Synthesis and structure-activity relationship of 2-amino-3-heteroaryl-quinoxalines as non-peptide, small-molecule antagonists for interleukin-8 receptor

Article abstract of DOI:10.1016/S0968-0896(03)00399-7

Interleukin-8 modulation is implicated in many inflammatory and cancer diseases. Starting from a mass-screening hit, the synthesis and structure-activity relationship of 2-amino-3-heteroarylquinoxalines as non-peptide, small molecule interleukine-8 receptor antagonists have been developed. The optimized derivatives, PD 0210293 (13y) and PD 0220245 (13r), show inhibition of both IL-8 receptor binding and IL-8-mediated neutrophil chemotaxis.

Full text of DOI:10.1016/S0968-0896(03)00399-7

Bioorganic & Medicinal Chemistry 11 (2003) 3777–3790
Synthesis and Structure–Activity Relationship of 2-Amino-3-
heteroaryl-quinoxalines as Non-peptide, Small-Molecule
Antagonists for Interleukin-8 Receptor
Jie Jack Li,a,* Kenneth G. Carson,c Bharat K. Trivedi,a Wen Song Yue,a Qing Ye,c
Roberta A. Glynn,c Steven R. Miller,a David T. Connor,a Bruce D. Roth,a Jay R. Luly,c
Joseph E. Low,b David J. Heilig,b Weixing Yang,d Shixin Qind and Stephen Huntb
aChemistry Department, Pfizer Global R&D, 2800 Plymouth Rd., Ann Arbor, MI48105, USA
bDepartment of Molecular Biology, Pfizer Global R&D, 2800 Plymouth Rd., Ann Arbor, MI48105, USA
cChemistry Department, Millennium Pharmaceuticals, 75 Sidney St. Cambridge, MA 02139, USA
dInflammation Biology Department, Millennium Pharmaceuticals, 75 Sidney St. Cambridge, MA 02139, USA
Received 25 January 2002; accepted 5 May 2003
Abstract—Interleukin-8 modulation is implicated in many inflammatory and cancer diseases. Starting from a mass-screening hit,
the synthesis and structure–activity relationship of 2-amino-3-heteroarylquinoxalines as non-peptide, small molecule interleukine-8
receptor antagonists have been developed. The optimized derivatives, PD 0210293 (13y) and PD 0220245 (13r), show inhibition of
both IL-8 receptor binding and IL-8-mediated neutrophil chemotaxis.
# 2003 Elsevier Ltd. All rights reserved.
Introduction
and basophils.7 IL-8 binding to CXCR1- and CXCR2-
bearing neutrophils causes calcium flux,8 degranula-
tion,9 and chemotaxis.10 IL-8 has also been linked to a
number of inflammatory conditions such as psoriasis,11
rheumatoid arthritis,12 acute respiratory distress syn-
drome (ARDS),13 and chronic obstructive pulmonary
disease (COPD).14 Anti-IL-8 antibody blockade studies
have demonstrated significant effects in rabbit models of
ischemia-reperfusion injury15 and ARDS.16 However, it
is worth noting that fully human anti-IL-8 monoclonal
antibody ABX-IL-8 has failed to show efficacy in phase
II studies for the indications of both psoriasis and
rheumatoid arthritis.
Chemokines1 are a class of proinflammatory cytokines
involved in leukocyte trafficking. The chemokines
themselves are 70–80 kDa proteins that have been divi-
ded into different subclasses based on the orientation of
two key cysteine residues in the N-terminus. In general,
C–C chemokines are active in monocytes, macrophages,
and T-cells, while the C–X–C chemokines act pre-
dominantly on lymphocytes and neutrophils. Most che-
mokine receptors are members of the G-protein-
coupled-receptor (GPCR) superfamily. On the other
hand, interleukin-8 (IL-8) is a CXC chemokine that
binds to two known receptors, CXCR1 and CXCR2.2,3
CXCR1 is a receptor for IL-8 and granulocyte chemo-
tactic protein 2 (GCP-2) whereas CXCR2 binds IL-8
and a few other related chemokines containing the Glu-
Leu-Arg (ELR) amino-acid sequence (Gro-a, b, ENA-
78). CXCR1 and CXCR2 are expressed on a number of
different cell types including neutrophils,4 the CD4+,
CD8+ population of peripheral T-cells,5 eosinophils,6
Due to the close relationship between IL-8 and inflam-
matory diseases, CXCR1 and CXCR2 antagonists are
targets of small molecule drug discovery. For instance,
diarylureas 1–4 depicted in Figure 1 are found to be
specific antagonists of the CXCR2 receptor.17,18 In par-
ticular, SB 225002 (1) inhibited IL-8 binding to CHO-
CXCR2 transfectant membranes with an IC50 of 22 nM,
whereas it inhibited GRO-a-stimulated calcium flux in
human neutrophil with an IC50 of 30 nM. In binding
studies, 1 has been shown to have greater than 150-fold
selectivity for CXCR2 against CXCR1 and four other
*Corresponding author. Tel.: +1-734-622–3576; fax: +1-734-622-
3107; e-mail: jack.li@pfizer.com
0968-0896/03/$ - see front matter # 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/S0968-0896(03)00399-7

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J. J. Li et al. / Bioorg. Med. Chem. 11 (2003) 3777–3790
diamines. Thus, as shown in Scheme 1, condensation of
phenylene diamine 6 with diethyl oxalate gave quinox-
alinedione 7. Bromination of 7 was accomplished using
one of two methods to furnish dibromide 8. The first
method consisted of treatment with molten PBr5 at
150 ꢀC. The alternate method involved refluxing 7 with
POBr3 in THF. The latter method was proven to be
more convenient. Single SNAr displacement on dibro-
mide 8 afforded 2-amino-3-bromo-quinoxaline 9 as the
desired substrate. The regiochemical outcome of such
SNAr displacement was dependent on the substituents
on the phenyl ring. The results were disclosed in our
earlier communication.20 With the electrophile 9 in
hand, the Stille coupling reactions with heterocyclic
stannanes gave rise to 2-amino-3-bromo-quinoxaline 10.
Deprotonation of 10 with one equivalent of NaH was
Figure 1.
GPCRs including fMLP, LTB4, LTD4, and C5a. In
addition, data from a rabbit in vivo model indicated
that co-administration of 1 with chemokines inhibited
IL-8 but not fMLP effects on peripheral blood leuko-
cyte margination in a dose-dependent manner with sig-
nificant inhibition observed at 2.78 or 5.5 mg/kg/min
dose, respectively
During screening of our compound collection against
CXCR2, PD 068238 (5) was identified as an IL-8
receptor antagonist with an IC50 of 3.0 mM. Our inves-
tigation on the structure–activity relationship (SAR)
around PD 068238 (5) resulted in a series of analogues
possessing activities in both the binding and chemotaxis
assays. Herein, we report the synthesis and SAR studies
of 2-amino-3-heteroaryl-quinoxaline analogues as non-
peptide, small-molecule IL-8 receptor antagonists.
Scheme 2. Synthetic route 2.
Table 1. Initial amine SAR
Chemistry
Compd
Diamine linker
CXCR binding
IC50 (mM)
The original synthesis for 2-amino-3-heteroaryl-quinox-
alines was long and not amenable to our SAR investi-
gations.19 By taking advantage of the Stille coupling
tactic, we devised an alternative synthetic route that was
more suitable for our SAR studies.20 Since the initial
SAR investigation on the benzene ring substituents
demonstrated that the 6,7-dichloro pattern was pre-
ferred in terms of both chemical and biological proper-
ties, it was chosen for our later stage SAR studies. The
electrophilic coupling partners 9 of the Stille coupling
reaction were prepared in three steps from phenylene
15a
15b
15c
15d
15e
15f
15g
15h
15i
>40
17
4.0
8.7
7.0
5.0
11.5
30
20
Scheme 1. Synthetic route 1.

J. J. Li et al. / Bioorg. Med. Chem. 11 (2003) 3777–3790
3779
followed by treatment with alkyl halides to deliver the
desired analogues 11 in good yield.
contamination for stannanes at times tend to give false
binding activities to some receptors.
Alternatively, a more efficient route was designed to
prepare additional analogues. As depicted in Scheme 2,
single SNAr displacement on dibromide 8a afforded 2-
amino-3-bromo-quinoxaline 12 as the desired substrate.
The second SNAr displacement did not proceed due to
deactivation by the electron-donating amine sub-
stituent. With the electrophile 12 in hand, various pal-
ladium-catalyzed coupling reactions with heterocyclic
organometallics then delivered the desired analogues 13
in good yield. For the Stille coupling reactions in parti-
cular, Careful workup including hexane/acetonitrile
extraction was instituted to thoroughly remove the tin
SAR Study
Initial diamine SAR
Our initial efforts were focused on the optimal chain
length for the diamine side chain. Starting material 14
was prepared according to the original literature pre-
cedent using with 4,5-dichlorophenylenediamine and
ethyl 2-pyridylglyoxylate oxime.19 Treatment of 14 with
diamines with different lengths of diamine linkage furn-
ished the desired derivatives 15 in good yields (Scheme 3).
From the results of compounds 15a–15i (Table 1), it was
concluded that the diamine side chain containing a four-
carbon linker 15c is optimal in terms of potency in the
IL-8 receptor binding assay. The dimethylamino-
cyclohexyl analogue 15f also showed reasonable activ-
ity, although the other tethered analogues 15g–15i were
not as potent as the linear four-carbon linker, com-
pound 15c. The data showed that dimethylamino ter-
minus was preferable since 15c and 15f possessed similar
activities, whereas 15g–15i were less potent.
Scheme 3.
Table 2. SAR of 3-substituted derivatives 13
Compd
R0
R
CXCR binding
IC50 (mM)
13a
33
13b
13c
13d
13e
13f
13g
–Br
6.0
14
–OCH3
30
2.9
2.0
7.5
13h
12
(continued)

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J. J. Li et al. / Bioorg. Med. Chem. 11 (2003) 3777–3790
Table 2 (continued)
Compd
R0
R
CXCR binding
IC50 (mM)
13i
5.0
13j
1.5
1.5
13k
13l
3.0
13m
13n
13o
0.90
0.66
0.64
13p
13q
0.29
0.24
13r
13s
13t
0.11
0.11
2.5
13u
13v
13w
13x
13y
3.25
0.95
0.45
0.32
0.09

J. J. Li et al. / Bioorg. Med. Chem. 11 (2003) 3777–3790
3781
Table 3. Bis-thiophene diamine SAR
Compd
Diamine
CXCR binding
IC50 (mM)
5-HT1a binding
IC50 (mM)
NK2 binding
IC50 (mM)
M2 binding
IC50 (mM)
13r
16a
16b
16c
0.11
0.52
0.18
0.20
1.0
1.1
0.63
1.4
1.7
3.6
6.5
0.47
6.6
0.21
0.29
2.7
16d
0.21
2.2
1.0
2.7
16e
16f
3.4
0.57
0.38
0.1
2.0
0.21
0.10
0.10
SAR of heterocycles
Table 4. The in vitro binding profile of the two most potent analogues
Initial replacement of the C-3 pyridyl substituent with a
variety of heterocycles including indole, oxazole, pyr-
role, imidazole, phenyl, and pyrazole derivatives (Table 2,
compounds 13e–13i) did not result in significant
improvement in binding affinity. Only a small increment
in potency was observed for indole derivatives (com-
pounds 13j, 13k). On the other hand, many thienyl
analogues (Table 2, compounds 13l–13s) proved to be
more potent antagonists of the IL-8 receptor. While the
electron-density modifications did not have much
impact on the IC50 values, the binding activity was sig-
nificantly affected by steric effects of substituents on the
thiophene ring, with the bisthienyl and the terthienyl
analogues, 13r and 13s, as the most potent analogues. A
similar trend was observed for the furanyl derivatives
13t–13y, with the benzofuran analogue 13y as the most
active compound. Although 13r and 13s possessed the
same binding activity, 13r was preferable in comparison
to 13s because the former had better solubility than the
latter. Therefore, the bis-thiophene and the benzofuran
analogues provided the most potent IL-8 receptor
Receptors
Compd 13y,
IC50 (mM)
Compd 13r,
IC50 (mM)
IL-8 (binding)
CXCR1
CXCR2
IL-8 (chemotaxis)
5HT1a
0.09
0.37
0.16
0.2
0.97 (11ꢁ)
0.15 (2ꢁ)
0.53 (6ꢁ)
>40 (>444ꢁ)
0.11
0.23
0.03
0.17
0.57 (5ꢁ)
0.78 (7ꢁ)
3.6 (33ꢁ)
>40 (>364ꢁ)
3.6 (33ꢁ)
10 (91ꢁ)
>10 (>91ꢁ)
>10 (>91ꢁ)
NK2
M2
MCP-1
CX3CR1
5HT6
5HT7
a2C

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J. J. Li et al. / Bioorg. Med. Chem. 11 (2003) 3777–3790
anatagonists (entries 13r, 13y), with IC50 values as 110
and 90 nM, respectively.
respectively. In contrast to SB225002 (1) that has been
shown to have greater than 150-fold selectivity for
CXCR2 against CXCR1 in binding studies, PD 0210293
(13y) and PD 0220245 (13r) bind to both CXCR1 and
CXCR2 (Table 4), thus are dual inhibitors. These ana-
logues can potentially serve as a useful tool to better
define the role of IL-8 in inflammatory diseases.
Subsequent diamine SAR
Upon the identification of compound 13r, we then
undertook further exploration of the diamine SAR, this
time keeping the C-3 substituent constant as the bis-
thiophene. We made several modifications to the dia-
mine in order to increase potency as well as to enhance
the selectivity and physical properties of our series.
Since 5-HT1a, NK2, and M2 had been identified as
selectivity problems in our large selectivity panel, these
assays were chosen as selectivity checks for the new
diamine modifications. We found that it was possible to
maintain good potency against the IL-8 receptor while
changing the diamine side chain within the scope deli-
neated in Table 3. Several of the amine analogues had
potencies very similar to compound 13r. The other
GPCR binding activities could be modulated somewhat
by side-chain modifications. The tethered analogue 16f
showed a marked decrease in selectivity. Compounds
16c and 16d showed similar selectivities to compound
13r. We concluded from this exercise that selectivity
could be moderately modified through the diamine, but
not improved significantly. Our most selective com-
Experimental
General methods
1
Melting points are uncorrected. The H NMR spectra
were recorded at 400 MHz, and the 13C NMR spectra
were recorded at 100 MHz in CDCl3 or DMSO-d6.
Chemical shifts are reported in ppm (d) and referenced
to the residual proton signal for CDCl3 (7.26 ppm) or
DMSO-d6 (2.49 ppm). The J coupling constants are
reported in Hz. Elemental analyses were performed by
Quantitative Technologies Inc. and are within 0.4% of
theory. Reagents were purchased from commercial sup-
pliers and used without further purification. Merck
silica gel 60 was used for flash chromatography (230–
400 mesh). CXCR binding assay, chemotaxis assay, as
well as calcium flux assay were carried out according to
literature procedures.22,23
pounds showed approximately
a 10-fold window
between IL-8 receptor binding and other GPCRs. Some
of the diamine modifications did result in less lipophilic
compounds such as example 16c.
6,7-Dichloro-1,4-dihydroquinoxaline-2,3-dione (7).
A
mixture of 4,5-dichlorophenylenediamine (6, 54 g,
305 mmol) and diethyl oxalate (124 mL, 146.1 g,
920 mmol) was heated at reflux overnight, cooled to
room temperature and filtered. The residue was washed
with ethanol and dried in vacuo to give the titled pro-
duct 7 as a gray powder (67.5 g, 96% yield); mp
>320 ꢀC; IR (KBr, cmꢂ1) 3188, 3156, 3057, 2918, 1724,
1693, 1613, 1497, 1452, 1340, 1338, 1250, 1131, 877,
811, 676, 669, 565; 1H NMR (DMSO-d6) d 7.18 (s, 2H),
12.00 (s, 2H); 13C NMR (DMSO-d6) d 154.8, 126.0,
124.4, 116.0; MS (APCI), m/z 231.0 (M+). Anal.
(C8H4N2O2Cl2) C, H, N.
For the two most potent analogues 13r and 13y, we
have shown that the binding activities correspond well
with activity in neutrophil chemotaxis assays (Table 4).
These derivatives show comparable antagonism of IL-8
binding to both CXCR1 and CXCR2, therefore are
CXCR1/2 dual inhibitors. Further investigation
revealed these compounds also bind to some other
seven-membrane G-protein-coupled receptors including
M2, NK2, and 5HT1a receptors. Analogues 13r and
13y were not further pursued as drug candidates due to
the lack of selectivities towards other GPCRs. The
results are in accord to previous literature observa-
tions,21 in which N,N0-dialkylaminobutylamino-styryl-
quinolines have demonstrated promiscuity towards
some GPCRs. It was speculated that the styr-
ylquinolines bind to a common motif of GPCRs which
is most likely distinct from the ligand-binding domains.
The promiscuity of N,N-dialkylaminobutylaminoquino-
lines towards GPCRs should serve as a precaution in
designing future highly selective drug candidates.
2,3-Dibromo-6,7-dichloroquinoxaline (8). 6,7-Dichloro-
1,4-dihydro-quinoxaline-2,3-dione (7, 5.39 g, 23.3 mmol)
and phosphorus pentabromide (20.1 g, 46.7 mmol) were
combined in a 100 mL round-bottom flask equipped
with a condenser with an outlet half submerged in 10%
NaOH aqueous solution (to absorb HBr generated
during the reaction). The reaction was heated at 155 ꢀC
using an oil-bath for 2 h, upon which the formation of
HBr ceased. The reaction mixture was poured into ice-
water (100 mL) and basified with NH4OH. After fil-
tration, the solid was dried and recrystallized from
EtOH to give the desired product as a white solid.
(7.84 g, 94% yield): mp 169–70 ꢀC; Rf=0.50, CH2Cl2;
IR (KBr, cmꢂ1) 3088, 1539, 1451, 1240, 1128, 964, 997;
1H NMR (CDCl3) d 8.13 (s, 2H); 13C NMR (CDCl3) d
142.4, 139.7, 136.3; MS (APCI), m/z 338.4 (MH+);
anal. (C8H2N2Cl2Br2) C, H, N.
Conclusions
In our SAR studies of 2-amino-3-heteroaryl-quinox-
alines as IL-8 receptor antagonists, we identified the
benzofuran and bis-thiophene analogues, PD 0210293
(13y) and PD 0220245 (13r), as the most potent IL-8
antagonists (90 and 110 nM, respectively). In addition
both PD 0210293 (13y) and PD 0220245 (13r), inhibited
both IL-8 receptor binding and IL-8-mediated neu-
trophil chemotaxis with IC50 values of 200 and 170 nM,
2-Bromo-3amino-6,7-dichloroquinoxaline
(9).
2,3-
Dibromo-6,7-dichloro-quinoxaline (5 g, 14.0 mmol) was
dissolved in THF (100 mL). To this orange solution

J. J. Li et al. / Bioorg. Med. Chem. 11 (2003) 3777–3790
3783
concd ammonium hydroxide (50 mL) was added in one
portion, causing a white precipitate to fall out of solu-
tion and the reaction to turn a dark green in color. The
temperature decreased from 18.0 to 13.5 ꢀC. The reac-
tion was allowed to stir overnight at ambient tempera-
ture. THF was then removed in vacuo and the
precipitate filtered off and washed with distilled water (3
ꢁ 30 mL). The orange solid was then dried in vacuo at
50 ꢀC for 4 h. The solid was then triturated with t-butyl-
methyl ether to give a light orange solid (4.1 g, 99%
yield): mp 222–224 ꢀC; IR (KBr, cmꢂ1) 3488, 3347,
1617, 1588, 1443, 1406, 1338, 1114, 1037, 966, 894, 869,
1351, 1329, 1227, 1110, 948, 879, 849, 728, 597; 1H
NMR (DMSO-d6) d 7.19 (broad s, 1H), 7.24 (dd,
J=5.1, 3.8 Hz, 1H), 7.72 (s, 1H), 7.83 (dd, J=5.1,
0.9 Hz, 1H), 7.94 (dd, J=5.1, 0.9 Hz, 1H), 7.96 (s,
1H); 13C NMR (DMSO-d6) d 151.1, 140.4, 140.3,
140.2, 135.3, 131.7, 130.8, 128.8, 126.2, 125.6; MS
(APCI), m/z 295.9 [M+], 293.9 [Mꢂ2]; anal.
(C12H7N3Cl2S) C, H, N.
2-Amino-3-(2-thiazole)-6,7-dichloroquinoxaline (10d, het
=2-thiazole). The title compound was prepared
according to the experimental procedure for example
10a and was obtained as a bright yellow crystalline solid
(81% yield): mp 219–221 ꢀC; Rf=0.19, EtOAc–hexane
(1:2); IR (KBr, cmꢂ1) 3426, 3363, 3320, 3200, 1624,
1
577, 557; H NMR (DMSO-d6) d 7.45 (broad s, 2H,
NH2), 7.70 (s, 1H), 7.96 (s, 1H); 13C NMR (DMSO-d6)
d 152.1, 141.0, 135.8, 133.3, 133.2, 128.8, 126.7, 126.3;
MS (APCI), m/z 291.8 [Mꢂ1]; anal. (C8H4N3BrCl2) C,
H, N.
1
1459, 1341, 1235, 1208, 1109, 953, 884, 812, 462; H
NMR (DMSO-d6) d 7.29 (broad s, 1H), 7.79 (s,
1H), 8.05 (s, 1H), 8.67 (s, 1H), 9.31 (s, 1H); 13C
NMR (DMSO-d6) d 158.0, 151.4, 143.8, 140.4, 139.2,
135.7, 132.4, 128.8, 126.5, 125.8; MS (APCI), m/z
296.9 [M+1], 298.9 [M+3]; anal. (C11H6N4Cl2S) C,
H, N.
3-(1-Benzenesulfonyl-1H-indol-2-yl)-6,7-dichloro-quinox-
alin-2-ylamine (10a, het=1-benzenesulfonyl-1H-indole).
A50 -mL round-bottom flask was charged with com-
pound 9 (1.03 g, 3.52 mmol), 1-benzenesulfonyl-2-tribu-
tylstannyl-1H-indole (2.30 g, 4.21 mmol), bis(triphenyl-
phosphine)palladium
(II)
chloride
(259 mg,
Compound 13a: 6,7-dichloro-N,N0-bis-(4-diethylamino-
butyl)-quinoxaline-2,3-diamine. To a solution of com-
pound 8 (850 mg, 2.38 mmol) in THF (50 mL), 4-(di-
ethylamino)butyl amine (1.37 g, 9.52 mmol) was added.
The reaction mixture was refluxed overnight. After the
removal of the solvent in vacuo, the residue was chro-
matographed on silica gel, eluting with 80% EtOAc,
10% MeOH, and 10% Et3N, to give the desired product
0.352 mmol), CuI (77 mg, 0.703 mmol), and THF
(40 mL). The suspension was refluxed for 30 min and
cooled to room temperature. Charcoal was added and
the reaction mixture was heated to boiling and filtered
through a pad of Celite (1 inch thick). The filtrate was
concentrated in vacuo and the residue was chromato-
graphed using neutral alumina, eluting with 0–5%
CH3OH/EtOAc, to give the desired product as a yellow
solid (1.51 g, 92% yield): mp 129–122 ꢀC; Rf=0.26,
EtOAc–hexane (1:1); 1H NMR (DMSO-d6) d 7.17
(broad s, 2H), 7.31 (dt, J=7.32, 0.9 Hz, 1H), 7.43 (dt,
J=7.32, 1.1 Hz, 1H), 7.63 (m, 4H), 7.84 (d, 1H), 7.86 (d,
J=1.6 Hz, 1H), 8.03 (d, J=8.4 Hz, 1H), 8.14 (s, 1H);
13C NMR (DMSO-d6) d 153.6, 141.8, 141.1, 136.7,
136.4, 134.7, 134.6, 134.3, 132.8, 130.0, 129.6, 129.4,
126.9, 125.9, 125.7, 125.6, 124.2, 122.0, 114.7; MS
(APCI), m/z 469.0 [M+1], 471.0 [M+3]; anal.
(C22H14N4Cl2O2S) C, H, N.
1
as a light pink to off-white wax (1.14 g, 99% yield): H
NMR (CDCl3) d 0.89 (t, J=7.10 Hz, 12H), 1.45 (m,
4H), 1.60 (m, 4H), 2.39 (m, 6H), 3.43 (m, 4H), 7.15 (t,
J=4.58 Hz, 2H), 7.58 (s, 2H); MS (APCI), m/z 497
.
[M+1], 499 [M+3]; anal. (C24H40N6Cl2 0.82H2O) C,
H, N.
Compound 13b: N0-(3-Bromo-6,7-dichloro-quinoxalin-2-
yl)-N,N-diethyl-butane-1,4-diamine. To a solution of
compound 8 (10.35 g, 29.0 mmol) in THF (100 mL), 4-
(diethylamino) butyl amine (8.35 g, 58.0 mmol) was
added at room temperature. After 30 min, the reaction
mixture was filtered to remove the precipitate. After the
removal of the solvent in vacuo, the residue was chro-
matographed using silica gel, eluted with 2.5% Et3N,
2.5% MeOH, 95% EtOAc, to give the desired product
2-Amino-3-(2-furanyl)- 6,7-dichloroquinoxaline (10b, het
=2-furanyl). The title compound was prepared accord-
ing to the experimental procedure for example 10a and
was obtained as a yellow crystalline solid (84% yield):
mp 222–223 ꢀC; Rf=0.16, EtOAc–hexane (1:2); IR
(KBr, cmꢂ1) 3507, 3312, 1617, 1590, 1480, 1460, 1414,
1
as a orange-yellow oil (12.18 g, 100% yield): H NMR
(CDCl3) d 1.03 (t, J=7.14 Hz, 6H), 1.61 (m, 2H), 1.72
(m, 2H), 2.52 (m, 6H), 3.56 (m, 2H), 5.96 (t, J=4.94 Hz,
1H), 7.79 (s, 1H), 7.87 (s, 1H); MS (APCI), m/z 419
[M+1], 421 [M+3]. Anal. (C16H21N4Br1Cl2) C, H, N.
1
1157, 1107, 876, 745, 591; H NMR (DMSO-d6) 6.80
(dd, J1=1.5 Hz, J2=3.3 Hz, 1H), 7.30 (broad s, 2H),
7.41 (d, J=3.3 Hz, 1H), 7.73 (s, 1H), 7.80 (d, J=1.1 Hz,
1H), 8.02 (s, 1H); 13C NMR (DMSO-d6) d 150.5, 150.3,
145.7, 140.3, 135.6, 135.2, 131.8, 128.8, 126.2, 125.7,
114.1, 112.6; MS (ACPI), m/z 280.0 [M+1], 282.0
[M+3]; anal. (C12H7N3Cl2O) C, H, N.
Compound 13c: (6,7-dichloro-3-methoxy-quinoxalin-2-yl)-
(4-pyrrolidin-1-yl-butyl)-amine. Step 1: (3-bromo-6,7 -
dichloro-quinoxalin-2-yl)-(4-pyrrolidin-1-yl-butyl)-amine.
To a solution of compound 8 (31.00 g, 87.00 mmol) in
THF (150 mL), K2CO3 (24.00 g, 174.00 mmol) and 4-
pyrrolidinyl-1-butylamine (17.00 g, 119.70 mmol) were
added. The reaction mixture was stirred at room tem-
perature for 1 day. Then saturated NaHCO3 solution
(10 mL) was added to quench the reaction. The phases
were separated and the aqueous layer was extracted
2-Amino-3-(2-thioenyl)- 6,7-dichloroquinoxaline (10c, het
=2-thienyl). The title compound was prepared accord-
ing to the experimental procedure for example 10a and
was obtained as a yellow crystalline solid (77% yield):
mp 235–237 ꢀC; Rf=0.17, EtOAc–hexane (1:2); IR
(KBr, cmꢂ1) 3472, 3311, 1614, 1588, 1463, 1432, 1404,

3784
J. J. Li et al. / Bioorg. Med. Chem. 11 (2003) 3777–3790
with EtOAc (3ꢁ15 mL). The combined organic phase
was dried over MgSO4. The crude product was chro-
matographed using silica gel, eluting with 1% Et3N in
EtOAc, to give the desired product as a yellow solid
(21.00 g, 58% yield): 1H NMR (MeOD) d 1.61–1.82 (m,
8H), 2.49–2.58 (m, 6H), 3.53 (t, J=6.6 Hz, 2H), 7.67 (s,
1H), 7.79 (s, 1H); MS (ESI+), m/z 419 [M+1].
(354 mg, 2.6 mmol) in THF (10 mL) and allowed to
warm to room temperature. After 30 min, the resulting
organozinc reagent was treated with (3-bromo-6,7-
dichloro-quinoxalin-2-yl)-(4-pyrrolidin-1-yl-butyl)-amine
and the catalyst mixture (prepared by pre-treating a
THF (3 mL) solution of PdCl2(PPh3)2 (42 mg,
0.06 mmol) with n-butyllithium (0.048 mL, 0.12 mmol)
to generate the palladate complex). The mixture was
heated to reflux for 18 h, followed by removal of the
solvent in vacuo. The residue was chromatographed on
silica gel eluting with 10% CH3OH and 3% Et3N in
ethyl acetate to give the title compound as a viscous oil
Step 2: (6,7-dichloro-3-methoxy-quinoxalin-2-yl)-(4-
pyrrolidin-1-yl-butyl)-amine. Asolution of (3-bromo-
6,7-dichloro-quinoxalin-2-yl)-(4-pyrrolidin-1-yl-butyl)-
amine (298 mg, 0.70 mmol) in anhydrous THF (10 mL)
was treated with methanol (0.085 mL, 2.1 mmol), Et3N
(0.190 mL, 1.4 mmol), and Ni(CO)2(PPh3)2 (575 mg,
0.9 mmol). The mixture was heated to reflux for 18 h,
followed by removal of the solvent in vacuo. The resi-
due was chromatographed on silica gel eluting with
10% CH3OH and 3% Et3N in ethyl acetate to give the
free base as a viscous oil (194 mg, 74% yield). The
.
(67 mg, 20% yield). The bis HCl salt was prepared by
1
treating the free base with methanolic HCl. H NMR
(free-base, CDCl3) d 1.38 (t, 3H), 1.80 (m, 8H), 2.55 (m,
6H), 3.65 (m, 2H), 4.65 (m, 2H), 7.18 (m, 1H), 7.46 (m,
5H), 7.73 (s, 1H), 7.81 (s, 2H), 10.16 (broad s, 1H); MS
.
(ESI+), m/z 509 [M+1]; anal. (C27H30N6Cl2 2HCl) C,
H, N.
.
bis HCl salt was prepared by treating the free base with
1
methanolic HCl. H NMR (free-base, CDCl3) d, 1.80
(m, 8H), 2.55 (m, 6H), 3.56 (m, 2H), 4.10 (s, 3H), 6.13
(broad s, 1H), 7.70 (m, 2H); MS (ESI+), m/z 335
Example 13g: (6,7-dichloro-3-(1-phenyl-pyrazol-5-yl)-
quinoxalin-2-yl)-(4-pyrrolidin-1-yl-butyl)-amine. The title
compound was prepared using the experimental proce-
dure for example 10a, starting with (3-bromo-6,7-
dichloro-quinoxalin-2-yl)-(4-pyrrolidin-1-yl-butyl)-amine
.
[M+1]; anal. (C17H22N4O1Cl2 2HCl 2H2O) C, H, N.
.
Compound 13d: N0-[6,7-dichloro-3-(1-ethoxy-vinyl)-qui-
noxalin-2-yl]-N,N-diethyl-butane-1,4-diamine. The title
compound was prepared according to the experimental
procedure for example 10a using starting material 13b,
and was obtained as a yellow-orange oil: 1H NMR
(CDCl3) d 1.04 (m, 6H), 1.24 (m, 6H), 1.69 (m, 4H),
2.04 (m, 1H), 2.29 (m, 1H), 2.55 (m, 6H), 3.51 (m, 2H),
3.64 (m, 1H), 3.81 (m, 1H), 6.67 (s, 1H), 7.08 (s, 1H),
3.37 (broad t, J=4.59 Hz, 1H), 7.68 (s, 1H), 7.76(s, 1H);
MS (APCI), m/z 411 [M+1], 413 [M+3]; anal.
(C20H28N4Cl2O1) C, H, N.
and
1-phenyl-5-tributylstannanyl-1H-pyrazole.
1H
NMR (free-base, CDCl3) d 1.53 (m, 4H) 1.75 (m, 4H),
2.44 (m, 6H), 3.41 (m, 2H), 5.29 (m, 1H), 6.81 (d,
J=1.8 Hz, 1H), 7.29 (m, 5H), 7.77 (s, 1H), 7.78 (s, 1H),
7.86 (d, J=1.8 Hz, 1H); MS (ESI+), m/z 481 [M+1];
.
.
anal. (C25H26N6Cl2 2HCl 1H2O) C, H, N.
Example 13h: (6,7-dichloro-3-(1-phenyl-imidazol-2-yl)-
quinoxalin-2-yl)-(4-pyrrolidin-1-yl-butyl)-amine. The title
compound was prepared using the experimental for
1
example 13f, starting with 1-phenylimidazole. H NMR
(free-base, CDCl3) d 1.80 (m, 8H), 2.60 (m, 6H), 3.64 (m,
2H), 7.02 (m, 1H), 7.30 (m, 4H), 7.45 (m, 3H), 7.68 (m,
1H), 9.66 (broad s, 1H); MS (ESI+), m/z 481 [M+1];
Compound 13e: (6,7-dichloro-3-(5-phenyl-oxazol-2-yl)-
quinoxalin-2-yl)-(4-pyrrolidin-1-yl-butyl)-amine. Asolu-
tion of (3-bromo-6,7-dichloro-quinoxalin-2-yl)-(4-pyr-
rolidin-1-yl-butyl)-amine (159 mg, 0.38 mmol) in
anhydrous THF (10 mL) was treated with 5-phenylox-
azole (73 mg, 0.50 mmol), PdCl2(PPh3)2 (18 mg,
0.025 mmol), CuI (10 mg, 0.05 mmol), and potassium
acetate (74 mg, 0.75 mmol). The mixture was heated to
reflux under argon for 24 h. Volatiles were removed in
vacuo, and the residue was chromatographed on silica
gel eluting with 10% CH3OH and 3% Et3N in ethyl
acetate to give the free base as a viscous oil ( 80 mg,
.
.
.
anal. (C25H26N6Cl2 2HCl 0.6H2O 0.3CH3OH) C, H, N.
Example 13i: N0-(6,7-dichloro-3-thiazol-2-yl-quinoxalin-
2-yl)-N,N-dimethyl-propane-1,3-diamine. To a solution
of NaH (150 mg, 60% in mineral oil, 3.75 mmol) in
DMF (10 mL) was added compound 10d (420 mg,
1.50 mmol) and 3-dimethylaminopropyl chloride
hydrochloride (237 mg, 1.5 mmol). The reaction was
heated at 80 ꢀC for 2 h, cooled to room temperature.
After removal of DMF in vacuo, the residue was chro-
matographed using neutral alumina, eluted with 5–15%
CH3OH/EtOAc to give the desired product as a dark-
.
44% yield). The bis HCl salt was prepared by treating
the free base with methanolic HCl. 1H NMR (free-base,
CDCl3) d 1.80 (m, 8H), 2.54 (m, 6H), 3.62 (m, 2H), 7.43
(m, 3H), 7.72 (s, 1H), 7.80 (m, 2H), 8.00 (s, 1H), 8.86
(broad t, 1H); MS (ESI+), m/z 482 [M+1]; anal.
1
yellow solid (94 mg, 60% yield). H NMR (DMSO-d6)
2.08 (m, 2H), 2.74 (d, J=4.95 Hz, 6H), 3.14 (m, 2H),
3.57 (m, 2H), 7.59 (m, 1H), 7.87 (s, 1H), 8.05 (s, 1H),
8.70 (s, 1H), 7.37 (s, 1H), 10.59 (broad s, 1H); MS
(APCI), m/z 382 [M+1], 384 [M+3]; anal.
.
.
(C25H25N5OCl2 2HCl 1.9H2O) C, H, N.
.
Example 13f: (6,7-dichloro-3-(1-ethyl-5-phenyl-imidazol-
2-yl)-quinoxalin-2-yl)-(4-pyrrolidin-1-yl-butyl)-amine.
(C16H17N5Cl2S 1.5HCl) C, H, N.
A
solution of 1 - ethyl - 5 - phenylimidazole (220 mg,
1.28 mmol) in anhydrous THF (10 mL) was cooled in an
ice bath and treated with n-butyllithium (2.5 M,
0.56 mL, 1.41 mmol), and stirred for 30 min. The result-
ing brown solution was treated with anhydrous ZnCl2
Example 13j: N0-[3-(1-benzenesulfonyl-1H-indol-2-yl)-
6,7-dichloro-quinoxalin-2-yl]-N,N-diethyl-butane-1,4-dia-
mine. The title compound was prepared according to the
experimental procedure for example 10a using starting
material 13b, and was obtained as an orange oil:

J. J. Li et al. / Bioorg. Med. Chem. 11 (2003) 3777–3790
3785
1H NMR (CDCl3) d 0.99 (t, J=7.15 Hz, 6H), 1.59 (m,
2H), 1.68 (m, 2H), 2.55 (m, 6H), 3.57 (dd, J=12.45,
5.49 Hz, 2H), 5.36 (broad t, J=5.49 Hz, 1H), 6.95 (d,
J=0.73 Hz, 1H), 7.45 (m, 6H), 7.69 (s, 1H), 7.72 (s, 1H),
7.89 (s, 1H), 7.95 (s, 1H), 8.19 (dd, J=8.33, 0.85 Hz,
1H); MS (APCI), m/z 598.1 [M+1], 599.1 [M+2]; anal.
Example 13o: 5-[6,7-dichloro-3-(4-diethylamino-butyl-
amino)-quinoxaline-2-yl]-thiophene-2-carboxylic acid di-
methyl amide. The title compound was prepared
according to the experimental procedure for example
10a using starting material 13b, and the product was
1
obtained as a yellow wax (quantitative yield): H NMR
.
(C16H10N4Cl2 2.88HCl) C, H, N.
(CDCl3) d 1.01 (t, J=7.0 Hz, 6H), 1.61 (m, 2H), 1.70
(m, 2H), 2.51 (m, 6H), 3.23 (broad s, 6H) 3.58 (m, 2H),
5.81 (m, 1H), 7.41(d, J=3.9 Hz, 1H), 7.61 (d, J=3.9 Hz,
1H), 7.80 (s, 1H), 7.95 (s, 1H); MS (APCI), m/z 494
[M+1], 496 [M+3].
Example 13k: N0-[6,7-dichloro-3-(1H-indol-2-yl)-quinox-
alin-2-yl]-N,N-diethyl-butane-1,4-diamine. The final pro-
duct was prepared by refluxing a sodium hydroxide
solution of compound 13j in methanol to remove the
sulfonamide protecting group. The title compound was
obtained as a red-orange oil. The compound was then
dissolved in EtOAc, and treated with HCl in EtOAc to
form the HCl salt, a brown-orange solid: mp 145–
147 ꢀC; Salt 1H NMR (DMSO-d6) d 1.15 (br t,
J=6.8 Hz, 6H), 1.72 (br s, 4H), 3.04 (br. s, 6H), 3.57 (br
s, 2H), 7.03 (t, J=7.32 Hz, 1H), 7.19 (t, J=7.78 Hz,
1H), 7.38 (br s, 1H), 7.49 (d, J=8.05 Hz, 1H), 7.63 (d,
J=7.81 Hz, 1H), 7.80 (s, 1H), 7.94 (s, 1H), 10.17 (br s,
1H), 11.76 (s, 1H); MS (APCI), m/z 456 [M+1], 458
Example 13p: N0-(3-benzo[b]thiophen-2-yl-6,7-dichloro-
quinoxalin-2-yl)-N,N-diethyl-butane-1,4-diamine. The
title compound was prepared according to the experi-
mental procedure for example 10a using starting mate-
1
rial 13b, and was obtained as a yellow oil: H NMR
(CDCl3) d 0.99 (t, J=7.14 Hz, 6H), 1.61 (m, 2H), 1.75
(m, 2H), 2.49 (m, 6H), 3.61 (dd, J=12.35, 6.84 Hz, 2H),
6.00 (br t, J=5.13 Hz, 1H), 7.43 (m, 2H), 7.81 (s, 1H),
7.86 (m, 2H), 7.92 (s, 1H), 7.99 (s, 1H); MS (APCI),
m/z, 473 [M+1], 475 [M+3]; anal. (C24H26N4-
.
.
.
[M+3]. Anal. (C24H27N5Cl2 2HCl 1.58H2O) C, H, N.
Cl2S 0.19CHCl3) C, H, N.
Example 13l: N0-(6,7-dichloro-3-thiophen-2-yl-quinoxa-
lin-2-yl)-N,N-dimethyl-propane-1,3-diamine. The title
compound was prepared according to the experimental
procedure for example 13i, starting with compound 10c,
Example 13q: N0-[6,7-dichloro-3-(5-phenyl-thiophen-2-yl)-
quinoxalin-2-yl]-N,N-diethyl-butane-1,4-diamine. Step 1:
1-phenyl thiophene. To a solution of 2-bromothiophene
(1.18 mL, 12.26 mmol) and phenyl boronic acid (1.64 g,
13.49 mmol) in toluene (50 mL), 2 M solution of
Na2CO3 (13 mL, 27.00 mmol) and Pd(PPh3)4 (709 mg,
0.61 mmol) were added. The reaction mixture was
heated to reflux for 5 h. The phases were separated and
the aqueous layer was extracted with EtOAc (3ꢁ15 mL).
The combined organic phase was dried over MgSO4 and
concentrated. The residue was chromatographed using
silica gel, eluting with hexane–EtOAc (4:1), to give the
.
and was obtained as the bis HCl salt, a yellow solid.
mp=220–223 ꢀC; H NMR (DMSO-d6) d 2.10 (m, 2H),
1
2.73 (d, J=4.8 Hz, 6H), 3.13 (m, 2H), 7.28 (dd, 5.1,
3.7 Hz, 1H), 7.58 (broad t, 1H), 7.86 (s, 1H), 7.88 (dd,
J=5.1, 1.0 Hz, 1H), 7.98 (dd, J=4.0, 1.0 Hz, 1H), 8.00
(s, 1H), 10.80 (broad s, 1H); MS (APCI), m/z 381
.
[M+1], 383 [M+3]; anal. (C17H18N4Cl2O 2.0HCl) C,
H, N.
1
desired product as a white solid (2.11 g, 98% yield): H
NMR (CDCl3) d 7.01–7.05 (m, 1H), 7.21–7.43 (m, 5H),
7.56–7.60 (m, 2H).
Example 13m: N0-(6,7-dichloro-3-thiophen-2-yl-quinoxa-
lin-2-yl)-N,N-diethyl-butane-1,4-diamine. The title com-
pound was prepared according to the experimental
procedure for example 10a using starting material 13b,
and was obtained as a yellow-orange oil. The compound
was then dissolved in EtOAc, and bubbled with HCl gas
to make the corresponding HCl salt. The salt was a
yellow hygroscopic powder: 1H NMR (free-base,
CDCl3) d 1.00 (t, J=7.1 Hz, 6H), 1.60 (m, 2H), 1.72 (m,
2H), 2.50 (m, 6H), 3.57 (m, 2H), 5.85 (t, J=5.2 Hz, 1H),
7.19 (dd, 5.0, 3.6 Hz, 1H), 7.57 (dd, 5.0, 1.1 Hz, 1H),
7.68 (dd, 4.8, 1.0 Hz, 1H), 7.79 (s, 1H), 7.95 (s, 1H); MS
(APCI), m/z 423 [M+1], 425 [M+3]; anal.
Step 2: 5-phenyl-1-tributylstannyl thiophene. To a solu-
tion of 1-phenyl thiophene (0.30 g, 1.87 mmol) in THF
(10 mL) under Ar, n-BuLi (0.90 mL, 2.25 mmol, 2.5 M
solution in hexane) was added. The reaction mixture
was heated to reflux for 30 min and cooled to room
temperature. Then tributyltin chloride was added. The
mixture was stirred at room temperature for overnight.
Then saturated NH4Cl solution (10 mL) was added
dropwise to quench the reaction. The phases were sepa-
rated and the aqueous layer was extracted with EtOAc
(3ꢁ10 mL). The combined organic phase was dried over
MgSO4 and concentrated to yield a crude desired pro-
duct as a colorless oil (841 mg, 100% yield).
.
.
(C20H24N4Cl2S 2HCl 1.24H2O) C, H, N.
Example 13n: N0-[6,7-dichloro-3-(5-methyl-thiophen-2-
yl)-quinoxalin-2-yl]-N,N-diethyl-butane-1,4-diamine. The
title compound was prepared according to the experi-
mental procedure for example 10a using starting mate-
rial 13b, and the product was obtained as a yellow oil:
1H NMR (DMSO-d6) d 0.89 (t, J=7.14 Hz, 6H), 1.45
(m, 2H), 1.64 (m, 2H), 2.48 (m, 2H), 2.51 (s, 3H), 3.44
(t, J=6.23 Hz, 2H), 6.95 (d, J=3.66 Hz, 1H), 7.27 (t,
J=5.31 Hz, 1H), 7.69 (d, J=3.66 Hz, 1H), 7.73 (s, 1H),
7.91 (s, 1H); MS (APCI), m/z 437 [M+1], 439 [M+3];
anal. (C21H26N4Cl2S) C, H, N.
Step 3: N0 -[6,7-dichloro-3-(5-phenyl-thiophen-2-yl)-
quinoxalin-2-yl]-N,N-diethyl-butane-1,4-diamine. The
title compound was prepared according to the general
experimental procedure for example 10a using starting
material 13b and was obtained as a light brown solid
1
(90% yield): H NMR (free base, CDCl3) d 0.96–1.03
(m, 6H), 1.57–1.78 (m, 4H), 2.47–2.56 (m, 6H), 3.61 (q,
J=6.9 Hz, 2H), 5.88 (t, J=5.1 Hz, 1H), 7.34–7.47 (m,
4H), 7.65–7.71 (m, 3H), 7.81 (s, 1H), 7.97 (s, 1H); MS

3786
J. J. Li et al. / Bioorg. Med. Chem. 11 (2003) 3777–3790
.
(ESI+) m/z 472 [M+1]; anal (C26H28N4Cl2S 2HCl 1.5-
H2O) C, H, N.
.
(APCI), m/z 365 [M+1], 367 [M+3]; anal.
.
(C18H20N4O1Cl2 2HCl 2.82H2O) C, H, N.
.
Example 13r: N-(3-[2,20]bithiophenyl-5-yl-6,7-dichloro-
Example 13u: N0-(6,7-dichloro-3-furan-2-yl-quinoxalin-2-
yl)-N,N-dimethyl-propane-1,3-diamine. The title com-
pound was prepared according to the experimental
procedure for example 13i, starting with compound 10b,
and was obtained and then made into the HCl salt by
treatment wiꢀth EtOAc/HCl. The salt is a yellow solid:
quinoxalin-2-yl)-N,N-diethyl-butane-1,4-diamine.
The
title compound was prepared according to the experi-
mental procedure for example 10a using starting mate-
rial 13b, and the product was obtained as a brown oil.
(77% yield): 1H NMR (CDCl3) d 1.02 (t, J=6.9 Hz,
6H), 1.64 (m, 2H), 1.74 (m, 2H), 2.53 (m, 6H), 3.60 (m,
2H), 5.86 (m, 1H), 7.08 (m, 1H), 7.23 (d, J=4.0 Hz,
1H), 7.31 (d, J=4.8 Hz, 1H), 7.63 (d, J=3.9 Hz, 1H),
7.79 (s, 1H), 7.96 (s, 1H); MS (APCI), m/z 503 [Mꢂ1];
1
mp 247–248 C ; H NMR (DMSO-d6) d 2.10(m, 2H),
2.73 (d, J=4.8 Hz, 6H), 3.13 (m, 2H), 3.60 (m, 2H), 7.44
(dd, J=3.7, 0.7 Hz, 1H), 7.66 (broad t, J=5.5 Hz, 1H,
NH), 7.83 (s, 1H), 8.03 (m, 1H), 10.06 (broad s, 1H);
MS (APCI), m/z [M+1], 367 [M+3]; anal.
.
anal. (C24H26N4Cl2S2 2.0HCl) C, H, N.
.
.
(C17H18N4O1Cl2 2HCl 2.0H2O) C, H, N.
Example 13s: N-(6,7-dichloro-3-[2,20;50,20]terthiophen-
5yl-quinoxalin-2-yl)-N,N-diethyl-butane-1,4-diamine.
The title compound was prepared according to the
experimental procedure for example 10a using starting
material 13b, and the product was obtained as a yellow-
Example 13v: N0-[6,7-dichloro-3-(5-pyridin-2-yl-furan-2-
yl)-quinoxalin-2-yl]-N,N-diethyl-butane-1,4-diamine.
Step 1: 2-furan-2-yl-pyridine; step 1 of the procedure
for compound 13q was followed, to give the desired
1
1
orange oil. (97% yield): H NMR (CDCl3) d 1.00 (t,
product as a white solid (6.68 g, 89% yield). H NMR
J=7.2 Hz, 6H), 1.65 (m, 2H), 1.75 (m, 2H), 2.55 (m,
6H), 3.60 (m, 2H), 5.86 (m, 1H), 7.05 (m, 1H), 7.13 (d,
J=3.7 Hz, 1H), 7.22 (m, 2H), 7.64 (d, J=4.0 Hz, 1H),
7.79 (s, ꢂ1H), 7.95 (s, 1H); MS (APCI), m/z 585 [Mꢂꢂ1],
(CDCl3) d 6.52–6.54 (m, 1H), 7.04–7.06 (m, 1H), 7.11–
7.17 (m, 1H), 7.52–7.53 (m, 1H), 7.66–7.74 (m, 2H),
8.57–8.60 (m, 1H).
.
.
587 [M +1]; anal. (C28H28N4Cl2S3 2HCl 0.32H2O) C,
H, N.
Step 2: 2-(5-tributylstannanyl-furan-2-yl)-pyridine. The
procedure from step 2 of example 13q was followed, to
give the desired product as a colorless oil (0.89 g, 15%
yield): 1H NMR (CDCl3) d 0.90 (t, J=7.3 Hz, 9H), 1.12
(t, J=7.7 Hz, 6H), 1.25–1.43 (m, 6H), 1.54–1.65 (m,
6H), 6.68 (d, J=3.2 Hz, 1H), 7.08–7.10 (m, 2H), 7.68–
7.71 (m, 2H), 8.56 (d, J=5.0 Hz, 1H).
Compound 13t, N0-(3-furan-2-yl-6,7-dichloro-quinoxalin-
2-yl)-N,N-dimethyl-butane-1,4-diamine. Step 1: N0-(3-
bromo-6,7-dichloro-quinoxalin-2-yl)-N,N-dimethyl-
butane-1,4-diamine. To a solution of compound 8
(10.35 g, 29.0 mmol) in THF (100 mL), 4-(dimethyl-
amino) butyl amine (8.35 g, 58.0 mmol) was added at
room temperature. After 30 min, the reaction mixture
was filtered to remove precipitate. After the removal of
the solvent in vacuo, the residue was chromatographed
using silica gel, eluted with 2.5% Et3N, 2.5% MeOH,
95% EtOAc, to give the desired product as a orange-
Step 3: N0-[6,7-dichloro-3-(5-pyridin-2-yl-furan-2-yl)-
quinoxalin-2-yl]-N,N-diethyl-butane-1,4-diamine. The
title compound was prepared according to the general
experimental procedure for example 10a, and was
1
obtained as a brown solid (89% yield): H NMR (free
base, CDCl3) d 0.94 (t, J=7.1 Hz, 6H), 1.59–1.77 (m,
4H), 2.43–2.52 (m, 6H), 3.52–3.59 (m, 2H), 6.92 (br,
1H), 7.11–7.19 (m, 2H), 7.37 (d, J=3.8 Hz, 1H), 7.53 (d,
J=7 Hz, 1H), 7.63–7.71 (m, 2H), 7.76 (s, 1H), 8.55–8.58
(m, 1H); MS (ESI+) m/z 484 [M+1]; anal
1
yellow oil (12.18 g, 100% yield): H NMR (CDCl3) d,
1.63 (m, 2H), 1.75 (m, 2H), 2.25 (s, 6H), 2.35 (t,
J=6.8 Hz, 2H), 3.55 (m, 2H), 6.37 (broad s, 1H), 7.78
(s, 1H), 7.86 (s, 1H). MS (APCI), m/z 391 [M+1], 393
[M+3].
.
.
(C25H27N5Cl2O 2HCl 2.5H2O) C, H, N.
Step 2: N0-(3-furan-2-yl-6,7-dichloro-quinoxalin-2-yl)-
N,N-dimethyl-butane-1,4-diamine. N0 -(3-Bromo-6,7-
dichloro-quinoxalin-2-yl)-N,N-dimethyl-butane-1,4-
diamine (890 mg, 2.27 mmol) was dissolved in THF
(30 mL). To this solution was added tributylstannyl-2-
furan (1.05 g, 2.95 mmol), PdCl2.(PPh3)2 (80 mg,
0.113 mmol), and CuI (25 mg, 0.23 mmol). The resulting
suspension was refluxed for 2 h, cooled to room tem-
perature, and filtered. The volatiles were removed in
vacuo, and the residue was chromatographed using
silica gel eluting with 5% Et3N and 5% CH3OH in
EtOAc to give the desired product as a viscous oil. The
Example 13w: N0-[6,7-dichloro-3-(5-pyridin-4-yl-furan-2-
yl)-quinoxalin-2-yl]-N,N-diethyl-butane-1,4-diamine.
Step 1: 4-furan-2-yl-pyridine. To a solution of 4-bro-
mopyridine (5.00 g, 31.64 mmol) in THF (50 mL) under
Ar,
CuI
(0.60 g,
3.16 mmol),
bis(triphenyl-
phospine)palladium (II) chloride (1.11 g, 1.56 mmol)
and 2-(tributylstannyl) furan (9.90 mL, 31.64 mmol)
were added. The reaction mixture was heated to reflux
for overnight. The reaction mixture was cooled to RT.
EtOAc (30 mL) was added into the resulting residue.
The organic phase was washed with saturated KF
solution (3ꢁ20 mL). The resulting organic layer was
dried over MgSO4. The crude product was chromato-
graphed using silica gel, eluting with EtOAc–hexane
(1:3), to give the desired product as a light orange solid
.
bis HCl salt was prepared by bubbling HCl gas into the
ꢀ
1
EtOAc solution of the free base. Mp 247–248 C; H
NMR (DMSO-d6) d 1.64 (m, 2H), 2.10 (m, 2H), 2.73 (d,
J=4.8 Hz, 6H), 3.13 (m, 2H), 3.60 (m, 2H), 7.44 (dd,
J=3.7, 0.7 Hz, 1H), 7.66 (broad t, J=5.5 Hz, 1H, NH),
7.83 (s, 1H), 8.03 (m, 1H), 10.06 (broad s, 1H); MS
1
(3.50 g, 69% yield). H NMR (CDCl3) d 6.51–6.53 (m,
1H), 6.87–6.88 (m, 1H), 7.50–7.55 (m, 3H), 8.58–8.60
(m, 2H).

J. J. Li et al. / Bioorg. Med. Chem. 11 (2003) 3777–3790
3787
Step 2: 4-(5-tributylstannanyl-furan-2-yl)-pyridine. The
procedure from step 2 of example 13q was followed, to
give the desired product as a colorless oil (0.60 g, 10%
yield): 1H NMR (CDCl3) d 0.90 (t, J=7.3 Hz, 9H), 1.12
(t, J=7.7 Hz, 6H), 1.26–1.43 (m, 6H), 1.54–1.63 (m,
6H), 6.65 (d, J=3.2 Hz, 1H), 6.89(d, J=3.2 Hz, 1H),
7.49–7.53 (m, 2H), 8.56–8.58 (m, 2H).
7.73 (s, 1H), 7.85 (dt, J=8.1, 1.9 Hz, 1H), 8.59 (m, 1H),
8.68 (d, J=8.3 Hz, 1H), 10.37 (m, 1H); MS (APCI),
m/z, 362 [M+1], 364 [M+3]; anal. (C17H17N5Cl2) C, H,
N.
N0-(6,7-Dichloro-3-pyridin-2-yl-quinoxalin-2-yl)-N,N-di-
methyl-propane-1,3-diamine (15b, n=3). The procedure
from example 15a was followed, to afford the title
compound as a yellow powder (0.43 g, 73% yield): mp
Step 3: N0-[6,7-dichloro-3-(5-pyridin-4-yl-furan-2-yl)-
quinoxalin-2-yl]-N,N-diethyl-butane-1,4-diamine. The
title compound was prepared according to the general
experimental procedure for example 10a using starting
material 13b and was obtained as a brown solid (82%
yield): 1H NMR (free base, CDCl3) d 0.96 (t, J=7.1 Hz,
6H), 1.57–1.76 (m, 4H), 2.45–2.54 (m, 6H), 3.51–3.59
(m, 2H), 6.58 (br, 1H), 6.98 (d, J=3.7 Hz, 1H), 7.35 (d,
J=3.7 Hz, 1H), 7.40 (dd, J=4.7, 1.5 Hz, 2H), 7.61 (s,
1H), 7.74 (s, 1H), 8.60 (dd, J=4.7, 1.5 Hz, 2H); MS
ꢀ
1
105–106 C; H NMR (CDCl3) d 1.91 (m, 2H), 2.25 (s,
6H), 2.43 (t, J=7.2 Hz, 2H), 3.66 (m, 2H), 7.38 (m, 1H),
7.73 (s, 1H), 7.88 (t, J=7.9 Hz, 1H), 7.93(s, 1H), 8.60
(m, 1H), 8.69 (d, J=7.9 Hz, 1H), 10.25 (broad s, 1H);
MS (APCI), m/z 376 [M+1], 378 [M+3]; anal.
(C18H19N5Cl2) C, H, N.
N0-(6,7-Dichloro-3-pyridin-2-yl-quinoxalin-2-yl)-N,N-di-
methyl-butane-1,4-diamine (15c, n=4). The procedure
from example 15a was followed, to afford the title
compound as a yellow powder (0.34 g, 55% yield): mp
81–83 ꢀC; 1NMR (CDCl3) d 1.62 (m, 2H), 1.73 (m, 2H),
2.18 (s, 6H), 2.30 (t, J=7.3 Hz, 2H), 3.59 (m, 2H), 7.34
(m, 1H), 7.70 (s, 1H), 7.84 (dt, J=7.8, 1.7 Hz, 1H), 7.89
(s, 1H), 8.56 (m, 1H), 8.67 (d, J=8.3 Hz, 1H), 10.20
(broad s, 1H); MS (APCI), m/z 390 [M+1], 392 [M+3].
Anal. (C19H21N5Cl2) C, H, N.
.
(ESI+) m/z 484 [M+1]; anal (C25H27N5Cl2O
.
3HCl 1.4H2O) C, H, N.
Example 13x: N0-[6,7-dichloro-3-(5-phenyl-furan-2-yl)-
quinoxalin-2-yl]-N,N-diethyl-butane-1,4-diamine. Step 1:
tributyl-(5-phenyl-furan-2-yl)-stannane. The procedure
from step 2 of example 13v was followed, to give the
desired product as a brown oil, which was carried on to
product without further purification.
N0-(6,7-Dichloro-3-pyridin-2-yl-quinoxalin-2-yl)-N,N-di-
methyl-pentane-1,5-diamine (15d, n=5). Asolution of 3-
(2-pyridyl)-2,6,7-trichloroquinoxaline (2.1 g, 6.9 mmol)
and (5-amino-pentyl)-carbamic acid tert-butyl ester
(2.8 g, 14 mmol), in toluene (50 mL) was heated to reflux
for 16 h. The resulting solution was cooled, filtered, and
the filtrate concentrated in vacuo. The residue was pur-
ified by flash chromatography on silica gel (50% ethyl
acetate/hexane) to give 2.09 g of orange powder (yield
64%). This powder was added to a solution of methanol
(60 mL) and HCl. The resulting mixture was stirred 2 h,
then treated with 2 N aqueous KOH (40 mL) and stirred
10 min, diluted with water and filtered. The precipitate
was dried in vacuo to give 1.9 g of a orange solid. The
crude aminoquinoxaline was added to a solution of
water (10 mL), 90% formic acid (1.6 g, 32 mmol), and
formalin (1.1 g, 14 mmol). This mixture was refluxed for
2 h, then heated below boiling for 16 h. After cooling,
the reaction mixture was filtered, dissolved in methanol,
treated with 2 N HCl (5 mL), stirred 20 min, treated with
2 N aqueous KOH (5 mL), and filtered. The precipitate
was purified by flash chromatography over silica gel (1:5
methanol–chloroform) to give the title compound as a
Step 2 N0-[6,7-dichloro-3-(5-phenyl-furan-2-yl)-quinox-
alin-2-yl]-N,N-diethyl-butane-1,4-diamine. The title
compound was prepared according to the general
experimental procedure for example 10a, and was
1
obtained as a brown solid (70% yield): H NMR (free
base, CDCl3) d 1.02 (t, J=7.1 Hz, 6H), 1.25–1.42 (m,
4H), 2.45–2.65 (m, 6H), 4.12 (dd, J=6.5, 2.2 Hz, 2H),
6.71–6.73 (m, 2H), 7.31–7.56 (m, 4H), 7.62–7.69 (m,
3H), 8.02 (s, 1H); MS (ESI+) m/z 484 [M+1]; anal
.
.
(C26H28N4Cl2O 2HCl 1H2O) C, H, N.
Example 13y: N-(3-benzofuran-2-yl-6,7-dichloro-quinox-
alin-2-yl)-N,N-diethyl-butane-1,4-diamine. The
title
compound was prepared according to the experimental
procedure for example 10a, and the product was
obtained as a red-orange oil. The free base was dis-
solved in EtOAc and treated with HCl gas to produce
the corresponding salt as a yellow-orange powder (88%
yield). 1H NMR (CDCl3) d 1.02 (t, J=6.9 Hz, 6H), 1.64
(m, 2H), 1.74 (m, 2H), 2.53 (m, 6H), 3.60 (m, 2H), 7.34
(m, 1H), 7.43(m, 1H), 7.64 (m, 1H), 7.71(m, 2H), 7.79
(s, 1H), 7.93 (s, 1H); MS (APCI), m/z 457 [M+1]; anal.
(C24H26N4Cl2O 2HCl 0.22H2O) C, H, N.
yellow powder (0.83 g, 34% yield): mp 100–102 ꢀC; H
1
.
.
NMR (CDCl3) d 1.46 (m, 2H), 1.57 (m, 2H), 1.80 (m,
2H), 2.23 (s, 6H), 2.31 (t, J=7.3 Hz, 2H), 3.61 (m, 2H),
7.38 (m, 1H), 7.73 (s, 1H), 7.86 (dt, J=8.0, 1.9 Hz, 1H),
7.92 (s, 1H), 8.61 (m, 1H), 8.70 (d, J=8.3 Hz, 1H), 10.22
(broad t, J=4.6 Hz, 1H); MS (APCI), m/z 404 [M+1],
406 [M+3]; anal. (C20H27N5Cl2) C, H, N.
N0-(6,7-Dichloro-3-pyridin-2-yl-quinoxalin-2-yl)-N,N-di-
methyl-ethane-1,2-diamine (15a, n=2). Asolution of 3-
(2-pyridyl)-2,6,7-trichloroquinoxaline, (compound 14,
0.50 g, 1.6 mmol) and dimethylaminoethylamine (0.28 g,
3.2 mmol) in toluene (20 mL) was heated to reflux for
16 h. The resulting solution was cooled, filtered, and the
filtrate concentrated in vacuo. The residue was purified
by flash chromatography on silica gel (5–10% metha-
nol/chloroform) to give a yellow powder (0.253 g, 45%
N0-(6,7-Dichloro-3-pyridin-2-yl-quinoxalin-2-yl)-N,N-di-
methyl-hexane-1,6-diamine (15e, n=6). The procedure
from example 15a was followed, to afford the title
compound as a yellow powder (0.41 g, 62% yield): mp
ꢀ
1
yield): mp 95–97 C; H NMR (CDCl3) d 2.33 (s, 6H),
2.64 (t, J=6.35 Hz, 2H), 3.71 (m, 2H), 7.36 (m, 1H),
88–90 ꢀC; H NMR (CDCl3) d 1.36 (m, 2H), 1.43 (m,
1

3788
J. J. Li et al. / Bioorg. Med. Chem. 11 (2003) 3777–3790
4H), 1.69 (m, 2H), 2.15 (s, 6H), 2.20 (m, 2H), 3.56 (m,
2H), 7.34 (m, 1H), 7.70 (s, 1H), 7.85 (dt, J=8.0, 1.7 Hz,
1H), 7.89 (s, 1H), 8.57 (m, 1H), 8.68 (d, J=8.1 Hz, 1H),
10.20 (s, 1H); MS (APCI), m/z 418 [M+1], 420 [M+3];
anal. (C21H25N5Cl2) C, H, N.
product was chromatographed on silica gel, eluting with
EtOAc–hexane (1:8 to 1:3), to give the desired product
as a white solid (1.00 g, 75% yield): 1H NMR (CDCl3) d
2.31 (t, J=2.4 Hz, 1H), 4.35 (dd, J=5.3, 2.4 Hz, 2H),
5.85 (br, 1H), 7.86 (s, 1H), 7.91 (s, 1H); MS (ESI), m/z
332 [M+1].
Compound 15f: N-(6,7-dichloro-3-pyridin-2-yl-quinoxa-
The
lin-2-yl)-N0,N0-dimethyl-cyclohexane-1,4-diamine.
title compound was prepared according to the experi-
Step 2: N0-(3-bromo-6,7-dichloro-quinoxalin-2-yl)-N,N-
dimethyl-but-2-yne-1,4-diamine. To a solution of para-
formaldehyde (65.85 mg, 2.20 mmol), copper (II) acetate
(20.00 mg, 0.11 mmol) in dioxane (10 mL) in a sealed
tube, dimethylamine (1.10 mL, 2.20 mmol, 2 M solution
in THF) was added. The reaction mixture was heated
to 60 ꢀC for 1 h. Then the mixture was cooled to room
temperature and (3-bromo-6,7-dichloro-quinoxalin-2-
yl)-prop-2-ynyl-amine (0.72 g, 2.20 mmol) was added.
The final reaction mixture was heated to 80 ꢀC over-
night. After cooling to rt, 10% KOH solution (5 mL)
was added to quench the reaction. The phases were
separated and the aqueous layer was extracted with
EtOAc (3ꢁ5 mL). The combined organic phases were
dried over MgSO4. The crude product was chromato-
graphed on silica gel, eluting with EtOAc–MeOH–
Et3N (10:1:0.1), to give the desired product as a white
mental procedure for example 15a and was obtained as
a yellow solid (84% yield). Mp 180–182 ꢀC; H NMR
1
(DMSO-d6) d 1.80–2.45 (m, 8H), 2.92 (s, 6H), 4.58
(broad s, 1H), 7.80 (m, 1H), 7.75 (s, 1H), 8.07 (s, 1H),
8.10 (m, 1H), 8.82 (m, 1H); MS (APCI), m/z 417
.
[M+1], 419 [M+3]; anal. (C21H23N5Cl2 1.04HCl) C, H,
N.
Compound 15g: N-(6,7-dichloro-3-pyridin-2-yl-quinoxa-
lin-2-yl)-cyclohexane-1,4-diamine. The title compound
was prepared according to the experimental procedure
for example 15a and was obtained as a yellow solid
(98% yield): mp 280–282 ꢀC (dec.); H NMR (DMSO-
1
d6) d 1.82 (m, 4H), 2.22 (m, 2H), 2.46 (m, 2H), 4.38
(broad, s, 1H), 7.74 (dd, J=7.0, 4.7 Hz, 1H), 8.21 (dd,
J=15.0, 7.0 Hz, 1H), 8.82 (dd, J=8.0, 4.0 Hz, 1H); MS
(APCI), m/z 388 [M+1], 390 [M+3]; anal.
1
solid (0.44 g, 52% yield): H NMR (CDCl3) d 2.30 (s,
6H), 3.25–3.26 (m, 2H), 4.34–4.38 (m, 2H), 5.87 (br,
1H), 7.81 (s, 1H), 7.87 (s, 1H); MS (ESI), m/z 389
[M+1].
.
(C19H19N5Cl2 2.0HCl) C, H, N.
Compound 15h: 2-[1,40]bipiperidinyl-10-yl-6,7-dichloro-3-
pyridin-2-yl-quinoxaline. The title compound was pre-
pared according to the experimental procedure for
example 15a and was obtained as a bright yellow solid
(92% yield): mp 275–277 ꢀC (dec.); 1H NMR (CDCl3) d
1.33–1.82 (m, 12H), 2.48 (s, 3H), 2.75 (t, J=12.7 Hz,
2H), 7.35 (t, J=6.1 Hz, 1H), 7.87 (s, 1H), 7.37 (m, 1H),
8.06 (s, 1H), 8.76 (s, 1H); MS (APCI), m/z 441 [M+1],
Step 3: N0-(3-[2,20]bithiophenyl-5-yl-6,7-dichloro-quin-
oxalin-2-yl)-N,N-dimethyl-but-2-yne-1,4-diamine. The
title compound was prepared according to the general
experimental procedure for example 10a, and was
1
obtained as a light brown solid (37% yield): H NMR
(free base, CDCl3) d 2.29 (s, 6H), 3.24 (S, 2H), 4.37–4.39
(m, 2H), 5.70 (br, 1H), 7.06–7.07 (m, 1H), 7.19 (d,
J=3.9 Hz, 1H), 7.28–7.31 (m, 2H), 7.62 (d, J=3.9 Hz,
1H), 7.78 (s, 1H), 7.94 (s, 1H); MS (ESI+) m/z 473
.
444 [M+3]; anal. (C23H25N5Cl2 1.32HCl) C, H, N.
.
.
.
Compound 15i: (6,7-dichloro-3-pyridin-2-yl-quinoxalin-2-
yl)-(4-diethylaminomethyl-phenyl)-amine. The title com-
pound was prepared according to the experimental
procedure for example 15a and was obtained as an
[M+1]; anal (C22H18N4Cl2S2 HCl 0.8H2O 0.2MeOH)
C, H, N.
Example 16b: N0-(3-[2,20]bithiophenyl-5-yl-6,7-dichloro-
quinoxalin-2-yl)-N,N-dimethyl-but-2-ene-1,4-diamine. To
a solution of 16a (150.00 mg, 0.31 mmol) in THF
(30 mL), Lindlar catalyst (15.00 mg, 10 wt%) was added.
The reaction mixture was hydrogenated on a Parr
apparatus under H2 at 40 PSI for 3 days. The mixture
was filtered through Celite and concentrated. The
resulting crude product was chromatographed using
silica gel, eluting with EtOAc–MeOH–Et3N (10:1:0.1),
to give the desired product as a yellow solid (62.10 mg,
42% yield). The HCl salt was prepared by treating a
solution of free base in EtOAc with 1 M HCl solution in
orange powder (83% yield). Mp 250–252 ꢀC (dec.); H
1
NMR (CDCl3) d 1.04 (t, J=7.1 Hz, 6H), 2.57 (q,
J=7.1 Hz, 4H), 3.61 (s, 2H), 7.38 (d, J=8.4 Hz, 2H),
7.48 (dd, J=5.0, 1.0 Hz, 1H), 7.93 (s, 1H), 7.90(s, 2H),
7.97 (dt, J=8.1, 2.0 Hz, 1H), 8.03 (s, 1H), 8.73 (d,
J=4.8 Hz, 1H), 8.84 (d, J=8.1 Hz, 1H), 12.87 (s, 1H);
MS (APCI), m/z 347 [M+1], 349 [M+3]; anal.
.
(C24H23N5Cl2 0.42H2O) C, H, N.
Example 16a: N0-(3-[2,20]bithiophenyl-5-yl-6,7-dichloro-
quinoxalin-2-yl)-N,N-dimethyl-but-2-yne-1,4-diamine.
Step 1: (3-bromo-6,7-dichloro-quinoxalin-2-yl)-prop-2-
ynyl-amine. To a solution of 2,3-dibromo-6,7-dichloro-
quinoxaline (1.50 g, 4.20 mmol) in THF (20 mL),
K2CO3 (1.16 g, 8.40 mmol) and propargylamine
(0.58 mL, 8.40 mmol) were added. The reaction mixture
was stirred at room temperature overnight. Saturated
NaHCO3 solution (10 mL) was added to quench the
reaction. The phases were separated and the aqueous
layer was extracted with EtOAc (3ꢁ10 mL). The com-
bined organic phase was dried over MgSO4. The crude
1
Et2O: H NMR (free base, CDCl3) d 2.21 (s, 6H), 3.03
(d, J=6.6 Hz, 2H), 4.21 (t, J=5.3 Hz, 2H), 5.80–5.90
(m, 2), 6.43 (br, 1H), 7.05–7.08 (m, 1H), 7.21 (d,
J=3.9 Hz, 1H), 7.29–7.31 (m, 2H), 7.64 (d, J=3.9 Hz,
1H), 7.78 (s, 1H), 7.95 (s, 1H); MS (ESI), m/z 475
.
.
[M+1]; anal (C22H20N4Cl2S2 HCl 0.5EtOAc) C, H, N.
Example 16c: 1-[4-(3-[2,20]bithiophenyl-5-yl-6,7-dichloro-
quinoxalin-2-ylamino)-butyl]-piperidin-4-ol. Step 1: 1-[4-
(3-bromo-6,7-dichloro-quinoxalin-2-ylamino)-butyl]-

J. J. Li et al. / Bioorg. Med. Chem. 11 (2003) 3777–3790
3789
piperidin-4-ol. The procedure for example 13b was fol-
lowed, to yield a tan solid (61% yield): 1H NMR
(CDCl3) d 1.51–1.81 (m, 7H), 1.83–2.0 (m, 2H), 2.14 (t,
J=9.0 Hz, 2H), 2.38 (t, J=7.0 Hz, 2H), 2.78 (m, 2H),
3.57 (m, 2H), 3.70 (m, 1H), 5.80 (m, 1H), 7.78 (s, 1H),
7.86 (s, 0H); MS (ESI+), m/z 447 [M+1].
Step 3: (3-[2,20]bithiophenyl-5-yl-6,7-dichloro-quinox-
alin-2-yl)-piperidin-4-yl-amine. (4-(3-[2,20]bithiophenyl-
5-yl-6,7-dichloro-quinoxalin-2-ylamino)-piperidine-1-
carboxylic acid tert-butyl ester, (220 mg, 0.416 mmol)
was dissolved in HCl/dioxane (4 M, 5 mL, 20 mmol) and
stirred for 1 h at rt. The solvent was removed in vacuo,
and the residue was partitioned between aqueous
NaOH and ethyl acetate. The organic layers were dried,
evaporated, and chromatographed on silica gel, eluting
with EtOAc–MeOH–Et3N (10:1:0.1), to give the desired
product as an orange solid (111 mg, 58% yield). The
HCl salt was prepared by treating a solution of free base
in methanol with 1 M HCl solution in methanol: 1H
NMR (free base, CDCl3) d 1.40–1.50 (m, 2H), 2.12–2.25
(m, 2H), 2.75–2.90 (m, 2H), 3.10–3.25 (m, 2H), 3.50 (s,
1H), 4.25 (m, 1H), 5.56 (d, J=7.3 Hz, 1H), 7.05–7.10
(m, 1H), 7.20–7.35 (m, 3H), 7.58 (d, J=4.0 Hz, 1H),
7.78 (s, 1H), 7.95 (s, 1H); MS (ESI+), m/z 461 [M+1];
Step 2: 1-[4-(3,[2,20]bithiophenyl-5-yl-6,7-dichloro-quin-
oxalin-2-ylamino)-butyl]-piperidin-4-ol. The title com-
pound was prepared according to the procedure for
example 10a, to yield a dark red solid (30 mg, 32%
yield): 1H NMR (free base, CDCl3) d 1.51–2.00 (m,
8H), 2.24 (m, 2H), 2.40–2.55 (m, 3H), 2.82 (m, 2H),
3.59 (m, 2H), 3.70 (m, 1H), 5.80 (m, 1H), 7.05–7.10
(m, 1H), 7.15–7.36 (m, 3H), 7.62 (d, J=4.0 Hz, 1H),
7.77 (s, 1H), 7.94 (s, 1H); MS (ESI+) m/z 533
.
.
.
[M+1]; anal (C25H28N4O1Cl2S2 2HCl 1H2O 1CH3OH)
C, H, N.
.
.
.
anal (C21H18N4Cl2S2 2HCl 0.5H2O 1.0MeOH) C, H, N.
Example 16d: (3-[2,20]bithiophenyl-5-yl-6,7-dichloro-quin-
oxalin-2-yl)-(8-methyl-8-aza-bicyclo[3.2.1]oct-3-yl)-amine.
Step 4: (1-benzyl-piperidin-4-yl)-(3-[2,20]bithiophenyl-5-
yl-6,7-dichloro-quinoxalin-2-yl)-amine. Asolution of (3-
[2,20]bithiophenyl-5-yl-6,7-dichloro-quinoxalin-2-yl)-
Step
methyl-8-aza-bicyclo[3.2.1]oct-3-yl)-amine. The proce-
1:
(3-bromo-6,7-dichloro-quinoxalin-2-yl)-(8-
.
dure for example 13b was followed, to yield a light
1
piperidin-4-yl-amine 2HCl (108 mg, 0.203 mmol) in
brown solid (0.59 g, 80% yield): H NMR (CDCl3) d
methanol (10 mL) was treated with benzaldehyde
(0.05 mL, 0.5 mmol) and sodium cyanoborohydride
(31 mg, 0.5 mmol). The mixture was brought to pH=6.0
with methanolic sodium methoxide, and stirred 12 h at
room temperature. The solvent was removed in vacuo,
and the residue was partitioned between aqueous
NaOH and ethyl acetate. The organic layers were dried,
evaporated, and chromatographed on silica gel, eluting
with EtOAc–MeOH–Et3N (10:1:0.1), to give the title
compound as an orange solid (20 mg, 18% yield). The
HCl salt was prepared by treating a solution of free base
in methanol with 1 M HCl solution in methanol: 1H
NMR (free base, CDCl3) d 1.50–1.72 (m, 2H), 2.08–2.25
(m, 2H), 2.28 (t, J=10.8 Hz, 2H), 2.75–2.90 (m, 2H),
3.56 (s, 2H), 4.15 (m, 1H), 5.53 (d, J=7.0 Hz, 1H), 7.05–
7.10 (m, 1H), 7.20–7.50 (m, 8H), 7.54 (d, J=4.0 Hz,
1H), 7.76 (s, 1H), 7.93 (s, 1H); MS (ESI+), m/z 551
1.80–1.87 (m, 4H), 2.15–2.25 (m, 2H), 2.31–2.42 (m,
5H), 3.21–3.33 (m, 2H), 4.24–4.37 (m, 1H), 6.23 (d,
J=6.2 Hz, 1H), 7.80 (s, 1H), 6.87 (s, 1H); MS (ESI),
m/z, 419 [M+1].
Step 2: (3-[2,20]bithiophenyl-5-yl-6,7-dichloro-quinox-
alin-2-yl)-(8-methyl-8-aza-bicyclo[3.2.1]oct-3-yl)-amine.
The title compound was prepared using the procedure
1
for example 10a, to yield a brown solid (75% yield): H
NMR (free base, CDCl3) d 1.80–1.87 (m, 4H), 2.17–2.21
(m, 2H), 2.32–2.44 (m, 5H), 3.18–3.30 (m, 2H), 4.28–
4.40 (m, 1H), 6.00 (d, J=6.2 Hz, 1H), 7.07–7.10 (m,
1H), 7.26–7.29 (m, 2H), 7.31 (d, J=3.8 Hz, 1H), 7.61 (d,
J=3.8 Hz, 1H), 7.80 (s, 1H), 7.96 (s, 1H); MS (ESI), m/z
.
.
.
502 [M+1]; anal (C24H22N4Cl2S2 2HCl 1.5H2O
0.5EtOAc) C, H, N.
.
.
.
[M+1]; anal (C28H24N4Cl2S2 2HCl 1.0H2O 1.0CH2Cl2)
C, H, N.
Example 16e: (1-benzyl-piperidin-4-yl)-(3-[2,20]bithio-
phenyl-5-yl-6,7-dichloro-quinoxalin-2-yl)-amine. Step 1:
4-(3-bromo-6,7-dichloro-quinoxalin-2-ylamino)-piper-
idine-1-carboxylic acid tert-butyl ester. The procedure
from example 13b was followed, starting with 4-amino-
piperidine-1-carboxylic acid tert-butyl ester. The bro-
mide intermediate was obtained as a brown solid
(736 mg, 62% yield): 1H NMR (free base, CDCl3) d
1.40–1.62 (m, 11H), 2.09–2.20 (m, 2H), 3.01 (t,
J=11.5 Hz, 2H), 4.03–4.29 (m, 3H), 5.60 (d, J=7.5 Hz,
1H), 7.77 (s, 1H), 7.84 (s, 1H).
Example 16f: (3-[2,20]bithiophenyl-5-yl-6,7-dichloro-quin-
oxalin-2-yl)-(1-ethyl-piperidin-4-yl)-amine. The title
compound was prepared using the procedure for
example 16e, step 4, to yield an orange solid (73 mg,
66% yield): 1H NMR (free base, CDCl3) d 1.11 (t,
J=7.0 Hz, 3H), 1.50–1.72 (m, 2H), 2.10–2.35 (m, 4H),
2.44 (q, J=7.25 Hz, 2H), 2.75–2.90 (m, 2H), 4.13 (m,
1H), 5.53 (d, J=7.0 Hz, 1H), 7.05–7.10 (m, 1H), 7.18
(d, J=3.8 Hz, 2H), 7.26–7.36 (m, 2H), 7.54 (d,
J=3.9 Hz, 1H), 7.74 (s, 1H), 7.90 (s, 1H); MS (ESI+),
Step 2: 4-(3-[2,20]bithiophenyl-5-yl-6,7-dichloro-quinox-
alin-2-ylamino)-piperidine-1-carboxylic acid tert-butyl
ester. The procedure from example 10a was followed, to
yield an orange solid (706 mg, 95% yield): 1H NMR
(CDCl3) d 1.42–1.56 (m, 9H), 2.12–2.25 (m, 2H), 3.04 (t,
J=11.2 Hz, 2H), 3.95–4.08 (m, 2H), 4.20–4.40 (m, 1H),
5.50 (d, J=7.0 Hz, 1H), 7.06 (dd, J=4.8, 4.0 Hz, 1H),
7.20 (d, J=3.9 Hz, 2H), 7.29 (m, 2H), 7.54 (d,
J=3.9 Hz, 1H), 7.77 (s, 1H), 7.93 (s, 1H).
m/z 489 [M+1]; anal (C23H22N4Cl2S2 2HCl 1.0H2O) C,
H, N.
.
.
Receptor binding assay.22 The receptor-binding assay
was carried out in RPMI-1640 culture media supple-
mented with 20 mM HEPES buffer and 0.2% BSA, pH
7.4. The binding mixture consist of 80 mL of 125I-IL-8
(40 pM) with or without cold excess IL-8 (38 nM), 50 mL
of the compound to be tested, and 120 mL containing

3790
J. J. Li et al. / Bioorg. Med. Chem. 11 (2003) 3777–3790
40,000 human neutrophils. The mixture was incubated
at room temperature for 3 h. The reaction was termi-
nated by centrifuging the cells through a sucrose solu-
tion and the radioactivity in the pellet was measured
using a gamma counter.
6. Warringa, R. A. J.; Koenderman, L.; Kok, P. T. M.;
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Chemotaxis assay. Freshly isolated human neutrophils
were resuspended in RPMI-1640 culture media-based
chemotaxis buffer. The cells were pre-incubated with or
without compounds for 60 min and placed into the top
chamber. rhIL-8 with or without drug was placed into
the lower chambers of chemotaxis plate. The plates were
incubated at 37 ꢀC for 30 min. The top chamber was
then removed and the number of chemotaxed neu-
trophils in the bottom chamber were counted using a
FACs.
Calcium flux assay.23 Human neutrophils were incu-
bated with the fluorescence dye FLUO3, for 1 h. The
cells were washed after this loading period, resuspended
in Hank’s buffer, and loaded into a 96-well plate. Com-
pound was added to each well. After a 60-min incu-
bation period, the cells were stimulated with human IL-
8 in a 96-well FLIPR instrument and the calcium flux
response recorded and quantified.
Selectivity assays. Materials for NK2, M2 and 5HT1a
binding were purchased from NEN Life Science Pro-
ducts (Boston, MA, USA), using protocols supplied by
the manufacturer. Binding of 5HT6, 5HT7 and a2C was
carried out at MDS Panlabs Pharmacology Services
(Bothell, WA, USA).
18. Palovich, M. R.; Widdowson, K.; Elliottt, J. D.; White, J.
R.; Sarau, H. M.; Rutledge, M. C.; Bi, J.; Dede, K. A.; Ben-
son, G. M.; Griswold, D. E.; Martin, L. D.; Nhe, H.; Schmidt,
D. M.; Foley, J. J. Book of Abstracts, 219th ACS National
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was previously communicated: 220th ACS National Meeting,
Washington, DC, March 29–April 2, 2000.
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