Buchwald reaction as the key step for the synthesis of metabolically more stable analogs of amodiaquine

Article abstract of DOI:10.1016/j.ejmech.2011.04.047

Amodiaquine is one of the most active anti-malarial 4-aminoquinoline but its metabolization is believed to generate hepatotoxic derivatives. Previously, we described new analogs of amodiaquine and amopyroquine, in which hydroxyl group was replaced by vari

Full text of DOI:10.1016/j.ejmech.2011.04.047

European Journal of Medicinal Chemistry 46 (2011) 3052e3057
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European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Buchwald reaction as the key step for the synthesis of metabolically more stable
analogs of amodiaquine
,
b
,
,
b
,
,
b
,
,b,c,
Nicolas Le Fur a c, Guillaume Hochart a c, Paul-Emmanuel Larchanché a c, Patricia Melnyk a
*
a Univ Lille Nord de France, F-59000 Lille, France
b UDSL, EA 4481, UFR Pharmacie, F-59006 Lille, France
c UMR CNRS 8161, F-59000 Lille, France
a r t i c l e i n f o
a b s t r a c t
Article history:
Amodiaquine is one of the most active anti-malarial 4-aminoquinoline but its metabolization is believed
to generate hepatotoxic derivatives. Previously, we described new analogs of amodiaquine and amo-
pyroquine, in which hydroxyl group was replaced by various amino groups and identified highly potent
compounds with lower toxicity. We describe here the synthesis of new analogs that have been modified
on their 40- and 50-positions in order to reduce their metabolization. A new synthetic strategy was
developed using Buchwald coupling reaction as the key step.
Received 15 February 2011
Received in revised form
14 April 2011
Accepted 15 April 2011
Available online 21 April 2011
Ó 2011 Elsevier Masson SAS. All rights reserved.
Keywords:
Drugs
Heterocycles
Quinolines
Palladium
Substitution
1. Introduction
4-aminoquinoline, proved to be effective against CQ-resistant
strains [4,5]. But in the 1980s, cases of agranulocytosis, neu-
In spite of the recent decline of the pathology, malaria still
remains a major health problem with about 243 million cases
worldwide in 2008 and 860 000 deaths in more than 100 countries
[1,2]. 85e90% of cases and deaths were in the African Region and
this constitutes one of the main obstacles to socio-economic
development in sub-Saharian Africa and other tropical regions in
the world.
Chloroquine (CQ, Fig. 1) was a mainstream drug in the fight
against Plasmodium falciparum, but its efficacy was restricted by the
emergence of resistant parasites. Quinoline anti-malarials
concentrate in the parasite food vacuole and are thought to exert
their activity by preventing effective formation of hemozoin by
tropenia and hepatisis were reported associated with AQ prophy-
laxis and its prophylactic use was then stopped [6].
AQ toxicity has been explained by the presence of its
4-hydroxyanilino moiety, which is believed to undergo extensive
metabolization to its quinoneimine variant and nucleophilic attack
on its 50-position (Fig. 2) [7,8]. Formation of this reactive species
in vivo and subsequent binding to cellular proteins and lipids could
affect cellular functions either directly or by immunological
response [9,10]. This bio-activation was found to be accompanied by
the expression of a drug-related antigen on the cell surface, sug-
gesting a type II hypersensitivity reaction and causing the myelo-
toxicity of AQ [11,12]. Nevertheless, AQ is commercialised in
combination with an artemisinin derivative as CoarsucamÒ speci-
ality for curative treatment.
For years, our laboratory has been involved in the design and
synthesis of AQ-analogs in order to improve the anti-malarial activity
while preventing metabolization [13e15]. Furthermore, as AQ-
analogs obtained by the replacement of the N-diethylamino func-
tion of the side chain with a pyrrolidine cycle or a N-tert-butyl group
were proved to be metabolically less labile [16,17], we completed our
study with the development of parallel amopyroquine-analogs
series. Amopyroquine (ApQ, Fig. 1), a structural analog of AQ in
interacting to heme through pep stacking of their planar aromatic
structures, resulting in heme-mediated toxicity towards the para-
site [3]. The lack of an enzyme drug target for quinoline anti-
malarials is probably a chief reason why resistance development to
these drugs is relatively slow. Amodiaquine (AQ, Fig. 1), another
* Corresponding author. EA 4481 GRIIOT, UDSL, UFR Pharmacie, 3 rue du Pr
Laguesse, BP83, F-59006 Lille cedex, France. Fax: þ33 (0) 3 20 95 90 09.
E-mail address: patricia.melnyk@univ-lille2.fr (P. Melnyk).
0223-5234/$ e see front matter Ó 2011 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2011.04.047

N. Le Fur et al. / European Journal of Medicinal Chemistry 46 (2011) 3052e3057
3053
5'
5'
4'
3'
4'
OH
NR2
NR2
NR'2
NR2
N
HN
N
HN
N
HN
HN
3'
4
N
Cl
Cl
Cl
N
Cl
N
Chloroquine (CQ)
Amodiaquine (AQ) : NR = NEt
2
2
1 NR = N-methylpiperazino, NR' = pyrrolidino
3 NR = N-methylpiperazino
2
2
2
Amopyroquine (ApQ) : NR = pyrrolidine
2
2 NR = morpholino, NR' = pyrrolidino
4 NR = morpholino
2
2
2
Fig. 1. Structure of some aminoquinoline anti-malarials.
Fig. 3. Structure of some potent amodiaquine analogs and target compounds.
which the diethylamino group in the side chain is replaced with
a pyrrolidine cycle was shown to be more active than both CQ and AQ
against 11 CQ-resistant isolates of P. falciparum [18,19].
defluorobenzyl amine 7 (33%) were isolated. The synthesis of target
compounds from fluoro starting material was then given up.
A first attempt of Buchwald coupling reaction was realized on
phtalimido compound 5b using different conditions: Pd(OAc)2 or
Pd2(dba)3 as palladium source, P(o-tolyl)3 as ligand, tBuONa or
Cs2CO3 as base, toluene or dioxane as solvent and diverse reaction
conditions from room temperature to 90 ꢀC. All our efforts failed,
compound 5b remained unchanged. We decided then to build the
amino side chain before the coupling reaction. As expected [21],
hydrazinolysis of compound 5b with hydrazine hydrate provided
benzylamine 6b with good yield.
We recently developed a series of analogs where 40-hydroxyl
group was replaced by various amino substituents (Fig. 3) [20]. The
substitution of 40-hydroxy by N-methylpiperazino (compound 1) or
morpholino group (compound 2) provided low nanomolar activity
upon K1 chloroquino-resistant strain and good cytotoxicity. The
most potent morpholino analog 2 was selected for in vivo experi-
ments. This compound presented good in vivo anti-malarial
activity, very close to that of the reference compound AQ, with
a >99.9% reduction of parasitaemia observed at day 4 and day 11.
In order to avoid potential metabolization in 50-position, we
decided to modify our best compounds 1 and 2 by preparing their
50-methylated analogs 3 and 4 (Fig. 3).
Benzylamine 6b was reacted with dibromobutane to yield
compound 9. Unfortunately all attempts to realize Buchwald
coupling from benzylamine 6b as a substrate failed.
We then decided to protect the amino side chain by preparing
Boc derivative 10. This compound was then subjected to diverse
experimental conditions. Optimized yields of 68% for compound 11
and 71% for 12 were obtained with Pd2(dba)3 as palladium source,
racemic BINAP as ligand, Cs2CO3 as base, dioxane as solvent, 90 ꢀC
for about 20 h. BINAP was the only ligand allowing us to obtain the
expected compounds. These conditions were unsuccessful when
pyrrolidino intermediate 9 was used as the substrate.
The end of the synthesis was classically performed with an acidic
deprotection of Boc group, reduction of nitro group and regiose-
lective nucleophilic aromatic substitution of the chlorine atom in
position 4 of the 4,7-dichloroquinoline by aniline compounds 17
and 18 (Scheme 2) to afford derivatives 3 and 4 in good yields. The
yield of the last step was considerably improved by the use of one
equivalent of HCl, enhancing therefore C4 electrophilicity of the
quinoline nucleus. Target compounds were finally obtained after an
eight step procedure with global yields of 19% (3) and 18% (4).
In our previous work, 40-amino analogs were synthesized
thanks to an SNAr reaction of activated fluoro derivatives [16] and
40-alkyl or aryl analogs were successfully obtained [21] using
SuzukieMiyaura cross-coupling reaction [22], as in the case of
tebuquine [23].
In the present work, both 3-methyl-4-fluoronitro and 3-methyl-
4-bromonitro aryl precursor were commercially available and we
planned to test both synthetic approaches to yield our target
compounds 3 and 4 (Fig. 4): Buchwald cross-coupling reaction [24]
with bromo derivative or SNAr reaction with fluoro compound. As
previously described by our group, Mannich amino side chain could
be introduced through Tcherniak-Einhorn reaction [21].
2. Results and discussion
In order to obtain key intermediates 11 and 12 (Scheme 1), the
30-amino side chain was introduced via a super-electrophilic Tcher-
niak-Einhorn amidomethylation of the commercially available
4-fluoro-3-methylnitro-benzene and 4-bromo-3-methylnitro-
benzene with N-hydroxymethylphtalimide in trifluoromethanes-
ulfonic acid according to Olah et al. procedure [25]. As the substrates
were strongly deactivated, the use of a super acid as catalyst and
solvent was necessary. When deprotection of phtalimido group was
engaged for fluoro compound 5a, amino derivative 6a could not
be obtained. Within a complex mixture, indazole 8 (31%) and
3. Conclusion
Despite recent progress, malaria still remains a major health
problem. Aminoquinoline derivatives are historically interesting
compounds to treat this pathology but some of them, such as
amodiaquine, can present metabolization issues leading to hepa-
totoxic effects. We have described here a new synthesis of amo-
diaquine analogs in order to prevent their metabolization. Target
Nucleophilic attack
Buchwald or SN reaction
Ar
5'
X
X
OH
NEt2
O
N
N
N
Y
NEt2
HN
N
N
N
HN
N
O2N
O2N
Binding to cellular
proteins
HEPATOTOXICITY
P450 [O]
N
Y = F, Br
Cl
Cl
Cl
Amodiaquine (AQ)
3 X = N-Me
4 X = O
Tcherniak-Einhorn reaction
Fig. 2. Oxidation of AQ to the toxic quinoneimine electrophilic metabolite mediated by
cytochrome P450.
Fig. 4. Retrosynthetic strategy.

3054
N. Le Fur et al. / European Journal of Medicinal Chemistry 46 (2011) 3052e3057
H
F
N
N
O2N
O2N
O2N
O2N
Br
NH2
NH2
b
b
6a
7
8
Y = F
X
Y
Y
N
Br
N
a
d
e
Y = Br
O2N
Y = F, Br
O2N
O2N
O2N
NH2
NHBoc
O
O
NHBoc
11 X = N-Me
6b
10
c
5a Y = F
5b Y = Br
12 X = O
Br
N
O2N
9
Scheme 1. Synthesis of key intermediates 11 and 12. Reagents: (a) PhtCH2OH, TfOH, 0ꢀC to r.t. (70-94%); (b) hydrazine hydrate, CH3CN, reflux (75%); (c) Br(CH2)4Br, K2CO3, CH3CN,
reflux (67%); (d) Boc2O, THF, r.t (90%); (e) N-methylpiperazine or morpholine, Pd2dba3, (þ/ꢁ) BINAP, Cs2CO3, 1,4-dioxanne, 90ꢀC (68-71%).
compounds 3 and 4 were efficiently obtained thanks to Buchwald
coupling reaction and Tcherniak-Einhorn amidomethylation. Fur-
ther work will evaluate the impact of this methyl group for meta-
bolic stability and anti-malarial activity.
4.2. Synthesis of key intermediates 11 and 12
4.2.1. 2-[(2-Fluoro-3-methyl-5-nitrophenyl)methyl]-2,3-dihydro-
1H-isoindole-1,3-dione 5a
N-(Hydroxymethyl)phtalimide (7.09 g, 40.0 mmol) was dis-
solved in 25 mL of triflic acid at 0 ꢀC. The mixture was stirred for
20 min and then 2-fluoro-5-nitrotoluene (6.2 g, 1eq) was added.
This solution was allowed to warm to rt and was stirred overnight.
The mixture was poured slowly into 500 mL of ice-cold water. The
aqueous layer was extracted twice with CH2Cl2. The combined
organic layers were washed with 200 mL of water, dried over
Na2SO4, filtered and evaporated to yield expected compound 5a as
4. Experimental section
4.1. General procedures
All reactions were monitored by thin-layer chromatography
carried out on 0.2 mm E. Merck silica gel plates (60F-254) using UV
light as a visualizing agent. 1H and 13C NMR spectra were obtained
a white powder (8.6 g, 70% yield). 1H NMR (300 MHz, CDCl3)
(s, 1H, H-4), 8.04 (s, 1H, H-6), 7.90 (m, 2H, H-Ar), 7.71 (m, 2H, H-Ar),
4.97 (s, 2H, CH2), 2.38 (s, 3H, CH3); 13C NMR (75 MHz, CDCl3)
167.9
d 8.06
using a Bruker 300 MHz spectrometer, chemical shifts (d) were
d
expressed in ppm relative to TMS used as an internal standard.
Purity and identity of intermediate compounds were checked by
LC/MS, using a Waters Alliance 2695 system (X-Terra column,
ionization mass spectrometer). The following eluent systems were
used: A (H2O/TFA, 100:0.01) and B (CH3CN/H2O/TFA, 80:20:0.01).
Retention times (tR) were obtained, at flow rate of 0.3 mL/min,
using the following conditions: a gradient run from 100% eluent A
to 100% eluent B over 8 min, then 100% eluent B for 90 s. The purity
of final compounds was verified by two types of high pressure
liquid chromatography (HPLC) columns: C18 Deltapak (C18 N) and
C4 Interchrom UP5WC4-25QS (C4) on a Shimadzu system equipped
with a UV detector set at 254 nm, same eluents as for LCMS
method, at flow rate of 1 mL/min, with a 40 min method: a gradient
run from 100% eluent A during 1 min, then to 100% eluent B over
the next 30 min. For some compounds mass spectra were recorded
on a MALDI-TOF Voyager-DE-STR (Applied Biosystems) apparatus.
Reagents were obtained from Acros, Aldrich, Lancaster, Nova-
biochem and Avocado.
(C), 164.6 (C), 161.1 (C), 134.7 (CH), 132.1 (C), 127.2 (d, C, JC-
¼ 19.9 Hz), 126.8 (d, CH, JC-F ¼ 6.8 Hz), 124.7 (d, CH, JC-F ¼ 18.3 Hz),
F
124.0 (CH), 123.4 (d, CH, JC-F ¼ 5.4 Hz), 35.4 (CH2), 15.0 (CH3); LC/MS
tR ¼ 4.8 min; PHPLC > 99%.
4.2.2. 2-[(2-Bromo-3-methyl-5-nitrophenyl)methyl]-2,3-dihydro-
1H-isoindole-1,3-dione 5b
N-(Hydroxymethyl)phtalimide (2.36 g, 13.3 mmol) was dis-
solved in 20 mL of triflic acid at 0 ꢀC. The mixture was stirred for
20 min and then 2-bromo-5-nitrotoluene (2.88 g, 1eq) was added.
This solution was allowed to warm to rt and was stirred for 18 h.
The mixture was poured slowly into 300 mL of ice-cold water. The
aqueous layer was extracted with CH2Cl2. The combined organic
layers were washed with 100 mL of water, dried over Na2SO4,
filtered and evaporated to yield expected compound 5b as a white
solid (4.71 g, 94% yield). 1H NMR (300 MHz, CDCl3)
J ¼ 2.6 Hz, H-4), 7.84 (m, 2H, H-Ar), 7.71 (m, 3H, H-Ar, H-6), 4.95 (s,
2H, CH2), 2.48 (s, 3H, CH3); 13C NMR (75 MHz, CDCl3)
167.7 (C),
146.7 (C), 140.9 (C), 137.3 (C), 134.5 (CH), 132.3 (C), 131.7 (C), 124.1
d 7.97 (d, 1H,
d
The following abbreviations were used: AcOEt (ethyl acetate), rt
(room temperature), Quino (quinoline).
X
X
X
X
X
N
N
N
N
N
N
N
N
a
b
c
d
O2N
O2N
O2N
H2N
HN
N
NHBoc
11 X = N-Me
NH2
15 X = N-Me
16 X = O
13 X = N-Me
14 X = O
17 X = N-Me
18 X = O
Cl
12X = O
3 X = N-Me
4 X = O
Scheme 2. Synthesis of target compounds 3 and 4. Reagents: (a) HCl, MeOH, r.t. (quant.); (b) Br(CH2)4Br K2CO3, CH3CN, reflux (53-58%); (c) HCOONH4, Pd/C (10%), EtOH, r.t. (99%);
(d) 4,7-dichloroquinoline, HCl (1M, aq.), CH3CN, reflux (84-71%).

N. Le Fur et al. / European Journal of Medicinal Chemistry 46 (2011) 3052e3057
3055
(CH), 123.8 (CH), 119.9 (CH), 42.3 (CH2), 23.8 (CH3); LC/MS
tR ¼ 9.9 min; PHPLC ¼ 99%.
4.2.8. tert-Butyl N-{[3-methyl-2-(4-methylpiperazino)-5-
nitrophenyl]methyl}carbamate 11
In a oven-dried flask and under a nitrogen atmosphere, were
placed tert-butyl N-[(2-bromo-3-methyl-5-nitrophenyl)methyl]
carbamate 10 (150 mg, 0.43 mmol), (þ/ꢁ) BINAP (14 mg, 0.05 eq),
Cs2CO3 (196 mg, 1.4 eq), Pd2dba3 (10 mg, 0.05 eq) and 3 mL of dry
4.2.3. (2-Bromo-3-methyl-5-nitrophenyl)methanamine 6b
4.4 mL of hydrazine hydrate was added to 2-[(2-bromo-3-
methyl-5-nitrophenyl)methyl]-2,3-dihydro-1H-isoindole-1,3-
dione 5b (4.4 g, 11.7 mmol) in 220 mL of acetonitrile. The mixture
was stirred under reflux overnight and then was allowed to cool to
rt. The phtalhydrazide side product was removed by filtration and
washed with 100 mL portions of acetonitrile. The combined
acetonitrile filtrates were evaporated and the residue was parti-
tioned between water and AcOEt. The organic layer was extracted
with two 100 mL portions of aqueous HCl 1 M. The combined acidic
aqueous layers were basified to pH ¼ 10 with solid potassium
hydroxide and then extracted with AcOEt. The organic layer was
dried over Na2SO4 filtered and evaporated to yield expected
compound 6b as an orange powder (2.15 g, 75% yield). 1H NMR
1,4-dioxane. N-Methylpiperazine (58 mL, 1.2 eq) was added and the
mixture was stirred at 90 ꢀC for 16 h. The solution was filtered
through a celite pad and evaporated. The residue was purified by
flash chromatography on silica gel (CH2Cl2/MeOH//9/1 with 1%
triethylamine) to yield expected compound 11 as a pale brown
powder (106 mg, 68% yield). 1H NMR (300 MHz, CDCl3)
d 7.91 (s,1H,
H-4), 7.82 (s, 1H, H-6), 5.04 (br, 1H, NH), 4.34 (d, 2H, J ¼ 6.1 Hz,
NeCH2), 3.3e2.9 (m, 4H, 2NeCH2), 2.6e2.3 (m, 7H, 2NeCH2, CH3),
1.40 (s, 9H, 3CH3); 13C NMR (75 MHz, CDCl3)
d 156.0 (C), 153.5 (C),
144.6 (C), 139.1 (C), 137.9 (C), 125.6 (CH), 120.5 (CH), 55.8 (CH2), 49.6
(CH2), 46.4 (CH3), 41.5 (CH2), 28.3 (CH3), 20.1 (CH3). LC/MS
tR ¼ 5.4 min; PHPLC > 99%; m/z (ESI) 365.2 [M þ H]þ.
(300 MHz, CDCl3)
d
8.10 (d, 1H, J ¼ 2.8 Hz, H-4), 7.94 (d, 1H,
J ¼ 2.6 Hz, H-6), 3.96 (s, 2H), 2.47 (s, 3H); 13C NMR (75 MHz, CDCl3)
d
146.8 (C), 144.4(C), 140.4(C), 132.9(C), 123.4 (CH), 120.6 (CH), 47.0
4.2.9. tert-Butyl N-{[3-methyl-2-morpholino-5-nitrophenyl]
methyl}carbamate 12
In a oven-dried flask and under a nitrogen atmosphere, were
placed tert-butyl N-[(2-bromo-3-methyl-5-nitrophenyl)methyl]
carbamate 10 (500 mg,1.45 mmol), (þ/ꢁ) BINAP (45 mg, 0.07 mmol),
Cs2CO3 (661 mg, 2.03 mmol), Pd2dba3 (33 mg, 0.07 eq) and 10 mL of
(CH2), 23.8 (CH3). LC/MS tR ¼ 5.4 min; PHPLC > 99%; m/z (ESI)
244.9e246.9 [M þ H]þ.
4.2.4. (3-Methyl-5-nitrophenyl)methanamine 7
Brown oil (1.5 g, 33% yield). 1H NMR (300 MHz, CDCl3)
d
8.00 (s,
1H, H-6), 7.91 (s, 1H, H-4), 7.48 (s, 1H, H-2), 3.96 (s, 2H, CH2), 2.45 (s,
3H, CH3); 13C NMR (75 MHz, CDCl3)
148.7 (C), 145.1 (C), 140.2 (C),
dry 1,4-dioxane. Morpholine (152 mL, 1.74 mmol) was added and the
d
mixture was stirred at 90 ꢀC for 24 h. The solution was filtered
through a celite pad and evaporated. The residuewaspurified by flash
chromatography on silica gel (CH2Cl2/AcOEt//9/1) to yield expected
compound 12 as a pale brown powder (360 mg, 71% yield). 1H NMR
134.7 (CH), 122.6 (CH), 119.5 (CH), 45.9 (CH2), 21.5 (CH3). LC/MS
tR ¼ 4.9 min; PHPLC ¼ 95%; m/z (ESI) 167.1 [M þ H]þ.
4.2.5. 7-Methyl-5-nitro-1H-indazole 8
(300 MHz, CDCl3)
d
8.00 (d,1H, J ¼ 2.1 Hz, H-4), 7.92 (d,1H, J ¼ 2.7 Hz,
Brown solid (1.5 g, 31% yield). 1H NMR (300 MHz, CD3OD)
d
8.63
(s, 1H, H-4), 8.31 (s, 1H, H-3), 8.04 (s, 1H, H-6), 2.65 (s, 3H, CH3); 13
NMR (75 MHz, CD3OD) 144.9 (C), 144.7 (C), 139.1 (CH), 124.1 (C),
H-6), 5.05 (brs, 1H, NH), 4.46 (d, 2H, J ¼ 6.0 Hz, NeCH2), 3.9e3.8
(m, 4H, 2OeCH2), 3.5e2.7 (m, 4H, 2NeCH2), 2.45 (s, 3H, CH3), 1.46
C
d
(s, 9H, 3 CH3); 13C NMR (75 MHz, CDCl3)
d 156.5 (C), 153.5 (C), 145.4
122.7 (CH), 118.2 (CH), 18.0 (CH3). LC/MS tR ¼ 7.1 min; PHPLC ¼ 95%;
(C), 139.8 (C), 138.6 (C), 126.3 (CH), 121.3 (CH), 68.3 (CH2), 50.6 (CH2),
42.1 (CH2), 29.0 (CH3), 20.7 (CH3). LC/MS tR ¼ 9.0 min; PHPLC ¼ 99%;
m/z (ESI) 352.2 [M þ H]þ.
m/z (ESI) 177.9 [M þ H]þ.
4.2.6. 1-(2-Bromo-3-methyl-5-nitro-benzyl)-pyrrolidine 9
A mixture of (2-bromo-3-methyl-5-nitrophenyl)methanamine
6b (735 mg, 3 mmol), 1,4-dibromobutane (0.54 mL, 1.5eq) and
K2CO3 (2.07 g, 5eq) in 125 mL of acetonitrile was refluxed for 48 h.
After filtration and evaporation of the filtrate, the residue was
purified by flash chromatography (CH2Cl2/MeOH/NH4OH//9/1/0.1)
to yield expected compound 9 as a yellow powder (601 mg, 67%
4.3. Synthesis of target compounds 3 and 4
4.3.1. [3-Methyl-2-(4-methylpiperazino)-5-nitrophenyl]
methanamine 13
1.2 mL of acetyl chloride was slowly added to 10 mL of MeOH at
0 ꢀC. The solution was stirred for 30 min at rt and then tert-butyl
N-{[3-methyl-2-(4-methylpiperazino)-5-nitrophenyl]methyl}carba-
mate 11 (300 mg, 0.82 mmol) dissolved in 5 mL of MeOH was added.
The reaction mixture was stirred for 2 h and then evaporated. The
residue was dissolved in 15 mL of water and washed with diethyl
ether. The aqueous layer was made alkaline (pH ¼ 10) with an
aqueous NaOH 1 M and extracted with CH2Cl2. The combined organic
layers were dried over Na2SO4, filtered and evaporated to yield
expected compound 13 as a pale yellow oil (216 mg, quantitative
yield). 1H NMR (300 MHz, CDCl3)
(d, 1H, J ¼ 2.8 Hz, H-6), 3.79 (s, 2H, CH2), 2.6 (m, 4H, 2NeCH2), 2.46
(s, 3H, CH3), 1.78 (m, 4H, 2CH2); 13C NMR (75 MHz, CDCl3)
147.0
d
8.21 (d, 1H, J ¼ 2.8 Hz, H-4), 7.98
d
(C), 141.7 (C), 140.2 (C), 133.5 (C), 123.3 (CH), 122.2 (CH), 60.2 (CH2),
54.5 (CH2), 24.0 (CH3), 23.9 (CH2). LC/MS tR ¼ 5.9 min; PHPLC ¼ 99%;
m/z (ESI) 298.3e300.3 [M þ H]þ.
4.2.7. tert-Butyl N-[(2-bromo-3-methyl-5-nitrophenyl)methyl]
carbamate 10
yield). 1H NMR (300 MHz, CDCl3)
(d, J ¼ 2.8 Hz,1H, H-6), 3.89 (s, 2H, NeCH2), 3.4e2.8 (m, 4H, 2NeCH2),
2.7e2.3 (m, 4H, 2NeCH2), 2.37 (s, 3H, NeCH3), 2.32 (s, 3H, CH3); 13
NMR (75 MHz, CDCl3) 153.9 (C), 144.6 (C), 143.1 (C), 137.9 (C), 125.2
d
8.05 (d, J ¼ 2.9 Hz, 1H, H-4), 7.85
Di-tert-butyl dicarbonate (1.51 g, 6.90 mmol) was added to (2-
bromo-3-methyl-5-nitrophenyl) methanamine 6b (1.54 g, 1.1 eq) in
60 mL of THF. The mixture was stirred overnight at rt. After evap-
oration of the solvent, the residue was thoroughly washed with
pentane and filtered off to yield expected compound 10 as off-
white powder (1.93 g, 90% yield). 1H NMR (300 MHz, CDCl3)
C
d
(CH), 121.3 (CH), 55.9 (CH2), 49.8 (CH2), 46.4 (CH3), 43.4 (CH2), 20.1
(CH3). LC/MS tR ¼ 4.4 min; PHPLC ¼ 99%; m/z (ESI) 265.2 [M þ H]þ.
d
7.95 (s, 2H, H-4, H-6), 5.12 (br, 1H, NH), 4.37 (d, 2H, J ¼ 6.3 Hz,
NeCH2), 2.45 (s, 3H, CH3), 1.41 (s, 9H, 3 CH3); 13C NMR (75 MHz,
CDCl3) 155.7 (C), 146.8 (C), 140.5 (C), 140.4 (C), 132.5 (C), 123.7
4.3.2. (3-Methyl-2-morpholino-5-nitrophenyl)methanamine
hydrochloride 14
0.81 mL of acetyl chloride was slowly added to 5 mL of MeOH
at 0 ꢀC. The solution was stirred for 30 min at rt and then tert-
butyl N-{[3-methyl-2-morpholino-5-nitrophenyl]methyl}carbamate
12 (200 mg, 0.57 mmol) dissolved in 5 mL of MeOH was added. The
d
(CH), 120.4 (CH), 45.2 (CH2), 28.3(CH3), 23.7 (CH3). LC/MS
tR ¼ 9.5 min;
P
HPLC > 99%; m/z (ESI) 369.0e371.0 [M þ Na]þ;
330.0e331.9 [M þ H-Me]þ; 244.9e247.0 [M þ H-Boc]þ.

3056
N. Le Fur et al. / European Journal of Medicinal Chemistry 46 (2011) 3052e3057
reaction mixture was stirred for 3 h and then evaporated to yield
in 2 mL of EtOH. The mixture was stirred overnight at rt and then
filtrated through a celite pad. The filtrate was evaporated and the
residue was dissolved in CH2Cl2 and washed with a saturated
aqueous solution of Na2CO3. The aqueous layer was extracted with
CH2Cl2. The combined organic layers were dried over Na2SO4,
filtered and evaporated to yield expected compound 18 as a pale
expected compound 14 as an orange powder (162 mg, 99% yield). 1H
NMR (300 MHz,)
H-6), 3.9e3.7 (m, 6H, 2OeCH2, CH2), 3.2e3.1 (m, 4H, 2NeCH2),
2.6e2.5 (m, 4H, 2NeCH2), 2.48 (s, 3H, CH3),1.9e1.8 (m, 4H, 2CH2); 13
NMR (75 MHz, CD3OD) 153.8 (C),145.1 (C),139.4 (C),133.9 (C),127.3
d
8.16 (d, J ¼ 3.0 Hz, 1H, H-4), 7.98 (d, J ¼ 2.7 Hz, 1H,
C
d
(CH),121.4 (CH), 67.4 (CH2), 50.2 (CH2), 39.4 (CH2),19.1 (CH3). MALDI-
TOF m/z ¼ 306.3 [M þ H]þ. HPLC (C4) tR ¼ 5.4 min; PHPLC > 99%; HPLC
(C18) tR ¼ 13.3 min; PHPLC > 99%.
yellow oil (55 mg, 99% yield). 1H NMR (300 MHz, CD3OD)
d 6.63 (d,
J ¼ 3 Hz, 1H, H-4), 6.45 (d, J ¼ 3 Hz, 1H, H-6), 3.8e3.7 (m, 8H,
2OeCH2, CH2, NH2), 3.3e3.2 (m, 2H, NeCH2), 2.9e2.8 (m, 2H,
NeCH2), 2.5e2.6 (m, 4H, 2NeCH2), 2.28 (s, 3H, CH3), 1.8e1.7 (m, 4H,
4.3.3. 1-Methyl-4-[2-methyl-4-nitro-6-(pyrrolidinomethyl)phenyl]
piperazine 15
A mixture of [3-methyl-2-(4-methylpiperazino)-5-nitrophenyl]
methanamine 13 (188 mg, 0.71 mmol), 1,4-dibromobutane (93 mL,
2CH2); 13C NMR (75 MHz, CD3OD)
d 144.8 (C), 139.2 (C), 137.9 (2C),
117.6 (CH), 114.8 (CH), 67.9 (2CH2), 56.0 (CH2), 54.0 (2CH2), 50.8
(2CH2), 22.9 (2CH2), 18.3 (CH3). LC/MS tR ¼ 4.6 min; PHPLC ¼ 95%; m/
z (ESI) 276.3 [M þ H]þ.
1.1 eq) and K2CO3 (490 mg, 5 eq) in 15 mL of acetonitrile was
refluxed for 48 h. After filtration and evaporation of the filtrate, the
residue was purified by flash chromatography (CH2Cl2/MeOH/
NH4OH//9/1/0.1) to yield expected compound 15 as a pale yellow oil
4.3.7. 7-Chloro-N-[3-methyl-4-(4-methylpiperazino)-5-
(pyrrolidinomethyl)phenyl]quinolin-4-amine 3
3-Methyl-4-(4-methylpiperazino)-5-(pyrrolidinomethyl)aniline
17 (70 mg, 0.24 mmol) and 4,7-dichloroquinoline (50 mg,1eq) were
refluxed overnight in 5 mL of acetonitrile with 1.25 mL of HCl 1 M.
The reaction mixture was then evaporated and purified by flash
chromatography (CH2Cl2/MeOH/NH4OH 9:1:0.1) to yield expected
compound 3 as a white powder (92 mg, 84% yield). 1H NMR
(120 mg, 53% yield). 1H NMR (300 MHz, CDCl3)
1H, H-4), 7.76 (d, J ¼ 2.8 Hz, 1H, H-6), 3.58 (s, 2H, CH2), 3.1e3.0 (m,
4H, 2NeCH2), 2.5e2.3 (m, 8H, 4NeCH2), 2.28 (s, 3H, NeCH3), 2.25
(s, 3H, CH3), 1.7e1.6 (m, 4H, 2CH2); 13C NMR (75 MHz, CDCl3)
d
8.02 (d, J ¼ 2.9 Hz,
d
154.5 (C), 143.8 (C), 139.0 (C), 137.3 (C), 125.0 (CH), 123.5 (CH), 57.0
(CH2), 55.8 (CH2), 54.0 (CH2), 49.7 (CH2), 46.7 (CH3), 23.5 (CH2), 20.3
(300 MHz, CDCl3)
d
8.55 (d, J ¼ 5.3 Hz, 1H, QuinoH-2), 8.03 (d,
(CH3). LC/MS tR ¼ 4.2 min; PHPLC ¼ 95%; m/z (ESI) 319.3 [M þ H]þ.
J ¼ 2.1 Hz,1H, QuinoH-8), 7.83 (d, J ¼ 9.0 Hz,1H, QuinoH-5), 7.45 (dd,
J ¼ 2.1 and 9.0 Hz, 1H, QuinoH-6), 7.27 (m, 1H, H-4), 7.02 (d,
J ¼ 2.7 Hz, 1H, H-6), 6.96 (d, J ¼ 5.3 Hz, 1H, QuinoH-3), 6.57 (brs, 1H,
NH), 3.76 (s, 2H, CH2), 3.3e3.1 (m, 4H, 2NeCH2), 2.7e2.4 (m, 8H,
4NeCH2), 2.40 (s, 3H, NeCH3), 2.38 (s, 3H, CH3), 1.8e1.7 (m, 4H,
4.3.4. 4-[2-Methyl-4-nitro-6-(pyrrolidinomethyl)phenyl]
morpholine 16
A mixture of (3-methyl-2-morpholino-5-nitrophenyl)methan-
amine hydrochloride 14 (160 mg, 0.56 mmol), 1,4-dibromobutane
2CH2). 13C NMR (300 MHz, MeOH-d4)
d 151.2 (CH), 150.2 (C), 148.5
(80
m
L, 0.67 mmol) and K2CO3 (542 mg, 3.92 mmol) in 10 mL of
(C), 144.6 (C), 138.8 (C), 137.7 (C), 135.2 (C), 126.6 (C), 125.3 (CH),
123.5 (CH),122.7 (CH),118.8 (C),101.4 (CH), 56.15 (CH2), 55.65 (CH2),
54.07 (CH2), 49.38 (CH2), 45.34 (CH2), 22.96 (CH2), 18.95 (CH3).
LC/MS tR ¼ 5.5 min; PHPLC > 99%; m/z (ESI) 450.1 [M þ H]þ. HPLC (C4)
tR ¼ 7.1 min; PHPLC ¼ 97%; HPLC (C18) tR ¼ 15.9 min; PHPLC > 99%.
acetonitrile was heated at 60 ꢀC for 48 h. After filtration and evapo-
ration of the filtrate, the residue was purified by flash chromatog-
raphy (CH2Cl2/MeOH/NH4OH//9/1/0.1) to yield expected compound
16 asa paleyellowoil (100 mg, 58% yield).1H NMR (300 MHz, CD3OD)
d
8.16 (d, J ¼ 3.0 Hz, 1H, H-4), 7.98 (d, J ¼ 2.7 Hz, 1H, H-6), 3.9e3.7
(m, 6H, CH2, 2OeCH2), 3.3e3.2 (m, 4H, 2NeCH2), 2.6e2.5 (m, 4H,
4.3.8. 7-Chloro-N-[3-methyl-4-morpholino-5-(pyrrolidinomethyl)
phenyl]quinolin-4-amine 4
2NeCH2), 2.48 (s, 3H, CH3), 1.90e1.80 (m, 4H, 2CH2); 13C NMR
(75 MHz, CD3OD)
d
154.5 (C),144.6 (C),139.2 (C),138.4 (C),125.0 (CH),
3-Methyl-4-morpholino-5-(pyrrolidinomethyl)aniline 18 (46 mg,
0.17 mmol) and 4,7-dichloroquinoline (40 mg, 0.20 mmol) were
refluxed overnight in 5 mL of acetonitrile with 0.51 mL of HCl 1 M.
The reaction mixture was then evaporated and purified by flash
chromatography (CH2Cl2/MeOH/NH4OH//95/5/0 to 90/10/1) to yield
expected compound 4 as a white powder (53 mg, 71% yield). 1H NMR
123.3 (CH), 67.8 (CH2), 57.0 (CH2), 54.1 (CH2), 50.4 (CH2), 23.4 (CH2),
19.3 (CH3). LC/MS tR ¼ 6.2 min; PHPLC ¼ 99%; m/z (ESI) 306.3 [M þ H]þ.
4.3.5. 3-Methyl-4-(4-methylpiperazino)-5-(pyrrolidinomethyl)
aniline 17
1-Methyl-4-[2-methyl-4-nitro-6-(pyrrolidinomethyl)phenyl]
piperazine 15 (90 mg, 0.28 mmol) was hydrogenated using ammo-
nium formate (107 mg, 6 eq) and Pd/C (10% Pd, 15 mg, 0.05 eq) in
2 mL of EtOH. The mixture was stirred overnight at rt and then
filtered through a celite pad. The filtrate was evaporated and the
residue was dissolved in CH2Cl2 and washed with a saturated
aqueous solution of Na2CO3. The aqueous layer was extracted with
CH2Cl2. The combined organic layers were dried over Na2SO4, filtered
and evaporated to yield expected compound 17 as a pale yellow oil
(300 MHz, CDCl3)
d
8.43 (d, J ¼ 5.5 Hz, 1H, QuinoH-2), 8.24
(d, J ¼ 9.0 Hz, 1H, QuinoH-5), 7.90 (d, J ¼ 1.9 Hz, 1H, QuinoH-8), 7.55
(d, J ¼ 2.1 Hz,1H, H-4), 7.30 (dd, J ¼ 1.9 and 9.0 Hz,1H, QuinoH-6), 7.15
(d, J ¼ 2.0 Hz, 1H, H-6), 6.89 (d, J ¼ 5.5 Hz, 1H, QuinoH-3), 4.15 (s, 1H,
NH), 3.89 (s, 2H, CH2), 3.69 (t, J ¼ 9.2 Hz, 2H, OeCH2), 3.38
(t, J ¼ 9.4 Hz, 2H, OeCH2), 3.1e3.0 (m, 4H, 2NeCH2), 2.8e2.7 (m, 4H,
2NeCH2), 2.37 (s, 3H, CH3),1.9e1.8 (m, 4H, 2CH2); 13C NMR (75 MHz,
CDCl3) d 151.0 (CH), 148.8 (C), 148.7 (C), 144.3 (C), 138.8 (C), 137.9 (C),
135.8 (C),134.4(C),127.6(CH),126.1 (CH),125.8(CH),123.6(CH),122.6
(CH), 118.5 (C), 102.5 (CH), 68.2 (CH2), 55.1 (CH2), 54.3 (CH2), 50.8
(CH2), 23.7 (CH2), 20.5 (CH3). LC/MS tR ¼ 6.2 min; PHPLC > 99%; m/z
(ESI) 437.3 [M þ H]þ; HPLC (C4) tR ¼ 7.9 min; PHPLC > 99%; HPLC (C18)
tR ¼ 15.3 min; PHPLC > 99%.
(84 mg, quantitative yield). 1H NMR (300 MHz, CDCl3)
d 6.65 (d,
J ¼ 2.8 Hz,1H, H-4), 6.30 (d, J ¼ 2.8 Hz,1H, H-6), 3.64 (s, 2H, CH2), 3.45
(brs, 2H, NH2), 3.2e2.9 (m, 4H, 2NeCH2), 2.5e2.3 (m, 8H, 4NeCH2),
2.28 (s, 3H, NeCH3), 2.20 (s, 3H, CH3), 1.77e1.67 (m, 4H, 2CH2); 13
C
NMR (75 MHz, CDCl3) d 144.1 (C), 141.0 (C), 139.6 (C), 138.5 (C), 117.1
(CH), 114.3 (CH), 56.5 (CH2), 56.0 (CH2), 54.3 (CH2), 50.3 (CH2), 46.7
Acknowledgments
(CH3), 23.7 (CH2), 19.9 (CH3). LC/MS m/z (ESI) 289.3 [M þ H]þ.
We express our thanks to Gérard Montagne, Emmanuelle Boll and
Hervé Drobecq for analytical and spectroscopic analysis and Robin
Segard for his contribution in organic synthesis. The authors thank Dr
Laurence Agouridas for fruitful discussion and proofreading of the
manuscript. This work was supported by Université de Lille II.
4.3.6. 3-Methyl-4-morpholino-5-(pyrrolidinomethyl)aniline 18
4-[2-Methyl-4-nitro-6-(pyrrolidinomethyl)phenyl] morpholine
16 (62 mg, 0.20 mmol) was hydrogenated using ammonium
formate (128 mg, 2.00 mmol) and Pd/C (10% Pd, 21 mg, 0.02 mmol)

N. Le Fur et al. / European Journal of Medicinal Chemistry 46 (2011) 3052e3057
3057
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