Synthesis and activity of a new class of pathway-selective estrogen receptor ligands: Hydroxybenzoyl-3,4-dihydroquinoxalin-2(1H)-ones

Article abstract of DOI:10.1016/j.bmc.2006.01.001

The anti-inflammatory activity of non-selective estrogens has been attributed to their ability to antagonize the activity of nuclear factor κB (NF-κB), a known mediator of inflammatory responses. Here we report the identification of a potent new class of

Full text of DOI:10.1016/j.bmc.2006.01.001

Bioorganic & Medicinal Chemistry 14 (2006) 3455–3466
Synthesis and activity of a new class of pathway-selective
estrogen receptor ligands: Hydroxybenzoyl-3,4-
dihydroquinoxalin-2(1H)-ones
Paige E. Mahaney,a,* Michael B. Webb,a Fei Ye,a Joseph P. Sabatucci,a Robert J. Steffan,a
Christopher C. Chadwick,b,ꢀ Douglas C. Harnishb and Eugene J. Trybulskia
aChemical and Screening Sciences, Wyeth Research, Discovery Medicinal Chemistry, 500 Arcola Road, Collegeville, PA 19465, USA
bCardiovascular/Metabolic Diseases, Wyeth Research, 500 Arcola Road, Collegeville, PA 19465, USA
Received 28 November 2005; revised 3 January 2006; accepted 3 January 2006
Available online 19 January 2006
Abstract—The anti-inflammatory activity of non-selective estrogens has been attributed to their ability to antagonize the activity of
nuclear factor jB (NF-jB), a known mediator of inflammatory responses. Here we report the identification of a potent new class of
pathway-selective ER ligands that selectively antagonize NF-jB functional activity, while exhibiting a lack of classical estrogenic effect.
ꢀ 2006 Elsevier Ltd. All rights reserved.
1. Introduction
screened in vitro in HAECT-1 cells11 that were transfec-
ted with human ERa12 and the reporter gene, NF-jB-lu-
ciferase. These cells were then treated with IL-1b and the
test compound. The amount of luciferace present in the
assay correlates directly to the degree of NF-jB tran-
scriptional activity. Efficacy as classical estrogenic
agents, characterized by stimulation of uterine prolifer-
ation, was measured by in vitro creatine kinase (CK)
expression. Target in vitro profiles for drug candidate
selection included an IC50 < 100 nM in the ER/NF-jB
luciferase assay with an efficacy compared to that of
E2 near 100% and minimal efficacy in the CK assay.
Many diseases, including arthritis, asthma, atherosclero-
sis, inflammatory bowel disease, and sepsis, are now con-
sidered to be primarily caused by inflammatory
pathways.1 Although non-selective estrogens are known
to have classical effects on the reproductive system, com-
pounds within this class such as 17b-estradiol (E2) also
have antiinflammatory activity2–5 and have been shown
to be active in several disease models of inflamma-
tion.6–8 Estrogens bind to two estrogen receptors (ERa
and ERb), both of which can antagonize the functional
activity of nuclear factor jB (NF-jB),9,10 a known pro-
moter of pro-inflammatory genes such as TNFa and
IL-6.11 A study in endothelial cells revealed that IL-1b-
induced NF-jB reporter activity and IL-6 expression
were inhibited by 17b-estradiol in an estrogen receptor
(ER)-dependent fashion,11,12 which correlates to the
antiinflammatory activity of E2 in vivo.13
Previously, two novel structural scaffolds have been
reported as pathway-selective ER ligands that selectively
antagonize NF-jB functional activity.14,15 Herein, we de-
scribethehydroxybenzoyl-3,4-dihydroquinoxalin-2(1H)-
onesasanew,novelscaffoldidentifiedwithinthisprogram.
Thus, a drug discovery project was initiated to identify
selective non-steroidal ligands for ER that could block
the transcription of NF-jB, but would be devoid of
conventional estrogenic activities. Compounds were
2. Chemistry and results
R
N
Cl
O
R1
Keywords: Hydroxybenzoyl-3,4-dihydroquinoxalin-2(1H)-ones; Estro-
gen receptor ligands; NF-jB; Anti-inflammatory activity.
*
N
O S
O
N
S
O
O
*
Corresponding author. Tel.: +1 484 865 0627; fax: +1 484 865
9399; e-mail: mahanep@wyeth.com
ꢀ
OH
HO
Present address: Life Diagnostics Inc., West Chester, PA 19380,
USA.
1
2
0968-0896/$ - see front matter ꢀ 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2006.01.001

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P. E. Mahaney et al. / Bioorg. Med. Chem. 14 (2006) 3455–3466
An HTS screen identified a class of 4-hydroxyphenyl
sulfonamides, that is, compound 1 (ER/NF-jB-luc
IC50 = 43 nM [% E2 = 108]) CK EC50 = 166 nM [%
E2 = 53]), which was the focus of a medicinal chemistry
program, the SAR of which has been previously de-
scribed.16 An effort to design constrained analogs of
the 4-hydroxyphenyl sulfonamides first led to the identi-
fication of a series of pyrrolo[1,2-a]quinoxalin-5(4H)-
yl)sulfonyl]phenols, which will be the subject of a future
publication. Additional efforts to design constrained
analogs that (1) were readily synthesized via chiral meth-
ods, (2) had improved aqueous solubility, and (3) pos-
sessed improved metabolic stability led to the
identification of (4-hydroxyphenyl)sulfonyl-3,4-dihydro-
quinoxalin-2(1H)-ones, for example, compound 2, the
synthesis of which is depicted in Scheme 1.
A series of N-1-substituted (4-hydroxyphenyl)sulfonyl-
3,4-dihydroquinoxalin-2(1H)-ones are depicted in Table
1. When the effect of stereochemistry was evaluated, it
was found that the 3-S enantiomer was more potent
and efficacious in the ER/NF-jB-luciferase assay com-
pared to the 3-R enantiomer (2a vs 2b). When aromatic
substitution on the quinoxalinone ring was examined,
the 6-fluoro analogs were more potent and efficacious
compared to the 7-fluoro analogs (2b vs 2c and 2d vs
2e). Substitution at the N-1 position significantly affect-
ed potency and efficacy. Increasing the length of the
non-branching carbon chain at this position resulted in
an increase in potency and efficacy in the ER/NF-jB-lu-
ciferase assay (2c, 2e–2h); however, incorporating
branching into the substituent (2i and 2j) resulted in a
complete loss of activity. Fortunately, all compounds
within this series were selective, having minimal efficacy
in the CK assay.
The 3,4-dihydroquinoxalin-2(1H)-one core, compound
5, can be synthesized as a pure enantiomer in two steps
starting with an appropriately substituted ortho-fluoro-
nitrobenzene, compound 3, and either (R)- or (S)-2-ami-
nobutyric acid. Nucleophilic aromatic substitution
under basic conditions afforded the 2-[(2-nitrophen-
yl)amnio]-butanoic acid 4, reduction of which via
hydrogenation facilitated spontaneous ring cyclization
to form the optically pure 3,4-dihydroquinoxalin-
2(1H)-one 5. Selective sulfonylation at the N-4 position
with ethyl (4-chlorosulfonyl)phenyl carbonate17 and
pyridine afforded sulfonamide 6, which was alkylated
at the N-1 position with an alkyl halide in refluxing ace-
tone using cesium carbonate as base. The carbonate pro-
tecting group was selected, because deprotection could
occur in situ to afford the desired (4-hydroxyphenyl)sul-
fonyl-3,4-dihydroquinoxalin-2(1H)-one 2 with minimal
side products.
Although the (4-hydroxyphenyl)sulfonyl-3,4-dihydro-
quinoxalin-2(1H)-one series afforded active compounds
in the luciferase assay with good efficacy, the in vitro
target for potency (<100 nM) for the program was not
achieved. Therefore, in an effort to improve potency,
an amide linker (compound 9, Scheme 2) was explored
as a replacement for the sulfonamide in compound 2.
The synthesis of the hydroxybenzoyl-3,4-dihydroqui-
noxalin-2(1H)-ones 9 starting from the common 3,4-
dihydroquinoxalin-2(1H)-one intermediate is depicted
in Scheme 2. Again, the N-4 position can be selectively
acylated with an appropriately substituted meth-
oxybenzoylchloride in the presence of a base, followed
by alkylation of the N-1 position with an alkyl halide
under basic conditions. Alternatively, the N-1 position
can be alkylated with an activated alcohol using Mitsun-
obu conditions. Deprotection of the phenol was best
performed with boron trichloride and tetrabutylammo-
nium iodide18 to avoid the formation of brominated
side-products that were observed when boron tribro-
mide was used.
H
NO2
F
N
O
NO2
NH
R1
R1
a
R1
b
*
N
H
An examination of the preferred stereochemistry for
the hydroxybenzoyl-3,4-dihydroquinoxalin-2(1H)-ones
yielded a surprising result. While the 3-S stereochem-
istry was optimal for potency and efficacy in
the sulfonamide series (Table 1), the 3-R stereochemis-
try was found to be preferred in the amide series
(Table 2). Additionally, these preliminary compounds
showed that replacing the sulfonamide with an amide
afforded an increase in potency and efficacy in the ER/
NF-jB-luciferase assay (compound 2e vs compound
9c) while maintaining selectivity over CK expression.
CO2H
*
3a = 5-F
5a = 3R, 7-F
5b = 3S, 7-F
5c = 3R, 6-F
5d = 3S, 6-F
3b = 4-F
4a = 2R, 4-F
4b = 2S, 4-F
4c = 2R, 5-F
4d = 2S, 5-F
R
N
H
c
d
N
O
O
R1
R1
*
*
N
S
N
S
O
O
O
O
EtO2CO
HO
Next, a series of N-1-substituted 4-hydroxybenzoyl-3,4-
dihydroquinoxalin-2(1H)-ones was synthesized (Table
3). A SAR trend similar to that seen in the (4-hydroxy-
phenyl)sulfonyl-3,4-dihydroquinoxalin-2(1H)-one series
was observed. Again, in general, increasing the length
of the non-branching carbon chain (9a–9i) resulted in
an increase in potency and efficacy in the ER/NF-jB-lu-
ciferase assay. In most cases, branching of the carbon
chain was again detrimental to potency in the luciferase
6a = 3R, 7-F
6b = 3S, 7-F
6c = 3S, 6-F
2
Scheme 1. Synthesis of (4-hydroxyphenyl)sulfonyl-3,4-dihydroquinox-
alin-2(1H)-ones. Reagents and conditions: (a) (R)- or (S)-2-aminobu-
tyric acid, K2CO3, DMF, 100 ꢁC; (b) 10% Pd/C, H2 (50 psi), EtOH;
49–53% yield for two steps; (c) ethyl (4-chlorosulfonyl)phenyl carbon-
ate, pyridine, CH2Cl2, 74–81% yield; (d) RI, Cs2CO3, acetone, reflux;
then 2 N NaOH; 15–81% yield depending on alkyl group.

P. E. Mahaney et al. / Bioorg. Med. Chem. 14 (2006) 3455–3466
3457
Table 1. Effect of N-1 substitution on the (4-hydroxyphenyl)sulfonyl-3,4-dihydroquinoxalin-2(1H)-ones versus E2 on NF-jB and CK expression in
Ad5-wt-ERa-infected HAECT-1 cellsa
R
N
O
R1
*
N
S
O
O
HO
2
Compound
R
R1
Stereochemistry
ER/NFjB-luc IC50 (nM)
% E2—NFjB
CK EC50 (nM)
% E2—CK
2a
2b
2c
2d
2e
2f
Methyl
Methyl
Methyl
Ethyl
7-F
7-F
6-F
7-F
6-F
6-F
6-F
6-F
6-F
6-F
R
S
S
S
S
S
S
S
S
S
IAb
1169
681
738
339
5604
157
313
IAb
IAb
1227
344
1897
43
IAb
IAb
4.7
IAb
IAb
IAb
34
20
35
9
85
108
63
Ethyl
Allyl
81
55
2g
2h
2i
n-Propyl
n-Butyl
i-Propyl
Cyclopentyl
79
106
17
2j
a All compounds were ER dependent (only active when ER is coexpressed with NF-jB-luciferase in HAECT cells).
b IA, inactive to 1 lM; % E2, efficacy (relative inhibition of test compound a 10 lM vs E2 at 0.1 nM).
H
N
The final group of compounds was synthesized to exam-
ine the importance of the presence and the position of the
hydroxyl moiety in the hydroxybenzoyl-3,4-dihydroqui-
noxalin-2(1H)-one series (Table 4). These compounds
were synthesized in the same manner as compound 9
(Scheme 2). The importance of the presence of the
hydroxyl group was determined through the synthesis
of compounds 10f-10 h, all of which were nearly inactive
in the ER/NF-jB-luciferase assay. Moving the hydroxyl
group to the meta position on the benzoyl group (com-
pounds 10a–10c) resulted in a loss of potency and efficacy
when compared to their para-substituted analogs; how-
ever, the introduction of an additional hydroxyl group
at the ortho position on the benzoyl moiety in combina-
tion with one at the para position yielded the most potent
compounds in the series (compounds 10d and 10e).
H
N
O
R1
b or c
O
a
R1
*
*
N
N
H
O
MeO
5a = 3R, 7-F
5b = 3S, 7-F
5c = 3R, 6-F
5d = 3S, 6-F
7a = 3R, 7-F,4'-OMe
7b = 3S, 7-F,3''-OMe
7c = 3R, 6-F, 4'-OMe
7d = 3S, 6-F, 4'-OMe
7e = 3R, 6-F, (2',4'-di-OMe)
7f = 3R, 6F, 4'-Me
7g= 3R, 6F, 4'-NO2
R
N
R
N
O
O
R1
R1
d
*
*
N
N
O
O
HO
MeO
9a - 9k , R1 = 6-F
9l - 9n, R1 = 7-F
8
Having met the project’s potency and efficacy goals,
the solubility and microsomal stability properties of
the hydroxybenzoyl-3,4-dihydroquinoxalin-2(1H)-ones
were then examined (Table 5).
Scheme 2. Synthesis of hydroxybenzoyl-3,4-dihydroquinoxalin-2(1H)-
ones. Reagents: (a) methoxybenzoylchloride, Et3N, CH2Cl2; 64–76%
yield; (b) RI, K2CO3 or Cs2CO3, acetone; (c) ROH, PPh3, DIAD,
CH2Cl2; 14% yield for two steps; (d) BCl3, Bu4NH4+Iꢀ, CH2Cl2, 22–
81% yield for two steps depending on alkyl group.
As was expected, the aqueous solubility of the com-
pounds decreased as the lipophilicity of the substituent
on the N-1 position increased. Compounds with the poor-
est solubility at pH 7.4 possessed the substituents allyl
(9e), n-pentyl (9i), cyclopentyl (9k), and benzyl (9o). In
general, compounds in this class were found to have poor
stability in rat liver microsomes, possessing very short
half-lives; however, some surprising results were ob-
served. Unfortunately, the 3-R enantiomers (9a and 9c),
which possessed the preferred stereochemistry for poten-
cy and efficacy, were significantly less stable than the 3-S
enantiomers (9b and 9d). However, we were fortunate to
find that the 2,4-dihydroxylbenzoyl-3,4-dihydroquinoxa-
lin-2(1H)-ones (compounds 10d and 10e), the most potent
compounds in the series, had very acceptable stability in
rat liver microsomes with half-lives >30 min.
assay (9h vs 9j and 9k), with the possible exception of
the n-propyl versus the iso-propyl substituent (9f vs
9g). The most dramatic loss in potency was observed
with the N-benzyl substitution (9o). One notable differ-
ence in the SAR of the sulfonamide series when com-
pared to the amide series was observed in the N-1 allyl
analogs. While this substituent afforded a highly potent
and efficacious compound in the amide series (com-
pound 9e), the substituent was not tolerated in the
sulfonamide series (compound 2f). This difference
notwithstanding, it was surprising how similar the
SAR trends in the two series were considering the
observed reversal of preferred stereochemistry.

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P. E. Mahaney et al. / Bioorg. Med. Chem. 14 (2006) 3455–3466
Table 2. Effect of stereochemistry on the 4-hydroxybenzoyl-3,4-dihydroquinoxalin-2(1H)-ones versus E2 on NF-jB and CK expression in
Ad5-wt-ERa-infected HAECT-1 cellsa
R
N
O
*
F
N
O
HO
9
Compound
R
Stereochemistry
ER/NFjB-luc IC50 (nM)
% E2—NFjB
CK EC50 (nM)
% E2—CK
27
*
9a
9b
9c
9d
Methyl
Methyl
Ethyl
R
S
R
S
102
303
139
285
84
44
99
44
IAb
IAb
107
IAb
Ethyl
a All compounds were ER dependent (only active when ER is coexpressed with NF-jB-luciferase in HAECT cells).
b IA, inactive to 1 lM; % E2 = efficacy (relative inhibition of test compound a 10 lM vs E2 at 0.1 nM).
Table 3. Effect of N-1 substitution on the 4-hydroxybenzoyl-3,4-dihydroquinoxalin-2(1H)-ones versus E2 on NF-jB and CK expression in
Ad5-wt-ERa-infected HAECT-1 cellsa
R
N
O
R1
N
O
HO
9- (R)
Compound
R
R1
ER/NFjB-luc IC50 (nM)
% E2—NFjB
CK EC50 (nM)
% E2—CK
9a
9c
9e
9f
Methyl
Ethyl
Allyl
6-F
6-F
6-F
6-F
6-F
6-F
6-F
6-F
6-F
6-F
7-F
7-F
7-F
102
139
57
84
99
IAb
107
27
20
38
95
96
208
311
n-Propyl
i-Propyl
n-Butyl
222
105
52
9g
9h
9i
91
95
IAb
IAb
n-Pentyl
i-Butyl
89
102
87
>1000
IAb
IAb
IAb
89
13
9j
262
445
204
74
9k
9l
Cyclopentyl
2,2,2-Trifluoroethyl
Methyl
96
83
9m
9n
9o
99
16
29
24
Ethyl
Benzyl
72
1228
104
80
103
>10,000
a All compounds were ER dependent (only active when ER is coexpressed with NF-jB-luciferase in HAECT cells).
b IA, inactive to 1 lM; % E2, efficacy (relative inhibition of test compound a 10 lM vs E2 at 0.1 nM).
3. Conclusions
4. Experimental
4.1. General methods: chemistry
In conclusion, we have identified a new class of potent,
and efficacious pathway-selective ERa ligands that antag-
onize ER/NF-jB functional activity. Furthermore, these
compounds have weak efficacy in the creatine kinase as-
say relative to 17b-estradiol; therefore, they should not
exhibit classical estrogenic activities. In addition to their
in vitro activity, the hydroxybenzoyl-3,4-dihydroquinox-
alin-2(1H)-ones in general have good aqueous solubility,
and the 2,4-dihydroxybenzoyl analogs also have good sta-
bility in rat liver microsomes. Taken together, these data
show that the hydroxybenzoyl-3,4-dihydroquinoxalin-
2(1H)-one series yields drug-like compounds that could
warrant further in vivo studies.
Solvents were purchased as anhydrous grade and were
used without further purification. Melting points were
measured on a Mel-Temp II (Laboratory Device, Inc.)
melting point apparatus and are uncorrected. 1H
NMR spectra were recorded on a Varian INOVA 400
instrument, and chemical shifts are reported in d values
(parts per million, ppm) relative to an internal standard
tetramethylsilane in CDCl3 or DMSO-d6. Electrospray
(ESI) mass spectra were recorded on a Waters Alli-
ance-ZMD mass spectrometer. Electron impact ioniza-
tion (EI, EE = 70 eV) mass spectra were recorded on a

P. E. Mahaney et al. / Bioorg. Med. Chem. 14 (2006) 3455–3466
3459
Table 4. Effect of benzoyl aromatic substitution on the benzoyl-3,4-dihydroquinoxalin-2(1H)-ones versus E2 on NF-jB and CK expression in Ad5-
wt-ERa-infected HAECT-1 cellsa
R
N
O
R1
R2
N
O
Compound
R
R1
R2
ER/NFjB-luc IC50 (nM)
% E2—NFjB
CK EC50 (nM)
% E2—CK
19
10a
10b
10c
10d
10e
10f
10g
10h
Methyl
Ethyl
7-F
7-F
7-F
6-F
6-F
6-F
6-F
6-F
m-OH
m-OH
m-OH
520
IAb
542
20
57
126
IAb
255
169
50
IAb
IAb
329
Benzyl
Methyl
Ethyl
65
96
92
66
17
36
44
o,p-Di-OH
o,p-Di-OH
p-OMe
p-Me
5.4
Ethyl
Methyl
Methyl
2679
IAb
IAb
4-NO2
2
a All compounds were ER dependent (only active when ER is coexpressed with NF-jB-luciferase in HAECT cells).
b IA, inactive to 1 lM; % E2, efficacy (relative inhibition of test compound a 10 lM vs E2 at 0.1 nM).
Table 5. Effect of substitution on the hydroxybenzoyl-3,4-dihydroquinoxalin-2(1H)-ones on pharmaceutical profiling parametersa
Compound
R
R1 R2
Stereochemistry Aqueous solubility at pH 7.4 (lg/mL) Microsomal stabilityb (rat) t1/2 (min)
9a
9b
9c
Methyl
Methyl
Ethyl
6-F p-OH
6-F p-OH
6-F p-OH
6-F p-OH
6-F p-OH
6-F p-OH
6-F p-OH
6-F p-OH
6-F p-OH
6-F p-OH
R
S
>100
>100
>100
>100
10
6
>30
5
R
S
9d
9e
Ethyl
Allyl
16
6
R
R
R
R
R
R
R
R
R
R
R
R
9f
n-Propyl
i-Propyl
n-Butyl
n-Pentyl
i-Butyl
>100
>100
66
7
9g
9h
9i
10
5
14
68
5
9j
5
9k
9m
9n
9o
10d
10e
Cyclopentyl 6-F p-OH
Methyl
Ethyl
14
0
7-F p-OH
7-F p-OH
>100
>100
9
8
9
Benzyl
Methyl
Ethyl
7-F p-OH
6-F o,p-di-OH
6-F o,p-di-OH
9
>100
>100
>30
>30
a Values are means of three experiments.
b Incubated in rat liver microsomes at a concentration of 1 lM for 15 min at 37 ꢁC.
Finnigan Trace mass spectrometer. Combustion analy-
ses were performed by Robertson Microlit. Analytical
thin-layer chromatography (TLC) was performed on
precoated plates (silica gel, 60 F-254) and visualized
using UV light and/or staining with a phosphomolybdic
acid solution in ethanol. In general, compound purity
was assessed by 1H NMR and an LC/UV/MS method.19
Biological results were obtained on compounds of >97%
chemical purity as determined by the above methods.
ate (13.9 g in 125 mL) and washed twice with ether.
Concentrated hydrochloric acid (approximately 17 mL)
was added dropwise with stirring. The mixture was
extracted with ethyl acetate (3· 100 mL), and the ex-
tracts were washed with water (3· 100 mL). The solu-
tion was dried over magnesium sulfate and the solvent
was evaporated. The resulting residue was dissolved in
ethanol (200 mL) and treated in a Parr apparatus with
10% palladium on carbon (1.50 g) and 50 psi hydrogen
gas for 1.5 h, after which time hydrogen uptake had
ceased. The mixture was then filtered through Celite,
and the solvent was evaporated at reduced pressure.
The product was purified via Biotage Horizonꢂ (40 M,
silica, gradient from 15% EtOAc/hexane to 50%
EtOAc/hexane).
4.2. General procedure 1: synthesis of the 3,4-dihydro-
quinoxalin-2(1H)-one cores (5a–5d)
A solution of difluoronitrobenzene (39.5 mmol), either
(S)- or (R)-2-aminobutyric acid (43.0 mmol), and potas-
sium carbonate (16.2 mmol) in dimethylformamide
(40 mL), under nitrogen, was stirred at 100 ꢁC for
14 h. The solvent was evaporated at reduced pressure,
and the residue was dissolved in 11% potassium carbon-
4.2.1.
(3R)-3-Ethyl-7-fluoro-3,4-dihydroquinoxalin-
1
2(1H)-one (5a). Yield: 53% of a light brown solid; H
NMR (DMSO-d6, 400 MHz) d 0.92 (t, J = 7.5 Hz,

3460
P. E. Mahaney et al. / Bioorg. Med. Chem. 14 (2006) 3455–3466
3H), 1.55–1.68 (m, 2H), 3.62 (ddd, J = 2.1, 5.2, 6.9 Hz,
1H), 5.95 (d, J = 1.6, 1H), 6.52–6.60 (m, 2H), 6.69 (dd,
J = 5.4, 8.6 Hz, 1H), 10.26 (br s, 1H); HRMS: calcd
1H), 6.58 (dd, J = 2.9, 9.5 Hz, 1H), 6.98 (ddd, J = 2.9,
8.7, 8.7 Hz, 1H), 7.40–7.46 (m, 4H), 7.60 (dd, J = 5.7,
9.0 Hz, 1H); 10.44 (br s, 1H); MS (ESI) m/z 423; MS
for C10H11FN2O, 194.08558; found (ESI, [M+H]1+),
(ESI) m/z 421. HRMS: calcd for C19H19FN2O6S+H+,
25
D
25
D
195.09281. ½aꢁ ꢀ43.5ꢁ (c 0.01 g/mL, DMSO); Anal.
423.10206; found (ESI, [M+H]+), 423.1036. ½aꢁ
Calcd for C10H11FN2O: C, 61.85; H, 5.71; N, 14.42.
Found: C, 61.85; H, 5.85; N, 14.46.
+12.3ꢁ (c 0.0058 g/mL, DMSO).
4.3.2. Ethyl 4-{[(2S)-2-ethyl-6-fluoro-3-oxo-3,4-dihydro-
(6b).
4.2.2.
(3S)-3-Ethyl-7-fluoro-3,4-dihydroquinoxalin-
quinoxalin-1(2H)-yl]sulfonyl}phenyl
carbonate
1
1
2(1H)-one (5b). Yield: 49% of a beige solid; H NMR
(DMSO-d6, 400 MHz) d 0.92 (t, J = 7.4 Hz, 3H), 1.52–
1.70 (m, 2H), 3.62 (ddd, J = 2.3, 5.2, 6.8 Hz, 1H), 5.95
(d, J = 1.9, 1H), 6.51–6.60 (m, 2H), 6.69 (dd, J = 5.4,
Yield: 81% of a white solid; mp 133–136 ꢁC; H NMR
(DMSO-d6, 400 MHz) d 0.93 (t, J = 7.3 Hz, 3H), 1.20–
1.31 (m, 1H), 1.29 (t, J = 7.2 Hz, 3H), 1.51–1.62 (m,
1H), 4.27 (quar, J = 7.0 Hz, 2H), 4.32 (dd, J = 5.2,
10.4 Hz, 1H), 6.59 (dd, J = 2.9, 9.3 Hz, 1H), 6.98 (ddd,
J = 2.9, 8.8, 8.8 Hz, 1H), 7.40–7.46 (m, 4H), 7.60 (dd,
8.5 Hz, 1H), 10.26 (br s, 1H); MS (ESI) m/z 195
25
([M+H]+); ½aꢁ +33.4ꢁ (c 0.01 g/mL, DMSO); Anal.
D
Calcd for C10H11FN2O: C, 61.85; H, 5.71; N, 14.42.
Found: C, 61.84; H, 5.72; N, 14.24.
J = 5.7, 9.2 Hz, 1H); 10.44 (br s, 1H); MS (ESI) m/z
25
D
423; MS (ESI) m/z 421. ½aꢁ ꢀ17.4ꢁ (c 0.0058 g/mL,
DMSO). Anal. Calcd for C19H19FN2O6S: C, 54.02; H,
4.53; N, 6.63. Found: C, 53.95; H, 4.56; N, 6.68.
4.2.3.
(3R)-3-Ethyl-6-fluoro-3,4-dihydroquinoxalin-
1
2(1H)-one (5c). Yield: 45% of a beige solid; H NMR
(CDCl3, 400 MHz) d 1.03 (t, J = 7.5 Hz, 3H), 1.74–
1.90 (m, 2H), 3.62 (ddd, J = 2.3, 4.3, 6.3 Hz, 1H), 4.03
(br s, 1H), 6.39–6.45 (m, 2H), 5.64 (dd, J = 5.3,
8.3 Hz, 1H), 8.56 (br s, 1H); HRMS: calcd for
4.3.3. Ethyl 4-{[(2S)-2-ethyl-7-fluoro-3-oxo-3,4-dihydro-
quinoxalin-1(2H)- yl]sulfonyl}phenyl carbonate (6c).
Yield: 77% of a white solid; mp 140–143 ꢁC; H NMR
1
(DMSO-d6, 400 MHz) d 0.87 (t, J = 7.4 Hz, 3H), 1.22
(m, 1H), 1.25 (t, J = 7.1 Hz, 3H), 1.52 (m, 1H), 4.22
(quar, J = 7.1 Hz, 2H), 4.29 (dd, J = 5.1, 10.3 Hz, 1H),
6.79 (dd, J = 5.4, 8.9 Hz, 1H), 7.13 (ddd, J = 2.8, 8.5,
8.5 Hz, 1H), 7.34–7.39 (m, 1H), 7.37 (dd, J = 2.2,
6.8 Hz, 2H); 7.46 (dd, J = 2.2, 6.8 Hz, 2H), 10.34 (br s,
1H); MS (ES) m/z 423.1 ([M+H]+); MS (ES) m/z 440.1
([M+NH4]+); MS (ES) m/z 445.1 ([M+NA]+); MS (ES)
C10H11FN2O, 194.08558; found (ESI-FT, [M+H]1+),
25
D
195.08807. ½aꢁ ꢀ9.2ꢁ (c 0.01 g/mL, DMSO); Anal.
Calcd for C10H11FN2O: C, 61.85; H, 5.71; N, 14.42.
Found: C, 61.77; H, 5.76; N, 14.33.
4.2.4.
(3S)-3-Ethyl-6-fluoro-3,4-dihydroquinoxalin-
2(1H)-one (5d). Yield: 63% of an off-white solid; 1H
NMR (DMSO-d6, 400 MHz) d 0.87 (t, J = 7.4 Hz,
3H), 1.59 (m, 2H), 3.65 (ddd, J = 1.8, 1.8, 5.1 Hz, 1H),
6.24 (br s, 1H), 6.29 (ddd, J = 2.8, 8.8, 8.8 Hz, 1H),
6.45 (dd, J = 2.8, 10.5 Hz, 1H), 6.61 (dd, J = 5.6,
m/z 486.1 ([M+ACN+NA]+); MS (ES) m/z 862.2
25
D
([2M+NH4]+); MS (ES) m/z 867.1 ([2M+NA]+); ½aꢁ
+10.0ꢁ (c 0.0085 g/mL, DMSO); Anal. Calcd for
C19H19FN2O6S: C, 54.02; H, 4.53; N, 6.63. Found: C,
54.06; H, 4.68; N, 6.45.
8.5 Hz, 1H), 10.15 (br s, 1H); MS (ESI) m/z 195
25
D
([M+H]+); ½aꢁ +18.6ꢁ (c 0.01 g/mL, DMSO); Anal.
Calcd for C10H11FN2O: C, 61.85; H, 5.71; N, 14.42.
Found: C, 61.72; H, 5.80; N, 14.33.
4.4. General procedure 3: preparation of 4-(hydroxyphe-
nyl)sulfonyl-3,4-dihydroquinoxalin-2(1H)-ones (2a–2j)
4.3. General procedure 2: preparation of ethyl 4-{[3-oxo-
3,4-dihydroquinoxalin-1(2H)-yl]sulfonyl}phenyl carbon-
ates (6a–6c)
To a solution of ethyl 4-{[3-oxo-3,4-dihydroquinoxalin-
1(2H)-yl]sulfonyl}phenyl carbonate (0.83 mmol) in ace-
tone (5 mL) were added cesium carbonate (0.3 g,
0.91 mmol) and the appropriate alkyl iodide
(3.32 mmol). The mixture was heated at 62 ꢁC for
2.5 h, cooled to 25 ꢁC, and treated with a 2 N aqueous
solution of sodium hydroxide (3 mL). The reaction
was then stirred at 25 ꢁC for 2 h and was acidified to
pH <2 with the addition of a 2 N aqueous solution of
hydrochloric acid. The resulting mixture was partitioned
between ethyl acetate and a saturated aqueous solution
of sodium chloride. The organic layer was separated,
dried over magnesium sulfate, and concentrated. The
product was purified via flash column chromatography.
A
solution
of
3,4-dihydroquinoxalin-2(1H)-one
(11.2 mmol) in methylene chloride (30 mL) was degassed
by bubbling nitrogen through the solution for 5 min.
Ethyl (4-chlorosulfonyl)phenyl carbonate17 (3.0 g,
11.3 mmol) followed by pyridine (0.92 mL, 11.4 mmol)
was added. The reaction mixture was stirred at 25 ꢁC
for 14 h, after which time the solvent was removed in
vacuo. The resulting residue was dissolved in ethyl ace-
tate and filtered through a plug of silica gel (eluting with
60% EtOAc:hexane). The solution was concentrated in
vacuo, and the resulting solid was recrystallized from
ethyl acetate/hexane and dried in a vacuum oven.
4.4.1. (3R)-3-Ethyl-7-fluoro-4-[(4-hydroxyphenyl)sulfo-
nyl]-1-methyl-3,4-dihydroquinoxalin-2(1H)-one
(2a).
4.3.1. Ethyl 4-{[(2R)-2-ethyl-6-fluoro-3-oxo-3,4-dihydro-
quinoxalin-1(2H)-yl]sulfonyl}phenyl
Yield: 74% of a white solid; mp 128–131 ꢁC; H NMR
(DMSO-d6, 400 MHz) d 0.93 (t, J = 7.3 Hz, 3H), 1.23–
1.33 (m, 1H), 1.29 (t, J = 7.2 Hz), 1.53–1.61 (m, 1H),
4.27 (quar, J = 7.2 Hz, 2H), 4.32 (dd, J = 5.2, 10.3 Hz,
Yield: 73% of a white solid; 1H NMR (DMSO-d6,
400 MHz) d 0.90 (t, J = 7.3 Hz, 3H), 1.16–1.24 (m,
1H), 1.47–1.54 (m, 1H), 2.69 (s, 3H), 4.35 (dd, J = 5.2,
10.3 Hz, 1H), 6.78 (d, J = 8.8 Hz, 2H), 7.01–7.08 (m,
2H), 7.12 (d, J = 8.8 Hz, 2H), 7.56 (dd, J = 5.9, 8.3 Hz,
1H), 10.61 (br s, 1H); MS (ESI) m/z 365 ([M+H]+);
carbonate (6a).
1

P. E. Mahaney et al. / Bioorg. Med. Chem. 14 (2006) 3455–3466
3461
25
MS (ESI) m/z 363 ([MꢀH]ꢀ). ½aꢁ +28.4ꢁ (c 0.010 g/mL,
25
(ESI) m/z 389 ([MꢀH]ꢀ). ½aꢁ ꢀ20ꢁ (c 0.005 g/mL,
D
D
DMSO).
DMSO).
4.4.2. (3S)-3-Ethyl-7-fluoro-4-[(4-hydroxyphenyl)sulfo-
4.4.7. (3S)-3-Ethyl-6-fluoro-4-[(4-hydroxyphenyl)sulfo-
nyl]-1-methyl-3,4-dihydroquinoxalin-2(1H)-one
(2b).
nyl]-1-propyl-3,4-dihydroquinoxalin-2(1H)-one
Yield: 31% as a white solid; 1H NMR (DMSO-d6,
400 MHz) 0.68 (t, J = 7.5 Hz, 3H), 0.89 (t,
(2g).
Yield: 78% of a white solid; 1H NMR (DMSO-d6,
400 MHz) d 0.90 (t, J = 7.3 Hz, 3H), 1.16–1.26 (m,
1H), 1.47–1.54 (m, 1H), 2.69 (s, 3H), 4.35 (dd, J = 5.3,
10.4 Hz, 1H), 6.78 (d, J = 8.8 Hz, 2H), 7.01–7.07 (m,
2H), 7.12 (d, J = 8.8 Hz, 2H), 7.56 (dd, J = 6.0, 8.5 Hz,
d
J = 7.5 Hz, 3H), 1.06–1.15 (m, 1H), 1.18–1.28 (m, 1H),
1.46–1.56 (m, 1H), 3.26–3.42 (m, 2H), 4.39 (dd,
J = 5.2, 10.3 Hz, 1H), 6.78 (d, J = 8.8 Hz, 2H), 7.17–
7.26 (m, 4H), 7.42 (dd, J = 2.9, 9.3 Hz, 1H), 10.61 (br
1H), 10.61 (br s, 1H); MS (ESI) m/z 365 ([M+H]+); MS
25
(ESI) m/z 363 ([MꢀH]ꢀ). ½aꢁ ꢀ37ꢁ (c 0.0056 g/mL,
s, 1H); mp >250 ꢁC. MS (ESI) m/z 393 ([M+H]+); MS
D
25
(ESI) m/z 391 ([MꢀH]ꢀ). ½aꢁ ꢀ6ꢁ (c 0.005 g/mL,
DMSO). Anal. Calcd for C17H17FN2O4S: C, 56.03; H,
4.70; N, 7.69. Found: C, 56.12; H, 4.03; N, 7.45.
D
DMSO).
4.4.3. (3S)-3-Ethyl-6-fluoro-4-[(4-hydroxyphenyl)sulfo-
4.4.8.
nyl)sulfonyl]-3,4-dihydroquinoxalin-2(1H)-one
(3S)-1-Butyl-3-ethyl-6-fluoro-4-[(4-hydroxyphe-
(2h).
nyl]-1-methyl-3,4-dihydroquinoxalin-2(1H)-one
(2c).
Yield: 81% of a white solid; 1H NMR (DMSO-d6,
400 MHz) d 0.89 (t, J = 7.4 Hz, 3H), 1.13–1.26 (m,
1H), 1.45–1.56 (m, 1H), 2.73 (s, 3H), 4.35 (dd, J = 5.0,
10.0 Hz, 1H), 6.79 (d, J = 8.5 Hz, 2H), 7.10–7.19 (m,
1H), 7.18 (d, J = 8.5 Hz, 2H), 7.26 (ddd, J = 2.6, 8.6,
8.6 Hz, 1H), 7.39 (dd, J = 2.6, 9.1 Hz, 1H), 10.60 (br s,
1H); MS (ESI) m/z 365 ([M+H]+); MS (ESI) m/z 363
Yield: 42% as a white solid; mp 177–178 ꢁC. H NMR
(DMSO-d6, 400 MHz) d 0.78 (t, J = 7.3 Hz, 3H), 0.90
(t, J = 7.3 Hz, 3H), 0.99–1.10 (m, 4H), 1.16–1.28 (m,
1H), 1.46–1.56 (m, 1H), 3.30–3.37 (m, 1H), 3.49–3.57
(m, 1H), 4.46 (dd, J = 5.2, 10.1 Hz, 1H), 6.78 (d,
J = 8.8 Hz, 2H), 7.17–7.26 (m, 2H), 7.21 (d,
J = 8.8 Hz, 2H), 7.43 (dd, J = 2.9, 9.4 Hz, 1H), 10.59
1
([MꢀH]ꢀ). HRMS: calcd for C17H17FN2O4S+H+,
(br s, 1H); MS (ESI) m/z 407 ([M+H]+); MS (ESI) m/z
25
D
25
405 ([MꢀH]ꢀ). ½aꢁ ꢀ4ꢁ (c 0.0058G/ML, DMSO). Anal.
365.09658; found (ESI+, [M+H]1+), 365.09603; ½aꢁ
D
ꢀ14ꢁ (c 0.041 g/mL, DMSO).
Calcd for C20H23FN2O4S: C, 59.10; H, 5.70; N, 6.89.
Found: C, 58.73; H, 5.55; N, 6.76.
4.4.4. (3S)-1,3-Diethyl-7-fluoro-4-[(4-hydroxyphenyl)sul-
fonyl]-3,4-dihydroquinoxalin-2(1H)-one (2d). Yield: 72%
4.4.9. (3S)-3-Ethyl-6-fluoro-4-[(4-hydroxyphenyl)sulfo-
nyl]-1-isopropyl-3,4-dihydroquinoxalin-2(1H)-one
1
of a white solid; mp 171–172 ꢁC. H NMR (DMSO-d6,
(2i).
1
400 MHz)
d
0.61 (t, J = 7.1 Hz, 3H), 0.90 (t,
Yield: 24% as a white solid; mp 122–124 ꢁC. H NMR
(DMSO-d6, 400 MHz) d 0.92 (d, J = 7.5 Hz, 3H), 1.20–
1.31 (m, 1H), 1.26 (d, J = 6.0 Hz, 6H), 1.50–1.60 (m,
1H), 4.28 (dd, J = 5.2, 10.3 Hz, 1H), 4.66–4.72 (m,
1H), 6.81 (dd, J = 5.4, 8.8 Hz, 1H), 6.98 (d, J = 8.8 Hz,
2H), 7.15 (ddd, J = 2.8, 8.6, 8.6 Hz, 1H), 7.30 (d,
J = 7.4 Hz, 3H), 1.17–1.27 (m, 1H), 1.44–1.55 (m, 1H),
3.28–3.40 (m, 1H), 3.47–3.54 (m, 1H), 4.38 (dd,
J = 5.3, 10.3 Hz, 1H), 6.77 (d, J = 8.7 Hz, 2H), 7.01–
7.09 (m, 2H), 7.15 (d, J = 8.8 Hz, 2H), 7.60 (dd,
J = 5.9, 8.8 Hz, 1H), 10.59 (br s, 1H); MS (ESI) m/z
379 ([M+H]+); MS (ESI) m/z 377 ([MꢀH]ꢀ).
J = 8.8 Hz, 2H), 7.38 (dd, J = 2.8, 9.6 Hz, 1H), 10.35
25
(br s, 1H); MS (ESI) m/z 393; MS (ESI) m/z 391. ½aꢁ
D
4.4.5. (3S)-3-Ethyl-6-fluoro-4-[(4-hydroxyphenyl)sulfo-
nyl]-1-ethyl-3,4-dihydroquinoxalin-2(1H)-one (2e). Yield:
81% of a white solid; H NMR (DMSO-d6, 400 MHz)
+8ꢁ (c 0.0054 g/mL, DMSO).
1
4.4.10. (3S)-1-Cyclopentyl-3-ethyl-6-fluoro-4-[(4-hydroxy-
phenyl)sulfonyl]-3,4-dihydroquinoxalin-2(1H)-one
d 0.63 (t, J = 7.2 Hz, 3H), 1.11 (t, J = 7.3 Hz, 3H),
1.18–1.28 (m, 1H), 1.46–1.55 (m, 1H), 3.35–3.56 (m,
2H), 4.66 (dd, J = 5.2, 9.3 Hz, 1H), 6.77 (d, J = 8.8 Hz,
2H), 7.17–7.21 (m, 1H), 7.19 (d, J = 8.8 Hz, 2H), 7.27
(ddd, J = 2.8, 8.8, 8.8 Hz, 1H), 7.41 (dd, J = 2.8,
9.1 Hz, 1H), 10.60 (br s, 1H); MS (ESI) m/z 379
([M+H]+); MS (ESI) m/z 377 ([MꢀH]ꢀ). HRMS: calcd
(2j).
1
Yield: 15% as a white solid; mp 137–140 ꢁC. H NMR
(DMSO-d6, 400 MHz) d 0.92 (t, J = 7.3 Hz, 3H), 1.21–
1.29 (m, 1H), 1.50–1.71 (m, 7H), 1.89–1.97 (m, 2H),
4.27 (dd, J = 5.2, 10.1 Hz, 1H), 4.84–4.88 (m, 1H),
6.81 (dd, J = 5.4, 8.8 Hz, 1H), 6.96 (d, J = 9.0 Hz, 2H),
7.16 (ddd, J = 2.8, 8.6, 8.6 Hz, 1H), 7.30 (d,
for C18H19FN2O4S+H+, 379.11223; found (ESI+,
J = 9.0 Hz, 2H), 7.38 (dd, J = 2.8, 9.6 Hz, 1H), 10.34
25
25
D
[M+H]1+), 379.11178 ½aꢁ ꢀ26ꢁ (c 0.008 g/mL, DMSO).
(br s, 1H); MS (ESI) m/z 419; MS (ESI) m/z 417. ½aꢁ
D
+15ꢁ (c 0.005 g/mL, DMSO). Anal. Calcd for
C21H23FN2O4S: C, 60.27; H, 5.54; N, 6.69. Found: C,
60.48; H, 5.51; N, 6.36.
4.4.6.
nyl)sulfonyl]-3,4-dihydroquinoxalin-2(1H)-one
(3S)-1-allyl-3-ethyl-6-fluoro-4-[(4-hydroxyphe-
(2f).
1
Yield: 72% as a white solid; mp 181–182 ꢁC. H NMR
(DMSO-d6, 400 MHz) d 0.91 (t, J = 7.3 Hz, 3H), 1.23–
1.33 (m, 1H), 1.50–1.58 (m, 1H), 3.83–3.89 (m, 1H),
3.97–4.10 (m, 1H), 4.42 (dd, J = 5.4, 10.1 Hz, 1H),
4.85 (dd, J = 1.6, 17.1 Hz, 1H), 4.99 (dd, J = 1.6,
10.6 Hz, 1H), 5.27–5.37 (m, 1H), 6.79 (d, J = 9.0 Hz,
2H), 7.03 (dd, J = 5.2, 9.1 Hz, 1H), 7.19–7.26 (m, 1H),
7.22 (d, J = 8.9 Hz, 2H), 7.42 (dd, J = 2.8, 9.3 Hz, 1H),
10.63 (br s, 1H); MS (ESI) m/z 391 ([M+H]+); MS
4.5. General procedure 4: preparation of methoxybenzoyl-
3,4-dihydroquinoxalin-2(1H)-ones (7a–7g)
To a solution of the appropriate 3,4-dihydroquinoxalin-
2(1H)-one (6.7 mmol) in methylene chloride (50 mL) un-
der nitrogen were added triethylamine (1.1 mL, 0.80 g,
7.9 mmol) and the appropriate methoxybenzoyl chloride
(6.9 mmol). The solution was stirred for 16 h and was

3462
P. E. Mahaney et al. / Bioorg. Med. Chem. 14 (2006) 3455–3466
then washed successively with a 1 N aqueous solution of
hydrochloric acid, a 1 N aqueous solution of sodium
hydroxide, water, and brine successively. The combined
organic extracts were dried over magnesium sulfate and
evaporated under reduced pressure. The product was
purified via flash column chromatography.
d 0.87 (t, J = 7.4 Hz, 3H), 1.30–1.42 (m, 1H), 1.50–1.59
(m, 1H), 3.36 (s, 3H), 4.89 (dd, J = 6.3, 9.3 Hz, 1H),
6.59 (dd, J = 2.5, 9.8 Hz, 1H), 6.71 (d, J = 8.8 Hz, 2H),
7.07 (ddd, J = 2.8, 9.1, 9.1 Hz, 1H), 7.19 (d,
J = 8.8 Hz, 2H), 7.30 (dd, J = 5.4, 9.1 Hz, 1H), 10.07
(br s, 1H); MS (ESI) m/z 329 ([M+H]+); MS (ESI) m/z
327 ([MꢀH]ꢀ); HRMS: calcd for C18H17FN2O3,
25
D
4.5.1. (3R)-3-Ethyl-7-fluoro-4-(4-methoxybenzoyl)-3,4-
dihydroquinoxalin-2(1H)-one (7a). Yield: 64%; d 0.88 (t,
J = 7.5 Hz, 3H), 1.33–1.44 (m, 1H), 1.55–1.66 (m, 1H),
3.77 (s, 3H), 4.83 (dd, J = 6.2, 9.0 Hz, 1H), 6.63 (ddd,
J = 2.6, 8.7, 8.7 Hz, 1H), 6.68 (br s, 1H), 6.90 (d,
J = 8.8 Hz, 2H), 7.25 (d, J = 8.8 Hz, 2H), 10.89 (br s,
328.1223; found (ESI-FT, [M+H]1+), 329.12887. ½aꢁ
ꢀ290ꢁ (c 0.0095 g/mL, CHCl3).
4.6.2. (3S)-3-Ethyl-6-fluoro-4-(4-hydroxybenzoyl)-1-
methyl-3,4-dihydroquinoxalin-2(1H)-one (9b). Yield:
1
72% as a white solid; H NMR (DMSO-d6, 400 MHz)
1H); HRMS: calcd for C18H17FN2O3, 328.12238; found
d 0.87 (t, J = 7.2 Hz, 3H), 1.30–1.42 (m, 1H), 1.50–1.61
(m, 1H), 3.36 (s, 3H), 4.89 (dd, J = 6.1, 9.3 Hz, 1H),
6.60 (dd, J = 2.6, 9.5 Hz, 1H), 6.70 (d, J = 8.8 Hz, 2H),
7.07 (ddd, J = 2.8, 9.5, 9.5 Hz, 1H), 7.19 (d,
J = 8.8 Hz, 2H), 7.30 (dd, J = 5.3, 9.1 Hz, 1H), 10.07
(br s, 1H); MS (ESI) m/z 329 ([M+H]+); MS (ESI) m/z
25
(ESI+, [M+H]1+), 329.12930. ½aꢁ ꢀ287ꢁ (c 0.010 g/mL,
D
DMSO).
4.5.2. (3R)-3-Ethyl-6-fluoro-4-(4-methoxybenzoyl)-3,4-
dihydroquinoxalin-2(1H)-one (7c). Yield: 76% as a white
solid; d 1.18 (t, J = 7.2 Hz, 3H), 1.34–1.45 (m, 1H), 1.54–
1.65 (m, 1H), 3.78 (s, 3H), 4.77 (dd, J = 6.2, 9.0 Hz, 1H),
6.57 (d, J = 9.5 Hz, 1H), 6.92 (d, J = 8.8 Hz, 2H), 6.94–
7.04 (m, 2H), 7.28 (d, J = 8.8 Hz, 2H), 10.80 (br s, 1H);
327 ([MꢀH]ꢀ). HRMS: calcd for C18H17FN2O3,
25
D
328.1223; found (ESI-FT, [M+H]1+), 329.12904. ½aꢁ
+301ꢁ (c 0.0107 g/mL, CHCl3).
HRMS: calcd for C18H17FN2O3, 328.12238; found (ESI-
4.6.3.
(3R)-1,3-diethyl-6-fluoro-4-(4-hydroxybenzoyl)-
25
FT, [M+H]1+), 329.12878. ½aꢁ ꢀ336ꢁ (c 0.0098 g/mL,
3,4-dihydroquinoxalin-2(1H)-one (9c). Yield: 80% as a
white solid; 1H NMR (DMSO-d6, 400 MHz) d 0.87
(t, J = 7.5 Hz, 3H), 1.19 (t, J = 7.0 Hz, 3H), 1.30–
1.41 (m, 1H), 1.49–1.60 (m, 1H), 3.95–4.05 (m, 2H),
4.87 (dd, J = 6.4, 9.1 Hz, 1H), 6.61 (dd, J = 2.7,
9.3 Hz, 1H), 6.72 (d, J = 9.0 Hz, 2H), 7.06 (ddd,
J = 2.9, 9.1, 9.1 Hz, 1H), 7.16 (d, J = 8.8 Hz, 2H),
7.35 (dd, J = 5.3, 9.1 Hz, 1H), 10.08 (br s, 1H); MS
(ESI) m/z 343 ([M+H]+); MS (ESI) m/z 341 ([MꢀH]ꢀ).
D
CHCl3). Anal. Calcd for C18H17FN2O3: C, 65.85; H,
5.22; N, 8.53. Found: C, 65.48; H, 5.16; N, 8.15.
4.6. General procedure 4: preparation of 1-alkyl-4-(4-
hydroxybenzoyl)-3,4-dihydroquinoxalin-2(1H)-ones
(9a–9j, 9l–9o, 10a–10g)
To
a stirred solution of the appropriate meth-
oxybenzoyl-3,4-dihydroquinoxalin-2(1H)-one (0.61 mmol)
in acetone (10 mL) under nitrogen were added either
potassium carbonate or cesium carbonate (17 mmol),
the appropriate alkyl iodide or alkyl bromide
(3.0 mmol), and potassium iodide (3.1 mmol) in cases
where the alkyl bromide was employed. The mixture
was heated at reflux for 2 days, after which time the
acetone was evaporated. The residue was partitioned
between ethyl acetate and water, and the layers were
separated and washed with water. The organic layer
was dried over magnesium sulfate and evaporated under
reduced pressure. The product was purified via flash
column chromatography. The resulting product was
then dissolved in methylene chloride (6 mL) and treated
with tetrabutylammonium iodide (1.13 mmol) at ꢀ78 ꢁC
followed by a 1.0 M solution of boron trichloride in
methylene chloride (4.2 mL, 4.2 mmol). Stirring was
continued at ꢀ78 ꢁC for 5 min, and the reaction mixture
was warmed to 0 ꢁC, where it was stirred for 10 h. Ice
water was then added and the mixture was stirred
thoroughly. The layers were separated. The organic
layer was washed with water and brine, and dried over
magnesium sulfate. Evaporation of the solvent under
reduced pressure gave an oil, which was purified via
Biotage Horizonꢂ (SiO2, gradient from 5% EtOAc/hex-
ane to 35% EtOAc/hexane).
HRMS: calcd for C19H19FN2O3, 342.1380; found
25
(ESI-FT, [M+H]1+), 343.14482. ½aꢁ
ꢀ300ꢁ (c
D
0.010 g/mL, CHCl3). Anal. Calcd for C19H19FN2O3:
C, 66.66; H, 5.59; N, 8.18. Found: C, 66.60; H, 5.49;
N, 8.11.
4.6.4. (3S)-1,3-Diethyl-6-fluoro-4-(4-hydroxybenzoyl)-
3,4-dihydroquinoxalin-2(1H)-one (9d). Yield: 70% as a
white solid; H NMR (DMSO-d6, 400 MHz) d 0.87 (t,
1
J = 7.5 Hz, 3H), 1.18 (t, J = 7.0 Hz, 3H), 1.30–1.41 (m,
1H), 1.49–1.60 (m, 1H), 3.95–4.05 (m, 2H), 4.87 (dd,
J = 6.3, 9.1 Hz, 1H), 6.61 (dd, J = 2.9, 9.6 Hz, 1H),
6.71 (d, J = 8.8 Hz, 2H), 7.06 (ddd, J = 2.8, 9.0, 9.0 Hz,
1H), 7.15 (d, J = 8.8 Hz, 2H), 7.35 (dd, J = 5.4, 9.2 Hz,
1H), 10.09 (br s, 1H); MS (ESI) m/z 343 ([M+H]+); MS
(ESI) m/z 341 ([MꢀH]ꢀ); HRMS: calcd for
C19H19FN2O3, 342.1380; found (ESI-FT, [M+H]1+),
25
343.14475. ½aꢁ +295ꢁ (c 0.0098 g/mL, CHCl3).
D
4.6.5. (3R)-1-allyl-3-ethyl-6-fluoro-4-(4-hydroxybenzoyl)-
3,4-dihydroquinoxalin-2(1H)-one (9e). Yield: 74% as a
white solid; H NMR (DMSO-d6, 400 MHz) d 0.89 (t,
1
J = 7.5 Hz, 3H), 1.36–1.47 (m, 1H), 1.54–1.64 (m, 1H),
4.43–4.50 (m, 1H), 4.68–4.74 (m, 1H), 4.92 (dd,
J = 6.2, 9.3 Hz, 1H), 5.08 (ddd, J = 1.7, 3.2, 17.4 Hz,
1H), 5.20 (ddd, J = 1.6, 2.9, 10.6 Hz, 1H), 5.87–5.96
(m, 1H), 6.61 (dd, J = 2.7, 9.6 Hz, 1H), 6.71 (d,
J = 8.8 Hz, 2H), 7.03 (ddd, J = 2.8, 8.7, 8.7 Hz, 1H),
7.16–7.21 (m, 3H), 10.10 (br s, 1H); MS (ESI) m/z 355
([M+H]+); MS (ESI) m/z 353 ([MꢀH]ꢀ); HRMS: calcd
4.6.1. (3R)-3-Ethyl-6-fluoro-4-(4-hydroxybenzoyl)-1-
methyl-3,4-dihydroquinoxalin-2(1H)-one (9a). Yield:
1
71% as a white solid; H NMR (DMSO-d6, 400 MHz)

P. E. Mahaney et al. / Bioorg. Med. Chem. 14 (2006) 3455–3466
3463
for C20H19FN2O3, 354.1380; found (ESI-FT, [M+H]1+),
355.1449. ½aꢁ ꢀ285ꢁ (c 0.0102 g/mL, CHCl3).
1H), 1.97–2.06 (m, 1H), 3.74 (dd, J = 5.7, 14.1 Hz,
1H), 3.99 (dd, J = 9.3, 14.1 Hz, 1H), 4.91 (dd, J = 6.2,
9.6 Hz, 1H), 6.64 (dd, J = 2.6, 9.6 Hz, 1H), 6.72 (d,
J = 8.8 Hz, 2H), 7.06 (ddd, J = 2.8, 9.1, 9.1 Hz, 1H),
7.15 (d, J = 8.8 Hz, 2H), 7.41 (dd, J = 5.2, 9.1 Hz, 1H),
10.12 (br s, 1H); MS (ESI) m/z 371 ([M+H]+); MS
(ESI) m/z 369 ([MꢀH]ꢀ); HRMS: calcd for
25
D
4.6.6. (3R)-3-Ethyl-6-fluoro-4-(4-hydroxybenzoyl)-1-pro-
pyl-3,4-dihydroquinoxalin-2(1H)-one (9f). Yield: 81% as a
1
white solid; H NMR (DMSO-d6, 400 MHz) d 0.87 (t,
J = 7.3 Hz, 3H), 0.90 (t, J = 7.3 Hz, 3H), 1.30–1.41 (m,
1H), 1.49–1.66 (m, 3H), 3.86–4.03 (m, 2H), 4.88 (dd,
J = 6.1, 9.3 Hz, 1H), 6.62 (dd, J = 2.9, 9.8 Hz, 1H),
6.72 (d, J = 8.6 Hz, 2H), 7.05 (ddd, J = 2.9, 8.8, 8.8 Hz,
1H), 7.15 (d, J = 8.6 Hz, 2H), 7.36 (dd, J = 5.3, 9.1 Hz,
1H), 10.10 (br s, 1H); MS (ESI) m/z 357 ([M+H]+); MS
(ESI) m/z 355 ([MꢀH]ꢀ); HRMS: calcd for
C21H23FN2O3, 370.1693; found (ESI-FT, [M+H]1+),
25
371.17594. ½aꢁ ꢀ272ꢁ (c 0.010 g/mL, CHCl3). Anal.
D
Calcd for C21H23FN2O3: C, 68.09; H, 6.26; N, 7.56.
Found: C, 67.85; H, 6.24; N, 7.65.
4.6.11. (3R)-3-Ethyl-6-fluoro-4-(4-hydroxybenzoyl)-1-
(2,2,2-trifluoroethyl)-3,4-dihydroquinoxalin-2(1H)-one
C20H21FN2O3, 356.1536; found (ESI-FT, [M+H]1+),
25
1
(9l). Yield: 44% as a white solid; H NMR (DMSO-d6,
357.16057. ½aꢁ ꢀ298ꢁ (c 0.0102 g/mL, CHCl3).
D
400 MHz) d 0.89 (t, J = 7.4 Hz, 3H), 1.31–1.41 (m,
1H), 1.52–1.62 (m, 1H), 4.96–5.04 (m, 3H), 6.67 (dd,
J = 2.8, 9.8 Hz, 1H), 6.70 (d, J = 8.8 Hz, 2H), 7.14–
7.09 (m, 1H), 7.14 (d, J = 8.8 Hz, 2H), 7.58 (dd,
J = 5.2, 9.1 Hz, 1H), 10.13 (br s, 1H); MS (ESI) m/z
397 ([M+H]+); MS (ESI) m/z 395 ([MꢀH]ꢀ); HRMS:
4.6.7. (3R)-3-Ethyl-6-fluoro-4-(4-hydroxybenzoyl)-1-iso-
propyl-3,4-dihydroquinoxalin-2(1H)-one (9g). Yield:
50% as a white solid; H NMR (DMSO-d6, 400 MHz)
1
d 0.84 (t, J = 7.3 Hz, 3H), 1.22–1.34 (m, 1H), 1.45–1.58
(m, 1H), 1.46 (d, J = 7.1 Hz, 3H), 1.52 (d, J = 7.0 Hz,
3H), 4.64–4.71 (m, 1H), 4.83 (dd, J = 6.1, 9.3 Hz, 1H),
6.58 (dd, J = 2.4, 9.4 Hz, 1H), 6.72 (d, J = 8.8 Hz, 2H),
7.03 (ddd, J = 2.9, 9.1, 9.1 Hz, 1H), 7.18 (d,
J = 8.8 Hz, 2H), 7.42 (dd, J = 5.3, 9.1 Hz, 1H), 10.09
(br s, 1H); MS (ESI) m/z 357 ([M+H]+); MS (ESI) m/z
calcd for C19H16F4N2O3, 396.1097; found (ESI-FT,
25
D
[M+H]1+), 397.11588. ½aꢁ
ꢀ137ꢁ (c 0.010 g/mL,
CHCl3).
4.6.12. (3R)-3-Ethyl-7-fluoro-4-(4-hydroxybenzoyl)-1-
methyl-3,4-dihydroquinoxalin-2(1H)-one (9m). Yield:
355 ([MꢀH]ꢀ); HRMS: calcd for C20H21FN2O3,
25
D
356.1536; found (ESI-FT, [M+H]1+), 357.16064. ½aꢁ
1
88% as a white solid; H NMR (DMSO-d6, 400 MHz)
ꢀ309ꢁ (c 0.0099 g/mL, CHCl3).
d 0.86 (t, J = 7.5 Hz, 3H), 1.28–1.37 (m, 1H), 1.50–1.61
(m, 1H), 3.35 (s, 3H), 4.94 (dd, J = 6.0, 9.6 Hz, 1H),
6.67–6.73 (m, 4H), 7.15 (d, J = 8.7 Hz, 2H), 7.21 (ddd,
J = 1.7, 1.7, 10.4 Hz, 1 H), 10.01 (br s, 1H); MS (ESI)
4.6.8. (3R)-1-Butyl-3-ethyl-6-fluoro-4-(4-hydrox-
ybenzoyl)-3,4-dihydroquinoxalin-2(1H)-one (9h). Yield:
1
71% as a white solid; H NMR (DMSO-d6, 400 MHz)
m/z 327 ([MꢀH]ꢀ); HRMS: calcd for C18H17FN2O3,
25
D
d 0.87 (t, J = 7.5 Hz, 3H), 0.91 (t, J = 7.3 Hz, 3H),
1.28–1.41 (m, 3H), 1.49–1.61 (m, 3H), 3.87–4.08 (m,
2H), 4.88 (dd, J = 6.2, 9.3 Hz, 1H), 6.63 (dd, J = 2.5,
9.5 Hz, 1H), 6.71 (d, J = 8.8 Hz, 2H), 7.06 (ddd,
J = 2.8, 8.8, 8.8 Hz, 1H), 7.14 (d, J = 8.8 Hz, 2H), 7.36
(dd, J = 5.2, 9.0 Hz, 1H), 10.10 (br s, 1H); MS (ESI)
m/z 371 ([M+H]+); MS (ESI) m/z 369 ([MꢀH]ꢀ);
328.1223; found (ESI+, [M+H]1+), 329.13036. ½aꢁ
ꢀ300ꢁ (c 0.009 g/mL, DMSO). Anal. Calcd for
C18H17FN2O3: C, 65.85; H, 5.22; N, 8.53. Found: C,
65.73; H, 5.46; N, 8.28.
4.6.13. (3R)-1,3-Diethyl-7-fluoro-4-(4-hydroxybenzoyl)-
3,4-dihydroquinoxalin-2(1H)-one (9n). Yield: 77% as a
1
HRMS: calcd for C21H23FN2O3, 370.1693; found
white solid; H NMR (DMSO-d6, 400 MHz) d 0.86 (t,
25
(ESI-FT, [M+H]1+), 371.17594. ½aꢁ ꢀ268ꢁ (c 0.0103 g/
J = 7.3 Hz, 3H), 1.18 (t, J = 7.3 Hz, 3H), 1.29–1.37 (m,
1H), 1.49–1.58 (m, 1H), 3.99 (quar, J = 7.3 Hz, 2H),
4.91 (dd, J = 6.2, 9.4 Hz, 1H), 6.68 (d, J = 8.7 Hz, 2H),
6.67–6.73 (m, 2H), 7.12 (d, J = 8.7 Hz, 2H), 7.27 (ddd,
J = 1.5, 1.5, 10.6 Hz, 1H), 10.03 (br s, 1H); MS (ESI)
D
mL, CHCl3. Anal. Calcd for C21H23FN2O3: C, 68.09;
H, 6.26; N, 7.56. Found: C, 67.96; H, 6.60; N, 7.67.
4.6.9. (3R)-3-Ethyl-6-fluoro-4-(4-hydroxybenzoyl)-1-pen-
tyl-3,4-dihydroquinoxalin-2(1H)-one (9i). Yield: 53% as a
m/z 341 ([MꢀH]ꢀ); HRMS: calcd for C19H19FN2O3+H+,
25
D
1
white solid; H NMR (DMSO-d6, 400 MHz) d 0.85 (t,
343.14525; found (ESI-FT, [M+H]1+), 343.14456. ½aꢁ
J = 7.3 Hz, 3H), 0.87 (t, J = 7.5 Hz, 3H), 1.23–1.41 (m,
5H), 1.49–1.63 (m, 3H), 3.87–4.08 (m, 2H), 4.89 (dd,
J = 6.2, 9.2 Hz, 1H), 6.63 (dd, J = 2.6, 9.6 Hz, 1H), 6.71
(d, J = 8.8 Hz, 2H), 7.06 (ddd, J = 3.0, 8.6, 8.6 Hz, 1H),
7.15 (d, J = 8.8 Hz, 2H), 7.36 (dd, J = 5.3, 9.1 Hz, 1H),
10.10 (br s, 1H); MS (ESI) m/z 385 ([M+H]+); MS (ESI)
m/z 383 ([MꢀH]ꢀ); HRMS: calcd for C22H25FN2O3
ꢀ248ꢁ (c 0.0096 g/mL, CHCl3). Anal. Calcd for
C19H19FN2O3Æ0.10H2O: C, 66.31; H, 5.62; N, 8.14.
Found: C, 66.05; H, 5.36; N, 8.02.
4.6.14. (3R)-1-Benzyl-3-ethyl-7-fluoro-4-(4-hydrox-
ybenzoyl)-3,4-dihydroquinoxalin-2(1H)-one (9o). Yield:
1
74% as a white solid; H NMR (DMSO-d6, 400 MHz)
+H+, 385.19220; found (ESI-FT, [M+H]1+), 385.19204.
d 0.92 (t, J = 7.5 Hz, 3H), 1.37–1.48 (m, 1H), 1.62–1.72
(m, 1H), 5.06 (dd, J = 5.9, 9.6 Hz, 1H), 5.18 (d,
J = 16.0 Hz, 1H), 5.30 (d, J = 16.0 Hz, 1H), 6.62 (d,
J = 8.8 Hz, 2H), 6.67–6.74 (m, 2H), 7.05 (d,
J = 8.8 Hz, 2H), 7.11 (dd, J = 2.4, 10.2 Hz, 1H), 7.26–
7.30 (m, 3H), 7.35–7.39 (m, 2H), 10. 03 (br s, 1H);
MS (ESI) m/z 405 ([M+H]+); MS (ESI) m/z 403
([MꢀH]ꢀ); HRMS: calcd for C24H21FN2O3+H+,
25
½aꢁ ꢀ294ꢁ (c 0.0095 g/mL, CHCl3).
D
4.6.10. (3R)-3-Ethyl-6-fluoro-4-(4-hydroxybenzoyl)-1-iso-
butyl-3,4-dihydroquinoxalin-2(1H)-one (9j). Yield: 33%
as a white solid; 1H NMR (DMSO-d6, 400 MHz) d
0.83 (d, J = 6.7 Hz, 3H), 0.88 (t, J = 7.3 Hz, 3H), 0.94
(d, J = 6.7 Hz, 3H), 1.29–1.41 (m, 1H), 1.50–1.61 (m,

3464
P. E. Mahaney et al. / Bioorg. Med. Chem. 14 (2006) 3455–3466
25
D
405.16090; found (ESI-FT, [M+H]1+), 405.16006. ½aꢁ
(br s, 1H), 6.14 (d, J = 2.2 Hz, 1H), 6.28 (dd, J = 2.2,
8.3 Hz, 1H), 6.77 (br s, 1H), 7.02 (ddd, J = 2.8, 8.7,
8.7 Hz, 1H), 7.11 (d, J = 8.3 Hz, 1H), 7.29 (dd, J = 5.3,
9.1 Hz, 1H), 9.58 (s, 1H), 9.71 (s, 1H); MS (ESI) m/z
345 ([M+H]+); MS (ESI) m/z 359 ([M+H]+); MS (ESI)
+250ꢁ (c 0.0097 g/mL, CHCl3).
4.6.15. (3R)-3-Ethyl-7-fluoro-4-(3-hydroxybenzoyl)-1-
methyl-3,4-dihydroquinoxalin-2(1H)-one (10a). Yield:
1
72% as a white solid; H NMR (DMSO-d6, 400 MHz)
m/z 357 ([MꢀH]ꢀ); HRMS: calcd for C19H19FN2O4,
25
D
d 0.86 (t, J = 7.5 Hz, 3H), 1.30–1.39 (m, 1H), 1.51–1.60
(m, 1H), 3.34 (s, 3H), 4.91 (br s, 1H), 6.68 (d,
J = 7.4 Hz, 1H), 6.70–6.75 (m, 3H), 6.82 (ddd, J = 1.8,
2.3, 8.0 Hz, 1H), 7.14 (t, J = 8.0 Hz, 1H), 7.21 (dd,
J = 2.8, 10.4 Hz, 1H), 9.68 (br s, 1H); MS (ESI) m/z
329 ([M+H]+); MS (ESI) m/z 327 ([MꢀH]ꢀ) HRMS:
358.1329; found (ESI-FT, [M+H]1+), 359.13972. ½aꢁ
ꢀ293ꢁ (c 0.0102 g/mL, CHCl3).
4.7. (3R)-1-Cyclopentyl-3-ethyl-6-fluoro-4-(4-hydroxy-
benzoyl)-3,4-dihydroquinoxalin-2(1H)-one (9k)
calcd for C18H17FN2O3+H+, 329.12960; found (ESI-
To a stirred solution of (3R)-3-ethyl-6-fluoro-4-(4-
methoxybenzoyl)-3,4-dihydroquinoxalin-2(1H)-one (7c)
(0.47 g, 1.4 mmol) in tetrahydrofuran (4 mL) under
nitrogen at 0 ꢁC were added cyclopentanol (0.20 mL,
25
D
FT, [M+H]1+), 329.12884. ½aꢁ ꢀ281ꢁ (c 0.0098 g/mL,
CHCl3). Anal. Calcd for C18H17FN2O3Æ0.10H2O: C,
65.49; H, 5.25; N, 8.49. Found: C, 65.29; H, 4.93; N, 8.33.
0.19 g,
2.2 mmol),
triphenylphosphine
(0.58 g,
4.6.16. (3R)-1,3-Diethyl-7-fluoro-4-(3-hydroxybenzoyl)-
3,4-dihydroquinoxalin-2(1H)-one (10b). Yield: 74% as a
white solid; d 0.86 (t, J = 7.5 Hz, 3H), 1.18 (t,
J = 6.9 Hz, 3H), 1.27–1.39 (m, 1H), 1.50–1.61 (m, 1H),
4.00 (quar, J = 6.9 Hz, 2H), 4.90 (br s, 1H), 6.64 (d,
J = 7.4 Hz, 1H), 6.69–6.76 (m, 3H), 6.83 (ddd, J = 1.8,
2.5, 8.2 Hz, 1H), 7.14 (t, J = 8.0 Hz, 1H), 7.27 (dd,
J = 2.6, 10.4 Hz, 1H), 9.69 (br s, 1H); MS (ESI) m/z
343; MS (ESI) m/z 341. HRMS: calcd for
2.2 mmol), and diethyl azodicaboxylate (0.44 mL,
0.46 g, 0.22 mmol). The reaction mixture was warmed
to 25 ꢁC and was stirred for 12 h. The solvent was evap-
orated in vacuo, and the product was purified via Biotage
Horizonꢂ (SiO2, gradient from 5% EtOAc/hexane to 40%
EtOAc/hexane) to yield 0.20 g (36%) of (3R)-1-cyclopen-
tyl-3-ethyl-6-fluoro-4-(4-methoxybenzoyl)-3,4- dihydro-
quinoxalin-2(1H)-one. MS (ESI) m/z 397 ([M+H]+).
C19H19FN2O3+H+, 343.14525; found (ESI+, [M+H]1+),
The resulting product was then dissolved in methylene
chloride (5 mL) and treated with tetrabutylammonium
iodide (0.34 g, 0.93 mmol) at ꢀ78 ꢁC followed by a 1.0
M solution of boron trichloride in methylene chloride
(3.4 mL, 3.4 mmol). Stirring was continued at ꢀ78 ꢁC
for 5 min, and the reaction mixture was warmed to
0 ꢁC, where it was stirred for 10 h. Ice water was then
added and the mixture was stirred thoroughly. The layers
were separated. The organic layer was washed with water
and brine, and dried over magnesium sulfate. Evapora-
tion of the solvent under reduced pressure gave an oil,
which was purified via Biotage Horizonꢂ (SiO2, gradient
from 5% EtOAc/hexane to 35% EtOAc/hexane) to yield
76 mg (40%) of 11g as a white solid. 1H NMR (DMSO-
d6, 400 MHz) d 0.84 (t, J = 7.4 Hz, 3H), 1.23–1.34 (m,
1H), 1.46–1.55 (m, 1H), 1.57–1.65 (m, 2H), 1.86–2.08
(m, 5H), 2.16–2.24 (m, 1H), 4.64–4.73 (m, 1H), 4.83
(dd, J = 6.2, 9.6 Hz, 1H), 6.61 (d, J = 9.1 Hz, 1H), 6.72
(d, J = 8.9 Hz, 2H), 7.05 (ddd, J = 2.9, 9.1, 9.1 Hz, 1H),
7.17 (d, J = 8.9 Hz, 2H), 7.38 (dd, J = 5.5, 9.1 Hz, 1H),
10.09 (br s, 1H); MS (ESI) m/z 383 ([M+H]+); MS
(ESI) m/z 381 ([MꢀH]ꢀ); HRMS: calcd for
25
D
343.14462. ½aꢁ ꢀ275ꢁ (c 0.0083 g/mL, CHCl3). Anal.
Calcd for C19H19FN2O3Æ0.10H2O: C, 66.31; H, 5.62; N,
8.14. Found: C, 66.14; H, 5.46; N, 7.92.
4.6.17.
(3R)-1-Benzyl-3-ethyl-7-fluoro-4-(3-hydroxy-
benzoyl)-3,4-dihydroquinoxalin-2(1H)-one (10c). Yield:
63% as a white solid; d 0.91 (t, J = 7.5 Hz, 3H), 1.38–
1.49 (m, 1H), 1.62–1.73 (m, 1H), 5.04 (br s, 1H), 5.20
(d, J = 16.3 Hz, 1H), 5.26 (d, J = 16.3 Hz, 1H), 6.52
(d, J = 6.1 Hz, 1H), 6.70–6.83 (m, 4H), 7.04–7.10 (m,
2H), 7.26–7.30 (m, 3H), 7.34–7.39 (m, 2H), 9.71 (br s,
1H); MS (ESI) m/z 405 ([M+H]+); MS (ESI) m/z 403
([MꢀH]ꢀ); HRMS: calcd for C24H21FN2O3+H+,
25
D
405.16090; found (ESI-FT, [M+H]+1), 405.16003. ½aꢁ
ꢀ279ꢁ (c 0.0095 g/mL, CHCl3). Anal. Calcd for
C24H21FN2O3Æ0.25H2O: C, 70.49; H, 5.30; N, 6.85.
Found: C, 70.42; H, 5.19; N, 6.75.
4.6.18. (3R)-4-(2,4-dihydroxybenzoyl)-3-ethyl-6-fluoro-1-
methyl-3,4-dihydroquinoxalin-2(1H)-one (10d). Yield:
38% as a white solid; H NMR (DMSO-d6, 400 MHz)
1
d 0.81 (t, J = 7.3 Hz, 3H), 1.23–1.35 (m, 1H), 1.46–1.55
(m, 1H), 3.32 (s, 3H), 4.80 (br s, 1H), 6.15 (d,
J = 2.2 Hz, 1H), 6.27 (dd, J = 2.2, 8.3 Hz, 1H), 6.85
(br s, 1H), 7.05 (ddd, J = 2.9, 8.7, 8.7 Hz, 1H), 7.10 (d,
J = 8.5 Hz, 1H), 7.24 (dd, J = 5.4, 9.1 Hz, 1H), 9.68 (s,
1H), 9.71 (s, 1H); MS (ESI) m/z 345 ([M+H]+); MS
(ESI) m/z 343 ([MꢀH]ꢀ); HRMS: calcd for
C22H23FN2O3, 382.1693; found (ESI-FT, [M+H]1+),
25
383.17555. ½aꢁ ꢀ309ꢁ (c 0.0095 g/mL, CHCl3).
D
4.8. General procedure 5: preparation of 1-alkyl-4-
benzoyl-3,4-dihydroquinoxalin-2(1H)-ones (10f–10h)
To a solution of the appropriate 3,4-dihydroquinoxalin-
2(1H)-one (0.67 mmol) in methylene chloride (5 mL)
under nitrogen were added triethylamine (0.11 mL,
0.79 mmol) and the appropriate benzoyl chloride
(0.69 mmol). The solution was stirred for 16 h and was
then washed successively with a 1 N aqueous solution of
hydrochloric acid, a 1 N aqueous solution of sodium
hydroxide, water, and brine successively. The combined
organic extracts were dried over magnesium sulfate and
C18H17FN2O4, 344.1172; found (ESI-FT, [M+H]1+),
25
345.12407. ½aꢁ ꢀ289ꢁ (c 0.0099 g/mL, CHCl3).
D
4.6.19. (3R)-4-(2,4-Dihydroxybenzoyl)-1,3-diethyl-6-fluo-
ro-3,4-dihydroquinoxalin-2(1H)-one (10e). Yield: 22% as
1
a white solid; H NMR (DMSO-d6, 400 MHz) d 0.82
(t, J = 7.4 Hz, 3H), 1.13 (t, J = 7.1 Hz, 3H), 1.22–1.34
(m, 1H), 1.45–1.56 (m, 1H), 3.87–4.06 (m, 2H), 4.81

P. E. Mahaney et al. / Bioorg. Med. Chem. 14 (2006) 3455–3466
3465
evaporated under reduced pressure. The resulting residue
was dissolved in acetone (11 mL) under nitrogen to which
were added cesium carbonate (18.7 mmol) and the appro-
priate alkyl iodide (3.3 mmol). The mixture was heated at
reflux for 2 days, after which time the acetone was evapo-
rated. The residue was partitioned between ethyl acetate
and water, and the layers were separated and washed with
water. The organic layer was dried over magnesium sul-
fate and evaporated under reduced pressure. The product
was purified via flash column chromatography.
4.9.2.
(3S)-3-Ethyl-6-fluoro-4-(4-hydroxybenzoyl)-1-
methyl-3,4-dihydroquinoxalin-2(1H)-one (9b). The enan-
tiomeric purity was determined to be 95.7% (with 4.3%
of the undesired enantiomer). Retention time: 4.91 min.
4.9.3.
(3R)-1,3-diethyl-6-fluoro-4-(4-hydroxybenzoyl)-
3,4-dihydroquinoxalin-2(1H)-one (9c). The enantiomeric
purity was determined to be 97.6% (with 2.4% of the
undesired enantiomer). Retention time: 3.42 min.
4.9.4. (3S)-1,3-diethyl-6-fluoro-4-(4-hydroxybenzoyl)-3,4-
dihydroquinoxalin-2(1H)-one (9d). The enantiomeric
purity was determined to be 95.8% (with 4.2% of the
undesired enantiomer). Retention time: 5.02 min.
4.8.1. (3R)-1,3-Diethyl-6-fluoro-4-(4-methoxybenzoyl)-
3,4-dihydroquinoxalin-2(1H)-one (10f). Yield: 84%. 1H
NMR (DMSO-d6, 400 MHz) d 0.88 (t, J = 7.3 Hz, 3H),
1.19 (t, J = 7.1 Hz, 3H), 1.31–1.42 (m, 1H), 1.51–1.61
(m, 1H), 3.79 (s, 3H), 4.01 (quar., J = 7.3 Hz, 2H), 4.89
(dd, J = 6.3, 9.3 Hz, 1H), 6.65 (d, J = 7.6 Hz, 1H), 6.92
(d, J = 8.7 Hz, 2H), 7.07 (ddd, J = 3.3, 9.1, 9.1 Hz, 1H),
7.27 (d, J = 8.7 Hz, 2H), 7.36 (dd, J = 5.2, 9.1 Hz, 1H);
4.9.5. ((3R)-3-Ethyl-7-fluoro-4-[(4-hydroxyphenyl)sulfo-
nyl]-1-methyl-3,4-dihydroquinoxalin-2(1H)-one (2a). The
enantiomeric purity was determined to be 95.8% (with
4.2% of the undesired enantiomer). Retention time:
3.82 min.
MS (ESI) m/z 357. HRMS: calcd for C20H21FN2O3+H+,
25
D
357.16090; found (ESI-FT, [M+H]1+), 357.16057. ½aꢁ
ꢀ290ꢁ (c 0.0102 g/mL, CHCl3). Anal. Calcd for
C20H21FN2O3Æ0.30H2O: C, 66.40; H, 6.02; N, 7.74.
Found: C, 66.42; H, 5.92; N, 7.74.
4.9.6. ((3S)-3-Ethyl-7-fluoro-4-[(4-hydroxyphenyl)sulfo-
nyl]-1-methyl-3,4-dihydroquinoxalin-2(1H)-one (2b). The
enantiomeric purity was determined to be 97.3% (with
2.7% of the undesired enantiomer). Retention time:
4.87 min.
4.8.2.
(3R)-3-Ethyl-6-fluoro-1-methyl-4-(4-meth-
ylbenzoyl)-3,4-dihydroquinoxalin-2(1H)-one (10g). Yield:
88% as a white solid; 1H NMR (DMSO-d6, 400 MHz) d
0.83 (t, J = 7.4 Hz, 3H), 1.27–1.38 (m, 1H), 1.48–1.57 (m,
1H), 2.28 (s, 3H), 3.32 (s, 3H), 4.86 (br s, 1H), 6.61 (br s,
1H), 7.04 (ddd, J = 2.8, 8.8, 8.8 Hz, 1H), 7.14 (d,
J = 7.9 Hz, 2H), 7.21 (d, J = 8.2 Hz, 2H), 7.27 (dd,
J = 8.3, 9.1 Hz, 2H); MS (ESI) m/z 327. HRMS: calcd
4.10. General procedure 7: solubility assay conditions
Solid compound was dissolved in DMSO at 8 mg/mL to
make a stock solution from which 13 lL was added to
1.0 mL of aqueous buffer (part number 110090, pION
Inc., Woburn, MA, USA) at pH 7.4 in a 96-deep well
plate (2 mL polypropylene). The solution was incubated
for 18 h at ambient temperature and then filtered using a
96-well filter plate (0.2 lm, Corning, Acton, MA, USA).
The supernatant was quantitated in a UV plate (part
number 110614, pION Inc.) using a UV plate reader
(Molecular Devices, Spectra Max 190, Sunnyvale, CA,
USA). Liquid handling was carried out on a Tecan
Genesis robot under the control of pION PSR4S
software version 1.3.
for C19H19FN2O2+H+, 327.15033; found (ESI-FT,
25
[M+H]1+), 327.14989. ½aꢁ ꢀ258ꢁ (c 0.010 g/mL, CHCl3).
D
4.8.3. (3R)-3-Ethyl-6-fluoro-1-methyl-4-(4-nitrobenzoyl)-
3,4-dihydroquinoxalin-2(1H)-one (10h). Yield: 74% as a
1
white solid; H NMR (DMSO-d6, 400 MHz) d 0.86 (t,
J = 7.2 Hz, 3H), 1.29–1.41 (m, 1H), 1.50–1.60 (m, 1H),
3.28 (s, 3H), 4.93 (br s, 1H), 6.65 (br s, 1H), 7.07 (t,
J = 7.4 Hz, 1H), 7.29 (dd, J = 5.3, 9.1 Hz, 1H), 7.63 (d,
J = 8.0 Hz, 2H), 8.18 (d, J = 8.0 Hz, 2H); MS (ESI)
m/z 358. HRMS: calcd for C18H16FN3O4+H+,
4.11. General procedure 8: ER/NF-jB luciferase and CK
assay conditions
25
D
358.11976; found (ESI-FT, [M+H]1+), 358.1193. ½aꢁ
ꢀ315ꢁ (c 0.0098 g/mL, CHCl3).
4.11.1. Cell preparation. T-175 flasks of 100% confluent
HAECT-1 cells (immortalized human aortic endothelial
cells) were washed with 8 mL HBSS (HEPES-buffered
saline solution) and infected for 4 h with 6 mL of a
1:10 dilution of Ad5-wt-hERa virus (an adenovirus
transfection vector that mediates CMV promoter-driven
expression of human ERa) in phenol red free Endothe-
lial Cell Basal medium (Clonetics, San Diego, CA, Cat-
alog # CC-3129) containing 0.25% bovine serum
albumin (EBM-BSA). After 4 h, cells were washed with
EBM-BSA and incubated overnight in the same medi-
um. Following overnight incubation, cells were washed
with EBM-BSA and infected for 2 h with 6 mL of a
1:10 dilution of Ad5-3x(NF-jB). Luc virus (Adenovirus
luciferase expression vector driven by 3 repeats of
the MHC NFjb site 50 to the thymidine kinase promot-
er) in EBM-BSA. After 2 h, cells were washed and
4.9. General procedure 6: Optical purity assessment
The enantiomeric purity of each compound was deter-
mined using a Chiralpak AD-H 5u, 250 mm · 4.6 mm
ID column at 2.0 mL/min flow rate via Analytical
Supercritical Fluid Chromatography (Berger Instru-
ments, Inc. Newark, DE, USA) at 35 ꢁC with a detection
wavelength of 220 nm. The SFC modifier utilized was
20% MeOH. The chiral method was developed by mix-
ing enantiomeric pairs and achieving baseline separa-
tion. Retention times for each enantiomer are reported.
4.9.1.
(3R)-3-Ethyl-6-fluoro-4-(4-hydroxybenzoyl)-1-
methyl-3,4-dihydroquinoxalin-2(1H)-one (9a). The enan-
tiomeric purity was determined to be 97.3% (with 2.7%
of the undesired enantiomer). Retention time: 3.59 min.

3466
P. E. Mahaney et al. / Bioorg. Med. Chem. 14 (2006) 3455–3466
5. Caulin-Glaser, T.; Watson, C. A.; Pardi, R.; Bender, J. R.
J. Clin. Invest. 1996, 98, 36–42.
6. Evans, M. J.; Lai, K.; Shaw, L. J.; Harnish, D. C.;
Chadwick, C. C. Endocrinology 2002, 143, 2559–2570.
7. Hodgin, J. B.; Maeda, N. Endocrinology 2002, 143, 4495–
4501.
8. Harnish, D. C.; Albert, L. M.; Leathurby, Y.; Eckert, A.
M.; Ciarletta, A.; Kasaian, M.; Keith, J. C., Jr. Am. J.
Physiol. 2004, 286, G118–G125.
9. Tyree, C. M.; Zou, A.; Allegretto, E. A. J. Steroid
Biochem. Mol. Biol. 2002, 80, 291–297.
10. Valentine, J. E.; Kalkhoven, E.; White, R.; Hoare, S.;
Parker, M. G. J. Biol. Chem. 2000, 275, 25322–25329.
11. Chadwick, C. C.; Chippari, S.; Matelan, E.; Borges-
Marcucci, L.; Eckert, A. M.; Keith, J. C., Jr.; Albert, L.
M.; Leathurby, Y.; Harris, H. A.; Bhat, R. A.; Ashwell,
M.; Trybulski, E. J.; Winneker, R. C.; Adelman, S. J.;
Steffan, R. J.; Harnish, D. C. Proc. Natl. Acad. Sci. U.S.A.
2005, 102, 2543–2548.
12. Selectivity over ERb for this compound series was not
determined.
13. Thomas, T. N.; Rhodin, J. A.; Clark, L.; Garces, A.;
Bryant, M. Inflamm. Res. 2003, 52, 452–460.
14. Steffan, R. J.; Matelan, E.; Ashwell, M. A.; Moore, W. J.;
Solvibile, W. R.; Trybulski, E. J.; Chadwick, C. C.;
Chippari, S.; Kinney, T.; Eckert, A.; Borges-Marcucci, L.;
Keith, J. C.; Xu, Z.; Mosyak, L.; Harnish, D. C. J. Med.
Chem. 2004, 47, 6435–6438.
15. Caggiano, T. J.; Brazzale, A.; Ho, D. M.; Kraml, C. M.;
Trybulski, E. J.; Chadwick, C. C.; Chappari, S.; Borges-
Marcucci, L.; Eckert, A.; Keith, J. C.; Kenney, T.;
Harnish, D. C. J. Med. Chem., submitted for publication.
16. Sabatucci, J. P.; Ashwell, M. A.; Trybulski, E. J.;
O’Donnell, M.-M.; Moore, W. J.; Harnish, D. C.;
Chadwick, C. C. Bioorg. Med. Chem. Lett. 2006, 16,
854–858.
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A. A.; Moore, W. J. PCT Int. Appl. WO 2004050631.
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Chem. 1999, 64, 9719–9721.
19. Compound purity was assessed using an LC/UV/MS
method. The mass spectrometry was performed on a
Waters ZQ quadrupole MS scanned from 100–800 amu.
incubated at 34 ꢁC for 1 h. Cells were then washed, tryp-
sinized, counted, and resuspended in 95%FBS/5%
dimethylsulfoxide at a concentration of 4 · 106 cells/
mL, frozen as 1 or 5 mL aliquots in cryo-vials, and stored
at ꢀ150 ꢁC. Control (no ER infection) cells were pro-
cessed as above without Ad5-wt-hERa virus infection.
4.11.2. IL-6 and creatine kinase assays. ERa infected
HAECT-1 cells or control cells were thawed, diluted
42· in warm EBM-BSA, plated into 96-well plates at
0.1 mL/well, and incubated for 4 h at 34 ꢁC. Test com-
pounds were added to the cells as 2· stocks in EBM-
BSA containing 2 ng/mL IL-1b (R&D Systems) and
plates were returned to the incubator (34 ꢁC). After
15-20 h, 100 lL aliquots of media were removed from
the cells and assayed for IL-6 content using a BioSource
human IL-6 ELISA Kit. Cells were subsequently washed
with 300 lL of Dulbecco’s phosphate-buffered saline
and lysed in 50 lL of Cell Culture Lysis Reagent (Pro-
mega). The amount of luciferase was quantified on a
Wallac Victor2 Luminometer (Gaithersburg, MD) using
10 lL of lysate and mixing with 100 lL of Promega
Luciferase Assay reagent. Creatine kinase was deter-
mined from the rate of increase in A340 following addi-
tion of 100 lL of CK assay reagent (Sigma, cat. No
47-10) to the remainder of the cell lysate.
Acknowledgments
The authors thank members of the Discovery Analytical
Chemistry group in Chemical Technologies at Wyeth,
particularly Scott Brecker, Christopher Petucci, Rebecca
Dooley, Larry Mallis, and Oliver McConnell and Ed-
ward Kerns for compound analysis as well as pharma-
ceutical profiling data. Their efforts and dedication
are greatly appreciated. In addition, we thank Susan
Chippari for performing the biological assays.
The UV was detected on
a Waters 996 PDA at
References and notes
254 nm. The LC was performed on a Waters 2790
HPLC instrument using a Keystone Aquasil column
(2 mm · 50 mm, 5 lm). All compounds were run using
a linear gradient from 100% mobile phase A (95:5
water/CH3CN with 10 mM ammonium acetate) to
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3. Tyree, C. M.; Zou, A.; Allegretto, E. A. J. Steroid
Biochem. Mol. Biol. 2002, 80, 291–297.
100% mobile phase
B
(95:5 CH3CN/water with
10 mM ammonium acetate) over 4 min at a rate of
0.8 mL/min.
4. Mukherjee, T. K.; Nathan, L.; Dinh, H.; Reddy, S. T.;
Chaudhuri, G. J. Biol. Chem. 2003, 278, 11746–11752.