Structure-activity studies for a novel series of tricyclic dihydropyridopyrazolones and dihydropyridoisoxazolones as KATP channel openers

Article abstract of DOI:10.1016/j.bmc.2004.01.038

In search of a novel chemotype of K_ATP channel openers a series of tricyclic dihydropyridopyrazolones and dihydropyridoisoxazolones was synthesized. It was found that cyclopentanone in the left hand portion of the molecule was 4-fold more potent than cyclohexanone. Introduction of gem-dimethyl groups as well as incorporation of oxygen in the cyclohexanone ring in the left hand portion of the molecule increased the potency 10-fold. In the right hand portion of the molecule, the NH-group of the pyrazolone can be effectively substituted by oxygen increasing the activity 5-fold. Incorporation of a methyl group adjacent to the dihydropyridine (DHP) nitrogen not only significantly boosted activity, but also provided an additional benefit of increased metabolic stability. In vitro tests on the tissue from pig bladder strips provided further confirmation of K_ATP activity of these compounds.

Full text of DOI:10.1016/j.bmc.2004.01.038

Bioorganic & Medicinal Chemistry 12 (2004) 1895–1904
Structure–activity studies for a novel series of tricyclic
dihydropyridopyrazolones and dihydropyridoisoxazolones as KATP
channel openers§
Irene Drizin,* Robert J. Altenbach, Steven A. Buckner, Kristi L. Whiteaker,
Victoria E. Scott, John F. Darbyshire, Venkata Jayanti, Rodger F. Henry,
Michael J. Coghlan, Murali Gopalakrishnan and William A. Carroll
Neuroscience Research, GPRD, Abbott Laboratories, 100 Abbott Park Road, Abbott Park, IL 60064-6101, USA
Received 17 November 2003; accepted 26 January 2004
Abstract—In search of a novel chemotype of KATP channel openers a series of tricyclic dihydropyridopyrazolones and dihy-
dropyridoisoxazolones was synthesized. It was found that cyclopentanone in the left hand portion of the molecule was 4-fold more
potent than cyclohexanone. Introduction of gem-dimethyl groups as well as incorporation of oxygen in the cyclohexanone ring in
the left hand portion of the molecule increased the potency 10-fold. In the right hand portion of the molecule, the NH-group of the
pyrazolone can be effectively substituted by oxygen increasing the activity 5-fold. Incorporation of a methyl group adjacent to
the dihydropyridine (DHP) nitrogen not only significantly boosted activity, but also provided an additional benefit of increased
metabolic stability. In vitro tests on the tissue from pig bladder strips provided further confirmation of KATP activity of these
compounds.
# 2004 Elsevier Ltd. All rights reserved.
1. Introduction
Continued SAR investigation around our previously
disclosed series of tricyclic dihydropyridines7 focused on
a new chemotype with pyrazolone and isoxazolone ser-
ving as isosteres of a lactam or a lactone ring (Chart 2).
SAR studies on this novel series examined the effects
of aromatic substitution as well as modifications of
the left- and right-hand portions of the molecule.
Potassium channels play an important role in regulating
cell membrane excitability, action potential generation
and epithelial electrolyte transport. KATP channel
openers are amongst the most widely explored channels
modulators with regard to their potential for the treat-
ment of various diseases such as bladder overactivity.1
KATP channels exist in the bladder and the ability of
potassium channel openers (KCO’s) to hyperpolarize
cells and relax smooth muscle may provide a method for
controlling bladder overactivity. Since a clinical study
with cromakalim indicated potential usefulness of
KCO’s for this application, newer generation of KATP
channel openers such as ZM244085,1 ZD61692À4 and
WAY 1335365,6 are reported to have enhanced bladder
selectivity (Chart 1).
§Supplementary data associated with this article can be found, in the
online version at, 10.1016/j.bmc.2004.01.038
* Corresponding author. Fax 1-847-935-5466; e-mail: irene.drizin@
abbott.com
Chart 1.
0968-0896/$ - see front matter # 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2004.01.038

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I. Drizin et al. / Bioorg. Med. Chem. 12 (2004) 1895–1904
component Hantzsch reaction as shown on Scheme 1. A
mixture of aldehyde 2, 1,3-cyclopentanedione 3, and 5-
amino-3-pyrazolones 4a–g10,11 was heated at reflux in
EtOH to yield the desired dihydropyridopyrazolones
6a–g. Dihydropyridoisoxazolones 7 were obtained by
substituting 4 for 3-amino-5-isoxazolone 512 in this
reaction. Variations in the aromatic substitution were
introduced by replacing of 2 with a variety of aldehydes,
either commercially available or synthesized by the
methods described in the literature. Variations of the left
hand portion of the molecule were accomplished by
substituting 1,3-cyclopentanedione 3 in the Hantzsch
reaction with the different cyclic diketones, available
from commercial sources or synthesized in accordance
with the literature methods. Thus, use of 1,3-cyclohex-
anedione afforded pyrazolone 16 and isoxazolone 24,
and use of 4,4-dimethyl-1,3-cyclohexanedione in the
Hantzsch reaction yielded pyrazolone 17 and iso-
xazolone 25. Introduction of heteroatoms in the left
hand portion of the core was realized by substituting
1,3-cyclopentadione 3 with 2H-pyran-3,5(4H,6H)-dione13
to yield 21 and 28 or d-lactone14,15 to obtain 20. Repla-
cement of carbonyl groups with sulfone groups was
accomplished by substituting 1,3-cyclopentanedione 3 in
the Hantzsch reaction with tetrahydrothiophene-3-oxo-
1,1-dioxide13 to yield 14 and tetrahydrothiopyran-3-
one-1,1-dioxide16 to afford 15. Lactone derivatives 13
and 23 were synthesized by a two-step sequence outlined
in Scheme 2. The Hantzsch reaction was performed with
the ester 11,17 aldehyde 2 and aminopyrazolone 4b to
yield the bicyclic dihydropyridine 12, that in turn was
cyclized to the desired lactone 13. A similar sequence
was used for the synthesis of lactone isoxazolone 23.
Chart 2.
Compounds were evaluated in cell and tissue-based in-
vitro models.
A common property of many dihydropyridine-contain-
ing molecules is a susceptibility to CYP3A4 mediated
oxidation to the pyridine.8,9 The tricyclic pyrazolones
and isoxazolones described herein offered the potential
to increase the metabolic stability by introduction of
substituents that sterically hinder access to the dihy-
dropyridine nucleus as well as change the electronic
environment of the core. This new series of compounds
was tested for its metabolic stability in pooled human
liver microsomes and showed superior metabolic stabi-
lity compared to the reference standards.
2. Chemistry
A series of tricyclic dihydropyridopyrazolones and di-
hydropyridoisoxazolones was synthesized using the three
Resolution of racemic dihydropyridopyrazolones could
not be accomplished directly because of the poor solu-
bility and high polarity of these compounds. Boc-deri-
vatives of these compounds also were not amenable to
chiral separation. Acetylation of 6b yielded pre-
dominantly O-acetyl derivative 8 that was separated on
a Chiracel OJ column. The resolved O-acetyl inter-
mediates were cleaved under acidic conditions to the
desired enantiomers 9 and 10 (Scheme 3). A similar
strategy was applied to the separation of racemic pyr-
azolone 17. Racemic dihydropyridoisoxazolones 25 and
28, being more soluble, could be resolved on Chiracel
AS column without prior derivatisation.
The absolute stereochemistry of dihydropyridoisox-
azolones 26, 27, 28, and 29 was determined by X-ray
Scheme 1. Conditions and reagents: (a) EtOH, reflux.
Scheme 2. Synthesis of lactone analogues. Conditions and reagents (a) EtOH, reflux, (b) K2CO3, MeOH.

I. Drizin et al. / Bioorg. Med. Chem. 12 (2004) 1895–1904
1897
Scheme 3. Resolution of enantiomers. Conditions and reagents: (a) acetic anhydride, reflux; (b) Chiracel OJ column hexane:EtOH (3:1); (c) MeOH,
6N HCl.
crystallography. Similar analysis of dihydropyridopyr-
azolones 9, 10, 18, and 19 was not possible, since we
failed to grow crystals large enough to be analyzed.
in the same position yielded a very potent compound 7,
when R2=CH3.
We further focused our efforts on the optimization of
the left hand portion of the two promising leads 6b and
7. SAR for both classes of compounds (Table 2) is
3. Results and discussion
Compounds were assayed for their activity as KATP
openers using primary cultured guinea pig bladder cells.
The SAR study reported here was focused on the fol-
lowing issues (i) study of the spatial and electronic limi-
tations of the right hand portion of the molecule, (ii)
tolerance to variations of the left hand portion of the
molecule, (iii) effects of the substituents on the aromatic
ring.
Table 2. SAR of the left hand side of the tricyclic dihydropyridines
The initial effort was directed at improving the potency
of 6a by modification of the right hand portion of the
molecule. As is evident from Table 1, introduction of a
methyl group adjacent to the dihydropyridine nitrogen
(6b) resulted in a very significant increase in activity.
Further expansion of the steric bulk around that region
revealed limitations of that pocket. Incorporation of an
ethyl group as in 6c was still tolerated, but introduction
of t-butyl or aromatic and heteroaromatic groups (6d–f)
in this region resulted in a complete loss of activity.
Interestingly, moving the methyl group to the nitrogen
adjacent to carbonyl group (6g) was detrimental for
activity. (In parallel SAR studies X=NMe and R2=Me
was found to be an allowed substitution pattern on the
core with the left hand piece from example 21). Oxygen
A
X=NH
EC50 (mM)a
X=O
EC50 (mM)a
6b
7
0.55
0.071
(À)9
(+)10
13
0.59
>10
0.35
>10
>10
1.97b
0.18
0.18
>10
1.14
0.19
—
23
—
0.013
14
15
—
Table 1. SAR of the right-hand side of the tricyclic dihydropyridines
16
24
2.30
0.13
17
25
(+)18
(À)19
20
(R)(+)26
(S)(À)27
0.11
>10
Compd
X
R2
EC50 (mM)a
6a
6b
6c
6d
6e
6f
6g
7
NH
NH
NH
NH
H
CH3
C2H5
t-butyl
2-pyridyl
NH
2.77b
0.55
21
28
0.13
0.27b
>10
—
(S)(À)29
(R)(+)30
0.25b
0.025
NH
>10
>10b
>10
N-phenyl
N-CH3
O
H
CH3
—
—
0.071
a Values are means of three experiments.
b Values are means of two experiments.
a Values are means of three experiments.
b Values are means of two experiments.

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I. Drizin et al. / Bioorg. Med. Chem. 12 (2004) 1895–1904
Table 3. SAR of the aromatic substitution of the dihydropyridopyr-
azolones
Table 4. SAR of the aromatic substitution of the dihydropyr-
idoisoxazolones
Compd
R
EC50 (mM)a
Compd
R
EC50 (mM)a
>10
28
38
39
40
41
42
3-Br, 4-F0.13
3-Br, 4-CH3
3-CF3, 4-F3.24
3-NO2, 4-Cl
3-I, 4-F0.057
3-CN
6b
31
32
33
34
35
36
3-Br, 4-F0.56
4-OCF3
0.21
b
3-Br, 4-CH3
3-CF3, 4-F0.69
3-NO2, 4-Cl
3-I, 4-F0.32
3,4-diCl
0.48b
b
0.099
2.3b
b
>10
0.67b
43
0.023
37
>10
a Values are means of three experiments.
b Values are means of two experiments.
a Values are means of three experiments.
b Values are means of two experiments.
almost identical. It was shown that cyclopentanone, as a
left hand portion of the molecule (6b and 7), is more
potent than cyclohexanone (16 and 24). Surprisingly,
introduction of gem-dimethyl groups in the cyclohex-
anone ring (17 and 25) restored potency to the level of
6b and 7. Incorporation of oxygen in the cyclohexanone
ring (20, 21 and 28) also had a favorable effect, that was
particularly pronounced with 21 and 28. Oxygen was
also well tolerated in the cyclopentanone rings (13 and
23). Replacement of the carbonyl group in the ring A
with sulfone (14 and 15) resulted in a complete loss of
activity. Resolution of enantiomers (9, 10, 18, 19, 29,
and 30) showed that absolute stereochemistry was cri-
tical for KATP activity as activity resided predominantly
with one enantiomer.
The more potent compounds representing both dihy-
dropyridopyrazolones and dihydropyridoisoxazolones
were also evaluated in vitro using tissue strips obtained
from Landrace pig bladders. The results of this study
are presented in Table 5. All of the compounds exhibit
activity comparable to cromakalim.
An interesting property of this series of compounds was
discovered with the evaluation of their metabolic stabi-
lity. As is known from the literature, dihydropyridines
as a class of compound are subject to rapid metabolism
catalyzed by the cytochrome P450(CYP) 3A4 isoform.
Shown in Table 6 are metabolism results for a selection
of compounds compared with a structural analogue
Table 5. Functional KCO activity in isolated bladder strips
Further elucidation of structural and electronic limi-
tations of the pharmacophore was accomplished by
exploring the effect elicited by changes in aromatic sub-
stitution. SAR for the core structure of 6b is summar-
ized in Table 3. As was previously established for other
dihydropyridine KCO’s,7 monosubstitution with OCF3
group (31) results in a loss of activity. 3, 4-Disubstituted
compounds, in particular, di-halogen compounds (6b,
35, and 36) were more potent. The 3-Br group could be
replaced with 3-CF3 as in 33 or I as in 35 with the
retention of potency. The 4-Fgroup could be replaced
by 4-CH3, as in 32, without adverse effect on activity.
However, the oxadiazole group in 37 and 3-NO2, 4-Cl
pattern in 34 had unfavorable effect on the potency of
compounds.
a
Compd
pEC50
Cromakalim
6.34
6.14
6.46
6.68
6.52
6.35
6.71
6b
13
17
21
24
23
a Efficacy(%P1075)ꢀ90%.
Table 6. Metabolic stability in human microsomes
Compd
% Compound remaining
Nifedipine
Felodipine
17
23
20
95
92
90
98
92
86
83
86
1c
17
21
6b
35
27
23
13
6c
Similar studies of the aromatic substitution SAR for the
core structure 7 are summarized in Table 4. For the most
part SAR for core structures 6b and 7 is parallel. There
are a few exceptions, however, for example, 3-Br group
could not be replaced with the 3-CF3 group (39) with
the retention of potency, and for the core structure 7
both 3-NO2, 4-Cl (40) and oxadiazole (43) moieties were
well tolerated as a replacement for 3-Br, 4-F-pattern.

I. Drizin et al. / Bioorg. Med. Chem. 12 (2004) 1895–1904
1899
from previous work 1c and the calcium channel
antagonist standards: nifedipine and felodipine. As is
evident from data introduction of the methylpyrazolone
and methyloxazolone in the scaffold not only increased
potency, but also imparted greater metabolic stability
for these compounds. It is especially evident when
comparing the metabolic stability of tricyclic lactone 1c
to compounds 6b and 17. This can be explained by a
steric and electronic effects of groups adjacent to the
dyhydropyridine nitrogen.
of MeOH/acetonitrile (v/v 1:1), containing 15 mM nife-
dipine, an internal standard, followed by vigorous mix-
ing. After protein precipitation and centrifugation a 100
mL aliquot of the supernatant was taken for HPLC
analysis.
The compounds and their metabolites were analyzed by
reverse phase HPLC. Separation was achieved at room
temperature using a YMC C8 column (4.5ꢁ150 mm,
pore size 5 mm) with a YMC C8 guard column on a
Hewlett-Packard 1050 series HPLC system. Elution was
conducted at 1 mL/min using a linear gradient of 80–
40–20–0–0–60% of 50 mM ammonium acetate buffer,
pH 4.0, water and methanol over 40 min. The methanol
was increased from 60% to 80% by 47 min. The gra-
dient was ramped back to 80% buffer and 20% water
step wise in next 13 min followed by equilibration of 10
min before the next injection. The parent and metabo-
lites were detected using an Applied Biosystems UV
detector at a wavelength of 346 nM.
In summary, we have identified a new class of potas-
sium channel openers. SAR studies on both dihy-
dropyridooxazolones and dihydropyridopyrazolones
helped identify compounds that not only exhibited great
potency but were also metabolically stable. We exam-
ined the effect of the ring size and substituents in the left
hand side portion of the molecule as well as established
the optimal aromatic substitution for both classes of
compounds. We have also demonstrated novel method
for the preparation of enantiomers for these structural
classes. The obtained compounds were evaluated for
KATP activity in pig bladder strips and they demon-
strated activity comparable to cromakalim.
4.3. Chemistry
Proton NMR spectra were obtained on a General Elec-
tric QE 300 or QZ 300 MHz instrument with chemical
shifts (d) reported relative to tetramethylsilane as inter-
nal standard. Melting points were determined on a
Thomas-Hoover Capillary Melting Point apparatus and
are uncorrected. Elemental analyses were performed by
Robertson Microlit Laboratories. Column chromato-
graphy was carried out on silica gel 60 (230–400 mesh).
Thin-layer chromatography (TLC) was performed using
250 mm silica gel 60 glass-backed plates with F254 as
indicator. Optical rotations were measured with a Per-
kin–Elmer 541 Polarimeter. X-ray crystal structures
were obtained on a Bruker SMART system.
4. Experimental
4.1. Biology
The series of compounds was evaluated for potassium
channel opening activity using primary cultured guinea
pig urinary bladder (GPB) cells.18 Functional activity at
potassium channels was measured by evaluating chan-
ges in membrane potential using DIBAC dye in a 96-
well cell based kinetic assay system, Fluorescent Ima-
ging Plate Reader (FLIPR). Changes in fluorescence
were measured and compared to the effect elicited by
P1075 — a potent KCO. The effects of all compounds
were reversed by glyburide.
4.4. General procedure
4.4.1. 4-(3-Bromo-4-fluorophenyl)-1,2,4,6,7,8-hexahydro-
cyclopenta[b]pyrazolo[4,3-e]pyridine-3,5-dione (6a). 5-
Amino-1,2-dihydropyrazol-3-one (0.15 g, 1.5 mmol), 3-
bromo-4-fluorobenzaldehyde (0.31 g, 1.5 mmol), and
1,3-cyclopentanedione (0.15 g, 1.5 mmol) in EtOH (3
mL) were heated at 80 ꢁC for 2 days in a sealed tube.
The reaction mixture was evaporated under reduced
pressure and the residue was chromatographed on silica
gel eluting with EtOAc:HCO2H:H2O (18:1:1) to provide
0.125 g of 6a as a tan solid. 1H NMR (DMSO-d6) d 2.22
(t, 2H), 2.61 (m, 2H), 4.73 (s, 1H), 7.15 (m, 1H), 7.2 (m,
1H), 7.4 (dd, 1H), 9.75 (s, 1H), 10.21 (s, 1H), 11.3 (bs,
1H); MS (ESI-) m/z 362 (M-H)À Anal. (C15H11N3
In vitro tissue tests were conducted on strips obtained
from Landrace pig bladders.19 Tissues were stimulated
by a low frequency current that produced a stable
twitch response. P1075 completely eliminated the sti-
mulated twitch response in a dose-dependant fashion.
The maximal efficacy of each compound was expressed
in comparison to P1075. The amount of agent necessary
to cause 50% of the agent’s maximal response (EC50)
was calculated and agonist potencies were expressed as
pEC50 (the negative logarithm).
.
BrFO2 0.5H2O) C, H, N.
4.2. Human liver microsomal incubations
A standard 0.15 mL incubation mixture contained
pooled human liver microsomal protein (0.5 mg/mL) in
50 mM phosphate buffer (pH 7.4) and 25 mM substrate.
The microsomes were a mixture of human liver micro-
somes from eight donors pooled on equal weight basis.
Following a 5 min preincubation, reactions were started
by the addition of 2 mM NADPH and conducted at
37 ꢁC in a shaking incubator for 30 min. The reaction
was stopped by the addition of 100 mL of a mixture
4.4.2. 4-(3-Bromo-4-fluorophenyl)-1-methyl-1,2,4,6,7,8-
hexahydrocyclopenta[b]pyrazolo[4,3-e]pyridine-3,5-dione
(6b). 5-Amino-1-methyl-1,2-dihydropyrazol-3-one (0.23
g, 2 mmol),10 3-bromo-4-fluorobenzaldehyde (0.4 g, 2
mmol), and 1,3-cyclopentanedione (0.2 g, 2 mmol) in
EtOH (4 mL) were treated as described for 6a. The
reaction was cooled and the resulting precipitate was
collected to provide 0.6 g (79%) of 6b as a tan solid. 1H
NMR (DMSO-d6) d 2.3 (t, 2H), 2.69 (m, 2H), 3.5 (s,

1900
I. Drizin et al. / Bioorg. Med. Chem. 12 (2004) 1895–1904
3H), 4.7 (s, 1H), 7.15 (m, 1H), 7.2 (t, 1H), 7.39 (dd, 1H),
9.56 (s, 1H), 10.42(s, 1H); MS (ESI+) m/z 380
1,3-cyclopentanedione (0.15 g, 1.5 mmol), and 5-amino-
2-methyl-1,2-dihydropyrazol-3-one (0.17 g, 1.5 mmol),
prepared by the method of words of Taylor10 were pro-
cessed as described in 6a. The reaction was cooled and
the resulting precipitate was collected to provide 0.32 g
of 6g. 1H NMR (DMSO-d6) d 2.21 (t, 2H), 2.59 (m, 2H),
3.38 (s, 3H), 4.75 (s, 1H), 7.13 (m, 1H), 7.2 (t, 1H), 7.42
(dd, 1H), 10.16 (s, 1H), 10.51 (bs, 1H). MS (ESI-) m/z
378 (MÀH)À. Anal. (C16H13N3BrFO2) C, H, N.
+
.
(M+H) . Anal. (C16H13N3BrFO2 C2H6O) C, H, N.
4.4.3. 4-(3-Bromo-4-fluorophenyl)-1-ethyl-1,2,4,6,7,8-hexa-
hydrocyclopenta[b]pyrazolo[4,3-e]pyridine-3,5-dione (6c).
5-Amino-1-ethyl-1,2-dihydropyrazol-3-one (0.13 g, 1
mmol), prepared by the method of Weisberger11 from
ethylhydrazine and ethyl cyanoacetate, 3-bromo-4-fluoro-
benzaldehyde (0.2 g, 1 mmol), and 1,3-cyclopentane-
dione (0.1 g, 1 mmol) were processed as in 6a. The
reaction was cooled and the resulting precipitate was
collected to provide 0.23 g (58%) of 6c as a tan solid. 1H
NMR (DMSO-d6) d 1.22 (t, 3H), 2.28 (t, 2H), 2.68 (m,
2H), 3.82 (q, 2H), 4.7 (s, 1H), 7.17 (m, 1H), 7.2 (t, 1H),
7.4 (dd, 1H), 9.64 (bs, 1H), 10.4 (s, 1H); MS (ESI-) m/z
4.4.8. 4-(3-Bromo-4-fluorophenyl)-1-methyl-4,6,7,8-tetra-
hydro - 1H - cyclopenta[b]isoxazolo[4,3 - e]pyridine - 3,5 -
dione (7). 3-Amino-2-methyl-5(2H)-isoxazolone (0.11 g,
1 mmol), 3-bromo-4-fluorobenzaldehyde (0.2 g, 1
mmol), and 1,3-cyclopentanedione (0.1 g, 1 mmol) in
EtOH (2 mL) were processed as in 6a. The reaction
mixture was allowed to cool to room temperature and
was evaporated under reduced pressure. The residue was
chromatographed eluting with EtOAc:HCO2H:H2O
(19:0.5:0.5) to provide 7 as a tan solid (0.07 g). 1H NMR
(DMSO-d6) d 2.35 (t, 2H), 2.72 (m, 2H), 3.29 (s, 3H),
4.6 (s, 1H), 7.23 (d, 2H), 7.5 (d, 1H) 11.0 (s, 1H). MS
(ESI) m/z 379 (MÀH)À. Anal. (C16H12N3FBrO3) C, H, N.
À
.
392 (MÀH) . Anal. (C17H15N3BrFO2 0.5H2O) C, H, N.
4.4.4. 4-(3-Bromo-4-fluorophenyl)-1-tert-butyl-1,2,4,6,7,8-
hexahydrocyclopenta[b]pyrazolo[4,3-e]pyridine-3,5-dione
(6d). 5-Amino-1-tert-butyl-1,2-dihydropyrazol-3-one
(0.23 g, 1.5 mmol), prepared by the method of Weisber-
ger11 from tert-butylhydrazine and ethyl cyanoacetate,
3-bromo-4-fluorobenzaldehyde (0.3 g, 1.5 mmol), and
1,3-cyclopentanedione (0.147 g, 1.5 mmol) in EtOH (3
mL) were processed as in 6a. The reaction was cooled
and the resulting precipitate was collected to provide
0.12 g of 6d as a tan solid. 1H NMR (DMSO-d6) d 1.51 (s,
9H), 2.28 (m, 2H), 2.71 (m, 2H), 4.69 (s, 1H), 7.12 (m,
1H), 7.21 (t, 1H), 7.39 (dd, 1H), 9.43 (bs, 1H), 9.57 (s, 1H);
MS (ESI-) m/z 420 (MÀH)À. Anal. (C19H19N3BrFO2)
C, H, N.
4.4.9. 4-(3-Bromo-4-fluorophenyl)-1-methyl-5-oxo-1,4,5,
6,7,8-hexahydrocyclopenta[b]pyrazolo[4,3-e]pyridin-3-yl
acetate (8). Dihydropyridopyrazolone 6b 1 (0.4 g, 1
mmol) was heated on a steam bath in acetic anhydride
(5 mL) for 15 min. The reaction mixture was evaporated
under reduced pressure and the residue was chromato-
graphed on silica gel eluting with 5% EtOH/CH2Cl2 to
provide 0.27 g of 8 as white crystals. 1H NMR (DMSO-
d6) d 2.35 (t, 2H), 2.36 (s, 3H), 2.74 (m, 2H), 3.35 (s,
3H), 4.59 (s, 1H), 7.25 (d, 2H), 7.55 (d, 1H), 11.0 (s, 1H).
MS (ESI-) m/z 423 (MÀH)À. Anal. (C18H15N3FBrO3)
C, H, N.
4.4.5. 4-(3-Bromo-4-fluorophenyl)-1-(2-pyridinyl)-1,2,4,6,
7,8 -hexahydrocyclopenta[b]pyrazolo[4,3 - e]pyridine- 3,5-
dione (6e). 5-Amino-1-(2-pyridyl)-1,2-dihydropyrazol-3-
one (0.26 g, 1.5 mmol),11 (3-bromo-4-fluorobenzaldehyde
(0.3 g, 1.5 mmol), and 1,3-cyclopentanedione (0.147 g,
1.5 mmol) were processed as in 6a. The reaction was
cooled and the resulting precipitate was collected to
4.4.10. (+) 4-(3-Bromo-4-fluorophenyl)-1-methyl-1,2,4,6,
7,8 - hexahydrocyclopenta[b]pyrazolo[4,3 - e]pyridine-3,5 -
dione (9). Acetate 8 (0.4 g) was chromatographed on a
chiral column (Chiracel OJ 4.6Â250 mm using hex-
ane:EtOH (75:25) at 1 mL/min) to provide two enan-
tiomers. The less polar enantiomer had a retention time
of 10.9 min (0.174 g). The more polar enantiomer had a
retention time of 18.4 min (0.16 g).
1
provide 0.2 g of 6e as a tan solid. H NMR (DMSO-d6)
d 2.32 (m, 2H), 2.8 (m, 2H), 4.82 (s, 1H), 7.22 (m, 3H),
7.48 (dd, 1H), 7.55 (dd, 1H), 7.92 (t, 1H), 8.41 (m, 1H),
10.42 (Às, 1H), 10.55 (bs, 1H); MS (ESI-) m/z 439
.
(MÀH) . Anal. (C20H14N4BrFO2 0.25H2O) C, H, N.
4.4.6. 4-(3-Bromo-4-fluorophenyl)-2-phenyl-1,2,4,6,7,8-
hexahydrocyclopenta [b]pyrazolo[4,3-e]pyridine-3,5-dione
(6f). 3-Bromo-4-fluorobenzaldehyde (0.3 g, 1.5 mmol),
1,3-cyclopentanedione (0.15 g, 1.5 mmol), and 5-amino-
2-phenyl-1,2-dihydropyrazol-3-one (0.26 g, 1.5 mmol)
were processed as in 6a. The reaction mixture was con-
centrated in vacuo and the obtained residue was chro-
matographed on silica gel eluting with 10% EtOH/
The less polar enantiomer (0.17 g) in aqueous MeOH
(10 mL) was treated with 6 N HCl (1 mL) and then
heated at reflux for 1 h. The reaction mixture was eva-
porated under reduced pressure and the residue was
chromatographed eluting with 15% EtOH/CH2Cl2 to
ꢁ
provide 0.09 g of 9. [a]2D3 +168.1 (DMSO); H NMR
1
(DMSO-d6) d 2.3 (t, 2H), 2.7 (m, 2H), 3.5 (s, 3H), 4.7 (s,
1H), 7.18 (m, 1H), 7.2 (t, 1H), 7.39 (dd, 1H), 9.51 (bs,
1H), 10.42(s, 1H). MS (ESI-) m/z 378 (MÀH)À. Anal.
(C16H13N3BrFO2) C, H, N.
1
CH2Cl2 to provide 0.32 g of 6f. H NMR (DMSO-d6) d
2.26 (m, 2H), 2.63 (m, 2H), 4.86 (s, 1H), 7.21 (m, 3H),
7.4 (t, 2H), 7.51 (d, 1H), 7.67 (d, 2H), 10.47 (s, 1H), 11.2
(s, 1H). MS (ESI-) m/z 438 (MÀH)À. Anal.
(C21H15N3FBrO2) C, H, N.
4.4.11. (À) 4-(3-Bromo-4-fluorophenyl)-1-methyl-1,2,4,6,
7,8 - hexahydrocyclopenta[b]pyrazolo[4,3 - e]pyridine-3,5 -
dione (10). The more polar enantiomer (0.16 g) in aqu-
eous MeOH (10 mL) was treated with 6 N HCl (1 mL)
and then heated at reflux for 1 h. The reaction mixture
was evaporated under reduced pressure and the residue
4.4.7. 4-(3-Bromo-4-fluorophenyl)-2-methyl-1,2,4,6,7,8-
hexahydrocyclopenta[b]pyrazolo[4,3-e]pyridine-3,5-dione
(6g). 3-Bromo-4-fluorobenzaldehyde (0.3 g, 1.5 mmol),

I. Drizin et al. / Bioorg. Med. Chem. 12 (2004) 1895–1904
1901
was chromatographed eluting with 15% EtOH/CH2Cl2
to provide 0.09 g of 10. [a]2D3 À166.7ꢁ (DMSO); 1H
NMR (DMSO-d6) d 2.3 (t, 2H), 2.7 (m, 2H), 3.5 (s, 3H),
4.7 (s, 1H), 7.18 (m, 1H), 7.2 (t, 1H), 7.39 (dd, 1H), 9.51
(bs, 1H), 10.42 (s, 1H). MS (ESI-) m/z 378 (MÀH)À.
Anal. (C16H13N3BrFO2) C, H, N.
1,3-cyclohexanedione (0.11 g, 1.0 mmol), and 5-amino-
1-methyl-1,2-dihydropyrazol-3-one (0.11 g, 1.0 mmol)
were processed as described for 6a. The reaction was
cooled and the resulting precipitate was collected to
1
provide 0.27 g of 16. H NMR (DMSO-d6) d 1.9 (m,
2H), 2.2 (m, 2H), 2.6 (m, 2H), 3.45 (s, 3H), 4.88 (s, 1H),
7.12 (m, 1H), 7.18 (t, 1H), 7.38 (dd, 1H), 9.53 (s, 1H),
9.72 (s, 1H); MS (ESI-) m/z 390 (MÀH)À. Anal.
4.4.12. Ethyl 6-[(acetyloxy)methyl]-4-(3-bromo-4-fluoro-
phenyl)-1-methyl-3-oxo-2,3,4,7-tetrahydro-1H-pyrazolo-
[3,4-b]pyridine-5-carboxylate (12). Ethyl 4-(acetyloxy)-3-
oxobutanoate 11 (0.19 g, 1 mmol),17 3-bromo-4-fluor-
obenzaldehyde (0.2 g, 1 mmol) and 5-amino-1-methyl-
1,2-dihydropyrazol-3-one (0.11 g, 1 mmol) in EtOH (3
mL) were heated at 80 ꢁC for 24 h in a sealed tube. The
reaction mixture was evaporated under reduced pres-
sure and chromatographed on silica gel eluting with 5%
EtOH/CH2Cl2 to provide 0.1 g of 12. 1H NMR
(DMSO-d6) d 1.03 (t, 3H), 2.1 (s,3H), 3.46 (s, 3H), 3.92
(q, 2H), 4.95 (s, 1H), 5.12 (q, 2H), 7.18 (m, 1H), 7.22 (t,
1H), 7.38 (dd, 1H), 9.43 (s, 1H). MS (ESI-) m/z
468(MÀH)À.
.
(C17H15N3BrFO2 C2H6O) C, H, N.
4.4.17. 4-(3-Bromo-4-fluorophenyl)-1,6,6-trimethyl-4,7,8,9-
tetrahydro - 1H - pyrazolo[3,4 - b]quinoline - 3,5(2H,6H) -
dione (17). 5-Amino-1-methyl-1,2-dihydropyrazol-3-one
(0.23 g, 2 mmol), 3-bromo-4-fluorobenzaldehyde (0.4 g,
2 mmol), and 4,4-dimethyl-1,3-cyclohexanedione (0.28
g, 2 mmol) were treated as in 6a to provide after fil-
tration of the reaction mixture 0.55 g of 17 as a tan
solid. 1H NMR (DMSO-d6) d 0.92 (s, 3H), 0.98 (s, 3H),
1.78 (t, 2H), 2.63 (m, 2H), 3.43 (s, 3H), 4.83 (s, 1H), 7.11
(m, 1H), 7.17 (t, 1H), 7.33 (dd, 1H), 9.53 (s, 1H), 9.66 (s,
1H). MS (ESI-) m/z 420 (MÀH)À. Anal.
(C19H19N3BrFO2) C, H, N.
4.4.13. 4-(3-Bromo-4-fluorophenyl)-1-methyl-4,8-dihydro-
1H-furo[3,4-b]pyrazolo[4,3-e]pyridine-3,5(2H,7H)-dione
(13). Diester 12 (0.09 g) and K2CO3 (0.03 g) in MeOH
(10 mL) were stirred at ambient temperature for 1 h.
The solvent was evaporated under reduced pressure and
the obtained residue was chromatographed on silica gel
eluting with 10% EtOH/CH2Cl2 to provide 0.04 g of 13.
1H NMR (DMSO-d6) d 3.49 (s, 3H), 4.76 (s, 1H), 4.9 (q,
2H), 7.23 (m, 2H), 7.42 (dd, 1H), 9.51 (bs, 1H),
9.78 (s, 1H). MS (ESI-) m/z 378 (MÀH)À. Anal.
4.4.18. (+) 4-(3-Bromo-4-fluorophenyl)-1,6,6-trimethyl-
4,7,8,9 - tetrahydro - 1H - pyrazolo[3,4 - b]quinoline - 3,5-
(2H,6H)-dione(18) and (À) 4-(3-bromo-4-fluorophenyl)-
1,6,6-trimethyl-4,7,8,9-tetrahydro-1H-pyrazolo[3,4-b]-
quinoline-3,5(2H,6H)-dione (19). Compound 17 (0.6 g)
in 5 mL of acetic anhydride was heated for 10 min on a
steam bath. The reaction mixture was evaporated under
reduced pressure and chromatographed on silica gel to
provide 0.36 g of 4-(3-bromo-4-fluorophenyl)-1,6,6-tri-
methyl-5-oxo-4,5,6,7,8,9-hexahydro-1H-pyrazolo[3,4-
b]quinolin-3-yl acetate as a less polar compound.
.
(C15H11N3BrFO3 0.5 C2H6O) C, H, N.
4.4.14. 4-(3-Bromo-4-fluorophenyl)-1-methyl-1,2,4,6,7,8-
hexahydro-3H-pyrazolo[3,4-b]thieno[2,3-e]pyridin-3-one
5,5-dioxide (14). 5-Amino-1-methyl-1,2-dihydropyrazol-
3-one (0.17 g, 1.5 mmol), 3-bromo-4-fluorobenzaldehyde
(0.3 g, 1.5 mmol), and tetrahydrothiophene-3-oxo-1,1-
dioxide (0.2 g,1.5 mmol) were treated as described for
6a. The reaction was cooled and the resulting precipitate
was filtered off to provide 0.41 g of 14 as a tan solid. 1H
NMR (DMSO-d6) d 2.88 (m, 1H), 3.03 (m, 1H), 3.4 (m,
2H), 3.48 (s, 3H), 4.92 (s, 1H), 7.21 (m, 1H), 7.24 (t,
1H), 7.4 (d, 1H), 9.55 (s, 1H), 9.89 (s, 1H). MS (ESI-) m/
z 414 (MÀH)À. Anal. (C15H13N3BrFO3S) C, H, N.
The intermediate acetate (0.36 g) was chromatographed
on a chiral column (Chiracel OJ column 4.6Â250 mm
using hexane:EtOH (85:15) at 1 mL/min) to provide two
enantiomers. The less polar enantiomer (0.14 g) had a
retention time of 7.63 min. The more polar enantiomer
(0.14 g) had a retention time of 10.18 min.
The less polar enantiomer (0.14 g), from above, in aqueous
MeOH (10 mL) was treated with 6 N HCl (1 mL) and
heated at reflux for 2 h. The reaction mixture was eva-
porated under reduced pressure and chromatographed
on silica gel eluting with 10% EtOH/CH2Cl2 to provide
0.09 g of 18. [a]2D3 +25.3ꢁ (DMSO); H NMR (DMSO-
1
4.4.15. 4-(3-Bromo-4-fluorophenyl)-1-methyl-3,4,6,7,8-
hexahydro-2H-thiopyrano[3,2-b]pyrazolo[2,3-e]pyridin-3-
one, 5,5-dioxide (15). Tetrahydrothiopyran-3-one-1,1-
dioxide (0.148 g, 1 mmol), 3-bromo-4-fluoro-benzalde-
hyde (0.20 g, 1 mmol), and 5-amino-1-methyl-1,2-dihy-
dropyrazol-3-one (0.11 g, 1 mmol) were processed as in
6a. The reaction was cooled and the resulting precipitate
was collected to provide 0.24 g (46%) of 15 as a tan
solid. 1H NMR (DMSO-d6) d 2.21 (m, 2H), 2.6 (m, 2H),
3.12 (m, 2H), 5.05 (s, 1H), 7.18 (m, 2H), 7.21 (t, 1H), 7.49
(d, 1H), 9.3 (s, 1H), 9.55 (bs, 1H). MS (ESI-) m/z 428
(MÀH)À. Anal. (C16H15N3BrFO3S. 0.5 C2H6O) C, H, N.
d6) d 0.92 (s, 3H), 0.98 (s, 3H), 1.78 (t, 2H), 2.63 (m,
2H), 3.44 (s, 3H), 4.83 (s, 1H), 7.12 (m, 1H), 7.16 (t,
1H), 7.33 (dd, 1H), 9.52 (bs, 1H), 9.63 (s, 1H). MS (ESI-)
m/z 420 (MÀH)À. Anal. (C19H19N3BrFO2) C, H, N.
The more polar enantiomer from above (0.16 g) was
treated with 6 N HCl (1 mL) and then heated at reflux
for 1 h. The reaction mixture was evaporated under
reduced pressure and the residue was chromatographed
eluting with 15% EtOH/CH2Cl2 to provide 0.08 g of 19.
ꢁ
[a]2D3 À23.9 (DMSO). H NMR (DMSO-d6) d 0.92 (s,
1
3H), 0.98 (s, 3H), 1.78 (t, 2H), 2.63 (m, 2H), 3.44 (s,
3H), 4.83 (s, 1H), 7.12 (m, 1H), 7.16 (t, 1H), 7.33 (dd,
1H), 9.52 (bs, 1H), 9.63 (s, 1H). MS (ESI-) m/z 420
(MÀH)À. Anal. (C19H19N3BrFO2): C, H, N.
4.4.16. 4-(3-Bromo-4-fluorophenyl)-1-methyl-4,7,8,9-tetra-
hydro - 1H - pyrazolo[3,4 - b]quinoline - 3,5(2H,6H) - dione
(16). 3-Bromo-4-fluorobenzaldehyde (0.2 g, 1.0 mmol),

1902
I. Drizin et al. / Bioorg. Med. Chem. 12 (2004) 1895–1904
4.4.19. 4-(3-Bromo-4-fluorophenyl)-1-methyl-1,2,4,7,8,9-
hexahydropyrano[4,3-b]pyrazolo[4,3-e]pyridine-3,5-dione
(20). Dihydro-2H-pyran-2,4(3H)-dione (0.11 g, 1 mmol
), 3-bromo-4-fluoro-benzaldehyde (0.2 g, 1 mmol) and
5-amino-1-methyl-1,2-dihydropyrazol-3-one (0.12 g, 1
mmol) were processed as described in 6a to provide 0.27
4.4.24. 4-(3-Bromo-4-fluorophenyl)-1,6,6-trimethyl-4,7,8,9-
tetrahydroisoxazolo[3,4 - b]quinoline - 3,5(1H,6H) - dione
(25). 3-Amino-2-methyl-5(2H)-isoxazolone (0.11 g, 1
mmol), 3-bromo-4-fluoro-benzaldehyde (0.2 g, 1 mmol),
and 4,4-dimethyl-1,3-cyclohexanedione (0.11 g, 1 mmol)
in EtOH (3 mL) were treated as in 6a. The reaction
mixture was allowed to cool to ambient temperature
and evaporated under reduced pressure. The residue
was chromatographed eluting with 5%EtOH/CH2Cl2 to
yield 0.13 g of 25 as a white solid. 1H NMR (DMSO-d6)
d 0.92 (s, 3H), 1.0 (s, 3H), 1.82 (t, 2H), 2.65 (m, 2H),
3.22 (s, 3H), 4.67 (s, 1H), 7.21 (m, 2HC, 7.43 (dd, 1H),
10.39 (s, 1H). MS (ESI) m/z 419,421 (MÀH)À. Anal.
(C19H18BrFN2O3) C, H, N.
1
g of 20 as a tan solid H NMR (DMSO-d6) d 2.55 (m,
1H), 2.8 (m, 1H), 3.5 (s, 3H), 4.22 (m, 2H), 4.86 (s, 1H),
7.2 (m, 2H), 7.41 (dd, 1H),À9.49 (s, 1H), 9.92 (s, 1H). MS
C2H6O) C, H, N.
.-
(ESI-) m/z 392 (MÀH) . Anal. (C16H13N3BrFO3
4.4.20. 4-(3-Bromo-4-fluorophenyl)-1-methyl-1,2,4,9-tet-
rahydropyrano[3,4-b]pyrazolo[4,3-e]pyridine-3,5(6H,8H)-
dione (21). 2H-Pyran-3,5(4H,6H)-dione (0.34 g,
3
mmol), 3-bromo-4-fluoro-benzaldehyde (0.61 g, 3 mmol),
and 5-amino-1-methyl-1,2-dihydropyrazol-3-one (0.34 g, 3
mmol) in EtOH (6 mL) were processed as in 6a to pro-
vide 0.55 g (46%) of 19 as a tan solid. 1H NMR
(DMSO-d6) d 3.5 (s, 3H), 4.1 (s, 2H), 4.53 (q, 2H), 4.98
(s, 1H), 7.18 (m, 1H), 7.21 (t, 1H), 7.4 (dd, 1H), 9.65 (bs,
1H), 10.52 (s, 1H). MS (ESI-) m/z 394,392 (MÀH)À.
Anal. (C16H13N3BrFO3) C, H, N.
4.4.25. (R)(+)-4-(3-Bromo-4-fluorophenyl)-1,6,6-trimethyl-
4,7,8,9-tetrahydroisoxazolo[3,4-b]quinoline-3,5(1H,6H)-
dione (26) and (S)(À)-4-(3-bromo-4-fluorophenyl)-1,6,6-
trimethyl - 4,7,8,9 - tetrahydroisoxazolo[3,4 - b]quinoline -
3,5(1H,6H)-dione (27). Dihydropyridoisoxazolone 25
(0.25 g) was separated on chiral column (Chiracel AS
4.6Â250 mm using 90:10 hexane:EtOH at 1 mL/min) to
provide 0.1 g of enantiomer 26 (retention time of 17
min). [a]2D3 +93.33ꢁ (DMSO); H NMR (DMSO-d6) d
1
4.4.21. Ethyl 6-[(acetyloxy)methyl]-4-(3-bromo-4-fluoro-
phenyl)-1-methyl-3-oxo-1,3,4,7-tetrahydroisoxazolo[3,4-
b]pyridine-5-carboxylate (22). 3-Amino-2-methyl-5(2H)-
isoxazolone (0.17 g, 1.5 mmol), ethyl 4-(acetylox-
y)butanoate 11 (0.28 g, 1.5 mmol17 and 3-bromo-4-
fluorobenzaldehyde (0.3 g, 1.5 mmol) in EtOH (4 mL)
were heated at 80 ꢁC for 24 h in a sealed tube. The
reaction mixture was evaporated under reduced pres-
sure and the residue chromatographed on silica gel
eluting with 5% EtOH/CH2Cl2 to provide 22 (0.2 g). 1H
NMR (DMSO-d6) d 1.03 (t, 3H), 2.1 (s, 3H), 3.23 (s,
3H), 3.82 (q, 2H), 4.8 (s, 1H), 5.12 (q, 2H), 7.25 (m, 1H),
7.3 (t, 1H), 7.48 (dd, 1H), 10.2 (s, 1H). MS (ESI-) m/z
467 (M-H)À.
0.92 (s, 3H), 1.0 (s, 3H), 1.82 (t, 2H), 2.65 (m, 2H), 3.22
(s, 3H), 4.67 (s, 1H), 7.21 (m, 2HC, 7.43 (dd, 1H), 10.39
(s, 1H). MS (ESI) m/z 419,421 (MÀH)À. Anal.
(C19H18BrFN2O3) C, H, N.
Continued elution of the column provided 0.08 g of 27
(retention time 28.5 min). [a]2D3 À96.36ꢁ (DMSO); H
1
NMR (DMSO-d6) d 0.92 (s, 3H), 1.0 (s, 3H), 1.82 (t,
2H), 2.65 (m, 2H), 3.22 (s, 3H), 4.67 (s, 1H), 7.21 (m,
2HC, 7.43 (dd, 1H), 10.39 (s, 1H). MS (ESI) m/z
419,421 (MÀH)À. Anal. (C19H18BrFN2O3) C, H, N.
4.4.26. 4-(3-Bromo-4-fluorophenyl)-1-methyl-4,9-dihydro-
1H - isoxazolo[3,4 - b]pyrano[4,3 - e]pyridine - 3,5(6H,8H) -
dione (28). 3-Amino-2-methyl-5(2H)-isoxazolone (0.11
g, 1 mmol), 3-bromo-4-fluoro-benzaldehyde (0.2 g, 1
mmol), and 2H-pyran-3,5(4H,6H)-dione (0.11 g, 1
mmol) were treated as in 6a to provide 28 as a white
4.4.22.
4-(3-Bromo-4-fluorophenyl)-1-methyl-4,8-dihy-
dro-1H,3H-furo[3,4-b]isoxazolo[4,3-e]pyridine-3,5(7H)-
dione (23). The intermediate diester 22 (0.16 g) in
MeOH (10 mL) was treated with K2CO3 (0.05 g) at
ambient temperature. After stirring for 1 h, the solvent
was evaporated under reduced pressure and the residue
was chromatographed on silica gel eluting with 5%
EtOH/CH2Cl2 to provide 23 (0.04 g). 1H NMR
(DMSO-d6) d 3.28 (s, 3H), 4.71 (s, 1H), 4.96 (q, 2H),
7.32 (m, 2H), 7.58 (dd, 1H), 11.18 (bs, 1H). MS
(ESI-) m/z 381 (MÀH)À. Anal. (C15H10BrFN2O4) C, H,
N.
1
solid (0.09 g). H NMR (DMSO-d6) d 3.27 (s, 3H), 4.05
(s, 2H), 4.57 (q, 2H), 4.78 (s, 1H), 7.28 (m, 2H), 7.54 (d,
1H), 10.77 (s, 1H). MS (ESI) m/z 395 (MÀH)À. Anal.
(C16H12BrFN2O4) C, H, N.
4.4.27. (S)(À)4-(3-Bromo-4-fluorophenyl)-1-methyl-4,9-
dihydro - 1H - isoxazolo[3,4 - b]pyrano[4,3 - e]pyridine -
3,5(6H, 8H)-dione (29) and (R )(+)4-(3-bromo-4-fluoro-
phenyl)-1-methyl - 4,9 - dihydro - 1H - isoxazolo[3,4 - b]pyr-
ano[4,3 - e]pyridine-3,5(6H,8H)-dione (30). Racemic 27
(0.25 g) was separated on Chiracel AS column eluting
with 20% of EtOH/hexane to provide 0.06 g of 29 as the
less polar enantiomer. [a]2D3 +83.33ꢁ (DMSO); 1H
NMR (DMSO-d6) d 3.27 (s, 3H), 4.05 (s, 2H), 4.57 (q,
2H), 4.78 (s, 1H), 7.28 (m, 2H), 7.54 (d, 1H), 10.77 (s, 1H);
MS (ESI) m/z 395 (MÀH)À. Anal. (C16H12BrFN2O4) C,
H, N.
4.4.23. 4-(3-Bromo-4-fluorophenyl)-1-methyl-4,7,8,9-tetra-
hydroisoxazolo[3,4-b]quinoline-3,5(1H,6H)-dione (24). 3-
Amino-2-methyl-5(2H)-isoxazolone (0.086 g, 0.75 mmol),
3-bromo-4-fluorobenzaldehyde (0.15 g, 0.075 mmol),
and 1,3-cyclohexanedione (0.084 g, 0.75 mmol) were
processed as in 6a to provide 24 as a tan solid
1
(0.09 g). H NMR (DMSO-d6) d 1.95 (m, 2H), 2.27 (m,
2H), 2.63 (m, 2H), 3.24 (s, 3H), 4.69 (s, 1H), 7.2
(m, 1H), 7.23 (t, 1H), 7.45 (dd, 1H), 10.2 (s, 1H). S
(ESI) m/z 393 (MÀH)À. Anal. (C17H14N2BrFO3) C, H,
N.
Continued elution of column afforded 0.07 g of 30 as
more polar enentiomer [a]2D3 À83.07ꢁ (DMSO); 1H NMR
(DMSO-d6) d 3.27 (s, 3H), 4.05 (s, 2H), 4.57 (q, 2H), 4.78

I. Drizin et al. / Bioorg. Med. Chem. 12 (2004) 1895–1904
1903
(s, 1H), 7.28 (m, 2H), 7.54 (d, 1H), 10.77 (s, 1H); MS (ESI)
m/z 395 (M-H)À. Anal. (C16H12BrFN2O4) C, H, N.
3,4-Dichlorobenzaldehyde (0.17 g, 1.0 mmol), 1,3-cyclo-
pentanedione (0.1 g, 1.0 mmol), and 5-amino-1-methyl-
1,2-dihydropyrazol-3-one (0.11 g, 1.0 mmol) were pro-
cessed as described in 6a. The reaction was cooled and
the resulting precipitate was collected to provide 0.24 g
of 36. 1H NMR DMSO-d6) d 2.28 (t, 2H), 2.68 (m, 2H),
3.5 (s, 3H), 4.7 (s, 1H), 7.13 (dd, 1H), 7.33 (d, 1H), 7.49
(d, 1H), 9.58 (s, 1H), 10.45 (s, 1H); MS (ESI-) m/z 348
(MÀH)À. Anal. (C16H13N3Cl2O2) C, H, N.
4.4.28. 1-Methyl - 4 - [4 - (trifluoromethoxy)phenyl] - 1,2,4,
6,7,8-hexahydrocyclopenta[b]pyrazolo[4,3-e]pyridine-3,5-
dione (31). 4-Trifluoromethoxybenzaldehyde (0.28 g,
1.5 mmol), 1,3-cyclopentanedione (0.15 g, 1.5 mmol),
and 5-amino-1-methyl-1,2-dihydropyrazol-3-one (0.17
g, 1.5 mmol) were processed as in 6a to provide 0.15 g of
1
31. H NMR (DMSO-d6) d 2.3 (t, 2H), 2.68 (m, 2H),
3.49 (s, 3H), 4.72 (s, 1H), 7.18 (d, 2H), 7.23 (d, 2H), 9.5
4.4.34. 4-(2,1,3-Benzoxadiazol-5-yl)-1-methyl-1,2,4,6,7,8-
hexahydrocyclopenta[b]pyrazolo[4,3-e]pyridine-3,5-dione
(37). 2,1,3-Benzoxadiazole-5-carboxaldehyde (0.15 g,
1.0 mmol),21 1,3-cyclopentanedione (0.1 g, 1.0 mmol),
and 5-amino-1-methyl-1,2-dihydropyrazol-3-one (0.11
g, 1.0 mmol) were processed as in 6a. The reaction was
cooled and the resulting precipitate was collected to
(bs, 1H) 10.37 (s, 1H); MS (ESI-) m/z 364 (MÀH)À.
.
Anal. (C17H14N3F3O3 0.25H2O) C, H, N.
4.4.29. 4-(3-Bromo-4-methylphenyl)-1-methyl-1,2,4,6,7,8-
hexahydrocyclopenta[b]pyrazolo[4,3-e]pyridine-3,5-dione
(32). 4-Methyl-3-bromobenzaldehyde (0.3 g, 1.5
mmol),20 1,3-cyclopentanedione (0.15 g, 1.5 mmol), and
5-amino-1-methyl-1,2-dihydropyrazol-3-one (0.17 g, 1.5
mmol) were processed as in 6a to provide 0.34 g of 32.
1H NMR (DMSO-d6) d 2.27 (s, 3H), 2.29 (t, 2H), 2.67
(m, 2H), 3.5 (s, 3H), 4.63 (s, 1H), 7.04 (dd, 1H), 7.18 (d,
1H), 7.29 (ds, 1H), 9.51 (bs, 1H), 10.37 (s, 1H); MS (ESI-)
m/z 361 (MÀH)À. Anal. (C17H16N3BrO2) C, H, N.
1
provide 0.17 g of 37. H NMR (DMSO-d6) d 2.32 (m,
2H), 2.71 (m, 2H), 3.51 (s, 3H), 4.87 (s, 1H), 7.5 (dd,
1H), 7.6 (s, 1H), 7.9 (d, 1H), 9.61 (bs, 1H), 10.52 (s, 1H);
MS (ESI-) m/z 322 (MÀH)À. Anal. (C16H13N5O3) C, H,
N.
4.4.35. 4-(3-Bromo-4-methylphenyl)-1-methyl-4,9-dihydro-
1H - isoxazolo[3,4 - b]pyrano[4,3 - e]pyridine - 3,5(6H,8H) -
dione (38). 3-Amino-2-methyl-5(2H)-isoxazolone (0.11
g, 1 mmol), 4-methyl-3-bromobenzaldehyde20 (0.2 g, 1
mmol), and 2H-pyran-3,5(4H,6H)-dione (0.11 g, 1
mmol) were processed as in 6a. The reaction mixture
was allowed to cool to ambient temperature and was
evaporated under reduced pressure. The residue was
chromatographed eluting with EtOAc:HCO2H: H2O
(19:0.5:0.5) to provide 38 (0.07 g). 1H NMR (DMSO-d6)
d 2.29 (s, 3H), 3.23 (s, 3H), 4.05 (s, 2H), 4.55 (d, 2H), 4.7
(s, 1H), 7.11 (dd, 1H), 7.23 (d, 1H), 7.47 (d, 1H),
10.8 (s, 1H); MS (ESI) m/z 389 (MÀH)À. Anal.
4.4.30. 4-[4-Fluoro-3-(trifluoromethyl)phenyl]-1-methyl-
1,2,4,6,7,8 - hexahydrocyclopenta[b]pyrazolo[4,3 - e]pyri-
dine-3,5-dione (33). 4-Fluoro-3-trifluoromethylbenzalde-
hyde (0.28 g, 1.5 mmol), 1,3-cyclopentanedione (0.15 g,
1.5 mmol), and 5-amino-1-methyl-1,2-dihydropyrazol-
3-one (0.17 g, 1.5 mmol) were processed as in 6a. The
reaction was cooled and the resulting precipitate was
1
filtered off to provide 0.35 g of 33. H NMR (DMSO-
d6) d 2.21 (m, 2H), 2.7 (m, 2H), 3.51 (s, 3H), 4.8 (s,
1H), 7.35 (t, 1H), 7.45 (m, 1H), 7.55 (d, 1H), 9.6 (bs,
1H), 10.48 (s, 1H); MS (ESI-) m/z 366 (MÀH)À. Anal.
(C17H13N3F4O2) C, H, N.
.
(C17H15N2BrO4 0.5C2H6O) C, H, N.
4.4.31. 4-(4-Chloro-3-nitrophenyl)-1-methyl-1,2,4,6,7,8-
hexahydrocyclopenta[b]pyrazolo[4,3-e]pyridine-3,5-dione
(34). 4-Chloro-3-nitrobenzaldehyde (0.27 g, 1.5 mmol),
1,3-cyclopentanedione (0.15 g, 1.5 mmol), and 5-amino-
1-methyl-1,2-dihydropyrazol-3-one (0.17 g, 1.5 mmol)
were treated as in 6a. The reaction was cooled and the
resulting precipitate was collected to provide 0.3 g of 34.
1H NMR (DMSO-d6) d 2.3 (t, 2H), 2.68 (m, 2H), 3.5 (s,
3H), 4.81 (s, 1H), 7.48 (dd, 1H), 7.6 (d, 1H), 7.78 (d,
1H), 9.61 (bs, 1H), 10.49 (s, 1H); MS (ESI-) m/z 359
(MÀH)À. Anal. (C16H13N4ClO4) C, H, N.
4.4.36. 4-[4-Fluoro-3-(trifluoromethyl)phenyl]-1-methyl-
4,9-dihydro-1H-isoxazolo[3,4-b]pyrano[4,3-e]pyridine-3,5
(6H,8H)-dione (39). 3-Amino-2-methyl-5(2H)-isoxazo-
lone (0.11 g,
1 mmol), 4-fluoro-3-trifluromethyl-
benzaldehyde and 2H-pyran-3,5(4H,6H)-dione (0.11 g,
1 mmol) were processed as in 6a. The reaction mixture
was allowed to cool to ambient temperature and was
evaporated under reduced pressure. The residue was
chromatographed on silica gel eluting with EtOAc:H-
1
CO2H:H2O (19:0.5:0.5) to yield 39 (0.08 g) H NMR
(DMSO-d6) d 3.28 (s, 3H), 4.07 (s, 2H), 4.58 (q, 2H),
4.87 (s, 1H), 7.42 (t, 1H), 7.59 (m, 2H), 10.8 (s, 1H); MS
(ESI) m/z 383 (MÀH)À. Anal. (C16H12N2F4O4) C, H,
N.
4.4.32. 4-(4-Fluoro-3-iodophenyl)-1-methyl-1,2,4,6,7,8-
hexahydrocyclopenta[b]pyrazolo[4,3-e]pyridine-3,5-dione
(35). 4-Fluoro-3-iodobenzaldehyde21 (0.25 g, 1.0 mmol),
1,3-cyclopentanedione (0.1 g, 1.0 mmol) and 5-amino-1-
methyl-1,2-dihydropyrazol-3-one (0.11 g, 1.0 mmol)
4.4.37. 4-(4-Chloro-3-nitrophenyl)-1-methyl-4,9-dihydro-
1H - isoxazolo[3,4 - b]pyrano[4,3 - e]pyridine - 3,5(6H,8H) -
dione (40). 3-Amino-2-methyl-5(2H)-isoxazolone (0.085
g, 0.75 mmol), 3-nitro-4-chlorobenzaldehyde (0.14 g,
0.75 mmol) and 2H-pyran-3,5(4H,6H)-dione (0.085 g,
0.75 mmol) were processed as in 6a to provide 40 (0.09
1
were treated as in 6a to provide 0.27 g of 35. H NMR
(DMSO-d6) d 2.3 (m, 2H), 2.68 (m, 2H), 3.5 (s, 3H),
4.67 (s, 1H), 7.1 (t, 1H), 7.15 (m, 1H), 7.52 (dd, 1H),
9.52 (s, 1H), 10.4 (s, 1H); MS (ESI-) m/z 424 (MÀH)À.
Anal. (C16H13N3FIO2) C, H, N.
1
g). H NMR (DMSO-d6) d 3.28 (s, 3H), 4.06 (s, 2H),
4.58 (s, 2H), 4.88 (s, 1H), 7.6 (dd, 1H), 7.7 (d, 1H), 7.9
(d, 1H), 10.8 (s, 1H); MS (ESI) m/z 376 (MÀH)À. Anal.
(C16H12N3ClO6) C, H, N.
4.4.33. 4-(3,4-Dichlorophenyl)-1-methyl-1,2,4,6,7,8-hexa-
hydrocyclopenta[b]pyrazolo[4,3-e]pyridine-3,5-dione (36).

1904
I. Drizin et al. / Bioorg. Med. Chem. 12 (2004) 1895–1904
4.4.38. 4-(4-Fluoro-3-iodophenyl)-1-methyl-4,9-dihydro-
1H-isoxazolo[3,4 - b]pyrano[4,3 - e]pyridine - 3,5(6H,8H) -
dione (41). 3-Amino-2-methyl-5(2H)-isoxazolone (0.086
g, 0.75 mmol), 4-fluoro-3-iodobenzaldehyde21 (0.19 g,
0.75 mmol) and 2H-pyran-3,5(4H,6H)-dione (0.085 g,
0.75 mmol) were processed as in 6a. The residue was
chromatographed eluting with 5% MeOH/CH2Cl2 to
provide 41 (0.03 g). 1H NMR (DMSO-d6) d 3.23 (s, 3H),
4.06 (s, 2H), 4.58 (q, 2H), 4.72 (s, 1H), 7.18 (t, 1H), 7.25
(m, 1H), 7.63 (dd, 1H), 10.9 (s, 1H); MS (ESI) m/z 441
(M-H)À. Anal. (C16H12N2FIO4) C, H, N.
Korstanje, C.; Chapple, C. R. Br. J. Urology 1997, 80,
405.
5. Butera, J. A.; Antane, M. M.; Antane, S. A.; Argentieri,
T. M.; Freeden, C.; Graceffa, R. F.; Hirth, B. H.;
Jenkins, D.; Lennox, J. R.; Matelan, E.; Norton, N. W.;
Quagliato, D.; Sheldon, J. H.; Spinelli, W.; Warga, D.;
Wojdan, A.; Woods, M. J. Med. Chem. 2000, 43, 1187.
6. Gilbert, A. M.; Antane, M. M.; Argentieri, T. M.; Butera,
J. A.; Francisco, G. D.; Freeden, C.; Gundersen, E. G.;
Graceffa, R. F.; Herbst, D.; Hirth, B. H.; Lennox, J. R.;
McFarlane, G.; Norton, N. W.; Quagliato, D.; Sheldon,
J. H.; Warga, D.; Wojdan, A.; Woods, M. 2000, 43, 1203
7. Carroll, W. A.; Agrios, K. A.; Altenbach, R. J.; Buckner, S.
A.; Chen, Y.; Coghlan, M. J.; Daza, A.V.; Drizin, I.; Gopa-
lakrishnan, M.; Henry, R. F.; Kort, M. E.; Kym, P. R.;
Milicic, I.; Smith, J. C.; Tang, R.; Turner, S. C.; Whiteaker,
K.L.; Sullivan, J. P.; Zhang, H. J. Med. Chem. (in press).
8. Baarnhielm, C.; Skanberg, I.; Borg, K. O. Xenobiotica
1984, 14, 719.
9. Baarnhielm, C.; Hansson, G. Biochem. Pharmac. 1986,
35, 1419.
10. Taylor, C.; Barton, J. J. Am. Chem. Soc. 1959, 81, 2448.
11. Weisberger, A.; Porter, A. J. Am. Chem. Soc. 1944, 66,
1849.
12. Barbieri, W.; Bernardi, L.; Coda, S.; Colo, V.; Palami-
dessi, G. Tetrahedron 1967, 23, 4395.
13. Carroll, W. A.; Agrios, K. A.; Altenbach, R. J.; Drizin, I.;
Kort, M. E. US 6, 190, 140 B1 2001.
4.4.39. 3-(1-Methyl-3,5-dioxo-3,4,5,6,8,9-hexahydro-1H-
isoxazolo[3,4 - b]pyrano[4,3 - e]pyridin - 4 - yl)benzonitrile
(42). 3-Amino-2-methyl-5(2H)-isoxazolone (0.085 g,
0.75 mmol), 3-cyanobenzaldehyde (0.14 g, 0.75 mmol)
and 2H-pyran-3,5(4H,6H)-dione (0.085 g, 0.75 mmol)
were processed as in 6a. The residue was chromato-
graphed eluting with 5% MeOH/CH2Cl2 to provide 42
1
(0.09 g) as a tan solid. H NMR (DMSO-d6) d 3.28 (s,
3H), 4.05 (s, 2H), 4.59 (q, 2H), 4.81 (s, 1H), 7.5 (t, 1H),
7.6 (m, 1H), 7.62 (m, 1H), 7.64 (d, 1H), 10.8 (s, 1H); MS
À
.
(ESI) m/z 322 (MÀH) .Anal. (C17H13N3O4 0.25H2O)
C, H, N.
4.4.40. 4-(2,1,3-Benzoxadiazol-5-yl)-1-methyl-4,9-dihydro-
1H - isoxazolo[3,4 - b]pyrano[4,3 - e]pyridine - 3,5(6H,8H) -
dione (43). 3-Amino-2-methyl-5(2H)-isoxazolone (0.11
g, 1 mmol), 2,1,3-benzoxadiazole-5-carboxaldehyde22
(0.15 g, 1 mmol), and 2H-pyran-3,5(4H,6H)-dione (0.11
g, 1 mmol) were processed as in 6a to provide 43 (0.09
g). 1H NMR (DMSO-d6) d 3.28 (s, 3H), 4.08 (s, 2H), 4.6
(q, 2H), 4.92 (s, 1H), 7.62 (dd, 1H), 7.76 (s, 1H), 8.0 (dd,
1H), 10.8 (s, 1H); MS (ESI) m/z 339 (MÀH)À. Anal.
(C16H12N4O5) C, H, N.
14. Nakagawa, S. Heterocycles 1979, 13, 477.
15. D’Angelo, J.; Gomez-Pardo, D. Tetrahedron Lett. 1991,
32, 3063.
16. Fehnel, E. J. Am. Chem. Soc. 1952, 74, 1569.
17. Husbands, S.; Fraser, W.; Suckling, C. J.; Wood, H. C. S.
Tetrahedron 1995, 51, 865.
18. Gopalakrishnan, M.; Whitaekar, K.; Molinari, E.; Davis-
Taber, R.; Scott, V.; Shieh, C. C.; Buckner, S.; Milicic, I.;
Cain, J.; Postl, S.; Sullivan, J.; Brioni, J. J. J. Pharm. Exp.
Therap. 1999, 289, 551.
19. Buckner, S. A.; Milicic, I.; Daza, A.; Davis-Taber, R.;
Scott, V. E.; Sullivan, J. P.; Brioni, J. D. Eur. J. Pharma-
col. 2000, 400, 287.
20. Pearson, J. Org. Chem. 1958, 23, 1412.
References and notes
21. Liu, G.; Xin, Z.; Pei, Z.; Hajduk, P. J.; Abad-Zapatero,
C.; Hutchins, C. W.; Zhao, H.; Lubben, T. H.; Ballaron,
S. J.; Haasch, D. L.; Kaszubska, W.; Rondinone, C. M.;
Trevillyan, J. M.; Jirousek, M. R. J. Med. Chem. 2003, 46,
4232.
1. Li, J. H. Drug Rev. 1997, 15, 220.
2. Chess-Williams, R. M.; Martin, S.W; Korstanje, C.;
Chapple, C. R. Br. J. Urol. 1999, 83, 1050.
3. Zografos, P.; Li, J. H.; Kau, S. T. Pharmacology 1992, 45, 216.
4. Martin, S. W.; Radley, S. C.; Chess-Williams, R.;
22. Gasco, A. M.; Ermondi, G.; Fruttero, R.; Gasco, A. Eur.
J. Med. Chem. 1996, 31, 3.