed on silica gel eluted with 1:9
EtOAc:Hex to give 3a (7.6 g, 99%) as a white crystalline
solid. Mp 104–106 ꢀC. H NMR d 13.12 (s, 1H), 7.20–
1
7.26 (m, 2H), 7.03–7.09 (m, 2H), 3.68 (s, 3H), 2.52 (s,
3H), 2.10–2.16 (m, 1H), 1.55–1.72 (m, 7H), 1.02–1.20
(m, 3H). 13C NMR d 180.8, 173.5, 137.2, 131.8, 131.7,
126.2, 101.9, 51.9, 41.2, 29.5, 25.7, 15.7. MS m/z 307
(MH+), 324 (MNH+4 ). Anal. calcd (C17H22O3S): C,
66.64; H, 7.24; N, 10.46. Found: C, 66.61; H, 7.34; N,
10.39.
5.2. General procedures
All reagents and anhydrous solvents were generally used
as received from the commercial supplier. Reactions
were routinely performed under a nitrogen atmosphere
in oven-dried glassware. Melting points were deter-
mined with an electrothermal heating block (Mettler)
5.3.3. 3-Cyclohexyl-1-(2-hydroxyethyl)-4-(4-methylthio-
phenyl)pyrazol-5-ol (4a). A mixture of 3a (5.52 g, 18.0
mmol) and 2-hydroxyethylhydrazine (6.17 g, 81.2
mmol) in glacial AcOH (24 mL) was heated at 100 ꢀC
for 1 h. The solvent was evaporated and dried under
vacuum to give a pale yellow solid which was dis-
solved in 1:9 MeOH:CH2Cl2. To this solution, water
was added and the resultant precipitate was filtered,
washed with water and then hexane to give 4a (2.75 g,
46%) as an off-white solid. Mp 204–205 ꢀC. 1H
NMR (d4-MeOH) d 7.26–7.32 (m, 4H), 3.98 (t, J=5.7
Hz, 2H), 3.80 (t, J=5.6 Hz, 2H), 2.76–2.84 (m,
1H), 2.47 (s, 3H), 1.22–1.87 (m, 10H). 13C NMR
(d4-MeOH) d 152.8, 138.0, 130.8, 130.3, 127.7, 105.4,
60.9, 47.6, 37.1, 32.9, 27.4, 26.9, 15.9. MS m/z 333
(MH+). Anal. calcd (C18H24N2O2S): C, 65.03; H, 7.28;
N, 8.43; S, 9.64. Found: C, 64.80; H, 7.30; N, 8.30; S,
9.53.
1
and are uncorrected. H and 13C NMR spectra were
recorded at 300 and 75 MHz, respectively. NMR spectra
were recorded in CDCl3 unless otherwise specified, and
chemical shifts are reported relative to tetramethylsilane
as an internal standard. Low-resolution mass spectra
were obtained using atmospheric pressure-turbo ion
spray ionization. Elemental analyses were performed by
Robertson Microlit Laboratories Inc., Madison, NJ.
Gravity and flash column chromatography were per-
formed using EM Science silica gel 60 (230–400 mesh).
Analytical TLC was performed on 250 mM pre-coated
EM Science silica gel 60 F254 aluminum sheets. Pre-
parative TLC was performed using 20Â20 cm 1000 mM
pre-coated silica gel plates (Whatman). Spots were
visualized under 254 nm light or after staining with
phosphomolybdate spray.

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R. R. Ranatunge et al. / Bioorg. Med. Chem. 12 (2004) 1357–1366
5.3.4. 1-[3-Cyclohexyl-5-hydroxy-1-(2-hydroxyethyl)pyr-
azol-4-yl]-4-(methylsulfonyl) benzene (5a). To a solution
of 4a (316 mg, 0.95 mmol) in MeOH (18 mL) was added
dropwise a solution of Oxone1 (1.35 g, 2.20 mmol) in
water (4 mL). The white suspension was stirred at room
temperature for 30 min. The solid was filtered and
washed with CH2Cl2. The filtrate was treated with water
to give a white precipitate. The precipitate was filtered
and washed with water and hexane to give 5a (0.15 g,
43%) as a white solid. Mp 247–249 C. H NMR (d4-
MeOH) d 7.96 (d, J=8.1 Hz, 2H), 7.69 (d, J=8.2 Hz,
2H), 4.02 (t, J=5.6 Hz, 2H), 3.81 (t, J=5.6 Hz, 2H),
3.13 (s, 3H), 2.84–2.96 (m, 1H), 1.20–1.95 (m, 10H). 13C
NMR (CDCl3/d4-MeOH) d 152.7, 139.8, 138.7, 130.2,
and then at room temperature for 1 h. The reaction
mixture was cooled to À78 ꢀC, and benzoyl chloride
(6.45 g, 45.9 mmol) was added dropwise. The mixture
was allowed to warm to room temperature over 1 h and
stirred at room temperature for 16 h. The mixture was
cooled to 0 ꢀC. To this solution, saturated NH4Cl was
added, and the organic layer was separated. The aqu-
eous phase was extracted with EtOAc, and the com-
bined organic phases were washed with brine and dried
over Na2SO4. The residue after filtration and evapora-
tion of the solvent was recrystallized from CH2Cl2/Hex
to ꢀgive 3b (7.97 g, 87%) as a pale yellow solid. Mp 82–
83 C. 1H NMR d 7.88–7.95 (m, 2H), 7.77–7.82 (m, 1H),
7.18–7.54 (m, 6H), 5.56 (s, 1H), 3.73 (s, 3H), 2.42 (s,
3H). MS m/z 301 (MH+), 318 (MNH4+).
ꢀ
1
128.3, 103.6, 60.7, 47.5, 44.6, 36.8, 32.7, 27.2, 26.6. MS
+
.
m/z 365 (MH ). Anal. calcd (C18H24N2O4S 1/2 mol
H2O): C, 57.89; H, 6.74; N, 7.50; S, 8.58. Found: C,
58.18; H, 6.54; N, 7.40; S, 8.40.
5.4.2. 1-(2-Hydroxyethyl)-4-(4-methylthiophenyl)-3-phenyl-
pyrazol-5-ol (4b). A mixture of 3b (3.5 g, 11.7 mmol)
and 2-hydroxyethylhydrazine (3.99 g, 52.4 mmol) in
glacial AcOH (35 mL) was heated at 100 ꢀC for 1 h. The
solvent was evaporated to give a pale yellow oil which
was dissolved in EtOAc. To this solution, water was
added, the resultant precipitate was filtered and washed
with water, hexane and then dried under vacuum to give
5.3.5. 1-[1-(2-bromoethyl)-3-cyclohexyl-5-hydroxypyrazol-
4-yl]-4-(methylsulfonyl)benzene (6a). To a stirred solu-
tion of 5a (140 mg, 0.38 mmol) and carbon tetra-
bromide (191 mg, 0.57 mmol) in CH2Cl2 (0.8 mL) at
0 ꢀC under nitrogen was added a solution of triphenyl-
phosphine (151 mg, 0.57 mmol) in CH2Cl2 (0.4 mL).
The resultant orange solution was stirred at room
temperature for 3 days. The residue after evaporation of
the solvent was chromatographed on silica gel eluted
with 0.5:9.5 MeOH: CH2Cl2 to give 6a (152 mg, 93%) as
a pale yellow foam. 1H NMR d 7.90 (d, J=8.2 Hz, 2H),
7.63 (d, J=8.3 Hz, 2H), 4.22 (t, J=6.0 Hz, 2H), 3.66 (t,
J=5.9 Hz, 2H), 3.07 (s, 3H), 2.78–2.82 (m, 1H), 1.20–
1.92 (m, 10H). MS m/z 427 / 429 (MH+).
4b (2.36 g, 62%) as a white solid. Mp 235–237 ꢀC. H
1
NMR (DMSO-d6) d 7.14–7.36 (m, 9H), 4.02 (t, J=6.2
Hz, 2H), 3.76 (t, J=6.3 Hz, 2H), 2.46 (s, 3H). 13C NMR
(DMSO-d6) d 145.7, 135.1, 129.7, 129.5, 128.2, 127.6,
125.9, 101.5, 59.5, 48.4, 14.8. MS m/z 327 (MH+), 349
(MNa+). Anal. calcd (C18H18N2O2S): C, 66.23; H, 5.56;
N, 8.58; S, 9.82. Found: C, 66.03; H, 5.57; N, 8.47; S,
9.82.
5.4.3. 1-(2-Bromoethyl)-4-(4-methylthiophenyl)-3-phenyl-
pyrazol-5-ol (8b). To a stirred solution of 4b (0.81 g,
2.48 mmol) in DMF (16 mL) was added polymer sup-
ported triphenylphosphine (1.65 g of resin, 3 mmol of P/
g of resin, 5 mmol). The mixture was stirred at room
temperature for 30 min under nitrogen. To this mixture,
carbon tetrabromide (1 g, 2.98 mmol) was added por-
tionwise. The resultant mixture was stirred at room
temperature for 4 days. The solid was filtered and
washed with EtOAc. The residue after evaporation of
the solvent was dissolved in EtOAc/MeOH, washed
with water, brine and then dried over Na2SO4. Fil-
tration and evaporation of the solvent gave 8b (0.76 g,
5.3.6. 1-(5-Cyclohexyl(2H,3H-pyrazolo[5,1-b]1,3-oxazo-
lidin-6-yl)-4-(methylsulfonyl) benzene (7a). To a solution
of 6a (0.15 g, 0.35 mmol) in DMF (9 mL), K2CO3 (58
mg, 0.45 mmol) was added. The resultant mixture was
stirred at room temperature for 3 h. The solid was fil-
tered and the solvent was evaporated. The residue was
extracted with EtOAc and the organic phase was
washed with water, brine and then dried over Na2SO4 .
The residue after filtration and evaporation of the sol-
vent was chromatographed on silica gel eluted with 1:1
EtOAc:CH2Cl2 to give 7a (75 mg, 62%) as a white solid.
Mp 172–173 C. H NMR d 7.94 (d, J=8.5 Hz, 2H),
7.61 (d, J=8.4 Hz, 2H), 5.15 (t, J=7.7 Hz, 2H), 4.36 (t,
J=8.3 Hz, 2H), 3.10 (s, 3H), 2.80–2.92 (m, 1H), 1.25–
2.05 (m, 10H). 13C NMR d 160.9, 157.4, 138.7, 136.7,
127.9, 127.2, 94.0, 75.7, 45.5, 44.8, 38.2, 32.7, 26.8, 26.2.
MS m/z 347 (MH+). Anal. calcd (C18H22N2O3S): C,
62.40; H, 6.40; N, 8.09. Found: C, 62.32; H, 6.30; N,
8.02.
ꢀ
1
1
78%) as a pale yellow foam. H NMR d 7.15–7.42 (m,
9H), 4.34 (t, J=6.5 Hz, 2H), 3.67 (t, J=7.1 Hz, 2H),
2.47 (s, 3H). MS m/z 390/ 392 (MH+).
5.4.4. 4-Methylthio-1-(5-phenyl(2H,3H-pyrazolo[5,1-b]1,3-
oxazolidin-6-yl))benzene (9b). Compound 9b was syn-
thesized in a manner similar to the synthesis of 7a using
8b (0.47 g, 1.21 mmol) and K2CO3 (0.22 g, 1.56 mmol)
in DMF (30 mL) to give 9b (0.2 g, 54%) as a white
foam. 1H NMR d 7.50–7.56 (m, 2H), 7.32–7.38 (m, 3H),
7.15–7.25 (m, 4H), 5.12 (t, J=7.7 Hz, 2H), 4.40 (t,
J=8.3 Hz, 2H), 2.47 (s, 3H). 13C NMR d 157.1, 154.5,
135.6, 134.5, 128.8, 128.5, 128.4, 128.1, 127.0, 95.4, 75.4,
45.6, 16.2. MS m/z 309 (MH+).
5.4. 4-(Methylsulfonyl)-1-(5-phenyl(2H,3H-pyrazolo[5,1-
b]1,3-oxazolidin-6-yl))benzene (7b)
5.4.1. Methyl 2-(4-methylthiophenyl)-3-oxo-3-phenylpro-
panoate (3b). To a stirred solution of 2 (6.0 g, 36.0
mmol) in THF (60 mL) was added dropwise a solution
of lithium bis(trimethylsilyl)amide (1 M solution in
THF, 76.5 mL, 76.5 mmol) at À78 ꢀC under nitrogen.
The resulting solution was stirred at À78 ꢀC for 10 min
5.4.5. 4-(Methysulfonyl)-1-(5-phenyl(2H,3H-pyrazolo[5,1-
b]1,3-oxazolidin-6 yl))benzene (7b). To a solution of 9b

R. R. Ranatunge et al. / Bioorg. Med. Chem. 12 (2004) 1357–1366
1363
(0.22 g, 0.71 mmol) in MeOH (9 mL) was added drop-
wise a solution of Oxone1 (0.88 g, 1.43 mmol) in water
(3 mL). The white suspension was stirred at room
temperature for 1 h. The solid was filtered and washed
with CH2Cl2. The filtrate was diluted with CH2Cl2, and
the layers were separated. The organic phase was
washed with water and then dried over Na2SO4. The
residue after filtration and evaporation of the solvent
was recrystallized from CH2Cl2/EtOAc/Hex to give 7b
(0.23 g, 95%) as a white crystalline solid. Mp 194–
after evaporation of the solvent was chromatographed
on silica gel eluted with 1:1:2 EtOAc:Hex:CH2Cl2 to
give 9c (0.34 g) contaminated with triphenylphosphine
as a white foam which was used for the next step with-
out further purification. MS m/z 323 (MH+).
5.6.1. 4-(Methysulfonyl)-1-(5-benzyl(2H,3H-pyrazolo[5,1-
b]1,3-oxazolidin-6-yl))benzene (7c). Compound 7c was
synthesized in a manner similar to the synthesis of 7b
using 9c (0.34 g, 1.06 mmol) in MeOH (13 mL) and
Oxone1 (1.29 g, 2.1 mmol) in water (4 mL). The residue
after filtration and evaporation of the solvent was
chromatographed on silica gel eluted with 1:1:2 EtOAc:
Hex:CH2Cl2 to give 7c (70 mg, 19%) as a white solid.
Mp 169–170 ꢀC. 1H NMR d 7.81 (d, J=8.6 Hz, 2H), 7.52
(d, J=8.6 Hz, 2H), 7.19–7.30 (m, 5H), 5.17 (t, J=7.8
Hz, 2H), 4.38 (t, J=7.7 Hz, 2H), 4.15 (s, 2H), 3.01 (s,
3H). 13C NMR d 157.7, 154.0, 138.7, 138.0, 136.6,
128.7, 128.5, 127.8, 126.8, 126.6, 95.2, 75.8, 45.5, 44.7,
35.6. MS m/z 355 (MH+). Anal. calcd (C19H18N2O3S):
C, 64.39; H, 5.12; N, 7.90; S, 9.05. Found: 64.41; H,
5.07; N, 7.84; S, 8.99.
195 ꢀC. H NMR d 7.79 (d, J=8.5 Hz, 2H), 7.35–7.52
1
(m, 7H), 5.20 (t, J=7.8 Hz, 2H), 4.44 (t, J=7.8 Hz,
2H), 3.04 (s, 3H). 13C NMR d 157.7, 154.9, 138.0, 137.0,
134.0, 128.8, 128.6, 128.6, 127.8, 127.6, 94.6, 75.9, 45.6,
44.7. MS m/z 341 (MH+). Anal. calcd (C18H16N2O3S):
C, 63.51; H, 4.74; N, 8.23; S, 9.42. Found: C, 63.26; H,
4.70; N, 8.14; S, 9.32.
5.5. 4-(Methylsulfonyl)-1-(5-benzyl(2H,3H-pyrazolo[5,1-
b]1,3-oxazolidin-6-yl))benzene (7c)
5.5.1. Methyl 2-(4-methylthiophenyl)-3-oxo-4-phenylbuta-
noate (3c). Compound 3c was synthesized in a manner
similar to the synthesis of 3b using 2 (8.39 g, 42.8
mmol), phenyl acetyl chloride (9.9 g, 64.2 mmol) and
lithium bis(trimethylsilyl)amide (1 M solution in THF,
107 mL, 107 mmol) in THF (60 mL). The residue after
filtration and evaporation of the solvent was chromato-
graphed on silica gel eluted with 1:9 EtOAc:Hex to give
a mixture of ketoenol tautomers, 3c (10 g, 75%) as a
colorless oil. MS m/z 315 (MH+), 332 (MNH4+).
5.7. 1-(2-Cyclohexyl(5H,6H,7H-pyrazolo[5,1-b]1,3-oxaza-
perhydroin-3-yl))-4-(methylsulfonyl)benzene, (12a)
5.7.1. 3-Cyclohexyl-1-(3-hydroxypropyl)-4-(4-methylthio-
phenyl)pyrazol-5-ol (10). A mixture of 3a (1.4 g, 4.6
mmol) and 3-hydroxypropylhydrazine29 (1.85 g, 20.6
mmol) in glacial AcOH (10 mL) was heated at 100 ꢀC
for 1 h. The resultant solution was cooled to room
temperature, neutralized with saturated NaHCO3 and
extracted with 9:1 CH2Cl2/MeOH. The combined
extracts were dried over Na2SO4, filtered and evapo-
rated. The residue was chromatographed on silica gel
eluted with MeOH:CH2Cl2 to give 10 (0.85 g, 52%) as
an oil. 1H NMR (DMSO-d6) d 7.20–7.50 (m, 4H), 3.90–
4.10 (m, 2H), 3.40–3.70 (m, 2H), 2.80–3.00 (m, 1H), 2.45
(s, 3H), 1.20–2.20 (m, 12H). MS m/z 361 (MH+).
5.5.2. 1-(2-Hydroxyethyl)-4-(4-methylthiophenyl)-3-benzyl-
pyrazol-5-ol (4c). A mixture of 3c (4.89 g, 15.6 mmol)
and 2-hydroxyethylhydrazine (5.33 g, 70.0 mmol) in
glacial AcOH (35 mL) was heated at 100 ꢀC for 1 h.
The residue after evaporation of the solvent was chro-
matographed on silica gel eluting with 0.2:9.8 to
0.5:9.5 MeOH:CH2Cl2 to give 4c (2 g, 38%) as a pale
yellow solid. Mp 121–123 ꢀC. H NMR d 7.00–7.26 (m,
1
9H), 3.75–3.85 (m, 4H), 3.60–3.75 (m, 2H), 2.41 (s, 3H).
13C NMR d 160.3, 145.5, 137.2, 136.5, 129.1, 128.8,
128.5, 128.5, 126.9, 126.7, 105.9, 61.0, 47.3, 32.1, 15.9.
5.7.2. 1-(2-Cyclohexyl(5H,6H,7H-pyrazolo[5,1-b]1,3-ox-
azaperhydroin-3-yl))-4-methylthiobenzene, (11). To a
stirred solution of 10 (0.8 g, 2.3 mmol) in DMF (20 mL)
was added polymer supported triphenylphosphine (1.54
g of resin, 3 mmol of P/g of resin, 4.6 mmol). The mix-
ture was stirred at room temperature for 30 min under
nitrogen. To this mixture, carbon tetrabromide (0.92 g,
2.8 mmol) was added portionwise. The resultant mix-
ture was stirred at room temperature for 5 days. The
solid was filtered and washed with EtOAc. The residue
after evaporation of the solvent was diluted with 9:1
CHCl3:MeOH washed with water, brine and then dried
over Na2SO4. The residue after filtration and evapora-
tion of the solvent was chromatographed on silica gel
eluted with 9:1 CH2Cl2:MeOH to give 11 (0.4 g, 53%).
1H NMR d 7.19–7.42 (m, 4H), 3.80–4.02 (m, 4H), 2.72–
2.85 (m, 1H), 2.52–2.69 (m, 2H), 2.41 (s, 3H), 1.20–2.05
(m, 10H). MS m/z 329 (MH+).
+
.
MS m/z 341 (MH ). Anal. calcd (C19H20N2O2S 1/2 mol
H2O): 65.30; H, 6.05; N, 8.02. Found: C, 65.33; H, 5.88;
N, 8.13.
5.5.3. 1-(2-Bromoethyl)-4-(4-methylthiophenyl)-3-benzyl-
pyrazol-5-ol (8c). Compound 8c was synthesized in a
manner similar to the synthesis of 6a using 4c (1 g, 2.94
mmol), carbon tetrabromide (1.17 g, 3.53 mmol) and
triphenylphosphine (0.93 g, 3.53 mmol) in CH2Cl2 to
give 8c (1.08 g, 91%) as a pale yellow foam. 1H NMR d
7.13–7.30 (m, 9H), 4.25 (bt, J=6.4 Hz, 2H), 3.95 (s,
2H), 3.65 (bs, 1H), 3.62 (bt, J=6.4 Hz, 2H), 2.47 (s,
3H). MS m/z 403/405 (MH+).
5.6. 4-Methylthio-1-(5-benzyl(2H,3H-pyrazolo[5,1-b]1,3-
oxazolidin-6-yl))benzene (9c)
5.7.3. 1-(2-Cyclohexyl(5H,6H,7H-pyrazolo[5,1-b]1,3-ox-
azaperhydroin-3-yl))-4-(methylsulfonyl)benzene,
The compound 9c was synthesized in a manner similar
to the synthesis of 7a using 8c (1.1 g, 2.7 mmol) and
K2CO3 (0.49 g, 3.53 mmol) in DMF (10 mL). The residue
(12a).
Compound 12a was synthesized in a manner similar to
the synthesis of 7b using 11 (50 mg, 0.15 mmol) in

1364
R. R. Ranatunge et al. / Bioorg. Med. Chem. 12 (2004) 1357–1366
MeOH (2 mL) and Oxone1 (0.19 g, 0.3 mmol) in water
(1 mL). The residue after workup was chromatographed
on silica gel eluted with 1:9 MeOH:CH2Cl2 to give 12a
(30 mg, 55%) as a white solid. Mp 145–148 ꢀC. 1H
NMR d 7.97 (d, J=8.5 Hz, 2H), 7.66 (d, J=8.4 Hz,
2H), 3.80–4.05 (m, 4H), 3.10 (s, 3H), 2.75–2.93 (m, 1H),
2.60–2.75 (m, 2H); 1.20–2.05 (m, 10H). 13C NMR d
159.8, 148.9, 138.8, 137.4, 129.6, 127.4, 108.4, 46.7, 44.6,
40.6, 36.2, 31.1, 27.4, 26.2, 25.7. MS m/z 361 (MH+).
Anal. calcd (C16H19NOS): C, 70.29; H, 7.01; N, 5.12.
Found: C, 70.41; H, 7.08; N, 4.90.
5.8.4. 2-[5-Amino-3-cyclohexyl-4-(4-methylthiophenyl)pyr-
azolyl]ethan-1-ol (17). A mixture of 16 (2.89 g, 10.6
mmol) and 2-hydroxyethylhydrazine (3.63 g, 47.6
mmol) in glacial AcOH (12 mL) was heated at 100 ꢀC
for 1 h. The residue after evaporation of the solvent
was chromatographed on silica gel eluted with
1:10 MeOH:CH2Cl2 to give 17 (2.25 g, 64%) as a white
.
Anal. calcd (C19H24N2O3S 1/4 mol H2O): C, 62.52; H,
6.77; N, 7.67. Found: C, 62.27; H, 6.76; N, 7.57.
solid. Mp 108–110 ꢀC. H NMR d 7.16–7.40 (m, 4H),
1
3.95–4.15 (m, 4H), 3.75 (bs, 2H), 2.51–2.62 (m, 1H),
2.52 (s, 3H), 2.10 (bs, 1H), 1.15–1.95 (m, 10H). 13C
NMR d 149.0, 137.5, 130.9, 125.4, 124.5, 122.0, 98.4,
57.0, 44.0, 31.1, 27.6, 21.5, 20.9, 10.7. MS m/z 332
(MH+). Anal. calcd (C18H25N3OS): C, 65.22; H, 7.60;
N, 12.68. Found: 64.82; H, 7.50; N, 12.47.
5.8. 1-(2-Cyclohexylimidazolidino[1,2-d]pyrazol-3-yl)-4-
(methylsulfonyl)benzene (20)
5.8.1. 1-(Chloromethyl)-4-methylthiobenzene (14). To a
solution of 4-methylthiobenzyl alcohol 13 (8.5 g, 55.1
mmol) in toluene (85 mL) was added dropwise neat
thionyl chloride (4.82 mL, 7.87 g, 66.1 mmol) at room
temperature. The resultant pale yellow solution was stir-
red at room temperature for 30 min, and brine was
added. The organic phase was separated, washed with
brine, dried over Na2SO4 and filtered. The solvent was
5.8.5. 2-[5-Amino-3-cyclohexyl-4-(4-methylthiophenyl)-
pyrazolyl]ethyl methylsulfonate (18). To a stirred solu-
tion of 17 (1.32 g, 3.98 mmol) and triethylamine (0.83
mL, 0.67 g, 5.97 mmol) in CH2Cl2 (20 mL) at 0 ꢀC
under nitrogen, was added dropwise methanesulfonyl
chloride (0.46 g, 0.31 mL, 3.98 mmol). The mixture was
stirred at 0 ꢀC for 10 min. Water was added, and the
layers were separated. The organic phase was washed
with water and dried over Na2SO4. The residue after
filtration and evaporation of the solvent was chromato-
graphed on silica gel eluted with 1:1 EtOAc:Hex to give
1
evaporated to give 14 (9.2 g, 97%) as a viscous oil. H
NMR d 7.20–7.35 (m, 4H), 4.56 (s, 2H), 2.49 (s, 3H).
13C NMR d 139.3, 134.3, 129.2, 126.7, 46.1, 15.8.
5.8.2. 2-(4-Methylthiophenyl)ethanenitrile (15). To a
stirred suspension of sodium cyanide (3.15 g, 64.2
mmol) in DMSO (15 mL) was added dropwise a solu-
tion of 14 (9.2 g, 53.4 mmol) in DMSO (5 mL). The
resultant mixture was stirred at room temperature for 2
h to give a pale yellow solution. Saturated NaCl was
added, and the crude reaction mixture was extracted
with EtOAc. The combined organic phases were washed
with saturated NaCl, dried over Na2SO4 and filtered.
The solvent was evaporated to give 15 (7.74 g, 89%) as
1
18 (1.04 g, 64%) as a colorless oil. H NMR d 7.31 (d,
J=8.2 Hz, 2H), 7.16 (d, J=8.1 Hz, 2H), 4.60 (t, J=4.9
Hz, 2H), 4.31 (t, J=4.9 Hz, 2H), 3.63 (bs, 2H), 2.84 (s,
3H), 2.45–2.65 (m, 1H), 2.50 (s, 3H), 1.15–1.85 (m,
10H). 13C NMR d 155.6, 143.1, 136.9, 130.7, 130.2,
127.6, 104.9, 69.6, 46.9, 37.4, 36.8, 33.4, 27.1, 26.5, 16.4.
MS m/z 410 (MH+).
a pale yellow solid. Mp 35–36 ꢀC. H NMR d 7.20–7.30
5.8.6. 1-(2-Cyclohexylimidazolidino[1,2-d]pyrazol-3-yl)-4-
methylthiobenzene (19). Potassium carbonate (1.01 g,
7.33 mmol) was added to a solution of 18 (1.0 g, 2.44
mmol) in DMF (30 mL). The resultant mixture was
stirred at room temperature for 1 h and at 60 ꢀC for 16
h. The solid was filtered and the solvent was evaporated.
Ethyl acetate was added, and the organic phase washed
with water and dried over Na2SO4. The residue after
filtration and evaporation of the solvent was chromato-
graphed on silica gel eluted with 1:1 EtOAc:Hex to
0.1:1:1 MeOH:EtOAc:Hex to give 19 (0.34 g, 44%) as a
pale brown solid. Mp 128–130 ꢀC. 1H NMR d 7.20–7.35
(m, 4H), 4.12–4.25 (m, 2H), 3.90–4.05 (m, 2H), 3.70 (bs,
1H), 2.65–2.80 (m, 1H), 2.50 (s, 3H), 1.48–2.00 (m, 7H),
1.20–1.43 (m, 3H). 13C NMR d 160.3, 150.9, 134.9,
131.2, 128.0, 127.5, 98.3, 49.2, 46.2, 37.3, 33.2, 26.9,
26.3, 16.3. MS m/z 314 (MH+). Anal. calcd
1
(m, 4H), 3.69 (s, 2H), 2.47 (s, 3H). 13C NMR d 138.8,
128.4, 127.1, 126.6, 117.9, 23.2, 15.8.
5.8.3. 3-Cyclohexyl-2-(4-methylthiophenyl)-3-oxopropane-
nitrile (16). To a stirred solution of 15 (4.0 g, 24.5
mmol) in THF (95 mL) was added dropwise a solution
of lithium bis(trimethylsilyl)amide (1 M solution in
THF, 61.3 mL, 61.3 mmol) at À78 ꢀC under nitrogen.
The resulting solution was stirred at À78 ꢀC for 10 min
and then at room temperature for 1 h. The reaction
mixture was cooled to À78 ꢀC, and cyclohexanecarbonyl
chloride (5.40 g, 36.8 mmol) was added dropwise. The
mixture was allowed to warm to 0 ꢀC over 1 h and stir-
red at 0 ꢀC for 1.5 h. Saturated NH4Cl was added, and
the organic layer was separated. The aqueous phase was
extracted with EtOAc, and the combined organic phases
were washed with brine and dried over Na2SO4. The
residue after filtration and evaporation of the solvent
was chromatographed on silica gel eluted with 1:5 to 1:3
to 1:1 EtOAc:Hex to give 16 (4.48 g, 67%) as a pale
.
(C18H23N3S 1/4 mol H2O): C, 67.99; H, 7.45; N, 13.22.
Found: C, 68.27; H, 7.19; N, 13.07.
5.8.7. 1-(2-Cyclohexylimidazolidino[1,2-d]pyrazol-3-yl)-4-
(methylsulfonyl)benzene (20). To a solution of 19 (100
mg, 0.32 mmol) in MeOH (3 mL) was added dropwise a
solution of Oxone1 (294 mg, 0.47 mmol) in water (0.6
mL) at 0 ꢀC. The white suspension was stirred at 0 ꢀC
for 2 h. The solid was filtered and washed with CH2Cl2.
ꢀ
1
yellow solid. Mp 64–65 C. H NMR d 7.20–7.38 (m,
4H), 4.75 (bs, 1H), 2.57–2.68 (m, 1H), 2.48 (s, 3H),
1.10–1.80 (m, 10H). 13C NMR (CDCl3/d4-MeOH) d
201.9, 140.5, 128.5, 127.7, 126.9, 126.0, 116.5, 29.0, 28.5,
25.3, 25.0, 15.2. MS m/z 274 (MH+), 291 (MNH4+).

R. R. Ranatunge et al. / Bioorg. Med. Chem. 12 (2004) 1357–1366
1365
1
The filtrate was diluted with CH2Cl2, and the layers
were separated. The organic phase was washed with
water and dried over Na2SO4. The residue after fil-
tration and evaporation of the solvent was chromato-
graphed on silica gel eluted with 0.1:1:1 MeOH/EtOAc/
Hex to give 20 (60 mg, 54%) as a white foam. Mp 57 ꢀC.
1H NMR d 7.84 (d, J=8.3 Hz, 2H), 7.47 (d, J=8.3 Hz,
2H), 4.32 (bs, 1H), 4.16 (t, J=7.3 Hz, 2H), 4.00 (t,
J=7.3 Hz, 2H), 3.05 (s, 3H), 2.78 (tt, J=3.1 Hz and
11.8 Hz, 1H), 1.45–2.00 (m, 7H), 1.15–1.42 (m, 3H). 13C
NMR d 154.8, 146.6, 135.2, 130.8, 122.6, 121.9, 92.1,
43.9, 40.8, 39.4, 32.2, 27.7, 21.5, 20.9. MS m/z 346
oil. H NMR d 7.21–7.27 (m, 2H), 7.12–7.21 (m, 2H),
4.19 (t, J=7.4 Hz, 2H), 3.91 (t, J=8.4 Hz, 2H), 3.57 (s,
2H), 2.51 (s, 3H), 2.42–2.64 (m, 1H), 1.42–1.95 (m, 7H),
1.39 (s, 9H), 1.12–1.32 (m, 3H). 13C NMR d 168.7,
160.8, 150.6, 136.0, 130.4, 129.9, 126.7, 97.9, 81.8, 55.4,
51.3, 45.8, 36.8, 33.2, 28.1, 26.8, 26.2, 16.0. MS m/z 428
(MH+).
5.9.2. tert-Butyl 2-{2-cyclohexyl-3-[4-(methylsulfonyl)-
phenyl]imidazolidino[1,2-d]pyrazol-4-yl}acetate (24). To
a solution of 23 (70 mg, 0.16 mmol) in MeOH (1.5 mL)
was added dropwise a solution of Oxone1 (150 mg, 0.25
mmol) in water (0.4 mL) at 0 ꢀC. The white suspension
was stirred at 0 ꢀC for 6 h. The solid was filtered and
washed with CH2Cl2. The filtrate was diluted with
CH2Cl2 and the layers were separated. The organic
phase was washed with water, 5% NaHCO3, dried over
Na2SO4 and filtered. The residue after evaporation of
the solvent was chromatographed on silica gel eluted
with 1:1 EtOAc:CH2Cl2 to give 24 (68 mg, 90%) as a
+
.
(MH ). Anal. calcd (C18H23N3O2S 1/4 mol H2O): C,
61.77; H, 6.77; N, 12.00. Found: C, 61.70; H, 6.81; N,
11.81.
5.8.8. 4-Acetyl-2-cyclohexyl-3-[4-(methylsulfonyl)phenyl]-
imidazolidino[1,2-d]pyrazole (21). To a solution of 20 (70
mg, 0.2 mmol) and DMAP (24.7 mg, 0.2 mmol) in
CH2Cl2 (1 mL) was added dropwise acetic anhydride
(38 mL, 41.4 mg, 0.2 mmol). The reaction mixture was
stirred at room temperature for 24 h. The residue after
evaporation of the solvent was dissolved in EtOAc,
washed with 0.1 N HCl, water, dried over Na2SO4, fil-
tered and evaporated. The crude material was recrys-
tallized from CH2Cl2/EtOAc/Hex to give 21 (28 mg,
36%) as a white solid. Mp 198–199 ꢀC. 1H NMR
(DMSO-d6) d 7.80–8.04 (m, 2H), 7.29–7.52 (m, 2H),
4.48–4.62 (bs, 2H), 4.22–4.48 (bs, 2H), 3.11 (s, 3H),
2.28–2.48 (m, 1H), 1.91–2.28 (m, 1H), 1.40–1.87 (m,
9H), 1.08–1.37 (m, 3H). 13C NMR (DMSO-d6 at 373 K)
d 166.2, 159.5, 142.3, 140.3, 139.3, 131.8, 126.2, 102.4,
51.3, 45.2, 44.4, 36.9, 33.1, 26.5, 26.2, 22.7. MS m/z 388
(MH+), 405 (MNH+4 ). Anal. calcd (C20H25N3O3S): C,
61.99; H, 6.50; N, 10.84. Found: C, 61.76; H, 6.22; N,
10.68.
white foam. Mp 56–58 ꢀC. H NMR d 7.91 (d, J=8.3
1
Hz, 2H), 7.42 (d, J=8.3 Hz, 2H), 4.22 (t, J=7.5 Hz,
2H), 3.95 (t, J=7.4 Hz, 2H), 3.56 (s, 2H), 3.10 (s, 3H),
2.42–2.62 (m, 1H), 1.50–1.95 (m, 7H), 1.36 (s, 9H),
1.10–1.30 (m, 3H). 13C NMR d 168.5, 160.5, 151.1,
139.6, 137.7, 130.0, 127.6, 97.1, 82.2, 55.7, 51.4, 45.9,
44.7, 36.9, 33.2, 28.1, 26.8, 26.2. MS m/z 460 (MH+).
5.9.3. 2-{6-Cyclohexyl-7-[4-(methylsulfonyl)phenyl]-imid-
azolidino[1,2-d]pyrazolyl}acetic acid (25). To a solution
of 24 (0.14 g, 0.3 mmol) in CH2Cl2 (1 mL) was added
dropwise TFA (1 mL) at room temperature. The mix-
ture was stirred at room temperature for 3 h. The sol-
vent was evaporated. The residue was chromatographed
on silica gel eluted with 0.1:1:1 MeOH:EtOA:Hex to
2:8 MeOH:CH2Cl2 to give 25 (84 mg, 69%) as an off-
white solid. Mp 83 ꢀC. H NMR d 7.93 (d, J=8.1 Hz,
1
5.8.9. 1-(6-Cyclohexyl-1-methylimidazolidino[1,2-d]pyra-
zol-7-yl)-4-(methylsulfonyl) benzene (22). A mixture of
20 (25 mg, 0.07 mmol), methyl iodide (4.5 mL, 10.3 mg,
0.07 mol) and K2CO3 (10 mg, 0.07 mmol) in DMF (0.4
mL) was stirred at room temperature for 7 days. The
solvent was evaporated. The residue was chromato-
graphed using preparative layer chromatography eluted
with 1:1ꢀEtOAc:Hex to give 22 (10.2 mg, 39%). Mp
138–140 C. 1H NMR d 7.93 (d, J=8.4 Hz, 2H), 7.45 (d,
J=8.4 Hz, 2H), 4.16 (t, J=7.4 Hz, 2H), 3.73 (t, J=7.3
Hz, 2H), 3.10 (s, 3H), 2.57 (s, 3H), 2.41–2.57 (m, 1H);
1.15–1.90 (m, 10H). MS m/z 360 (MH+).
2H), 7.44 (d, J=8.2 Hz, 2H), 4.24 (t, J=7.5 Hz, 2H),
3.98 (t, J=7.7 Hz, 2H), 3.71 (s, 2H), 3.10 (s, 3H), 2.47–
2.57 (m, 1H), 1.67–1.82 (m, 4H), 1.40–1.60 (m, 2H);
1.10–1.32 (m, 4H). 13C NMR d 160.6, 151.3, 152.0,
138.1, 130.2, 127.8, 127.5, 97.4, 55.7, 50.6, 46.0, 44.7,
36.8, 33.0, 26.7, 26.1. MS m/z 404 (MH+). LCMS
(100%).
5.10. 1-(6-Cyclohexyl-2,2-dimethyl(3H-pyrazolo[5,1-b]1,3-
oxazolidin-7-yl))-4-(methylsulfonyl)benzene (28)
5.10.1. 3-Cyclohexyl-1-(2-hydroxy-2-methylpropyl)-4-(4-
methylthiophenyl)pyrazol-5-ol (26). A mixture of 3a
(0.25 g, 0.82 mmol) and 1-hydrazino-2-methyl-2-propa-
nol30 (0.38 g, 3.7 mmol) in glacial AcOH (3 mL) was
heated at 95 ꢀC for 5 h. The solvent was evaporated.
The residue was recrystallized from CHCl3/Hex to give
26 (0.2 g, 68%) as a white solid. MS m/z 361 (MH+).
5.9. tert-Butyl 2-{2-cyclohexyl-3-[4-(methylsulfonyl)phe-
nyl]-imidazolidino[1,2-d]pyrazol-4-yl}acetate (24)
5.9.1. tert-Butyl 2-[2-cyclohexyl-3-(4-methylthiophenyl)-
imidazolidino[1,2-d]pyrazol-4-yl]acetate (23). Compound
19 (0.22 g, 0.7 mmol) was dissolved in DMF (5 mL) and
K2CO3 (0.19 g, 1.4 mmol) added followed by tert-
butylbromoacetate (0.16 mL, 0.21 g, 1.1 mmol). The
resulting solution was stirred at room temperature for 5
days, diluted with a large volume of EtOAc, washed
with water, dried over Na2SO4, filtered and evaporated.
The residue was chromatographed on silica gel eluted
with 1:1 EtOAc:CH2Cl2 to give 23 (0.24 g, 80%) as an
5.10.2. 1-(6-Cyclohexyl-2,2-dimethyl(3H-pyrazolo[5,1-
b]1,3-oxazolidin-7-yl))-4-methylthiobenzene (27). A solu-
tion of 26 (0.16 g, 0.44 mmol) in neat phosphoric acid (1
mL) was heated at 70 ꢀC for 6 h. The reaction mixture
was diluted with CH2Cl2, and cooled to 0 ꢀC. Saturated
NaHCO3 was added, and the layers were separated. The
aqueous layer was extracted with CH2Cl2, the combined

1366
R. R. Ranatunge et al. / Bioorg. Med. Chem. 12 (2004) 1357–1366
organic phase was washed with saturated NaHCO3 and
dried over Na2SO4. The residue after filtration and eva-
poration of the solvent was chromatographed on silica
gel eluted with 1:1 EtOAc:Hex to give 27 (50 mg, 33%)
9. Hinz, B.; Brune, K. J. Pharm. Exp. Therap. 2002, 300,
367.
10. DeWitt, D. L. Mol. Pharmacol. 1999, 55, 625.
11. Mitchell, J. A.; Akarasereenont, P.; Thiemermann, C.;
Flower, R. J.; Vane, J. R. Proc. Natl. Acad. Sci. U.S.A.
1993, 90, 11693.
1
as an oil. H NMR d 7.15–7.32 (m, 4H), 4.03 (s, 2H),
2.70–2.88 (m, 1H), 2.49 (s, 3H), 1.65 (s, 6H), 1.22–1.95
(m, 10H). 13C NMR d 160.3, 155.6, 134.9, 130.0, 127.8,
127.5, 94.6, 76.7, 57.3, 37.8, 32.9, 27.8, 26.9, 26.4, 16.5.
MS m/z 343 (MH+).
12. Penning, T. D.; Tally, J. J.; Bertenshaw, S. R.; Carter,
J. S.; Collins, P. W.; Doctor, S.; Graneto, M. J.; Lee, L. F.;
Malecha, J. W.; Miyashiro, J. M.; Rogers, R. S.; Rogier,
D. J.; Yu, S. S.; Anderson, G. D.; Burton, E. G.; Cog-
burn, J. N.; Gregory, S. A.; Koboldt, C. M.; Perkins,
W. E.; Seibert, K.; Veenhuizen, A. W.; Zhang, Y. Y.;
Isakson, P. C. J. Med. Chem. 1997, 40, 1347.
13. Prasit, P.; Wang, Z.; Brideau, C.; Chan, C.-C.; Charleson,
S.; Cromlish, W.; Ethier, D.; Evans, J. F.; Ford-Hutch-
inson, A. W.; Gauthier, J. Y.; Gordon, R.; Guay, J.;
Gresser, M.; Kargman, S.; Kennedy, B.; Leblanc, Y.;
Leger, S.; Mancini, J.; O’Neill, G. P.; Ouellet, M.; Percival,
M. D.; Perrier, H.; Riendeau, D.; Rodger, I.; Tagari, P.;
Therien, M.; Vikers, P.; Wong, E.; Xu, L.-J.; Young, R. N.;
Zamboni, R.; Boyce, S.; Rupniak, N.; Forrest, M.; Visco,
D.; Patrick, D. Bioorg. Med. Chem. Lett. 1999, 9, 1773.
14. Talley, J. J.; Brown, D. L.; Carter, J. S.; Graneto, M. J.;
Koboldt, C. M.; Masferrer, J. L.; Perkins, W. E.; Rogers,
R. S.; Shaffer, A. F.; Zhang, Y. Y.; Zweifel, B. S.; Seibert,
K. J. Med. Chem. 2000, 43, 775.
5.10.3. 1-(6-Cyclohexyl-2,2-dimethyl(3H-pyrazolo[5,1-
b]1,3-oxazolidin-7-yl))-4-(methylsulfonyl)benzene (28). To
a solution of 27 (30 mg, 0.09 mmol) in MeOH (1.1 mL)
was added dropwise a solution of Oxone1 (0.11 g, 0.18
mmol) in water (0.3 mL). The white suspension was
stirred at room temperature for 1 h. The solid was fil-
tered, and washed with CH2Cl2. The filtrate was diluted
with CH2Cl2, and the layers were separated. The
organic phase was washed with water and then dried
over Na2SO4. The residue after filtration and evapora-
tion of the solvent was chromatographed on silica gel
eluted with 0.1:1:1 MeOH:EtOAc:Hex to give 28 (18
mg, 55%) as a white solid. Mp 210 ꢀC with dec. 1H
NMR d 7.91 (d, J=8.6 Hz, 2H), 7.58 (d, J=8.6 Hz,
2H), 4.06 (s, 2H), 3.06 (s, 3H), 2.73–2.81 (m, 1H), 1.69
(s, 6H), 1.10–2.05 (m, 10H). MS m/z 375 (MH+).
LCMS (97.6%).
15. Meyer-Kirchrath, J.; Schror, K. Curr. Med. Chem. 2000,
7, 1121.
16. Catella-Lawson, F.; Crofford, L. J. Am. J. Med. 2001,
110, 28 S.
17. Mukherjee, D.; Nissen, S. E.; Topol, E. J. JAMA 2001,
286, 954.
Acknowledgements
18. Wolfe, M. M.; Lichtenstein, D. R.; Singh, G. N. Engl. J.
Med. 1999, 340, 1888.
19. de Gaetano, G.; Donati, M. B.; Cerletti, C. Trends Pharm.
Sci. 2003, 24, 245.
20. Beswick, P.; Campbell, I.; Naylor, A. PCT Appl. WO 96/
31509, Oct. 10, 1996.
The authors wish to thank Dr. Radha Iyengar for help-
ful comments and suggestions.
21. Beswick, P.; Campbell, I.; Mathews, N.; Naylor, A. PCT
Appl. WO 99/12930, March 18, 1999.
References and notes
22. Cossy, J.; Belotti, D. Tetrahedron 1999, 55, 5145.
23. Laufer, S. A.; Augustin, J.; Dannhardt, G.; Kiefer, W. J.
Med. Chem. 1994, 37, 1894.
24. Kirschning, A.; Ries, M.; Domann, S.; Martin, W.;
Albrecht, W.; Arnold, P.; Laufer, S. Bioorg. Med. Chem.
Lett. 1997, 7, 903.
1. Skoutakis, V. A.; Carter, C. A.; Micklee, T. R.; Smith,
V. H.; Arkin, C. R.; Allissantros, J.; Petty, D. A. Drug
Intell. Clin. Pharm. 1988, 3, 850.
2. Lombardino, G. Non Steroidal Anti-inflammatory Drugs;
John Wiley & Sons: New York, 1985.
3. Dannhardt, G.; Kiefer, W. Eur. J. Med. Chem. 2001, 36, 109.
4. Carter, J. S. Exp. Opin. Ther. Pat 2000, 10, 1011.
5. Talley, J. J. Prog. Med. Chem. 1999, 36, 201.
6. Xie, W.; Chipman, J. G.; Robertson, D. L.; Erikson,
R. L.; Simmons, D. L. Proc. Natl. Acad. Sci. U.S.A. 1991,
88, 2692.
25. Dannhardt, G.; Steindl, L.; Lehr, M. US Patent
5,260,451, Nov. 9, 1993.
26. Isakson, P. C.; Anderson, G. D.; Gregory, S. A. US
Patent 6,136,839, Oct. 24, 2000.
27. Laufer, S.; Striegel, H. G.; Dannhardt, G. US Patent
5,939,415, Aug. 17, 1999.
7. Kujubu, D. A.; Fletcher, B. S.; Varnum, B. C.; Lim,
R. W.; Herschman, H. R. J. Biol. Chem. 1991, 266, 12866.
8. Chan, C. C.; Boyce, S.; Brideau, C.; Charleson, S.;
Cromlish, W.; Ethier, D.; Evans, J.; Ford-Hutchinson,
A. W.; Forrest, M. J.; Gauthier, J. Y.; Gordon, R.; Gresser,
M.; Guay, J.; Kargman, S.; Kennedy, B.; Leblanc, Y.;
Leger, S.; Mancini, J.; O’Neill, G. P.; Ouellet, M.; Patrick,
D.; Percival, M. D.; Perrier, H.; Prasit, P.; Rodger, I.;
Tagari, P.; Therien, M.; Vickers, P.; Visco, D.; Wang, Z.;
Webb, J.; Wong, E.; Xu, L. J.; Young, R. N.; Zamboni, R.;
Rienddeau, D. J. Pharmacol. Exp. Therap. 1999, 290, 551.
28. (a) Kolasa, T.; Patel, M. V. US Patent 6,472,416 B1, Oct.
29, 2002 (b) Kolasa, T.; Patel, M. V. PCT Int. Appl., WO
01/016138, March 8, 2001.
29. Gever, G. J. Am. Chem. Soc. 1954, 76, 1283.
30. Potekhin, A. A.; Barkova, T. F. J. Org. Chem. USSR
1973, 1209.
31. Young, J. M.; Panah, S.; Satchawatcharaphong, C.;
Cheung, P. S. Inflamm. Res. 1996, 45, 246.
´
32. Glaser, K.; Sung, M. L.; ONeill, K.; Belfast, M.; Hart-
man, D.; Carlson, R.; Kreft, A.; Kubrak, D.; Hsiao, C. L.;
Weichman, B. Eur. J. Pharmacol. 1995, 281, 107.