Synthesis and SAR of novel di- and trisubstituted 1,4-dihydroquinoxaline-2,3-diones related to licostinel (Acea 1021) as NMDA/glycine site antagonists

Article abstract of DOI:10.1016/S0968-0896(03)00059-2

A series of novel di- and trisubstituted 1,4-dihydroquinoxaline-2,3-diones (QXs) related to licostinel (Acea 1021) was synthesized and evaluated as antagonists for the glycine site of the N-methyl-D-asparate (NMDA) receptor. The in vitro potency of these

Full text of DOI:10.1016/S0968-0896(03)00059-2

Bioorganic & Medicinal Chemistry 11 (2003) 1769–1780
Synthesis and SAR of Novel Di- and Trisubstituted
1,4-Dihydroquinoxaline-2,3-diones Related to Licostinel
(Acea 1021) as NMDA/Glycine Site Antagonists
Zhang-Lin Zhou,a Sunil M. Kher,a Sui Xiong Cai,b Edward R. Whittemore,b
Stephen A. Espitia,b Jon E. Hawkinson,b Minhtam Tran,b
Richard M. Woodward,b Eckard Weberb and John F. W. Keanaa,*
aDepartment of Chemistry, University of Oregon, Eugene, OR 97403, USA
bCoCensys, Inc., 201 Technology Drive, Irvine, CA 92618, USA
Received 23 October 2002; accepted 16 December 2002
Abstract—A series of novel di- and trisubstituted 1,4-dihydroquinoxaline-2,3-diones (QXs) related to licostinel (Acea 1021) was
synthesized and evaluated as antagonists for the glycine site of the N-methyl-d-asparate (NMDA) receptor. The in vitro potency of
these antagonists was determined by displacement of the glycine site radioligand [3H]-5,7-dichlorokynurenic acid ([3H]DCKA) in
rat brain cortical membranes. Structure–activity relationship studies indicate that a cyano group is a good replacement for the nitro
group in the 5-position of licostinel while 5-carboxy, 5-ester, 5-ketone and 5-amide derivatives showed reduced potency. 5,6-
Cyclized analogues of licostinel also showed significantly reduced potency. Among the trisubstituted QXs investigated, 5-cyano-6,7-
dichloro QX and 5-cyano-7-chloro-6-methyl QX are the most potent with IC50 values of 32 nM and 26 nM, respectively.
# 2003 Elsevier Science Ltd. All rights reserved.
Introduction
diones (QXs) leading to licostinel (Acea 1021, 3),
7-chloro-6-methyl-5-nitro QX (4) and 7-bromo-6-
methyl-5-nitro QX (5) (Chart 1).5,6 As a continuation of
these studies, we report herein the synthesis of a series
of novel di- and trisubstituted QXs 7 and their eval-
uation as NMDA/glycine site antagonists.
N-Methyl-d-asparate (NMDA) receptors are a subclass
of ionotropic glutamate receptors. Overstimulation of
NMDA receptors has been implicated in a number of
pathophysiological conditions including CNS ischemia
and trauma that lead to neuronal death and degenera-
tion.1 Since the discovery that glycine is an essential co-
agonist for NMDA receptor activation,2 considerable
effort has been directed toward the discovery of NMDA
receptor glycine site antagonists useful for the treatment
of CNS disorders.
Chemistry
QXs 7a–k were prepared by condensation of oxalic acid
or diethyl oxalate with the corresponding 1,2-diamino-
benzenes 6a–k (Scheme 1). Diamines 6a,c,e were pre-
pared from the corresponding anilines 8 as follows. The
amino group of 8 was first protected by reaction with
acetic anhydride or trifluoroacetic anhydride to give the
corresponding amide, which was then nitrated in H2SO4
with KNO3 or HNO3. The nitrated amide 9 was then
hydrolyzed to give the corresponding o-nitroaniline 10,
which was then reduced to give the corresponding
1,2-diaminobenzene 6. 1,2-Diaminobenzene 6b was pre-
pared by selective reduction of 10b using ammonium
sulfide. Intermediate 10b was prepared7 (Scheme 2) by
dinitration of 2-fluorobenzoic acid (11) with fuming
Several structurally different classes of potent glycine site
antagonists have been identified (Chart 1). Examples
include 4-hydroxy-3-(3-phenoxyphenyl)quinoline-2(1H)-
ones such as 13 and 1,2,3,4-tetrahydroquinoline-2,3,4-
trione-3-oximes (QTOs) such as 2.4
We recently reported on the structure–activity relation-
ship (SAR) of substituted 1,4-dihydroquinoxaline-2,3-
*Corresponding author. Tel.: +1-541-346-4609; fax: +1-541-346-
0487; e-mail: jkeana@oregon.uoregon.edu
0968-0896/03/$ - see front matter # 2003 Elsevier Science Ltd. All rights reserved.
doi:10.1016/S0968-0896(03)00059-2

1770
Z.-L. Zhou et al. / Bioorg. Med. Chem. 11 (2003) 1769–1780
nitric acid in fuming sulfuric acid to give dinitro com-
pound 12, which was then reacted with aqueous
NH4OH to give 10b in 97% yield.
Diamines 6d,f–h were obtained from intermediates
10d,f–h, which were prepared from 2-amino-5-chloro-3-
nitro-benzoic acid (10c). Refluxing 10c in thionyl chlo-
ride gave the corresponding acid chloride, which was
treated with methanol to give ester 10d or alternatively,
with ammonia, dimethylamine or diethylamine to give
the corresponding amides 10f–h in excellent yields.
Chart 1.
Diamine 6i was prepared from methyl 2-acetylamino-5-
bromo-6-methyl-3-nitro-benzoate (9i) by way of 10i.
Ester 9i was prepared as shown in Scheme 3. Esterifica-
tion of benzoic acid 13 with methyl iodide, followed by
reduction by catalytic hydrogenation gave amino ester
14, which was then N-protected with acetic anhydride,
brominated and nitrated to give 9i.
Diamines 6j,k were prepared as described in Scheme 4.
Heck coupling of 1,4-dichloro-2-iodobenzene (15) with
acrylic acid gave acrylic acid 16, which was reduced to
3-(2,5-dichlorophenyl)propanoic acid (17). Acid 17
underwent an intramolecular Friedel–Crafts acylation
to give indanone 18j. Lactone 18k was prepared by
selective reduction of 4,7-dichloro-isobenzofuran-1,3-
dione (19) with sodium borohydride. Nitration of 18j,k
gave the corresponding nitro compounds 20j,k, which
were then treated with sodium azide to give the corre-
sponding azides 21j,k. Concomitant reduction of the
nitro and azide groups in these latter molecules led to
the desired diamines 6j,k, respectively.
Scheme 3. (a) (i) K2CO3, MeI, acetone; (ii) 10% Pd/C, H2; (b) (i)
(CH3CO)2O, rt; (ii) Br2, AcOH; (iii) 90% HNO3, TFA.
Scheme 1. (a) (CO2H)2, 2N HCl; (b) (CO2Et)2, EtOH; (c) (i)
(CH3CO)2O; (ii) KNO3/H2SO4; (d) (CF3CO)2O, CF3CO2H, then
.
KNO3; (e) 2 N HCl; (f) K2CO3 or NaOH; (g) SnCl2 2H2O; (h)
(NH4)2S; (i) H2, Pd/C.
Scheme 4. (a) CH2¼CHCO2H, Pd(OAc)2, TEA, CH3CN, 94%; (b)
PtO2, H2, EtOAc; (c) (i) SOCl2; (ii) AlCl3, CS2, 71%; (d) NaBH4,
DMF rt, 75%; (e) 90% HNO3, 43% or KNO3, H2SO4, 86%; (f)
NaN3, acetone, H2O, 75%; (g) 10% Pd/C, H2, EtOAc.
Scheme 2. (a) 90% HNO3, H2SO4 (fuming, 15% SO3), 145 ꢀC, 73%;
(b) 30% NH4OH, HCl, rt, 97%; (c) SOCl2, relfux; (d) CH3OH or NH3
or HN(CH3)2 or HN(CH2CH3)2, rt, 81–98%.

Z.-L. Zhou et al. / Bioorg. Med. Chem. 11 (2003) 1769–1780
1771
7-Chloro-5-cyano QX 26 was prepared as shown in
Results and Discussion
Scheme 5. Nitration of benzonitrile 22 with 70% HNO3
at 5 ꢀC gave nitro derivative 23 in 97% yield. Nucleo-
philic substitution of the methoxy group of 23 with
sodium glycinate yielded glycinate 24. Reduction fol-
lowed by cyclization led to quinoxalin-2(1H)-one 25,
which was oxidized to the desired QX 26 using nitric
acid.8
The structure–activity relationships of QXs in this series
as antagonists at NMDA/glycine site follow from the
IC50 values given in Table 1. Considering first the
5-carboxylic acid-substituted QXs, 5,7-disubstituted
QXs 7a and 7b are both about 2-fold less potent than
7c, suggesting that 7-chloro is slightly favored over
7-methyl and 7-nitro for high potency. We next varied
the substituent at the 5-position while retaining a
7-chloro group. The potencies of disubstituted QXs
7e,f,g,h containing a carbonyl group at the 5-position
were all within a factor of two to four of that of 7c, with
the exception of methyl ester 7d, which was about
10-fold less potent than 7c. Most strikingly, a 100-fold
increase in potency over 7c was seen when the 5-carboxy
group was replaced by 5-cyano to give 7-chloro-5-cyano
QX 26. These results confirm the importance of having
an electron withdrawing group at the 5-position of the
QX. Interestingly, replacement of the 5-cyano group in
26 by a nitro group resulted in disubstituted QX 32,5
which was only 10-fold more potent than 7c and 10-fold
less potent than 26. This result was unexpected given the
generally high potency of the (trisubstituted) 5-nitro
Qxs 3, 4 and 5.
5-Cyano-6,7-dichloro QX (31a) and 7-chloro-5-cyano-6-
methyl QX (31b) were prepared by a regiospecific oxi-
dative nitration procedure (Scheme 6).8 Nucleophilic
substitution of 2,6-dichloro-3-nitrobenzonitrile (27a)
and 2-chloro-6-methyl-3-nitrobenzonitrile (27b) by
sodium glycinate gave the respective substituted N-phe-
nylglycinate 28a,b. These were separately reduced and
cyclized to give the respective 5-cyano-3,4-dihydro-
quinoxalin-2(1H)-one 29a,b. Oxidative nitration of
29a,b gave 5-cyano-7-nitro QX 30a,b, respectively. The
nitro group in each compound was reduced to give the
corresponding amine, which was diazotized and chlori-
nated to give QX 31a,b.
Pharmacology
The affinity of the QXs for the NMDA receptor glycine
site was measured by inhibition of [3H] 5,7-dichloro-
kynurenic acid ([3H]DCKA) binding to rat brain cor-
tical membranes as described previously.9 Affinity is
expressed as IC50ÆSEM (n=3–4) estimated from dis-
placement of [3H]DCKA binding to the membrane.
We next investigated the effect on potency of adding a
third substituent to selected QXs discussed above. We
were also interested to see the effect of forming a ring
between positions 5 and 6 while retaining a carbonyl
group at position 5 and a chlorine atom at position 7.
Thus, tricyclic QXs 7j and 7k were prepared and eval-
uated. Disappointingly, these QXs were 2- to 4-fold less
potent than 7c. This result is surprising given that a
methyl group is well tolerated at the 6-position in 4 and
5. We speculate that the loss in potency may be because
Table 1. SAR of QXs at the NMDA receptor glycine site
Compd
R5
R6
R7
[3H]DCKA IC50 (mM)
Scheme 5. (a) HNO3, 5 ꢀC, 97%; (b) NH2CH2CO2Na, EtOH, reflux,
66%; (c) Na2S2O4, H2O, 70 ꢀC, 79%; (d) TFA, HNO3, rt, 75%.
7a
7b
7c
7d
7e
7f
7g
7h
7i
CO2H
CO2H
CO2H
CO2Me
COPh
CONH2
CONMe2
CONEt2
CO2Me
C(O)
C(O)
CN
CN
CN
NO2
NO2
NO2
NO2
H
H
H
H
H
H
H
H
Me
NO2
Cl
Cl
Cl
Cl
Cl
Cl
Br
Cl
Cl
Cl
Cl
Cl
Cl
Cl
13Æ3
10Æ3
6.4Æ0.5
65Æ9
6.7Æ0.8
3.1Æ0.2
13Æ2
24Æ3
Me
CH2CH2
OCH2
H
Cl
Me
Cl
Me
Me
H
0.40Æ0.08
4.6Æ0.5
7j
7k
26
31a
31b
3a
2.9Æ0.4
0.067Æ0.009
0.032Æ0.003
0.026Æ0.007
0.0059Æ0.001
0.0047Æ0.0006
0.0087Æ0.0004
0.65Æ0.04
4b
5b
Br
Cl
32a
.
Scheme 6. (a) NH2CH2CO2Na, EtOH, reflux; (b) SnCl2 2H2O, EtOH,
.
reflux; (c) TFA HNO3, rt; (d) (i) SnCl2 2H2O, EtOH, reflux; (ii)
NaNO2, CuCl, HCl.
aRef 5.
bRef 6.

1772
Z.-L. Zhou et al. / Bioorg. Med. Chem. 11 (2003) 1769–1780
the 5-carbonyl group in 7j,k is confined approximately
to the plane of the QX ring system whereas in licostinel
the nitro group is twisted out of the plane of the ring.5
6.6 mmol) was dissolved into 5 mL of THF. To this
solution was added dropwise 5 mL of trifluoroacetic
anhydride at 0 ꢀC. The resulting solution was allowed to
stir at room temperature for 12 h. The solution was
poured into ice-water. The mixture was filtered, washed
with water and dried to give 1.60 g (70%) of 2-[bis-
(2,2,2-trifluoro-acetyl)-amino]-5-methyl-benzoic acid as
The effect of adding a third substituent to 7-chloro-5-
cyano QX 26 is illustrated by 6-chloro QX 31a and
6-methyl QX 31b. 5-Cyano QXs 31a and 31b have IC50
values of 32 and 26 nM, respectively. Although both are
less potent than their 5-nitro counterparts 3 and 4, QXs
31a and 31b remain highly potent compounds in the QX
series. The results indicate that, in terms of potency, CN
and NO2 are comparable substituents in the 5-position.
Trisubstituted QX 7i is 200-fold less potent than its
5-nitro analogue 5, demonstrating again (cf. 7d) that
introduction of an ester group at the 5-position is not
well tolerated.
a white solid, mp 200–202 ꢀC. H NMR (CDCl3) d 2.53
1
(s, 3H), 7.68 (m, 2H), 8.07 (s, 1H).
To 7 mL of fuming nitric acid was added the above
anilide (1.6 g, 4.66 mmol) in one portion at 4 ꢀC. The
resulting solution was allowed to stir at 4 ꢀC for 1 h. The
solution was poured into ice-water (5 g), filtered, washed
with water and dried to give 1.18 g (87%) of the title
ꢀ
1
compound as a yellow solid, mp 198–200 C. H NMR
(CDCl3) d 8.09 (s, 1H), 8.22 (s, 1H), 10.99 (s, 1H).
Administered iv, several of these substituted QXs were
active anticonvulsants in the maximum electroshock-
induced seizure (MES) test in mice. Compound 31b has
an ED50 of 6.5 mg/kg, which is 6-fold less active than its
5-nitro counterpart 4. In contrast, 7-chloro-5-cyano QX
26 is highly active in vivo with an ED50 of 0.9 mg/kg,
which is 5 times more potent than licostinel (3). The
most obvious explanations would be increased blood–
brain permeability or a lower plasma-protein binding.
2-Amino-5-methyl-3-nitro-benzoicacid (10a). To a solu-
tion of 5-methyl-3-nitro-2-(2,2,2-trifluoro-acetylamino)-
benzoic acid (9a) (0.146 g, 0.5 mmol) in absolute alcohol
(3 mL) was added 10% aqueous sodium hydroxide
solution (3 mL). The solution was allowed to stir at
80 ꢀC (oil bath) for 3 h. Ethanol was evaporated in
vacuo to leave an orange solid, which was collected by
suction filtration and washed with water and dried in
vacuo, giving 90 mg (92%) of the title compound as an
1
In summary, a series of novel di- and trisubstituted QXs
related to licostinel (3) was synthesized and evaluated as
NMDA/glycine site antagonists. SAR of 5,7-dis-
ubstituted QXs shows that a cyano group is a
reasonable replacement for a nitro group in the 5-posi-
tion. Among those trisubstituted QXs investigated, 5-
cyano-6,7-dichloro QX (31a) and 7-chloro-5-cyano-6-
methyl QX (31b) are the two most potent glycine site
antagonists with IC50 values of 32 and 26 nM, respec-
tively. 7-Chloro-5-cyano QX (26) is highly active as an
anticonvulsant (iv) in MES test in mice with an ED50 of
0.9 mg/kg, a value 5-fold more potent than licostinel (3).
orange solid, mp 245–246 ꢀC. H NMR (DMSO-d6) d
2.20 (s, 3H), 8.03 (s, 1H), 8.10 (s, 1H), 8.30 (brs, 2H),
13.50 (brs, 1H).
2,3-Diamino-5-methyl-benzoicaidc (
6a). 2-Amino-5-
methyl-3-nitro-benzoic acid (10a) (80 mg, 0.38 mmol)
was dissolved into methanol (7 mL). To this solution
was added 5% Pd/C (20 mg, 20%). The mixture was
then stirred at room temperature under H2 at 45 psi for
3 h. The catalyst was removed through a column of
Celite (5 g) and washed with ethyl acetate under nitro-
gen. The extracts were combined and the solvent was
1
removed to give diamine 6a as a brown solid. H NMR
(CDCl3) d 2.10 (s, 3H), 2.65 (brs, 4H), 6.16 (s, 1H), 6.64
(s, 1H).
Experimental
Melting points were determined in open capillary tubes
1
7-Methyl-1,4-dihydro-quinoxaline-2,3-dione-5-carboxylic
acid (7a). 2,3-Diamino-5-methyl-benzoic acid (6a)
(300 mg, 1.68 mmol) was dissolved in 4 N hydrochloric
acid (30 mL), and oxalic acid dihydrate (352.8 mg,
2.8 mmol; Fisher) was added to this solution in one
portion with stirring under N2. The mixture was
refluxed using a 130–135 ꢀC oil bath for 3 h. A brown
solid came out which was collected by suction filtration
and dried in vacuo overnight and recrystallized from
DMF/H2O to give 240 mg (65%) of the title compound
on a Mel-Temp apparatus and are uncorrected. The H
NMR spectra were recorded at 300 MHz. Chemical
shifts are reported in ppm (d), and J coupling constants
are reported in Hz. Elemental analyses were performed
by Desert Analytics, Tucson, AZ, USA. Mass spectra
(MS) were obtained with a VG 12-250 or VG
ZAB-2FHF mass spectrometer. Reagent grade solvents
were used without further purification unless otherwise
specified. Reverse phase HPLC analyses were mon-
itored at 254 nM on a 4.6 Â 250 mM microsorb-MV
C18 column, using as solvents 0.1% trifluoroacetic acid
in water (A) and 0.1% trifluoroacetic acid in acetonitrile
(B). The linear gradient was 20% B in A to 95% B in A
with a flow rate of 1 mL/min.
as a white solid, mp >350 ꢀC. H NMR (DMSO-d6) d
1
2.28 (s, 3H), 7.14 (s, 1H), 7.53 (s, 1H), 11.49 (s, 1H),
12.06 (s, 1H). EI–MS m/e 220 (100, M+), 174 (98,
M+ÀCO2H). HR-MS calcd for C10H5N2O4: 220.1863.
Found: 220.1865 (HPLC 100%)
Preparation of 7a
Preparation of 7b
5-Methyl-3-nitro-2-(2,2,2-trifluoro-acetylamino)-benzoic
acid (9a). 2-Amino-5-methyl-benzoic acid (8a) (1.0 g,
2-Fluoro-3,5-dinitro-benzoicaidc ( 12). Fuming nitric
acid (5 mL) was added dropwise into fuming sulfuric

Z.-L. Zhou et al. / Bioorg. Med. Chem. 11 (2003) 1769–1780
1773
acid (15% SO3, 10 mL) cooled in an ice bath. The tem-
perature rise was limited to 40 ꢀC. After all the nitric
acid was added; the ice bath was removed and 2 g
(14.3 mmol) of 2-fluoro-benzoic acid (11) was added.
The resulting mixture was heated to 145 ꢀC for 1.5 h.
Then the mixture was cooled to room temperature and
poured into 60 g of crushed ice. The white solid was
collected, washed with water and dried to give 2.4 g
(73%) of the product, mp 196–198 ꢀC (dec. ) (lit.11 mp
poured into ice-water (10 g). The mixture was filtered
and washed with water and dried to give 1.8 g (67%) of
5-chloro-2-(2,2,2-trifluoro-acetylamino)benzoic acid as
a white solid, mp 198–200 ꢀC. H NMR (CDCl3) d 7.41
1
(dd, 1H, J1=8.6 Hz, J2=2.7 Hz), 7.94 (d, 1H,
J=2.7 Hz), 8.44 (d, 1H, J=8.6 Hz), 12.50 (s, 1H).
The above anilide was dissolved into 3 mL of con-
centrated sulfuric acid. To this solution was added
potassium nitrate (121 mg, 1.2 mmol) at 0 ꢀC. The
resulting mixture was allowed to stir at room tempera-
ture for 12 h. The mixture was poured into ice-water
(5 g), filtered, washed with water and dried to give
256 mg (82%) of 9c as a yellow solid, mp 179–180 ꢀC.
1H NMR (DMSO-d6) d 8.17 (d, 1H, J=2.4 Hz), 8.37 (d,
1H, J=2.4 Hz), 11.90 (s, 1H).
ꢀ
1
197–198 C). H NMR (CDCl3–DMSO-d6) d 8.77 (m,
2H).
2-Amino-3,5-dinitro-benzoiciadc (
10b). Ammonium
hydroxide solution (30%, 9 mL) was added dropwise
into 1 g (4.35 mmol) of 2-fluoro-3,5-dinitro-benzoic acid
(12). The resulting mixture was allowed to stir at room
temperature for 10 min. The precipitate was collected by
suction filtration and dried in the air, recrystallized from
water and then was acidified to pH 4 with 4 N HCl to
give 0.96 g (97%) of the product as a yellow solid, mp
266–268 ꢀC (lit.10 mp 268 ꢀC). 1H NMR (CDCl3–
DMSO-d6) d 8.398 (brs, 1H), 8.756 (dd, 1H, J=2.4 Hz),
8.884 (d, 1H,J=2.4 Hz), 9.398 (brs, 1H).
2-Amino-5-chloro-3-nitro-benzoic acid (10c). To a solu-
tion of 5-chloro-3-nitro-2-(2,2,2-trifluoro-acetylamino)-
benzoic acid (9c) (0.157 g, 0.5 mmol) in absolute alcohol
(3 mL) was added 10% aqueous sodium hydroxide
solution (3 mL). The solution was allowed to stir at
80 ꢀC (oil bath) for 3 h. Ethanol was evaporated in
vacuo to leave an orange solid, which was collected by
suction filtration and washed with water and dried in
vacuo, giving 90 mg (82%) of the title compound as an
2,3-Diamino-5-nitro-benzoicacid ( 6b). The procedure of
Gillespie7 was adapted for this reaction. To 14 mL of
freshly prepared 6% of ammonium sulfide was added
0.9 g (3.7 mmol) of 2-amino-3,5-dinitro-benzoic acid
(10b). The resulting mixture was allowed to stir at 90 ꢀC
for 2 h. and then boiled to remove the bulk of ammonia.
The hot solution was filtered to remove sulfur. After
cooling to 5 ꢀC, the filtrate was acidified with acetic
acid. The precipitate was filtered off, washed with water,
and recrystallized from 75% ethanol to give 495 mg
(68%) of the product as a red solid, mp 244–246 ꢀC
orange solid, mp 230–232 ꢀC. H NMR (DMSO-d6) d
1
8.10 (d, 1H, J=2.7 Hz), 8.28 (d, 1H, J=2.7 Hz), 8.45
(brs, 2H), 13.90 (brs, 1H).
7-Chloro-1,4-dihydro-quinoxaline-2,3-dione-5-carboxylic
acid (7c) (from 10c two steps). 2-Amino-5-chloro-3-
nitro-benzoic acid (10c) (300 mg, 1.4 mmol) was dis-
solved in ethyl acetate (30 mL). To this solution was
added 5% Pd/C (75 mg, 20%; Aldrich). The mixture
was then stirred at room temperature under H2 at 45 psi
for 3 h. The catalyst was removed through a column of
Celite (5 g) and washed with ethyl acetate (3 Â 15 mL)
under nitrogen. The extracts were combined and the
solvent was removed to give diamine 6c as a black solid.
The 1H NMR spectrum was consistent with the
assigned structure. Diamine 6c was dissolved in 4 N
hydrochloric acid (15 mL) and oxalic acid dihydrate
(252 mg, 2.00 mmol; Fisher) was added to this solution
in one portion with stirring under N2. The mixture was
refluxed using a 130–135 ꢀC oil bath for 3 h. A yellow
solid came out which was collected by suction filtration
and dried in vacuo overnight and recrystallized from
DMF/H2O to give 210 mg (62% based on 10c) of the
ꢀ
1
(dec.) (lit.7 mp 245 C). H NMR (DMSO-d6) d 5.40
(brs, 2H), 7.42 (brs, 2H), 7.433(d, 1H, J=2.7 Hz), 8.04
(d, 1H, J=2.7 Hz).
7-Nitro-1,4-dihydro-quinoxaline-2,3-dione-5-carboxylic
acid (7b). 2,3-Diamino-5-nitro-benzoic acid (6b)
(170 mg, 0.79 mmol) was dissolved in 4 N hydrochloric
acid (10 mL), and oxalic acid dihydrate (150 mg,
1.2 mmol; Fisher) was added to this solution in one
portion with stirring under N2. The mixture was
refluxed at 130–135 ꢀC (oil bath) for 3 h. A brown solid
came out which was collected by suction filtration and
dried in vacuo overnight and recrystallized from DMF/
H2O to give 240 mg (65%) of the title compound as a
yellow solid, mp >350 ꢀC (dec.). H NMR (DMSO-d6)
title compound as a red solid, mp >350 ꢀC. H NMR
1
1
d 8.09 (d, 1H, J=2.7 Hz), 8.40 (d, 1H, J=2.7 Hz), 11.79
(s, 1H), 12.36 (s, 1H). EI–MS m/e 251 (100, M+), 205
(78, M+ÀCO2H). HR-MS calcd for C9H5N3O6:
251.1567. Found: 251.1563.
(DMSO-d6) d 7.31 (d, 1H, J=2.1 Hz), 7.62 (d, 1H,
J=2.1 Hz), 11.49 (s, 1H), 12.17 (s, 1H). EI–MS m/e 240
(100, M+, 35Cl). HR-MS calcd for C9H5ClN2O4:
240.6042. Found: 240.6045 (HPLC >95%).
Preparation of 7c
Preparation of 7d
5-Chloro-3-nitro-2-(2,2,2-trifluoro-acetylamino)-benzoic
acid (9c). 2-Amino-5-chloro-benzoic acid (8c) (1.716 g,
10 mmol) was dissolved in 6 mL of dioxane. To this
solution was added dropwise 2 mL of trifluoroacetic
anhydride at 0 ꢀC. The resulting solution was allowed to
stir at room temperature for 12 h. The solution was
Methyl 2-amino-5-chloro-3-nitro-benzoate (10d). To a
25-mL round-bottomed flask was placed 2-amino-5-
chloro-3-nitro-benzoic acid (10c) (165 mg, 0.76 mmol)
and then was added 5 mL of thionyl chloride. The
resulting mixture was refluxed for 3 h. The mixture was
evaporated in vacuo to dryness and methanol (5 mL)

1774
Z.-L. Zhou et al. / Bioorg. Med. Chem. 11 (2003) 1769–1780
was added. The resulting solution was allowed to stir at
room temperature for 12 h. Methanol was evaporated
and water (6 mL) was added. A yellow solid was col-
lected by filtration, washed with water and dried to give
172 mg (98%) of 10d, mp 93–95 ꢀC. 1H NMR (CDCl3) d
3.99(s, 3H). 8.20 (d, J=2.7 Hz, 1H), 8.38 (d, J=2.7 Hz,
1H), 8.40 (brs, 2H).
alcohol (4 mL) was added 10% aqueous sodium
hydroxide solution (4 mL). The solution was allowed to
stir at room temperature for 24 h. Ethanol was evapo-
rated in vacuo to leave an orange solid, which was col-
lected by suction filtration and washed with water (3 Â
5 mL) and dried in vacuo, giving 200 mg (90%) of the
title compound as an orange solid, mp 110–112 ꢀC. H
1
NMR (CDCl3) d 7.50–7.54 (m, 3H), 7.62–7.63 (m, 2H),
7.73 (d, 1H, J=2.4 Hz), 8.41 (d, 1H, J=2.4 Hz), 8.53
(brs, 2H).
Methyl 7-chloro-1,4-dihydro-quinoxaline-2,3-dione-5-car-
boxylate (7d) (from 10d two steps). Methyl 2-amino-5-
chloro-3-nitro-benzoate (10d) (115 mg, 0.50 mmol) was
dissolved in methanol (25 mL). To this solution was
added 5% Pd/C (30 mg, 20%; Aldrich). The mixture
was then stirred at room temperature under H2 at 40 psi
for 3 h. The catalyst was removed through a column of
Celite (5 g) and washed with ethyl acetate (3 Â 15 mL)
under nitrogen. The extracts were combined and the
solvent was removed to give diamine 6d as a black solid.
The 1H NMR spectrum was consistent with the
assigned structure. Diamine 6d was mixed with diethyl
oxalate (4 mL; Fisher) with stirring under N2. The mix-
ture was allowed to stir at 120 ꢀC for 15 h. A brown
solid came out which was collected by suction filtration,
washed with ethyl acetate and dried in vacuo overnight
to give 51 mg (40% based on 10d) of the title compound
as a pale yellow solid, mp 244–246 ꢀC. 1H NMR
(DMSO-d6) d 3.89 (s, 3H), 7.33 (s, 1H), 7.61 (d,
J=2.1 Hz, 1H), 11.14 (s, 1H), 12.19 (s, 1H). EI–MS m/e
239 (254, 40, M+, 35Cl), 194 (100). HR-MS calcd for
C10H7ClN2O4: 254.0066. Found: 254.0080 (HPLC
>96%).
5-Benzoyl-7-chloro-1,4-dihydro-quinoxaline-2,3-dione
(7e) (from 10e two steps). (2-Amino-5-chloro-3-nitro-
phenyl)-phenyl-methanone (10e) (100 mg, 0.36 mmol)
was dissolved in ethyl acetate (5 mL). To this solution
was added 5% Pd/C (25 mg, 20%; Aldrich). The mix-
ture was then stirred at room temperature under H2 at
45 psi for 3 h. The catalyst was removed through a col-
umn of Celite (5 g) and washed with ethyl acetate (3 Â
15 mL) under nitrogen. The extracts were combined and
the solvent was removed to give diamine 6e as a black
1
solid. The H NMR spectrum was consistent with the
assigned structure. Diamine 6e was dissolved in 4 N
hydrochloric acid (15 mL) and oxalic acid dihydrate
(75.6 mg, 0.6 mmol; Fisher) was added to this solution
in one portion with stirring under N2. The mixture was
refluxed using a 130–135 ꢀC oil bath for 3 h. A yellow
solid came out which was collected by suction filtration,
washed with ethyl acetate and dried in vacuo overnight
to give 65 mg (60% based on 10e) of the title compound
as a pale yellow solid, mp 256–258 ꢀC. 1H NMR
(DMSO-d6) d 7.13 (d, 1H, J=2.1 Hz), 7.31 (d, 1H,
J=2.1 Hz), 7.54 (m, 2H), 7.71 (m, 3H), 11.34 (s, 1H),
12.19 (s, 1H). EI–MS m/e 300 (100, M+, 35Cl). HR-MS
calcd for C15H9ClN2O3: 300.0300. Found: 300.0301
(HPLC >98%).
Preparation of 7e
N-(2-Benzoyl-4-chloro-6-nitro-phenyl)-2,2,2-trifluoroace-
tamide (9e). (2-Amino-5-chloro-phenyl)-phenyl-metha-
none (8e) (4.634 g, 20 mmol) was dissolved in 6 mL of
THF. To this solution was added dropwise 5 mL of tri-
fluoroacetic anhydride at 0 ꢀC. The resulting solution
was allowed to stir at room temperature for 12 h. The
solution was poured into ice-water (10 g). The mixture
was filtered and washed with water and dried to give
6.5 g (99%) of N-(2-benzoyl-4-chloro-phenyl)-2,2,2-tri-
fluoroacetamide as a white solid, mp 95–97 ꢀC. 1H
NMR (CDCl3) d 7.55–7.71 (m, 7H), 8.61 (d, 1H,
J=8.4 Hz), 11.88 (s, 1H).
Preparation of 7f
2-Amino-5-chloro-3-nitro-benzamide (10f). To a 25-mL
round-bottomed flask was placed 2-amino-5-chloro-3-
nitro-benzoic acid (10c) (165 mg, 0.76 mmol) and then
was added 5 mL of thionyl chloride. The resulting mix-
ture was refluxed for 3 h. The mixture was evaporated in
vacuo to dryness and then 5 mL of THF was added. To
this solution was added a solution 5 mL of 30% aque-
ous ammonium hydroxide solution. The resulting solu-
tion was allowed to stir at room temperature for 12 h.
Water (10 mL) was added. The yellow precipitate was
collected by filtration and dried to give 147 mg (90%) of
N-(2-Benzoyl-4-chloro-phenyl)-2,2,2-trifluoroacetamide
(710 mg, 2.16 mmol) was dissolved into 8 mL of tri-
fluoroacetic acid. To this solution was added 0.432 mL
(4.32 mmol) of fuming nitric acid at room temperature.
The resulting solution was allowed to stir at 50 ꢀC for
24 h. The mixture was poured into ice-water (5 g), fil-
tered, washed with water and dried. Recrystallization
from ethyl acetate/hexanes gave 300 mg (39%) of 9e as a
white solid, mp 166–168 ꢀC. 1H NMR (CDCl3) d
7.52–7.57 (m, 2H), 7.67–7.69 (m, 2H), 7.77 (d, 1H,
J=2.1 Hz), 7.84 (d, 1H, J=7.5 Hz), 8.28 (d, 1H,
J=2.1 Hz), 10.36 (s, 1H). EI–MS m/e 372 (50, M+), 105
(100, PhCO).
10f, mp 240–242 ꢀC. H NMR (DMSO-d6) d 6.46 (brs,
1
1H), 7.68 (d, 1H, J=1.8 Hz), 7.80 (brs, 1H), 7.91 (d, 1H,
J=2.1 Hz), 8.21 (s, 2H).
7-Chloro-1,4-dihydro-quinoxaline-2,3-dione-5-carboxylic
acid amide (7f) (from 10f two steps). 2-Amino-4-chloro-
3-nitro-benzamide (10f) (85 mg, 0.394 mmol) was dis-
solved in methanol (25 mL). To this solution was added
5% Pd/C (25 mg, 20%; Aldrich). The mixture was then
stirred at room temperature under H2 at 40 psi for 3 h.
The catalyst was removed through a column of Celite
(5 g) and washed with ethyl acetate (3 Â 15 mL) under
nitrogen. The extracts were combined and the solvent
(2-Amino-5-chloro-3-nitro-phenyl)-phenyl-methanone
(10e). To a solution of 9e (0.30 g, 0.8 mmol) in absolute

Z.-L. Zhou et al. / Bioorg. Med. Chem. 11 (2003) 1769–1780
1775
was removed to give diamine 6f as a black solid. The 1H
NMR spectrum was consistent with the assigned struc-
ture. Diamine 6f was mixed with diethyl oxalate (4 mL;
Fisher) with stirring under N2. The mixture was allowed
to stir at 120 ꢀC for 15 h. A brown solid came out which
was collected by suction filtration, washed with ethyl
acetate and dried in vacuo overnight to give 25 mg (50%
based on 10f) of the title compound as a pale yellow
evaporated in vacuo to dryness and then 5 mL of THF
was added. To this solution was added a solution
0.52 mL of diethylamine in 2 mL of THF. The
resulting resolution was allowed to stir at room tem-
perature for 12 h and then water (10 mL) was added.
The yellow precipitate was collected by filtration and
dried to give 220 mg (81%) of 10h, mp 110–112 ꢀC.
1H NMR (CDCl3) d 1.22 (brs, 6H), 3.45 (brs, 4H),
6.60 (brs, 2H), 7.27 (d, 1H, J=2.4 Hz), 8.18 (d, 1H,
J=2.4 Hz).
solid, mp 330–332 ꢀC. H NMR (DMSO-d6) d 7.25 (s,
1
1H), 7.75 (s, 1H), 8.04 (s, 1H), 8.49 (s, 1H), 12.09 (s,
1H), 12.48 (s, 1H). EI–MS m/e 239 (40, M+, 35Cl).
HR-MS calcd for C9H6ClN3O3: 239.0110. Found:
239.0104 (HPLC >91%).
7-Chloro-1,4-dihydro-quinoxaline-2,3-dione-5-carboxylic
acid diethylamide (7h) (from 10h two steps). 2-Amino-5-
chloro-N,N-diethyl-3-nitro-benzamide (10h) (100 mg,
0.37 mmol) was dissolved in ethyl acetate (5 mL). To
this solution was added 5% Pd/C (25 mg). The mixture
was then stirred at room temperature under H2 at 40 psi
for 3 h. The catalyst was removed through a column of
Celite (5 g) and washed with ethyl acetate (3 Â 15 mL)
under nitrogen. The extracts were combined and the
solvent was removed to give diamine 6h as a black solid.
The 1H NMR spectrum was consistent with the
assigned structure. Diamine 6h was dissolved in ethanol
(2 mL), and diethyl oxalate (4 mL) was added to this
solution in one portion with stirring under N2. The
mixture was refluxed for 15 h. A yellow solid came out
which was collected by suction filtration, washed with
ethyl acetate and dried in vacuo overnight to give 79 mg
(72% based on 10h) of the title compound as a pale
Preparation of 7g
2 - Amino - 5 - chloro - N,N - dimethyl - 3 - nitro - benzamide
(10g). To a 25-mL round-bottomed flask was placed
2-amino-4-chloro-3-nitro-benzoic acid (10c) (320 mg,
1.48 mmol) and then was added 7.5 mL of thionyl chlo-
ride. The resulting mixture was refluxed for 3 h. The
mixture was evaporated in vacuo to dryness and then
5 mL of THF was added. To this solution was added a
solution 5 mL of 40% aqueous dimethylamine solution.
The resulting solution was allowed to stir at room tem-
perature for 12 h and then water (10 mL) was added.
The yellow precipitate was collected by filtration and
dried to give 317 mg (81%) of 10g, mp 134–136 ꢀC. H
1
NMR (CDCl3) d 3.08 (brs, 6H), 6.82 (brs, 2H), 7.31 (d,
1H, J=2.1 Hz), 8.20 (d, 1H, J=2.1 Hz).
yellow solid, mp 274–276 ꢀC. H NMR (DMSO-d6) d
1
0.96 (m, 3H), 1.13 (m, 3H), 3.09 (m, 2H), 3.40 ( m, 2H),
6.95 (d, 1H, J=2.1 Hz), 7.11 (d, 1H, J=2.1 Hz), 11.43
(s, 1H), 12.04 (s, 1H). EI–MS m/e 295 (60, M+, 35Cl).
HR-MS calcd for C13H14ClN3O3: 295.0710. Found:
295.0717 (HPLC >99%).
7-Chloro-1,4-dihydro-quinoxaline-2,3-dione-5-carboxylic
acid dimethylamide (7g) (from 10g two steps). 2-Amino-
5-chloro-N,N-dimethyl-3-nitro-benzamide (10g) (100 mg,
0.41 mmol) was dissolved in ethyl acetate (5 mL). To
this solution was added 5% Pd/C (25 mg, 20%;
Aldrich). The mixture was then stirred at room tem-
perature under H2 at 40 psi for 3 h. The catalyst was
removed through a column of Celite (5 g) and washed
with ethyl acetate (3 Â 15 mL) under nitrogen. The
extracts were combined and the solvent was removed to
give diamine 6g as a black solid. The 1H NMR spectrum
was consistent with the assigned structure. Diamine 6g
was dissolved in ethanol (2 mL), and diethyl oxalate
(4 mL) was added to this solution in one portion with
stirring under N2. The mixture was refluxed for 15 h. A
yellow solid came out which was collected by suction
filtration, washed with ethyl acetate and dried in vacuo
overnight to give 25 mg (23% based on compound 10g)
of the title compound as a pale yellow solid, mp
Preparation of 7i
Methyl 2-amino-6-methyl-benzoate (14). A suspension of
2-methyl-6-nitro-benzoic acid (13) (2.000 g, 11.04 mmol),
anhydrous K2CO3 (1.830 g, 13.24 mmol) and iodo-
methane (2.50 mL, 40.2 mmol) in acetone (40 mL) was
refluxed for 20 h. The solvent was removed in vacuo and
the residual slurry was diluted with water (40 mL) and
extracted with ethyl acetate (2 Â 40 mL). The extract
was washed with brine, dried over anhydrous Na2SO4
and removed in vacuo. The residual solid was dried and
purified on silica gel (5% EtOAc in hexane) to give
2.061 g (96%) of pure methyl 2-methyl-6-nitro-benzoate
as yellow powder, mp 45–47 ꢀC. H NMR (CDCl3) d
1
254–256 ꢀC. H NMR (DMSO-d6) d 2.764 (s, 3H), 2.92
2.42 (s, 3H), 3.96 (s, 3H), 7.46 (dd, 1H, J=8.1 Hz), 7.54
(d, 1H, J=7.5 Hz), 7.99 (d, 1H, J=8.1 Hz).
1
(s, 3H), 7.00 (d, 1H, J=1.8 Hz), 7.11 (d, 1H, J=1.8 Hz),
11.42 (s, 1H), 12.03 (s, 1H). EI–MS m/e 267 (40, M+,
35Cl). HR-MS calcd for C11H10ClN3O3: 267.0411.
Found: 267.0411 (HPLC >99%).
A
suspension of methyl 2-methyl-6-nitro-benzoate
(1.500 g, 7.685 mmol) and 10% Pd/C (50 mg) in EtOH
(50 mL) was stirred under H2 (maintained by a balloon
filled with H2) for 18 h. The catalyst was filtered and the
solvent was removed in vacuo. The residue was dried
further to give 1.146 g (90%) of the title compound as a
light red liquid which was used without further pur-
Preparation of 7h
2-Amino-5-chloro-N,N-diethyl-3-nitro-benzamide (10h).
To a 25-mL round-bottomed flask was placed 2-amino-
4-chloro-3-nitro-benzoic acid (10c) (216.5 mg, 1.0 mmol)
and then was added 5 mL of thionyl chloride. The
resulting mixture was refluxed for 3 h. The mixture was
1
ification. H NMR (CDCl3) d 2.43 (s, 3H), 3.89 (s, 3H),
5.45 (brs, 2H), 6.53 (d, 2H, J=7.8 Hz), 7.08 (d, 1H,
J=7.8 Hz).

1776
Z.-L. Zhou et al. / Bioorg. Med. Chem. 11 (2003) 1769–1780
Methyl 2-acetylamino-5-bromo-6-methyl-3-nitro-benzo-
ate (9i). A solution of methyl 2-amino-6-methyl-benzo-
ate (1.000 g, 6.054 mmol) in Ac2O (9 mL) was stirred
overnight at room temperature. It was then poured into
water (100 mL) and stirred at room temperature for
30 min. The white solid was collected by vacuum fil-
tration, dried and purified on silica gel (10% EtOAc in
hexane) to give 1.154 g (92%) of pure methyl 2-acetyl-
aminoꢀ-6-methyl-benzoate as white powder, mp
76–78 C. 1H NMR (CDCl3) d 2.18 (s, 3H), 2.46 (s, 3H),
3.95 (s, 3H), 6.96 (d, 1H, J=7.5 Hz), 7.34 (d, 1H,
J=7.5 Hz), 8.23 (d, 1H, J=7.8 Hz), 9.65 (br s, 1H).
Methyl 7-bromo-6-methyl-1,4-dihydro-quinoxaline-2,3-
dione-5-carboxylate (7i). A mixture of methyl 2,3-dia-
mino-5-bromo-6-methyl-benzoate (0.073 g, 0.28 mmol)
and oxalic acid dihydrate (0.053 g, 0.42 mmol) was
refluxed in 2 M HCl (4 mL) for 6 h. It was then cooled to
room temperature and the solid was collected by
vacuum filtration, washed with water (10 mL) and dried
in vacuo to give 0.047 g (53%) of crude product as a
brick red powder. A 0.043 g sample was purified by
refluxing in acetone (2 mL) for 10 min and then filtering
while hot. The residual solid was washed with hot ace-
tone and dried in vacuo to give 0.031 g (35%) of pure
title compound as a light burgundy powder, mp 282 ꢀC
(dec). 1H NMR (DMSO-d6) d 2.22 (s, 3H), 3.87 (s, 3H),
7.37 (s, 1H), 11.53 (s, 1H), 11.99 (s, 1H). Anal. calcd for
C11H9BrN2O4: C, 42.19; H, 2.90; N, 8.95. Found: C,
41.89; H, 2.89; N, 9.01. (HPLC 100%)
To a stirred solution of methyl 2-acetylamino-6-methyl-
benzoate (0.584 g, 2.82 mmol) in acetic acid (6.8 mL), a
solution of Br2 (0.17 mL, 3.3 mmol) in acetic acid
(1.5 mL) was added dropwise. The resulting orange
solution was allowed to stand overnight at room tem-
perature. The stirred orange suspension was diluted
with water followed by 10% aqueous sodium metabi-
sulfite to remove the yellow color. The white solid was
collected by vacuum filtration, washed with water
(100 mL) and dried in vacuo to give 0.709 (88%) of
methyl 6-acetylamino-3-bromo-2-methyl-benzoate as a
Preparation of 7j
3-(2,5-Dichloro-phenyl)-acrylic acid (16). A suspension
of 1,4-dichloro-2-iodo-benzene (15) (2.931g, 10.74 mmol),
acrylic acid (0.96 mL, 14 mmol), Pd(II) acetate (0.022 g,
0.10 mmol), triethylamine (3.5 mL) and acetonitrile
(4.0 mL) was heated in a sealed tube at 110 ꢀC for 1 h.
The suspension was cooled to room temperature and
the catalyst was removed by filtration. The filtrate was
poured into 10% HCl (250 mL) and the precipitated
solid was collected by vacuum filtration, washed with
water until the pH of the filtrate was ꢁ6 (pH paper). It
was further dried in vacuo to give 2.190 g (94%) of the
title compound as a light cream colored powder. 1H
NMR (DMSO-d6) d 6.69 (d, 1H, J=15.0 Hz), 7.47–7.55
(m, 2H), 7.73 (d, 1H, J=15.9 Hz), 8.01 (s, 1H), 12.71
(brs, 1H).
white powder, mp 66–69 ꢀC. H NMR (CDCl3) d 2.16
1
(s, 3H), 2.45 (s, 3H), 3.96 (s, 3H), 7.61 (d, 1H,
J=9.0 Hz), 8.03 (d, 1H, J=9.0 Hz), 8.85 (br s, 1H).
To a stirred solution of methyl 6-acetylamino-3-bromo-
2-methyl-benzoate (0.262 g, 0.916 mmol) in TFA (5 mL)
at 0 ꢀC, 90% HNO3 (0.080 mL) was added dropwise.
The solution was allowed to warm to room temperature
and stirred overnight at room temperature. It was then
poured into water (50 mL) and the solid was collected
by vacuum filtration, washed with water and dried in
vacuo to give 0.273 g (90%) of pure methyl 2-acetyl-
amino-5-bromo-6-methyl-3-nitro-benzoate (9i) as cream
3-(2,5-Dichlorophenyl)-propanoic acid (17). A suspen-
sion of 16 (1.825 g, 8.408 mmol) and Pt(IV) oxide
(0.025 g) was stirred in EtOAc (80 mL) under H2
(maintained by a balloon) at room temperature for 24 h.
The catalyst was removed by filtration and solvent from
the filtrate was removed on a rotavapor. The residue
was dried further in vacuo to give 1.734 g (95%) of the
colored powder, mp 164–167 ꢀC. H NMR (CDCl3) d
1
2.19 (s, 3H), 2.51 (s, 3H), 3.93 (s, 3H), 8.30 (s, 1H), 8.78
(brs, 1H).
Methyl 2-Amino-5-bromo-6-methyl-3-nitro-benzoate
(10i). A solution of 9i (0.296 g, 0.894 mmol) and con-
centrated HCl (1.4 mL) in EtOH (7 mL) was refluxed for
18 h. The solvent was removed in vacuo and the residue
was diluted with water (10 mL). The pH was adjusted
with 2 M NaOH to 5 and the shiny yellow solid was col-
lected by vacuum filtration, washed with water and dried
in air to give 0.223 g (86%) of the title compound as shiny
yellow needles, mp 121–124 ꢀC. 1H NMR (CDCl3) d 2.46
(s, 3H), 3.97 (s, 3H), 7.13 (brs, 2H), 8.46 (s, 1H).
1
title compound as white powder. H NMR (CDCl3) d
2.71 (t, 2H, J=8.1 Hz), 3.04 (t, 2H, J=8.1 Hz),
7.14–7.30 (m, 3H) 10.5–12 (br s, 1H).
4,7-Dichloro-indan-1-one (18j). A solution of 17 (1.542 g,
7.039 mmol) in SOCl2 (15 mL) was refluxed for 4 h and
then cooled to room temperature and the excess SOCl2
was distilled off. The residual liquid was dried at water
aspirator pressure and dissolved in CS2 (18 mL). Then
AlCl3 (1.200 g, 9.000 mmol) was added and the reaction
mixture was refluxed for 24 h under N2. The CS2 was
distilled off and the residual solid was cooled in an ice-
bath and worked up by slow addition of cold 10% HCl
(25 mL). The resulting suspension was stirred at room
temperature for 30 min and extracted with EtOAc. The
combined EtOAc was washed with 5% NaHCO3,
water, brine and dried over anhydrous Na2SO4.
Removal of the solvent on a rotavapor and drying the
residue under high vacuum gave 1.001 g (71%) of the
title compound as a yellow powder. 1H NMR (CDCl3) d
Methyl 2,3-diamino-5-bromo-6-methyl-benzoate (6i). The
wine red solution of methyl 2-amino-5-bromo-6-methyl-
.
3-nitro-benzoate (0.105 g, 0.363 mmol) and SnCl2 2H2O
(0.300 g, 1.33 mmol) in EtOH (4 mL) was refluxed for
2 h. The solution was poured into water (6 mL) and the
pH adjusted to ꢁ8 with 5% aq NaHCO3 (13.5 mL).
The suspension was extracted with EtOAc. The extract
was washed with brine, dried and removed in vacuo to
give 0.086 g (91%) of the title compound as a light red
1
powder. H NMR (CDCl3) d 2.36 (s, 3H), 3.92 (s, 3H),
6.99 (s, 1H).

Z.-L. Zhou et al. / Bioorg. Med. Chem. 11 (2003) 1769–1780
1777
2.77 (t, 2H, J=6.3 Hz), 3.09 (t, 2H, J=6.3 Hz), 7.28 (d,
1H, J=8.1 Hz), 7.48 (d, 1H, J=8.1 Hz).
DMF (1 mL) in an ice-bath, a solution of 4,7-dichloro-
isobenzofuran-1,3-dione (1.007 g, 4.64 mmol) in DMF
(3.5 mL) was added dropwise to it. The solution was
allowed to warm to room temperature and stirred for
1 h at room temperature. The yellow solution was again
cooled in ice-bath and decomposed with 6 N HCl (2 mL)
followed by water (10 mL). The white solid was col-
lected by vacuum filtration, washed with water and
dried in vacuo to give 0.708 g (75%) of ꢀthe title com-
4,7-Dichloro-6-nitro-indan-1-one (20j). To stirred fuming
HNO3 (3.0 mL) at 0 ꢀC, 18j (0.582 g, 2.89 mmol) was
added in one portion. The reaction mixture was stirred
in an ice-bath for 30 min and then stored in the freezer
(À20 ꢀC) for 2 days. The orange-red solution was added
dropwise to ice (50 g) and the precipitated solid was
collected by vacuum filtration and washed with water
until the filtrate was pH 7. The resulting solid was dried
under high vacuum to give 0.712 g (81%) of the title
1
pound as a white powder, mp 150–159 C. H NMR
(CDCl3) d 5.24 (s, 2H), 7.46 (d, 1H, J=8.4 Hz), 7.56 (d,
1H, J=8.4 Hz).
1
compound as a light-yellow powder. H NMR (CDCl3)
d 2.86–2.91 (m, 2H), 3.16–3.18 (m, 2H), 8.04 (s, 1H).
4,7-Dichloro-6-nitro-3H-isobenzofuran-1-one (20k). To a
stirred solution of 18k (0.700 g, 3.45 mmol) in con-
centrated H2SO4 (10 mL) in an ice-bath, KNO3 (0.418 g,
4.13 mmol) was added in one portion. The yellow solution
was then stirred overnight at room temperature and
poured into ice-water. The white solid was collected by
vacuum filtration, washed with water and dried in vacuo
to give 0.738 g (86%) of 20k as a white powder, mp
153–612 ꢀC. 1H NMR (CDCl3) d 5.31 (s, 2H), 8.13 (s, 1H).
7-Azido-4-chloro-6-nitro-indan-1-one (21j). To a stirred
solution of 20j (0.268 g, 1.09 mmol) in acetone (2.0 mL)
at 45 ꢀC, NaN3 (0.105 g, 1.62 mmol) in water (1.5 mL)
was added and the resulting suspension was stirred at
45 ꢀC for 24 h. TLC indicated the absence starting
material. The volatiles were removed on a rotavapor
and the residue was diluted with water (5 mL). The pre-
cipitated solid was collected by vacuum filtration,
washed with water (5 mL) and dried in vacuo to give
0.206 g (75%) of the title compound as a brown powder.
1H NMR (CDCl3) d 2.88 (t, 2H, J=6.0 Hz), 3.19 (t, 2H,
J=6.0 Hz), 8.09 (s, 1H).
7-Azido-4-chloro-6-nitro-3H-isobenzofuran-1-one (21k).
To a stirred solution of 20k (0.730 g, 2.94 mmol) in ace-
tone (12 mL) at room temperature, a solution of NaN3
(0.285 g, 4.38 mmol) was added dropwise. The resulting
suspension was stirred overnight at room temperature.
The suspension was concentrated on a rotavapor and
diluted with water (20 mL). The solid was collected by
vacuum filtration, washed with water (20 mL) and dried
in vacuo to give 0.690 g (92%) of the title compound as
a light yellow powder, mp 118–122 ꢀC. 1H NMR
6,7-Diamino-4-chloro-indan-1-one (6j). A suspension of
21j (0.200 g, 0.792 mmol) and 10% Pd/C (0.025 g) in
EtOAc (7.0 mL) was stirred under H2 (maintained by a
balloon) at room temperature for 24 h. The catalyst was
removed by filtration and the solvent from the filtrate
was removed on a rotavapor. The residue was dried
further in vacuo to give 0.140 g (90%) of the title com-
(CDCl3) d 5.34 (s, 2H), 8.04 (s, 1H); IR (KBr, cmÀ1
)
2173, 2139, 1770, 1525, 1327, 1088.
1
pound as a brown powder. H NMR (CDCl3) d 2.68 (t,
2H, J=6.0 Hz), 2.96 (t, 2H, J=6.0 Hz), 3.2–4.0 (brs,
4H), 6.87 (s, 1H).
6,7-Diamino-4-chloro-3H-isobenzofuran-1-one (6k). To a
suspension of 21k (0.666 g, 2.62 mmol) in EtOH
(15 mL), 10% Pd/C (0.080 g) was added and the mixture
was stirred under the H2 (maintained by a balloon) for
18 h. The insoluble material was filtered and washed
with EtOAc. The filtrate was removed in vacuo and the
residual solid was dried further to give 0.48 g of a mix-
ture of 6k and 7-amino-4-chloro-6-nitro-3H-iso-
6 - Chloro - 1,4,7,8 - tetrahydro - cyclopenta[f]quinoxaline -
2,3,9-trione (7j).
A
suspension of 6j (0.131 g,
0.666 mmol) in diethyl oxalate (1.5 mL) was refluxed for
24 h. It was then cooled to room temperature and dilu-
ted with hexane (15 mL). The precipitated solid was
collected by vacuum filtration, washed with hexane and
dried in vacuo to give 0.123 g of crude product as a
brown powder. A 0.120 g sample was stirred in 1 M
NaOH (40 mL) at room temperature for 30 min. The
solid was mostly undissolved and was removed by
vacuum filtration. The bright yellow filtrate was acid-
ified with concentrated HCl (4 mL) to pH ꢁ2 to give a
suspension, which was filtered in vacuo, washed with
water and dried to give 0.028 g (17%) of pure (97.7% by
HPLC) title compound as an off-white powder, mp
322 ꢀC (dec). 1H NMR (DMSO-d6) d 2.76–2.77 (m, 2H),
2.99 (t, 1H, J=4.5 Hz), 7.36 (s, 1H), 10.36 (s, 1H), 12.15
(s, 1H). HRMS calcd for C11H7ClN2O3: 250.0145.
Found: 250.0151.
1
benzofuran-1-one (ꢁ3:1 by NMR) as a red powder; H
NMR (CDCl3) d 5.14 (s, 2H), 6.88 (s, 1H) and 5.25 (s,
2H), 8.42 (s, 1H).
.
A solution of the mixture (0.168 g) and SnCl2 2H2O
(0.290 g, 1.29 mmol) in EtOH (5 mL) was refluxed for
45 min. The suspension was cooled to room temperature
and poured into water (5 mL). The pH was adjusted to
ꢁ7 with 2 M aqueous NaOH (1.5 mL). The suspension
was extracted with EtOAc. The combined extract was
washed with brine, dried over anhydrous Na2SO4 and
removed in vacuo to give 0.139 g (73% for two steps) of
6k as a cream colored powder, mp 172–178 ꢀC. 1H
NMR (CDCl3) d 3.48 (brs, 2H), 4.89 (brs, 2H), 5.14 (s,
2H), 6.88 (s, 1H).
Preparation of 7k
4-Chloro-6,9-dihydro-3H-2-oxa-6,9-diaza-cyclopenta[a]-
naphthalene-1,7,8-trione (7k). A solution of 6k (0.130 g,
0.655 mmol) in diethyl oxalate (3 mL) was stirred at
4,7-Dichloro-3H-isobenzofuran-1-one (18k). To a stirred
solution of sodium borohydride (0.175 g, 4.63 mmol) in

1778
Z.-L. Zhou et al. / Bioorg. Med. Chem. 11 (2003) 1769–1780
150 ꢀC for 3 h. The suspension was cooled to room
temperature and diluted with hexane (15 mL). The solid
was collected vacuum filtration and dried in vacuo to
give 0.082 g (50%) of crude 7k as a dark brown powder.
A 0.043 g sample was suspended in DMSO (2.5 mL) and
heated with a heat gun to a gentle boil. The resulting red
solution was allowed to stand overnight at room tem-
perature. The precipitated solid was collected by
vacuum filtration, washed with water (5 mL) and dried
to give 0.034 g (38%) of pure (purity by HPLC 100%)
Preparation of 31a
(3-Chloro-2-cyano-6-nitro-phenylamino)-acetic acid so-
dium salt (28a). To a stirred solution of 2,6-dichloro-3-
nitrobenzonitrile (27a) (3.935 g, 18.13 mmol) in DMF
(25 mL) at 70 ꢀC, an aqueous solution of sodium glyci-
nate (1.760 g, 18.13 mmol) in water (25.0 mL) was added
dropwise. The resulting solution was stirred at 70 ꢀC for
48 h. The suspension was cooled to room temperature
and the precipitated yellow solid was filtered, washed
with chloroform and dried under vacuum to furnish
2.020 g (44%) of the title compound as a yellow powder.
1H NMR (DMSO-d6) d 3.89 (d, 2H, J=3.9 Hz), 6.86 (d,
1H, J=9.0 Hz), 8.28 (d, 1H, J=9.3 Hz), 9.57 (s, 1H).
title compound as
a shiny cream powder, mp
342–346 ꢀC. H NMR (DMSO-d6) d 5.41 (s, 2H), 7.39
1
.
(s, 1H). Anal. calcd for C10H5ClN2O4 0.1H2O: C, 47.21;
H, 2.06; N, 11.01. Found: C, 46.87; H, 1.69; N, 10.93.
6-Chloro-2-oxo-1,2,3,4-tetrahydro-quinoxaline-5-carboni-
trile (29a). A suspension of 28a (2.000 g, 7.824 mmol)
and tin (II) chloride dihydrate (6.000 g, 26.59 mmol) in
ethanol (40 mL) was refluxed for 30 min. The resulting
suspension was cooled to room temperature and the
solid was filtered, washed with ethanol and dried under
vacuum to give 1.261 g (78%) of the title compound as
light yellow solid. H NMR (DMSO-d6) d 3.67 (s, 1H),
6.72 (d, 1H, J=8.4 Hz), 6.84 (d, 1H, J=8.1 Hz), 6.91 (s,
1H), 10.68 (s, 1H).
Preparation of 26
5-Chloro-2-methoxy-3-nitro-benzonitrile (23). To 15mL
of fuming nitric acid at 0 ꢀC was added portionwise
5-chloro-2-methoxy-benzonitrile (22) (2.51 g, 15.0 mmol).
After addition, the solution was allowed to stir at 5 ꢀC
for 3 h and then it was poured into ice-water (50 g). A
pale-yellow solid was collected by filtration and dried to
give 3.08 g (97%) of the title compound, mp 97–99 ꢀC.
1H NMR (CDCl3) d 4.18 (s, 3H), 7.79 (d, J=2.7 Hz,
1H), 8.01 (d, J=2.7 Hz, 1H).
1
6-Chloro-7-nitro-2,3-dioxo-1,2,3,4-tetrahydro-quinoxa-
line-5-carbonitrile (30a). To a suspension of 29a
(4-Chloro-2-cyano-6-nitro-phenylamino)-acetic acid so-
dium salt (24). To a stirred solution of 23 (0.319 g,
1.5 mmol) in methanol (5 mL) was added dropwise an
aqueous solution of sodium glycinate (0.291 g,
3.0 mmol) in water (3.0 mL) at room temperature. The
resulting solution was stirred at 60 ꢀC for 3 h. The sus-
pension was cooled to room temperature and the pre-
cipitated yellow solid was filtered, washed with
chloroform (20 mL) and dried under vacuum to furnish
0.277 g (67%) of the title compound, mp 220 ꢀC (dec.).
1H NMR (DMSO-d6) d 3.84 (s, 2H), 8.08 (d, J=2.1 Hz,
1H), 8.29 (d, J=2.1 Hz, 1H), 9.39 (s, 1H).
(0.300 g, 1.45 mmol) in CF3COOH (3.0 mL), fuming
nitric acid (0.50 mL) was added to give a dark red solu-
tion. (Lesser amounts of fuming nitric acid gave a sus-
pension, which gave a mixture of partially oxidized and
fully oxidized products.) The resulting solution was then
stirred overnight at room temperature. The volatiles
were removed under vacuum and the residue was dilu-
ted with water (9.0 mL). The yellow solid was filtered,
washed with water and dried under vacuum to furnish
0.207 g (54%) of the title compound as yellow powder.
1H NMR (DMSO-d6) d 7.95 (s, 1H), 12.38 (s, 1H).
7-Chloro-2-oxo-1,2,3,4-tetrahydro-quinoxaline-5-carboni-
trile (25). To a solution of 24 (0.277 g, 1.0 mmol) in
25 mL of water at 70 ꢀC was added 1.4 g (8.0 mmol) of
sodium dithionite in five equal portions at an interval
of 5 min each. The resulting white suspension was
allowed to stir at 70 ꢀC for 1 h. The suspension was cooled
to room temperature and the precipitated white solid was
filtered and dried under vacuum to furnish 0.125 g (60%)
6,7-Dichloro-2,3-dioxo-1,2,3,4-tetrahydro-quinoxaline-5-
A suspension of 30a (0.100 g,
carbonitrile (31a).
0.38 mmol) and tin(II) chloride dihydrate (0.508 g,
2.25 mmol) in ethanol (4.0 mL) was refluxed for 24 h. The
resulting suspension was then cooled to room tempera-
ture and the yellow solid was filtered, washed with etha-
nol and dried under vacuum to obtain 0.078 g (88%) of 7-
amino-6-chloro-2,3-dioxo-1,2,3,4-tetrahydro-quinox-
aline-5-carbonitrile as yellow powder; 1H NMR
(DMSO-d6) d 5.76 (brs, 2H), 6.82 (s, 1H), 11.69 (s, 1H),
12.03 (s, 1H).
ꢀ
1
of the title compound, mp 288–290 C (dec.). H NMR
(DMSO-d6) d 3.88 (s, 2H), 6.80 (s, 1H), 6.86 (d,
J=2.1 Hz, 1H), 7.19 (d, J=2.1 Hz, 1H), 10.67 (s, 1H).
7-Chloro-2,3-dioxo-1,2,3,4-tetrahydro-quinoxaline-5-car-
bonitrile (26). To a suspension of 25 (50 mg, 0.24 mmol)
in CF3COOH (1.0 mL), fuming nitric acid (84 mL) was
added to give a dark red solution. The resulting solution
was then stirred overnight at room temperature. The
volatiles were removed under vacuum and the residue
was diluted with water (9.0 mL). The yellow solid was
filtered, washed with water (6.0 mL) and dried under
vacuum to furnish 32 mg (60%) of the title compound,
To a stirred solution of 7-amino-6-chloro-2,3-dioxo-
1,2,3,4-tetrahydro-quinoxaline-5-carbonitrile (0.035 g,
0.15 mmol) in concentrated HCl (1.5 mL) at 0 ꢀC, an
aqueous solution of NaNO2 (0.060 g, 0.87 mmol) in
water (0.20 mL) was added and the resulting turbid
mixture was stirred in an ice bath for 2 h. An ice-cold
solution of CuCl (0.100 g, 1.01 mmol) in concentrated
HCl (1.0 mL) was added while cooling the flask in an ice
bath. An instant evolution of N2 ensued and the result-
ing dark green suspension was stirred at 0 ꢀC for 2 h.
Water (1.0 mL) was added and then the mixture was
ꢀ
1
mp 338–340 C (dec.). H NMR (DMSO-d6) d 7.32 (d,
J=2.1 Hz, 1H), 7.68 (d, J=2.1 Hz, 1H), 12.18 (s, 1H).

Z.-L. Zhou et al. / Bioorg. Med. Chem. 11 (2003) 1769–1780
1779
stirred overnight at room temperature. To the light
green suspension so formed, water (4.0 mL) was added
and again the mixture was stirred at room temperature
for 1 h. The precipitated solid was filtered, washed with
water (2.0 mL) and dried under vacuum to furnish
0.029 g (77%, 96% by HPLC) of the title compound as
50 mL of ice-water and the precipitate was allowed to
stand at room temperature for 2 days. It was filtered
and washed with water and dried to leave 390 mg (57%)
of the title compound as a yellow solid, mp >340 ꢀC.
1H NMR (DMSO-d6) d 2.66 (s, 3H), 7.95 (s, 1H), 12.27
(mb, 2H).
a cream colored solid, mp 327–335 ꢀC (dec). H NMR
1
(DMSO-d6) d 7.46 (d, 1H, J=1.2 Hz), 12.31 (s, 2H). IR
(KBr, cmÀ1): 3574, 3479, 2237, 1737, 1710, 1392, 1271,
1183. HRMS calcd for C9H3Cl2N3O2: 254.9602. Found:
254.9609.
7-Chloro-6-methyl-2,3-dioxo-1,2,3,4-tetrahydro-quinox-
mixture of 243 mg
aline-5-carbonitrile (31b).
A
(0.988 mmol) of 30b, 972 mg (4.31 mmol) of tin (II)
chloride dihydrate and 6 mL of absolute alcohol was
refluxed for 20 h. It was cooled to room temperature,
filtered and washed by water, dried to leave 202 mg
(94%) of 7-amino-6-methyl-2,3-dioxo-1,2,3,4-tetra-
hydro-quinoxaline-5-carbonitrile as a yellow solid, mp
>360 ꢀC. 1H NMR (DMSO-d6) d 2.20 (s, 3H), 5.35 (brs,
2H), 6.67 (s, 1H), 11.38 (s, 1H), 11.91 (s, 1H).
Preparation of 31b
2 - Chloro - 6 - methyl - 3 - nitrobenzonitrile (27b) and
2-chloro-6-methyl-5-nitrobenzonitrile (27b0). To a solu-
tion of 4.70 g (31.0 mmol) of 2-chloro-6-methylbenzoni-
trile in 30 mL of CF3CO2H stirred in ice-bath was added
dropwise 2 mL of fuming HNO3 and the solution was
stirred at room temperature overnight. To the solution
was added dropwise 2 mL of fuming HNO3 and the
solution was heated at 60 ꢀC for 5 days. The solution
was added into 200 mL of ice-water and stirred for 1 h.
The precipitate was filtered, washed by water and dried
to give 5.5 g of pale-yellow mixture, which was sepa-
rated by chromatography over silica gel. Elution with
1:20 (200 mL), 3:40 (200 mL), 1:10 (200 mL), 2:10
(200 mL) and 3:10 (500 mL) ethyl acetate/hexane gave
1.61 g of 27b as white solid, 1H NMR (CDCl3) d 2.68 (s,
3H), 7.41 (d, 1H, J=8.5 Hz), 8.01 (d, 1H, J=8.5 Hz),
To a mixture of 115 mg (0.532 mmol) of 7-amino-6-
methyl-2,3-dioxo-1,2,3,4-tetrahydro-quinoxaline-5-car-
bonitrile in 6 mL of 8 N HCl stirred in an ice bath was
added dropwise a solution of 78 mg (1.13 mmol) of
NaNO2 in 0.5 mL of water and then the mixture was
stirred in ice bath for 4 h. The mixture was added drop-
wise into a mixture of 115 mg of CuCl in 2 mL of con-
centrated HCl stirred in ice-bath. It was stirred in an
ice-bath for 3 h and at room temperature overnight. The
mixture was diluted by 4 mL of water, filtered, washed
with water and dried to leave 49 mg (39%) of the title
compound as a yellow solid, mp >370 ꢀC. H NMR
1
and 3.80 g of 27b0 as white solid, H NMR (CDCl3) d
(DMSO-d6) d 2.47 (s, 3H), 7.35 (s, 1H), 12.04 (s, 1H),
12.12 (s, 1H). Anal. calcd for C10H6ClN3O2.H2O: C,
47.35; H, 3.17; N, 16.56. Found: C, 46.94; H, 2.62; N,
16.87.
1
2.83 (s, 3H), 7.54 (d, 1H, J=8.8 Hz), 8.08 (d, 1H,
J=8.8 Hz).
(2-Cyano-3-methyl-6-nitro-phenylamino)-acetic acid so-
dium salt (28b). To a solution of 810 mg (4.12 mmol) of
27b in 6 mL of DMF kept at 70 ꢀC was added a solution
of 802 mg (6.97 mmol) of sodium glycinate in 5 mL of
water. The solution turned yellow and a precipitate was
observed. It was heated at 70 ꢀC for 18 h and a TLC
showed no more 27b. The solution was cooled to room
temperature and the resulting precipitate was filtered
and washed with water (2 mL) and dried to leave 416 mg
of crude 28b as a yellow solid, which was used for the
next reaction without further purification.
Acknowledgements
Financial support of research at the University of Ore-
gon by CoCensys, Inc. is gratefully acknowledged.
References and Notes
1. Meldrum, B.; Garthwaite, J. Trends Pharmacol. Sci. 1990,
11, 379.
2. Johnson, J. W.; Ascher, P. Nature (London) 1987, 325, 529.
3. Kulagowski, J. J.; Baker, R.; Curtis, N. R.; Leeson, P. D.;
Mawer, I. M.; Moseley, A. M.; Ridgill, M. P.; Rowley, M.;
Stansfield, I.; Foster, A. C.; Grimwood, S.; Hill, R. G.; Hemp,
J. A.; Marshall, G. R.; Saywell, K. L.; Tricklebank, M. D. J.
Med. Chem. 1994, 37, 1402.
4. Cai, S. X.; Zhou, Z. L.; Huang, J. C.; Whittemore, E. R.;
Egbuwoku, Z. O.; Lu, Y.; Hawkinson, J. E.; Woodward,
R. M.; Weber, E.; Keana, J. F. W. J. Med. Chem. 1996, 39,
3248.
5. Keana, J. F. W.; Kher, S. M.; Cai, S. X.; Dinsmore, C. M.;
Glenn, A. G.; Guastella, J.; Huang, J. C.; Ilyin, V.; Lu, Y.;
Mouser, P. L.; Woodward, R. M.; Weber, E. J. Med. Chem.
1995, 38, 4367.
6. Cai, S. X.; Kher, S. M.; Zhou, Z. L.; Ilyin, V.; Espitia, S. A.;
Tran, M.; Hawkinson, J. E.; Woodward, R. M.; Weber, E.;
Keana, J. F. W. J. Med. Chem. 1997, 40, 730.
7. Gillespie, H. B.; Spano, F.; Graff, S. J. Org. Chem. 1960,
25, 942.
6-Methyl-2-oxo-1,2,3,4-tetrahydro-quinoxaline-5-carbo-
nitrile (29b). A solution of 401 mg (1.70 mmol) of 28b,
1.41 g (6.24 mmol) of tin(II) chloride dihydrate and
8 mL of absolute alcohol was refluxed for 2 h to give a
yellow precipitate. The mixture was cooled to room
temperature, filtered and washed with water and dried
to leave 149 mg (47%) of the title compound as a yellow
solid. H NMR (DMSO-d6) d 2.27 (s, 1H), 3.84 (s, 1H),
6.52 (d, 1H, J=7.7 Hz), 6.79 (d, 1H, J=7.7 Hz), 10.46
(s, 1H).
1
6-Methyl-7-nitro-2-oxo-1,2,3,4-tetrahydro-quinoxaline-5-
carbonitrile (30b). To a mixture of 515 mg (2.75 mmol)
of 29b in 6 mL of CF3CO2H stirred in an ice bath was
added dropwise 2.4 mL of fuming HNO3. The resulting
red solution was stirred in an ice bath for 2 h and at
room temperature for 2 days. It was then added to

1780
Z.-L. Zhou et al. / Bioorg. Med. Chem. 11 (2003) 1769–1780
8. Kher, S. M.; Cai, S. X.; Weber, E.; Keana, J. F. W. J. Org.
Chem. 1995, 60, 5838.
9. Canton, T.; Doble, A.; Miquet, J. M.; Jimonet, P.; Blan-
chard, J. C. J. Pharm. Pharmacol. 1992, 44, 812.
10. Cai, S. X.; Huang, J. C.; Espitia, S. A.; Tran, M.; Ilyin,
V. I.; Hawkinson, J. E.; Woodward, R. M.; Weber, E.; Keana,
J . F. W.J. Med. Chem. 1997, 40, 3679.
11. Cohn, P. Monatsh. Chem. 1901, 22, 387.