Structure-activity relationship of quinoline derivatives as potent and selective α2c-adrenoceptor antagonists

Article abstract of DOI:10.1021/jm060262x

Starting from two acridine compounds identified in a high-throughput screening campaign (1 and 2, Table 1), a series of 4-aminoquinolines was synthesized and tested for their properties on the human α₂- adrenoceptor subtypes (α_2A, α_2B, and α_2C). A number of compounds with good antagonist potencies against the α_2C-adrenoceptor and excellent subtype selectivities over the other two subtypes were discovered. For example, (R)-{4-[4-(3,4-dimethylpiperazin-1-yl)phenylamino]quinolin-3-yl}methanol 6j had an antagonist potency of 8.5 nM against, and a subtype selectivity of more than 200-fold for, the α_2c-adrenoceptor. Investigation of the structure-activity relationship identified a number of structural features, the most critical of which was an absolute need for a substituent in the 3-position of the quinoline ring. The 3-position on the piperazine ring was also found to play an appreciable role, as substitutions in that position exerted a significant and stereospecific beneficial effect on the α_2C- adrenoceptor affinity and potency. Replacing the piperazine ring proved difficult, with 1,4-diazepanes representing the only viable alternative.

Full text of DOI:10.1021/jm060262x

J. Med. Chem. 2006, 49, 6351-6363
6351
Structure-Activity Relationship of Quinoline Derivatives as Potent and Selective
r2C-Adrenoceptor Antagonists
Iisa P. J. Ho¨glund,† Satu Silver, Mia T. Engstro¨m, Harri Salo,† Andrei Tauber,‡ Hanna-Kaisa Kyyro¨nen,§ Pauli Saarenketo,|
Anna-Marja Hoffre´n, Kurt Kokko,° Katariina Pohjanoksa, Jukka Sallinen,† Juha-Matti Savola, Siegfried Wurster,* and
Oili A. Kallatsa
JuVantia Pharma Ltd, Lemminka¨isenkatu 5, FI-20520 Turku, Finland
ReceiVed March 9, 2006
Starting from two acridine compounds identified in a high-throughput screening campaign (1 and 2, Table
1), a series of 4-aminoquinolines was synthesized and tested for their properties on the human R2-adrenoceptor
subtypes (R2A, R2B, and R2C). A number of compounds with good antagonist potencies against the R2C-
adrenoceptor and excellent subtype selectivities over the other two subtypes were discovered. For example,
(R)-{4-[4-(3,4-dimethylpiperazin-1-yl)phenylamino]quinolin-3-yl}methanol 6j had an antagonist potency of
8.5 nM against, and a subtype selectivity of more than 200-fold for, the R2C-adrenoceptor. Investigation of
the structure-activity relationship identified a number of structural features, the most critical of which was
an absolute need for a substituent in the 3-position of the quinoline ring. The 3-position on the piperazine
ring was also found to play an appreciable role, as substitutions in that position exerted a significant and
stereospecific beneficial effect on the R2C-adrenoceptor affinity and potency. Replacing the piperazine ring
proved difficult, with 1,4-diazepanes representing the only viable alternative.
Introduction
currently in clinical use tend to act on a multiplicity of
pharmacological targets, it has so far not been possible to
elucidate the contribution of R2C-antagonism to their pharma-
codynamic profile in a more precise manner.
The pleiotropic biological functions exerted in humans by
the endogenous catecholamines epinephrine and norepinephrine
are mediated by the adrenergic receptor family, which histori-
cally has been subdivided into R1-adrenoceptor, R2-adrenoceptor
and â-adrenoceptor.1 Each of these three different types of
adrenoceptor in turn consists of three separate subtypes. Thus,
in total, there are nine distinct human adrenoceptors, encoded
by nine individual genes, that belong to the superfamily of G
protein-coupled receptors.1
Among the three R2-adrenoceptor subtypes, the R2A-adreno-
ceoptor is the most prevalent one, with expression in a number
of peripheral and central tissues.2 In contrast, the R2B and the
R2C subtypes have a more limited distribution, with the R2B-
adrenoceptor being present mostly in the periphery2 and the R2C-
adrenoceptor being concentrated in particular central nervous
system (CNS) areas, such as olfactory tubercles, the striatum,
and the hippocampus.3,4 This has led to speculation that the R2C-
adrenoceptor may have a special role in the CNS,5 although it
has recently been suggested that it may also have a significant
role in certain pathologies of the cardiovascular system.6 In
addition, it has been proposed that R2C-adrenoceptor antagonism
may play a part in the therapeutically beneficial effects of certain
antipsychotic compounds, such as, for example, that of cloza-
pine.7,8 However, due to the fact that antipsychotic drugs
Unfortunately, the delineation of the roles of individual R2-
adrenoceptor subtypes is still hampered by the scarcity or
outright lack of sufficiently subtype-selective agonists and
antagonists.9 In the absence of such compounds, the assignment
of specific physiological and pathological functions towards
particular subtypes has relied on the use of genetically modified
mice, in which the subtype of interest has either been knocked
out or overexpressed.
Evidence from mice with knockout as well as overexpressing
mutations of the R2C-adrenoceptor suggests that this subtype
may have an important role in the modulation of central
monoamine neurotransmission, especially under stressful condi-
tions.2 Genetic deletion of the R2C-adrenoceptor produced
antidepressant-like effects in the forced swimming test,10 an
experimental paradigm in rodents widely used for the screening
of antipsychotic compounds,11 while the overexpression of the
R2C-adrenoceptor had the opposite effect. The prepulse inhibition
of the startle reflex, an experimental model relating to the so-
called sensorimotor gating phenomenon,12 is being used for the
screening of antipsychotic-like compounds. In genetically modi-
fied mice, the R2C-adrenoceptor knockout and the R2C-adreno-
ceptor overexpressing mutations were associated with lower and
higher levels of prepulse inhibition of the startle reflex,
respectively.13 On the basis of the studies mentioned above, it
has been suggested that R2C-adrenoceptor-specific ligands might
have therapeutic use in certain psychiatric disorders such as
depression and schizophrenia.5
* Corresponding author: tel +358 2 6517 1509; fax +358 2 6517 1599;
e-mail siegfried.wurster@juvantia.com.
† Present address: Orion Corporation, Orion Pharma, P. O. Box 425,
FI-21010 Turku, Finland.
‡ Present address: Kemira Oyj, Espoo Research Centre, P. O. Box 44,
FI-02271 Espoo, Finland.
§ Present address: Astra Zeneca Oy, Luomanportti 3, FI-02200 Espoo,
Finland.
Given the attractive therapeutic potential of R2C-adrenoceptor
ligands, we decided to launch a discovery project for such
compounds. In this paper we report on the identification of a
novel class of R2C-adrenoceptor antagonists in the form of
4-aminoquinoline-based compounds and aspects of their struc-
ture-activity relationship on human R2C-adrenoceptors.
| Present address: Employment and Economic Development Center for
Southwest Finland, Ratapihankatu 36, P. O. Box 523, FI-20101 Turku,
Finland.
Present address: FBD Ltd., Lemminka¨isenkatu 14-18 A U, FI-20520
Turku, Finland.
°Present address: National Bureau of Investigation, Jokiniemenkuja 4,
P. O. Box 285, FI-01301 Vantaa, Finland.
10.1021/jm060262x CCC: $33.50 © 2006 American Chemical Society
Published on Web 09/28/2006

6352 Journal of Medicinal Chemistry, 2006, Vol. 49, No. 21
Ho¨glund et al.
Scheme 1a
when reacting with 3a. However, in the presence of an acid,
the coupling reaction takes place selectively at the primary
aromatic amine.16 The regioselectivity of this coupling reaction
at low pH was also utilized in the synthesis of the unsubstituted
piperazine derivative 6k (Scheme 3). In this case, the reaction
of 3b and 4b yielded the ester derivative 10, which was then
reduced with lithium aluminum hydride to the intended hy-
droxymethyl compound 6k. The same reduction of ester- or
ketone-containing substituents on the quinoline ring was also
performed as the last step in all cases where hydroxymethyl or
1-hydroxyethyl substituents were desired (6e-o).
The formation of quinoline rings en route to building blocks
3a and 3c-q was conducted by modifying the original
procedures of Conrad and Limpach17 and Gould and Jacobs.18
For this purpose, ethyl acetoacetates 11a-e (Scheme 4) or
diethyl oxalopropionate (Scheme 5) were reacted with anilines
to afford the corresponding imines, which were then cyclized
in diphenyl ether. The obtained 4-hydroxyquinolines 12a-p
were subsequently chlorinated to 4-chloroquinolines 3a and
3c-q with thionyl chloride in the presence of N,N-dimethyl-
formamide (DMF).19 To obtain 4-chloro-3-methylquinoline 3r,
the 4-hydroxy-3-methylquinoline-2-carboxylic acid ethyl ester
12p was hydrolyzed and decarboxylated to 12q before chlorina-
tion with phosphorus oxychloride.20 The 5,6,7,8-tetrahydro-
quinoline derivative 13 (Scheme 6) was obtained by selective
a Reagents: HCl or p-TsOH‚H2O, MeOH, 60 °C or MW 130 °C.
Chemistry. The quinoline derivatives 5 and 6 in the present
study were prepared via a generic reaction that consisted of the
condensation of 4-chloroquinolines 3 with p-substituted anilines
4 in methanol and in the presence of an acid (Scheme 1). The
same scheme was also used for the pyridine compound 7 and
the tetrahydroquinoline compound 8. The majority of reactions
were conducted by use of microwave irradiation in a very fast
and clean manner. Addition of an acid was important in those
reactions where there was an electron-donating alkyl or aryl
substituent in the 3-position of the quinoline ring. This coupling
reaction yielded the final product for most compounds, except
when R was N-methylhexahydropyrimidine (6a) or when R1
or R2 was hydroxymethyl or hydroxyethyl (6e-o).
To obtain the hexahydropyrimidine derivative 6a (Scheme
2), the intermediate 9 was cyclized with formaldehyde in formic
acid.15 Building block 4a has two other possible reactive sites
Scheme 2a
a Reagents: (i) HCl, MeOH, MW 120 °C; (ii) formaldehyde, formic acid, 80 °C.
Scheme 3a
a Reagents: (i) p-TsOH‚H2O, MeOH, MW 130 °C; (ii) LiAlH4, THF.
Scheme 4a
a Reagents: (i) (optionally R3-substituted) aniline, p-TsOH‚H2O, toluene; (ii) Ph2O, 250 °C; (iii) SOCl2, DMF, 80 °C.

Quinoline DeriVatiVes as R2C Antagonists
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 21 6353
Scheme 5a
a Reagents: (i) aniline, p-TsOH‚H2O, toluene; (ii) Ph2O, 250 °C; (iii) SOCl2, DMF, 80 °C; (iv) 2 M NaOH, 100 °C; (v) Ph2O, 250 °C; (vi) POCl3, 105
°C.
Scheme 6a
group with ethyl bromoacetate and cyclization with the aid of
trifluoroacetic acid (TFA).26 The cyclic amide 22 thus prepared
was then reduced first with borane-tetrahydrofuran (THF)
complex and subsequently with hydrazine.
For the preparation of the chain derivatives 4j and 4k (Scheme
12), 2-aminoethanol was coupled with 1-chloro-4-nitrobenzene
to obtain 2-(4-nitrophenyl)aminoethanol (23). The hydroxy
group was mesylated, followed by amination with diethylamine
or pyrrolidine, and the resulting nitro derivatives were reduced
with hydrazine.
The synthesis of building block 4a (Scheme 13) was started
by coupling propane-1,3-diamine with 1-chloro-4-nitrobenzene,
followed by concomitant reductive alkylation27 of the primary
amino function and ring closure. The obtained 1-methylhexahy-
dropyrimidine ring of 25 was inadvertently opened during
hydrazine treatment, resulting in formation of 4a. However, the
ring was cyclized again after 4a was coupled with 3a (Scheme
2).
a Reagents: (i) H2, Ni, MeOH, 20 bar, 70 °C; (ii) SOCl2, DMF, 80 °C.
hydrogenation of the quinoline 12c in the presence of a nickel
catalyst21 to produce the corresponding 5,6,7,8-tetrahydroquino-
line 12r, which was then chlorinated.
To obtain building blocks with ester functions in the
3-position of the quinoline ring (Scheme 7), 15a was reacted
with anilines in pyridine to afford 2-phenylaminomethylenema-
lonic acid diethyl esters, which were cyclized in diphenyl ether.
The obtained 4-hydroxyquinolines 12s-u were chlorinated to
yield 3b, 3s, and 3t, respectively. The same scheme was applied
when combinations of a methyl substituent in the 2-position
with an ester (3u) or a ketone (3v) in the 3-position of the
quinoline ring were desired. The starting materials 15b and 15c
were obtained from triethyl orthoacetate by reacting it with
diethyl malonate 14a and ethyl acetoacetate 14b, respectively.22
Compounds 15b and 15c were reacted with aniline followed
by cyclization to obtain 12v and 12w, which were then
chlorinated to yield the building blocks 3u and 3v, respectively.
The only pyridine intermediate in the present study, 4-chloro-
3,5-dimethylpyridine 16, was obtained in hydrochloric acid salt
form by heating 3,5-lutidine in thionyl chloride (Scheme 8).23
The building blocks 4b-f (Scheme 9) were obtained by
reacting the piperazines 17a-d with 1-chloro-4-nitrobenzene
in DMSO in the presence of potassium carbonate.24 The
resulting 4-piperazine-1-nitrophenyl derivatives were optionally
methylated to afford 18a-f and then reduced to the correspond-
ing anilines (4b-g) either with hydrazine or with hydrogen gas
in the presence of a palladium on carbon catalyst.
This same strategy was also applied in those cases where
the piperazine ring itself was synthesized before being coupled
with 1-chloro-4-nitrobenzene (Scheme 10), where the piperazine
ring was built after a reaction with 1-chloro-4-nitrobenzene
(Scheme 11) or where the piperazine moiety was replaced by
an alkyl chain (Schemes 12 and 13).
For the preparation of 4h (Scheme 10), the starting material
hexahydropyrido[1,2-a]pyrazin-1-one (19) was synthesized via
the literature method.25 Compound 19 was reacted with 1-chloro-
4-nitrobenzene and the resulting nitro derivative was reduced
with hydrazine.
Results and Discussion
The starting point for the current study was the two acridine
compounds shown in Table 1, which had been identified via a
screening campaign as R2C-adrenoceptor selective antagonists
and are described in more detail in a patent application.14 As
such, 1 and 2 did already have a sufficiently large (50-100-
fold) degree of subtype selectivity and their affinity for the R2C-
adrenoceptor was reasonable. However, both hit compounds
were acridine-based structures and acridines, while being of
interest as antitumor28 and antiseptic29 agents, are expected to
have genotoxic properties due to their ability to intercalate into
DNA strands.30 In line with this, 1 was found to show activity
in the Ames test. The propensity of acridines for DNA
intercalation is considered to be due to the size and planar nature
of their ring system and its high degree of lipophilicity.31 The
goal of the present study therefore was to find replacements
for the screening hits that would retain their R2C-adrenoceptor
selectivity but would move away from the acridine 3-ring system
toward a less planar and less lipophilic alternative. For this
purpose, the acridine ring was replaced with a quinoline, which
in addition was endowed with a polar ring substituent. These
two structural features led to the identification of novel
compounds that, while devoid of mutagenic activity in the Ames
test (data not shown), displayed comparable or better antagonist
potencies against, and subtype selectivities for, the human R2C-
adrenoceptor than the initial hit molecules.
To guide the synthetic efforts, the binding affinities (Ki) and,
where warranted, the antagonism potencies (KB) of the com-
pounds were determined. Both pharmacological properties were
found to be in good agreement with each other throughout the
To obtain the 3,3-dimethylpiperazine derivative 4i (Scheme
11), 2-methylpropane-1,2-diamine was coupled with 1-chloro-
4-nitrobenzene followed by alkylation of the primary amino

6354 Journal of Medicinal Chemistry, 2006, Vol. 49, No. 21
Ho¨glund et al.
Scheme 7a
a Reagents: (i) triethyl orthoacetate, Ac2O, ZnCl2, 140 °C; (ii) (optionally R3-substituted) aniline, pyridine, 115 °C; (iii) Ph2O, 250 °C; (iv) SOCl2, DMF,
80 °C or POCl3, 105 °C.
Scheme 8a
moiety turned out not to be an absolute requirement, as its
replacement with a quinoline ring with short alkyl substituents
in the 2- and 3-positions (5b, 5c) fully retained the affinity and
subtype selectivity for the R2-adrenoceptor seen in the acridine
hit compounds. Even sterically quite large substituents, such
as an isopropyl (5d), a phenyl (5e), or a benzyl (5f) in the
3-position of the quinoline ring, were tolerated quite well by
the R2C-adrenoceptor. Nonetheless, in the case of the benzyl
(5f) a significant portion of the R2C-subtype selectivity was lost
due to a considerable gain in affinity for the other two
R2-adrenoceptor subtypes, in particular the R2B-adrenoceptor.
Of the substituents in the 2- and 3-positions of the quinoline
ring, the ones in the 3-position appeared to be much more
critical, as the presence of a 2-substituent alone (5g) resulted
in an affinity profile for the R2-subtypes that was essentially
the same as had been observed for the bare quinoline ring (5a).
We also tested whether the replacement of both flanking rings
in the acridine moiety of 1 by appropriately placed methyl
substituents on a pyridine ring would be feasible. However, this
turned out not to be the case, as the corresponding compound
(7) showed rather poor affinity for all the R2-adrenoceptor
subtypes. Somewhat more surprisingly, it was then also observed
that replacement of the quinoline by a tetrahydroquinoline ring
(8 versus 5b) was not possible either. The reason for this result
is not clear, but it might indicate a need for an aromatic
interaction of the quinoline moiety with the receptor.
a Reagents: SOCl2, 80 °C.
Scheme 9a
a Reagents: (i) 1-chloro-4-nitrobenzene, K2CO3, DMSO, 80 °C; (ii) MeI,
TBAI, NaOH, toluene, 60 °C; (iii) hydrazine hydrate, 10% Pd/C, EtOH,
90 °C or H2, 10% Pd/C, EtOH, 20 bar.
Scheme 10a
After establishing the suitability of quinoline as a substitute
for acridine, we started to explore the piperazine component.
Compared to the initial hit compounds, 8 had an additional
3-methyl substituent in the piperazine ring. This feature was
tested in combination with a number of differently substituted
quinoline moieties and systematically resulted in a substantial
gain in affinity and selectivity for the R2C-adrenoceptor. A direct
example is presented in 5h (Table 3), which shows 7-fold better
affinity for the R2C-adrenoceptor than 5e (Table 2). The gain in
affinity achieved with 3-piperazine substituents was not re-
stricted to the methyl group; it could also be observed by
enlarging the 3-and 4-methyl substituents of the piperazine to
a fused ring (5i, Table 3). In the case of 5i, gains of 15-fold in
affinity for, and 60-fold in antagonist potency against, the R2C-
adrenoceptor were obtained relative to 5b (Table 2). Even
introduction of a second methyl substituent in the 3-position of
the piperazine ring was possible without negative consequences
on the affinity for, or antagonist potency against, the R2C-
adrenoceptor (5j versus 5k). The latter two compounds also
confirm the notion mentioned earlier that a substitution in the
2-position of the quinoline ring is not necessary to achieve good
R2C-adrenoceptor affinity and subtype selectivity.
a Reagents: (i) 1-chloro-4-nitrobenzene, K2CO3, DMSO, 50 °C; (ii)
hydrazine hydrate, 10% Pd/C, EtOH, 90 °C.
study. More specifically, in the case of the R2C-adrenoceptor
subtype a sufficiently large number of 36 Ki and KB pairs were
collected such that a statistical analysis could be attempted. This
analysis was used to test whether differences between binding
affinities and antagonist potencies were due to typical scattering
of experimental values or whether there was any sign of a bias
that might indicate more than one type of ligand-receptor
interaction. The results of this analysis indicated a normal
distribution of experimental scatter (data not shown). While this
does not represent definitive proof, it leads us to assume that at
least as far as the R2C-adrenoceptor subtype is concerned the
compounds most likely interact in a similar manner with the
same binding site on the receptor.
The simple removal of one ring from the three-ring system,
that is, replacing the acridine with a quinoline, did not prove
feasible, as this caused a large drop in binding affinity for the
R2C-adrenoceptor accompanied by a complete loss of subtype
selectivity (5a, Table 2). However, the presence of a three-ring
As the addition of a substituent in the 3-position of the
piperazine ring introduced a chiral center, the affinity profile

Quinoline DeriVatiVes as R2C Antagonists
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 21 6355
Scheme 11a
a Reagents: (i) 1-chloro-4-nitrobenzene, MW 200 °C; (ii) NaH, ethyl bromoacetate, DMF; (iii) TFA, DCM, 50 °C; (iv) NaH, MeI, DMF; (v) borane-
THF complex, THF and then HCl; (vi) hydrazine hydrate, 10% Pd/C, EtOH, 90 °C.
Scheme 12a
Table 1. Binding Affinity for R2-Adrenoceptor of the Initial Acridine
Hit Compounds Identified in a HTS Campaigna
R
R
2A (Ki, nM)
R
2B (Ki, nM)
R
2C (Ki, nM)
1
2
Me
Et
3200 ( 100
3600 ( 300
1500 ( 100
1200 ( 100
28 ( 2
37 ( 5
a The Ki values (nanomolar) represent the affinities of the compounds
for the cloned human R2-adrenoceptor subtypes. More details on the
compounds are provided in a patent application.14 The Ki numbers (given
as mean values ( SEM, N >3 in all cases) were determined in competition
binding assays with 3H-rauwolscine and membranes of S115 cells expressing
cloned human R2-adrenoceptor.
a Reagents: (i) 1-chloro-4-nitrobenzene, 40 °C; (ii) TEA, methanesulfonyl
chloride, DCM and then diethylamine, TEA, DBU, DCM; (iii) hydrazine
hydrate, 10% Pd/C, EtOH, 90 °C; (iv) TEA, methanesulfonyl chloride, DCM
and then pyrrolidine, TEA, DBU, DCM; (v) hydrazine hydrate, 10% Pd/C,
EtOH, 90 °C.
Scheme 13a
significantly decreased but not totally lost (6b and 6c).
Compound 6b can be considered to be an opened N-ethyl-
substituted piperazine ring. Viewed from this perspective, 6b
can thus be compared to the acridine screening hit 2, which
possesses an ethyl substituent in the 4-piperazine position. The
only alternative to a piperazine that resulted in similar affinities
and subtype selectivities for the R2C-adrenoceptor was N-methyl-
1,4-diazepane, as illustrated by compound 6d.
In a further exploration, the effect of adding small substituents
to the phenyl ring side of the quinoline core was tested. As can
be seen from the pharmacological results of 5r (Table 3), a
methyl in the 8-position was well tolerated and this substituent
gave a reasonable affinity when located in the 7-position (5o).
However, it extracted a clear toll on the affinity for the R2C-
adrenoceptor when placed in the 5-position (5s). In accordance
with these observations, the combination of two methyl sub-
stituents in the 7- and 8-positions (5l) was well accepted by the
receptor, whereas the combinations of the 5- and 7-positions
(5t) or the 5- and 8-positions (5u) resulted in increasing losses
in affinity. The same pattern of tolerability in the 7-position
(5v) but deterioration in the 5-position (5w) was also obtained
when a chlorine instead of a methyl was used as the substituent.
A fluorine substituent in the 6-position (5x) was well accepted
by the receptor.
As mentioned above, the propensity of compounds containing
structural features such as acridine rings to intercalate into DNA
strands and thereby cause genotoxic effects is considered to be
driven by the size of the planar ring system and its lipophilic
nature. For this reason, the possibility of introducing polar
substituents into the quinoline ring was investigated. As can be
seen from the data presented in Table 5, introduction of a
hydroxymethyl (6e, 6f) or a 1-hydroxyethyl (6g) in the 3-posi-
tion of the quinoline ring was well tolerated by the R2C-
a Reagents: (i) 1-chloro-4-nitrobenzene, MW 200 °C; (ii) formaldehyde,
formic acid, 80 °C; (iii) hydrazine hydrate, 10% Pd/C, EtOH, 90 °C.
of the two enantiomers for the human R2-adrenoceptor subtypes
was studied. It turned out that there indeed was a difference of
about 1 order of magnitude between stereoisomer pairs (5m
versus 5n and 5p versus 5q) and that the R-enantiomer had the
higher affinity for, and antagonist potency against, the R2C-
adrenoceptor. Interestingly, it also appeared that this effect of
the chiral center was limited to the R2C-adrenoceptor subtype,
as the outcomes with the optically pure enantiomers on the other
two receptor subtypes were either not affected or were clearly
much less affected.
To study the role of the piperazine ring, it was replaced with
ring systems or acyclic motifs that maintained a basic amino
function at roughly the same distance from the central phenyl
ring as the aliphatic amino group in the piperazine-containing
compounds. The results for these compounds are presented in
Table 4.
If the distance was shorter than in piperazine, as was the
situation with the hexahydropyrimidine 6a (Table 4), the affinity
was lost. When the distance was kept about the same, but the
ring character of piperazine was removed, the affinity was

6356 Journal of Medicinal Chemistry, 2006, Vol. 49, No. 21
Ho¨glund et al.
Table 2. Binding and Functional Activities of Compounds 5a-g, 7, and 8 for R2-Adrenoceptor Subtypes
Kia (nM)
KBb (nM)
no.
R1
R2
R2A
R2B
R2C
R2A
nt
5900 ( 1900
2000 ( 400
3700 ( 800
1600 ( 400
590 ( 10
nt
R2B
R2C
5a
5b
5c
5d
5e
5f
5g
7
H
H
Me
Et
i-Pr
Ph
Bn
H
720 ( 60
2210 ( 20
1100 ( 100
1700 ( 300
1700 ( 200
580 ( 70
500 ( 60
3600 ( 100
630 ( 125
3800 ( 100
>5000 [3]
>10 000 [3]
3900 ( 300
>10 000 [3]
96 ( 22
3700 ( 1300
>30 000 [3]
2980 ( 390
1700 ( 600
35 ( 3
nt
nt
Me
Me
Me
Me
Me
Me
>3000 [3]
16 000 ( 2000
13 000 ( 3000
>3000 [3]
220 ( 50
nt
61 ( 8
22 ( 10
87 ( 23
48 ( 7
27 ( 3
nt
25 ( 3
52 ( 11
35 ( 3
35 ( 3
690 ( 280
>5000 [3]
110 ( 10
nt
nt
nt
8
1830 ( 160
10 500 ( 670
150 ( 15
a The Ki values (nanomolar) were derived from competition binding assays and represent the affinities of the compounds for the cloned human R2-
adrenoceptor subtypes. b The KB values (nanomolar) were determined in 35S-GTPγS binding assays against the agonist epinephrine and represent the antagonist
potencies of the compounds against the cloned human R2-adrenoceptor subtypes. Data are given as mean values ( SEM and, unless indicated otherwise in
brackets, are averaged from a minimum of three repeat experiments. Numbers preceded by a greater-than sign mean that the maximal effects of the compound
in the corresponding assay were too small to allow determination of their half-maximally effective concentration. In these cases it was therefore only
possible to determine that the Ki or KB value was greater than the given number. nt ) not tested.
Table 3. Binding and Functional Activities of Compounds 5h-x for R2-Adrenoceptor Subtypesa
Ki (nM)
KB (nM)
no.
R1
R2
Ph
R3
R4
H
R2A
R2B
R2C
R2A
R2B
R2C
5h
5i
5j
5k
5l
Me
H
1400 ( 200
715 ( 110
895 ( 75
1400 ( 50
1850 ( 890
1700 ( 220
1330 ( 125
1270 ( 20
3500 ( 400
580 ( 40
5.0 ( 0.4
2.3 ( 0.2
5.4 ( 1.0
8.5 ( 0.8
5.0 ( 0.3
6000 ( 2700
1700 ( 145
7400 ( 2100
7700 ( 1900
>3000 [3]
>1000 [3]
>1500 [3]
>3000 [3]
>3000 [3]
>3000 [3]
4.3 ( 1.1
0.8 ( 0.1
7.9 ( 1.1
8.9 ( 0.8
41( 7
H
H
Me
Me
Me
Me
H
H
Me
H
H
7-Me,
8-Me
7-Me,
8-Me
7-Me,
8-Me
7-Me
7-Me
7-Me
8-Me
5-Me
5-Me,
7-Me
5-Me,
8-Me
7-Cl
5m
5n
Me
Me
Me
Me
790 ( 40
600 ( 15
7.7 ( 0.4
84 ( 27
2100 ( 80
1750 ( 120
3500 ( 140
10 (1
74 ( 8
850 ( 220
1320 ( 180
2440 ( 100
5o
5p
5q
5r
5s
5t
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
H
840 ( 110
910 ( 100
1050 ( 110
1900 ( 100
680 ( 100
650 ( 30
1280 ( 110
1150 ( 110
2600 ( 100
1100 ( 60
2030 ( 250
910 ( 20
15 ( 3
8.3 ( 2.4
76 ( 5
6.9 ( 0.2
87 ( 10
132 ( 12
>3000 [3]
1500 [2]
3100 ( 300
8100 ( 1700
1400 [2]
>3000 [3]
>3000 [3]
9600 ( 400
>3000 [5]
3000 [2]
51 ( 18
11 ( 1
132 ( 12
22 ( 10
130 ( 40
130 [2]
H
H
H
1800 [2]
2100 [2]
5u
Me
Me
H
2300 [2]
3600 ( 1900
390 [2]
nt
nt
nt
5v
5w
5x
Me
Me
Me
Me
Me
Me
H
H
H
1430 ( 40
775 ( 95
1230 ( 210
880 ( 90
1120 ( 20
3470 ( 700
8.3 ( 1.5
135 ( 6
16 ( 3
>3000 [3]
>3000 [3]
3400 ( 160
>3000 [3]
>3000 [3]
>3000 [3]
11 ( 2
115 ( 15
16 ( 1
5-Cl
6-F
a See Table 2 for footnotes.
adrenoceptor. The same was also true when a hydroxymethyl
substituent was added to the 2-position of the quinoline ring
(6h), but, as seen before with compounds 5k and 5j, the
substituent in the 3-position alone was sufficient to provide good
R2C-adrenoceptor affinity and selectivity (6i and 6j).
The combination of a hydroxymethyl substituent in the
3-position and a halogen substituent in the 6- or 7-position of
the quinoline ring was also studied. In line with the results for
5v, a chlorine in the 7-position (6l) resulted in good R2C-
adrenoceptor affinity but was also accompanied by a decrease

Quinoline DeriVatiVes as R2C Antagonists
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 21 6357
Table 4. Binding and Functional Activities of Compounds 6a-d for R2-Adrenoceptor Subtypesa
a See Table 2 for footnotes.
Table 5. Binding and Functional Activities of Compounds 6e-o at R2-Adrenoceptor Subtypesa
Ki (nM)
KB (nM)
no.
R1
R3
R4
R5
R2A
R2B
R2C
R2A
R2B
R2C
6e
6f
6g
6h
6i
6j
6k
6l
Me
Me
Me
H
H
H
H
Me
H
H
H
Me
3100 ( 400
1170 ( 60
3100 ( 800
1870 ( 90
1850 ( 220
2200 ( 250
9600 ( 200
960 ( 160
1380 ( 140
1320 ( 140
980 ( 110
>10 000 [3]
7.5 ( 0.9
3.8 ( 0.8
4.9 ( 1.0
9.0 ( 1.8
6.4 ( 0.8
9.2 ( 2.1
205 ( 17
5.9 ( 0.5
43 ( 10
50 ( 7
>3000 [3]
6000 ( 1600
>3000 [3]
8100 ( 1500
>3000 [3]
>3000 [3]
>3000 [3]
1650 [2]
>3000 [3]
>3000 [3]
>3000 [3]
>3000 [3]
>3000 [3]
>3000 [3]
>3000 [3]
1150 [1]
7.7 ( 1.2
2.8 ( 0.4
5.0 ( 0.5
8.0 ( 0.7
12 ( 1.6
8.5 ( 0.8
655 ( 60
7.1 ( 0.5
119 ( 7
1470 ( 190
5100 ( 1600
1800 ( 140
1900 ( 240
2600 ( 300
17 600 ( 3400
420 ( 50
>10 000 [3]
1750 ( 100
3150 ( 240
H
H
H
Me
H
H
H
H
7-Cl
6-F
6-F
6-F
Me
H
Me
H
H
H
6m
6n
6o
5400 ( 900
5500 ( 1800
6400 ( 1500
>10 000 [3]
8500 ( 1200
122 ( 28
79 ( 8
38 ( 6
11 000 ( 1000
a See Table 2 for footnotes.
in subtype selectivity. The difference in affinities of 6l toward
the R2B and R2C subtypes was only 70-fold, while that of 6i
was 300-fold. In contrast to the 7-chloro substituent, introduction
of a 6-fluoro substituent did cause an appreciable deterioration
in the affinity for the R2C-adrenoceptor (6m-o).
In conclusion, we have discovered novel, selective R2C-
adrenoceptor antagonists containing a quinoline moiety and have
studied their structure-activity relationships. The most essential
features of the molecules needed to provide them with good
affinity and high selectivity toward the R2C-adrenoceptor were
found to be (1) the quinoline ring, (2) the presence of a
substituent in the 3-position of the quinoline ring, (3) N-
methylation of the piperazine ring, and (4) proper balance in
the order/degree in which the basic moieties in the molecules
are protonated. One of the most promising compounds, on the
basis of its primary pharmacology and in vivo properties, was
considered to be 6j. This compound was also found to possess
activity in animal models of depression, such as the rat forced
swimming assay, in which it statistically significantly extended
the active swimming time of the animals by 79% when applied
subcutaneously at a dose of 0.3 mg/kg (data not shown).
Experimental Section
Competition Binding Assays. The affinity of test compounds
for the three human R2-adrenoceptor subtypes was determined in
competition binding assays with 3H-rauwolscine as the radioligand.
The biological material for these assays consisted in membranes
from Shionogi S115 cells stably transfected with one of the three

6358 Journal of Medicinal Chemistry, 2006, Vol. 49, No. 21
Ho¨glund et al.
human R2-adrenoceptor subypes.32 The membrane suspensions (3-
15 µg of total protein per sample, depending on the expression
1H), 7.67 (m, 1H), 7.49 (m, 1H), 7.21 (m, 2H), 6.99 (m, 2H), 6.73
(m, 1H), 6.56 (br s, 1H), 3.24 (m, 4H), 2.61 (m, 4H), 2.37 (s,
3H).13C NMR (CDCl3, δ, ppm): 150.96, 149.24, 148.99, 148.80,
131.29, 130.17, 129.22, 125.54, 125.05, 119.37, 119.18, 117.04,
101.29, 55.14, 49.30, 46.18. HRMS m/z calcd for C20H23N4 [M +
H]+ 319.1923, found 319.1913.
3
level of individual subtypes) and 1 nM H-rauwolscine (specific
activity 75-85 Ci/mmol) were incubated with six concentrations
of the test compounds in a total volume of 90 µL (50 mM KH2-
PO4, pH 7.5, at room temperature). Nonspecific binding (4-10%
of total binding) was defined by 100 µM oxymetazoline. After 30
min at room temperature, the incubations were terminated by rapid
filtration (TomTec 96 harvester, Tomtec Inc., Hamden, CT) through
presoaked GF/B glass-fiber mats (Wallac Oy, Turku, Finland) which
were then immediately washed three times with ice-cold 50 mM
KH2PO4 (pH 7.5 at room temperature). After they were dried in a
microwave oven, a solid scintillate (Meltilex; Wallac Oy) was
melted onto the filter mats before the radioactivity contained in
them was measured (BetaPlate; Wallac Oy) by scintillation count-
ing. The determination of IC50 values from competition binding
experiments was carried out by nonlinear least-squares curve fitting
analysis. IC50s were then converted to Kis via the Cheng-Prusoff
equation.33
Functional Activity in Cellular Membranes. The R2-antagonist
properties of test compounds were assessed as their ability to
competitively inhibit the epinephrine-stimulated binding of 35S-
guanosine 5′-O-(3-thio)triphosphate (35S-GTPγS) binding to G
proteins34 in the membranes of CHO cells that had been stably
transfected with one of the three human R2-adrenoceptor subtypes.35
Membranes (2-6 µg of protein/sample) and six concentrations of
test compounds were preincubated for 30 min at room temperature
in 50 mM Tris, 5 mM MgCl2, 150 mM NaCl, 1 mM dithiothreitol
(DTT), 1 mM ethylenediaminetetraacetic acid (EDTA), 10 µM
guanosine diphosphate (GDP), and 30 µM ascorbic acid, pH 7.4,
with a fixed concentration of epinephrine (5 µM for R2A, 15 µM
for R2B, and 5 µM for R2C adrenoceptor). Then trace amounts of
35S-GTPγS (0.08-0.15 nM, specific activity 1250 Ci/mmol) were
added to the incubation mixture. After an additional 30 min at room
temperature, the incubations were terminated by rapid vacuum
filtration through glass fiber filters. The filters were immediately
washed three times with 5 mL of ice-cold wash buffer (20 mM
Tris, 5 mM MgCl2, and 1 mM EDTA, pH 7.4), dried, and counted
for their radioactivity in a scintillation counter. Experiments were
repeated at least three times and analyzed by nonlinear least-squares
curve fitting. IC50s were converted to KBs by using the equation
KB ) IC50/(1 + [epinephrine]/EC50,epinephrine) with EC50,epinephrine
values for R2A, R2B, and R2C adrenoceptors being 0.76, 2.4, and
0.71 µM, respectively.
Chemistry. NMR spectra were obtained by Bruker DMX NMR
spectrometer with 1H and 13C observed at 500 and 125 MHz,
respectively. Chemical shifts for NMR spectra were reported in δ
(parts per million, ppm) downfield from tetramethylsilane. Liquid
chromatographic-mass spectrometric (LC-MS) analyses were
performed employing a Waters 2960 Alliance HPLC and a
Micromass Micro triple quadrupole mass spectrometer with elec-
trospray (ES) ionization. Exact mass measurements of the final
products were carried out with a Micromass LCT time-of-flight
(TOF) mass spectrometer. Two diverse high-performance liquid
chromatography (HPLC) systems were used for purity determina-
tions (Supporting Information). Hydrogenations under pressure were
conducted in a Parr hydrogenation apparatus. A Creator (Biotage)
microwave reactor was used for reactions heated by microwave
irradiation. Reagents and solvents were purchased from Sigma-
Aldrich Finland (Helsinki, Finland) or Acros Organics (Geel,
Belgium). Chromatographic purifications were performed on Merck
silica gel 60 (0.063-0.200 mm).
[4-(4-Methylpiperazin-1-yl)phenyl]quinolin-4-ylamine (5a). A
solution of 4-chloroquinoline (49 mg, 0.30 mmol), 4g (57 mg, 0.30
mmol), and a drop of concentrated HCl in MeOH (2 mL) was
refluxed overnight. The solvent was evaporated in vacuo, and the
residue was purified by flash chromatography (CH2Cl2/MeOH/TEA
) 94:5:1). Salts were removed by partitioning the product between
CH2Cl2 and brine. The organic phase was dried over Na2SO4 and
evaporated in vacuo to yield 17 mg (17%) of 5a as a yellow solid.
1H NMR (CDCl3, δ, ppm): 8.51 (m, 1H), 8.02 (m, 1H), 7.90 (m,
(2,3-Dimethylquinolin-4-yl)-[4-(4-methylpiperazin-1-yl)phe-
nyl]amine (5b): Method A. A solution of 3c (96 mg, 0.50 mmol),
4g (96 mg, 0.50 mmol), and concentrated HCl (25 µL) in MeOH
(500 µL) was heated at 130 °C by microwave irradiation for 15
min. The solvent was evaporated in vacuo and the residue was
dissolved in water, which was made alkaline with aqueous saturated
NaHCO3 solution and extracted twice with CH2Cl2. The combined
organic phases were dried over Na2SO4 and evaporated in vacuo.
The product was purified by flash chromatography (CH2Cl2/MeOH
1
) 19:1) to obtain 77 mg (44%) of 5b as a yellow solid. H NMR
(CDCl3, δ, ppm): 8.04 (m, 1H), 7.80 (m, 1H), 7.59 (m, 1H), 7.34
(m, 1H), 6.85 (m, 2H), 6.71 (m, 2H), 6.00 (br s, 1H), 3.15 (m,
4H), 2.73 (s, 3H), 2.60 (m, 4H), 2.37 (s, 3H), 2.24 (s, 3H). 13C
NMR (CDCl3, δ, ppm): 158.94, 147.17, 145.64, 144.61, 139.30,
131.59, 128.56, 128.49, 124.90, 124.31, 124.08, 117.87, 117.59,
55.26, 49.96, 46.09, 28.17, 25.34, 21.16. HRMS: m/z calcd for
C22H27N4 [M + H]+ 347.2236, found 347.2243.
(3-Ethyl-2-methylquinolin-4-yl)-[4-(4-methylpiperazin-1-yl)-
phenyl]amine (5c). A solution of 3d (0.562 g, 3.0 mmol), 4g (0.574
g, 3.0 mmol), and a couple of drops of concentrated HCl in MeOH
(10 mL) was refluxed for 3 h. The reaction mixture was poured
into water (100 mL), made acidic with concentrated HCl, and
washed with CH2Cl2. The water phase was made alkaline with an
aqueous saturated NaHCO3 solution and extracted three times with
CH2Cl2. The combined organic phases were dried over Na2SO4 and
evaporated in vacuo. The product was purified by flash chroma-
tography (CH2Cl2/MeOH ) 9:1) to obtain 0.442 g (41%) of 5c as
a yellow solid. 1H NMR (CDCl3, δ, ppm): 8.00 (m, 1H), 7.71 (m,
1H), 7.55 (m, 1H), 7.25 (m, 1H), 6.80 (m, 2H), 6.69 (m, 2H), 5.81
(br s, 1H), 3.13 (m, 4H), 2.79 (q, J ) 7.7 Hz, 2H), 2.78 (s, 3H),
2.58 (m, 4H), 2.35 (s, 3H), 1.17 (t, J ) 7.7 Hz, 3H).13C NMR
(CDCl3, δ, ppm): 158.56, 146.89, 146.26, 144.46, 138.49, 128.64,
128.36, 126.95, 124.86, 124.13, 122.80, 118.79, 117.53, 55.19,
49.87, 46.04, 23.51, 21.07, 13.50. HRMS m/z calcd for C23H29N4
[M + H]+ 361.2392, found 361.2408.
(3-Isopropyl-2-methylquinolin-4-yl)-[4-(4-methylpiperazin-1-
yl)phenyl]amine (5d). Compound 5d was synthesized by method
A from 3e (110 mg, 0.50 mmol), 4g (96 mg, 0.50 mmol), and HCl
(25 µL) in MeOH (500 µL). The temperature was 130 °C and the
1
reaction time was 120 min. Yield 95 mg (51%), yellow solid. H
NMR (CDCl3, δ, ppm) 7.95 (m, 1H), 7.74 (m, 1H), 7.54 (m, 1H),
7.24 (m, 1H), 6.79 (m, 2H), 6.61 (m, 2H), 5.73 (br s, 1H), 3.61
(m, 1H), 3.11 (m, 4H), 2.81 (s, 3H), 2.56 (m, 4H), 2.34 (s, 3H),
1.38 (d, J ) 7.3 Hz, 6H). 13C NMR (CDCl3, δ, ppm): 159.27,
146.63, 146.15, 144.28, 137.72, 128.62, 128.41, 125.05, 122.74,
120.84, 118.50, 117.56, 55.18, 49.94, 46.05, 24.22, 14.61. HRMS
m/z calcd for C24H31N4 [M + H]+ 375.2549, found 375.2549.
(2-Methyl-3-phenylquinolin-4-yl)-[4-(4-methylpiperazin-1-yl)-
phenyl]amine (5e). Compound 5e was synthesized by method A
from 3f (127 mg, 0.50 mmol), 4g (96 mg, 0.50 mmol), and HCl
(25 µL) in MeOH (500 µL). The temperature was 130 °C and the
1
reaction time was 120 min. Yield 67 mg (33%), yellow solid. H
NMR (CDCl3, δ, ppm) 8.01 (m, 1H), 7.64 (m, 1H), 7.58 (m, 1H),
7.47 (m, 2H), 7.41 (m, 1H), 7.28 (m, 2H), 7.20 (m, 1H), 6.75 (m,
4H), 5.57 (br s, 1H), 3.13 (m, 4H), 2.56 (m, 4H), 2.44 (s, 3H),
2.34 (s, 3H). 13C NMR (CDCl3, δ, ppm): 157.77, 148.29, 147.23,
145.49, 137.67, 136.33, 129.91, 129.50, 129.05, 128.82, 128.19,
125.40, 124.73, 124.31, 121.37, 120.54, 116.98, 55.21, 49.60, 46.12,
24.95. HRMS m/z calcd for C27H29N4 [M + H]+ 409.2392, found
409.2401.
(3-Benzyl-2-methylquinolin-4-yl)-[4-(4-methylpiperazin-1-yl)-
phenyl]amine (5f). Compound 5f was synthesized by method A
from 3g (134 mg, 0.50 mmol), 4g (96 mg, 0.50 mmol), and HCl
(25 µL) in MeOH (500 µL). The temperature was 130 °C and the
1
reaction time was 120 min. Yield 34 mg (16%), yellow solid. H

Quinoline DeriVatiVes as R2C Antagonists
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 21 6359
NMR (CDCl3, δ, ppm) 8.01 (m, 1H), 7.73 (m, 1H), 7.59 (m, 1H),
7.27 (m, 3H), 7.20 (m, 1H), 7.08 (m, 2H), 6.77 (m, 2H), 6.61 (m,
2H), 5.70 (br s, 1H), 4.18 (s, 2H), 3.10 (m, 4H), 2.71 (s, 3H), 2.56
(m, 4H), 2.34 (s, 3H). 13C NMR (CDCl3, δ, ppm): 159.67, 147.94,
146.16, 145.36, 138.40, 138.20, 128.93, 128.84, 127.81, 126.60,
124.89, 124.36, 123.46, 123.01, 118.43, 117.54, 55.24, 50.00, 46.12,
33.78, 24.46. HRMS m/z calcd for C28H31N4 [M + H]+ 423.2549,
found 423.2550.
117.37, 57.85, 57.12, 55.65, 49.95, 42.50, 17.19, 16.05. HRMS m/z
calcd for C22H27N4 [M + H]+ 347.2236, found 347.2232.
[4-(3,4-Dimethylpiperazin-1-yl)phenyl]-(2,3,7,8-tetrameth-
ylquinolin-4-yl)amine (5l). Compound 5l was synthesized by
method A from 3h (214 mg, 1.0 mmol), 4c (103 mg, 0.50 mmol),
and HCl (a couple of drops) in MeOH (500 µL). The temperature
was 130 °C and the reaction time was 5 min. Yield 174 mg (90%),
1
red solid. H NMR (CDCl3, δ, ppm): 7.55 (d, J ) 8.6 Hz, 1H),
[4-(4-Methylpiperazin-1-yl)phenyl]-(2-methylquinolin-4-yl)-
amine (5g). Compound 5g was synthesized by method A from
4-chloroquinaldine (101 µL, 0.50 mmol), 4g (96 mg, 0.50 mmol),
and HCl (25 µL) in MeOH (500 µL). The temperature was 130 °C
and the reaction time was 5 min. Yield 123 mg (74%), yellow solid.
1H NMR (CDCl3, δ, ppm) 8.04 (m, 2H), 7.60 (m, 1H), 7.41 (m,
1H), 7.22 (m, 2H), 6.97 (m, 2H), 6.54 (s, 1H), 3.24 (m, 4H), 2.60
(m, 4H), 2.54 (s, 3H), 2.37 (s, 3H). 13C NMR (CDCl3, δ, ppm):
158.14, 150.33, 149.42, 130.65, 130.15, 127.11, 125.79, 124.95,
124.76, 120.19, 117.41, 116.90, 101.01, 55.13, 49.13, 46.17, 24.33.
HRMS m/z calcd for C21H25N4 [M + H]+ 333.2079, found
333.2070.
[4-(3,4-Dimethylpiperazin-1-yl)phenyl]-(2-methyl-3-phenylquin-
olin-4-yl)amine (5h). Compound 5h was synthesized by method
A from 3f (1.01 g, 4.0 mmol), 4c (500 mg, 2.4 mmol), and HCl (a
couple of drops) in MeOH (2 mL). The temperature was 145 °C
and the reaction time was 60 min. Yield 750 mg (73%), orange
solid. 1H NMR (CDCl3, δ, ppm): 8.02 (m, 1H), 7.63 (m, 1H), 7.58
(m, 1H), 7.48 (m, 2H), 7.41 (m, 1H), 7.28 (m, 2H), 7.20 (m, 1H),
6.77 (m, 2H), 6.73 (m, 2H), 5.59 (br s, 1H), 3.42 (m, 1H), 3.35
(m, 1H), 2.88 (m, 2H), 2.50 (m, 1H), 2.44 (s, 3H), 2.41 (m, 1H),
2.34 (s, 3H), 2.25 (m, 1H), 1.12 (d, J ) 6.1 Hz, 3H). 13C NMR
(CDCl3, δ, ppm): 154.86, 147.07, 136.18, 134.03, 129.90, 129.53,
129.13, 128.67, 128.22, 125.39, 124.33, 121.44, 116.94, 57.78,
56.83, 55.64, 49.67, 42.54, 24.87, 17.22. HRMS m/z calcd for
C28H31N4 [M + H]+ 423.2549, found 423.2550.
(2,3-Dimethylquinolin-4-yl)-[4-(octahydro-2H-pyrido[1,2-a]-
pyrazin-2-yl)phenyl]amine (5i). Compound 5i was synthesized by
method A from 3c (56 mg, 0.29 mmol), 4h (56 mg, 0.24 mmol),
and HCl (a couple of drops) in MeOH (750 µL). The temperature
was 145 °C and the reaction time was 15 min. Yield 19 mg (21%),
yellow oil. 1H NMR (CDCl3, δ, ppm): 8.02 (m, 1H), 7.81 (m, 1H),
7.56 (m, 1H), 7.32 (m, 1H), 6.82 (m, 2H), 6.72 (m, 2H), 5.92 (br
s, 1H), 3.42 (m, 1H), 3.33 (m, 1H), 2.92 (m, 3H), 2.70 (s, 3H),
2.49 (m, 2H), 2.18 (s, 3H), 2.12 (m, 3H), 1.81 (m, 1H), 1.69 (m,
1H), 1.60 (m, 1H), 1.34 (m, 2H), 1.17 (m, 2H). 13C NMR (CDCl3,
δ, ppm): 159.38, 147.67, 146.74, 137.91, 129.83, 129.18, 126.87,
125.18, 122.96, 120.43, 117.55, 61.32, 56.00, 55.55, 55.00, 49.68,
29.52, 23.76, 14.66. HRMS m/z calcd for C25H31N4 [M + H]+
387.2549, found 387.2538.
(3-Methylquinolin-4-yl)-[4-(3,3,4-trimethylpiperazin-1-yl)phe-
nyl]amine (5j). Compound 5j was synthesized by method A from
3r (45 mg, 0.25 mmol), 4i (50 mg, 0.23 mmol), and HCl (1 drop)
in MeOH (500 µL). The temperature was 130 °C and the reaction
time was 15 min. Yield 53 mg (64%), red solid. 1H NMR (CDCl3,
δ, ppm): 8.63 (s, 1H), 8.05 (m, 1H), 7.85 (m, 1H), 7.59 (m, 1H),
7.36 (m, 1H), 6.78 (m, 4H), 6.30 (br s, 1H), 3.23 (m, 2H), 2.98 (s,
2H), 2.86 (m, 2H), 2.42 (s, 3H), 2.25 (s, 3H), 1.24 (s, 6H). 13C
NMR (CDCl3, δ, ppm): 152.83, 147.84, 146.51, 144.87, 137.25,
129.20, 128.61, 125.56, 123.04, 122.88, 120.07, 119.68, 117.99,
62.47, 50.28, 49.43, 36.93, 20.17, 16.18. HRMS m/z calcd for
C23H29N4 [M + H]+ 361.2392, found 361.2410.
7.15 (d, J ) 8.6 Hz, 1H), 6.80 (m, 2H), 6.62 (m, 2H), 5.74 (br s,
1H), 3.36 (m, 1H), 3.31 (m, 1H), 2.90 (m, 2H), 2.76 (s, 3H), 2.72
(s, 3H), 2.51 (m, 2H), 2.44 (s, 3H), 2.35 (s, 3H), 2.30 (m, 1H),
2.21 (s, 3H), 1.13 (d, J ) 6.1 Hz, 3H). 13C NMR (CDCl3, δ, ppm):
158.29, 145.33, 143.50, 138.74, 135.94, 134.04, 127.79, 121.57,
119.45, 117.81, 117.55, 57.92, 57.44, 55.68, 50.22, 42.44, 24.96,
20.56, 17.11, 14.56, 13.37. HRMS m/z calcd for C25H33N4 [M +
H]+ 389.2705, found 389.2690.
(R)-[4-(3,4-Dimethylpiperazin-1-yl)phenyl]-(2,3,7,8-tetrameth-
ylquinolin-4-yl)amine (5m). Compound 5m was synthesized by
method A from 3h (68 mg, 0.31 mmol), 4d (52 mg, 0.25 mmol),
and HCl (a couple of drops) in MeOH (500 µL). The temperature
was 145 °C and the reaction time was 30 min. Yield 57 mg (58%),
1
red solid. H NMR (CDCl3, δ, ppm): 7.64 (d, J ) 8.5 Hz, 1H),
7.17 (d, J ) 8.5 Hz, 1H), 6.80 (m, 2H), 6.70 (m, 2H), 3.39 (m,
2H), 3.16 (m, 2H), 2.84 (m, 1H), 2.79 (s, 3H), 2.77 (s, 3H), 2.72
(m 2H), 2.55 (s, 3H), 2.44 (s, 3H), 2.13 (s, 3H), 1.31 (d, J ) 6.4
Hz, 3H). 13C NMR (CDCl3, δ, ppm): 157.74, 146.51, 144.95,
138.34, 132.18, 128.10, 121.11, 120.03, 119.96, 118.26, 58.74,
56.22, 54.89, 49.06, 41.53, 24.19, 20.66, 15.83, 14.72, 13.69. HRMS
m/z calcd for C25H33N4 [M + H]+ 389.2705, found 389.2722.
(S)-[4-(3,4-Dimethylpiperazin-1-yl)phenyl]-(2,3,7,8-tetrameth-
ylquinolin-4-yl)amine (5n). Compound 5n was synthesized by
method A from 3h (68 mg, 0.31 mmol), 4e (53 mg, 0.26 mmol),
and HCl (a couple of drops) in MeOH (500 µL). The temperature
was 145 °C and the reaction time was 20 min. Yield 75 mg (75%),
1
red solid. H NMR (CDCl3, CD3OD, δ, ppm): 7.78 (d, J ) 8.9
Hz, 1H), 7.29 (d, J ) 8.9 Hz, 1H), 7.02 (m 2H), 6.96 (m, 2H),
3.58 (m, 2H), 3.10 (m, 2H), 2.83 (s, 3H), 2.73 (m, 2H), 2.67 (s,
3H), 2.55 (s, 3H), 2.52 (s, 3H), 2.49 (m, 1H), 2.17 (s, 3H), 1.29 (d,
J ) 5.5 Hz, 3H). 13C NMR (CDCl3, CD3OD, δ, ppm): 158.56,
148.57, 143.86, 137.34, 129.34, 126.72, 124.25, 122.19, 117.75,
59.02, 55.94, 55.43, 48.90, 41.90, 20.92, 16.18, 14.65, 13.37. HRMS
m/z calcd for C25H33N4 [M + H]+ 389.2705, found 389.2683.
[4-(3,4-Dimethylpiperazin-1-yl)phenyl]-(2,3,7-trimethylquino-
lin-4-yl)amine (5o) and [4-(3,4-Dimethylpiperazin-1-yl)phenyl]-
(2,3,5-trimethylquinolin-4-yl)amine (5s). Compounds 5o and 5s
were synthesized by method A from a mixture of isomers 3i and
3j (206 mg, 1.0 mmol), 4c (103 mg, 0.50 mmol), and HCl (a couple
of drops) in MeOH (2.0 mL). The temperature was 130 °C and the
reaction time was 10 min. Products were separated by flash
chromatography (CH2Cl2/MeOH ) 9:1) to obtain 76 mg (41%) of
5s and 27 mg (14%) of 5o in pure form, both as orange solids. The
5-methyl isomer eluted first from the column. Analytical data for
5o: 1H NMR (CDCl3, δ, ppm) 7.82 (s, 1H), 7.65 (d, J ) 8.6 Hz,
1H), 7.15 (d, J ) 8.6 Hz, 1H), 6.82 (m, 2H), 6.69 (m, 2H), 5.94
(br s, 1H), 3.40 (m, 1H), 3.34 (m, 1H), 2.89 (m, 2H), 2.71 (s, 3H),
2.50 (m, 1H), 2.49 (s, 3H), 2.43 (m, 1H), 2.34 (s, 3H), 2.27 (m,
1H), 2.21 (s, 3H), 1.13 (d, J ) 6.4 Hz, 3H). 13C NMR (CDCl3, δ,
ppm) 159.09, 146.68, 146.06, 144.30, 138.88, 127.50, 127.24,
122.54, 120.58, 119.80, 118.65, 117.54, 57.81, 57.33, 55.72, 50.13,
42.56, 24.16, 21.61, 17.27, 14.49. HRMS m/z calcd for C24H31N4
[M + H]+ 375.2549, found 375.2534. Analytical data for 5s: 1H
NMR (CDCl3, δ, ppm) 7.84 (d, J ) 8.2 Hz, 1H), 7.24 (dd, J )
8.2, 7.0 Hz, 1H), 7.13 (d, J ) 7.0 Hz, 1H), 6.79 (m, 2H), 6.47 (m,
2H), 5.80 (br s, 1H), 3.33 (m, 1H), 3.28 (m, 1H), 2.85 (m, 2H),
2.72 (s, 3H), 2.66 (s, 3H), 2.43 (m, 2H), 2.31 (s, 3H), 2.24 (m,
1H), 2.18 (s, 3H), 1.09 (d, J ) 6.4 Hz, 3H). 13C NMR (CDCl3, δ,
ppm) 159.07, 148.72, 144.98, 144.54, 138.80, 133.26, 129.10,
128.02, 127.83, 125.46, 124.63, 118.08, 116.18, 57.89, 57.62, 55.79,
50.35, 42.55, 24.37, 24.08, 17.25, 14.78. HRMS m/z calcd for
C24H31N4 [M + H]+ 375.2549, found 375.2538.
[4-(3,4-Dimethylpiperazin-1-yl)phenyl]-(3-methylquinolin-4-
yl)amine (5k). Compound 5k was synthesized by method A from
3r (100 mg, 0.56 mmol), 4c (102 mg, 0.50 mmol), and HCl (1
drop) in MeOH (500 µL). The temperature was 145 °C and the
reaction time was 20 min. Yield 50 mg (29%), red solid. 1H NMR
(CDCl3, δ, ppm): 8.66 (s, 1H), 8.04 (m, 1H), 7.81 (m, 1H), 7.59
(m, 1H), 7.35 (m, 1H), 6.84 (m, 2H), 6.76 (m, 2H), 5.97 (br s,
1H), 3.42 (m, 1H), 3.36 (m, 1H), 2.90 (m, 2H), 2.53 (m, 1H), 2.45
(m, 1H), 2.35 (s, 3H), 2.29 (m, 1H), 2.27 (s, 3H), 1.14 (d, J ) 6.1
Hz, 3H). 13C NMR (CDCl3, δ, ppm): 153.35, 148.36, 146.50,
144.56, 136.95, 129.67, 128.41, 125.46, 122.86, 120.00, 119.77,

6360 Journal of Medicinal Chemistry, 2006, Vol. 49, No. 21
Ho¨glund et al.
(R)-[4-(3,4-Dimethylpiperazin-1-yl)phenyl]-(2,3,7-trimeth-
ylquinolin-4-yl)amine (5p). Compound 5p was synthesized by
method A from a mixture of isomers 3i and 3j (206 mg, 1.0 mmol),
4d (103 mg, 0.50 mmol), and HCl (a couple of drops) in MeOH
(1.0 mL). The temperature was 130 °C and the reaction time was
10 min. The desired 7-methyl isomer 5p was separated from the
5-methyl isomer by flash chromatography (CH2Cl2/MeOH ) 9:1).
Yield 46 mg (25%), yellow solid. 1H NMR (CDCl3, δ, ppm): 7.77
(s, 1H), 7.65 (d, J ) 8.6 Hz, 1H), 7.15 (dd, J ) 8.6, 1.5 Hz, 1H),
6.82 (m, 2H), 6.67 (m, 2H), 5.82 (br s, 1H), 3.38 (m, 1H), 3.33
(m, 1H), 2.87 (m, 2H), 2.69 (s, 3H), 2.49 (m, 1H), 2.49 (s, 3H),
2.43 (m, 1H), 2.33 (s, 3H), 2.25 (m, 1H), 2.22 (s, 3H), 1.12 (d, J
) 6.1 Hz, 3H). 13C NMR (CDCl3, δ, ppm): 159.52, 147.35, 145.84,
143.80, 138.55, 138.05, 127.97, 127.15, 122.47, 120.92, 120.32,
118.24, 117.60, 57.80, 57.46, 55.76, 50.24, 42.59, 24.53, 21.60,
17.31, 14.55. HRMS m/z calcd for C24H31N4 [M + H]+ 375.2549,
found 375.2531.
(S)-[4-(3,4-Dimethylpiperazin-1-yl)phenyl]-(2,3,7-trimeth-
ylquinolin-4-yl)amine (5q). Compound 5q was synthesized by
method A from a mixture of isomers 3i and 3j (206 mg, 1.0 mmol),
4e (103 mg, 0.50 mmol), and HCl (a couple of drops) in MeOH
(1.0 mL). The temperature was 130 °C and the reaction time was
10 min. The desired 7-methyl isomer 5q was separated from the
5-methyl isomer by flash chromatography (CH2Cl2/MeOH ) 9:1).
Yield 40 mg (21%), yellow solid. 1H NMR (CDCl3, δ, ppm): 7.88
(s, 1H), 7.66 (d, J ) 8.5 Hz, 1H), 7.15 (dd, J ) 8.5, 1.5 Hz, 1H),
6.83 (m, 2H), 6.75 (m, 2H), 6.25 (br s, 1H), 3.41 (m, 1H), 3.35
(m, 1H), 2.90 (m, 2H), 2.72 (s, 3H), 2.52 (m, 1H), 2.48 (s, 3H),
2.44 (m, 1H), 2.35 (s, 3H), 2.29 (m, 1H), 2.18 (s, 3H), 1.14 (d, J
) 6.1 Hz, 3H). 13C NMR (CDCl3, δ, ppm): 158.16, 146.45, 145.59,
144.05, 139.53, 136.96, 127.39, 126.38, 122.74, 120.16, 119.43,
118.75, 117.39, 57.82, 57.09, 55.63, 49.92, 42.51, 23.41, 21.62,
17.20, 14.43. HRMS m/z calcd for C24H31N4 [M + H]+ 375.2549,
found 375.2562.
1.12 (d, J ) 6.4 Hz, 3H). 13C NMR (CDCl3, δ, ppm): 157.80,
147.67, 144.66, 144.21, 139.19, 135.10, 130.79, 128.56, 128.12,
125.41, 124.63, 118.15, 115.86, 57.92, 57.67, 55.79, 50.39, 42.52,
24.79, 24.16, 18.54, 17.20, 14.69. HRMS m/z calcd for C25H33N4
[M + H]+ 389.2705, found 389.2721.
(7-Chloro-2,3-dimethylquinolin-4-yl)-[4-(3,4-dimethylpiper-
azin-1-yl)phenyl]amine (5v) and (5-Chloro-2,3-dimethylquino-
lin-4-yl)-[4-(3,4-dimethylpiperazin-1-yl)phenyl]a mine (5w). Com-
pounds 5v and 5w were synthesized by method A from a mixture
of isomers 3m and 3n (226 mg, 1.0 mmol), 4c (103 mg, 0.50
mmol), and HCl (a couple of drops) in MeOH (1.0 mL). The
temperature was 130 °C and the reaction time was 10 min. Products
were separated by flash chromatography (CH2Cl2/MeOH ) 9:1)
to obtain 25 mg (25%) of 5w and 14 mg (14%) of 5v in pure form,
both as orange solids. The 5-chloro isomer eluted first from the
column. Analytical data for 5v: 1H NMR (CDCl3, δ, ppm) 7.97
(d, J ) 2.0 Hz, 1H), 7.69 (d, J ) 8.9 Hz, 1H), 7.24 (dd, J ) 8.9,
2.0 Hz, 1H), 6.82 (m, 2H), 6.67 (m, 2H), 5.79 (br s, 1H), 3.39 (m,
1H), 3.34 (m, 1H), 2.89 (m, 2H), 2.70 (s, 3H), 2.52 (m, 1H), 2.45
(m, 1H), 2.35 (s, 3H), 2.29 (m, 1H), 2.24 (s, 3H), 1.13 (d, J ) 6.3
Hz, 3H). 13C NMR (CDCl3, δ, ppm) 160.89, 147.72, 146.12, 144.05,
137.64, 134.20, 127.84, 125.72, 124.56, 121.23, 121.05, 118.62,
117.62, 57.87, 57.21, 55.64, 50.01, 42.48, 24.64, 17.17, 14.47.
HRMS m/z calcd for C23H28N4Cl [M + H]+ 395.2002, found
395.1998. Analytical data for 5w: 1H NMR (CDCl3, δ, ppm) 7.92
(dd, J ) 7.9, 1.5 Hz, 1H), 7.44 (dd, J ) 7.9, 7.6 Hz, 1H), 7.42 (dd,
J ) 7.6, 1.5 Hz, 1H), 6.85 (m, 2H), 6.64 (m, 2H), 3.40 (m, 1H),
3.34 (m, 1H), 2.89 (m, 2H), 2.67 (s, 3H), 2.51 (m, 1H), 2.44 (m,
1H), 2.35 (s, 3H), 2.28 (m, 1H), 2.11 (s, 3H), 1.13 (d, J ) 6.1 Hz,
3H). 13C NMR (CDCl3, δ, ppm) 160.48, 149.02, 145.80, 144.28,
137.21, 129.25, 128.33, 127.74, 127.57, 123.92, 120.57, 118.37,
117.57, 57.87, 57.37, 55.74, 50.13, 42.54, 24.44, 17.23, 15.96.
HRMS m/z calcd for C23H28N4Cl [M + H]+ 395.2002, found
395.2014.
[4-(3,4-Dimethylpiperazin-1-yl)phenyl]-(2,3,8-trimethylquino-
lin-4-yl)amine (5r). Compound 5r was synthesized by method A
from 3a (137 mg, 0.67 mmol), 4c (153 mg, 0.74 mmol), and HCl
(a couple of drops) in MeOH (500 µL). The temperature was 130
°C and the reaction time was 5 min. Yield 133 mg (53%), yellow
solid. 1H NMR (CDCl3, δ, ppm): 7.65 (m, 1H), 7.43 (m, 1H), 7.22
(m, 1H), 6.81 (m, 2H), 6.63 (m, 2H), 5.76 (br s, 1H), 3.36 (m,
1H), 3.31 (m, 1H), 2.86 (m, 2H), 2.80 (s, 3H), 2.73 (s, 3H), 2.45
(m, 2H), 2.33 (s, 3H), 2.26 (m, 1H), 2.23 (s, 3H), 1.12 (d, J ) 6.2
Hz, 3H). 13C NMR (CDCl3, δ, ppm): 157.19, 146.53, 144.63,
136.39, 134.19, 129.26, 129.18, 126.42, 125.21, 121.21, 121.15,
118.65, 117.31, 55.46, 55.28, 54.54, 48.20, 45.86, 24.05, 18.66,
14.96, 8.66. HRMS m/z calcd for C24H31N4 [M + H]+ 375.2549,
found 375.2547.
[4-(3,4-Dimethylpiperazin-1-yl)phenyl]-(6-fluoro-2,3-dimeth-
ylquinolin-4-yl)amine (5x). Compound 5x was synthesized by
method A from 3o (210 mg, 1.0 mmol), 4c (102 mg, 0.50 mmol),
and HCl (a couple of drops) in MeOH (1.0 mL). The temperature
was 130 °C and the reaction time was 10 min. Yield 104 mg (55%),
1
yellow solid. H NMR (CDCl3, δ, ppm): 7.97 (m, 1H), 7.38 (m,
1H), 7.33 (m, 1H), 6.83 (m, 2H), 6.64 (m, 2H), 5.70 (br s, 1H),
3.39 (m, 1H), 3.33 (m, 1H), 2.88 (m, 2H), 2.70 (s, 3H), 2.50 (m,
1H), 2.44 (m, 1H), 2.34 (s, 3H), 2.28 (m, 1H), 2.26 (s, 3H), 1.13
(d, J ) 6.1 Hz, 3H). 13C NMR (CDCl3, δ, ppm): 160.77, 158.97,
158.82, 145.96, 144.28, 143.45, 137.69, 131.33, 131.26, 118.48,
118.28, 118.06, 117.74, 106.84, 106.65, 57.82, 57.39, 55.71, 50.18,
42.54, 24.48, 17.24, 14.62. HRMS m/z calcd for C23H28N4F [M +
H]+ 379.2298, found 379.2278.
[4-(3,4-Dimethylpiperazin-1-yl)phenyl]-(2,3,5,7-tetrameth-
ylquinolin-4-yl)amine (5t). Compound 5t was synthesized by
method A from 3k (220 mg, 1.0 mmol), 4c (60 mg, 0.30 mmol),
and HCl (a couple of drops) in MeOH (500 µL). The temperature
was 130 °C and the reaction time was 5 min. Yield 92 mg (78%),
[4-(3-Methyltetrahydropyrimidin-1(2H)-yl)phenyl]-(2,3,8-tri-
methylquinolin-4-yl)amine (6a). A solution of 9 (185 mg, 0.53
mmol) and aqueous 40% formaldehyde (100 µL, 1.3 mmol) in
formic acid (5 mL) was heated at 80 °C for 1 h. The reaction
mixture was poured into water (100 mL), made alkaline with 10
M NaOH, and extracted twice with CH2Cl2. Combined organic
phases were dried over Na2SO4 and evaporated in vacuo. The
product was purified by flash chromatography (CH2Cl2/MeOH )
1
yellow solid. H NMR (CDCl3, δ, ppm): 7.69 (s, 1H), 7.00 (s,
1H), 6.81 (m, 2H), 6.50 (m, 2H), 5.87 (br s, 1H), 3.36 (m, 1H),
3.31 (m, 1H), 2.87 (m, 2H), 2.71 (s, 3H), 2.67 (s, 3H), 2.47 (m,
2H), 2.44 (s, 3H), 2.34 (s, 3H), 2.27 (m, 1H), 2.18 (s, 3H), 1.12 (d,
J ) 6.1 Hz, 3H). 13C NMR (CDCl3, δ, ppm): 158.78, 148.75,
145.02, 138.74, 138.13, 132.92, 131.43, 126.62, 124.33, 122.43,
118.05, 116.35, 57.90, 57.59, 55.78, 50.32, 42.54, 24.13, 23.92,
21.26, 17.24, 14.67. HRMS m/z calcd for C25H33N4 [M + H]+
389.2705, found 389.2696.
1
9:1). Yield 48 mg (25%), yellow oil. H NMR (CDCl3, δ, ppm):
7.66 (d, J ) 8.2 Hz, 1H), 7.43 (d, J ) 6.9 Hz, 1H), 7.23 (dd, J )
8.2, 6.9 Hz, 1H), 6.85 (m, 2H), 6.63 (m, 2H), 5.82 (br s, 1H), 3.76
(s, 2H), 3.17 (t, J ) 5.5 Hz, 2H), 2.81 (s, 3H), 2.74 (s, 3H), 2.63
(t, J ) 5.5 Hz, 2H), 2.34 (s, 3H), 2.27 (s, 3H), 1.78 (m, 2H). 13C
NMR (CDCl3, δ, ppm): 158.40, 146.20, 144.11, 138.69, 136.68,
128.72, 124.77, 123.28, 121.58, 120.58, 118.98, 117.69, 74.99,
54.48, 49.52, 42.24, 24.84, 23.31, 18.22, 14.71. HRMS m/z calcd
for C23H29N4 [M + H]+ 361.2392, found 361.2395.
N-(2-Diethylaminoethyl)-N′-(3-ethyl-2,8-dimethylquinolin-4-
yl)benzene-1,4-diamine (6b). Compound 6b was synthesized by
method A from 3p (88 mg, 0.40 mmol), 4j (59 mg, 0.29 mmol),
and HCl (a couple of drops) in MeOH (750 µL). The temperature
was 100 °C and the reaction time was 20 min. Yield 45 mg (28%),
yellow solid. 1H NMR (CDCl3, δ, ppm): 7.63 (d, J ) 8.6 Hz, 1H),
[4-(3,4-Dimethylpiperazin-1-yl)phenyl]-(2,3,5,8-tetrameth-
ylquinolin-4-yl)amine (5u). Compound 5u was synthesized by
method A from 3l (220 mg, 1.0 mmol), 4c (103 mg, 0.50 mmol),
and HCl (a couple of drops) in MeOH (750 µL). The temperature
was 130 °C and the reaction time was 5 min. Yield 152 mg (78%),
brown solid. 1H NMR (CDCl3, δ, ppm): 7.31 (d, J ) 7.3 Hz, 1H),
7.04 (d, J ) 7.3 Hz, 1H), 6.80 (m, 2H), 6.47 (m, 2H), 5.76 (br s,
1H), 3.34 (m, 1H), 3.29 (m, 1H), 2.86 (m, 2H), 2.74 (s, 3H), 2.70
(s, 6H), 2.46 (m, 2H), 2.34 (s, 3H), 2.27 (m, 1H), 2.21 (s, 3H),

Quinoline DeriVatiVes as R2C Antagonists
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 21 6361
7.41 (d, J ) 7.0 Hz, 1H), 7.11 (dd, J ) 8.6, 7.0 Hz, 1H), 6.79 (m,
2H), 6.61 (m, 2H), 3.54 (m, 2H), 3.24 (m, 3H), 3.17 (s, 3H), 3.00
(m, 3H), 2.92 (s, 3H), 2.78 (q, J ) 7.6 Hz, 2H), 1.39 (t, J ) 7.3
6H), 1.15 (t, J ) 7.6 Hz, 3H). 13C NMR (CDCl3, δ, ppm): 159.06,
153.10, 146.41, 144.57, 138.02, 132.65, 129.85, 126.42, 124.86,
124.33, 122.68, 119.48, 117.85, 113.72, 56.51, 51.30, 47.37, 39.04,
32.78, 24.95, 12.81, 8.72. HRMS m/z calcd for C25H35N4 [M +
H]+ 391.2862, found 391.2864.
quinoline-3-carboxylic acid ethyl ester (119 mg, 0.28 mmol) was
treated with LiAlH4 (56 mg, 1.48 mmol) in THF to yield 24 mg
(22%) of 6f as a yellow solid. H NMR (CDCl3, δ, ppm): 7.94
(m, 1H), 7.65 (m, 1H), 7.54 (m, 1H), 7.41 (br s, 1H), 7.18 (m,
1H), 6.77 (m, 4H), 4.83 (s, 2H), 3.12 (m, 2H), 2.85 (s, 2H), 2.69
(m, 2H), 2.63 (s, 3H), 2.29 (s, 3H), 1.12 (s, 6H). 13C NMR (CDCl3,
δ, ppm): 157.18, 148.42, 147.33, 137.06, 129.60, 127.73, 124.90,
124.46, 121.42, 120.93, 120.11, 117.51, 63.15, 58.92, 53.80, 50.20,
49.98, 37.23, 23.43, 22.97, 20.07. HRMS m/z calcd for C24H31N4O
[M + H]+ 391.2498, found 391.2488.
1
N-(2,3-Dimethylquinolin-4-yl)-N′-(2-pyrrolidin-1-ylethyl)ben-
zene-1,4-diamine (6c). Compound 6c was synthesized by method
A from 3c (115 mg, 0.60 mmol), 4k (95 mg, 0.46 mmol), and HCl
(a couple of drops) in MeOH (750 µL). The temperature was 120
°C and the reaction time was 15 min. Yield 160 mg (96%), red
1-{4-[4-(3,4-Dimethylpiperazin-1-yl)phenylamino]-2-meth-
ylquinolin-3-yl}ethanol (6g). Compound 6g was synthesized by
method B starting from 3v (138 mg, 0.62 mmol), 4c (119 mg, 0.58
mmol), and p-TsOH‚H2O (1 mg) in MeOH (500 µL). The thus
obtained 1-{4-[4-(3,4-dimethylpiperazin-1-yl)phenylamino]-2-me-
thylquinolin-3-yl}ethanone (82 mg, 0.22 mmol) was treated with
LiAlH4 (20 mg, 0.44 mmol) in THF to yield 56 mg (65%) of 6g as
1
solid. H NMR (CD3OD, δ, ppm): 7.97 (m, 1H), 7.92 (m, 1H),
7.76 (m, 1H), 7.40 (m, 1H), 7.01 (m, 2H), 7.76 (m, 2H), 3.59 (t, J
) 6.1 Hz, 2H), 3.45-3.37 (m, 6H), 2.76 (s, 3H), 2.18 (s, 3H),
2.14 (m, 4H). 13C NMR (CDCl3, CD3OD, δ, ppm): 153.97, 152.93,
146.74, 138.99, 132.85, 131.50, 126.32, 125.74, 125.13, 120.31,
118.37, 113.88, 113.34, 54.66, 54.52, 40.45, 23.46, 19.68, 14.31.
HRMS m/z calcd for C23H29N4 [M + H]+ 361.2392, found
361.2391.
1
a yellow solid. H NMR (CDCl3, δ, ppm): 8.62 (br s, 1H), 7.91
(m, 1H), 7.56 (m, 1H), 7.48 (m, 1H), 7.08 (m, 1H), 6.78 (m, 2H),
6.73 (m, 2H), 5.34 (q, J ) 6.7 Hz, 1H), 3.37 (m, 2H), 2.87 (m,
2H), 2.50 (s, 3H), 2.49 (m, 1H), 2.41 (m, 1H), 2.32 (s, 3H), 2.26
(m, 1H), 1.48 (d, J ) 6.7 Hz, 3H), 1.11 (d, J ) 6.1 Hz, 3H). 13C
NMR (CDCl3, δ, ppm): 155.07, 148.65, 146.57, 137.59, 129.46,
127.00, 125.33, 124.18, 124.07, 122.12, 121.58, 120.50, 117.17,
116.92, 66.93, 57.82, 56.88, 55.66, 49.68, 42.52, 22.66, 21.08,
17.20. HRMS m/z calcd for C24H31N4O [M + H]+ 391.2498, found
391.2488.
(3-Ethyl-2,8-dimethylquinolin-4-yl)-[4-(4-methyl-[1,4]diazepan-
1-yl)phenyl]amine (6d). Compound 6d was synthesized by method
A from 3p (1.20 g, 5.5 mmol), 4f (808 mg, 3.9 mmol), and HCl (a
couple of drops) in MeOH (3.0 mL). The temperature was 120 °C
and the reaction time was 70 min. Yield 320 mg (21%), yellow
1
solid. H NMR (CDCl3, δ, ppm): 7.60 (d, J ) 8.5 Hz, 1H), 7.38
(d, J ) 6.9 Hz, 1H), 7.13 (dd, J ) 8.5, 6.9 Hz, 1H), 6.66 (m, 2H),
6.54 (m, 2H), 5.62 (br s, 1H), 3.52 (m, 2H), 3.40 (m, 2H), 2.78
(m, 2H), 2.78 (s, 3H), 2.77 (s, 3H), 2.71 (m, 2H), 2.61 (m, 2H),
2.40 (s, 3H), 2.01 (m, 2H), 1.16 (t, J ) 7.5 Hz, 3H). 13C NMR
(CDCl3, δ, ppm): 157.61, 146.53, 144.76, 144.76, 136.54, 135.95,
128.44, 126.37, 124.20, 122.84, 122.08, 119.56, 112.60, 58.36,
57.10, 48.44, 46.53, 27.67, 24.33, 21.15, 18.20, 13.60. HRMS m/z
calcd for C25H33N4 [M + H]+ 389.2705, found 389.2710.
(R)-{4-[4-(3,4-Dimethylpiperazin-1-yl)phenylamino]-3-meth-
ylquinolin-2-yl}methanol (6h). Compound 6h was synthesized by
method B starting from 3q (467 mg, 1.87 mmol), 4d (297 mg,
1.45 mmol), and p-TsOH‚H2O (5 mg) in MeOH (600 µL). The
thus-obtained (R)-4-[4-(3,4-dimethylpiperazin-1-yl)phenylamino]-
3-methylquinoline-2-carboxylic acid ethyl ester (170 mg, 0.41
mmol) was treated with LiAlH4 (76 mg, 2.03 mmol) in THF to
1
yield 97 mg (63%) of 6h as a yellow solid. H NMR (CDCl3, δ,
ppm): 8.03 (m, 1H), 7.82 (m, 1H), 7.62 (m, 1H), 7.37 (m, 1H),
6.83 (m, 2H), 6.71 (m, 2H), 5.92 (br s, 1H), 4.82 (s, 2H), 3.40 (m,
1H), 3.34 (m, 1H), 2.90 (m, 2H), 2.51 (m, 1H), 2.44 (m, 1H), 2.35
(s, 3H), 2.28 (m, 1H), 2.11 (s, 3H), 1.14 (d, J ) 6.1 Hz, 3H). 13C
NMR (CDCl3, δ, ppm): 158.14, 146.23, 145.92, 144.65, 137.49,
128.90, 128.78, 125.45, 123.15, 122.83, 118.91, 117.73, 117.53,
62.22, 57.84, 57.21, 55.66, 50.03, 42.51, 17.21, 11.82. HRMS m/z
calcd for C23H29N4O [M + H]+ 377.2341, found 377.2350.
{4-[4-(3,3,4-Trimethylpiperazin-1-yl)phenylamino]quinolin-
3-yl}methanol (6i). Compound 6i was synthesized by method B
starting from 3b (90 mg, 0.38 mmol), 4i (67 mg, 0.31 mmol), and
p-TsOH‚H2O (1 mg) in MeOH (700 µL). The thus-obtained 4-[4-
(3,3,4-trimethylpiperazin-1-yl)phenylamino]quinoline-3-carboxyl-
ic acid ethyl ester (42 mg, 0.10 mmol) was treated with LiAlH4
(26 mg, 0.68 mmol) in THF to yield 18 mg (48%) of 6i as a yellow
solid. 1H NMR (CDCl3, δ, ppm): 8.45 (s, 1H), 7.97 (m, 1H), 7.70
(m, 1H), 7.56 (m, 1H), 7.50 (br s, 1H), 7.22 (m, 1H), 6.82 (m,
2H), 6.78 (m 2H), 4.77 (s, 2H), 3.15 (m, 2H), 2.91 (s, 2H), 2.76
(m, 2H), 2.33 (s, 3H), 1.16 (s, 6H). 13C NMR (CDCl3, δ, ppm):
150.19, 149.05, 148.07, 147.46, 136.61, 129.38, 128.99, 124.95,
124.82, 121.63, 120.80, 120.96, 117.51, 63.49, 62.74, 61.77, 50.09,
49.65, 37.03, 20.10. HRMS m/z calcd for C23H29N4O [M + H]+
377.2341, found 377.2345.
{4-[4-(3,4-Dimethylpiperazin-1-yl)phenylamino]-2-methylquin-
olin-3-yl}methanol (6e): Method B. A solution of 3u (81 mg, 0.32
mmol), 4c (60 mg, 0.29 mmol), and p-TsOH‚H2O (1 mg, cat.) in
MeOH (500 µL) were heated at 125 °C by microwave irradiation
for 20 min. Solvent was evaporated in vacuo and the residue was
dissolved in water, made alkaline with aqueoue saturated NaHCO3
solution, and extracted twice with CH2Cl2. Combined organic phases
were dried over Na2SO4 and evaporated in vacuo. The product was
purified by flash chromatography (CH2Cl2/MeOH ) 19:1) to obtain
75 mg (62%) of 4-[4-(3,4-dimethylpiperazin-1-yl)phenylamino]-
2-methylquinoline-3-carboxylic acid ethyl ester as a yellow oil.
To a cooled (0 °C) mixture of LiAlH4 (34 mg, 0.90 mmol) in
THF (1.5 mL) under argon atmosphere, a solution of 4-[4-(3,4-
dimethylpiperazin-1-yl)phenylamino]-2-methylquinoline-3-carboxy-
lic acid ethyl ester (75 mg, 0.18 mmol) in THF (1.5 mL) was added
dropwise with the help of a syringe. After 30 min of reaction time
at 0 °C, the reaction mixture was allowed to warm to room
temperature and stirring was continued for 2 h. The reaction was
cooled (0 °C) and quenched by adding water. The mixture was
diluted with THF and filtered. The precipitate was washed a few
times with THF and the filtrate was evaporated in vacuo. The
product was purified by flash chromatography (CH2Cl2/MeOH )
1
9:1) to obtain 42 mg (62%) of 6e as a yellow solid. H NMR
(CDCl3, δ, ppm): 7.92 (m, 1H), 7.63 (m, 1H), 7.52 (m, 1H), 7.51
(br s, 1H), 7.15 (m, 1H), 6.78 (m, 4H), 4.82 (s, 2H), 3.40 (m, 1H),
3.34 (m, 1H), 2.86 (m, 2H), 2.57 (s, 3H), 2.49 (m, 1H), 2.42 (m,
1H), 2.33 (s, 3H), 2.26 (m, 1H), 1.12 (d, J ) 6.1 Hz, 3H). 13C
NMR (CDCl3, δ, ppm): 157.26, 148.37, 147.42, 146.64, 137.23,
129.55, 127.77, 124.92, 124.41, 121.43, 120.97, 120.14, 117.25,
58.87, 57.77, 57.05, 55.65, 49.88, 42.54, 22.97, 17.25. HRMS m/z
calcd for C23H29N4O [M + H]+ 377.2341, found 377.2325.
{2-Methyl-4-[4-(3,3,4-trimethylpiperazin-1-yl)phenylamino]-
quinolin-3-yl}methanol (6f). Compound 6f was synthesized by
method B starting from 3u (167 mg, 0.67 mmol), 4i (96 mg, 0.44
mmol), and p-TsOH‚H2O (1 mg) in MeOH (750 µL). The thus-
obtained2-methyl-4-[4-(3,3,4-trimethylpiperazin-1-yl)phenylamino]-
(R)-{4-[4-(3,4-Dimethylpiperazin-1-yl)phenylamino]quinolin-
3-yl}methanol (6j). Compound 6j was synthesized by method B
starting from 3b (0.744 g, 3.16 mmol), 4d (0.588 g, 2.87 mmol),
and p-TsOH‚H2O (3 mg) in MeOH (2.0 mL). The thus-obtained
(R)-4-[4-(3,4-dimethylpiperazin-1-yl)phenylamino]quinoline-3-car-
boxylic acid ethyl ester (0.875 g, 2.10 mmol) was treated with
LiAlH4 (0.431 g, 10.8 mmol) in THF to yield 0.635 g (85%) of 6j
as a yellow solid.1H NMR (CDCl3, δ, ppm): 8.34 (s, 1H), 7.94
(m, 1H), 7.70 (m, 1H), 7.53 (m, 1H), 7.47 (br s, 1H), 7.20 (m,
1H), 6.80 (m, 4H), 4.73 (s, 2H), 3.40 (m, 1H), 3.35 (m, 1H), 2.86
(m, 2H), 2.49 (m, 1H), 2.41 (m, 1H), 2.32 (s, 3H), 2.26 (m, 1H),
1.12 (d, J ) 6.1 Hz, 3H). 13C NMR (CDCl3, δ, ppm): 150.52,
149.42, 147.85, 146.89, 136.72, 129.26, 129.18, 124.96, 124.70,

6362 Journal of Medicinal Chemistry, 2006, Vol. 49, No. 21
Ho¨glund et al.
121.71, 121.11, 120.77, 117.12, 61.73, 57.77, 56.99, 55.63, 49.82,
42.53, 17.23. HRMS m/z calcd for C22H27N4O [M + H]+ 363.2185,
found 363.2181.
mmol), 4d (0.455 g, 2.21 mmol), and p-TsOH‚H2O (1 mg) in
MeOH (3.0 mL) was stirred at room temperature overnight. The
reaction mixture was diluted with water (100 mL), made alkaline
with aqueoue saturated NaHCO3 solution, and extracted twice with
CH2Cl2. The combined organic phases were dried over Na2SO4 and
evaporated in vacuo. The residue was purified by flash chroma-
tography (CH2Cl2/MeOH ) 19:1) to obtain 0.586 g (63%, 1.39
mmol) of (R)-4-[4-(3,4-dimethylpiperazin-1-yl)phenylamino]-6-
fluoroquinoline-3-carboxylic acid ethyl ester, which was treated with
LiAlH4 (0.487 g, 13.1 mmol) in THF according to method B to
(R)-{4-[4-(3-Methylpiperazin-1-yl)phenylamino]quinolin-3-
yl}methanol (6k). To a cooled (0 °C) mixture of LiAlH4 (0.645 g,
17.3 mmol) in THF (1.5 mL) under argon atmosphere, a solution
of 10 (0.933 g, 2.39 mmol) in THF (1.5 mL) was added dropwise
with the aid of a syringe. After 30 min of reaction time at 0 °C,
the reaction mixture was allowed to warm to room temperature
and stirring was continued for 2 h. The reaction was cooled (0 °C)
and quenched by adding water. The mixture was diluted with THF
and filtered. The precipitate was washed a few times with THF
and the filtrate was evaporated in vacuo. The product was purified
by flash chromatography (CH2Cl2/MeOH ) 9:1) to obtain 295 mg
(35%) of 6k as a yellow solid. 1H NMR (CDCl3, δ, ppm): 8.47 (s,
1H), 7.98 (m, 1H), 7.72 (m, 1H), 7.57 (m, 1H), 7.33 (br s, 1H),
7.23 (m, 1H), 6.82 (m, 4H), 4.78 (s, 2H), 3.42 (m, 2H), 3.09 (m,
1H), 3.04 (m, 1H), 2.98 (m, 1H), 2.66 (m, 1H), 2.31 (m, 1H), 1.11
(d, J ) 6.4 Hz, 3H). 13C NMR (CDCl3, δ, ppm): 150.47, 149.34,
147.88, 147.31, 136.77, 129.20, 124.98, 124.69, 121.69, 121.15,
120.78, 117.32, 61.67, 57.60, 50.70, 50.02, 45.85, 19.70. HRMS
m/z calcd for C21H25N4O [M + H]+ 349.2028, found 349.2040.
{7-Chloro-4-[4-(3,3,4-trimethylpiperazin-1-yl)phenylamino]-
quinolin-3-yl}methanol (6l). Compound 6l was synthesized by
method B starting from 3s (79 mg, 0.29 mmol), 4i (55 mg, 0.25
mmol), and p-TsOH‚H2O (9 mg, 0.05 mmol) in MeOH (500 µL).
The thus-obtained 7-chloro-4-[4-(3,3,4-trimethylpiperazin-1-yl)-
phenylamino]quinoline-3-carboxylic acid ethyl ester (77 mg, 0.17
mmol) was treated with LiAlH4 (36 mg, 0.94 mmol) in THF to
yield 39 mg (53%) of 6l as a yellow solid.1H NMR (CDCl3, δ,
ppm): 8.37 (s, 1H), 7.91 (d, J ) 1.8 Hz, 1H), 7.57 (d, J ) 9.2 Hz,
1H), 7.53 (br s, 1H), 7.11 (dd, J ) 9.2, 1.8 Hz, 1H), 6.78 (m, 4H),
4.76 (s, 2H), 3.15 (m, 2H), 2.89 (s, 2H), 2.73 (m, 2H), 2.31 (s,
3H), 1.15 (s, 6H). 13C NMR (CDCl3, δ, ppm): 151.50, 150.10,
148.11, 147.74, 136.17, 135.04, 128.12, 126.49, 125.44, 121.12,
120.79, 119.81, 117.44, 62.77, 61.75, 54.26, 50.15, 49.65, 37.15,
20.17. HRMS m/z calcd for C23H28N4OCl [M + H]+ 411.1952,
found 411.1954.
1
yield 386 mg (73%) of 6o as a yellow solid. H NMR (CDCl3, δ,
ppm): 8.36 (s, 1H), 7.91 (m, 1H), 7.37 (br s, 1H), 7.26 (m, 2H),
6.77 (m, 4H), 4.74 (s, 2H), 3.39 (m, 1H), 3.33 (m, 1H), 2.86 (m,
2H), 2.49 (m, 1H), 2.42 (m, 1H), 2.31 (s, 3H), 2.27 (m, 1H), 1.11
(d, J ) 6.1 Hz, 3H). 13C NMR (CDCl3, δ, ppm): 160.02, 158.06,
149.94, 147.42, 146.56, 136.14, 131.79, 122.56, 121.64, 120.79,
119.54, 119.33, 117.32, 108.72, 108.53, 61.66, 57.83, 56.86, 55.54,
49.71, 42.45, 17.11. HRMS m/z calcd for C22H26N4OF [M + H]+
381.2091, found 381.2093.
(3,5-Dimethyl-pyridin-4-yl)-[4-(4-methylpiperazin-1-yl)phe-
nyl]amine (7). Compounds 16 (179 mg, 1.0 mmol) and 4g (97
mg, 0.51 mmol) were mixed and heated in an open reaction vessel
by an electric mantle until they melted. The heating and stirring
was continued at that temperature for 1 h. The reaction mixture
was cooled and dissolved in water. The solution was made alkaline
with a saturated aqueous NaHCO3 solution and extracted with
CHCl3. The organic phase was dried over Na2SO4, evaporated in
vacuo, and purified by flash chromatography (CH2Cl2/MeOH )
9:1) to obtain 22 mg (15%) of the desired compound as a red solid.
1H NMR (CDCl3, δ, ppm): 8.14 (m, 2H), 6.87 (m, 2H), 6.78 (m,
2H), 5.71 (br s, 1H), 3.22 (m, 4H), 2.67 (m, 4H), 2.42 (s, 3H),
2.01 (s, 6H). 13C NMR (CDCl3, δ, ppm): 149.15, 147.51, 147.27,
135.01, 121.46, 117.14, 54.98, 49.39, 45.82, 15.97. HRMS m/z calcd
for C18H25N4 [M + H]+ 297.2079, found 297.2079.
[4-(3,4-Dimethylpiperazin-1-yl)phenyl]-(3-ethyl-2-methyl-5,6,7,8-
tetrahydroquinolin-4-yl)amine (8). Compound 8 was synthesized
by method A from 13 (169 mg, 0.81 mmol), 4c (82 mg, 0.40 mmol),
and HCl (a couple of drops) in MeOH (1.5 mL). The temperature
was 145 °C and the reaction time was 60 min. Yield 54 mg (36%),
{4-[4-(3,4-Dimethylpiperazin-1-yl)phenylamino]-6-fluoroquin-
olin-3-yl}methanol (6m). Compound 6m was synthesized by
method B starting from 3t (100 mg, 0.39 mmol), 4c (72 mg, 0.35
mmol), and p-TsOH‚H2O (1 mg) in MeOH (500 µL). The thus-
obtained 4-[4-(3,4-dimethylpiperazin-1-yl)phenylamino]-6-fluoro-
quinoline-3-carboxylic acid ethyl ester (123 mg, 0.29 mmol) was
treated with LiAlH4 (54 mg, 1.45 mmol) in THF to yield 30 mg
1
yellow solid. H NMR (CDCl3, δ, ppm): 6.79 (m, 2H), 6.60 (m,
2H), 5.25 (br s, 1H), 3.33 (m, 2H), 2.85 (m, 4H), 2.53 (q, J ) 7.6
Hz, 2H), 2.50 (s, 3H), 2.48-1.37 (m, 2H), 2.32 (t, J ) 6.1 Hz,
2H), 2.31 (s, 3H), 2.22 (m, 1H), 1.77 (m, 2H), 1.62 (m, 2H), 1.10
(d, J ) 6.1 Hz, 3H), 1.02 (t, J ) 7.6 Hz, 3H). 13C NMR (CDCl3,
δ, ppm): 145.86, 137.74, 127.79, 124.16, 118.51, 117.47, 57.83,
57.44, 55.79, 50.22, 42.60, 32.51, 25.31, 22.90, 22.72, 22.16, 20.82,
17.32, 13.64. HRMS m/z calcd for C24H35N4 [M + H]+ 379.2862,
found 379.2861.
1
(27%) of 6m as a yellow solid. H NMR (CDCl3, δ, ppm): 8.34
(s, 1H), 7.91 (m, 1H), 7.39 (br s, 1H), 7.26 (m, 2H), 6.76 (m, 4H),
4.73 (s, 2H), 3.38 (m, 1H), 3.33 (m, 1H), 2.85 (m, 2H), 2.49 (m,
1H), 2.41 (m, 1H), 2.31 (s, 3H), 2.27 (m, 1H), 1.10 (d, J ) 6.1 Hz,
3H). 13C NMR (CDCl3, δ, ppm): 160.01, 158.05, 149.91, 147.44,
146.53, 136.14, 131.76, 122.63, 121.67, 120.79, 119.53, 119.33,
117.32, 108.73, 108.54, 61.63, 57.82, 56.86, 55.53, 49.71, 42.45,
17.11. HRMS m/z calcd for C22H26N4OF [M + H]+ 381.2091, found
381.2095.
N-(3-Methylaminopropyl)-N′-(2,3,8-trimethylquinolin-4-yl)-
benzene-1,4-diamine (9). Compound 9 was synthesized by method
B from 3a (223 mg, 1.08 mmol), 4a (187 mg, 1.04 mmol), and
HCl (a couple of drops) in MeOH (750 µL). The temperature was
120 °C and the reaction time was 15 min. Yield 187 mg (52%),
red solid. MS (ESI) m/z 349 [M + H]+.
{6-Fluoro-4-[4-(3,3,4-trimethylpiperazin-1-yl)phenylamino]-
quinolin-3-yl}methanol (6n). Compound 6n was synthesized by
method B starting from 3t (97 mg, 0.38 mmol), 4i (73 mg, 0.33
mmol), and p-TsOH‚H2O (7 mg, 0.04 mmol) in MeOH (500 µL).
The thus-obtained 6-fluoro-4-[4-(3,3,4-trimethylpiperazin-1-yl)-
phenylamino]quinoline-3-carboxylic acid ethyl ester (111 mg, 0.25
mmol) was treated with LiAlH4 (52 mg, 1.37 mmol) in THF to
(R)-4-[4-(3-Methylpiperazin-1-yl)phenylamino]quinoline-3-
carboxylic Acid Ethyl Ester (10). Compound 10 was synthesized
by method B starting from five batches of 3b (0.293 g each, total
amount 1.464 g, 5.54 mmol), 4b (163 mg each, total amount 0.815
g, 4.26 mmol), and p-TsOH‚H2O (10 mg each, total amount 50
mg, 0.26 mmol) in MeOH (1.5 mL in each). Yield 0.933 g (56%),
yellow solid. MS (ESI) m/z 391 [M + H]+.
2-(1-Ethoxyethylidene)malonic Acid Diethyl Ester (15b):
Method C. A solution of 14a (1.59 mL, 10.5 mmol), triethyl
orthoacetate (5.61 mL, 30.8 mmol), Ac2O (35 µL, 0.32 mmol), and
ZnCl2 (0.4 mg, cat.) was heated in a reaction vessel equipped with
a distillation bridge and a thermometer. At a vapor temperature of
70 °C, side products formed in the reaction and started to distill
out. Ac2O (35 µL) was added three times every 30 min. After 4 h
of heating, the reaction mixture was allowed to cool to room
temperature. The reaction mixture was evaporated gently under
reduced pressure to remove low-volatile starting materials and side
1
yield 57 mg (57%) of 6n as a yellow solid. H NMR (CDCl3, δ,
ppm): 8.35 (s, 1H), 7.92 (m, 1H), 7.48 (br s, 1H), 7.29 (m, 2H),
6.76 (m, 4H), 4.75 (s, 2H), 3.13 (m, 2H), 2.88 (s, 2H), 2.72 (m,
2H), 2.30 (s, 3H), 1.15 (s, 6H). 13C NMR (CDCl3, δ, ppm): 159.99,
158.04, 149.97, 147.42, 146.47, 136.20, 131.70, 122.62, 121.92,
120.64, 119.48, 119.27, 117.65, 108.75, 108.56, 62.88, 61.50, 54.33,
50.17, 49.72, 37.13, 20.08. HRMS m/z calcd for C23H28N4OF [M
+ H]+ 395.2247, found 395.2270.
(R)-{4-[4-(3,4-Dimethylpiperazin-1-yl)phenylamino]-6-fluoro-
quinolin-3-yl}methanol (6o). A solution of 3t (0.613 g, 2.41

Quinoline DeriVatiVes as R2C Antagonists
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 21 6363
(14) Wurster, S.; Engstro¨m, M.; Savola, J.-M.; Ho¨glund, I.; Sallinen, J.;
Haapalinna, A.; Tauber, A.; Hoffren, A.-M.; Salo, H. Derivatives of
quinoline as alpha-2 antagonists. Patent WO 0164645, 2001.
(15) Roland, S.; Mangeney, P.; Alexakis, A. A practical and efficient
synthesis of enantiomerically pure di-tert-butyl-ethanediamine. Syn-
thesis 1999, 228-230.
(16) Cain, B. F.; Atwell, G. J.; Denny, W. A. Potential antitumor agents.
23. 4′-(9-acridinylamino)alkanesulfonamide congeners bearing hy-
drophilic functionality. J. Med. Chem. 1977, 20, 987-996.
(17) Conrad, M.; Limpach, L. Synthesen von Chinolin derivativen mittelst
Acetessigester. Ber. Dtsch. Chem. Ges. 1887, 20, 944.
(18) Gould, R. G.; Jacobs, W. A. The synthesis of certain substituted
quinolines and 5,6-benzoquinolines. J. Am. Chem. Soc. 1939, 61,
2890-2895.
(19) Cain, B. F.; Seeyle, R. N.; Atwell, G. J. Potential antitumor agents.
14. Acridylmethanesulfonanilides. J. Med. Chem. 1974, 17, 922-
930.
(20) Steck, E. A.; Hallock, L. L.; Holland, A. J.; Quinolines, I. The
synthesis of 3-methyl-4-(1′-methyl-4′-diethylaminobutylamino)-
quinoline and some 6-substituted derivatives. J. Am. Chem. Soc. 1946,
68, 129-132.
(21) Gildemeister, H.; Knorr, H.; Mildenberger, H.; Salbeck, G. Neue
4-Chinolinol- und 5,6,7,8-Tetrahydro-4-chinolinolabko¨mmlinge mit
biozider Wirkung. Liebigs Ann. Chem. 1982, 1656-1676.
(22) Ackermann, O.; Bleh, O.; Rogler, W. Method of preparing alkoxy-
methylenemalonic acid esters. U.S. Patent 4058553, 1977.
(23) Zoghbi, M., Chen, L. Synthesis of pharmaceutically useful pyridine
derivatives. U.S. Patent 6437139, 2002.
(24) Neuville, L.; Zhu, J. Solution phase combinatorial synthesis of
arylpiperazines. Tetrahedron Lett. 1997, 38, 4091-4094.
(25) Godek, D. M.; Murtiashaw, C. W.; Urban, F. J.; Vanderplas, B. C.
Process and intermediate for certain bis-aza-bicyclic anxiolytic agents.
U.S. Patent 5455350, 1995.
(26) Mickelson, J. W.; Belonga, K. L.; Jacobsen, E. J. Asymmetric
synthesis of 2,6-methylated piperazines. J. Org. Chem. 1995, 60,
4177-4183.
(27) Moore, M. L. The Leuckart Reaction. In Organic Reactions; John
Wiley & Sons Inc.: New York, 1949; Vol. V, Chapt. 7, pp 301-
323
(28) Su, T.-L.; Chen, C.-H.; Huang, L.-F.; Chen, C.-H.; Basu, M. K.;
Zhang, X.-G.; Chou, T.-C. Synthesis and structure-activity relation-
ships of potential anticancer agents: Alkylcarbamates of 3-(9-
acridinylamino)-5-hydroxymethylaniline. J. Med. Chem. 1999, 42,
4741-4748.
(29) Chen, Y.-L.; Lu, C.-M.; Chen, I.-L.; Tsao, L.-T.; Wang, J.-P.
Synthesis and antiinflammatory evaluation of 9-anilinoacridine and
9-phenoxyacridine derivatives. J. Med. Chem. 2002, 45, 4689-4694.
(30) Finlay, G. J.; Riou, J.-F.; Baguley, B. C. From Amsacrine to DACA
(N-[2-(dimethylamino)ethyl]acridine-4-carboxamide): selectivity for
topoisomerases I and II among acridine derivatives. Eur. J. Cancer
1996, 32A, 708-714.
(31) Wang, L.; Price, H. L.; Juusola, J.; Kline, M.; Phanstiel IV, O.
Influence of polyamine architecture on the transport and topoi-
somerase II inhibitory properties of polyamine DNA-intercalator
conjugates. J. Med. Chem. 2001, 44, 3682-3691.
(32) Marjama¨ki, A.; Luomala, K.; Ala-Uotila, S.; Scheinin, M. Use of
recombinant human alpha 2-adrenoceptors to characterize subtype
selectively of antagonist binding. Eur. J. Pharmacol. 1993, 246, 219-
226.
(33) Cheng, Y.; Prusoff, W. H. Relationship between the inhibition
constant (K1) and the concentration of inhibitor which causes 50%
inhibition (I50) of an enzymatic reaction. Biochem. Pharmacol. 1973,
22, 3099-3108.
(34) Jasper, J. R.; Lesnick, J. D.; Chang, L. K.; Yamanishi, S. S.; Chang,
T. K.; Hsu, S. A.; Daunt, D. A.; Bonhaus, D. W.; Eglen, R. M. Ligand
efficacy and potency at recombinant alpha2 adrenergic receptors:
agonist-mediated [35S]GTPgammaS binding. Biochem. Pharmacol.
1998, 55, 1035-1043.
(35) Pohjanoksa, K.; Jansson, C. C.; Luomala, K.; Marjamaki, A.; Savola,
J.-M.; Scheinin, M. Alpha2-adrenoceptor regulation of adenylyl
cyclase in CHO cells: dependence on receptor density, receptor
subtype and current activity of adenylyl cyclase. Eur. J. Pharmacol.
1997, 335, 53-63.
products. The residue was purified by flash chromatography
(hexane/EtOAc ) 3:1) to obtain 1.70 g (70%) of 15b as a yellowish
oil. MS (ESI) m/z 231 [M + H]+.
2-(1-Ethoxyethylidene)malonic Acid Diethyl Ester (15c).
Compound 15c was synthesized by method C from 14b (2.68 mL,
21 mmol), triethyl orthoacetate (11.2 mL, 61 mmol), Ac2O (420
µL, 4.4 mmol), and ZnCl2 (1 mg, cat.). Ac2O was added in six
portions every 30 min. Yield 1.20 g (29%), yellowish oil. MS (ESI)
m/z 201 [M + H]+.
4-Chloro-3,5-dimethylpyridine Hydrochloric Acid Salt (16).
A solution of 3,5-lutidine (5.76 mL, 50 mmol) in thionyl chloride
(30 mL, 0.41 mol) was refluxed for 100 h. The reaction mixture
was cooled to room temperature. The formed precipitate was filtered
and washed with toluene. Yield 2.82 g (32%), brown solid. 1H NMR
(CD3OD, δ, ppm) 8.71 (s, 2 H), 2.58 (s, 6 H).
Acknowledgment. We thank Ms. Mira Friman, Ms. Taina
Heimo, Ms. Liisa Huovinen, M.Sc. Topi Joutsamo, Ms. Leila
Kelanne, Ms. Johanna Kervinen, Ms. Mirja Koski, Ms. Sirpa
Oksman, Ms. Pa¨ivi Pohjola, M.Sc. Elina Tienari, and Ms. Raisa
Vuorinen for their assistance.
Supporting Information Available: 1H NMR spectra and LC-
MS data of compounds 5a-x, 6a-o, 7, and 8; experimental data
for 3a-v, 4a-k, 12a-w, 13, 18a-e, and 19-25. This material is
available free of charge via the Internet at http://pubs.acs.org.
References
(1) Hieble, J. P.; Ruffolo, R. R.; Starke, K. Identification, Characterization
and Subclassification of R2-Adrenoceptors: An Overview. In R2-
Adrenergic Receptors. Structure, Function and Therapeutic Implica-
tions; Lanier, S. M., Limbird, L. E., Eds.; Overseas Publishers
Association: Amsterdam, 1997; pp 1-18.
(2) MacDonald, E.; Kobilka, B. K.; Scheinin, M. Gene targeting-homing
in on R2-adrenoceptor-subtype function. Trends Pharmacol. Sci. 1997,
18, 211-219.
(3) Scheinin, M.; Lomasney, J. W.; Hayden-Hixson, D. M.; Schambra,
U. B.; Caron, M. G.; Lefkowitz, R. J.; Fremeau, R. T., Jr. Distribution
of alpha2-adrenergic receptor subtype gene expression in rat brain.
Brain Res. Mol. Brain Res. 1994, 21, 133-149.
(4) Rosin, D. L.; Talley, E. M.; Lee, A.; Stornetta, R. L.; Gaylinn, B.
D.; Guynet, P. G.; Lynch, K. R. Distribution of R2C-adrenergic
receptor-like immunoreactivity in the rat central nervous system. J.
Comp. Neurol. 1996, 372, 135-165.
(5) Scheinin, M.; Sallinen, J.; Haapalinna, A. Evaluation of the alpha2C-
adrenoceptor as a neuropsychiatric drug target studies in transgenic
mouse models. Life Sci. 2001, 68, 2277-2285.
(6) Brede, M.; Philipp, M.; Knaus, A.; Muthig, V.; Hein, L. Alpha2-
adrenergic receptor subtypes-novel functions uncovered in gene-
targeted mouse models. Biol. Cell 2004, 96, 343-348.
(7) Kalkman, H. O.; Loetscher, E. alpha2C-Adrenoceptor blockade by
clozapine and other antipsychotic drugs. Eur. J. Pharmacol. 2003,
462, 33-40.
(8) Arnsten, A. F. Adrenergic targets for the treatment of cognitive
deficits in schizophrenia. Psychopharmacology (Berlin) 2004, 174,
25-31.
(9) Mayer, P.; Imbert, T. Alpha2-Adrenoreceptor antagonists. IDrugs
2001, 4, 662-676.
(10) Sallinen, J.; Haapalinna, A.; MacDonald, E.; Viitamaa, T.; La¨hdes-
ma¨ki, J.; Rybnikova, E.; Pelto-Huikko, M.; Kobilka, B. K.; Scheinin,
M. Genetic alteration of the R2-adrenoceptor subtype c in mice affects
the development of behavioral despair and stress-induced increases
in plasma corticosterone levels. Mol. Psychiat. 1999, 4, 443-452.
(11) Petit-Demouliere, B.; Chenu, F.; Bourin, M. Forced swimming test
in mice: a review of antidepressant activity. Psychopharmacology
(Berlin) 2005, 177, 245-255.
(12) Swerdlow, N. R.; Braff, D. L.; Taaid, N.; Geyer, M. A. Assessing
the validity of an animal model of deficient sensorimotor gating in
schizophrenic patients. Arch. Gen. Psychiat. 1994, 51, 139-154.
(13) Sallinen, J.; Haapalinna, A.; Viitamaa, T.; Kobilka, B. K.; Scheinin,
M. Adrenergic R2C-receptors modulate the acoustic startle reflex,
prepulse inhibition, and aggression in mice. J. Neurosci. 1998, 18,
3035-3042.
JM060262X